JP2012236729A - In-Ga-Zn-BASED OXIDE, AND METHOD FOR MANUFACTURING THE SAME - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a novel In-Ga-Zn-based oxide useful as a semiconductor material etc., and a method for manufacturing the same.SOLUTION: The oxide containing In, Ga, and Zn includes a repeated structure in which four layered structures are assumed to be one unit, the layered structures each consist of an oxide containing at least one of In, Ga, and Zn.

Description

  The present invention relates to an oxide containing In, Ga and Zn, and a method for manufacturing the same.

Zinc oxide (ZnO), indium oxide (In ₂ O ₃ ), or an amorphous oxide film made of zinc oxide and gallium oxide (Ga ₂ O ₃ ) has visible light permeability and is a conductor. Alternatively, since it has wide electrical characteristics from a semiconductor to an insulator, it has attracted attention as a transparent conductive film or a semiconductor film (for example, used for various sensors, thin film transistors, etc.).
In particular, since the discovery of an n-type semiconductor material containing In ₂ O ₃ and ZnO by Hosokawa et al. (Patent Document 1), various oxide semiconductors containing In ₂ O ₃ and ZnO have attracted attention.

In recent years, the crystal structure of a hexagonal layered compound represented by the composition formula in the crystalline state is In _2−x Ga _x O ₃ (ZnO) _m (where 0 <x <2, m is a natural number) (homologus crystal structure) Oxide materials with the attention are attracting attention.

As the layered compound, in addition to the above, a known crystal type composition such as In ₂ O ₃ (ZnO) _m (m = 2 to 20), InGaZnO ₄ , In ₂ Ga ₂ ZnO ₇ , or a composition close to that is known. It is being studied mainly. Specifically, an oxide containing a hexagonal layered compound represented by the general formula In ₂ O ₃ (ZnO) _m (m = 2 to 20) containing In and Zn as main components, An oxide in which at least one element having a valence of at least a valence is doped at 20 atomic% or less is disclosed (Patent Document 2). In addition, oxides having a homologous crystal structure of InGaZnO ₄ or In ₂ Ga ₂ ZnO ₇ have been studied (Patent Documents 3, 4, and 5).

Furthermore, a mixture of a hexagonal layered compound of In ₂ O ₃ (ZnO) _m (m = 2 to 20) and In ₂ O ₃ or a homologous crystal of In ₂ O ₃ (ZnO) _m (m = 2 to 20). Oxidation utilizing the characteristics of the mixture, such as an oxide composed of a mixture of a structure and ZnO (Patent Document 2), an oxide composed of a mixture of a homologous crystal structure of InGaZnO ₄ and a spinel structure of ZnGa ₂ O ₄ (Patent Document 6) Development of products is under consideration.
Patent Document 7 discloses an oxide represented by InGaO ₃ (ZnO) _m (m = 1 to 20) such as InGaO ₃ (ZnO) ₂ and a synthesis method thereof.

  However, each of the above-described oxides that have been studied so far has a structure in which three layered structures composed of In, Ga, and Zn are repeated, and four layered structures composed of In, Ga, and Zn are repeated. An oxide containing a characteristic structure has not been obtained.

JP 2006-114928 A JP-A-6-234565 JP-A-8-245220 JP 2007-73312 A International Publication No. 2009/084537 Pamphlet International Publication No. 2008/072486 Pamphlet JP-A-63-239117

  An object of the present invention is to provide a novel In—Ga—Zn (IGZO) -based oxide useful as a semiconductor material or the like and a method for producing the same.

According to the present invention, the following oxides and the like are provided.
1. An oxide containing In, Ga, and Zn, including a repeating structure including four layered structures as one unit, wherein each of the layered structures is an oxide containing at least one of In, Ga, and Zn .
2. The repeating structure is represented by In ₂ -xGa _x O ₃ (ZnO) ₂ (wherein x is 0.45 ≦ x <1.0), and is the following crystal structure A, B, or both 1 The oxide described in 1.
Crystal structure A:
First layer: InO _1.5
Second layer: Zn _{(1 + x) / 2} In _{(1-x) / 2} O
Third layer: Ga _x Zn _1-x O _1.5
Fourth layer: Zn _{(1 + x) / 2} In _{(1-x) / 2} O
Crystal structure B:
First layer: InO _1.5
Second layer: Zn _x In _1-x O
Third layer: Ga _x Zn _1-x O _1.5
Fourth layer: ZnO
3. 3. The oxide according to 2, wherein x is 0.50 ≦ x ≦ 0.80.
4). The oxide in any one of 1-3 whose a axis and c axis satisfy | fill each of the lattice constants of the said oxide respectively.
3.29mm <a-axis <3.34mm
22.50 mm <c-axis <22.90 mm
5. After the zinc compound and the gallium compound raw material powder are mixed and first baking is performed at 500 ° C. to 1000 ° C. for 1 to 100 hours, the indium compound raw material powder is mixed and 800 ° C. to 1600 ° C. for 30 minutes to 360 ° The manufacturing method of the oxide in any one of 1-4 which performs 2nd baking by time.
6). The average temperature rising rate to the maximum baking temperature of the first baking and the second baking is 8 ° C./min or less, and the average temperature decreasing rate from the maximum baking temperature is 4 ° C./min or less. Production method of oxide.

