JP2008201653A - Method for controlling crystal growth rate, compound crystal, method for producing the crystal, and method for producing semiconductor device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for industrially and inexpensively producing a good quality compound crystal by growing a compound AX crystal in a solution, obtained by dissolving a compound ABX in an ionic solvent, at low pressure of ≤10 MPa or at normal pressure. <P>SOLUTION: A complex compound ABX being a raw material is dissolved in an ionic solvent such as a metal halide at a high temperature. Then, the crystal growth rate of a compound AX is controlled by adjusting the concentration of a solute component BX in the resulting solution by removing the solute component BX not used for crystal growth by evaporation or the like. Here, the combination of A and X is restricted: (i) A is a group 13 metal element and X is a group 15 element, (ii) A is a group 12 metal element and X is a group 16 element, and (iii) A is a group 14 element and X is carbon element. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a crystal growth rate control method and a production method of a compound crystal. The present invention also relates to a compound crystal manufactured by using these methods and a method for manufacturing a semiconductor device using these methods. The present invention particularly includes a crystal growth rate control method and a production method of a nitride crystal of a Group 13 metal such as a GaN crystal.

  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 manufacturing 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. In addition, even in the method using alkali metal as a flux, 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 are still problems to be solved for industrial use. .

  The present invention has been made in order to solve such problems of the prior art, and an object of the present invention is to be able to industrially produce high-quality compound crystals even at a low pressure of 10 MPa or less or normal pressure. . Another object of the present invention is to provide a method for manufacturing a semiconductor device such as a light emitting diode, a laser diode, a high frequency device, and a power IC using the above manufacturing method.

  In view of the above problems, the present inventors have a method of growing a high-quality compound semiconductor crystal having a crystal size that is industrially applicable and can be applied to a semiconductor device by an economical method. The present invention has been completed.

That is, the object of the present invention is achieved by the following crystal growth rate control method, compound crystal and manufacturing method thereof, and semiconductor device manufacturing method.
[1] A method for controlling a crystal growth rate when a compound AX is grown in a solution in which the compound ABX is dissolved in an ionic solvent,
A crystal growth rate control method comprising controlling the crystal growth rate of a compound AX by adjusting the concentration of a solute component BX in a solution in a crystal growth field.
[B is a Group 1 metal element or a Group 2 metal element,
The A is a Group 13 metal element and the X is a Group 15 element, the A is a Group 12 metal element and the X is a Group 16 element, or the A is a Group It is a group 14 element and said X is a carbon element. ]
[2] The crystal growth rate control method according to [1], wherein the concentration of the solute component BX in the solution in the crystal growth field is lowered by removing the solute component BX from the crystal growth field.
[3] The crystal growth rate control method according to [1], wherein the concentration of the solute component BX in the solution in the crystal growth field is lowered by evaporating and removing the solute component BX from the solution.
[4] By reacting the A metal and the solute component BX in the solution, or the gas phase substance G reacting with the solute component BX and the solute component BX in the solution or the interface between the solution and the gas phase. The crystal growth rate control method according to any one of [1] to [3], wherein the concentration of the solute component BX in the solution in the crystal growth field is lowered by reacting in step (1).
[5] Any one of [2] to [4], wherein the removal amount of the solute component BX from the solution is detected, and the removal rate of the solute component BX is controlled according to the detected removal amount. The crystal growth rate control method described in 1.
[6] In any one of [1] to [5], the concentration of the solute component BX in the solution in the crystal growth field is adjusted by causing the flow of the solution in the crystal growth field. The crystal growth rate control method as described.
[7] The crystal growth rate control method according to [6], wherein the flow of the solution is generated by mechanical means.
[8] The crystal growth rate control method according to [7], wherein the flow of the solution is generated by rotating a seed.
[9] The crystal growth rate control method according to [6], wherein the flow of the solution is generated by local heating of a reaction vessel.
[10] As described in any one of [1] to [9], continuous crystal growth is performed while maintaining the distance between the crystal growth field of compound AX and the dissolved portion of compound ABX substantially constant. Crystal growth rate control method.
[11] A partition wall is provided between the region where the compound ABX is continuously dissolved and the region where the crystal growth of the compound AX is performed. The partition wall restricts the amount of solution flow between the two regions. ] The crystal growth rate control method according to any one of [10] to [10].
[12] The crystal growth rate control method according to [11], wherein the solute component BX is removed only in a region where the crystal growth of the compound AX is performed.

