JPWO2016121230A1 - Method for manufacturing oxide protective film, oxide protective film, method for manufacturing thin film transistor, thin film transistor, and electronic device - Google Patents

Abstract

An oxide protective film precursor solution containing a solvent and a metal component containing at least 50 atom% of indium is applied onto the oxide semiconductor film containing indium formed on the substrate to form an oxide protective film precursor film. And a method for converting the oxide protective film precursor film into an oxide protective film having a specific resistance higher than that of the oxide semiconductor film, and a method for manufacturing the oxide protective film.

Description

  The present disclosure relates to an oxide protective film manufacturing method, an oxide protective film, a thin film transistor manufacturing method, a thin film transistor, and an electronic device.

A thin film transistor using an oxide semiconductor film has been put into practical use in manufacturing by a vacuum film forming method, and is currently attracting attention.
On the other hand, research and development have been actively conducted on the production of oxide semiconductor films by a liquid phase process for the purpose of easily forming oxide semiconductor films having high semiconductor characteristics at low temperature and atmospheric pressure. (For example, see International Publication No. 2009/081862).

  When an oxide semiconductor film is used for an electronic element, operation stability is deteriorated due to an external factor (water, contamination, or the like), and thus the oxide semiconductor film (active layer) needs to be covered with a protective film. As with the oxide semiconductor film, it is proposed to form the protective film by a liquid phase process (coating method) in order to form the protective film easily at a low temperature and under atmospheric pressure (for example, Japanese Patent Laid-Open 2010-103203).

  For example, in International Publication No. 2010/38566, a solution containing indium, zinc, and gallium is applied to a gate insulating film by an inkjet method to form a semiconductor precursor film, and the oxide semiconductor layer is formed by microwave irradiation. After the conversion, a surface treatment layer is formed on the oxide semiconductor layer where a protective layer is to be formed, and a polysilazane solution is applied onto the oxide semiconductor layer by an ink jet method, and further subjected to heat treatment, thereby comprising silicon dioxide. A method of manufacturing a thin film transistor for forming a protective layer is disclosed.

However, for example, when a protective film is formed on an oxide semiconductor film (active layer) by a liquid phase process in a manufacturing process of a thin film transistor (TFT), TFT characteristics such as a threshold shift are likely to be greatly affected.
For example, Japanese Patent Application Laid-Open No. 2010-103203 and International Publication No. 2010/38566 disclose that a protective film is formed on an oxide semiconductor film (active layer) by a liquid phase process. Improving operational stability without adversely affecting the oxide semiconductor film by appropriately selecting the metal components contained in the coating solution to be formed, the processing conditions of the conversion process, the solvent species contained in the coating solution, etc. Is not considered.

  The present invention suppresses changes in electrical characteristics of an oxide semiconductor film even when an oxide protective film is formed over the oxide semiconductor film by a liquid phase process, and stabilizes repeated operation of an electronic element including the oxide semiconductor film. Manufacturing method of oxide protective film in which deterioration of property is suppressed, and oxide protective film in which change in electrical characteristics of oxide semiconductor film is suppressed to be small, and deterioration in repeated operation stability of an electronic element is suppressed, It is an object to provide a thin film transistor, a method for manufacturing the thin film transistor, and an electronic device.

In order to achieve the above object, the following invention is provided.
<1> An oxide protective film precursor film including a solvent and an oxide protective film precursor solution containing a metal component in which 50 atom% or more is indium is applied on an oxide semiconductor film containing indium formed on a substrate. Forming a step;
Converting the oxide protective film precursor film into an oxide protective film having a higher specific resistance than the oxide semiconductor film; and
The manufacturing method of the oxide protective film containing this.

<2> The method for producing an oxide protective film according to <1>, wherein 50 atom% or more of the metal component contained in the oxide semiconductor film is indium.
<3> The method for producing an oxide protective film according to <1> or <2>, wherein the solvent includes a solvent having an acyl group.
<4> The method for producing an oxide protective film according to <3>, wherein the acyl group is an acetyl group.
<5> The method for producing an oxide protective film according to <1> or <2>, wherein the solvent contains a polyol.
<6> The method for producing an oxide protective film according to <4> or <5>, wherein the solvent contains at least one of acetylacetone and ethylene glycol.
<7> The method for producing an oxide protective film according to any one of <1> to <6>, wherein indium contained in the oxide protective film precursor solution is indium ions.
<8> The method for producing an oxide protective film according to any one of <1> to <7>, wherein the oxide protective film precursor solution contains nitrate ions.
<9> In the step of converting the oxide protective film precursor film into the oxide protective film, the oxide protective film precursor film is irradiated with ultraviolet rays under the condition that the oxide protective film precursor film is heated <1. The manufacturing method of the oxide protective film as described in any one of>-<8>.
<10> The oxide protective film according to any one of <1> to <9>, wherein the temperature of the substrate is maintained at over 120 ° C. in the step of converting the oxide protective film precursor film into the oxide protective film. Manufacturing method.
<11> The method for producing an oxide protective film according to <10>, wherein the temperature of the substrate is maintained at less than 200 ° C. in the step of converting the oxide protective film precursor film into the oxide protective film.
<12> An oxide semiconductor film is an oxide obtained by applying an oxide semiconductor precursor solution containing a solvent and indium on a substrate to form an oxide semiconductor precursor film, and then converting the oxide semiconductor precursor film. The manufacturing method of the oxide protective film as described in any one of <1>-<11> which is a semiconductor film.

<13> An oxide protective film produced by the method for producing an oxide protective film according to any one of <1> to <12>.

<14> A gate electrode, a gate insulating film, an oxide semiconductor film containing indium, and the oxide protective film according to <13> that protects at least part of the oxide semiconductor film, a source electrode, and a drain electrode And a thin film transistor.
<15> A gate electrode, a gate insulating film, an oxide semiconductor film containing indium, a source electrode, a drain electrode, and an oxide protective film that protects at least a part of the oxide semiconductor film. A thin film transistor that satisfies the following relational expression (I), where C _{S is} the carbon concentration in the physical semiconductor film and C _P is the carbon concentration in the oxide protective film.
100 ≧ C _P / C _S ≧ 10 (I)
In the formula (I), the units of C _P and C _S are both atoms / cm ³ .
<16> The thin film transistor according to the carbon concentration _{C S} in the oxide semiconductor film is not more than ^{1 × 10 21 atoms / cm 3} <15>.
The thin film transistor according to <17> carbon concentration _{C P} in the oxide protective film is 1 × ¹⁰ 22 atoms / cm ³ or more <15> or <16>.
<18> The thin film transistor according to any one of <14> to <17>, which has a bottom gate structure.
<19> A structure in which a source electrode and a drain electrode are formed on an oxide semiconductor film, and an oxide protective film is formed on the oxide semiconductor film exposed between the source electrode and the drain electrode. The thin film transistor according to <18>.

<20> forming a gate electrode on the substrate;
Forming a gate insulating film on the substrate and the gate electrode;
Forming an oxide semiconductor film containing indium over the gate insulating film;
Forming a source electrode and a drain electrode over the oxide semiconductor film;
The specific resistance is higher than that of the oxide semiconductor film by the method for manufacturing the oxide protective film according to any one of <1> to <12> over the oxide semiconductor film exposed between the source electrode and the drain electrode. Forming an oxide protective film;
The manufacturing method of the thin-film transistor which has this.

<21> An electronic device comprising the thin film transistor according to any one of <14> to <19>.

