JP4788524B2 - Group 13 metal nitride crystal production methods and solutions and melts used in these production methods - Google Patents

Description

  The present invention relates to a method for producing a nitride crystal of a Group 13 metal of a periodic table such as a GaN crystal and a method for producing a semiconductor device using the method. The present invention also relates to solutions and melts used in these production methods.

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

  However, in the above method, since the GaN crystal is epitaxially grown on different substrates having different lattice constants and thermal expansion coefficients, the obtained GaN crystal has many lattice defects. When such a GaN crystal having many lattice defects is used, the operation of the electronic device is adversely affected, and satisfactory performance for use in an application field such as a blue laser cannot be expressed. 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, the heteroepitaxial GaN crystal growth method by the vapor phase method requires a complicated and long process in order to reduce the defect concentration of the GaN crystal. For this reason, 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. However, it is difficult to implement industrially due to severe reaction conditions. Thus, many reports have been made on GaN crystal growth methods with lower reaction conditions. For example, a method of reacting Ga and NaN ₃ under pressure (Non-Patent Document 3), a flux growth method (see Patent Document 3, Non-Patent Documents 4, 5, 8, and 9) and the like have been proposed. Alkali metal is often used for the flux, but even when using a combined liquid obtained by adding an alkali metal to a Ga melt, the amount of N or GaN dissolved in the combined liquid is very small. It is difficult to increase the size. Furthermore, a method for synthesizing GaN by the ammonothermal method (see Non-Patent Document 6) has also been reported, but there are problems with the crystal size and the number of lattice defects, and it has not been industrialized because the manufacturing equipment is expensive. .

In addition, although a method for producing a GaN crystal by heating a mixture of GaN powder and an alkali metal halide has been proposed (see Patent Document 1), the solubility of GaN in the alkali metal halide is small 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 7 also reports crystal growth using a mixture of GaN powder and alkali metal halide, which is considered to be the same technique as in patent document 1. Patent Document 2 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, and crystal growth from a combined financial liquid is not used. 4 and 5 have the same problem.
JP 2005-127718 A Chinese Patent Publication No. 1288079A Japanese Patent Laying-Open No. 2005-306709A J. Appl. Phys. 37 (1998) 309 J. Crystal Growth 178 (1977) 174 J. Crystal Growth 218 (2000) 712 J. Crystal Growth 260 (2004) 327 Metal Vol.73 No.11 (2003) pp. 1060 Acta Physica Polonica A Vol.88 (1995) 137 J. Crystal Growth Vol.281 (2005) p. 5 J. Mater. Sci. Ele. 16 (2005) paragraph 29 J. Crystal Growth 284 (2005) p. 91

  As described above, a group 13 metal nitride crystal with few lattice defects cannot be obtained by a heteroepitaxial crystal growth method on a substrate by a vapor phase method. Also, other methods using high pressure require a large apparatus and are not economical. Furthermore, in the ammonothermal method using supercritical ammonia, the equipment and materials used are very expensive. Moreover, even in the method using alkali metal as a flux, the nitrogen solubility at low pressure is low, and there is a problem in the uniformity of the liquid phase in the reaction system, and there remains a problem to be solved in terms of industrial use. .

The present invention has been made to solve such problems of the prior art, so that a high-quality Group 13 metal nitride crystal such as a GaN crystal can be manufactured industrially at low pressure or normal pressure. And providing a solution and a melt used therefor.
Furthermore, another object of the present invention is to provide a method of manufacturing a semiconductor device such as a light emitting diode, a laser diode, a high frequency device, and a power IC using the manufacturing method.

  In view of the above-mentioned problems, the present inventors grow a high-quality metal nitride crystal having a crystal size that can be used industrially and can be applied to a semiconductor device by an economical method. The method has been intensively studied and the present invention has been completed.

That is, the object of the present invention is achieved by the following Group 13 metal nitride crystal manufacturing method, semiconductor device manufacturing method, and solution.
[1] A solution or melt prepared by dissolving a compound nitride containing a metal element other than Group 13 metal element of the periodic table and a metal element other than Group 13 of the periodic table in an ionic solvent is prepared. A method for producing a Group 13 metal nitride crystal comprising a step of growing a Group 13 metal nitride crystal.
[2] The method for producing a Group 13 metal nitride crystal according to [1], wherein the ionic solvent contains a molten salt as a main component.
[3] The method for producing a Group 13 metal nitride crystal according to [2], wherein the molten salt is one or more types of metal halides.
[4] The metal element other than Group 13 of the periodic table contained in the composite nitride is also contained in the ionic solvent, according to any one of [1] to [3] The manufacturing method of the group 13 metal nitride crystal | crystallization of this.
[5] The ratio of the total number of moles of metal elements other than Group 13 of the periodic table contained in the solution or melt to the total number of moles of Group 13 metal elements of the periodic table contained in the solution or melt is 16 to 16. It exists in the range of 80, The manufacturing method of the group 13 metal nitride crystal as described in any one of [1]-[4] characterized by the above-mentioned.
[6] Any one of [1] to [5], wherein a nitride of a metal element other than Group 13 of the periodic table contained in the composite nitride is dissolved in the ionic solvent by 1.0 mol% or more. A method for producing a Group 13 metal nitride crystal according to claim 1.
[7] The group 13 metal nitride crystal is grown by dissolving the composite nitride in the ionic solvent at a high temperature and then lowering the temperature of the obtained solution or melt. ] The manufacturing method of the group 13 metal nitride crystal as described in any one of [6].
[8] The dissolution field where the composite nitride is dissolved in the ionic solvent and the crystal growth field where the Group 13 metal nitride crystal grows are separated, and the temperature of the dissolution field is higher than the temperature of the growth field. The method for producing a Group 13 metal nitride crystal according to any one of [1] to [7], which is also high.
[9] The periodic table group 13 metal nitride crystal according to any one of [1] to [8], wherein the group 13 metal nitride crystal is grown on a seed crystal surface or a substrate. Manufacturing method.
[10] In the crystal growth field where the Group 13 metal nitride crystal grows, the metal nitride component concentration other than the Group 13 metal in the solution or melt is controlled. 9] The method for producing a Group 13 metal nitride crystal according to any one of [9].
[11] The group 13 according to [10], wherein metal nitride components other than the group 13 metal in the solution or melt are removed from the crystal growth field by evaporation, reaction, decomposition, or diffusion. A method for producing a metal nitride crystal.
[12] The group 13 metal nitride according to any one of [1] to [11], wherein the metal element other than the group 13 metal is an alkali metal element or an alkaline earth metal element Crystal production method.
[13] A group 13 metal nitride crystal is grown in a crystal growth apparatus containing the solution or melt while the solid phase of the composite nitride remains. [1] to [12] ] The manufacturing method of the group 13 metal nitride crystal as described in any one of.
[14] The crystal growth according to any one of [1] to [13], wherein the crystal growth is performed in a vessel mainly composed of an oxide of a Group 2 or Group 3 element in the periodic table. A method for producing a group 13 metal nitride crystal.
[15] The method for producing a Group 13 metal nitride crystal as described in [14], wherein the reaction vessel contains, as a main component, an oxide having a standard production energy of −930 kJ / mol or less at 1000 K.
[16] The method for producing a Group 13 metal nitride crystal according to any one of [1] to [15], wherein the crystal growth is performed at normal pressure.
[17] The method for producing a Group 13 metal nitride crystal according to any one of [1] to [16], wherein the crystal growth is performed in an argon atmosphere.
[18] Any of [1] to [17], wherein a Group 13 metal nitride crystal doped with the element is grown by allowing a doping element to exist in the solution or melt. A method for producing a Group 13 metal nitride crystal according to one item.
[19] The method for producing a Group 13 metal nitride crystal according to [1] to [18], wherein the solution or melt is the only liquid phase present in the crystal growth reaction system.
[20] The method for producing a Group 13 metal nitride crystal according to any one of [1] to [19], wherein the composite nitride is synthesized in the molten salt.
[21] The Group 13 metal nitriding according to [2] or [3], wherein the molten salt is a molten salt that has been dehydrated by passing a halogen or a halogenated gas in a molten state. Method for producing physical crystals.
[22] The molten salt is a mixture of a metal halide and a nitride of a metal other than Group 13 of the periodic table, according to any one of [2], [3], or [21] The manufacturing method of the group 13 metal nitride crystal | crystallization of this.
[23] The method for producing a Group 13 metal nitride crystal according to any one of [1] to [22], wherein the composite nitride is produced by a dry process.
[24] The method for producing a Group 13 metal nitride crystal according to any one of [1] to [23], wherein the crystal growth is performed in an atmosphere not containing nitrogen.

