BACKGROUND OF THE INVENTION(a) Field of the Invention[0001]
The present invention relates to liquid crystal displays and manufacturing methods thereof, more specifically to liquid crystal displays having electrode arrays for applying electric fields parallel to substrates and thin film transistors as switching elements and manufacturing methods thereof.[0002]
(b) Description of the Related Art[0003]
A liquid crystal display (LCD) having an electrode array for generating an electric field which is parallel to substrates (IPS mode; in-plane switching mode) is disclosed in U.S. Pat. No. 5,598,285 of Kondo et al.[0004]
The IPS mode LCD of Kondo et al. has two substrates opposite each other and a liquid crystal layer therebetween. Two kinds of electrodes for generating electric field, common electrodes and pixel electrodes are formed on one of the substrates. An alignment layer is coated on the electrodes.[0005]
However, since the two kinds of electrodes are made of different layers and have different thickness, the surface of the alignment layer may not be flat, and this causes non-uniform rubbing which may result in light leakage.[0006]
Moreover, the liquid crystal display of Kondo et al., in particular, transistors of the liquid crystal display are easily defected by the electrostatic discharge because the two electrodes are formed together on a single substrate.[0007]
For electrostatic discharge protection, all wires may be short-circuited during the manufacturing process and separated after the manufacture of the panel is completed. However, this method is complicated.[0008]
SUMMARY OF THE INVENTIONIn view of the above, it is an object of the present invention to reduce the light leakage of IPS mode liquid crystal displays.[0009]
It is another object of the present invention to prevent thin film transistors from being destroyed by the electrostatic discharge.[0010]
It is another object of the present invention to simplify the manufacturing process of IPS mode liquid crystal displays.[0011]
It is another object of the present invention to decrease the opening of wires.[0012]
It is another object of the present invention to increase the reliability of the contacts between pads and drivers.[0013]
These and other objects, features and advantages are provided, according to the present invention, by forming a pixel electrode using a thin single conductive layer, and a data line is formed as a double layer.[0014]
The thickness of the single conductive layer forming a pixel electrode may be equal to or less than 1,000 Å. It is more preferable that the thickness of the single conductive layer is equal to or less than 500 Å. The double layer forming a data line may include a lower layer, which is the same as the pixel electrode, and an upper layer having a low resistivity of 15 μΩcm or less. The single layer or the lower layer of the double layer may be formed using a metal having a low resistivity of 15 μΩcm or less, and the upper layer may be formed by a pad material which is not easily broken in the manufacturing process.[0015]
A passivation layer which is thick relative to the pixel wire may have relatively flat surface since the pixel wire is relatively thin. The flat surface may give rise to uniform rubbing and thus the light leakage may be reduced.[0016]
These and other objects, features and advantages are also provided, according to the present invention, by forming a common signal wire and a gate wire including a gate line, a gate electrode, a gate pad and a gate line connector on a substrate, forming a gate insulating layer over the common signal wire and the gate wire, forming a channel layer and an ohmic contact layer thereon, forming a pixel electrode and a data wire including a source and a drain electrodes, a data line, a data pad and a data line connector using a first conductive layer, forming a passivation layer on the data wire and the pixel electrode, forming a redundant data wire including a redundant data line, a redundant data pad and a redundant data line connector, a redundant gate pad and a redundant gate line connector using a second conductive layer. The redundant data wire is electrically connected to the data wire through the contact holes formed in the passivation layer. The redundant gate pad and the redundant gate line connector are connected to the gate pad and the gate line connector respectively through the contact holes formed in the gate insulating layer and the passivation layer. The redundant gate line connector and the redundant data line connector are connected with each other to short-circuit the gate lines and the data lines on the substrate.[0017]
After forming the panel, an alignment layer is printed and rubbed, and the gate line connector and the data line connector are removed by cutting out the edge of the panel.[0018]
The pixel electrode may be formed in the step of forming redundant data wire using the second conductive layer instead of the first conductive layer, and the thickness of the pixel electrode may be equal to or less than 500 Å.[0019]
The redundant data wire may be formed as a single or a double layer, and the single layer or the upper layer of the double layer may be formed using a pad material which is not easily broken in the manufacturing process.[0020]
BRIEF DESCRIPTION OF THE DRAWINGSFIG. 1 is a layout view of a panel for a liquid crystal display according to the first embodiment of the present invention.[0021]
FIG. 2 shows a cross-sectional view of the panel illustrated in FIG. 1 taken along the line II-II′.[0022]
FIGS.[0023]3A-3D are cross-sectional views of the intermediate structures of the panel shown in FIGS. 1 and 2 in the manufacturing steps.
