WO2018074607A1

WO2018074607A1 - Thin-film transistor, production method therefor, and solution for forming gate insulation film for thin-film transistor

Info

Publication number: WO2018074607A1
Application number: PCT/JP2017/038086
Authority: WO
Inventors: 下田　達也; 金望李; 浩晃小山
Original assignee: 凸版印刷株式会社; 国立大学法人北陸先端科学技術大学院大学
Priority date: 2016-10-21
Filing date: 2017-10-20
Publication date: 2018-04-26
Also published as: JPWO2018074607A1; JP7100851B2

Abstract

The purpose of the present invention is to provide: a thin-film transistor having excellent transistor characteristics; and a production method in which the process temperature is 200˚C or lower. This thin-film transistor is provided with: a gate insulation layer which is either formed from an oxide including Zr, and a metal element selected from the group consisting of Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, and Y, the atomic ratio of the metal element to the zirconium being such that the number of atoms of Zr is 1.5 or higher when the number of atoms of the metal element is 1, or formed from an oxide including at least one metal element selected from the group consisting of Hf, Zr, and Al; and an oxide semiconductor layer which is formed from an oxide selected from the group consisting of oxides including In, oxides including In and Sn, oxides including In and Zn, oxides including In, Zr, and Zn, oxides including In and Ga, and oxides including In, Zn, and Ga.

Description

THIN FILM TRANSISTOR, ITS MANUFACTURING METHOD, AND GATE INSULATING FILM FORMING SOLUTION FOR THIN FILM TRANSISTOR

The present disclosure relates to a thin film transistor, a manufacturing method thereof, and a gate insulating film forming solution for a thin film transistor.

In recent years, research on thin film transistors (hereinafter also referred to as TFTs) intended to be used for display driving elements has been actively conducted. As such research, the development of oxide TFTs is also in progress. Conventionally, vacuum processes such as sputtering have been the mainstream for manufacturing oxide TFTs, but there have been problems such as the need for expensive manufacturing equipment. On the other hand, there is an increasing trend to reduce costs by switching from vacuum processes to solution processes such as spin coating.

For example,

Patent Documents

1 and 2 disclose a thin film transistor including a gate insulating layer between a gate electrode and a channel. As a material for the gate insulating layer, an oxide composed of lanthanum and zirconium is used. Further, the firing temperature is set to about 400 ° C. when forming the gate insulating layer.

JP2015-60962A International Publication No. 2013/141197

By the way, in recent years, the development of flexible displays has accelerated. For example, in order to produce a device on a plastic substrate as a flexible display, the process temperature needs to be 200 ° C. or lower.

Further, when the thin film transistor is applied to, for example, a high-definition or large-area display, high field effect mobility is required for driving the thin film transistor.

An object of the present disclosure is to provide a thin film transistor having good transistor characteristics (particularly, high field effect mobility). Another object of the present invention is to provide a method for manufacturing a thin film transistor having a process temperature of 200 ° C. or lower. Furthermore, it is to provide a gate insulating film forming solution for a thin film transistor that can be used in the manufacturing method.

The thin film transistor of the present disclosure includes a gate electrode, a gate insulating layer, and an oxide semiconductor layer in this order, and the gate insulating layer includes cerium (Ce), praseodymium (Pr), neodymium (Nd), samarium (Sm), Europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), lutetium (Lu), and yttrium (Y) A metal element selected from the group consisting of zirconium and zirconium (Zr), wherein the atomic ratio of the metal element selected from the group and zirconium (Zr) is an atom of the metal element selected from the group Whether the number of zirconium (Zr) atoms is 1.5 or more and the oxide is formed when the number is 1 Alternatively, the oxide semiconductor layer is formed of an oxide containing at least one metal element selected from the group consisting of hafnium (Hf), zirconium (Zr), and aluminum (Al), and the oxide semiconductor layer includes indium (In ), Oxides containing indium (In) and tin (Sn), oxides containing indium (In) and zinc (Zn), indium (In), zirconium (Zr) and zinc (Zn) , An oxide containing indium (In) and gallium (Ga), and an oxide selected from the group consisting of oxides containing indium (In), zinc (Zn), and gallium (Ga). It is formed.

In addition, the method of manufacturing a thin film transistor according to the present disclosure includes a step of applying a gate insulating film forming solution on the gate electrode to form a gate insulating film, and an oxygen-containing environment on the surface of the gate insulating film. A step of baking the gate insulating film at 180 to 200 ° C. while irradiating ultraviolet rays to form a gate insulating layer, and applying an oxide semiconductor film forming solution on the gate insulating layer, A step of forming a film, and a step of baking the oxide semiconductor film at 180 to 200 ° C. while irradiating the surface of the oxide semiconductor film with ultraviolet rays to form an oxide semiconductor layer. The insulating film forming solution contains lanthanum (La), zirconium (Zr), and acetylacetonate, and the atomic ratio between lanthanum (La) and zirconium (Zr) is lanthanum (La). When the number of atoms is 1, it is a solution (i) in which the number of zirconium (Zr) atoms is 0.8 or more, cerium (Ce), praseodymium (Pr), neodymium (Nd), samarium (Sm) , Europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), lutetium (Lu), and yttrium (Y) A metal element selected from the group consisting of: zirconium (Zr), and acetylacetonate, wherein the atomic ratio of the metal element selected from the group and zirconium (Zr) is selected from the group Or a solution (ii) in which the number of atoms of zirconium (Zr) is 1.5 or more, where Is a solution (iii) containing at least one metal element selected from the group consisting of hafnium (Hf), zirconium (Zr), and aluminum (Al), and acetylacetonate, and the oxide semiconductor film The forming solutions are indium (In), indium (In) and tin (Sn), indium (In) and zinc (Zn), indium (In) and zirconium (Zr) and zinc (Zn), indium (In) and gallium. It contains (Ga), a metal selected from the group consisting of indium (In), zinc (Zn), and gallium (Ga), and an oxidizing agent.

Furthermore, the gate insulating film forming solution for a thin film transistor of the present disclosure includes lanthanum (La), zirconium (Zr), and acetylacetonate, and the atomic ratio of lanthanum (La) and zirconium (Zr) is When the number of atoms of lanthanum (La) is 1, it is a solution (i) in which the number of zirconium (Zr) atoms is 0.8 or more, cerium (Ce), praseodymium (Pr), neodymium (Nd) , Samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), lutetium (Lu) And a metal element selected from the group consisting of yttrium (Y), zirconium (Zr), and acetylacetona When the atomic ratio of the metal element selected from the group and zirconium (Zr) is 1 when the atomic number of the metal element selected from the group is 1, the atom of zirconium (Zr) A solution (ii) having a number of 1.5 or more, or at least one metal element selected from the group consisting of hafnium (Hf), zirconium (Zr), and aluminum (Al), and acetylacetate It is a solution (iii) containing natto.

The thin film transistor of the present disclosure has good transistor characteristics (particularly high field effect mobility). Further, according to the method of the present disclosure, a thin film transistor can be manufactured at a process temperature of 200 ° C. or lower. For this reason, the thin film transistor and the manufacturing method thereof of the present disclosure can be applied to a wide range of uses such as a flexible display.

It is sectional drawing which shows roughly an example of the thin-film transistor of this embodiment. 2A and 2B are cross-sectional views sequentially showing each step of the method of manufacturing the thin film transistor shown in FIG. 1, wherein FIG. 1A is a step of forming a gate electrode on the substrate, and FIG. (C) is a step of heating the gate insulating film formed in (b) while irradiating with ultraviolet rays to form a gate insulating layer, and (d) is an oxide semiconductor film on the gate insulating layer. (E) is a step in which the oxide semiconductor film formed in (d) is heated while being irradiated with ultraviolet rays to form an oxide semiconductor layer, and (f) is a step on the oxide semiconductor layer. (G) is a step of forming a resist film over part of the oxide semiconductor layer, the source electrode, and the drain electrode, and (h) is a step of forming (g). Etching a laminated body having a resist film Ri indicates the step of obtaining a thin film transistor. It is a figure which shows the result of having measured the ultraviolet light absorbency of the gate insulating film formation solution. It is a diagram showing the V _G -I _D characteristic and V _G -I _G characteristics of the thin film transistor in Example 2. V _G -I _D characteristic and V _G -I _G characteristics of the thin film transistor of Comparative Example 3 is a diagram showing a. It is a diagram showing the V _G -I _D characteristic and V _G -I _G characteristics of the thin film transistor of Comparative Example 4.

Hereinafter, embodiments of the present invention will be described in detail. In the following description, the drawings are referred to as appropriate, but the embodiments described in the drawings are examples of the present invention, and the present invention is not limited to the embodiments described in these drawings. In each figure, the same or similar reference numerals are given to components that exhibit the same or similar functions, and redundant description may be omitted. In addition, the dimensional ratios in the drawings are exaggerated for convenience of explanation, and may be different from the actual ratios. Further, in the present specification, “˜” is used to mean that the numerical values described before and after it are included as a lower limit value and an upper limit value.