  ADVANTAGE OF THE INVENTION According to this invention, the novel IGZO type oxide useful as a semiconductor material etc. and its manufacturing method can be provided.

The crystal structure of the oxide of the present invention, and the known _In 2 _O 3 _{(ZnO) 2} and InGaO _{3 (ZnO) 2} crystal structure is a view schematically showing.

Hereinafter, the oxide of this invention and its manufacturing method are demonstrated using drawing.
The oxide of the present invention is an oxide containing indium element (In), gallium element (Ga), and zinc element (Zn), and includes a repeating structure including four layered structures as one unit. Each of the layered structures is made of an oxide containing at least one of In, Ga, and Zn. For example, an In oxide, an In—Zn oxide, a Ga—Zn oxide, a Zn oxide, or the like can be given. All four layered structures need not be different from each other.

The oxide of the present invention is an oxide including a new crystal structure different from the conventionally known crystal types of In ₂ O ₃ (ZnO) _m and InGaO ₃ (ZnO) _m .

Specifically, the oxide of the present invention includes, for example, the following crystal structures A and B represented by In _2-x Ga _x O ₃ (ZnO) ₂ as a repeating structure.
Crystal structure A
First layer: InO _1.5
Second layer: Zn _{(1 + x) / 2} In _{(1-x) / 2} O
Third layer: Ga _x Zn _1-x O _1.5
Fourth layer: Zn _{(1 + x) / 2} In _{(1-x) / 2} O
Crystal structure B
First layer: InO _1.5
Second layer: Zn _x In _1-x O
Third layer: Ga _x Zn _1-x O _1.5
Fourth layer: ZnO

In the above, x is 0.45 ≦ x <1.0, and preferably 0.50 ≦ x ≦ 0.80.
The value of x can be adjusted by adjusting the raw material mixing ratio. It is preferable that x is the above value because the crystal structure of the present invention can be easily obtained.
FIG. 1 schematically shows the crystal structure of the oxide of the present invention.

The oxide of the present invention is not found in the JCPDS (Joint Committee of Power Diffraction Standards) card, and is a novel crystal that has not been identified so far.
The crystal phase constituting the oxide may be single crystal or polycrystalline.

When a peak search was performed on the XRD chart of the oxide of the present invention, it was close to the structure of InGaO ₃ (ZnO) ₂ which is a known compound, but the peak position and the peak intensity ratio were clearly different, so InGaO ₃ It became clear that it has a novel crystal structure different from (ZnO) ₂ .

The crystal structure of the oxide of the present invention is similar to the crystal structure of InGaO ₃ (ZnO) ₂ (JCPDS: 40-0252) and In ₂ O ₃ (ZnO) ₂ (JCPDS: 20-1442). The crystal structure is different.

For reference, FIG. 1 shows a crystal structure of In ₂ O ₃ (ZnO) _{2 and} a crystal structure of InGaO ₃ (ZnO) ₂ .

The crystal structure represented by In ₂ O ₃ (ZnO) _m (m is an integer of 1 to 20) or the crystal structure represented by InGaO ₃ (ZnO) _m (m is an integer of 1 to 20) is “hexagonal layered. It is called “compound” or “crystal structure of homologous phase”, and is a crystal having a “natural superlattice” structure having a long period in which several crystal layers of different substances are superposed. When the crystal cycle or thickness of each thin film layer is on the order of nanometers, depending on the combination of the chemical composition of these layers and the thickness of the layers, it differs from the properties of a single crystal or a mixed crystal in which each layer is uniformly mixed. Unique characteristics can be obtained.