[13] The crystal growth rate control method according to any one of [1] to [12], including the following steps (1) to (6):
(1) Step of dissolving compound ABX in an ionic solvent (2) Step of transporting a solution containing a solute in which the compound is dissolved to a crystal growth field of compound AX,
(3) Step of crystal growth of compound AX in the crystal growth field (4) Step of transporting the solution of the crystal growth field to a field for reducing the solute component BX (5) Solute in the solution in a field for reducing the solute component BX The step of reducing the concentration of the component BX (6) The step of transporting the solution having the reduced concentration of the solute component BX for use in the step (1), (2) or (3) [14] (1) The crystal growth rate control method according to [13], wherein the solution passes through a gap between the massive, granular or powdery compound ABX.
[15] The above-mentioned solution is forced to pass through the gap between the compound ABX by heating the solution that has entered the gap between the compound ABX and the compound ABX to cause an upward flow in the solution. [14] The crystal growth rate control method according to [14].
[16] The compound crystal according to [15], wherein the transport of (2) is performed in a laminar flow channel, and the channel is expanded after the crystal growth of (3). Production method.
[17] The method for producing a compound crystal according to [15] or [16], wherein the transport direction of (2) and the crystal growth surface of the crystal growth field are substantially orthogonal.
[18] The method for producing a compound crystal according to [15] or [16], wherein the transport direction of (2) and the crystal growth surface of the crystal growth field are substantially parallel.
[19] The crystal growth rate control method according to [15] or [16], wherein the crystal growth surface is rotated.
[20] Any of [1] to [19], wherein B constituting the solute component BX is one or more elements selected from the group consisting of Group 1 metal elements and Group 2 metal elements The crystal growth rate control method according to claim 1.
[21] The crystal growth rate control method according to any one of [1] to [20], wherein the ionic solvent is one or more types of metal halides.
[22] The crystal growth rate control method according to any one of [1] to [21], wherein the removal amount of the solute component BX is controlled by adjusting the composition of the ionic solvent.
[23] The crystal growth rate control according to any one of [1] to [22], wherein a crystal doped with the element is grown by dissolving a doping element in the solution. Method.
[24] The crystal growth rate control method according to [23], wherein the solution is adjusted using a solvent containing a doping element.
[25] The crystal growth according to any one of [1] to [24], wherein the solute component BX is removed from the compound ABX and used for the crystal growth after being brought close to the stoichiometric composition of ABX. Speed control method.
[26] The crystal growth rate control method according to [25], wherein the solute component BX is removed from the compound ABX before the compound ABX is dissolved in the ionic solvent.
[27] The crystal growth of the compound AX is performed in a reaction vessel having an inner wall mainly composed of an oxide having a standard generation energy of −930 kJ / mol or less at 1000 K. [1] to [26] The crystal growth rate control method according to any one of the above.
[28] The compound ABX is prepared in a reaction vessel having an inner wall mainly composed of an oxide having a standard generation energy of −930 kJ / mol or less at 1000 K, according to [1] to [27] The crystal growth rate control method according to any one of the above.
[29] The crystal growth rate control method according to [27] or [28], wherein the inner wall of the reaction vessel contains silicon carbide as a main component.
[30] The crystal of the compound AX is a crystal having a polar face, and the grown crystal area is made larger than the substrate area by performing crystal growth on the X face of a crystal substrate having a polar face. [1] The crystal growth rate control method according to any one of [29].
[31] A method for producing a compound crystal comprising the step according to any one of [1] to [29].

[32] A compound crystal grown by the crystal growth method according to [31].
[33] A method for producing a compound crystal substrate, comprising subjecting the compound crystal of [32] to impurity removal operation and smooth polishing of the crystal surface, and then performing vapor phase growth on the crystal surface.
[34] A method for producing a semiconductor device, comprising a step of producing a compound crystal by the crystal growth method according to [31].

According to the present invention, a high-quality compound crystal can be produced at a low pressure of 10 MPa or less or normal pressure. In particular, it is possible to solve the problems of conventional multi-nuclear generation under high pressure and a decrease in nitrogen concentration in the liquid under low pressure, and to perform crystal seed growth. That is, after dissolving the composite compound as a raw material in an ionic solvent at a high temperature, by controlling the concentration of solute components that are not used for crystal growth in the crystal growth field, the crystal growth speed, quality, and crystal size Can be controlled.
Thus, according to the present invention, a refractory material (ie, Mg, Ca, Al, Ti, Y, Ce, etc.) containing a Group 2 to 3 metal element in the periodic table without undergoing a high temperature and high pressure process. A compound crystal having a size sufficient to be applied to a semiconductor device using a container of an refractory material made of an oxide, in particular, an inexpensive refractory material such as yttrium oxide, lanthanum oxide, magnesium oxide, calcium oxide, zirconia) Can be manufactured.
Furthermore, according to the method for manufacturing a semiconductor device of the present invention, a power IC, a semiconductor device capable of handling a high frequency, and the like can be widely manufactured.

