JP2008174439A - Method for producing powder containing nitrogen and gallium elements and method for producing gallium nitride single crystal using the powder - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing a powder capable of being used as a raw material for producing a gallium nitride single crystal, the method being simpler and safer than a conventional method. <P>SOLUTION: A powder containing nitrogen and gallium elements is produced by pulverizing a metal gallium powder or a gallium compound powder in the presence of a nitrogen compound. Ammonia gas can be used as an atmospheric gas, and a gallium chloride powder can be used as the gallium compound powder. Further, the gallium compound powder and a powder of an alkali metal nitride can be pulverized in an oxygen-free atmosphere. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method for easily producing a powder containing nitrogen and gallium. The present invention also relates to a method for producing a gallium nitride single crystal using a powder produced by the method as a raw material.

  Gallium nitride (GaN), which is a kind of nitride semiconductor, is useful as a material applied to light-emitting devices such as light-emitting diodes and laser diodes and high-frequency and high-power electronic devices such as HEMT and HBT. For this reason, it is necessary to manufacture gallium nitride simply and efficiently. The most common method for producing gallium nitride powder is to circulate ammonia at a high temperature and react with ammonia using metallic gallium and / or gallium oxide as a starting material. However, this method is a process in which a large amount of ammonia is circulated at a high temperature of about 1000 ° C., and there is a problem that the production efficiency is low.

Therefore, it has been strongly desired to establish a new production technology for high-quality gallium nitride that replaces the above method, and various proposals have been made in recent years. For example, a method is proposed in which gallium vapor and ammonia gas are reacted to obtain gallium nitride crystal nuclei, and a reaction product of gallium chloride and ammonia is grown on the gallium nitride crystal nucleus (see Patent Document 1). In addition, a method for obtaining a nitrogen-containing adduct of metal halogen by reacting a metal-containing halogen compound with a nitrogen-containing compound at a temperature of 300 ° C. or lower has been proposed (see Patent Document 2). Furthermore, a method of obtaining gallium nitride by firing gallium oxide and alkali metal nitride at a low temperature and low pressure (500 ° C., 0.4 MPa) in a non-oxygen atmosphere has been reported (see Patent Document 3).
JP 2003-63810 A JP 2005-179138 A JP 2005-154193 A

  However, the methods proposed in these patent documents increase the size of the apparatus due to the complicated manufacturing process or the need for safety protection in order to use gallium vapor. It is not easy to implement industrially.

  Therefore, in order to solve the problems of the prior art, the present inventors have aimed to produce a powder that can be a raw material for producing a gallium nitride single crystal by a simpler and safer method. Set as. It was also set as an object of the present invention to provide a method for growing gallium nitride crystals efficiently in a monothermal manner using powder produced by a simple and safe method as a raw material.

  The present inventors have found that a powder containing nitrogen and gallium can be easily produced by performing a pulverization operation under predetermined conditions. In addition, the inventors have found that a gallium nitride single crystal can be efficiently produced by using the obtained powder, and have solved the problems of the prior art. That is, the following present invention has been provided as means for solving the problems.

[1] A method for producing a powder containing a nitrogen element and a gallium element, comprising a step of grinding a metal gallium powder or a gallium compound powder in the presence of a nitrogen compound.
[2] The method for producing a powder containing nitrogen and gallium elements according to [1], wherein the step is a step of pulverizing metal gallium powder in an ammonia gas atmosphere.
[3] The method for producing a powder containing nitrogen and gallium elements according to [1], wherein the step is a step of pulverizing a gallium compound powder in an ammonia gas atmosphere.
[4] The method for producing a powder containing nitrogen and gallium elements according to [3], wherein the gallium compound powder is gallium chloride powder.
[5] The method for producing a powder containing nitrogen and gallium elements according to [1], wherein the step is a step of pulverizing a gallium compound powder and an alkali metal nitride powder in a non-oxygen atmosphere. .
[6] The method for producing a powder containing nitrogen and gallium elements according to [5], wherein the non-oxygen atmosphere is a vacuum, a nitrogen gas atmosphere, an argon gas atmosphere, or an ammonia gas atmosphere.
[7] Any of [1] to [6], wherein the pulverization is performed by rotating a sealed container enclosing metal gallium powder or gallium compound powder, pulverization balls, and a nitrogen compound. A method for producing a powder containing the nitrogen element and the gallium element according to claim 1.
[8] When the metal gallium powder is pulverized, the sealed container is rotated at 600 to 800 rpm, and when the gallium compound powder is pulverized, the sealed container is rotated at 100 to 800 rpm. For producing powder containing nitrogen element and gallium element.
[9] When the metal gallium powder is pulverized, the sealed container is rotated for 1 to 4 hours, and when the gallium compound powder is pulverized, the sealed container is rotated for 30 minutes to 2 hours, [7] or The manufacturing method of the powder containing the nitrogen element and gallium element as described in [8].
[10] The method for producing a powder containing a nitrogen element and a gallium element according to any one of [7] to [9], wherein a diameter of the grinding ball is 5 to 15 mm.

[11] A powder containing a nitrogen element and a gallium element manufactured by the manufacturing method according to any one of [1] to [10].

[12] Use of the powder according to [11] as a gallium nitride synthesis raw material.

[13] Temperature and pressure in the autoclave containing at least a seed, a solvent containing nitrogen element, and the powder according to [11] are controlled so that the solvent is in a supercritical state and / or a subcritical state. Then, the method for producing a gallium nitride single crystal, comprising the step of growing gallium nitride crystallographically on the surface of the seed.
[14] The method for producing a gallium nitride single crystal according to [13], further comprising a mineralizer in the autoclave.
[15] The method for producing a gallium nitride single crystal according to [14], wherein the mineralizer is an acidic mineralizer.
[16] The method for producing a gallium nitride single crystal according to [15], wherein the acidic mineralizer contains an ammonium halide.
[17] The method for producing a gallium nitride single crystal according to any one of [13] to [16], wherein a raw material to be a gallium source is further contained in the autoclave in addition to the powder.

