JP2010190948A - Thin film transistor and image display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a thin film transistor and an image display device in which a gate leakage current and dielectric breakdown of an element due to ruggedness on a color filter surface can be suppressed. <P>SOLUTION: The thin film transistor includes a color filter formed on a transparent substrate, a gate line formed on the color filter, a capacitor line formed apart from the gate line, a transparent gate insulating film formed on the gate line and the capacitor line, a semiconductor active layer formed on the gate insulating film, a source line formed on the gate insulating film and the semiconductor active layer so as to partially overlap them, and a drain electrode partially overlapping the gate insulating film and the semiconductor active layer and formed apart from the source line. An overcoat layer includes a recessed part and the gate line is disposed in the recessed part. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a thin film transistor formed on a color filter and an image display device including the thin film transistor, which reduces unevenness on the surface of a gate insulating film and improves a withstand voltage of the thin film transistor.

  In recent years, thin film transistors using amorphous silicon, polycrystalline silicon, metal oxide semiconductor materials, organic semiconductor materials, or the like have been used as transistors for driving electronic devices. However, since amorphous silicon, polycrystalline silicon, and organic semiconductor materials have photosensitivity in the visible light region, a light shielding film is necessary.

  On the other hand, a metal oxide semiconductor material with a large band gap is characterized by being transparent without visible light sensitivity in the visible light region, and can be formed at low temperatures, so a flexible transparent thin film transistor is formed on a substrate such as a plastic substrate. It is possible to do (refer patent document 1). Thin film transistors using a metal oxide semiconductor material are attracting a lot of interest for improving the aperture ratio of active matrix display devices and realizing new display configurations.

  As a new display configuration using a transparent thin film transistor, there is a front drive structure in which a transparent thin film transistor is formed on a color filter (Non-Patent Document 2).

  In a display using a thin film transistor, the thin film transistor is generally formed directly on a substrate such as glass. For example, in the case of a bottom gate structure, a gate wiring is formed on glass and a gate insulating film is formed thereon. At this time, the withstand voltage of the thin film transistor is lowered due to the unevenness of the gate insulating film. In particular, when the thickness of the gate insulating film is thin or the film quality is not good, the tendency is remarkable, which causes a gate leakage current or a dielectric breakdown of the element. 4 and 5 show structural examples of thin film transistors in which such element defects are likely to occur. FIGS. 4A and 4B are cross-sectional views taken along the broken line S-S ′ of the transparent thin film transistor of FIG. 5 represented by a plan view showing almost one pixel. Since unevenness due to the colored layer 2 of the color filter also appears on the overcoat layer, a step is generated in the insulating film 6 of the thin film transistor formed on the overcoat layer, and a gate between the gate wiring and the wiring stacked thereon is formed. Leakage current and device breakdown occur.

JP 2000-150900 A JP 2006-165528 A

K. Nomura et. al. , Nature, Vol. 432, 488 (2004). M.M. Ito, et. al. , IEICE TRANS. ELECTRON. , Vol. E90-C, no. 11, 105 (2007).

  An object of the present invention is to provide a thin film transistor and an image display device capable of suppressing gate leakage current and element breakdown caused by unevenness on the surface of a color filter.

The invention according to claim 1
On a transparent substrate, a subpixel made of a colored layer, a pixel made of a plurality of the subpixels, a color filter made of a plurality of the pixels and an overcoat layer, a gate wiring, a capacitor wiring, and a gate insulating film In the thin film transistor having a semiconductor active layer, a source wiring, and a drain electrode, the overcoat layer has a recess, and the gate wiring is formed in the recess portion on the overcoat layer. Thin film transistor.

The invention according to claim 2
The thin film transistor according to claim 1, wherein the gate wiring and the source wiring are arranged on a region between the sub-pixels.

The invention according to claim 3 is:
The colored layer of each pixel of the color filter is red (R), green (G), blue (B), colorless (W), yellow (Y), magenta (M), and cyan (C). 3. The thin film transistor according to claim 1, wherein the thin film transistor is colorless (W), and an overcoat layer is provided on the colored layer.

The invention according to claim 4 is:
4. The thin film transistor according to claim 1, wherein the overcoat layer between the sub-pixels of the color filter forms a depression due to a difference in thickness between the colored layer and the black matrix or the colored layer and the substrate. It is a thing.

