JPWO2013103034A1 - Method for producing gallium hydroxide, method for producing gallium oxide powder, gallium oxide powder, sintered body of the gallium oxide, and sputtering target comprising the sintered body - Google Patents

Abstract

A method for producing gallium hydroxide, characterized in that liquid metal gallium is used as an anode and gallium hydroxide is crystallized by electrolysis in an aqueous ammonium nitrate solution. A method for producing gallium oxide powder, characterized in that gallium hydroxide is dried and roasted to obtain gallium oxide powder. The gallium hydroxide, gallium oxide powder, sintered body produced from the powder, and sputtering target that are easy to produce and can be produced at low cost, and are free from cracks and poor sintering in the target production process. Technology that can be applied to the manufacture of targets.

Description

  The present invention relates to a gallium oxide powder used as a raw material for producing a sputtering target, a method for producing a gallium hydroxide powder as a raw material for the gallium oxide powder, a sintered body using gallium oxide, and a sintered body sputtering target.

 In recent years, a thin film transistor using a transparent oxide semiconductor has been developed, and the transparent oxide semiconductor has attracted attention from the viewpoints of being capable of forming a film at a low temperature and having high mobility. Among them, In—Ga—Zn—O (hereinafter referred to as “IGZO”) materials containing indium, gallium, zinc, and oxygen as constituent elements, and Ga—Zn— containing gallium, zinc, and oxygen as constituent elements. O (hereinafter referred to as “GZO”)-based materials are promising.

 As a method for manufacturing the IGZO film or the GZO film, a sputtering method that is excellent in mass productivity is most appropriate. For this purpose, the IGZO target or the GZO target needs to have a high density. However, when a high-density IGZO target or GZO target is actually manufactured, products with a reduced density (lots) frequently occur, and further, problems such as target cracking and defective sintering occur. There were not a few.

 In order to solve such problems, efforts have been made to improve and improve the properties of the main raw material gallium oxide powder. For example, Patent Document 1 discloses that a gallium oxide powder having a sharp particle size distribution is obtained by advancing neutralization under specific conditions in the neutralization method in the presence of oxalic acid, and by using the powder, It is described that a high-density target can be obtained. However, oxalic acid is designated as a non-medicinal deleterious substance by the Poisonous and Deleterious Substances Control Law, and it is not preferable to use it for industrial production.

Non-Patent Document 1 discloses that α-type Ga ₂ O ₃ can be obtained by sintering crystalline α-GaOOH at 400 to 600 ° C. However, since a method of neutralizing gallium chloride with sodium hydroxide is adopted, chlorine and sodium will remain in the raw material powder, and will also remain in the sintered body produced using this. .

In Patent Document 2, metal gallium is dissolved in nitric acid to obtain an aqueous gallium nitrate solution, which is neutralized with aqueous ammonia, and the resulting precipitate is filtered, washed, dried, and then roasted at 600 ° C. The manufacture of gallium oxide powder is described.
However, since neutralization conditions are not optimized, a large amount of fine powder of 1 μm or less and coarse particles of about 100 μm or less are generated.

 Patent Document 3 discloses a method for producing gallium oxide by an electrolytic method. This method requires cooling the electrolyte to keep the gallium anode as a solid. For this reason, much electric power is required for cooling of electrolyte solution. In addition, even when the electrolyte is cooled, heat is always generated by energization, so the temperature of the electrode and its vicinity rises locally due to this heat generation. Is big. For this reason, there is a problem that stable operation is difficult and unsuitable for mass production.

