JPWO2009031381A1 - Method for producing metal oxide semiconductor, and thin film transistor obtained by the method - Google Patents

Abstract

The present invention improves variations in off current, etc., improves mobility, stabilizes TFT elements, and enables continuous formation on a resin substrate by a method such as coating and printing. A novel metal oxide semiconductor manufacturing method capable of improving production efficiency and flexibility, and a thin film transistor using the same. In the method for producing a metal oxide semiconductor according to the present invention, after a thin film containing a precursor of a metal oxide semiconductor is formed on a substrate, the thin film is irradiated with an electromagnetic wave in the presence of oxygen, thereby oxidizing the metal. It is characterized by manufacturing a physical semiconductor.

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.

  In addition, it is also known that an amorphous oxide is formed by decomposing and oxidizing (heating, decomposition reaction) an organic metal (for example, Patent Documents 2 and 3).

  Furthermore, methods for forming a semiconductor active layer by thermally converting a metal chloride coating film have been reported (for example, Non-Patent Documents 1 and 2 and Patent Document 4).

These use thermal oxidation or plasma oxidation for the oxidation of the precursor of the metal oxide semiconductor. However, when a normal thermal oxidation method is used, processing is performed in a very high temperature range of 300 ° C. or higher, so that energy efficiency is low, and a relatively long processing time is required, and the substrate temperature during processing Since the temperature rises to the same temperature as the processing temperature, it is difficult to apply it to a resin substrate that is light and flexible. 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 JP 2005-223231 A US Patent Application Publication No. 2007/0184576 Electrochemical and Solid-State Letters, 10 (5) H135-H138 (2007) Advanced Materials 2007, 19, 183-187

  An object of the present invention is to improve variation in off current and the like, improve mobility, stabilize a TFT element, and further enable formation by a method such as continuous application and printing on a resin substrate. Accordingly, it is an object of the present invention to provide a new metal oxide semiconductor manufacturing method capable of improving production efficiency and flexibility, and a thin film transistor using the same.

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

  1. A metal oxide semiconductor characterized by producing a metal oxide semiconductor by forming a thin film containing a metal oxide semiconductor precursor on a substrate and then irradiating the thin film with electromagnetic waves in the presence of oxygen. A method for manufacturing a semiconductor.

  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 as described in 1 or 2 above, wherein the precursor of the metal oxide semiconductor contains Ga or Al.

  4). 4. The method for producing a metal oxide semiconductor according to any one of 1 to 3, wherein the precursor of the metal oxide semiconductor is selected from any of a metal salt, a metal halide, and an organometallic compound.

  5. 5. The method for producing a metal oxide semiconductor according to any one of 1 to 4, wherein the precursor of the metal oxide semiconductor is a metal salt, and is selected from nitrate or acetate.

  6). 6. The method for producing a metal oxide semiconductor according to any one of 1 to 5, wherein the electromagnetic wave to be irradiated is a microwave (frequency: 0.3 to 30 GHz).

  7). 7. The method for producing a metal oxide semiconductor according to any one of 1 to 6, wherein a thin film containing a metal oxide semiconductor precursor is formed on a substrate by coating.

  8). Any one of 1 to 7 above, wherein the irradiation output and the irradiation time of the electromagnetic wave are adjusted so that the substrate temperature becomes 50 ° C. to 200 ° C. and the coating film surface temperature becomes 200 to 600 ° C. when the electromagnetic wave is irradiated. A method for producing a metal oxide semiconductor according to claim 1.

  9. 9. 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 8 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 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 10 Thin-film transistor sheet 11 Gate bus line 12 Source bus line 14 Thin-film transistor element 15 Storage capacitor 16 Output element 17 Vertical drive circuit 18 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. 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 electromagnetic waves in the presence of oxygen. Thus, a metal oxide semiconductor thin film is obtained by oxidation.

  In the present invention, examples of the metal atom-containing compound as a precursor of the metal oxide semiconductor include metal salts, metal halides, and organometallic compounds containing metal atoms.

  Metals such as metal salts, metal oxides, organometallic compounds, metal halides, and metal hydrides include Li, Be, B, Na, Mg, Al, Si, K, Ca, Sc, Ti, V, Cr, and 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 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 halides, 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, and examples of β-ketocarboxylic acid include 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.

  A metal atom-containing compound is preferable as the thin film forming material that is a precursor of the metal oxide semiconductor of the present invention. Examples of the metal atom-containing compound include metal salts, organometallic compounds, metal halides, metal hydrogen compounds, and the like. Particularly preferred organometallic compounds include those containing the metal atom represented by the general formula (I). Compounds.

  Of the above precursors, metal nitrates, 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.