  According to the present invention, even when an oxide protective film is formed over an oxide semiconductor film by a liquid phase process, a change in electrical characteristics of the oxide semiconductor film is suppressed to be small, and an electronic element having the oxide semiconductor film is repeatedly formed. Method for manufacturing oxide protective film in which deterioration in operation stability is suppressed, and oxide protection in which a change in electrical characteristics of an oxide semiconductor film is suppressed to be small and a decrease in repeated operation stability of an electronic element is suppressed A film, a thin film transistor, a method for manufacturing the thin film transistor, and an electronic device are provided.

It is the schematic which shows an example of a structure of the thin-film transistor provided with the oxide protective film manufactured by this indication. It is the schematic which shows the other example of a structure of the thin-film transistor provided with the oxide protective film manufactured by this indication. It is the schematic which shows the other example of a structure of the thin-film transistor provided with the oxide protective film manufactured by this indication. It is the schematic which shows a part of liquid crystal display device of embodiment. It is the schematic of the electrical wiring of the liquid crystal display device shown in FIG.

Hereinafter, embodiments of the present invention will be specifically described with reference to the accompanying drawings.
In the drawings, members (components) having the same or corresponding functions are denoted by the same reference numerals and description thereof is omitted as appropriate. Further, in the present specification, when a numerical range is indicated by the symbol “to”, numerical values described as the lower limit value and the upper limit value are included in the numerical range, respectively.

[Production Method of Oxide Protective Film]
An oxide protective film manufacturing method according to the present disclosure includes: an oxide protective film precursor solution containing a solvent and a metal component having 50 atom% or more of indium on an oxide semiconductor film containing indium formed on a substrate; A step of forming an oxide protective film precursor film by coating, and a step of converting the oxide protective film precursor film into an oxide protective film having a higher specific resistance than the oxide semiconductor film.
Hereinafter, the oxide protective film precursor solution may be referred to as “protective film precursor solution” or simply “solution”, and the oxide semiconductor film may be referred to as “semiconductor film”. The film precursor film may be referred to as a “protective film precursor film”, and the oxide protective film may be referred to as a “protective film”.

  When an oxide protective film is formed on the oxide semiconductor film by a liquid phase process, the reaction between the solution for forming the oxide protective film and the oxide semiconductor film, conversion from the protective film precursor film to the oxide protective film Alternatively, it is considered that characteristics of the oxide semiconductor film are easily changed by a reaction between the oxide protective film and the oxide semiconductor film. Therefore, even if an oxide protective film is formed on an oxide semiconductor film in a manufacturing process of an electronic device such as a thin film transistor (TFT) and the oxide semiconductor film is protected by the oxide protective film in a subsequent process, It is considered that the electrical characteristics of the element change or that the repeated operation stability (hereinafter, sometimes simply referred to as “operation stability”) decreases.

On the other hand, according to the method for manufacturing an oxide protective film according to the present disclosure, even if the oxide protective film is formed on the oxide semiconductor film by a liquid phase process, the electrical characteristics of the oxide semiconductor film (for example, TFT The change in linear mobility and threshold) is suppressed to a low level, and the decrease in the repetitive operation stability (for example, the threshold shift of the TFT) of the electronic element having the oxide semiconductor film is suppressed.
Although the reason is not clear, the oxide protective film precursor solution for forming the oxide protective film contains 50 atom% or more of indium, which is the same metal component as indium contained in the semiconductor film, with respect to the entire metal component. By including the ratio, indium diffusion at the interface between the semiconductor film and the protective film precursor film or the oxide protective film is suppressed at the time of forming the oxide protective film, and the change in the electrical characteristics of the semiconductor film is suppressed, It is considered that the specific resistance of the oxide protective film is higher than that of the oxide semiconductor film, so that the influence of the oxide protective film on the electrical conductivity of the semiconductor film is suppressed, and the stability of repeated operation of the electronic element is improved.

  Note that in this specification, an oxide protective film that protects an oxide semiconductor film is formed over the oxide semiconductor film and the influence of outside air or a solution on the oxide semiconductor film after the oxide semiconductor film is formed. A film provided for preventing or mitigating the influence of another layer and suppressing change in electrical characteristics of the oxide semiconductor film, which has higher specific resistance than the oxide semiconductor film and is at least one of the oxide semiconductor films. It is the film | membrane laminated | stacked in the state which contacted the part. The oxide protective film according to the present disclosure is preferably as the specific resistance is higher, and more preferably an insulating film.

In the present embodiment, the “conductive film” means a film having a specific resistance value of less than 10 ⁻² Ωcm, and the “semiconductor film” means a film having a specific resistance value of 10 ⁻² Ωcm or more and 10 ⁷ Ωcm or less. The “insulating film” means a film having a specific resistance value of more than 10 ⁷ Ωcm.
The specific resistance value of the film can be measured by a van der pauw method using a Hall effect / specific resistance measuring device (manufactured by Toyo Technica).

  According to the method for manufacturing an oxide protective film according to the present disclosure, it is possible to form an electronic element while suppressing changes in the original characteristics of the oxide semiconductor film. Therefore, for example, when applied to the formation of an oxide protective film for protecting an oxide semiconductor film of a thin film transistor, a thin film transistor having high electron transfer characteristics and extremely high operational stability is provided by the formation of the oxide protective film. It becomes possible.

In addition, since the oxide protective film according to the present disclosure can be manufactured by a liquid phase process, it is not necessary to use a large-scale vacuum apparatus, and since it can be formed at a relatively low temperature, it is inexpensive and has low heat resistance. In view of the fact that a simple resin substrate can be used and the raw material is inexpensive, the manufacturing cost of the electronic device can be greatly reduced.
Moreover, since the manufacturing method of the oxide protective film of this indication is applicable also to a resin substrate with low heat resistance, it becomes possible to produce flexible electronic devices, such as a flexible display, at low cost.

  Hereinafter, each process in the manufacturing method of the oxide protective film concerning this indication is explained concretely.

<Oxide protective film precursor film forming step>
In the oxide protective film precursor film forming step, an oxide protective film precursor solution containing a solvent and a metal component in which 50 atom% or more is indium is applied onto the oxide semiconductor film containing indium formed on the substrate. Thus, an oxide protective film precursor film is formed.

(substrate)
First, an object to be coated (a substrate with an oxide semiconductor film) in which an oxide semiconductor film containing indium is formed on a substrate as a film to be protected is prepared.
There is no restriction | limiting in particular about the shape of a board | substrate, a structure, a magnitude | size, It can select suitably according to the objective. The structure of the substrate may be a single layer structure or a laminated structure.