JP-A-11-322335 Japanese Patent No. 4178485 Japanese Patent Laid-Open No. 10-273318

Taichi Sato et al. Thermochimica Acta 53, p.281-288 (1982)

 The present invention has been made in view of such circumstances, and its purpose is suitable for manufacturing a sputtering target necessary for forming a transparent semiconductor IGZO film or a GZO film by sputtering at high density. Another object of the present invention is to efficiently and easily produce and provide gallium oxide powder and gallium hydroxide therefor. In addition, in the production of IGZO targets and GZO targets, we have earnestly investigated the causes of density reduction, target cracking and poor sintering, and the frequency of occurrence of these problems is the inevitable impurity chlorine. Since the content of sodium is related to the content of sodium, it was necessary to reduce these.

In addition, in the conventional method for producing gallium oxide powder by the neutralization method, the amount and balance of ions in the bath are different between the initial stage and the final stage, the powder properties become unstable, and NOx is not dissolved during nitric acid leaching. There is a problem that the environmental load is extremely large due to the generation of a large amount and the neutralized solution is a high concentration nitrogen-based wastewater.
On the other hand, in the case of the electrolytic method, the bath pH is kept constant, and stable leaching is possible by electrolysis, and hydroxide precipitation is possible. Therefore, the powder properties are uniform, sinterability is improved, and electrolytic leaching is improved. NOx gas is not generated and the electrolyte solution can be used repeatedly, so that the amount of waste water itself can be reduced and the concentration of nitrogen in waste water can be reduced.
However, in the conventional electrolysis method, it is necessary to cool the electrolyte and keep the gallium anode as a solid, and energy is required for cooling the electrolyte. Further, since the temperature of the electrode and the vicinity thereof increases due to heat generation during electrolysis, there is a risk that the gallium anode melts and falls off, so that stable operation is difficult and unsuitable for mass production.

Based on this knowledge, the following inventions are provided.
(1) A method for producing gallium hydroxide, characterized in that liquid metal gallium is used as an anode and gallium hydroxide is crystallized by electrolysis in an aqueous ammonium nitrate solution.
(2) Electrolysis is carried out at an electrolyte solution temperature of 30 to 60 ° C., pH of 4 to 7 and electrolyte solution concentration of 0.5 to 2 mol / L. Production method.
(3) A method for producing a gallium oxide powder, wherein the gallium hydroxide produced in (1) or (2) is dried and roasted to obtain a gallium oxide powder.
(4) The chlorine content is 10 wtppm or less, the sodium content is 10 wtppm or less, the average particle size is 0.5 μm to 3 μm, the particle size distribution is 0.1 to 10 μm, and the BET specific surface area is 5 to ²⁰ m ² / g. A gallium oxide powder obtained by the production method as described in (3) above.
(5) A gallium oxide sintered body produced using the gallium oxide powder described in (4) above as a raw material.
(6) A gallium oxide sputtering target comprising the gallium oxide sintered body of (5) above.

Disadvantages of the conventional method for producing gallium oxide powder by the neutralization method, that is, the amount and balance of ions in the bath are different between the initial stage and the final stage, the powder properties become unstable, and NOx is not dissolved during nitric acid leaching. Due to the generation of a large amount and the neutralized solution is a high concentration nitrogen-based wastewater, it has the effect of eliminating the problem of an extremely large environmental load.
In addition, the disadvantages of the conventional electrolysis method are that the electrolyte solution needs to be cooled to keep the gallium anode solid, energy is required for cooling the electrolyte solution, and the temperature of the electrode and its vicinity increases. The present invention provides a new electrolysis method that eliminates the risk of the gallium anode melting and falling off. As a result, stable operation is possible and the mass productivity can be improved.

In addition, it is possible to reduce the chlorine content and sodium content of impurities that cause cracking of the target and poor sintering.
As a result, gallium oxide powder suitable for manufacturing a sputtering target necessary for forming a transparent semiconductor IGZO film or GZO film by a sputtering method at a high density, and gallium hydroxide therefor can be efficiently and easily manufactured. It has an excellent effect that it can be provided. Moreover, in the production of an IGZO target and a GZO target, there is an effect that it is possible to suppress the density from being reduced, or the target from being cracked or poorly sintered.

