TW201616578A - Method for producing metal oxide semiconductor film and metal oxide semiconductor film, thin film transistor and electronic component - Google Patents

Abstract

Provided is a method for producing a metal oxide semiconductor film which can form an oxide semiconductor film which can be easily formed at a low temperature and at a high pressure and has high semiconductor characteristics, using an inexpensive material which does not contain indium as a rare metal. Metal oxide semiconductor film, thin film transistor, and electronic component. A method for producing a metal oxide semiconductor film according to the present invention includes a metal oxide semiconductor precursor film forming step of applying a solvent and a solution of zinc and tin as a metal component onto a substrate to form a metal oxide semiconductor precursor. a film; a conversion step of converting a metal oxide semiconductor precursor film into a metal oxide semiconductor film by performing ultraviolet irradiation in a state in which a metal oxide semiconductor precursor film is heated; and all of the metal oxide semiconductor precursor film More than 80% of the metal component is zinc and tin, and the composition ratio of zinc to tin is 0.7 ≦Sn/(Sn+Zn)≦0.9.

Description

Method for producing metal oxide semiconductor film and metal oxide semiconductor film, thin film transistor and electronic component

The present invention relates to a method for producing a metal oxide semiconductor film, a metal oxide semiconductor film, a thin film transistor, and an electronic device.

A metal oxide film which is an oxide semiconductor film or an oxide conductor film has been put into practical use in the production by a vacuum film formation method, and has been attracting attention. Further, in order to form a metal oxide semiconductor on a resin substrate having low heat resistance, it is required to form a metal oxide semiconductor film at a low temperature. For this reason, research and development have been actively carried out on the production of an oxide semiconductor film by a liquid phase process for the purpose of easily forming an oxide semiconductor film having high semiconductor characteristics at a low temperature and an atmospheric pressure. Recently, a method has been reported in which a thin film transistor (TFT) having high transfer characteristics is produced at a low temperature of 150 ° C or lower by applying a solution onto a substrate and using ultraviolet rays (refer to Patent Document 1).

Further, a method in which a solution containing a nitrate or the like is applied onto a substrate, and then heated at about 150 ° C to volatilize the solvent, thereby forming a film containing a precursor of the metal oxide semiconductor, and then, in the oxygen In the presence of ultraviolet light (Ultraviolet, UV), a metal oxide semiconductor is produced (see Patent Document 1).

In Non-Patent Document 1, it is reported that only high-transmission characteristics are included in the metal oxide semiconductor film, and in the Zn-Sn-O system containing no indium, the transistor operation cannot be confirmed. . Further, Patent Document 1 describes only a metal oxide semiconductor containing indium.

Indium is a rare metal with a limited production amount, and it is expected that shortage of supply in the future and soaring of raw material prices require a material that does not use indium as a material of a metal oxide semiconductor. Therefore, it has been studied to produce a metal oxide semiconductor containing no indium by a liquid phase process. For example, Non-Patent Document 2 has reported an attempt to apply an annealing treatment using ultraviolet rays in the production of a Zn-Sn-O thin film which is a metal oxide semiconductor containing no indium. [Prior Art Document] [Patent Literature]

[Patent Document 1] International Publication No. 2009/011224 [Non-Patent Document]

[Non-Patent Document 1] Nature, 489 (2012) 128. [Non-Patent Document 2] Electrochemical and Solid-State Letters, 15 (2012) H91.

[Problems to be solved by the invention]

However, in the method for producing a Zn—Sn—O-based thin film described in Non-Patent Document 2, in order to achieve a good transistor operation, after annealing treatment using ultraviolet irradiation, it is necessary to perform annealing treatment in vacuum. Therefore, there is a problem that the production cost increases.

SUMMARY OF THE INVENTION An object of the present invention is to solve the problems of the prior art, and an object of the invention is to provide an inexpensive semiconductor material which does not contain indium as a rare metal, and which can be formed at a low temperature and at a high pressure and which has a high semiconductor. A method of producing a metal oxide semiconductor film of a characteristic oxide semiconductor film, a metal oxide semiconductor film, a thin film transistor, and an electronic component. [Means for solving the problem]

In order to achieve the above object, the inventors of the present invention have conducted an effort to form a solution containing zinc and tin as a metal component on a substrate by a metal oxide semiconductor precursor film forming step. Forming a metal oxide semiconductor precursor film; and a conversion step of converting the metal oxide semiconductor precursor film into a metal oxide semiconductor film by performing ultraviolet irradiation while heating the metal oxide semiconductor precursor film; metal oxidation More than 80% of all metal components in the semiconductor precursor film are zinc and tin, and a composition ratio of zinc to tin is 0.7 ≦Sn/(Sn+Zn) ≦0.9, and an inexpensive material containing no indium can be used. The present invention has been completed by an oxide semiconductor film which can be easily formed at a low temperature and at a high pressure and has high semiconductor characteristics. That is, it was found that the object can be achieved by the following configuration.

[1] A method for producing a metal oxide semiconductor film, comprising: a metal oxide semiconductor precursor film forming step of applying a solvent and a solution of zinc and tin as a metal component onto a substrate to form a metal oxide a semiconductor precursor film; and a conversion step of converting a metal oxide semiconductor precursor film into a metal oxide semiconductor film by ultraviolet irradiation in a state in which a metal oxide semiconductor precursor film is heated; a metal oxide semiconductor precursor 80% or more of all the metal components in the film are zinc and tin, and the composition ratio of zinc to tin is 0.7 ≦Sn/(Sn+Zn)≦0.9. [2] The method for producing a metal oxide semiconductor film according to [1], wherein a composition ratio of indium in the metal oxide semiconductor precursor film is less than 5%. [3] The method for producing a metal oxide semiconductor film according to [1], wherein in the converting step, the temperature of the substrate during the ultraviolet irradiation is maintained at 250 ° C or lower. [4] The method for producing a metal oxide semiconductor film according to any one of [1] to [3] wherein, in the converting step, the ultraviolet ray having a wavelength of 300 nm or less is irradiated to the metal oxide semiconductor precursor film. The illuminance is 30 mW/cm ² or more. [5] The method for producing a metal oxide semiconductor film according to any one of [1] to [4] wherein the conversion step is carried out in an atmosphere containing 1% by volume or more of oxygen. [6] The method for producing a metal oxide semiconductor film according to any one of [1] to [5], wherein 95% or more of all metal components in the metal oxide semiconductor precursor film are zinc and tin. [7] The method for producing a metal oxide semiconductor film according to any one of [1] to [6] wherein the solution is obtained by dissolving a metal salt or a metal halide of zinc and tin in a solvent. [8] The method for producing a metal oxide semiconductor film according to any one of [1] to [7] wherein the solvent is methanol, methoxyethanol or water. [9] The method for producing a metal oxide semiconductor film according to any one of [1] to [8] wherein the concentration of the metal component in the solution is from 0.01 mol/L to 1.0 mol/L. [10] A metal oxide semiconductor film produced by the method for producing a metal oxide semiconductor film according to any one of [1] to [9]. [11] The metal oxide semiconductor film according to [10], wherein the carbon concentration in the film by secondary ion mass spectrometry is 1 × 10 ¹⁹ atoms / cm ³ or more and 1 × 10 ²⁰ atoms / cm ³ or less. . [12] The metal oxide semiconductor film according to [10] or [11], wherein a concentration of hydrogen in the film by secondary ion mass spectrometry is 2 × 10 ²² atoms / cm ³ or more and 4 × 10 ²² atoms /cm ³ or less. [13] A thin film transistor comprising: an active layer, a source electrode, a gate electrode, a gate insulating film, and the metal oxide semiconductor film according to any one of [10] to [12] Gate electrode. [14] An electronic component comprising the thin film transistor according to [13]. [Effects of the Invention]

