JPWO2009011224A1 - Method for producing metal oxide semiconductor and thin film transistor obtained thereby - Google Patents

Abstract

The object of the present invention is to improve the production efficiency by improving the variation of off current, etc., improving the mobility and stabilizing the TFT element by the new metal oxide semiconductor or the manufacturing method thereof. An object of the present invention is to provide a manufacturing method of a physical semiconductor and a thin film transistor using the same. The method for producing a metal oxide semiconductor according to the present invention produces a metal oxide semiconductor by forming a thin film containing a metal oxide semiconductor precursor and then irradiating the thin film with light in the presence of oxygen. It is characterized by doing.

Description

  The present invention relates to a method for manufacturing an oxide semiconductor thin film obtained by providing a thin film containing a precursor of a metal oxide semiconductor and oxidizing the thin film, and also relates to a thin film transistor using the oxide semiconductor.

  As a technology to oxidize a metal film and convert it to a metal oxide semiconductor film, an attempt is made to oxidize a metal film such as Cu, Zn, or Al formed on a substrate by thermal oxidation or plasma oxidation to convert it into a metal oxide semiconductor film. (For example, Patent Document 1). There is a description such as In in the dopant.

  Moreover, what forms an amorphous oxide by decomposing and oxidizing an organic metal (heating, decomposition reaction) is also known (for example, patent document 2).

These use thermal oxidation or plasma oxidation for oxidation of the precursor. However, when the thermal oxidation method is used, since the treatment is performed in a very high temperature range of 300 ° C. or higher, the energy efficiency is low, and application to a light resin substrate or the like becomes difficult. In the case of plasma oxidation, since processing is performed in a very reactive plasma space, in the thin film transistor manufacturing process, electrodes and insulating films are deteriorated, and mobility and off current (dark current) deteriorate. A problem occurred.
JP-A-8-264794 JP 2003-179242 A

  The object of the present invention is to manufacture a metal oxide semiconductor with improved production efficiency that improves variation in off current, etc., improves mobility, and stabilizes a TFT element by a new metal oxide semiconductor or a manufacturing method thereof. A method and a thin film transistor using the method.

  The above object of the present invention is achieved by the following means.

  1. A metal oxide semiconductor is produced by forming a thin film containing a precursor of a metal oxide semiconductor and then irradiating the thin film with light in the presence of oxygen. Method.

  2. 2. The method for producing a metal oxide semiconductor according to 1 above, wherein the precursor of the metal oxide semiconductor contains any element of In, Zn, and Sn.

3. 3. The method for producing a metal oxide semiconductor according to 1 or 2, wherein the precursor of the metal oxide semiconductor comprises metal fine particles.
4). 3. The method for producing a metal oxide semiconductor according to 1 or 2 above, wherein the precursor of the metal oxide semiconductor comprises a metal salt, a metal halide compound, or an organometallic compound containing a metal atom.

  5. 5. The method for producing a metal oxide semiconductor according to any one of 1 to 4, wherein the light to be irradiated is ultraviolet light.

  6). 6. The method for producing a metal oxide semiconductor according to any one of 1 to 5, wherein a substrate temperature at the time of light irradiation is 50 ° C. to 250 ° C.

  7). 7. A thin film transistor using an oxide semiconductor thin film manufactured by the method for manufacturing a metal oxide semiconductor according to any one of 1 to 6 as an active layer.

  The TFT element is stabilized, and a TFT element with high mobility and low off current can be obtained. Moreover, it can manufacture by processes, such as printing and application | coating, and can bring about the improvement of production efficiency.

It is a figure which shows typically the process in which melt | fusion progresses. It is a schematic diagram which shows typically the formation process of an oxide semiconductor thin film. It is sectional drawing which shows some structural examples of a thin-film transistor. It is a schematic equivalent circuit diagram of an example of a thin-film transistor sheet. The schematic diagram of a thin-film transistor manufacturing process is shown.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Semiconductor layer 2 Source electrode 3 Drain electrode 4 Gate electrode 5 Insulating layer 20 Thin-film transistor sheet 21 Gate bus line 22 Source bus line 24 Thin-film transistor element 25 Storage capacitor 26 Output element 27 Vertical drive circuit 28 Horizontal drive circuit

  The best mode for carrying out the present invention will be described below, but the present invention is not limited thereto.

  In the present invention, the semiconductor is a metal oxide, and in the present invention, after a thin film containing a metal component of a metal oxide serving as a precursor of a metal oxide semiconductor is provided, the thin film is irradiated with light in the presence of oxygen. Is oxidized to obtain a metal oxide semiconductor thin film.

