KR20100079320A - Metaloxide target for amorphous oxide semiconductor layer and method for preparing the same - Google Patents

Abstract

PURPOSE: A metal-oxide target for an amorphous oxide semiconductor layer and a method for preparing the same are provided to prevent abnormal discharge, crack, and a nodule by closely forming the target. CONSTITUTION: A composite metal oxides target is comprised of a third metal oxide including one or more than two kind groups which are formed with indium tin oxide(In2O3), zinc oxide(ZnO), IIIA group, IIIB group, and IVA group. The atomic ratio of the indium(In) metal among the whole metal element is 0.1~0.6. The atomic ratio of the zinc(Zn) metal among the whole metal element is 0.1~0.75. The atomic ratio of the third metal among the whole metal element is 0.02~0.35. The atomic ratio of the gallium among the third metal among the whole metal element is under 0~0.2.

Description

Metal oxide target for amorphous oxide semiconductor film and manufacturing method thereof {METALOXIDE TARGET FOR AMORPHOUS OXIDE SEMICONDUCTOR LAYER AND METHOD FOR PREPARING THE SAME}

The present invention relates to a composite metal oxide target used for forming an amorphous transparent oxide semiconductor film. More specifically, the present invention relates to a composite metal oxide target having a low occurrence of abnormal discharge and excellent homogeneity of the resulting film, and a method of manufacturing the same, due to the dense structure of the target when forming an amorphous transparent oxide semiconductor film. Since the amorphous oxide semiconductor film formed of the composite metal oxide target has high carrier mobility and high transmittance, a liquid crystal display (LCD), an electroluminescence display (ELD), and an electrophoretic display (EPD) It can be used for switching devices such as displays, driving circuit devices, and the like.

An amorphous transparent oxide semiconductor film is produced by sputtering or other methods. In particular, the sputtering method is effective when it is necessary to precisely control the film formation and the film thickness of a material having low vapor pressure, and its operation is very simple and convenient and widely used. In manufacturing a thin film by the sputtering method, a target, which is a raw material of the thin film, is used. The target is a solid containing a metal element constituting a thin film by film formation, and a sintered body such as metal, metal oxide, metal nitride, metal carbide, or the like is used, or a single crystal is used in some cases.

Oxide targets used in the fabrication of amorphous transparent oxide semiconductor films include zinc oxide (ZnO) targets and zinc oxide (ZTO) targets with tin oxide, and IZO (Indium Zinc) with zinc oxide added to indium oxide. Oxide) target, IZTO (Indium Zinc Tin Oxide) target with zinc oxide and tin oxide added, and IGZO (Indium Gallium Zinc Oxide) target with gallium oxide and zinc oxide added.

Among the targets, the amorphous oxide semiconductor film is formed with an IGZO target having a composition of In: Ga: Zn = 1: 1: 1 in a molar ratio, and it is known to exhibit much better characteristics than an amorphous silicon film.

In order to manufacture the IGZO target having the composition of In: Ga: Zn = 1: 1: 1 (molar ratio), use of expensive rare metals, indium and gallium, is essential, which greatly affects the manufacturing cost of the target. Accordingly, the present inventors have tried to find a method of not using expensive gallium or minimizing the amount thereof.

In addition, in the conventional method for producing an oxide-based target, three or more kinds of different oxide powders, for example, indium oxide, zinc oxide and gallium oxide powder, are mixed in a quantitative manner, and then wet pulverized with water as a medium, and then the pulverized powder is dried. And filtering and adding a binder to prepare a molded article having a desired target shape and sintering the molded article at high temperature in an air or oxygen atmosphere. However, the manufacturing method has a problem in that the phase separation (oxides are separated from each other) during the sintering process is not homogeneous or dense. Accordingly, cracks or nodules are generated in the target during sputtering, making it difficult to form a homogeneous film.

Accordingly, the present inventors synthesized a single phase or homogeneous oxide powder in the preparation of the sputtering target for the transparent amorphous oxide semiconductor film, thereby preventing phase separation in the sintering process, and thus an oxide target having excellent semiconductor characteristics even when a small amount of gallium is used. To provide. In addition, the present inventors have attempted to provide a sputtering target having a new composition for manufacturing a semiconductor thin film containing another element instead of gallium without using a gallium component.