The material constituting the substrate is not particularly limited. The substrate is made of glass, an inorganic material such as YSZ (Yttria-Stabilized Zirconia), a resin (organic material), or a composite material of an inorganic material and an organic material. Etc. can be used. Among them, a resin substrate or a substrate made of a composite material is preferable from the viewpoint of light weight and flexibility.
Specifically, as a resin substrate, polybutylene terephthalate, polyethylene terephthalate, polyethylene naphthalate, polybutylene naphthalate, polystyrene, polycarbonate, polysulfone, polyethersulfone, polyarylate, allyl diglycol carbonate, polyamide, polyimide, polyamideimide, Fluorine resins such as polyetherimide, polybenzazole, polyphenylene sulfide, polycycloolefin, norbornene resin, polychlorotrifluoroethylene, liquid crystal polymer, acrylic resin, epoxy resin, silicone resin, ionomer resin, cyanate resin, crosslinked fumaric acid diester , Synthetic trees such as cyclic polyolefin, aromatic ether, maleimide / olefin, cellulose, episulfide compound, etc. Board, and the like.
As a substrate made of a composite material, a composite plastic material containing silicon oxide particles, a composite plastic material containing metal nanoparticles, inorganic oxide nanoparticles, inorganic nitride nanoparticles, etc., a composite containing carbon fibers, carbon nanotubes, etc. Composite plastic material including plastic material, glass flake, glass fiber, glass bead, etc., composite plastic material including particles having clay mineral or mica-derived crystal structure, thin glass and any of the above-mentioned synthetic resins Examples thereof include a laminated plastic material having at least one bonding interface therebetween, and a substrate such as a composite material having at least one bonding interface by alternately laminating inorganic layers and organic layers and having barrier performance.
As a substrate made of an inorganic material, a stainless steel substrate, a metal multilayer substrate in which different metals are laminated with stainless steel, an aluminum substrate, or an oxide film with improved surface insulation by performing oxidation treatment (for example, anodic oxidation treatment) on the surface An aluminum substrate, a silicon substrate with an oxide film, or the like can be used.
The resin substrate is preferably excellent in heat resistance, dimensional stability, solvent resistance, electrical insulation, workability, low air permeability, low moisture absorption, and the like. The resin substrate may include a gas barrier layer for preventing permeation of moisture and oxygen, an undercoat layer for improving the flatness of the resin substrate and adhesion with the lower electrode, and the like.

  Although there is no restriction | limiting in particular in the thickness of the board | substrate used by this indication, It is preferable that they are 50 micrometers or more and 500 micrometers or less. When the thickness of the substrate is 50 μm or more, the flatness of the substrate itself is further improved. Further, 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 device becomes easier.

(Oxide semiconductor film)
There is no particular limitation on the oxide semiconductor film containing indium formed over the substrate as long as it contains indium and oxygen and functions as a semiconductor film and has electron transfer characteristics. In order to easily obtain high electron transfer characteristics, it is preferable that 50 atom% or more of the metal component contained in the oxide semiconductor film is indium.
Specifically, as a material for forming the oxide semiconductor film, indium oxide (In ₂ O ₃ ), In—Ga—Zn—O (IGZO), In—Zn—O (IZO), In—Ga—O ( IGO), In—Sn—O (ITO), In—Sn—Zn—O (ITZO), and the like.

  The oxide semiconductor film is not necessarily in direct contact with the substrate, and an insulating film, a conductive film, or the like may be provided between the substrate and the oxide semiconductor film as necessary.

  There is no limitation on the method for forming an oxide semiconductor film, and wet methods such as a printing method and a coating method, physical methods such as a vacuum deposition method, a sputtering method, and an ion plating method, and chemical vapor deposition (CVD). ), And a chemical method such as a plasma CVD method can be selected in consideration of suitability with the material to be used. It is preferable to use a wet method from the viewpoint that a film can be easily formed under atmospheric pressure.

  As a method of applying a coating solution (oxide semiconductor precursor solution) for forming an oxide semiconductor film on a substrate by a wet method, a spray coating method, a spin coating method, a blade coating method, a dip coating method, a casting method , Roll coating method, bar coating method, die coating method, mist method, ink jet method, dispenser method, screen printing method, relief printing method, intaglio printing method and the like. In particular, from the viewpoint of easily forming a fine pattern, it is preferable to use at least one coating method selected from an inkjet method, a dispenser method, a relief printing method, and an intaglio printing method.

  The solvent used for the oxide semiconductor precursor solution is not particularly limited as long as the metal atom-containing compound used as the solute is dissolved, and water, alcohol solvents (methanol, ethanol, propanol, ethylene glycol, etc.), amide solvents ( N, N-dimethylformamide, etc.), ketone solvents (acetone, N-methylpyrrolidone, sulfolane, N, N-dimethylimidazolidinone, etc.), ether solvents (tetrahydrofuran, methoxyethanol, etc.), nitrile solvents (acetonitrile, etc.), etc. Examples include heteroatom-containing solvents other than those described above. A solvent may be used individually by 1 type and may be used in mixture of 2 or more types. In particular, it is preferable to use at least one selected from methanol, methoxyethanol, and water from the viewpoints of improving solubility and wettability, and reducing cost and environmental burden.

In addition, from the viewpoint of obtaining a dense oxide semiconductor film at low temperature, an oxide semiconductor precursor film is formed by applying an oxide semiconductor precursor solution containing a solvent and indium on a substrate, and then forming an oxide semiconductor precursor film. An oxide semiconductor film in which is converted is preferable.
As a method for converting the oxide semiconductor precursor film into the oxide semiconductor film, it is preferable to convert the oxide semiconductor precursor film into an oxide semiconductor film by performing ultraviolet irradiation under conditions where the oxide semiconductor precursor film is heated. Note that the substrate heating temperature and ultraviolet irradiation conditions when the oxide semiconductor precursor film is converted into the oxide semiconductor film are the same as those in the process of converting the oxide protective film precursor film described later into the oxide protective film. The conditions can be applied.

(Oxide protective film precursor solution)
An oxide protective film precursor solution for forming an oxide protective film precursor film on the oxide semiconductor film is prepared. In the present disclosure, an oxide protective film precursor solution containing a solvent and a metal component in which 50 atom% or more is indium is used as the oxide protective film precursor solution. With a metal composition in which 50 atom% or more of the metal component contained in the solution is indium, an oxide protective film with extremely little reaction with the oxide semiconductor film containing indium can be formed.

  The proportion of indium in the metal component contained in the oxide protective film precursor solution is preferably high, and preferably contains no metal component other than indium, but from the viewpoint of forming an oxide protective film having a higher specific resistance. The oxide protective film precursor solution may contain other metal components other than indium as necessary. Examples of metal components other than indium include zinc, tin, gallium, and aluminum.

  The specific resistance (insulating property) of the oxide protective film produced in the present disclosure is, for example, the type and content of each metal component contained in the oxide protective film precursor solution, the metal contained in the oxide protective film precursor solution It varies depending on the type and content other than the components, the oxygen concentration contained in the atmosphere in the conversion step, the thickness of the protective film, and the like.

  On the other hand, the present inventors have found that the type of the solvent contained in the oxide protective film precursor solution greatly affects the specific resistance (insulating property) of the oxide protective film. From the viewpoint of increasing the specific resistance (insulating property) of the oxide protective film, the oxide protective film precursor solution used in the present disclosure preferably includes at least one of a solvent having an acyl group and a polyol as a solvent.

  Here, the acyl group means a group having an R—CO— skeleton obtained by removing OH from a carboxylic acid, and specifically includes an acetyl group, a formyl group, a propionyl group, a benzoyl group, an acryloyl group, and the like. . Among the acyl groups, a solvent having an acetyl group is preferable from the viewpoint of the specific resistance of the oxide protective film obtained. Examples of the solvent having an acetyl group include acetylacetone, acetic acid, acetoacetic acid, acetophenone, and the like, and acetylsetone is preferable from the viewpoint of solubility and wettability.

  The polyol means a compound containing two or more hydroxyl groups (—OH) in the molecular skeleton. Specific examples include ethylene glycol, propylene glycol, diethylene glycol, butanediol, glycerin and the like, and ethylene glycol is preferable from the viewpoint of solubility, wettability and the like.

  The oxide protective film precursor solution used in the present disclosure preferably includes at least one of acetylacetone and ethylene glycol as a solvent. Since the oxide protective film precursor solution contains at least one solvent of acetylacetone and ethylene glycol, even if 50 atom% or more of the metal component contained in the oxide protective film is indium, the conductivity of the oxide protective film is improved. Thus, it is possible to function as an insulating protective film rather than as a semiconductor.