  As a metal material used as a precursor of the metal oxide semiconductor, copper, indium, tin, zinc, gallium, aluminum, or the like can be used. Among these, it is preferable to include any element of In, Zn, and Sn.

  In order to form a thin film containing a metal as a precursor of these metal oxide semiconductors, a known film formation method, vacuum deposition method, molecular beam epitaxial growth method, ion cluster beam method, low energy ion beam method, ion A plating method, a CVD method, a sputtering method, an atmospheric pressure plasma method, or the like can be used.

  In the present invention, a metal oxide semiconductor is manufactured by forming a thin film containing a metal to be a precursor of these metal oxide semiconductors and then irradiating the thin film with light in the presence of oxygen.

(Composition ratio of metal)
In the case where the precursor of the metal oxide semiconductor contains In, the composition ratio of the metal is Zn _y Sn _1-y (where y is a positive number from 0 to 1) when In is 1, and 0.2 to 5 is preferable, and more preferably 0.5 to 2. In addition, when In is 1, the composition ratio of Ga and Al is preferably 0 to 5, and more preferably 0.5 to 2.

  The thickness of the thin film containing the metal to be formed is preferably 1 to 200 nm, more preferably 5 to 100 nm.

  As a thin film containing a metal that becomes a precursor of these metal oxide semiconductors, metal fine particles are dispersed in water or a dispersion medium that is an arbitrary organic solvent using a dispersion stabilizer mainly composed of an organic material. It is preferable to use a dispersion of fine metal particles.

  As a method for producing such a dispersion of metal fine particles, metal ions are reduced in a liquid phase, such as a physical generation method such as gas evaporation method, sputtering method, and metal vapor synthesis method, colloid method, and coprecipitation method. Examples of the chemical production method for producing metal fine particles include those described in JP-A-11-76800, JP-A-11-80647, JP-A-11-319538, JP-A-2000-239853, and the like. The colloid method described in Japanese Patent Application Laid-Open No. 2001-254185, 2001-53028, 2001-35255, 2000-124157, 2000-123634, Japanese Patent No. 2561537, etc. It is a dispersion of fine metal particles produced by a gas evaporation method.

  The average particle diameter of the metal fine particles is preferably 1 to 300 nm, and can promote the fusion described later and facilitate the conversion to an amorphous oxide semiconductor when an oxidation treatment is performed.

As the metal composition ratio, when In is 1, Zn _y Sn _1-y (where y is a positive number of 0 to ₁ ) is preferably 0.2 to 5, more preferably 0.5 to 2. is there. In addition, when In is 1, the composition ratio of Ga and Al is preferably 0 to 5, and more preferably 0.5 to 2.

(Film formation method, patterning method)
As a method for forming a thin film containing metal fine particles formed from a metal fine particle dispersion, that is, spray coating method, spin coating method, blade coating method, dip coating method, casting method, roll coating method, bar coating method, die coating method, etc. And a method of applying a dispersion, a method of patterning by a printing method such as relief printing, intaglio printing, planographic printing, screen printing, and ink jet. The coating film may be patterned by photolithography, laser ablation, or the like. Conventionally known methods can be applied to the formation and patterning of a thin film containing metal fine particles.

  Further, a thin film is formed by dropping a dispersion of metal fine particles by, for example, ink jetting and volatilizing the dispersion medium. Further, by heating the thin film made of the metal fine particles, the fine particles can be fused to obtain a metal thin film.

  In addition, a dispersion of metal fine particles is dropped by, for example, ink jet and the dispersion medium is volatilized to form a thin film. Further, the thin film containing the metal fine particles can be heated before the thin film oxidation step to fuse the fine particles to obtain a metal thin film.

  The degree of fusion between the metal fine particles by the heat treatment can be arbitrarily adjusted, and the thin film can be oxidized from any fusion state.

  FIG. 1 schematically shows a process in which fusion of a thin film containing metal fine particles proceeds by heating, but the presence / absence and extent of fusion can be arbitrarily adjusted, and FIG. 1 (A), (B) , (C) can be oxidized from any state.

  In the case of metal fine particles having a particle size of 300 nm or less, the fusing temperature can be performed at a low temperature of 400 ° C. or less.

