Oxide sintered body, sputtering target, oxide film, thin-film transistor, and electronic device

Abstract

The present disclosure provides an oxide sintered body in which the incidence of color unevenness is reduced and the incidence of white spots is reduced, a sputtering target provided with the oxide sintered body, an oxide film in which the sputtering target is used, a thin-film transistor including the oxide film, and an electronic device including the thin-film transistor. The present disclosure provides an oxide sintered body containing In and a prescribed X element or Z element as main components, the atomic ratio of In, Ga, Al, and the X element or the Z element satisfying a prescribed condition, and the oxide sintered body including: a bixbyite crystal phase; and a crystal phase in which a diffraction peak is observed in the incident angle (2θ) ranges (A) to (C) below, and a diffraction peak need not be observed in at least one of the incident angle (2θ) ranges (G') and (J) below, by X-ray (Cu-Kα ray) diffraction measurement.　(A) 36-39°; (B) 53-56°; (C) 62-66°; (G') 14-16°; (J) 8-10°

Description

Oxide sintered body, sputtering target, oxide film, thin film transistor, and electronic device

[0001] The present invention relates to an oxide sintered body, a sputtering target, an oxide film, a thin film transistor, and an electronic device.

[0002] Amorphous (non-crystalline) oxide semiconductors used in thin film transistors (hereinafter also referred to as "TFTs") have higher carrier mobility, a large optical band gap, and can be deposited at low temperatures compared to general-purpose amorphous silicon (hereinafter also referred to as "a-Si"). Therefore, amorphous oxide semiconductors are expected to be applied to next-generation displays that require large size, high resolution, and high-speed operation, as well as to resin substrates with low heat resistance. Furthermore, in recent years, research has been conducted into applying crystalline oxide semiconductors, rather than amorphous oxide semiconductors, to the channel layer of thin film transistors.

[0003] In forming the oxide semiconductor thin film, a sputtering method in which a sputtering target is sputtered is preferably used because a thin film formed by the sputtering method has excellent in-plane uniformity of component composition and film thickness in the film surface direction (within the film surface) compared to a thin film formed by an ion plating method, a vacuum deposition method, or an electron beam deposition method, and has the same component composition as the sputtering target.

[0004] In Patent Document 1, ２ O ３ A bixbyite phase composed of ３ B ５ O １２ The document describes an oxide sintered body containing a ZnO phase (wherein A is one or more elements selected from the group consisting of Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu, and B is one or more elements selected from the group consisting of Al and Ga).

[0005] Patent Document 2 describes a compound having the composition formula (In ｘ Ga ｙ Al ｚ ) ２ O ３(wherein 0.47≦x≦0.53, 0.17≦y≦0.43, 0.07≦z≦0.33, and x+y+z=1), and has diffraction peaks in the ranges of incident angles (2θ) observed by X-ray (Cu-Kα ray) diffraction measurement specified in the following (A) to (K): (A): 31° to 34°, (B): 36° to 39°, (C): 30° to 32°, (D): 51° to 53°, (E): 53° to 56°, (F): 62° to 66°, (G): 9° to 11°, (H): 19° to 21°, (I): 42° to 45°, (J): 8° to 10°, and (K): 17° to 19°.

[0006] Patent Document 3 describes a compound formed from indium element (In), gallium element (Ga), aluminum element (Al), and oxygen element (O), having lattice constants of a = 10.07 ± 0.15 Å, b = 10.45 ± 0.15 Å, c = 11.01 ± 0.15 Å, α = 111.70 ± 0.50°, β = 107.70 ± 0.50°, and γ = 90.00 ± 0.50°, and exhibiting a triclinic crystal system.

[0007] International Publication No. 2015 / 098060 International Publication No. 2020 / 027243 International Publication No. 2020 / 027244

[0008] For example, in a target using an oxide sintered body containing In (indium element), Ga (gallium element), and Al (aluminum element), color unevenness occurs in the oxide sintered body of the target, and white spots that appear white are generated due to small pores gathering on the surface of the oxide sintered body. The presence of color unevenness and white spots in the sintered body of the target makes abnormal discharge more likely to occur during the sputtering process.

[0009] Furthermore, when an oxide film is formed using a target including an oxide sintered body having color unevenness and white spots and a TFT element including the oxide film is fabricated, the color unevenness and white spots present in the sintered body of the target cause a decrease in mobility. Furthermore, the color unevenness and white spots present in the sintered body of the target cause a decrease in the in-plane uniformity of the TFT element characteristics. For this reason, further improvement has been required for targets using oxide sintered bodies containing In, Ga, and Al.

[0010] An object of the present invention is to provide an oxide sintered body in which the occurrence of color unevenness and the occurrence of white spots are reduced, a sputtering target including the oxide sintered body, an oxide film using the sputtering target, a thin film transistor including the oxide film, and an electronic device including the thin film transistor.

[0011] The present invention includes the following embodiments: <1> An oxide sintered body comprising, as main components, In, Ga, Al, and one or more X elements selected from the group consisting of Si, Ge, Zr, and Ce, wherein the atomic ratios of In, Ga, Al, and the X element satisfy the conditions shown in the following formulas (1) to (3), and comprising a bixbyite crystalline phase, and a crystalline phase in which a diffraction peak is observed in the following incident angle (2θ) ranges (A) to (C) by X-ray (Cu-Kα ray) diffraction measurement: 0.05≦Ga / (In+Ga)≦0.20 (1) 0.005≦Al / (In+Ga+Al+X)≦0.05 (2) 0.0003≦X / (In+Ga+Al+X)≦0.02 (3) (wherein In, Ga, Al, and X are the numbers of atoms of In, Ga, Al, and the X element in the oxide sintered body, respectively.) 36° to 39° (A) 53° to 56° (B) 62° to 66° (C) <2> The oxide sintered body according to <1>, wherein 99 at % or more of metal elements contained in the oxide sintered body are In, Ga, Al, and the X element. <3> The crystalline phase in which the diffraction peak is observed has a diffraction peak further observed in at least one range of incident angle (2θ) selected from the following (D) to (K) by X-ray (Cu-Kα ray) diffraction measurement. The oxide sintered body according to <1> or <2>.31° to 34° (D) 30° to 32° (E) 51° to 53° (F) 9° to 11° (G) 19° to 21° (H) 42° to 45° (I) 8° to 10° (J) 17° to 19° (K) <4> A glass substrate comprising, as main components, In, Ga, Al, and one or more Z elements selected from the group consisting of Si, Ge, Zr, Ce, Tb, Nd, Mn, Ru, Pd, and Pt, wherein the atomic ratios of In, Ga, Al, and the Z element satisfy the conditions shown in the following formulas (1), (4), and (5), and a bixbyite crystalline phase, and a crystalline phase in which, by X-ray (Cu-Kα ray) diffraction measurement, diffraction peaks are observed in the ranges of incident angles (2θ) of the following (A) to (C), and no diffraction peaks are observed in at least one of the ranges of incident angles (2θ) of the following (G') and (J). 0.05≦Ga / (In+Ga)≦0.20 (1) 0.005≦Al / (In+Ga+Al+Z)≦0.05 (4) 0.0003≦Z / (In+Ga+Al+Z)≦0.07 (5) (Where In, Ga, Al, and Z are the numbers of atoms of In, Ga, Al, and the Z element in the oxide sintered body, respectively.) 36° to 39° (A) 53° to 56° (B) 62° to 66° (C) 14° to 16° (G') 8° to 10° (J) <5> The oxide sintered body according to <4>, wherein the Z element is one or more selected from the group consisting of Tb and Nd. <6> The oxide sintered body according to <4> or <5>, wherein the atomic ratio represented by formula (5) is 0.0005 or more and 0.0500 or less. <7> The oxide sintered body according to any one of <4> to <6>, wherein 99 at % or more of the metal elements contained in the oxide sintered body are In, Ga, Al, and the Z element. <8> The oxide sintered body according to any one of <4> to <7>, wherein, in X-ray (Cu-Kα ray) diffraction measurement, the crystalline phase in which the diffraction peak is observed further has a diffraction peak observed in at least one range of incident angle (2θ) selected from the following (D) to (K):31° to 34° (D) 30° to 32° (E) 51° to 53° (F) 9° to 11° (G) 19° to 21° (H) 42° to 45° (I) 8° to 10° (J) 17° to 19° (K) <9> The oxide sintered body according to any one of <1> to <8>, wherein the crystalline phase in which the diffraction peaks are observed further has diffraction peaks in the following incident angle (2θ) ranges (D), (E), (F), (H), (I) and (K) by X-ray (Cu—Kα ray) diffraction measurement. 31° to 34° (D) 30° to 32° (E) 51° to 53° (F) 19° to 21° (H) 42° to 45° (I) 17° to 19° (K) <10> The oxide sintered body according to any one of <1> to <9>, wherein, in X-ray (Cu-Kα ray) diffraction measurement, the crystalline phase in which the diffraction peak is observed does not exhibit a diffraction peak within the range of incident angles (2θ) of the following (G'): 14° to 16° (G') <11> The oxide sintered body according to any one of <1> to <10>, wherein the atomic ratio represented by formula (1) is 0.05 or more and 0.18 or less. <12> The oxide sintered body according to any one of <1> to <11>, wherein the atomic ratio represented by formula (1) is 0.06 or more and 0.16 or less. <13> The oxide sintered body according to any one of <1> to <12>, wherein the atomic ratio represented by the formula (1) is 0.08 or more and 0.15 or less. <14> The oxide sintered body according to any one of <1> to <13>, wherein the atomic ratio represented by the formula (2) or (4) is 0.008 or more and 0.04 or less. <15> The oxide sintered body according to any one of <1> to <14>, wherein the atomic ratio represented by the formula (2) or (4) is 0.01 or more and 0.03 or less. <16> The oxide sintered body according to any one of <1> to <15>, wherein the atomic ratio represented by the formula (3) or (5) is 0.0005 or more and 0.015 or less. <17> The oxide sintered body according to any one of <1> to <16>, wherein the atomic ratio represented by the formula (3) or (5) is 0.0008 or more and 0.010 or less. <18> The oxide sintered body according to any one of <1> to <17>, having a bulk resistance of 10 mΩ cm or less.<19> A sputtering target comprising the oxide sintered body according to any one of <1> to <18>. <20> An oxide film formed using the sputtering target according to <19>. <21> A thin film transistor comprising the oxide film according to <20>. <22> An electronic device comprising the thin film transistor according to <21>.

[0012] According to the present invention, it is possible to provide an oxide sintered body in which the occurrence of color unevenness and the occurrence of white spots are reduced, a sputtering target including the oxide sintered body, an oxide film using the sputtering target, a thin film transistor including the oxide film, and an electronic device including the thin film transistor.

[0013] FIG. 2A is a perspective view showing the shape of a target according to the present embodiment; FIG. 2B is a perspective view showing the shape of a target according to the present embodiment; FIG. 2C is a perspective view showing the shape of a target according to the present embodiment; FIG. 2D is a longitudinal sectional view showing a state in which an oxide semiconductor film is formed on a glass substrate; and FIG. 2E is a perspective view showing a state in which an SiO.sub.2O.sub.2 film is formed on the oxide semiconductor film of FIG. ２1 is a longitudinal sectional view showing a state in which a film has been formed. FIG. 2 is a longitudinal sectional view showing a thin film transistor according to the present embodiment. FIG. 3 is a longitudinal sectional view showing a thin film transistor according to the present embodiment. FIG. 4 is a longitudinal sectional view showing a thin film transistor according to the present embodiment. FIG. 5 is a longitudinal sectional view showing a quantum tunnel field effect transistor according to the present embodiment. FIG. 6 is a longitudinal sectional view showing another embodiment of a quantum tunnel field effect transistor. FIG. 7 is a longitudinal sectional view for explaining a manufacturing procedure of a quantum tunnel field effect transistor. FIG. 8 is a longitudinal sectional view for explaining a manufacturing procedure of a quantum tunnel field effect transistor. FIG. 9 is a longitudinal sectional view for explaining a manufacturing procedure of a quantum tunnel field effect transistor. FIG. 10 is a longitudinal sectional view for explaining a manufacturing procedure of a quantum tunnel field effect transistor. FIG. 11 is a longitudinal sectional view for explaining a manufacturing procedure of a quantum tunnel field effect transistor. FIG. 12 is a top view showing a display device using the thin film transistor according to the present embodiment. FIG. 13 is a diagram showing a circuit of a pixel portion that can be applied to pixels of a VA-type liquid crystal display device. FIG. 14 is a diagram showing a circuit of a pixel portion of a display device using an organic EL element. FIG. 15 is a diagram showing a circuit of a pixel portion of a solid-state imaging element using the thin film transistor according to the present embodiment. FIG. 16 is an XRD chart of an oxide sintered body according to Example 4. FIG. 17 is an XRD chart of an oxide sintered body according to Example 13. FIG. 18 is an XRD chart of an oxide sintered body according to Example 14.

[0014] Hereinafter, embodiments will be described with reference to the drawings, etc. However, it will be readily understood by those skilled in the art that the embodiments can be implemented in many different ways and that various changes in form and details can be made without departing from the spirit and scope of the present invention. Therefore, the present invention should not be interpreted as being limited to the following description of the embodiments.

[0015] In the drawings, sizes, layer thicknesses, regions, etc. may be exaggerated for clarity. Therefore, the present invention is not limited to the illustrated sizes, layer thicknesses, regions, etc. Note that the drawings are schematic illustrations of ideal examples, and the present invention is not limited to the shapes, values, etc. shown in the drawings.

[0016] The ordinal numbers "first," "second," and "third" used in this specification are used to avoid confusion between components, and components that are not specified numerically are not limited in number.

[0017] In this specification and the like, the terms "film" or "thin film" and "layer" can be used interchangeably in some cases.

[0018] In the sintered body and oxide film of this specification and the like, the terms "compound" and "crystalline phase" can be interchangeable in some cases.

