JP5573225B2 - Method for producing Group 13 metal nitride crystal, Group 13 metal nitride crystal obtained by the production method, and method for producing semiconductor device - Google Patents

Description

  The present invention relates to a method for producing a nitride crystal of a Group 13 metal such as a gallium nitride (GaN) crystal, a Group 13 metal nitride crystal obtained by the production method, and a method for producing a semiconductor device using the production method. .

A compound crystal of a Group 13 metal element typified by gallium nitride (GaN) and a nitrogen element is useful as a substance used in a light-emitting diode, a laser diode, a high-frequency electronic device, or the like. In the case of GaN, a practical method for producing crystals is MOCVD (Metal Organic Chemical Vapor Deposition) on a substrate such as a sapphire substrate or silicon carbide.
A method of performing vapor phase epitaxial growth by a method has been proposed (see, for example, Non-Patent Document 1).

  However, in the above method, GaN crystals are epitaxially grown on different substrates having different lattice constants and thermal expansion coefficients, so that there are many lattice defects in the obtained GaN crystals. When a GaN crystal having many such lattice defects is used as an electronic device, it adversely affects the operation of the electronic device and cannot exhibit satisfactory performance for use in an application field such as a blue laser. For this reason, in recent years, it has been strongly desired to improve the quality of GaN crystals grown on a substrate and to establish a manufacturing technique for GaN bulk single crystals.

  Currently, in the heteroepitaxial GaN crystal growth method by the vapor phase method, a complicated and long process is required to reduce defects in the GaN crystal. Recently, vigorous research has been conducted on crystallization of GaN by a liquid phase method, and a high pressure method (see Non-Patent Document 2) in which nitrogen and Ga are reacted under high temperature and high pressure has been proposed. It is difficult to carry out industrially due to various reaction conditions.

  Thus, many reports have been made on GaN crystal growth methods with lower reaction conditions. The sodium flux method (see Patent Literature 1 and Non-Patent Literature 3) is a method for producing a GaN crystal in which Ga and nitrogen are reacted in a combined financial solution in which an alkali metal is added to a Ga melt to produce a GaN crystal. Since the amount of nitrogen or GaN dissolved in the combined financial solution is very small, it is difficult to increase the size of the GaN crystal.

  A method of heating a mixture of GaN powder and alkali metal halide to produce a GaN crystal has also been proposed (see Patent Document 2). However, the solubility of GaN in alkali metal halide is low and nitrogen is stable. This method is disadvantageous in terms of industrial crystal growth because it is necessary to perform crystal growth at a high pressure in order to dissolve it. Non-patent document 4 also reports a crystal growth on the polar surface of a GaN seed using a mixture of GaN powder and alkali metal halide, but has the same problems as in patent document 2 and has a growth rate. There is a problem that it is industrially disadvantageous because it is slow.

Patent Document 3 describes that a lithium compound is used as an auxiliary melting agent. However, in this document, a solution using a molten salt is not used. I have the same problem as 3rd.
As a technique for coping with such a problem, there is a method in which a solution or melt in which a composite metal nitride such as Li ₃ GaN ₂ is dissolved in an ionic solvent is prepared, and a GaN crystal is grown in the solution or melt. It has been proposed (see Patent Document 4). Here, a specific example in which a GaN crystal is grown on a seed of a GaN thin film prepared by a vapor phase method is described.

JP 2005-306709 A JP 2005-127718 A Chinese Patent Publication No. 1288079 JP 2007-84422 A

Jpn. J. Appl. Phys. 37 (1998) 309-312 J. Crystal Growth 178 (1997) pp. 174-188 J. Crystal Growth Vol. 260 (2004) 327-330 J. Crystal Growth Vol. 310 (2008) 3934-3940

As a result of various studies on the method described in Patent Document 4, the present inventors have found a new problem that unevenness of the growth surface of the crystal grown on the seed occurs.
The method described in Patent Document 4 has an advantage that it is industrially advantageous because a high-quality crystal can be produced at a low pressure or an ordinary pressure. When it is used for, for example, it is necessary to polish and remove all the uneven portions, and there is a problem that the utilization efficiency is lowered.

