JP2010018457A - Oxide sintered compact, and sputtering target composed of the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an oxide sintered compact and a sputtering target having a low bulk resistance and a high density, and a transparent amorphous oxide semiconductor film wherein a metal thin film can be etched selectively. <P>SOLUTION: The oxide sintered compact contains a spinel compound represented by an AB<SB>2</SB>O<SB>4</SB>-type compound composed of zinc oxide, gallium oxide and tin oxide, and having a lattice constant which is a middle one between the lattice constant of a spinel compound represented by ZnGa<SB>2</SB>O<SB>4</SB>and the lattice constant of a spinel compound represented by Zn<SB>2</SB>SnO<SB>4</SB>. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an oxide sintered body, a method for producing the same, a sputtering target obtained using the same, and a transparent amorphous semiconductor thin film produced therefrom.

  In recent years, the development of display devices has been remarkable, and various display devices such as liquid crystal display devices and EL display devices have been actively introduced into office automation equipment such as personal computers and word processors. Each of these display devices has a sandwich structure in which a display element is sandwiched between transparent conductive films.

  Currently, silicon-based semiconductor films dominate switching elements for driving these display devices. This is because the silicon-based thin film has good stability and processability, and has a high switching speed. This silicon-based thin film is generally produced by a chemical vapor deposition method (CVD) method.

  However, when the silicon thin film is amorphous, the switching speed is relatively slow, and there is a problem that an image cannot be displayed when displaying a high-speed moving image or the like. In the case of a crystalline silicon-based thin film, the switching speed is relatively fast, but crystallization requires a high temperature of 800 ° C. or higher, heating with a laser, and the like. I need it.

  Patent Document 1 discloses a transparent semiconductor film made of zinc oxide and magnesium oxide as a transparent semiconductor film that is more stable than a silicon-based thin film and has a light transmittance equivalent to that of an ITO (indium tin oxide) film. A transparent semiconductor film made of indium, gallium oxide, and zinc oxide has been proposed. Furthermore, a sputtering target containing each component is disclosed as a sputtering target for obtaining such a transparent semiconductor film.

  However, these transparent semiconductor films have very high etchability with a weak acid, but are also etched with a metal thin film etchant. Therefore, when the metal thin film on the transparent semiconductor film is etched, the metal thin film may be etched at the same time, which is inappropriate when only the metal thin film on the transparent semiconductor film is selectively etched.

On the other hand, in order to produce a transparent conductive film, a sputtering target made of zinc oxide-tin oxide has also been proposed.
For example, Patent Document 2 or the like, it is described that the compound consisting of Zn ₂ SnO ₄ is observed. However, the specific resistance of the obtained target is as high as several kΩcm. In addition, a thin film formed using this target is transparent and has been difficult to use as an oxide semiconductor.

Patent Document 3 discloses a transparent semiconductor film made of gallium oxide and zinc oxide. However, since the sputtering target used to form this film has a high bulk resistance, abnormal discharge such as arc discharge occurs during sputtering, and there is a possibility that the discharge cannot be performed.
JP 2004-119525 A JP 2007-277075 A JP 2007-123698 A

An object of the present invention is to provide a high-density oxide sintered body and a sputtering target with low bulk resistance.
An object of the present invention is to provide a transparent amorphous oxide semiconductor film that can be selectively etched with respect to a metal thin film.

The present invention provides the following oxide sintered bodies and the like.
1. Zinc oxide and gallium oxide consists of tin oxide, _AB 2 _{O 4} having an intermediate lattice constant between the lattice constant of the spinel compound represented by the lattice constant and _Zn 2 SnO ₄ spinel compound represented by ZnGa ₂ O ₄ An oxide sintered body containing a spinel compound represented by a mold compound.
2. _2. The oxide sintered body according to 1, comprising a ZnGa ₂ O ₄ compound doped with tin atoms.
3. 3. The oxide sintered body according to 1 or 2, comprising a Zn ₂ SnO ₄ compound doped with gallium atoms.
4). The atomic ratios are Zn / (Zn + Ga + Sn) = 0.2-0.8, Ga / (Zn + Ga + Sn) = 0.08-0.7, and Sn / (Zn + Ga + Sn) = 0.03-0.5. The oxide sintered body according to any one of the above.
5). A zinc compound, a gallium compound, and a tin compound are mixed at an atomic ratio of Zn: Ga: Sn = 0.2 to 0.8: 0.08 to 0.7: 0.03 to 0.5 to obtain a mixture. Obtaining a step;
Forming the mixture to obtain a molded product;
Sintering the molded article to obtain an oxide sintered body containing an AB ₂ O ₄ type compound.
The sputtering target which consists of an oxide sintered compact in any one of 6.1-4.
A transparent amorphous oxide semiconductor film obtained by sputtering the sputtering target according to 7.6.