  According to the method for producing a powder of the present invention, a powder that can be a raw material for producing a gallium nitride single crystal can be produced by a smaller apparatus without heating. Therefore, according to the production method of the present invention, the powder raw material can be produced more easily and safely than the conventional method. In addition, according to the method for producing a gallium nitride single crystal of the present invention using such a powder raw material, a high-quality gallium nitride single crystal can be produced efficiently and at low cost.

  Hereinafter, the powder of the present invention and the production method thereof will be described in detail. The description of the constituent elements described below may be made based on typical embodiments of the present invention, but the present invention is not limited to such embodiments. In the present specification, a numerical range represented by using “to” means a range including numerical values described before and after “to” as a lower limit value and an upper limit value.

(Method for producing powder of the present invention)
The method for producing a powder according to the present invention includes a step of pulverizing a metal gallium powder or a gallium compound powder in an ammonia gas atmosphere.

  The metal gallium powder used in the method for producing a powder of the present invention preferably has a metal gallium purity of 99% or more, more preferably 99.9% or more, and more preferably 99.99% or more. preferable. The diameter of the metal gallium powder is not particularly limited. For example, a powder having a diameter of about 1 to 15 mm, preferably about 3 to 10 mm can be used. For example, 3-4 mm granular metal gallium powder can be used.

Examples of the gallium compound constituting the gallium compound powder used in the powder production method of the present invention include gallium chloride, gallium fluoride, gallium bromide, gallium iodide, and gallium oxide. The type of gallium compound to be used is preferably selected as appropriate according to the production conditions of the production method of the present invention. For example, when the gallium compound powder is pulverized in an ammonia atmosphere, it is preferable to use a gallium-containing compound that does not contain oxygen atoms or carbon atoms. Specifically, gallium chloride, gallium fluoride, gallium bromide, and gallium iodide can be preferably used, and gallium chloride can be particularly preferably used. On the other hand, when pulverizing gallium compound powder and nitrogen compound powder, gallium oxide, gallium chloride, gallium fluoride, gallium bromide, and gallium iodide are preferably used, and gallium oxide and gallium chloride are more preferably used. It is particularly preferable to use gallium oxide.
In the method for producing a powder of the present invention, two or more kinds of gallium compound powders may be used in combination. The diameter of the gallium compound powder is preferably 100 to 10,000 μm, more preferably 100 to 1000 μm, and still more preferably 100 to 500 μm.

In the method for producing a powder of the present invention, pulverization is performed in a non-oxygen atmosphere. When ammonia gas is selected as the nitrogen compound, the gallium compound powder is pulverized in an ammonia gas atmosphere. The ammonia gas to be used preferably has a high purity, specifically, those having a purity of 99.9% or more are preferred, those having a purity of 99.99% or more are more preferred, and those having a purity of 99.999% or more are preferred. Further preferred. On the other hand, when a powdered nitrogen compound is selected and pulverized with the gallium compound powder, it may be pulverized in any atmosphere as long as it is a non-oxygen atmosphere. For example, it can be pulverized in an argon atmosphere, a nitrogen atmosphere, an ammonia atmosphere, or a helium atmosphere, or may be pulverized in a vacuum. Preference is given to grinding in an ammonia atmosphere.
Usually, a metal gallium powder or a gallium compound powder is introduced into a pulverization container in an inert gas atmosphere such as nitrogen or argon, and then the container is sealed and a gas for pulverization is introduced. When performing the pulverization operation, a part of the inert gas such as nitrogen or argon used at the beginning may remain.

  In the method for producing a powder of the present invention, the average diameter of the powder obtained after pulverization is preferably 10 to 200 μm, more preferably 10 to 100 μm, and further preferably 10 to 50 μm. By performing such pulverization, a powder containing nitrogen element and gallium element, which is useful as a raw material for producing a gallium nitride single crystal, can be obtained. The specific aspect of the pulverization employed in the method for producing a powder of the present invention is not particularly limited as long as the above conditions are satisfied.

  A preferred pulverization method is a method of pulverization in a closed container using a pulverization ball. That is, it is preferable to employ a method in which a metal gallium powder or a gallium compound powder, ammonia gas, and a grinding ball are enclosed in a sealed container, and the powder is pulverized by rotating the sealed container.

  Examples of the grinding balls used here include zirconia balls, balls whose surfaces are coated with organic substances, silicon nitride, and alumina. Usually, zirconia balls are used. However, when it is desired to avoid mixing zirconia into the obtained powder, it is preferable to use balls whose surfaces are coated with organic substances. The diameter of the pulverizing ball used is preferably 5 to 15 mm, more preferably 8 to 15 mm, and still more preferably 8 to 12 mm. The amount of the grinding balls used is preferably 20 to 50 times the weight of the metal gallium powder or gallium compound powder to be ground, more preferably 30 to 50 times, and 40 to 50 times. More preferably it is.

  The container used for pulverization is selected so that it does not wear during pulverization, can withstand conditions such as pressure during pulverization, and does not react with the material to be pulverized. For example, a zirconia container, an alumina container, or the like can be used. When crushing using a crushing ball, use a container that can be sealed.