  In view of such problems of the prior art, the present inventors provide an industrially advantageous and inexpensive method for producing a high-quality Group 13 metal nitride crystal with no unevenness on the growth surface. Were studied for the purpose of the present invention.

As a result of various investigations, the inventors of the present invention have grown a seed when a Group 13 metal nitride crystal is grown on the seed in a solution containing a nitrogen element and a Group 13 metal element in a molten salt. By selecting the polarity of the surface, it has been found that the unevenness of the growth surface of the Group 13 metal nitride crystal can be reduced, and the following inventions have been provided.
[1] A method for producing a Group 13 metal nitride crystal in which a Group 13 metal nitride crystal is grown on a seed in a solution containing a nitrogen element and a Group 13 metal element in a molten salt, the seed A method for producing a Group 13 metal nitride crystal, wherein the main surface is a semipolar surface.
[2] The Group 13 metal nitriding according to [1], including a step of obtaining a solution by dissolving a composite metal nitride containing a Group 13 metal element and a metal element other than the Group 13 in a molten salt. Method for producing physical crystals.
[3] The method for producing a Group 13 metal nitride crystal according to [1] or [2], wherein a main surface of the seed is composed of a Group 13 metal nitride crystal.
[4] The main surface of the seed is an (hkil) surface, h and k are integers satisfying h + k ≠ 0, i is an integer satisfying i = − (h + k), and l is a positive integer. ] The manufacturing method of the group 13 metal nitride crystal as described in any one of [3].
[5] The method for producing a Group 13 metal nitride crystal according to any one of [1] to [4], wherein the molten salt is a molten salt that is not a raw material for the Group 13 metal nitride crystal.
[6] A Group 13 metal nitride crystal obtained by the method for producing a Group 13 metal nitride crystal according to any one of [1] to [5].
[7] A method for producing a Group 13 metal nitride crystal on a substrate by the method for producing a Group 13 metal nitride crystal according to any one of [1] to [5], A method for manufacturing a semiconductor device.

  According to the production method of the present invention, it is possible to produce a Group 13 metal nitride crystal having no crystal irregularities on the growth surface, few impurities, and excellent crystallinity by an industrially inexpensive method. Moreover, according to the semiconductor device manufacturing method of the present invention, it is possible to manufacture a high-quality semiconductor device that can handle power ICs and high frequencies by an industrially inexpensive method.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic diagram for explaining reactors used in Examples 1 and 2 and Comparative Example 1. 2 is a CL-SEM photograph of a cross section of a GaN crystal obtained in Example 1. FIG. 4 is a CL-SEM photograph of a cross section of a GaN crystal obtained in Example 2. FIG. 4 is a CL-SEM photograph of a cross section of a GaN crystal obtained in Comparative Example 1. 4 is a CL-SEM photograph of a cross section of a GaN crystal obtained in Example 3. FIG.

Below, the manufacturing method of the group 13 metal nitride crystal of this invention and the manufacturing method of a semiconductor device are demonstrated in detail. The description of the constituent elements described below may be made based on representative examples of 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. The group 13 metal means a group 13 metal of the periodic table.

  The method for producing a Group 13 metal nitride crystal of the present invention is a method for growing a Group 13 metal nitride crystal on a seed in a solution containing a nitrogen element and a Group 13 metal element in a molten salt. In the manufacturing method, the main surface of the seed is a semipolar surface.