As described below, according to the present invention, it is possible to provide an oxide semiconductor which can be easily formed at a low temperature and an atmospheric pressure and which has high semiconductor characteristics by using an inexpensive material which does not contain indium as a rare metal. A method of producing a metal oxide semiconductor film of a film, a metal oxide semiconductor film, a thin film transistor, and an electronic component.

Hereinafter, the present invention will be described in detail. The description of the constituent elements described below may be performed based on a representative embodiment of the present invention, but the present invention is not limited to such an embodiment. In the present specification, the numerical range expressed by "~" means a range including the numerical values described before and after "~" as the lower limit and the upper limit.

<Method for Producing Metal Oxide Semiconductor Film> The method for producing a metal oxide semiconductor film according to the present invention (hereinafter also referred to as "the method for producing the present invention") includes a step of forming a metal oxide semiconductor precursor film, and a solution containing a solvent and a tin component as a main component and containing at least zinc on a substrate to form a metal oxide semiconductor precursor film; and a conversion step by heating the metal oxide semiconductor precursor film In the state of ultraviolet irradiation, the metal oxide semiconductor precursor film is converted into a metal oxide semiconductor film; more than 80% of all metal components in the metal oxide semiconductor precursor film are zinc and tin, and the composition ratio of zinc to tin It is 0.7 ≦Sn / (Sn + Zn) ≦ 0.9.

According to the study by the inventors of the present invention, it has been found that the effect of improving the characteristics of the metal oxide semiconductor film by the ultraviolet irradiation treatment can be extremely improved by appropriately selecting the composition ratio of zinc to tin. Specifically, by appropriately selecting the composition ratio of zinc to tin, grain boundary formation and surface roughness accompanying crystallization of the metal oxide semiconductor film can be suppressed, and the carrier density can be controlled appropriately. In the range, the effect of improving the characteristics of the metal oxide semiconductor film by the ultraviolet irradiation treatment can be extremely improved. By using the production method of the present invention, a metal oxide semiconductor film having high electron transport characteristics can be obtained in a low-temperature process at 250 ° C or lower under atmospheric pressure using a material containing no indium as a rare metal.

Since the production method of the present invention can produce a metal oxide semiconductor film at atmospheric pressure, it is not necessary to use a large-sized vacuum apparatus. Further, since it can be produced in a low-temperature process of 250 ° C or lower, an inexpensive resin substrate having low heat resistance can be used. An inexpensive material that does not contain indium as a rare metal can be used. Therefore, the manufacturing cost of the metal oxide semiconductor film can be greatly reduced. Moreover, since it can be applied to an inexpensive resin substrate having low heat resistance, a flexible electronic component such as a flexible display can be produced at low cost.

Hereinafter, each step will be specifically described.

[Metal Oxide Semiconductor Precursor Film Forming Step] First, a solution (metal oxide semiconductor precursor solution) containing a solvent and a tin component as a metal component and containing at least zinc as a metal component is prepared and applied to a substrate to form a metal. Oxide semiconductor precursor film. Here, in the present invention, the metal oxide semiconductor precursor film formed in the metal oxide semiconductor precursor film forming step, 80% or more of all the metal components in the film are zinc and tin, and the composition of zinc and tin The ratio is 0.7 ≦ Sn / (Sn + Zn) ≦ 0.9.

(Substrate) The shape, structure, size, and the like of the substrate are not particularly limited, and may be appropriately selected depending on the purpose. The structure of the substrate may be a single layer structure or a laminate structure.

The substrate is not particularly limited, and for example, an inorganic substrate such as Yttria-Stabilized Zirconia (YSZ) or glass, a resin substrate, or a composite material thereof can be used. Among them, a resin substrate and a composite material thereof are preferred in terms of light weight and flexibility. Specifically, it can be used: polybutylene terephthalate, polyethylene terephthalate, polyethylene naphthalate, polybutylene naphthalate, polystyrene, polycarbonate, polyfluorene, poly Ether oxime, polyarylate, allyl diethylene carbonate, polyamidamine, polyimine, polyamidimide, polyether phthalimide, polybenzoxazole, polyphenylene sulfide, polycyclic ring A olefin resin such as an olefin, a norbornene resin or a polychlorotrifluoroethylene, a liquid crystal polymer, an acrylic resin, an epoxy resin, an anthrone resin, an ionic polymer resin, a cyanate resin, and a crosslinked fumaric acid Synthetic resin substrate of ester, cyclic polyolefin, aromatic ether, maleimide-olefin, cellulose, episulfide compound, composite plastic material with cerium oxide particles, metal nanoparticles, inorganic oxidation Composite plastic materials such as nano-particles, inorganic nitride nanoparticles, composite plastic materials with carbon fibers and carbon nanotubes, composite plastic materials with glass fragments, glass fibers, glass beads, clay minerals or mica-derived Crystalline structured particles of composite plastic material, a laminated plastic material having at least one bonding interface between the thin glass and the separate organic material, a barrier material having a barrier property by alternately laminating the inorganic layer and the organic layer, at least one bonding interface, a stainless steel substrate or A metal multilayer substrate in which a metal different from stainless steel is laminated, an aluminum substrate or an aluminum substrate with an oxide film which is improved in surface insulation by oxidation treatment (for example, anodizing treatment). Further, the resin substrate is excellent in heat resistance, dimensional stability, solvent resistance, electrical insulating properties, workability, low air permeability, or low moisture absorption property. The resin substrate may include a gas barrier layer for preventing moisture or oxygen from permeating, or an undercoat layer for improving the flatness of the resin substrate or the adhesion to the lower electrode.

Further, the thickness of the substrate in the present invention is not particularly limited, but is preferably 50 μm or more and 500 μm or less. When the thickness of the substrate is 50 μm or more, the flatness of the substrate itself is further improved. In addition, when the thickness of the substrate is 500 μm or less, the flexibility of the substrate itself is further improved, and the use as a substrate for a flexible element becomes easier.

