JP2013227661A - Method for producing group iii nitride crystal - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method by which a group III nitride crystal can be mass-produced at a high yield and low cost.SOLUTION: In a method for producing a group III nitride crystal, a group III nitride crystal to be synthesized in a reaction vessel is allowed to adhere to a structure disposed in the reaction vessel. A ratio (B/A) between an inner surface area A of the reaction vessel and a surface area B of the structure is 0.3 or more.

Description

  The present invention relates to a method for producing a group III nitride crystal using raw materials efficiently.

  Group III nitride semiconductor substrates such as GaN substrates have been applied to a wide range of applications including single crystal substrates for blue light emitting diodes (LEDs) and blue semiconductor lasers (LDs). The demand is expected to increase further. For this reason, various methods for producing a group III nitride single crystal using a group III nitride polycrystal as a raw material have been studied in producing a group III nitride semiconductor substrate. For example, using a nitrogen-containing solvent such as ammonia in a supercritical state and / or a subcritical state, a group III nitride single crystal is produced by an ammonothermal method in which a desired material is produced using a dissolution-precipitation reaction of raw materials. Is manufactured and processed into a group III nitride semiconductor substrate. In order to mass-produce a group III nitride single crystal by such a method, a method capable of mass-producing a group III nitride crystal serving as a raw material such as a nitride polycrystal with high yield and low cost is required.

Numerous studies have been made so far on methods for producing Group III nitride crystals including gallium nitride crystals.
For example, Patent Document 1 describes a method of growing crystals by reacting on gallium nitride crystal nuclei by introducing ammonia gas while generating gallium chloride in a reaction tube. The grown gallium nitride crystal is collected by a filter installed downstream of the gas flow, and the remaining gas is discharged without being subjected to the reaction.

  Patent Document 2 describes a method for producing a gallium nitride crystal from metal gallium in a reaction vessel having an inner wall surface formed of a non-oxide. It is described that by making the inner wall surface non-oxide, it is possible to obtain a high-quality gallium nitride crystal with few impurities, and the recovery rate of the obtained gallium nitride crystal can be increased.

  Patent Document 3 describes a method of growing a gallium nitride crystal by disposing a seed crystal around a base substrate placed on a susceptor in a reaction vessel. It is described that by arranging a seed crystal around the base substrate, generation of polycrystals on the seed crystal can be suppressed and a single crystal can be grown on the base substrate at high speed.

JP 2003-63810 A JP 2006-83055 A JP 2011-246323 A

Conventionally proposed methods for producing gallium nitride crystals all have a low yield of 10% or less and have a problem that they are not suitable for mass production. For example, the method described in Patent Document 1 collects the produced GaN crystals with a filter and discharges the gas containing Ga that remains without being subjected to the reaction, so that the raw material utilization efficiency is low. Met. In addition, the method described in Patent Document 2 has a difficulty in recovery due to the large amount of nitride crystals adhering to the inner wall of the reaction vessel, and the yield cannot be increased. Furthermore, although the method described in Patent Document 3 can obtain a high-quality GaN crystal, the raw material utilization efficiency is extremely low.
In view of such problems of the prior art, the present inventors have studied for the purpose of providing a method capable of mass-producing group III nitride crystals with high yield and low cost.

  As a result of diligent investigations by the present inventors, it has been found that it is extremely effective to install a specific structure in the reaction vessel and attach the generated group III nitride crystal to the structure. It was. The present invention has been made based on such discovery, and provides the following configuration as means for solving the problems.

[1] A method for producing a group III nitride crystal in which a group III nitride crystal synthesized in a reaction vessel is attached to a structure installed in the reaction vessel, the inner surface area A of the reaction vessel A method for producing a group III nitride crystal, wherein the ratio of the surface area B of the structure (B / A) is 0.3 or more.
[2] The method for producing a group III nitride crystal according to [1], wherein the structure has a surface roughness (Ra) of 10 μm or less.
[3] The method for producing a group III nitride crystal according to [2], wherein the structure has a surface roughness (Ra) of 1.45 μm or less.
[4] The total amount of group III metal raw material supplied to the reaction vessel, 10% by weight or more is attached to the structure installed in the reaction vessel, according to any one of [1] to [3] A method for producing a group III nitride crystal.
[5] The method for producing a group III nitride crystal according to any one of [1] to [4], wherein the material of the surface of the structure is a carbon compound, a silicon compound, or boron nitride.
[6] The method for producing a Group III nitride crystal according to [5], wherein the material of the surface of the structure is pyrolytic boron nitride or pyrolytic carbon.
[7] The method for producing a group III nitride crystal according to any one of [1] to [6], wherein the structure has a plate shape, a rod shape, or a mesh shape.
[8] The method for producing a group III nitride crystal according to any one of [1] to [7], wherein the synthesis of the group III nitride crystal is performed by a hydride vapor phase deposition (HVPE) method.
[9] When growing a group III nitride crystal by the hydride vapor phase deposition (HVPE) method, nitrogen gas flow rate N and hydrogen gas flow rate H introduced into the reaction vessel using nitrogen gas and hydrogen gas as carrier gases The method for producing a group III nitride crystal according to [8], wherein the ratio (N / H) of the above is 1.0 or more.
[10] The method for producing a group III nitride crystal according to any one of [1] to [9], wherein the synthesis rate of the group III nitride crystal is 0.2 kg / day or more.
[11] A group III nitride crystal produced by the production method according to any one of [1] to [10].
[12] The group III nitride crystal according to [11], wherein the oxygen concentration is 80 ppm by weight or less.
[13] The group III nitride crystal according to [11] or [12], wherein the maximum particle size is 100 μm or more.

