JP2020152585A - Method of crushing gallium nitride - Google Patents

Abstract

To provide a method of crushing gallium nitride, capable of preventing gallium nitride from being contaminated with impurities, when a medium crusher is used for crushing.SOLUTION: The method of crushing gallium nitride comprises a step of crushing gallium nitride at a temperature lower than the melting point of gallium, using a medium crusher with the surface of a crushing medium and the inner surface of a crushing container coated with a gallium film.SELECTED DRAWING: None

Description

The present invention relates to a method for pulverizing gallium nitride.

Nitride powder such as gallium nitride is usually produced by pulverizing a nitride bulk with a pulverizing medium. However, impurities derived from the pulverization medium are likely to be mixed in when pulverizing the bulk. In fact, it has been reported that when silicon nitride bulk was ball-milled with silicon nitride balls, the sintering aid (8mass%, MgAl2O4) contained in the silicon nitride balls was mixed in and the silicon nitride was contaminated (non-patented). Document 1).

Conventionally, a technique for preventing contamination due to the mixing of impurities during crushing has been studied, and it has been reported that, for example, by coating a crushing container or a crushing medium with a resin, the mixing of metals and ceramics can be suppressed (Patent Document 1). ~ 3).

Jikkenhei 3-7940 Japanese Unexamined Patent Publication No. 2000-33282 JP-A-2002-121077

Journal of the Ceramic Society of Japan, 104, 4 (1996)

Nitride powders such as gallium nitride are used as semiconductor raw materials, and high-purity powders that are not contaminated with impurities are required. However, when a nitride having high hardness is pulverized by applying the methods described in Patent Documents 1 to 3, the resin is scraped or peeled off and mixed as an impurity. Since the resin mixed in the nitride is insoluble in acid or alkali, it cannot be removed by acid or alkali. Further, although the mixed resin can be removed by firing, it is difficult to remove the resin by firing because the nitride is oxidized at the same time.
An object of the present invention is to provide a method for pulverizing gallium nitride in which contamination of impurities is suppressed when pulverized using a medium pulverizer, and a method for producing high-purity gallium nitride and a method for producing high-purity pulverized gallium nitride. It is in.

The present inventors have found that the mixing of impurities can be suppressed by covering the surface of the crushing medium and the inner surface of the crushing container of the medium crushing apparatus with a gallium film and crushing gallium nitride by controlling the temperature at the time of crushing. It was.

That is, the present invention provides the following [1] to [6].
[1] A method for pulverizing gallium nitride, which comprises pulverizing gallium nitride at a temperature lower than the melting point of gallium by using a medium pulverizer in which the surface of the pulverization medium and the inner surface of the pulverization vessel are coated with a gallium film.
[2] The method for pulverizing gallium nitride according to the above [1], wherein after pulverization, the pulverized product is heated to a temperature equal to or higher than the melting point of gallium.
[3] The method for crushing gallium nitride according to the above [1] or [2], which is pulverized using a mill.
[4] The method for crushing gallium nitride according to any one of [1] to [3] above, wherein the average particle size of gallium nitride after pulverization is 30 μm or less.
[5] Gallium nitride is pulverized at a temperature lower than the melting point of gallium by using a medium pulverizer in which the surface of the pulverization medium and the inner surface of the pulverization vessel are coated with a gallium film, and the pulverized product is pulverized at a temperature equal to or higher than the melting point of gallium. A high-purity method of milled gallium nitride to heat.
[6] Gallium nitride is pulverized at a temperature lower than the melting point of gallium by using a medium pulverizer in which the surface of the pulverization medium and the inner surface of the pulverization vessel are coated with a gallium film, and the pulverized product is pulverized at a temperature equal to or higher than the melting point of gallium. A method for producing high-purity pulverized gallium nitride to be heated.

In the present specification, "high purity" means that the content of the elements of Group 14 of the periodic table and the elements of the 4th period of the periodic table is less than 15 parts by mass in gallium nitride, preferably less than 10 parts by mass. More preferably, it is 5 mass ppm.