The present invention is to solve the problems of the prior art as described above, the present invention is selected from the group consisting of indium oxide (In ₂ O ₃ ), zinc oxide (ZnO), and group IIIA, IIIB and IVA group. It consists of three or more kinds of third metal oxides, the atomic ratio of the indium (In) metal in the total metal element is 0.1 to 0.6, the atomic ratio of the zinc (Zn) metal is 0.1 to 0.75, and the atomic ratio of the third metal is 0.02 to 0.35, and the atomic ratio of gallium in the third metal provides a target having 0 to less than 0.2 of all metal elements.

The present invention provides a composite metal oxide target having a sintered density of at least 95% of the theoretical density of the composite metal oxide target.

In addition, the present invention provides an amorphous metal oxide semiconductor film formed by the sputtering method from the composite metal oxide target.

In addition, the present invention is a composite metal oxide target is synthesized in a single phase or homogeneous oxide by using the coprecipitation method from three or more kinds of metal salts different from each other, thereby preventing the phase separation in the sintering process to provide a composite metal oxide target having a dense structure to provide.

The present invention is the coprecipitation method

a) preparing a solution containing at least three different metal salts,

b) co-precipitating the metal hydroxide by adding alkali to the metal salt solution,

c) separating and drying the precipitate,

d) heat treating and pulverizing the heat treated powder,

e) producing a target shaped body of a predetermined shape, and

f) sintering and cooling the shaped body to provide a composite metal oxide target.

The sputtering target of the present invention has a value of 95% or more of the theoretical density and has the effect of preventing abnormal discharge, cracks, and nodules during sputtering. Since the amorphous oxide semiconductor film formed of the composite metal oxide target of the present invention has high carrier mobility and high transmittance, a liquid crystal display (LCD), an electroluminescence display (ELD), and an electrophoretic display (EPD) there is an effect that can be used for switching devices such as electrophoretic displays, driving circuit devices, and the like.

Hereinafter, the present invention will be described in detail.

In the composite metal oxide target of the present invention, the atomic ratio of the indium (In) metal in the total metal elements is 0.1 to 0.6. If the atomic ratio is less than 0.1, the carrier mobility may decrease when the oxide semiconductor film is formed. If it exceeds, the resistance inherent indium oxide is low, which is not suitable as a semiconductor film. The atomic ratio of the indium metal is preferably 0.1 to 0.5.

The atomic ratio of zinc (Zn) metal of all the metal elements is 0.1 to 0.75. When the atomic ratio is less than 0.1, the oxide semiconductor film is crystallized. When the atomic ratio is greater than 0.75, problems of abrasion resistance and thermal stability of the obtained oxide semiconductor film are generated. V) There is a disadvantage that the shift is large.

The atomic ratio of one or two or more kinds of the third metal oxides selected from the group consisting of Groups IIIA, IIIB, and IVA among all the metal elements is 0.02 to 0.35. When the atomic ratio is less than 0.02, the resistance is too low and the semiconductor film There is a disadvantage in that it is not suitable, and if it is more than 0.35, the amount of expensive third metal is increased, which is not economical. In particular, the present invention does not use gallium in the third metal or control the atomic ratio to the total metal element less than 0.2, preferably does not use gallium or controls to 0.02 to 0.15.

The third metal of the present invention is preferably scandium (Sc), yttrium (Y), lanthanum (La), titanium (Ti), zirconium (Zr), hafnium (Hf), aluminum (Al), gallium (Ga) and the like. to be.

The composite metal oxide target of the present invention makes it possible to use it as a semiconductor even without using or reducing gallium, which is an expensive rare metal.

The composite metal oxide target of the present invention may be prepared by mixing oxide powders of component metals or using synthetic powders through a coprecipitation method. In particular, when a gallium component is used, a uniform target showing excellent semiconductor properties with a small amount of gallium through a coprecipitation method. To prepare.

Hereinafter, the method for producing the target of the present invention will be described taking the coprecipitation method as an example.

First, a solution containing three or more different metal salts is prepared. In this case, the metal salt may be selected from inorganic salts and organic salts as metal precursors. For example, the metal salt solution may include at least three different metal salts, wherein the metal salt is a parent selected from indium (In) or zinc (Zn), and at least one metal salt selected from Groups IIIA, IIIB, and IVA, preferably Includes at least one metal salt selected from scandium (Sc), yttrium (Y), lanthanum (La), titanium (Ti), zirconium (Zr), hafnium (Hf), aluminum (Al), gallium (Ga) and the like.