It is a schematic diagram which shows an example of the manufacturing method of the gallium hydroxide by electrolysis of this invention. 2 is an SEM image of Ga (OH) ₃ particles crystallized in the solution of Example 1. FIG. 4 is a SEM image of Ga (OH) ₃ particles crystallized in the solution of Comparative Example 1.

A typical application of gallium oxide is a sputtering target. In order to use it as a target, high purity is required to improve film properties and sintering properties after sputtering.
When hydrochloric acid, sodium hydroxide, or the like is used, it is difficult to clean impurities, and nitric acid leaching ammonia neutralization is mainly known as a production method for high purity.
However, in the neutralization method, the amount and balance of ions in the bath are different between the initial and final stages of the reaction, and the powder properties may be unstable. In addition, there is a problem that the environmental load is extremely large due to the large amount of NOx generated during leaching of nitric acid and the post-neutralization liquid being a high concentration nitrogen-based wastewater.

 On the other hand, in the case of the electrolytic method, the pH of the bath is kept constant, and stable leaching is possible by electrolysis and hydroxide precipitation is possible, so that the powder properties are uniform and the sinterability is improved. NOx gas is not generated in electrolytic leaching. In addition, since the electrolytic solution can be used repeatedly, the amount of waste water itself can be reduced and the concentration of nitrogen in waste water can be reduced.

 Patent Document 3 discloses a method for producing gallium oxide by electrolysis. As described above, it is necessary to cool the electrolyte and keep the gallium anode as a solid, and energy is required for cooling the electrolyte. And Further, since the temperature of the electrode and the vicinity thereof increases due to heat generation during electrolysis, there is a risk that the gallium anode melts and falls off, so that stable operation is difficult and unsuitable for mass production.

 The present invention employs an electrolysis method, but the gallium hydroxide production method of the present invention is a method of crystallizing gallium hydroxide by electrolysis in an aqueous ammonium nitrate solution using liquid metal gallium as an anode. is there. That is, the anode does not use a solid, but uses liquid gallium as the anode.

An example of the method for producing gallium hydroxide by electrolysis according to the present invention is shown in FIG. As shown in FIG. 1, liquid metal gallium 1 exists in the lower part of the electrolytic cell, and this liquid gallium 1 serves as an anode. Reference numeral 2 denotes a current-carrying metal. Reference numeral 3 denotes a cathode.
Gallium hydroxide 6 is crystallized in the electrolytic solution (ammonium nitrate aqueous solution) 5 by electrolysis. Reference numeral 4 denotes an insulating portion. The energizing metal 2 is made of a material that does not dissolve in gallium and has good wettability with liquid metal gallium, but is not particularly limited as long as it has these properties.

 As a result, there is no need to cool the electrolytic solution and keep the gallium anode as a solid, and there is an advantage that the gallium anode can be stably operated without the risk of melting and dropping. This is a novel idea that is not disclosed in the prior art. Further, since the neutralization method is not adopted, there is no problem in sinterability, and it is an excellent method in that there is no environmental load (generation of nitrogen-based wastewater and NOx).

That is, in the electrolysis method, NOx gas is not generated and the electrolytic solution can be used repeatedly, so that the amount of waste water can be reduced and the concentration of nitrogen in the waste water can be reduced.
In order to produce gallium oxide, a method is employed in which gallium hydroxide is prepared in advance and baked to obtain gallium oxide. Therefore, high purity is achieved in the manufacturing process of gallium hydroxide.

In the production of the gallium hydroxide, it is preferable to electrolyze the electrolytic solution at a temperature of 30 to 60 ° C., a pH of 4 to 7, and an electrolytic solution concentration of 0.5 to 2 mol / L. Usually manufactured in this range.
If the liquid temperature is too low, gallium solidifies, making stable production difficult. In addition, if liquid gallium exists within a range that does not hinder electrolysis, no particular problem will occur even if it is partially solidified in the electrolytic cell.