<Thin film transistor>
The thin film transistor of the present disclosure includes a gate electrode, a gate insulating layer, and an oxide semiconductor layer in this order. Here, the gate insulating layer includes lanthanum (La) and zirconium (Zr), and the atomic ratio of lanthanum (La) to zirconium (Zr) is set to 1 for the number of lanthanum (La) atoms. Sometimes zirconium (Zr) is formed from an oxide having 0.8 or more atoms. Alternatively, the gate insulating layer is formed of cerium (Ce), praseodymium (Pr), neodymium (Nd), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho). ), Erbium (Er), thulium (Tm), ytterbium (Yb), lutetium (Lu), and yttrium (Y), and zirconium (Zr). When the atomic ratio between the metal element and zirconium (Zr) is 1 when the number of atoms of the metal element selected from the group is 1, the number of atoms of zirconium (Zr) is 1.5 or more. It is formed from an oxide. Alternatively, the gate insulating layer is formed of an oxide containing at least one metal element selected from the group consisting of hafnium (Hf), zirconium (Zr), and aluminum (Al). The oxide semiconductor layer includes an oxide containing indium (In), an oxide containing indium (In) and tin (Sn), an oxide containing indium (In) and zinc (Zn), and indium (In ), Zirconium (Zr) and zinc (Zn) -containing oxide, indium (In) and gallium (Ga) oxide, and indium (In), zinc (Zn) and gallium (Ga). It is formed from an oxide selected from the group of oxides.

FIG. 1 is a cross-sectional view schematically showing an example of the thin film transistor of this embodiment. The thin film transistor 10 shown in the figure includes a gate electrode 14, a gate insulating layer 16, an oxide semiconductor layer 18, a source electrode 32, and a drain electrode 34 in this order on a substrate 12.

Although the thin film transistor 10 shown in FIG. 1 has a bottom gate structure, it is not limited to this structure. For example, other structures such as a top gate structure may be used. Further, in order to simplify the drawing, the patterning of the extraction electrode from each electrode is not shown.

Hereinafter, components of the thin film transistor 10 shown in FIG. 1 will be described.

(substrate)
As the substrate 12, a substrate used in a known thin film transistor can be applied.

Examples of the substrate 12 include a high heat-resistant glass, a SiO ₂ / Si substrate (a substrate in which a silicon oxide film is formed on a silicon substrate), an alumina (Al ₂ O ₃ ) substrate, an STO (SrTiO) substrate, and a Si substrate. Insulating substrates and semiconductor substrates (for example, Si substrates, SiC substrates, Ge substrates) in which an STO (SrTiO) layer is formed via an SiO ₂ layer and a Ti layer are included. Further, a plastic substrate made of a resin such as polyethylene naphthalate (PEN), polycarbonate (PC), polyimide (PI), or a flexible substrate such as paper is also included.

(Gate electrode)
As the gate electrode 14, a gate electrode used in a known thin film transistor can be adopted. Examples of the material of the gate electrode 14 include metal materials such as refractory metals such as platinum, gold, silver, copper, titanium, aluminum, molybdenum, palladium, ruthenium, iridium, and tungsten, or alloys thereof, or indium tin. Oxide (ITO) or ruthenium oxide (RuO ₂ ) can be used.

(Gate insulation layer)
The gate insulating layer 16 is formed from an oxide containing a specific metal element.

The oxide containing a specific metal element is an oxide containing lanthanum (La) and zirconium (Zr) (hereinafter also simply referred to as “oxide (i)”), cerium (Ce), praseodymium ( Pr), neodymium (Nd), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium ( Yb), lutetium (Lu), and a metal element selected from the group consisting of yttrium (Y) and an oxide containing zirconium (Zr) (hereinafter also simply referred to as “oxide (ii)”), At least one metal element selected from the group consisting of hafnium (Hf), zirconium (Zr), and aluminum (Al) Oxides containing (hereinafter, simply referred to as "oxide (iii)") it is. In the oxide (i) and the oxide (ii), tantalum (Ta) may be used instead of zirconium (Zr).

The “oxide containing a specific metal element” typically means an oxide containing a specific metal element as a main component, but the oxide contains impurities (for example, impurities derived from raw materials). ) May be included. In order to obtain good transistor performance, the content of impurities other than carbon and hydrogen in the oxide is preferably 0.2% by mass or less.

When the oxide containing a specific metal element is oxide (i), when the atomic ratio of lanthanum (La) and zirconium (Zr) is set to 1 as the number of atoms of lanthanum (La), The number of zirconium (Zr) atoms is 0.8 or more, preferably 0.8 to 10, and more preferably 1.5 to 4. When the oxide containing the specific metal element is the oxide (ii), the atomic ratio between the metal element selected from the specific group and zirconium (Zr) is from the viewpoint of obtaining good transistor performance. When the number of atoms of the metal element is 1, the number of zirconium (Zr) atoms is 1.5 or more, preferably 1.5 to 9, and more preferably 2.3 to 9. In the present disclosure, the atomic ratio can be obtained by performing elemental analysis using Rutherford backscattering spectroscopy (RBS method).

The content of carbon (C) in the gate insulating layer 16 is not particularly limited, but is preferably 0.5 atom% to 20 atom% from the viewpoint of obtaining good transistor performance.

Regarding the content of carbon (C) and hydrogen (H), Rutherford Backscattering Spectrometry (RBS analysis method), Hydrogen forward scattering analysis method (Hdr forward analysis method), using Pelletron 3SDH manufactured by National Electrostatics Corporation. : HFS analysis method) and nuclear reaction analysis method (Nuclear Reaction Analysis: NRA analysis method).

The thickness of the gate insulating layer 16 is not particularly limited, but is preferably 30 nm to 500 nm from the viewpoint of reducing the operating voltage while suppressing leakage.

(Oxide semiconductor layer)
The oxide semiconductor layer 18 includes an oxide containing indium (In), an oxide containing indium (In) and tin (Sn), an oxide containing indium (In) and zinc (Zn), and indium (In). , An oxide containing zirconium (Zr) and zinc (Zn), an oxide containing indium (In) and gallium (Ga), and an oxide containing indium (In), zinc (Zn) and gallium (Ga) Formed from an oxide selected from the group consisting of:

The “oxide containing indium (In)” typically means an oxide containing indium (In) as a main component, but the oxide contains impurities (for example, impurities derived from raw materials). ) May be included. In order to obtain good transistor performance, the content of impurities other than carbon and hydrogen in the oxide is preferably 0.2% by mass or less. The content of carbon (C) in the oxide semiconductor layer 18 is preferably 0.2 atom% to 15.0 atom% from the viewpoint of obtaining good transistor performance. In addition, the content of hydrogen (H) in the oxide semiconductor layer 18 is preferably 1 atom% to 20 atom%. The same applies to the other five oxides.

In the case of using an oxide containing indium (In) and tin (Sn), the atomic ratio of indium (In) to tin (Sn) in the oxide semiconductor layer 18 is set so that the number of atoms of indium (In) is 1. However, from the viewpoint of obtaining good transistor performance, it is preferable that the number of tin (Sn) atoms be 0.005 to 0.03.

In the case of using an oxide containing indium (In) and zinc (Zn), the atomic ratio of indium (In) to zinc (Zn) in the oxide semiconductor layer 18 is such that the number of atoms of indium (In) is 1. However, from the viewpoint of obtaining good transistor performance, the number of zinc (Zn) atoms is preferably 0.1 to 1.0.

In the case of using an oxide containing indium (In), zirconium (Zr), and zinc (Zn), the atomic ratio of indium (In), zirconium (Zr), and zinc (Zn) in the oxide semiconductor layer 18 is When the number of atoms of indium (In) is 1, it is not particularly limited, but from the viewpoint of obtaining good transistor performance, the number of zirconium (Zr) atoms is 0.005 to 0.03, zinc ( The number of atoms of Zn) is preferably 0.1 to 1.0.

In the case of using an oxide containing indium (In) and gallium (Ga), the atomic ratio of indium (In) to gallium (Ga) in the oxide semiconductor layer 18 is such that the number of atoms of indium (In) is 1. In this case, gallium (Ga) is preferably 0.1 to 1.0 from the viewpoint of obtaining good transistor performance.

In the case of using an oxide containing indium (In), zinc (Zn), and gallium (Ga), the atomic ratio of indium (In), zinc (Zn), and gallium (Ga) in the oxide semiconductor layer 18 is When the number of atoms of indium (In) is 1, it is not particularly limited, but from the viewpoint of obtaining good transistor performance, zinc (Zn) is 0.1 to 1.0 and gallium (Ga) is 0. 1 to 1.2 is preferable.

The thickness of the oxide semiconductor layer 18 is not particularly limited, but is preferably 10 nm to 100 nm from the viewpoint of securing a sufficient operating current and realizing a thin film.

(Source electrode and drain electrode)
As the source electrode 32 and the drain electrode 34, the source electrode 32 and the drain electrode 34 used in a known thin film transistor can be adopted. The material of the source electrode 32 and the drain electrode 34 is not limited, but for example, indium tin oxide (ITO), ruthenium oxide (RuO ₂ ), molybdenum (Mo), platinum (Pt), or the like is used. it can.

As described above, the thin film transistor 10 includes lanthanum (La) and zirconium (Zr), and the atomic ratio of lanthanum (La) and zirconium (Zr) is equal to 1 in the number of lanthanum (La) atoms. When the number of atoms of zirconium (Zr) is 0.8 or more, it is formed of an oxide or contains a specific rare earth metal element and zirconium (Zr), and the number of atoms of the rare earth metal element Is formed from an oxide having zirconium (Zr) atoms of 1.5 or more, or from the group consisting of hafnium (Hf), zirconium (Zr), and aluminum (Al) A gate insulating layer 16 formed of an oxide containing at least one selected metal element is included. The thin film transistor 10 includes an oxide semiconductor layer 18 formed from a specific oxide containing indium (In). Thereby, the thin film transistor 10 of the present disclosure has good electrical characteristics, in particular, high field effect mobility.

Next, a method for manufacturing the thin film transistor 10 of the present disclosure will be described.