(Solution) The metal oxide semiconductor precursor solution contains a solvent and a metal component containing tin as a main component and containing at least zinc. Here, the main component in the present invention means that tin accounts for 50% or more of all metal components in the solution, and may contain a small amount of other metal components as needed. Further, from the viewpoint of the semiconductor characteristics of the formed metal oxide semiconductor film, the composition of zinc and tin in all the metal components is preferably 90% or more, more preferably 95% or more. Additionally, the solution may contain less than 5% of a small amount of indium, more preferably 1% or less. Here, the metal component in the solution is substantially the same as the metal component in the metal oxide semiconductor precursor film. Therefore, in the present invention, the composition ratio of zinc to tin of the solution is 0.7 ≦Sn / (Sn + Zn) ≦ 0.9.

The solution in the present invention is obtained by weighing a solute which is a raw material so that the solution has a desired concentration, stirring it in a solvent, and dissolving it. The time of stirring or the temperature of the solution during stirring is not particularly limited as long as the solute is sufficiently dissolved.

The metal oxide semiconductor precursor solution is obtained by dissolving a compound containing zinc and tin, and preferably a metal salt or a metal halide of zinc and tin. By using a metal salt or a metal halide, the solute can be easily dissolved in various solvents, and high electron transport characteristics are easily obtained. Examples of the metal salt include a sulfate, a phosphate, a carbonate, an acetate, and an oxalate. Examples of the metal halide include a chloride, an iodide, and a bromide. Further, the solution in the present invention is preferably a solution containing no insoluble matter such as metal oxide particles in the solution. By using a solution containing no insoluble matter such as metal oxide particles in the solution, the surface roughness when the metal oxide semiconductor film is formed becomes small, and a metal oxide semiconductor film excellent in in-plane uniformity can be formed.

The solvent used in the solution of the present invention is not particularly limited as long as it contains a compound containing zinc and tin as a solute, and examples thereof include water and an alcohol solvent (methanol, ethanol, propanol, ethylene glycol, etc.). ), guanamine solvent (formamide, N,N-dimethylformamide, etc.), ketone solvent (acetone, N-methylpyrrolidone, cyclobutyl hydrazine, N,N-dimethylimidazolidone) Etc.), an ether solvent (tetrahydrofuran, methoxyethanol, etc.), a nitrile solvent (acetonitrile or the like), a heterocyclic compound (pyridine, thiazole, etc.), and a hetero atom-containing solvent other than the above. In particular, methanol, methoxyethanol, or water is preferably used from the viewpoint of solubility and coatability.

The concentration of the metal component in the metal oxide semiconductor precursor solution can be arbitrarily selected depending on the viscosity or the film thickness to be obtained, and is preferably 0.01 mol/L or more from the viewpoint of flatness and productivity of the film. 1.0 mol / L or less.

(Coating) Examples of the method of applying the metal oxide semiconductor film precursor solution onto a substrate include a spray coating method, a spin coating method, a knife coating method, a dip coating method, a casting method, and a roll coating method. , bar coating, die coating, spray, inkjet, dispenser, screen printing, letterpress, and gravure. In particular, from the viewpoint of easily forming a fine pattern, it is preferred to use at least one coating method selected from the group consisting of an inkjet method, a dispenser method, a relief printing method, and a gravure printing method.

(Drying) After the metal oxide semiconductor precursor solution is applied onto a substrate, natural drying can be performed to form a metal oxide semiconductor precursor film, preferably by drying the coating film by heat treatment. Metal oxide semiconductor precursor film. By drying, the fluidity of the coating film can be lowered, and the flatness of the finally obtained metal oxide semiconductor film can be improved. Further, by selecting an appropriate drying temperature (35° C. or higher and 100° C. or lower), it is finally easy to obtain a metal oxide semiconductor film having higher electron transport characteristics. The method of the heat treatment is not particularly limited, and may be selected from heating of a hot plate, electric furnace heating, infrared heating, microwave heating, or the like.

From the viewpoint of uniformly maintaining the flatness of the film, the drying is preferably started within 5 minutes after the solution is applied onto the substrate. Further, the time for drying is not particularly limited, and from the viewpoint of film uniformity and productivity, it is preferably 15 seconds or longer and 10 minutes or shorter. Further, the environment at the time of drying is not particularly limited, and from the viewpoint of production cost and the like, it is preferably carried out under atmospheric pressure in the atmosphere.

[Conversion Step] Then, the metal oxide semiconductor precursor film is converted into a metal oxide semiconductor film by performing ultraviolet irradiation treatment in a state where the metal oxide semiconductor precursor film is heated. Here, as described above, the metal oxide semiconductor precursor film is composed of zinc and tin in an amount of more than 80% of the total metal component in the film, and the composition ratio of zinc to tin is 0.7 ≦Sn / (Sn + Zn) ≦ 0.9. Therefore, the effect of improving the characteristics of the metal oxide semiconductor film can be extremely enhanced by the ultraviolet irradiation treatment at a low temperature of 250 ° C or lower under atmospheric pressure.

(Heat Treatment) The substrate temperature in the conversion step to the metal oxide semiconductor film is preferably 250 ° C or lower, and preferably 120 ° C or higher. When the substrate temperature in the conversion step is 250° C. or less, the increase in thermal energy can be suppressed, and the manufacturing cost can be suppressed to a low level, and application to a resin substrate having low heat resistance can be facilitated. In addition, when the substrate temperature in the conversion step is more than 120 ° C, a metal oxide semiconductor film having high electron transport characteristics can be obtained in a shorter time. Moreover, it is more preferably more than 120 ° C and not more than 200 ° C from the viewpoint of the production cost and the application to the resin substrate. The heating method of the substrate in the conversion step is not particularly limited, and may be selected from the group consisting of heating plate heating, electric furnace heating, infrared heating, microwave heating, and the like.

(Ultraviolet Light Irradiation) In the conversion step, the illuminance at a wavelength of 300 nm or less of ultraviolet rays irradiated to the metal oxide semiconductor precursor film is preferably 30 mW/cm ² or more, and more preferably 50 mW/cm ² . By setting the illuminance to 30 mW/cm ² or more, a metal oxide semiconductor film having high electron transport characteristics can be obtained. Further, from the viewpoint of device cost, the upper limit of the illuminance is preferably 500 mW/cm ² or less.

The ultraviolet irradiation in the conversion step may be carried out until the metal oxide semiconductor precursor film is converted into a metal oxide semiconductor film. Although it depends on the composition of the precursor film, the heating temperature, the ultraviolet illuminance, etc., from the viewpoint of productivity, the ultraviolet irradiation time is preferably 5 minutes or longer and 120 minutes or shorter.