According to the method for pulverizing gallium nitride of the present invention, contamination of impurities when pulverized using a medium pulverizer is suppressed and the pulverized gallium nitride can be highly purified. Therefore, high-purity pulverized gallium nitride can be produced by a simple operation. can do.

Hereinafter, the present invention will be described in detail.
The method for crushing gallium nitride of the present invention is to crush gallium nitride at a temperature lower than the melting point of gallium by using a medium crushing device in which the surface of the crushing medium and the inner surface of the crushing container are coated with a gallium film.

(Gallium nitride)
The gallium nitride may be a synthetic product from gallium or a commercially available product. As a method for synthesizing gallium nitride, a known method can be adopted.
Further, the gallium nitride may be a single crystal or a polycrystal, and a mixture thereof can be used.

(Crushing)
For crushing, a medium crushing device is used.
The medium crushing device is not particularly limited as long as it has a crushing container having a space inside and can be sealed, and a crushing medium arranged inside the crushing container.
The medium crushing device may be, for example, a rolling type, a vibration type or a planetary type, but the planetary type is preferable from the viewpoint of crushing speed and small particle size. Further, the medium crushing device may be a batch type or a continuous type.

Examples of the pulverizing medium include a rod-shaped medium (rod), a spherical medium (ball), and a cylindrical medium (ring), and one type or a combination of two or more of these can be used. Of these, a spherical medium is preferable from the viewpoint of pulverization speed and particle size reduction.
The size of the crushing medium can be appropriately selected according to the size of the crushing container. For example, in the case of a spherical medium, it is preferably 0.5 mm or more, more preferably 0.5 mm or more, from the viewpoint of improving the collision force and the crushing speed. It is 1 mm or more, more preferably 5 mm or more, preferably 40 mm or less, more preferably 30 mm or less, still more preferably 20 mm or less. The size of the spherical medium means the diameter of the sphere.
The material of the pulverization medium is not particularly limited as long as gallium nitride can be pulverized, and examples thereof include metals such as iron, high chrome steel, and stainless steel, alloys, and ceramics.

The shape of the space inside the container is preferably a cylindrical shape having a substantially circular bottom surface such as a perfect circle or an ellipse from the viewpoint of uniformly pulverizing.
The size of the container is not particularly limited as long as it can accommodate the pulverizing medium and pulverize gallium nitride. For example, when the above-mentioned spherical medium is used, the capacity of the container is preferably 10 to 25000 cc, more preferably 50 to 1000 cc. , More preferably 100 to 500 cc.
The material of the container may be the same as the material of the crushing medium.

Examples of such a medium crushing device include a mill. Specific examples include, for example, planetary ball mills, ball mills, disc mills, and the like.

In the medium crushing apparatus used in the present invention, the portion that comes into contact with gallium nitride during crushing is covered with a gallium film. That is, the surface of the pulverization medium is coated with a gallium film. Further, as long as the inner surface of the crushing container is at least coated with the gallium film, the other portion may be coated with the gallium film.
The coating method is not particularly limited, and examples thereof include immersion and vapor deposition. For example, gallium may be heated to a temperature equal to or higher than the melting point, for example, about 50 ° C., and the crushing medium and the crushing container may be immersed in the gallium solution. The immersion can be performed a plurality of times.