  The conductivity of an oxide film is generally greatly influenced by oxygen defects in the film, and the conductivity tends to decrease as the number of oxygen defects decreases. When a protective film precursor film is formed using the above-mentioned solvent and converted to an oxide protective film, oxygen is easily combined with indium, which is a main metal component, and oxygen defects are estimated to be reduced. . On the other hand, according to experiments by the present inventors, it was found that when the protective film precursor film according to the present disclosure was formed using the above-described solvent, the carbon concentration in the oxide protective film was increased. If carbon is contained as a simple impurity in the film, the electrical stability of the electronic device will be affected and the operational stability will be degraded. It is presumed that the influence on the device is suppressed and contributes to the operational stability of the electronic device.

  Indium contained in the oxide protective film precursor solution is preferably contained as indium ions from the viewpoint of easy preparation of the solution, flatness of the oxide protective film, and the like. The indium ion in the present disclosure may be an indium complex ion coordinated with a ligand such as a solvent molecule. Moreover, it is preferable that other metal components other than indium which can be contained in the solution are also contained as ions.

In the oxide protective film precursor solution used in the present disclosure, a metal atom-containing compound (solute) is used as a raw material for the metal component. Examples of the metal atom-containing compound include metal salts, metal halides, and organometallic compounds.
The oxide protective film precursor solution is obtained by weighing a solute such as a metal salt as a raw material so that the solution has a desired concentration, and stirring and dissolving in a solvent. The time for stirring and the temperature of the solution during stirring are not particularly limited as long as the solute is sufficiently dissolved.

  Metal salts include nitrates, sulfates, phosphates, carbonates, acetates, oxalates, metal halides include chlorides, iodides, bromides, etc., and organometallic compounds include metal alkoxides, organic acid salts, metal Examples include β-diketonate.

  The oxide protective film precursor solution preferably contains nitrate ions in addition to indium, and more preferably a solution in which at least indium nitrate is dissolved. An oxide protective film precursor film obtained by applying a solution in which indium nitrate is dissolved can be easily converted into a dense indium-containing oxide protective film at a relatively low temperature. Indium nitrate may be a hydrate.

  The total concentration of the metal components in the oxide protective film precursor solution can be selected according to the target viscosity, film thickness, specific resistance, and the like. From the viewpoint of flatness and productivity of the oxide protective film, it is preferably 0.01 mol / L or more and 0.5 mol / L or less.

(Application)
Next, an oxide protective film precursor solution is applied onto the oxide semiconductor film.
As a method of applying the oxide protective film precursor solution, spray coating method, spin coating method, blade coating method, dip coating method, casting method, roll coating method, bar coating method, die coating method, mist method, inkjet method, Examples thereof include a dispenser method, a screen printing method, a relief printing method, and an intaglio printing method. In particular, from the viewpoint of selectively forming a pattern on the oxide semiconductor film, it is preferable to use at least one coating method selected from an inkjet method, a dispenser method, a relief printing method, and an intaglio printing method.

(Dry)
After the oxide protective film precursor solution is applied on the oxide semiconductor film, it may be naturally dried to obtain an oxide protective film precursor film. However, the coating film is dried by heat treatment, and the oxide protective film precursor film is then dried. It is preferable to obtain By drying, the fluidity of the coating film can be reduced, and the flatness of the finally obtained oxide protective film can be improved. Further, by selecting an appropriate drying temperature (for example, 35 ° C. or more and 100 ° C. or less), a denser oxide protective film can be finally obtained. The method for the heat treatment is not particularly limited, and can be selected from hot plate heating, electric furnace heating, infrared heating, microwave heating, and the like.
Drying is preferably started within 5 minutes after applying the solution on the substrate from the viewpoint of keeping the flatness of the film uniform.
The drying time is not particularly limited, but is preferably 15 seconds or longer and 10 minutes or shorter from the viewpoint of film uniformity and productivity.
Moreover, there is no restriction | limiting in particular in the atmosphere in drying, but it is preferable to carry out in air | atmosphere under atmospheric pressure from viewpoints, such as manufacturing cost.

<Conversion process to oxide protective film>
In the conversion step to the oxide protective film (hereinafter sometimes referred to as “conversion step”), the oxide protective film precursor film is converted into an oxide protective film having a higher specific resistance than the oxide semiconductor film.
There is no particular limitation on the method for converting the oxide protective film precursor film into the oxide protective film, and examples include a method using heating, plasma, ultraviolet light, microwave, etc. From the viewpoint of performing, a method of performing ultraviolet irradiation under conditions where the oxide protective film precursor film is heated is preferable.

The atmosphere at the time of conversion preferably has an oxygen concentration of 8% or less (80000 ppm or less), and more preferably 3% or less (30000 ppm or less). If the oxygen concentration is 80,000 ppm or less, a denser oxide protective film can be easily obtained, and the repeated operation stability as an electronic device is easily improved.
As a means for adjusting the oxygen concentration in the atmosphere in the conversion step to the above concentration range, for example, the flow rate of an inert gas such as nitrogen gas supplied into the processing chamber for converting the oxide protective film precursor film on the substrate is adjusted. Examples thereof include a method, a method of adjusting the oxygen concentration in the gas supplied into the processing chamber, and a method of evacuating the processing chamber in advance and filling it with a gas having a desired oxygen concentration.

The substrate temperature in the conversion step is preferably less than 200 ° C and more preferably more than 120 ° C. If it is less than 200 ° C., it can be easily applied to a resin substrate having low heat resistance, and if it exceeds 120 ° C., a dense oxide protective film can be obtained in a short time.
The heating means for the substrate in the conversion step is not particularly limited, and may be selected from hot plate heating, electric furnace heating, infrared heating, microwave heating, and the like. Further, from the viewpoint of obtaining a dense oxide protective film in a short time, it is preferable that the rate at which the substrate is heated or lowered in the conversion step is within ± 0.5 ° C./min, and the substrate temperature can be kept constant. More preferred.
The conversion step is preferably from 5 seconds to 120 minutes from the viewpoint of productivity.

  Also, from the viewpoint of achieving high electron transfer characteristics, it is preferable that the rate of temperature rise or fall of the substrate during ultraviolet irradiation is within ± 0.5 ° C / min, and the substrate temperature during ultraviolet irradiation is constant. Is more preferable. The substrate temperature during ultraviolet irradiation can be controlled by adjusting the output of a heating means such as a hot plate for heating the substrate. The substrate temperature can be measured with a Si substrate with a thermocouple.

The film surface of the oxide protective film precursor film is preferably irradiated with ultraviolet light having a wavelength of 300 nm or less at an illuminance of 10 mW / cm ² or more. By irradiating ultraviolet light in the wavelength range within the illuminance range, conversion from the oxide protective film precursor film to the oxide protective film can be performed in a shorter time.

  The illuminance of ultraviolet rays can be adjusted by selecting a light source to be used, a light collecting mechanism, a neutral density filter, and the like.

  Examples of the ultraviolet light source used in the conversion step include a UV (ultraviolet) lamp and a laser. A UV lamp is preferable from the viewpoint of uniformly irradiating ultraviolet rays with inexpensive equipment uniformly over a large area. Examples of UV lamps include excimer lamps, deuterium lamps, low pressure mercury lamps, high pressure mercury lamps, ultrahigh pressure mercury lamps, metal halide lamps, helium lamps, carbon arc lamps, cadmium lamps, electrodeless discharge lamps, etc. Use of a mercury lamp is preferable because conversion from the oxide protective film precursor film to the oxide protective film can be easily performed.