Further, the conversion step can be carried out under atmospheric pressure in the atmosphere, preferably in an environment containing 1% by volume or more of oxygen. In the case of containing oxygen, it is easy to obtain a metal oxide semiconductor film which exhibits high electron transport characteristics. Further, from the viewpoint of production cost, it is preferably treated in the atmosphere.

The light source for ultraviolet irradiation in the heat treatment in the conversion step is preferably a UV lamp from the viewpoint of ultraviolet irradiation of a large area uniformly by an inexpensive device, such as a UV lamp or a UV laser. Examples of the UV lamp include an excimer lamp, a xenon lamp, a low pressure mercury lamp, a high pressure mercury lamp, an ultrahigh pressure mercury lamp, a metal halide lamp, a xenon lamp, a carbon arc lamp, a cadmium lamp, an electrodeless discharge lamp, and the like, particularly if The use of a low-pressure mercury lamp is preferred because it is easily converted from a metal oxide semiconductor precursor film to a metal oxide semiconductor film.

Here, the carbon oxide concentration of the metal oxide semiconductor film formed by the conversion step is preferably 1 × 10 ¹⁹ atoms / cm ³ or more, 1 × 10 ²⁰ atoms / cm ³ or less, and the hydrogen concentration is preferably 2 ×. 10 ²² atoms/cm ³ or more and 4 × 10 ²² atoms/cm ³ or less. If it is the said concentration range, it is easy to acquire high electron-transmission characteristics. Further, the hydrogen concentration and the carbon concentration in the metal oxide semiconductor film are values measured by Secondary Ion Mass Spectroscopy (SIMS). SIMS is known as an analysis method capable of detecting an element constituting an object with a very high sensitivity, and causes a beam-shaped ion (primary ion) to collide with an analysis object, and ionizes a substance constituting the object by collision ( Secondary ion). The constituent elements and their amounts are detected by mass analysis of the secondary ions.

Further, the metal component in the metal oxide semiconductor film produced by the production method of the present invention is substantially the same as the metal component in the metal oxide semiconductor precursor film. Therefore, 80% or more of all the metal components in the metal oxide semiconductor film are zinc and tin, and the composition ratio of zinc to tin is 0.7 ≦Sn / (Sn + Zn) ≦ 0.9. A metal oxide semiconductor film can be measured by X-ray photoelectron spectro The number of atoms of a metal such as zinc or tin on the surface of the film is calculated by the ratio of zinc to tin and the composition ratio of zinc to tin. Alternatively, the metal oxide semiconductor film can be sliced and processed by an energy dispersive X-ray (EDX (Energy Dispersive X-ray) method of a transmission electron microscope (TEM) of a film). Then, the ratio of zinc to tin and the composition ratio were calculated.

<Thin Film Transistor> The metal oxide semiconductor film produced by the production method of the present invention can be suitably used for an active layer of a thin film transistor (TFT) because it exhibits high electron transport characteristics.

Hereinafter, an embodiment in which a metal oxide semiconductor film produced by the production method of the present invention is used as an active layer of a thin film transistor will be described. In addition, the method for producing a metal oxide semiconductor film of the present invention and the metal oxide semiconductor film produced by the above-described production method are not limited to the active layer of the TFT.

The element structure of the TFT of the present invention is not particularly limited, and may be any of a so-called inverse staggered structure (also referred to as a bottom gate type) and a staggered structure (also referred to as a top gate type) based on the position of the gate electrode. form. Further, it may be in the form of a so-called top contact type or bottom contact type based on the contact portion between the active layer and the source electrode and the drain electrode (referred to as "source-drain electrode" as appropriate).

In the case of the top gate type, when the substrate on which the TFT is formed is the lowermost layer, a gate electrode is disposed on the upper side of the gate insulating film, and an active layer is formed on the lower side of the gate insulating film. In the gate type, a gate electrode is disposed on the lower side of the gate insulating film, and an active layer is formed on the upper side of the gate insulating film. In addition, the bottom contact type is a form in which the source-drain electrode is formed earlier than the active layer and the lower surface of the active layer is in contact with the source-drain electrode, and the so-called top contact type is the active layer than the source-drain The electrode is formed first and the upper surface of the active layer is in contact with the source-drain electrode.

Fig. 1 is a schematic view showing an example of a TFT of the present invention having a top gate structure and a top contact type. In the thin film transistor (TFT) 10 shown in FIG. 1, the oxide semiconductor film as the active layer 14 is laminated on one main surface of the substrate 12. Further, on the active layer 14, the source electrode 16 and the drain electrode 18 are spaced apart from each other, and then the gate insulating film 20 and the gate electrode 22 are sequentially laminated on the above.

Fig. 2 is a schematic view showing an example of a TFT of the present invention having a top gate structure and a bottom contact type. In the TFT 30 shown in FIG. 2, the source electrode 16 and the drain electrode 18 are provided apart from each other on one main surface of the substrate 12. Further, the oxide semiconductor film, the gate insulating film 20, and the gate electrode 22 of the active layer 14 are sequentially laminated.

Fig. 3 is a schematic view showing an example of a TFT of the present invention having a bottom gate structure and a top contact type. In the TFT 40 shown in FIG. 3, a gate electrode 22, a gate insulating film 20, and the oxide semiconductor film as the active layer 14 are sequentially laminated on one main surface of the substrate 12. Further, the source electrode 16 and the drain electrode 18 are provided apart from each other on the surface of the active layer 14.

4 is a schematic view showing an example of a TFT of the present invention having a bottom gate structure and a bottom contact type. In the TFT 50 shown in FIG. 4, the gate electrode 22 and the gate insulating film 20 are sequentially laminated on one main surface of the substrate 12. Further, the source electrode 16 and the drain electrode 18 are provided apart from each other on the surface of the gate insulating film 20, and then the oxide semiconductor film as the active layer 14 is laminated thereon.

As the following embodiment, the top gate type thin film transistor 10 shown in FIG. 1 is mainly described. However, the thin film transistor of the present invention is not limited to the top gate type, and may be a bottom gate type film. Transistor.

(Active Layer) When the thin film transistor 10 of the present embodiment is produced, first, a metal oxide semiconductor film is formed on the substrate 12 through the metal oxide semiconductor precursor film forming step and the conversion step, and the metal is oxidized. The semiconductor film is patterned into the shape of the active layer. Preferably, the patterning is performed by any one of the inkjet method, the dispenser method, the relief printing method, and the gravure printing method, in which a metal oxide semiconductor precursor film having a pattern of an active layer is formed in advance, and converted into a metal. An oxide semiconductor film.

The thickness of the active layer 14 is preferably 5 nm or more and 50 nm or less from the viewpoint of flatness and time required for film formation.

