A kind of thin film transistor (TFT) based on zinc-oxide filmTechnical field
The present invention relates to technical field of semiconductor device, and in particular to a kind of thin film transistor (TFT) based on zinc-oxide film.
Background technique
In recent years, not with the rapid proliferation and high-clear display of the mobile terminals such as smart phone and tablet computerDisconnected development, requirement of the people to display technology is higher and higher, such as large scale, high contrast, high-resolution, low-power consumption, Gao KaiMouth rate etc..Pixel unit of the thin film transistor (TFT) as liquid crystal display panel (LCD) and Organic Light Emitting Diode (OLED) display panelControl switch component, influence of the performance to screen display technology are most important.Film crystal used by traditional liquid crystal panelThere are mainly two types of pipes, and one is amorphous silicon film transistors, and since its is at low cost and technology relative maturity, thus application is the widestIt is general, but the very low (generally less than < 1cm of the mobility of amorphous silicon material2/ Vs), uniformity is poor, leads to amorphous silicon display panelPower consumption is big, sensitive to visible light additionally, due to silicon materials, is also easy to produce photo-generated carrier, needs to install black matrix additional in liquid crystal display panelBacklight is shielded, manufacturing cost and technical difficulty is increased in this way, can also reduce yields.Another kind application more is lowWarm polycrystalline SiTFT, the mobility of polysilicon are high (up to 100cm2/ Vs), reduce display power consumption, but polysiliconIt is same light sensitive, it needs to recrystallize silicon by the way of quasi-molecule laser annealing additionally due to preparing polysilicon, techniqueIt is at high cost, and due to the limitation of process technique, it also cannot achieve the volume production of large scale low tempterature poly silicon at present.
Nomura in 2003 et al. has delivered the high performance thin film transistor based on multi-element metal oxide on NatureDevice, MOS transistor are increasingly becoming research hotspot, including tin indium oxide, indium gallium zinc oxide, zinc oxide etc., andWherein zinc oxide is as a kind of binary oxide, because its structure is simple, rich content, and feature at low cost, by more and moreConcern, become the following field of display technology replace silicon important selection.Zinc oxide is a kind of wide-band gap material, forbidden bandwidthAbout 3.37eV to visible transparent, and is easy to produce the film of high quality at relatively low temperature, at present zinc oxide filmsFilm transistor can obtain relatively good performance, such as up to 60cm2The mobility of/Vs, more than 107On-off ratio, connectIt is bordering on the cut-in voltage etc. of 0V.
But two main problems are also faced with for the functionization of zinc oxide thin-film transistor at present.It is that vacuum is heavy firstThe zinc-oxide film carrier concentration usually with higher that product technology obtains, causes device to be difficult within the scope of suitable grid voltageRealize shutdown.Another problem is that zinc-oxide film is extremely sensitive to the moisture in air, lack the design of reasonable structure andEncapsulation, which all will lead to device performance, degenerates even lose performance rapidly.In order to improve the electric property of zinc oxide thin-film transistor,Researcher had done considerable work, but can solve the research of zinc oxide thin-film transistor stability very well not yetOccur.For example, the overwhelming majority is all bottom grating structure about the report of zinc oxide thin-film transistor, zinc-oxide film in this structureIt is directly exposed to air, convenient for handling semiconductor layer, such as annealing, ion implanting, to improve its performance, but byIt can not be practical in the device of the sensibility of zinc oxide, this structure.On the other hand, also there is the zinc-oxide film of a small number of top gate structuresThe research of transistor is reported, in this configuration, zinc oxide material how is protected in subsequent photoetching and wet etching, andHow to reduce the boundary defect of zinc oxide material and insulating layer is two problems urgently to be resolved.
Summary of the invention
In view of the deficiencies of the prior art, the present invention provides one kind high stability, high reliability be can be realized and compared with Gao QianThe thin film transistor (TFT) based on zinc-oxide film of shifting rate.
The invention proposes a kind of thin film transistor (TFT)s based on zinc-oxide film, including semiconductor channel layer, source electrode, leakageThe gate insulation layer of pole, grid and bilayer, using the device architecture of top-gated and staggered electrode, structure, that is, finger source electrode of staggered electrodeWith drain electrode below semiconductor channel layer, grid is located at the top of semiconductor channel layer, and gate insulation layer is by semiconductor channel layerAnd gate isolation, including the first insulating layer and second insulating layer double-layer structure, the first insulating layer directly connect with semiconductor channel layerTouching, the semiconductor channel layer use zinc-oxide film.The zinc-oxide film is the N-shaped conductive thin of monocrystalline or heteromorphsFilm
In the present invention, the first insulating layer of thin film transistor (TFT) be located at semiconductor channel layer top and zinc-oxide film it is straightContact, the defect of interface is relatively fewer when due to aluminum oxide film and zinc-oxide film contact, thus can selectMaterial of the aluminum oxide as the first insulating layer.The second insulating layer of thin film transistor (TFT) can then use aluminum oxide, oxygenChange the materials such as hafnium, silica, silicon nitride.