The crushing conditions can be appropriately set depending on the type of the medium crushing device and the production scale. For example, when crushing 1 kg of nitride with a mill, the rotation speed is usually 50 to 400 rpm for 1 to 60 minutes.
The crushing temperature is lower than the melting point of gallium. As a result, melting of gallium coated on the crushing medium and the crushing container can be prevented, and mixing of gallium into the crushed product can be suppressed.
In the present invention, since the melting point of gallium is about 30 ° C., the temperature at the time of pulverization is controlled so as not to exceed that temperature. For example, the crushing atmosphere temperature is set to be lower than the melting point of gallium, and the temperature inside the crushing container is controlled so as not to exceed the melting point of gallium while monitoring the temperature near the motor of the medium crushing device, which is the highest temperature during crushing. .. If there is a possibility that the crushing atmosphere temperature and the temperature inside the crushing container exceed the melting point of gallium, crushing may be temporarily suspended to cool, and crushing may be continued after cooling. The crushing atmosphere temperature and the temperature inside the crushing container are preferably 15 ° C. or lower, more preferably 10 ° C. or lower, and even more preferably 5 ° C. or lower.

The atmosphere at the time of pulverization is preferably an oxygen-free atmosphere. Examples of the oxygen-free atmosphere include an inert gas atmosphere, and specific examples thereof include a nitrogen gas atmosphere, an argon gas atmosphere, a nitrogen-hydrogen mixed gas atmosphere, and an argon-hydrogen mixed gas atmosphere. When a nitrogen-hydrogen mixed gas or an argon-hydrogen mixed gas is used, the hydrogen content is preferably 3 to 5% by volume.
To make the atmosphere at the time of crushing an oxygen-free atmosphere, for example, when a mill is used, the gas phase in the gallium film-coated pulverization vessel is replaced in the gallium-free atmosphere glove box, and then the pulverization vessel is charged. The gallium film-coated pulverization medium and gallium nitride may be contained, and the opening of the gallium film-coated pulverization container may be sealed.

(Post-processing)
After pulverization, the pulverized product can be heated to a temperature equal to or higher than the melting point of gallium.
The crushed product may contain gallium exfoliated from the crushing medium or crushing container as an impurity. Higher purity gallium nitride can be obtained by heating the pulverized product to a temperature equal to or higher than the melting point of gallium and melting and removing the gallium contained in the pulverized product. For example, the pulverized product can be placed on a sieve and gallium is heated to a temperature equal to or higher than the melting point, for example, about 50 ° C. to melt the gallium contained in the pulverized product and separate it into gallium nitride and gallium. The mesh size of the sieve is not particularly limited as long as gallium nitride and molten gallium can be separated, but is usually 10 to 500 meshes.
After the post-treatment, the recovered gallium nitride may be dried. The drying method is not particularly limited, and examples thereof include a hot air drying method and a cold air drying method.

The gallium nitride thus obtained is highly purified because the inclusion of impurities is suppressed. Specifically, the gallium nitride obtained by the method of the present invention contains elements of Group 14 of the periodic table and elements of the 4th period of the periodic table, usually less than 15 parts by mass, preferably less than 10 parts by mass, more preferably less than 10 parts by mass. It can be 5 mass ppm. The content of these elements can be measured using, for example, an ICP emission spectroscopic analyzer.

Further, the gallium nitride after pulverization preferably has an average particle diameter of 30 μm or less, more preferably 20 μm or less, and further preferably 10 μm or less. The lower limit of the average particle size is not particularly limited, but from the viewpoint of production efficiency, 0.1 μm or more is preferable, and 1 μm or more is more preferable. Here, the term "average particle size" as used herein refers to the case where the particle size distribution of a sample is prepared on a volume basis in accordance with JIS R 1629 "Method for measuring particle size distribution by laser diffraction / scattering method for fine ceramic materials". It means the particle size (d ₅₀ ) corresponding to 50% of the integrated distribution curve. As a particle size distribution measuring device by a laser diffraction / scattering method, for example, Microtrack MT3300EX II (manufactured by Microtrack Bell) can be used.

Hereinafter, embodiments of the present invention will be described in more detail with reference to examples. However, the present invention is not limited to the following examples.