FIG. 4 is a schematic diagram of the LCD panel according to the second embodiment of the present invention.[0024]
FIG. 5 shows a layout view of a panel for a liquid crystal display according to the second embodiment of the present invention.[0025]
FIGS.[0026]6-10 are cross-sectional views of the panel shown in FIG. 5 taken along the lines VI-VI′, VII-VII′, VIII-VIII′, IX-IX′ and X-X′ respectively.
FIGS.[0027]11A-14E are cross-sectional views of the intermediate structures of the panel shown in FIGS.4-10 in the manufacturing steps.
FIGS.[0028]15A-17E are cross-sectional views of the intermediate structures of the panel for a liquid crystal display according to another embodiment of the present invention.
FIG. 18 shows a layout view of a panel for liquid crystal display according to another embodiment of the present invention.[0029]
FIGS.[0030]19-23 are cross-sectional views of the panel shown in FIG. 18 taken along the lines XIX-XIX′, XX-XX′, XXI-XXI′, XXII-XXII′ and XXIII -XXIII′ respectively.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTSThe present invention will now be described more fully hereinafter with reference to the accompanying drawings, in which preferred embodiments of the present invention are shown. This invention may, however, be embodied in different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. In the drawings, the thickness of layers and regions are exaggerated for clarity.[0031]
First, the structure of a panel for a liquid crystal display according to the first embodiment of the present invention will be described. FIG. 1 is a layout view of a panel, and FIG. 2 is a cross-sectional view of the panel illustrated in FIG. 1 taken along the line II-II′.[0032]
A gate wire including a[0033]transverse gate line200 and agate electrode210 which is a branch of thegate line200 is formed on asubstrate100. A common signal wire including acommon signal line300 parallel to thegate line200 and a plurality of linearcommon electrodes310 connected to thecommon signal line300 is also formed on thesubstrate100. Thecommon electrodes310 extend toward thegate line200, and they are spaced apart from each other and parallel to each other.
A[0034]gate insulating layer400 is formed over thegate wire200 and210 and thecommon signal wire300 and310.
A[0035]channel layer800 and anohmic contact layer910 and920 are sequentially formed on a portion of thegate insulating layer400 over thegate electrode210. The ohmic contact layer has twoportions910 and920 separated from each other with respect to thegate electrode210. Alongitudinal data line500 are formed on thegate insulating layer300, and asource electrode510, a branch of thedata line500 extending to thegate electrode210, is formed on oneportion910 of the ohmic contact layer. Thedata line500 intersects thegate line200 near thegate electrode210, and has a double-layered structure including alower chromium layer501 of about 500 Å and anupper aluminum layer502 of about 2,000 Å, while thesource electrode210 has a single chromium layer. On thegate insulating layer400, a pixel wire including a transversepixel electrode line600 and a plurality ofpixel electrodes610 which are branches of thepixel electrode line600 extending toward thecommon signal line300 is also formed between thegate line20 and thecommon electrode line300. Thepixel electrodes610 and thecommon electrodes310 are parallel and spaced apart. Adrain electrode620, which is connected to an end portion of thepixel electrode line600, is formed on theother portion920 of the ohmic contact layer. Thepixel wire600 and610 and thedrain electrode620 are formed of a single chromium layer of about 500 Å.
A[0036]passivation layer700 is formed over thepixel wire600 and610, thedata line500, the source and thedrain electrodes510 and620.
Since the[0037]data line500 has a double-layered structure, although thepixel wire600 and610 is relatively thin, for example, has thickness of around 500 Å, thedata line500 may not be easily opened. Accordingly, thepassivation layer700 which is thick relative to thepixel wire600 and610 may have relatively flat surface. The flat surface may give rise to uniform rubbing and thus the light leakage may be reduced. The measured contrast ratio of the liquid crystal display according to the first embodiment of the present invention is about 120, while that in the conventional liquid crystal displays is about 60.
The thickness of the[0038]pixel wire600 and610 may be equal to or less than 1,000 Å, and that of thepassivation layer700 may be 2,000-4,000 Å such that thepassivation layer700 has a relatively flat surface. It is more preferable that the thickness of thepixel wire600 and610 is equal to or less than 500 Å. Although the small thickness of thepixel wire600 and610 may cause relatively large resistance, it may be allowed for the LCD.
The[0039]lower layer501 and theupper layer502 forming thedata line500 are not restricted to chromium and aluminum respectively. Thelower layer501 may be made of a conductive material having low resistivity of 15 μΩcm or less, and theupper layer502 may be made of a pad material which is not easily broken in the manufacturing process.