<Method for Manufacturing Thin Film Transistor>
The method of manufacturing a thin film transistor of the present disclosure includes a step of applying a gate insulating film forming solution on a gate electrode to form a gate insulating film, and irradiating the surface of the gate insulating film with ultraviolet light in an environment containing oxygen. However, the gate insulating film is baked at 180 to 200 ° C. to form the gate insulating layer, and the oxide semiconductor film forming solution is applied on the gate insulating layer to form the oxide semiconductor film. And a step of baking the oxide semiconductor film at 180 to 200 ° C. while irradiating the surface of the oxide semiconductor film with ultraviolet rays to form an oxide semiconductor layer.

2A and 2B are cross-sectional views sequentially showing each step of the method of manufacturing the thin film transistor 10 shown in FIG. 1, wherein FIG. 2A is a step of forming the gate electrode 14 on the substrate 12, and FIG. (C) is a step of heating the gate insulating film 16 ′ formed in (b) while irradiating it with ultraviolet rays to form a gate insulating layer 16; (d) ) Is a step of forming the oxide semiconductor film 18 ′ on the gate insulating layer 16, and (e) is a step of heating the oxide semiconductor film 18 ′ formed in (d) while irradiating with ultraviolet rays, thereby The step of forming the semiconductor layer 18, (f) is the step of forming the source electrode 32 and the drain electrode 34 on the oxide semiconductor layer 18, and (g) is the part of the oxide semiconductor layer 18, the source electrode 32. And the resist film 3 on the drain electrode 34 Forming a, (h) shows the step of obtaining a thin film transistor 10. The steps (a) to (h) corresponding to FIGS. 2 (a) to (h) will be described in detail below.

(Process (a))
This step is a step of forming the gate electrode 14 on the substrate 12 (FIG. 2A).

It is preferable to use a cleaned substrate 12, and any known method such as plasma ashing using oxygen gas can be adopted as the cleaning method.

As a method for forming the gate electrode 14, any known method such as a vacuum deposition method (for example, a sputtering method) can be employed.

(Process (b))
This step is a step of forming a gate insulating film 16 ′ by applying a gate insulating film forming solution on the gate electrode 14 (FIG. 2B).

The coating method of the gate insulating film forming solution is not limited, but for example, spin coating method, dip coating method, die coating method, bar coating method, blade coating method, roll coating method, spray coating method, capillary coating method A known method such as a nozzle coating method, an ink jet method, a screen printing method, a gravure printing method, a flexographic printing method, a relief printing, or a reverse offset printing can be used.

The gate insulating film forming solution contains lanthanum (La), zirconium (Zr), and acetylacetonate, and the atomic ratio of lanthanum (La) and zirconium (Zr) is the number of atoms of lanthanum (La). Is a solution (i) in which the number of zirconium (Zr) atoms is 0.8 or more, or cerium (Ce), praseodymium (Pr), neodymium (Nd), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), lutetium (Lu), and yttrium (Y) A metal element selected from the group consisting of zirconium (Zr) and acetylacetonate, selected from the group When the atomic ratio between the genus element and zirconium (Zr) is 1, the number of atoms of zirconium (Zr) is 1.5 or more when the number of atoms of the metal element selected from the group is 1 (ii) Or a solution (iii) containing at least one metal element selected from the group consisting of hafnium (Hf), zirconium (Zr), and aluminum (Al) and acetylacetonate. The ratio of acetylacetonate contained in each of solutions (i) to (iii) is 20 to 400 mol% with respect to the total number of moles of the metal elements shown above contained in each solution. be able to.

Without being bound by theory, when referring to the molecular structure in the gate insulating film forming solution, it is considered that an anion or a solvent is coordinated to the core containing the metal to form a cluster. The present inventors have found that the absorption of ultraviolet rays is remarkably increased when acetylacetonate is coordinated to this core. Taking advantage of this characteristic, in the present disclosure, in the step (c) described later, the irradiation temperature of about 400 ° C., which has been conventionally applied, is set to 200 ° C. or less by using ultraviolet irradiation together with heating. Furthermore, it has been confirmed by experiments that the transistor characteristics of the finally fabricated TFT are improved when a gate insulating film forming solution containing a specific metal element and acetylacetonate is used as the material of the gate insulating layer 16. is doing.

As described above, the gate insulating film forming solution of the present disclosure contributes to reduction of the firing temperature of the gate insulating film and improvement of the transistor characteristics of the TFT.

The gate insulating film forming solution can be prepared as follows.

When the gate insulating film forming solution contains only one kind of metal element, a predetermined metal compound is dissolved in a solvent to prepare a solution having a predetermined molar concentration (for example, 0.2 mol / kg). Can do. When two or more kinds of metal elements are contained in the gate insulating film forming solution, after preparing a solution by dissolving a predetermined metal compound in a solvent for each metal element, The gate insulating film forming solution can be prepared by mixing so that the atomic ratio is Alternatively, a gate insulating film forming solution may be prepared by adding and dissolving two or more kinds of metal compounds in a solvent so that the metal element has a predetermined atomic ratio. Furthermore, when a predetermined amount of acetylacetonate is not contained in the solution prepared as described above, a gate insulating film forming solution can be prepared by adding acetylacetonate to the solution. In addition, when preparing a solution, you may perform refinement | purification, for example, filtration with a filter suitably. Moreover, when dissolving a metal compound in a solvent, you may heat suitably.

In preparing the solution (i), a lanthanum compound and a zirconium compound can be used as the metal compound. Examples of the lanthanum compound include lanthanum acetylacetonate, lanthanum alkoxide, and organic acid salt of lanthanum. Examples of zirconium compounds include zirconium acetylacetonate, zirconium nitrate, zirconium chloride, or zirconium alkoxide (eg, zirconium isopropoxide, zirconium butoxide, zirconium ethoxide, zirconium methoxyethoxide).

In preparing the solution (ii), examples of the metal compound include metal acetylacetonate and acetate. Here, the metal is cerium (Ce), praseodymium (Pr), neodymium (Nd), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho). , Erbium (Er), thulium (Tm), ytterbium (Yb), lutetium (Lu), and a metal selected from the group consisting of yttrium (Y). Examples of the zirconium compound include the same compounds as those used when preparing the solution (i).

When preparing the solution (iii), zirconium, hafnium, and an aluminum compound can be used as the metal compound. Examples of zirconium, hafnium, and aluminum compounds include the corresponding metal acetylacetonates, nitrates, chlorides, or alkoxides (eg, isopropoxide, butoxide, ethoxide, methoxyethoxide).

The solvent used at the time of preparing the gate insulating film forming solution is preferably a solvent that does not prevent acetylacetonate from coordinating to the metal-containing core. Examples of such solvents include, but are not limited to, alcohol solvents selected from the group of ethanol, propanol, butanol, 2-methoxyethanol, 2-ethoxyethanol, and 2-butoxyethanol. it can.

Furthermore, it is preferable to subject the gate insulating film forming solution described above to heat treatment in a hermetically sealed container from the viewpoints of cluster formation, uniform structure, and ultraviolet absorption efficiency.

The heat treatment in the sealed container can be performed, for example, by transferring the gate insulating film forming solution to a pressure-resistant container such as an autoclave and at a temperature not lower than the boiling point of the solvent (for example, 150 to 200 ° C.).

When the solution (i) or the solution (ii) is used as the gate insulating film forming solution and tantalum is used instead of zirconium, in the above description, zirconium can be replaced with tantalum. And

(Process (c))
This step is a step of forming the gate insulating layer 16 by heating the gate insulating film 16 ′ while irradiating the surface of the gate insulating film 16 ′ of the stacked body 20 ′ formed in the step (b) with ultraviolet rays. (FIG. 2 (c)).

The ultraviolet irradiation is preferably performed uniformly over the entire surface of the gate insulating film 16 ′ in order to form a uniform gate insulating layer 16 with little unevenness. In this case, the illuminance of the ultraviolet rays to be irradiated is not particularly limited when the solution (i) is used as the gate insulating film forming solution, but can be 7.0 to 12.0 mW / cm ² . When the solution (ii) or solution (iii) is used as the gate insulating film forming solution, it is preferably 5.0 to 15.0 mW / cm ² , more preferably 7.0 to 12.0 mW / cm ² . is there. In this way, the illuminance of the ultraviolet rays irradiated in this step can be lowered to the same level as the illuminance used in a general surface cleaning UV apparatus. This is because a high illuminance is not required because the ultraviolet absorption of the gate insulating film 16 ′ is high.

The heating method of the laminated body 20 ′ is not particularly limited. For example, the laminated body 20 ′ can be installed so that the surface of the substrate 12 is in contact with the heating surface of the heater.

As for the heating condition of the laminate 20 ′, it is preferable that initial heating is first performed at 80 to 170 ° C. and then baking is performed at 180 to 200 ° C. in an environment containing oxygen such as the air. The initial heating is mainly intended to evaporate the solvent contained in the gate insulating film 16 '.

The gate insulating layer 16 may be formed of a plurality of layers. In the case of forming a plurality of layers, the step of forming the gate insulating film 16 'in the step (b) and the above series of initial heating and baking operations may be repeated a plurality of times.

(Process (d))
This step is a step of applying the oxide semiconductor film forming solution onto the gate insulating layer 16 to form the oxide semiconductor film 18 ′ (FIG. 2D).

The application method of the oxide semiconductor film forming solution is not limited, but spin coating, dip coating, die coating, bar coating, blade coating, roll coating, spray coating, capillary coating, Known methods such as a nozzle coating method, an inkjet method, a screen printing method, a gravure printing method, a flexographic printing method, a relief printing, and a reverse offset printing can be used.

The oxide semiconductor film formation solution includes indium (In), indium (In) and tin (Sn), indium (In) and zinc (Zn), indium (In), zirconium (Zr), zinc (Zn), indium ( A metal element selected from the group consisting of In), gallium (Ga), indium (In), zinc (Zn), and gallium (Ga), and an oxidizing agent. The oxide semiconductor film forming solution can be prepared, for example, as follows.