1. 1. Impurity analysis 5 g of gallium nitride powder is placed in a 100 mL polytetrafluoroethylene container (HU-100 manufactured by San-Ai Kagaku Co., Ltd.), and together with 5 mL nitric acid (Kanto Chemical Co., Ltd., reagent, special grade), 240 ° C. in a pressurized container. Was heated to a pressure acid decomposition treatment for 24 hours. The obtained solution was made up to 100 mL. This solution was measured with an ICP emission spectrophotometer (ULTIMA II manufactured by HORIBA / JOVIN YVON), and the contents of the elements of Group 14 of the periodic table and the elements of the 4th period of the periodic table were calculated.
The content of metallic gallium was measured by the following method. 5 g of gallium nitride powder was placed in a 100 mL beaker made of polytetrafluoroethylene, and acid-immersed in 30 mL of 3N hydrochloric acid, which was a 1: 1 mixture of 6N hydrochloric acid (manufactured by Kanto Chemical Co., Inc., reagent, special grade) and distilled water. Was done. After acid dissolution, the gallium nitride powder was separated, and the obtained solution was dispensed to 100 mL. This solution was measured with an ICP emission spectrophotometer (ULTIMA II manufactured by HORIBA / JOVIN YVON), and the content of metallic gallium was calculated.

2. 2. Measurement of average particle size The particle size distribution of gallium nitride was prepared on a volume basis in accordance with JIS R 1629 “Method for measuring particle size distribution by laser diffraction / scattering method for fine ceramic materials”. Then, the particle diameter (d ₅₀ ) corresponding to 50% of the integrated distribution curve was obtained. A Microtrack MT3300EX II (manufactured by Microtrack Bell) was used as a particle size distribution measuring device by a laser diffraction / scattering method.

Manufacturing example 1
Manufacture of gallium nitride bulk Weigh 10 g of metal gallium, put it in an alumina boat, and set it in a core tube having a diameter of 50 mm and a length of 600 mm. The inside of the core tube was evacuated and replaced with nitrogen gas, and the gas was switched to ammonia and flowed at 0.5 L / min for 15 minutes to create an ammonia atmosphere inside the core tube. After raising the temperature to 1050 ° C. at a heating rate of 5 ° C./min, the mixture was held for 12 hours and nitrided. After nitriding, the mixture was slowly cooled to room temperature to recover the gallium nitride bulk.

Manufacturing example 2
Manufacture of gallium film-coated crushing medium and gallium film-coated crushing container A planetary ball mill (manufactured by Fritsch Japan Co., Ltd., P-5) was used as a medium crushing device.
First, in an environment of room temperature of 5 ° C. or lower, a high chrome steel crushing ball (φ10 mm), which is a crushing medium, is immersed in a gallium solution heated to about 50 ° C., and then immediately pulled out of the solution, which is repeated 5 times. , The crushed balls were coated with gallium to obtain crushed balls made of high chrome steel coated with gallium film.
Next, in the same environment of room temperature of 5 ° C. or lower, a gallium solution heated to about 50 ° C. was placed in a crushing container (high chrome steel, 125 cc), the lid was closed, and the inside of the container was evenly distributed. Shake to coat with gallium. Then, the uncoated gallium solution was returned to the heated gallium solution container. This operation was repeated 5 times, and gallium was coated in the crushing container to obtain a gallium film-coated high chrome steel crushing container.