  According to the production method of the present invention, a group III nitride crystal can be produced with good yield and low cost. The production method of the present invention is also suitable for mass production of group III nitride crystals.

It is a schematic diagram of the crystal manufacturing apparatus which can be used by this invention. It is a top view which shows the structural example of a structure. It is a top view which shows the structural example of a structure. It is a top view which shows the structural example of a structure. It is a top view which shows the structural example of a structure. It is a top view which shows the structural example of a structure.

  Hereinafter, the method for producing a group III nitride crystal of the present invention and the crystal production apparatus and members used therefor 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. Further, the notation “%” means “% by weight” unless otherwise specified.

[Production Method of Group III Nitride Crystal]
(Feature)
In the group III nitride crystal production method of the present invention, a group III nitride crystal synthesized by reacting a group III metal raw material in a reaction vessel is attached to a structure installed in the reaction vessel. In particular, the present invention is characterized in that the ratio (B / A) of the inner surface area A of the reaction vessel to the surface area B of the structure is 0.3 or more. Moreover, in this invention, 10 weight% or more can be made to adhere to the structure installed in the said reaction container among the whole quantity of a group III metal raw material.
In the conventional manufacturing method, a group III nitride crystal is mainly grown on the surface of a small base substrate or a seed crystal placed in a reaction vessel, but this method uses a large amount of raw material. There are few Group III nitride crystals obtained. Here, a group III nitride crystal is deposited on the inner wall of the reaction vessel or the surface of a member such as a susceptor and is wasted, or raw materials not used in the reaction are discharged out of the reaction vessel. It was. By installing the structure in the reaction vessel according to the present invention and attaching the synthesized group III nitride crystal to the structure, the utilization efficiency of the raw materials can be increased, and the attachment to the inner wall and members of the reaction vessel As a result, wasteful group III nitride crystals can be reduced.

(Adhesion rate)
In the present invention, in the method for producing a group III nitride crystal synthesized by reacting a group III metal raw material in a reaction vessel, 10% by weight or more of the total amount of the group III metal raw material is placed in the reaction vessel. It can be attached to the structure.
Here, the group III metal raw material refers to a group III metal raw material such as Ga, In, and Al supplied for synthesizing a group III nitride crystal in the reaction vessel. Therefore, of the total amount of the Group III metal raw material supplied to the reaction vessel, the ratio of the amount to be attached to the structure installed in the reaction vessel (hereinafter sometimes referred to as the adhesion rate) is 10% by weight or more. Then, a group III nitride crystal can be produced efficiently. The adhesion rate is preferably 20% by weight or more, more preferably 30% by weight, and still more preferably 40% by weight.
As will be described in detail later, the Group III raw material supplied into the reaction vessel is not necessarily in the state of a Group III metal, but may be supplied in the form of a gas or the like as a compound containing a Group III element. In such a case, the “total amount of the Group III metal raw material” means the total amount of the Group III metal contained in the compound containing the Group III metal and the Group III element supplied into the reaction vessel. In addition, the amount of the group III metal raw material attached to the structure is not only the amount attached in the state of the group III metal but also the amount including the group III nitride crystal synthesized by reacting the group III metal raw material. Shall mean. From the above, as a method for calculating the adhesion rate, the following cases can be specifically considered. For example, in a case where GaN is synthesized by spraying HCl onto metal Ga and supplying GaCl into the reaction vessel and reacting the GaCl and NH ₃ , the total amount of the Group III metal raw material is within the reaction vessel. Is the total weight of Ga in the metal Ga and GaCl supplied to the metal, and the ratio of the total weight of the metal Ga attached to the structure and Ga in the GaN is the adhesion rate.

(Surface area of the structure)
By determining the structure of the structure used in the present invention in consideration of the inner surface area of the reaction vessel in which the structure is installed, the above-described adhesion rate can be within a predetermined range. When the inner surface area of the reaction vessel is A and the surface area of the structure is B, the ratio (B / A) of the inner surface area of the reaction vessel to the inner surface area of the reaction vessel is 0.3 or more. By setting the ratio (B / A) of the inner surface area of the reaction vessel to the inner surface area of the reaction vessel to be 0.3 or more, the raw material can be more efficiently attached to the surface of the structure. Thereby, the amount of group III nitride crystals adhering to the inner wall of the reaction vessel can be reduced. For this reason, the yield of the group III nitride crystal can be further increased. The value of the ratio (B / A) is more preferably 1 or more, further preferably 1.5 or more, and particularly preferably 5 or more. The upper limit can be, for example, 30 or less, preferably 20 or less, and more preferably 15 or less.
Here, the inner surface area A of the reaction vessel means the total area of the inner surface with which the material or gas introduced into the reaction vessel can come into contact. For example, if a part of the inner surface of the reaction container is covered with the member by installing the member in the reaction container, the area of the part covered in that way is not counted. Moreover, the surface area B of the structure here also means the total area of the surface where the material or gas introduced into the reaction vessel can come into contact. For example, surfaces that are hidden by contact with the susceptor when the structure is placed on the susceptor are not counted. Also, the surface hidden by contact with the fixture used to fix the structure is not counted.

