US20080191278A1 - Semiconductor device, method for manufacturing the same, liquid crystal television, and EL television - Google Patents

Abstract

A method for manufacturing a semiconductor device by a small number of processes and by a means with high usability of materials to have high-definition and a gate insulating with a high step coverage property is disclosed. According to the present invention, a method for manufacturing a semiconductor device comprises the steps of forming a plurality of first conductive layers over a substrate; forming a first insulating layer to fill the gaps of the plurality of the first conductive layers; forming a second insulating layer over the first insulating layer and the plurality of the first conductive layers; and forming a semiconductor region and a second conductive layer over the second insulating layer.

Description

BACKGROUND OF THE INVENTION
• 1. Field of the Invention
• The present invention relates to a semiconductor device formed by droplet discharging as typified by an ink jetting method, and a method for manufacturing the semiconductor device.
• 2. Related Art
• Conventionally, a so-called active matrix driving display panel or a semiconductor integrated circuit, each of which is composed of a semiconductor element as typified by a thin film transistor (hereinafter, TFT) over a glass substrate, is manufactured by patterning a various kinds of thin films by a light exposure process using a photomask (hereinafter, photolithography process).
• By the photolithography process, resist is coated allover the surface of a substrate to be pre-baked, and an ultraviolet ray or the like is emitted thereto via a photomask, then, a resist pattern is formed by developing. Thereafter, a thin film (that is formed by a semiconductor material, an insulating material, or a conducting material) presented in a portion to be a film pattern is etched off by using the resist pattern as a mask pattern, and the thin film is patterned to form a film pattern, then, a semiconductor element is formed.
• On the other hand, a bottom gate TFT is used as a driver element of a pixel of a liquid crystal display. In the bottom gate TFT, a gate electrode has a tapered portion at its edge portion to prevent electric field concentration at the vicinity of the edge portion of the gate electrode in a gate insulating film that overlaps with the gate electrode. Further, a tapered portion is provided to the gate electrode to improve step coverage of the gate insulating film provided over the gate electrode (Unexamined Patent Publication No. 10-170960).
• However, in order to form a gate electrode having a tapered portion, processes of etching, cleaning, and drying are required to be repeated at plurality of times in addition to the photolithography process. Therefore, there have been problems that most materials for the gate electrode and the resist are wasted, and throughput becomes deteriorated since a large number of processes for forming the resist mask pattern and the gate electrode is required in a manufacturing process of a semiconductor device.
• It is difficult for an exposure device used for the photolithography process to perform exposure processing of a large substrate at once. Therefore, a manufacturing method of a semiconductor device using a large substrate has problems that exposure processing is required to be performed at a plurality of times and manufacturing yields are deteriorated due to a mismatch between adjacent patterns.
SUMMARY OF THE INVENTION
• In view of the foregoing, it is an object of the present invention to provide a method for manufacturing a semiconductor device by a small number of processes and by a means by which high usability of materials is realized.
• It is another object of the present invention to provide a method for manufacturing a semiconductor device with high resist pressure that has a gate insulating film with high step coverage, moreover, to provide a liquid crystal television, and an EL television, each of which has the foregoing semiconductor device.
• According to one aspect of the present invention, a plurality of conductive layers is formed over a substrate, and an insulating layer is formed to fill the gaps of the conductive layers.
• According to another aspect of the present invention, a plurality of conductive layers is formed over a substrate, a first insulating layer is formed to fill the gaps of the conductive layers, and a second insulating layer is formed over the plurality of the conductive layers and the first insulating layer that fills the gaps of the conductive layers.
• According to further another aspect of the present invention, a plurality of conductive layers is formed over a substrate, a first insulating layer is formed to fill the gaps of the conductive layers, and a second insulating layer is formed over a part of the plurality of the conductive layers and a part of the first insulating layer adjacent to the conductive layers.
• According to the present invention, a method for manufacturing a semiconductor device comprises the steps of forming a plurality of first conductive layers over a substrate; forming a first insulating layer to fill the gaps of the plurality of the first conductive layers; forming a second insulating layer over the first insulating layer and the plurality of the first conductive layers; and forming a semiconductor region and a second conductive layer over the second insulating layer.
• According to the present invention, a method for manufacturing a semiconductor device comprises the steps of forming a plurality of first conductive layers over a substrate; forming first insulating layer to cover a side of the plurality of the first conductive layers; forming a second insulating layer over the first insulating layer and the plurality of the first conductive layers; and forming a semiconductor region and a second conductive layer over the second insulating layer.
• According to the present invention, a method for manufacturing a semiconductor device comprises the steps of forming a plurality of first conductive layers over a substrate; forming a first insulating layer by discharging an insulating material between the plurality of the first conductive layers; forming a second insulating layer over the first insulating layer and the plurality of the first conductive layers; and forming a semiconductor region and a second conductive layer over the second insulating layer.
• A so-called bottom gate TFT in which the first conductive layers serve as gate electrodes, the second insulating layer serves as a gate insulating film, and the second conductive layer serves as a source electrode and a drain electrode is formed. A source region and a drain region may be formed between the semiconductor region and the second conductive layer.
• A so-called top gate TFT in which the first conductive layers serve as a source electrode and a drain electrode, the second insulating layer serves as a gate insulating film, and the second conductive layer serves as a gate electrode is formed. A source region and a drain region may be formed between the second conductive layer and the semiconductor region.
• According to the present invention, a method for manufacturing a semiconductor device comprises the steps of forming a plurality of first conductive layers over a substrate; forming a first insulating layer by discharging an insulating material between the plurality of the first conductive layers; forming a second insulating layer over a part of the first insulating layer and a part of the plurality of the first conductive layers; and forming a semiconductor region over the second insulating layer and the first conductive layer.
• A so-called bottom gate coplanar TFT in which the first conductive layers serve as a gate electrode, a source electrode, and a drain electrode; and the second insulating layer serves as a gate insulating film is formed. A source region and a drain region may be formed between a semiconductor region and the source and the drain electrode.
• According to the present invention, a semiconductor device comprises a plurality of first conductive layers formed over an insulating surface; a first insulating layer formed between the plurality of the first conductive layers; a second insulating layer formed on a surface of the plurality of the first conductive layers and the first insulating layer; a semiconductor region formed over the second insulating layer; and a second conductive layer provided over the semiconductor region; wherein the semiconductor region has a first region that overlaps with the first conductive layers, first insulating layer, and the second insulating layer; and a second region that overlaps with the first conductive layers and the second insulating layer.
• In the case that thicknesses of the first conductive layers are larger than that of the first insulating layer, a ratio b/a (b<a) between a thickness b of the first insulating layer and thicknesses a of the first conductive layers is 0.7 or more and 1 or less.
• In the case that the thicknesses of the first conductive layers are smaller than that of the first insulating layer, the difference in a thickness b−a between the first insulating layer and the first conductive layers is smaller than that of the thickness c of the second insulating layer, that is, the relation of 0<b−a<c (b<a) is satisfied.
• The first insulating layer may be swelled along with the side of the first conductive layers. That is, the first insulating layer is formed to be a concave shape with respect to the insulating surface.
• On the other hand, a region of the first insulating layer that is in contact with the first conductive layers may have a dent with the side of the first conductive layer. That is, the first insulating layer is formed to be a convex shape with respect to the insulating surface.
• Further, a contact angle of the first conductive layer against the insulating surface is 70° or more and 135 or less.
• In the present invention, as a semiconductor device, an integrated circuit, a display device, a wireless, tag, an IC tag, and the like, each of which is composed of a semiconductor element can be nominated. As the display device, a liquid crystal display device, a light-emitting display device, a DMD (Digital Micromirror Device), a PDP (Plasma Display Panel), an FED (Field Emission Display), and an electrophoretic display device (electronic paper), and the like can be typically nominated. The TFT is a forward staggered TFT, a reverse staggered TFT (channel etch TFT or channel protective TFT), a coplanar TFT of a bottom gate TFT, or the like.
• As used herein, the term “display device” refers to a device using a display element, that is, an image display device. Further, a module attached with a connector such as FPC (Flexible Printed Circuit), TAB (Tape Automated Bonding), or TCP (Tape Carrier Package); a module having the TAB or the TCP mounted with a printed wiring board on its tip; and a module installed directly with IC (Integrated Circuit) by COG (Chip On Glass) are all included in the display device.
• According to the present invention, a liquid crystal television or an EL television, each of which is composed of the foregoing semiconductor device, is provided.
• According to the present invention, filling the gaps of a plurality of the conductive layers by the insulating layer can reduce irregularities of the gate insulating film formed over the insulating layer, and so step coverage can be improved. Therefore, step cut over conductive edges can be prevented, and manufacturing yields of the semiconductor device having the conducive layer and the gate insulating film can be improved.
• Since the semiconductor device according to the present invention can increase the uniformity of the thickness of the gate insulating layer, the resistance to pressure of the gate insulating film can be improved and the reliability of the semiconductor device can also be improved.
• The gate insulating film having high step coverage and high resistance to pressure can be formed without forming a gate electrode having a tapered portion, the way of which can be applied to various kinds of processes.
• By forming the insulating film that fills the gaps of a plurality of the conductive layers by droplet discharging, droplets can be dropped to a predetermined place by varying the relative positions of a substrate and a nozzle that is a discharge opening of the droplets containing a material of these films. The relative relationship among a nozzle diameter, a discharge rate of a droplet, and movement speed of the nozzle and the substrate discharged with the droplets can adjust the thickness or the width of a pattern to be formed. Therefore, an insulating film can be formed by discharging with high accuracy at a desired place even when a large substrate with a side of 1 to 2 m or more is used. Further, the number of manufacturing processes can be reduced, the throughput can be increased, and the cost can be reduced since the insulating layer can be formed at a predetermined place without using a photolithography process.
• Moreover, a liquid crystal television and an EL television having the semiconductor device manufactured by the foregoing processes can be manufactured at low costs with high throughput and high manufacturing yields.
• These and other objects, features and advantages of the present invention will become more apparent upon reading of the following detailed description along with the accompanied drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
• FIGS. 1A to 1E are explanatory cross-sectional views for showing a manufacturing process of a semiconductor device according to the present invention;
• FIGS. 2A to 2E are explanatory cross-sectional views for showing a manufacturing process of a semiconductor device according to the present invention;
• FIGS. 3A to 3E are explanatory cross-sectional views for showing a structure of a first conductive layer of a semiconductor device according to the present invention;
• FIGS. 4A and 4B are explanatory cross-sectional views for showing a structure of a first insulating layer of a semiconductor device according to the present invention;
• FIGS. 5A to 5D are explanatory cross-sectional views for showing a manufacturing process of a semiconductor device according to the present invention;
• FIGS. 6A to 6D are explanatory cross-sectional views for showing a manufacturing process of a semiconductor device according to the present invention;
• FIGS. 7A and 7B are explanatory cross-sectional views for showing a structure of a semiconductor device according to the present invention;
• FIG. 8 is an explanatory view for showing a structure of a droplet discharging apparatus that can be applied to the present invention;
• FIGS. 9A to 9C are explanatory top views for showing a mounting method of a driver circuit of a display device according to the present invention;
• FIGS. 10A to 10D are explanatory cross-sectional views for showing a mounting method of a driver circuit of a display device according to the present invention;
• FIG. 11 is an explanatory block diagram for showing a structure of an electronic device;
• FIG. 12 is an explanatory diagram of an example of an electronic device;
• FIGS. 13A and 13B are explanatory diagrams of an example of an electronic device;
• FIG. 14 is a view for showing a circuit structure in the case of forming a scanning line driver circuit by a TFT in a liquid crystal display panel according to the present invention;
• FIG. 15 is a view for showing a circuit structure in the case of forming a scanning line driver circuit by a TFT in a liquid crystal display panel according to the present invention (shift resistor circuit);
• FIG. 16 is a view for showing a circuit structure in the case of forming a scanning line driver circuit by a TFT in a liquid crystal display panel according to the present invention (buffer circuit);
• FIGS. 17A to 17E are explanatory cross-sectional views for showing a manufacturing process of a semiconductor device according to the present invention;
• FIGS. 18A to 18D are explanatory cross-sectional views for showing a manufacturing process of a semiconductor device according to the present invention;
• FIGS. 19A to 19C are explanatory cross-sectional views for showing a manufacturing process of a semiconductor device according to the present invention;
• FIG. 20 is an explanatory top view for showing a manufacturing process of a semiconductor device according to the present invention;
• FIG. 21 is an explanatory top view for showing a manufacturing process of a semiconductor device according to the present invention;
• FIG. 22 is an explanatory top view for showing a manufacturing process of a semiconductor device according to the present invention;
• FIG. 23 is an explanatory top view for showing a manufacturing process of a semiconductor device according to the present invention;
• FIGS. 24A and 24C are explanatory top and cross-sectional views for showing a structure of a light-emitting display panel according to the present invention;
• FIGS. 25A and 25B are explanatory views for showing droplet discharging that can be applied to the present invention;
• FIG. 26 is an explanatory view for showing a structure of a liquid crystal display module according to the present invention;
• FIGS. 27A to 27C are explanatory cross-sectional views for showing a manufacturing process of a semiconductor device according to the present invention;
• FIGS. 28A to 28C are explanatory cross-sectional views for showing a manufacturing process of a semiconductor device according to the present invention;
• FIGS. 29A and 29B are explanatory cross-sectional views for showing a manufacturing process of a semiconductor device according to the present invention;
• FIGS. 30A and 30B are explanatory cross-sectional views for showing a manufacturing process of a semiconductor device according to the present invention;
• FIG. 31 is an explanatory top view for showing a manufacturing process of a semiconductor device according to the present invention;
• FIG. 32 is an explanatory top view for showing a manufacturing process of a semiconductor device according to the present invention;
• FIG. 33 is an explanatory top view for showing a manufacturing process of a semiconductor device according to the present invention;
• FIG. 34 is an explanatory top view for showing a manufacturing process of a semiconductor device according to the present invention;
• FIGS. 35A to 35C are explanatory views for showing a structure of a light-emitting display module according to the present invention;
• FIGS. 36A to 36D are explanatory views for showing a mode of a light-emitting element that can be applied to the present invention;
• FIGS. 37A to 37F are explanatory cross-sectional views for showing a structure of a pixel that can be applied to a light-emitting display panel according to the present invention;
• FIGS. 38A to 38E are explanatory surface views for showing a structure of a semiconductor device according to the present invention; and
• FIGS. 39A and 39B are explanatory cross-sectional views for showing a structure of a semiconductor device according to the present invention.
DESCRIPTION OF THEINVENTIONEmbodiment 1
• In this embodiment, a semiconductor device, which includes an insulating layer for filling between a plurality of conductive layers, and which has lower height than that of the conductive layers, and a manufacturing process of the semiconductor device are explained with reference toFIGS. 1A to 1E,4A,4B,7A, and39A. In this embodiment, a channel etch TFT is used in a bottom gate TFT as a semiconductor device.
• As illustrated inFIG. 1A, a plurality of firstconductive layers102,103 is formed over asubstrate101, and first insulatinglayers104 to106 are formed to fill between the plurality of the firstconductive layers102,103.
• As thesubstrate101, a substrate made from an insulating substance such as glass, quartz, or alumina; a plastic substrate having heat resistance that can resist processing temperature in the following process; a silicon wafer, a metal plate, or the like can be used. In this instance, an insulating film for preventing impurities from dispersing from the substrate is preferably provided such as silicon oxide (SiOx), silicon nitride (SiNx), silicon oxynitride (SiOxNy) (x>y), or silicon nitride oxide (SiNxOy) (x>y). Alternatively, a substrate that is prepared by forming an insulating film such as silicon oxide or silicon nitride over the surface of a metal substrate such as stainless or a semiconductor substrate can be used. In the case that thesubstrate101 is a glass substrate, a large substrate of 320×400 mm, 370×470 mm, 550×650 mm, 600×720 mm, 680×880 mm, 1000×1200 mm, 1100×1250 mm, or 1150×1300 mm can be used. In this instance, a glass substrate is used as thesubstrate101.
• In the case that a plastic substrate is used as thesubstrate101, PC (polycarbonate), PES (poly(ether sulfone)), PET (poly(ethylene terephthalate)), or PEN (poly(ethylene naphthalate)), each of which has a comparative high glass transition point, is used.
• As a material for the firstconducive layers102,103, a material having a conducting property is used. The firstconducive layers102,103 are formed by droplet discharging, printing, electroplating, PVD (physical vapor deposition), CVD (chemical vapor deposition), vapor deposition, or the like. In the case of using the PVD, the CVD, vapor deposition, or the like, the firstconducive layers102,103 are etched in a desired shape after depositing by the foregoing methods.
• As the material having a conducting property, metal such as Ag, Au, Cu, Ni, Pt, Pd, Ir, Rh, W, Al, Ta, Mo, Cd, Zn, Fe, Ti, Si, Ge, Zr, or Ba; indium tin oxide (ITO), zinc oxide (ZnO), indium zinc oxide (IZO), zinc oxide doped with gallium (GZO), indium tin oxide containing silicon oxide, organic indium, organic tin, each of which is used as a transparent conductive film; titanium nitride (TiN); or the like is appropriately used. Alternatively, a conductive layer made from these materials may be stacked as the firstconducive layers102,103.
• In the case that the first conductive layer is formed by droplet discharging, a conductor dissolved or dispersed in solvent is used as a composite for discharging from a discharge opening. As the conductor, metal of the foregoing material having a conducting property, silver halide fine particles, or dispersing nanoparticles can be used.