In the case of forming the oxide semiconductor film 18 ′ containing indium (In), an indium (In) compound and optionally an oxidizing agent are dissolved in a solvent to obtain a predetermined molar concentration (for example, 0.2 mol / kg). An indium (In) solution is prepared.

When forming the oxide semiconductor film 18 ′ containing indium (In) and tin (Sn), an indium (In) compound and a tin (Sn) compound, and optionally an oxidizing agent are dissolved in a solvent, An indium (In) / tin (Sn) solution having a predetermined molar concentration (for example, 0.2 mol / kg) is prepared.

In the case of forming the oxide semiconductor film 18 ′ containing indium (In) and zinc (Zn), an indium (In) compound and a zinc (Zn) compound, and optionally an oxidizing agent are dissolved in a solvent, An indium (In) / zinc (Zn) solution having a predetermined molar concentration (for example, 0.2 mol / kg) is prepared.

In the case of forming the oxide semiconductor film 18 ′ containing indium (In), zirconium (Zr), and zinc (Zn), an indium (In) compound, a zirconium (Zr) compound, a zinc (Zn) compound, and a case Thus, the oxidizing agent is dissolved in a solvent to prepare an indium (In) / zirconium (Zr) / zinc (Zn) solution having a predetermined molar concentration (for example, 0.2 mol / kg).

In the case of forming the oxide semiconductor film 18 ′ containing indium (In) and gallium (Ga), an indium (In) compound and a gallium (Ga) compound, and optionally an oxidizing agent are dissolved in a solvent, An indium (In) / gallium (Ga) solution having a predetermined molar concentration (for example, 0.2 mol / kg) is prepared.

In the case of forming the oxide semiconductor film 18 ′ containing indium (In), zinc (Zn), and gallium (Ga), an indium (In) compound, a zinc (Zn) compound, a gallium (Ga) compound, and In some cases, an oxidizing agent is dissolved in a solvent to prepare an indium (In) / zinc (Zn) / gallium (Ga) solution having a predetermined molar concentration (for example, 0.2 mol / kg).

Examples of indium (In) compounds include indium nitrate, indium acetylacetonate, indium acetate, indium chloride, or indium alkoxide (eg, indium isopropoxide, indium butoxide, indium ethoxide, indium methoxyethoxide). Can do.

Examples of tin (Sn) compounds include tin chloride, tin nitrate, tin acetate, or tin alkoxide (eg, tin isopropoxide, tin butoxide, tin ethoxide, tin methoxyethoxide).

Examples of zinc (Zn) compounds include zinc chloride, zinc nitrate, zinc acetate, or zinc alkoxide (for example, zinc isopropoxide, zinc butoxide, zinc ethoxide, zinc methoxyethoxide).

Examples of zirconium compounds include zirconium nitrate, zirconium chloride, or zirconium alkoxide (eg, zirconium isopropoxide, zirconium butoxide, zirconium ethoxide, zirconium methoxyethoxide).

Examples of gallium (Ga) compounds include gallium nitrate, gallium chloride, gallium acetate, gallium acetylacetonate or gallium alkoxide (gallium methoxide, gallium ethoxide, gallium propoxide, gallium butoxide).

The solvent used for the oxide semiconductor film forming solution is not particularly limited. For example, an alcohol solvent selected from the group of 2-methoxyethanol, ethanol, propanol, butanol, 2-ethoxyethanol, 2-butoxyethanol, A solvent of carboxylic acid selected from the group of acetic acid, propionic acid and octylic acid, or water can be employed. From the viewpoint of improving the characteristics of the TFT, it is preferable to use water as the solvent.

Examples of the oxidizing agent used in the oxide semiconductor film forming solution include, but are not limited to, nitric acid, nitrate, peroxide, or perchlorate. Here, for example, when indium nitrate is used as the indium (In) compound when preparing the oxide semiconductor film forming solution, it is not necessary to add an oxidizing agent separately because it is itself a nitrate.

Further, the oxide semiconductor film forming solution may contain a co-firing agent in order to adjust the firing temperature and firing strength of the solution. Examples of co-firing agents include, but are not limited to, acetylacetone, acetylacetonate, urea, or ammonium acetate.

When preparing the oxide semiconductor film forming solution, a solute may be added to the solvent and heated appropriately.

(Process (e))
In this step, the oxide semiconductor film 18 ′ is heated while irradiating the surface of the oxide semiconductor film 18 ′ of the stacked body 30 ′ formed in the step (d) with ultraviolet rays, so that the oxide semiconductor layer 18 is formed. (FIG. 2 (e)).

Irradiation with ultraviolet rays is preferably performed uniformly over the entire surface of the oxide semiconductor film 18 ′ in order to form a uniform oxide semiconductor layer 18 without unevenness. At this time, the illuminance of the ultraviolet rays to be irradiated is not particularly limited, but can be 5.0 to 15.0 mW / cm ² , preferably 7.0 to 12.0 mW / cm ² . In this way, the illuminance of the ultraviolet rays irradiated in this step can be lowered to the same level as the illuminance used in a general surface cleaning UV apparatus.

The heating method of the stacked body 30 ′ is not particularly limited, but for example, the stacked body 30 ′ can be installed so that the surface of the substrate 12 is in contact with the heating surface of the heater.

As for the heating condition of the laminate 30 ′, it is preferable that initial heating is first performed at 80 to 170 ° C. and then baking is performed at 180 to 200 ° C. in an environment containing oxygen such as the air. The initial heating is mainly intended to evaporate the solvent contained in the oxide semiconductor film 18 '.

(Process (f))
This step is a step of forming the source electrode 32 and the drain electrode 34 on the oxide semiconductor layer 18 (FIG. 2F).

As the formation of the source electrode 32 and the drain electrode 34, any known method such as a lift-off method can be employed.

When forming by lift-off method, it can be performed by the following procedure.

A resist film patterned by a photolithography method is formed on the oxide semiconductor layer 18, and a metal layer is formed on the oxide semiconductor layer 18 and the resist film by a sputtering method or the like. Thereafter, the source film 32 and the drain electrode 34 can be formed over the oxide semiconductor layer 18 by removing the resist film.

As a material for the resist film, a commonly used lift-off layer material such as LOL2000 manufactured by Rohm and Haas and TSMR8900 manufactured by Tokyo Ohka Kogyo Co., Ltd. can be used.

For example, when the metal layer is formed of indium tin oxide (ITO), ITO containing 5% by mass of tin oxide (SnO ₂ ) can be used as the ITO layer target material. The metal layer is, for example, when it is formed by ruthenium oxide (RuO ₂₎ as the target material, it is possible to use ruthenium oxide (RuO _2).

(Process (g))
This step is a step of forming a resist film 36 on part of the oxide semiconductor layer 18, the source electrode 32, and the drain electrode 34 (FIG. 2G).

The resist film 36 can be formed by patterning by a known method such as a photolithography method.

As a material of the resist film 36, a resist material that is usually used, for example, OMR85 manufactured by Tokyo Ohka Kogyo Co., Ltd. can be used.

(Process (h))
In this step, the stacked body 40 including the resist film 36 formed in the step (g) is etched to remove the oxide semiconductor layer 18 not covered with the resist film 36, thereby obtaining the thin film transistor 10 (FIG. 2 (h)).

As the etching, for example, a wet etching method using an etchant such as an etchant for ITO (ITO series manufactured by Kanto Chemical Co., Ltd.) or a dry etching method using argon plasma can be used.

After element separation of the oxide semiconductor layer (step (h)), the thin film transistor 10 is preferably post-annealed in order to improve adhesion between the source electrode 32 and the drain electrode 34 and the oxide semiconductor layer 18. The post-annealing is not particularly limited, but can be performed by heat treatment at 100 to 200 ° C., preferably 180 to 200 ° C. for 10 minutes or more using a heating means such as a heater. In addition to heat treatment, ultraviolet irradiation may be performed. In this case, the illuminance of the ultraviolet rays is not particularly limited, but can be 5.0 to 15.0 mW / cm ² , preferably 7.0 to 12.0 mW / cm ² .

As described above, according to the method of the present disclosure, a thin film transistor can be manufactured at a process temperature of 200 ° C. or less. Therefore, for example, a TFT can be manufactured on a plastic substrate. As described above, the method of the present disclosure can be applied to a wide range of applications such as a flexible display manufacturing application. Therefore, the realization of cost reduction can be expected.

Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited to the following examples.

<Examination of gate insulating film forming solution>
[Preparation of gate insulating film forming solution]
Example 1
Lanthanum acetylacetonate and zirconium butoxide were added to 2-methoxyethanol so that the atomic ratio of lanthanum and zirconium was 3: 7, and the mixture was heated and stirred at 110 ° C. for 30 minutes. Next, the obtained solution was transferred to a pressure vessel, heated to 160 ° C., held for 1 hour, and then returned to room temperature to prepare a 0.1 mol / kg lanthanum / zirconium mixed solution. Thereafter, filtration was performed with a 0.2 um PTFE filter to obtain a gate insulating film forming solution (Example 1).

(Comparative Example 1)
To 2-methoxyethanol, lanthanum nitrate and zirconium nitrate were added so that the atomic ratio of lanthanum and zirconium was 3: 7, and the mixture was heated and stirred at 110 ° C. for 30 minutes. Next, the obtained solution was transferred to a pressure vessel, heated to 120 ° C., held for 1 hour, and then returned to room temperature to prepare a 0.1 mol / kg lanthanum / zirconium mixed solution. Thereafter, filtration was performed with a 0.2 um PTFE filter to obtain a gate insulating film forming solution (Comparative Example 1).