(Surface roughness of the structure)
The structure used in the present invention preferably has a smooth surface. The surface roughness (Ra) of the structure is preferably 10 μm or less, more preferably 5 μm or less, and even more preferably 3 μm or less. Most preferably, it is 1.45 μm or less. By making the surface roughness of the structure 10 μm or less, the deposition efficiency of the group III nitride crystal to the structure can be further increased. Furthermore, the peelability between the structure and the group III nitride crystal can be improved by setting the surface roughness of the structure to 1.45 μm or less. However, if it becomes smaller than 0.5 μm, the peelability is lowered again, so that it is preferably 0.5 μm or more. In addition, all the structures used in the present invention may be similarly smooth, or may have a mixture of portions having different surface roughness. For example, it is possible to use a structure in which members having different surface roughness are combined.

  In addition, the surface roughness (Ra) as used in the field of this invention is the value measured by the brand name Surfcom by Tokyo Seimitsu Co., Ltd.

(Material of structure)
The structure used in the present invention is preferably a material different from the obtained group III nitride crystal, and preferably the attached group III nitride crystal can be peeled off without being integrated with the structure. . The material of the structure must be selected from materials that have the property of easily adhering group III nitride crystals, that can easily hold the adhering nitride crystals on the surface, and that do not react with group III nitride crystals. Is preferred. Examples of such materials include sintered materials obtained by sintering refractories such as ceramics and refractory bricks, oxides, nitrides, carbides and the like. For example, a carbon compound, a silicon compound, and boron nitride can be mentioned. Moreover, it is preferable that it is a non-oxide at the point which can suppress the oxygen concentration in the group III nitride crystal obtained. Examples of preferable materials for the structure include SiC, Si ₃ N ₄ , BN, carbon, and graphite. These are preferably polycrystals or sintered bodies, and more preferably pyrolytic boron nitride (pBN). And pyrolytic carbon.

  The structure may be composed entirely of the above-mentioned material, or only the surface may be coated with the above-mentioned material. Further, the surface of the structure used in the present invention may be composed of only one of the above materials, or may be composed of two or more materials. . For example, it is possible to use a structure in which a plurality of members made of different materials are combined.

(Structure shape)
The shape of the structure used in the present invention is preferably a structure that allows group III nitride crystals to adhere as much as possible. For this purpose, it is preferable to have a structure that is easy to come into contact with the raw material gas and the crystal nucleus flowing in the reaction vessel. Further, the space occupied in the reaction vessel is preferably large to some extent.
The structure may be composed of a single member or may be composed of a plurality of members. Examples of such constituent members include plate-like bodies, rod-like bodies, block bodies, and the like. The plate-like body is relatively thin and has a planar spread, and the thickness is preferably 2 mm or more, more preferably 4 mm or more, and preferably 15 mm or less, more preferably 10 mm or less. The shape of the plane can be various shapes such as a circle, an ellipse, a rectangle, and a star, but a shape that is a circle, an ellipse, and a rectangle is preferable. The rod-like body preferably has a length of 50 mm or more, more preferably 100 mm or more, and the upper limit is a size that can be accommodated in the reaction vessel. The rod-shaped body preferably has a diameter of 2 mm or more, more preferably 4 mm or more, more preferably 15 mm or less, and even more preferably 10 mm or less. The block body has a lump shape, and can take various shapes such as a spherical shape, a rugby ball shape, a rectangular parallelepiped shape, and a rectangular parallelepiped shape.

  A through-hole may be formed in a member constituting the structure. The diameter of such a through hole is preferably 2 mm or more, more preferably 8 mm or more, more preferably 50 mm or less, and even more preferably 30 mm or less. For example, a through-hole can be provided in the plate-like body. The through-holes may be provided regularly or irregularly. Further, the through hole is not limited to the one formed by making a hole in the plate-like body, and is formed by weaving a thread-like body or by forming with a net-like mold. It may be a product.

Specific examples of the structure will be described with reference to the drawings. 2 to 6 are top views of the structure. Here, “upper” means the direction of the raw material supply source in the reaction vessel, and the raw material is supplied from the top to the bottom. The structure shown in FIG. 2 is a structure in which rod-like bodies 2 are installed between plate-like bodies 1 configured radially as shown in the figure. Both the plate-like body and the rod-like body extend in the vertical direction. The structure shown in FIG. 3 has a structure in which a large number of through holes 3 are regularly provided in one plate-like body 1. The gas and crystal nuclei can move through the through-holes. In the structure of FIG. 4, a plurality of rod-like bodies 2 are regularly arranged. Each rod-like body extends in the vertical direction, and all have the same shape and size. The rod-shaped bodies are fixed to each other by a fixing tool (not shown). The structure shown in FIG. 5 is a structure in which a plurality of plate-like bodies 1 are regularly arranged with a constant interval. Each plate-like body extends in the vertical direction, and all have the same shape and size. The plate-like bodies are fixed to each other by a fixing tool (not shown). The structure shown in FIG. 6 is a structure made up of blocks 4. This block is rectangular.
The embodiment of the structure shown above is given as a specific example, and the structure that can be used in the present invention is not limited to these structures.

(Gas supply)
The production method of the present invention is characterized in that a group III nitride crystal is adhered using a structure, but the yield can be increased by devising the supply of raw materials. When a hydride vapor phase deposition (HVPE) method is employed as a method for growing a group III nitride crystal, hydrogen gas is usually used as a carrier gas. By reducing the use ratio of the hydrogen gas, the nitride can be obtained. It is possible to increase the yield of crystals. In order to reduce the use ratio of hydrogen gas, it is preferable to use another inert gas as a carrier gas. Examples of such an inert gas include nitrogen gas and argon gas, but it is preferable to employ nitrogen gas from the viewpoint of cost.
In the present invention, the ratio (N / H) of the nitrogen gas flow rate N and the hydrogen gas flow rate H introduced into the reaction vessel is preferably 1.0 or more, more preferably 3 or more, and 5 or more. Is more preferable, and it is particularly preferably 9 or more. There is no particular limitation on the upper limit value, and hydrogen gas does not have to flow. Further, when the partial pressure of hydrogen gas in the production atmosphere is high, a reducing atmosphere is formed, and impurities derived from the reaction vessel (reactor) tend to be easily taken into the group III nitride crystal. Therefore, it is preferable to perform crystal growth by setting the ratio (N / H) of the nitrogen gas flow rate N and the hydrogen gas flow rate H to be large because the obtained group III nitride crystal can be highly purified. The nitrogen gas flow rate N and the hydrogen gas flow rate H here mean the total amount of each gas supplied into the reaction vessel.