[0019] In this specification, the “oxide sintered body” may be simply referred to as the “sintered body.” In this specification, the “sputtering target” may be simply referred to as the “target.”

[0020] In this specification, "electrically connected" includes connection via "something that has some kind of electrical function." Here, "something that has some kind of electrical function" is not particularly limited as long as it allows electrical signals to be transmitted and received between the connected objects. For example, "something that has some kind of electrical function" includes electrodes, wiring, switching elements (such as transistors), resistive elements, inductors, capacitors, and other elements with various functions.

[0021] In this specification, the functions of the source and drain of a transistor may be interchanged when transistors of different polarities are used or when the direction of current flow changes during circuit operation, etc. Therefore, in this specification, the terms source and drain may be used interchangeably.

[0022] In this specification, a numerical range expressed using "to" means a range that includes the numerical value written before "to" as the lower limit and the numerical value written after "to" as the upper limit.

[0023] When the composition of an oxide in an oxide sintered body or an oxide film is indicated, In is an indium element, Ga is a gallium element, Al is an aluminum element, Si is a silicon element, Ge is a germanium element, Zr is a zirconium element, Ce is a cerium element, Tb is a terbium element, Nd is a neodymium element, Mn is a manganese element, Ru is a ruthenium element, Pd is a palladium element, and Pt is a platinum element. These elements coexist with oxygen in the oxide.

[0024] The present inventors have invented the present invention based on the following findings. The present inventors have discovered that in an oxide sintered body containing the metal elements In, Ga, and Al and including a bixbyite crystalline phase and a crystalline phase A or crystalline phase B having a specific diffraction peak as described below, by adding one or more X elements selected from the group consisting of Si, Ge, Zr, and Ce (hereinafter also simply referred to as "X elements"), or one or more Z elements selected from the group consisting of Si, Ge, Zr, Ce, Tb, Nd, Mn, Ru, Pd, and Pt (hereinafter also simply referred to as "Z elements"), the occurrence of color unevenness in the target can be reduced and the occurrence of white spots can be reduced. Furthermore, when the oxide sintered body contains an X element, the atomic ratio of "Ga" to the "total of In and Ga", the atomic ratio of "Al" to the "total of In, Ga, Al, and the X element", and the atomic ratio of the "X element" are considered, and the occurrence of color unevenness in the target can be reduced and the occurrence of white spots can be reduced. Similarly, when the oxide sintered body contains the Z element, the occurrence of color unevenness in the target can be reduced and the occurrence of white spots can be reduced by examining the atomic ratio of "Ga" to the "total of In and Ga", the atomic ratio of "Al" to the "total of In, Ga, Al, and the Z element", and the atomic ratio of the "Z element".

[0025] [Oxide Sintered Body] The oxide sintered body according to a first aspect of the present embodiment comprises, as main components, In, Ga, Al, and one or more X elements selected from the group consisting of Si, Ge, Zr, and Ce, wherein the atomic ratios of In, Ga, Al, and the X element satisfy the conditions shown in the following formulas (1) to (3), and comprises a bixbyite crystalline phase, and a crystalline phase in which a diffraction peak is observed in the following range of incident angles (2θ) (A) to (C) by X-ray (Cu-Kα ray) diffraction measurement. 0.05≦Ga / (In+Ga)≦0.20 (1) 0.005≦Al / (In+Ga+Al+X)≦0.05 (2) 0.0003≦X / (In+Ga+Al+X)≦0.02 (3) (wherein In, Ga, Al, and X are the numbers of atoms of In, Ga, Al, and the X element in the oxide sintered body, respectively.) 36° to 39° (A) 53° to 56° (B) 62° to 66° (C)

[0026] According to the oxide sintered body according to the first aspect, the occurrence of color unevenness and the occurrence of white spots are reduced. As a result of the reduction in the occurrence of color unevenness and the occurrence of white spots, a thin film transistor having an oxide film formed from the oxide sintered body exhibits an appropriate linear mobility value and a threshold voltage (Vth) close to zero.

[0027] The oxide sintered body according to the first aspect contains In, Ga, Al, and an X element as main components as metal elements. In this specification, "main component" means a component that accounts for 50 at% or more of the total number of atoms of the constituent metal elements. In the oxide sintered body according to this embodiment, the total number of atoms of In, Ga, Al, and the X element accounts for 50 at% or more of the total number of atoms of the constituent metal elements.

[0028] 99 at% or more of the metal elements contained in the oxide sintered body according to the first aspect may be In, Ga, Al, and X elements, or 99.9 at% or more of the metal elements contained in the oxide sintered body may be In, Ga, Al, and X elements. In the oxide sintered body according to the first aspect, the metal elements contained in the oxide sintered body may consist essentially of only In, Ga, Al, and X elements. Here, "substantially" means that the oxide sintered body according to the first aspect may contain metal elements as long as the effects of the present invention resulting from the oxide related to the combination of In, Ga, Al, and X elements are produced.

[0029] The oxide sintered body according to the first aspect may consist essentially of only In, Ga, Al, the X element, and O (oxygen). Here, "substantially" means that the oxide sintered body according to the first aspect may contain other components as long as the effects of the present invention resulting from the combination of In, Ga, Al, the X element, and O are produced. The oxide sintered body according to the first aspect may contain elements that are impurities. 99 at% or more of the elements contained in the oxide sintered body may be In, Ga, Al, the X element, and O, or 99.9 at% or more of the elements contained in the oxide sintered body may be In, Ga, Al, the X element, and O.

[0030] In this embodiment, examples of impurities include one or more elements selected from the group consisting of alkali metal elements (e.g., elements such as Li (lithium), Na (sodium), K (potassium), and Rb (rubidium)), alkaline earth metal elements (e.g., elements such as Mg (magnesium), Ca (calcium), Sr (strontium), and Ba (barium)), H (hydrogen), B (boron), C (carbon), N (nitrogen), F (fluorine), Fe (iron), Zn (zinc), Sn (tin), and Cl (chlorine). These impurities may be, for example, elements that are mixed in at least one of the raw materials and the manufacturing process. In other words, impurities may be unavoidable impurities that are inevitably contained. The same applies to the following description.

[0031] In this embodiment, the content of impurities is not particularly limited, but may be, in atomic ratio with respect to all metal elements, preferably 0 to 1 at%, more preferably 0 to 0.1 at%, even more preferably 0 to 0.01 at%, and still more preferably 0 to 0.001 at%. The concentration of the above-mentioned impurities in the oxide sintered body can be analyzed by ICP (Inductive Coupled Plasma) measurement.

[0032] In the oxide sintered body according to this embodiment, the content of In, in atomic ratio with respect to all metal elements, is preferably 50 at% or more, more preferably 70 at% or more, even more preferably 78 at% or more, and still more preferably 82 at% or more. Note that, if 50 at% or more of the total number of atoms of metal elements constituting the oxide sintered body are In, a crystalline oxide film exhibiting sufficiently high saturated mobility can be formed from the oxide sintered body according to this embodiment.

[0033] In the first embodiment, Ga is a positive trivalent metal element, and the inclusion of this element reduces the amount of In in the oxide. ２ O ３ The oxygen defects can be controlled, and the resulting oxide film exhibits excellent transistor characteristics. The Ga content in the oxide sintered body is, in atomic ratio with respect to all metal elements, preferably 5 to 25 at %, more preferably 7 to 20 at %, and even more preferably 10 to 18 at %. When the Ga content is 5 at % or more, good transistor characteristics are exhibited. Furthermore, when the Ga content is 25 at % or less, the crystallization temperature is lowered, making it easier to obtain a crystallized oxide film.

[0034] In this embodiment, Al is a positive trivalent metal element, and the inclusion of this element reduces the amount of In in the oxide. ２ O ３The oxygen defects can be controlled, and the resulting oxide film exhibits excellent transistor characteristics. The Al content in the oxide sintered body is, in atomic ratio with respect to all metal elements, preferably 0.1 to 7 at %, more preferably 1 to 6 at %, and even more preferably 2 to 5 at %. When the Al content is 0.1 at % or more, good transistor characteristics are exhibited. Furthermore, when the Al content is 7 at % or less, the crystallization temperature is lowered, making it easier to obtain a crystallized oxide film.

[0035] The X element contained in the oxide sintered body according to the first aspect is one or more elements selected from the group consisting of Si, Ge, Zr, and Ce. The X element is an element exhibiting a positive tetravalent atomic valence. The bulk resistance of the oxide sintered body tends to decrease when the X element is contained. Furthermore, when the oxide sintered body is sintered, the occurrence of color unevenness and white spots can be suppressed. In this embodiment, the X element may be Si, Ge, Zr, Ce, or two or more of these elements.

[0036] In the oxide sintered body according to the first aspect, the atomic ratios of In, Ga, Al, and the X element satisfy the conditions shown in the following formulas (1) to (3): 0.05≦Ga / (In+Ga)≦0.20 (1) 0.005≦Al / (In+Ga+Al+X)≦0.05 (2) 0.0003≦X / (In+Ga+Al+X)≦0.02 (3) (where In, Ga, Al, and X are the numbers of atoms of In, Ga, Al, and the X element in the oxide sintered body, respectively.)

[0037] When the atomic ratio shown in the formula (1) is 0.05 or more, a crystalline phase having a diffraction peak in the range of incident angles (2θ) observed by X-ray (Cu-Kα ray) diffraction measurement defined in (A) to (K) described later is easily generated, and the effect of reducing color unevenness and the effect of reducing white spots in the oxide sintered body are improved. On the other hand, when the atomic ratio shown in the formula (1) is 0.20 or less, a crystalline oxide film is easily obtained when an oxide film formed using a sputtering target including the oxide sintered body according to the first aspect is annealed, and a TFT element with high mobility is obtained. From this viewpoint, the atomic ratio represented by the formula (1) is preferably 0.050 or more and 0.200 or less, more preferably 0.05 or more and 0.18 or less, or 0.050 or more and 0.180 or less, even more preferably 0.06 or more and 0.16 or less, or 0.060 or more and 0.160 or less, and still more preferably 0.08 or more and 0.15 or less, or 0.080 or more and 0.150 or less.

[0038] When the atomic ratio represented by the formula (2) is 0.005 or more, the effect of reducing color unevenness and white spots in the oxide sintered body is improved, and stable sputtering is possible. Furthermore, in-plane variations in a TFT element including an oxide film formed using a sputtering target including the oxide sintered body according to the first aspect are suppressed. On the other hand, when the atomic ratio represented by the formula (2) is 0.05 or less, an increase in the resistance value of the oxide sintered body is suppressed, abnormal discharge is less likely to occur, and a high-mobility TFT element is obtained. From this perspective, the atomic ratio represented by the formula (2) is preferably 0.005 or more and 0.050 or less, more preferably 0.008 or more and 0.04 or less, or 0.008 or more and 0.040 or less, even more preferably 0.01 or more and 0.035 or less, and particularly preferably 0.010 or more and 0.030 or less.

[0039] When the atomic ratio represented by the formula (3) is 0.0003 or more and 0.02 or less, the effect of reducing color unevenness of the oxide sintered body and the effect of reducing white spots are improved, and stable sputtering is possible. From this viewpoint, the atomic ratio represented by the formula (3) is preferably 0.0003 or more and 0.0200 or less, more preferably 0.0005 or more and 0.015 or less, or 0.0005 or more and 0.0150 or less, and even more preferably 0.0008 or more and 0.010 or less, or 0.0008 or more and 0.0100 or less. The atomic ratios of the X elements may each independently be within the range of (3).

[0040] The content and atomic ratio of each metal element in the oxide sintered body according to this embodiment can be measured by an inductively coupled plasma atomic emission spectrometer (ICP-AES).

[0041] The oxide sintered body according to this embodiment contains a bixbyite crystalline phase. ２ O ３ The bixbyite crystal phase is a bixbyite crystal structure of In ２ O ３ The bixbyite crystalline phase can be confirmed by measuring the X-ray diffraction (XRD) of the oxide sintered body.

[0042] In the oxide sintered body according to the first aspect, ２ O ３ The bixbyite crystal phase may contain at least one element selected from the group consisting of Ga, Al, and X. Examples of the form in which the bixbyite crystal phase contains at least one element selected from the group consisting of Ga, Al, and X include solid solution forms such as substitutional solid solution and interstitial solid solution. ２ O ３ The phase preferably contains a solid solution of at least one of Ga, Al, and the X element.

[0043] The oxide sintered body according to the first aspect contains a crystalline phase (hereinafter also referred to as "crystalline phase A") in which diffraction peaks are observed in the ranges of incident angles (2θ) of the following (A) to (C) by X-ray (Cu-Kα ray) diffraction measurement: 36° to 39° (A), 53° to 56° (B), and 62° to 66° (C).

[0044] In the oxide sintered body according to the first aspect, it is preferable that a diffraction peak is observed in at least one range of incident angle (2θ) selected from the following (D) to (K) by X-ray (Cu-Kα ray) diffraction measurement. In the crystalline phase A, it is preferable that two or more are observed in the range of incident angle (2θ) of the following (D) to (K), more preferably three or more are observed, even more preferably four or more are observed, even more preferably five or more are observed, even more preferably six or more are observed, even more preferably seven or more are observed, and even more preferably eight or more are observed. In the oxide sintered body according to the first aspect, it is preferable that a diffraction peak is not observed in the range of incident angle (2θ) of (G') described below, and a diffraction peak is observed in the range of incident angle (2θ) of the following (J). 31° to 34°...(D) 30° to 32°...(E) 51° to 53°...(F) 9° to 11°...(G) 19° to 21°...(H) 42° to 45°...(I) 8° to 10°...(J) 17° to 19°...(K)

[0045] The oxide sintered body according to the first aspect may contain, instead of the crystalline phase A, a crystalline phase B in which a diffraction peak is observed in at least one incident angle (2θ) range selected from the following (D) to (F), (G'), (H), (I), and (K) by X-ray (Cu-Kα ray) diffraction measurement. The crystalline phase B is preferably observed in two or more of the incident angle (2θ) ranges of the following (D) to (F), (G'), (H), (I), and (K), more preferably three or more, even more preferably four or more, even more preferably five or more, even more preferably six or more, and even more preferably seven or more. The crystalline phase B in the oxide sintered body according to the first aspect is preferably not observed in the incident angle (2θ) range of the above (J), and is observed in the incident angle (2θ) range of the following (G'). 31° to 34°...(D) 30° to 32°...(E) 51° to 53°...(F) 14° to 16°...(G') 19° to 21°...(H) 42° to 45°...(I) 17° to 19°...(K)

[0046] In particular, it is preferable that the crystalline phase in the oxide sintered body according to the first aspect has diffraction peaks observed in the ranges of the incident angle (2θ) of (D), (E), (F), (H), (I), and (K) described above. In this case, a diffraction peak may or may not be observed in the range of the incident angle (2θ) of (G). Also, a diffraction peak may or may not be observed in the range of the incident angle (2θ) of (J).