[Group 13 metal nitride crystals]
The group 13 metal nitride crystal obtained by the production method of the present invention is not particularly limited as long as it is a nitride containing a group 13 metal. For example, nitrogen gallium (GaN), aluminum nitride (AlN), indium nitride (InN) ) Or a nitride of a solid solution composition such as gallium nitride / indium (GaInN) or gallium nitride / aluminum (GaAlN). A crystal containing at least gallium (Ga) as a Group 13 metal, preferably a method for producing a GaN crystal is particularly preferable.

  Group 13 metal nitride crystals are obtained by growing crystals on these seeds using massive, rod-like, or plate-like seeds, and have good crystallinity and a sufficient size can be easily obtained. To preferred.

[Molten salt]
In the production method of the present invention, a solution containing a nitrogen element and a Group 13 metal element in a molten salt is used.
Here, the molten salt is obtained by melting a solid salt at room temperature. The type of molten salt is not particularly limited as long as it does not inhibit the epitaxial growth of crystals on the seed, and examples thereof include halides, carbonates, nitrates, and sulfurides. In general, it is preferable to use a halide because it has a high ability to stably dissolve a Group 13 metal element as a metal ion. Specifically, the molten salt is LiCl, KCl, NaCl, CsCl, MgCl ₂ , CaCl ₂ , SrCl ₂ , BaCl ₂ , AlCl ₃ , GaCl ₃ , LiBr, KBr, N
_{aBr, CsBr, LiF, KF,} NaF, AlF 3, GaF 3, LiI, NaI, KI, CsI, preferably a metal halide, such as _{CaI 2, BaI 2, LiCl,} KCl, NaCl, CsCl, MgCl 2 , CaCl ₂ , SrCl ₂ , BaCl ₂ and mixed salts thereof are preferable because the melting point of the solution is lowered. When the melting point of the solution is lowered, crystal growth can be performed at a relatively low temperature, which is preferable in terms of crystallinity of the obtained crystal and industrial implementation.

In addition, it is preferable to use a salt containing an alkali metal and / or an alkaline earth metal because it has a high ability to dissolve nitrogen element as nitride ions. Specifically, the molten salt is preferably a molten salt composed of an alkali metal salt such as Li, Na, or K and / or a salt containing an alkaline earth metal such as Mg, Ca, or Sr. LiCl, KCl, NaCl , CsCl, Li ₄ NCl, MgCl ₂ , CaCl ₂ , SrCl ₂ , BaCl _{2 and the} like.

The molten salt is preferably a molten salt that does not become a raw material for the obtained Group 13 metal nitride crystal in order to adjust the solubility of the raw material to appropriately control the crystal growth rate. That is, any salt that does not contain a Group 13 metal element and a nitrogen element may be used, and examples thereof include LiCl, KCl, NaCl, CsCl, MgCl ₂ , CaCl ₂ , SrCl ₂ , and BaCl ₂ .
In this case, the manufacturing method of the invention of the present application dissolves a compound containing a nitrogen element and / or a Group 13 metal element in a molten salt as a raw material for the Group 13 metal nitride crystal, and combines the nitrogen element and the Group 13 metal element. Obtaining a solution containing.

  In a solution containing a nitrogen element and a Group 13 metal element in a molten salt, a mixture of a plurality of salts is used as the molten salt in order to control the solubility of the nitrogen element in the molten salt and the solubility of the Group 13 metal element. You can also. A molten salt of a mixture of a plurality of salts can be prepared by introducing two or more kinds of salts as separate solids into a reaction system and melting them by heating. However, a mixed salt such as a mixed salt of LiCl and NaCl can be prepared. It is desirable to heat and melt the solid from the viewpoint of uniformity in the system.

  The molten salt used in the present invention is preferably composed of lithium halide and one or more halides selected from the group consisting of sodium halide, potassium halide and cesium halide. More preferably, it consists of sodium halide or potassium halide, more preferably lithium halide and sodium halide.