[25] a solution or melt having a nitrogen concentration X _N represented by the following formula (1), Group 13 metal nitride and having a step of performing growth of the Group 13 metal nitride crystal Crystal production method.

[In the above formula, X _N is the nitrogen concentration (mol%) in the solution or melt, K is a proportionality constant represented by the following formula (2), and P is a crystal growth apparatus containing the solution or melt. Pressure (MPa). ]

[In the above formula, T is the temperature (K) of the solution or melt. ]
[26] The method for producing a Group 13 metal nitride crystal according to [25], wherein the Group 13 metal nitride crystal is grown at 10 MPa or less.
[27] The method for producing a Group 13 metal nitride crystal as described in [25] or [26], wherein the Group 13 metal nitride crystal is grown at 600 ° C. to 1000 ° C.
[28] The solution or melt is a solution or melt obtained by dissolving a composite nitride containing a metal element other than Group 13 metal element of Periodic Table and Group 13 in an ionic solvent. The method for growing a Group 13 metal nitride crystal according to any one of [25] to [27].

[29] A method for manufacturing a semiconductor device, comprising a step of manufacturing a Group 13 metal nitride crystal by the manufacturing method according to any one of [1] to [28].
[30] A solution or melt in which a composite nitride containing a Group 13 metal element of the periodic table and a metal element other than Group 13 of the periodic table is dissolved in an ionic solvent.
[31] The solution or melt according to [30], wherein the ionic solvent is a molten salt.
[32] The ratio of the total number of moles of metal elements other than Group 13 of the periodic table contained in the solution to the total number of moles of Group 13 metal elements of the periodic table contained in the solution is in the range of 16-80. [30] or [31], wherein the solution or melt.
[33] The solution or melt according to any one of [30] to [32], wherein the metal element other than the Group 13 metal is an alkali metal element or an alkaline earth metal element.
[34] The solution or melt according to any one of [30] to [33], wherein the ionic solvent is a metal halide.
[35] The solution or melt according to any one of [30] to [34], wherein the ionic solvent is a mixture of a plurality of types of metal halides.

According to the production method of the present invention, a high-quality Group 13 metal nitride bulk crystal can be produced at low pressure or normal pressure. In particular, the problems of polynuclear generation under high pressure and a decrease in nitrogen concentration in the liquid under low pressure, which have been problems in the past, can be solved, and crystal seed growth can be performed. That is, the composite nitride is dissolved in an ionic solvent at a high temperature and then seeded by lowering the temperature, or the composite nitride is placed in a high temperature portion and dissolved in the ionic solvent, while the low temperature portion is seeded. By placing, thick film or bulk crystals can be made efficiently. Further, by controlling the concentration of the metal nitride component other than the dissolved group 13 metal in the vicinity of the crystal growth interface, the crystal growth rate, quality, and crystal size can be controlled.
As a result, according to the present invention, the refractory material containing the second and third group metal elements of the periodic table, that is, Mg, Ca, Al, Ti, Y, Ce, etc., is oxidized without undergoing a high temperature and high pressure process. A Group 13 metal nitride crystal having a size sufficient for application to a semiconductor device is manufactured using a container of an inexpensive basic refractory material such as magnesium oxide, calcium oxide, zirconia, etc. it can.

  The method for manufacturing a semiconductor device of the present invention includes a step of manufacturing the Group 13 metal nitride crystal of the present invention. As a result, according to the present invention, a power IC and a semiconductor device that can handle high frequencies can be manufactured, which has a great industrial advantage.

Below, the manufacturing method of the group 13 metal nitride crystal | crystallization of this invention, the manufacturing method of a semiconductor device, and the solution and melt used for these manufacturing methods 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. In addition, in this specification, “seed” includes, in addition to a 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. .

[Method for producing Group 13 metal nitride crystal and solution and melt used therefor]
The production method of the present invention is characterized in that a compound nitride containing a Group 13 metal and a metal element other than Group 13 is dissolved in an ionic solvent (particularly, a molten salt) and crystal seed growth is performed.

The composite nitride containing a Group 13 metal and a metal element other than Group 13 used in the production method of the present invention includes a Group 13 metal nitride powder and a metal nitride powder other than the Group 13 metal. (For example, Li ₃ N, Ca ₃ N ₂ ) may be mixed and then subjected to a solid phase reaction at elevated temperature, or may be synthesized in a molten salt. Alternatively, a metal alloy contained in the composite nitride may be made and nitrided with nitrogen gas or the like. Preferred examples of the Group 13 metal 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 nitrides include Li ₃ GaN ₂ , Ca ₃ Ga ₂ N ₄ , Ba ₃ Ga ₂ N ₄ , Mg ₃ GaN _{3 and the} like. The composite nitride in the present invention may be chemically synthesized or may be obtained by a dry process such as reactive sputtering, and is a mixture of elements that are not necessarily of stoichiometric composition. It doesn't matter. In the present invention, two or more kinds of composite nitrides may be used.

  The composite nitride containing a Group 13 metal and a metal element other than Group 13 used in the production method of the present invention is a raw material for growing a Group 13 metal nitride crystal. In the present invention, this composite nitride is usually easily synthesized by forming an alloy of a Group 13 metal and a metal element other than Group 13 and dissolving it while raising the temperature 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, although it is inferior in economic efficiency, it can also be synthesized by subjecting fine powder of Group 13 metal nitride crystal and nitride of an element other than Group 13 metal to a solid phase reaction at a high temperature. The composite nitride may not be a chemically synthesized crystalline material. For example, a substrate such as 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 above may also be used. When the composite 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, and a diffusion-dominated nitride dissolved phase can be formed 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 a dry process, it is possible to easily manufacture even a nitride that is difficult to synthesize chemically.

The ionic solvent 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. In the present invention, it is preferable to select an ionic solvent having the following functions (A) to (D).
(A) A function of dissolving a composite nitride and creating a solution.
(B) A function of dissolving the generated Group 13 metal nitride crystal.
(C) A function of promoting the precipitation of the Group 13 metal nitride crystal from the solution or melt.
(D) A function of dissolving nitrides of metal elements other than Group 13 of the periodic table contained in the composite nitride.

In order to exhibit the function (A), for example, an ionic solvent containing a metal element other than Group 13 of the periodic table contained in the composite nitride can be used. This is because if the ionic solvent contains ions of the same type as the ions contained in the composite nitride, the affinity of the ions is high and the composite nitride is easily dissolved. In this regard, for example, when Li ₃ GaN ₂ is used as the composite nitride, it is preferable to use LiCl as the ionic solvent.