Below, the manufacturing method of the group 13 metal nitride crystal | crystallization of this invention and the manufacturing method of a semiconductor device are demonstrated in detail. The description of the constituent elements described below may be made based on representative examples of embodiments of the present invention, but the present invention is not limited to such embodiments.
In the present specification, a numerical range represented by using “to” means a range including numerical values described before and after “to” as a lower limit value and an upper limit value. 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. .

[Production method and growth rate control of compound crystals]
(Combination of elements A, B, X)
In the present invention, the compound AX is crystal-grown in a solution in which the compound ABX is dissolved in an ionic solvent.
The combinations of A and X are limited. (I) A is a Group 13 metal element and X is a Group 15 element, (ii) A is a Group 12 metal element and X is a Group 16 element, or (Iii) A is a Group 14 element and X is a carbon element.

When (i) A is a Group 13 metal element and X is a Group 15 element, examples of the Group 13 metal element that A can take include Ga, Al, In, GaAl, and GaIn. Group 15 elements that X can take include N and P, and compound single crystal AX includes GaN, AlN, InN, AlGaN, InGaN, AlGaInN, AlGaInP, GaP, InP, and InGaP. Examples of the B element include Li, Na, Ca, Sr, Ba, Mg, and the like. Among them, Li, Ca, Ba, and Mg are preferable elements. Examples of the compound BX include Li ₃ N, Ca ₃ N ₂ , Ba ₃ N ₂ , Sr ₃ N ₂ , and Ca ₃ P ₂ . Examples of the solvent used for crystal growth include alkali halide molten salts such as Group 1 metal halides and Group 2 metal halides, and specific examples include mixed ionic solvents such as LiCl and LiCl-NaCl.

(Ii) When A is a Group 12 metal element and X is a Group 16 element, Group 12 metal elements that A can take include Zn and Cd, and Group 16 elements that X can take Examples of the compound single crystal AX include ZnO, ZnS, and ZnSe. Examples of the B element include Group 1 metals such as Li, Na, K, Rb, and Cs, and Group 2 metals such as Mg, Ca, Sr, and Ba. Examples of the compound BX include Li ₂ O, Na _{2. O, Li 2 S, Na 2} S , and the like. Examples of the solvent used for crystal growth include group 1 metals and carbonates of group 2 metals.

  When (iii) A is a Group 14 element and X is a carbon element, examples of the Group 14 element that A can take include Si, Ge, Sn, etc. Group 2 metal carbides may be mentioned. Examples of the solvent used for crystal growth include group 1 metals and carbonates of group 2 metals.

  Hereinafter, a case where A in (i) is a Group 13 metal element and X is a Group 15 element will be described in detail as a representative example. In particular, an embodiment in which the A metal is Ga, the B metal is Li, and the X element is N (nitrogen) may be described in detail, but the scope of the present invention is not limited to this embodiment. In addition, the following explanation regarding the specific embodiments can be applied to the embodiments included in the above (ii) and (iii) with appropriate modifications obvious to those skilled in the art.

(Reaction formula)
The reaction formula of the present invention will be described by taking as an example a case where a composite nitride of gallium and lithium (Li ₃ GaN ₂ ) is used as the raw material compound ABX. In this case, precipitation of GaN from a solution in which Li ₃ GaN ₂ is dissolved in a solvent is expressed by the following equation.

Production of GaN crystals by heating and mixing GaN powder, Ga metal, LiGa alloy and the like with a lithium compound is also described in J. Crystal Growth 247 (2003) pp. 275-278 and Patent Document 3 above. However, in Patent Document 3, the 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 becomes possible to create a uniform solution or melt with a high nitrogen concentration at a low pressure of 10 MPa or less or normal pressure, which makes it easy to manage the substance / concentration distribution in the system and grow crystals. Large crystals can be grown because the environment is stable. In other words, by changing each solute composition in the solution, it is possible to freely control the conditions for GaN crystals from dissolution to precipitation, so that a single crystal manufacturing process becomes possible for the first time.

On the other hand, in the conventional flux growth method described in Patent Document 3 and the like, a group 1 metal such as Na or Li is added as an auxiliary melting agent in order to increase the amount of nitrogen dissolved in Ga. At low pressure and 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, Li ₃ GaN ₂ is used as a raw material and LiCl is used as a solvent, so that sufficient nitrogen solubility can be obtained even at a normal pressure or a low pressure of 10 MPa or less, and GaN precipitation is controlled rather than pressure. It is possible to control by the method which is easy to do.