  As for the crystal structure of the homologous phase, for example, the X-ray diffraction pattern measured directly from the pulverized product of the sintered body, the cut piece, or the sintered body itself matches the crystal structure X-ray diffraction pattern of the homologous phase assumed from the composition ratio It can be confirmed by doing. Specifically, it can be confirmed from the coincidence with the crystal structure X-ray diffraction pattern of the homologous phase obtained from the JCPDS card.

The crystal structure represented by In ₂ O ₃ (ZnO) _m (m is an integer of 1 to 20) is such that the InO _1.5 layer, the InZnO _2.5 layer, and the ZnO layer are 1: 1: (m−1). It is believed to have a structure that is periodically repeated in proportion.
The crystal structure represented by InGaO ₃ (ZnO) _m (m is an integer of 1 to 20) is such that the InO _1.5 layer, the GaZnO _2.5 layer, and the ZnO layer are 1: 1: (m−1). It is believed to be repeated periodically at a rate.
Thus, a crystal structure represented by In ₂ O ₃ (ZnO) _m (m is an integer of 1 to 20) or a crystal structure represented by InGaO ₃ (ZnO) _m (m is an integer of 1 to 20). As a result of X-ray diffraction measurement, the peak positions are different (interstitial distances are different), but the patterns are similar.

  Furthermore, when the form of the oxide of the present invention was observed with EPMA, it was confirmed to be a single phase. This also shows that the present invention is a novel crystal.

  That is, the oxide of the present invention consists of a single phase of the above crystal phase (substantially consists only of the repetition of the above crystal structures A and B). The term “single phase” as used herein refers to a crystal structure in which all peaks confirmed from the measurement results are made of any one of In, Ga, and Zn when the oxide powder is measured with an X-ray diffractometer. IGZO-based crystal structure), meaning that no peak due to impurities is observed. Therefore, even if the oxide powder contains a trace amount of impurities that cannot be confirmed by X-ray diffraction measurement, it can be said that the oxide consists of a single phase.

  Since the oxide of the present invention is composed of a single phase having an IGZO-based crystal structure, it suppresses the occurrence of electron scattering at grain boundaries and the like, compared to the case where a plurality of crystal structures are mixed, and moves carriers (electrons). It is suitable for optical sensors, gas sensors, semiconductor elements, solar cell electrode materials, and the like.

The structure of the oxide of the present invention can be identified in detail by Rietveld analysis. Various conditions used for Rietveld analysis are as follows, for example.
Use program TOPAS3.0 (manufactured by Bruker AXS)
Profile function Psude-Voight function (asymmetric)
Selective orientation function Modified March-Dollase function ((001) orientation: 0.885 (1))

The procedure for Rietveld analysis is shown below.
Refine the background by polynomial fitting to the XRD chart. As the fitting function, for example, a Pseudo-Voigt function and a Fundamental Parameter function can be used. This is a method of performing peak fitting by theoretically adding a peak spread by an optical system (apparatus) to a peak function.

The programs that can be used for analysis are TOPAS and Rietan-FP.
As a specific analysis procedure, first, the lattice constant, background, and peak shape functions are used as variables, and these variables are converged, and then the atomic coordinates are moved to converge. After this converges, the temperature factor and seat occupancy can be moved as parameters.
Basically, it is general to try to converge on heavy atoms, and in the present invention, it is preferable to increase the accuracy of fitting so that the parameters converge on cations. After that, for oxygen, the temperature factor and the seat occupancy are moved to search for conditions for the fitting to converge.

  The oxide of the present invention contains other metal elements other than the above-mentioned In, Ga, Zn, such as Sn, Ge, Si, Ti, Zr, Hf, etc., as long as the crystal structure is A, B, or both. You may contain as an impurity.

The oxide of the present invention can be produced, for example, by sintering raw material powder containing each metal element in a blending amount corresponding to the composition of the crystal structures A and B.
Specifically, an indium compound and a gallium compound are mixed and calcined, and then a zinc compound is mixed and baked.

As the raw material, powders such as indium compound powder, gallium compound powder, and zinc compound powder are used.
Examples of the indium compound include In ₂ O ₃ and indium hydroxide (In (OH) ₃ ). Examples of the gallium compound include Ga ₂ O ₃ and gallium hydroxide (Ga (OH) ₃ ). Examples of the zinc compound include ZnO and zinc hydroxide (Zn (OH) ₂ ).
As each compound, an oxide is preferable because it is easy to sinter and it is difficult to leave a by-product.