The invention according to claim 5 is:
5. The thin film transistor according to claim 1, wherein the semiconductor active layer is a material mainly composed of a metal oxide.

The invention according to claim 6 is:
An image display device using the thin film transistor according to claim 1.

The invention according to claim 7 is:
On a transparent substrate, a subpixel made of a colored layer, a pixel made of a plurality of the subpixels, a color filter made of a plurality of the pixels and an overcoat layer, a gate wiring, a capacitor wiring, and a gate insulating film In the thin film transistor having a semiconductor active layer, a source wiring, and a drain electrode, the overcoat layer has a recess, and the gate wiring is formed in the recess portion on the overcoat layer. This is a method of manufacturing a thin film transistor.

The invention according to claim 8 is:
The step of forming the depression in the overcoat layer is a step in which the overcoat layer between the sub-pixels of the color filter forms a depression due to a difference in film thickness between the colored layer and the black matrix or the colored layer and the substrate. 8. The method of manufacturing a thin film transistor according to claim 7, wherein the thin film transistor is a thin film transistor.

  In the thin film transistor formed on the color filter, when the overcoat layer of the color filter is formed, a depression is formed on the overcoat surface between the subpixels of each color of the color filter, and the gate wiring is connected to the subpixel of each color of the color filter. By disposing on the region between, the unevenness of the surface of the gate insulating film can be reduced and the withstand voltage of the thin film transistor can be improved.

It is a fragmentary sectional view which shows about 1 pixel of the thin-film transistor concerning embodiment of this invention. It is a fragmentary top view which shows about 1 pixel of the thin-film transistor concerning embodiment of this invention. Note that the overcoat layer 4, the gate insulating film 5, the interlayer insulating film 11, and the pixel electrode 11 are not shown. It is a figure which shows the color filter part of the thin-film transistor concerning embodiment of this invention. It is a fragmentary sectional view which shows 1 pixel part of the thin-film transistor concerning the comparative example of this invention. It is a fragmentary top view which shows about 1 pixel of the thin-film transistor concerning the comparative example of this invention.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that, in the embodiments, the same components are denoted by the same reference numerals, and redundant description among the embodiments is omitted.

  1 and 2 show a transparent thin film transistor according to an embodiment of the present invention. FIG. 1 is a cross-sectional view taken along the broken line S-S ′ of the transparent thin film transistor of FIG. 2 represented by a plan view showing approximately one pixel. The thin film transistor used in the image display device according to the embodiment of the present invention includes a transparent substrate 1, a color filter coloring layer 2, a black matrix 3, an overcoat layer 4, a gate wiring 5, a gate insulating film 6, and a semiconductor active layer 7. Source wiring 8 and drain electrode 9. Furthermore, the capacitor wiring 10, the interlayer insulation film 11, and the pixel electrode 12 are provided.

  Further, as shown in FIG. 2, the thin film transistor used in the image display device according to the embodiment of the present invention is formed on a transparent layer, a transparent substrate, and a colored layer. A color filter formed of an overcoat layer; a gate wiring formed on the overcoat layer; a capacitor wiring formed apart from the gate wiring; a transparent gate insulating film formed on the gate wiring and the capacitor wiring; A semiconductor active layer formed on the gate insulating film, a source wiring formed to partially overlap the gate insulating film and the semiconductor active layer, and a source partially overlapping on the gate insulating film and the semiconductor active layer. A drain electrode formed separately from the wiring is provided, the overcoat layer has a recess, and the gate wiring is disposed in the recess.

  1 and 2 has a top contact structure in which a semiconductor active layer is formed under the source wiring and the drain electrode, but the source wiring and the drain electrode are under the semiconductor active layer. It may be a bottom contact in which is formed. Further, in the embodiment of the present invention, the source wiring, the drain electrode, and the semiconductor active layer may be overlaid in random order.

  “Transparent” means that the transmittance is 70% or more within the wavelength range of 400 nm to 700 nm that is visible light.