According to the present invention, it is possible to provide a high-density oxide sintered body and sputtering target with low bulk resistance.
ADVANTAGE OF THE INVENTION According to this invention, the transparent amorphous oxide semiconductor film which can be selectively etched with respect to a metal thin film can be provided.

The oxide sintered body of the present invention comprises zinc oxide, gallium oxide, and tin oxide, and has a lattice constant of a spinel compound represented by ZnGa ₂ O ₄ and a lattice constant of a spinel compound represented by Zn ₂ SnO ₄ . An oxide (AB ₂ O ₄ type compound) (spinel compound) represented by the general formula AB ₂ O ₄ having an intermediate lattice constant is contained.

The lattice constant of the spinel compound represented by ZnGa ₂ O ₄ is 8.3349Å (ICDD No86-0415), and the lattice constant of the spinel compound represented by Zn ₂ SnO ₄ is 8.6574Å (ICDD No73-1725). It is. The AB ₂ O ₄ type compound has a lattice constant between these lattice constants of a value greater than 8.3349 and less than 8.6574.

The oxide sintered body of the present invention contains, for example, a ZnGa ₂ O ₄ compound doped with a tin element and / or a Zn ₂ SnO ₄ compound doped with a gallium atom.
The oxide sintered body of the present invention may consist essentially, Zn ₂ SnO ₄ compound ZnGa ₂ O ₄ compound and / or gallium atoms doped tin element is doped.
Here, the doping is not limited to solid solution substitution, but also includes interstitial solid solution in which atoms enter between the crystal lattices of the AB ₂ O ₄ type compound.

The sintered body of the present invention may contain SnO ₂ , ZnO, Ga ₂ O ₃ , Ga ₄ SnO ₈ , and ZnSnO ₃ in addition to the AB ₂ O ₄ type compound.

In the case of solid solution substitution, only Zn is present at the A site of Zn ₂ SnO ₄ type AB ₂ O ₄ , and Zn and Sn are present at the B site.
At this time, Ga can be substituted with the B site of Zn ₂ SnO ₄ type AB ₂ O ₄ . Therefore, the concentration of Ga, Ga is the _Zn 2 SnO ₄ was dissolved replaced is generated.

Further, in the A site of ZnGa ₂ O ₄ type _AB 2 _{O 4,} only Zn is present, B-site is composed of only Ga.
At this time, Sn can be substituted with the B site of ZnGa ₂ O ₄ type AB ₂ O ₄ . Therefore, ZnGa ₂ O ₄ in which Sn is solid solution substituted is generated depending on the Sn concentration.

When the sintered body of the present invention contains an AB ₂ O ₄ type compound, the bulk resistance is lowered. This is thought to be due to the fact that the crystal lattice is distorted, so that oxygen vacancies are likely to occur and the bulk resistance is lowered. In addition, oxygen deficiency occurs, the theoretical amount of oxygen does not exist, and it becomes a reducible sintered body. A sputtering target that can be stably sputtered is obtained from such a sintered body.

  The bulk resistance is preferably less than 100 Ωcm. More preferably, it is less than 5 ohm-cm, More preferably, it is less than 1 ohm-cm.

  In the oxide sintered body of the present invention, the relative density = (actual density) / (theoretical density) is preferably 90% or more, more preferably 95% or more and less than 100%. If the relative density is less than 90%, the bulk resistance of the resulting sputtering target becomes too high, and abnormal discharge such as arc discharge may occur during sputtering.

  The sintered body of the present invention can be suitably used as a sputtering target. For example, the sintered body is processed and polished to an appropriate size, bonded to a copper backing plate, and used as sputtering. The target is mounted on a sputtering apparatus, and a thin film is formed on the substrate by sputtering film formation under appropriate conditions. The thin film can be processed into a desired shape by etching.

  In the sintered body of the present invention, the composition of zinc, gallium and tin is atomic ratio: Zn / (Zn + Ga + Sn) = 0.2-0.8, Ga / (Zn + Ga + Sn) = 0.08-0.7, Sn /(Zn+Ga+Sn)=0.03 to 0.5 is preferable. The atomic ratio can be determined by ICP emission analysis.