  Through the above steps, an oxide protective film containing indium can be easily manufactured over the oxide semiconductor film containing indium.

[Thin Film Transistor Manufacturing Method and Thin Film Transistor]
Since the oxide protective film manufactured according to the present disclosure can suppress deterioration of the semiconductor characteristics of the oxide semiconductor film and provide high operational stability, an active layer (semiconductor layer) in a thin film transistor (TFT) is provided. It can be suitably used as an oxide protective film to be protected.

  Hereinafter, an embodiment in which an oxide protective film manufactured using the manufacturing method according to the present disclosure is used as an oxide protective film for protecting an active layer of a thin film transistor will be described. In addition, the manufacturing method of the oxide protective film which concerns on this indication, and the oxide protective film manufactured by it are not limited to the use in preparation of TFT.

In general, in the element structure of a TFT, when the substrate on which the TFT is formed is the lowermost layer, a gate electrode is disposed above the gate insulating film and an active layer is formed below the gate insulating film. A so-called staggered structure (also referred to as a top gate type or top gate structure) and an inverted staggered structure (bottom gate type or bottom gate type) in which a gate electrode is disposed below the gate insulating film and an active layer is formed above the gate insulating film. Also called bottom gate structure).
Further, based on the contact portion between the active layer and the source and drain electrodes (referred to as “source / drain electrodes” as appropriate), the source / drain electrodes are formed prior to the semiconductor layer, and the lower surface of the semiconductor layer is the source / drain electrode. A bottom contact type (bottom contact structure) in contact with the drain electrode, and a top contact type (top contact structure) in which the semiconductor layer is formed before the source / drain electrodes and the upper surface of the semiconductor layer is in contact with the source / drain electrodes. There is.

  When the manufacturing method of the oxide protective film according to the present disclosure is applied to a thin film transistor, the element structure of the thin film transistor is not particularly limited. However, after manufacturing the bottom gate structure TFT, after forming the oxide semiconductor film serving as an active layer The electrical characteristics of the oxide semiconductor film are easily affected by the outside air, solution, upper layer, and the like. Therefore, when the manufacturing method of the oxide protective film according to the present disclosure is applied to the formation of the protective film that protects the oxide semiconductor film when manufacturing the TFT having the bottom gate structure, the effect is easily manifested.

  Hereinafter, as a representative example of an electronic device manufactured by applying the method for manufacturing an oxide protective film according to the present disclosure, at least a gate electrode, a gate insulating film, an oxide semiconductor film containing indium, and an oxide semiconductor film A thin film transistor having the oxide protective film, the source electrode, and the drain electrode according to the above-described embodiment that partially protects, and a manufacturing method thereof will be described.

  The method for manufacturing a thin film transistor according to the present disclosure preferably includes a step of forming a gate electrode on a substrate, a step of forming a gate insulating film on the substrate and the gate electrode, and an oxide semiconductor containing indium on the gate insulating film. Forming the film; forming the source electrode and the drain electrode on the oxide semiconductor film; and protecting the oxide according to the above-described embodiment on the oxide semiconductor film exposed between the source electrode and the drain electrode. Forming an oxide protective film having a specific resistance higher than that of the oxide semiconductor film by the film manufacturing method.

  FIG. 1 is a schematic diagram illustrating an example of a configuration of a TFT according to the present disclosure. The TFT 10 shown in FIG. 1 has a bottom gate structure and a top contact structure. On one main surface of the substrate 12, a gate electrode 14, a gate insulating film 16, an oxide semiconductor film 18 containing indium as an active layer, Are stacked in order. On the surface of the active layer 18, a source electrode 20 and a drain electrode 22 (referred to as “source / drain electrodes” as appropriate) are provided with a gap, and are further exposed from the gap between the source electrode 20 and the drain electrode 22. An oxide protective film 24 that protects the oxide semiconductor film 18 is provided over the oxide semiconductor film 18 to be formed.

  FIG. 2 is a schematic diagram illustrating another example of the configuration of the TFT according to the present disclosure. The TFT 30 shown in FIG. 2 also has a bottom gate structure, and the arrangement of the substrate 12, the gate electrode 14, the gate insulating film 16, and the oxide semiconductor film 18 is the same as that of the TFT 10 shown in FIG. An oxide protective film 24 is provided on the oxide semiconductor film 18, and a source electrode 20 and a drain electrode 22 are provided on the oxide protective film 24 with a gap.

  FIG. 3 is a schematic diagram illustrating another example of the configuration of the TFT according to the present disclosure. The TFT 40 shown in FIG. 3 also has a bottom gate structure and a bottom contact structure, and the arrangement of the substrate 12, the gate electrode 14, and the gate insulating film 16 is the same as that of the TFT 10 shown in FIG. On the gate insulating film 16, a source electrode 20 and a drain electrode 22 are provided with a gap, and an oxide semiconductor film 18 is provided in contact with the source electrode 20 and the drain electrode 22. Further, an oxide protective film 24 is provided on the oxide semiconductor film 18.

1 to 3, the TFT 10, 30, and 40 can be easily manufactured, the oxide semiconductor film 18 can be effectively protected by the oxide protective film 24, linear mobility, and threshold shift (repeatedly). In view of excellent TFT characteristics such as (operational stability), the TFT 10 has a bottom gate structure, and the source electrode 20 and the drain electrode 22 are formed on the oxide semiconductor film 18 as shown in FIG. In addition, the oxide protective film 24 is particularly preferably formed on the oxide semiconductor film 18 exposed between the source electrode 20 and the drain electrode 22.
Hereinafter, as a representative example, the structure and manufacturing method of the TFT 10 mainly shown in FIG. 1 will be described in detail. In the following description, reference numerals are omitted as appropriate.

(Gate electrode)
A gate electrode is formed on the substrate. The gate electrode is made of a material having high conductivity. For example, a metal such as Al, Mo, Cr, Ta, Ti, Au, Ag, Al—Nd, Ag alloy, tin oxide, zinc oxide, indium oxide, indium tin oxide ( It can be formed using a conductive film of a metal oxide such as ITO), indium zinc oxide (IZO), or In—Ga—Zn—O (IGZO). As the gate electrode, these conductive films can be used as a single layer structure or a stacked structure of two or more layers.

The gate electrode is a material used from a wet method such as a printing method or a coating method, a physical method such as a vacuum deposition method, a sputtering method or an ion plating method, or a chemical method such as CVD or plasma CVD method. The film is formed according to a method appropriately selected in consideration of the suitability of the above.
The film thickness of the conductive film for forming the gate electrode is preferably 10 nm or more and 1000 nm or less, preferably 50 nm or more and 200 nm or less in consideration of film forming property, patterning property by etching or lift-off method, conductivity, and the like. It is more preferable.
After film formation, the gate electrode may be formed by patterning into a predetermined shape by an etching or lift-off method, or the pattern may be directly formed by an inkjet method or the like. At this time, it is preferable to pattern the gate electrode and the gate wiring at the same time.

(Gate insulation film)
After forming the gate electrode and the wiring, a gate insulating film is formed. The gate insulating film is preferably a highly insulating film, for example, an insulating film such as SiO ₂ , SiN _x , SiON, Al ₂ O ₃ , Y ₂ O ₃ , Ta ₂ O ₅ , HfO ₂ , or a compound thereof. It may be an insulating film including two or more, and may have a single layer structure or a laminated structure.
The gate insulating film is a material used from a wet method such as a printing method and a coating method, a physical method such as a vacuum deposition method, a sputtering method, and an ion plating method, and a chemical method such as a CVD and a plasma CVD method. The film is formed according to a method appropriately selected in consideration of the suitability of the above.