  As the transparent substrate 1 according to the embodiment of the present invention, specifically, polymethyl methacrylate, polyacrylate, polycarbonate, polystyrene, polyethylene sulfide, polyethersulfone, polyolefin, polyethylene terephthalate, polyethylene naphthalate, cycloolefin polymer, poly Ether sulfone, triacetyl cellulose, polyvinyl fluoride film, ethylene-tetrafluoroethylene copolymer resin, weather resistant polyethylene terephthalate, weather resistant polypropylene, glass fiber reinforced acrylic resin film, glass fiber reinforced polycarbonate, transparent polyimide, fluorine resin In addition, cyclic polyolefin resins, glass, quartz, and the like can be used, but the present invention is not limited to these. These may be used as a single transparent substrate 1, but can also be used as a composite transparent substrate 1 in which two or more kinds are laminated.

When the transparent substrate 1 according to the embodiment of the present invention is an organic film, a transparent gas barrier layer (not shown) can be formed in order to improve the durability of the element of the thin film transistor. Examples of the gas barrier layer include aluminum oxide (Al ₂ O ₃ ), silicon oxide (SiO ₂ ), silicon nitride (SiN), silicon oxynitride (SiON), silicon carbide (SiC), and diamond-like carbon (DLC). The present invention is not limited to these. These gas barrier layers can also be used by laminating two or more layers. The gas barrier layer may be formed only on one side of the transparent substrate 1 using an organic film, or may be formed on both sides. The gas barrier layer can be formed using a vacuum deposition method, an ion plating method, a sputtering method, a laser ablation method, a plasma CVD (Chemical Vapor Deposition) method, a hot wire CVD method, a sol-gel method, and the like. It is not limited.

  The colored layer 2 according to the embodiment of the present invention is formed on a transparent substrate 1, and is a red filter (R), a red filter (R), a green filter (G), and a blue color filter (B), or a red filter (R). , Green filter (G), blue color filter (B) and white color filter (W), or a combination of cyan color filter (C), magenta color filter (M) and yellow color filter (Y) However, the present invention is not limited to these. Each color of the color filter coloring layer 2 is patterned with a film thickness of 0.7 μm or more and 2.0 μm or less in an appropriate pattern such as a stripe (stripe) having a predetermined width, a matrix, or a rectangular matrix having a predetermined size. ing. Further, a black black matrix 3 having a film thickness of 0.1 μm or more and 0.5 μm or less may or may not be provided between the colored layers 2 of the respective colors.

  After the patterning of the colored layer 2, a transparent overcoat layer 4 is provided on the transparent substrate 1 and the colored layer 2 in order to protect the colored pattern. At this time, a portion between the color sub-pixels of the colored layer 2 is formed with the black matrix 3 having a thickness smaller than that of the colored layer 2 or nothing is formed. 3 or a difference in height between the colored layer 2 and the substrate 1 can be used to form concave depressions between the sub-pixels of each color on the color filter surface (FIG. 3A). (See (b)).

  In forming the depression, specifically, it is preferable that the distance between each color sub-pixel of the colored layer 2 is 5 μm or more, and the difference in film thickness between the colored layer 2 and the black matrix 3 or the height of the colored layer 2 and the substrate 1 The difference is preferably 0.3 μm or more and 2.0 μm or less. The thickness of the overcoat layer 4 can be appropriately changed depending on the relationship between the colored layer 2 and the black matrix 3 and the height difference between the colored layer 2 and the surface of the substrate 1, and is preferably 1 μm or more and 4 μm or less, Thereby, a recess of 0.1 μm to 0.3 μm can be formed on the surface of the overcoat layer 4.

  As a material for the transparent overcoat layer 4, a thermosetting transparent resin such as an epoxy resin is preferably used, but is not limited to this in the present invention.

  When a color filter is formed between the transparent substrate 1 and the layer on which the gate wiring 5 is formed, the color filter and the thin film transistor can be easily aligned, and an image display device using the color filter is manufactured. The yield can be prevented from decreasing due to poor alignment.

  The gate wiring 5 according to the embodiment of the present invention is formed in a recess on the overcoat layer 4 and is formed from a thin film of a conductive material. Further, two or more conductive material thin films may be stacked and used.

  The film thickness of the gate wiring 5 is preferably equal to the value of the height difference of the recessed portion, and the value equivalent to the value of the height difference of the recessed portion is the difference with respect to the value of the height difference of the recessed portion. It means within ± 20%. By making the film thickness of the gate wiring 5 equal to the height difference value of the recessed portion, the unevenness of the gate insulating film formed on the gate wiring can be reduced and the withstand voltage of the thin film transistor can be improved.