  In the production method of the present invention, the yield can be further increased by increasing the partial pressure of the raw material gas. For example, in the HVPE method, the yield can be increased by increasing the partial pressure of ammonia gas. Specifically, it is preferably 0.02 atm or more, more preferably 0.05 atm or more, and further preferably 0.2 atm or more.

(Yield (Raw material utilization efficiency))
By carrying out the production method of the present invention, the yield can be drastically improved. In the present invention, for example, when producing a GaN crystal, the yield is evaluated based on the Ga raw material utilization efficiency. That is, it is evaluated by calculating how much Ga is obtained as a GaN crystal out of the total amount of Ga supplied into the reaction vessel as a raw material. In the present invention, the raw material utilization efficiency exceeds 10%, can achieve 30% or more, can achieve 50% or more, and can also achieve 60% or more. It is. Here, the GaN crystal obtained when calculating the raw material utilization efficiency includes not only the GaN crystal attached to the structure but also the GaN crystal attached to the inner wall of the reaction vessel.

  Moreover, according to the production method of the present invention, the synthesis rate of the group III nitride crystal can be increased. The synthesis rate of the group III nitride crystal in the present invention can be 0.2 kg / day or more, can be 1 kg / day or more, and further can be 5 kg / day or more. is there. Since the production method of the present invention can increase the synthesis rate and increase the yield, a large amount of group III nitride crystals can be produced efficiently.

(Synthesis of Group III nitride crystals)
In the production method of the present invention, a group III nitride crystal is synthesized in a reaction vessel. As a method for synthesizing the group III nitride crystal, for example, a vapor phase method such as a hydride vapor phase deposition (HVPE) method, a metal organic chemical vapor deposition (MOCVD) method, a sublimation method, or the like can be employed. The method can be preferably used. In the following, as an example of a preferable manufacturing apparatus, an HVPE manufacturing apparatus will be described with reference to FIG.

1) Basic Structure The manufacturing apparatus of FIG. 1 includes a susceptor for mounting the structure 107 and a reservoir 105 for storing a group III nitride crystal material to be grown in a reactor 100. In addition, introduction pipes 101 to 104 for introducing gas into the reactor 100 and an exhaust pipe 108 for exhausting are installed. Further, a heater 106 for heating the reactor 100 from the side surface is installed.

2) Reactor material, gas type of atmospheric gas As the material of the reactor 100, quartz, sintered boron nitride, stainless steel, silicon nitride or the like is used. Preferred materials are silicon nitride and quartz. The reactor 100 is filled with atmospheric gas in advance before starting the reaction. Examples of the atmospheric gas (carrier gas) include inert gases such as hydrogen, nitrogen, He, Ne, and Ar. These gases may be mixed and used. From the viewpoint of increasing the adhesion rate to the structure, it is preferable to contain at least nitrogen, and the ratio of nitrogen in the carrier gas is preferably 50% or more.

3) Material and shape of susceptor, distance from growth surface to susceptor As a material of the susceptor for holding the structure 107, carbon is preferable, and a material whose surface is coated with SiC is more preferable. The shape of the susceptor is not particularly limited as long as the structure used in the present invention can be installed.

4) Reservoir The reservoir 105 is charged with the raw material of the group III nitride crystal to be grown. Specifically, the raw material which becomes a group III source is put. Examples of the raw material to be a group III source include Ga, Al, and In. A gas that reacts with the raw material put in the reservoir 105 is supplied from an introduction pipe 103 for introducing the gas into the reservoir 105. For example, when Ga serving as a group III source is put in the reservoir 105, HCl gas can be supplied from the introduction pipe 103, and thereby, GaCl gas is supplied into the reaction vessel as a group III source gas. At this time, the carrier gas may be supplied from the introduction pipe 103 together with the HCl gas. Examples of the carrier gas include hydrogen, nitrogen, an inert gas such as He, Ne, and Ar. These gases may be mixed and used.

5) Nitrogen source (ammonia), separate gas, dopant gas From the introduction pipe 104, a raw material gas serving as a nitrogen source is supplied. Usually, NH ₃ is supplied. A carrier gas is supplied from the introduction pipe 101. As the carrier gas, the same carrier gas supplied from the introduction pipe 103 can be exemplified. This carrier gas also has an effect of suppressing the reaction in the gas phase between the raw material gases and preventing polycrystals from adhering to the nozzle tip. A dopant gas can also be supplied from the introduction pipe 102. For example, an n-type dopant gas such as SiH ₄ , SiH ₂ Cl ₂ , or H ₂ S can be supplied.
The ratio (N / H) of the nitrogen gas flow rate N introduced into the reaction vessel and the hydrogen gas flow rate H (N / H) is preferably adjusted as described above.