  From the viewpoint of dispersion stability, the metal fine particles are preferably dispersed in a dispersion medium using a dispersant, but the thin film containing the metal fine particles is formed, before the fusion, and before the oxidation step. For example, it is preferable to perform cleaning by a dry cleaning process such as oxygen plasma or UV ozone cleaning, and decompose and clean organic substances contained in the thin film such as a dispersant to exclude organic substances other than metal components. FIG. 2 schematically shows a process of forming an oxide semiconductor thin film by a thin film oxidation process by forming a metal thin film from the metal fine particles by dry-cleaning and heating the thin film containing the metal fine particles and heating it. .

  Moreover, as a thin film containing a metal that becomes a precursor of a metal oxide semiconductor, a thin film containing a metal atom-containing compound can be mentioned, and the metal atom-containing compound includes a metal salt containing a metal atom, a metal halide compound, An organometallic compound etc. can be mentioned.

  Metals of metal salts, halogen metal compounds, and organometallic compounds include Li, Be, B, Na, Mg, Al, Si, K, Ca, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu Zn, Ga, Ge, Rb, Sr, Y, Zr, Nb, Mo, Cd, In, Ir, Sn, Sb, Cs, Ba, La, Hf, Ta, W, Tl, Pb, Bi, Ce, Pr Nd, Pm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu and the like.

  Among these metal salts, it is preferable to contain any metal ion of indium, tin, and zinc, and they may be used in combination.

  Moreover, it is preferable that a gallium or aluminum is included as another metal.

  As metal salts, nitrates, acetates and the like can be suitably used, and as halogen metal compounds, chlorides, iodides, bromides and the like can be suitably used.

  Examples of the organometallic compound include those represented by the following general formula (I).

Formula (I) R ¹ _x MR ² _y R ³ _z
In the formula, M is a metal, R ¹ is an alkyl group, R ² is an alkoxy group, R ³ is a β-diketone complex group, a β-ketocarboxylic acid ester complex group, a β-ketocarboxylic acid complex group, and a ketooxy group (ketooxy complex group). X + y + z = m, x = 0 to m, or x = 0 to m−1, and y = 0 to m, z = 0. ~ M, each of which is 0 or a positive integer. Examples of the alkyl group for R ¹ include a methyl group, an ethyl group, a propyl group, and a butyl group. Examples of the alkoxy group for R ² include a methoxy group, an ethoxy group, a propoxy group, a butoxy group, and a 3,3,3-trifluoropropoxy group. Moreover, the hydrogen atom of the alkyl group may be substituted with a fluorine atom. Examples of the group selected from the β-diketone complex group, the β-ketocarboxylic acid ester complex group, the β-ketocarboxylic acid complex group, and the ketooxy group (ketooxy complex group) of R ³ include, for example, 2,4 -Pentanedione (also called acetylacetone or acetoacetone), 1,1,1,5,5,5-hexamethyl-2,4-pentanedione, 2,2,6,6-tetramethyl-3,5-heptanedione , 1,1,1-trifluoro-2,4-pentanedione and the like, as the β-ketocarboxylic acid ester complex group, for example, acetoacetic acid methyl ester, acetoacetic acid ethyl ester, acetoacetic acid propyl ester, trimethylacetate Examples thereof include ethyl acetate, methyl trifluoroacetoacetate and the like. As β-ketocarboxylic acid, For example, acetoacetic acid, trimethylacetoacetic acid and the like can be mentioned, and examples of ketooxy include acetooxy group (or acetoxy group), propionyloxy group, butyryloxy group, acryloyloxy group, methacryloyloxy group and the like. These groups preferably have 18 or less carbon atoms. Further, it may be linear or branched, or a hydrogen atom may be a fluorine atom. Among organometallic compounds, those having at least one oxygen in the molecule are preferable. As such, an organometallic compound containing at least one alkoxy group of R ² , a β-diketone complex group, a β-ketocarboxylic acid ester complex group, a β-ketocarboxylic acid complex group and a ketooxy group (ketooxy group) of R ³ Most preferred are metal compounds having at least one group selected from (complex groups). Among the metal salts, nitrate is preferable. Nitrate is easily available as a high-purity product and has high solubility in water, which is preferable as a medium for use. Examples of nitrates include indium nitrate, tin nitrate, zinc nitrate, and gallium nitrate.

  Of the above metal oxide semiconductor precursors, metal nitrates, metal halides, and alkoxides are preferable. Specific examples include indium nitrate, zinc nitrate, gallium nitrate, tin nitrate, aluminum nitrate, indium chloride, zinc chloride, tin chloride (divalent), tin chloride (tetravalent), gallium chloride, aluminum chloride, tri-i-. Examples include propoxyindium, diethoxyzinc, bis (dipivaloylmethanato) zinc, tetraethoxytin, tetra-i-propoxytin, tri-i-propoxygallium, and tri-i-propoxyaluminum.