(Ionic solvent)
In the present invention, the compound AX is crystal-grown in a solution in which the compound ABX is dissolved in an ionic solvent. The ionic solvent used in the present invention is not particularly limited as long as it does not inhibit the crystal growth of the compound AX in the present invention. In the present invention, it is preferable to select an ionic solvent that satisfies the following conditions (A) to (D) and a solution thereof.
(A) The generated compound crystal AX is substantially insoluble, and the composite compound ABX is dissolved. Here, “substantially insoluble” means that the solubility is 0.001% by weight or less at a crystal growth temperature (for example, 760 ° C.), and “dissolving” means that the solubility is 0.01% by weight or more. means.
(B) Compound BX is dissolved.
(C) The compound crystal AX has solubility in a solution obtained by dissolving the compound BX in the solvent. Here, having solubility means that the solubility is 0.01% by weight or more.
(D) The solubility of the compound crystal AX in the solution varies depending on the solute concentration of the compound BX in the solution. Specifically, the solubility of the compound crystal AX in the solution increases when the solute concentration of the compound BX in the solution increases, and the solubility of the compound crystal AX in the solution when the solute concentration of the compound BX in the solution decreases. Is preferably lowered.

For each of the above conditions (A) to (D), the A metal is Ga, the B metal is Li, the X element is N (nitrogen), the AX crystal is GaN, the compound BX is Li ₃ N, and the complex nitrogen compound is Li _3. The case where GaN ₂ is used will be described in detail below as an example.
As for (A), since the crystal quality deteriorates if the GaN crystal has a property of being dissolved in a solvent, it is preferably substantially insoluble in the solvent. An alkali halide molten salt such as LiCl is a preferred solvent in that it does not dissolve GaN crystals. Examples of the compound having a function of dissolving a complex nitride such as Li ₃ GaN ₂ include molten salts such as Group 1 metal halides and Group 2 metal halides which are ionic melts. When Li ₃ GaN ₂ is used as the composite nitride, LiCl alone or a mixed ionic solvent such as LiCl—NaCl can be used.
Examples of the solvent satisfying (B) include ionic solvents such as Group 1 metal halides and Group 2 metal halides. In particular, an ionic solvent containing a metal element other than Group 13 of the periodic table contained in the composite nitride is used. When used, it is preferable because of its high solubility. In particular, in this case, as a solvent for the nitride Li ₃ N, it is preferable to use an ionic solvent LiCl containing Li or a mixed salt thereof.
For (C), for example, it has a function of solution and dissolving the Li ₃ N in LiCl, solution of Li ₃ N in a mixed salt of LiCl and NaCl or the like to dissolve the GaN crystal.
The (D), for example, Li ₃ N LiCl solution and dissolving the solubility of GaN crystal to mixed salt solution of LiCl, NaCl or the like by dissolving Li ₃ N, the concentration of Li ₃ N solute in solution Can be changed.

(Molten salt)
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 to the seed, but has a chemical affinity with the metal element nitride other than the Group 13 metal element in the composite nitride as a raw material. Strong ones are preferred, and those that form compounds in chemical equilibrium are more preferred. 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 a Group 1 metal and / or a Group 2 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 composed of a Group 1 metal salt such as Li, Na, K, or Cs and / or a Group 2 metal salt such as Mg, Ca, Sr, or Ba. Further molten salt, LiCl, KCl, NaCl, CsCl , CaCl 2, BaCl 2, 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.
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 or chlorine.

When Li ₃ GaN ₂ is used as the compound ABX, since Li is contained in the compound, Li is contained in the molten salt used as the ionic solvent from the affinity at the time of dissolution and the difference in density between solvent ions and solute ions. It is preferably included. LiCl is particularly preferable as the molten salt containing Li.
In the solution, 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. There is a problem that a large crystal cannot be obtained with a small amount. 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.
In actual crystal growth, a crushed powdered or massive Li ₃ GaN ₂ solid phase is placed in LiCl or a LiCl-NaCl solvent, and Li ₃ GaN ₂ is gradually added by circulating the solvent. A method of continuously dissolving is preferably employed.