The functions of (B) and (C) are seemingly contradictory functions, but these two points are both important functions for crystal growth from the liquid phase. In order to precipitate a large and high-quality crystal, it is preferable to appropriately control both dissolution and precipitation of the Group 13 metal nitride crystal to be formed.
Without the function (B), when the Group 13 metal nitride is produced by the production method of the present invention, it immediately precipitates as a solid, making it difficult to obtain a large and high quality crystal. Therefore, the ionic solvent preferably has a function of dissolving the Group 13 metal nitride crystal.
In order to exert the function (B), for example, when Li ₃ GaN ₂ is used as the composite nitride, a mixed ionic solvent of LiCl and Li ₃ N can be used. This is because GaN dissolves in the solvent due to the presence of Li ₃ N. When Li ₃ N coexists with LiCl, it becomes a liquid phase at a low temperature and becomes an ionic solvent. Even when only LiCl is used as an ionic solvent for dissolving the composite nitride, Li ₃ N is generated as a by-product by the reaction of the present invention, and becomes a mixed ionic solvent of LiCl and Li ₃ N in the system. In order to use the function of (B) more effectively (see formula (3) below), it is also preferable to use a mixed ion solvent containing LiCl and Li ₃ N in advance and dissolve the composite nitride in this. Done.

The contents of the function (C) are as follows. In order to precipitate a Group 13 metal nitride crystal from a solution or melt in which a composite nitride is dissolved in an ionic solvent, a method of lowering the liquid temperature or adding a temperature difference to the solution or melt can be cited. However, all of these methods utilize the fact that the saturated dissolution amount of the Group 13 metal nitride dissolved in the ionic solvent is reduced by lowering the temperature. For this reason, when the ionic solvent having a large decrease in the saturated dissolution amount of the Group 13 metal nitride is used when the temperature of the solution or melt is lowered, the amount of the Group 13 metal nitride obtained is increased. It is preferable because large crystals can be obtained.
In order to exert the function (C), for example, an ionic solvent that does not contain a metal element belonging to Group 13 of the periodic table contained in the composite nitride is added to the ionic solvent having the functions (A) and (B). Can be used. NaCl is preferred when Li ₃ GaN ₂ is used as the composite nitride. As the ionic solvent having the functions of (B) and (C), for example, a mixed ionic solvent of LiCl and NaCl or a mixed ionic solvent of LiCl, Li ₃ N, and NaCl can be preferably used.
Further, in order to exert the function (C), it is also possible to suitably use removal of Li ₃ N from the GaN crystal growth field. This is because GaN and Li ₃ GaN ₂ are dissolved due to the presence of Li ₃ N contained in Li ₃ GaN ₂ , so that precipitation of GaN can be promoted by appropriately removing Li ₃ N from the crystal growth field. Because.
In order to appropriately control the functions (B) and (C) of the solvent, appropriately controlling the concentration of metal nitride other than the Group 13 metal in the crystal growth field contained in the composite nitride, temperature control By performing the above, a Group 13 metal nitride crystal can be obtained.

The contents of the function (D) are as follows. When the Group 13 metal nitride is generated from the composite nitride, a nitride of an element other than the Group 13 metal contained in the composite nitride is generated as a by-product. In this case, when the by-product is precipitated as a solid, problems such as incorporation into the Group 13 metal nitride crystal as an impurity or a crystal nucleus when the Group 13 metal crystal grows are likely to occur. Therefore, the ionic solvent preferably has a function of dissolving a by-product, for example, a nitride of an element other than the Group 13 metal contained in the composite nitride.
In order to exert the function (D), for example, when Li ₃ GaN ₂ is used as the composite nitride, it is preferable to use LiCl that dissolves the by-product Li ₃ N as a solvent.

  The ionic solvent used in the present invention preferably contains a molten salt as a main component. Specifically, 50% by weight or more of the ionic solvent used is preferably a molten salt, more preferably 70% by weight or more is a molten salt, and 90% by weight or more is a molten salt. preferable.

The type of the molten salt is not particularly limited as long as it does not inhibit the epitaxial growth on the seed, but preferably has a strong chemical affinity with a metal element nitride other than the group 13 metal element in the composite nitride as a raw material, More preferably, they form compounds in chemical equilibrium. For example, halides, carbonates, nitrates, sulfurates and the like can be mentioned. For example, when the nitride is Li ₃ N, it is preferably a molten salt containing LiCl having a large amount of dissolution. In general, it is preferable to use a halide which is stable and has a high solubility of nitrogen compounds, and the molten salt is a salt containing an alkali metal and / or an alkaline earth metal and is used for a reaction for generating a nitrogen ion source. More preferably, it is a compound.

Specifically, the molten salt is preferably a molten salt made of an alkali metal salt such as Li, Na, or K and / or an alkaline earth metal salt such as Mg, Ca, or Sr. Further molten salt, LiCl, KCl, NaCl, CaCl 2, BaCl 2, CsCl, LiBr, KBr, CsBr, LiF, KF, NaF, LiI, NaI, also be metal halides such as CaI _2, BaI ₂ preferably , LiCl, KCl, NaCl, CsCl, CaCl ₂ , BaCl ₂ and mixed salts thereof are also preferable because the melting point is lowered.

  In addition, a mixture of a plurality of salts can be used as described above in order to control the solubility of the composite nitride in the molten salt and the solubility of the Group 13 metal nitride. 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 is heated. It is desirable to make it melted from the viewpoint of uniformity in the system.

  When impurities such as water are contained in the molten salt, it is desirable to purify the molten salt in advance by blowing a reactive gas. 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.

In order to increase the solubility of the composite metal nitride, a nitride of a metal element other than the Group 13 metal element can be added to the molten salt. As a nitride of a metal element other than the Group 13 metal element, Li ₃ N, Ca ₃ N ₂ or the like is preferably used.

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. Specifically, a seed crystal of a group 13 metal nitride such as GaN, InGaN, or AlGaN which has been vapor-phase grown can be used. 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.
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, a standard production energy is −930 kJ / mol or less at 1000 K and a chemically stable oxide, specifically Y ₂ O ₃ , CaO, La ₂ O ₃ , MgO, etc. is preferred, and standard production is particularly preferred. An oxide having an energy of −1000 kJ / mol or less at 1000 K, specifically, Y ₂ O ₃ , CaO, La ₂ O ₃ or the like is preferable.

In the present invention, a composite nitride composed of a Group 13 metal and a metal element other than the Group 13 metal is used as a raw material.
Hereinafter, a case where a composite nitride of gallium and lithium is used will be described as an example. In this case, precipitation of GaN from a solution or melt obtained by dissolving Li ₃ GaN ₂ in a molten salt is expressed by the following equation.

Heating and mixing GaN powder, Ga metal, LiGa alloy and the like with a lithium compound to form a GaN crystal is also described in J. Crystal Growth 247 (2003) pages 275-278 and Chinese Patent Publication No. 1288079A. Yes. However, in Chinese Patent Publication No. 1288079A, a lithium compound is not a raw material of GaN but an auxiliary melting agent that compensates for the low solubility of GaN. Further, when a metal melt such as Ga or LiGa is used, there is a problem that it is difficult to create and control a uniform melt because a concentration distribution is likely to occur due to a difference in density of components in the metal melt.

In order to solve these problems, the present invention is characterized in that a homogeneous solution or melt containing a sufficient amount of nitrogen for GaN production is prepared by dissolving Li ₃ GaN ₂ in a molten salt. Li ₃ GaN ₂ is considered to dissolve by forming a chemical species such as ionic species GaN ₂ ^{3− in} an ionic solvent. Therefore, by using an ionic solvent, it is possible to create a uniform solution or melt with a high nitrogen concentration at a low pressure or normal pressure, making it easy to manage the substance / concentration distribution in the system and stabilizing the crystal growth environment. Therefore, a large crystal can be grown.