If the composition of Zn is less than 0.2, the etching rate of the resulting thin film becomes too slow, and etching may not be possible with an organic acid. On the other hand, if it exceeds 0.8, the etching rate becomes too fast and cannot be controlled, and a desired etching pattern may not be obtained.
If the composition of Ga is less than 0.08, a ZnGa ₂ O ₄ compound doped with a desired tin element may not be obtained, and a sputtering target of a sintered body made of the oxide has a high bulk resistance and is stable. Sputtering may not be obtained. On the other hand, if it exceeds 0.7, the bulk resistance may also be high, and stable sputtering may not be obtained.
If the composition of Sn is less than 0.03, the effect of reducing the bulk resistance, which is the effect of adding tin, is small, the bulk resistance becomes high, and stable sputtering may not be obtained. If it exceeds 0.5, a ZnGa ₂ O ₄ compound doped with a desired tin element may not be obtained, and the density may not be increased. Also in this case, stable sputtering may not be obtained.

More preferable ranges of the composition are Zn / (Zn + Ga + Sn) = 0.3 to 0.7, Ga / (Zn + Ga + Sn) = 0.2 to 0.6, and Sn / (Zn + Ga + Sn) = 0.05 to 0.4. .
Further preferable ranges are Zn / (Zn + Ga + Sn) = 0.3 to 0.7, Ga / (Zn + Ga + Sn) = 0.2 to 0.6, and Sn / (Zn + Ga + Sn) = 0.1 to 0.4.

  Since the sintered body of the present invention contains gallium element (Ga), the band gap of the obtained thin film can be expanded and the transparency can be improved.

  Since the oxide sintered body of the present invention contains tin element (Sn), it can be easily controlled to have an arbitrary resistance, and stable discharge is possible when sputtering is performed using the obtained target. It becomes. When the concentration of tin element is higher than that of gallium oxide, the bulk resistance tends to decrease.

  Moreover, it becomes possible to control an etching rate by containing a tin element. When the concentration of tin element is higher than that of zinc oxide, the etching rate decreases, and when the concentration of tin element is low, the etching rate tends to increase, so the etching rate can be adjusted to an arbitrary value by adjusting the tin concentration. Can be adjusted.

  Furthermore, if the concentration of the tin element is higher than that of zinc oxide, it will be resistant (cannot be etched) to the mixed acid (phosphoric acid, acetic acid, nitric acid) that etches the metal wiring, and selective etching with the metal wiring will be possible. It tends to be possible.

The oxide sintered body of the present invention includes a step of mixing a zinc compound, a gallium compound, and a tin compound to obtain a mixture, a step of pressing the mixture to obtain a molded product, and sintering the molded product. And a step of obtaining an oxide sintered body containing an AB ₂ O ₄ type compound.

More specifically, the oxide sintered body of the present invention can be produced by the following method.
(1) Weighing, mixing, and crushing raw material oxide powder composed of indium oxide, gallium oxide and zinc oxide (mixing step)
(2) Optionally, a step of heat-treating the obtained mixture (calcination step)
(3) Process of molding the resulting mixture (molding process)
(4) Step of sintering the obtained molded body (sintering step)
(5) Step of reducing the obtained sintered body arbitrarily (reduction step)

Hereinafter, each step will be described.
(1) Mixing Step As the zinc compound, gallium compound, and tin compound, an oxide or an oxide (oxide precursor) that becomes an oxide after sintering can be used. An oxide is preferably used.

Zinc oxide precursor, gallium oxide precursor, and tin oxide precursor include zinc, gallium, tin sulfide, sulfate, nitrate, halide (chloride, bromide, etc.), carbonate, organic Acid salts (acetate, propionate, naphthenate, etc.), alkoxides (methoxide, ethoxide, etc.), organometallic complexes (acetylacetonate, etc.) and the like can be mentioned.
Among these, nitrates, organic acid salts, alkoxides, and organometallic complexes are preferably used in order to completely thermally decompose at low temperatures so that no impurities remain.

  The zinc compound, gallium compound, and tin compound are preferably mixed by a solution method (coprecipitation method) or a physical mixing method. A physical mixing method is more preferable.

  In the physical mixing method, the above-described zinc compound, gallium compound, and tin compound are put into a mixer such as a ball mill, roll mill, jet mill, pearl mill, or bead mill, and the compounds are mixed uniformly. The mixing time is preferably 1 to 200 hours. This is because homogenization tends to be insufficient if the time is less than 1 hour, and productivity decreases if the time exceeds 200 hours. A particularly preferred mixing time is 10 to 120 hours.

  It is preferable to mix using a ball mill, a roll mill, a pearl mill, a jet mill, a bead mill or the like so that the particle diameter is 0.01 to 1.0 μm. If the particle diameter is less than 0.01 μm, the powder tends to aggregate, handling becomes poor, and a dense sintered body is difficult to obtain. On the other hand, if it exceeds 1.0 μm, it is difficult to obtain a dense sintered body.