 On the other hand, if it is too high, the electrolytic solution and ammonia are largely volatilized, which increases the consumption of chemicals. Further, if the temperature is higher than necessary, the heating equipment for maintaining the liquid temperature is increased in size or the material of the equipment is limited. Therefore, the liquid temperature of the electrolytic solution is desirable. If the pH is too high, the particles aggregate and the sinterability deteriorates. If the pH is too low, gallium hydroxide will be chemically dissolved and the yield will be reduced, so the above range is preferred.

As for the electrolytic solution concentration, if the concentration is too high, the particles agglomerate and the sinterability is deteriorated. Nitric acid and aqueous ammonia are added to cope with this pH fluctuation, but at this time, it becomes easy to add more than necessary, so the pH becomes unstable. For this reason, it is a preferable condition to set it as said range.
However, depending on the amount and conditions to manufacture, it may be outside this range, and some changes are allowed.

Next, the crystallized Ga (OH) ₃ particles are subjected to solid-liquid separation, and then dried at about 120 ° C. to obtain GaO (OH). Next, this is baked at 400 ° C. or higher for 1 to 10 hours to obtain gallium oxide (Ga ₂ O ₃ ) powder. The upper limit of the roasting temperature is not limited by changes in physical properties, but is preferably set to 1200 ° C. or less from the viewpoint of the material and life of the equipment.

Accordingly, the chlorine content is 10 wtppm or less, the sodium content is 10 wtppm or less, the average particle size is 0.5 μm to 3 μm, the particle size distribution is 0.1 to 10 μm, and the BET specific surface area is 5 to ²⁰ m ² / g. A certain gallium oxide powder can be manufactured. In order to avoid the influence on the decrease in density due to impurities, it is desirable to use a raw material having a purity of 4N or higher. This purity excludes impurities inevitably contained.

When the content of chlorine and sodium exceeds 10 wtppm, the BET specific surface area of the gallium oxide (Ga ₂ O ₃ ) powder becomes low, which is not preferable. On the other hand, since chlorine and sodium are inevitable impurities, they cannot be completely removed, but it is preferable to reduce them as much as possible. An average particle size of 0.5 μm to 3 μm, a particle size distribution of 0.1 to 10 μm, and a BET specific surface area of 5 to ²⁰ m ² / g are conditions that can improve the sinterability, and are preferable. It is in the form of gallium oxide powder. In the present invention, gallium oxide powder having these preferable conditions can be produced.

Further, the gallium oxide powder of the present invention can have an α-type or β-type crystal structure. In addition to α-type or β-type, gallium oxide has γ-type, δ-type, and ε-type crystal structures.
When sintering using gallium oxide powder, α-type or β-type gallium oxide powder which is usually mass-productive is used, but powders of other crystal structures can also be used. The phase structure of the (α, β) gallium oxide powder can be arbitrarily obtained by adjusting the roasting temperature. When gallium oxide powder having these phase structures is sintered, it is usually transformed into a β phase.

 A gallium oxide sintered body can be produced using the gallium oxide powder described above as a raw material, and a gallium oxide sputtering target made of the gallium oxide sintered body, for example, In—Ga—Zn—O (IGZO) -based oxidation. It is useful as an object sintered compact target and a Ga-Zn-O (GZO) -based oxide sintered compact target.

As described above, the oxide sintered body sputtering target of the present invention has a chlorine content of 10 wtppm or less, a sodium content of 10 wtppm or less, an average particle size of 0.5 μm to 3 μm, and a particle size distribution of 0.1 to 0.1 μm. 10 μm, a BET specific surface area of 5 to ²⁰ m ² / g, and a gallium oxide powder whose crystal structure is α-type is used as a raw material. By using this gallium oxide powder, oxidation is performed in the target manufacturing process. There is no generation of cracks and poor sintering due to gallium, and a high-density sputtering target can be easily manufactured.