(Metal oxide semiconductor precursor thin film deposition method, patterning method)
In order to form a thin film containing a metal as a precursor of these metal oxide semiconductors, a known film formation method, vacuum deposition method, molecular beam epitaxial growth method, ion cluster beam method, low energy ion beam method, ion A plating method, a CVD method, a sputtering method, an atmospheric pressure plasma method, and the like can be used. In the present invention, a solution in which a metal salt, a halide, an organometallic compound, or the like is dissolved in an appropriate solvent is used on the substrate. The continuous coating is preferable because it can greatly improve the productivity. Also from this point, it is more preferable from the viewpoint of solubility to use a chloride, nitrate, acetate, metal alkoxide or the like as the metal compound.

  The solvent is not particularly limited as long as it dissolves the metal compound to be used in addition to water, but water, alcohols such as ethanol, propanol, and ethylene glycol, ethers such as tetrahydrofuran and dioxane, acetic acid, and the like. Esters such as methyl and ethyl acetate, ketones such as acetone, methyl ethyl ketone and cyclohexanone, glycol ethers such as diethylene glycol monomethyl ether, acetonitrile, and aromatic hydrocarbon solvents such as xylene and toluene, o-dichlorobenzene Aromatic solvents such as nitrobenzene and m-cresol, aliphatic hydrocarbon solvents such as hexane, cyclohexane and tridecane, α-terpineol, and halogenated alkyl solvents such as chloroform and 1,2-dichloroethane , N- methylpyrrolidone, can be preferably used carbon disulfide and the like.

  When a metal halide and / or metal alkoxide is used, a solvent having a relatively high polarity is preferable. Among them, water having a boiling point of 100 ° C. or less, alcohols such as ethanol and propanol, acetonitrile, or a mixture thereof is dried. Since the temperature can be lowered, it is possible to coat the resin substrate, which is more preferable.

  Addition of metal alkoxide and various chelating ligands such as alkanolamines, α-hydroxy ketones, β-diketones, etc. to the solvent stabilizes the metal alkoxide and the solubility of the carboxylate. It is preferable to add it in a range that does not cause adverse effects.

  Examples of methods for forming a thin film by applying a liquid containing a semiconductor precursor material onto a substrate include spin coating, spray coating, blade coating, dip coating, casting, bar coating, and die coating. Examples of the coating method include a method by coating in a broad sense, such as a printing method such as a relief printing plate, an intaglio plate, a planographic printing method, a screen printing method, and an ink jet printing method. Alternatively, the coating film may be patterned by photolithography, laser ablation, or the like. Among these, the ink jet method, spray coating method, etc. which can apply | coat a thin film are preferable.

  In the case of film formation, a thin film of a metal oxide precursor is formed by volatilizing the solvent at about 150 ° C. after coating. In addition, when dropping the solution, it is preferable that the substrate itself is heated to about 150 ° C. because two processes of coating and drying can be performed simultaneously.

(Composition ratio of metal)
As a preferred metal composition ratio, when In is 1, Zn _y Sn _1-y (where y is a positive number from 0 to ₁ ) is 0.2 to 5, preferably 0.5. Let ~ 2. Further, when In is 1, the composition ratio of Ga and Al is preferably 0 to 5, and more preferably 0.5 to 2.

  Moreover, the film thickness of the thin film containing the metal used as a precursor is 1-200 nm, More preferably, it is 5-100 nm.

(Thin film oxidation process)
A UV ozone method is used as a method for oxidizing a thin film formed from a metal material which is a precursor of a metal oxide semiconductor. The UV ozone method is a method of irradiating ultraviolet light in the presence of oxygen to advance an oxidation reaction. It is preferable to irradiate so-called vacuum ultraviolet light having a wavelength of ultraviolet light of 100 nm to 450 nm, particularly preferably about 150 to 300 nm. As the light source, a low-pressure mercury lamp, a deuterium lamp, a xenon excimer lamp, a metal halide lamp, an excimer laser, or the like can be used. It is preferable to heat the substrate in the range of 50 ° C to 400 ° C, preferably 100 ° C to 250 ° C.

(Amorphous oxide)
The electron carrier concentration of an amorphous oxide, which is a metal oxide according to the present invention, formed from a metal material that is a precursor of a metal oxide semiconductor only needs to be less than 10 ¹⁸ / cm ³ .