  The purity of each raw material is usually 99.9% by mass (3N) or more, preferably 99.99% by mass (4N) or more, more preferably 99.995% by mass or more, particularly preferably 99.999% by mass (5N). That's it. If the purity of each raw material is 99.9% by mass (3N) or more, the semiconductor characteristics are not deteriorated by impurities such as Fe, Al, Si, Ni, Cu, and the reliability can be sufficiently maintained. In particular, it is preferable that the Na content is less than 100 ppm because reliability is improved when a thin film transistor (TFT) is produced from the thin film of the present invention.

  The average particle diameter of the mixture obtained after mixing and pulverization is usually 10 μm or less, preferably 1 to 9 μm, particularly preferably 1 to 6 μm. When the average particle size is 10 μm or less, the density of the obtained sputtering target can be increased. Here, the average particle diameter can be measured by the method described in JIS R 1619.

(2) Calcination process This process is an optional process. A step of calcining the mixture after the mixing step and before the forming step may be included. By performing calcination, it becomes easy to increase the density of the finally obtained sputtering target.
In the calcination step, the mixture is usually heat treated at 500 to 1200 ° C. for 1 to 100 hours.
Furthermore, it is preferable to grind the calcined product obtained here before the subsequent molding step. The calcination is suitably pulverized using a ball mill, roll mill, pearl mill, jet mill or the like.

(3) Molding step Molding of the mixture is performed by die molding, casting molding, injection molding, or the like, but press molding is preferred in order to obtain a sintered body having a high sintering density. In particular, it is preferable to perform molding by CIP (cold isostatic pressure) or the like, and then sintering. Although a molded body having a desired shape can be obtained, various shapes suitable as a sputtering target can be obtained.

  During molding, a molding aid such as PVA (polyvinyl alcohol), MC (methyl cellulose), polywax, oleic acid, or the like may be used.

For the press molding, a known molding method such as a cold press method or a hot press method can be used. For example, the obtained mixed powder is filled in a mold and pressure-molded with a cold press machine. Pressure molding, for example, room temperature (25 ° C.) under, 100~100000kg / cm ^2, preferably, at a pressure of from 500~10000kg / cm ^2. Further, in the temperature profile, it is preferable that the temperature increase rate up to 1000 ° C. is 30 ° C./hour or more, and the temperature decrease rate during cooling is 30 ° C./hour or more.

(4) Sintering Step Sintering after molding is performed by atmospheric pressure firing, HIP (hot isostatic pressure) firing or the like. Sintering temperature, zinc compounds, gallium compounds, tin compounds are reacted may be any temperature or higher to generate the ZnGa ₂ O ₄ or _{Zn AB} 2 _{O 4} type compounds such as 2 SnO _4, usually 1200 to 1500 ° C. preferable. If the temperature exceeds 1500 ° C., zinc oxide is sublimated and the composition shifts, which is not preferable. A particularly preferable sintering temperature is 1300 to 1450 ° C. Although the sintering time depends on the sintering temperature, it is usually preferably 1 to 50 hours, particularly 2 to 30 hours.

Sintering may be performed in an oxidizing atmosphere, and examples of the oxidizing atmosphere include an atmosphere in which air or oxygen gas is introduced. In addition, it can also sinter under oxygen pressurization. In order to prevent sublimation of zinc oxide, it is preferable to carry out under oxygen inflow and oxygen pressurization.
By performing this manner sintered, Zn, as main components Ga and Sn, can be obtained oxide sintered body containing a spinel compound represented by AB ₂ O ₄ type compound.

(5) Reduction step This step is an optional step. By carrying out the reduction treatment, the bulk specific resistance of the sintered body can be made uniform. Examples of the reducing method include a method of circulating a reducing gas, a method of baking in a vacuum, and a method of baking in an inert gas. As the reducing gas, for example, hydrogen, methane, carbon monoxide, a mixed gas of these gases and oxygen, or the like can be used. As the inert gas, nitrogen, argon, a mixed gas of these gases and oxygen, or the like can be used.

  The sintered body of the present invention is processed into a shape suitable for mounting on a sputtering apparatus to obtain a sputtering target.

  A transparent amorphous oxide semiconductor film is obtained by sputtering this sputtering target.

  Examples of sputtering methods include RF magnetron sputtering, DC magnetron sputtering, AC magnetron sputtering, and pulsed DC magnetron sputtering.