 The oxide sintered compact sputtering target of the present invention can be applied to all targets containing the gallium oxide as a target component. Therefore, it will be easily understood that there are no particular restrictions on other components and contents.

  Hereinafter, description will be made based on Examples and Comparative Examples. In addition, a present Example is an example to the last, and is not restrict | limited at all by this example. In other words, the present invention is limited only by the scope of the claims, and includes various modifications other than the examples included in the present invention.

In the following examples and comparative examples, various measurements and evaluations are required, and the conditions are shown below.
(Measurement of particle size distribution)
The particle size distribution was measured using a particle size distribution measuring device (manufactured by Nikkiso Co., Ltd., Microtrac MT3000).
(Measurement of specific surface area)
The specific surface area (BET) was measured by an automatic surface area meter beta soap (manufactured by Nikkiso Co., Ltd., MODEL-4200).

Example 1
Liquid metal gallium having a purity of 4N was placed in an electrolytic cell as shown in FIG. 1, and electrolysis was performed using an aqueous ammonium nitrate solution as the electrolytic solution. At this time, the temperature of the electrolytic solution was 30 ° C., the pH was 6, and the concentration of the electrolytic solution was 1.0 mol / L.
As another condition, the DSE as current-carrying material to the anode, using a Ti cathode, and a current density of 10A / dm ^2.

Thereby, Ga (OH) ₃ crystallized in the solution was obtained. An SEM image of the crystallized particles is shown in FIG. As shown in FIG. 2, finely dispersed particles were obtained. Next, this Ga (OH) ₃ was subjected to suction filtration for solid-liquid separation, and then dried at about 120 ° C. to obtain GaO (OH). Next, this dried powder was roasted at about 1000 ° C. for 4 hours to produce a gallium oxide powder.

As a result, the chlorine and sodium contents in the gallium oxide powder were below the detection limit, that is, less than 10 wtppm. Further, the BET specific surface area was as high as 12.58 m ² / g, and the average particle size obtained from the particle size distribution was 0.83 μm, which was within the range of the present invention. The crystals of the roasted powder were in the β phase (β type).

Moreover, when the (111) composition of the IGZO sintered compact target was manufactured using the obtained gallium oxide powder as a manufacturing raw material and the density was measured, the Archimedes density was 6.25 g / cm ³ and the high density. This is considered to be due to the fact that the obtained gallium oxide has good pulverization properties and is easy to mix and pulverize in the sintering operation. The results are shown in Table 1.

(Example 2)
In the same manner as in Example 1, liquid metal gallium having a purity of 4N was placed in an electrolytic cell as shown in FIG. 1, and electrolysis was performed using an aqueous ammonium nitrate solution as the electrolytic solution. The temperature of the electrolytic solution at this time was 40 ° C., the pH was 4, and the concentration of the electrolytic solution was 1.0 mol / L.
As another condition, the DSE as current-carrying material to the anode, using a Ti cathode, and a current density of 10A / dm ^2.

Thereby, Ga (OH) ₃ crystallized in the solution was obtained. Similar to Example 1, finely dispersed particles were obtained. Next, this Ga (OH) ₃ was subjected to suction filtration for solid-liquid separation, and then dried at about 120 ° C. to obtain GaO (OH). Next, this dried powder was roasted at about 1000 ° C. for 4 hours to produce a gallium oxide powder.

As a result, the chlorine and sodium contents in the gallium oxide powder were below the detection limit, that is, less than 10 wtppm. Further, the BET specific surface area was as high as 10.72 m ² / g, and the average particle size obtained from the particle size distribution was 0.86 μm, which was within the range of the present invention. The crystals of the roasted powder were in the β phase (β type).