Further, it is preferable to form a protective film (not shown) on the active layer 14 for protecting the active layer 14 during etching of the source electrode 16 and the drain electrode 18. The film formation method of the protective film is not particularly limited, and it may be formed continuously with the metal oxide semiconductor film, or may be formed after patterning of the metal oxide semiconductor film. Further, the protective film may be a metal oxide layer or an organic material such as a resin. In addition, the protective layer can be removed after the source-drain electrode is formed.

(Source-drain electrode) The source electrode 16 and the drain electrode 18 are formed on the active layer 14. The source-drain electrodes are respectively used to have a high conductivity to function as an electrode, and metals such as Al, Mo, Cr, Ta, Ti, Au, and Ag, Al-Nd, Ag alloy, tin oxide, and the like can be used. It is formed by a thin film of a metal oxide conductor such as zinc oxide, indium oxide, indium tin oxide (ITO), indium zinc oxide (IZO), or In-Ga-Zn-O.

The source electrode 16 and the drain electrode 18 are formed by a wet method such as a printing method or a coating method depending on the suitability of the material to be used, such as a vacuum deposition method, a sputtering method, an ion plating method, or the like. A physical method, a chemical vapor deposition (CVD), a plasma CVD method, or the like may be appropriately selected to form a film.

In consideration of film formability, patterning by etching or lift-off method, conductivity, and the like, the film thickness of each electrode is preferably 10 nm or more and 1000 nm or less, and more preferably 50 nm or more. , below 100 nm.

The source electrode 16 and the drain electrode 18 can be formed by patterning into a specific shape by etching or lift-off, and can be directly patterned by an inkjet method or the like. At this time, it is preferable to simultaneously pattern all the layers of the source electrode 16 and the drain electrode 18 and the wiring connected to the electrode.

(Gate Insulation Film) After the source electrode 16, the drain electrode 18, and the wiring are formed, the gate insulating film 20 is formed. The gate insulating film 20 preferably has high insulating properties, and may be, for example, an insulating film such as SiO ₂ , SiNx, SiON, Al ₂ O ₃ , Y ₂ O ₃ , Ta ₂ O ₅ , HfO ₂ , or the like. The insulating film of two or more of the above compounds may have a single layer structure or a laminated structure. The gate insulating film 20 can be in a wet manner such as a printing method or a coating method in consideration of the suitability of the material to be used, a physical method such as a vacuum vapor deposition method, a sputtering method, or an ion plating method, CVD or plasma. Film formation is carried out by a method selected as appropriate in a chemical method such as a CVD method.

Further, the gate insulating film 20 must have a thickness for reducing leakage current and increasing voltage resistance. On the other hand, if the thickness of the gate insulating film 20 is too large, the driving voltage is increased. Although depending on the material of the gate insulating film 20, the thickness of the gate insulating film 20 is preferably 10 nm or more and 10 μm or less, more preferably 50 nm or more and 1000 nm or less, and particularly preferably 100 nm or more and 400. Below nm.

(Gate Electrode) After the gate insulating film 20 is formed, the gate electrode 22 is formed. The gate electrode 22 is made of a metal having high conductivity. For example, a metal such as Al, Mo, Cr, Ta, Ti, Au, or Ag, Al-Nd, Ag alloy, tin oxide, zinc oxide, indium oxide, or indium tin oxide can be used. It is formed by a metal oxide conductive film such as (ITO), indium zinc oxide (IZO) or IGZO. As the gate electrode 22, the conductive film can be used in a single layer structure or a laminated structure of two or more layers.

The gate electrode 22 is in a wet manner such as a printing method or a coating method in consideration of the suitability of the material to be used, a physical method such as a vacuum deposition method, a sputtering method, or an ion plating method, CVD or plasma CVD. Film formation is carried out by a method selected as appropriate in a chemical method such as a method. The film thickness of the gate electrode 22 is preferably 10 nm or more and 1000 nm or less, and more preferably 50, in consideration of film formability, patterning property by etching or lift-off method, conductivity, and the like. Above nm, below 200 nm. After the film formation, the gate electrode 22 can be formed by patterning by etching or lift-off, and the pattern can be directly formed by an inkjet method or the like. At this time, it is preferable to simultaneously pattern the gate electrode 22 and the wiring connected to the gate electrode 22.

The use of the thin film transistor of the present invention described above is not particularly limited, and for example, it is suitable for use in an electro-optical device (for example, a liquid crystal display device or an organic EL (Electro Luminescence) display) in terms of exhibiting high transmission characteristics. A drive element in a display device such as a device or an inorganic EL display device, or a flexible display formed on a resin substrate having low heat resistance. Further, the thin film transistor of the present invention is suitably used as a driving element (drive circuit) in various electronic components such as X-ray sensors and various electronic components such as a micro electro mechanical system (MEMS).

<Liquid Crystal Display Device> FIG. 5 is a schematic cross-sectional view showing a part of a liquid crystal display device using the thin film transistor of the present invention, and FIG. 6 is a schematic configuration view of the electric wiring.

As shown in FIG. 5, the liquid crystal display device 100 of the present embodiment has a top-gate type TFT 10 having a top gate structure as shown in FIG. 1, and a gate electrode 22 protected by a passivation layer 102 of the TFT 10. The upper pixel 104 and the liquid crystal layer 108 sandwiched between the upper electrode 106 and the color filter corresponding to each pixel for emitting R (red) G (green) B (blue) of different colors 110, and a polarizing plate 112a and a polarizing plate 112b are provided on the substrate 12 side of the TFT 10 and the RGB color filter 110, respectively.

In addition, as shown in FIG. 6, the liquid crystal display device 100 of the present embodiment includes a plurality of gate wirings 113 that are parallel to each other, and a data wiring 114 that is parallel to the gate wirings 113. Here, the gate wiring 113 is electrically insulated from the data wiring 114. The TFT 10 is provided in the vicinity of the intersection of the gate wiring 113 and the data wiring 114.

The gate electrode 22 of the TFT 10 is connected to the gate wiring 113, and the source electrode 16 of the TFT 10 is connected to the data wiring 114. Further, the drain electrode 18 of the TFT 10 is connected to the pixel lower electrode 104 via a contact hole 116 provided in the gate insulating film 20 (a conductor is embedded in the contact hole 116). The pixel lower electrode 104 and the grounded pair upper electrode 106 together form a capacitor 118.

<Organic EL display device> FIG. 7 is a schematic cross-sectional view showing an example of an active matrix type organic EL display device using the thin film transistor of the present invention, and FIG. 8 is a schematic configuration view of the electric wiring.