  It is preferable to set the oxygen partial pressure during sputtering film formation to 1% or more and 20% or less. If it is less than 1%, the transparent amorphous film immediately after film formation may have conductivity, and it may be difficult to use it as an oxide semiconductor. On the other hand, if it exceeds 20%, the transparent amorphous film becomes an insulator, and it may be difficult to use it as an oxide semiconductor. Preferably, it is 3 to 10%.

  The substrate temperature during film formation is preferably from room temperature to 300 ° C. It is too costly to cool below room temperature, and it is too costly to exceed 300 ° C. Preferably, the temperature is from room temperature (no substrate heating) to 200 ° C. In the case of continuous sputtering, the substrate may be heated by the plasma being sputtered, and in the case of a film substrate or the like, it is preferable to carry out cooling while maintaining the temperature at about room temperature. In the case of forming a film on a heat resistant substrate such as a glass substrate, when the substrate is heated to 150 ° C. to 350 ° C. after sputtering, a transparent amorphous oxide semiconductor film can be stably and uniformly manufactured. If it is less than 150 degreeC, the stabilization effect will be small by heating, and if it exceeds 350 degreeC, heating may cost too much. 200 to 300 degreeC is preferable. The heating time is preferably 10 minutes to 120 minutes. If it is less than 10 minutes, the heating effect may not be seen, and if it exceeds 120 minutes, the heating time may be too long and the cost may be too high. 30 minutes to 90 minutes is preferred. The heating atmosphere is preferably an air atmosphere or an oxygen circulation atmosphere. In the case of an amorphous oxide semiconductor thin film, electron carriers present in the semiconductor thin film are considered to be generated by oxygen vacancies, and the concentration of electron carriers is considered to be proportional to the concentration of oxygen vacancies. Therefore, when the electron carrier concentration is controlled, it is necessary to control the oxygen deficiency concentration. When heat treatment is performed in an atmosphere having a higher oxygen concentration, the oxygen deficiency concentration can be reduced at a lower heating temperature, which is economical. However, when heated to a high temperature in pure oxygen, oxygen vacancies may disappear completely and become an insulator. A preferable oxygen concentration is 19% to 50%.

Since the sputtering target of the present invention contains an AB ₂ O ₄ type compound, the bulk resistance is low and the density is high. By increasing the density, the occurrence of yellow flakes, which are particles generated during sputtering, is suppressed, and abnormal discharge does not occur. In addition, it is considered that the occurrence of yellow flakes is suppressed and nodules deposited on the target are also suppressed. Therefore, abnormal discharge such as arc discharge does not occur during sputtering, and no black protrusions called nodules are generated on the target, so that a thin film free from massive foreign matters can be obtained.

  When massive foreign matters are generated, the etching is not performed at the time of etching, a desired pattern cannot be obtained, and the upper and lower wiring metals may be short-circuited by the foreign matters. Therefore, from the transparent amorphous oxide semiconductor manufactured using the sputtering target of the present invention, a highly reliable TFT element with improved yield can be obtained.

  The thin film thus obtained can be used as a semiconductor film for a thin film transistor, a thin film transistor channel layer, a solar cell, a gas sensor, or the like as it is or by heat treatment. If necessary, heat treatment is performed after film formation.

Examples of the present invention are shown below.
The measuring method of the characteristic of the obtained sintered compact and transparent film is as follows.
(1) The bulk resistance of the sintered body was determined using a Loresta made by Mitsubishi Chemical.
(2) The sintered density of the sintered body was determined as a relative density (measured density / theoretical density). The theoretical density was determined by dividing the theoretical density of the raw material to be mixed into the weight fraction and calculating the density of the mixture. The measured density was measured by the Archimedes method using water as a solvent.
(3) The dispersion state of Zn, Ga, and Sn in the sintered body was confirmed by EPMA measurement.
(4) The etching rate of the transparent film was calculated from the thickness of the thin film by dipping in an acid aqueous solution, measuring the dipping time and resistance, and setting the point at which the measured resistance was 2 MΩ or more as the etching end time.

Example 1
Zinc oxide 600 g, gallium oxide 100 g, and tin oxide 300 g were dispersed in ion-exchanged water, PVA as a granulating agent was also mixed, and pulverized and mixed in a ZrO ₂ bead mill.
The resulting slurry was dried and granulated by a spray dryer was charged resulting powder in a mold having a diameter of 140 mm, it was pre-molded at a pressure of 100 kg / cm ² by a die press molding machine. Next, after consolidation with a cold isostatic press molding machine at a pressure of 4 t / cm ² , sintering was performed at 1400 ° C. for 15 hours to obtain a sintered body.
The composition of this sintered body was Zn / (Zn + Ga + Sn) = 0.7, Ga / (Zn + Ga + Sn) = 0.1, and Sn / (Zn + Ga + Sn) = 0.2.