[0047] In the crystalline phase A in the oxide sintered body according to this embodiment, it is preferable that no diffraction peak is observed in the range of the incident angle (2θ) of (G)′ as follows by X-ray (Cu—Kα ray) diffraction measurement: 14° to 16° (G′):

[0048] The criteria for determining whether a diffraction peak is present by X-ray (Cu-Kα ray) diffraction (XRD: X-ray Diffraction) measurement of the crystalline phase in the oxide sintered body according to this embodiment are as follows.

[0049] <Conditions for X-ray diffraction (XRD) measurement> X-ray: Cu-Kα ray (wavelength 1.5418 × 10 －１０ m) Scanning Mode: 2θ / θ Scanning Type: Continuous scan X-ray intensity: 45 kV / 200 mA Entrance slit: 1.000 mm Receiving slit 1: 1.000 mm Receiving slit 2: 1.000 mm IS length: 10.0 mm Sampling interval: 0.02° Speed ​​counting time: 2.0° / min The XRD pattern obtained under the above measurement conditions using SmartLab (manufactured by Rigaku Corporation) was subjected to peak detection using JADE6's "Peak Search and Labeling" with a threshold σ of 2.1, a cutoff peak intensity of 0.19%, a background determination range of 0.5, and the number of background averaging points set to 7. The peak position was defined using the centroid method.

[0050] In the sintered body according to the first aspect, the crystalline phase A having a diffraction peak within the range of the incident angle (2θ) defined in (A) to (K) each independently has a diffraction peak within the range of the incident angle (2θ) defined in (A) to (K). For example, when the peak within the range defined in (D) has a diffraction peak at 31°, the diffraction peak within the range defined in (E) has a diffraction peak at an incident angle (2θ) lower than 31°, and when the peak within the range defined in (J) has a diffraction peak at 53°, the diffraction peak within the range defined in (F) has a diffraction peak at an incident angle (2θ) lower than 53°.

[0051] The crystalline phase having a diffraction peak within the range of the incident angle (2θ) defined in (A) to (K) is a crystalline structure compound disclosed in WO 2020 / 027243. For example, FIG. 12 shows an X-ray diffraction pattern of the oxide sintered body according to this embodiment. As shown in FIG. 12, the oxide sintered body used in the target according to this embodiment contains a crystalline phase having a diffraction peak within the range of the incident angle (2θ) defined in (A) to (K). The X-ray diffraction pattern shown in FIG. 12 further contains In having a bixbyite crystal structure. ２ O ３ It contains diffraction peaks originating from the phase.

[0052] The oxide sintered body according to this embodiment preferably contains a bixbyite crystalline phase as a main component (main phase) and crystalline phase A as a subcomponent (subphase). That is, the oxide sintered body according to this embodiment preferably contains more bixbyite crystalline phase than crystalline phase A.

[0053] The bulk resistance value of the oxide sintered body according to this embodiment is preferably 10 mΩ cm or less. If the bulk resistance value of the oxide sintered body is 10 mΩ cm or less, the sintered body has sufficiently low resistance, and the oxide sintered body according to this embodiment can be more suitably used as a sputtering target. If the bulk resistance value of the oxide sintered body is low, the resistance of the obtained target will be low, and stable plasma will be generated. Furthermore, if the bulk resistance value of the oxide sintered body is low, arc discharge, also known as fireball discharge, will be less likely to occur, and melting of the target surface and cracking of the target can be suppressed. The bulk resistance value can be measured by the method described in the examples.

[0054] [Oxide sintered body] An oxide sintered body according to a second aspect of the present embodiment comprises, as main components, In, Ga, Al, and one or more Z elements selected from the group consisting of Si, Ge, Zr, Ce, Tb, Nd, Mn, Ru, Pd, and Pt, wherein the atomic ratios of In, Ga, Al, and the Z element satisfy the conditions shown in the following formulas (1), (4), and (5), and comprises a bixbyite crystalline phase, and a crystalline phase in which, by X-ray (Cu-Kα ray) diffraction measurement, a diffraction peak is observed in the incident angle (2θ) ranges of the following (A) to (C), and no diffraction peak is observed in at least one of the incident angle (2θ) ranges of the following (G') and (J). 0.05≦Ga / (In+Ga)≦0.20 (1) 0.005≦Al / (In+Ga+Al+Z)≦0.05 (4) 0.0003≦Z / (In+Ga+Al+Z)≦0.07 (5) (In, Ga, Al, and Z are the numbers of atoms of In, Ga, Al, and the Z element in the oxide sintered body, respectively.) 36° to 39° (A) 53° to 56° (B) 62° to 66° (C) 14° to 16° (G') 8° to 10° (J)

[0055] According to the oxide sintered body of the second aspect, the occurrence of color unevenness is reduced and the occurrence of white spots is also reduced. As the occurrence of color unevenness and the occurrence of white spots are reduced, a thin film transistor having an oxide film formed from the oxide sintered body exhibits an appropriate linear mobility value and a threshold voltage (Vth) close to zero. The oxide sintered body of the second aspect will be described below, but a description of parts that may be the same as the oxide sintered body of the first aspect will be omitted.

[0056] The oxide sintered body according to the second aspect contains In, Ga, Al, and Z element as main components as metal elements. In this specification, "main component" means a component that accounts for 50 at% or more of the total number of atoms of the constituent metal elements. In the oxide sintered body according to the second aspect, the total number of atoms of In, Ga, Al, and Z element is 50 at% or more of the total number of atoms of the constituent metal elements.

[0057] 99 at% or more of the metal elements contained in the oxide sintered body according to the second aspect may be In, Ga, Al, and Z elements, or 99.9 at% or more of the metal elements contained in the oxide sintered body may be In, Ga, Al, and Z elements. In the oxide sintered body according to the second aspect, the metal elements contained in the oxide sintered body may consist essentially of only In, Ga, Al, and Z elements. Here, "substantially" means that the oxide sintered body according to the second aspect may contain metal elements as long as the effects of the present invention resulting from the oxides related to the combination of In, Ga, Al, and Z elements are produced.

[0058] The oxide sintered body according to the second aspect may consist essentially of only In, Ga, Al, Z element, and O (oxygen). Here, "substantially" means that the oxide sintered body according to the second aspect may contain other components as long as the effects of the present invention resulting from the combination of In, Ga, Al, Z element, and O are produced. The oxide sintered body according to the second aspect may contain elements that are impurities. 99 at% or more of the elements contained in the oxide sintered body may be In, Ga, Al, Z element, and O, or 99.9 at% or more of the elements contained in the oxide sintered body may be In, Ga, Al, Z element, and O.

[0059] In the second embodiment, Ga is a positive trivalent metal element, and the inclusion of this element makes it possible to obtain a ２ O ３ The oxygen defects can be controlled, and the resulting oxide film exhibits excellent transistor characteristics. In the second aspect, the Ga content in the oxide sintered body is, in atomic ratio with respect to all metal elements, preferably 5 to 25 at %, more preferably 6 to 20 at %, and even more preferably 7 to 18 at %. When the Ga content is 5 at % or more, good transistor characteristics are exhibited. Furthermore, when the Ga content is 25 at % or less, the crystallization temperature is lowered, making it easier to obtain a crystallized oxide film.

[0060] The Z element contained in the oxide sintered body according to the second aspect is one or more elements selected from the group consisting of Si, Ge, Zr, Ce, Tb, Nd, Mn, Ru, Pd, and Pt. The bulk resistance of the oxide sintered body tends to decrease when the Z element is contained. Furthermore, when the oxide sintered body is sintered, the occurrence of color unevenness and white spots can be suppressed. In this embodiment, the Z element may be Si, Ge, Zr, Ce, Tb, Nd, Mn, Ru, Pd, Pt, or two or more of these elements. Among these, the Z element is preferably one or more elements selected from the group consisting of Tb and Nb.

[0061] The content of Si in the oxide sintered body is, in atomic ratio with respect to all metal elements, preferably 0.10 to 7.00 at%, more preferably 0.30 to 3.00 at%, still more preferably 0.50 to 2.00 at%, and still more preferably 0.70 to 1.50 at%.

[0062] The content of Ge in the oxide sintered body is, in atomic ratio with respect to all metal elements, preferably 0.10 to 7.00 at%, more preferably 0.30 to 3.00 at%, still more preferably 0.50 to 2.00 at%, and still more preferably 0.70 to 1.50 at%.

[0063] The content of Zr in the oxide sintered body is, in atomic ratio with respect to all metal elements, preferably 0.01 to 7.00 at%, more preferably 0.02 to 3.00 at%, still more preferably 0.03 to 0.50 at%, and still more preferably 0.04 to 0.10 at%.

[0064] The content of Ce in the oxide sintered body is, in atomic ratio with respect to all metal elements, preferably 0.01 to 7.00 at%, more preferably 0.10 to 5.00 at%, still more preferably 0.50 to 3.00 at%, and still more preferably 1.00 to 2.00 at%.

[0065] The content of Nd in the oxide sintered body is, in atomic ratio with respect to all metal elements, preferably 0.10 to 7.00 at%, more preferably 0.50 to 6.00 at%, still more preferably 1.00 to 5.00 at%, and still more preferably 2.00 to 4.00 at%.

[0066] The content of Tb in the oxide sintered body is, in atomic ratio with respect to all metal elements, preferably 0.10 to 7.00 at%, more preferably 0.50 to 6.00 at%, still more preferably 1.00 to 5.00 at%, and still more preferably 2.00 to 4.00 at%.

[0067] The content of Mn in the oxide sintered body is, in atomic ratio with respect to all metal elements, preferably 0.001 to 7.00 at%, more preferably 0.005 to 1.00 at%, still more preferably 0.010 to 0.50 at%, and still more preferably 0.02 to 0.10 at%.

[0068] The content of Ru in the oxide sintered body is, in atomic ratio with respect to all metal elements, preferably 0.01 to 7.00 at%, more preferably 0.03 to 1.00 at%, still more preferably 0.05 to 0.50 at%, and still more preferably 0.07 to 0.20 at%.

[0069] The content of Pd in ​​the oxide sintered body is preferably 0.10 to 7.00 at %, more preferably 1.00 to 6.00 at %, and even more preferably 3.00 to 5.00 at %, in atomic ratio with respect to all metal elements.

[0070] The content of Pt in the oxide sintered body is, in atomic ratio with respect to all metal elements, preferably 0.10 to 7.00 at%, more preferably 1.00 to 6.50 at%, even more preferably 3.00 to 6.00 at%, and still more preferably 4.00 to 5.50 at%.

[0071] The total content of the Z element in the oxide sintered body is preferably 0.01 to 7.00 at%, more preferably 1.00 to 6.00 at%, still more preferably 2.00 to 5.00 at%, and still more preferably 2.50 to 4.50 at%, in atomic ratio with respect to all metal elements.

[0072] In the oxide sintered body according to the second aspect, the atomic ratios of In, Ga, Al, and the Z element satisfy the conditions shown in the following formulas (1), (4), and (5): 0.05≦Ga / (In+Ga)≦0.20 (1) 0.005≦Al / (In+Ga+Al+Z)≦0.05 (4) 0.0003≦Z / (In+Ga+Al+Z)≦0.07 (5) (In, Ga, Al, and Z are the numbers of atoms of In, Ga, Al, and the Z element in the oxide sintered body, respectively.)

[0073] When the atomic ratio represented by the formula (1) is 0.05 or more, the crystalline phase A or crystalline phase B described below is easily generated, and the effect of reducing color unevenness and white spots in the oxide sintered body is improved. On the other hand, when the atomic ratio represented by the formula (1) is 0.20 or less, when an oxide film formed using a sputtering target including the oxide sintered body according to the second aspect is annealed, a crystalline oxide film is easily obtained, and a high-mobility TFT element is obtained. From this viewpoint, the atomic ratio represented by the formula (1) is preferably 0.050 or more and 0.200 or less, more preferably 0.05 or more and 0.18 or less, or 0.050 or more and 0.180 or less, even more preferably 0.06 or more and 0.16 or less, or 0.060 or more and 0.160 or less, and even more preferably 0.08 or more and 0.15 or less, or 0.080 or more and 0.150 or less.

[0074] When the atomic ratio represented by the formula (4) is 0.005 or more, the effect of reducing color unevenness of the oxide sintered body and the effect of reducing white spots are improved, allowing stable sputtering. Furthermore, the in-plane variation of a TFT element including an oxide film formed using a sputtering target including the oxide sintered body according to the second aspect is suppressed. On the other hand, when the atomic ratio represented by the formula (4) is 0.05 or less, an increase in the resistance value of the oxide sintered body is suppressed, abnormal discharge is less likely to occur, and a high-mobility TFT element is obtained. From this perspective, the atomic ratio represented by the formula (4) is preferably 0.005 or more and 0.050 or less, more preferably 0.008 or more and 0.04 or less, or 0.008 or more and 0.040 or less, even more preferably 0.01 or more and 0.035 or less, and particularly preferably 0.010 or more and 0.030 or less.