  When pulverization is performed using a pulverizing ball, the metal gallium powder or the gallium compound powder, ammonia gas, and the pulverizing ball are sealed in the container, and then the powder is pulverized by rotating the sealed container. In the case of metallic gallium powder, the rotational speed of the sealed container is preferably 600 to 800 rpm, more preferably 650 to 800 rpm, and further preferably 700 to 800 rpm. When pulverizing a gallium compound powder such as gallium chloride in an ammonia atmosphere, 100 to 800 rpm is preferable, 100 to 600 rpm is more preferable, and 100 to 400 rpm is more preferable. On the other hand, when pulverizing gallium compound powder such as gallium oxide together with nitrogen compound powder such as lithium nitride powder, 100 to 800 rpm is preferable, 100 to 600 rpm is more preferable, and 100 to 400 rpm is more preferable.

  The pressure during pulverization is preferably 0.1 to 1.0 MPa. By adopting such a pressure range, there is an advantage that the reaction is accelerated. The pressure during pulverization is more preferably 0.4 to 1.0 MPa, and further preferably 0.6 to 1.0 MPa. The pressure during pulverization can be adjusted by adjusting the pressure of ammonia gas introduced into the sealed container.

  Although the pulverization time varies depending on other pulverization conditions, in the case of metallic gallium powder, it is preferably 1 to 4 hours, more preferably 2 to 4 hours, and further preferably 3 to 4 hours. . In the case of gallium compound powder, it is preferably 30 minutes to 4 hours. In particular, when a gallium compound powder such as gallium chloride is pulverized in an ammonia atmosphere, it is preferably 30 to 120 minutes, more preferably 30 to 90 minutes, and even more preferably 30 to 60 minutes. On the other hand, when pulverizing gallium compound powder such as gallium oxide together with nitrogen compound powder such as lithium nitride powder, it is preferably 30 minutes to 4 hours, more preferably 1 hour to 3 hours, and even more preferably 1 hour to 2 hours.

  The temperature at the time of grinding may be room temperature. Therefore, in the powder manufacturing method of the present invention, no special equipment or operation is required for temperature control. However, the powder production method of the present invention does not exclude pulverization while heating or cooling, but it is preferably performed without heating or cooling for cost reduction and simplification of equipment.

The production method of the present invention utilizes a mechanochemical reaction that promotes a chemical reaction by applying mechanical energy to a metal gallium powder or a gallium compound powder. The powder produced by the production method of the present invention is a powder containing nitrogen element and gallium element. Specifically, when the production method of the present invention is carried out using metal gallium as a raw material, gallium nitride powder can be obtained. Further, when the production method of the present invention is carried out using a gallium compound such as gallium chloride as a raw material in an ammonia gas atmosphere, a gallium nitride precursor powder or a gallium nitride powder can be obtained. The gallium nitride precursor here is a compound that can generate gallium nitride by thermal decomposition or the like, and examples thereof include Ga (NH ₃ ) ₆ Cl ₃ and Ga (NH ₃ ) ₆ Cl ₃ . Further, when a powder of a gallium compound such as gallium oxide and a nitrogen compound is pulverized, the following reaction proceeds in part to obtain a gallium nitride precursor powder or a gallium nitride powder.

(Use of the powder of the present invention)
The powder of the present invention can be used for various applications. For example, the powder of the present invention containing no carbon atoms or oxygen atoms can be a useful inorganic precursor for the thermal decomposition synthesis of gallium nitride.

  In particular, the powder of the present invention is extremely useful as a raw material for crystal growth of gallium nitride in an ammonothermal manner. Specifically, the temperature and pressure in the autoclave containing the seed, the nitrogen-containing solvent, and the powder of the present invention are controlled so that the solvent is in a supercritical state and / or a subcritical state. It can be preferably used in the production method of the present invention characterized in that gallium nitride is crystallically grown on the surface in an ammonothermal manner. Therefore, in the following, the method for producing gallium nitride of the present invention will be described in detail.

(Materials used)
In the method for producing gallium nitride of the present invention, a solvent containing nitrogen element is used as a solvent. Examples of the solvent containing nitrogen element include solvents that do not impair the stability of the gallium nitride single crystal to be grown. Specifically, ammonia, hydrazine, urea, amines (for example, methylamine) Primary amines, secondary amines such as dimethylamine, tertiary amines such as trimethylamine, diamines such as ethylenediamine, and melamine. These solvents may be used alone or in combination.

  The amount of water and oxygen contained in the solvent used in the present invention is desirably as small as possible, and the content thereof is preferably 1000 ppm or less, more preferably 10 ppm or less, and preferably 0.1 ppm or less. Further preferred. When ammonia is used as a solvent, the purity is usually 99.9% or more, preferably 99.99% or more, more preferably 99.999% or more, and particularly preferably 99.9999% or more. .

  A mineralizer can be used in the production method of the present invention. The mineralizer used is a compound that increases the solubility of the raw material in the solvent. In order to prevent the grown crystal from containing oxygen element, it is preferable to use a compound containing nitrogen element in the form of ammonium ion (ammonium salt) or amide, and nitrogen element in the form of ammonium ion (ammonium salt) It is more preferable to use a compound containing In the present invention, only one type of chemical species may be selected and used as the mineralizer, or two or more types of chemical species may be used in combination. When it is necessary to increase the crystal growth rate, two or more chemical species are used in combination.

  In order to prevent impurities from being mixed into the gallium nitride single crystal grown in the present invention, the mineralizer is used after being purified and dried as necessary. The purity of the mineralizer used in the present invention is usually 95% or higher, preferably 99% or higher, more preferably 99.99% or higher. It is desirable that the amount of water and oxygen contained in the mineralizer is as small as possible, and the content thereof is preferably 1000 ppm or less, more preferably 10 ppm or less, and further preferably 1.0 ppm or less. .