The electron carrier concentration is a value when measured at room temperature. The room temperature is, for example, 25 ° C., specifically, a certain temperature appropriately selected from a range of about 0 ° C. to 40 ° C. Note that the electron carrier concentration of the amorphous oxide according to the present invention does not need to satisfy less than 10 ¹⁸ / cm ³ in the entire range of 0 ° C. to 40 ° C. For example, a carrier electron density of less than 10 ¹⁸ / cm ³ may be realized at 25 ° C. Further, when the electron carrier concentration is further reduced to 10 ¹⁷ / cm ³ or less, more preferably 10 ¹⁶ / cm ³ or less, a normally-off TFT can be obtained with a high yield.

  The electron carrier concentration can be measured by Hall effect measurement.

  The film thickness of the semiconductor that is a metal oxide is not particularly limited, but the characteristics of the obtained transistor are often greatly influenced by the film thickness of the semiconductor film, and the film thickness varies depending on the semiconductor. Generally, 1 μm or less, particularly 10 to 300 nm is preferable.

In the present invention, the material, composition ratio, production conditions, and the like are controlled so that, for example, the electron carrier concentration is 10 ¹² / cm ³ or more and less than 10 ¹⁸ / cm ³ . More preferably, it is in the range of 10 ¹³ / cm ³ or more and 10 ¹⁷ / cm ³ or less, and more preferably 10 ¹⁵ / cm ³ or more and 10 ¹⁶ / cm ³ or less.

  The oxide semiconductor thin film according to the present invention can be used for a field effect thin film transistor (TFT).

(electrode)
In the present invention, the conductive material used for the electrodes such as the source electrode, the drain electrode, and the gate electrode constituting the TFT element is not particularly limited as long as it has conductivity at a practical level as an electrode. , Gold, silver, nickel, chromium, copper, iron, tin, antimony lead, tantalum, indium, palladium, tellurium, rhenium, iridium, aluminum, ruthenium, germanium, molybdenum, tungsten, tin / antimony oxide, indium / tin oxide ( ITO), fluorine-doped zinc oxide, zinc, carbon, graphite, glassy carbon, silver paste and carbon paste, lithium, beryllium, sodium, magnesium, potassium, calcium, scandium, titanium, manganese, zirconium, gallium, niobium, sodium Sodium - potassium alloy, magnesium, lithium, aluminum, magnesium / copper mixture, a magnesium / silver mixture, a magnesium / aluminum mixture, magnesium / indium mixture, aluminum / aluminum oxide mixture, a lithium / aluminum mixture, or the like is used.

  Moreover, as a conductive material, a conductive polymer, metal fine particles, or the like can be suitably used. As the dispersion containing metal fine particles, for example, a known conductive paste may be used, but a dispersion containing metal fine particles having a particle diameter of 1 nm to 50 nm, preferably 1 nm to 10 nm is preferable. In order to form an electrode from metal fine particles, the above-described method can be used in the same manner, and the metal described above can be used as the material of the metal fine particles.

(Method for forming electrodes, etc.)
As a method for forming an electrode, a method for forming an electrode using a known photolithographic method or a lift-off method from a conductive thin film formed by using a method such as vapor deposition or sputtering using the above as a raw material, or a metal foil such as aluminum or copper There is a method in which a resist is formed and etched by thermal transfer, ink jet or the like. Alternatively, a conductive polymer solution or dispersion, a dispersion containing metal fine particles, or the like may be directly patterned by an ink jet method, or may be formed from a coating film by lithography or laser ablation. Further, a method of patterning a conductive ink or conductive paste containing a conductive polymer or metal fine particles by a printing method such as relief printing, intaglio printing, planographic printing, or screen printing can also be used.

  As a method for forming an electrode such as a source, drain, or gate electrode, a gate, or a source bus line without patterning a metal thin film using a photosensitive resin such as etching or lift-off, an electroless plating method is used. Are known.

  Regarding the method for forming an electrode by an electroless plating method, as described in Japanese Patent Application Laid-Open No. 2004-158805, a liquid containing a plating catalyst that acts on a plating agent to cause electroless plating is applied to a portion where the electrode is provided. For example, after patterning by a printing method (including inkjet printing), a plating agent is brought into contact with a portion where an electrode is provided. If it does so, electroless plating will be performed to the said part by the contact of the said catalyst and a plating agent, and an electrode pattern will be formed.