[0075] When the atomic ratio shown in the formula (5) is 0.0003 or more and 0.07 or less, the effect of reducing color unevenness and the effect of reducing white spots in the oxide sintered body are improved, and stable sputtering is possible. From this viewpoint, the atomic ratio shown in the formula (5) is preferably 0.0003 or more and 0.0700 or less, more preferably 0.0005 or more and 0.05 or less, or 0.0005 or more and 0.0500 or less, and even more preferably 0.0008 or more and 0.01 or less, or 0.0008 or more and 0.0100 or less.

[0076] In the oxide sintered body according to the second aspect, ２ O ３ The bixbyite crystal phase may contain at least one element selected from the group consisting of Ga, Al, and Z. Examples of the form in which the bixbyite crystal phase contains at least one element selected from the group consisting of Ga, Al, and Z include solid solution forms such as substitutional solid solution and interstitial solid solution. In the sintered body according to this embodiment, the bixbyite crystal phase contains In having a bixbyite crystal structure. ２ O ３ The phase preferably contains a solid solution of at least one of Ga, Al, and Z elements.

[0077] The oxide sintered body according to the second aspect contains a crystalline phase in which diffraction peaks are observed in the ranges of the incident angle (2θ) of the following (A) to (C) by X-ray (Cu-Kα ray) diffraction measurement: 36° to 39° (A), 53° to 56° (B), and 62° to 66° (C).

[0078] In the crystalline phase of the oxide sintered body according to the second aspect, no diffraction peak is observed in at least one of the following incident angle (2θ) ranges (G') and (J) by X-ray (Cu-Kα ray) diffraction measurement. It is preferable that the crystalline phase of the oxide sintered body according to the second aspect is observed in one of the following incident angle (2θ) ranges (G') and (J), and no diffraction peak is observed in the other incident angle (2θ) range: 14° to 16° (G') 8° to 10° (J)

[0079] In the crystalline phase in the oxide sintered body according to the second aspect, a diffraction peak is preferably observed in at least one range of incident angle (2θ) selected from the following (D) to (K) by X-ray (Cu-Kα ray) diffraction measurement: 31° to 34° (D) 30° to 32° (E) 51° to 53° (F) 9° to 11° (G) 19° to 21° (H) 42° to 45° (I) 8° to 10° (J) 17° to 19° (K)

[0080] The crystalline phase in the oxide sintered body according to the second aspect may be a crystalline phase (hereinafter also referred to as "crystalline phase A") in which no diffraction peak is observed in the range of incident angles (2θ) of (G') above. In the oxide sintered body according to the second aspect, it is preferable that 2 or more are observed in the range of incident angles (2θ) of (D) to (K) above, more preferably 3 or more are observed, even more preferably 4 or more are observed, even more preferably 5 or more are observed, even more preferably 6 or more are observed, even more preferably 7 or more are observed, and even more preferably 8 or more are observed. In the oxide sintered body according to the second aspect, it is preferable that no diffraction peak is observed in the range of incident angles (2θ) of (G') above, and a diffraction peak is observed in the range of incident angles (2θ) of (J) above. When the oxide sintered body according to the second aspect contains such crystalline phase A, the Z element is selected from the group consisting of Si, Ge, Zr, Ce, Tb, Nd, Mn, Ru, Pd and Pt, preferably selected from the group consisting of Si, Ge, Zr, Ce, Nd, Mn, Ru, Pd and Pt, more preferably selected from the group consisting of Si, Ge, Zr, Ce and Nd. The crystalline phase A in the oxide sintered body according to the second aspect may have the same structure as the crystalline phase A in the oxide sintered body according to the first aspect, and a diffraction peak may be observed in the same range.

[0081] The crystalline phase in the oxide sintered body according to the second aspect may be a crystalline phase (hereinafter also referred to as "crystalline phase B") in which no diffraction peak is observed in the range of incident angle (2θ) of (J) above. The crystalline phase B in the oxide sintered body according to the second aspect is preferably observed in at least one incident angle (2θ) range selected from the following (D) to the following (F), (G'), (H), (I), and (K) by X-ray (Cu-Kα ray) diffraction measurement. The crystalline phase B in the oxide sintered body according to the second aspect is preferably observed in two or more of the incident angle (2θ) ranges of the following (D) to the following (F), (G'), (H), (I), and (K), more preferably observed in three or more, even more preferably observed in four or more, even more preferably observed in five or more, even more preferably observed in six or more, and even more preferably observed in seven or more. It is preferable that the crystalline phase B in the oxide sintered body according to the second aspect does not show a diffraction peak in the range of incident angle (2θ) of (J) above, but shows a diffraction peak in the range of incident angle (2θ) of (G') below. When the oxide sintered body according to the second aspect contains such crystalline phase B, the Z element is selected from the group consisting of Si, Ge, Zr, Ce, Tb, Nd, Mn, Ru, Pd and Pt, and is preferably Tb. The crystalline phase B in the oxide sintered body according to the second aspect may have a structure similar to that of the crystalline phase B in the oxide sintered body according to the first aspect, and diffraction peaks may be observed in the same ranges. 31° to 34° (D) 30° to 32° (E) 51° to 53° (F) 14° to 16° (G') 19° to 21° (H) 42° to 45° (I) 17° to 19° (K)

[0082] In particular, it is preferable that the crystalline phase in the oxide sintered body according to the second aspect has diffraction peaks observed in the ranges of the incident angle (2θ) of (D), (E), (F), (H), (I), and (K) described above. In this case, a diffraction peak may or may not be observed in the range of the incident angle (2θ) of (G'). Also, a diffraction peak may or may not be observed in the range of the incident angle (2θ) of (J).

[0083] [Method for manufacturing sintered body] The oxide sintered body according to this embodiment can be manufactured by mixing raw material powders, molding, and sintering. In the first aspect, raw materials include indium compounds, gallium compounds, aluminum compounds, and compounds of X element, and oxides of these compounds are preferred. That is, indium oxide (In ２ O ３ ), gallium oxide (Ga ２ O ３ ), aluminum oxide (Al ２ O ３ ), and oxides of the X element are preferably used.

[0084] In the second embodiment, the raw materials include indium compounds, gallium compounds, aluminum compounds, and compounds of the Z element, and oxides of these compounds are preferred. ２ O ３ ), gallium oxide (Ga ２ O ３ ), aluminum oxide (Al ２ O ３ ), and oxides of Z elements are preferably used.

[0085] The indium oxide powder is not particularly limited, and commercially available indium oxide powder can be used. The indium oxide powder is preferably high-purity, for example, 4N (99.99%) or higher. Indium compounds may be indium salts such as chlorides, nitrates, or acetates, in addition to oxides.

[0086] The gallium oxide powder is not particularly limited, and commercially available gallium oxide powder can be used. The gallium oxide powder is preferably high purity, for example, 4N (99.99%) or higher. In addition, as the gallium compound, not only oxides but also gallium salts such as chlorides, nitrates, or acetates can be used.

[0087] The aluminum oxide powder is not particularly limited, and commercially available aluminum oxide powders can be used. The aluminum oxide powder preferably has a high purity, for example, 4N (99.99%) or higher. Furthermore, the aluminum compound may be not only an oxide but also an aluminum salt such as a chloride, a nitrate, or an acetate.

[0088] In the first embodiment, the raw material powder of the compound of the X element is not particularly limited, and at least one raw material powder selected from the group consisting of silicon oxide, germanium oxide, zirconium oxide, and cerium oxide, which are commercially available industrially, can be used. The raw material powder of the compound of the X element is preferably highly pure, for example, 4N (99.99%) or higher. Furthermore, as the compound of the X element, not only oxides but also chlorides, nitrates, acetates, etc. may be used.

[0089] In the second aspect, the raw material powder of the Z element compound is not particularly limited, and at least one raw material powder selected from the group consisting of silicon oxide, germanium oxide, zirconium oxide, and cerium oxide, which are commercially available industrially, can be used. The raw material powder of the Z element compound is preferably high in purity, for example, 4N (99.99%) or higher. Furthermore, as the compound of the Z element, not only oxides but also chlorides, nitrates, acetates, etc. may be used.

[0090] The raw material powders used may be mixed by wet mixing or dry mixing, and a mixing method in which wet mixing is performed after dry mixing is preferred.

[0091] The mixing step is not particularly limited, and can be carried out by mixing and grinding the raw material powders once or twice or more times. As the mixing and grinding means, known devices such as a ball mill, a bead mill, a jet mill, or an ultrasonic device can be used. As the mixing and grinding means, wet mixing using a bead mill is preferred.

[0092] The raw materials prepared in the above mixing step are molded by a known method to obtain a molded body, and this molded body is sintered to obtain an oxide sintered body. In the molding step, the mixed powder obtained in the mixing step is molded, for example, by pressure molding to obtain a molded body. This process molds the powder into the shape of the product (for example, a shape suitable for a sputtering target). Examples of molding processes include mold molding, slip casting, and injection molding. In order to obtain a sintered body with a high sintered density, it is preferable to use cold isostatic pressing (CIP) or the like for the molding process. A molding aid may be used during the molding process. Examples of molding aids include polyvinyl alcohol, methyl cellulose, polywax, and oleic acid.

[0093] In the sintering step, the compact obtained in the molding step is fired. Sintering conditions are atmospheric pressure, an oxygen gas atmosphere, or pressurized oxygen gas, typically at 1200°C to 1550°C for 30 minutes to 360 hours, preferably 8 hours to 180 hours, and more preferably 12 hours to 96 hours. If the sintering temperature is less than 1200°C, it may be difficult to increase the target density or the sintering time may be too long. On the other hand, if the sintering temperature exceeds 1550°C, the vaporization of components may cause compositional deviation or damage to the furnace. A sintering time of 30 minutes or more makes it easier to increase the target density. Sintering times longer than 360 hours are not practically feasible due to the excessive manufacturing time and high costs. A sintering time within the above range makes it easier to improve the relative density and reduce the bulk resistance.

[0094] The oxide sintered body according to the first aspect has an atomic ratio of In, Ga, Al, and the X element that satisfies the conditions shown in the formulas (1) to (3) and contains a bixbyite crystalline phase and crystalline phase A, and therefore stable sputtering can be achieved by using a sputtering target containing the oxide sintered body. Furthermore, a TFT having an oxide film obtained by sputtering a sputtering target containing the oxide sintered body can be realized, which has high mobility and excellent in-plane uniformity.

[0095] The oxide sintered body according to the second aspect has an atomic ratio of In, Ga, Al, and the Z element that satisfies the conditions shown in the formulas (1), (4), and (5), and contains a bixbyite crystalline phase and crystalline phase A or crystalline phase B. Therefore, stable sputtering can be achieved by using a sputtering target containing the oxide sintered body. Furthermore, a TFT having an oxide film obtained by sputtering a sputtering target containing the oxide sintered body can be realized, which has high mobility and excellent in-plane uniformity.

[0096] [Sputtering Target] The sputtering target according to this embodiment includes the oxide sintered body according to this embodiment. That is, the sputtering target according to this embodiment can be obtained by using the oxide sintered body according to this embodiment.

[0097] For example, the sputtering target according to this embodiment can be obtained by cutting and polishing an oxide sintered body and bonding it to a backing plate. The bonding rate between the sintered body and the backing plate is preferably 95% or more. The bonding rate can be confirmed by X-ray CT.

[0098] In one aspect, the sputtering target according to this embodiment includes the oxide sintered body according to this embodiment and a backing plate. In one aspect, the sputtering target according to this embodiment may be a target consisting only of the oxide sintered body. The sputtering target according to this embodiment preferably includes the oxide sintered body according to this embodiment and a cooling and holding member such as a backing plate that is provided on the sintered body as needed. The oxide sintered body (target material) constituting the sputtering target according to this embodiment is obtained by grinding the oxide sintered body according to this embodiment. Therefore, the target material is the same as the oxide sintered body according to this embodiment in terms of substance. Therefore, the description of the oxide sintered body according to this embodiment also applies to the target material.

[0099] 1A to 1D show perspective views showing the shape of a sputtering target. The sputtering target may be plate-shaped as shown by reference numeral 1 in FIG. 1A. The sputtering target may be cylindrical as shown by reference numeral 1A in FIG. 1B. When the sputtering target is plate-shaped, the planar shape may be rectangular as shown by reference numeral 1 in FIG. 1A, or circular as shown by reference numeral 1B in FIG. 1C. The oxide sintered body may be integrally molded, or may be a multi-piece type in which multiple divided oxide sintered bodies (reference numeral 1C) are each fixed to a backing plate 3 as shown in FIG. 1D. The backing plate 3 is a member for holding and cooling the oxide sintered body. It is preferable that the material be a material with excellent thermal conductivity, such as copper. The shape of the oxide sintered body constituting the sputtering target is not limited to the shapes shown in FIGS. 1A to 1D.

[0100] The sputtering target is manufactured, for example, by the following steps: A step of grinding the surface of the oxide sintered body (grinding step) A step of bonding the oxide sintered body to a backing plate (bonding step) Each step will be specifically described below.

[0101] <Grinding step> In the grinding step, the oxide sintered body is cut into a shape suitable for installation in a sputtering device. The surface of the oxide sintered body often has sintered portions in a highly oxidized state or is uneven. In addition, it is necessary to cut the oxide sintered body to a predetermined size. The surface of the oxide sintered body is preferably ground to a depth of 0.3 mm or more. The grinding depth is preferably 0.5 mm or more, and more preferably 2 mm or more. By grinding to a depth of 0.3 mm or more, it is possible to remove portions of the oxide sintered body with a fluctuating crystal structure near the surface.