The active matrix type organic EL display device 200 of the present embodiment has a configuration in which a TFT 10 having a top gate structure shown in FIG. 1 is provided as a thin film transistor (TFT) for driving on a substrate 12 including a passivation layer 202. 10a and a thin film transistor (TFT) 10b for switching, an organic EL light-emitting element 214 including an organic light-emitting layer 212 sandwiched between a lower electrode 208 and an upper electrode 210 is provided on the TFT 10a and the TFT 10b, and the upper surface is also protected by a passivation layer 216.

In addition, as shown in FIG. 8 , the organic EL display device 200 of the present embodiment includes a plurality of gate wirings 220 that are parallel to each other, and a data wiring 222 and a driving wiring 224 that are parallel to each other across the gate wiring 220 . Here, the gate wiring 220 is electrically insulated from the data wiring 222 and the driving wiring 224. The gate electrode 22 of the switching TFT 10b is connected to the gate wiring 220, and the source electrode 16 of the switching TFT 10b is connected to the data wiring 222. Further, the drain electrode 18 of the switching TFT 10b is connected to the gate electrode 22 of the driving TFT 10a, and the driving TFT 10a is kept in an ON state by using the capacitor 226. The source electrode 16 of the driving TFT 10a is connected to the driving wiring 224, and the drain electrode 18 is connected to the organic EL light emitting element 214.

Further, in the organic EL display device shown in FIG. 7, the upper electrode 210 can be a transparent electrode and can be a top emission type, and the lower electrode 208 and each electrode of the TFT can be used as a transparent electrode. It is a bottom type.

<X-ray sensor> FIG. 9 is a schematic cross-sectional view showing an example of an X-ray sensor using the thin film transistor of the present invention, and FIG. 10 is a schematic configuration view of the electric wiring.

The X-ray sensor 300 of the present embodiment includes a TFT 10 and a capacitor 310 formed on the substrate 12, a charge collection electrode 302 formed on the capacitor 310, an X-ray conversion layer 304, and an upper electrode 306. A passivation film 308 is provided on the TFT 10.

The capacitor 310 has a structure in which the insulating film 316 is sandwiched between the capacitor lower electrode 312 and the capacitor upper electrode 314. The capacitor upper electrode 314 is connected to any of the source electrode 16 and the drain electrode 18 of the TFT 10 (the drain electrode 18 in FIG. 9) via the contact hole 318 provided in the insulating film 316.

The charge collection electrode 302 is provided on the capacitor upper electrode 314 of the capacitor 310, and is in contact with the capacitor upper electrode 314. The X-ray conversion layer 304 is a layer containing amorphous selenium and is provided to cover the TFT 10 and the capacitor 310. The upper electrode 306 is disposed on the X-ray conversion layer 304 and is in contact with the X-ray conversion layer 304.

As shown in FIG. 10, the X-ray sensor 300 of the present embodiment includes a plurality of gate wirings 320 that are parallel to each other, and a plurality of data wirings 322 that are parallel to each other and that intersect with the gate wirings 320. Here, the gate wiring 320 is electrically insulated from the data wiring 322. The TFT 10 is provided in the vicinity of the intersection of the gate wiring 320 and the data wiring 322.

The gate electrode 22 of the TFT 10 is connected to the gate wiring 320, and the source electrode 16 of the TFT 10 is connected to the data wiring 322. Further, the drain electrode 18 of the TFT 10 is connected to the charge collection electrode 302, and the charge collection electrode 302 is connected to the capacitor 310.

In the X-ray sensor 300 of the present embodiment, in FIG. 9, X-rays are incident from the upper electrode 306 side, and an electron-hole pair is generated in the X-ray conversion layer 304. A high electric field is applied to the X-ray conversion layer 304 by the upper electrode 306 in advance, whereby the generated charges are stored in the capacitor 310, and are read by sequentially scanning the TFT 10.

Further, in the liquid crystal display device 100, the organic EL display device 200, and the X-ray sensor 300 of the above-described embodiment, the TFT having the top gate structure is used, but the TFT is not limited thereto. The TFT of the structure shown in FIGS. 2 to 4 can be used. [Examples]

The invention will now be described in more detail on the basis of examples. The materials, the amounts, the ratios, the treatment contents, the treatment procedures, and the like shown in the following examples can be appropriately changed without departing from the gist of the invention. Therefore, the scope of the invention should not be construed as being limited by the embodiments shown below.

[Example 1] <Production of Metal Oxide Semiconductor Film> The solution shown below was applied onto a substrate to form a metal oxide semiconductor precursor film in a state in which the metal oxide semiconductor precursor film was heated. Ultraviolet irradiation is performed to convert a metal oxide semiconductor precursor film into a metal oxide semiconductor film, thereby fabricating a metal oxide semiconductor film.

[Metal Oxide Semiconductor Precursor Film Forming Step] (Solution) Tin chloride (SnCl ₄ ·xH ₂ O, 3 N, manufactured by High Purity Chemical Research Co., Ltd.) and zinc acetate (Zn(CH ₃ COO) ₂ · 2H ₂ O, manufactured by High Purity Chemical Research Co., Ltd.) was dissolved in 2-methoxyethanol (reagent grade, manufactured by Wako Pure Chemical Industries Co., Ltd.) to prepare chlorination at a concentration of 0.3 mol/L. A tin solution and a zinc acetate solution were then mixed with a zinc chloride solution in a ratio of 9:1 to prepare a metal oxide semiconductor precursor solution. That is, the ratio of zinc to tin of the solution was 100%, and the composition ratio of Sn to tin (Sn + Zn) was 0.9.

(Substrate) A p-type germanium substrate with a thermal oxide film was used as the substrate. It is assumed that the thermal oxide film of the substrate is used as the gate insulating film of the TFT.

(Coating, Drying) The prepared solution was spin-coated at a rotational speed of 5000 rpm for 30 seconds on a p-type 吋1 inch × 1 inch substrate with a thermal oxide film, and then heated to 60 ° C. Dry on a hot plate for 5 minutes.

[Conversion Step] The conversion of the obtained metal oxide semiconductor precursor film to the metal oxide semiconductor film was carried out under the following conditions. As a device, a vacuum ultraviolet (VUV) dry processor (manufactured by ORC MANUFACTURING Co., Ltd., VUE-3400-F) equipped with a low-pressure mercury lamp was used.

After the sample was placed on an unheated hot plate in the apparatus, it stood by for 5 minutes. During this time, 20 L/min of dry air was flowed through the device processing chamber. After the standby for 5 minutes, the gate in the apparatus was opened, and the temperature was raised to 250 ° C over 30 minutes. After reaching 250 ° C, the ultraviolet ray irradiation treatment was performed while maintaining the temperature for 60 minutes, thereby obtaining a metal oxide semiconductor film. During the ultraviolet irradiation treatment under the heat treatment, 20 L/min of dry air was always flowed. The position of the sample was measured using an ultraviolet cumulometer (manufactured by Hamamatsu Photonics Co., Ltd., controller C9536, sensor head H9536-254, spectroscopic sensitivity in the range of more than 200 nm and 300 nm) The ultraviolet illuminance at a wavelength of 254 nm was set as a peak wavelength, and as a result, it was 51 mW/cm ² .