  The total content of one or more halides selected from the group consisting of sodium halide, potassium halide and cesium halide is preferably from 5 to 85 mol%, preferably from 15 to 60 mol, based on the total amount of the molten salt. % Is more preferable. When the content of these halides is 5 mol% or more, it is preferable in that the crystal growth rate is high. Further, it is preferable that the total content is 85 mol% or less in that the generation of miscellaneous crystals is small and the crystal growth rate on the seed is increased.

  When the molten salt contains impurities such as water, it is desirable to purify the molten salt in advance. The purification method is not particularly limited, and examples thereof include a method of blowing a reactive gas into the molten salt. Examples of the reactive gas include hydrogen chloride, hydrogen iodide, hydrogen bromide, ammonium chloride, ammonium bromide, ammonium iodide, chlorine, bromine, iodine and the like. In particular, it is preferable to use hydrogen chloride.

[Composition of solution]
The solution for growing the Group 13 metal nitride crystal is a solution containing a nitrogen element and a Group 13 metal element in the molten salt, and includes a Group 13 metal element and a nitrogen element in addition to the molten salt. .
The Group 13 metal element and the nitrogen element can be present in the solution by dissolving a Group 13 metal, a compound containing a Group 13 metal element, or a compound containing nitrogen gas or a nitrogen element in the molten salt. Here, the Group 13 metal element contained in the solution is a Group 13 metal element of the Group 13 metal nitride crystal to be crystal-grown. Therefore, when a GaN crystal is to be grown, Ga or a Ga compound is dissolved in the molten salt.

Examples of the compound containing a Group 13 metal element include halides and nitrides. Specifically GaCl _{3, GaF 3, GaN,} and the like LiGaF _4, NaGaF 4. Among these, GaN, LiGaF ₄ and NaGaF ₄ are preferable from the viewpoint of stability at high temperatures.
Examples of the compound containing nitrogen element include ammonia, ammonia salt, metal amide, and metal nitride. Examples of the nitride include alkali metal or alkaline earth metal nitrides such as Li ₃ N, Ca ₃ N ₂ , Mg ₃ N ₂ , Sr ₃ N ₂ , and Ba ₃ N ₂ . When LiCl is used as the main component of the molten salt, it is preferable to employ Li ₃ N as the nitride.

  By dissolving these nitrides, the solubility of the composite metal nitride described later can be increased. At that time, the ratio of the nitrogen element and the group 13 metal element present in the solution is 1 to 30 in terms of nitrogen element / group 13 metal element (molar ratio) in order to efficiently grow a crystal having few nitrogen defects. More preferably, it is 1-15, More preferably, it is 2-10. It is preferable to dissolve the substance containing nitrogen element so as to be in such a range.

[Composite nitride]
A solution for growing a Group 13 metal nitride crystal can also be prepared by dissolving a composite metal nitride containing a Group 13 metal and a metal element other than Group 13 in a molten salt as a solvent. .
A composite metal nitride containing a Group 13 metal and a metal element other than Group 13 includes a Group 13 metal nitride powder and a metal nitride powder other than Group 13 metal (for example, Li ₃ N, After mixing with Ca ₃ N ₂ ), it can be obtained by a method such as raising the temperature and causing a solid phase reaction. Preferred examples of Group 13 metals include Ga, Al, In, GaAl, and GaIn. In addition, examples of metal elements other than Group 13 include Li, Na, Ca, Sr, Ba, and Mg. Among them, Li, Ca, Ba, and Mg can be cited as preferable elements.

Preferred composite metal nitrides include Group 13 metals such as Li ₃ GaN ₂ , Ca ₃ Ga ₂ N ₄ , Ba ₃ Ga ₂ N ₄ , Mg ₃ GaN ₃ , CaGaN and alkalis because of their high solubility in molten salts. A composite metal nitride with a metal or an alkaline earth metal can be mentioned, and Li ₃ GaN ₂ is more preferable. When Li ₃ GaN ₂ is used, the content of Li ₃ N is adjusted in advance by removing Li ₃ N which is an impurity contained in Li ₃ GaN ₂ or by adding Li ₃ N on the contrary. It is preferable to obtain a nitride crystal with few nitrogen defects.