[0102] The oxide sintered body is preferably made into a material with an average surface roughness Ra of 5 μm or less by, for example, grinding the surface of the oxide sintered body with a surface grinder. Furthermore, the sputtering surface of the sputtering target may be mirror-finished to have an average surface roughness Ra of 1000 × 10-10 m or less. Known polishing techniques, such as mechanical polishing, chemical polishing, and mechanochemical polishing (a combination of mechanical and chemical polishing), can be used for mirror-finishing (polishing). For example, polishing to #2000 or higher with a fixed abrasive polisher (using water as the polishing liquid) may be performed, or lapping may be performed with a free abrasive lap (using SiC paste or the like as the abrasive), followed by lapping using a diamond paste as the abrasive. The polishing method is not limited to these methods. Examples of abrasives include #200, #400, and #800 abrasives.

[0103] After the grinding process, the oxide sintered body is preferably cleaned by air blowing, running water washing, or the like. When removing foreign matter by air blowing, removal can be more effective if a dust collector is used to suck air from the opposite side of the nozzle. Note that, since air blowing and running water washing have limitations in their cleaning power, ultrasonic cleaning or the like can also be performed. An effective ultrasonic cleaning method is to use multiple oscillations at a frequency between 25 kHz and 300 kHz. For example, it is recommended to perform ultrasonic cleaning by multiple oscillations at 12 different frequencies in 25 kHz increments between 25 kHz and 300 kHz.

[0104] <Bonding step> In the bonding step, the ground oxide sintered body is bonded to a backing plate using a low-melting-point metal. Metallic indium is preferably used as the low-melting-point metal. Metallic indium containing at least one of metal gallium and metal tin can also be preferably used as the low-melting-point metal.

[0105] According to the sputtering target of the first aspect, the atomic ratios of In, Ga, Al, and the X element satisfy the conditions shown in the formulas (1) to (3), and an oxide sintered body containing a bixbyite crystalline phase and crystalline phase A is used, so that stable sputtering can be achieved by using the sputtering target. Furthermore, a TFT having an oxide film obtained by sputtering a sputtering target containing the oxide sintered body can be achieved, which has high mobility and excellent in-plane uniformity.

[0106] According to the sputtering target of the second aspect, the atomic ratios of In, Ga, Al, and the Z element satisfy the conditions shown in the formulas (1), (4), and (5), and an oxide sintered body containing a bixbyite crystalline phase and crystalline phase A or crystalline phase B is used, so that stable sputtering can be achieved by using the sputtering target. Furthermore, a TFT having an oxide film obtained by sputtering a sputtering target containing the oxide sintered body can be realized, which has high mobility and excellent in-plane uniformity.

[0107] [Oxide Film] The oxide film according to this embodiment is an oxide film formed using the sputtering target according to this embodiment. The oxide film according to this embodiment is obtained by forming the oxide film by a sputtering method using the sputtering target according to this embodiment. The oxide film according to this embodiment can be formed by a method other than the sputtering method, such as a vapor deposition method, an ion plating method, and a pulsed laser vapor deposition method. The oxide film according to this embodiment is preferably formed by a sputtering method using the sputtering target according to this embodiment. The oxide film according to this embodiment may be an amorphous oxide semiconductor film or a crystalline oxide semiconductor film. The oxide film according to this embodiment may be either amorphous or crystalline. The oxide film according to this embodiment is preferably a crystalline oxide semiconductor film.

[0108] The oxide film according to the present embodiment is formed using a target having the same atomic composition (atomic ratio) as the oxide sintered body according to the present embodiment, and therefore the atomic composition of the oxide film according to the present embodiment usually reflects the atomic composition of the oxide sintered body included in the sputtering target according to the present embodiment used for film formation. Therefore, the oxide film according to the present embodiment allows for the production of a TFT with high mobility and excellent in-plane uniformity.

[0109] Whether an oxide film is amorphous or crystalline can be confirmed by subjecting each oxide film to X-ray diffraction (XRD) measurement. When an oxide film is subjected to XRD measurement, if no clear peak is observed but a broad pattern is, the oxide film can be determined to be amorphous, and if a clear peak is observed, the oxide film can be determined to be crystalline.

[0110] In the first aspect, 99 at% or more of the metal elements contained in the oxide film sintered compact may be In, Ga, Al, and an X element, or 99.9 at% or more of the metal elements contained in the oxide film sintered compact may be In, Ga, Al, and an X element. The metal elements contained in the oxide film according to the first aspect may consist essentially of only In, Ga, Al, and an X element. Furthermore, 99 at% or more of the elements contained in the oxide film according to this embodiment may be In, Ga, Al, an X element, and O, or 99.9 at% or more of the elements contained in the oxide film sintered compact may be In, Ga, Al, an X element, and O.

[0111] In the second aspect, 99 at% or more of the metal elements contained in the oxide film sintered compact may be In, Ga, Al, and Z elements, or 99.9 at% or more of the metal elements contained in the oxide film sintered compact may be In, Ga, Al, and Z elements. The metal elements contained in the oxide film according to the second aspect may consist essentially of only In, Ga, Al, and Z elements. Furthermore, 99 at% or more of the elements contained in the oxide film according to this embodiment may be In, Ga, Al, Z elements, and O, or 99.9 at% or more of the elements contained in the oxide film sintered compact may be In, Ga, Al, Z elements, and O.

[0112] In this specification, the atomic ratio of the oxide film (crystalline oxide film and amorphous oxide film) can be determined by measuring the amount of each element present by inductively coupled plasma atomic emission spectroscopy (ICP-AES) or X-ray fluorescence spectroscopy (XRF). An inductively coupled plasma atomic emission spectroscopy analyzer can be used for the ICP measurement. A thin film X-ray fluorescence analyzer (AZX400, manufactured by Rigaku Corporation) can be used for the XRF measurement.

[0113] The atomic composition ratio of an oxide film obtained by sputtering reflects the atomic composition ratio of the oxide sintered body in the sputtering target. Therefore, it is preferable to form a film using a sputtering target containing an oxide sintered body having an atomic composition ratio similar to that of a desired oxide film. Therefore, the description of the content of each atom in the crystalline oxide film according to this embodiment can be used as the description of the content of each atom in the oxide sintered body in the sputtering target.

[0114] The content and atomic ratio of each metal element in the oxide film according to this embodiment can be measured by an inductively coupled plasma atomic emission spectrometry (ICP-AES).The oxide film in the TFT element can be analyzed by TEM-EDS (Energy Dispersive X-ray Spectroscopy) measurement using an electron microscope.

[0115] The thickness of the oxide film according to this embodiment is preferably 1 to 500 nm, more preferably 5 to 300 nm, and even more preferably 10 to 100 nm.

[0116] [Method for forming oxide film] The oxide film according to this embodiment is preferably obtained by a production method including, for example, a step of forming an oxide film by sputtering using the sputtering target according to this embodiment, and a step of subjecting the oxide film to a heat treatment (annealing treatment) as necessary.

[0117] Hereinafter, a case where an oxide film is formed on a substrate by sputtering a sputtering target obtained from the oxide sintered body according to this embodiment will be described. Referring to Fig. 2A, Fig. 2A shows a state in which an oxide film 83 is formed on a glass substrate 81.

[0118] The sputtering may be performed by a method selected from the group consisting of DC sputtering, RF sputtering, AC sputtering, and pulsed DC sputtering. Any of these methods can perform sputtering without abnormal discharge. A mixed gas of argon and an oxidizing gas can be used as the sputtering gas. The oxidizing gas may be O. ２ , CO ２ , O ３ , and H ２ The gas may be selected from the group consisting of O and the like.

[0119] The sputtering gas used is a gas that is substantially free of impurity gases. The phrase "substantially free of impurity gases" means that no impurity gases other than the sputtering gas used as the sputtering gas are actively introduced, excluding adsorbed water brought in with the gas introduction and gases that cannot be eliminated (unavoidable impurity gases) such as gases leaking from the chamber or adsorbed gases. The proportion of impurity gases in the sputtering gas is preferably 0.1% by volume or less, and more preferably 0.05% by volume or less.

[0120] The oxide film formed on the substrate by sputtering is annealed as necessary. The crystallinity of the oxide film on the substrate is improved by annealing after sputtering, resulting in a crystalline oxide film. Even when the oxide film on the substrate is annealed, the oxide film is likely to maintain an amorphous state if the annealing conditions are as follows: The annealing temperature is, for example, 500°C or less, preferably 100°C or more and 500°C or less, more preferably 150°C or more and 400°C or less, and even more preferably 250°C or more and 400°C or less. The annealing time is usually 0.01 hours or more and 5.0 hours or less, preferably 0.1 hours or more and 3.0 hours or less, and more preferably 0.5 hours or more and 2.0 hours or less.

[0121] The heating atmosphere during the annealing treatment is not particularly limited, and an air atmosphere or an oxygen-flowing atmosphere is preferred from the viewpoint of carrier controllability, and an air atmosphere is more preferred. In the annealing treatment, an apparatus selected from the group consisting of a lamp annealing apparatus, a laser annealing apparatus, a thermal plasma apparatus, a hot air heating apparatus, and a contact heating apparatus can be used in the presence or absence of oxygen.

[0122] The oxide film according to this embodiment can also be manufactured as a part of a laminate including, for example, an oxide film and a protective film. For example, referring to FIG. 2B, a SiO 2 protective film is formed on an oxide film 83. ２ The protective film 85 is formed on the substrate 10. The protective film 85 may be made of, for example, SiO ２ , SiON, Al ２ O ３ , Ta ２ O ５ , TiO ２ , MgO, ZrO ２ , CeO ２ , K. ２ O, Li ２ O, Na ２ O, Rb ２ O, Sc ２ O ３ , Y ２ O ３ , Hf ２ O ３ , CaHfO３ , PbTiO ３ ,BaTa ２ O ６ , and SrTiO ３ Among these, the protective film is preferably a film made of SiO ２ , SiON, Al ２ O ３ , Y ２ O ３ , Hf ２ O ３ , and CaHfO ３ and more preferably, SiO ２ or Al ２ O ３ The number of oxygen atoms in these oxides does not necessarily have to match the stoichiometric ratio (for example, SiO ２ But SiO ｘ (where x is a real number greater than 0). These protective films can function as protective insulating films. The protective film can be formed using plasma CVD or sputtering, and is preferably formed by sputtering in an oxygen-containing rare gas atmosphere. The thickness of the protective film can be set appropriately, and is, for example, 50 nm or more and 500 nm or less.

[0123] When a protective film is formed on an oxide film, the annealing treatment can be performed (1) after the oxide film is formed on the substrate but before the protective film is formed, (2) after the protective film is formed so as to cover the oxide film on the substrate, or (3) in either of (1) and (2).

[0124] The oxide film according to this embodiment can be applied to various integrated circuits such as logic circuits, memory circuits, and differential amplifier circuits, and can be applied to electronic devices, etc. The oxide film according to this embodiment can also be applied as a partial layer of a solar cell, and a partial layer of a display device such as a liquid crystal element, an organic electroluminescence element, an inorganic electroluminescence element, a micro organic EL display, a micro LED (Light Emitting Diode) display, and a mini LED display. Furthermore, the oxide film according to this embodiment can be applied as a partial layer of a solid-state imaging element, an X-ray sensor, a power semiconductor element, a touch panel, an LSI (Large Scale Integrated Circuits), a resistance change memory, a DRAM (Dynamic Random Access Memory), a ferroelectric memory, a BEOL (Back End of Line), and a microprocessor. The oxide film according to this embodiment can also be used as a semiconductor layer of a field-effect transistor, a static induction transistor, a quantum tunnel field-effect transistor, a Schottky barrier transistor, a Schottky diode, a PN diode, and a resistor element, or as a part of any of these layers.

[0125] [Thin Film Transistor and Electronic Device] The thin film transistor according to this embodiment may be a thin film transistor including the oxide film according to this embodiment. The thin film transistor according to this embodiment may be a thin film transistor including an amorphous oxide film, a thin film transistor including a crystalline oxide film, or a thin film transistor including both an amorphous oxide film and a crystalline oxide film. The oxide film included in the thin film transistor according to this embodiment is preferably a crystalline oxide semiconductor film.

[0126] It is preferable to use the oxide film according to this embodiment as the channel layer of a thin film transistor.

[0127] When the thin film transistor according to this embodiment has the oxide film according to this embodiment as a channel layer, other element configurations in the thin film transistor are not particularly limited, and known element configurations can be adopted.

[0128] The thin film transistor according to this embodiment can be suitably used in electronic devices. Specifically, the thin film transistor according to this embodiment can be suitably used in display devices such as liquid crystal displays and organic EL displays.

[0129] The thickness of the channel layer in the thin film transistor according to this embodiment is usually 10 nm or more and 300 nm or less, and preferably 20 nm or more and 250 nm or less.

[0130] The channel layer in the thin film transistor according to this embodiment is usually used in an N-type region, but can also be used in various semiconductor devices such as a PN junction transistor in combination with various P-type semiconductors, such as a P-type Si-based semiconductor, a P-type oxide semiconductor, and a P-type organic semiconductor.

[0131] The thin film transistor according to this embodiment can be applied to various integrated circuits such as field-effect transistors, logic circuits, memory circuits, and differential amplifier circuits. Furthermore, in addition to field-effect transistors, the thin film transistor can also be applied to static induction transistors, Schottky barrier transistors, Schottky diodes, and resistor elements. That is, the thin film transistor according to this embodiment can be applied to the applications exemplified in the "Applications of Thin Film Transistors" section described later.

[0132] The structure of the thin film transistor according to this embodiment can be selected from known structures such as bottom gate, bottom contact, and top contact, without any restrictions. The bottom gate structure is particularly advantageous because it provides higher performance than amorphous silicon or ZnO thin film transistors. The bottom gate structure is preferred because it can easily reduce the number of masks used during manufacturing and thus reduce manufacturing costs for applications such as large displays.