• As the composition discharged from a discharge opening, any one of gold, silver, and copper dissolved or dispersed in solvent in consideration of a specific resistance value is preferably used. Further preferably, silver or copper which is low resistant and inexpensive is used. In the case of using copper, a barrier film may be additionally provided to prevent contamination due to impurities. As the solvent, organic solvent, for example, esters such as butyl acetate and ethyl acetate, alcohols such as isopropyl alcohol and ethyl alcohol, methyl ethyl ketone, or acetone may be used.
• As the barrier film in the case of using copper as a wiring, an insulating or conductive material containing nitrogen such as silicon nitride, silicon oxynitride, aluminum nitride, titanium nitride, or tantalum nitride may be preferably used to be formed by droplet discharging.
• The composition used for droplet discharging has preferably viscosity of from 5 to 20 mPa·s since the composition can be prevented from drying and the composition can be smoothly discharged from a discharge opening. Further, the composition has preferably the surface tension of 40 mN/m or less. The viscosity and the like of the composition may be appropriately adjusted in accordance with solvent or purposes. As an example, a composition prepared by dissolving or dispersing ITO, ZnO, IZO, GZO, indium tin oxide containing silicon oxide, organic indium, or organic tin in solvent has viscosity of from 5 to 50 mPa·s, a composition prepared by dissolving or dispersing silver in solvent has viscosity of from 5 to 20 mPa·s, and a composition prepared by dissolving or dispersing gold in solvent has viscosity of from 10 to 20 mPa·s.
• The diameter of a particle of the conductor is preferably as small as possible, for example, 0.1 μm or less, for the purpose of preventing a nozzle from clogging and manufacturing a high-definition pattern, although it depends on the diameter of each nozzle, a desired shape of a pattern, and the like. The composition is formed by a known method such as an electrolyzing method, an atomizing method, or a wet reducing method to have generally a particle size of approximately from 0.5 to 10 μm. Note that, in the case of forming the composition by a gas evaporation method, the nanoparticles protected by dispersant have fine grain diameters of approximately 7 nm. In addition, in the case that the nanoparticles are each protected by a cladding material, the nanoparticles are dispersed stably at room temperature without aggregation in solution and behave similarly to liquid. Therefore, the cladding material is preferably used.
• The process of discharging a composition may be performed under reduced pressure since the solvent of the composition is evaporated during a period during which the composition is discharged to land on a subject. Accordingly, later processes of drying and baking can be omitted or shortened. After discharging the solution, either or both processes of drying and baking is/are performed at normal pressure or under reduced pressure depending on the material of the solution by laser light irradiation, rapid thermal annealing, a heating furnace, or the like. Each process of drying and baking is a process of heat treatment. For example, a drying process is performed for three minutes at 100° C., whereas a baking process is performed for from 15 to 120 minutes at temperature of from 200 to 350° C., each of which has a different purpose, temperature, and period. In order to perform favorably the processes of drying and baking, the substrate may be heated to from 100 to 800° C. (preferably, from 200 to 350° C.) though it depends on the material of the substrate. According to the process, fusion and welding are accelerated by evaporating the solvent in the solution, or chemically removing the dispersant to yield hardening and shrinking of a peripheral resin. The processes are performed in the presence of oxygen or nitrogen, or an atmospheric air. The processes are preferably performed in the presence of oxygen where the solvent dissolved or dispersed with metal elements is easily removed. A binder made from an organic matter is left in the conductive layer depending on heating temperature, atmosphere, and time.
• In this embodiment, a conductive layer containing silver as its main component is formed by selectively discharging solution dispersed with silver particles of several nm (hereinafter, Ag paste) to be dried and baked as the firstconductive layers102,103. The first conductive layer is formed by overlapping conductive fine particles irregularly in three-dimension. That is, the first conductive layer is formed by three-dimensional aggregate particles. Therefore, the surface thereof has microscopic irregularities. Due to the temperature and the heating time of the Ag paste, the fine particles are melted to be aggregation formed by the fine particles. The size of the aggregation is increased by the temperature and the heating time of the Ag paste, and so the difference in height of the surface is large. A region where the fine particles are melted may become a polycrystalline structure.
• As the first insulatinglayers104 to106, an insulating material is formed to fill the gaps of the plurality of the firstconductive layers102,103 by droplet discharging, ink jetting, spin coating, roll coating, slot coating, or the like. In the case of using the droplet discharging, the ink jetting, or the like, a material for the first insulating layer is discharged to the predetermined position. In the case of using the spin coating, the roll coating, the slot coating, or the like, the first insulating layer is formed to expose a part of (an upper part of) the first conductive layer by appropriately adjusting the viscosity, the surface tension, or the like of the first material.
• As typical examples of a material for the first insulatinglayers104 to106, polyimide, acrylic, novolac resin, melamine resin, phenol resin, epoxy resin, silicon resin, furan resin, and diallyl phthalate resin can be nominated. Alternatively, solution dispersed with fine particles of inorganic oxide, PSG (phosphorous glass), BPSG (boron phosphorous silicon glass), a film, silicate SOG (spin on glass), alkoxysilicate SOG, polysilazane SOG, SiO₂having the bond of Si—CH₃as typified by polymethyl siloxane can be used.
• Here, the shapes of the first insulatinglayers104 to106 are explained with reference toFIGS. 4A,4B, and7A. As illustrated inFIG. 7A, the first insulatinglayers104 and105 have thinner thicknesses b than a thickness a of the firstconductive layer102. Typically, ratio of b/a (b<a), that is, the ratio of the thickness b of the first insulatinglayers104,105 to the thickness a of the firstconductive layer102 is preferably 0.7 or more to 1 or less. In the case that the ratio of the thickness b of the first insulatinglayers104,105 to the thickness a of the firstconductive layer102 is within the foregoing range, a second insulating layer can be formed with a few irregularities, uniformity of a film thickness is improved, and step coverage is improved. Therefore, a semiconductor device that has high resist pressure and hardly leakage current can be manufactured with good yields.
• The shapes of theinsulting layers104,105 being in contact with the firstconductive layer102 are explained with reference toFIGS. 4A and 4B. The first insulatinglayers104,105 inFIGS. 1A to 1E are denoted byreference numeral401,402, respectively inFIG. 4A; and411,412, respectively inFIG. 4B.
• As illustrated inFIG. 4A, the first insulatinglayers401,402 may be swelled along with the side of the firstconductive layer102. That is, afirst region403 of the first insulating layer that is in contact with the firstconductive layer102 is swelled higher than asecond region404 of the first insulating layer that is not in contact with the firstconductive layer102. In other words, the first insulatinglayers401,402 form a concave shape with respect to the surface of thesubstrate101. The insulatinglayers401,402 having such the shape can be formed by using an insulating material having comparative low viscosity.
• On the other hand, as illustrated inFIG. 4B, a region of the first insulatinglayers411,412 may be depressed at a region being in contact with the firstconductive layer102. That is, afirst region413 of the first insulating layer that is in contact with the firstconductive layer102 is depressed lower than asecond region413 of the first insulating layer that is not in contact with the firstconductive layer102. In other words, the first insulatinglayers411,412 form a convex shape with respect to thesubstrate101. The insulatinglayers411,412 having such the shape can be formed by using an insulating material having comparative high viscosity.
• As illustrated inFIG. 1B, a second insulatinglayer121 serving as a gate insulating film, afirst semiconductor film122, and asecond semiconductor film123 having a conducting property are formed over the firstconductive layers102,103, and the first insulatinglayers104 to106.
• The secondinsulating layer121 is formed by a thin film formation method such as plasma CVD or sputtering to have a single layered or a laminated layered structure including silicon nitride, silicon oxide, or another silicon. Further, the second insulating layer is preferably formed to have a laminated layered structure by stacking a silicon nitride film (silicon nitride oxide film), silicon oxide film, and silicon nitride film (silicon nitride oxide film) from the side being in contact with a gate electrode. The gate electrode is in contact with the silicon nitride film in the structure whereby deterioration due to oxidization can be prevented.
• Further, the second insulatinglayer121 can be formed by using solution having an insulating property by droplet discharging, coating, sol-gel, or the like. As typical examples of the solution having an insulating property, solution dispersed with fine particles of inorganic oxide, polyimide, polyamide, polyester, acrylic, PSG (phosphorous glass), BPSG (boron phosphorous silicon glass), a film, silicate SOG (spin on glass), alkoxysilicate SOG, polysilazane SOG, SiO₂having the bond of Si—CH₃as typified by polymethyl siloxane can be appropriately used.
• Thefirst semiconductor film122 can be formed by a film having a state selected from the group consisting of an amorphous semiconductor, a semiamorphous semiconductor (that may be referred to as SAS) formed by mixing an amorphous state and a crystalline state, a microcrystalline semiconductor in which a crystal grain of 0.5 to 20 nm can be observed in an amorphous semiconductor, and a crystalline semiconductor. The microcrystalline semiconductor in which a crystal grain of 0.5 to 20 nm can be observed is referred to as a microcrystal (μc). As a film containing silicon, silicon germanium (SiGe), or the like as its main components, a semiconductor film with a thickness of 10 to 60 nm can be used.
• The SAS has an intermediate structure between an amorphous structure and a crystalline structure (including single crystals and poly crystals). The SAS has a stable third state with respect to free energy, and a crystalline region having a short-range order and lattice distortion. At least a part of the film includes crystal region of 0.5 to 20 nm. In case that SAS includes silicon as its main component, Raman spectrum is shifted to a lower wave number than 520 cm⁻¹. By X-ray diffraction, diffraction peaks (111), (220) that may be derived from a silicon crystalline lattice are observed. Hydrogen or halogen of 1 atomic % or more is contained in the SAS as neutralizer for dangling bond.
• The SAS can be obtained by glow discharge decomposition of a silicide gas. As a typical example of the silicide gas, SiH₄is nominated. Alternatively, Si₂H₆, SiH₂Cl₂, SiHCl₃, SiCl₄, SiF₄, or the like can be used. The SAS can be formed easily by diluting the silicide gas by hydrogen or fluorine; or the hydrogen or fluorine and one or a plurality of rare gas elements selected from the group consisting of helium, argon, krypton, and neon. The silicide gas is preferably diluted with the dilution rate is in the range of from 10 to 1000 times. Alternatively, the SAS can be formed by using Si₂H₆and GeF₄to be diluted by a helium gas. The production of a film by reaction by glow discharge decomposition is preferably performed at reduced pressure. An applied voltage is in the range of from 0.1 to 133 Pa. Power for producing glow discharge decomposition may be supplied with high frequency power in the range of from 1 to 120 MHz, preferably, 13 to 60 MHz. A heat temperature for a substrate is 300° C. or less, preferably, 100 to 250° C.
• A crystalline semiconductor film can be formed by crystallization of an amorphous semiconductor film or SAS by heating or laser irradiation. Alternatively, the crystalline semiconductor film can be directly formed. In this instance, the crystalline semiconductor film can be directly formed by utilizing heat or plasma with a fluoride gas such as GeF₄or F₂; or a silane gas such as SiH₄or Si₂H₆.
• Thesecond semiconductor film123 has a conducting property. In the case of forming an n-channel type TFT, an element belonging 15 group in the periodic table, typically, phosphorus or arsenic is doped. In the case of forming a p-channel type TFT, an element belonging 13 group in the periodic table, typically, boron is doped. Thesecond semiconductor film123 is formed by plasma CVD using a silicide gas including a gas that includes an element belonging 13 or 15 group in the periodic table such as boron, phosphorus, or arsenic. Further, a second semiconductor film having a conducting property can be formed by coating solution including an element belonging 13 or 15 group in the periodic table over a semiconductor film to be irradiated with laser light after forming the semiconductor film. As the laser beam, laser beam emitted from a known pulse or continuous oscillation laser is appropriately used.
• As illustrated inFIG. 1C,first mask patterns131 to134 are formed over thesemiconductor film123. The first mask patterns are preferably formed by droplet discharging of a heat resistant high molecular material, which includes an aromatic ring or a cyclic ring as a principle chain, and which includes a high polarity hetero atomic weight with a few aliphatic groups. As typical examples of such the high molecular material, polyimide or polybenzimidazole can be nominated. In the case of using the polyimide, thefirst mask patterns131 to134 can be formed by discharging solution containing polyimide from a discharge opening over thesecond semiconductor film123 and baking at 200° C. for 30 minutes.
• Further, the first mask patterns can be formed by providing preliminarily a mask pattern having a liquid-shedding surface and coating or discharging a high molecular material to the region that is not covered by the liquid-shedding surface.
• Then,second semiconductor film123 is etched by using thefirst mask patterns131 to134 to form first semiconductor regions (also referred to as a source or drain region, or contact layer)135 to138. Thereafter, the first mask patterns are removed.
• The second semiconductor film can be etched by using a chloride gas as typified by Cl₂, BCl₃, SiCl₄or CCl₄; a fluoride gas such as CF₄, SF₆, NF₃, or CHF₃; or O₂.
• Then, as illustrated inFIG. 1D,second mask patterns141,142 are formed over the substrate. The second mask patterns can be formed by using the same material as that of the first mask patterns.
• And then, second semiconductor regions (channel formation regions)143,144 are formed by etching thefirst semiconductor film122 using thesecond mask patterns141,142 as masks. As the etching condition for the first semiconductor film, the etching condition of the second semiconductor film can be used. Thereafter, the second mask patterns are removed by processing using stripper, ashing using oxygen, or the like.
• FIG. 39A is an enlarged view of the vicinity of thesecond semiconductor region143 and the firstconductive layer102.
• FIG. 39A illustrates a region provided with the firstconductive layer102, the first insulatinglayers104,105 that fill the outside of the firstconductive layer102, the second insulatinglayer121, and thesecond semiconductor region143. Thesecond semiconductor region143 includes aregion161 overlapped with the firstconductive layer102 and the second insulatinglayer121, and aregion162 that overlaps with the firstconductive layer102, the first insulatinglayers104 and105, and the second insulatinglayer121.
• That is, the gate insulating film of a TFT according to the present invention includes a region formed by a single layered insulating film and a region formed by a two-layered insulating film.
• As illustrated inFIG. 1D, thesecond semiconductor regions143,144 can be formed using an organic semiconductor material by printing, spraying, droplet discharging, or the like. In this instance, the number of processes can be reduced since the foregoing etching process is not required. As the organic semiconductor material used in the present invention, a π-conjugated system high molecular material including a conjugated double bond is preferably used. Typically, a soluble high molecular material such as polythiophene, poly(3-alkylthiophene), polythiophene derivatives, or pentacene can be used.
• As another organic semiconductor material that can be used in the present invention, a material that can form a first semiconductor region by being processed after forming a soluble precursor can be used. As the organic material through the precursor, polythienylenevinylene, poly(2,5-thienylenevinylene), polyacetylene, polyacetylene derivatives, polyarylenevinylene, or the like can be used.
• When the precursor is converted into an organic semiconductor, not only heat treatment is performed, but also a catalyst such as a hydrochloric gas is doped. As typical solvent that dissolves these soluble organic semiconductor material, toluene, xylene, chlorobenzene, dichlorobenzene, anisole, chloroform, dichloromethane, y-butyl lactone, butyl cellosolve, cyclohexane, N-methyl-2-pyrrolidone (NMP), cyclohexanone, 2-butanone, dioxane, dimethylformamide (DMF), tetrahydrofuran (THF), or the like can be used.
• In the case that an organic semiconductor is used for thesecond semiconductor regions143,144, a conductive layer made from an organic conductive material such as polyacetylene, polyaniline, PEDOT (poly-ethylenedioxythiophene), or PSS (poly-styrenesulfonate) can be formed instead of forming thefirst semiconductor regions135 to138. The conductive layer serves as a contact layer, or source and drain regions.
• Instead of thefirst semiconductor regions135 to138, a conductive layer made from a metal element can be used. In this instance, since many organic semiconductor materials are p-type semiconductors which transport holes as a carrier, metal having a high work function is preferably used to make an ohmic contact to the semiconductor layer.
• Specifically, metal, alloy, or the like of gold, platinum, chromium, palladium, aluminum, indium, molybdenum, nickel, or the like is desirably used. The conductive layer can be formed by a conductive paste using these metal or alloy materials by printing, roll coating or droplet discharging.
• Furthermore, the second semiconductor region made from an organic semiconductor material, a conductive layer made from an organic conductive material and a conductive layer made from a metal element may be stacked.
• In the case that the second semiconductor region is made from a SAS, in addition to a structure in which a gate electrode is covered by source and drain regions as in this embodiment, a so-called self-aligning structure in which the edge portions of source and drain regions and the edge portion of a gate electrode are aligned can be formed. Furthermore, a structure in which the gate electrode is not covered by the source and drain regions, and the source and drain regions are separated from each other with a certain distance can be formed. In the case of forming this structure, contrast can be enhanced when the TFT is used for a switching element of a display device since OFF current can be reduced. Moreover, the TFT can be formed to have a multigate structure in which the second semiconductor region covers a plurality of the gate electrodes. In this instance, OFF current can also be reduced.
• Next, as shown inFIG. 1E, source and drainelectrodes151 to154 are formed over thefirst semiconductor regions135 to138 using a conductive material. The source and drainelectrodes151 to154 are formed by the same material and the same method as those of the first conductive layer. In this instance, the source and drainelectrodes151 to154 are formed by discharging selectively solution of Ag paste dispersed with silver particles having a grain size of several nm and drying.
• Then, a passivation film is preferably formed over the source and drainelectrodes151 to154. The passivation film can be formed by a thin film formation method such as plasma CVD or sputtering using silicon nitride, silicon oxide, silicon nitride oxide, silicon oxynitride, aluminum oxynitride, aluminum oxide, diamond like carbon (DLC), carbon nitride (CN), or other insulating materials.
• According to the foregoing processes, a channel etch TFT having high resist pressure and reduced leak current can be manufactured with high manufacturing yields.
Embodiment 2
• In this embodiment, a process for manufacturing a semiconductor device inEmbodiment 1 in which a first insulating layer has a larger thickness than that of a first conductive layer is explained with reference toFIGS. 2A,2B,7B, and39B. In this embodiment, a channel etch TFT in a bottom gate TFT is explained as the semiconductor device.
• As illustrated inFIG. 2A, firstconductive layers102,103 are formed over asubstrate101 as is the case withEmbodiment 1. Then, first insulatinglayers204 to206 are formed. The first insulatinglayers204 to206 have larger thicknesses than those of the firstconductive layers102,103 and cover a part of the side and top of the firstconductive layers102,103.
• The first insulatinglayers204 to206 can be formed by the same material and the same method as those of the first insulatinglayers104 to106 inEmbodiment 1.
• As illustrated inFIG. 2B, a second insulatinglayer221, afirst semiconductor film122, and asecond semiconductor film123 having a conducting property are sequentially formed as is the case withEmbodiment 1. Further, the second insulatinglayer221 can be formed by the same material and the same method as those of the second insulatinglayer121 inEmbodiment 1.