  The gate insulating film needs to have a thickness for reducing the leakage current and improving the voltage resistance. On the other hand, if the thickness of the gate insulating film is too large, the driving voltage is increased. Although depending on the material of the gate insulating film, the thickness of the gate insulating film is preferably 10 nm to 10 μm, more preferably 50 nm to 1000 nm, and particularly preferably 100 nm to 400 nm.

(Oxide semiconductor film)
An active layer including an oxide semiconductor film is patterned on the gate insulating film. The pattern formation of the active layer may be performed by forming an oxide semiconductor precursor film having an active layer pattern in advance by the inkjet method, the dispenser method, the relief printing method, and the intaglio printing method, and converting the oxide layer into an oxide semiconductor film. Alternatively, the oxide semiconductor film may be patterned into the shape of the active layer by photolithography and etching. In order to form a pattern by photolithography and etching, a resist pattern is formed by photolithography on the remaining portion, and etching is performed with an acid solution such as hydrochloric acid, nitric acid, dilute sulfuric acid, or a mixed solution of phosphoric acid, nitric acid and acetic acid. Form a pattern.
The thickness of the oxide semiconductor film (active layer) is preferably 5 nm or more and 50 nm or less from the viewpoint of flatness and time required for film formation.

(Source / drain electrodes)
Source / drain electrodes are formed on the active layer. The source / drain electrodes are made of materials having high conductivity so as to function as electrodes, respectively, such as metals such as Al, Mo, Cr, Ta, Ti, Au, and Ag, Al—Nd, Ag alloy, tin oxide, and zinc oxide. In addition, a conductive film of a metal oxide such as indium oxide, indium tin oxide (ITO), zinc indium oxide (IZO), or In—Ga—Zn—O (IGZO) can be used.

The source / drain electrodes can be formed from, for example, a printing method, a wet method such as a coating method, a physical method such as a vacuum deposition method, a sputtering method, or an ion plating method, or a chemical method such as CVD or plasma CVD method. The film may be formed according to a method selected appropriately in consideration of suitability with the material to be used.
The film thickness of the source / drain electrodes is preferably 10 nm or more and 1000 nm or less, and more preferably 50 nm or more and 100 nm or less in consideration of film formability, patterning property by etching or lift-off method, conductivity, and the like.
The source / drain electrodes may be formed by patterning into a predetermined shape by an etching or lift-off method, or may be directly formed by an inkjet method or the like. At this time, it is preferable to pattern all layers of the source / drain electrodes and wirings connected to these electrodes simultaneously.

(Oxide protective film)
An oxide protective film is formed over the oxide semiconductor film according to the method of the above-described embodiment.
The oxide protective film is formed over the oxide semiconductor film after the oxide semiconductor film is formed. The oxide protective film may be formed after the oxide semiconductor film is formed, or after the oxide semiconductor film is patterned into the shape of the active layer.
The oxide protective film may be formed on the oxide semiconductor film exposed between the source and drain electrodes after the formation of the source and drain electrodes, as in the TFT 10 shown in FIG. 1, or the TFT 30 shown in FIG. As described above, it may be formed on the oxide semiconductor film before forming the source / drain electrodes. Alternatively, as in the TFT 40 shown in FIG. 3, an oxide semiconductor film may be formed after the source / drain electrodes are formed, and an oxide protective film may be formed over the oxide semiconductor film.

When the carbon concentration in the oxide semiconductor film in the thin film transistor manufactured according to the present disclosure is C _S (atom / cm ³ ) and the carbon concentration in the oxide protective film is C _P (atom / cm ³ ), the following relationship is established. It is preferable to satisfy Formula (I-1).
C _P / C _S ≧ 10 (I-1)

By satisfying the formula (I-1), a thin film transistor having high linear mobility and improved repeated operation stability (threshold shift is small) can be obtained.
From this viewpoint, it is more preferable to satisfy the following formula (I).
100 ≧ C _P / C _S ≧ 10 (I)

When the carbon concentration C _P in the oxide protective film satisfies the relational expression (I) with respect to the carbon concentration C _S in the oxide semiconductor film, the conductivity of the oxide protective film is suppressed, not the semiconductor, It becomes possible to function as an insulating protective film.
As a method for obtaining an oxide semiconductor film and an oxide protective film satisfying the above relational expression, a method of forming the oxide semiconductor film and the oxide protective film by different film formation methods (for example, vacuum film formation of an oxide semiconductor film, In the case where the oxide protective film is formed by a solution process), and when both the oxide semiconductor film and the oxide protective film are formed by a solution process, a method using a solution of a different solvent type may be used.

The carbon concentration C _S in the oxide semiconductor film is preferably 1 × 10 ²¹ atoms / cm ³ or less. By setting the carbon concentration range, an oxide semiconductor film having high electron transfer characteristics can be easily obtained.

Carbon concentration _{C P} in the oxide protective film is preferably at most ^{1 × 10 22 atoms / cm 3} . High operational stability is easily obtained by adjusting the carbon concentration range.

  The carbon concentration, the nitrogen concentration, and the hydrogen concentration in the oxide semiconductor film and the oxide protective film can be obtained by measurement by secondary ion mass spectrometry (SIMS). SIMS is known to be difficult to obtain accurate data in the vicinity of the sample surface and in the vicinity of the interface between different materials due to its principle. When analyzing the distribution of the impurity concentration in the film in the thickness direction by SIMS, a value in a region where an almost constant intensity is obtained without any extreme intensity fluctuation in the range where the film to be measured exists is adopted.

  The thickness of the oxide protective film is preferably 5 nm or more and 50 nm or less from the viewpoint of protecting the oxide semiconductor film, and further from flatness and time required for film formation.

[Electronic device]
The application of the thin film transistor according to the present disclosure described above is not particularly limited. However, since the thin film transistor according to the present disclosure exhibits high TFT characteristics, for example, an electro-optical device (for example, a liquid crystal display device, an organic EL (Electro Luminescence) display) As a drive element in a display device such as a device or an inorganic EL display device, it is suitable for use in a flexible display formed on a resin substrate having low heat resistance.
In addition, the electronic element according to the present disclosure is suitably used as a driving element (driving circuit) in various electronic devices such as various sensors such as an X-ray sensor and MEMS (Micro Electro Mechanical System).
By applying the thin film transistor manufactured according to the present disclosure, the manufacturing cost of an electronic device having excellent electrical characteristics can be suppressed.

  Hereinafter, as a representative example of the electronic device according to the present disclosure, a liquid crystal display device including the thin film transistor manufactured according to the present embodiment will be specifically described.

<Liquid crystal display device>
FIG. 4 shows a schematic sectional view of a part of a liquid crystal display device according to an embodiment of the present invention, and FIG. 5 shows a schematic configuration diagram of electrical wiring.

  As shown in FIG. 4, the liquid crystal display device 100 of this embodiment includes a liquid crystal layer sandwiched between the TFT 10 having the bottom gate structure shown in FIG. 1, the pixel lower electrode 104 on the passivation layer 102 and the counter upper electrode 106. 108 and an R (red), G (green), and B (blue) color filter 110 for developing different colors corresponding to each pixel, and polarized on the substrate 12 side of the TFT 10 and the RGB color filter 110, respectively. It is the structure provided with board 120a, 120b.