6) Gas introduction method The gases supplied from the introduction pipes 101, 102, and 104 may be replaced with each other and supplied from different introduction pipes. In addition, the source gas and the carrier gas serving as a nitrogen source may be mixed and supplied from the same introduction pipe. Further, a carrier gas may be mixed from another introduction pipe. These supply modes can be appropriately determined according to the size and shape of the reactor 100, the reactivity of the raw materials, the target crystal growth rate, and the like.

7) Location of Exhaust Pipe The gas exhaust pipe 108 can be installed on the top, bottom, and side surfaces of the reactor inner wall. From the viewpoint of dust drop, it is preferably located below the crystal growth end, and more preferably a gas exhaust pipe 108 is installed on the bottom of the reactor as shown in FIG.

8) Crystal Growth Conditions Crystal growth using the above production apparatus is preferably performed at 950 ° C. or higher, more preferably at 970 ° C. or higher, and further preferably at 980 ° C. or higher. Moreover, it is preferable to carry out at 1120 degrees C or less, It is more preferable to carry out at 1100 degrees C or less, It is further more preferable to carry out at 1090 degrees C or less. The temperature drop during crystal growth is preferably controlled within 60 ° C, more preferably controlled within 40 ° C, and even more preferably controlled within 20 ° C. The pressure in the reactor is preferably 10 kPa or more, more preferably 30 kPa or more, and further preferably 50 kPa or more. Moreover, it is preferable to set it as 200 kPa or less, It is more preferable to set it as 150 kPa or less, It is further more preferable to set it as 120 kPa or less.

(Crystal processing)
The group III nitride crystal produced by the production method of the present invention may be used as it is as a raw material for producing a nitride semiconductor substrate, or may be used after being processed.
In the case of processing, slicing, outer shape processing, etching, cleaning, and the like can be appropriately performed to obtain a desired shape. Any one of these methods may be selected and used, or may be used in combination.

[Nitride crystals]
(Feature)
According to the production method of the present invention, a group III nitride crystal having a large particle size can be produced. For example, one having a maximum particle size of 300 μm or more, 500 μm or more can be manufactured, and one having a maximum particle size of 1 mm or more can also be manufactured. Since the group III nitride crystal produced by the production method of the present invention has a particle size distribution, it can be sized by sieving if necessary according to the application. The particle size distribution of the group III nitride crystal produced by the production method of the present invention is similar to that of the conventional method, but the oxygen concentration tends to be low.

Moreover, according to the production method of the present invention, a group III nitride polycrystal can be produced more efficiently. In the group III nitride polycrystal obtained in the present invention, group III nitride single crystals in a fine powder state gather to form a lump. Group III nitride crystal fine powder, which is a group III nitride single crystal in a fine powder state (primary particles), has a needle-like or granular major diameter of usually 0.1 μm or more, preferably 0.5 μm or more, More preferably, it is 1 micrometer or more, More preferably, it is 3 micrometers or more. The upper limit is not particularly limited, but for example, the major axis is preferably 500 μm or less, more preferably 100 μm or less, and particularly preferably 50 μm or less.
The lump containing the group III nitride crystal fine powder is not particularly limited in shape, but the maximum width (major axis) of the lump is preferably 1 mm or more for ease of handling, and is preferably 2 mm or more. More preferably, it is 5 mm or more. Moreover, although it does not restrict | limit in particular about an upper limit, For example, a major axis is preferable 10 mm or less, and 7 mm or less may be sufficient.
Furthermore, it is preferable that it is a group III nitride polycrystal which forms the tertiary particle | grains which a secondary particle aggregates. The particle size of the secondary particles is preferably 10 μm or more, more preferably 50 μm or more, and further preferably 100 μm or more. Moreover, it is preferable that it is 1000 micrometers or less, It is more preferable that it is 900 micrometers or less, It is further more preferable that it is 800 micrometers or less. The particle size of the tertiary particles is preferably 1 mm or more, more preferably 5 mm or more, further preferably 10 mm or more, and preferably 120 mm or less, more preferably 60 mm or less. Preferably, it is 20 mm or less. The particle size of the secondary particles can be measured with an optical microscope or the like. If it is 1 mm or more as in the case of tertiary particles, it can be visually confirmed, and can be measured, for example, with calipers or a ruler. Further, for tertiary particles formed by agglomerating secondary particles, the maximum diameter of the tertiary particles coincides with the above-mentioned “particle diameter”.
In addition, in the group III nitride polycrystal that forms tertiary particles formed by aggregation of secondary particles, primary particles mean nano-unit single crystals, and these single crystals are aggregated and bonded to each other. The secondary particle which is a polycrystal is comprised. Usually, primary particles cannot be discriminated as particles because they are combined and integrated with each other.

Furthermore, according to the production method of the present invention, a group III nitride crystal having a certain range of L ^* value, a ^* value, and b ^* value is produced when expressed in the L ^* a ^* b ^* color system. It is possible. Here, in the L ^* a ^* b ^* color system, the L ^* value indicates the brightness of the crystal, and the higher the value (closer to 100), the higher the brightness. The a ^* value indicates red-green, and the smaller value indicates green and the larger value indicates red. In other words, the larger the L ^* value, the brighter the color, and the larger the absolute value of the a ^* and b ^* values, the clearer the color.