In this case, the metal salt serving as the mother may be, for example, inorganic salts such as indium nitride, indium chloride, indium sulfide, zinc nitride, zinc nitride, zinc chloride, zinc sulfide, etc., and indium alkoxide or zinc alkoxide. Organic salts of can be used. In addition, salts of metals selected from Groups IIIA, IIIB, and IVA include scandium nitride, scandium chloride, scandium sulfide, yttrium nitride, yttrium chloride, yttrium sulfate, lanthanum nitride, lanthanum chloride, lanthanum sulfide, titanium nitride, titanium chloride, One or two or more selected from titanium sulfide, zirconium nitride, hafnium nitride, aluminum nitride, aluminum chloride, aluminum sulfide, gallium nitride, gallium chloride, gallium sulfide and the like may be used in combination.

As described above, after preparing a solution containing three or more different metal salts, a pH adjusting agent is added to the solution so as to have a pH of 1 to 4, and stirred at 30 to 80 ° C. for 5 to 20 hours to obtain a metal salt solution. An alkali (NH ₄ OH, an aqueous hydroxide solution of an alkali metal or alkaline earth metal, etc.) is added to the metal salt solution to obtain a pH of 10 to 10 to obtain a metal hydroxide precipitate. By this coprecipitation reaction, a composite obtained by synthesizing three or more different metals is obtained. That is, the precipitates are precipitated (coprecipitated) under conditions in which three or more different metal salts coexist, and the precipitate has a structure in which three or more metals are synthesized. The synthesized precipitate particles have a uniform particle size distribution of 100 nm or less.

After obtaining a precipitate as described above (metal hydroxide precipitate of three or more metals), the precipitate is filtered and separated using a filter press or a centrifuge. The separated precipitate is washed with ultrapure water or alcohol, and then dried by hot air drying or the like.

After the drying process as described above is subjected to a heat treatment (calcination) at a temperature of 500 ~ 800 ℃. Metal hydroxide powder is formed into a metal oxide powder by the heat treatment. The metal oxide powder obtained through such heat processing has a distribution whose average particle diameter is 1.0-10.0 micrometers. Next, the heat-treated powder is pulverized. Grinding may be performed by a method such as wet ball grinding, and through this grinding, a target having a higher density can be produced.

As described above, after the grinding process is carried out to produce a target molded body of a predetermined shape. At this time, by adding a molding aid (binder) to the pulverized powder is coated on the surface of the particles, it is possible to proceed to the process of drying (powder processing step). When such a powder processing process is advanced, molding density and sintering density can be increased.

After the molded product is manufactured as described above, the molded product is sintered. The sintering is carried out by maintaining the oxygen concentration inside the sintering furnace higher than the oxygen concentration in the atmosphere. Sintering is recommended to proceed for 10 to 20 hours at the internal temperature of 1250 ~ 1550 ℃ sintering furnace. At this time, it is good to increase the temperature in the sintering furnace at a rate of 1.0 ~ 1.5 ℃ / min to be in the above temperature range.

After sintering in the same manner as described above, the obtained sintered body is cooled. The cooling proceeds gradually while the sintered compact is charged into the sintering furnace and is gradually cooled while giving a sufficient time of 20 to 40 hours to room temperature.

According to the manufacturing method of the present invention described above, by the coprecipitation method, an ultrafine synthetic powder having a uniform particle size distribution of 100 nm or less is formed, and the ultrafine synthetic powder has a high sintering driving force and has a high density with excellent densification. A target (oxide sintered compact) can be manufactured. Specifically, a target having a density of 95% or more, preferably 98% or more of the theoretical density measured by the Archimedes method can be produced.

The present invention is synthesized by coprecipitation and sintered so that phase separation by high temperature does not occur, so that cracks or nodules do not occur during deposition (sputtering) and form a uniform thin film.

The target according to the invention is usefully used as an amorphous transparent semiconductor oxide material. In addition, the target according to the present invention may be formed on a substrate by a deposition method such as a sputtering method or an ion plasma method to produce a transparent oxide semiconductor film. The target according to the present invention is thermally and chemically stable and is usefully applied to the DC sputtering method using high DC power. The target according to the present invention prevents abnormal discharge, crack generation, and nodule generation even when high voltage is applied by the DC sputtering method. Accordingly, the target according to the present invention can be usefully applied to the DC sputtering method having an advantage in the film forming speed, productivity and manufacturing cost, it is possible to produce a low-cost transparent metal oxide semiconductor film and a product containing the same.