From the X-ray diffraction result of the obtained sintered body, the peak of Zn ₂ SnO ₄ was shifted to the peak side of Zn ₂ GaO ₄ and the lattice constant was 8.6146 （(FIG. 1).
The bulk resistance of the sintered body was 30 Ωcm. The dispersion state of Zn, Ga, and Sn was substantially uniform. The relative density of this sintered body was 95%.

  This sintered body was ground and polished to obtain a sputtering target having a diameter of 4 inches and a thickness of 5 mm.

The thin film formed using this target could be etched with an aqueous oxalic acid (4 wt%) solution, and the rate was 100 nm / min. In addition, etching was not possible with a mixed acid (phosphoric acid / acetic acid / nitric acid).
When sputtering was performed continuously for 10 hours, no abnormal discharge was observed. After sputtering, the target surface was observed to confirm the generation of nodules, but no nodules were observed.

Example 2
A sintered body was obtained in the same manner as in Example 1, except that 500 g of zinc oxide, 200 g of gallium oxide, and 300 g of tin oxide were used.
The composition of this sintered body was Zn / (Zn + Ga + Sn) = 0.6, Ga / (Zn + Ga + Sn) = 0.2, and Sn / (Zn + Ga + Sn) = 0.2.

From the X-ray diffraction result of the obtained sintered body, the peak of Zn ₂ SnO ₄ was shifted to the peak side of Zn ₂ GaO ₄ and the lattice constant was 8.5244Å (FIG. 2).
The bulk resistance of the sintered body was 3 Ωcm. The dispersion state of Zn, Ga, and Sn was substantially uniform. The relative density of this sintered body was 94%.

  This sintered body was ground and polished to obtain a sputtering target having a diameter of 4 inches and a thickness of 5 mm.

The thin film formed using this target could be etched with an aqueous oxalic acid (4 wt%) solution, and the rate was 50 nm / min. In addition, etching was not possible with a mixed acid (phosphoric acid / acetic acid / nitric acid).
When sputtering was performed continuously for 10 hours, no abnormal discharge was observed. After sputtering, the target surface was observed to confirm the generation of nodules, but no nodules were observed.

Example 3
A sintered body was obtained in the same manner as in Example 1, except that 400 g of zinc oxide, 300 g of gallium oxide, and 300 g of tin oxide were used.
The composition of this sintered body was Zn / (Zn + Ga + Sn) = 0.5, Ga / (Zn + Ga + Sn) = 0.3, and Sn / (Zn + Ga + Sn) = 0.2.

From X-ray diffraction results of the obtained sintered _body, the peak of Zn 2 SnO _{4 is,} Zn 2 GaO is shifted to the peak side of the _4, the peak of the Zn 2 GaO ₄ is to the peak side of _Zn 2 SnO ₄ compound The lattice constant was 8.4491 Å (FIG. 3).
The bulk resistance of this sintered body was 5 Ωcm. The dispersion state of Zn, Ga, and Sn was substantially uniform. The relative density of this sintered body was 91%.

  The sintered body was ground and polished to obtain a sputtering target having a diameter of 4 inches and a thickness of 5 mm.

The thin film formed using this target could be etched with an aqueous oxalic acid (4 wt%) solution, and the rate was 30 nm / min. In addition, etching was not possible with a mixed acid (phosphoric acid / acetic acid / nitric acid).
When sputtering was performed continuously for 10 hours, no abnormal discharge was observed. After sputtering, the target surface was observed to confirm the generation of nodules, but no nodules were observed.

Example 4
A sintered body was obtained in the same manner as in Example 1, except that 240 g of zinc oxide, 260 g of gallium oxide, and 430 g of tin oxide were used.
The composition of this sintered body was Zn / (Zn + Ga + Sn) = 0.33, Ga / (Zn + Ga + Sn) = 0.34, and Sn / (Zn + Ga + Sn) = 0.33.

From X-ray diffraction results of the obtained sintered body, the peaks obtained _is the peak of the Zn 2 SnO _4, its lattice constant is _8.3948A, located in the middle of the peak of the Zn 2 GaO ₄ I was able to confirm.
The bulk resistance of this sintered body was 0.9 Ωcm. The dispersion state of Zn, Ga, and Sn was substantially uniform. The relative density of this sintered body was 93%.

  The sintered body was ground and polished to obtain a sputtering target having a diameter of 4 inches and a thickness of 5 mm.