The L ^* value of the group III nitride crystal obtained by the production method of the present invention is preferably 50 or more, more preferably 55 or more, and further preferably 60 or more. Further, the a ^* value of the group III nitride crystal is preferably −10 or more, more preferably −5 or more, and preferably 10 or less, more preferably 5 or less. . Furthermore, the b ^* value is preferably −20 or more, more preferably −10 or more, more preferably 20 or less, and even more preferably 15 or less. By setting the color difference (L ^* value, a ^* value, b ^* value) of the group III nitride crystal within the above range, a growth crystal with less coloring can be obtained.
The color difference (L ^* value, a ^* value, b ^* value) of the group III nitride crystal is, for example, Nippon Denshoku ZE-2000 colorimetric colorimeter (standard white plate Y = 95.03, X = 95. 03, Z = 112.02).

  The group III nitride crystal produced by the production method of the present invention can produce an oxygen concentration of, for example, 80 ppm by weight or less, preferably 50 ppm by weight or less, more preferably 30 ppm by weight or less. Can also be manufactured. In addition, the group III nitride crystal produced by the production method of the present invention also tends to emit yellow light under UV irradiation. This indicates that the group III nitride crystal has good crystallinity and high purity.

(Use)
The group III nitride crystal produced by the production method of the present invention can be used for various applications. In particular, it is preferably used as a raw material for producing a nitride semiconductor crystal for use for a specific purpose. Specifically, it can be effectively used as a raw material for producing a nitride semiconductor substrate. For example, a group III nitride crystal produced by the production method of the present invention is placed in a raw material dissolution region in a reaction vessel as a raw material of an ammonothermal method, and heated with a nitrogen-containing solvent such as ammonia or a mineralizer. A nitride crystal can be grown on the seed crystal placed in the crystal growth region in a supercritical state and / or a subcritical state. The obtained crystal can be processed into a nitride semiconductor substrate through slicing, polishing, and the like. Nitride semiconductor substrates such as gallium nitride substrates are useful as single crystal substrates for light-emitting diodes (LEDs) and semiconductor lasers (LDs). It is highly useful as a crystal substrate.

The features of the present invention will be described more specifically with reference to examples and comparative 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.
The gases (hydrogen, nitrogen, ammonia, hydrogen chloride) used in the reactions in Examples and Comparative Examples have a purity of 99.999% or more. The gas which cannot obtain 99.999% or more gas cylinders was used after the purity was increased by a purifier or a purifier. In the examples and comparative examples, the reaction apparatus shown in FIG. 1 was used.

Example 1
A structure 107 having a surface area 2.033 times as large as the inner area of the quartz reaction vessel (reactor) was placed in the reaction vessel. This structure has the structure shown in FIG. The structure is made of pyrolytic carbon having a surface roughness (Ra) of 1.29 μm. The surface roughness was measured by the trade name Surfcom manufactured by Tokyo Seimitsu Co., Ltd. During the reaction, the structure was rotated at 0.1 to 40 rpm in the direction indicated by the arrow in FIG.
The reaction vessel 100 was purged with nitrogen. After that, the amount of gallium consumed in one crystal growth (batch) was charged into the III-group material (gallium) reservoir 105 at the top of the reaction vessel.
The susceptor to which the structure 107 was fixed was placed on a weighing scale, the tare weight was measured, and the susceptor was installed in the reaction vessel 100. After purging the inside of the reaction vessel 100 with an inert gas, hydrogen gas was introduced and the temperature was raised to the synthesis temperature. The introduction of hydrogen gas has an effect of removing oxides in the reaction vessel.
A carrier gas set to hydrogen: nitrogen = 1.5: 8.5 was introduced at 0.825 atm to a place where the temperature had risen to a predetermined temperature, and ammonia gas was introduced at 0.154 atm along with the carrier gas, Further, hydrogen chloride gas was introduced into the gallium reservoir 105 at 0.014 atm and supplied to the reaction section as gallium chloride gas. At that time, in order to prevent the reverse reaction of gallium chloride, 0.007 atm hydrogen chloride was supplied into the reaction vessel from a single line, and crystals of gallium nitride were deposited on the structure 107 for 8 hours.

When the flow of hydrogen chloride gas corresponding to the amount of gallium input was finished, the supply of hydrogen chloride was stopped and the cooling process was started. After cooling was completed, the structure to which the nitride crystal was attached was taken out.
The weight of the polycrystalline gallium nitride attached to the structure fixed to the susceptor was 205.8 g. From the value obtained by subtracting the weight of nitrogen atoms from the weight of the polycrystalline gallium nitride, the reaction rate was converted to 57.1% when all the gallium weights for the input were converted to gallium nitride as 100%. there were. Therefore, the adhesion rate in Example 1 was 57.1%, and some polycrystalline GaN adhered to the inner wall in the reaction vessel, so the yield (raw material utilization efficiency) was over 57.1%. I found out.

When the oxygen concentration of the polycrystalline gallium nitride taken out from the reaction vessel was analyzed with an oxygen-nitrogen / hydrogen analyzer (TCH-600 manufactured by LECO), it was 0.0047% by weight.
The synthesis rate of the gallium nitride polycrystal is 0.617 g / day, and the particle size of the secondary particles of the gallium nitride polycrystal is 20 μm to 470 μm, and they aggregate to form a lump (tertiary particle) of several mm to 50 mm. A gallium nitride polycrystal was obtained. The particle size of the secondary particles was measured by observation with an optical microscope. Further, there was little adhesion of gallium nitride to the inner wall of the reaction vessel.

(Examples 2-9)
The synthesis was performed under the same conditions as in Example 1 except that the conditions were changed to those described in Table 1. Table 1 shows the observation results of the synthesized gallium nitride crystal. In any of the examples, since some polycrystalline GaN adhered to the inner wall in the reaction vessel, it was found that the yield (raw material utilization efficiency) exceeded the adhesion rate.