  The purity of the raw material is usually 2N (99% by mass) or more, preferably 3N (99.9% by mass) or more, particularly preferably 4N (99.99% by mass) or more. If the purity is lower than 2N, the oxide according to the present invention may not be obtained. It is preferable to use metallic zinc (zinc powder) as a part of the raw material.

When using an oxide as a raw material, the specific surface areas (BET specific surface areas) of indium oxide, gallium oxide, and zinc oxide are usually 3 to 18 m ² / g, 3 to 18 m ² / g, and 3 to 18 m ² / g, respectively. Yes, preferably 7 to 16 m ² / g, 7 to 16 m ² / g, 3 to 10 m ² / g, and more preferably 7 to 15 m ² / g, 7 to 15 m ² / g, and 4 to 10 m ² , respectively. / g, and particularly preferably each ^{11~15m 2 / g, 11~15m 2 /} g, 4~5m 2 / g.
If the specific surface area is too small, aggregates of the respective elements may grow in the sintered body, the crystal form of the raw material powder may remain, an unexpected crystal form may be generated, and the properties may change. If the specific surface area is too large, an unexpected crystal form may be generated and the properties may be changed, and the crystal structure of the oxide of the present invention may not be obtained.
Each step will be described below.

(1) Compounding Step The compounding step of the raw material is a step of mixing a zinc compound and a gallium compound among the metal element compounds contained in the oxide of the present invention.
It is preferable to mix the above raw materials and uniformly mix and pulverize them using an ordinary mixing and grinding machine such as a wet ball mill, a bead mill, or an ultrasonic device. Moreover, it is preferable to perform drying by spray drying after mixing and pulverizing the raw materials.

(2) Calcination step (first firing)
In the calcining step, the mixed and pulverized product obtained in the above (1) is calcined.

In the calcination step, the above mixture is preferably heat-treated at 500 to 1000 ° C. for 1 to 100 hours. A heat treatment of less than 500 ° C. or less than 1 hour may result in insufficient thermal decomposition of the gallium compound or zinc compound. On the other hand, when the heat treatment condition exceeds 1100 ° C. or exceeds 100 hours, grain coarsening may occur. Moreover, a zinc compound may sublime.
Therefore, it is particularly preferable to perform heat treatment (calcination) for 2 to 50 hours in a temperature range of 800 to 1200 ° C.

  The calcination step is preferably performed under an air atmosphere, a nitrogen atmosphere, an oxygen gas atmosphere, or an oxygen gas pressurization in order to bak In and Ga to react uniformly.

  In addition, it is preferable that the calcined product obtained here is pulverized before the following firing step and sufficiently mixed together with the raw material powder of the indium compound (for example, indium oxide). The pulverization may be performed so that the raw material powder has a median diameter (D50) in the volume average particle diameter of preferably 2 μm or less, more preferably 1 μm or less, and particularly preferably 0.5 μm or less. The purpose is uniform dispersion of raw materials. If raw material powder having a large particle size is present, compositional unevenness may occur depending on the location, and the crystal structure of the present oxide may not be obtained.

(3) Firing step (second firing)
A baking process is a process of baking the mixture obtained by mixing an indium compound with calcined material.
Firing can be performed by hot isostatic pressure (HIP) firing or the like.
The firing conditions are usually 800 to 1600 ° C., preferably 1100 to 1600 ° C., usually 30 minutes to 360 hours, preferably 8 to 180 hours, more preferably 12 to 96 hours in an oxygen gas atmosphere or oxygen gas pressurization. Bake.
If the firing temperature is less than 800 ° C., the oxide density may be difficult to increase, or the sintering may take too long. On the other hand, if the temperature exceeds 1600 ° C., the composition may shift due to vaporization of the components, or the furnace may be damaged. If the burning time is less than 30 minutes, the density of the IGZO oxide is difficult to increase, and if it is longer than 360 hours, it takes too much production time and the cost becomes high, so that it cannot be used practically.
On the other hand, if the firing is performed in an atmosphere not containing oxygen or the firing is performed at a temperature higher than 1600 ° C., the density of the obtained oxide may not be sufficiently improved.

The average rate of temperature increase during the first and second firing is usually 8 ° C./min or less, preferably 4 ° C./min or less, more preferably 2 ° C./min or less. The oxide of this invention is easy to be obtained as it is 8 degrees C / min or less.
Moreover, the average temperature-fall rate at the time of the 1st and 2nd baking is 4 degrees C / min or less normally, Preferably it is 2 degrees C / min or less. The oxide of this invention is easy to be obtained as it is 4 degrees C / min or less.