  On the other hand, in the conventional flux growth method described in Patent Document 3 and the like, alkali metals such as Na and Li are added as auxiliary melting agents in order to increase the amount of nitrogen dissolved in Ga. At normal pressure, the amount of nitrogen dissolved in the solution or melt is very small compared to the amount of nitriding all Ga in the system. For this reason, in the flux method, the dissolution of nitrogen from the gas phase into the solution or melt is the rate-determining rate of GaN precipitation. If the pressure is low, a sufficient nitrogen concentration cannot be obtained because GaN grows. Therefore, in order to precipitate a GaN crystal, it is necessary to apply a high pressure to vapor phase nitrogen. On the other hand, if the pressure of vapor phase nitrogen is too high with respect to the crystal growth rate, a large number of microcrystal nuclei are generated, and innumerable GaN small crystals are generated, so that the GaN crystal cannot be grown greatly. It is difficult to appropriately control the pressure in the gas phase in accordance with the crystal growth rate under high pressure conditions, which is considered to be the reason why large crystals cannot be obtained by the conventional flux method.

On the other hand, in the present invention, for example, since Li ₃ GaN ₂ is used as a raw material and LiCl is used as a solvent, a sufficient nitrogen solubility can be obtained even at normal pressure or low pressure, and the deposition of GaN is easy to control rather than pressure. It is possible to control with.

  In general, the amount of the gas phase component dissolved in the liquid phase by gas-liquid equilibrium is expressed by the following formula (1) according to Sievert's law. From the following equation (1), the amount of gas dissolved in the liquid phase at a given pressure and temperature is determined by the value of the proportionality constant K. The present invention is characterized in that a GaN crystal is grown using a solution or melt having a high nitrogen concentration with a proportionality constant K that satisfies the following formula (2). The use of such a solution or melt that satisfies the conditions of formula (1) and formula (2) is not described in the literature such as the conventional flux method, and such a solution or melt is prepared. No means are suggested.

[In the above formula, X _N is the nitrogen concentration (mol%) in the solution or melt, K is a proportionality constant represented by the following formula (2), and P is a crystal growth apparatus containing the solution or melt. Pressure (MPa). ]

[In the above formula, T is the temperature (K) of the solution or melt. ]

  In the present invention, it is preferable that the proportionality constant K in the formula (1) satisfies the following formula (2A).

[In the above formula, T is the temperature (K) of the solution or melt. ]

In a solution or melt having a nitrogen concentration lower than the nitrogen concentration calculated when the range of K defined by equation (2) is applied to equation (1), the nitrogen concentration is too small to precipitate large GaN crystals. It is difficult to make it.
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. However, under such pressure conditions, the nitrogen concentration in the solution or melt is not affected by the pressure. Rather, if the pressure in the gas phase is made too high, a large number of microcrystals due to spontaneous nucleation are precipitated and become large. A GaN crystal cannot be obtained. Therefore, it is required that the value of P in equation (1) is not too large, that is, the value of K is within the range represented by equation (2).

In the present invention, the reaction atmosphere can be carried out even in a system in which the gas phase does not contain nitrogen, for example, in an argon atmosphere. Argon is easier to suppress the mixing of oxygen than nitrogen, and by performing crystal growth in an argon atmosphere, the mixing of oxygen into the crystal can be reduced. The reaction atmosphere means a gas phase component around a reaction vessel containing a solution or melt obtained by dissolving Li ₃ GaN ₂ in a molten salt.

Since Li ₃ GaN ₂ contains Li, it is preferable that the molten salt used as the ionic solvent contains Li from the affinity at the time of dissolution and the difference in density between solvent ions and solute ions. LiCl is particularly preferable as the molten salt containing Li.

If the ratio of LiCl to Li ₃ GaN ₂ is too small (LiCl is too small), the amount as a solvent is so small that Li ₃ GaN ₂ is not sufficiently dissolved. As a result, a large crystal with a small amount of GaN is obtained. There is a problem that it cannot be obtained. On the other hand, if the ratio of LiCl to Li ₃ GaN ₂ is too large (too much LiCl), the concentration of Li ₃ GaN ₂ in the solvent decreases, making it difficult to fold the crystal and making it difficult to obtain large crystals with a small amount. There is. The ratio of the sum of Li in Li ₃ GaN ₂ and Li in LiCl to Ga in Li ₃ GaN ₂ used for the reaction is preferably in the range of 16-80, more preferably 18-70. Preferably, it is 20-50. On the other hand, in the above-mentioned Chinese Patent Publication No. 1288079A, the ratio of Li to Ga is 0.11 to 12. This is because this known document does not assume that a solvent containing Li is used. In order to produce a uniform solution or melt as in the present invention, it is desirable to use LiCl as a solvent. For this reason, the ratio of Li to Ga needs to be larger than the value of the known literature.

It is desirable that the molten salt to be used has a property of dissolving Li ₃ N produced by the formula (3). If a molten salt that does not have the property of dissolving Li ₃ N is used, the reaction of the formula (3) from the solution or melt will cause simultaneous precipitation of solid-phase GaN and solid-phase Li ₃ N. This is because it becomes difficult to control crystal growth.

The molten salt may be a mixture of a plurality of compounds, for example, a mixture of a plurality of alkali metal halides. By using a molten salt of a mixture of two or more alkali metal halides as a solvent, the range of control when adjusting the solubility of Li ₃ GaN ₂ and the solubility of GaN so that the precipitation of GaN is optimized is widened. It can be adjusted to the optimum solvent conditions for crystal precipitation. Among the mixed molten salts of various alkali metal halides, it is desirable to use a mixed molten salt of LiCl and NaCl.

Since Li ₃ N produced in Formula (3) dissolves in the molten salt of alkali metal halide, the component of Li ₃ N concentration in the solvent increases with the progress of the reaction, and the Li ₃ N concentration is not controlled. The reaction of equation (3) reaches equilibrium and stops. For these reasons, the inventors of the present invention considered that the growth of crystals is slow in the conventional technique and that only small crystals can be obtained, and the present inventors have reached the present invention having means for solving this problem.

In the present invention, GaN can be precipitated by controlling the concentration by removing the Li ₃ N concentration in the solvent that rises with the progress of the reaction of formula (3) by some means. The Li ₃ N concentration can be controlled by evaporation, decomposition reaction, reaction with other chemical species (for example, W metal), diffusion, or the like. The method of controlling the concentration of Li ₃ N may be performed using one of these methods or using several methods simultaneously.

For example, as a removing method by evaporation, crystal growth can be continuously advanced by continuously evaporating Li ₃ N under N ₂ flow and removing it from the reaction system. Under high pressure, the removal of Li ₃ N by evaporation is hindered, so that the equilibrium of equation (3) is less likely to shift to the right, and the GaN solubility in the solution or melt decreases. Accordingly, it is desirable that crystal growth be performed at a low pressure, specifically, 10 MPa or less.

Further, as a removal method by reaction, for example, when Ga metal is present in the molten salt, the concentration of Li ₃ N in the molten salt is lowered by the reaction of the formulas (4) and (5), and crystallization according to the formula (3). The reaction proceeds continuously. Li discharged from the reaction field by the reactions of the formulas (4) and (5) is absorbed by the Ga metal and becomes an alloy. It is also possible to remove Li ₃ N by introducing into the system a substance that forms a nitride by reacting with Li ₃ N such as W mesh.

Further, by taking a sufficiently large amount of the molten salt as a solvent, it is possible to reduce the change in the Li ₃ N concentration in the crystal growth portion as a result of diffusion.
As a method for removing by decomposition of Li ₃ N in the molten salt, for example by blowing hydrogen chloride or chlorine, it may be decomposed to Li ₃ N in LiCl, N _2, H ₂ (the case of hydrogen chloride). In order to proceed the reaction more gently, hydrogen chloride decomposed on the surface of the molten salt by supplying ammonium chloride as a gas may be used.

In this way, in the growth of the group 13 nitride crystal, the concentration of Li ₃ N in the system is appropriately controlled to stop the thick film-like or bulk-like 13th without stopping at the equilibrium of the formula (3). It becomes possible to grow group metal nitride crystals. The quality and growth rate of the Group 13 nitride crystal obtained by the present invention also depend on the reaction rate controlled in this way.