• The thicknesses of the first insulatinglayers204 to206 and the second insulatinglayer221 are explained with reference toFIG. 7B. As illustrated inFIG. 7B, the thickness b of the first insulating layer is larger than the thickness a of the first conductive layer. Accordingly, the first insulating layer covers a part of the side and top of the first conductive layer. The difference in a thickness b−a between the first insulating layer and the first conductive layer is preferably smaller than that of the thickness c of the second insulating layer. Therefore, it is preferably to satisfy the relation of 0<thickness difference (b−a)≦c≦(b>a). In the case that the thicknesses of the first insulatinglayers204 to206, the first conductive layer, and the second insulating layer are within the foregoing range, the second insulating layer can be formed to have a few irregularities, the uniformity of the thickness is improved, and step coverage is also improved. Therefore, a semiconductor device that has high resist pressure and hardly leakage current can be manufactured with good yields.
• Thereafter, as illustrated inFIGS. 2C to 2E,first semiconductor regions135 to138 serving as a source region and a drain region,second semiconductor regions143,144 serving as a channel formation region, source and drainelectrodes151 to154 can be formed in accordance with the same process described inEmbodiment 1.
• FIG. 39B is an enlarged view of the vicinity of thesecond semiconductor region143 and the firstconductive layer102.
• FIG. 39B illustrates that the firstconductive layer102; and first insulatinglayers204,205 that fill the outside of the firstconductive layer102, a second insulatinglayer221, and asecond semiconductor region143, are formed. Thesecond semiconductor region143 has aregion261 that overlaps with the firstconductive layer102 and the second insulatinglayer221; and aregion262 that overlaps with the firstconductive layer102, the first insulatinglayers204,205, and the second insulatinglayer221.
• Therefore, the gate insulating film of a TFT according to the present invention has a region formed by a single layered insulating film and a region formed by a two-layered insulating film. Further, the second semiconductor region (channel formation region) of the TFT according to this embodiment is formed to have a concave shape with respect to the substrate surface.
• By the foregoing process, a channel etch TFT having high resist pressure and reduced leak current can be manufactured with high manufacturing yields.
Embodiment 3
• The shapes of firstconductive layers102,103 that can be applied to the present invention inEmbodiment 1 or 2 are explained with reference toFIGS. 3A to 3E. This embodiment gives an explanation with Embodiment 2. Further,Embodiment 1 can also be appropriately used.
• As illustrated inFIG. 3A, a conductive film having a tapered portion with a contact angle θ₁of 70 to 90° against asubstrate101 at an edge portion, that is, aconductive layer301 is formed to have a cross-section in a trapezoidal shape, and first insulatinglayers204,205 are formed. Conventionally, there have been problems that a step coverage property of a film is deteriorated and stepped cut is produced with the increase of a contact angle in the case of the film is formed over a film pattern having a contact angle θ₁of 70° or more. However, the stepped cut of a film formed afterwards can be prevented and the uniformity of a film thickness can be improved by forming the first insulatinglayers204,205. Theconductive layer301 having such a shape can be formed by dry etching of a film using a mask pattern formed by a known photolithography process.
• As illustrated inFIG. 3B, aconductive layer311 having a contact angle θ₂of 90° against thesubstrate101 at a lower edge portion and having a slope portion or a radius ofcurvature portion312 at an upper edge portion is formed. Then, first insulatinglayers204,205 are formed.FIG. 3B illustrates a conductive layer having the radius ofcurvature portion312. Conventionally, there have been problems that a step coverage property of a film is deteriorated and stepped cut is produced in the case of the film is formed over a film pattern having a contact angle θ of 90°. However, the stepped cut of a film formed afterwards can be prevented and the uniformity of a film thickness can be improved by forming the first insulatinglayers204,205. The conductive layer having such a shape can be formed by discharging drops by droplet discharging, ink jetting, or the like and drying and baking.
• As illustrated inFIG. 3C, aconductive layer321 having a contact angle θ₃of 90° against thesubstrate101 at a lower edge portion and having a contact angle θ₄of 90° against thesubstrate101 at an upper edge portion, that is, having a cross section in a rectangular shape, is formed. Then, first insulatinglayers204,205 are formed. Conventionally, there have been problems that a step coverage property of a film is deteriorated and stepped cut is produced in the case of forming the film over a film pattern in a rectangular shape. However, the stepped cut of a film formed afterwards can be prevented and the uniformity of a film thickness can be improved by forming the first insulatinglayers204,205. Theconductive layer321 having such a shape can be formed by dry etching of a film using a mask pattern formed by a known photolithography process. Alternatively, printing, electroplating, or the like can be used.
• As illustrated inFIG. 3D, aconductive layer331 having a contact angle θ₅of 90° or more and 135° or less against asubstrate101, that is, having a reverse tapered portion is formed. Then, first insulatinglayers204,205 are formed. Conventionally, there have been problems that it is difficult to form a film at the vicinity of a lower edge portion that is covered by an upper edge portion, thereby a step coverage property of a film is deteriorated, and stepped cut is produced in the case of forming the film over a film pattern having a contact angle θ of 90° or more. However, the stepped cut of a film formed afterwards can be prevented and the uniformity of a film thickness can be improved by forming the first insulatinglayers204,205.
• As illustrated inFIG. 3E, aconductive layer341 havingconcave portions342 at the side of theconductive layer341 is formed. Then, first insulatinglayers204,205 are formed. Conventionally, there have been problems that a film pattern has markedly irregularities, a step coverage property of a film is deteriorated, and stepped cut is produced in the case that the film is formed over the film pattern having a concave portion. However, the stepped cut of a film formed afterwards can be prevented and the uniformity of a film thickness can be improved by forming the first insulatinglayers204,205. Theconductive layer341 having such a shape can be formed by wet etching of a film using a mask pattern formed by a known photolithography process.
• The present invention can form a TFT using a conductive film in various shapes as noted above, and so an applicable range of the manufacturing method can be expanded.
Embodiment 4
• In this embodiment, a manufacturing process of a channel protective type TFT in a bottom gate TFT according to the present invention is explained. A first insulating layer is formed by using, but not exclusively,Embodiment 1. Embodiment 2 can also be used. Further, the first conductive layer explained in Embodiment 3 can be appropriately used as a first conductive layer in this embodiment.
• As illustrated inFIG. 5A, firstconductive layers102,103 are formed over asubstrate101 usingEmbodiment 1. First insulatinglayers104 to106 are formed to fill between the firstconductive layers102,103.
• As illustrated inFIG. 5B, a second insulatinglayer121 which serves as a gate insulating film, and afirst semiconductor film122 are formed over the firstconductive layers102,103 and the first insulatinglayers104 to106. Then,protective films501,502 are formed over regions, which are over thefirst semiconductor film122, and which overlap with the firstconductive layers102,103, respectively. Theprotective films501,502 are formed by the same material and the same method as those of thefirst mask patterns131 to134 as shown in the first embodiment.
• Then, a second semiconductor film (semiconductor film having a conducting property)523 is formed. Further, thesecond semiconductor film523 can be formed by the same material and the same method as those of thesecond semiconductor film123 described inEmbodiment 1.
• As illustrated inFIG. 5C,first mask patterns531,532 are formed. Thefirst mask patterns531,532 can be formed by the same material and the same method as those of thesecond mask patterns141,142 described inEmbodiment 1.
• The first semiconductor film and the second semiconductor film are etched by using the first mask patterns to formfirst semiconductor regions533,534, andsecond semiconductor regions543,544. Thereafter, the first mask patterns are removed.
• As illustrated inFIG. 5D, source electrodes anddrain electrode551 to554 are formed over thefirst semiconductor regions533,534.
• The exposed portion of thefirst semiconductor regions533,534 are etched and divided by using the source electrodes anddrain electrode551 to554 as masks to form source regions and drainregions535 to538. By this process, theprotective films501,502 are exposed.
• As a method for forming the source regions and drainregions535 to538, not only this embodiment but also a manufacturing process of the first semiconductor region explained inEmbodiment 1 can be used. The forming process of the source regions and drain regions according to this embodiment can be applied toEmbodiment 1.
• By the foregoing process, a channel protective TFT having high resist pressure and reduced leak current can be manufactured with high manufacturing yields.
Embodiment 5
• A process for manufacturing a forward staggered TFT among top gate TFTs according to the present invention is explained with reference toFIGS. 6A to 6D. A first insulating layer is formed by, but not exclusively,Embodiment 1. Embodiment 2 can also be used. Further, the first conductive layer explained in Embodiment 3 can be appropriately used as a first conductive layer in this embodiment.
• As illustrated inFIG. 6A, firstconductive layers601,602 serving as a source electrode and a drain electrode are formed over asubstrate101. The firstconductive layers601,602 are formed by appropriately using the same material and the same method as those of the firstconductive layers102,103 inEmbodiment 1. Then, afirst semiconductor film603 having a conducting property is formed over the firstconductive layers601,602. Thefirst semiconductor film603 is formed by the same material and the same method as those of the second semiconductor film inEmbodiment 1. And then,first mask patterns604,605 are formed over thefirst semiconductor film603. Since the first mask patterns are used as masks for forming a source region and a drain region, the first mask patterns are formed by the same material and the same method as those of thefirst mask patterns131 to134 inEmbodiment 1.
• As illustrated inFIG. 6B, the first semiconductor film is etched by using the first mask patterns to formfirst semiconductor regions611,612. Thefirst semiconductor regions611,612 serve as a source region and a drain region. Further, thefirst semiconductor regions611,612 are formed by using appropriately the same material and the same method as those of thefirst semiconductor regions135 to138 inEmbodiment 1.
• First insulatinglayers613 to615 are formed between the stacked firstconductive layers601,602, and the first semiconductor regions. The first insulatinglayers613 to615 are formed by the same material and the same manufacturing process as those of the first insulatinglayers104 to106 inEmbodiment 1.
• As illustrated inFIG. 6C, asecond semiconductor film621 is formed over the first insulatinglayers613 to615, the firstconductive layers601,602, and thefirst semiconductor regions611,612. Thesecond semiconductor film621 is formed by using appropriately the same material and the same manufacturing method as those of thefirst semiconductor film122 inEmbodiment 1.
• Then, asecond film pattern622 is formed over thesecond semiconductor film621. The second film pattern is a mask for forming a channel formation region and is formed by using appropriately the same method and the same manufacturing process as those of thesecond mask patterns141,142 inEmbodiment 1.
• And then, as illustrated inFIG. 6D, asecond semiconductor region631 is formed by etching thesecond semiconductor film621 using thesecond film pattern622. The second semiconductor region serves as a channel formation region.
• A second insulatinglayer632 and a secondconductive layer633 are formed. Since the second insulatinglayer632 serves as a gate insulating film, the second insulatinglayer632 is formed by the same method and the same manufacturing process as those of the second insulatinglayer121 inEmbodiment 1. Further, since the secondconductive layer633 serves as a gate electrode, the secondconductive layer633 is formed by the same material and the same manufacturing process as those of the firstconductive layers102,103 inEmbodiment 1.
• By the foregoing process, a forward staggered TFT having high resist pressure and reduced leak current can be manufactured with high manufacturing yields.
Embodiment 6
• In this embodiment, a method for forming a contact hole of a TFT is explained with reference toFIGS. 38A to 38E.
• According to Embodiment 5, a forward staggered TFT as illustrated inFIG. 38A is formed. Here, firstconductive layers601,602, first insulatinglayers613 to615,first semiconductor regions611,612 having a conducting property, asecond semiconductor region631, a second insulatinglayer632, and a secondconductive layer633 are formed over asubstrate101. Thereafter, aprotective film715 is formed to cover the TFT. Further, the first semiconductor regions serve as a source region and a drain region, whereas the second semiconductor region serves as a channel formation region.
• First mask patterns751 are formed by discharging solution for forming a liquid-shedding surface over regions where the firstconductive layers601,602, the second insulatinglayer632, theprotective layer715 and the first and second semiconductor regions are overlapped with each other as illustrated inFIG. 38B.
• A region having a liquid-shedding surface is a region that has a large contact angle of the surface of the region against liquid. On the surface, liquid is shed to be formed into a hemispheroid. On the other hand, a region having a liquid-lyophilic surface is the region that has a small contact angle of the surface of the region against liquid. Liquid is penetrated into and spread on the surface.
• Therefore, in the case that two regions having different contact angles are adjacent to each other, a region having a relative large contact angle is a region having a liquid-shedding surface, whereas a region having a relative small contact angle is a liquid-lyophilic surface. In the case that solution is coated or discharged to the two regions, the solution is penetrated into and spread over the surface of the region having the liquid-lyophilic surface and shed at an interface between the region having the liquid-lyophilic surface and the region having the liquid-shedding surface to be formed into a hemispheroid.
• In the case that the surface has irregularities, the contact angle of the region having the liquid-shedding surface becomes further increased, that is, a liquid-shedding property is enhanced. On the other hand, the contact angle of the region having the liquid-lyophilic surface becomes further decreased, that is, a liquid-lyophilic property is enhanced. Therefore, a layer can be formed to have each of the liquid-lyophilic region and the liquid-shedding region with a uniform edge portion by coating or discharging solution that has a composite over each surface having irregularities.
• Here, a region having a liquid-shedding surface is formed by coating or discharging a material for forming a liquid-shedding surface. As an example of the material of solution for forming a liquid-shedding surface, a silane coupling agent as represented by a chemical formula Rn—Si—X_(4-n)(n=1, 2, 3) is used. In the formula, R includes a comparative inactive group such as an alkyl group, and X is formed by a hydrolysis group such as halogen, a methoxy group, an ethoxy group, or an acetoxy group that is capable of bonding by condensation with a hydroxyl group or adsorption water over a substrate surface.
• A liquid-shedding property can be further enhanced by using fluorite silane coupling agent (fluoroalkylsilane (FAS)) having a fluoroalkyl group as R, which is a typical example of the silane-coupling agent. The fluoroalkyl group R of FAS has a structure of (CF₃)(CF₂)_x(CH₂)_y, wherein x is an integer from 0 or more to 10 or less and y is an integer from 0 or more to 4 or less. When a plurality of R or X is coupled to Si, R or X may be the same or different. As a typical example of the FAS, such as heptadefluorotetrahydrodecyltriethoxysilane, heptadecafluorotetrahydrodecyltrichlorosilane, tridecafluorotetrahydrooctyltrichlorosilane, and trifluoropropyltrimethoxysilane can be nominated.
• As solvent of solution for forming a liquid-shedding surface, hydrocarbon-based solvent such as n-pentane, n-hexane, n-heptane, n-octane, n-decane, dicyclopentane, benzene, toluene, xylene, durene, indene, tetrahydronaphthalene, decahydronaphthalene, and squalene; or tetrahydrofuran can be used.
• As an example of solution for forming the liquid-shedding surface, a material having a fluorocarbon chain (fluorinated resin) can be used. As the fluorinated resin, polytetrafluoroethylene (PTFE; 4-fluorinated ethylene resin), perfluoroalkoxy alkane (PFA; 4-fluorinated ethylene perfluoroalkylvinylether copolymer resin), perfluoroethylenepropene copolymer (PFEP; 4-fluorinated ethylene 6-fluorinated propylene copolymer resin), ethylene-tetrafluoroethylene copolymer (ETFE; 4-fluorinated ethylene-ethylene copolymer resin), polyvinylidene fluoride (PVDF; fluorinated vinylidene resin), polychlorotrifluoroethylene (PCTFE; 3-fluorinated ethylene chloride resin), ethylene-chlorotrifluoroethylene copolymer (ECTFE; 3-fluorinated ethylene chloride-ethylene copolymer resin), polytetrafluoroethylene-perfluorodioxole copolymer (TFE/PDD), polyvinyl fluoride (PVF; fluorinated vinyl resin), or the like can be used.
• Then, the surface attached with solution for forming a liquid-shedding surface is cleaned by ethanol, and then, an extreme thin liquid-shedding surface can be formed.
• Alternatively, an organic matter that does not form a liquid-shedding surface (that is, the organic matter forms a liquid-lyophilic surface) is used as a mask pattern, and treatment by CF₄plasma or the like is carried out, then, a liquid-shedding surface can be formed. For example, a material prepared by mixing water-soluble resin such as polyvinyl alcohol (PVA) into solvent such as H₂O can be used as the organic matter. Alternatively, the PVA and another water-soluble resin can be combined. Moreover, a liquid-shedding property can be further improved by performing the plasma treatment even when the mask pattern has a liquid-shedding surface.
• Further, an electrode provided with a dielectric material is prepared, and plasma treatment can be performed by producing plasma so that the dielectric material is exposed to the air or the plasma using oxygen or nitrogen. In this instance, the dielectric material is not required to cover entirely the surface of the electrode. As the dielectric material, fluoride resin can be used. In the case of using fluoride resin, surface modification is carried out to have a liquid-shedding property by forming CF₄bonding over a subject surface. In addition, plasma treatment is carried out.
• Then, asecond mask pattern752 is formed by discharging solution that forms a liquid-lyophilic surface. As a typical example of solution having a liquid-lyophilic property, organic resin such as acrylic resin, polyimide resin, melamine resin, polyester resin, polycarbonate resin, phenol resin, epoxy resin, polyacetal, polyether, polyurethane, polyamide (nylon), furan resin, or diallyl phthalate resin; siloxane; or polysilazane can be nominated. Further, solution using polar solvent such as water, alcohols, ethers, dimethylformamide, dimethylacetamide, dimethylsulfoxide, N-methylpyrrolidone, hexamethylphosphamide, chloroform, or methylene chloride can be used. As a method for forming the second mask pattern, droplet discharging, an ink jetting method, a spin coating method, a roll coating method, a slot coating method, or the like can be employed.
• Since thefirst mask patterns751 have liquid-shedding surfaces, thesecond mask pattern752 is formed in the outer edges of the first mask patterns, that is, a region that is not provided with the first mask patterns.
• Instead of the foregoing processes, the second mask patterns may be formed by coating the second solution after drying solvent of the first mask patterns. By these processes, an extreme thin liquid-shedding surface can be formed.
• As shown inFIG. 38C, thefirst mask patterns751, theprotective film715, and the second insulatinglayer632 are etched by using thesecond mask pattern752 as a mask to expose a part of thesecond semiconductor region631.
• As shown inFIG. 38D, a thirdconductive layers764 are formed after thesecond mask pattern752 is removed. The thirdconductive layers764 serve as a source wiring layer and a drain wiring layer.
• As shown inFIG. 38E, it is possible that thesecond mask pattern752 is not removed to be used as an interlayer insulating film, and a thirdconductive layer764 is formed.
• By the foregoing processes, a contact hole can be formed without using a photomask.
Embodiment 7
• A droplet discharging apparatus which can be used for a film pattern formation in the above embodiments is explained in this embodiment. InFIG. 8, a region over asubstrate1900 in which onepanel1930 is formed is denoted by chain line.
• FIG. 8 illustrates one mode of a droplet discharging apparatus used to form a pattern such as a wiring. A droplet discharge means1905 has a head. The head has a plurality of nozzles. This embodiment explains the case that three heads (1903a,1903b, and1903c) are respectively provided with ten nozzles. However, the number of nozzles or heads can be set in accordance with an area to be treated, a process, or the like.