  The line width of the gate wiring 5 is preferably the same as or less than the width between the color sub-pixels of the colored layer 2, and is the same as or less than the width between the color sub-pixels of the colored layer 2. This means that the difference is −20% or more and 5% or less with respect to the width value between the sub-pixels of each color.

As the gate wiring 5, gold (Au), silver (Ag), copper (Cu), titanium (Ti), tantalum (Ta), molybdenum (Mo), chromium (Cr), aluminum (Al), nickel (Ni) Further, a metal material such as tungsten (W) or platinum (Pt), or an alloy of these metal materials or a laminate of a plurality of metal material thin films can be used. In addition, indium oxide (In ₂ O ₃ ), tin oxide (SnO ₂ ), zinc oxide (ZnO), cadmium oxide (CdO), indium cadmium oxide (CdIn ₂ O ₄ ), cadmium tin oxide (Cd ₂ SnO ₄ ) In addition, oxide materials such as zinc tin oxide (Zn ₂ SnO ₄ ), and those oxide materials doped with impurities can also be used. Examples of the oxide material doped with impurities include indium oxide with tin (Sn), molybdenum (Mo), titanium (Ti), tungsten (W), gallium (Ga), cerium (Ce), and zinc (Zn). ), And zinc oxide doped with aluminum (Al) or gallium (Ga). A laminate of a plurality of these metal materials and oxide materials can also be used, but the present invention is not limited to these.

  A thin film of a conductive material used for the gate wiring 5 can be formed by a vacuum deposition method, an ion plating method, a sputtering method, a laser ablation method, a plasma CVD method, a photo CVD method, a hot wire CVD method, or the like. It is not limited to these.

The gate insulating film 6 of the thin film transistor according to the embodiment of the present invention is formed on the gate wiring and the overcoat layer, and the material used is not particularly limited, but silicon oxide, silicon nitride, silicon oxynitride, aluminum oxide, oxidation Inorganic materials such as tantalum (Ta ₂ O ₅ ), yttrium oxide (Y ₂ O ₃ ), hafnium oxide (HfO ₂ ), hafnium aluminate (HfAlO), zirconium oxide (ZrO ₂ ), and titanium oxide (TiO ₂ ), or Examples include organic materials such as polyacrylates such as polymethyl methacrylate (PMMA), polyvinyl alcohol (PVA), polystyrene (PS), transparent polyimide, polyester, epoxy resin, and polyvinylphenol, but the present invention is not limited thereto. is not. In order to suppress the gate leakage current, it is preferable that the resistivity of the insulating material is 1011 Ω · cm or more, desirably 1014 Ω · cm or more.

  The gate insulating film 6 is formed using a method such as vacuum deposition, ion plating, sputtering, laser ablation, plasma CVD, photo CVD, hot wire CVD, spin coating, dip coating, or screen printing. However, the present invention is not limited to these. The film thickness of the gate insulating film 6 is desirably 50 nm or more and 2 μm or less. These gate insulating films 6 may be used as a single layer, may be a laminate of a plurality of layers, or may have a composition inclined in the growth direction.

The semiconductor active layer 7 used in the thin film transistor according to the embodiment of the present invention is formed on a region between the colors of the colored layer, and an oxide semiconductor material containing a metal oxide as a main component can be used as the material thereof. The oxide semiconductor material is an oxide containing one or more elements of zinc (Zn), indium (In), tin (Sn), tungsten (W), magnesium (Mg), and gallium (Ga). (ZnO), indium oxide (In ₂ O ₃ ), indium zinc oxide (In—Zn—O), tin oxide (SnO ₂ ), tungsten oxide (WO), and zinc gallium indium oxide (In—Ga—Zn—O) However, the present invention is not limited to these materials. These materials are transparent and have a band gap of 2.8 eV or more, and preferably a band gap of 3.2 eV or more. The structure of these materials may be any of single crystal, polycrystal, microcrystal, mixed crystal of crystal and amorphous, nanocrystal scattered amorphous, and amorphous. The thickness of the semiconductor active layer 7 is desirably 20 nm or more.

  Since the metal oxide material used for the semiconductor active layer 7 does not have photosensitivity in the visible light region, it is not necessary to provide a light shielding layer unlike a conventional thin film transistor using silicon. There is a possibility of improvement and realization of a new display configuration.