[Production of TFT] A source-drain electrode was formed on the obtained metal oxide semiconductor film by vapor deposition to form a simple TFT. The source-drain electrode film formation was performed by film formation using a metal mask pattern, and Ti was formed into a film of 50 nm. The source-drain electrode dimensions were set to 1 mm × 1 mm, and the distance between the electrodes was set to 0.2 mm.

[Example 2] A solution was prepared by setting a mixing ratio of a tin chloride solution and a zinc acetate solution to 7:3, and a composition ratio of Sn/(Sn+Zn) of zinc to tin of the metal oxide semiconductor precursor film was set to In the same manner as in Example 1, a metal oxide semiconductor film was formed in the same manner as in Example 1, and a simple TFT was produced.

[Example 3] A metal oxide semiconductor film was formed in the same manner as in Example 1 except that the substrate temperature in the ultraviolet irradiation treatment in the conversion step was changed to 230 ° C, and a simple TFT was produced.

[Example 4] A metal oxide semiconductor film was formed in the same manner as in Example 1 except that the ultraviolet illuminance at the time of the ultraviolet irradiation treatment in the conversion step was changed to 80 mW/cm ² , and a simple TFT was produced. .

[Example 5] A metal oxide semiconductor film was formed in the same manner as in Example 1 except that the metal oxide semiconductor precursor solution shown below was used, and a simple TFT was produced.

Gallium nitrate (Ga(NO ₃ ) ₃ ·xH ₂ O, 5 N, manufactured by High Purity Chemical Research Co., Ltd.) and indium nitrate (In(NO ₃ ) ₃ ·xH ₂ O, 4 N, high purity chemistry The company's manufacturing company is dissolved in 2-methoxyethanol (reagent special grade, manufactured by Wako Pure Chemical Industries Co., Ltd.) to prepare a 0.3 mol/L gallium nitrate solution and an indium nitrate solution, and then The gallium nitrate solution and the indium nitrate solution were mixed at a ratio of 1:4, thereby adjusting the gallium-indium mixed solution. Then, a metal oxide semiconductor precursor is prepared by mixing a solution having a composition ratio of zinc/tin of Sn/(Sn+Zn) of 0.9 used in Example 1 and a mixed solution of gallium and indium in a ratio of 4:1. Solution. That is, the ratio of zinc to tin of the solution was 80%, and the composition ratio of Sn to tin (Sn + Zn) was 0.9.

[Example 6] The mixing ratio of the solution of the zinc/tin composition ratio of Sn/(Sn+Zn) used in Example 1 to 0.9 and the gallium-indium mixed solution was set to 9:1, and In the same manner as in Example 5, a metal oxide semiconductor precursor solution was prepared to form a metal oxide semiconductor film, and a simple TFT was produced. That is, the ratio of zinc to tin of the solution was 90%, and the composition ratio of Sn to tin (Sn + Zn) was 0.9.

[Comparative Example 1] The same procedure as in Example 1 except that the composition ratio of Sn to Sn (Sn + Zn) of the metal oxide semiconductor precursor film was set to 1 using a tin chloride solution as a solution. In the manner, a metal oxide semiconductor film is formed, and a simple TFT is fabricated.

[Comparative Example 2] A solution was prepared by setting a mixing ratio of a tin chloride solution and a zinc acetate solution to 6:4, and a composition ratio of Sn/(Sn+Zn) of zinc to tin of the metal oxide semiconductor precursor film was set to In the same manner as in Example 1, a metal oxide semiconductor film was formed in the same manner as in Example 1, and a simple TFT was produced.

[Comparative Example 3] A metal oxide semiconductor film was formed in the same manner as in Example 1 except that the ultraviolet light was not irradiated in the conversion step, and a simple TFT was produced.

[Comparative Example 4] A metal oxide semiconductor film was formed in the same manner as in Comparative Example 1 except that the ultraviolet light was not irradiated in the conversion step, and a simple TFT was produced.

<SIMS Analysis> The hydrogen concentration and the carbon concentration in the film were determined for the metal oxide semiconductor films produced in Example 1 and Comparative Example 3 by SIMS analysis (secondary ion mass spectrometry). The measuring device used PHI ADEPT-1010 manufactured by ULVAC-PHI Co., Ltd. As the measurement conditions, the primary ion species was set to Cs ⁺ , the primary acceleration voltage was set to 1.0 kV, and the detection region was set to 140 μm × 140 μm. The concentrations of hydrogen and carbon estimated by SIMS analysis are shown in Table 1. Furthermore, since the difference in the depth direction is different, it is expressed by the concentration range.

[Table 1]

According to the comparison between Example 1 and Comparative Example 3 of Table 1, the metal oxide semiconductor film produced by the method of the present invention has a reduced hydrogen concentration and carbon concentration in the film by ultraviolet irradiation.

[Evaluation] <Electrode Characteristics> Using a semiconductor parameter analyzer 4156C (manufactured by Agilent Technologies, Inc.), the transistor characteristics V _g -I _{d were} measured for each of the prepared simple TFTs, and linear migration was determined. rate. The measurement of the transistor characteristics V _g -I _d is carried out by fixing the gate voltage (V _d ) to +20 V and the gate voltage (V _g ) in the range of -15 V to +30 V. Change, measure the drain current (I _d ) at each gate voltage. Further, in Comparative Example 1, the conduction-off operation could not be confirmed, and the behavior of the conductor was exhibited. Further, regarding Comparative Example 3, electrical conductivity was not exhibited, and the behavior of the insulator was exhibited. The evaluation results are shown in Table 2. Further, the graphs of the transistor characteristics V _g -I _d of Example 1, Example 2, Comparative Example 1, and Comparative Example 2 are shown in Fig. 11 . Further, a graph of the transistor characteristics V _{g -} I _d of Comparative Example 1 and Comparative Example 4 is shown in Fig. 12 .

[Table 2]

As shown in Table 2, the simple TFT having the embodiment of the metal oxide semiconductor film produced by the production method of the present invention has a large linear mobility and a high semiconductor as compared with the simple TFT of the comparative example. characteristic. Here, according to the comparison between Example 1, Example 2, and Comparative Example 1 and Comparative Example 2, the composition ratio of zinc to tin of the metal oxide semiconductor precursor film was set to 0.7 ≦ Sn / (Sn + Zn). ) ≦ 0.9 range, and can increase linear mobility. Further, according to the comparison between Example 1 and Example 5 and Example 6, it is understood that the higher the ratio of tin to zinc in all the metal components, the higher the linear mobility can be. Further, from the comparison between Example 1 and Example 4, it is understood that the linear mobility does not change even if the illuminance of the ultraviolet ray in the conversion step is increased. From this, it is understood that ultraviolet rays having sufficient illuminance necessary for the conversion of the metal oxide semiconductor precursor film are irradiated. Further, according to Examples 1 to 4, it is understood that the linear mobility can be increased even at a low temperature of 250 ° C or lower.