(Comparative Example 2)
Lanthanum acetate was dissolved in propionic acid, and this was stirred at 110 ° C. and a rotation speed of 1000 rpm for 30 minutes to prepare a 0.2 mol / kg lanthanum solution. Next, zirconium butoxide was dissolved in propionic acid, and this was stirred at 110 ° C. and a rotation speed of 1000 rpm for 30 minutes to prepare a 0.2 mol / kg zirconium solution. The prepared lanthanum solution and zirconium solution were mixed so that the atomic ratio of lanthanum and zirconium was 3: 7, then filtered through a 0.2 um PTFE filter, and a gate insulating film forming solution (comparison) Example 2) was obtained. Next, the obtained gate insulating film forming solution was transferred to an autoclave and heated until the internal temperature reached 180 ° C. In this state, it was held for 5 hours, and the inside of the container was returned to room temperature to obtain an autoclaved gate insulating film forming solution (Comparative Example 2).

[UV absorbance measurement]
The ultraviolet absorbance of the prepared gate insulating film forming solution was measured using an ultraviolet-visible spectrophotometer (V-630 UV-visible spectrophotometer manufactured by JASCO International Co., Ltd.). The result is shown in FIG.

As shown in FIG. 3, the gate insulating film forming solution (Example 1) had higher absorbance values in the ultraviolet wavelength region than the gate insulating film forming solutions (Comparative Example 1) and (Comparative Example 2).

Therefore, it can be said that the gate insulating film forming solution (Example 1) absorbs ultraviolet rays more than the gate insulating film forming solutions (Comparative Example 1) and (Comparative Example 2).

This result is not bound by theory, but is presumed to be due to the following reasons.

When a lanthanum compound and a zirconium compound are dissolved in a solvent, a La—O—Zr core in which lanthanum (La) and zirconium (Zr) are bonded through an oxygen atom (O) is generated, and the compound is surrounded by the shadow of the compound. Ions or solvents coordinate to form clusters.

In Example 1, Comparative Example 1 and Comparative Example 2, only the anion and / or solvent of the compound is different, and therefore the type of anion and / or solvent coordinated to the La—O—Zr core is different from that of the solution. It is thought to affect the ultraviolet absorption.

In Example 1, lanthanum acetylacetonate is used as the lanthanum compound. Acetylacetonate is widely known as a bidentate ligand that coordinates to many metal ions, and it is considered that acetylacetonate is preferentially coordinated to the core even in this solution. On the other hand, in Comparative Examples 1 and 2, the gate insulating film forming solution does not contain acetylacetonate.

Therefore, it can be said that the gate insulating film forming solution of Example 1 absorbed ultraviolet rays more than Comparative Example 1 and Comparative Example 2 because it contained acetylacetonate.

[Manufacture of thin film transistors]
(Example 2)
Using the gate insulating film forming solution prepared in Example 1, a thin film transistor was manufactured as follows.

First, a gate electrode made of a titanium / platinum (Ti / Pt) layer was formed on a cleaned Si wafer substrate by a sputtering method. Next, the substrate surface on which the titanium / platinum (Ti / Pt) layer was formed was subjected to ashing treatment with oxygen plasma (15 W for 180 seconds).

Thereafter, an Ag paste was formed at the four corners of the substrate for gate electrode contact.

Next, the gate insulating film forming solution prepared in Example 1 was applied onto the gate electrode layer by spin coating (rotation speed: 2000 rpm, rotation time: 25 seconds) to form a gate insulating film.

Next, the stacked body on which the gate insulating film is formed is allowed to stand on a hot plate set at 150 ° C. for 5 minutes and heated, and then the temperature is increased to 200 ° C. The whole surface of the gate insulating film was irradiated with ultraviolet rays of 10 mW / cm ² for 60 minutes to form a gate insulating layer. Here, UV irradiation was performed using a UV ozone cleaner (Samco UV-300H-E). By repeating the above-described series of operations of forming a gate insulating film by spin coating, heating at 150 ° C., and heating at 200 ° C. accompanied by ultraviolet irradiation, a total of three gate insulating layers were laminated. The total thickness of the gate insulating layer was 50 nm.

Subsequently, the previously formed Ag paste was removed from the obtained laminate, and the gate electrode for measurement was taken out.

After that, an oxide semiconductor film forming solution was applied over the gate insulating layer by a spin coating method (rotation speed: 3000 rpm, rotation time: 30 seconds). The obtained laminate was allowed to stand on a hot plate set at 150 ° C. for 5 minutes and heated, and then the temperature was increased to 200 ° C., and the illuminance was 10 mW / cm ² while heating at the same temperature. The entire surface of the oxide semiconductor film was irradiated with ultraviolet rays for 60 minutes to form an oxide semiconductor layer. Here, UV irradiation was performed using a UV ozone cleaner (Samco UV-300H-E). The thickness of the oxide semiconductor layer was 20 nm. As the oxide semiconductor film forming solution, indium nitrate and zinc nitrate were added to 2-methoxyethanol so that the atomic ratio of indium to zinc was 8: 1, and the temperature was 110 ° C. and the rotation speed was 1000 rpm for 30 minutes. , And an indium / zinc solution prepared at 0.2 mol / kg was used.

Subsequently, a source electrode and a drain electrode were formed on the obtained oxide semiconductor layer by a lift-off method.

Thereafter, a resist film is formed by photolithography for element isolation (patterning of the oxide semiconductor layer), and the obtained laminate is wet etched using ITO-07 (an ITO etchant manufactured by Kanto Chemical Co., Inc.). Etched.

Next, the obtained laminate was heated on a hot plate at 200 ° C. for 10 minutes to produce a thin film transistor.

(Comparative Example 3)
A thin film transistor was produced in the same manner as in Example 2 except that the gate insulating film forming solution prepared in Comparative Example 1 was used instead of the gate insulating film forming solution prepared in Example 1.

(Comparative Example 4)
A thin film transistor was fabricated in the same manner as in Example 2, except that the gate insulating film forming solution prepared in Comparative Example 2 was used instead of the gate insulating film forming solution prepared in Example 1.

[Characteristic evaluation of thin film transistor]
The characteristics of the thin film transistors fabricated in Example 2 and Comparative Examples 3 and 4 were evaluated. Specifically, using a Semiconductor Parameter Analyzer (manufactured by Agilent, 4155C), the gate voltage V _G (V) -drain current I _D (A) characteristics and the gate voltage V _G (V) -gate current I _G (A) Characteristics were measured. The results are shown in FIGS. 4A to 4C. 4A shows the characteristics of the thin film transistor of Example 2, FIG. 4B shows the characteristics of the thin film transistor of Comparative Example 3, and FIG. 4C shows the characteristics of the thin film transistor of Comparative Example 4. Note that the voltage V _D = 5V shown in FIGS. 4A to 4C indicates that the voltage applied between the source electrode and the drain electrode of the thin film transistor is 5V.

According to this result, the V _G -I _D characteristic and the V _G -I _G characteristic of the thin film transistor of Example 2 were better than those of Comparative Examples 3 and 4.

As described above, a gate insulating film forming solution containing lanthanum (La), zirconium (Zr), and acetylacetonate is used for manufacturing a TFT, so that a TFT having good electrical characteristics can be obtained at a process temperature of 200 ° C. It was confirmed that it could be manufactured.

In the following examples, TFTs were manufactured from the gate insulating film forming solution, and more detailed electrical characteristics were evaluated.

<Manufacture of thin film transistor and evaluation of transistor characteristics>
[Manufacture of thin film transistors]
(Example 3)
First, a gate electrode made of a titanium / platinum (Ti / Pt) layer was formed on a cleaned Si wafer substrate by sputtering. Next, the substrate surface on which the titanium / platinum (Ti / Pt) layer was formed was subjected to ashing treatment with oxygen plasma (15 W for 180 seconds).

Next, a gate insulating film forming solution was applied onto the gate electrode layer by spin coating (rotation speed: 2000 rpm, rotation time: 25 seconds) to form a gate insulating film. The gate insulating film forming solution was prepared as follows. First, lanthanum acetylacetonate and zirconium butoxide were added to 2-methoxyethanol so that the atomic ratio of lanthanum and zirconium was 3: 7, and the mixture was heated and stirred at 110 ° C. for 30 minutes. Next, this solution was transferred to a pressure vessel, heated to 160 ° C., held for 1 hour, and then returned to room temperature to prepare a 0.1 mol / kg lanthanum / zirconium mixed solution. Thereafter, filtration was performed with a 0.2 um PTFE filter to obtain a gate insulating film forming solution.

Next, the stacked body on which the gate insulating film is formed is allowed to stand on a hot plate set at 150 ° C. for 5 minutes and heated, and then the temperature is increased to 200 ° C. The whole surface of the gate insulating film was irradiated with ultraviolet rays of 10 mW / cm ² for 60 minutes to form a gate insulating layer. By repeating the above-described series of operations of forming a gate insulating film by spin coating, heating at 150 ° C., and heating at 200 ° C. accompanied by ultraviolet irradiation, a total of three gate insulating layers were laminated. The total thickness of the gate insulating layer was 50 nm.

After that, an oxide semiconductor film forming solution was applied over the gate insulating layer by a spin coating method (rotation speed: 3000 rpm, rotation time: 30 seconds). The obtained laminate was allowed to stand on a hot plate set at 100 ° C. for 5 minutes and heated, and then the temperature was increased to 200 ° C., and the illuminance was 10 mW / cm ² while heating at the same temperature. The entire surface of the oxide semiconductor film was irradiated with ultraviolet rays for 60 minutes to form an oxide semiconductor layer. The thickness of the oxide semiconductor layer was 20 nm. As the oxide semiconductor film formation solution, an indium solution prepared by adding indium nitrate to water and stirring at 110 ° C. and a rotation speed of 1000 rpm for 30 minutes to adjust to 0.1 mol / kg was used.