  The semiconductor active layer 7 is formed by using a sputtering method, a pulse laser deposition method, a vacuum deposition method, a CVD method, an MBE (Molecular Beam Epitaxy) method, an ALD (Atomic Layer Deposition) method, a sol-gel method, or the like. Of these, a sputtering method, a pulse laser deposition method, a vacuum evaporation method, and a CVD method are preferable. Examples of the sputtering method include RF magnetron sputtering method and DC sputtering method, vacuum evaporation method includes resistance heating evaporation method, electron beam evaporation method and ion plating method, CVD method includes hot wire CVD method and plasma CVD method. It is not limited to these.

  When the structure of the thin film transistor according to the embodiment of the present invention is a bottom gate type, a protective film (not shown) that covers the semiconductor active layer 7 can be provided. By using the protective film, it is possible to prevent the semiconductor active layer 7 from being changed over time due to humidity or the like or affected by the interlayer insulating film 11. As the protective film, inorganic materials such as silicon oxide, silicon nitride, silicon oxynitride, aluminum oxide, tantalum oxide, yttrium oxide, hafnium oxide, hafnium aluminate, zirconia oxide and titanium oxide, or polymethyl methacrylate (PMMA), etc. Examples of the organic material include polyacrylate, polyvinyl alcohol (PVA), polystyrene (PS), transparent polyimide, polyester, epoxy resin, polyvinyl phenol, and fluorine resin, but the invention is not limited thereto. These protective films may be used as a single layer or may be a laminate of a plurality of layers.

An opaque metal material such as gold (Au), silver (Ag), copper (Cu), titanium (Ti), tantalum (Ta), molybdenum (Mo) as a material of the source wiring 8 of the thin film transistor according to the embodiment of the present invention. ), Chromium (Cr), aluminum (Al), nickel (Ni), tungsten (W), platinum (Pt), etc., the source wiring 8 is formed on the region between the sub-pixels. Moreover, the metal material mentioned above may laminate | stack two or more thin films of an alloy or a metal material. Further, a transparent oxide material such as indium oxide (In ₂ O ₃ ), tin oxide (SnO ₂ ), zinc oxide (ZnO), cadmium oxide (CdO), indium cadmium oxide (CdIn ₂ O) is used as the material of the source wiring 8. ₄ ), cadmium tin oxide (Cd ₂ SnO ₄ ), zinc tin oxide (Zn ₂ SnO ₄ ), etc., they may be anywhere on the sub-pixel. In addition, the above-described oxide material may be doped with impurities. Examples of the oxide material doped with impurities include indium oxide with tin (Sn), molybdenum (Mo), titanium (Ti), and tungsten ( W), gallium (Ga), cerium (Ce) and zinc (Zn) doped, zinc oxide doped with aluminum (Al) and gallium (Ga), and the like. A laminate in which a plurality of metal materials and oxide materials described above are stacked can also be used, but the present invention is not limited to these.

  Examples of the method for forming a thin film of a conductive material used for the source wiring 8 include a vacuum deposition method, an ion plating method, a sputtering method, a laser ablation method, a plasma CVD method, a photo CVD method, and a hot wire CVD method. However, it is not limited to these.

The drain electrode 9 according to the embodiment of the present invention is formed on a gate insulating film, and the materials thereof are gold (Au), silver (Ag), copper (Cu), titanium (Ti), tantalum (Ta), A plurality of metal materials such as molybdenum (Mo), chromium (Cr), aluminum (Al), nickel (Ni), tungsten (W), platinum (Pt), and alloys of these metal materials and thin films of metal materials were stacked. Things can also be used. In addition, indium oxide (In ₂ O ₃ ), tin oxide (SnO ₂ ), zinc oxide (ZnO), cadmium oxide (CdO), indium cadmium oxide (CdIn ₂ O ₄ ), cadmium tin oxide (Cd ₂ SnO ₄ ) In addition, oxide materials such as zinc tin oxide (Zn ₂ SnO ₄ ), and those oxide materials doped with impurities can also be used. Examples of the oxide material doped with impurities include indium oxide with tin (Sn), molybdenum (Mo), titanium (Ti), tungsten (W), gallium (Ga), cerium (Ce), and zinc (Zn). ), And zinc oxide doped with aluminum (Al) or gallium (Ga). A laminate of a plurality of these metal materials and oxide materials can also be used, but the present invention is not limited to these.