The thin film formed using this target could be etched with an aqueous oxalic acid (4 wt%) solution, and the rate was 10 nm / min. In addition, etching was not possible with a mixed acid (phosphoric acid / acetic acid / nitric acid).
When sputtering was performed continuously for 10 hours, no abnormal discharge was observed. After sputtering, the target surface was observed to confirm the generation of nodules, but no nodules were observed.

Example 5
A sintered body was obtained in the same manner as in Example 1, except that 200 g of zinc oxide, 450 g of gallium oxide, and 350 g of tin oxide were used.
The composition of this sintered body was Zn / (Zn + Ga + Sn) = 0.25, Ga / (Zn + Ga + Sn) = 0.50, and Sn / (Zn + Ga + Sn) = 0.25.

From the X-ray diffraction result of the obtained sintered body, the peak of Zn ₂ GaO ₄ was shifted to the peak side of the Zn ₂ SnO ₄ compound, and the lattice constant was 8.3382Å (FIG. 5).
The bulk resistance of this sintered body was 5 Ωcm. The dispersion state of Zn, Ga, and Sn was substantially uniform. The relative density of this sintered body was 90%.

  The sintered body was ground and polished to obtain a sputtering target having a diameter of 4 inches and a thickness of 5 mm.

The thin film formed using this target could be etched with an oxalic acid (4 wt%) aqueous solution, and the rate was 20 nm / min. In addition, etching was not possible with a mixed acid (phosphoric acid / acetic acid / nitric acid).
When sputtering was performed continuously for 10 hours, no abnormal discharge was observed. After sputtering, the target surface was observed to confirm the generation of nodules, but no nodules were observed.

Example 6
Using the sputtering target obtained in Example 3, a transparent amorphous oxide semiconductor film was produced as follows.
First, a substrate (glass plate with a thickness of 1.1 mm) was mounted on a pulsed DC magnetron sputtering apparatus (pulse is 150 KHz, On / Off = 50%), and the inside of the vacuum chamber was decompressed to 5 × 10 ⁻⁴ Pa or less. Thereafter, argon gas containing 8% oxygen was introduced to a vacuum pressure of 3 × 10 ⁻¹ Pa, and sputtering was performed under the conditions of an output of 100 W and a substrate temperature of room temperature to form a transparent film having a thickness of 50 nm.
After film formation, the film was annealed at 300 ° C. for 1 hour and then evaluated.

As a result of X-ray diffraction measurement, the obtained transparent film was confirmed to be amorphous.
The specific resistance of the transparent film was 10 ² Ωcm, a semiconductor film, and the visible light transmittance was 83.2%. It was found that the energy gap of the transparent amorphous oxide semiconductor film is 3.1 eV or more, is inactive to visible light, and can be used as a transparent TFT element.

It was found that the transparent amorphous oxide semiconductor film can be etched when immersed in a 4 wt% aqueous solution of oxalic acid such as amorphous ITO or IZO for 5 minutes at 40 ° C.
40 ° C., humidity resistance test after 1000 hours even resistivity no change 10 ² [Omega] cm at conditions of 90% RH, the transparent amorphous oxide semiconductor film, it was confirmed to have excellent moisture resistance.
The transparent amorphous oxide semiconductor film was immersed in an aluminum etching solution, phosphoric acid / acetic acid / nitric acid solution at 30 ° C. for 5 minutes, but no change was observed.
Furthermore, as a result of immersing the transparent amorphous oxide semiconductor film in a 3% aqueous sodium hydroxide solution at 30 ° C. for 5 minutes, it was revealed that the resistance value did not change and the alkali resistance was sufficient.

  Similarly, the transparent amorphous oxide semiconductor film obtained by using the sputtering target obtained in Examples 1, 2, 4 and 5 was immersed in the phosphoric acid / acetic acid / nitric acid solution at 30 ° C. for 5 minutes, but the change was observed. Was not seen. Moreover, it was found that the energy gap of these transparent amorphous oxide semiconductor films is 3.0 eV or more, is inactive to visible light, and can be used as a transparent TFT element.

  As described above, the transparent amorphous oxide semiconductor film of the example can be etched with the aqueous oxalic acid solution, but is not dissolved in the phosphoric acid / acetic acid / nitric acid solution. Therefore, Mo, Al, Cu, etc., which are wiring metals formed on the transparent amorphous oxide semiconductor film, can be processed with phosphoric acid, acetic acid, nitric acid solution, etc., but the transparent amorphous oxide semiconductor film Therefore, selective etching is possible, and a back channel etch type TFT can be formed.

Comparative Example 1
A sintered body was obtained in the same manner as in Example 1, except that 700 g of zinc oxide, 50 g of gallium oxide, and 250 g of tin oxide were used.
The composition of this sintered body was Zn / (Zn + Ga + Sn) = 0.57, Ga / (Zn + Ga + Sn) = 0.05, and Sn / (Zn + Ga + Sn) = 0.38.