Now, a manufacturing method of the panel according to the first embodiment of the present invention will be described. FIGS.[0040]3A-3D are cross-sectional views of the intermediate structures of the panel shown in FIGS. 1 and 2 in the manufacturing steps.
A metal layer is deposited and patterned to form a[0041]gate wire200 and210 and acommon signal wire300 and310, as shown in FIG. 3A.
A[0042]gate insulating layer400, an intrinsicamorphous silicon layer800 and a dopedamorphous silicon layer900 are deposited in sequence, and as shown in FIG. 3B, the intrinsic and the doped amorphous silicon layers are patterned together.
A[0043]chromium layer600 of around 500 Å and an aluminum layer of around 2,000 Å are deposited in sequence. As shown in FIG. 3C, the aluminum layer is patterned to form anupper layer502 of adata line500. Next, as shown in FIG. 3D, thechromium layer600 is patterned to form alower layer501 of thedata line500, asource electrode510, adrain electrode620 and apixel wire600 and610. The dopedamorphous silicon layer900 is etched to form anohmic contact layer910 and920 using the source and thedrain electrodes510 and620 and thedata line500 as a mask. Apassivation layer700 is deposited thereon, as shown in FIG. 2.
Now, the second embodiment of the present invention is described, where a pixel wire and a data wire have small thickness and a relatively thick redundant data pattern connected to the data wire is provided on a passivation layer.[0044]
First, the structure of the panel for a liquid crystal display according to the second embodiment will be described. FIG. 4 is a schematic diagram of the LCD panel according to the second embodiment.[0045]
As shown in FIG. 4, a plurality of[0046]gate lines20 extending in a transverse direction are formed on asubstrate100, and a plurality ofcommon signal lines10 on thesubstrate100 are arranged parallel to the gate lines20. A plurality ofgate pads22, which are connected to external gate drivers (not shown), are formed to be connected to the ends of the gate lines20. Agate line connector24 is formed in a longitudinal direction and connected to thegate pads22 via its branches. A plurality ofdata lines60 extending in the longitudinal direction intersect and are insulated from the gate lines20 and the common signal lines10. A plurality ofdata pads63, which are connected to external data drivers (not shown), are formed to be connected to the ends of the data lines60. Adata line connector64 is formed in the transverse direction and connected to thedata pads63 via its branches. Thegate line connector24 and thedata line connector64 are connected to each other so that all the wires including the gate lines20 and the data lines60 on thesubstrate100 are short-circuited.
This structure causes the electrostatic charges generated during the manufacturing process to be spread over the substrates, thereby protecting thin film transistors effectively. When manufacture of the panel is completed, the wires are separated by cutting out the gate and the[0047]data line connectors24 and64 along the dottedline200 in FIG. 4.
In the meantime, a pixel region is defined by the gate lines[0048]20 and the data lines60, and thesubstrate100 includes a plurality of pixels. A linear pixel electrode and a linear common electrode, not shown in FIG. 4, are formed alternately in the pixel region, and a thin film transistor connected to the gate line, the data line and the pixel electrode is also formed in the pixel region.
Now, the structure of the panel according to the second embodiment will be more fully described. FIG. 5 shows a layout view of a panel for a liquid crystal display according to the second embodiment of the present invention. FIGS.[0049]610 are cross-sectional views of the panel shown in FIG. 5 taken along the lines VI-VI′, VII-VII′, VIII-VIII′, IX-IX′ and X-X′ respectively.
As shown in FIGS.[0050]5-10, a plurality ofgate lines20 extending in a transverse direction are formed on a transparent insulatingsubstrate100. The end portions of the gate lines20 are enlarged to formgate pads22, and several portions of the gate lines20 serve asgate electrodes21. Agate line connector24 extending in a longitudinal direction is formed on thesubstrate100 and connected to thegate pads22 via its branches. A pair ofcommon signal lines10 and a plurality of spaced apart linearcommon electrodes11 connected to both thecommon signal lines10 are formed between the gate lines20 on thesubstrate100. Thecommon electrodes11 extend in the longitudinal direction and are parallel to each other.
A[0051]gate insulating layer30 made of insulator such as silicon nitride is formed over agate wire20,21,22 and24 and acommon signal wire10 and11.