In the present invention, two or more kinds of composite metal nitrides may be used.
The composite metal nitride used in the production method of the present invention can be easily produced by usually forming an alloy of a Group 13 metal and a metal other than Group 13 and heating in a nitrogen atmosphere. For example, Li ₃ GaN ₂ can be manufactured by heat-treating a Ga—Li alloy at 600 to 800 ° C. in a nitrogen atmosphere. Usually, in the ammonothermal method or the like, the fine powder or crystallite of the target Group 13 metal nitride crystal is synthesized and dissolved in a solvent. However, compared with such a process, it is very easy to make a raw material. Yes, and industrial value is great. In addition, the composite metal nitride may not be a chemically synthesized crystalline material, for example, a sapphire substrate or quartz produced by reacting a target made of an alloy thereof with nitrogen plasma by reactive sputtering. A mixed nitride film deviated from the stoichiometric composition generated on the substrate may be used. When the composite metal nitride thin film produced by such a dry process is kept in contact with the molten salt, the nitride gradually dissolves from the nitride thin film to the molten salt, forming a diffusion-dominated nitride dissolved phase near the interface. Crystal growth can be easily achieved by placing the seed in the vicinity of this interface. Further, as a feature of using the dry process, it is possible to easily produce even a nitride that is difficult to synthesize chemically. Although the method for synthesizing a solid composite metal nitride has been described here, in the present invention, two types of nitrides are reacted in a solution to synthesize a composite metal nitride dissolved in the solution, and crystal growth is performed as it is. You may use for.

  When a compound containing nitrogen element such as nitride is added to the molten salt, the substance to be added and the gas phase entrained in the reaction system at the time of addition are oxygenated so that oxygen or moisture does not enter the reaction system. Or it is preferable to operate so that moisture does not enter.

[seed]
In the manufacturing method of the present invention, a Group 13 metal nitride crystal is grown on a seed whose main surface is a semipolar surface. The main surface of the seed means a surface having the largest surface area occupied by the surface with respect to the total surface area of the seed. For example, when the seed is plate-shaped, there may be two main surfaces, but one of the main surfaces may be a semipolar surface.

The kind of seed to be used is not particularly limited, and may be the same as the target Group 13 metal nitride crystal, or may be a heterogeneous crystal such as sapphire, SiC, ZnO or the like. The case where the main surface of the seed is composed of a Group 13 metal nitride crystal is preferred, and the case where a Group 13 metal nitride crystal or a substrate is used as the seed is more preferred. The shape of the seed is not particularly limited, and may be a block shape, a flat plate shape, or a rod shape.
Further, it may be a seed for homoepitaxial growth or a seed for heteroepitaxial growth. Specific examples include seeds of group 13 metal nitrides such as vapor grown GaN, InGaN, and AlGaN. In addition, metal oxides such as sapphire, silica, ZnO, and BeO, silicon-containing materials such as SiC and Si, and materials used as substrates in vapor phase growth methods such as GaAs can also be exemplified. The seed material is preferably selected as close as possible to the lattice constant of the Group 13 metal nitride crystal grown in the present invention.

Hereinafter, GaN is taken as an example of the group 13 metal nitride, and the GaN in a solution containing the nitrogen of the seed and the group 13 metal element in the molten salt (hereinafter sometimes simply referred to as “solution”). The planarity relationship of the crystal growth layer will be described, but the present invention is not limited to the GaN crystal manufacturing method.
The polar plane in the GaN crystal is a plane in which only one of Ga and N is arranged on the surface. The polar surface is electrically positively or negatively charged due to the bias of atoms present on the surface. The nonpolar plane is a plane in which the same number of Ga and N are present on the surface, and the surface is electrically neutral. The semipolar surface is a surface in which both Ga and N are present on the surface but the abundance ratio is not 1: 1, and therefore the surface is less charged than the polar surface.