[0133] The shape of the thin film transistor according to this embodiment is not particularly limited, and is preferably a back channel etch type transistor, an etch stopper type transistor, a top gate type transistor, a double gate type transistor, etc. Each transistor may have a self-aligned structure.

[0134] Specific examples of thin film transistors are shown in Figures 3, 4, 5, and 6. As shown in Figure 3, a thin film transistor 100 includes a silicon wafer 20, a gate insulating film 30, an oxide film 40, a source electrode 50, a drain electrode 60, and interlayer insulating films 70 and 70A.

[0135] The silicon wafer 20 is a gate electrode. The gate insulating film 30 is an insulating film that blocks electrical conduction between the gate electrode and the oxide film 40, and is provided on the silicon wafer 20. The oxide film 40 is a channel layer and is provided on the gate insulating film 30. The oxide film according to this embodiment is used for the oxide film 40.

[0136] The source electrode 50 and the drain electrode 60 are conductive terminals for passing source current and drain current through the oxide film 40, and are provided so as to be in contact with the vicinity of both ends of the oxide film 40. The interlayer insulating film 70 is an insulating film that blocks conduction between the source electrode 50 and the drain electrode 60 and the oxide film 40 except at the contact portions between the source electrode 50 and the drain electrode 60 and the oxide film 40. The interlayer insulating film 70A is an insulating film that blocks conduction between the source electrode 50 and the drain electrode 60 and the oxide film 40 except at the contact portions between the source electrode 50 and the drain electrode 60 and the oxide film 40. The interlayer insulating film 70A is also an insulating film that blocks conduction between the source electrode 50 and the drain electrode 60. The interlayer insulating film 70A also functions as a channel layer protective layer.

[0137] 4, the structure of the thin film transistor 100A is similar to that of the thin film transistor 100, but differs in that the source electrode 50 and the drain electrode 60 are provided so as to be in contact with both the gate insulating film 30 and the oxide film 40. Another difference is that an interlayer insulating film 70B is provided integrally so as to cover the gate insulating film 30, the oxide film 40, the source electrode 50, and the drain electrode 60.

[0138] The materials for forming the drain electrode 60, source electrode 50, and gate electrode are not particularly limited, and any commonly used material can be selected. In the examples shown in FIGS. 3 and 4 , a silicon wafer is used as the substrate, and the silicon wafer also functions as the electrode, but the electrode material is not limited to silicon. For example, transparent electrodes such as indium tin oxide (ITO), indium zinc oxide (IZO), ZnO, and SnO 2 can be used, as well as metal electrodes such as Al, Ag, Cu, Cr, Ni, Mo, Au, Ti, and Ta, or metal electrodes or laminated electrodes made of alloys containing these metals. Furthermore, in FIGS. 3 , 4 , 5 , and 6 , the gate electrode may be formed on a substrate such as glass.

[0139] There are no particular limitations on the materials for forming the interlayer insulating films 70, 70A, and 70B, and any commonly used material can be selected. Compounds expressed by MOx, MNx, and MNxOy, for example, can be used as materials for forming the interlayer insulating films 70, 70A, and 70B (where M is a metal element, and x and y are real numbers greater than 0. The same applies to x and y in the compounds exemplified below). Specific examples of such materials include SiO ２ , SiO ｘ , SiN ｘ , and SiN ｘ O ｙ Furthermore, the material can be, for example, Al ２ O ３ , Ta ２ O ５ , TiO ２ , MgO, ZrO ２ , CeO ２ , K. ２ O, Li ２ O, Na ２ O, Rb ２ O, Sc ２ O ３ , Y ２ O ３ , HfO ２ , CaHfO ３ , PbTiO ３ ,BaTa ２ O ６ , SrTiO ３ , Sm ２ O３ Compounds such as AlN can also be used. The valence of the anions (oxygen anions and nitrogen anions) in these oxide compounds and nitride compounds is not particularly limited as long as it is a real number greater than 0.

[0140] When the thin film transistor according to this embodiment is a back channel etch type (bottom gate type), it is preferable to provide a protective film on the drain electrode, the source electrode, and the channel layer. By providing a protective film, the durability of the TFT is likely to be improved even when the TFT is driven for a long time. In the case of a top gate type TFT, for example, a gate insulating film is formed on the channel layer.

[0141] When the thin-film transistor according to this embodiment is a top-gate TFT, for example, it has a structure in which an interlayer insulating film is formed as a buffer layer on a substrate and a gate insulating film is formed on a channel layer. As shown in FIG. 5 , the thin-film transistor 100B includes a substrate 21, a buffer layer 22, a channel layer (oxide film) 11, a first low-resistance region 11A-1, a second low-resistance region 11A-2 (oxide film), a semiconductor region 11B (oxide film), a gate insulating film 24, a gate electrode 25, an interlayer insulating film 26, a source electrode 27, a drain electrode 28, and a protective film 29. In the thin-film transistor 100B, the first low-resistance region 11A-1 and the second low-resistance region 11A-2 are formed, for example, by dry processes such as ion implantation and plasma treatment. An electrode layer may also be provided between the substrate 21 and the buffer layer 22 as a write shield layer.

[0142] 6 shows another example of a top-gate thin-film transistor according to the present embodiment. The thin-film transistor 100C has a similar structure to the thin-film transistor 100B, except that the interlayer insulating film 26 has a two-layer structure (a first interlayer insulating film 26-1 and a second interlayer insulating film 26-2). In the thin-film transistor 100C, the first low-resistance region 11A-1 and the second low-resistance region 11A-2 are formed by, for example, ion implantation.

[0143] The protective film or insulating film can be formed by, for example, CVD, which may require high-temperature processes. Furthermore, the protective film or insulating film often contains impurity gases immediately after deposition, so it is preferable to subject it to a heat treatment (annealing treatment). Removing the impurity gases through the heat treatment results in a stable protective film or insulating film, which facilitates the formation of highly durable TFT elements.

[0144] By using the oxide film according to this embodiment, the film is less susceptible to the effects of temperature in the CVD process and subsequent heat treatment, and therefore the stability of the TFT characteristics can be improved even when a protective film or an insulating film is formed.

[0145] In the characteristics of the thin film transistor according to this embodiment, the On / Off ratio is 10 ６ That's it, 10 １２ Preferably, it is 10 ７ That's it, 10 １１ More preferably, it is 10 ８ That's it, 10 １０ It is more preferable that the On / Off ratio is 10 or less. ６ An On / Off ratio of 10 or more is preferable for driving liquid crystal and OLED displays. １２ If the On / Off ratio is 10 or less, an organic EL display with high contrast can be driven. １２ If the off-state current is 10 －１１ A or less, and when the thin film transistor is used as a transfer transistor or reset transistor in a CMOS image sensor, it is possible to extend the image retention time and improve the sensitivity. The On / Off ratio is found by determining the ratio [On current value / Off current value], where the value of Id when Vg = -10 V is the Off current value and the value of Id when Vg = 20 V is the On current value.

[0146] The mobility of the TFT according to this embodiment is 5 cm ２ / Vs or more, and ２ / Vs or more, and 15 cm ２ / Vs or more, and more preferably 20 cm２ The linear mobility is expressed by the transconductance (Gm) for each Vg calculated from a graph of transfer characteristics, and the maximum mobility within a Vg range of −10 V to 20 V can be defined as the linear mobility.

[0147] In the characteristics of the thin film transistor according to this embodiment, the threshold voltage (Vth) is preferably −3.0 V or more and 3.0 V or less, more preferably −2.0 V or more and 2.0 V or less, and even more preferably −1.0 V or more and 1.0 V or less. When the threshold voltage (Vth) is −3.0 V or more, a high-mobility thin film transistor is obtained. When the threshold voltage (Vth) is 3.0 V or less, a thin film transistor with a small off-current and a large on-off ratio is obtained. Furthermore, when the threshold voltage (Vth) is −3.0 V or more and 3.0 V or less, a Vth correction circuit can be installed in the TFT to correct Vth to 0 V. When the TFT thus obtained is installed in a panel, it is possible to drive a display without uneven brightness or burn-in. From the transfer characteristic graph, the threshold voltage (Vth) is determined by the current value Id between the source and drain = 10 －９ It can be defined as the gate voltage Vg at A.

[0148] <Quantum Tunnel Field Effect Transistor> The oxide film according to this embodiment can also be used in a quantum tunnel field effect transistor (FET), which may also be referred to as a quantum tunnel field effect transistor.

[0149] 7 is a schematic diagram (longitudinal cross-sectional view) of a quantum tunnel field effect transistor (FET) according to one embodiment. The quantum tunnel field effect transistor 501 includes a p-type semiconductor layer 503, an n-type semiconductor layer 507, a gate insulating film 509, a gate electrode 511, a source electrode 513, and a drain electrode 515.

[0150] The p-type semiconductor layer 503, the n-type semiconductor layer 507, the gate insulating film 509, and the gate electrode 511 are stacked in this order. The source electrode 513 is provided on the p-type semiconductor layer 503. The drain electrode 515 is provided on the n-type semiconductor layer 507. The p-type semiconductor layer 503 is a p-type Group IV semiconductor layer, and is a p-type silicon layer in this case. The n-type semiconductor layer 507 is an n-type oxide film according to the above embodiment. The source electrode 513 and the drain electrode 515 are conductive films.

[0151] 7, an insulating layer may be formed on the p-type semiconductor layer 503. In this case, the p-type semiconductor layer 503 and the n-type semiconductor layer 507 are connected via a contact hole, which is a region where the insulating layer is partially opened. Although not shown in FIG. 7, the quantum tunnel field effect transistor 501 may also have an interlayer insulating film covering its upper surface.

[0152] The quantum tunnel field effect transistor 501 is a quantum tunnel field effect transistor (FET) that performs current switching by controlling the current tunneling through the energy barrier formed by the p-type semiconductor layer 503 and the n-type semiconductor layer 507 using the voltage of the gate electrode 511. In this structure, the band gap of the oxide film that constitutes the n-type semiconductor layer 507 is large, making it possible to reduce the off-current.

[0153] FIG. 8 is a schematic diagram (longitudinal cross-sectional view) of a quantum tunnel field-effect transistor 501A according to another embodiment. The quantum tunnel field-effect transistor 501A has the same configuration as the quantum tunnel field-effect transistor 501, except that a silicon oxide layer 505 is formed between a p-type semiconductor layer 503 and an n-type semiconductor layer 507. The presence of the silicon oxide layer reduces the off-state current. The thickness of the silicon oxide layer 505 is preferably 10 nm or less. By making the thickness of the silicon oxide layer 505 10 nm or less, it is possible to prevent tunneling current from flowing, energy barriers from being formed, and changes in barrier height, thereby preventing a decrease or change in the tunneling current. The thickness of the silicon oxide layer 505 is preferably 8 nm or less, more preferably 5 nm or less, even more preferably 3 nm or less, and even more preferably 1 nm or less.

[0154] In the quantum tunnel field effect transistors 501 and 501A, the n-type semiconductor layer 507 is also an n-type oxide semiconductor.

[0155] The oxide film constituting the n-type semiconductor layer 507 may be amorphous. When the oxide film constituting the n-type semiconductor layer 507 is amorphous, it can be etched with an organic acid such as oxalic acid, the difference in etching rate with other layers becomes large, and etching can be performed satisfactorily without affecting metal layers such as wiring.

[0156] The oxide film constituting the n-type semiconductor layer 507 may be crystalline. When the oxide film constituting the n-type semiconductor layer 507 is crystalline, the band gap becomes larger than in the case of an amorphous material, and the off-current can be reduced. Since the work function can also be increased, it becomes easier to control the current tunneling through the energy barrier formed by the p-type Group IV semiconductor material and the n-type semiconductor layer 507.

[0157] The method for manufacturing the quantum tunnel field effect transistor 501 is not particularly limited, but the following method can be exemplified. First, as shown in Fig. 9A, an insulating film 505A is formed on a p-type semiconductor layer 503, and a part of the insulating film 505A is opened by etching or the like to form a contact hole 505B. Next, as shown in Fig. 9B, an n-type semiconductor layer 507 is formed on the p-type semiconductor layer 503 and the insulating film 505A. At this time, the p-type semiconductor layer 503 and the n-type semiconductor layer 507 are connected via the contact hole 505B.

[0158] 9C, a gate insulating film 509 and a gate electrode 511 are formed in this order on the n-type semiconductor layer 507. Next, as shown in FIG. 9D, an interlayer insulating film 519 is provided so as to cover the insulating film 505A, the n-type semiconductor layer 507, the gate insulating film 509, and the gate electrode 511.

[0159] 9E, a contact hole 519A is formed by opening a portion of the insulating film 505A and interlayer insulating film 519 on the p-type semiconductor layer 503, and a source electrode 513 is provided in the contact hole 519A. Furthermore, as shown in FIG. 9E, a contact hole 519B is formed by opening a portion of the gate insulating film 509 and interlayer insulating film 519 on the n-type semiconductor layer 507, and a drain electrode 515 is formed in the contact hole 519B. Through the above procedure, the quantum tunnel field effect transistor 501 can be manufactured.

[0160] After forming n-type semiconductor layer 507 on p-type semiconductor layer 503, heat treatment is performed at a temperature of 150° C. or higher and 600° C. or lower, thereby forming silicon oxide layer 505 between p-type semiconductor layer 503 and n-type semiconductor layer 507. By adding this step, quantum tunnel field effect transistor 501A can be manufactured.

[0161] The thin film transistor according to this embodiment is preferably a channel-doped thin film transistor, which is a transistor in which carriers in the channel are appropriately controlled by n-type doping rather than by oxygen deficiency, which is susceptible to fluctuations in response to external stimuli such as atmosphere and temperature, and which has the effect of achieving both high mobility and high reliability.