  The application of the electroless plating catalyst and the plating agent may be reversed, and the pattern formation may be performed either. However, a method of forming a plating catalyst pattern and applying the plating agent to this is preferable.

  As the printing method, for example, screen printing, planographic printing, letterpress printing, intaglio printing, printing by ink jet printing, or the like is used.

(Element structure)
FIG. 3 is a diagram showing a typical element configuration of a thin film transistor element using an oxide semiconductor thin film according to the present invention.

  FIGS. 2A to 2F are cross-sectional views showing examples of the structure of a thin film transistor using a semiconductor thin film manufactured by the method for manufacturing an oxide semiconductor thin film according to the present invention. In FIG. 2, the semiconductor thin film is preferably configured such that a source electrode and a drain electrode are connected as a channel.

  In FIG. 5A, a source electrode 2 and a drain electrode 3 are formed on a support 6 with a metal foil or the like, and this is used as a base material (substrate). A field effect thin film transistor is formed by forming a semiconductor layer 1 made of a thin semiconductor film, forming an insulating layer 5 thereon, and further forming a gate electrode 4 thereon. FIG. 6B shows the semiconductor layer 1 formed between the electrodes in FIG. 6A so as to cover the entire surface of the electrode and the support using a coating method or the like. (C) shows that the semiconductor layer 1 is first formed on the support 6 using the method of the present invention, and then the source electrode 2, the drain electrode 3, the insulating layer 5, and the gate electrode 4 are formed.

  In FIG. 4D, after forming the gate electrode 4 on the support 6 with a metal foil or the like, the insulating layer 5 is formed, and the source electrode 2 and the drain electrode 3 are formed on the metal foil or the like thereon, A semiconductor layer 1 formed of the oxide semiconductor thin film of the present invention is formed between the electrodes. In addition, it is also possible to adopt a configuration as shown in FIGS.

  FIG. 4 is a schematic equivalent circuit diagram of an example of a thin film transistor sheet 20 in which a plurality of thin film transistor elements of the present invention are arranged.

  The thin film transistor sheet 20 has a large number of thin film transistor elements 24 arranged in a matrix. Reference numeral 21 denotes a gate bus line of the gate electrode of each thin film transistor element 24, and reference numeral 22 denotes a source bus line of the source electrode of each thin film transistor element 24. An output element 26 is connected to the drain electrode of each thin film transistor element 24. The output element 26 is, for example, a liquid crystal or an electrophoretic element, and constitutes a pixel in the display device. In the illustrated example, a liquid crystal is shown as an output element 26 by an equivalent circuit composed of a resistor and a capacitor. Reference numeral 25 denotes a storage capacitor, 27 denotes a vertical drive circuit, and 28 denotes a horizontal drive circuit.

  The method of the present invention can be used for producing such a thin film transistor sheet in which TFT elements are two-dimensionally arranged on a support.

(Gate insulation film)
Although various insulating films can be used as the gate insulating film of the thin film transistor of the present invention, an inorganic oxide film having a high relative dielectric constant is particularly preferable. Inorganic oxides include silicon oxide, aluminum oxide, tantalum oxide, titanium oxide, tin oxide, vanadium oxide, barium strontium titanate, barium zirconate titanate, lead zirconate titanate, lead lanthanum titanate, strontium titanate, Examples thereof include barium titanate, barium magnesium fluoride, bismuth titanate, strontium bismuth titanate, strontium bismuth tantalate, bismuth tantalate niobate, and yttrium trioxide. Of these, silicon oxide, aluminum oxide, tantalum oxide, and titanium oxide are preferable. Inorganic nitrides such as silicon nitride and aluminum nitride can also be suitably used.

  Examples of the method for forming the film include a vacuum process, a molecular beam epitaxial growth method, an ion cluster beam method, a low energy ion beam method, an ion plating method, a CVD method, a sputtering method, an atmospheric pressure plasma method and the like, spraying Wet processes such as coating methods, spin coating methods, blade coating methods, dip coating methods, casting methods, roll coating methods, bar coating methods, die coating methods, and other wet processes such as printing and ink jet patterning methods, etc. Can be used depending on the material.

  The wet process is a method of applying and drying a liquid in which fine particles of inorganic oxide are dispersed in an arbitrary organic solvent or water using a dispersion aid such as a surfactant as required, or an oxide precursor, for example, A so-called sol-gel method in which a solution of an alkoxide body is applied and dried is used.

  Of these, the atmospheric pressure plasma method described above is preferable.