(Example 10)
As Example 10, the surface roughness (Ra) of the structure was 1.59 μm (measured by a trade name Surfcom manufactured by Tokyo Seimitsu Co., Ltd.), and the same conditions as in Example 1 except for the conditions described in Table 1 As a result of the synthesis, similar crystals were obtained. Furthermore, it was confirmed that the raw material utilization efficiency was equal or higher.
In Example 10, the weight of the gallium nitride polycrystal attached to the inner surface of the reaction vessel other than the structure was 12 g. Since the weight of the gallium nitride polycrystal attached to the structure was 254.0 g, the total weight of the nitrogen gallium polycrystal produced in the reaction vessel was 266.0 g, and the yield (raw material utilization efficiency) was It was 73.8%.

(Comparative Example 1)
A structure 107 having a surface area 0.183 times as large as the inner area of a quartz reaction vessel (reactor) was placed in the reaction vessel 100.
The reaction vessel was purged with nitrogen. After that, the amount of gallium consumed in one crystal growth (batch) was charged into the III-group material (gallium) reservoir 105 at the top of the reaction vessel.
The susceptor to which the structure 107 was fixed was placed on a weighing scale, the tare weight was measured, and the susceptor was placed in the reaction vessel 100. After purging the inside of the reaction vessel 100 with an inert gas, hydrogen gas was introduced. The temperature was raised to the synthesis temperature. The introduction of hydrogen gas has an effect of removing oxides in the reaction vessel.
A carrier gas set to hydrogen: nitrogen = 10: 0 is introduced at 0.953 atm to a place where the temperature has risen to a predetermined temperature, ammonia gas is introduced at 0.0341 at the same time as the carrier gas, and the gallium reservoir 105 is further introduced. Hydrogen chloride gas was introduced at 0.00553 atm and supplied to the reaction section as gallium chloride gas. At that time, in order to prevent the reverse reaction of gallium chloride, 0.007 atm of hydrogen chloride was supplied into the reaction vessel from a single line, and crystals of gallium nitride were deposited on the structure 107 for 60 hours.

When the flow of hydrogen chloride gas corresponding to the amount of gallium input was finished, the supply of hydrogen chloride was stopped and the cooling process was started. After cooling was completed, the structure to which the nitride crystal was attached was taken out.
The weight of the gallium nitride polycrystal attached to the structure fixed to the susceptor was 85.2 g. From the value obtained by subtracting the weight of the nitrogen atom from the weight of the gallium nitride polycrystal, the conversion rate when converted to 100% when all the gallium weight of the input was converted to gallium nitride was converted to 5.1%. there were. Therefore, the adhesion rate in Comparative Example 1 was 5.1%, and a large amount of polycrystalline GaN adhered to the inner wall and the introduction tube in the reaction vessel, so the yield (raw material utilization efficiency) was 5.1. It was found to be over%. However, damage to the reaction vessel itself increased because a large amount of polycrystalline GaN adhered to the reaction vessel depending on the shape of the structure and the choice of carrier gas.

When the oxygen concentration of the gallium nitride crystal taken out from the reaction vessel was analyzed with an oxygen-nitrogen / hydrogen analyzer (TCH-600 manufactured by LECO), it was 0.0100% by weight.
The synthesis rate of gallium nitride was 0.034 g / day, which was slower than the example. When the particle size of the gallium nitride polycrystal was measured with an optical microscope, a particle size as large as 480 μm to 1400 μm was obtained. However, the gallium nitride polycrystal was often attached to the inner wall of the reaction vessel, and Examples 1 to 10 Yield was low.

(Comparative Example 2)
A gallium nitride single crystal base substrate having a diameter of 76 mm and a surface area of 0.046 times the surface of the quartz reaction vessel (reactor) is placed in the reaction vessel 100 instead of the structure 107. It was.
The reaction vessel was purged with nitrogen. After that, the amount of gallium consumed in one crystal growth (batch) was charged into the III-group material (gallium) reservoir 105 at the top of the reaction vessel.
The base substrate of the gallium nitride single crystal was placed on a weighing scale, and the tare weight was measured and put in the reaction vessel 100. After purging the inside of the reaction vessel 100 with an inert gas, hydrogen gas was introduced. The temperature was raised to the synthesis temperature.
A carrier gas set to hydrogen: nitrogen = 10: 0 is introduced at 0.888 atm to a place where the temperature has risen to a predetermined temperature, and ammonia gas is introduced at 0.101 atm together with the carrier gas. Hydrogen chloride gas was introduced at 0.00107 atm and supplied to the reaction section as gallium chloride gas. At that time, in order to prevent the reverse reaction of gallium chloride, 0.0003 atm of hydrogen chloride was supplied into the reaction vessel from a single line to deposit a gallium nitride crystal on the gallium nitride single crystal base substrate for 40 hours.

When the flow of hydrogen chloride gas corresponding to the amount of gallium input was finished, the supply of hydrogen chloride was stopped and the cooling process was started. After cooling was completed, the nitride single crystal including the underlying substrate of the gallium nitride single crystal to which the nitride crystal was grown was taken out.
The weight of the gallium nitride single crystal grown on the nitride single crystal base substrate was 370 g. From the value obtained by subtracting the weight of nitrogen atoms from the weight of the polycrystalline gallium nitride, the reaction rate when the case where all the gallium weight of the input is converted to gallium nitride is defined as 100% is converted to 9.0%. there were. Therefore, the adhesion rate in Comparative Example 2 was 9.0%, and a large amount of polycrystalline GaN adhered to the inner wall and the introduction tube in the reaction vessel.