A plurality of channel layers[0052]40 made of semiconductor such as amorphous silicon are formed on portions of thegate insulating layer30 over thegate electrodes21. A plurality of ohmic contact layers51 and52 made of a material reducing the contact resistance between the channel layers40 and wires thereon such as heavily doped amorphous silicon are formed on the amorphous silicon layers40, and each ohmic contact layer is divided into twoportions51 and52 with respect to thegate electrode21.
A plurality of[0053]data lines60 are formed on thegate insulating layer30 and extend longitudinally. The end portions of the data lines60 are enlarged to form a plurality ofdata pads63. A plurality ofsource electrodes61 connected to the data lines60 anddrain electrodes62 are formed on the respective portions of the ohmic contact layers51 and52. A pair of thepixel electrode lines66 are formed on thegate insulating layer30 and overlap the common signal lines10.Linear pixel electrodes65 connected to both thepixel electrode lines66 are also formed on thegate insulating layer30 and eachpixel electrode65 is placed between adjacent two of thecommon electrodes11. A transversedata line connector64 is formed on thegate insulating layer30 and connected to thedata pads63 via its branches.
The[0054]gate electrode21, thegate insulating layer30, theamorphous silicon layer40, theohmic contact layer51 and52, and the source and thedrain electrodes61 and62 form a thin film transistor for switching the display signals from thedata line60 responsive to the scanning signal from thegate line10. Thesource electrode61 is U-shaped while thedrain electrode62 is linear. The end of thedrain electrode62 is placed pointing towards the convex part of thesource electrode61. This arrangement of the source and thedrain electrodes61 and62 enlarge the on current of the TFT.
A[0055]passivation layer70 made of silicon nitride or the like is formed over the thin film transistor and the remainingdata wire60,63,64 and65. Thepassivation layer70 has contact holes71,73 and75 which expose the midportions of thedata line60, thedata pad63 and thedata line connector64 respectively. In addition, thepassivation layer70 and the gate insulating layer havecontact holes72 and74 exposing thepate pads22 and thegate line connector24.
A[0056]conductor pattern80 and83 which has the similar shape to thedata wire60 and63 is formed on thepassivation layer70 and connected to thedata wire60 and63 through the contact holes71 and73 in thepassivation layer70. Therefore, theconductor pattern80 and83 functions as a redundant data wire. Another conductor pattern having atransverse portion85 and alongitudinal portion84 connected to each other is formed on thepassivation layer70. Thetransverse portion85 has branches connected to theconductor pattern83 and connected to thedata line connector64 via the contact holes75, and thelongitudinal portion84 is connected to thegate line connector24 through the contact holes74. Conductor patters82 are also formed on thepassivation layer70 and connected to thegate pads22 through the contact holes72.
A manufacturing method of a panel for a liquid crystal display according to the second embodiment of the present invention will be now described. FIGS.[0057]11A-14E are cross-sectional views of the intermediate structures of the panel shown in FIGS.4-10 in the manufacturing steps. The manufacturing method according to the second embodiment uses 5 masks. The figures having the view numbers including the capital letters A, B, C, D and E following Arabic numerals correspond to the FIGS.6-10, respectively.
First, as shown in FIGS.[0058]11A-11E, a metal layer of 3,000 Å is deposited and patterned using a first mask to form a gate wire including agate line20, agate electrode21, agate pad22 and agate line connector24 and a common signal wire including acommon signal line10 andcommon electrodes11. The gate wire and the common signal wire may be a single layer of chromium, aluminum, aluminum alloy, or molybdenum, etc., or may have a double-layered structure composed of two metal layers.
As shown in FIGS.[0059]12A-12E, agate insulating layer30 made of silicon nitride or organic insulating material, etc., a hydrogenatedamorphous silicon layer40 and an n+ hydrogenatedamorphous silicon layer50 heavily doped with n type impurities such as phosphorous are deposited in sequence. The thickness of the three layers are 3,000-5,000 Å, 500-2,000 Å and 500 Å, respectively. The dopedamorphous silicon layer50 and the intrinsicamorphous silicon layer40 are photo etched using a second mask to have an island shape on thegate electrode21. As shown in FIGS. 12C and 12D, the gate pad and the data pad are also covered with thegate insulating layer30.
As shown in FIGS.[0060]13A-13E, a metal layer made of chromium, aluminum alloy or molybdenum having thickness of around 500 Å or less is deposited, and etched using a third mask to form a data wire including adata line60, a source and adrain electrodes61 and62, adata pad63 and adata line connector64 and a pixel wire including pixel electrodes line66 (in FIG. 5) andpixel electrodes65. Then, the exposed portions of the dopedamorphous silicon layer50 are removed using the data wire as an etch mask to expose the intrinsicamorphous silicon layer40.