Hereinafter, the Example and comparative example of this invention are illustrated. The following examples are merely provided to aid the understanding of the present invention, whereby the technical scope of the present invention is not limited.

Example 1

The content of zinc (Zn) and zirconium (Zr) in the total metals in the indium nitrate (In (NO ₃ ) ₃ ) solution was [Zn] / [[In] + [Zn] + [Zr] = 0.48, Mix the zinc nitrate (Zn (NO ₃ ) ₂ ) and zirconium nitrate (Zr (NO ₃ ) ₂ ) solutions to make [Zr] / [[In] + [Zn] + [Zr]] = 0.04, and add ultrapure water. The mixture was stirred at 50 ° C. for 12 hours to obtain an In / Zn / Zr mixed salt solution having a pH of 3.2. Next, after adding NH ₄ OH aqueous solution to the mixed salt solution to pH 10, and reacted at 40 ℃ 20 hours to prepare an In-Zn-Zr-OH synthetic hydroxide precipitate. The precipitate was separated by filtration, washed three times with ultrapure water, and dried with hot air at 120 ° C. The dried powder was found to have a uniform particle size distribution of 70 ~ 150nm. Next, the dried powder was put into an electric furnace and heat-treated (calcined) at a temperature of 800 ° C. for 2 hours to obtain an In—Zn—Zr—O synthetic composite oxide powder. The In-Zn-Zr-O synthetic composite oxide powder obtained by heat treatment as described above was found to have a uniform particle size distribution of 1 to 10 µm as fine particles of 20 µm or less. In addition, it was found that the specific surface area of the In-Zn-Zr-O synthetic oxide powder was measured by the BET method to be 12 m 2 / g.

Next, the In-Zn-Zr-O synthetic oxide powder was placed in a pot and wet ball mill pulverized with water as a medium. At this time, the shredding medium used a YTZ ball, and during grinding, a binder (polyvinyl alcohol) was added to the pot to grind / mix, and the grind / mix was performed for 20 hours. As a result of pulverizing for 20 hours, it was found that the powder had an average particle size distribution of 0.5 to 1.0 μm, and 90% or more had a particle size distribution of 1.0 μm or less. Thereafter, the mixed slurry was spray dried to obtain a spherical powder having a thickness of 70 to 90 μm, and a compact of 150 mm × 150 mm × 10 mm T was prepared by applying a pressure of 2.5 ton / cm 2 using CIP. Thereafter, the molded body was put into an electric furnace having a maximum temperature of 1550 ° C., and then heated at a temperature rising rate of 1.2 ° C./mim to reach the temperature, and then maintained for 12 hours and sintered. At this time, the electric furnace was supplied with 400 L of oxygen per 1 m 3 of the internal volume to maintain the inside of the electric furnace with an oxygen atmosphere, after which cooling was performed, and 200 L of pure air per 1 m 3 of volume was added to the electric furnace and allowed to cool. A sputtering target was manufactured from the sintered body obtained through the above process through a grinding and cutting process.

As a result of elemental analysis using ICP (Inductively Coupled Plasma) for the target (sintered body) manufactured as described above

[In] / [[In] + [Zn] + [Zr]] = 0.4796, [Zn] / [[In] + [Zn] + [Zr]] = 0.4774,

[Zr] / [[In] + [Zn] + [Zr]] = 0.0431, and the density measurement showed 6.500 g / cm3, which corresponds to 98.9% of theoretical density, and measured bulk resistance. As a result, it was found that 6.52 x 10 ^-4 Pa · cm.

[Example 2]

[Zn] / [[In] + [Zn] + [Zr]] = 0.465 in the content of zinc (Zn) and zirconium (Zr) in the total metal in the solution of indium nitrate (In (NO ₃ ) ₃ ) Co-precipitation reaction was performed by mixing a solution of zinc nitrate (Zn (NO ₃ ) ₂ ) and yttrium nitrate (Zr (NO ₃ ) ₂ ) so that [Zr] / [[In] + [Zn] + [Zr]] = 0.07. The process was carried out in the same manner as in Example 1 to obtain a powder and a sputtering target. As a result of elemental analysis using ICP on the target (sintered body) thus prepared

[In] / [[In] + [Zn] + [Zr]] = 0.4669, [Zn] / [[In] + [Zn] + [Zr]] = 0.4634,

[Zr] / [[In] + [Zn] + [Zr]] = 0.0697, and the density measurement showed 6.503 g / cm3, corresponding to 99.2% of the theoretical density. As a result, it was found that it was 7.49 x 10 ^-4 Pa · cm.