  In the present invention, it is preferable to use an acidic mineralizer. The acidic mineralizer increases the solubility of the powder of the present invention and other gallium sources in an ammonia solvent in a supercritical state, and has an effect of decreasing a suitable reaction pressure. Furthermore, it has an advantageous characteristic that the reactivity with noble metals such as Pt constituting the inner wall of the autoclave is small. The acidic mineralizer is a compound containing a halogen element, and examples thereof include ammonium halide. Specific examples include ammonium chloride, ammonium iodide, and ammonium bromide. Among them, ammonium chloride is preferable.

In the present invention, it is preferable to use an acidic mineralizer obtained by combining a plurality of chemical species. If an acidic mineralizer combining a plurality of chemical species is used, the solubility of the raw material in the solvent can be increased and the crystal growth rate can be further increased. In particular, in the ammonium halide mineralizer (NH ₄ X), for example, an ammonium halide mineralizer (NH ₄ Br, NH ₄ I) containing Br, I which is a halogen having higher reactivity with NH ₄ Cl. By mixing the gallium nitride, the solubility of gallium nitride in the supercritical ammonia solvent can be improved.

  The use ratio of the mineralizer and the gallium source containing the powder of the present invention is preferably within the range where the mineralizer / gallium element (molar ratio) is 0.001-20. The ratio of use can be appropriately determined in consideration of the types of raw materials and mineralizers, the target crystal size, and the like.

  In the method for producing a gallium nitride single crystal of the present invention, the powder of the present invention is used as a gallium source. Here, in addition to the powder of the present invention, gallium nitride polycrystal and / or metal gallium may be used. The gallium nitride polycrystal raw material does not need to be a complete nitride, and may contain a metal component in which the group 13 element is in a metal state (zero valence), that is, metal gallium, depending on conditions.

  The manufacturing method of the gallium nitride polycrystal used as a raw material in this invention is not restrict | limited in particular. For example, gallium nitride polycrystal produced by reacting metal gallium or its oxide or hydroxide with ammonia in a reaction vessel in which ammonia gas is circulated can be used. Moreover, compounds having a covalent MN bond, such as halides, amide compounds, imide compounds, and galazane, can be used as more reactive raw materials. Furthermore, gallium nitride polycrystal prepared by reacting metal gallium with nitrogen at high temperature and high pressure can be used.

  The amount of water or oxygen contained in the gallium nitride polycrystal used as a raw material in the present invention is preferably small. The oxygen content in the gallium nitride polycrystal is usually 1.0% by mass or less, preferably 0.1% by mass or less, and particularly preferably 0.0001% by mass or less. The ease of mixing oxygen into the gallium nitride polycrystal is related to the reactivity with water or the absorption ability. The worse the crystallinity of the gallium nitride polycrystal, the more active groups such as NH groups are present on the surface, which may react with water and partially generate oxides or hydroxides. For this reason, it is usually preferable to use a gallium nitride polycrystal having a crystallinity as high as possible. The crystallinity can be estimated by the half width of powder X-ray diffraction. The half width of the (100) diffraction line (2θ = about 32.5 ° for hexagonal gallium nitride) is usually 0.25 ° or less, preferably It is 0.20 ° or less, more preferably 0.17 ° or less.

  In the manufacturing method of the present invention, a seed is used. As the seed, it is desirable to use a gallium nitride single crystal grown by the manufacturing method of the present invention, but it is not necessarily limited to gallium nitride. However, in that case, it is a seed with a lattice constant, crystal lattice size parameter that matches or matches the gallium nitride to be grown, or heteroepitaxy (ie, coincidence of the crystallographic position of some atoms). It is necessary to use seeds composed of single crystal material pieces or polycrystalline material pieces coordinated to ensure. Specific examples of the seed include gallium nitride single crystal, aluminum nitride (AlN) single crystal, zinc oxide (ZnO) single crystal, silicon carbide (SiC) single crystal, and the like.

  The seed can be determined in consideration of the solubility in the solvent and the reactivity with the mineralizer. For example, the seed of gallium nitride is a single crystal obtained by epitaxial growth on a dissimilar substrate such as sapphire by MOCVD method or HVPE method, and obtained by crystal growth using Na, Li, or Bi as flux from metal Ga. Single crystals produced by homoepitaxial growth using the LPE method, single crystals produced based on the solution growth method including the production method of the present invention, and crystals obtained by cutting them can be used.

  In the present invention, it is also preferable to perform crystal growth using a seed having a surface generated by cleavage. High quality gallium nitride single crystals are faster when seeds with cleaved surfaces are used than when seeds with unpolished surfaces or seeds with precision polished surfaces are used for crystal growth. It can be manufactured at a growth rate.

(Autoclave)
The method for producing a gallium nitride single crystal of the present invention is carried out in an autoclave.
The autoclave used in the present invention is selected from those that can withstand high temperature and high pressure conditions when growing a gallium nitride single crystal. The autoclave used in the present invention is preferably composed of a material having pressure resistance and erosion resistance. In particular, an Ni-based alloy having excellent erosion resistance against a solvent such as ammonia, Stellite (Derolo Stellite Company It is preferable to use a Co-based alloy such as a registered trademark of Incorporated. More preferably, it is a Ni-based alloy, specifically, Inconel 625 (Inconel is a registered trademark of Huntington Alloys Canada Limited, the same applies hereinafter), Nimonic 90 (Nimonic is a registered trademark of Special Metals Wiggin Limited, the same applies hereinafter), and RENE 41. It is done.

  The composition ratio of these alloys depends on the temperature and pressure conditions of the solvent in the system, and the reactivity with the mineralizers and their reactants contained in the system and / or the oxidizing power / reducing power, pH conditions, What is necessary is just to select suitably. In order to use these as materials constituting the inner surface of the autoclave, the autoclave itself may be manufactured using these alloys, or a thin film may be formed as an inner cylinder and installed in the autoclave. The inner surface of the material may be plated.