Next, the obtained laminate was allowed to stand on a hot plate at 200 ° C. and heated for 10 minutes while irradiating ultraviolet rays having an illuminance of 10 mW / cm ² , thereby producing a thin film transistor.

[Evaluation of transistor characteristics]
Regarding the thin film transistor manufactured in Example 3, the on / off ratio, threshold voltage (Vth), subthreshold characteristic (SS), field effect mobility (μ _sat ), hysteresis (Hys), and gate leakage current (A) are measured. Then, the transistor characteristics were evaluated. Note that these transistor characteristics were measured using a Semiconductor Parameter Analyzer (Agilent 4155C). The measurement results are shown in Table 1.

Table 1 Measurement results of transistor characteristics

As shown in Table 1, the thin film transistor of Example 3 had good transistor characteristics. In particular, the field effect mobility (μ) was 2 cm ² / Vs or more, and the gate leakage current was as good as 8.1 × 10 ⁻¹⁰ A.

As described above, when the solution (i) containing lanthanum (La), zirconium (Zr), and acetylacetonate is used as the gate insulating film forming solution, the thin film transistor has good transistor characteristics. It was. Next, the electrical characteristics of the thin film transistor were measured when a solution (ii) and a solution (iii) containing other specific metal elements and acetylacetonate were used as the gate insulating film forming solution. First, the results when using the solution (ii) are shown below.

<Manufacture of thin film transistor>
Example 4
First, a gate electrode made of a titanium / platinum (Ti / Pt) layer was formed on a cleaned Si wafer substrate by sputtering. Next, the substrate surface on which the titanium / platinum (Ti / Pt) layer was formed was subjected to ashing treatment with oxygen plasma (15 W for 180 seconds).

Thereafter, Ag paste was formed at the four corners of the substrate in order to form gate electrode contact regions.

Next, a gate insulating film forming solution was applied onto the gate electrode layer by spin coating (rotation speed: 2000 rpm, rotation time: 25 seconds) to form a gate insulating film. A gate insulating film forming solution was prepared as follows. First, samarium acetylacetonate and zirconium acetylacetonate were added to 2-methoxyethanol so that the atomic ratio of samarium and zirconium was 1: 9, and the mixture was stirred with heating at 110 ° C. for 30 minutes, 0.1 mol / wt. kg of samarium / zirconium solution was obtained. Next, the obtained solution was transferred to a pressure vessel, heated to 160 ° C., held for 1 hour, and then returned to room temperature to prepare a 0.1 mol / kg samarium / zirconium solution. Thereafter, filtration was performed with a 0.2 um PTFE filter to obtain a gate insulating film forming solution.

Next, the stacked body on which the gate insulating film is formed is allowed to stand on a hot plate set at 150 ° C. for 5 minutes and heated, and then the temperature is increased to 200 ° C. The entire surface of the gate insulating film was irradiated with ultraviolet rays of 10.0 mW / cm ² for 60 minutes to form a gate insulating layer. Here, UV irradiation was performed using a UV ozone cleaner (Samco UV-300H-E). By repeating the above-described series of operations of forming a gate insulating film by spin coating, heating at 150 ° C., and heating at 200 ° C. accompanied by ultraviolet irradiation, a total of three gate insulating layers were laminated. The total thickness of the gate insulating layer was 50 nm.

Thereafter, an oxide semiconductor film forming solution is applied onto the gate insulating layer by a spin coating method (rotation speed: 3000 rpm, rotation time: 30 seconds), and the obtained stacked body is placed on a hot plate set at 150 ° C. After standing and heating for 5 minutes, the temperature was raised to 200 ° C., and the surface of the oxide semiconductor film was irradiated with ultraviolet rays having an illuminance of 10.0 mW / cm ² for 60 minutes while heating at the same temperature. An oxide semiconductor layer (InZnO layer) was formed. Here, UV irradiation was performed using a UV ozone cleaner (Samco UV-300H-E). The thickness of the oxide semiconductor layer was 15 nm. As the oxide semiconductor film forming solution, indium nitrate and zinc nitrate were added to 2-methoxyethanol so that the atomic ratio of indium to zinc was 8: 1, and the solution was 30 ° C. at 110 ° C. and 1000 rpm. A mixture prepared by stirring for 0.2 minutes to 0.2 mol / kg was used.

Subsequently, a source electrode and a drain electrode were formed on the oxide semiconductor layer by a lift-off method.

Then, for element isolation (patterning of the oxide semiconductor layer), a resist film is formed by photolithography, and the obtained laminate is wet-etched using ITO-02 (an ITO etchant manufactured by Kanto Chemical Co., Inc.). Etched.

Next, the obtained laminate was allowed to stand on a hot plate at 200 ° C. and heated for 10 minutes while irradiating ultraviolet rays having an illuminance of 10.0 mW / cm ² , thereby producing a thin film transistor. Here, UV irradiation was performed using a UV ozone cleaner (Samco UV-300H-E).

(Example 5)
A thin film transistor was prepared in the same manner as in Example 4 except that samarium acetylacetonate and zirconium acetylacetonate were added so that the atomic ratio of samarium to zirconium was 2: 8 when the gate insulating film forming solution was prepared. Was made.

(Example 6)
A thin film transistor was prepared in the same manner as in Example 4 except that samarium acetylacetonate and zirconium acetylacetonate were added so that the atomic ratio of samarium to zirconium was 3: 7 when the gate insulating film forming solution was prepared. Was made.

(Example 7)
Europium acetylacetonate is used instead of samarium acetylacetonate when preparing the gate insulating film forming solution, and zinc nitrate is not used when preparing the oxide semiconductor film forming solution, and water is used instead of 2-methoxyethanol. A thin film transistor was fabricated in the same manner as in Example 4 except that it was used.

(Example 8)
When preparing the gate insulating film forming solution, europium acetylacetonate is used instead of samarium acetylacetonate, and europium acetylacetonate and zirconium acetylacetonate are mixed so that the atomic ratio of europium and zirconium is 2: 8. A thin film transistor was produced in the same manner as in Example 4 except that zinc nitrate was not used in preparing the oxide semiconductor film forming solution and water was used instead of 2-methoxyethanol.

Example 9
When preparing the gate insulating film forming solution, europium acetylacetonate is used instead of samarium acetylacetonate, and europium acetylacetonate and zirconium acetylacetonate are mixed so that the atomic ratio of europium and zirconium is 3: 7. A thin film transistor was produced in the same manner as in Example 4 except that zinc nitrate was not used in preparing the oxide semiconductor film forming solution and water was used instead of 2-methoxyethanol.

(Example 10)
When preparing the gate insulating film forming solution, yttrium acetate was used instead of samarium acetylacetonate, and yttrium acetate and zirconium acetylacetonate were added so that the atomic ratio of yttrium to zirconium was 1: 9. A thin film transistor was fabricated in the same manner as in Example 4 except that zinc nitrate was not used in the preparation of the physical semiconductor film forming solution and water was used instead of 2-methoxyethanol.

(Example 11)
When preparing the gate insulating film forming solution, cerium acetate was used in place of samarium acetylacetonate, and cerium acetate and zirconium acetylacetonate were added so that the atomic ratio of cerium and zirconium was 1: 9. A thin film transistor was fabricated in the same manner as in Example 4 except that zinc nitrate was not used in the preparation of the physical semiconductor film forming solution and water was used instead of 2-methoxyethanol.

(Example 12)
When preparing the gate insulating film forming solution, praseodymium acetate is used instead of samarium acetylacetonate, and praseodymium acetate and zirconium acetylacetonate are added so that the atomic ratio of praseodymium and zirconium is 1: 9, and oxidation is performed. A thin film transistor was fabricated in the same manner as in Example 4 except that zinc nitrate was not used in the preparation of the physical semiconductor film forming solution and water was used instead of 2-methoxyethanol.

(Example 13)
When preparing the gate insulating film forming solution, neodymium acetate was used instead of samarium acetylacetonate, and neodymium acetate and zirconium acetylacetonate were added so that the atomic ratio of neodymium and zirconium was 1: 9. A thin film transistor was fabricated in the same manner as in Example 4 except that zinc nitrate was not used in the preparation of the physical semiconductor film forming solution and water was used instead of 2-methoxyethanol.

(Example 14)
When preparing the gate insulating film forming solution, samarium acetate is used instead of samarium acetylacetonate, and samarium acetate and zirconium acetylacetonate are added so that the atomic ratio of samarium and zirconium is 1: 9. A thin film transistor was fabricated in the same manner as in Example 4 except that zinc nitrate was not used in the preparation of the physical semiconductor film forming solution and water was used instead of 2-methoxyethanol.

(Example 15)
When preparing the gate insulating film forming solution, europium acetate is used instead of samarium acetylacetonate, and europium acetate and zirconium acetylacetonate are added so that the atomic ratio of europium and zirconium is 1: 9. A thin film transistor was fabricated in the same manner as in Example 4 except that zinc nitrate was not used in the preparation of the physical semiconductor film forming solution and water was used instead of 2-methoxyethanol.

(Example 16)
When preparing the gate insulating film forming solution, gadolinium acetate was used instead of samarium acetylacetonate, gadolinium acetate and zirconium acetylacetonate were added so that the atomic ratio of gadolinium and zirconium was 1: 9, and oxidation was performed. A thin film transistor was fabricated in the same manner as in Example 4 except that zinc nitrate was not used in the preparation of the physical semiconductor film forming solution and water was used instead of 2-methoxyethanol.