(Precursor thin film formation 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. Productivity can be greatly improved by coating continuously. As the metal compound, it is more preferable from the viewpoint of solubility to use chloride, nitrate, acetate, metal alkoxide and the like.

  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, and in particular, 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 ligands such as alkanolamines, α-hydroxy ketones, β-diketones and other chelating ligands in 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.

  In the present invention, as a method of forming a thin film containing a metal oxide semiconductor precursor by applying a liquid containing a thin film forming material on a substrate, a spray coating method, a spin coating method, a blade coating method, Dip coating method, casting method, roll coating method, bar coating method, die coating method, mist method, etc., printing method such as relief printing, intaglio printing, lithographic printing, screen printing, ink jet, etc. Moreover, the method of patterning by this is mentioned. 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.

  For example, when forming a film using an ink jet method, the substrate is kept at about 50 to 200 ° C., and the metal compound solution is dropped, whereby the solvent is volatilized and a thin film of a metal oxide precursor is formed. If the substrate temperature is too low, the droplets applied to the substrate are likely to combine with each other, making it difficult to draw a fine pattern.If the substrate temperature is too high, the solvent volatilizes before the droplets land on the substrate. Since a large amount of solution is required, it is preferable to hold at about 50 to 200 ° C.

(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 to 2. . Furthermore, when In is set to 1, the composition ratio of Ga is 0.2 to 5, 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.

(Microwave irradiation)
In the present invention, microwave irradiation in the presence of oxygen is used as a method for oxidizing a thin film formed from a metal material which is a precursor of a metal oxide semiconductor.

  That is, after forming a thin film containing a metal as a precursor of these metal oxide semiconductors, the thin film is irradiated with electromagnetic waves, particularly microwaves (frequency 0.3 to 30 GHz) in the presence of oxygen. The metal oxide semiconductor is manufactured by heating the thin film itself from the inside and consequently selectively heating only the thin film portion.

  In the present invention, by irradiating the formed thin film containing a metal which is a precursor of these metal oxide semiconductors with microwaves, electrons in the metal oxide precursor vibrate and Joule heat is generated to generate the thin film. Is heated from the inside and uniformly. On the other hand, when glass or resin is used as the substrate, since there is almost no absorption in the microwave region, the substrate itself hardly generates heat and only the thin film portion can be selectively heated.

  Further, as is generally the case with microwave heating such as ceramics, microwave absorption concentrates on strongly absorbing substances and can be heated to 500-600 ° C. in a very short time. When this method is used in the configuration of the invention, the base material itself is hardly affected by heating by electromagnetic waves, and only the precursor thin film can be heated up to a temperature at which an oxidation reaction occurs in a short time, and the metal oxide precursor Can be converted into a metal oxide. Further, the heating temperature and the heating time can be controlled by the output of the microwave to be irradiated and the irradiation time, and can be adjusted according to the precursor material and the substrate material.

  In addition, a thin film containing a metal oxide precursor is cleaned by a dry cleaning process such as oxygen plasma or UV ozone cleaning after formation and before microwave irradiation, and is present in the thin film and on the surface of the thin film. It is also preferable to decompose and wash the organic matter to be removed to exclude organic matters other than the metal component.

  In general, the microwave refers to an electromagnetic wave having a frequency of 0.3 to 30 GHz, and is used in 0.8 MHz and 1.5 GHz band, 2 GHz band, amateur radio, aircraft radar, etc. used in mobile communication. .2 GHz band, microwave oven, local radio, 2.4 GHz band used for VICS, 3 GHz band used for ship radar, etc., and 5.6 GHz used for other ETC communications are all electromagnetic waves in the microwave category. is there.

  In the field of ceramics, it is already known to use such electromagnetic waves for sintering. When a material containing magnetism is irradiated with an electromagnetic wave, heat can be generated in accordance with the size of the loss portion of the complex permeability of the substance, and the temperature can be increased uniformly and in a short time. On the other hand, it is well known that when a metal is irradiated with microwaves, free electrons start to move at a high frequency, so that arc discharge occurs and heating cannot be performed.

  Based on such a technical background, the inventors have intensively studied and found that the precursor of the metal oxide semiconductor of the present invention can be selectively heated uniformly to a high temperature in a short time like ceramics. I found it. Unlike the field of ceramics, since the material of the present invention has almost no magnetism, the loss component related to electron and / or dipole motion such as Joule loss and / or dielectric loss is the main cause of heat generation. It is conceivable that the reason why such a phenomenon occurs in a thin film that has only been coated / dried with a metal ion-containing solution is not clear.