  Hereinafter, the oxide of the present invention and the production method thereof will be described with reference to examples, but the present invention is not limited to these examples.

Example 1
(1) Production of IGZO-based oxides As raw materials for IGZO-based oxides, In ₂ O ₃ (purity 4N, manufactured by Asian Physical Materials Company), Ga ₂ O ₃ (purity 4N, manufactured by Asian Physical Materials Company) and ZnO (purity) 4N, high purity chemical) was used.
The sintered bodies (pellets) from which these raw materials were obtained were weighed so as to have the composition shown in Table 1. First, a mixture of ZnO and Ga ₂ O ₃ was mixed and ground using a wet medium stirring mill. In addition, 1 mmφ zirconia beads were used as the medium of the wet medium stirring mill. And after mixing and grinding, it was dried with a spray dryer.

The obtained powder was molded by uniaxial pressing. The pressure was 400 kgf / cm ² and the product was molded into pellets. The pellet was calcined in an electric furnace in a sealed state. The calcination conditions were as follows. In this step, In and Ga are sufficiently mixed, and the IGZO-based oxide of the present invention is more easily obtained.
Temperature increase rate: 2 ° C / min Sintering temperature: 1000 ° C
Sintering time: 6 hours Sintering atmosphere: Oxygen inflow Temperature drop time: 72 hours Temperature drop rate: 8 ° C / min

The pre-sintered body was pulverized in an agate mortar, and In ₂ O ₃ weighed earlier was added and mixed. The obtained powder was molded again into a pellet by a uniaxial press. The pressure at that time was molded at 400 kgf / cm ² as before the calcination step.
The pellet was fired in an electric furnace. The conditions for the main firing were as follows.
Temperature increase rate: 2 ° C / min Sintering temperature: 1500 ° C
Sintering time: 6 hours Sintering atmosphere: oxygen inflow Temperature drop time: 72 hours Temperature drop rate: 4 ° C./min The composition of the obtained oxide sintered body (pellet) was measured by an ICP emission spectrometer. The results are shown in Table 1.

(2) Structural analysis of IGZO-based oxide X-ray diffraction (XRD) measurement was performed on the obtained oxide sintered body (pellet). XRD measurement was performed under the following conditions. The sample was packed in a standard glass holder and measured by wide angle X-ray diffraction.
-X-ray diffractometer Bruker AXS D8ADVANCE (enclosed tube type)
X-ray source: Cu-Kα ray Wavelength: 1.5406 mm (single color with graphite monochromator)
Output: 40kV, 40mA
Slit system: DS: 0.6 °, RS: 0.2 mm
Detector: Scintillation counter / scan method 2θ-θ step scan / measurement range (2θ) 5 to 155 °
・ Step width (2θ) 0.02 °
・ Measurement time 15 seconds / step

  The obtained IGZO-based oxide was not found in the JCPDS card, and was a new crystal that had not been confirmed so far.

In order to identify the structure of this new crystal, Rietveld analysis was performed on the XRD chart. The conditions for Rietveld analysis are as follows.
・ Use program TOPAS3.0 (manufactured by Bruker AXS)
Profile function Psude-Voight function (asymmetric)
-Selective orientation function Modified March-Dollase function ((001) orientation: 0.885 (1))

First, Rietveld analysis was performed on InGaO ₃ (ZnO) ₂ which is a known compound.
The space group used for the fitting is P6 ₃ / mmc. In the fitting result by the Rietveld analysis, the XRD chart strengths near 23 ° and 32 ° greatly deviated, and the GOF indicating the fitting accuracy was a large value of 2 or more. The value of GOF is shown in Table 1.
This also indicates that the IGZO-based oxide of the present invention is different from InGaO ₃ (ZnO) ₂ which is a known compound.

Note that GOF (Goodness Of Fit) is a fitting error and is obtained by the following equation.
GOF = Rw / Reexp
Rw: weighted mean square error Rexp: mean square error with respect to experimental value If GOF is 2 or less, the accuracy by fitting is high, and it can be said that the structure has been identified.