In the present invention, the composite nitride Li ₃ GaN ₂ which is a GaN raw material is dissolved in a molten salt of an alkali metal halide to form a solution or melt, and the temperature of the solution or melt is lowered, or the reaction Solid GaN can be deposited from a solution or melt at a low temperature provided in the system. At this time, Li ₃ N remains dissolved in the molten salt. As the alkali metal halide used as a solvent, a high affinity compound that forms a compound in thermal equilibrium with Li ₃ N as a by-product is preferable because of its high solubility. In equation (3), the equilibrium shifts to the production system side when the temperature is low, so that the dissolved portion of Li ₃ GaN _{2 in} the molten salt is heated to a high temperature, and the crystal growth portion is relatively It is also a good method to keep the temperature low.

  In the present invention, the reaction 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.

  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, since the composite nitride is used by dissolving it in a molten salt, it can be used at a temperature lower than the melting point of the composite nitride. In addition, it is preferable to add excess composite nitride because the concentration in the molten salt near the composite nitride becomes equal to the saturation solubility, and the activity of Li ₃ GaN ₂ in formula (3) is 1.
Further, when a substance other than the Group 13 metal is doped into the crystal, it may be dissolved in the molten salt in the form of a nitride, and the object can be achieved within the production process of the present invention.

Li ₃ GaN ₂ can be produced by reacting GaN and Li ₃ N at about 800 ° C., or by heating a Ga—Li alloy at 600 to 800 ° C. in a nitrogen atmosphere. Alternatively, it can be produced by reacting GaN and Li ₃ N in an ionic solvent. In this method, when the composite nitride is formed, it is already a solution or melt dissolved in the ionic solvent. Therefore, the composite nitride and the ionic solvent are mixed by a method of lowering the temperature of the solution or melt. A solid is obtained. When this mixed solid is used as a raw material for crystal growth, there is an advantage that a uniform solution or melt can be easily obtained as compared with the case where both the composite nitride and the ionic solvent are separately charged into the crystal growth apparatus. As another method, reactive sputtering by nitrogen plasma is performed using Li metal and a Ga—Li alloy as a target to form a mixed composition film of Li—N and Ga—Li—N, which is formed of Li ₃ GaN ₂ . It can also be substituted. In this case, it is not only convenient for producing a thin film crystal, but also has an advantage that it can be produced even in a material system that is chemically difficult to synthesize.
As a reaction vessel when producing Li ₃ GaN ₂ , a refractory material made of an oxide containing a metal of Group 2 to 3 of the periodic table, specifically an oxide such as Mg, Ca, Al, Ti, Y, Ce, In particular, inexpensive refractory materials such as magnesium oxide, calcium oxide, and zirconia can be used.
Complex nitrides other than Li ₃ GaN ₂ can also be produced by a method similar to the above Li ₃ GaN ₂ .

  Generally, in liquid phase crystal growth, the same powder or microcrystal as the single crystal of the product is used as a raw material. For example, when considering the production of a GaN single crystal, it is costly to produce a raw material GaN powder, but the method according to the present invention uses a composite nitride that can be produced at a low cost, which is advantageous as an industrial process. There is.

  The Group 13 metal nitride crystal obtained by the production method of the present invention is a single metal nitride (for example, GaN, AlN, InN) or a nitride of a synthetic composition (for example, GaInN, GaAlN), particularly GaN. It can be suitably used as a crystal production method. The crystal growth of the Group 13 metal nitride is preferably performed by growing a crystal on a seed or a substrate.

  Next, the manufacturing method of the present invention will be described more specifically with reference to the drawings. 1 to 3 show a configuration example of a manufacturing apparatus for growing a Group 13 metal nitride crystal used in carrying out the present invention. FIG. 4, FIG. 5, FIG. 11, and FIG. It is a figure which shows the apparatus used in the Example of invention. FIG. 6 is a schematic explanatory diagram of the apparatus for purifying molten salt. The molten salt used for crystal growth is purified (mainly dehydrated) by this apparatus in advance.

  Molten salts such as chlorides generally contain a large amount of moisture because of their high hygroscopicity. When a molten salt containing water is used in carrying out the present invention, it is not preferable because an oxide of a Group 13 metal is formed in the reaction vessel and the reaction vessel is easily corroded. Therefore, it is preferable to remove impurities such as water in advance by using a sample-sealed pretreatment apparatus as shown in FIG. 6 (molten salt, basics of thermal technology, see p266 issued by Agne Technical Center Co., Ltd.). . When purifying using the apparatus shown in FIG. 6, first, the metal salt to be purified is put into the purification container 21, and the inside of the purification container 21 is evacuated from the gas outlet 19 under vacuum or for the salt purification apparatus. The temperature of the electric furnace 15 is raised, and the metal salt is melted by switching to an inert gas atmosphere such as argon gas or a reactive gas atmosphere such as hydrogen chloride gas. Thereafter, a reactive gas such as hydrogen chloride gas is blown into the molten metal salt from the gas introduction pipe 20 through the porous filter 22 for about 1 hour or longer to perform bubbling. After the bubbling is completed, the gas introduction pipe 20 side is depressurized, and the molten salt is transferred to the sample reservoir 23 by applying pressure using an inert gas from the gas discharge port 19 side as necessary. After cooling, the purified sample is vacuum-sealed and stored by evacuating and sealing the top of the sample reservoir 23. In addition, when heavy metals etc. which cannot be removed by the above method are contained in the molten salt, it is preferable to further purify the salt by the zone melt method.

Next, the step of growing a Group 13 metal nitride crystal according to the production method of the present invention will be specifically described. Here, a LiCl molten salt purified from the composite nitride Li ₃ GaN ₂ composed of a Group 13 metal element and a metal element other than Group 13 as a raw material using the apparatus shown in FIG. 6, the Group 13 metal A case where Ga is used as a nitrogen compound of a metal element other than that in order to reduce the Li ₃ N concentration will be described as an example. The following description can also be applied when other materials are selected.

FIG. 1 is a schematic view of a typical manufacturing apparatus used in carrying out the present invention. First, the purified LiCl salt 6 is put in a reaction vessel 14 of magnesium oxide or calcium oxide and dissolved at 650 to 780 ° C. Li ₃ GaN ₂ composite nitride 8 prepared in advance is placed on the part partitioned by the partition plate 5 and dissolved in the molten salt 6. It is considered that the dissolved Li ₃ GaN ₂ composite nitride dissolves while forming a complex salt with LiCl as a solvent. In this state, the Li ₃ GaN ₂ complex nitride reaches the surface of the GaN crystal 1 and grows by the reaction of the formula (3). The concentration of Li ₃ N as a by-product increases in the vicinity. In order to promote uniform crystal growth on the crystal surface, it is preferable that the Li ₃ N concentration in the solution or melt is also free of spots, so that the GaN crystal 1 gradually passes through the substrate 2 and the substrate holding mechanism 3. It is preferred to exercise in solution or melt. When the amount of the molten salt is sufficient and the thickness of the GaN crystal 1 to be grown is not so necessary, the reaction can be performed until the crystal growth stops spontaneously due to the increase of the Li ₃ N concentration accompanying the crystal growth. Although it is good, in order to grow a large bulk crystal, it is preferable to place a Ga metal behind the GaN crystal 1 as shown in FIG. Li ₃ N whose concentration has increased near the crystal growth portion becomes a GaLi alloy by the reaction of Ga metal with the formula (4), and at the same time, GaN and Li ₃ GaN ₂ are generated near the surface of the GaLi alloy. Li ₃ GaN ₂ again serves as a raw material for crystal epitaxial growth. In this way, GaN crystals can be continuously grown as long as the raw material of Li ₃ GaN ₂ exists. In Equation (4), since the equilibrium is shifted to the production side (right side) at the low temperature side, the dissolution rate of Li ₃ GaN ₂ is raised and the crystal growth rate is lowered at a low temperature. There is an advantage.