  When a GaN crystal is grown in a solution, the molten salt is partially or completely ionized to exist as cations and anions, and the solution is charged. It is considered that a charged polar surface or semipolar surface is easily formed on the surface. For this reason, when a seed having a non-polar surface as a main surface is used, a polar surface or a semipolar surface that is likely to be formed in a solution appears as the crystal growth proceeds, and as a result, the growth surface of the GaN crystal appears. It is inferred that many irregularities appear and the flatness deteriorates. On the other hand, if a seed having a polar surface or semipolar surface as the main surface is used, crystal growth starts from the surface that is easy to form originally, so that the crystal grows while maintaining the same surface as the main surface of the seed, It is considered that the flatness of the growth surface of the GaN crystal is maintained.

However, in the polar plane, for example, when only Ga is arranged, N atoms must be supplied in order for GaN to grow, but in a solution in which both Ga and N are present, only N atoms are faced. It is difficult for the composition of the solution to be biased to be supplied at a high concentration. For this reason, it is presumed that the growth rate is significantly slower on the polar surface than on the semipolar surface.
For this reason, in the manufacturing method of the present invention, a Group 13 metal nitride crystal is grown on a seed whose main surface is a semipolar surface.

  When a wurtzite group 13 metal nitride crystal seed is used, the semipolar plane is the (hkil) plane, h and k are integers satisfying h + k ≠ 0, and i is i = − (h + k) The integer, l is not limited as long as it is a plane represented by an integer other than 0. Examples include (10-1-1) plane, (20-2-1) plane, (10-1-2) plane, ( 10-11) plane, (20-21) plane, (10-12) plane, (11-22) plane, and (11-2-2) plane. Since the growth surface of the crystal tends to be flatter, it is more preferably a (hkil) plane, h and k are integers satisfying h + k ≠ 0, i is an integer satisfying i = − (h + k), and l is positive It is a surface indicated by an integer. Examples include (10-11) plane, (20-21) plane, (10-12) plane, and (11-22) plane. Most preferably, the (10-11) plane and the (20-21) plane are used.

[Reaction vessel]
The reaction vessel used in the present invention is not particularly limited as long as it does not inhibit the reaction in the production method of the present invention. However, the reaction is mainly composed of thermally and chemically stable metals, oxides, nitrides and carbides. A container is preferred. A metal containing a Group 4 element (Ti, Zr, Hf) of the periodic table is suitable, and Ti is preferably used.

Further, it is preferable to use a metal whose 90% by weight or more is the Group 4 element. More preferably, 99% by weight or more of a metal that is the Group 4 element is used.
The surfaces of these reaction vessel members are preferably made of a nitride of the Group 4 element of the periodic table, and it is preferable to form the nitride in advance by a nitriding method described later.

[Nitriding method]
In the present invention, nitriding refers to a step of nitriding at least the surface of the reaction vessel member. It is preferable to nitride the member in advance before crystal growth to form a strong and stable nitride on the surface of the member that contacts the solution or melt. Further, the nitride may be formed in the form of a nitride film in consideration of the difficulty of cracking the member and mechanical strength.

The nitriding treatment method is not particularly limited as long as the nitride formed on the surface is stable. For example, the member of the reaction vessel is heated and held in a nitrogen atmosphere at 700 ° C. or higher, so that stable nitriding is performed on the surface of the member. A film can be formed.
Furthermore, the surface of the member can be nitrided using an alkali metal nitride or alkaline earth metal nitride as a nitriding agent at a high temperature, preferably an alkali metal halide or an alkaline earth metal halide. A stable nitride film can be formed by holding it in a mixed melt with the alkali metal nitride or alkaline earth metal nitride. In addition, the nitriding treatment can be easily performed by holding the member under the same conditions as the actual crystal growth conditions.