Protective layer of first insulating layer of thin film transistor (TFT) as zinc-oxide film, in etched thin film transistors channel regionWhen, semiconductor channel layer and the first insulating layer are subjected to photoetching and wet etching together, zinc oxide can be effectively protected and partly ledBody layer is not influenced by external environment and process, while ensure that the good contact of semiconductor channel layer and insulating layer, is subtractedFew interface defect density.
First thickness of insulating layer is 9 to 15nm, in order to method using fast wet etching, is reduced in etching to below halfThe influence of the lateral undercutting of conductor channel layer.
After deposition obtains zinc-oxide film, short annealing under oxygen atmosphere is carried out to it, by zinc oxide semi-conductor ditchThe resistivity of channel layer is controlled 1 × 105Ω cm to 1 × 107Between Ω cm.
After wet etching obtains channel region, short annealing under second of oxygen atmosphere is carried out, to zinc oxide semi-conductorLayer carries out hydrogenation treatment, while repairing the defect at part channel layer and interfacial dielectric layer.
After having deposited second insulating layer, short annealing under third time oxygen atmosphere is carried out, weight is carried out to the second layer insulatingInternal flaw is repaired in crystallization, in subsequent gate lithography step, improves insulating layer to the resistance to corrosion of alkaline-based developer,Reduce the generation of electric leakage.
In the present invention, source electrode, the drain and gate of the thin film transistor (TFT) be can be used with stronger resistance to corrosionMetal or metal alloy, such as the transparent conductive oxide of gold, platinum, titanium and amorphous or heteromorphs, as tin indium oxide,The zinc oxide etc. of adulterated al.
The substrate material of thin film transistor (TFT) can be one of, but be not limited to following several, glass, quartz, listCrystal silicon chip etc. is also possible to cover the stainless steel of electric insulation layer.
Compared with prior art, the advantages of thin film transistor (TFT) of the invention based on zinc-oxide film, is, using topGrid structure, and double-deck gate insulation layer is added, the first insulating layer effectively protects semiconductor channel layer rear as protective layerIt is not influenced by external environment and subsequent technique in continuous processing step, second insulating layer, which has further functioned as, carries out channel layerThe effect of isolation and packaging protection.By the quick thermal annealing process under oxygen atmosphere three times, so that zinc oxide semi-conductor channelThe carrier concentration of layer is effectively controlled, so that the cut-in voltage of thin film transistor (TFT) is controlled in 0V or so；So that channel layer andDefect at interfacial dielectric layer is repaired, and plays hydrogenization to zinc oxide, so that the stability of thin film transistor (TFT) is bigIt is big to improve；So that the second layer insulating internal flaw is repaired, its internal crystallographic structure is improved, in subsequent photoetched gridTechnique in, the corrosion resistance of alkaline-based developer is enhanced, the generation of electric leakage is reduced.Using process proposed by the present inventionWith device architecture can produce good uniformity, high stability, high reliability, high mobility zinc oxide thin-film transistor, it is rightThe functionization of zinc oxide thin-film transistor is made that significant improvement and raising, shows for next-generation high definition, Flexible Displays and transparentDisplay technology provides strong support.
Detailed description of the invention
Fig. 1 is the schematic diagram of the section structure of the top-grate structure thin film transistor；
Fig. 2 is the schematic diagram of the section structure for carrying out short annealing processing after depositing zinc oxide film on source-drain electrode；
Fig. 3 is to deposit the first insulating layer on zinc-oxide film and etch the section knot made annealing treatment after active areaStructure schematic diagram；
Fig. 4 is to continue to deposit the schematic diagram of the section structure made annealing treatment after second insulating layer on the first insulating layer；
Fig. 5 is to deposit the schematic diagram of the section structure after grid and transition diagram over the second dielectric；
Fig. 6 is the transfer characteristic curve of the thin film transistor (TFT) of the embodiment；
Symbol description in figure:
Specific embodiment
It is clearer in order to illustrate the purpose of the present invention, technical solution and advantage, with reference to the accompanying drawings and examplesThe present invention is described in further detail.
The structural schematic diagram of the thin film transistor (TFT) based on zinc-oxide film of the present embodiment as shown in Figure 1, using top-gated andThe structure of staggered electrode, from bottom to up successively include substrate 1, source electrode 2 and drain electrode 3, semiconductor channel layer 4, the first insulating layer 5,The shape of second insulating layer 6, grid 7 and passivation insulation 8, the first insulating layer 5 is consistent with 4 shape of semiconductor channel layer, asThe protective layer of semiconductor channel layer 4, source electrode 2, drain electrode 3 and grid 7 pass through source metal lead 10, drain metal lead 11 respectivelyIt is led to except passivation insulation 8 with gate metal lead 9.The length and width of the channel of thin film transistor (TFT) is equal in the present embodimentIt is 20 μm.