Example 3

The content of indium (In), zinc (Zn), gallium (Ga), and aluminum (Al) in the total metal is [In] / [[In] + [Zn] + [Ga] + [Al]] = 0.4, [Zn] / [[In] + [Zn] + [Ga] + [Al]] = 0.45, [Ga] / [[In] + [Zn] + [Ga] + [Al]] = 0.1 Indium nitrate (In (NO ₃ ) ₃ ), zinc nitrate (Zn (NO ₃ ) ₂ ), gallium nitrate, so that [Al] / [[In] + [Zn] + [Ga] + [Al]] = 0.05 (Ga (NO ₃ ) ₃ ) and aluminum nitrate (Al (NO ₃ ) ₃ ) solution were mixed and stirred for 12 hours at 50 ° C. by adding ultrapure water to prepare an In / Zn / Ga / Al mixed salt solution having a pH of 3.9. Powder and a molded product were obtained in the same manner as in Example 1, and then heated under an oxygen atmosphere of 1350 ° C. for 12 hours to obtain a sputtering target. As a result of elemental analysis using ICP on the target (sintered body) thus prepared

[In] / [[In] + [Zn] + [Ga] + [Al]] = 0.3978, [Zn] / [[In] + [Zn] + [Ga] + [Al]] = 0.4521,

[Ga] / [[In] + [Zn] + [Ga] + [Al]] = 0.099, [Al] / [[In] + [Zn] + [Ga] + [Al]] = 0.0506 As a result of measuring the density, 6.328 g / cm 3 corresponding to 98.5% of the theoretical density was obtained, and the bulk resistance of the target was found to be 8.62 × 10 ⁻⁴ Pa · cm.

Example 4

The content of indium (In), zinc (Zn), gallium (Ga) and titanium (Ti) in the total metal is [In] / [[In] + [Zn] + [Ga] + [Ti]] = 0.4, [Zn] / [[In] + [Zn] + [Ga] + [Ti]] = 0.4, [Ga] / [[In] + [Zn] + [Ga] + [Ti]] = 0.144 Indium nitrate (In (NO ₃ ) ₃ ), zinc nitrate (Zn (NO ₃ ) ₂ ), gallium nitrate, so that [Ti] / [[In] + [Zn] + [Ga] + [Ti]] = 0.056 (Ga (NO ₃ ) ₃ ). Titanium chloride (TiCl ₂ ) solution was mixed, ultrapure water was added and stirred at 50 ° C. for 12 hours to obtain an In / Zn / Ga / Ti mixed salt solution having a pH of 3.5, followed by the same method as in Example 1 to powder And a molded product were obtained and heated for 12 hours under an oxygen atmosphere of 1350 ° C. to obtain a sputtering target. As a result of elemental analysis using ICP on the target (sintered body) thus prepared

[In] / [[In] + [Zn] + [Ga] + [Ti]] = 0.3964, [Zn] / [[In] + [Zn] + [Ga] + [Ti]] = 0.4004,

[Ga] / [[In] + [Zn] + [Ga] + [Ti]] = 0.1474, [Ti] / [[In] + [Zn] + [Ga] + [Ti]] = 0.0558 As a result of measuring the density, it showed 6.35 g / cm 3 corresponding to 99.2% of the theoretical density at 1350 ° C., and the bulk resistance of the target was found to be 9.17 × 10 ⁻⁴ Pa · cm.

Example 5

53% by weight of indium oxide (In ₂ O ₃ ), 9% by weight of gallium oxide (Ga ₂ O ₃ ), 35.5% by weight of zinc oxide (ZnO) and 2.5% by weight of aluminum oxide (Al ₂ O ₃ ) Wet ball mills were mixed by mixing%, and the crushing medium used was a high purity alumina (Al ₂ O ₃ ) ball having a purity of 99.5% or more, and grinding / mixing was performed for 42 hours to obtain an average particle size distribution of 0.5 to 1.0 μm. It was found. Since the process was carried out in the same manner as in Example 3.

