JP2010260752A - Method for producing group 13 metal nitride crystal - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for efficiently producing a bulk single crystal of group 13 metal nitride of high quality by preparing a solution or a melt containing high concentrations of Ga and nitrogen, which is suitable for growing the crystal of the group 13 metal nitride. <P>SOLUTION: The method for producing the group 13 metal nitride includes a step of preparing the solution or the melt by dissolving a raw material in a solvent and a step of growing the group 13 metal nitride crystal in the solution or the melt, provided that two or more nitrides are used as the solvent. The nitrides used as the solvent are preferably alkali metal nitrides or alkaline earth metal nitrides, more preferably a combination of one or more alkali metal nitrides and one or more alkaline earth metal nitrides, more preferably a combination of lithium nitride and barium nitride. Use of two or more nitrides as the solvent stabilizes the solution, thereby suppressing decomposition of the group 13 metal nitride component and increasing solubility of the raw material under ordinary pressure. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a method for producing a Group 13 metal nitride represented by gallium nitride, and more particularly to a method for producing a high-quality Group 13 metal nitride bulk single crystal.

  Gallium nitride (GaN) is useful as a material applied to electronic devices such as light emitting diodes and laser diodes. The most common method for producing this gallium nitride crystal is a method of performing vapor phase epitaxial growth by MOCVD (Metal-Organic Chemical Vapor Deposition) on a substrate such as sapphire or silicon carbide. However, since this method uses heteroepitaxial growth in which the lattice constant and thermal expansion coefficient of the substrate and GaN are different, lattice defects are likely to occur in the obtained GaN, and a high-quality crystal that can be applied with a blue laser or the like is obtained. There is a problem that is difficult. Various methods for reducing lattice defects have been proposed, but problems such as complicated processes and increased costs occur.

Therefore, in recent years, there has been a strong demand for establishment of a new manufacturing technique for high-quality gallium nitride massive single crystals for homoepitaxial substrates, which can replace the above method. Various methods have been proposed for producing such a new gallium nitride crystal.
Ito et al. Have proposed a method of obtaining gallium nitride by crystal growth by heating and melting a mixture of a Group 13 metal nitride raw material and a metal halide under a pressure of 500 MPa or less (see Patent Document 1).

Iwata et al. Have proposed a method of crystal growth of gallium nitride using Na and Ga under a pressure of 8 MPa and further using nitrogen gas and lithium nitride as raw materials (see Patent Document 2).
Frazier et al. Have obtained a gallium nitride crystal by preparing a solution by dissolving GaN in a mixed solvent of lithium nitride and barium fluoride under a pressure of 0.2 MPa (see Non-Patent Document 1).

JP 2005-127718 A JP 2004-307322 A

Journal of Crystal Growth 310 (2008) 3934- 3940

In the method of Patent Document 1, in an example in which crystal growth is performed by heating and melting a mixture of a Group 13 metal nitride raw material and a metal halide, pressurization of 81 MPa to 152 MPa is required for the purpose of suppressing nitrogen decomposition during crystal growth. It is said that. Thus, since pressurization of the order of 100 MPa is necessary at the time of crystal growth, expensive high-pressure equipment is necessary and there is a problem in terms of production cost.
In the method of Patent Document 2, lithium nitride is added as a substance for increasing the solubility of nitrogen in the Na—Ga compound financial solution, but the solubility is not necessarily high. Moreover, since the pressurization for the purpose of suppressing decomposition | disassembly of nitrogen is required like patent document 1, an expensive high voltage | pressure installation is required and there exists a subject in terms of production cost. In addition, since a highly reactive alkali metal is used as a flux, safety must be strictly ensured, and it is therefore difficult to obtain high production efficiency.

Further, even in the method of Non-Patent Document 1, pressure is applied in order to suppress the decomposition of nitrogen as in Patent Documents 1 and 2, and crystals having an industrially sufficient size have not been grown.
As described above, nitride crystal growth methods by these methods have not been established industrially, and are only a preliminary study. Due to its low solubility, large single-piece high-quality single crystals have not been obtained, and because it is a high-pressure device, very expensive equipment is required, or because highly reactive alkali metals are used, it is safe. It is difficult to ensure high production efficiency.

In view of the above-mentioned problems, the present inventors made a high-quality Group 13 metal nitride massive single crystal by a method that can be industrially applied without using a highly toxic or dangerous substance. The method which can be manufactured earnestly examined. As a result, according to the crystal growth method using two or more types of nitrides as the solvent for dissolving the raw material, the solution is stabilized and the decomposition of the Group 13 metal nitride component is suppressed, and the raw material The present inventors have found that the solubility is high and have reached the present invention. The present invention provides a crystal growth method in which a raw material is dissolved in a solvent to prepare a solution or a melt, and a Group 13 metal nitride crystal is grown in the solution or the melt. It exists in the manufacturing method of the group 13 metal nitride crystal characterized by using. That is,
[1] Production of a Group 13 metal nitride crystal comprising a step of dissolving a raw material in a solvent to prepare a solution or a melt, and a step of growing a Group 13 metal nitride crystal in the solution or the melt In the method, a method for producing a Group 13 metal nitride crystal, wherein two or more types of nitrides are used as a solvent.