As shown in FIGS.[0061]14A-14E, a silicon nitride or an organic insulating material layer is deposited to a thickness of 1,500-2,500 Å to form apassivation layer70, and thepassivation layer70 is patterned to form contact holes71,73 and75 exposing thedata line60, thedata pad63 and thedata line connector64 respectively. Contact holes72 and74 are also formed by removing portions of thegate insulating layer30 and thepassivation layer70 on both of thegate pad22 and thegate line connector24.
As shown in FIGS.[0062]6-10, a metal layer of 2,000-2,500 Å made of molybdenum, molybdenum alloy or aluminum alloy is deposited and patterned to formconductor patterns80,83,85,82 and84. Theconductor patterns80,83,85,82 and84 may have a double-layered structure.
An alignment layer is coated on the substrate and rubbed. The gate line connector and the data line connector are removed by cutting off their branches.[0063]
The liquid crystal display according to the second embodiment of the present invention, the thickness of the pixel electrode is preferably about 500 Å or less, and that of the redundant data wire is preferably about 2,000-2,500 Å. The thin pixel electrode enables the passivation layer to have flat surface and thus reduces the light leakage due to the non-uniform rubbing. The thick redundant data wire has relatively small resistance, and thus it reduces the resistance of the data wire as well as prevents the open of the data wire.[0064]
In the meantime, since the redundant data wire forms an upper layer of the pad region, a pad material which is not easily broken in the manufacturing process may be used for the redundant data wire in order to improve the contact characteristic between the pad and the external driving integrated circuits. ITO (indium tin oxide) is an example of a pad material.[0065]
The redundant wire may have a double-layered structure including an upper ITO layer, such that the contact characteristic between the pad and the external driving integrated circuits is much more improved.[0066]
The pixel wire may be formed of the same layer as the redundant data wire.[0067]
That is, as shown in FIGS.[0068]15A-16E. A gate wire including agate line20, agate electrode21, agate pad22 and agate line connector24 and a common signal wire including acommon signal line10 andcommon electrodes11 are formed. Agate insulating layer30, a hydrogenatedamorphous silicon layer40 and an n+ hydrogenatedamorphous silicon layer50 are deposited in sequence. The dopedamorphous silicon layer50 and the intrinsicamorphous silicon layer40 are photo etched. Adata wire60,61,62 and63 is formed on thegate insulating layer30, and apassivation layer70 having acontact hole76 exposing thedrain 500 Å or less. In this case, the pixel wire and the redundant data wires are preferably formed of a material suitable for pad such as chromium, molybdenum or molybdenum alloy.
In the above embodiments of the present invention, several small portions of the passivation layer on the data wire are removed, and the data wire and the redundant data wire are electrically connected through the removed portions. However, as shown in FIGS.[0069]18-23, a portion of thepassivation layer70 on thedata wire60,63 and64 may be removed completely, and theredundant data wire80,83 and85 may be formed directly on thedata wire60,63 and64 to decrease the contact resistance between the data wire and the redundant data wire and to reduce the height difference between the upper surfaces of the redundant data wire and of the passivation layer.
In the second embodiment of the present invention, both the gate line connector and the data fine connector are formed to have redundant wires, and the redundant gate line connector (or the longitudinal portion of the conductor pattern) and the redundant data line connector (or the transverse portion of the conductor pattern) which are formed of the same layer are short-circuited. However, one or both of the redundant gate line connector and the redundant data line connector may not be formed, and a conductor pattern connecting the data line connector and the gate line connector may be formed when the redundant data wire is formed.[0070]
Since the pixel electrode is formed thin in the liquid crystal displays according to the embodiments of the present invention, the height difference of the upper surfaces of the pixel electrodes and of the common electrodes is compensated by the relatively thick passivation layer formed on the pixel electrode. Therefore, the surfaces of the passivation layer and of the alignment layer thereon are flat and thus the uniform rubbing is possible. Accordingly, the contrast ratio increases due to the decrease of the light leakage. The data wire may have a open-free structure by forming the data wire as a double-layered structure or forming the redundant data wire. The manufacturing process is simple since only 5 masks are used. The contact characteristic between the driver IC (integrated circuit) and the pads is improved by using a pad material, which is not broken easily in the manufacturing process, as the pad or the redundant pad.[0071]
In the drawings and specification, there have been disclosed typical preferred embodiments of the invention and, although specific terms are employed, they are used in a generic and descriptive sense only and not for purposes of limitation, the scope of the invention being set forth in the following claims.[0072]