[Reaction temperature, reaction pressure]
The temperature at which the Group 13 metal nitride crystal is grown in the reaction vessel is usually 200 to 1000 ° C., preferably 400, because decomposition and evaporation of the raw material and molten salt can be suppressed and the growth rate can be increased. It is -850 degreeC, More preferably, it is 600-800 degreeC. Further, the pressure in the reaction vessel when growing the Group 13 metal nitride crystal can be appropriately selected depending on the conditions and is not particularly limited. However, since the production apparatus is simple and can be advantageously produced industrially, It is 10 MPa or less, preferably 3 MPa or less, more preferably 0.3 MPa or less, more preferably 0.11 MPa or less, and usually 0.01 MPa or more, more preferably 0.09 MPa or more. Especially when it is desired to increase the crystal growth rate, 0.0%
It is also preferable to set it to 9 MPa or less.

[Method for Manufacturing Semiconductor Device]
The manufacturing method of this invention can be used for the process of manufacturing the group 13 metal nitride crystal in the manufacturing method of a semiconductor device. The raw materials, conditions, and apparatuses used in general semiconductor device manufacturing methods can be applied as they are for the raw materials, manufacturing conditions, and apparatuses in other processes. According to the manufacturing method of the present invention, it is possible to manufacture a power IC, a semiconductor device capable of handling high frequencies, and the like.

  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.

Example 1
Solid Li ₃ GaN _{2 (} 1.44 g) is placed in a nitriding-treated Ti vessel having an outer diameter of 34 mm, an inner diameter of 30 mm, and a height of 200 mm. Next, 8.64 g of NaCl and 20.16 g of LiCl are used as solvents. The mixture was pulverized and mixed well in a tungsten carbide mortar and placed in a Ti reaction vessel. Solid Li ₃ GaN ₂ was selected from a particle size of 600 μm or more and 2 mm or less using a sieve. The nitriding treatment of the Ti reaction vessel was performed in advance by putting 28.8 g of LiCl and 0.10 g of Li ₃ N into the Ti reaction vessel and heating them at 745 ° C. for 2 hours in a nitrogen atmosphere.

Next, the Ti reaction vessel (5) was set in the quartz reaction tube (4), and the gas introduction port (1) and the gas exhaust port (2) of the quartz reaction tube were closed. All these operations were performed in an Ar box.
Next, the quartz reaction tube (4) was taken out of the Ar box and set in the electric furnace (3). After connecting the gas introduction tube to the quartz reaction tube (4) and reducing the pressure in the introduction tube, the gas introduction port (1) of the quartz reaction tube is opened to reduce the pressure in the quartz reaction tube (4). From N ₂ to atmospheric pressure, and the inside of the quartz reaction tube (4) was N ₂ atmosphere. Thereafter, the gas exhaust port (2) of the quartz reaction tube (4) was opened, and N ₂ was circulated at 100 ccm.

Next, heating of the electric furnace is started, and the temperature inside the Ti reaction vessel (5) is raised from room temperature to 745 ° C. over 1 hour, and NaCl and LiCl are melted to form a molten salt. Li ₃ GaN ₂ as the raw material (7) was dissolved into a solution. After holding at 745 ° C. for 7 hours, the seed (6) attached to the tip of the seed holding rod (8) is immersed in the solution (9) in the reaction vessel (5), and the seed is rotated at 100 rpm to grow crystals. Started. At the bottom of the reaction vessel (5), Li ₃ GaN ₂ exceeding the solubility of the solution was present in a solid state. As the seed, a GaN substrate having a (10-11) plane as a main surface was used.