  Examples of a method for forming a thin film of a conductive material used for the drain electrode 9 include a vacuum deposition method, an ion plating method, a sputtering method, a laser ablation method, a plasma CVD method, a photo CVD method, and a hot wire CVD method. It is not limited to these.

  When the area of the drain electrode 9 is larger than the pixel region, the aperture ratio of the thin film transistor can be increased by forming the drain electrode 9 using a transparent conductive material as compared with the case where the drain electrode 9 is formed using an opaque conductive material. .

As the capacitor wiring 10 according to the embodiment of the present invention, gold (Au), silver (Ag), copper (Cu), titanium (Ti), tantalum (Ta), molybdenum (Mo), chromium (Cr), aluminum A metal material such as (Al), nickel (Ni), tungsten (W), platinum (Pt), etc., and an alloy of these metal materials or a laminate of a plurality of metal material thin films can also be used. In addition, indium oxide (In ₂ O ₃ ), tin oxide (SnO ₂ ), zinc oxide (ZnO), cadmium oxide (CdO), indium cadmium oxide (CdIn ₂ O ₄ ), cadmium tin oxide (Cd ₂ SnO ₄ ) In addition, oxide materials such as zinc tin oxide (Zn2SnO4), and those oxide materials doped with impurities can also be used. Examples of the oxide material doped with impurities include indium oxide with tin (Sn), molybdenum (Mo), titanium (Ti), tungsten (W), gallium (Ga), cerium (Ce), and zinc (Zn). ), And zinc oxide doped with aluminum (Al) or gallium (Ga). A laminate of a plurality of these metal materials and oxide materials can also be used, but the present invention is not limited to these.

  A thin film of a conductive material used for the capacitor wiring 10 can be formed by a vacuum deposition method, an ion plating method, a sputtering method, a laser ablation method, a plasma CVD method, a photo CVD method, a hot wire CVD method, or the like. It is not limited to these.

  Further, by forming the capacitor wiring 10 with a transparent conductive material, the aperture ratio of the thin film transistor can be increased as compared with a case where the capacitor wiring 10 is formed with an opaque conductive material.

  The interlayer insulating film 11 according to the embodiment of the present invention is not particularly limited as long as it is insulating and transparent. For example, inorganic materials such as silicon oxide, silicon nitride, silicon oxynitride, aluminum oxide, tantalum oxide, yttrium oxide, hafnium oxide, hafnium aluminate, zirconia oxide and titanium oxide, or polyacrylate such as polymethyl methacrylate (PMMA) , Organic materials such as polyvinyl alcohol (PVA), polystyrene (PS), transparent polyimide, polyester, epoxy resin, and polyvinylphenol, but are not limited to these in the present invention. The interlayer insulating film 11 may be made of the same material as the gate insulating film 6 or may be made of a different material. These interlayer insulating films 11 may be used as a single layer or may be a laminate of a plurality of layers.

  The pixel electrode 12 according to the embodiment of the present invention is formed of a transparent thin film of a conductive material, and must be electrically connected to the drain electrode 9 of the thin film transistor. Specifically, the interlayer insulating film 11 is pattern-printed by a method such as screen printing, and the interlayer insulating film 11 is not provided on the drain electrode 9, or the interlayer insulating film 11 is applied over the entire surface, and then the laser is applied. A method of making a hole in the interlayer insulating film 11 using a beam or the like can be mentioned, but the present invention is not limited to this.

As the pixel electrode 12, indium oxide (In ₂ O ₃ ), tin oxide (SnO ₂ ), zinc oxide (ZnO), cadmium oxide (CdO), indium cadmium oxide (CdIn ₂ O ₄ ), cadmium tin oxide (Cd _2). An oxide material such as SnO ₄ ) and zinc tin oxide (Zn ₂ SnO ₄ ), or an oxide doped with these oxide materials can also be used. Examples of the oxide material doped with impurities include indium oxide with tin (Sn), molybdenum (Mo), titanium (Ti), tungsten (W), gallium (Ga), cerium (Ce), and zinc (Zn). ), And zinc oxide doped with aluminum (Al) or gallium (Ga). A material obtained by laminating a plurality of these materials can also be used, but the present invention is not limited thereto.