(Example 17)
When preparing the gate insulating film forming solution, terbium acetate was used instead of samarium acetylacetonate, terbium acetate and zirconium acetylacetonate were added so that the atomic ratio of terbium and zirconium was 1: 9, and oxidation was performed. A thin film transistor was fabricated in the same manner as in Example 4 except that zinc nitrate was not used in the preparation of the physical semiconductor film forming solution and water was used instead of 2-methoxyethanol.

(Example 18)
When preparing the gate insulating film forming solution, dysprosium acetate was used instead of samarium acetylacetonate, and dysprosium acetate and zirconium acetylacetonate were added so that the atomic ratio of dysprosium and zirconium was 1: 9. A thin film transistor was fabricated in the same manner as in Example 4 except that zinc nitrate was not used in the preparation of the physical semiconductor film forming solution and water was used instead of 2-methoxyethanol.

(Example 19)
When preparing the gate insulating film forming solution, holmium acetate was used instead of samarium acetylacetonate, and holmium acetate and zirconium acetylacetonate were added so that the atomic ratio of holmium and zirconium was 1: 9. A thin film transistor was fabricated in the same manner as in Example 4 except that zinc nitrate was not used in the preparation of the physical semiconductor film forming solution and water was used instead of 2-methoxyethanol.

(Example 20)
When preparing the gate insulating film forming solution, erbium acetate was used instead of samarium acetylacetonate, and erbium acetate and zirconium acetylacetonate were added so that the atomic ratio of erbium and zirconium was 1: 9. A thin film transistor was fabricated in the same manner as in Example 4 except that zinc nitrate was not used in the preparation of the physical semiconductor film forming solution and water was used instead of 2-methoxyethanol.

(Example 21)
When preparing the gate insulating film forming solution, thulium acetate is used instead of samarium acetylacetonate, and thulium acetate and zirconium acetylacetonate are added so that the atomic ratio of thulium and zirconium is 1: 9, and oxidation is performed. A thin film transistor was fabricated in the same manner as in Example 4 except that zinc nitrate was not used in the preparation of the physical semiconductor film forming solution and water was used instead of 2-methoxyethanol.

(Example 22)
When preparing the gate insulating film forming solution, ytterbium acetate was used instead of samarium acetylacetonate, and ytterbium acetate and zirconium acetylacetonate were added so that the atomic ratio of ytterbium and zirconium was 1: 9. A thin film transistor was fabricated in the same manner as in Example 4 except that zinc nitrate was not used in the preparation of the physical semiconductor film forming solution and water was used instead of 2-methoxyethanol.

(Example 23)
When preparing the gate insulating film forming solution, lutetium acetate was used instead of samarium acetylacetonate, and lutetium acetate and zirconium acetylacetonate were added so that the atomic ratio of lutetium and zirconium was 1: 9. A thin film transistor was fabricated in the same manner as in Example 4 except that zinc nitrate was not used in the preparation of the physical semiconductor film forming solution and water was used instead of 2-methoxyethanol.

(Example 24)
When preparing the gate insulating film forming solution, europium acetylacetonate is used instead of samarium acetylacetonate, and europium acetylacetonate and zirconium acetylacetonate are mixed so that the atomic ratio of europium and zirconium is 4: 6. A thin film transistor was fabricated in the same manner as in Example 4 except that the above was added.

(Example 25)
In preparing the oxide semiconductor film forming solution, gallium nitrate is used instead of zinc nitrate, indium nitrate and gallium nitrate are added so that the atomic ratio of indium to gallium is 8: 1, and 2-methoxy is added. A thin film transistor was produced in the same manner as in Example 4 except that water was used instead of ethanol.

(Example 26)
When preparing the gate insulating film forming solution, samarium acetylacetonate and zirconium acetylacetonate are added so that the atomic ratio of samarium and zirconium is 1:99, and when preparing the oxide semiconductor film forming solution, zinc nitrate is added. A thin film transistor was manufactured in the same manner as in Example 4 except that water was used instead of 2-methoxyethanol.

(Example 27)
When preparing the gate insulating film forming solution, samarium acetylacetonate and zirconium acetylacetonate are added so that the atomic ratio of samarium and zirconium is 4:96, and when preparing the oxide semiconductor film forming solution, zinc nitrate is added. A thin film transistor was manufactured in the same manner as in Example 4 except that water was used instead of 2-methoxyethanol.

(Example 28)
During the preparation of the gate insulating film forming solution, samarium acetylacetonate and zirconium acetylacetonate are added so that the atomic ratio of samarium and zirconium is 8:92, and during the preparation of the oxide semiconductor film forming solution, zinc nitrate is added. A thin film transistor was manufactured in the same manner as in Example 4 except that water was used instead of 2-methoxyethanol.

(Comparative Example 5)
A thin film transistor was prepared in the same manner as in Example 4 except that samarium acetylacetonate and zirconium acetylacetonate were added so that the atomic ratio of samarium to zirconium was 1: 1 when the gate insulating film forming solution was prepared. Was made.

<Evaluation of transistor characteristics>
Regarding the thin film transistors manufactured in the above examples and comparative examples, the on / off ratio, threshold voltage (Vth), subthreshold characteristic (SS), field effect mobility (μ _sat ), hysteresis (Hys), and gate leakage current (A ) Was measured to evaluate the transistor characteristics. Note that these transistor characteristics were measured using a Semiconductor Parameter Analyzer (Agilent 4155C). The measurement results are shown in Table 2.

(Table 2-1)
Table 2 Measurement results of transistor characteristics

(Table 2-2)
(Continued from Table 2)

As shown in Table 2, the atomic ratio of Zr to a metal element selected from the group consisting of Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, and Y The thin film transistors of Examples 4 to 28 having a ratio of 1: 1.5 to 1:99 had very good electrical characteristics. When the thin film transistor is applied to, for example, a high-definition or large-area display, a field effect mobility of approximately 50 cm ² / vs or more is required for driving the thin film transistor. It met the requirements.

On the other hand, the thin film transistor of Comparative Example 5 was inferior in electrical characteristics as compared with Examples 4 to 28. As described above, in the oxide constituting the gate insulating layer, when the atomic ratio of the metal element (Sm) and zirconium (Zr) is about 1: 1, the electrical characteristics are remarkably deteriorated.

As described above, the thin film transistors of Examples 4 to 28 had very good electrical characteristics even when manufactured at a process temperature of 200 ° C. From this, it is possible to apply the said thin-film transistor and its manufacturing method to wide uses, such as a flexible display use.

Next, the results when the solution (iii) is used as the gate insulating film forming solution are shown below.

<Manufacture of thin film transistor>
(Example 29)
First, a gate electrode made of a titanium / platinum (Ti / Pt) layer was formed on a cleaned Si wafer substrate by sputtering. Next, the substrate surface on which the titanium / platinum (Ti / Pt) layer was formed was subjected to ashing treatment with oxygen plasma (15 W for 180 seconds).

Next, a gate insulating film forming solution was applied onto the gate electrode layer by spin coating (rotation speed: 2000 rpm, rotation time: 25 seconds) to form a gate insulating film. A gate insulating film forming solution was prepared as follows. First, zirconium acetylacetonate was added to 2-methoxyethanol, and the mixture was heated and stirred at 110 ° C. for 30 minutes to obtain a 0.4 mol / kg zirconium solution. Next, the obtained solution was transferred to a pressure vessel, heated to 160 ° C., held for 1 hour, and then returned to room temperature to prepare a 0.4 mol / kg zirconium solution. Thereafter, filtration was performed with a 0.2 um PTFE filter to obtain a gate insulating film forming solution.

Thereafter, an oxide semiconductor film forming solution is applied onto the gate insulating layer by a spin coating method (rotation speed: 3000 rpm, rotation time: 30 seconds), and the obtained stacked body is placed on a hot plate set at 150 ° C. After standing and heating for 5 minutes, the temperature was raised to 200 ° C., and the surface of the oxide semiconductor film was irradiated with ultraviolet rays having an illuminance of 10.0 mW / cm ² for 60 minutes while heating at the same temperature. An oxide semiconductor layer (InO layer) was formed. Here, UV irradiation was performed using a UV ozone cleaner (Samco UV-300H-E). The thickness of the oxide semiconductor layer was 15 nm. As the oxide semiconductor film forming solution, a solution prepared by adding indium nitrate to water and stirring at 110 ° C. and a rotation speed of 1000 rpm for 30 minutes to be 0.2 mol / kg was used.

(Example 30)
A thin film transistor was fabricated in the same manner as in Example 29 except that hafnium acetylacetonate was used instead of zirconium acetylacetonate when preparing the gate insulating film forming solution.

(Example 31)
A thin film transistor was fabricated in the same manner as in Example 29 except that aluminum acetylacetonate was used instead of zirconium acetylacetonate when preparing the gate insulating film forming solution.

(Example 32)
A thin film transistor was fabricated in the same manner as in Example 29 except that in the preparation of the oxide semiconductor forming solution, indium nitrate and zinc nitrate were mixed so that the atomic ratio of indium to zinc was 8: 2.

(Example 33)
A thin film transistor was manufactured in the same manner as in Example 29 except that in the preparation of the oxide semiconductor forming solution, indium nitrate and gallium nitrate were mixed so that the atomic ratio of indium to gallium was 8: 2.

(Example 34)
Hafnium acetylacetonate is used in place of zirconium acetylacetonate when preparing the gate insulating film forming solution, and indium nitrate and zinc nitrate are used in the preparation of the oxide semiconductor forming solution, and the atomic ratio of indium and zinc is 8: A thin film transistor was manufactured in the same manner as in Example 29 except that the mixing was performed so as to be 2.