• The heads are connected to a control means1907. By controlling the control means by acomputer1910, a preset pattern can be drawn. The timing in drawing may depend on, for example, amarker1911 that is formed over thesubstrate1900 or the like fixed to astage1931 as a reference point. Alternatively, an edge of thesubstrate1900 may be used as the reference point. The reference point is detected by an imaging means1904 such as a CCD to be converted into a digital signal by an image processing means1909. The signal converted into a digital signal is recognized by thecomputer1910 to generate a control signal, and the control signal is sent to the control means1907. When drawing a pattern in such a way, the interval between a pattern formation surface and a nozzle tip is preferably set 0.1 to 5 cm, more preferably 0.1 to 2 cm, further more preferably, approximately 0.1 cm. By setting the interval shortly, landing accuracy of a droplet is improved.
• At this time, information of a pattern to be formed over thesubstrate1900 is stored in astorage medium1908, and a control signal is transmitted to the control means1907 based on the information, then, theheads1903a,1903b, and1903ccan be individually controlled. In other words, different materials can be discharged from each nozzle of theheads1903a,1903b, and1903c. For example, the nozzles of theheads1903aand1903bcan discharge a composite including an insulating film material and the nozzles of thehead1903ccan discharge a composite including a conductive film material.
• Further, the nozzles of the head can also be individually controlled. Since the nozzles can be individually controlled, different composites can be discharged from a specific nozzle. For example, one head1903acan be provided with a nozzle which discharges a composite including a conductive film material and a nozzle which discharges a composite including an insulating film material.
• Further, the nozzle is connected to a tank filled with a composite.
• In the case of performing droplet discharging treatment on a large area like a formation process of an interlayer insulating film, a composite including an interlayer insulating film material is preferably discharged from all nozzles. Further, a composite including an interlayer insulating film material may be discharged from all nozzles of a plurality of heads. Accordingly, throughput can be improved. Needless to say, droplet discharging treatment may be performed on a large area by discharging a composite including an interlayer insulating film material from one nozzle and by scanning at a plurality of times in a formation process of the interlayer insulating film.
• A pattern can be formed on a large mother glass by moving a head in zigzag or by shuttling the head. At this time, the head and the substrate may be relatively scanned at a plurality of times. When the head scans the substrate, the head is preferably inclined toward a direction of movement.
• In the case of forming a plurality of panels from a large mother glass, the head has preferably the same width as a panel. A pattern can be formed by scanning at once against a region to be provided with apanel1930, and so high throughput can be expected.
• The width of the head may be narrower than that of the panel. At this time, a plurality of heads having a narrow width may be arranged in series to have a width equal to that of one panel. By arranging a plurality of heads having a narrow width in series, deflection of the head that is worried as increasing a width of the head can be prevented. Needless to say, a pattern can be formed by moving a head having a narrow width at a plurality of times.
• A process of discharging a droplet of a composite by such droplet discharging is preferably performed under reduced pressure. Hence, solvent of the composite is evaporated during a period between discharging the composite and landing the composite on a subject, and so processes of drying and baking the composite can be omitted. Further, an oxide film or the like is not formed on the surface of a conductor in this instance. In addition, the step of dropping solution may be performed in a nitrogen atmosphere or an organic gas atmosphere.
• In addition, a piezo technique can be used as droplet discharging. Since the piezo technique has superior controllability of a droplet and a high degree of freedom for selecting ink, the piezo technique is also used in an inkjet printer. In addition, there are various types of the piezo technique; for example, a bender type (typically, an MLP (Multi Layer Piezo) type), a piston type (typically, an ML Chip (Multi Layer Ceramic Hyper Integrated Piezo segments) type), a side wall type, and a roof wall type. Alternatively, droplet discharging utilizing a thermal technique, which induces a heating element to generate a fever, and which produces bubbles to push out solution may be used depending on solvent of solution.
Example 1
• Manufacturing methods of an active matrix substrate and a display panel having the active matrix substrate are explained with reference toFIGS. 17A to 23. In this example, the methods are explained by using a liquid crystal display panel as a display panel.FIGS. 17A to 19C illustrates schematically longitudinal sectional structures of a pixel portion and a connecting terminal portion.FIGS. 20 to 23 illustrate planar structures ofFIGS. 17A to 19C taken along lines of A-B and C-D. In this example, a first insulating layer is, but not exclusively, formed by usingEmbodiment 1. Embodiment 2 can also be used for forming the first insulating layer. A first conductive layer explained in Embodiment 3 can be appropriately used as a gate wiring layer, a gate electrode layer, and a connecting conductive layer.
• As illustrated inFIG. 17A, the surface of asubstrate800 is oxidized at 400° C. to form an insulatingfilm801 having a thickness of 100 nm. The insulatingfilm801 serves as an etching stopper film for a conductive layer that is formed afterward. Then, a first conductive film is formed over the insulatingfilm801; and then, a first mask pattern is formed by droplet discharging over the first conductive film. As the substrate, AN100 glass substrate from Asahi Glass Co., Ltd. is used. As the first conductive film, a tungsten film is formed to have a thickness of 100 nm by sputtering using a tungsten target and an argon gas. As the first mask pattern, polyimide is discharged by droplet discharging to be baked by heating at 200° C. for 30 minutes. The first mask pattern is formed by discharging over a gate wiring layer, a gate electrode layer, and a connecting conductive layer, each of which is formed afterwards.
• Then, agate wiring layer803, agate electrode layer804, and a connectingconductive layer805 are formed by etching a part of the first conductive film by using the first mask pattern. Here, a first conductive layer having a taper portion of 70 to 90° is formed. Thereafter, the first mask pattern is exfoliated by stripper.FIG. 17A illustrating a longitudinal sectional structure andFIG. 20 illustrating a planar structure ofFIG. 17A after removing the first mask pattern taken along line of A-B and C-D are referred simultaneously.
• First insulatinglayers806 to809 are formed to fill between thegate wiring layer803, thegate electrode layer804, and the connectingconductive layer805. Here, a first insulating layer is formed by discharging polyimide by droplet discharging.
• As illustrated inFIG. 17B, agate insulating film814 is formed by plasma CVD. As thegate insulating film814, an oxynitride silicon film (H: 1.8%, N: 2.6%, O: 63.9%, and Si: 31.7%) is formed by plasma CVD using SiH₄and N₂O (flow ratio of SiH₄:N₂O=1:200) to have a thickness of 110 nm in a chamber heated at 400° C.
• According to the process, a gate insulating film having excellent uniformity of a thickness and excellent step coverage property can be formed.
• Afirst semiconductor film815 and asecond semiconductor film816 imparting n-type conductivity are formed. As thefirst semiconductor film815, an amorphous silicon film having a thickness of 150 nm is formed by plasma CVD. Then, an oxide film at the surface of the amorphous silicon film is removed, and then, a semiamorphous silicon film having a thickness of 50 nm is formed by using a silane gas and a phosphine gas as thesecond semiconductor film816.
• Second mask patterns817,818 are formed over thesecond semiconductor film816. The second mask patterns are formed by discharging polyimide by droplet discharging over thesecond semiconductor film816 to be heated at 200° C. for 30 minutes. Thesecond mask patterns817,818 are formed over a region provided with a first semiconductor region afterwards.
• As illustrated inFIG. 17C, first semiconductor regions (source and drain regions, contact layer)821,822 are formed by etching thesecond semiconductor film816 using thesecond mask patterns817,818. Thesecond semiconductor film816 is etched by a mixed gas with a flow ratio of CF₄:O₂=10:9. Thereafter, thesecond mask patterns817,818 are exfoliated by using stripper.
• Athird mask pattern823 covering thefirst semiconductor regions821,822, and thefirst semiconductor film815 formed between thefirst semiconductor regions821,822 is formed. Thethird mask pattern823 is formed by the same material and the same method as those used for the second mask pattern. Thefirst semiconductor film815 is etched by using the third mask pattern to form asecond semiconductor region831 as illustrated inFIG. 17D and to expose thegate insulating film814. The first semiconductor film is etched by using a mixed gas with a flow ratio of CF₄:O₂=10:9. Then, ashing treatment using oxygen is performed. Thereafter, thethird mask pattern823 is exfoliated by stripper.FIG. 17D illustrating a longitudinal sectional structure andFIG. 21 illustrating a planar structure ofFIG. 17D taken along lines of A-B and C-D are referred simultaneously.
• Then, as illustrated inFIG. 17E, afourth mask pattern832 is formed. The fourth mask pattern is formed by droplet discharging of solution forming a liquid-shedding surface to a region where thegate insulating film814 and the connectingconductive layer805 are overlapped with each other. As the solution forming a liquid-shedding surface, solution prepared by dissolving fluorinated silane coupling agent into alcohol solvent is used. Thefourth mask pattern832 is a protective film for forming a fifth mask pattern for forming a contact hole to a region where a subsequent drain electrode and the connectingconductive film813 are connected to each other.
• Thefifth mask pattern833 is formed. The fifth mask pattern is a mask for forming a first contact hole formed by discharging polyimide by droplet discharging at 200° C. for 30 minutes. Since thefourth mask pattern832 has a liquid-shedding property whereas thefifth mask pattern833 has a liquid-attracting property, thefifth mask pattern833 is not provided to a region provided with the fourth mask pattern.
• Then, a part of thegate insulating film814 is exposed by removing thefourth mask pattern832 by oxygen ashing. Then, a part of the exposed gate insulating film is etched by using thefifth mask pattern833. The gate insulating film is etched by using CHF₃. Thereafter, the fifth mask pattern is exfoliated by oxygen ashing and etching using stripper.
• As illustrated inFIG. 18A, secondconductive layers841,842 are formed by droplet discharging. The second conductive layer serves as a source wiring layer and a drain wiring layer afterwards. Here, the secondconductive layer841 is formed to connect to thefirst semiconductor region821, whereas the second conductive842 is formed to connect to thefirst semiconductor region822 and the connectingconductive layer805. The secondconductive layers841,842 are formed by discharging solution dispersed with Ag (silver) particles, and heating to be dried at 100° C. for 30 minutes, then, heating to be baked at 230° C. for 1 hour in the presence of oxygen having concentration of 10%.FIG. 18A illustrating a longitudinal sectional structure andFIG. 22 illustrating a planar structure ofFIG. 18A taken along line A-B and C-D are referred simultaneously.
• Then, aprotective film843 is formed. A silicon nitride film is formed by sputtering using a silicon target and a sputtering gas of argon and nitrogen (flow ratio of Ar:N₂=1:1) to have a thickness of 100 nm as the protective film.
• As illustrated inFIG. 18B,sixth mask patterns851,852 are formed over a region where theprotective film843 is overlapped with the connectingconductive layer805, a region where theprotective film843 is overlapped with a region where the gate wiring layer is connected to a connecting terminal, and a region where theprotective film843 is overlapped with a region where the source wiring layer is connected to a connecting terminal (not shown). Then, aninterlayer insulating film853 is formed. The sixth mask pattern is a mask used for forming an interlayer insulating film afterwards. As the sixth mask pattern, solution for forming a liquid-shedding surface (solution prepared by dissolving fluoride silane coupling agent into solvent) is discharged, and polyimide is discharged by droplet discharging as theinterlayer insulating film853, and both of the discharged layers are heated to be baked at 200° C. for 30 minutes and 300° C. for 1 hour.
• As a material for theinterlayer insulating film853, heat-resisting organic resin such as polyimide, acrylic, polyamide, or siloxane; inorganic material; low dielectric constant (low-k) material; silicon oxide; silicon nitride; silicon oxynitride; silicon nitride oxide; PSG (phosphorus glass), BPSG (phosphorus boron glass); an alumina film; and the like can be used.
• Then, as shown inFIG. 18C, thesixth mask pattern851,852 are etched by using a mixed gas of CF₄, O₂, He (flow ratio of CF₄:O₂:He 8:12:7), and a part of theprotective film843 and thegate insulating film814 is etched to form a second contact hole. By this etching process, theprotective film843 and thegate insulating film814 in the region where the gate wiring layer is connected to the connecting terminal and the region where the source wiring layer is connected to the connecting terminal are also etched.
• After forming the thirdconductive layer861, aseventh mask pattern862 is formed. The thirdconductive film861 is formed by using indium tin oxide (ITO) containing silicon oxide to have a thickness of 110 nm by sputtering, and discharging polyimide serving a eighth mask pattern by dropping into a region provided with a pixel electrode afterwards to be heated at 200° C. for 30 minutes.
• In this example, the pixel electrode is formed by ITO containing silicon oxide to manufacture a transparent liquid crystal display panel. Instead, the pixel electrode may be formed by forming a predetermined pattern by solution including indium tin oxide (ITO), zinc oxide (ZnO), indium zinc oxide (IZO), zinc oxide doped with gallium (GZO), or indium tin oxide containing silicon oxide, and baking the pattern. In the case of manufacturing a reflective liquid crystal display panel, solution including metal particles as its main component such as Ag (silver), Au (gold), Cu (copper), W (tungsten), or Al (aluminum) can be used.
• As illustrated inFIG. 18D, afirst pixel electrode871 is formed by etching the thirdconductive layer861 by using the seventh mask pattern. By this etching process, the thirdconductive layer861 provided to the region where the gate wiring layer is connected to the connecting terminal and the region where the source wiring layer is connected to the connecting terminal is also etched. Thereafter, the seventh mask pattern is exfoliated by using stripper.FIG. 23 is a plain view ofFIG. 18D taken along lines A-B and C-D.
• Thefirst pixel electrode871 is connected to the connectingconductive layer805 in the second contact hole. Since the connectingconductive layer805 is connected to the secondconductive layer842, thefirst pixel electrode871 and the secondconductive layer842 are electrically conducted to each other. In this example, the secondconductive layer842 is made from silver (Ag), and thepixel electrode871 is made from ITO containing silicon oxide. The secondconductive layer842 andpixel electrode871 are not directly connected with each other, and so silver is not oxidized. Accordingly, the drain wiring and the pixel electrode can be electrically connected without increasing contact resistance.
• As another method for forming thefirst pixel electrode871, the pixel electrode can be formed by selectively dropping solution containing a conductive material by droplet discharging without an etching process. Moreover, the pixel electrode can be formed by discharging solution having a conducting property after forming solution for forming a liquid-shedding surface as a mask pattern to a region where pixel electrode is not provided afterwards. In this instance, a mask pattern can be removed by ashing using oxygen. Alternatively, the mask pattern may not be removed to be left.
• In accordance with the foregoing processes, an active matrix substrate can be formed.
• As illustrated inFIG. 19A, an insulating film is formed to cover thefirst pixel electrode871 by printing or spin coating, and an orientedfilm872 is formed by rubbing treatment. In addition, the orientedfilm872 can be formed by oblique evaporation.
• Sealant873 in the shape of a closed loop is formed by droplet discharging to the peripheral region of the pixel. A liquid crystal material is dropped inside the closed loop formed by thesealant873 by dispenser (dropping) technique.
• A process of dropping a liquid crystal material is explained with reference toFIGS. 25A and 25B.FIG. 25A is a perspective view of a process for dropping a liquid crystal material by adispenser2701.FIG. 25B is a cross-sectional view ofFIG. 25A taken along line of A-B.
• Aliquid crystal material2704 is dropped or discharged from aliquid crystal dispenser2701 to cover apixel portion2703 surrounded bysealant2702. A liquid crystal layer can be formed by moving theliquid crystal dispenser2701, or fixing theliquid crystal dispenser2701 and moving asubstrate2700. Alternatively, a plurality of liquid crystal dispensers can be installed to drop a liquid crystal material to a plurality of pixel portions simultaneously.
• As illustrated inFIG. 25B, theliquid crystal material2704 can be selectively dropped or discharged only to a region surrounded by thesealant2702.
• Here, the liquid crystal material is dropped to the pixel portion. Alternatively, a substrate having a pixel portion can be pasted onto an opposing substrate after dropping the liquid crystal material at the side of the opposing substrate.
• As illustrated inFIG. 19B, an opposingsubstrate881 provided with an orientedfilm883 and a second pixel electrode (opposing electrode)882 is pasted to thesubstrate800 in vacuo, and aliquid crystal layer884 filled with a liquid crystal material is formed by ultra violet curing.
• Thesealant873 may be mixed with filler, and the opposingsubstrate881 may be provided with a color filter, a shielding film (black matrix), and the like. Further, dispenser technique (dropping technique) or dip technique (pumping technique) by which a liquid crystal material is injected by utilizing a capillary phenomenon after pasting the opposing substrate can be used as a method for forming theliquid crystal layer884.
• As illustrated inFIG. 19C, in the case that an insulating film is formed over each terminal portion of thegate wiring layer803 and a source wiring layer (not shown), a connecting terminal is pasted onto thegate wiring layer803 and the source wiring layer via an anisotropicconductive layer885 after removing the insulating film (a connectingterminal886 connected to the gate wiring layer; the connecting terminal connected to the source wiring layer are not shown). Moreover, connecting portions of each of the wiring layers and the connecting terminals are preferably sealed by resin. The structure can prevent moisture from a cross section from penetrating into the pixel portion and prevent deterioration of the panel. In accordance with the foregoing processes, a liquid crystal display panel can be formed.
• In accordance with the foregoing processes, a liquid crystal display panel can be formed. A protective circuit for preventing electrostatic destruction as typified by a diode may be provided between the connecting terminal and the source wiring (gate wiring), or in a pixel portion. In this instance, the diode can be operated as a diode by forming in accordance with the same process as that of the foregoing TFT and connecting to the gate wiring layer of the pixel portion and the drain or the source wiring layer of the diode.
• Any one ofEmbodiments 1 to 7 can be applied to this example.
Example 2
• In this example, a method for manufacturing a light-emitting display panel as a display panel is explained with reference toFIGS. 27A to 34.FIGS. 27A to 34 illustrate schematic longitudinal sectional structures of a pixel portion and a connecting terminal portion.FIGS. 31 to 34 are plane views ofFIGS. 27A to 34 taken along lines of C-D, and E-F. Line A-B inFIGS. 27A to 34 indicates connecting terminal portions, and lines C-D and E-F inFIGS. 27A to 34 indicates regions provided with a switching TFT, a driver TFT, and a light-emitting element in each pixel in a pixel portion. In this example, a first insulating layer is, but not exclusively, formed by usingEmbodiment 1. Embodiment 2 can also be used for forming the first insulating layer. In addition, the first conductive layer explained in Embodiment 3 can be appropriately used as a first conductive layer.
• As illustrated inFIG. 27A, the surface of asubstrate2001 is oxidized at 400° C. to form an insulatingfilm2002 having a thickness of 100 nm as is the case with Example 1. Then, firstconductive layers2003 to2006 are formed. In this example, Ag paste is discharged by droplet discharging to be dried and baked. Then, the firstconductive layers2003 to2006 are formed. The firstconductive layer2003 serves as a gate wiring layer, the firstconductive layers2004 and2006 serve as gate electrode layers, and the firstconductive layer2005 serves as a capacitor electrode layer.
• First insulatinglayers2007 to2012 are formed to fill between thegate wiring layer2003, thegate electrode layers2004,2006, and thecapacitor electrode layer2005. The insulating layers are formed by discharging polyimide by droplet discharging.
• As illustrated inFIG. 28B, agate insulating film2021, afirst semiconductor film2022, and asecond semiconductor film2023 imparting n-type conductivity are formed by plasma CVD as is the case with Example 1.First mask patterns2024 to2027 are formed over the second semiconductor film to be formed over a region where the first semiconductor region is formed afterwards. The first mask patterns can be formed similarly to thesecond mask patterns817,818 explained in Example 1.
• According to the process, thegate insulating film2021 having excellent uniformity in a thickness and a excellent step coverage property can be formed.