After crystal growth at 745 ° C. for 70 hours, the seed (6) was pulled up from the solution (9), and then the heating of the furnace was stopped, and the quartz reaction tube (4) was rapidly cooled.
When the seed (6) was taken out from the quartz reaction tube (4), a GaN crystal in which a GaN growth layer was formed on the seed was obtained.
The obtained GaN crystal was poured into warm water to dissolve the adhered salt such as NaCl or LiCl. The weight of the GaN crystal increased by 12.6 wt% compared to the weight of the seed before crystal growth, and a GaN growth layer made of GaN crystal was formed on the main surface of the seed. When a cross section of the GaN crystal including the GaN growth layer was observed with a cathodoluminescence-scanning electron microscope (CL-SEM), a GaN growth layer having a flat growth surface shown in FIG. 2 was confirmed.

(Example 2)
A GaN crystal in which a GaN growth layer was formed on the seed was obtained by the same method as in Example 1 except that a GaN substrate having a (20-21) plane as a main surface was used as a seed. The weight of the GaN crystal increased by 15.3 wt% compared to the weight of the seed before crystal growth, and a GaN growth layer made of GaN crystal was formed on the main surface of the seed. When the cross section of the GaN crystal including the GaN growth layer was observed with a CL-SEM, a GaN growth layer having a flat growth surface shown in FIG. 3 was confirmed.

(Example 3)
The solid Li3GaN2 is 2.88 g, the solvent is 11.52 g NaCl and 17.28 g LiCl, and the solution is formed and held at 745 ° C. for 10.5 hours, and the seed is immersed to grow crystals. A GaN crystal having a GaN growth layer formed on the seed was obtained in the same manner as in Example 1 except that the time was changed to 304 hours. The weight of the GaN crystal increased by 61.9 wt% compared to the weight of the seed before crystal growth, and a GaN growth layer made of GaN crystal was formed on the main surface of the seed. When a cross-section of the GaN crystal including the GaN growth layer was observed with a CL-SEM, a GaN growth layer with a flat growth surface shown in FIG. 5 was confirmed.

(Comparative Example 1)
A GaN crystal in which a GaN growth layer was formed on the seed was obtained in the same manner as in Example 1 except that a GaN substrate having a (10-20) plane as a main surface was used as a seed. The weight of the GaN crystal increased by 12.1 wt% compared to the weight of the seed before crystal growth, and a GaN growth layer made of GaN crystal was formed on the main surface of the seed. When a cross-section of the GaN crystal including the GaN growth layer was observed with a CL-SEM, sawtooth-like irregularities were confirmed on the growth surface as shown in FIG.

  According to the method for producing a Group 13 metal nitride crystal of the present invention, a Group 13 metal nitride crystal having a size sufficient for application to a semiconductor device can be industrially advantageous using an inexpensive apparatus. Can be manufactured. Therefore, the present invention has high industrial applicability.

DESCRIPTION OF SYMBOLS 1 Gas inlet 2 Gas outlet 3 Electric furnace 4 Quartz reaction tube 5 Reaction vessel 6 Seed 7 Raw material 8 Seed holding rod 9 Solution

Claims (6)

In a solution containing a nitrogen element and a Group 13 metal element in a molten salt, the main surface of the seed having a main surface which is a (10-11) plane or (20-21) of a Group 13 metal nitride crystal A method for growing a Group 13 metal nitride crystal, comprising a crystal growth step for growing a Group 13 metal nitride crystal on the top. 2. The method according to claim 1, further comprising a step of dissolving the composite metal nitride containing a Group 13 metal element and a metal element other than Group 13 in a molten salt to obtain the solution before the crystal growth step. Growth method. The growth method according to claim 1, wherein the growth method is a GaN crystal growth method. The growth method according to claim 1, wherein a main surface of the seed is a (10-11) plane or a (20-21) plane of a GaN crystal. The growth method according to any one of claims 1 to 4, wherein the molten salt is a molten salt that does not contain a Group 13 metal element and a nitrogen element. A method for manufacturing a semiconductor device, comprising the step of growing a Group 13 metal nitride crystal on a substrate by the growth method according to claim 1.