[0162] <Applications of Thin Film Transistor> The thin film transistor according to this embodiment can be suitably used in solar cells, display elements (liquid crystal elements, organic electroluminescence elements, inorganic electroluminescence elements, etc.), and power semiconductor elements. The thin film transistor according to this embodiment can be suitably used as a transistor in active matrix devices such as display devices (liquid crystal displays, organic electroluminescence (EL) displays, micro organic EL displays, micro light-emitting diode (LED) displays, mini LED displays, etc.), solid-state imaging elements, and touch panels. The thin film transistor according to this embodiment can also be applied to various integrated circuits such as field-effect transistors, logic circuits, memory circuits, and differential amplifier circuits, which can be applied to electronic devices, etc. The electronic device according to this embodiment preferably includes a thin film transistor. Furthermore, the thin film transistor according to this embodiment can be applied to static induction transistors and Schottky barrier transistors in addition to field-effect transistors. The thin film transistor according to this embodiment can also be applied as a transistor for sensors such as image sensors, X-ray sensors, and biosensors.

[0163] Hereinafter, the case where the thin film transistor according to this embodiment is used in a display device and a solid-state image sensor will be described.

[0164] First, a case where the thin film transistor according to this embodiment is used in a display device will be described with reference to Figures 10A to 10C. Figure 10A is a top view of the display device according to this embodiment. Figure 10B is a circuit diagram for explaining the circuit of the pixel portion when a liquid crystal element is applied to the pixel portion of the display device according to this embodiment. Also, Figure 10C is a circuit diagram for explaining the circuit of the pixel portion when an organic EL element is applied to the pixel portion of the display device according to this embodiment.

[0165] The thin film transistor according to this embodiment can be used as a transistor disposed in a pixel portion. Since the thin film transistor according to this embodiment can be easily made into an n-channel type, part of a driver circuit that can be configured with an n-channel transistor is formed over the same substrate as the transistor in the pixel portion. By using the thin film transistor described in this embodiment for the pixel portion or the driver circuit, a highly reliable display device can be provided.

[0166] 10A shows an example of a top view of an active matrix display device. A pixel portion 301, a first scanning line driver circuit 302, a second scanning line driver circuit 303, and a signal line driver circuit 304 are formed on a substrate 300 of the display device. A plurality of signal lines are arranged in the pixel portion 301, extending from the signal line driver circuit 304, and a plurality of scanning lines are arranged in the pixel portion 301, extending from the first scanning line driver circuit 302 and the second scanning line driver circuit 303. Pixels each having a display element are provided in a matrix at an intersection between the scanning lines and the signal lines. The substrate 300 of the display device is connected to a timing control circuit (also referred to as a controller or a control IC) via a connection portion such as an FPC (Flexible Printed Circuit).

[0167] 10A , the first scanning line driver circuit 302, the second scanning line driver circuit 303, and the signal line driver circuit 304 are formed on the same substrate 300 as the pixel portion 301. This reduces the number of components, such as external driver circuits, and thus reduces costs. Furthermore, if the driver circuits are provided outside the substrate 300, it becomes necessary to extend the wiring, which increases the number of connections between the wiring. If the driver circuits are provided on the same substrate 300, the number of connections between the wiring can be reduced, thereby improving reliability and yield.

[0168] 10B shows an example of a circuit configuration of a pixel, which is applicable to the pixel portion of a VA-type liquid crystal display device.

[0169] This pixel circuit can be applied to a configuration in which one pixel has multiple pixel electrodes. Each pixel electrode is connected to a different transistor, and each transistor is configured to be driven by a different gate signal. This allows the signals applied to each pixel electrode of a multi-domain pixel to be controlled independently.

[0170] The gate wiring 312 of the transistor 316 and the gate wiring 313 of the transistor 317 are separated so as to receive different gate signals. On the other hand, the source or drain electrode 314 functioning as a data line is used in common by the transistors 316 and 317. The thin film transistors according to this embodiment can be used for the transistors 316 and 317. This makes it possible to provide a highly reliable liquid crystal display device.

[0171] The transistor 316 is electrically connected to a first pixel electrode, and the transistor 317 is electrically connected to a second pixel electrode. The first pixel electrode and the second pixel electrode are separated from each other. The shapes of the first pixel electrode and the second pixel electrode are not particularly limited. For example, the first pixel electrode may be V-shaped.

[0172] The gate electrode of the transistor 316 is connected to the gate wiring 312, and the gate electrode of the transistor 317 is connected to the gate wiring 313. By applying different gate signals to the gate wiring 312 and the gate wiring 313, the operation timing of the transistors 316 and 317 can be made different, thereby controlling the alignment of the liquid crystal.

[0173] Furthermore, a storage capacitor may be formed by the capacitor wiring 310, a gate insulating film that functions as a dielectric, and a capacitor electrode that is electrically connected to the first pixel electrode or the second pixel electrode.

[0174] The multi-domain structure has one pixel having a first liquid crystal element 318 and a second liquid crystal element 319. The first liquid crystal element 318 is composed of a first pixel electrode, a counter electrode, and a liquid crystal layer therebetween, and the second liquid crystal element 319 is composed of a second pixel electrode, a counter electrode, and a liquid crystal layer therebetween.

[0175] The pixel portion is not limited to the configuration shown in Fig. 10B, and may include a switch, a resistor, a capacitor, a transistor, a sensor, or a logic circuit.

[0176] Another example of the circuit configuration of a pixel is shown in Fig. 10C, which shows the structure of a pixel portion of a display device using organic EL elements.

[0177] 10C is a diagram showing an example of an applicable circuit of the pixel portion 320. Here, an example is shown in which two n-channel transistors are used in one pixel. The oxide film according to this embodiment can be used in the channel formation region of the n-channel transistor. Digital time gray scale driving can be applied to the circuit of the pixel portion.

[0178] The thin film transistor according to this embodiment can be used for the switching transistor 321 and the driving transistor 322. This makes it possible to provide a highly reliable organic EL display device.

[0179] The configuration of the circuit in the pixel portion is not limited to the configuration shown in Fig. 10C. A switch, a resistor, a capacitor, a sensor, a transistor, or a logic circuit may be added to the circuit in the pixel portion shown in Fig. 10C. This completes the description of the case where the thin film transistor according to this embodiment is used in a display device.

[0180] Next, a case where the thin film transistor according to this embodiment is used in a solid-state imaging device will be described with reference to FIG.

[0181] A CMOS (Complementary Metal Oxide Semiconductor) image sensor is a solid-state imaging device that holds a potential in a signal charge storage section and outputs that potential to a vertical output line via an amplification transistor. If a leak current occurs in the reset transistor and / or transfer transistor included in the CMOS image sensor, the leak current causes charging or discharging, changing the potential of the signal charge storage section. When the potential of the signal charge storage section changes, the potential of the amplification transistor also changes, resulting in a value that deviates from the original potential, degrading the captured image.

[0182] The following describes the operational effects when the thin film transistor according to this embodiment is applied to the reset transistor and transfer transistor of a CMOS image sensor. Either a thin film transistor or a bulk transistor may be applied to the amplifying transistor.

[0183] 11 is a diagram showing an example of the pixel configuration of a CMOS image sensor. A pixel is composed of a photodiode 3002, which is a photoelectric conversion element, a transfer transistor 3004, a reset transistor 3006, an amplifier transistor 3008, and various wirings, and a plurality of pixels are arranged in a matrix to form a sensor. A selection transistor electrically connected to the amplifier transistor 3008 may be provided. The transistor symbols "OS" and "Si" represent oxide semiconductor and silicon, respectively, and represent materials that are preferable for use in the respective transistors. This also applies to the subsequent drawings.

[0184] The photodiode 3002 is connected to the source side of the transfer transistor 3004, and a signal charge storage region 3010 (also called FD: floating diffusion) is formed on the drain side of the transfer transistor 3004. The source of the reset transistor 3006 and the gate of the amplification transistor 3008 are connected to the signal charge storage region 3010. As an alternative configuration, the reset power supply line 3110 can be eliminated. For example, the drain of the reset transistor 3006 can be connected to the power supply line 3100 or the vertical output line 3120 instead of the reset power supply line 3110. Note that the oxide film according to this embodiment may be used for the photodiode 3002, and the same material as the oxide films used for the transfer transistor 3004 and the reset transistor 3006 may be used.

[0185] The present invention will be specifically described below based on examples, but the present invention is not limited to these examples.

[0186] [Production of oxide sintered body] (Examples 1 to 18) Gallium oxide powder, aluminum oxide powder, indium oxide powder, and powder of an oxide of X element or Z element were weighed out so as to have the compositions (at %) shown in Tables 1 to 3, placed in a polyethylene pot, and mixed and pulverized for 72 hours using a dry ball mill to produce mixed powders. The powder of the oxide of X element or Z element was at least one powder selected from the group consisting of silicon oxide, gallium oxide, zirconium oxide, cerium oxide, terbium oxide, neodymium oxide, manganese oxide, ruthenium oxide, palladium oxide, and platinum oxide. Note that the oxide sintered body according to the first aspect described above corresponds to Examples 1 to 12, and the oxide sintered body according to the second aspect described above corresponds to Examples 1 to 18. This mixed powder was placed in a mold and subjected to a pressure of 500 kg / cm. ２ This press-molded body was subjected to a pressure of 2000 kg / cm. ２ The compact was densified by CIP at a pressure of 100°C. Next, this densified press-molded body was placed in an atmospheric pressure sintering furnace and held at 350°C for 3 hours. Thereafter, the temperature was increased at a rate of 100°C / hour, sintered at 1400°C for 24 hours, and allowed to cool to obtain an oxide sintered body measuring 5 cm x 5 cm. The obtained oxide sintered body was evaluated as follows. The evaluation results are shown in Tables 1 to 3.

[0187] (Comparative Examples 1 to 7) Oxide sintered bodies were produced in the same manner as in Example 1, etc., except that gallium oxide powder, aluminum oxide powder, indium oxide powder, and powder of an oxide of the X element or Z element were weighed so as to obtain the composition (at %) shown in Table 4. Note that in Comparative Examples 1 and 2, powder of an oxide of the X element and Z element was not used. The obtained oxide sintered bodies were evaluated as follows in the same manner as in Example 1, etc. The evaluation results are shown in Table 4.

[0188] In Tables 1 to 4, the numerical values ​​shown as "at %" indicate the atomic composition ratio of indium element, gallium element, aluminum element, X element, and Z element expressed as a percentage.

[0189] Evaluation of Properties of Oxide Sintered Body (1) Composition (at %) of Oxide Sintered Body The compositions of In, Ga, Al, and X element or Z element in the sintered bodies obtained in each of the above Examples and Comparative Examples were measured using an inductively coupled plasma atomic emission spectrometer (ICP-AES, manufactured by Shimadzu Corporation).

[0190] (2) Crystal structure The X-ray diffraction (XRD) of the oxide sintered bodies obtained in each of the above examples and comparative examples was measured using an X-ray diffraction measuring device SmartLab under the following conditions. The obtained XRD chart was analyzed using JADE6 to confirm the crystalline phase in the oxide sintered body. Device: SmartLab (manufactured by Rigaku Corporation) X-ray: Cu-Kα ray (wavelength 1.5418 × 10 －１０ m) ・2θ-θ reflection method, continuous scan (2.0° / min) ・Sampling interval: 0.02° ・Entrance slit, receiving slit 1, receiving slit 2: 1 mm

[0191] In Tables 1 to 4, In ２ O ３ The bixbyite crystalline phase represented by the formula (A) to (K) is referred to as "bixbyite", and the crystalline phase having a diffraction peak within the range of incident angle (2θ) observed by X-ray (Cu-Kα ray) diffraction measurement specified in (A) to (K) is referred to as "crystalline phase A".

[0192] Figure 12 shows the X-ray diffraction pattern of the oxide sintered body used in the target produced in Example 4. As shown in Figure 12, it can be seen that the oxide sintered body contains a crystalline phase having a diffraction peak in the range of incident angles (2θ) observed by X-ray (Cu-Kα ray) diffraction measurement specified in (A) to (K). In Figure 12, (I) is observed near 44.1°, and (K) is observed near 18.1°.

[0193] Fig. 13 shows the X-ray diffraction pattern of the oxide sintered body used in the target produced in Example 13. As shown in Fig. 13, it is found that the oxide sintered body contains a crystalline phase A having a diffraction peak in the range of incident angles (2θ) observed by X-ray (Cu-Kα ray) diffraction measurement defined in (A) to (K) above.

[0194] Fig. 14 shows the X-ray diffraction pattern of the oxide sintered body used in the target produced in Example 14. As shown in Fig. 14, it is found that the oxide sintered body contains a crystalline phase B having a diffraction peak in the range of incident angle (2θ) observed by X-ray (Cu-Kα ray) diffraction measurement defined in (A) to (F), (G'), (H), (I), and (K).

[0195] (3) Bulk Resistivity (mΩ cm) The bulk resistance (mΩ cm) of the oxide sintered bodies obtained in the above-mentioned respective Examples and Comparative Examples was measured using a resistivity meter Loresta (manufactured by Mitsubishi Chemical Corporation) based on the four-probe method (JIS R 1637:1998). The measurement was performed at five points in total, namely, the center of the oxide sintered body and four points midpoints between the four corners and the center of the oxide sintered body, and the average value of the five points was taken as the bulk resistance.

[0196] (4) Color Unevenness The color unevenness of the oxide sintered bodies obtained in each of the above Examples and Comparative Examples was evaluated by visually inspecting the sintered bodies, which were kept in a size of 5 cm x 5 cm, from a distance of 50 cm under the daylight of a north window. The surface of the sintered body is usually colored yellow-green or green, and if there was any variation in the color, it was judged that there was color unevenness. Note that if there is color unevenness in the sintered body, it may be difficult to determine the state of color unevenness, for example, when using the target.

[0197] (5) White Spots The white spots of the oxide sintered bodies obtained in the above-mentioned respective Examples and Comparative Examples were surface-ground to a thickness of 5 mm by grinding, and then visually observed while maintaining the size of 5 cm × 5 cm, and the number of white spots having a diameter of 0.5 mmφ or more was counted.