• Then,second semiconductor film2032 is etched by using the first mask pattern as is the case with Example 1 to formfirst semiconductor regions2031 to2034 as illustrated inFIG. 27C. Thereafter, the first mask pattern is exfoliated by using stripper.
• Second mask patterns2035,2036 are formed to cover thefirst semiconductor regions2031 to2034 and thefirst semiconductor film2022 formed between thefirst semiconductor regions2031 to2034.Second semiconductor regions2041,2042 as illustrated inFIG. 28A are formed and a part of thegate insulating film2021 is exposed by etching thefirst semiconductor film2022 by using thesecond mask patterns2035,2036. Thereafter, thesecond mask patterns2035,2036 are exfoliated by using stripper.FIG. 31 illustrating the planar structure taken along lines of C-D and E-F is also referred.
• Third mask patterns2043,2044 are formed as is the case with Example 1. Thethird mask patterns2043,2044 are formed by discharging solution for forming a liquid-shedding surface by droplet discharging to a region where thegate insulating film2021 and thecapacitor electrode layer2005 are overlapped with each other and a region where thegate insulating film2021 and thegate wiring layer2003 are overlapped with each other. Then,fourth mask patterns2045,2046 are formed. The fourth mask patterns are masks for forming a first contact hole and formed by droplet discharging of polyimide to be heated at 200° C. for 30 minutes. In this instance, since thethird mask patterns2043,2044 have a liquid-shedding property and thefourth mask patterns2045,2046 have a liquid-attracting property, thefourth mask patterns2045,2046 are not formed in a region provided with thethird mask patterns2043,2044.
• A part of thegate insulating film2021 is exposed by removing thethird mask patterns2043,2044 by oxygen ashing. Then, the exposed gate insulating film is etched by using thefourth mask patterns2045,2046 in accordance with the procedure conducted in Example 1. Thereafter, the fourth mask patterns are exfoliated by oxygen ashing and etching treatment using stripper.
• As illustrated inFIG. 28C, the secondconductive layers2051 to2054 are formed by droplet discharging. The second conductive layer serves as source and drain wiring layers afterwards. Here, the secondconductive layer2051 is connected to thefirst semiconductor region2031; the secondconductive layer2052 is connected to thefirst semiconductor region2032 and thecapacitor electrode layer2005; the secondconductive layer2053 is connected to thefirst semiconductor region2033; and the secondconductive layer2054 is connected to thefirst semiconductor region2034. Further,FIG. 32 is a planar view ofFIG. 28C taken along lines of C-D and E-F. As illustrated inFIG. 32, the secondconductive layer2053 serves as a power source line and a capacitor wiring.
• By the foregoing processes, a switchingTFT2060a, adriver TFT2060c, acapacitor2060b, and an active matrix substrate comprising the foregoing components can be formed.
• As illustrated inFIG. 29A, a third conductive film is formed to be etched into a desired shape by using a fifth mask pattern, and afirst pixel electrode2055 connected to the secondconductive layer2054 of thedriver TFT2060cis formed. The third conductive film is formed by using indium tin oxide (ITO) containing silicon oxide to have a thickness of 110 nm as is the case with Example 1, and etching into a desired shape to form thefirst pixel electrode2055. In this etching process, the third conductive layer may be etched, which is provided in a region where the gate wiring layer and the source wiring layer are connected to the connecting terminal.
• As another method for forming a pixel electrode, the pixel electrode can be formed by dropping selectively solution containing a conductive material by droplet discharging without etching treatment. Moreover, the pixel electrode can also be formed by forming solution for forming a liquid shedding surface as a mask pattern to a region where the pixel electrode is not provided afterwards, and discharging solution having a conducting property. In this instance, the mask pattern can be removed by ashing using oxygen. Alternatively, the mask pattern may not be removed to be left.
• Instead of the foregoing materials for the pixel electrode, indium tin oxide (ITO), zinc oxide (ZnO), indium zinc oxide (IZO), zinc oxide doped with gallium (GZO), or indium tin oxide containing silicon oxide can be used.
• In this example, since the panel has the structure in which light is emitted in the direction of thesubstrate2001, that is, a transparent light-emitting display panel, the pixel electrode is formed by a conductive film transparent to light. In the case that a panel having the structure in which light is emitted in the opposite direction of thesubstrate2001, that is, a reflective light-emitting display panel, solution containing metal particles such as Ag (silver), Au (gold), Cu (copper), W (tungsten), or Al (aluminum) as its main components can be used.
• Thereafter, a fifth mask pattern is exfoliated by using stripper.FIG. 33 is a planar view ofFIG. 29A taken along lines C-D and E-F.
• Aprotective layer2061 of silicon nitride or silicon nitride oxide and aninsulator layer2062 are formed all over the surface. Theinsulator layer2062 is formed by spin coating or dipping all over the surface, and an opening is formed thereto by etching as illustrated inFIG. 29B. By etching the protective layer below the insulator layer, thefirst pixel electrode2055 is processed to be exposed. Further, the etching processing is not always required in the case of forming theinsulator layer2062 by droplet discharging.
• Theinsulator layer2062 is formed around the position that is provided with a pixel corresponding to thefirst pixel electrode2055. Theinsulator layer2062 can be formed by an inorganic insulating material such as silicon oxide, silicon nitride, silicon oxynitride, aluminum oxide, aluminum nitride, aluminum oxynitride, or another material; acrylic acid; methacrylic acid; derivatives of these materials; heat resistant high molecular material such as polyimide, aromatic polyamide, or polybenzimidazole; an inorganic siloxane insulating material including a Si—O—Si bond, among the compound made from silicon, oxygen, and hydrogen, formed by using a siloxane-based material as a start material; or an organic siloxane insulating material in which hydrogen connected to silicon is substituted by an organic group such as methyl or phenyl can be used. A photosensitive or non-photosensitive material such as polyimide and acrylic is preferably used for forming the insulator layer since the insulator layer can be formed to have a radius of curvature varying consistently and a thin upper film formed without stepped cut. Further, an interlayer insulating film can be formed by an insulating film containing coloring pigment, resist, or the like. In this instance, the contrast of a display device manufactured afterwards is improved since the interlayer insulating film serves as a light-shielding film.FIG. 34 is a planar view ofFIG. 29B taken along lines of C-D and E-F.
• As illustrated inFIG. 30A, alayer2073 containing a light-emitting substance is formed by vapor deposition, spin coating, or coating such as ink jetting, and asecond pixel electrode2074 is formed, then, a light-emittingelement2075 is formed. The light-emittingelement2075 is connected to thedriver TFT2060c. Thereafter, a protective lamination layer (not shown) is formed to seal the light-emittingelement2075. The protective lamination layer is composed of a first inorganic insulating film, a stress relieving film, and a second inorganic insulating film.
• Before forming a layer containing a light-emittingsubstance2073, moisture adsorbed into theinsulator layer2062 or to the surface thereof is removed by heat treatment at 200° C. in the atmosphere. Thelayer2073 containing a light-emitting substance is preferably formed by heat treatment at a reduced pressure at 200 to 400° C., preferably, 250 to 350° C., and vapor deposition without exposing to the air or droplet discharging under reduced pressure.
• The surface treatment of the surface of thefirst pixel electrode2055 may be carried out by treating in oxygen plasma or emitting ultraviolet light.
• The layer containing a light-emittingsubstance2073 can be formed by a light-emitting material and a charge injecting transporting substance containing an organic or inorganic compound to contain one kind or a plurality kinds of layers selected from the group consisting of a low molecular based organic compound, a intermediate molecular based organic compound (an organic compound which does not have a subliming property and has molecularity of 20 or less, or the length of continuous molecule is 10 μm or less, typically, dendrimer, oligomer, or the like), and high molecular based organic compound, and can be combined with an inorganic compound having an electron injecting and transporting property or a hole injecting and transporting property.
• Among charge injecting transporting substances, as a material having especially a high electron transporting property, for example, a metal complex or the like having a quinoline skeleton or a benzoquinoline skeleton such as tris(8-quinolinolato)aluminum (abbreviated as Alq₃), tris(4-methyl-8-quinolinolato)aluminum (abbreviated as Almq₃), bis(10-hydroxybenzo[h]-quinolinato)beryllium (abbreviated as BeBq₂), bis(2-methyl-8-quinolinolato)(4-phenylphenolato)aluminum (abbreviated as BAlq).
• As a material having a high hole transporting property, for example, aromatic amine (that is, the one having a benzene ring-nitrogen bond) based compounds such as 4,4′-bis[N-(1-naphthyl)-N-phenyl-amino]-biphenyl (abbreviated as α-NPD), 4,4′-bis[N-(3-methylphenyl)-N-phenyl-amino]biphenyl (abbreviated as TPD), 4,4′,4″-tris(N,N-diphenyl-amino)-triphenylamine (abbreviated as TDATA), 4,4′,4″tris[N-(3-methylphenyl)-N-phenyl-amino]-triphenylamine (abbreviated as MTDATA).
• Among charge injecting transporting substances, as a material having a high electron injecting property, a compound of an alkali metal or an alkali earth metal such as lithium fluoride (LiF), cesium fluoride (CsF), calcium fluoride (CaF₂), or the like can be nominated. Besides, a mixture of a material having a high electron transportation property such as Alq₃and an alkali earth metal such as magnesium (Mg).
• Among charge injecting transporting substances, as a material having a high hole injecting property, for example, metal oxide such as molybdenum oxide (MoOx), vanadium oxide (VOx), ruthenium oxide (RuOx), tungsten oxide (WOx), manganese oxide (MnOx), or the like can be nominated. Besides, a phthalocyanine compound such as phthalocyanine (abbreviated H₂Pc) or copper phthalocyanine (CuPc) can be nominated.
• A light-emitting layer may have the structure in which each of light-emitting layers having different emission wavelength bands is respectively provided to each pixel for color display. Typically, light-emitting layers corresponding to color of R (red), G (green), and B (blue) are formed. In this instance, color purity can be improved and a pixel portion can be prevented from being a mirror surface (reflection) by providing a filter (colored layer) transparent to light in each emission wavelength bands at the light emission side of the pixel. By providing the filter (colored layer), a circularly-polarized light plate or the like that is conventionally required becomes not required, further, light can be emitted from the light-emitting layer without loss of light. Moreover, color changes occurred in the case of viewing obliquely the pixel portion (display screen) can be further reduced.
• There are various light-emitting materials for forming a light-emitting layer As a low molecular based organic light-emitting material. 4-dicyanomethylene-2-methyl-6-[2-(1,1,7,7-tetramethyljulolidine-9-yl)ethenyl]-4H-pyran (abbreviated as DCJT), 4-dicyanomethylene-2-t-butyl-6-[2-(1,1,7,7-tetramethyljulolidine-9-yl)ethenyl]-4H-pyran, periflanthen, 2,5-dicyano-1,4-bis[2-(10-methoxy-1,1,7,7-tetramethyljulolidine-9-yl)ethenyl]benzene, N,N′-dimethylquinacridon (abbreviated as DMQd), coumarin6, coumarin545T, tris(8-quinolinolato)aluminum (abbreviated as Alq₃), 9,9′bianthryl, 9,10-diphenylanthracene (abbreviated as DPA), 9,10-bis(2-naphthyl)anthracene (abbreviated as DNA), or the like can be used. Another material may be used.
• A high molecular based organic light-emitting material has higher physical strength than that of a low molecular based organic light-emitting material, and so a light-emitting element can be manufactured to have high durability. A light-emitting element can be comparatively readily manufactured since a light-emitting layer can be formed by coating. A structure of a light-emitting element using a high molecular based organic light-emitting material is basically same as that of a light-emitting element using a low molecular based organic light-emitting material. The structure is formed by stacking sequentially a cathode, an organic light-emitting layer, and an anode. However, in the case of forming a layer containing a light-emitting substance by using a high molecular based organic light-emitting material, it is difficult to form a layered structure like in the case of using a low molecular based organic light-emitting material. Most light-emitting structures have a two-layered structure. Specifically, a structure formed by stacking sequentially a cathode, a light-emitting layer, a hole transporting layer, and an anode.
• Since emission color is dependent on a material for forming a light-emitting layer. By selecting the material, a light-emitting element that exhibits desired light emission can be formed. As a high molecular based light-emitting material, a polyparaphenylene vinylene based material, a polyparaphenylene based material, polythiophene based material, or a polyfluorene based material can be nominated.
• As the polyparaphenylene vinylene based material, a derivative of poly(paraphenylene vinylene) [PPV], poly(2,5-dialkoxy-1,4-phenylen vinylene) [RO—PPV], poly(2-(2′-ethyl-hexoxy)-5-methoxy-1,4-phenylene vinylene) [MEH-PPV], poly(2-dialkoxyphenyl)-1,4-phenylenevinylene] [ROPh-PPV], and the like are nominated. As the polyparaphenylene based material, a derivative of polyparaphenylene [PPP], poly(2,5-dialkoxy-1,4-phenylene) [RO—PPP], poly(2,5-dihexoxy-1,4-phenylene), and the like are nominated. As the polythiophene based material, a derivative of polythiophene [PT], poly(3-alkylthiophene) [PAT], poly(3-hexylthiophene) [PHT], poly(3-cyclohexylthiophene) [PCHT], poly(3-cyclohexyl-4-methylthiophene) [PCMHT], poly(3,4-dicyclohexylthiophene) [PDCHT], poly[3-(4-octylphenyl)-thiophene] [POPT], poly[3-(4-octylphenyl)-2,2-bithiophene] [PTOPT], and the like are nominated. As the polyfluorene based material, a derivative of polyfluorene [PF], poly(9,9-dialkylfluorene) [PDAF], poly(9,9-dioctylfluorene) [PDOF], and the like are nominated.
• A hole injecting property from the anode can be improved by interposing a high molecular based organic light-emitting material having a hole transporting property between the anode and a high molecular based organic light-emitting material having a light-emitting property. Generally, the high molecular based organic light-emitting material having a hole transporting property and an acceptor material dissolved in water is coated by spin coating. The high molecular based organic light-emitting material having a hole transporting property is not dissolved in organic solvent, accordingly, the material can be stacked over the organic light-emitting material having a light-emitting property. As the high molecular based organic light-emitting material having a hole transporting property, mixture of PEDOT and camphoric sulfonic acid (CSA) as an acceptor material, mixture of polyaniline [PANI] and polystyrene sulfonic acid [PSS] as an acceptor material, and the like can be nominated.
• The light-emitting layer can be formed to exhibit mono emission color or white emission color. In the case of using a white emission material, color display can be realized when a color filter that transmits light at a specified wavelength is provided at the side of light emission of a pixel.
• To form a light-emitting layer that exhibits white emission, for example, Alq₃, Alq₃partly doped with Nile red (Nile red is a red pigment), Alq₃, p-EtTAZ, TPD (aromatic diamine) are deposited sequentially by vapor deposition. In the case that the light-emitting layer is formed by coating using spin coating, the material is preferably baked by vacuum heating after being coated. For example, poly(ethylene dioxythiophene)/poly(styrene sulfonate) solution (PEDOT/PSS) may be coated over a whole surface and baked, and polyvinylcarbazole (PVK) doped with emission center pigments (1,1,4,4-tetraphenyl-1,3-butadiene (abbreviated TPB), 4-dicyanomethylene-2-methyl-6-(p-dimethylamino-styryl)-4H-pyran (DCM1), Nile red, coumarin 6, or the like) solution may be coated over a whole surface and baked to form the light-emitting layer.
• The light-emitting layer may be formed by a single layer. In this instance, the light-emitting layer may be made from polyvinylcarbazole (PVK) having a hole transport property dispersed with a 1,3,4-oxadiazole derivative (PBD) having an electron transporting property. Further, white emission can be obtained by dispersing PBD of 30 wt % as an electron transporting agent and dispersing an appropriate amount of four kinds of pigments (TPB, coumarin 6, DCM1, and Nile red). In addition to the light-emitting element that exhibits white emission as explained in the foregoing, a light-emitting element that can exhibit red emission, green emission, or blue emission can be manufactured by selecting approximately a material of a light-emitting layer.
• Furthermore, a triplet excited light-emitting material including a metal complex or the like may be used for the light-emitting layer in addition to a singlet excited light-emitting material. For example, among a pixel having red light-emitting properties, a pixel having green light-emitting properties, and a pixel having blue light-emitting properties, the pixel having red light-emitting properties with comparatively short half reduced luminescence time is formed from a triplet excited light-emitting material, and other pixels are formed from a singlet excited light-emitting material. Since the triplet excited light-emitting material has superior luminous efficiency, there is a feature that lower power consumption is required to obtain the same luminance. In other words, in the case of applying the triplet excited light-emitting material to a red pixel, a few amount of current flown to a light-emitting element is required; therefore, the reliability can be enhanced. The pixel having red light-emitting properties and the pixel having green light-emitting properties may be formed from a triplet excited light-emitting material and the pixel having blue light-emitting properties may be formed from a singlet excited light-emitting material to reduce the power consumption. Further low power consumption can be realized by also forming the green light-emitting element, which has high human spectral luminous efficacy, from a triplet excited light-emitting material.
• A metal complex used as a dopant, and a metal complex in which platinum, which is a third transition series element, serves as a center metal, a metal complex in which iridium serves as a center metal, or the like is known as an example of a triplet excited light-emitting material. The triplet excited light-emitting material is not limited to these compounds, and it is also possible to use a compound having the above structure and having an element belonging to Groups 8 to 10 of a periodic table for a center metal.
• The substance mentioned above that forms the layer containing light-emitting substance is just an example, and a light-emitting element can be formed by appropriately laminating each functional layer such as a hole injecting transporting layer, a hole transporting layer, an electron injecting transporting layer, an electron transporting layer, a light-emitting layer, an electron blocking layer, or a hole blocking k layer. In addition, a mixed layer or a mixed junction may be formed with the combination of each layer. The layer structure of the light-emitting layer can be varied. Instead of not equipping a particular electron injection region or light-emitting region, the variation of providing an electrode entirely for this purpose or providing a light-emitting material by dispersing can be permitted under the scope not departing the content of the present invention.
• The light-emitting element formed by using the material mentioned above is emitted by having bias in the forward direction. A pixel of a display device formed by using the light-emitting element can be driven by a simple matrix system or an active matrix system. In either system, each pixel is emitted by applying bias in the forward direction at particular timing; however, the pixel is in non-luminescent state within the specified period. The reliability of the light-emitting element can be enhanced by applying bias in the opposite direction during non-luminescent time. The light-emitting element becomes a decline mode when light-emitting intensity is deteriorated under a certain driving condition or when luminance is apparently deteriorated due to the expansion of non-luminescent region in a pixel. However, the deterioration can be delayed and the reliability of a display device can be enhanced by alternating current driving.
• As illustrated inFIG. 30B,sealant2081 is formed to seal thesubstrate2001 by using asealing substrate2082. Thereafter, a connecting terminal (a connecting terminal2084 connected to the gate wiring layer, a connecting terminal connected to the source wiring that is not shown) is pasted onto each edge portion of thegate wiring layer2003 and the source wiring layer (not shown) via an anisotropicconductive layer2083. A connecting portion of each of the wiring layer and the connecting terminal is preferably sealed by sealingresin2085. According to the structure, moisture from the cross section can be prevented from being penetrated into the light-emitting element, and so the deterioration of the light-emitting element can be prevented.
• In accordance with the foregoing processes, a light-emitting display panel can be formed. A protective circuit for preventing electrostatic destruction as typified by a diode may be provided between the connecting terminal and the source wiring (gate wiring), or in a pixel portion. In this instance, the diode is formed to be operated as a diode in accordance with the same process as that of the foregoing TFT and connected to the gate wiring layer of the pixel portion and the drain or the source wiring layer of the diode.