  It is also preferable that the gate insulating film (layer) is composed of an anodized film or the anodized film and an insulating film. The anodized film is preferably sealed. The anodized film is formed by anodizing a metal that can be anodized by a known method.

  Examples of the metal that can be anodized include aluminum and tantalum, and the anodizing method is not particularly limited, and a known method can be used.

  Examples of organic compound films include polyimides, polyamides, polyesters, polyacrylates, photo-radical polymerization-type, photo-cation polymerization-type photo-curing resins, copolymers containing acrylonitrile components, polyvinyl phenol, polyvinyl alcohol, novolac resins, etc. Can also be used.

  An inorganic oxide film and an organic oxide film can be laminated and used together. The thickness of these insulating films is generally 50 nm to 3 μm, preferably 100 nm to 1 μm.

(substrate)
Various materials can be used as the support material constituting the substrate. For example, ceramic substrates such as glass, quartz, aluminum oxide, sapphire, silicon nitride, silicon carbide, silicon, germanium, gallium arsenide, gallium phosphide. In addition, a semiconductor substrate such as gallium nitrogen, paper, and non-woven fabric can be used. In the present invention, the support is preferably made of a resin, for example, a plastic film sheet can be used. Examples of plastic films include polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polyethersulfone (PES), polyetherimide, polyetheretherketone, polyphenylene sulfide, polyarylate, polyimide, polycarbonate (PC), and cellulose. Examples include films made of triacetate (TAC), cellulose acetate propionate (CAP), and the like. By using a plastic film, the weight can be reduced as compared with the case of using a glass substrate, the portability can be improved, and the resistance to impact can be improved.

  An element protective layer can be provided on the thin film transistor element of the present invention. Examples of the protective layer include the inorganic oxides and inorganic nitrides described above, and the protective layer is preferably formed by the atmospheric pressure plasma method described above.

  Hereinafter, an example of a thin film transistor using an oxide semiconductor thin film obtained by irradiating the thin film containing the precursor of the metal oxide semiconductor according to the present invention with light in the presence of oxygen will be described.

  This will be described with reference to the schematic view of the thin film transistor manufacturing process of FIG.

Example 1
A polyethersulfone resin film (200 μm) was used as the resin support 11, and first, this was subjected to corona discharge treatment under the condition of 50 W / m ² / min. Thereafter, an undercoat layer was formed in order to improve adhesion as follows.

(Formation of undercoat layer)
A coating solution having the following composition was applied to a dry film thickness of 2 μm, dried at 90 ° C. for 5 minutes, and then cured for 4 seconds from a distance of 10 cm under a 60 W / cm high-pressure mercury lamp.

Dipentaerythritol hexaacrylate monomer 60g
Dipentaerythritol hexaacrylate dimer 20g
Dipentaerythritol hexaacrylate trimer or higher component 20g
Diethoxybenzophenone UV initiator 2g
Silicone surfactant 1g
75g of methyl ethyl ketone
Methyl propylene glycol 75g
Further, a 50 nm thick silicon oxide film was provided on the layer by continuous atmospheric pressure plasma treatment under the following conditions, and these layers were used as the undercoat layer 18 (FIG. 5 (1)).

(Used gas)
Inert gas: helium 98.25% by volume
Reactive gas: oxygen gas 1.5 volume%
Reactive gas: Tetraethoxysilane vapor (bubbled with helium gas) 0.25% by volume
(Discharge conditions)
Discharge output: 10W / cm2
(Electrode condition)
The electrode is coated with 1 mm of alumina by ceramic spraying on a stainless steel jacket roll base material having cooling means with cooling water, and then a solution obtained by diluting tetramethoxysilane with ethyl acetate is applied and dried, and then sealed by ultraviolet irradiation. This is a roll electrode having a dielectric (relative permittivity of 10) that has been subjected to hole treatment and has a smooth surface and an Rmax of 5 μm, and is grounded. On the other hand, as the application electrode, a hollow rectangular stainless steel pipe was coated with the same dielectric as described above under the same conditions.

  Next, a gate electrode is formed. An aluminum film having a thickness of 300 nm was formed on one surface by sputtering, and then etched by photolithography to form the gate electrode 12 (FIG. 5 (2)).

(Anodized film forming process)
After the gate electrode 12 is formed, the substrate is thoroughly cleaned, and the thickness of the anodic oxide film is 120 nm using a direct current supplied from a 30 V constant voltage power source in a 30% by mass aqueous ammonium phosphate solution for 2 minutes. Anodization was performed (not shown in the figure).