Moreover, when the (111) composition of the IGZO sintered compact target was manufactured using the obtained gallium oxide powder as a manufacturing raw material and the density was measured, the Archimedes density was 6.25 g / cm ³ and the high density. This is considered to be due to the fact that the obtained gallium oxide has good pulverization properties and is easy to mix and pulverize in the sintering operation. The above results are similarly shown in Table 1.

(Example 3)
In the same manner as in Example 1, liquid metal gallium having a purity of 4N was placed in an electrolytic cell as shown in FIG. 1, and electrolysis was performed using an aqueous ammonium nitrate solution as the electrolytic solution. The temperature of the electrolytic solution at this time was 40 ° C., the pH was 7, and the concentration of the electrolytic solution was 1.0 mol / L.
As another condition, the DSE as current-carrying material to the anode, using a Ti cathode, and a current density of 10A / dm ^2.

Thereby, Ga (OH) ₃ crystallized in the solution was obtained. Similar to Example 1, finely dispersed particles were obtained. Next, this Ga (OH) ₃ was subjected to suction filtration for solid-liquid separation, and then dried at about 120 ° C. to obtain GaO (OH). Next, this dried powder was roasted at about 1000 ° C. for 4 hours to produce a gallium oxide powder.

As a result, the chlorine and sodium contents in the gallium oxide powder were below the detection limit, that is, less than 10 wtppm. The BET specific surface area was as high as 8.73 m ² / g, and the average particle size obtained from the particle size distribution was 1.06 μm, which was within the range of the present invention. The crystals of the roasted powder were in the β phase (β type).

Moreover, when the (111) composition of the IGZO sintered compact target was manufactured and the density was measured using the obtained gallium oxide powder as a manufacturing raw material, the Archimedes density was 6.26 g / cm ³ and the high density. This is considered to be due to the fact that the obtained gallium oxide has good pulverization properties and is easy to mix and pulverize in the sintering operation. The above results are similarly shown in Table 1.

Example 4
In the same manner as in Example 1, liquid metal gallium having a purity of 4N was placed in an electrolytic cell as shown in FIG. 1, and electrolysis was performed using an aqueous ammonium nitrate solution as the electrolytic solution. The temperature of the electrolytic solution at this time was 40 ° C., the pH was 6, and the concentration of the electrolytic solution was 0.5 mol / L.
As another condition, the DSE as current-carrying material to the anode, using a Ti cathode, and a current density of 10A / dm ^2.

Thereby, Ga (OH) ₃ crystallized in the solution was obtained. Similar to Example 1, finely dispersed particles were obtained. Next, this Ga (OH) ₃ was subjected to suction filtration for solid-liquid separation, and then dried at about 120 ° C. to obtain GaO (OH). Next, this dried powder was roasted at about 1000 ° C. for 4 hours to produce a gallium oxide powder.

As a result, the chlorine and sodium contents in the gallium oxide powder were below the detection limit, that is, less than 10 wtppm. The BET specific surface area was as high as 10.46 m ² / g, and the average particle size obtained from the particle size distribution was 0.91 μm, which was within the range of the present invention. The crystals of the roasted powder were in the β phase (β type).

Moreover, when the (111) composition of the IGZO sintered compact target was manufactured using the obtained gallium oxide powder as a manufacturing raw material and the density was measured, the Archimedes density was 6.27 g / cm ³ and the high density. This is considered to be due to the fact that the obtained gallium oxide has good pulverization properties and is easy to mix and pulverize in the sintering operation. The above results are similarly shown in Table 1.

(Example 5)
In the same manner as in Example 1, liquid metal gallium having a purity of 4N was placed in an electrolytic cell as shown in FIG. 1, and electrolysis was performed using an aqueous ammonium nitrate solution as the electrolytic solution. The temperature of the electrolytic solution at this time was 50 ° C., the pH was 6, and the concentration of the electrolytic solution was 2.0 mol / L.
As another condition, the DSE as current-carrying material to the anode, using a Ti cathode, and a current density of 10A / dm ^2.