• Any one of Embodiments, 2 to 10 can be applied to this example. A liquid crystal display panel and a light-emitting display panel are explained as a display panel in Examples 1 and 2, but the display panel is not limited to theses panels. This example can be appropriately applied to an active display panel such as a DMD (Digital Micromirror Device), a PDP (Plasma Display Panel), an FED (Field Emission Display, and an electrophoretic display device (electronic paper).
Example 3
• A light-emitting element that is applicable to the foregoing examples is explained with reference toFIGS. 36A to 36D.
• FIG. 36A shows an example of forming afirst pixel electrode11 by an oxide conductive material transparent to light, which contains silicon oxide at a concentration of 1 to 15 atom %. Alayer16 containing a light-emitting substance formed by stacking a hole injecting layer or ahole transporting layer41, a light-emittinglayer42, and electron transporting or injectinglayer43 is provided over thefirst pixel electrode11. Asecond pixel electrode17 is formed by athird electrode layer33 containing an alkali metal or an alkali earth metal such as LiF or MgAg, and asecond electrode layer34 formed by a metal material such as aluminum. A pixel in the structure can emit light from the side of thefirst pixel electrode11 as indicated by arrows in theFIG. 36A.
• FIG. 36B shows an example of emitting light from thesecond pixel electrode17, in which thefirst pixel electrode11 is composed of afirst electrode layer35 made from a metal material such as aluminum or titanium, or a metal material containing the metal and the nitrogen at stoichiometric composition ratio or less; and asecond electrode layer32 made from an oxide conductive material containing silicon oxide at a concentration of 1 to 15 atom %. Alayer16 containing a light-emitting substance formed by stacking a hole injecting or hole transportinglayer41, a light-emittinglayer42, and an electron transporting layer or anelectron injecting layer43 is provided over thefirst pixel electrode11. Thesecond pixel electrode17 is formed by athird electrode layer33 containing an alkali metal or an alkali earth metal such as LiF or CaF, and afourth electrode layer34 formed by a metal material such as aluminum. Light can be emitted passing through thesecond electrode17 by forming each of the layers to have a thickness of 100 nm or less to be capable of transmitting light.
• In the case that light is emitted from the both direction, that is, the first electrode and the second electrode in the light-emitting element having the structure illustrated inFIG. 36A or36B, thefirst pixel electrode11 is formed by a conductive film having transmittance and a large work function, whereas asecond pixel electrode17 is formed by a conductive film having transmittance and a small work function. Typically, thefirst pixel electrode11 is formed by an oxide conductive material containing silicon oxide at a concentration of 1 to 15 atom %, and thesecond electrode17 is formed by thethird electrode layer33 containing an alkali metal or an alkali earth metal such as LiF or CaF having a thickness of 100 nm or less, and thefourth electrode layer34 formed by a metal material such as aluminum having a thickness of 100 nm or less.
• FIG. 36C shows an example of emitting light from afirst pixel electrode11, in which alayer16 containing a light-emitting substance is formed by stacking sequentially an electron transporting or anelectron injecting layer43, a light-emittinglayer42, and a hole injecting or a hole injecting transportinglayer41. Asecond pixel electrode17 is formed by sequentially stacking asecond electrode layer32 made from an oxide conductive material containing silicon oxide at a concentration of 1 to 15 atom %; and afirst electrode layer35 made from a metal material such as aluminum or titanium, or a metal material containing the metal and nitrogen at stoichiometric composition ratio or less over thelayer16 containing a light-emitting substance. Thefirst pixel electrode11 is formed by athird electrode layer33 containing an alkali metal or an alkali earth metal such as LiF or CaF, and afourth electrode layer34 formed by a metal material such as aluminum. Light can be emitted passing through thefirst pixel electrode11 by forming each of the layers to have a thickness of 100 nm or less to be capable of transmitting light.
• FIG. 36D shows an example of emitting light from thesecond pixel electrode17, in which alayer16 containing a light-emitting substance is formed by stacking sequentially an electron transporting layer or anelectron injecting layer43, a light-emittinglayer42, a hole injecting or ahole transporting layer41. Thefirst pixel electrode11 is formed to have the same structure as that illustrated inFIG. 35C to have a thickness that can reflect light emitted from the layer containing a light-emitting substance. Asecond pixel electrode17 is made from an oxide conductive material containing silicon oxide at a concentration of 1 to 15 atom %. In this structure, thehole injecting layer41 is made from a metal oxide that is an inorganic material (typically, molybdenum oxide or vanadium oxide); and so oxygen that is introduced in forming thesecond pixel electrode17, a hole injecting property is improved, and driver voltage can be lowered.
• In the case that light is emitted from the both direction, that is, the first electrode and the second electrode in the light-emitting element having the structure illustrated inFIG. 36C or36D, thefirst pixel electrode11 is formed by a conductive film having transmittance and a small work function, whereas asecond pixel electrode17 is formed by a conductive film having transmittance and a large work function. Typically, thefirst pixel electrode11 may be composed of athird electrode layer33 containing an alkali metal or an alkali earth metal such as LiF or CaF having a thickness of 100 nm or less, and afourth electrode layer34 made from a metal material such as aluminum. Thesecond pixel electrode17 may be formed by an oxide conductive material containing silicon oxide at a concentration of 1 to 15 atom %.
Example 4
• A pixel circuit and an operation structure thereof of the light-emitting display panel explained in the foregoing examples are explained with reference toFIGS. 37A to 37F. In a display device using digital video signals, the operation structure of the light-emitting display panel can be divided into operation in which a video signal inputted in a pixel is regulated by voltage and operation in which a video signal inputted in a pixel is regulated by current. As the operation in which a video signal inputted in a pixel is regulated by voltage, operation in which voltage that is applied to a light-emitting element constant is constant (CVCV), and operation in which current that is applied to a light-emitting element is constant (CVCC) can be nominated. As the operation in which a video signal inputted in a pixel is regulated by current, operation in which voltage that is applied to a light-emitting element is constant (CCCV), and operation in which current that is applied to a light-emitting element is constant (CCCC) can be nominated. In this example, pixels of CVCV operation are explained with reference toFIGS. 37A and 37B. Pixels of CVCC operation are explained with reference toFIGS. 37C to 37F.
• In pixels illustrated inFIGS. 37A and 37B, asignal line3710 and apower source line3711 are arranged in column, whereas asignal line3714 is arranged in rows. The pixels have aswitching TFT3701, adriver TFT3703, acapacitor3702, and a light-emittingelement3705.
• The switchingTFT3701 and thedriver TFT3703 operate in a linear region when they are ON. Thedriver TFT3703 serves to control whether or not applying voltage to the light-emittingelement3705. Both of the TFTs have preferably have the same conductivity type in the light of the manufacturing steps. In this example, both of the TFTs are formed to have n-channel TFTs. As thedriver TFT3703, not only an enhancement type but also a depletion type can be used. The ratio of a channel width W of thedriver TFT3703 and a channel length L of the driver TFT3703 (W/L) are preferably 1 to 1000 though it depends on TFT mobility. The electric property of the TFT is improved with increasing the W/L.
• In the pixels illustrated inFIGS. 37A and 37B, the switchingTFT3701 serves to control the input of a video signal to a pixel. Upon turning theTFT3701 into ON, a video signal is inputted to the pixel. Then, the voltage of the video signal is retained in acapacitor3702.
• In the case that thepower source line3711 is Vss and an opposing electrode of the light-emittingelement3705 is Vdd inFIG. 37A, that is, in the case ofFIGS. 36C and 36D, the opposing electrode of the light-emitting element is an anode, and the electrode connected to thedriver TFT3703 is a cathode. In this instance, it is possible of suppress luminance irregularity due to variable characteristics of thedriver TFT3703.
• In the case that thepower source line3711 is Vdd and an opposing electrode of the light-emittingelement3705 is Vss inFIG. 37A, that is, in the case ofFIGS. 36A and 36B, the opposing electrode of the light-emitting element is a cathode, and the electrode connected to thedriver TFT3703 is an anode. In this instance, a video signal having higher voltage than that of the Vdd is inputted to thesignal line3710, and so voltage of the video signal is retained in thecapacitor3702 and thedriver TFT3701 operates in a linear region. Accordingly, luminance irregularity due to variable characteristics of the TFT can be improved.
• The pixel illustrated inFIG. 37B has the same pixel structure as that illustrated inFIG. 37A except the point of adding aTFT3706 and ascanning line3715.
• The ON/OFF of theTFT3706 is controlled by thescanning line3715 that is newly provided. Upon turning theTFT3706 into ON, charges retained in thecapacitor3702 are discharged and theTFT3703 is turned into OFF. That is, the arrangement of theTFT3706 can make the state in which current is forced to stop flowing in the light-emittingelement3705. Accordingly, theTFT3706 can be referred to as an erasing TFT. Therefore, the structure illustrated inFIG. 37B can start a lighting period simultaneously with or immediately after the start of a writing period without waiting writing of a signal to all pixels. As a result, duty ratio of light emission can be improved.
• In a pixel having the foregoing structure, the current value of the light-emittingelement3705 can be determined by thedriver TFT3703 that operates in a linear region. According to the foregoing structure, variation of TFT characteristics can be suppressed. Accordingly, a display device with improved image quality can be provided by improving luminance irregularity of the light-emitting element due to variable TFT characteristics.
• Then, pixels of CVCC operation are explained with reference toFIGS. 37C to 37F. The pixel illustrated inFIG. 37C is formed by providing apower source line3712 and acurrent control TFT3704 to the pixel structure illustrated inFIG. 37A.
• The pixel illustrated inFIG. 37E has the same structure as that illustrated inFIG. 37C except the point that the gate electrode of thedriver TFT3703 is connected to thepower source line3712, which is arranged in rows. That is, both of the pixels illustrated inFIGS. 37C and 37E have the same equivalent circuits. However, each power source line is formed by conductive films of different layers in the case of arranging apower source line3712 in column (FIG. 37C) and in the case of arranging apower source line3712 in rows (FIG. 37E). Here, attention is attracted to a wiring connected with the gate electrode of thedriver TFT3703.FIGS. 37C and 37E illustrate that the each power source lines are formed in different layers.
• The switchingTFT3701 operates in a linear region, whereas thedriver TFT3703 operates in a saturation region. Further, thedriver TFT3703 serves to control the value of current flowing through the light-emittingelement3705, whereas theTFT3704 operates in the saturation region and serves to control the supply of current to the light-emittingelement3705.
• The pixels illustrated inFIGS. 37D and 37F have the same pixel structures as that illustrated inFIGS. 37C and 37E except the point that the erasingTFT3706 and thescanning line3715 are added to the pixels illustrated inFIGS. 37C and 37E.
• The pixels illustrated inFIGS. 37A and 37B can operate CVCC. The pixels having operation structures illustrated inFIGS. 37C to 37E can appropriately change Vdd and Vss depending on the direction of current flow of the light-emitting element likeFIG. 37A andFIG. 37B.
• In the pixel having the foregoing structure, a slight change of Vgs of theTFT3704 does not affect the current value of the light-emittingelement3705 since theTFT3704 operates in a linear region. That is, the current value of the light-emittingelement3705 can be determined by thedriver TFT3703 operating in a saturation region. According to the foregoing structure, a display device with improved image quality can be provided by improving luminance irregularity of the light-emitting element due to variable TFT characteristics.
• Especially in the case of forming a thin film transistor having an amorphous semiconductor or the like, it is preferably to increase the semiconductor film area of the driver TFT since variation of the TFT can be reduced. Therefore, the pixels illustrated inFIGS. 37A and 37B can increase aperture ratio since they have the small number of TFT.
• The structure in which thecapacitor3702 is, but not exclusively, provided is explained. The present invention is not limited thereto. Thecapacitor3702 is not always provided if gate capacitance can serve as retention volume for a video signal.
• A thin film transistor formed by an amorphous semiconductor film preferably provides a circuit for correcting a threshold value in a pixel or the periphery of the pixel since the threshold value tends to shift.
• It is considered that such the active matrix light-emitting device has advantage in driving at low voltage since TFTs are provided to each pixel in the case of increasing pixel density. At the same time, a passive matrix light-emitting device in which TFTs are provided to row-by-row can be formed. The passive matrix light-emitting device has high aperture ratio since TFTs are not provided to each pixel.
• In the display device according to the present invention, the driving method of screen display is not especially limited, for example, a dot sequential driving method, a line sequential driving method, or a plane sequential driving method may be used. Typically, a line sequential driving method is used and a time-division gradation driving method or an area gradation driving method may be appropriately used. A video signal inputted to the source line of a display device may be an analog signal or a digital signal. A driver circuit and the like may be appropriately designed in accordance with the video signal.
• As noted above, various pixel circuits can be adopted.
Example 5
• In this embodiment, the mounting of driver circuits (a signalline driver circuit1402 and scanningline driver circuits1403aand1403b) on a display panel described in the above examples is explained with reference toFIGS. 9A to 9C.
• As illustrated inFIG. 9A, the signalline driver circuit1402 and the scanningline driver circuits1403aand1403bare mounted on a periphery of apixel portion1401. InFIG. 9A, anIC chip1405 is mounted on asubstrate1400 by a COG method as the signalline driver circuit1402 and the scanningline driver circuits1403a,1403band the like. Then, the IC chip is connected to an external circuit via an FPC (flexible printed circuit)1406.
• As illustrated inFIG. 9B, in the case of forming a TFT by a semiamorphous semiconductor or a crystalline semiconductor, apixel portion1401, scanningline driver circuits1403aand1403band the like may be integrally formed over asubstrate1400, and a signalline driver circuit1402 or the like may be separately mounted as an IC chip. InFIG. 9B, anIC chip1405 is mounted on asubstrate1400 by a COG method as the signalline driver circuit1402. Then, the IC chip is connected to an external circuit through the FPC (flexible printed circuit)1406.
• Furthermore, as illustrated inFIG. 9C, a signalline driver circuit1402 or the like may be mounted by a TAB method instead of the COG method. Then, anIC chip1405 is connected to an external circuit via an FPC (flexible printed circuit)1406. InFIG. 9C, the signal line driver circuit is mounted by a TAB method; however, the scanning line driver circuit may be mounted by a TAB method.
• When the IC chip is mounted by a TAB method, a large scale of a pixel portion against a substrate can be provided thereto, and thus, a frame can be narrowed.
• The IC chip is formed by using a silicon wafer; however, an IC formed over a glass substrate (hereinafter, driver IC) may be provided instead of the IC chip. Since the IC chip is taken out of a circular silicon wafer, there is limitation on a shape of a mother substrate. On the other hand, the driver IC has a glass mother substrate and there is no limitation on the shape; therefore, the productivity can be enhanced. Accordingly, the shape and dimension of the driver IC can be arbitrarily set. For example, when the driver IC is formed to have a long side of from 15 mm to 80 mm, the required number of the driver ICs can be reduced compared with the case of mounting the IC chip. Consequently, the number of connection terminals can be reduced, and manufacturing yields can be improved.
• The driver IC can be formed by using a crystalline semiconductor formed over a substrate, and the crystalline semiconductor is preferably formed by continuous-wave laser light irradiation. A semiconductor film obtained by being irradiated with continuous-wave laser light has few crystal defects and has crystal grains with large grain sizes. As a result, a transistor having such the semiconductor film becomes to have satisfactory mobility and response speed; consequently, high-speed driving can be performed. Therefore the transistor is suitable for the driver IC.
Example 6
• In this example, a method for mounting driver circuits (a signalline driver circuit1402 and scanningline driver circuits1403aand1403b) on a display panel described in the above example is described with reference toFIGS. 10A to 10D. As the mounting method, a connection method using an anisotropic conductive material, a wire bonding method, or the like may be applied. An example thereof is described with reference toFIGS. 10A to 10D. An example using a driver IC for the signalline driver circuit1402 and the scanningline driver circuits1403aand1403bis described in this example. An IC chip can be appropriately used instead of the driver IC.
• FIG. 10A illustrates an example of adriver IC1703 mounted on anactive matrix substrate1701 by using an anisotropic conductive material. Each wiring (not shown) such as a source or gate wiring, andelectrode pads1702aand1702bof the wirings are formed over theactive matrix substrate1701.
• Connection terminals1704aand1704bare provided on the surface of thedriver IC1703, and a protectiveinsulating film1705 is formed in the periphery portion.
• Thedriver IC1703 is fixed to theactive matrix substrate1701 with an anisotropic conductive adhesive1706. Theconnection terminal1704ais electrically connected to theelectrode pad1702a, whereasconnection terminal1704belectrically connected to theelectrode pad1702b, respectively byconductive particles1707 contained in the anisotropic conductive adhesive. The anisotropic conductive adhesive is adhesive resin dispersed with the conductive particles (with a grain size of approximately from several μm to several hundreds μm) to be contained. Epoxy resin, phenol resin, or the like can be given as an example of the anisotropic conductive adhesive. In addition, the conductive particles (with a grain size of approximately from several μm to several hundreds μm) are formed by an element selected from the group consisting of gold, silver, copper, palladium and platinum; or alloy particles of a plurality of the foregoing elements. Alternatively, the conductive particles may have multilayer structures formed by the foregoing elements. Furthermore, resin particles coated with an element selected from the group consisting of gold, silver, copper, palladium and platinum; or coated with alloy particles of a plurality of the foregoing elements may also be used.
• In addition, an anisotropic conductive film formed over a base film in a filmed shape may be transferred to be used instead of the anisotropic conductive adhesive. The conductive particles that are similar to those in the anisotropic conductive adhesive are dispersed in the anisotropic conductive film. By forming theconductive particles1707 mixed in the anisotropic conductive adhesive1706 to have proper sizes and concentration, the driver IC in such a mode can be mounted on the active matrix substrate. This mounting method is suitable for mounting the driver ICs inFIGS. 9A and 9B.
• FIG. 10B illustrates an example of a mounting method of utilizing the force of contraction of organic resin. Buffer layers1711aand1711bare formed on the surface of the connection terminals of a driver IC by using Ta, Ti or the like, and Au is formed thereover to be approximately 20 μm in thick by an electroless plating method or the like to formbumps1712aand1712b. The driver IC can be mounted in accordance with the procedure, that is, photocuring insulatingresin1713 is interposed between the driver IC and the active matrix substrate, and electrodes are welded with pressure by photocuring. This mounting method is suitable for mounting the driver IC inFIGS. 9A and 9B.
• As illustrated inFIG. 10C, adriver IC1703 may be fixed to anactive matrix substrate1701 by using an adhesive1721, and theconnection terminals1704aand1704bof a CPU may be connected toelectrode pads1702aand1702bover the active matrix substrate bywirings1722aand1722b. Then, panel is sealed by anorganic resin1723. This mounting method is suitable for mounting the driver IC inFIGS. 9A and 9B.
• In addition, as illustrated inFIG. 10D, adriver IC1703 may be provided via awiring1732 over an FPC (Flexible printed circuit)1731 and an anisotropic conductive adhesive1706 containingconductive particles1707. This structure is extremely useful in an electronic device that is limited in the housing size such as a portable terminal. This mounting method is suitable for mounting the driver IC inFIG. 9C.