  In order to further improve the erosion resistance of the autoclave, the inner surface of the autoclave may be lined or coated using the superior erosion resistance of the noble metal. The material of the autoclave can be a noble metal. Examples of the noble metal include Pt, Au, Ir, Ru, Rh, Pd, Ag, and alloys containing these noble metals as main components. Among them, it is preferable to use Pt having excellent erosion resistance.

  A specific example of a crystal production apparatus including an autoclave that can be used in the production method of the present invention is shown in FIG. In the figure, 1 is a valve, 2 is a pressure gauge, 3 is an autoclave, 4 is a crystal growth part, 5 is a raw material filling part, 6 is a baffle plate, 7 is an electric furnace, 8 is a thermocouple, 9 is a raw material, 10 is a seed , 11 indicates a conduit.

  The baffle plate 6 divides the crystal growth part 4 and the raw material filling part 5 and preferably has a hole area ratio of 2 to 20%, more preferably 3 to 10%. The material of the surface of the baffle plate is preferably the same as the material of the reaction vessel. Further, in order to give more erosion resistance and to purify the crystal to be grown, the surface of the baffle plate is preferably Ni, Ta, Ti, Nb, Pd, Pt, Au, Ir, pBN, Pd, Pt, Au, Ir, and pBN are more preferable, and Pt is particularly preferable.

  As for the valve 1, the pressure gauge 2, and the conduit 11, it is preferable that at least the surface is made of an erosion resistant material. For example, it is SUS316 (JIS standard), and it is more preferable to use Inconel 625. In addition, a valve, a pressure gauge, and a conduit are not necessarily installed in the crystal manufacturing apparatus used when the manufacturing method of the present invention is carried out.

(Manufacturing process)
In carrying out the production method of the present invention, first, a seed, a solvent containing nitrogen element, a raw material containing the powder of the present invention, and a mineralizer as necessary are sealed in an autoclave. . Prior to introducing these materials into the autoclave, the autoclave may be degassed. Moreover, you may distribute | circulate inert gas, such as nitrogen gas, at the time of introduction | transduction of material.

  The seeds are usually loaded into the autoclave at the same time as or after the filling with the raw material and the mineralizer as the gallium source. The seed is preferably fixed to a noble metal jig similar to the noble metal constituting the inner surface of the autoclave. After loading, heat deaeration may be performed as necessary.

  In the supercritical state, the viscosity is generally low and it is more easily diffused than the liquid, but has the same solvating power as the liquid. The subcritical state means a liquid state having a density substantially equal to the critical density near the critical temperature. For example, in the raw material filling part, the raw material is melted as a supercritical state, and in the crystal growth part, the temperature is changed so as to be in the subcritical state, and crystal growth utilizing the difference in solubility between the supercritical state and the subcritical state raw material is also performed. Is possible.

  When in the supercritical state, the reaction mixture is generally maintained at a temperature above the critical point of the solvent. When an ammonia solvent is used, the critical point is a critical temperature of 132 ° C. and a critical pressure of 11.35 MPa. However, if the filling rate with respect to the volume of the autoclave is high, the pressure far exceeds the critical pressure even at a temperature below the critical temperature. In the present invention, the “supercritical state” includes such a state exceeding the critical pressure. Since the reaction mixture is enclosed in a fixed volume autoclave, the temperature increase increases the pressure of the fluid. In general, if T> Tc (critical temperature of one solvent) and P> Pc (critical pressure of one solvent), the fluid is in a supercritical state.

  Under supercritical conditions, a sufficient growth rate of the gallium nitride single crystal can be obtained. The reaction time depends in particular on the reactivity of the mineralizer and the thermodynamic parameters, ie temperature and pressure values. During the synthesis or growth of the gallium nitride single crystal, the autoclave is preferably held at a pressure of about 10 MPa to 500 MPa. The pressure is appropriately determined depending on the filling rate of the solvent volume with respect to the temperature and the volume of the autoclave. Originally, the pressure in the autoclave is uniquely determined by the temperature and filling rate, but in reality, there are raw materials, additives such as mineralizers, temperature heterogeneity in the autoclave, and the existence of dead volume. It will vary slightly.

  As for the temperature range in the autoclave, the lower limit is usually 150 ° C or higher, preferably 200 ° C or higher, particularly preferably 300 ° C or higher, and the upper limit is usually 800 ° C or lower, preferably 700 ° C or lower, particularly preferably 600 ° C or lower. It is. A preferable temperature range is 150 to 800 ° C, more preferably 200 to 700 ° C, and still more preferably 300 to 600 ° C. The pressure range in the autoclave is usually 10 MPa or more, preferably 20 MPa or more, more preferably 30 MPa or more, still more preferably 50 MPa or more, particularly preferably 80 MPa or more, and the upper limit is usually 500 MPa or less, preferably 10 MPa or more. 400 MPa or less, more preferably 300 MPa or less, particularly preferably 200 MPa or less. A preferable pressure range is 20 to 500 MPa, more preferably 50 to 300 MPa, and still more preferably 80 to 200 MPa.

  The injection ratio of the solvent into the autoclave to achieve the above autoclave temperature range and pressure range, i.e., the filling rate, is the free volume of the autoclave, i.e., when a polycrystalline raw material and seed are used in the autoclave, Subtract the volume of the structure where it is installed from the autoclave volume, and if a baffle plate is installed, subtract the volume of the baffle plate from the autoclave volume at the boiling point of the remaining solvent. Based on the liquid density, it is usually 20 to 95%, preferably 30 to 80%, more preferably 40 to 70%.