Example 1
10 g of the gallium nitride bulk obtained in Production Example 1 was placed in a gallium film-coated high chrome steel container (125 cc) obtained in Production Example 2 in a glove box having an oxygen-free atmosphere maintained at a dew point of −90 ° C. or lower. And 100 g of gallium film-coated high chrome steel balls (φ10 mm) were placed and sealed. Then, it was taken out from a glove box and pulverized at 100 rpm using a planetary ball mill (P-5, manufactured by Fritsch Japan Co., Ltd.) in a thermostatic chamber at room temperature of 5 ° C. The apparatus was pulverized while maintaining the temperature at about 10 ° C. so that the temperature did not exceed the melting point of gallium, 29 ° C. The temperature is controlled by monitoring the temperature near the motor, which is the hottest during crushing, suspending crushing when it is about to exceed 10 ° C, cooling it, and continuing after cooling for a total of 10 minutes. Crushed.
After pulverization, the pulverized material was taken out from a closed pulverized container in a glove box having an oxygen-free atmosphere, and the collected pulverized material was transferred onto a JIS sieve (diameter 75 mm) having a mesh size of 325 mesh, and the sieve was heated to 50 ° C. Next, the gallium contained in the pulverized product was liquefied, and the gallium was separated into a saucer under the sieve to obtain pulverized gallium nitride.
Then, the impurities in the pulverized gallium nitride were analyzed using an ICP emission spectroscopic analyzer, and the average particle size was measured. The results are shown in Table 1. Regarding the analysis results of impurities in Table 1, the contents of the 14th group elements of the periodic table and the main elements of the 4th period of the periodic table are shown, but the contents of all other elements are less than 1 ppm (detection limit). Below). It was confirmed that gallium was also less than 1 ppm, there was no metallic gallium in the gallium nitride powder, and it could be separated and removed by heating.

Comparative Example 1
Example 1 except that a high chrome steel crushing ball (φ10 mm) not coated with a gallium film was used as the crushing medium and a high chrome steel container (125 cc) not coated with a gallium film was used as the crushing container. Grinded gallium nitride was obtained by the same operation as in the above. No gallium removal operation was performed after pulverization. Then, the impurities in the pulverized gallium nitride were analyzed using an ICP emission spectroscopic analyzer, and the average particle size was measured. The results are shown in Table 1. Regarding the analysis results of impurities in Table 1, the contents of the 14th group elements of the periodic table and the main elements of the 4th period of the periodic table are shown, but the contents of all other elements are less than 1 ppm (detection limit). Below).

Comparative Example 2
A pulverized gallium nitride was obtained by the same operation as in Example 1 except that 250 g of silicon nitride balls (φ5 mm) was used as the pulverization medium and a silicon nitride container (250 cc) was used as the pulverization container. No gallium removal operation was performed after pulverization. Then, the impurities in the pulverized gallium nitride were analyzed using an ICP emission spectroscopic analyzer, and the average particle size was measured. The results are shown in Table 1. Regarding the analysis results of impurities in Table 1, the contents of the 14th group elements of the periodic table and the main elements of the 4th period of the periodic table are shown, but the contents of all other elements are less than 1 ppm (detection limit). Below).

From Table 1, gallium nitride is pulverized at a temperature lower than the melting point of gallium by using a medium pulverizer in which the surface of the pulverizing medium and the inner surface of the container are coated with a gallium film to achieve high purity without being contaminated with impurities. It can be seen that the pulverized nitride of is obtained.

Claims (6)

A method for pulverizing gallium nitride, which comprises pulverizing gallium nitride at a temperature lower than the melting point of gallium using a medium pulverizer in which the surface of the pulverization medium and the inner surface of the pulverization vessel are coated with a gallium film. The method for pulverizing gallium nitride according to claim 1, wherein after pulverization, the pulverized product is heated to a temperature equal to or higher than the melting point of gallium. The method for pulverizing gallium nitride according to claim 1 or 2, wherein the gallium nitride is pulverized using a mill. The method for pulverizing gallium nitride according to any one of claims 1 to 3, wherein the average particle size of gallium nitride after pulverization is 30 μm or less. Gallium nitride is pulverized at a temperature lower than the melting point of gallium by using a medium pulverizer in which the surface of the pulverization medium and the inner surface of the pulverization vessel are coated with a gallium film, and the pulverized product is heated at a temperature equal to or higher than the melting point of gallium. High-purity method for pulverized gallium nitride. Gallium nitride is pulverized at a temperature lower than the melting point of gallium by using a medium pulverizer in which the surface of the pulverization medium and the inner surface of the pulverization vessel are coated with a gallium film, and the pulverized product is heated at a temperature equal to or higher than the melting point of gallium. A method for producing high-purity pulverized gallium nitride.