• A method for mounting the driver IC is not especially limited. A known COG method, a wire bonding method, a TAB method, or reflow treatment using a solder bump can be used. In the case of performing reflow treatment, plastic that has great heat resistance, typically, a polyimide substrate, an HT substrate (manufactured by Nippon Steel Chemical Co., Ltd.), ARTON made from norbornene resin with a polar group (manufactured by JSR Corp.), or the like is preferably used for a substrate used for a driver IC or an active matrix substrate
Example 7
• A driver circuit in the case that the driver circuit at the side of a scanning line is formed over asubstrate1400 as illustrated inFIGS. 9B and 9C by forming a semiconductor layer by a semiamorphous semiconductor (SAS) in a light-emitting display panel described in Example 6 is explained.
• FIG. 14 shows a block diagram of the scanning line driver circuit composed of n-channel type TFTs using a SAS that can obtain field effect mobility of from 1 to 15 cm²/V·sec.
• InFIG. 14, a block denoted byreference numeral1500 corresponds to a pulse output circuit for outputting a sampling pulse for one stage, and a shift register is composed of n number of pulse output circuits. A pixel is connected at the end of abuffer circuit1501.
• FIG. 15 illustrates a specific structure of thepulse output circuit1500 that is composed of n-channel type TFTs3601 to3613. The size of the TFTs may be decided in consideration of an operating characteristic of the n-channel type TFTs using a SAS. For example, when a channel length is set to be 8 μm, a channel width can be set ranging from 10 to 80 μm.
• In addition,FIG. 16 shows a specific structure of thebuffer circuit1501. The buffer circuit includes n-channel type TFTs3621 to3636 in the same manner. The size of the TFTs may be decided at this time in consideration of an operating characteristic of the n-channel type TFTs using a SAS. For example, when a channel length is set to be 10 μm, a channel width can be set ranging from 10 to 1800 μm.
Example 8
• A display module is described in this example. A liquid crystal module is described as an example of the display module with reference toFIG. 26.
• Anactive matrix substrate1601 and an opposingsubstrate1602 are fixed with asealant1600, and apixel portion1603 and aliquid crystal layer1604 are provided therebetween to form a display region.
• Acolored layer1605 is required to realize a color display. Each of colored layers corresponding to each color of red, green, and blue is provided to each pixel in the case of RGB system. Polarizingplates1606 and1607 are arranged outside theactive matrix substrate1601 and the opposingsubstrate1602. In addition, aprotective film1616 is formed over the surface of thepolarizing plate1606 to relieve impact from outside.
• Aconnection terminal1608 provided to theactive matrix substrate1601 is connected to awiring board1610 via anFPC1609. The FPC is provided with a pixel driver circuit (an IC chip, a driver IC, or the like)1611, and anexternal circuit1612 such as a control circuit or a power supply circuit is incorporated in thewiring substrate1610.
• Acold cathode tube1613, areflection board1614, and anoptical film1615, which are a backlight unit, serve as a light source to project light on a liquid crystal display panel. The liquid crystal display panel, the light source, the wiring board, the FPC, and the like are held and protected by abezel1617.
• This example can be applied to any one ofEmbodiments 1 to 9.
Example 9
• A cross-sectional view of a light-emitting display module is explained as an example of a display module with reference toFIGS. 35A to 35C in this example.
• FIG. 35A illustrates a cross-sectional view of a light-emitting display module in which anactive matrix substrate1201 and an opposingsubstrate1202 are fixed to each other with asealant1200, and apixel portion1203 is interposed therebetween to form a display region.
• Aspace1204 is formed between the opposingsubstrate1202 and thepixel portion1203. The space may be filled with an inert gas, for example, a nitrogen gas or provided with a highly water absorbing light-transmitting resin to prevent further the penetration of moisture or oxygen. In addition, light-transmitting resin having a high water-absorbing property may be formed. By providing the light-transmitting resin, the display module can be formed without decreasing the transmittance even in the case that light from a light-emitting element is emitted to the opposing substrate.
• In order to enhance the contrast, a polarizing plate or a circularly polarizing plate (a polarizing plate, ¼λ plate and ½λ plate) is preferably provided at least in a pixel portion of a module. When display is recognized from the side of the opposingsubstrate1202, a ¼λ plate and½λ plate1205, and apolarizing plate1206 may be sequentially provided over the opposingsubstrate1202. Furthermore, an antireflection film may be provided over the polarizing plate.
• In addition, when display is recognized from both sides of the opposingsubstrate1202 and theactive matrix substrate1201, the surface of the active matrix substrate is preferably provided with the ¼λ plate and½λ plate1205, and the polarizing plate in the same manner.
• Aconnection terminal1208 provided to theactive matrix substrate1201 is connected to awiring board1210 via anFPC1209. The FPC is provided with a pixel driver circuit1211 (an IC chip, a driver IC or the like), and thewiring board1210 is incorporated with anexternal circuit1212 such as a control circuit or a power supply circuit.
• As illustrated inFIG. 35B, acolored layer1207 can be provided between apixel portion1203 and the polarizing plate or between the pixel portion and the circularly polarizing plate. In this instance, full color display can be realized by providing a light-emitting element that is capable of emitting white light to the pixel portion and providing separately a colored layer that exhibits RGB. In addition, full color display can be realized by providing a light-emitting element capable of emitting blue light to the pixel portion and providing separately a color conversion layer or the like. Furthermore, light-emitting elements capable of emitting red, green, and blue light can be provided to each of the pixel portion; moreover, a colored layer can be used in the pixel portions. Such a display module can exhibits RGB with high color purity and display high-definition images.
• Unlike in the case ofFIG. 35A,FIG. 35C illustrates the case of sealing an active matrix substrate and a light-emitting element by using aprotective film1221 in a film or resin without using an opposing substrate. Theprotective film1221 is provided to cover a second pixel electrode in apixel portion1203. As theprotective film1221, an organic material such as epoxy resin, urethane resin or silicone resin can be used. In addition, theprotective film1221 may be formed by dropping a polymer material by a droplet discharging. In this example, epoxy resin is discharged by using a dispenser and dried. Furthermore, an opposing substrate may be provided over the protective film. The other structures are the same as inFIG. 35A.
• A display device can be reduced in weight, size and thickness by sealing without using an opposing substrate in such a manner.
• Thewiring board1210 is, but not exclusively, mounted by using theFPC1209 in the module described in this example. Thepixel driver circuit1211 and theexternal circuit1212 may be directly mounted on the substrate by using a COG (Chip on Glass) method.
• Any one ofEmbodiments 1 to 9 can be applied to this example. A liquid crystal display module and a light-emitting display module are, but not exclusively, described as an example of a display module. For example, the present invention can be appropriately applied to a display module such as a DMD (Digital Micromirror Device), a PDP (Plasma Display Panel), an FED (Field Emission Display) or an electrophoretic display device (electronic paper).
Example 10
• This embodiment describes a drying agent of a display panel described in the above embodiment with reference toFIGS. 24A to 24C.
• FIG. 24A is a surface view of the display panel.FIG. 24B is a cross-sectional view ofFIG. 24A taken along a line A-B.FIG. 24C is a cross-sectional view taken along a line C-D inFIG. 24A.
• As illustrated inFIG. 24A, anactive matrix substrate1800 and an opposingsubstrate1801 are sealed with asealant1802. A pixel region is provided between the active matrix substrate and the opposing substrate. Apixel1807 is provided to thepixel region1803 in a region where asource wiring1805 and agate wiring1806 cross each other. Adrying agent1804 is provided between thepixel region1803 and thesealant1802. In the pixel region, dryingagents1814 are provided above the gate or source wiring. Here, the dryingagents1814 are provided above the gate wiring; however, it can also be provided over the gate and source wirings.
• As thedrying agent1804, a substance that adsorbs water (H₂O) by chemical adsorption, for example, oxides of an alkaline earth metal such as calcium oxide (CaO) or barium oxide (BaO) is preferably used. Alternatively, a substance that adsorbs water by physical adsorption such as zeolite or silica gel can also be used.
• The drying agent can be fixed to the substrate in the state of being contained as a granular substance in resin having high moisture permeability. The following can be given as an example of the resin having high moisture permeability: acrylic resin such as ester acrylate, ether acrylate, ester urethane acrylate, ether urethane acrylate, butadiene urethane acrylate, special urethane acrylate, epoxy acrylate, amino resin acrylate or acrylic resin acrylate. In addition, epoxy resin such as bisphenol A type liquid resin, bisphenol A type solid resin, resin containing bromo-epoxy, bisphenol F type resin, bisphenol AD type resin, phenol type resin, cresol type resin, novolac type resin, cyclic aliphatic epoxy resin, epi-bis type epoxy resin, glycidyl ester resin, glycidyl amine resin, heterocyclic epoxy resin, or modified epoxy resin can be used. Alternatively, the other substances may be used. For example, an inorganic substance such as siloxane may be used.
• As a water-absorbing substance, for example, solution that is prepared by mixing a molecule that can absorb water by chemical absorption into organic solvent and become solidified can be used.
• As the resin or the inorganic substance having high moisture permeability, a substance having higher moisture permeability than that of a substance used as the sealant is preferably selected to be used.
• In the light-emitting device according to the present invention as described above, moisture penetrated into the light-emitting device from outside can be absorbed before the moisture reaches to a region provided with a light-emitting element. Accordingly, the deterioration due to moisture of an element provided to a pixel, typically, a light-emitting element can be suppressed.
• As illustrated inFIG. 24B, adrying agent1804 is provided between asealant1802 and apixel region1803 in the periphery of a display panel. In addition, the display panel can be reduced its thickness by providing a depression to an opposing substrate or an active matrix substrate to provide thedrying agent1804 to the depression.
• As illustrated inFIG. 24C, apixel1807 is provided with asemiconductor region1811 that is part of a semiconductor element for driving a display element, agate wiring1806, asource wiring1805, and apixel electrode1812. In the pixel portion of a display panel, adrying agent1814 is provided to the opposing substrate to overlap with thegate wiring1806. The gate wiring has a width of two to four times as that of the source wiring. Therefore, an aperture ratio is not lowered, moisture can be prevented from penetrating into a display element, and deterioration of the display element due to moisture can be suppressed by providing thedrying agent1814 over thegate wiring1806 that is a nondisplay region. In addition, a display panel can be reduced its thickness by providing a depressed portion to the opposing substrate to provide the drying agent to the depressed portion.
Example 11
• According to the present invention, a semiconductor device with a circuit composed of highly integrated semiconductor elements with high reliability that can reduce OFF current, typically, a signal line driver circuit, a controller, a CPU; a converter of an audio processing circuit, a power supply circuit, a transmit and receive circuit, a memory, an amplifier of an audio processing circuit, or the like can be manufactured. Further, a system-on-chip capable of high-speed driving with high reliability and low power consumption can be provided, where circuits constituting one system (functional circuit) such as an MPU (micro processor unit), a memory, and an I/O interface are mounted to be monolithic.
Example 12
• Various electronic devices can be manufactured by incorporating the semiconductor device described in the above examples into housing. Examples of electronic devices can be given as follows: a television set, a camera such as a video camera or a digital camera, a goggle type display (head mount display), a navigation system, an audio reproducing device (a car audio, an audio component, or the like), a personal computer, a game machine, a personal digital assistant (a mobile computer, a cellular phone, a portable game machine, an electronic book, or the like), an image reproducing device including a recording medium (specifically, a device capable of processing data in a recording medium such as a Digital Versatile Disc (DVD) and having a display that can display the image of the data), or the like. As typical examples of the electronic devices,FIG. 11 andFIG. 12 illustrate the television set and a block diagram thereof, respectively; andFIGS. 13A and 13B illustrate a digital camera.
• FIG. 11 is a diagram showing a general structure of a television set that receives analog television broadcasting. InFIG. 11, the airwaves for television broadcasting received by anantenna1101 are inputted into atuner1102. Thetuner1102 generates and outputs intermediate frequency (IF) signals by mixing the high frequency television signals inputted from theantenna1101 with locally-oscillating frequency signals that are controlled in accordance with the desired reception frequency.
• The IF signals taken out by thetuner1102 are amplified to the required voltage by an intermediate frequency amplifier (IF amplifier)1103. Thereafter, the amplified IF signals are detected by animage detection circuit1104 and anaudio detection circuit1105. The image signals outputted from theimage detection circuit1104 are divided into luminance signals and chrominance signals by animage processing circuit1106. Further, the luminance signals and the chrominance signals are subjected to the predetermined image signal processing to be image signals, so that the image signals are outputted to animage output portion1108 of a display device that is a semiconductor device of the present invention, typically, a liquid crystal display device, a light-emitting display device, a DMD (Digital Micromirror Device), a PDP (Plasma Display Panel), an FED (Field Emission Display), an electrophoretic display device (an electronic paper) or the like. Note that a liquid crystal television uses the liquid crystal display device for the display device, and an EL television uses the light-emitting display device for the display device. The same is true in using another display device.
• The signals outputted from theaudio detection circuit1105 are subjected to processing such as FM demodulation in anaudio processing circuit1107 to be audio signals. The audio signals are then amplified appropriately to be outputted to anaudio output portion1109 such as a speaker or the like.
• The television set according to the invention may be a television that is compatible with not only analog broadcastings such as terrestrial broadcasting in a VHF band or a UHF band, cable broadcasting, and BS broadcasting, but also digital broadcastings such as terrestrial digital broadcasting, cable digital broadcasting, and BS digital broadcasting.
• FIG. 12 is a front perspective view of the television set, which includes ahousing1151, adisplay portion1152, aspeaker portion1153, anoperational portion1154, avideo input terminal1155, and the like. The television set has a structure illustrated inFIG. 11.
• Thedisplay portion1152 is an example of theimage output portion1108 illustrated inFIG. 11. The display portion displays images thereon.
• Thespeaker portion1153 is an example of the audio output portion illustrated inFIG. 11. The speaker portion outputs audio therefrom.
• Theoperational portion1154 is provided with a power source switch, a volume switch, a channel select switch, a tuning switch, a selection switch, and the like to turn ON and/or OFF the television set, select images, control sound, select a tuner and the like, respectively by holding the switches down. Note that the selections mentioned above can be performed also by a remote-control operation unit, though not shown in the drawing.
• Thevideo input terminal1155 inputs image signals into the television set from an external device such as a VTR, a DVD or a game machine.
• In the case of a wall-mounted television set, a portion for hanging on walls is provided on the rear of the television set described in this embodiment.
• A television set with high contrast and high-definition can be manufactured at low cost with high throughput and high manufacturing yields by applying the display device that is an example of a semiconductor device according to the invention to the display portion of the television set. In addition, a television set can be manufactured at low cost with high throughput and yield by applying a semiconductor device according to the invention to a CPU for controlling an image detection circuit, an image processing circuit, an audio detection circuit, and an audio processing circuit of a television set. Consequently, such the television can be used for various purposes particularly as a large area display medium such as wall-mounted television set; information display boards in railway stations, airports, or the like; or advertisement display boards on the streets.
• FIGS. 13A and 13B show an example of a digital camera.FIG. 13A is a front perspective view of the digital camera, andFIG. 13B is a rear perspective view thereof. InFIG. 13A, a digital camera is provided with arelease button1301, amain switch1302, aviewfinder window1303, aflash1304, alens1305, acamera cone1306, and ahousing1307.
• InFIG. 13B, the digital camera is provided with aviewfinder eyepiece1311, amonitor1312, and anoperational button1313.
• When holding down half therelease button1301, a focus adjustment mechanism and an exposure adjustment mechanism are operated. When holding down the release button completely, a shutter is released.
• The digital camera is turned ON and/or OFF by holding down or rotating themain switch1302.
• Theviewfinder window1303 is disposed above thelens1305 on the front face of the digital camera, and is used to check a shooting range and a focusing point through theviewfinder eyepiece1311 that is illustrated inFIG. 13B.
• Theflash1304 is disposed at the upper portion of the front face of the digital camera body. When an object of shooting has low luminance, the release button is held down and auxiliary light is emitted simultaneously with releasing the shutter.
• Thelens1305 is disposed on the front of the digital camera. The lens is composed of a focusing lens, a zoom lens, and the like. Together with a shutter and an aperture, each of which is not shown, the lens constitutes an optical shooting system. An image sensing device such as a CCD (charge coupled device) is located in the region posterior to the lens.
• Thecamera cone1306 is used to moving the position of the lens in order to bring the focusing lens, the zoom lens, or the like into focus. When taking a picture, thelens1305 is moved forward by sending out the camera cone forward. When carrying the camera, thelens1305 is stored inside the main body to be reduced in size. The camera according to this example can take a picture in zooming by sending out the camera cone to the fore. However, it is not limited to this structure. The camera may be a digital camera that can take a picture in zooming without sending out the camera cone to the fore owing to an optical shooting system inside thecasing1307.
• Theviewfinder eyepiece1311 is provided at the upper portion of the rear of the digital camera whereby the shooting range and the focusing point are checked by sight.
• Theoperational button1313 is provided on the rear of the digital camera and composed of various kinds of operational functions such as a setup button, a menu button, a display button, a functional button, and a selection button.
• A digital camera with high contrast and high-definition can be manufactured at low cost with high throughput and high manufacturing yields by applying the display device that is an example of a semiconductor device according to the invention to a monitor A digital camera can be manufactured at low cost with high throughput and high manufacturing yields by applying the semiconductor device according to the invention to a CPU for processing in response to input operation of various functional buttons, a main switch, a release button and the like, a CPU for controlling various circuits such as a circuit for auto-focusing and auto-focusing adjustment, a timing control circuit for controlling electric flash drive and CCD drive, an imaging circuit for generating an image signal from a signal that is photo-electrically converted by an imaging device such as a CCD, an A/D converter circuit for converting an image signal generated in an imaging circuit into a digital signal or a memory interface for writing and reading image data in a memory.
• Although the present invention has been fully described by way of examples with reference to the accompanying drawings, it is to be understood that various changes and modifications will be apparent to those skilled in the art. Therefore, unless otherwise such changes and modifications depart from the scope of the present invention hereinafter described, they should be construed as being included therein.
• The present application is based on Japanese Priority Application No. 2004-091223 filed on Mar. 26, 2004 with the Japanese Patent Office, the entire contents of which are hereby incorporated by reference.