[2] The method for producing a Group 13 metal nitride crystal as described in [1], wherein at least an alkali metal nitride is used as the solvent.
[3] The method for producing a Group 13 metal nitride crystal as described in [1], wherein at least an alkaline earth metal nitride is used as the solvent.
[4] The method for producing a Group 13 metal nitride crystal as described in [1], wherein at least alkali metal nitride and alkaline earth metal nitride are used as the solvent.

[5] The method for producing a Group 13 metal nitride crystal according to [2] or [4], wherein the alkali metal nitride contains lithium nitride.
[6] The method for producing a Group 13 metal nitride crystal as described in [3] or [4], wherein the alkaline earth metal nitride contains barium nitride.
[7] The solution or melt contains Ga and nitrogen, the Ga concentration in the solution or melt is 0.20 to 83 wt%, and the nitrogen concentration is 0.30 to 17 wt%. The method for producing a Group 13 metal nitride crystal according to any one of Claims [1] to [6].

[8] The group 13 metal nitride crystal production as described in any one of [1] to [7], wherein a metal halide is further added as an auxiliary solubilizer to the solution or melt. Method.
[9] Any one of [1] to [8], wherein the step of preparing the solution or melt and / or the step of growing the Group 13 metal nitride crystal is performed at normal pressure. A method for producing a Group 13 metal nitride crystal according to Item.

  [10] The process according to [1] to [9], wherein the step of preparing the solution or melt and / or the step of growing the Group 13 metal nitride crystal is performed in an inert gas atmosphere. The manufacturing method of the group 13 metal nitride crystal as described in any one.

  According to the production method of the present invention, a solution or melt containing Ga and nitrogen at a high concentration suitable for crystal growth of a Group 13 metal nitride can be obtained. Further, the production method of the present invention can efficiently produce a high-quality group 13 metal nitride massive single crystal by a simpler and safer method than before. Further, according to the production method of the present invention, it is possible to produce at a low pressure or normal pressure without using a highly toxic or reactive substance, so that safety is high and industrial implementation is easy.

  Hereinafter, the present invention will be described in detail. The description of the constituent requirements described below is an example of embodiments of the present invention, and the present invention is not limited to these 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. In addition, in the present specification, “seed” includes, in addition to the group 13 metal nitride crystal, a group 13 metal nitride crystal formed by crystal growth in addition to a heterogeneous substrate such as sapphire, SiC, or ZnO. .

(Group 13 metal nitride)
As the Group 13 metal nitride which is the production target of the present invention, a single metal nitride of a Group 13 element of the periodic table such as B, Al, Ga, In or the like (for example, GaN, AlN, InN) is usually mentioned. Further, alloy group nitrides (eg, GaInN, GaAlN) are also included. Of these, the present invention is particularly suitable for obtaining gallium nitride crystals.

(material)
In the method of the present invention, the raw material is not particularly limited as long as it is a nitride containing a Group 13 element. For example, composite nitrides, such as gallium nitride (GaN) and Li3GaN2, are mentioned.
The form of the raw material may be powder or lump. For example, a nitride polycrystalline powder raw material (hereinafter sometimes referred to as “polycrystalline raw material”) may be used.

  There is no particular limitation on the method for producing the polycrystalline raw material. For example, in a reaction vessel in which ammonia gas is circulated, as a Group 13 metal oxide, hydroxide, or more reactive metal compound, halogen A nitride polycrystal can be obtained by reacting a compound having a covalent MN bond, such as a compound, an amide compound, an imide compound, and a galazan with the ammonia. Furthermore, it is also possible to use a nitride polycrystal produced by reacting a Group 13 metal with nitrogen at high temperature and pressure. The nitride polycrystalline raw material as the raw material for producing the nitride crystal of the present invention is not particularly required to be a complete nitride. Depending on the conditions, the Group 13 metal itself, that is, the metal state (ie, zero valence) is used. The metal component is usually 1 ppm or more, and the upper limit is not particularly limited as long as it does not inhibit crystal growth, but it may contain up to about 20% by weight. This is because when a trace amount of oxygen is mixed in the reaction system, the metal component is expected to play a role like an oxygen trap agent that prevents the oxygen from diffusing into the flux.