  The growth of a gallium nitride single crystal in an autoclave is to maintain the autoclave in a subcritical or supercritical state of a solvent such as ammonia by heating and heating the autoclave using an electric furnace having a thermocouple. Is done. The heating method and the rate of temperature increase to a predetermined reaction temperature are not particularly limited, but are usually performed over several hours to several days. If necessary, the temperature can be raised in multiple stages, or the temperature raising speed can be changed in the temperature range. It can also be heated while being partially cooled.

  The above “reaction temperature” is measured by a thermocouple provided in contact with the outer surface of the autoclave, and can be approximated to the internal temperature of the autoclave.

  The reaction time after reaching a predetermined temperature varies depending on the type of gallium nitride single crystal, the raw material used, the type of mineralizer, and the size and amount of the crystal to be produced. can do. During the reaction, the reaction temperature may be constant, or the temperature may be gradually raised or lowered. After a reaction time for producing desired crystals, the temperature is lowered. The method for lowering the temperature is not particularly limited, but the heating of the heater may be stopped and the autoclave may be allowed to cool as it is installed in the furnace, or the autoclave may be removed from the electric furnace and air cooled. If necessary, quenching with a refrigerant is also preferably used.

After the temperature of the outer surface of the autoclave or the estimated temperature inside the autoclave has fallen below the predetermined temperature, the autoclave is opened. The predetermined temperature at this time is not particularly limited, and is usually −80 ° C. to 200 ° C., preferably −33 ° C. to 100 ° C. Here, a pipe may be connected to a pipe connection port of a valve attached to the autoclave, and the valve may be opened by passing through a container filled with water or the like.
Furthermore, if necessary, after removing the ammonia solvent in the autoclave sufficiently by making a vacuum or the like, it is dried and the autoclave lid is opened, etc. to produce nitride crystals and unreacted raw materials and mineralizers, etc. The additive can be removed.

  Thus, a gallium nitride single crystal can be manufactured by the manufacturing method of the present invention. In order to manufacture a gallium nitride single crystal having a desired crystal structure, it is necessary to appropriately adjust the manufacturing conditions.

  A gallium nitride single crystal having a desired shape can be obtained by appropriately selecting the shape of the seed used in carrying out the manufacturing method of the present invention. The gallium nitride single crystal produced by the production method of the present invention may be used as it is or after being processed.

(Use of gallium nitride single crystal)
A wafer (semiconductor substrate) having an arbitrary crystal orientation can be obtained by cutting a gallium nitride single crystal manufactured by the manufacturing method of the present invention in a desired direction. As a result, a wafer having a polar surface such as the C surface and a nonpolar surface such as the M surface can be obtained. An epitaxial wafer can be further obtained by performing desired epitaxial growth using the thus obtained wafer as a substrate.

  The gallium nitride single crystal and wafer manufactured by the manufacturing method of the present invention are suitably used for devices such as light emitting elements and electronic devices. Examples of the light emitting device using the gallium nitride single crystal or wafer manufactured by the manufacturing method of the present invention include a light emitting diode, a laser diode, and a light emitting device combining them with a phosphor. Further, examples of the electronic device using the gallium nitride single crystal or wafer manufactured by the manufacturing method of the present invention include a high frequency element, a high withstand voltage high output element, and the like. Examples of the high frequency element include a transistor (HEMT, HBT), and an example of the high breakdown voltage high output element includes a thyristor (IGBT).

  The features of the present invention will be described more specifically with reference to the following examples. The materials, amounts used, ratios, processing details, processing procedures, and the like shown in the following examples can be changed as appropriate without departing from the spirit of the present invention. Therefore, the scope of the present invention should not be construed as being limited by the specific examples shown below.

(Example 1) Production of powder containing nitrogen element and gallium element (1)
In a glove box in a nitrogen atmosphere, 72 g of zirconia grinding balls having a diameter of 40 mm and 2 g of metal gallium powder having a diameter of 10 mm were filled in a zirconia grinding container, and after complete sealing with a stainless steel overpot, the vacuum evacuation was performed. The internal volume in the sealed container at this time was about 50 cm ³ . Next, high-purity ammonia gas was charged into the grinding container so that the pressure became 1 MPa, and the grinding container was rotated at 700 rpm for 2 hours to perform ball collision. Thereafter, the obtained powder was recovered from the container.

  By carrying out the above powder production process with the metal gallium powder filling amount changed to 0.2 g, 0.4 g and 1 g, respectively, powders were obtained.

  Each powder obtained had an average particle size of about 3 μm. When each of the obtained powders was analyzed by X-ray diffraction, each powder was a powder composed of gallium nitride and metal gallium. FIG. 1 shows the results of analysis by X-ray diffraction. A peak corresponding to zirconia is also observed, but mixing of zirconia into the powder can be easily avoided by changing the type of ball for grinding to an organic coating ball.

(Example 2) Production of powder containing nitrogen element and gallium element (2)
In a glove box in a nitrogen atmosphere, 72 g of zirconia grinding balls having a diameter of 40 mm and 2 g of gallium chloride powder having a diameter of 10 mm were filled in a zirconia grinding container, and after complete sealing with a stainless steel overpot, the vacuum evacuation was performed. The internal volume in the sealed container at this time was about 50 cm ³ . Next, high-purity ammonia gas was charged into the grinding container so that the pressure became 1 MPa, and the grinding container was rotated at 500 rpm for 30 minutes to perform ball collision. Thereafter, the obtained powder was recovered from the container.

  Another powder was obtained by carrying out the above powder production process by changing the rotation speed of the grinding container to 200 rpm.