FIG. 2 is another vertical type crystal growth apparatus suitable for carrying out the present invention. Molten salt 6 having a low melting point such as purified LiCl or binary eutectic salt LiCl-NaCl is placed in a reaction vessel 14 of magnesium oxide or calcium oxide, and tungsten is added to Li ₃ GaN ₂ composite nitride 8 separately prepared. When the seed 2 attached to the tip of the substrate support rod 3 having a rotation function is placed on the top of the reaction vessel 14 and placed on the top of the reaction vessel 14, a solution or melt of Li ₃ GaN ₂ is dissolved in the GaN. Crystals break up and epitaxial growth from the liquid phase occurs. When a GaN crystal grows on the crystal surface, the Li ₃ N component increases in the solution or melt, but the solution or melt flows in the direction of the arrow shown in the figure as the crystal rotates. , Partly rises and the concentration of the Li ₃ N component in the solution or melt increases. In the case of growing a thin film-like crystal as a seed, the amount of the solution or melt may be increased. However, in order to continuously grow a bulk crystal, the Li ₃ N component in the solution or melt is used. Must be removed continuously. In FIG. 2, hydrogen chloride is blown into a solution or melt from a gas blowing tube 12 to decompose a Li ₃ N component into LiCl, N ₂ , and H ₂ . Alternatively, in order to obtain a milder condition, nitrogen or argon was used as a carrier gas from the gas introduction pipes 10 and 11, and ammonium chloride gas was introduced into the reaction vessel 14 to decompose from the solution or melt interface. Hydrogen chloride may be diffused into the molten salt.

  As the seed 2, for example, sapphire, SiC or the like can be used, but a plate-like GaN crystal is preferably used. It is preferable to homoepitaxially grow a GaN crystal on a plate-like GaN crystal, to make several wafers from these, and to use one of them as a substrate for the next crystal growth.

FIG. 3 shows that a thin film 17 made of a mixture of Ga—Li—N or the like is formed on a substrate 2 made of quartz, sapphire, GaN or the like by using a dry process such as sputtering, and this is dissolved in the LiCl molten salt 6. Then, a GaN crystal is grown on the substrate 2. In the figure, reference numeral 18 denotes a partition plate for preventing the reaction between the nitride thin film 17 and the LiCl molten salt 6 at a portion other than the crystal growth portion, and tungsten or the like is used as the material.
The atmosphere 7 in the reaction vessel 14 is an inert atmosphere such as nitrogen or argon.
The dissociation pressure of the generated GaN is 1 atm at 650 ° C. when calculated from the free energy of generation, and it is generally said that decomposition starts when the temperature reaches 650 ° C. or higher at normal pressure. However, according to the present invention, GaN does not decompose into Ga metal and nitrogen gas in the molten salt even at a normal pressure of 600 to 800 ° C. Further, as apparent from the equation (3), since dissolution / precipitation of the GaN crystal can be controlled by the Li ₃ N concentration in the molten salt, remelting and recrystallization can be repeated at the solid-liquid interface of crystal growth. As a result, since the quality of the crystal can be improved, the present invention is extremely advantageous.

[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.

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

(Production example) Synthesis of composite nitride Polycrystalline gallium nitride and lithium nitride reagent (manufactured by Mitsuwa Chemical Co., Ltd.) were mixed at a molar ratio of about 1: 1 using a mortar, and about 2 g of the resulting mixture was added to a magnesia reaction vessel ( The composite nitride was produced by placing in a crucible and firing under a nitrogen flow of 60 Nml / min. In the temperature control of firing, the temperature was raised from room temperature to 800 ° C. over 1 hour, held at 800 ° C. for 20 hours, and then the electric furnace power was turned off to allow natural cooling. The sample had a mixed color of gray and magenta before firing, but changed to whitish gray after firing. The X-ray data of this sample is shown in FIG. It can be seen that Li ₃ GaN ₂ was formed.

(Example 1)
Using the apparatus shown in FIG. 4, Li ₃ GaN ₂ composite nitride 8 was submerged in molten salt made of LiCl without using a GaN seed or substrate, and GaN crystal growth was performed. As a molten salt, 1.0 g of LiCl and 0.15 g of composite nitride Li ₃ GaN ₂ are placed in a first reaction vessel (crucible) 14 made of MgO, and then the first reaction vessel 14 and quartz (SiO 2) containing it. ₂ ) The inside of the second reaction vessel 25 was an argon atmosphere (normal pressure). The molar ratio of Li to Ga in the system is 22. In addition, LiCl refine | purified the salt according to the said description using the apparatus shown by FIG.

The second reaction vessel 25 containing the first reaction vessel 14 was heated to 780 ° C. in 1 hour using the electric furnace 15. As shown in FIG. 4, Li ₃ GaN ₂ has a higher density than LiCl, and therefore sinks to the bottom of the first reaction vessel 14. In this state, after maintaining at 780 ° C. for 8 hours, the temperature was lowered to 660 ° C. at a rate of 12 ° C. per hour. As shown in FIG. 4, the upper part of the first reaction vessel 14 is appropriately closed, there is almost no pressure difference inside and outside the first reaction vessel, and volatile components in the vessel are not removed outside the vessel. After that, the electric furnace was turned off and allowed to cool naturally. Firing was performed at normal pressure under a nitrogen flow of 60 Nml / min. After the experiment was completed, the sample was allowed to stand and cooled to room temperature. The contents of the first reaction vessel 14 were dissolved and filtered with water, and the solid was further eluted with concentrated hydrochloric acid. It was observed that the transparent crystalline powder grew from the inside of the first reaction vessel 14.

  An optical micrograph of the GaN crystal thus taken out is shown in FIG. Yield was 9 mg. It can be seen that colorless, highly transparent 100 μm plate-like crystals are growing.

(Example 2)
Using the apparatus shown in FIG. 5, 0.13 g of Li ₃ GaN ₂ and 3.0 g of LiCl are used, and a GaN thin film produced by a vapor phase method (MOCVD and H-VPE method) as a seed crystal is used as a seed 2 and a molten salt I put it inside. GaN crystal growth was performed under the same conditions as in Example 1. FIG. 9 shows an SEM photograph of GaN grown on the seed surface. It can be seen that hexagonal crystals have grown on the surface, and that the liquid phase has grown epitaxially on GaN produced by the vapor phase method.

(Example 3)
Crystal growth of GaN was performed under the same conditions as in Example 1 except that the amount of LiCl in the system was 3.0 g and the molar ratio of Li to Ga was 60. The yield was 12 mg, which was a mixture of plate crystals and columnar crystals.

Example 4
Crystal growth of GaN was performed under the same conditions as in Example 1 except that 0.017 g of Li ₃ N was added, the annealing rate was 1 ° C./h, and the lower limit of the annealing temperature range was 730 ° C. The yield was 3 mg, and thin plate-like crystals were obtained. The size of the crystal was about 500 μm.

(Example 5)
Instead of LiCl, 1.1 g of eutectic salt of LiCl and NaCl (mol: Li: Na = 85: 15) was used, 0.007 g of Li ₃ N was added, and the holding time at 780 ° C. was gradually increased for 14 hours. GaN crystal growth was performed under the same conditions as in Example 1 except that the cooling rate was 1 ° C./h and the lower limit of the annealing temperature range was 730 ° C. Yield was 37 mg. A columnar crystal having a length of about 700 μm and a thickness of about 150 μm was obtained.
FIG. 10 shows X-ray diffraction data. Table 1 shows the half widths of typical diffraction peaks of the X-ray diffraction data of the obtained crystals.

(Example 6)
GaN crystal growth was performed under the same conditions as in Example 5 except that the slow cooling rate was 2 ° C./h. Yield was 4 mg. A columnar crystal having a length of about 1.7 mm and a thickness of 50 μm was obtained.