  A thin film of a transparent conductive material used for the pixel electrode 12 can be formed by a vacuum deposition method, an ion plating method, a sputtering method, a laser ablation method, a plasma CVD method, a photo CVD method, a hot wire CVD method, etc. The invention is not limited to these.

  Examples of the display element combined with the thin film transistor of the present invention include an electrophoretic reflective display device, a transmissive liquid crystal display device, a reflective liquid crystal display device, a transflective liquid crystal display device, an organic EL display device, and an inorganic EL display device. .

  FIG. 2 is a partial cross-sectional view of approximately one pixel of the image display apparatus of the present embodiment, and FIG. 3 is a partial plan view of approximately one pixel of the image display apparatus of the embodiment. Note that the ratio of the film thickness and area of each layer in these drawings does not accurately represent the film thickness and area ratio of the thin film transistor in the image display device of this embodiment.

  EXAMPLES The present invention will be specifically described below with reference to examples and comparative examples, but the present invention is not limited to the following description.

<Example>
An image display device using the thin film transistor shown in FIG. 1B and FIG. 2 was manufactured by the following procedure.
As the transparent substrate 1, non-alkali glass 1737 (thickness 0.7 mm) manufactured by Corning Co., Ltd. is used. From one color, red (R), green (G), blue (B), and colorless (W) A color filter coloring layer 2 was formed. More specifically, the color filter coloring layers 2 (R), 2 (G), 2 (B), and 2 (W) are applied to the entire glass substrate 1 and then a photomask having a predetermined shape. Was formed by exposure, development, and baking. In this example, the colored layer 2 (R) was first formed, and then formed in the order of 2 (G), 2 (B), and 2 (W). On top of this, an overcoat layer 4 which is a thermosetting transparent resin was applied and baked to form a color filter. The space between the sub-pixels of each color layer is 10 μm, and a depression of about 0.1 μm is formed between the sub-pixels of each color layer 2 of the overcoat layer 4.

  A 100 nm film of indium-tin oxide (In—Sn—O, commonly known as “ITO”) is formed thereon by DC magnetron sputtering, and this is patterned into a desired shape by photolithography to form gate wiring 5 and The capacitor wiring 10 was obtained. Note that the gate wiring 5 is arranged in a recessed portion existing between the sub-pixels of each color of the colored layer 2. A 200 nm thick silicon oxynitride (SiON) film was formed on the gate wiring 5 and the capacitor wiring 10 by RF magnetron sputtering to form a gate insulating film 6. Further, 40 nm of zinc indium gallium oxide (In—Ga—Zn—O) was formed by RF magnetron sputtering, and patterned into a desired shape by photolithography to form the semiconductor active layer 7. A resist was applied thereon, dried and developed, and then a film of ITO 100 nm was formed by DC magnetron sputtering, and a registry shift-off was performed to form a source wiring 8 and a drain electrode 9. Further on this, an epoxy resin was applied in a thickness of 5 μm by using a printing method to form an interlayer insulating film 11. Finally, an ITO film having a thickness of 100 nm was formed by a DC magnetron sputtering method, and was patterned into a desired shape by a photolithography method to form a pixel electrode 12. A Vizplex Imaging Film manufactured by E Ink Co. was pasted as an electrophoretic reflective display element including a common electrode on the thin film transistor thus manufactured, and an image display device of an example was manufactured. Note that the image display apparatus of this embodiment is configured to display the display through the thin film transistor from the color filter side.