Wherein the material of the substrate 1 is glass or quartz, and source electrode 2 and the material of drain electrode 3 are chromium gold double-level-metal, chromiumThe thickness of layer gold is respectively 5nm and 60nm, and the material of semiconductor channel layer 4 is the N-shaped zinc oxide conduction of monocrystalline or heteromorphsFilm, with a thickness of 20nm, the material of the first insulating layer 5 is aluminum oxide, and with a thickness of 10nm, the material of second insulating layer 6 isAluminum oxide, with a thickness of 20nm, the material of grid 7 is gold, and with a thickness of 60nm, the material of passivation insulation 8 is silica,With a thickness of 300nm.
As shown in Figure 1, the thin film transistor (TFT) is top-gated and staggered electrode configuration, grid 7 is located at semiconductor channel layer 4Top, source electrode 2 and drain electrode 3 be located at semiconductor channel layer 4 below.
As shown in Figure 1, the semiconductor channel layer 4 of thin film transistor (TFT) with below source electrode 2 and drain electrode it is 3 be overlapped respectively, respectivelyLap width l is identical, is 20 μm.
The resistivity of the zinc oxide semi-conductor channel layer 4 of the thin film transistor (TFT) is 8 × 105Ω·cm。
A kind of specific structure of thin film transistor (TFT) proposed by the present invention based on zinc-oxide film can be through but not limited toFollowing methods preparation:
(1) one layer of chromium gold thin film is deposited on substrate 1, and shifts the figure of source electrode 2 and drain electrode 3 by stripping technology, soAfter continue deposit one layer of zinc-oxide film as semiconductor channel layer 4, as shown in Fig. 2, and to zinc oxide semi-conductor channel layer 4 intoShort annealing under row oxygen atmosphere, to control the carrier concentration of zinc-oxide film；
(2) protective layer of the one layer of aluminum oxide film as semiconductor channel layer 4 is deposited in structure shown in Fig. 2,That is the first insulating layer 5, then the first insulating layer 5 to semiconductor channel layer 4 and its above carries out wet etching together, shiftsTo the figure of active area (channel region), as shown in figure 3, then carrying out short annealing under oxygen atmosphere；By semiconductor channel layer andFirst insulating layer carries out photoetching and wet etching together, can be effectively protected zinc oxide semiconductor layer not by external environment and workThe influence of skill processing, while ensure that the good contact of semiconductor channel layer and insulating layer, reduce interface defect density；After etchingAnnealing is carried out under oxygen atmosphere can carry out hydrogenation treatment to zinc oxide semiconductor layer, while repair part channel layer and insulationDefect at bed boundary；
(3) continue to deposit second insulating layer of the one layer of aluminum oxide as thin film transistor (TFT) in structure shown in Fig. 36, as shown in figure 4, then carrying out short annealing under oxygen atmosphere, second insulating layer can be recrystallized, repair internal lackIt falls into, in subsequent gate lithography step, improves insulating layer to the resistance to corrosion of alkaline-based developer, reduce the generation of electric leakage；
(4) continue to deposit one layer of gold thin film in structure shown in Fig. 4, by the figure of stripping technology transfer gate 7, such asShown in Fig. 5；
(5) continue to deposit passivation insulation of the layer insulating as the thin film transistor (TFT) in structure shown in Fig. 58, protect device, as shown in Figure 1, and etch lead hole in passivation insulation 8 using the technique of wet etching later,Expose source electrode 2, drain electrode 3 and 7 part of grid, then proceed to one layer of metal of deposition, gate metal is obtained by stripping technology and is drawnLine 9, source metal lead 10 and drain metal lead 11.
Semiconductor channel layer 4, the first insulating layer 5 and second insulating layer 6 can by atomic layer deposition, magnetron sputtering,The technologies such as pulse laser deposition, chemical vapor deposition deposit to obtain, and this embodiment uses technique for atomic layer deposition.
The metal layer of source electrode 2, drain electrode 3 and grid 7 can pass through the technologies such as thermal evaporation, electron beam evaporation, magnetron sputteringDeposition obtains, and in this embodiment, chromium thin film is deposited using electron beam evaporation, and gold thin film is obtained using thermal evaporation deposition.
Process manufacturing technology needed for process flow described in Fig. 1 to Fig. 5 and traditional FPD manufacturing process technologyIt is compatible, such as chemical vapor deposition, magnetron sputtering, photoetching technique etc..
Fig. 6 show the transfer characteristic curve of the thin film transistor (TFT) based on zinc-oxide film made from the present embodiment, to devicePart carries out continuous 5 scanning transfer characteristic curve, cut-in voltage VONVariable quantity be less than 0.1V, device has excellent electricity steadyIt is qualitative.
The above description is merely a specific embodiment, but scope of protection of the present invention is not limited thereto, anyIn the technical scope disclosed by the present invention, any changes or substitutions that can be easily thought of by those familiar with the art, all answersIt is included within the scope of the present invention.Therefore, protection scope of the present invention should be with the scope of protection of the claimsIt is quasi-.