Further, as shown in FIG. 12, in Comparative Example 1 and Comparative Example 4, the behavior of the conductor was exhibited. However, compared with Comparative Example 1 in which ultraviolet irradiation was performed, the electron transport characteristics of Comparative Example 4 in which ultraviolet irradiation was not performed were changed. high. From this, it is understood that in order to obtain the effect of the ultraviolet irradiation treatment, it is necessary to appropriately select the range of the composition ratio of zinc to tin. The effects of the present invention can be known from the above.

10‧‧‧film transistor
10a‧‧‧Drive film transistor
10b‧‧‧Transistor film transistor
12‧‧‧Substrate
14‧‧‧Active layer (oxide semiconductor layer)
16‧‧‧Source electrode
18‧‧‧汲electrode
20‧‧‧gate insulating film
22‧‧‧gate electrode
30, 40, 50‧‧‧ film transistor
100‧‧‧Liquid crystal display device
102, 202, 216‧‧ ‧ passivation layer
104‧‧‧ pixel lower electrode
106‧‧‧for the upper electrode
108‧‧‧Liquid layer
110‧‧‧Color filters
112a, 112b‧‧‧ polarizing plate
113, 220, 320‧‧‧ gate wiring
114, 222, 322‧‧‧ data wiring
116, 318‧‧‧ contact holes
118, 226, 310‧‧‧ capacitors
200‧‧‧Organic EL display device
208‧‧‧lower electrode
210, 306‧‧‧ upper electrode
212‧‧‧Organic light-emitting layer
214‧‧‧Organic EL light-emitting elements
224‧‧‧Drive wiring
300‧‧‧X-ray sensor
302‧‧‧Electrical electrodes for charge collection
304‧‧‧X-ray conversion layer
308‧‧‧passivation film
312‧‧‧The lower electrode for capacitors
314‧‧‧Upper electrode for capacitor
316‧‧‧Insulation film

1 is a schematic view showing a configuration of an example (top gate-top contact type) of a thin film transistor of the present invention using a metal oxide semiconductor film produced by the production method of the present invention. FIG. 2 is a schematic view showing a configuration of an example of a thin film transistor (top gate-bottom contact type) of the present invention using the metal oxide semiconductor film produced by the production method of the present invention. 3 is a schematic view showing a configuration of an example (bottom gate-top contact type) of the thin film transistor of the present invention using the metal oxide semiconductor film produced by the production method of the present invention. FIG. 4 is a schematic view showing a configuration of an example (bottom gate-bottom contact type) of the thin film transistor of the present invention using the metal oxide semiconductor film produced by the production method of the present invention. Fig. 5 is a schematic cross-sectional view showing a part of a liquid crystal display device using the thin film transistor of the present invention. Fig. 6 is a schematic configuration diagram of electrical wiring of the liquid crystal display device of Fig. 5; Fig. 7 is a schematic cross-sectional view showing a part of an organic electroluminescence (EL) display device using the thin film transistor of the present invention. Fig. 8 is a schematic configuration diagram of electrical wiring of the organic EL display device of Fig. 7; Fig. 9 is a schematic cross-sectional view showing a part of an X-ray sensor array using the thin film transistor of the present invention. Fig. 10 is a schematic configuration diagram of electrical wiring of the X-ray sensor array of Fig. 9; FIG. 11 is a graph showing the results of measuring the relationship between the gate voltage and the drain current of the thin film transistor produced in Example 1, Example 2, Comparative Example 1, and Comparative Example 2. FIG. FIG. 12 is a graph showing the results of measuring the relationship between the gate voltage and the drain current of the thin film transistor produced in Comparative Example 1 and Comparative Example 4. FIG.

Claims (14)

A method for producing a metal oxide semiconductor film, comprising: a metal oxide semiconductor precursor film forming step of applying a solvent and a solution of zinc and tin as a metal component on a substrate to form a metal oxide semiconductor a precursor film; and a conversion step of converting the metal oxide semiconductor precursor film into a metal oxide semiconductor film by performing ultraviolet irradiation in a state in which the metal oxide semiconductor precursor film is heated; 80% or more of all the metal components in the oxide semiconductor precursor film are zinc and tin, and the composition ratio of zinc to tin is 0.7 ≦Sn / (Sn + Zn) ≦ 0.9. The method for producing a metal oxide semiconductor film according to claim 1, wherein a composition ratio of indium in the metal oxide semiconductor precursor film is less than 5%. The method for producing a metal oxide semiconductor film according to the above aspect, wherein in the converting step, the temperature of the substrate during ultraviolet irradiation is maintained at 250 ° C or lower. The method for producing a metal oxide semiconductor film according to the above aspect, wherein in the converting step, ultraviolet rays having a wavelength of 300 nm or less irradiated to the metal oxide semiconductor precursor film are used. The illuminance is 30 mW/cm ² or more. The method for producing a metal oxide semiconductor film according to the above aspect, wherein the conversion step is carried out in an atmosphere containing 1% by volume or more of oxygen. The method for producing a metal oxide semiconductor film according to the first or second aspect of the invention, wherein the metal oxide semiconductor precursor film contains 95% or more of all metal components of zinc and tin. The method for producing a metal oxide semiconductor film according to the first or second aspect of the invention, wherein the solution is obtained by dissolving a metal salt or a metal halide of zinc and tin in a solvent. The method for producing a metal oxide semiconductor film according to the first or second aspect of the invention, wherein the solvent is methanol, methoxyethanol or water. The method for producing a metal oxide semiconductor film according to the above aspect, wherein the concentration of the metal component in the solution is from 0.01 mol/L to 1.0 mol/L. A metal oxide semiconductor film produced by the method for producing a metal oxide semiconductor film according to any one of claims 1 to 9. The metal oxide semiconductor film according to claim 10, wherein the carbon concentration in the film by secondary ion mass spectrometry is 1 × 10 ¹⁹ atoms / cm ³ or more and 1 × 10 ²⁰ atoms / cm ³ or less. . The metal oxide semiconductor film according to claim 10, wherein a concentration of hydrogen in the film by secondary ion mass spectrometry is 2 × 10 ²² atoms/cm ³ or more and 4 × 10 ²² atoms/cm ³ or less. . A thin film transistor comprising: an active layer, a source electrode, a gate electrode, a gate insulating film, and the metal oxide semiconductor film according to any one of claims 10 to 12; Gate electrode. An electronic component comprising the thin film transistor according to claim 13 of the patent application.