(Example 35)
Hafnium acetylacetonate was used instead of zirconium acetylacetonate when preparing the gate insulating film forming solution, and when preparing the oxide semiconductor forming solution, the atomic ratio of indium and gallium was 8: A thin film transistor was manufactured in the same manner as in Example 29 except that the mixing was performed so as to be 2.

(Example 36)
A thin film transistor was prepared in the same manner as in Example 29 except that aluminum acetylacetonate and zirconium acetylacetonate were mixed so that the atomic ratio of aluminum to zirconium was 9: 1 when preparing the gate insulating film forming solution. Was made.

(Example 37)
A thin film transistor was prepared in the same manner as in Example 29 except that aluminum acetylacetonate and zirconium acetylacetonate were mixed so that the atomic ratio of aluminum to zirconium was 7: 3 when preparing the gate insulating film forming solution. Was made.

(Example 38)
A thin film transistor was prepared in the same manner as in Example 29 except that aluminum acetylacetonate and zirconium acetylacetonate were mixed so that the atomic ratio of aluminum to zirconium was 1: 1 at the time of preparing the gate insulating film forming solution. Was made.

(Example 39)
A thin film transistor was prepared in the same manner as in Example 29 except that aluminum acetylacetonate and zirconium acetylacetonate were mixed so that the atomic ratio of aluminum to zirconium was 3: 7 when preparing the gate insulating film forming solution. Was made.

(Example 40)
A thin film transistor was prepared in the same manner as in Example 29, except that aluminum acetylacetonate and zirconium acetylacetonate were mixed so that the atomic ratio of aluminum to zirconium was 1: 9 when the gate insulating film forming solution was prepared. Was made.

(Example 41)
A thin film transistor was prepared in the same manner as in Example 29 except that hafnium acetylacetonate and zirconium acetylacetonate were mixed so that the atomic ratio of hafnium and zirconium was 1: 1 at the time of preparing the gate insulating film forming solution. Was made.

(Example 42)
A thin film transistor was obtained in the same manner as in Example 29 except that hafnium acetylacetonate and zirconium acetylacetonate were mixed so that the atomic ratio of hafnium and zirconium was 9: 1 at the time of preparing the gate insulating film forming solution. Was made.

(Example 43)
Except for mixing the aluminum acetylacetonate, hafnium acetylacetonate, and zirconium acetylacetonate so that the atomic ratio of aluminum, hafnium, and zirconium was 1: 1: 1 during the preparation of the gate insulating film forming solution, A thin film transistor was fabricated in the same manner as in Example 29.

<Evaluation of transistor characteristics>
Regarding the manufactured thin film transistor, the on / off ratio, threshold voltage (Vth), subthreshold characteristic (SS), field effect mobility (μ _sat ), hysteresis (Hys), and gate leakage current (A) were measured, Transistor characteristics were evaluated. Note that these transistor characteristics were measured using a Semiconductor Parameter Analyzer (Agilent 4155C). The measurement results are shown in Table 3.

Table 3 Measurement results of transistor characteristics

As shown in Table 3, the thin film transistors of Examples 29 to 43 had very good electrical characteristics. When the thin film transistor is applied to, for example, a high-definition or large-area display, a field-effect mobility of approximately 50 cm ² / vs or more is required for driving the thin film transistor. It met the requirements.

As described above, the thin film transistors of Examples 29 to 43 had very good electrical characteristics even when manufactured at a process temperature of 200 ° C. From this, it is possible to apply the said thin-film transistor and its manufacturing method to wide uses, such as a flexible display use.

DESCRIPTION OF SYMBOLS 10 Thin-film transistor 12 Substrate 14 Gate electrode 16 Gate insulating layer 16 'Gate insulating film 18 Oxide semiconductor layer 18' Oxide semiconductor film 32 Source electrode 34 Drain electrode

Claims

A thin film transistor comprising a gate electrode, a gate insulating layer, and an oxide semiconductor layer in this order,
The gate insulating layer is
Cerium (Ce), praseodymium (Pr), neodymium (Nd), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), A metal element selected from the group consisting of thulium (Tm), ytterbium (Yb), lutetium (Lu), and yttrium (Y), and zirconium (Zr), and a metal element selected from the group, zirconium Whether the atomic ratio with respect to (Zr) is made of an oxide having an atomic number of zirconium (Zr) of 1.5 or more when the atomic number of a metal element selected from the group is 1 Or
Formed of an oxide containing at least one metal element selected from the group consisting of hafnium (Hf), zirconium (Zr), and aluminum (Al);
The oxide semiconductor layer includes an oxide containing indium (In), an oxide containing indium (In) and tin (Sn), an oxide containing indium (In) and zinc (Zn), and indium (In). , An oxide containing zirconium (Zr) and zinc (Zn), an oxide containing indium (In) and gallium (Ga), and an oxide containing indium (In), zinc (Zn) and gallium (Ga) A thin film transistor, characterized in that it is made of an oxide selected from the group of objects.
A method of manufacturing a thin film transistor comprising a gate electrode, a gate insulating layer, and an oxide semiconductor layer in this order,
Applying a gate insulating film forming solution on the gate electrode to form a gate insulating film;
Baking the gate insulating film at 180 to 200 ° C. while irradiating the surface of the gate insulating film with ultraviolet rays in an oxygen-containing environment to form a gate insulating layer;
Applying an oxide semiconductor film forming solution on the gate insulating layer to form an oxide semiconductor film;
Firing the oxide semiconductor film at 180 to 200 ° C. while irradiating the surface of the oxide semiconductor film with ultraviolet rays to form an oxide semiconductor layer;
Including
The gate insulating film forming solution is
When lanthanum (La), zirconium (Zr), and acetylacetonate are included, and the atomic ratio of lanthanum (La) and zirconium (Zr) is 1, the number of lanthanum (La) atoms is 1, A solution (i) in which the number of atoms of zirconium (Zr) is 0.8 or more,
Cerium (Ce), praseodymium (Pr), neodymium (Nd), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), Comprising a metal element selected from the group consisting of thulium (Tm), ytterbium (Yb), lutetium (Lu), and yttrium (Y), zirconium (Zr), and acetylacetonate, and selected from the group When the atomic ratio between the metal element and zirconium (Zr) is 1 when the number of atoms of the metal element selected from the above group is 1, a solution having a zirconium (Zr) atom number of 1.5 or more (ii) ) Or
A solution (iii) containing at least one metal element selected from the group consisting of hafnium (Hf), zirconium (Zr), and aluminum (Al), and acetylacetonate;
The oxide semiconductor film forming solution includes indium (In), indium (In) and tin (Sn), indium (In) and zinc (Zn), indium (In), zirconium (Zr), zinc (Zn), and indium. A manufacturing method comprising a metal element selected from the group consisting of (In), gallium (Ga), indium (In), zinc (Zn), and gallium (Ga), and an oxidizing agent.
The illuminance of ultraviolet rays irradiated in the step of forming the gate insulating layer when the gate insulating film forming solution is the solution (i) is 7 to 12 mW / cm 2. 2. The production method according to 2.
In the step of forming the gate insulating layer, when the gate insulating film forming solution is the solution (ii) or the solution (iii), the illuminance of the irradiated ultraviolet rays is 5 to 15 mW / cm 2. The manufacturing method according to claim 2.
In the step of forming the oxide semiconductor layer, when the gate insulating film forming solution is the solution (i), the illuminance of ultraviolet rays to be irradiated is 7 to 12 mW / cm 2. Item 3. The manufacturing method according to Item 2.
In the step of forming the oxide semiconductor layer, when the gate insulating film forming solution is the solution (ii) or the solution (iii), the illuminance of the irradiated ultraviolet ray is 5 to 15 mW / cm 2. The manufacturing method according to claim 2, wherein the manufacturing method is characterized.
7. The gate insulating film forming solution according to claim 2, wherein the gate insulating film forming solution is heat-treated at 150 to 200 ° C. in a sealed container before being applied on the gate electrode. Manufacturing method.
The manufacturing method according to any one of claims 2 to 7, wherein a solvent of the gate insulating film forming solution is an alcohol solvent.
The method according to any one of claims 2 to 8, wherein the oxidizing agent is selected from the group consisting of nitric acid, nitrate, peroxide, and perchlorate.
A solution for forming a gate insulating film for a thin film transistor,
The gate insulating film forming solution is
When lanthanum (La), zirconium (Zr), and acetylacetonate are included, and the atomic ratio of lanthanum (La) and zirconium (Zr) is 1, the number of lanthanum (La) atoms is 1, A solution (i) in which the number of atoms of zirconium (Zr) is 0.8 or more,
Cerium (Ce), praseodymium (Pr), neodymium (Nd), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), Comprising a metal element selected from the group consisting of thulium (Tm), ytterbium (Yb), lutetium (Lu), and yttrium (Y), zirconium (Zr), and acetylacetonate, and selected from the group When the atomic ratio between the metal element and zirconium (Zr) is 1 when the number of atoms of the metal element selected from the above group is 1, a solution having a zirconium (Zr) atom number of 1.5 or more (ii) ) Or
It is a solution (iii) containing at least one metal element selected from the group consisting of hafnium (Hf), zirconium (Zr), and aluminum (Al), and acetylacetonate, for a thin film transistor Gate insulating film forming solution.
11. The gate insulating film forming solution for a thin film transistor according to claim 10, wherein the solution is heat-treated at 150 to 200 ° C. in a sealed container.
12. The gate insulating film forming solution for a thin film transistor according to claim 10 or 11, wherein the solvent of the gate insulating film forming solution is an alcohol solvent.