[0198] [Production of sputtering targets] The oxide sintered bodies obtained in each of the examples and comparative examples were ground and polished to produce sputtering targets of 4 inches diameter x 5 mm thickness. Specifically, the cut and polished oxide sintered bodies were bonded to a backing plate to produce the sputtering targets. In all targets, the bonding rate was 98% or higher. Furthermore, almost no warping was observed. The bonding rate (bonding rate) was confirmed by X-ray CT.

[0199] Evaluation of sputtering target characteristics (abnormal discharge (sputtering stability)) Using the prepared sputtering target, DC sputtering was carried out continuously for 5 hours at 400 W (power density: 4.9 W / cm2). During sputtering, the presence or absence of abnormal discharge was determined using an arcing counter (μ Arc Monitor, manufactured by Landmark Technology Co., Ltd.). The arcing counter was set to the following detection mode: energy, arc detection voltage: 100 V, large-medium energy boundary: 50 mJ, and minimum hard arc time: 100 μs.

[0200] [Manufacturing of Thin Film Transistors] (1) Film Formation Step The oxide sintered bodies obtained in each Example and Comparative Example were ground and polished to manufacture sputtering targets measuring 4 inches in diameter and 5 mm thick. Using the manufactured sputtering targets, a 50 nm thin film (oxide semiconductor layer) was formed on a silicon wafer with a thermal oxide film (gate insulating film) via a metal mask under the following film formation conditions. In this case, sputtering was performed using a mixed gas of high-purity argon and 1% high-purity oxygen as the sputtering gas. A sample in which only a 50 nm thick oxide semiconductor layer was formed on a glass substrate was also manufactured under the same conditions. The glass substrate used was ABC-G manufactured by Nippon Electric Glass Co., Ltd.

[0201] <Film formation conditions> Substrate temperature during film formation: room temperature Back pressure before film formation: 5×10 －４ Pa or less Atmosphere gas: Ar (argon) + O ２ (Oxygen) Oxygen partial pressure during film formation: 1% by volume Sputtering pressure (total pressure) during film formation: 0.5 Pa Direct current (DC) output: 300 W

[0202] (2) Formation of Source and Drain Electrodes Next, titanium metal was sputtered using a metal mask in the shape of source and drain contact holes so that the ratio of the distance to the width (W / L) between the two electrodes of the source electrode and the drain electrode was 200 / 1000, and titanium electrodes were formed as source and drain electrodes. The obtained laminate was heated to 350°C at a heating rate of 10°C / min in the atmosphere, and then heat-treated at 350°C for 60 minutes to produce a thin film transistor (TFT) before the formation of a protective insulating film.

[0203] <Evaluation of TFT characteristics> (1) Linear mobility The protective insulating film (SiO ２ The linear mobility was evaluated for the TFT before the formation of the thin film. The linear mobility was determined from the transfer characteristics when a drain voltage of 0.1 V was applied. Specifically, a graph of the transfer characteristics Id-Vg was created, the transconductance (Gm) for each Vg was calculated, and the mobility was derived using the linear region equation. Gm is expressed as ∂(Id) / ∂(Vg), and Vg was applied from -10 V to 20 V, with the maximum mobility within that range defined as the linear mobility. Unless otherwise specified in the present invention, the linear mobility was evaluated using this method. Id is the current value between the source electrode and the drain electrode, and Vg is the gate voltage when a voltage Vd is applied between the source electrode and the drain electrode.

[0204] (2) Threshold voltage (Vth) The threshold voltage (Vth) is determined by applying Vd = 0.1 V, measuring the Id-Vg characteristics, and determining Id = 10 －９ Vg at A was defined.

[0205]

[0206]

[0207]

[0208]

[0209] From the results shown in Tables 1 to 2 and Table 4, the sintered bodies according to Examples 1 to 12 have atomic ratios of In, Ga, Al, and X elements that satisfy the conditions shown in formulas (1), (2), and (3), and further contain a bixbyite crystalline phase (bixbyite in the table) and a crystalline phase (crystalline phase A in the table) having a diffraction peak within the range of incident angles (2θ) observed by X-ray (Cu-Kα ray) diffraction measurement defined in (A) to (C). Therefore, it can be seen that in Examples 1 to 12, oxide sintered bodies were obtained in which the occurrence of color unevenness was reduced and the occurrence of white spots was reduced. On the other hand, the sintered bodies according to Comparative Examples 1 to 7 were unable to achieve both reduced color unevenness and reduced white spots. Furthermore, from the results shown in Tables 1 to 2 and Table 4, the threshold voltages of the TFTs according to Examples 1 to 12 were in the range of −0.5 to +0.5. Therefore, it is understood that the TFTs according to Examples 1 to 12 have excellent normally-off characteristics and excellent in-plane uniformity. In particular, the TFTs according to Examples 10 and 11 have higher linear mobility than the TFTs according to Comparative Examples 1 to 7, and it is understood that TFTs with particularly high mobility have been obtained.

[0210] Furthermore, from the results shown in Tables 1 to 4, the sintered bodies according to Examples 1 to 18 have atomic ratios of In, Ga, Al, and Z elements that satisfy the conditions shown in formulas (1), (4), and (5), and further include a bixbyite crystalline phase (bixbyite in the table) and a crystalline phase (crystalline phase A or crystalline phase B in the table) that has a diffraction peak in the range of incident angles (2θ) observed by X-ray (Cu-Kα ray) diffraction measurement specified in (A) to (C), and does not have a diffraction peak in at least one of the ranges of incident angles (2θ) specified in (G') and (J). Therefore, it can be seen that in Examples 1 to 18, oxide sintered bodies were obtained in which the occurrence of color unevenness was reduced and the occurrence of white spots was reduced. On the other hand, the sintered bodies according to Comparative Examples 1 to 7 were unable to achieve both a reduction in the occurrence of color unevenness and a reduction in the occurrence of white spots. Furthermore, from the results shown in Tables 1 to 4, the threshold voltages of the TFTs according to Examples 1 to 18 are in the range of -0.5 to +0.5. Therefore, it is understood that the TFTs according to Examples 1 to 18 have excellent normally-off characteristics and excellent in-plane uniformity. In particular, the TFTs according to Examples 10 to 11 and Example 13 have higher linear mobility than the TFTs according to Comparative Examples 1 to 7, and it is understood that TFTs with particularly high mobility have been obtained.

[0211] This application is based on a Japanese patent application (Patent Application No. 2024-111618) filed on July 11, 2024, the contents of which are incorporated herein by reference.

[0212] 1, 1A, 1B: oxide sintered body (sputtering target), 1C: oxide sintered body, 3: backing plate, 20: silicon wafer, 30: gate insulating film, 40: oxide film, 50: source electrode, 60: drain electrode, 70: interlayer insulating film, 70A: interlayer insulating film, 70B: interlayer insulating film, 81: glass substrate, 83: oxide film, 85: SiO2 film, 100: thin film transistor, 100A: thin film transistor, 11: channel layer (oxide film), 11 A-1: first low resistance region, 11B: semiconductor region, 11A-2: second low resistance region, 21: substrate, 22: buffer layer, 24: gate insulating film, 25: gate electrode, 26: interlayer insulating film, 27: source electrode, 28: drain electrode, 29: protective film, 100B: thin film transistor, 100C: thin film transistor, 300: substrate, 301: pixel section, 302: first scanning line driving circuit, 303: second scanning line driving circuit, 304: signal line driving circuit, 310: capacitor Wiring, 312: gate wiring, 313: gate wiring, 314: drain electrode, 316: transistor, 317: transistor, 318: first liquid crystal element, 319: second liquid crystal element, 320: pixel portion, 321: switching transistor, 322: driving transistor, 3002: photodiode, 3004: transfer transistor, 3006: reset transistor, 3008: amplification transistor, 3010: signal charge storage portion, 3100: electrode Power line, 3110: reset power line, 3120: vertical output line, 501: quantum tunnel field effect transistor, 501A: quantum tunnel field effect transistor, 503: p-type semiconductor layer, 505: silicon oxide layer, 505A: insulating film, 505B: contact hole, 507: n-type semiconductor layer, 509: gate insulating film, 511: gate electrode, 513: source electrode, 515: drain electrode, 519: interlayer insulating film, 519A, 519B: contact holes.

Claims

1. An oxide sintered body comprising, as main components, In, Ga, Al, and one or more X elements selected from the group consisting of Si, Ge, Zr, and Ce, wherein the atomic ratios of In, Ga, Al, and the X element satisfy the conditions shown in the following formulas (1) to (3), and comprising a bixbyite crystalline phase, and a crystalline phase in which a diffraction peak is observed in the following incident angle (2θ) ranges (A) to (C) by X-ray (Cu-Kα ray) diffraction measurement: 0.05≦Ga / (In+Ga)≦0.20 (1) 0.005≦Al / (In+Ga+Al+X)≦0.05 (2) 0.0003≦X / (In+Ga+Al+X)≦0.02 (3) (wherein In, Ga, Al, and X are the numbers of atoms of In, Ga, Al, and the X element in the oxide sintered body, respectively.) 36° to 39° (A) 53° to 56° (B) 62° to 66° (C) 2. The oxide sintered body according to claim 1, wherein 99 at % or more of the metal elements contained in the oxide sintered body are In, Ga, Al, and the X element.

3. The oxide sintered body according to claim 1 or 2, wherein the crystalline phase in which the diffraction peak is observed further has a diffraction peak in at least one range of incident angle (2θ) selected from the following (D) to (K) by X-ray (Cu-Kα ray) diffraction measurement: 31° to 34° (D), 30° to 32° (E), 51° to 53° (F), 9° to 11° (G), 19° to 21° (H), 42° to 45° (I), 8° to 10° (J), and 17° to 19° (K).

4. An oxide sintered body comprising, as main components, In, Ga, Al, and one or more Z elements selected from the group consisting of Si, Ge, Zr, Ce, Tb, Nd, Mn, Ru, Pd, and Pt, wherein the atomic ratios of In, Ga, Al, and the Z elements satisfy the conditions shown in the following formulas (1), (4), and (5), and comprising a bixbyite crystalline phase, and a crystalline phase in which, by X-ray (Cu-Kα ray) diffraction measurement, a diffraction peak is observed in the incident angle (2θ) ranges of the following (A) to (C), and no diffraction peak is observed in at least one of the incident angle (2θ) ranges of the following (G') and (J). 0.05≦Ga / (In+Ga)≦0.20 (1) 0.005≦Al / (In+Ga+Al+Z)≦0.05 (4) 0.0003≦Z / (In+Ga+Al+Z)≦0.07 (5) (In, Ga, Al, and Z are the numbers of atoms of In, Ga, Al, and the Z element in the oxide sintered body, respectively.) 36° to 39° (A) 53° to 56° (B) 62° to 66° (C) 14° to 16° (G') 8° to 10° (J) 5. The oxide sintered body according to claim 4, wherein the element Z is at least one selected from the group consisting of Tb and Nd.

6. The oxide sintered body according to claim 4 or 5, wherein the atomic ratio represented by the formula (5) is 0.0005 or more and 0.0500 or less.

7. The oxide sintered body according to any one of claims 4 to 6, wherein 99 at % or more of the metal elements contained in the oxide sintered body are In, Ga, Al, and the Z element.

8. The oxide sintered body according to any one of claims 4 to 7, wherein the crystalline phase in which the diffraction peak is observed further has a diffraction peak in at least one range of incident angle (2θ) selected from the following (D) to (K) by X-ray (Cu-Kα ray) diffraction measurement: 31° to 34° (D), 30° to 32° (E), 51° to 53° (F), 9° to 11° (G), 19° to 21° (H), 42° to 45° (I), 8° to 10° (J), and 17° to 19° (K).

9. The oxide sintered body according to any one of claims 1 to 8, wherein the crystalline phase in which the diffraction peaks are observed further has diffraction peaks in the following ranges of incident angles (2θ) (D), (E), (F), (H), (I), and (K) by X-ray (Cu-Kα ray) diffraction measurement: 31° to 34° (D), 30° to 32° (E), 51° to 53° (F), 19° to 21° (H), 42° to 45° (I), and 17° to 19° (K).

10. The oxide sintered body according to any one of claims 1 to 9, wherein the crystalline phase in which the diffraction peak is observed does not exhibit a diffraction peak in the range of the incident angle (2θ) of the following (G') by X-ray (Cu-Kα ray) diffraction measurement: 14° to 16° ... (G') 11. The oxide sintered body according to any one of claims 1 to 10, wherein the atomic ratio represented by the formula (1) is 0.05 or more and 0.18 or less.

12. The oxide sintered body according to any one of claims 1 to 11, wherein the atomic ratio represented by the formula (1) is 0.06 or more and 0.16 or less.

13. The oxide sintered body according to any one of claims 1 to 12, wherein the atomic ratio represented by the formula (1) is 0.08 or more and 0.15 or less.

14. The oxide sintered body according to any one of claims 1 to 13, wherein the atomic ratio represented by the formula (2) or (4) is 0.008 or more and 0.04 or less.

15. The oxide sintered body according to any one of claims 1 to 14, wherein the atomic ratio represented by the formula (2) or (4) is 0.01 or more and 0.03 or less.

16. The oxide sintered body according to any one of claims 1 to 15, wherein the atomic ratio represented by the formula (3) or (5) is 0.0005 or more and 0.015 or less.

17. The oxide sintered body according to any one of claims 1 to 16, wherein the atomic ratio represented by the formula (3) or (5) is 0.0008 or more and 0.010 or less.

18. The oxide sintered body according to any one of claims 1 to 17, having a bulk resistivity of 10 mΩ·cm or less.

19. A sputtering target comprising the oxide sintered body according to any one of claims 1 to 18.

20. An oxide film formed using the sputtering target according to claim 19.

21. A thin film transistor comprising the oxide film of claim 20.

22. An electronic device comprising the thin film transistor of claim 21.

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