Thereby, Ga (OH) ₃ crystallized in the solution was obtained. Similar to Example 1, finely dispersed particles were obtained. Next, this Ga (OH) ₃ was subjected to suction filtration for solid-liquid separation, and then dried at about 120 ° C. to obtain GaO (OH). Next, this dried powder was roasted at about 1000 ° C. for 4 hours to produce a gallium oxide powder.

As a result, the chlorine and sodium contents in the gallium oxide powder were below the detection limit, that is, less than 10 wtppm. Further, the BET specific surface area was as high as 7.85 m ² / g, and the average particle size obtained from the particle size distribution was 1.41 μm, which was within the range of the present invention. The crystals of the roasted powder were in the β phase (β type).

Moreover, when the (111) composition of the IGZO sintered compact target was manufactured using the obtained gallium oxide powder as a manufacturing raw material and the density was measured, the Archimedes density was 6.25 g / cm ³ and the high density. This is considered to be due to the fact that the obtained gallium oxide has good pulverization properties and is easy to mix and pulverize in the sintering operation. The above results are similarly shown in Table 1.

(Example 6)
In the same manner as in Example 1, liquid metal gallium having a purity of 4N was placed in an electrolytic cell as shown in FIG. 1, and electrolysis was performed using an aqueous ammonium nitrate solution as the electrolytic solution. The temperature of the electrolytic solution at this time was 40 ° C., the pH was 5, and the concentration of the electrolytic solution was 1.0 mol / L.
As another condition, the DSE as current-carrying material to the anode, using a Ti cathode, and a current density of 10A / dm ^2.

Thereby, Ga (OH) ₃ crystallized in the solution was obtained. Similar to Example 1, finely dispersed particles were obtained. Next, this Ga (OH) ₃ was subjected to suction filtration for solid-liquid separation, and then dried at about 120 ° C. to obtain GaO (OH). Next, this dried powder was baked at about 500 ° C. for 4 hours to produce a gallium oxide powder.

As a result, the chlorine and sodium contents in the gallium oxide powder were below the detection limit, that is, less than 10 wtppm. The BET specific surface area was as high as 19.83 m ² / g, and the average particle size obtained from the particle size distribution was 0.55 μm, which was within the range of the present invention. The crystals of the roasted powder were α phase (α type).

Moreover, when the (111) composition of the IGZO sintered compact target was manufactured and the density was measured using the obtained gallium oxide powder as a manufacturing raw material, the Archimedes density was 6.26 g / cm ³ and the high density. This is considered to be due to the fact that the obtained gallium oxide has good pulverization properties and is easy to mix and pulverize in the sintering operation. The above results are similarly shown in Table 1.

(Comparative Example 1)
In the same manner as in Example 1, liquid metal gallium having a purity of 4N was placed in an electrolytic cell as shown in FIG. 1, and electrolysis was performed using an aqueous ammonium nitrate solution as the electrolytic solution. The temperature of the electrolytic solution at this time was 30 ° C., the pH was 6, and the concentration of the electrolytic solution was 4.0 mol / L. The concentration of the electrolytic solution is outside the conditions of the present application.
As another condition, the DSE as current-carrying material to the anode, using a Ti cathode, and a current density of 10A / dm ^2.

Thereby, Ga (OH) ₃ crystallized in the solution was obtained. An SEM image of the crystallized particles is shown in FIG. As shown in FIG. 3, agglomerated particles were obtained. Next, this Ga (OH) ₃ was subjected to suction filtration for solid-liquid separation, and then dried at about 120 ° C. to obtain GaO (OH). Next, this dried powder was roasted at about 1000 ° C. for 4 hours to produce a gallium oxide powder.

As a result, the chlorine and sodium contents in the gallium oxide powder were below the detection limit, that is, less than 10 wtppm. Further, the BET specific surface area was as low as 1.02 m ² / g, and the average particle size obtained from the particle size distribution was 32.92 μm, which was greatly deviated from the scope of the present invention.