(Example 7)
Crystal growth of GaN was performed under the same conditions as in Example 1 except that the amount of LiCl was 0.3 g and the amount of Li ₃ GaN ₂ was 0.3 g (the molar ratio of Li to Ga was 3). The amount of the obtained crystal was 1 mg or less, and the size of the crystal was 5 to 10 μm.

(Example 8)
Crystal growth of GaN was performed under the same conditions as in Example 1 except that the amount of LiCl was 5.0 g (the molar ratio of Li to Ga was 97). The amount of the obtained crystal was 1 mg or less, and the size of the crystal was 5 to 10 μm.

Example 9
Using the apparatus shown in FIG. 11, 2.5 g of LiCl and 0.4 g of Li ₃ GaN ₂ composite nitride were mixed well and placed in a first MgO reaction vessel (a crucible having an inner diameter of 25 mm and a height of 90 mm) 14. . Subsequently, a GaN substrate (0.5 mm × 0.5 mm) produced by a vapor phase method (MOCVD and H-VPE method) as a seed crystal was placed in the first reaction vessel 14 as a seed 2. Nitrogen was passed through the second reaction vessel 25 of quartz (SiO ₂ ) containing the first reaction vessel 14 at a flow rate of 70 ml / min. The molar ratio of Li to Ga in the system is 22.
The second reaction vessel 25 containing the first reaction vessel 14 was heated from room temperature to 760 ° C. in 1 hour using the electric furnace 15. As shown in FIG. 11, the first reaction vessel 14 is appropriately opened to a nitrogen atmosphere, and volatile components in the first reaction vessel containing Li ₃ N are gradually evaporated from the first reaction vessel and removed. In this state, it was kept at 760 ° C. for 20 hours. Then, the 2nd reaction container 25 was taken out from the electric furnace with the 1st reaction container 14 built in, and it cooled rapidly. After the experiment was completed, the sample was allowed to stand and cooled to room temperature. The contents of the first reaction vessel 14 were dissolved and filtered with water, and the solid was further eluted with concentrated hydrochloric acid. After completion of the reaction, GaN crystal growth was confirmed on the surface of the charged seed crystal substrate, and the growth film thickness was 3 μm. The obtained single crystal was 63 mg and was a plate-like or columnar crystal having a size of about 500 μm.

(Example 10)
A GaN crystal was grown under the same conditions as in Example 9 except that LiCl was changed to 5 g.
After the completion of the reaction, GaN crystal growth was confirmed on the surface of the charged seed crystal substrate, and the growth film thickness was 4 μm. The obtained single crystal was 84 mg and was a plate-like or columnar crystal having a size of about 500 μm.

(Example 11)
GaN crystal growth was performed under the same conditions as in Example 9 except that 0.04 g of Li ₃ N was added to the raw material.
After completion of the reaction, the obtained single crystal was 32 mg, and GaN crystal growth was confirmed on the surface of the charged seed crystal substrate, and the growth film thickness was 4 μm.

(Example 12)
Using the apparatus shown in FIG. 12, GaN was grown under the same conditions as in Example 9 except that no seed crystal was added.
After completion of the reaction, the obtained single crystal was 62 mg and was a plate-like or columnar crystal having a size of about 500 μm.

(Example 13)
GaN crystal growth was performed under the same conditions as in Example 9 except that the reaction temperature was 715 ° C.
After completion of the reaction, the obtained single crystal was 1 mg, and GaN crystal growth was partially confirmed on the surface of the charged seed crystal substrate, and the film thickness of the growth part was 1 μm.

(Example 14)
GaN crystal growth was performed under the same conditions as in Example 9 except that the reaction holding time was 10 hours.
After completion of the reaction, the obtained single crystal was 10 mg, and GaN crystal growth was partially confirmed on the surface of the charged seed crystal substrate.

(Example 15)
GaN crystal growth was performed under the same conditions as in Example 9 except that LiCl was 2.5 g and the reaction holding time was 40 hours.
After completion of the reaction, the obtained single crystal was 63 mg, and GaN crystal growth was partially confirmed on the surface of the charged seed crystal substrate, and the growth film thickness was 5 μm.

(Example 16)
GaN crystal growth was performed under the same conditions as in Example 9, except that a W net was laid on the bottom of the first reaction vessel 14.
After completion of the reaction, the obtained single crystal was 68 mg, and GaN crystal growth was partially confirmed on the surface of the charged seed crystal substrate, and the growth film thickness was 5 μm. FIG. 13 shows an SEM image of a cross section of the growth portion grown on the seed crystal. Further, FIG. 14 shows the results of X-ray rocking curve measurement of the GaN (002) plane grown on the seed crystal (ω = 15.505 deg, half-value width = 106.2 arcsec, intensity = 10766.7 cps).

(Example 17)
Using the apparatus shown in FIG. 15, 0.2 g of Li ₃ GaN ₂ and 3 g of LiCl were placed in the first reaction vessel 14 made of MgO. Nitrogen was passed through the second reaction vessel 25 of quartz (SiO ₂ ) containing the first reaction vessel 14 at a flow rate of 70 ml / min.
The second reaction vessel 25 containing the first reaction vessel 14 was heated from room temperature to 775 ° C. in 1 hour using the electric furnace 15 and held at that temperature for 20 hours. As shown in FIG. 15, the first reaction vessel 14 has a lid 26, and the volatile components in the first reaction vessel containing Li ₃ N are not removed from the first reaction vessel.
After the completion of the reaction, the second reaction vessel 25 was taken out of the electric furnace with the first reaction vessel 14 built in and rapidly cooled. Elemental analysis in the solidified molten salt was performed. As a result, the Ga concentration contained in the molten salt was 0.13 mol% and the nitrogen concentration was 0.4 mol%. The value of K in the formula (1) was calculated from the nitrogen concentration in the molten salt to be 1.26. It was.

(Example 18)
The experiment was performed under the same conditions as in Example 17 except that the apparatus shown in FIG. As shown in FIG. 11, the first reaction vessel 14 was opened to a nitrogen atmosphere, and volatile components in the first reaction vessel containing Li ₃ N were gradually evaporated from the first reaction vessel and removed.
After completion of the reaction, the obtained single crystal was 17 mg.

(Example 19)
The experiment was performed under the same conditions as in Example 17 except that the temperature was maintained at 765 ° C. for 20 hours.
After completion of the reaction, elemental analysis of the molten salt that was rapidly cooled and solidified was performed. As a result, Ga contained in the molten salt was 0.1 mol% and the nitrogen concentration was 0.25 mol%, and the value of K in the formula (1) was found to be 0.79 from the nitrogen concentration in the molten salt. .

(Example 20)
An experiment was performed under the same conditions as in Example 19 except that the apparatus shown in FIG.
After completion of the reaction, the obtained single crystal was 6 mg.

(Example 21)
The experiment was performed under the same conditions as in Example 17 except that Y ₂ O ₃ was used for the first reaction vessel and the temperature was maintained at 760 ° C. for 20 hours.
After completion of the reaction, elemental analysis was performed in the molten salt that was rapidly cooled and solidified. As a result, Ga contained in the molten salt was 0.01 mol% and the nitrogen concentration was 0.11 mol%. The value of K in the formula (1) was found from the nitrogen concentration in the molten salt to be 0.33. .

(Example 22)
An experiment was performed under the same conditions as in Example 21 except that the apparatus shown in FIG.
After completion of the reaction, the obtained single crystal was 6 mg.

(Example 23)
The experiment was performed under the same conditions as in Example 21 except that the temperature was maintained at 660 ° C. for 20 hours.
After completion of the reaction, elemental analysis was performed in the molten salt that was rapidly cooled and solidified. As a result, Ga contained in the molten salt was 0.006 mol% and the nitrogen concentration was 0.044 mol%, and the value of K in the formula (1) was found to be 0.14 from the nitrogen concentration in the molten salt. .