<Comparative example>
An image display device using the thin film transistor shown in FIG. 4B and FIG. 5 was manufactured by the following procedure.
As the transparent substrate 1, non-alkali glass 1737 (thickness 0.7 mm) manufactured by Corning Co., Ltd. is used. From one color, red (R), green (G), blue (B), and colorless (W) A color filter coloring layer 2 was formed. More specifically, the color filter coloring layers 2 (R), (G), (B), and (W) are coated on the entire glass substrate 1 using a photomask having a predetermined shape. , Exposure, development, and baking. In this example, first, the color filter layer 2 (R) was formed and formed in the order of (G), (B), and (W). On top of this, an overcoat layer 4 which is a thermosetting transparent resin was applied and baked, followed by polishing to flatten the surface and form a color filter.
An ITO 100 nm film was formed thereon by DC magnetron sputtering, and this was patterned into a desired shape by photolithography to form gate wiring 5 and capacitor wiring 10. A 200 nm thick silicon oxynitride (SiON) film was formed on the gate wiring 5 and the capacitor wiring 10 by RF magnetron sputtering to form a gate insulating film 6. Further, 40 nm of zinc indium gallium oxide (In—Ga—Zn—O) was formed by RF magnetron sputtering, and patterned into a desired shape by photolithography to form the semiconductor active layer 7. A resist was applied, dried and developed thereon, and then a film of ITO 100 nm was formed by DC magnetron sputtering, and a registry shift-off was performed to form a source wiring 8 and a drain electrode 9. Further on this, an epoxy resin was applied in a thickness of 5 μm by using a printing method to form an interlayer insulating film 11. Finally, an ITO film having a thickness of 100 nm was formed by a DC magnetron sputtering method, and was patterned into a desired shape by a photolithography method to form a pixel electrode 12. A Vizplex Imaging Film manufactured by E Ink Co. was pasted as an electrophoretic reflective display element including a common electrode on the thin film transistor thus manufactured, and an image display device of a comparative example was manufactured. Note that the image display device of this comparative example is configured to display the display through the thin film transistor from the color filter side.

<Comparison result>
In the embodiment, a recess of about 0.1 μm is provided on the surface of the overcoat layer between the sub-pixels of each color of the color filter, and the gate insulating film formed on the gate wiring 5 is formed by passing the gate wiring 5 therethrough. Unevenness can be reduced. On the other hand, in the comparative example, since the surface of the gate insulating film 6 due to the gate wiring 5 is uneven, the thickness of the gate insulating film 6 is partially reduced between the gate wiring 5 and the source wiring 8. A part arises.

  Specifically, in the comparative example not using the present invention, dielectric breakdown occurred when the gate voltage of the thin film transistor was 52 V. However, in the thin film transistor in the example using the present invention, the gate voltage was set to 100 V. Dielectric breakdown did not occur.

  From the above results, by using the present invention, the withstand voltage can be improved by reducing the unevenness of the gate insulating film.

DESCRIPTION OF SYMBOLS 1 ... Transparent substrate 2 ... Color filter coloring layer 3 ... Black matrix 4 ... Overcoat layer 5 ... Gate wiring 6 ... Gate insulating film 7 ... Semiconductor active layer 8 ... Source wiring 9 ... Drain electrode 10 ... Capacitor wiring 11 ... Interlayer insulation Film 12 ... Pixel electrode 13 ... Image display element 14 ... Common electrode 15 ... Back substrate

Claims (8)

  On a transparent substrate, a subpixel made of a colored layer, a pixel made of a plurality of the subpixels, a color filter made of a plurality of the pixels and an overcoat layer, a gate wiring, a capacitor wiring, and a gate insulating film In the thin film transistor having a semiconductor active layer, a source wiring, and a drain electrode, the overcoat layer has a recess, and the gate wiring is formed in the recess portion on the overcoat layer. Thin film transistor.   The thin film transistor according to claim 1, wherein the gate wiring is disposed on a region between the sub-pixels.   The colored layer of each pixel of the color filter is red (R), green (G), blue (B), colorless (W), yellow (Y), magenta (M), and cyan (C). 3. The thin film transistor according to claim 1, wherein the thin film transistor is made of colorless (W), and an overcoat layer is provided on the colored layer.   4. The thin film transistor according to claim 1, wherein the overcoat layer between the sub-pixels of the color filter forms a depression due to a difference in film thickness between the colored layer and the black matrix or the colored layer and the substrate.   5. The thin film transistor according to claim 1, wherein the semiconductor active layer is a material mainly composed of a metal oxide.   An image display device using the thin film transistor according to claim 1.   On a transparent substrate, a subpixel made of a colored layer, a pixel made of a plurality of the subpixels, a color filter made of a plurality of the pixels and an overcoat layer, a gate wiring, a capacitor wiring, and a gate insulating film In the thin film transistor having a semiconductor active layer, a source wiring, and a drain electrode, the overcoat layer has a recess, and the gate wiring is formed in the recess portion on the overcoat layer. A method for manufacturing a thin film transistor.   The step of forming the depression in the overcoat layer is a step in which the overcoat layer between the sub-pixels of the color filter forms a depression due to a difference in film thickness between the colored layer and the black matrix or between the colored layer and the substrate. The method of manufacturing a thin film transistor according to claim 7.

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