When the (111) composition of the IGZO sintered compact target was manufactured using the obtained gallium oxide powder as a manufacturing raw material and the density was measured, the Archimedes density decreased to 6.05 g / cm ³ . This is considered to be the effect that the obtained gallium oxide has poor grindability and mixing and grinding are not sufficient in the sintering operation. The above results are similarly shown in Table 1.

(Comparative Example 2)
In the same manner as in Example 1, liquid metal gallium having a purity of 4N was placed in an electrolytic cell as shown in FIG. 1, and electrolysis was performed using an aqueous ammonium nitrate solution as the electrolytic solution. At this time, the temperature of the electrolytic solution was 30 ° C., the pH was 9, and the concentration of the electrolytic solution was 2.0 mol / L. The pH in this case is outside the conditions of the present application.
As another condition, the DSE as current-carrying material to the anode, using a Ti cathode, and a current density of 10A / dm ^2.

Thereby, Ga (OH) ₃ crystallized in the solution was obtained. The crystallized particles were agglomerated as in Comparative Example 1. Next, this Ga (OH) ₃ was subjected to suction filtration for solid-liquid separation, and then dried at about 120 ° C. to obtain GaO (OH). Next, this dried powder was roasted at about 1000 ° C. for 4 hours to produce a gallium oxide powder.

As a result, the chlorine and sodium contents in the gallium oxide powder were below the detection limit, that is, less than 10 wtppm. Further, the BET specific surface area was 3.77 m ² / g, and the average particle size obtained from the particle size distribution was 10.39 μm, which deviated from the present invention.

When the (111) composition of the IGZO sintered compact target was manufactured using the obtained gallium oxide powder as a raw material and the density was measured, the Archimedes density decreased to 6.13 g / cm ³ . This is considered to be the effect that the obtained gallium oxide has poor grindability and mixing and grinding are not sufficient in the sintering operation. The above results are similarly shown in Table 1.

The present invention uses a liquid metal gallium as an anode and gallium hydroxide produced by crystallizing gallium hydroxide by electrolysis in an aqueous ammonia nitrate solution, and using this powder as a starting material, the target has a high density. It is possible to prevent cracking and sintering failure during the manufacturing process of the target, further suppress the generation of nodules during sputtering, suppress abnormal discharge, and enable stable sputtering. Has an excellent effect.
The gallium oxide powder produced according to the present invention is particularly useful for producing an In—Ga—Zn—O (IGZO) -based or Ga—Zn—O (GZO) -based sputtering target and has industrial utility value. Is expensive.

1: Anode (liquid metallic gallium)
2: Metal for energization to the anode 3: Cathode 4: Insulating part 5: Electrolytic solution (ammonium nitrate aqueous solution)
6: Gallium hydroxide

Claims (6)

  A method for producing gallium hydroxide, characterized in that liquid metal gallium is used as an anode and gallium hydroxide is crystallized by electrolysis in an aqueous ammonia nitrate solution.   2. The method for producing gallium hydroxide according to claim 1, wherein the electrolytic solution is electrolyzed at a temperature of 30 to 60 ° C., a pH of 4 to 7 and an electrolyte concentration of 0.5 to 2 mol / L.   A method for producing a gallium oxide powder, comprising drying and roasting the gallium hydroxide produced in claim 1 or 2 to obtain a gallium oxide powder. The chlorine content is 10 wtppm or less, the sodium content is 10 wtppm or less, the average particle size is 0.5 μm to 3 μm, the particle size distribution is 0.1 to 10 μm, and the BET specific surface area is 5 to ²⁰ m ² / g. A gallium oxide powder obtained by the production method according to claim 3.   A gallium oxide sintered body produced using the gallium oxide powder according to claim 4 as a raw material.   A gallium oxide sputtering target comprising the gallium oxide sintered body according to claim 5.