From X-ray diffraction results of the obtained sintered body, the lattice constant of the sintered body is 8.6574Å the lattice constant of _Zn 2 SnO _4, the sintered body was confirmed to contain _Zn 2 SnO ₄ (FIG. 6).
The bulk resistance of this sintered body was 1 KΩcm. The dispersion state of Zn, Ga, and Sn was substantially uniform. Moreover, the relative density of this sintered compact was 90% or more.

  The sintered body was ground and polished to obtain a sputtering target having a diameter of 4 inches and a thickness of 5 mm.

The thin film formed using this target could be etched with an aqueous oxalic acid (4 wt%) solution, and the rate was 30 nm / min. In addition, etching was not possible with a mixed acid (phosphoric acid / acetic acid / nitric acid).
When sputtering was performed continuously for 10 hours, the occurrence of yellow flakes was confirmed, and several abnormal discharges were observed. After sputtering, the target surface was observed to confirm the generation of nodules, but the generation of several nodules was observed.

Furthermore, the thin film was obtained like Example 6 using the obtained target. This thin film had a specific resistance of 10 ⁻² Ωcm and was conductive.

Comparative Example 2
A sintered body was obtained in the same manner as in Example 1 except that 520 g of zinc oxide and 480 g of tin oxide were used.
The composition of the sintered body was Zn / (Zn + Ga + Sn) = 0.67, Ga / (Zn + Ga + Sn) = 0.00, and Sn / (Zn + Ga + Sn) = 0.33.

From the X-ray diffraction result of the obtained sintered body, it was confirmed that the sintered body had a lattice constant of 8.6574 which is the lattice constant of Zn ₂ SnO ₄ , and the sintered body was made of Zn ₂ SnO ₄ . .
The bulk resistance of this sintered body was 102 KΩcm. The relative density of this sintered body was 84%.

This sintered body was ground and polished to obtain a sputtering target having a diameter of 4 inches and a thickness of 5 mm.
A thin film formed using this target could be etched with an aqueous oxalic acid (4 wt%) solution, but could also be etched with a mixed acid (phosphoric acid / acetic acid / nitric acid).
Moreover, the target resistance was high, and sputtering discharge by DC was impossible.

A thin film obtained in the same manner as in Example 6 was obtained using the obtained target. This thin film had a specific resistance of 10 ⁻² Ωcm and was conductive.

  A sputtering target can be produced from the oxide sintered body of the present invention, and a thin film obtained from this sputtering target can be used as a semiconductor film of a semiconductor element. For example, it can be used as a semiconductor film for TFT, solar cell, gas sensor and the like.

2 is an X-ray diffraction chart of a sintered body obtained in Example 1. FIG. 3 is an X-ray diffraction chart of a sintered body obtained in Example 2. FIG. 3 is an X-ray diffraction chart of a sintered body obtained in Example 3. 6 is an X-ray diffraction chart of a sintered body obtained in Example 4. 6 is an X-ray diffraction chart of a sintered body obtained in Example 5. FIG. 3 is an X-ray diffraction chart of a sintered body obtained in Comparative Example 1.

Claims (7)

Zinc oxide and gallium oxide consists of tin oxide, _AB 2 _{O 4} having an intermediate lattice constant between the lattice constant of the spinel compound represented by the lattice constant and _Zn 2 SnO ₄ spinel compound represented by ZnGa ₂ O ₄ An oxide sintered body containing a spinel compound represented by a mold compound. The oxide sintered body according to claim 1, comprising a ZnGa ₂ O ₄ compound doped with tin atoms. Claim 1 or 2 The oxide sintered body according containing Zn ₂ SnO ₄ compounds gallium atoms doped.   2. The atomic ratio is Zn / (Zn + Ga + Sn) = 0.2-0.8, Ga / (Zn + Ga + Sn) = 0.08-0.7, Sn / (Zn + Ga + Sn) = 0.03-0.5. The oxide sintered body according to any one of to 3. A zinc compound, a gallium compound, and a tin compound are mixed at an atomic ratio of Zn: Ga: Sn = 0.2 to 0.8: 0.08 to 0.7: 0.03 to 0.5 to obtain a mixture. Obtaining a step;
Forming the mixture to obtain a molded product;
Sintering the molded article to obtain an oxide sintered body containing an AB ₂ O ₄ type compound.   A sputtering target comprising the oxide sintered body according to claim 1.   A transparent amorphous oxide semiconductor film obtained by sputtering the sputtering target according to claim 6.