  Next, at a film temperature of 200 ° C., a silicon oxide film having a thickness of 30 nm is provided by the atmospheric pressure plasma method described above, and the above-described anodized aluminum layer is combined to form a gate insulating film 13 having a thickness of 150 nm (FIG. 5 (3)).

  Next, a dispersion liquid (produced by the method described in Japanese Patent No. 2561537) in which fine particles having an average particle diameter of 8 nm made of an alloy of Sn and Zn with a composition ratio of 1: 1 are dispersed in toluene is used by using an inkjet apparatus. Then, it was discharged onto the gate insulating film on which the gate electrode was arranged, and the dispersion medium was cast to form a thin film containing metal fine particles (FIG. 5 (4)). The average film thickness was 30 nm. Further, dry cleaning was performed by irradiating a 50 W low-pressure mercury lamp in the atmosphere at a distance of 30 mm from the film surface for 2 minutes. Further, using the same apparatus, the substrate was irradiated with vacuum ultraviolet light in an atmosphere having a partial pressure of oxygen and nitrogen of 1: 1 and a pressure of 50,000 Pa, and an oxidation treatment was performed at a resin support (film) temperature of 200 ° C. As a result, the alloy thin film turned transparent and was converted to a metal oxide thin film having a thickness of about 60 nm.

  Next, gold was deposited using a mask to form the source electrode 15 and the drain electrode 16 (FIG. 5 (5)). Each size is 10 μm wide, 50 μm long (channel width) and 50 nm thick, and the distance (channel length) between the source electrode 15 and the drain electrode 16 is 15 μm.

The thin film transistor manufactured by the above method was driven well and showed n-type enhancement operation. An increase in drain current (transfer characteristics) was observed when the drain bias was 10 V and the gate bias was swept from -10 V to +20 V. The mobility estimated from the saturation region was 12 cm ² / Vs, and the on / off ratio was 5 digits.

Example 2
As in Example 1, a polyethersulfone resin film (200 μm) was formed on the resin support 11 up to the gate electrode and further to the gate insulating film 13 (FIG. 5 (3)).
Next, a 10% by mass aqueous solution in which indium nitrate and zinc nitrate were mixed at a metal ratio of 1: 1 (molar ratio) was applied onto the gate insulating film as an ink by ink-jet coating on the channel forming portion, and similarly at 150 ° C. The semiconductor precursor material thin film 1 'was formed by treatment for 10 minutes and drying (FIG. 5 (4)). The average film thickness was 30 nm.

  Next, using a low-pressure mercury lamp of 50 W in the atmosphere, irradiation with vacuum ultraviolet light is performed in an atmosphere where the partial pressure of oxygen and nitrogen is 1: 1 and the pressure is 50,000 Pa, and the resin support (film) temperature is 200 ° C. Oxidation treatment was applied. As a result, the precursor material thin film made of the metal salt was converted into a metal oxide thin film having a thickness of about 60 nm.

  Next, gold was deposited using a mask in the same manner as in Example 1 to form the source electrode 15 and the drain electrode 16.

The manufactured thin film transistor was driven well and showed n-type enhancement operation. An increase in drain current (transfer characteristics) was observed when the drain bias was 10 V and the gate bias was swept from -10 V to +20 V. The mobility estimated from the saturation region was 12 cm ² / Vs, and the on / off ratio was 5 digits.

Claims (7)

A metal oxide semiconductor is produced by forming a thin film containing a precursor of a metal oxide semiconductor and then irradiating the thin film with light in the presence of oxygen. Method. 2. The method for producing a metal oxide semiconductor according to claim 1, wherein the precursor of the metal oxide semiconductor contains any element of In, Zn, and Sn. The method for producing a metal oxide semiconductor according to claim 1 or 2, wherein the precursor of the metal oxide semiconductor comprises metal fine particles. The metal oxide semiconductor precursor according to claim 1 or 2, wherein the metal oxide semiconductor precursor comprises a metal salt, metal halide compound, or organometallic compound containing a metal atom. Production method. The method for producing a metal oxide semiconductor according to any one of claims 1 to 4, wherein the irradiated light is ultraviolet light. The method for producing a metal oxide semiconductor according to any one of claims 1 to 5, wherein the substrate temperature during light irradiation is 50 ° C to 250 ° C. A thin film transistor using an oxide semiconductor thin film produced by the method for producing a metal oxide semiconductor according to any one of claims 1 to 6 as an active layer.