Claims (15)

1. A semiconductor device comprising:

a first conductive layer over an insulating surface;

a second conductive layer over the insulating surface;

a first insulating layer over the insulating surface;

a second insulating layer over the first conductive layer, the second conductive layer and the first insulating layer;

a first semiconductor layer over the second insulating layer;

a second semiconductor layer over the second insulating layer;

a third conductive layer over the first semiconductor layer;

a fourth conductive layer over the first semiconductor layer;

a fifth conductive layer over the second semiconductor layer; and

a sixth conductive layer over the second semiconductor layer,

wherein at least a part of the first insulating layer is located between the first conductive layer and the second conductive layer.

2. A semiconductor device according toclaim 1,

wherein the first semiconductor layer comprises:

a first region that overlaps the first conductive layer, the first insulating layer, and the second insulating layer; and

a second region that overlaps the first conductive layer and the second insulating layer, and

wherein the second semiconductor layer comprises:

a third region that overlaps the second conductive layer, the first insulating layer, and the second insulating layer; and

a fourth region that overlaps the second conductive layer and the second insulating layer.

3. A semiconductor device according toclaim 1, wherein a thickness of the first conductive layer and a thickness of the second conductive layer are smaller than a thickness of the first insulating layer, and a difference between the thickness of the first insulating layer and the thickness of the first conductive layer is smaller than a thickness of the second insulating layer.

4. A semiconductor device according toclaim 1, wherein a surface of a region of the first insulating layer that is in contact with the first conductive layer is higher than a surface of a region of the first insulating layer that is not in contact with the first conductive layer.

5. A semiconductor device according toclaim 1, wherein the first insulating layer is formed to be a concave shape with respect to the insulating surface.

6. A semiconductor device according toclaim 1, wherein a surface of a region of the first insulating layer that is in contact with the first conductive layer is lower than a surface of a region of the first insulating layer that is not in contact with the first conductive layer.

7. A semiconductor device according toclaim 1, wherein the first insulating layer is formed to be a convex shape with respect to the insulating surface.

8. A semiconductor device according toclaim 1, further comprising:

a first source region between the first semiconductor layer and the first conductive layer;

a first drain region between the first semiconductor layer and the second conductive layer;

a second source region between the second semiconductor layer and the third conductive layer; and

a second drain region between the second semiconductor layer and the fourth conductive layer.

9. A semiconductor device comprising:

a first conductive layer over an insulating surface;

a second conductive layer over the insulating surface;

a first insulating layer over the insulating surface;

a semiconductor layer over the first conductive layer, the second conductive layer and the first insulating layer;

a second insulating layer over the semiconductor layer;

a third conductive layer over the second insulating layer; and

wherein at least a part of the first insulating layer is located between the first conductive layer and the second conductive layer.

10. A semiconductor device according toclaim 9,

wherein the first semiconductor layer includes:

a first region that overlaps the first conductive layer, the first insulating layer, and the second insulating layer; and

a second region that overlaps the first conductive layer and the second insulating layer.

11. A semiconductor device according toclaim 9, wherein a surface of a region of the first insulating layer that is in contact with the first conductive layer is higher than a surface of a region of the first insulating layer that is not in contact with the first conductive layer.

12. A semiconductor device according toclaim 9, wherein the first insulating layer is formed to be a concave shape with respect to the insulating surface.

13. A semiconductor device according toclaim 9, wherein a surface of a region of the first insulating layer that is in contact with the first conductive layer is lower than a surface of a region of the first insulating layer that is not in contact with the first conductive layer.

14. A semiconductor device according toclaim 9, wherein the first insulating layer is formed to be a convex shape with respect to the insulating surface.

15. A semiconductor device according toclaim 9, further comprising:

a source region between the semiconductor layer and the first conductive layer; and

a drain region between the semiconductor layer and the second conductive layer.

Images