When the oxygen concentration of the gallium nitride crystal taken out from the reaction vessel was analyzed with an oxygen-nitrogen / hydrogen analyzer (TCH-600 manufactured by LECO), it was 0.0100% by weight.
The synthesis rate of gallium nitride was 0.222 g / day, which was slower than that of the example. Further, a large crystal having a diameter of 76.2 mm and a thickness of 13.3 mm was obtained, but the gallium nitride polycrystal was often attached to the inner wall of the reaction vessel, and the yield (utilization of raw materials) Efficiency) was low.

Further, SIMS analysis and color difference measurement of the oxygen concentration and Si concentration of the gallium nitride crystals obtained in Example 9 and Comparative Example 1 were performed.
The SIMS analysis of the oxygen concentration and the Si concentration was measured by SIMS using Ims-4f manufactured by CAMECA. The color difference measurement was performed in the following manner using a Nippon Denshoku ZE-2000 colorimetric color difference meter (standard white board Y = 95.03, X = 95.03, Z = 112.02). About 2 cc of the gallium nitride polycrystal powder pulverized to 100 micrometers or less was packed in the bottom of the 35 mmφ transparent round cell attached to the color difference meter, and loaded from the top without any gap. The sample was placed on a powder / paste sample stage and covered with a cap, and then the reflection was measured for a sample area of 30 mmφ. The analysis results are shown in Table 2.

The Si concentration of the gallium nitride crystal obtained in Example 9 was an order of magnitude less than that of Comparative Example 1, and it was found that a crystal having a low Si concentration was obtained with high purity gallium nitride.
This is because when the partial pressure of the hydrogen gas in the growth atmosphere is high, a reducing atmosphere is formed, and impurities derived from the reactor are easily taken into the gallium nitride crystal. Therefore, as in Examples 1 to 10, the partial pressure of the hydrogen gas is lowered. This is because the gallium nitride crystal can be highly purified by performing this growth.

In Examples 1 to 10, the Ga utilization efficiency, the synthesis rate, and the acquisition amount of gallium nitride crystals could all be increased, and adhesion of gallium nitride to the inner surface of the reaction vessel was small. For this reason, according to the manufacturing method of this invention, it has confirmed that the nitride crystal was obtained efficiently in large quantities. On the other hand, in the comparative example, the Ga utilization efficiency, the synthesis rate, and the acquisition amount of gallium nitride crystals were all low.
In addition, gallium nitride was often attached to the inner surface of the reaction vessel.
Further, in Examples 1 to 9 using pyrolytic carbon, it was found that there was an advantage that the peelability from the adhesion structure was good, and when pBN was used, there was an advantage that the yield could be further improved. .

  According to the production method of the present invention, a group III nitride crystal can be produced with good yield and low cost. The production method of the present invention is also suitable for mass production of group III nitride crystals. In addition, the group III nitride crystal provided by the production method of the present invention can be effectively used as a raw material for producing a nitride semiconductor substrate. Nitride semiconductor substrates are applied to a wide range of applications including blue light emitting diode (LED) and blue semiconductor laser (LD) substrates. For this reason, the industrial applicability of the present invention is extremely high.

DESCRIPTION OF SYMBOLS 100 Reactor 101-104 Gas introduction pipe 105 Group III raw material reservoir 106 Heater 107 Structure 108 Exhaust pipe 1 Plate body 2 Rod-shaped body 3 Through-hole 4 Block

Claims (13)

  A method for producing a group III nitride crystal in which a group III nitride crystal synthesized in a reaction vessel is attached to a structure installed in the reaction vessel, wherein the inner surface area A of the reaction vessel and the structure A method for producing a Group III nitride crystal, wherein the ratio of the surface area B (B / A) is 0.3 or more.   The method for producing a group III nitride crystal according to claim 1, wherein the structure has a surface roughness (Ra) of 10 μm or less.   The method for producing a group III nitride crystal according to claim 2, wherein the structure has a surface roughness (Ra) of 1.45 µm or less.   The group III nitriding according to any one of claims 1 to 3, wherein 10% by weight or more of the total amount of the group III metal raw material supplied to the reaction vessel is attached to the structure installed in the reaction vessel. Method for producing physical crystals.   The method for producing a group III nitride crystal according to any one of claims 1 to 4, wherein a material of a surface of the structure is a carbon compound, a silicon compound, or boron nitride.   The method for producing a group III nitride crystal according to claim 5, wherein the material of the surface of the structure is pyrolytic boron nitride or pyrolytic carbon.   The method for producing a group III nitride crystal according to any one of claims 1 to 6, wherein the structure has a plate shape, a rod shape, or a mesh shape.   The method for producing a group III nitride crystal according to any one of claims 1 to 7, wherein the synthesis of the group III nitride crystal is performed by a hydride vapor phase deposition (HVPE) method.   When growing a group III nitride crystal by the hydride vapor deposition (HVPE) method, nitrogen gas and hydrogen gas are used as carrier gases, and the ratio of the nitrogen gas flow rate N and the hydrogen gas flow rate H introduced into the reaction vessel ( The method for producing a group III nitride crystal according to claim 8, wherein N / H) is 1.0 or more.   The method for producing a group III nitride crystal according to any one of claims 1 to 9, wherein a synthesis rate of the group III nitride crystal is 0.2 kg / day or more.   The group III nitride crystal manufactured with the manufacturing method of any one of Claims 1-10.   The group III nitride crystal according to claim 11, wherein the oxygen concentration is 80 ppm by weight or less.   The group III nitride crystal according to claim 11 or 12, wherein the maximum particle size is 100 µm or more.

Images