The coordination numbers of In, Zn, and Ga are mainly 6-coordinate, 4-coordinate, and 5-coordinate, respectively. As a result of intensive studies, in the IGZO-based oxide of the present invention, excess In is present at the Zn site. And a new crystal model in which Zn is partly located at the Ga site.
Therefore, the Rietveld analysis was further advanced under the above model, and the fitting of the XRD chart was performed. As a result, the fitting could be performed with high accuracy. The value of GOF is shown in Table 1. The number of layers contained in one unit of this IGZO-based oxide was four. In addition, when the GOF was 2 or less after fitting by Rietveld analysis with a new crystal model, the number of layers was determined to be 4.
As a result, the IGZO-based oxide of Example 1 was identified as a new crystal model having a structure in which four layered structures represented by crystal structures A, B, or both are repeated.

As a result of measuring the lattice constant of the IGZO-based oxide by Rietveld analysis, the a-axis length was 3.32993 mm and the c-axis length was 22.896 mm. The space group is considered to be P6 ₃ / mmc.

Examples 2-5
Pellets were prepared and evaluated in the same manner as in Example 1 except that the raw material mixing ratio was changed. The results are shown in Table 1. In Examples 2 to 5, the GOF value using the new crystal as a model was 2 or less, and the number of layers contained in one unit was 4.

Comparative Example 1
Pellets were prepared and evaluated in the same manner as in Example 1 except that the raw material mixing ratio was changed. When InGaO ₃ (ZnO) ₂ was used as a model, fitting by Rietveld analysis did not converge. When the new crystal was used as a model, the GOF was more than 2. Therefore, the number of layers included in one unit could not be determined.

Comparative Example 2
Pellets were prepared and evaluated in the same manner as in Example 1 except that the raw material mixing ratio was changed. The fitting by Rietveld analysis using InGaO ₃ (ZnO) ₂ as a model converged, and the GOF value was 2 or less. Since the number of layers contained in one unit is the known crystal structure InGaO ₃ (ZnO) ₂ having three layers, the analysis by the new crystal model of the present invention could not be performed.

尚、実施例１〜５の酸化物は半導体特性に優れ、ガスセンサーや光センサー、太陽電池用の電極材料、ダイオード、液晶表示装置やＥＬ表示装置等として使用できることが確認された。

In addition, it was confirmed that the oxides of Examples 1 to 5 have excellent semiconductor characteristics and can be used as gas sensors, optical sensors, electrode materials for solar cells, diodes, liquid crystal display devices, EL display devices, and the like.

  The oxide obtained by the present invention is useful as a photofunctional material, a semiconductor material, a photocatalyst material, and the like. For example, it can be used for phosphors, semiconductor elements, coated semiconductor inks, sputtering targets, electrode materials for solar cells, diodes, optical sensors, gas sensors, liquid crystal display devices, EL display devices, and the like.

Claims (6)

  An oxide containing In, Ga, and Zn, including a repeating structure including four layered structures as one unit, wherein each of the layered structures is an oxide containing at least one of In, Ga, and Zn . The repeating structure is the following crystal structure A, B, or both represented by In _2-x Ga _x O ₃ (ZnO) ₂ (where x is 0.45 ≦ x <1.0). Item 2. The oxide according to Item 1.
Crystal structure A:
First layer: InO _1.5
Second layer: Zn _{(1 + x) / 2} In _{(1-x) / 2} O
Third layer: Ga _x Zn _1-x O _1.5
Fourth layer: Zn _{(1 + x) / 2} In _{(1-x) / 2} O
Crystal structure B:
First layer: InO _1.5
Second layer: Zn _x In _1-x O
Third layer: Ga _x Zn _1-x O _1.5
Fourth layer: ZnO   The oxide according to claim 2, wherein x is 0.50 ≦ x ≦ 0.80. The oxide in any one of Claims 1-3 in which the a-axis and c-axis satisfy | fill the following among the lattice constants of the said oxide, respectively.
3.29mm <a-axis <3.34mm
22.50 mm <c-axis <22.90 mm   After the zinc compound and the gallium compound raw material powder are mixed and first baking is performed at 500 ° C. to 1000 ° C. for 1 to 100 hours, the indium compound raw material powder is mixed and 800 ° C. to 1600 ° C. for 30 minutes to 360 ° The method for producing an oxide according to any one of claims 1 to 4, wherein the second baking is performed with time.   6. The average temperature rising rate up to the maximum baking temperature of the first baking and the second baking is 8 ° C./min or less, and the average temperature decreasing rate from the maximum baking temperature is 4 ° C./min or less. The manufacturing method of the oxide of description.

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