  Further, as shown in FIG. 5, the liquid crystal display device 100 according to the present embodiment includes a plurality of gate lines 112 that are parallel to each other and data lines 114 that are parallel to each other and intersect the gate lines 112. Here, the gate wiring 112 and the data wiring 114 are electrically insulated. The TFT 10 is provided in the vicinity of the intersection between the gate wiring 112 and the data wiring 114.

  The gate electrode 14 of the TFT 10 is connected to the gate wiring 112, and the source electrode 20 of the TFT 10 is connected to the data wiring 114. Further, the drain electrode 22 of the TFT 10 is connected to the pixel lower electrode 104 through a contact hole 116 provided in the passivation layer 102 (a conductor is embedded in the contact hole 116). The pixel lower electrode 104 forms a capacitor 118 together with the grounded counter upper electrode 106.

In the liquid crystal display device 100 of the above embodiment, the TFT having the structure shown in FIG. 1 is provided. However, the TFT is not limited to the TFT having the structure shown in FIG. Also good.
In addition, the electronic device according to the present disclosure is not limited to the liquid crystal display device having the configuration illustrated in FIGS. 4 and 5, and the manufacturing method of the oxide protective film according to the present disclosure includes an organic EL display device, an X-ray sensor, and the like. It can also be applied to other electronic devices.

  Examples will be described below, but the present invention is not limited to these examples.

<Example 1>
A TFT was fabricated and evaluated according to the following procedure.

An oxide semiconductor film was formed over the substrate by the following method.
Indium nitrate (In (NO ₃ ) ₃ xH ₂ O, purity: 4N, manufactured by Kojundo Chemical Laboratory Co., Ltd.) was dissolved in 2-methoxyethanol (special grade reagent, manufactured by Wako Pure Chemical Industries, Ltd.), and 0 An indium nitrate solution (oxide semiconductor precursor solution) having a concentration of 1 mol / L was prepared.
A simple TFT using a p-type silicon substrate with a thermal oxide film as a substrate and using the thermal oxide film as a gate insulating film was fabricated. The prepared indium nitrate solution was spin coated on a p-type silicon 25 mm square substrate with a thermal oxide film at a rotational speed of 1500 rpm for 30 seconds, and then dried on a hot plate heated to 60 ° C. for 5 minutes.

The obtained oxide semiconductor precursor film was converted into an oxide semiconductor film under the following conditions.
As an apparatus, a vacuum ultraviolet (VUV) dry processor (manufactured by Oak Manufacturing Co., Ltd., VUE-3400-F) equipped with a low-pressure mercury lamp was used.
The sample was set on a hot plate heated to a surface temperature of 160 ° C. in the apparatus, and waited for 5 minutes. During this time, the oxygen concentration in the processing chamber was set to 27000 ppm by flowing nitrogen of 30 L / min into the processing chamber. The oxygen concentration in the apparatus treatment chamber was measured using an oxygen concentration meter (Yokogawa Electric Corporation, OX100).

After waiting for 5 minutes, the shutter in the apparatus was opened, and the oxide semiconductor precursor film was subjected to ultraviolet irradiation treatment at 160 ° C. for 90 minutes to obtain an oxide semiconductor film. During the ultraviolet irradiation treatment under the heat treatment, 50 L / min of nitrogen was always flowed.
Ultraviolet illuminance with a wavelength of 254 nm as a peak wavelength at the sample position is measured using an ultraviolet integrated light meter (manufactured by Hamamatsu Photonics, controller C9536, sensor head H9536-254, having a spectral sensitivity in the range of more than 200 nm to less than 300 nm) The measured value was 105 mW / cm ² . In addition, the ultraviolet illuminance with a wavelength of 185 nm as a peak wavelength is measured using an ultraviolet integrating light meter (manufactured by Hamamatsu Photonics, controller C9536, sensor head H9536-185, having a spectral sensitivity in the range of about 150 to 200 nm) It was 8.2 mW / cm ² .

  A source / drain electrode was formed on the obtained oxide semiconductor film by vapor deposition. The source / drain electrodes were formed by pattern formation using a metal mask, and a Ti film was formed to a thickness of 50 nm. The size of the source / drain electrodes was 1 mm square, and the distance between the electrodes was 0.2 mm.

Next, an oxide protective film was formed on the oxide semiconductor film between the source and drain electrodes by an inkjet method.
As the oxide protective film precursor solution, indium nitrate (In (NO ₃ ) ₃ × H ₂ O, purity: 4N, manufactured by Kojundo Chemical Laboratory Co., Ltd.) was used as ethylene glycol (special reagent grade, Wako Pure Chemical Industries, Ltd.). The indium nitrate solution having a concentration of 0.3 mol / L was prepared.
Oxide protective film precursor solution (indium nitrate solution) is patterned using a material printer DMP-2831 manufactured by Fuji Film Co., Ltd. to form a 2 mm x 0.4 mm oxide protective film precursor film covering the entire area between the source and drain electrodes. did. The ink cartridge was at room temperature, the stage with a heating function on which the substrate was placed was heated to 60 ° C., and the indium nitrate solution was applied by inkjet.

Next, the oxide protective film precursor film was converted into an oxide protective film. The conversion process to the oxide protective film is performed under the same conditions as the conversion process of the oxide semiconductor film by ultraviolet irradiation under the same heat treatment (90 minutes, 160 ° C.) as the conversion process to the oxide semiconductor film described above. It was.
Through the above steps, a thin film transistor was manufactured.

<Example 2>
A thin film transistor was fabricated in the same manner as in Example 1 except that an oxide protective film was formed on the oxide semiconductor film using acetylacetone (special grade, manufactured by Wako Pure Chemical Industries, Ltd.) as a solvent for the oxide protective film precursor solution. Produced.

<Comparative Example 1>
As a protective film precursor solution, NN120-20 (polysilazane 20% by mass, xylene 80% by mass, manufactured by AZ Electronic Materials) was diluted twice with AZ-Thinner (2-ethoxyethyl acetate) to obtain a polysilazane solution. It was. A thin film transistor was manufactured in the same manner as in Example 1 except that a silicon oxynitride protective film was formed on the oxide semiconductor film using this polysilazane solution.

<Comparative example 2>
A thin film transistor was fabricated in the same manner as in Example 1 except that the oxide protective film was not formed after the source / drain electrodes were formed.

<Example 3>
As the oxide protective film precursor solution, an indium nitrate solution having a concentration of 0.3 mol / L used in Example 1, zinc nitrate (Zn (NO ₃ ) ₂ .6H ₂ O, purity: 3N, high by Co., Ltd. A zinc nitrate solution having a concentration of 0.3 mol / L prepared by dissolving (purity chemical laboratory) in ethylene glycol is mixed at a ratio of 1: 1, and 50 atom% of the metal component contained in the solution is indium. An oxide protective film precursor solution was prepared. An oxide protective film was produced on the oxide semiconductor film by the same method as in Example 1 except that this oxide protective film precursor solution was used, and a thin film transistor was produced.

<Comparative Example 3>
As the oxide protective film precursor solution, the indium nitrate solution having a concentration of 0.3 mol / L used in Example 1 and the zinc nitrate solution having a concentration of 0.3 mol / L used in Example 3 were 1: 4. The oxide protective film precursor solution in which 20 atom% of the metal component contained in the solution was indium was mixed at a ratio. An oxide protective film was produced on the oxide semiconductor film by the same method as in Example 1 except that this oxide protective film precursor solution was used, and a thin film transistor was produced.