  That is, the method of irradiating the thin film containing the metal oxide precursor of the present invention with microwaves in the presence of oxygen is a method in which the oxidation reaction is selectively advanced in a short time. However, heat is transferred to the base material due to heat conduction, so in the case of a base material with low heat resistance such as a resin substrate, the substrate can be controlled by controlling the microwave output, irradiation time, and the number of times of irradiation. It is preferable to perform the treatment so that the temperature is 50 to 200 ° C. and the surface temperature of the thin film containing the precursor is 200 to 600 ° C. The surface temperature of the thin film, the temperature of the substrate, etc. can be measured with a surface thermometer using a thermocouple.

(Amorphous oxide)
As the metal oxide semiconductor to be formed, any state of single crystal, polycrystal, and amorphous can be used, but an amorphous thin film is preferably used.

The electron carrier concentration of an amorphous oxide, which is a metal oxide according to the present invention, formed from a metal compound 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 precursor material, composition ratio, production conditions, etc. 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 metal oxide semiconductor thin film according to the present invention can be used for a field effect thin film transistor (TFT).

  Hereinafter, each element constituting the thin film transistor will be described.

(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 of 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, there is a method by an electroless plating method. Are known.

  Regarding the method of forming an electrode by electroless plating, as described in Japanese Patent Application Laid-Open No. 2004-158805, a liquid containing a plating catalyst that causes electroless plating by acting with a plating agent on a portion where an electrode is provided After patterning, for example, 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. 1 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.

  FIG. 1A to FIG. 1F are cross-sectional views showing several structural examples 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. 1, 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. 2B shows the semiconductor layer 1 formed between the electrodes in FIG. 1A 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 on the insulating layer 5. 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. In the present invention, for the purpose of making it difficult to transmit thermal damage to the base material, an insulating film is formed between the base material and the semiconductor layer. For example, the structure shown in FIGS. preferable.

  FIG. 2 is a schematic equivalent circuit diagram of an example of a thin film transistor sheet 10 in which a plurality of thin film transistor elements of the present invention are arranged.

  The thin film transistor sheet 10 has a large number of thin film transistor elements 14 arranged in a matrix. Reference numeral 11 denotes a gate bus line of the gate electrode of each thin film transistor element 14, and reference numeral 12 denotes a source bus line of the source electrode of each thin film transistor element 14. An output element 16 is connected to the drain electrode of each thin film transistor element 14, and the output element 16 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 16 by an equivalent circuit composed of a resistor and a capacitor. 15 is a storage capacitor, 17 is a vertical drive circuit, and 18 is a horizontal drive circuit.

  The method of the present invention can be used to produce 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 it is preferable to form the protective layer by the atmospheric pressure plasma method described above.

  Hereinafter, specific examples of an oxide semiconductor thin film obtained by irradiating an electromagnetic wave in the presence of oxygen on a thin film containing a metal oxide semiconductor precursor according to the present invention, and a thin film transistor using the oxide semiconductor thin film will be described. explain.

Example 1
This will be described with reference to the schematic view of the thin film transistor manufacturing process of FIG.

A polyethersulfone resin film (200 μm) was used as the resin support 6, and first, a corona discharge treatment was performed thereon 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 silicon oxide film having a thickness of 50 nm was formed on the layer by continuous atmospheric pressure plasma treatment under the following conditions, and these layers were used as the undercoat layer 8 (FIG. 3 (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)
High frequency power supply: 13.56 MHz
Discharge output: 10 W / cm ²
(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 a gate electrode 4 (FIG. 3 (2)).

(Anodized film forming process)
After forming the gate electrode 4, the substrate is thoroughly washed, and in an aqueous 30 mass% ammonium phosphate solution, using direct current supplied from a constant voltage power supply of 30 V for 2 minutes, until the thickness of the anodic oxide film reaches 120 nm 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 was provided by the atmospheric pressure plasma method described above, and the above-described anodized aluminum layer was combined to form a gate insulating film 5 having a thickness of 150 nm (FIG. 3 (3)).

Next, InCl ₃ , ZnCl ₂ , and GaCl ₃ (all manufactured by Aldrich; purity 99.999%) were mixed in acetonitrile at a solid concentration so that the composition ratio of In, Zn, and Ga was 1: 1: 1. After adding 20% by mass and stirring for 10 minutes at room temperature, ultrasonic dispersion was performed for 10 minutes to obtain a colorless and transparent solution. This solution is discharged onto a gate insulating film having a gate electrode controlled at 80 ° C. by a heater disposed on the back side of the substrate using an ink jet apparatus and cast to form a metal ion-containing thin film. Filmed. Further, a dehydration treatment was performed at 150 ° C. for 30 minutes to form a metal oxide semiconductor precursor thin film. The average film thickness of the thin film was 100 nm.