(solvent)
In the method of the present invention, the nitride used for the solvent is preferably an alkali metal nitride (lithium nitride, sodium nitride, etc.) or an alkaline earth metal nitride (magnesium nitride, calcium nitride, strontium nitride, barium nitride, etc.), More preferably, one or more alkali metal nitrides and one or more alkaline earth metal nitrides are selected and combined. More preferably, lithium nitride and barium nitride are used in combination.

(Ga concentration and nitrogen concentration in solution or melt)
According to the method of the present invention, by using two or more types of nitrides as a solvent, a solution or melt containing Ga and nitrogen at a high concentration suitable for crystal growth of a Group 13 metal nitride can be obtained. .
In the present invention, the Ga concentration in the solution or melt is usually 0.20 to 83 wt%, preferably 2.2 to 83 wt%, more preferably 9.9 to 83 wt%, and the solution or melt The nitrogen concentration inside is usually 0.30 to 17 wt%, preferably 3.0 to 17 wt%, and more preferably 5.2 to 17 wt%.

(Auxiliary solubilizer)
In the method of the present invention, the metal halide used as an auxiliary solubilizer includes an alkali metal such as lithium (Li), sodium (Na), potassium (K), rubidium (Rb), and cesium (Cs), Alkaline earth metals and transition metals such as magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), and halogen components are fluorine (F), chlorine (Cl), bromine (Br), It is preferable to use iodine (I) or the like that forms a compound by combining these components. Such metal halides may be used not only in one type but also in several types. The optimum metal halide type should be selected depending on the combination with the crystal raw materials and the conditions of crystal growth. Usually, alkali halides and alkaline earth halides are preferably used. In this case, it is preferable to use an alkaline chloride such as lithium chloride and an alkaline earth chloride such as barium chloride among the alkaline earth halides.

(Crystal growth method)
As a crystal growth method, the temperature difference used in the flux method (Gradient Transport)
Method, Slow Cooling method, Temperature Cycling method, Accelerated Crucible-Rotation Technique (ACRT) method, Top-Seeded Solution Growth (TSSG) method, solvent transfer method and its A modified solvent migration floating zone (Traveling-Solvent Floating-Zone: TSFZ) method or the like can be used. A combination of these methods can also be used.

  In the present invention, a raw material and a solvent as described above, and a mixture of an auxiliary solubilizer as required are filled in a reaction vessel, and heated and melted in an inert gas atmosphere to prepare a solution or a melt to grow crystals. I do. In this case, in order to obtain a higher quality nitride crystal, mixing of water and oxygen should be avoided as much as possible. Therefore, the oxygen atom content in each component or mixture should be usually 5% by weight or less, preferably 2% by weight or less, particularly preferably 0.5% by weight or less. In addition, when using a hygroscopic material, it is sufficiently dried by heating and degassing before filling, and each component is mixed and filled in an inert gas atmosphere where oxygen and moisture are eliminated as much as possible. Should be done promptly.

(Reaction vessel)
The reaction vessel used in the present invention is preferably a reaction vessel mainly composed of a thermally and chemically stable oxide. The main component here means a component that occupies 90% by weight or more of the oxide component contained in the material constituting the wall in contact with the solution or melt in the reaction vessel, preferably the solution or melt in the reaction vessel. It is a component that occupies 95% by weight or more in the oxide component contained in the material constituting the wall surface in contact with the liquid. When the reaction vessel is made of a uniform material, it is equal to a component occupying 90% by weight or more, preferably 95% by weight or more in the oxide component contained in the material constituting the entire reaction vessel. Moreover, it is preferable that an oxide here is an oxide containing periodic table 2nd-3rd group metal elements, such as Mg, Ca, Al, Ti, Y, Ce, La. More preferably, oxides having a standard generation energy of −930 kJ / mol or less at 1000 K and chemically stable, specifically Y 2 O 3, CaO, La 2 O 3, MgO, etc. are preferable, and particularly preferably −1000 kJ at a standard generation energy of 1000 K. Oxides of less than / mol, specifically Y2O3, CaO, La2O3, etc. are preferred.

(Inert gas atmosphere)
There are no particular restrictions on the type of inert gas, but helium (He), nitrogen (N2), argon (Ar), and the like are preferably used. Further, a substance that functions as a scavenger that selectively absorbs oxygen and moisture (for example, a metal piece such as titanium) may be accompanied in the reaction vessel.

(Pressure and temperature)
Although the best mode for carrying out the present invention is to grow a GaN crystal at normal pressure or low pressure, the present invention can be applied even when the gas phase pressure is set to a higher pressure. In the present invention, the pressure in the reaction vessel for precipitating the Group 13 metal nitride crystal is usually 10 MPa or less, preferably 3 MPa or less, more preferably 0.3 MPa or less, more preferably 0.11 MPa or less. is there.