[Evaluation]
(Evaluation of TFT characteristics)
The thin film transistor manufactured in Examples and Comparative Examples, using a semiconductor parameter analyzer 4156C (manufactured by Agilent Technologies), it was measured transistor characteristics V _g -I _d. Measurement of V _g -I _d characteristics, the drain voltage _{(V d)} is fixed to + 1V, the gate voltage _{(V g)} is changed within the range of -15V~ + 30V, the drain current at gate voltages _(I d) It was performed by measuring.

In addition, after completion of the gate voltage sweep of −15 V to +30 V to −15 V, the operation of performing the sweep of −15 V to +30 V to −15 V again after 10 minutes is repeated 10 times, and the threshold value (V _th ) and it was determined the difference between the 10 th _{V th} at the time of the sweep as a threshold shift (ΔV _th).

Linear mobility was determined from the ratio and the kind of solvent _and, V _g -I _d characteristics of the indium (In) to the total amount of metal components contained in the protective film precursor solution used in Examples and Comparative Examples in Table 1, V _th, ΔV _th is shown.

Examples 1 to 3 show linear mobility and _Vth equivalent to the characteristics before the formation of the protective film (Comparative Example 2), and the characteristics of the oxide semiconductor film are hardly changed by the formation of the protective film. Recognize.
In addition, it can be seen that the threshold shift (ΔV _th ) due to repeated driving was extremely large before the formation of the oxide protective film, whereas ΔV _th was significantly reduced by the formation of the oxide protective film. In the formation of the oxide protective film using the polysilazane solution of Comparative Example 1, the threshold value (V _th ) was significantly shifted in the negative direction due to the formation of the protective film.
When the indium content of the metal component in the oxide protective film is 50 atom% or more, stable operation is possible where ΔV _th is less than −2 V, but when the indium content is 20 atom% (Comparative Example 3), ΔV _th It can be seen that the operation becomes unstable.

(Evaluation of carbon concentration)
The SIMS analysis was performed about the oxide protective film produced on the conditions of Example 1 and Comparative Example 1. The measurement apparatus used was PHI ADEPT1010 manufactured by ULVAC PHI. The measurement conditions were Cs + for the primary ion species, 1.0 kV for the primary acceleration voltage, and 140 μm × 140 μm for the detection region.

Table 2 was estimated by SIMS, showing the carbon concentration _{C P} of the protective oxide film of Examples 1 to 3 and Comparative Examples 1 and 3.
Note that the carbon concentration C _S in the oxide semiconductor film in each example is 5.0 × 10 ²⁰ [atoms / cm ³ ]. The ratio of the carbon concentration _C S in the oxide semiconductor film (atoms / cm ³⁾ and the carbon concentration _C P of the protective oxide film _{^{(atoms / cm 3) (C}} P / C S) are also shown in Table 2.

That is, the relationship between the carbon concentration C _S in the oxide semiconductor film and the carbon concentration C _P in the oxide protective film was 100 ≧ C _P / C _S ≧ 10 in Examples 1 to 3. In Example 1, C _P / C _S <10, and in Comparative Example 3, C _P / C _S > 100.
From the above, the ratio between the carbon concentration C _P in the oxide protective film and the carbon concentration C _S in the oxide semiconductor film has a great influence on the operational stability (ΔV _th ) of the TFT, particularly 100 ≧ C _P It is considered that the operation stability of the TFT is improved by satisfying the relationship of / C _S ≧ 10.

The disclosure of Japanese Patent Application No. 2015-014626 filed on January 28, 2015 is incorporated herein by reference in its entirety.
All documents, patents, patent applications, and technical standards mentioned in this specification are specifically and individually described as individual documents, patents, patent applications, and technical standards are incorporated by reference. To the same extent, it is incorporated herein by reference.

Claims (21)

An oxide protective film precursor solution containing a solvent and a metal component containing at least 50 atom% of indium is applied onto the oxide semiconductor film containing indium formed on the substrate to form an oxide protective film precursor film. Process,
Converting the oxide protective film precursor film into an oxide protective film having a higher specific resistance than the oxide semiconductor film;
The manufacturing method of the oxide protective film containing this.   The method for producing an oxide protective film according to claim 1, wherein 50 atom% or more of a metal component contained in the oxide semiconductor film is indium.   The manufacturing method of the oxide protective film of Claim 1 or Claim 2 in which the said solvent contains the solvent which has an acyl group.   The method for producing an oxide protective film according to claim 3, wherein the acyl group is an acetyl group.   The manufacturing method of the oxide protective film of Claim 1 or Claim 2 in which the said solvent contains a polyol.   The method for producing an oxide protective film according to claim 4, wherein the solvent contains at least one of acetylacetone and ethylene glycol.   The method for producing an oxide protective film according to claim 1, wherein indium contained in the oxide protective film precursor solution is indium ions.   The method for producing an oxide protective film according to claim 1, wherein the oxide protective film precursor solution contains nitrate ions.   Claims: In the step of converting the oxide protective film precursor film into the oxide protective film, the oxide protective film precursor film is irradiated with ultraviolet rays under the condition that the oxide protective film precursor film is heated. The manufacturing method of the oxide protective film of any one of Claims 1-8.   10. The oxide protective film according to claim 1, wherein in the step of converting the oxide protective film precursor film into the oxide protective film, the temperature of the substrate is maintained at over 120 ° C. 10. Manufacturing method.   The method for producing an oxide protective film according to claim 10, wherein the temperature of the substrate is maintained at less than 200 ° C. in the step of converting the oxide protective film precursor film into the oxide protective film.   The oxide semiconductor film is formed by applying an oxide semiconductor precursor solution containing a solvent and indium on the substrate to form an oxide semiconductor precursor film, and then converting the oxide semiconductor precursor film. It is a semiconductor film, The manufacturing method of the oxide protective film of any one of Claims 1-11.   The oxide protective film manufactured by the manufacturing method of the oxide protective film of any one of Claims 1-12.   A gate electrode, a gate insulating film, an oxide semiconductor film containing indium, the oxide protective film according to claim 13 protecting at least a part of the oxide semiconductor film, a source electrode, a drain electrode, Thin film transistor. A gate electrode; a gate insulating film; an oxide semiconductor film containing indium; a source electrode; a drain electrode; and an oxide protective film that protects at least part of the oxide semiconductor film. A thin film transistor that satisfies the following relational expression (I), where C _{S is} the carbon concentration in the semiconductor film and C _P is the carbon concentration in the oxide protective film.
100 ≧ C _P / C _S ≧ 10 (I)
In the formula (I), the units of C _P and C _S are both atoms / cm ³ . The thin film transistor according to claim 15, wherein a carbon concentration C _S in the oxide semiconductor film is 1 × 10 ²¹ atoms / cm ³ or less. The thin film transistor according to claim 15 or claim 16 carbon concentration _{C P} is 1 × ¹⁰ 22 atoms / cm ³ or more of said protective oxide film.   The thin film transistor according to any one of claims 14 to 17, which has a bottom gate structure.   The source electrode and the drain electrode are formed on the oxide semiconductor film, and the oxide protective film is formed on the oxide semiconductor film exposed between the source electrode and the drain electrode. The thin film transistor according to claim 18, having a structure as described above. Forming a gate electrode on the substrate;
Forming a gate insulating film on the substrate and the gate electrode;
Forming an oxide semiconductor film containing indium on the gate insulating film;
Forming a source electrode and a drain electrode on the oxide semiconductor film;
The method for manufacturing an oxide protective film according to claim 1, wherein the oxide protective film is exposed between the source electrode and the drain electrode. Forming an oxide protective film having a high specific resistance;
The manufacturing method of the thin-film transistor which has this.   The electronic device provided with the thin-film transistor of any one of Claims 14-19.