  Thereafter, 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. Thereafter, using a multi-mode type 2.45 GHz microwave irradiator (μ-reactor manufactured by Shikoku Keiki Kogyo Co., Ltd.), an output of 500 W under an atmospheric pressure condition in an atmosphere where the partial pressure of oxygen and nitrogen is 1: 1. And irradiated with microwaves. Microwave irradiation was performed for 3 cycles with 1 cycle being 90 sec. As a result, the metal oxide semiconductor precursor thin film turned transparent and converted to a metal oxide thin film with a thickness of about 120 nm, forming the semiconductor layer 1 (FIG. 3D). The flatness due to the deformation of the resin base material was not accompanied.

  Incidentally, the substrate temperature (measured from the back surface) and the surface temperature of the thin film were measured using a thermocouple surface thermometer, which were 150 ° C. and 400 ° C. at the maximum, respectively.

  Subsequently, gold was vapor-deposited using the mask, and the source electrode 2 and the drain electrode 3 were formed (FIG. 3 (5)). Each size was 10 μm wide, 50 μm long (channel width), and 50 nm thick, and the distance (channel length) between the source electrode 2 and the drain electrode 3 was 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 10 cm ² / Vs, and the on / off ratio was 5 digits.

Example 2
In the same manner as in Example 1, except that the gate insulating film 5 was formed, and then the thin film formation and microwave irradiation of the metal oxide semiconductor precursor thin film were changed as follows to produce a thin film transistor.

  That is, a 10% by mass aqueous solution in which indium nitrate, zinc nitrate, and gallium nitrate are mixed at a metal ratio of 1: 1: 1 (molar ratio) is used as ink, and ink is applied to the channel forming portion while maintaining the substrate temperature at 100 ° C. It was applied, treated at 150 ° C. for 10 minutes and dried to form a semiconductor precursor thin film.

  Then, using this substrate with a multimode type 2.45 GHz microwave irradiator (μ-reactor manufactured by Shikoku Keiki Kogyo Co., Ltd.), the microwave (2 .45 GHz). Only the semiconductor surface side is kept warm with a heat insulating material, and after heating up to 300 ° C. at 500 W output using a thermocouple surface thermometer, the surface temperature of the thin film is kept at 300 ° C. while PID controlling the microwave output. Microwave irradiation was performed. Thereby, the thin film of the precursor was converted into the semiconductor layer 1 (FIG. 3 (4)).

  Further, in the same manner as in Example 1, gold was deposited using a mask to form the source electrode 2 and the drain electrode 3 (FIG. 3 (5)), and a thin film transistor was manufactured.

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 20 cm ² / Vs, and the on / off ratio was 7 digits.

Comparative Example In the same manner as in Example 1, a metal oxide semiconductor precursor thin film was formed using InCl ₃ , ZnCl ₂ , and GaCl ₃ .

  Next, instead of performing microwave irradiation, heat treatment was performed at 300 ° C. for 30 minutes in an air atmosphere.

  Similarly, a source electrode and a drain electrode were formed by gold vapor deposition to produce a thin film transistor.

When the mobility of the thin film transistor manufactured by the above method was estimated, it was 1.0 cm ² / Vs and the on / off ratio was 5 digits.

Claims (9)

A metal oxide semiconductor characterized by producing a metal oxide semiconductor by forming a thin film containing a metal oxide semiconductor precursor on a substrate and then irradiating the thin film with electromagnetic waves in the presence of oxygen. A method for manufacturing a semiconductor. 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 contains Ga or Al. The metal oxide semiconductor precursor according to any one of claims 1 to 3, wherein the precursor of the metal oxide semiconductor is selected from a metal salt, a metal halide, and an organometallic compound. A method for manufacturing a semiconductor. The metal oxide semiconductor precursor according to any one of claims 1 to 4, wherein the precursor of the metal oxide semiconductor is a metal salt, and is selected from nitrates or acetates. Production method. The method for producing a metal oxide semiconductor according to any one of claims 1 to 5, wherein an electromagnetic wave to be irradiated is a microwave (frequency: 0.3 to 30 GHz). The method for producing a metal oxide semiconductor according to any one of claims 1 to 6, wherein a thin film containing a metal oxide semiconductor precursor is formed on a substrate by coating. 2. The electromagnetic wave irradiation output and irradiation time are adjusted so that the substrate temperature is 50 ° C. to 200 ° C. and the coating surface temperature is 200 to 600 ° C. when irradiated with electromagnetic waves. The manufacturing method of the metal oxide semiconductor of any one of -7. 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 8 as an active layer.