Each powder obtained had an average particle size of about 3 μm. Moreover, when the powder obtained was analyzed by X-ray diffraction, all of the powder was also gallium nitride precursors _{Ga (NH 3) 6 Cl 3} . FIG. 2 shows the analysis result by X-ray diffraction.

(Example 3) Production of powder containing nitrogen element and gallium element (3)
By performing the following steps (a) to (d), powders were obtained.
(A) In a glove box in an argon atmosphere, a zirconia pulverization container is filled with 72 g of zirconia pulverizing balls 72 g, 0.03 mm gallium oxide powder 2 g, and 0.03 mm lithium nitride powder 1.12 g. Then, after completely sealed with a stainless steel overpot, it was evacuated. The pulverization container was rotated at 700 rpm for 2 hours by a pulverizer to induce ball collision. Thereafter, the obtained powder was recovered from the container.
(B) The point which did not evacuate after sealing was changed, and the same process as (a) was implemented others.
(C) After the evacuation, the same process as in (a) was performed except that the high-purity nitrogen gas was charged in the pulverization container and pulverized so that the pressure became 0.8 MPa.
(D) After the evacuation, the same process as in (a) was performed except that the high-purity ammonia gas was charged into the pulverization vessel and pulverized after the evacuation.

  The result of having analyzed the powder obtained by implementing the process of (a)-(d) by XRD is shown to Fig.3 (a)-(d), respectively. It was confirmed that gallium nitride powder was obtained when any step was performed. Although peaks corresponding to zirconia are also observed in FIGS. 3A to 3C, this can be easily avoided by changing the type of ball to an organic coating ball.

(Example 4) Production of powder containing nitrogen element and gallium element (4)
By performing the following steps (a) to (d), powders were obtained.
(A) In a glove box in an argon atmosphere, a zirconia pulverization container is filled with 72 g of zirconia pulverizing balls 72 g, 0.03 mm gallium oxide powder 2 g, and 0.03 mm lithium nitride powder 1.12 g. Then, after completely sealed with a stainless steel overpot, it was evacuated. Next, high-purity ammonia gas was charged into the pulverization container so that the pressure became 0.8 MPa, and the pulverization apparatus was rotated at 700 rpm for 2 hours by a pulverizer to induce ball collision. Thereafter, the obtained powder was recovered from the container.
(B) The point which made the rotational speed of the grinding | pulverization container 500 rpm was changed, and the same process as (a) was implemented others.
(C) The point which made the rotational speed of the grinding | pulverization container 300 rpm was changed, and the same process as (a) was implemented others.

  The result of having analyzed the powder obtained by implementing the process of (a)-(c) by XRD is shown to FIG.4 (a)-(c), respectively. It was confirmed that gallium nitride powder was obtained when any step was performed. In FIGS. 4A and 4B, a peak corresponding to zirconia is also observed, but this can be easily avoided by changing the type of the ball to an organic coating ball.

(Example 5) Production of powder containing nitrogen element and gallium element (5)
By performing the following steps (a) to (c), powders were obtained.
(A) In a glove box in an argon atmosphere, a zirconia pulverization container is filled with 72 g of zirconia pulverizing balls 72 g, 0.03 mm gallium oxide powder 2 g, and 0.03 mm lithium nitride powder 1.12 g. Then, after completely sealed with a stainless steel overpot, it was evacuated. Next, high-purity ammonia gas was charged into the pulverization container so that the pressure became 0.8 MPa, and the pulverization apparatus was rotated at 300 rpm for 1 hour by a pulverizer to induce ball collision. Thereafter, the obtained powder was recovered from the container.
(B) The point which made the rotation time of the grinding | pulverization container 2 hours was changed, and others performed the same process as (a).
(C) The point which made the rotation time of the grinding | pulverization container into 4 hours was changed, and the others performed the same process as (a).

  The result of having analyzed the powder obtained by implementing the process of (a)-(c) by XRD is shown to FIG.5 (a)-(c), respectively. Moreover, the result of having observed the powder obtained by implementing the process of (b) by SEM is shown in FIG. It was confirmed that gallium nitride powder was obtained when any step was performed.

(Example 6) Manufacture of gallium nitride single crystal Using each powder obtained in Examples 1 to 5 as a raw material, gallium nitride is grown in an ammonothermal manner in the apparatus shown in FIG. Can be made.
Using autoclave 3 (made of Inconel 625, approx. 30 ml) with an inner dimension of 16 mm in diameter and 160 mm in length, the powder obtained in Example 1 as raw material 9 is placed in autoclave raw material filling section 5 and then mineralized A sufficiently dried powder of NH ₄ Cl (purity 99.99%) is further charged from above as an agent.

Next, after setting the baffle plate 6 at a position of 80 mm from the bottom and setting a seed of gallium nitride on the crystal growth part 4 thereon, quickly close the lid of the autoclave equipped with the valve and weigh the autoclave 3. Do. Next, the conduit 11 is operated through the valve 1 attached to the autoclave so as to pass through the vacuum pump, the valve 1 is opened, and the autoclave 3 is evacuated. Thereafter, the autoclave 3 is cooled with a dry ice methanol solvent while maintaining the vacuum state, and the valve 1 is once closed. Next, after the conduit is operated to lead to the NH ₃ cylinder, the valve 1 is opened again, and NH ₃ is continuously filled in the autoclave 3 without touching the outside air. Based on the flow rate control, NH ₃ is filled as a liquid corresponding to about 65% of the cavity portion of the autoclave (converted with an NH ₃ density of −33 ° C.), and then the valve 1 is closed again. The temperature of the autoclave 3 is cooled to room temperature, carried out the increase in the weighing of the NH ₃ filled with outer surface is sufficiently dried.