As a result of elemental analysis using ICP for the target (sintered body) thus prepared,

[In] / [[In] + [Zn] + [Ga] + [Al]] = 0.3923, [Zn] / [[In] + [Zn] + [Ga] + [Al]] = 0.4540,

[Ga] / [[In] + [Zn] + [Ga] + [Al]] = 0.1010, showing [Al] / [[In] + [Zn] + [Ga] + [Al]] = 0.0527 As a result of measuring the density, 6.18 g / cm 3 corresponding to 96.4% of the theoretical density was obtained, and the bulk resistance of the target was found to be 3.68 × 10 ⁻³ Pa · cm.

Comparative Example 1

A wet ball mill was conducted by mixing 45% by weight of indium oxide (In ₂ O ₃ ) having an purity of 99.99% or more, 15% by weight of zinc oxide (ZnO), and 40% by weight of zirconium oxide (ZrO ₂ ). Was used a high purity alumina (Al ₂ O ₃ ) ball with a purity of 99.5% or more, it was found that the grinding / mixing was carried out for 25 hours to have an average particle size distribution of 0.5 ~ 1.0㎛. Thereafter, the process was carried out in the same manner as in Example 1 to obtain a sputtering target. As a result of elemental analysis using ICP on the target (sintered body) thus prepared

[In] / [[In] + [Zn] + [Zr]] = 0.3835, [Zn] / [[In] + [Zn] + [Zr]] = 0.2305,

[Zr] / [[In] + [Zn] + [Zr]] = 0.3859, and the density measurement showed 5.88 g / cm3, which corresponds to 91% of theoretical density, and measured bulk resistance. The result was found to be 5.16 × 10 ⁻² Pa · cm.

The above results are shown in the following [Table 1].

As shown in Table 1, it can be seen that the target according to the present invention has a high density, and a sputtering target having excellent film quality using a DC sputter can be manufactured.

[Test Example 1] Preparation of semiconductor film with targets of Examples 3 and 4

The targets prepared in Examples 3 and 4 (100 mm × 100 mm × 7 mmT) were bonded to the backing plate, mounted on a DC sputtering device, and formed into 150 W under an Ar gas atmosphere of 0.35 Pa. The results are shown in FIGS. 2 and 3. . 2 and 3, it can be seen that an excellent oxide semiconductor film is formed from the target of the present invention.

1 is a schematic view showing a method for producing a target of the present invention by coprecipitation method.

2 shows the characteristics of the oxide semiconductor film using the target prepared in Example 3.

3 shows the characteristics of the oxide semiconductor film using the target prepared in Example 4.

Claims (6)

Indium oxide (In ₂ O ₃ ), zinc oxide (ZnO), and one or two or more kinds of third metal oxides selected from the group consisting of Groups IIIA, IIIB, and IVA; In) the atomic ratio of the metal is 0.1 to 0.6, the atomic ratio of the zinc (Zn) metal is 0.1 to 0.75, the atomic ratio of the third metal is 0.02 to 0.35, and the atomic ratio of gallium in the third metal is 0 to 0.2 of all metal elements. Composite metal oxide targets less than. The method according to claim 1, One or two or more kinds of third metals selected from the group consisting of Groups IIIA, IIIB, and IVA are scandium (Sc), yttrium (Y), lanthanum (La), titanium (Ti), zirconium (Zr), and hafnium (Hf), aluminum (Al) or gallium (Ga) composite metal oxide target. The method according to claim 1, A composite metal oxide target wherein said composite metal oxide target is synthesized from a single phase or a homogeneous oxide using three or more kinds of metal salts different from each other using a coprecipitation method. The method according to claim 3, The coprecipitation method a) preparing a solution containing at least three different metal salts, b) co-precipitating the metal hydroxide by adding alkali to the metal salt solution, c) separating and drying the precipitate, d) heat treating and pulverizing the heat treated powder, e) producing a target shaped body of a predetermined shape, and f) sintering and cooling the shaped body. The method according to any one of claims 1 to 4, The composite metal oxide target of which the sintered density of the said composite metal oxide target is 95% or more of theoretical density. An amorphous metal oxide semiconductor film formed by a sputtering method from the composite metal oxide target of claim 1.

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