(Example 24)
The experiment was performed under the same conditions as in Example 23 except that the apparatus shown in FIG.
After completion of the reaction, the obtained single crystal was 1 mg.

(Comparative Example 1)
The experiment was performed under the same conditions as in Example 17 except that 0.2 g of GaN and 3 g of LiCl were placed in the first reaction vessel 14.
After completion of the reaction, elemental analysis was performed in the molten salt that was rapidly cooled and solidified. As a result, the concentration of Ga contained in the molten salt was below the detection limit (0.002 mol% or less) and very low, and dissolution of GaN in the solution or melt was not observed.

(Comparative Example 2)
Using the apparatus shown in FIG. 15, 1 g of LiCl, 0.15 g of Li ₃ GaN ₂ composite nitride, and 0.017 g of Li ₃ N were mixed well, and the resulting mixture was put into a first reaction container (inner diameter 9 mm, height 60 mm) 14 of MgO. I put it in. The experiment was performed under the same conditions as in Example 9 except that the reaction temperature was 780 ° C.
Since the inner surface of the first reaction vessel 14 was narrow, the surface area of the solution was small, and the reaction was carried out with the lid 26. Therefore, the evaporation of Li ₃ N was suppressed, and no precipitation of GaN single crystals was observed after the reaction.

  According to the method for producing a Group 13 metal nitride crystal of the present invention using the solution or melt of the present invention, a Group 13 metal having a size sufficient to be easily applied to a semiconductor device using an inexpensive apparatus. Nitride crystals can be produced. In particular, since it can be used for the manufacture of a semiconductor device capable of supporting frequencies, which has been considered difficult to manufacture, there is a great industrial advantage.

It is a schematic explanatory drawing which shows the suitable crystal growth apparatus (the 1) used by manufacture of the crystal | crystallization of the group 13 metal nitride of this invention. It is a schematic explanatory drawing which shows the suitable crystal growth apparatus (the 2) used by manufacture of the crystal | crystallization of the group 13 metal nitride of this invention. It is a schematic explanatory drawing which shows the suitable crystal growth apparatus (the 3) used by manufacture of the crystal | crystallization of the group 13 metal nitride of this invention. It is a schematic explanatory drawing which shows the crystal growth apparatus (the 1) used in the Example. It is a schematic explanatory drawing which shows the crystal growth apparatus (the 2) used in the Example. It is a schematic explanatory drawing which shows one embodiment of the refiner | purifier of the molten salt used by this invention. It is an XRD pattern of the obtained Li ₃ GaN ₂ crystals in Production Example. 2 is an optical micrograph of a GaN crystal obtained in Example 1. 4 is a SEM photograph of the GaN crystal obtained in Example 2. 6 is an XRD pattern of a GaN crystal obtained in Example 5. It is a schematic explanatory drawing which shows the crystal growth apparatus (the 3) used in the Example. It is a schematic explanatory drawing which shows the crystal growth apparatus (the 4) used in the Example. 4 is a SEM photograph of the GaN crystal obtained in Example 16. 18 is a result of measuring an X-ray rocking curve of a GaN crystal obtained in Example 16. It is a schematic explanatory drawing which shows the crystal growth apparatus (the 5) used in the Example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 GaN crystal 2 Substrate or seed 3 Substrate or crystal holding and rotation mechanism 4 Ga-Li alloy 5 Partition plate 6 Molten salt 7 Nitrogen or argon 8 Compound nitride 9 Net 10 Gas introduction pipe 11 Gas introduction pipe 12 Gas blowing pipe 13 Nitrogen 14 reaction vessel (first reaction vessel)
15 Electric furnace 16 Gas blowing pipe 17 Ga-Li-N thin film 18 Partition plate 19 Gas outlet 20 Gas introduction pipe 21 Purification vessel 22 Porous filter 23 Sample reservoir 24 Hydrogen chloride gas 25 Second reaction vessel 26 Lid

Claims (18)

A solution or melt is prepared by dissolving a complex nitride containing a metal element other than Group 13 metal element of the periodic table and a metal element other than Group 13 of the periodic table in an ionic solvent containing a molten salt as a main component. A method for producing a Group 13 metal nitride crystal, comprising a step of growing a Group 13 metal nitride crystal in a liquid. The method for producing a Group 13 metal nitride crystal according to claim 1 , wherein the molten salt is one or more types of metal halides. 3. The production of a Group 13 metal nitride crystal according to claim 1, wherein a metal element other than Group 13 of the periodic table contained in the composite nitride is also contained in the ionic solvent. Method. The ratio of the total number of moles of metal elements other than Group 13 of the periodic table contained in the solution or melt to the total number of moles of Group 13 metal elements of the periodic table contained in the solution or melt is in the range of 16-80. The method for producing a Group 13 metal nitride crystal according to any one of claims 1 to 3 , wherein the method is provided. According to any one of claims 1 to 4, characterized in that the nitride of a metal element other than periodic table Group 13 contained in the composite nitride is dissolved 1.0 mol% in the ionic solvent The manufacturing method of the group 13 metal nitride crystal | crystallization of this. After said composite nitride was dissolved at elevated temperature in the ionic solvent, claim, characterized in that growing a Group 13 metal nitride crystal by lowering the temperature of the resulting solution or melt 1-5 The manufacturing method of the group 13 metal nitride crystal as described in any one of these. The dissolution field where the composite nitride is dissolved in the ionic solvent and the crystal growth field where the Group 13 metal nitride crystal grows are separated, and the temperature of the dissolution field is higher than the temperature of the growth field The method for producing a Group 13 metal nitride crystal according to any one of claims 1 to 6 , wherein: The method for producing a Group 13 metal nitride crystal of the periodic table according to any one of claims 1 to 7 , wherein the Group 13 metal nitride crystal is grown on a seed crystal surface or a substrate. The metal nitride component other than said Group 13 metal in said solution or melt, claim 1-8, characterized in that removal from the crystal growth field the Group 13 metal nitride crystal is grown one A method for producing a Group 13 metal nitride crystal according to Item. The group 13 metal nitride according to claim 9 , wherein metal nitride components other than the group 13 metal in the solution or melt are removed from the crystal growth field by evaporation, reaction, decomposition, or diffusion. Crystal production method. The method for producing a Group 13 metal nitride crystal according to any one of Claims 1 to 10 , wherein the metal element other than the Group 13 metal is an alkali metal element or an alkaline earth metal element. In the crystal growth apparatus containing said solution or melt, any one of claims 1 to 11 in which the solid phase of the composite nitride is characterized by performing the growth of the state in the Group 13 metal nitride crystal remaining A method for producing a Group 13 metal nitride crystal according to Item. The group 13 metal nitriding according to any one of claims 1 to 12 , wherein the crystal growth is performed in a reaction vessel mainly composed of an oxide of a group 2 or group 3 element of the periodic table. Method for producing physical crystals. 14. The method for producing a Group 13 metal nitride crystal according to claim 13 , wherein the reaction vessel is mainly composed of an oxide having a standard generation energy of -930 kJ / mol or less at 1000K. The method for producing a Group 13 metal nitride crystal according to any one of claims 1 to 14 , wherein the crystal growth is performed at normal pressure. The method for producing a group 13 metal nitride crystal according to any one of claims 1 to 15 , wherein the crystal growth is performed in an argon atmosphere. The group 13 metal nitride crystal doped with the element is grown by allowing a doping element to be present in the solution or melt, according to any one of claims 1 to 16 . A method for producing a Group 13 metal nitride crystal. A solution or melt obtained by dissolving a composite nitride containing a metal element other than Group 13 metal element of Periodic Table and Group 13 element in an ionic solvent containing a molten salt as a main component .