Subsequently, the autoclave 3 is housed in an electric furnace 7 composed of a heater divided into two parts in the vertical direction. The temperature of the lower outer surface of the autoclave is increased to 550 ° C. and the temperature of the upper outer surface is increased to 500 ° C. over 6 hours, and the temperature of the lower outer surface of the autoclave is increased to 550 ° C. After reaching 500 ° C., hold at that temperature for an additional 96 hours. Thereafter, the temperature of the lower outer surface of the autoclave 3 is lowered for about 9 hours until the temperature reaches 50 ° C., and then the heating by the heater is stopped, and the air is naturally cooled in the electric furnace 7. After confirming that the temperature of the lower outer surface of the autoclave 3 has dropped to about room temperature, the valve 1 attached to the autoclave is first opened, and NH ₃ in the autoclave ₃ is removed. Then weighing the autoclave 3 to confirm the discharge of NH _3. Thereafter, the valve 1 is once closed and operated so as to communicate with the vacuum pump, the valve 1 is opened again, and NH ₃ in the autoclave ₃ is almost completely removed. Thereby, the growth of the gallium nitride single crystal is confirmed in the auto claim 3.

  According to the method for producing a powder of the present invention, a powder that can be a raw material for producing a gallium nitride single crystal can be produced by a smaller apparatus without heating. For this reason, there is no need for temperature control such as heating, and a powder raw material can be produced safely and efficiently at low cost. Moreover, if such a powder raw material is used, a gallium nitride single crystal can be efficiently produced while suppressing the total production cost, and therefore the present invention has high industrial applicability. Further, since the manufactured gallium nitride single crystal is of high quality, it can be widely used for light-emitting devices and electronic devices. Therefore, the present invention has high industrial applicability.

2 is a chart showing the analysis results of the powder obtained in Example 1 by X-ray diffraction. 4 is a chart showing analysis results of powder obtained in Example 2 by X-ray diffraction. 6 is a chart showing the results of analysis by X-ray diffraction of the powder obtained in Example 3. 6 is a chart showing the analysis results by X-ray diffraction of the powder obtained in Example 4. 6 is a chart showing analysis results by X-ray diffraction of the powder obtained in Example 5. FIG. It is a photograph which shows the SEM observation result of the powder obtained in Example 5 (b). It is a schematic sectional drawing of the crystal manufacturing apparatus which can be used for the manufacturing method of the gallium nitride single crystal of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Valve | bulb 2 Pressure gauge 3 Autoclave 4 Crystal growth part 5 Raw material filling part 6 Baffle plate 7 Electric furnace 8 Thermocouple 9 Raw material 10 Seed 11 Conduit

Claims (17)

  A method for producing a powder containing a nitrogen element and a gallium element, comprising a step of grinding a metal gallium powder or a gallium compound powder in the presence of a nitrogen compound.   The method for producing a powder containing nitrogen element and gallium element according to claim 1, wherein the step is a step of pulverizing the metal gallium powder in an ammonia gas atmosphere.   The method for producing a powder containing nitrogen element and gallium element according to claim 1, wherein the step is a step of pulverizing the gallium compound powder in an ammonia gas atmosphere.   The said gallium compound powder is a gallium chloride powder, The manufacturing method of the powder containing the nitrogen element and gallium element of Claim 3 characterized by the above-mentioned.   The method for producing a powder containing nitrogen and gallium elements according to claim 1, wherein the process is a process of pulverizing the gallium compound powder and the alkali metal nitride powder in a non-oxygen atmosphere.   The method for producing a powder containing a nitrogen element and a gallium element according to claim 5, wherein the non-oxygen atmosphere is a vacuum, a nitrogen gas atmosphere, an argon gas atmosphere, or an ammonia gas atmosphere.   The said grinding | pulverization is performed by rotating the sealed container which enclosed the metal gallium powder or the gallium compound powder, the ball | bowl for grinding | pulverization, and the nitrogen compound, It is characterized by the above-mentioned. For producing powder containing nitrogen element and gallium element.   The nitrogen element according to claim 7, wherein when the metal gallium powder is pulverized, the sealed container is rotated at 600 to 800 rpm, and when the gallium compound powder is pulverized, the sealed container is rotated at 100 to 800 rpm. And manufacturing method of powder containing gallium element.   9. The method according to claim 7, wherein when the metal gallium powder is pulverized, the sealed container is rotated for 1 to 4 hours, and when the gallium compound powder is pulverized, the sealed container is rotated for 30 minutes to 4 hours. For producing powder containing nitrogen element and gallium element.   The method for producing a powder containing nitrogen and gallium elements according to any one of claims 7 to 9, wherein the diameter of the ball for grinding is 5 to 15 mm.   The powder containing the nitrogen element and gallium element which were manufactured by the manufacturing method as described in any one of Claims 1-10.   Use of the powder according to claim 11 as a raw material for gallium nitride synthesis.   The temperature and pressure in an autoclave containing at least a seed, a solvent containing nitrogen element, and the powder according to claim 11 are controlled so that the solvent is in a supercritical state and / or a subcritical state. A method for producing a gallium nitride single crystal, comprising a step of crystal-growing gallium nitride on a seed surface in an ammonothermal manner.   The method for producing a gallium nitride single crystal according to claim 13, further comprising a mineralizer in the autoclave.   The method for producing a gallium nitride single crystal according to claim 14, wherein the mineralizer is an acidic mineralizer.   The method for producing a gallium nitride single crystal according to claim 15, wherein the acidic mineralizer contains ammonium halide.   The method for producing a gallium nitride single crystal according to any one of claims 13 to 16, wherein a raw material to be a gallium source is further contained in the autoclave in addition to the powder.