In the present invention, the growth temperature for precipitating the Group 13 metal nitride crystal is usually 200 to 1000 ° C., preferably 400 to 850 ° C., more preferably 600 to 800 ° C.
(Seed crystal)
In the production method of the present invention, it is preferable to use a Group 13 metal nitride crystal or a substrate as a seed (seed crystal) for crystal growth. The shape of the seed is not particularly limited, and may be 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 seed crystals 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 a substrate in vapor phase growth of GaAs and the like can be given. 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. In the case of using a rod-shaped seed crystal, it is possible to produce a bulk crystal by first growing in the seed crystal portion and then performing crystal growth in the vertical direction while also performing crystal growth in the horizontal direction.

(Semiconductor device manufacturing method)
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.

Hereinafter, the present invention will be described in more detail based on examples. In addition, this invention is not limited to an Example unless it is contrary to the meaning.
Example 1
In a glove box filled with argon gas, in a yttria crucible (reaction vessel) with an inner diameter of 17 mm, 1.00 g of gallium nitride powder, 0.43 g of lithium nitride as a solvent, 0.90 g of barium nitride, and lithium chloride-chloride as an auxiliary solubilizer 2.92 g of barium eutectic salt (barium chloride concentration 40 mol%) was added and sealed in a quartz reaction tube equipped with a gas inlet / outlet. The quartz tube taken out from the glove box is put into a resistance heating type electric furnace, and nitrogen gas circulation and heating of the electric furnace are started.
Heated to ° C. Holding at 745 ° C. for 20 h, a solution containing Ga and nitrogen was prepared. Thereafter, in order to measure the concentrations of Ga and nitrogen, a quartz tube having an inner diameter of 2 mm was inserted into the crucible, and about 200 mg of the solution was collected at a height of 5 mm from the bottom of the crucible. All of the solidified product collected was dissolved in acid to prepare an analysis solution. When the analysis solution was analyzed by ICP-AES and ion chromatography, the Ga concentration was 9.9 wt% and the nitrogen concentration was 5.2 wt%.

(Comparative Example 1)
A solution was prepared in the same manner as in Example 1 except that barium nitride was used as the solvent and the conditions shown in Table 1 were used, and analysis was performed in the same manner as in Example 1. As a result, Ga concentration is 0.12wt%
The nitrogen concentration was 0.24 wt%.
(Comparative Example 2)
A solution was prepared in the same manner as in Example 1 except that lithium nitride was used as the solvent and the conditions shown in Table 1 were used, and analysis was performed in the same manner as in Example 1. As a result, the Ga concentration was 0.025 wt%, and the nitrogen concentration was 0.12 wt%.

  The present invention is useful in that a solution or melt containing Ga and nitrogen at a high concentration suitable for crystal growth of a Group 13 metal nitride can be obtained. Further, the present invention is useful in that a high-quality group 13 metal nitride massive single crystal can be efficiently produced by a simple and safe method.

Claims (10)

  In a method for producing a Group 13 metal nitride crystal, comprising: dissolving a raw material in a solvent to prepare a solution or melt; and growing a Group 13 metal nitride crystal in the solution or melt. A method for producing a Group 13 metal nitride crystal, wherein two or more types of nitrides are used as a solvent.   The method for producing a Group 13 metal nitride crystal according to claim 1, wherein at least an alkali metal nitride is used as the solvent.   The method for producing a Group 13 metal nitride crystal according to claim 1, wherein at least an alkaline earth metal nitride is used as the solvent.   2. The method for producing a Group 13 metal nitride crystal according to claim 1, wherein at least alkali metal nitride and alkaline earth metal nitride are used as the solvent.   The method for producing a Group 13 metal nitride crystal according to claim 2 or 4, wherein the alkali metal nitride contains lithium nitride.   The method for producing a Group 13 metal nitride crystal according to claim 3 or 4, wherein the alkaline earth metal nitride contains barium nitride.   The solution or melt contains Ga and nitrogen, and the Ga concentration in the solution or melt is 0.20 to 83 wt%, and the nitrogen concentration is 0.30 to 17 wt%. The manufacturing method of the group 13 metal nitride crystal as described in any one of -6.   The method for producing a Group 13 metal nitride crystal according to any one of claims 1 to 7, further comprising adding a metal halide as an auxiliary solubilizer in the solution or melt.   9. The method according to claim 1, wherein the step of creating the solution or melt and / or the step of growing the Group 13 metal nitride crystal is performed at normal pressure. A method for producing a group 13 metal nitride crystal.   10. The method according to claim 1, wherein the step of creating the solution or melt and / or the step of growing the Group 13 metal nitride crystal is performed in an inert gas atmosphere. The manufacturing method of the group 13 metal nitride crystal of description.