It is desirable that the molten salt used has a property of dissolving Li ₃ N produced by the formula (A). If a molten salt that does not have the property of dissolving Li ₃ N is used, the reaction of formula (A) from the solution or melt results in the 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 Group 1 metal halides. By using a molten salt of a mixture of two or more Group 1 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 GaN crystal precipitation. It is also possible to control the solubility of the composite nitride in the molten salt and the amount of evaporation from a solution of a metal nitride other than the Group 13 metal nitride. Among the mixed molten salts of various Group 1 metal halides, it is desirable to use a mixed molten salt of LiCl and NaCl. 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 (for example, a mixed salt of LiCl and NaCl) can be prepared. From the viewpoint of uniformity in the system, it is desirable to heat and melt the material.

(Control of Li ₃ N concentration)
Since Li ₃ N produced according to the formula (A) is dissolved in the molten salt of Group 1 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 stops when it reaches equilibrium. 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. That is, 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 (A) by some means. As a method for controlling the Li ₃ N concentration, evaporation, decomposition reaction, reaction with other chemical species (for example, A metal such as Ga, tungsten, etc.), diffusion into a solvent other than the reaction field, and the like are also possible. The method for controlling the concentration of Li ₃ N may be performed using one of these methods or by combining several methods.

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 formula (A) 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. By adjusting the degree of evaporation of Li ₃ N, it is possible to control the growth rate, size and quality of the crystal. In order to adjust the degree of evaporation of Li ₃ N, for example, conditions such as pressure, flow rate and flow rate of atmospheric gas, evaporation time, stirring, and the proportion of other alkali halides mixed with LiCl may be adjusted as appropriate.
Further, in the method of removing the Li ₃ N solute component in the molten salt by evaporation from the solution surface, mixing NaCl with LiCl is preferable because the evaporation rate of the Li ₃ N solute component increases. At this time, 0.01 to 70 parts by weight of NaCl is preferably used relative to LiCl (100 parts by weight), more preferably 0.1 to 50 parts by weight, and further preferably 0.1 to 40 parts by weight. preferable.
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. Specifically, it is preferable to use a molten salt as a solvent in an amount of 2 to 1000 times, more preferably 5 to 100 times the amount of the compound ABX which is a raw material.

As a method of removing Li ₃ N in the molten salt by decomposition, for example, hydrogen chloride or chlorine is introduced into a reaction vessel together with a carrier gas and reacted at a gas-liquid interface or directly blown into a solution. Li ₃ N may be decomposed into LiCl, N ₂ and H ₂ (in 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 in a gas may be used. The reaction gas concentration when introducing such a reactive gas into the reaction vessel together with the carrier gas is preferably 0.01 to 50%, more preferably 0.01 to 10% of the total gas. 0.05 to 5% is more preferable. The flow rate of the carrier gas containing the reactive gas is preferably 1 to 1000 ml / min, more preferably 1 to 500 ml / min, and further preferably 10 to 100 ml / min.
Further, a compound containing an A metal such as Ga or an A metal element is placed in a solution and away from the crystal growth field, and Li ₃ N is added according to the reaction formula of the following formula (B). It can also be removed.

Li generated according to the formula (B) is removed by alloying with Ga, for example. Li can also be a raw material for the solute component Li ₃ GaN ₂ necessary for crystal growth.

In this way, in the growth of the Group 13 nitride crystal, by controlling the concentration of Li ₃ N in the system appropriately, the reaction is not stopped at the equilibrium of the formula (A), but the thick film or bulk It becomes possible to continuously grow Group 13 metal nitride crystals. That is, the compound nitride Li ₃ GaN ₂ which is a raw material of the nitride crystal is dissolved in a solvent by using the function (A), and the growth rate of the nitride GaN crystal is obtained by using the function (D). By precisely controlling, a high quality GaN single crystal can be obtained. In the reaction vessel, there are also GaN microcrystals that are self-nucleated in addition to the substrate, which may affect the solute concentration near the crystal substrate. In such a case, in order to keep the growth rate on the substrate crystal constant, it is preferable to control the speed at which Li ₃ N is removed in accordance with the situation in the crystal growth vessel. For example, in the production apparatus, the Li ₃ N removal rate can be controlled while monitoring the amount of Li ₃ N removed from the solution by some means. The quality and growth rate of the Group 13 nitride crystals obtained by the present invention depend on the reaction rate thus controlled.

(Compound ABX)
In the present invention, compound ABX is used as a raw material for crystal growth of compound AX. Each of A, B, and X constituting the compound ABX is as described above. Preferred compounds ABX include Li ₃ GaN ₂ , Ca ₃ Ga ₂ N ₄ , Ba ₃ Ga ₂ N ₄ , Mg ₃ GaN _{3 and the} like.
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 compound ABX used in the present invention may be chemically synthesized or may be obtained by a dry process such as reactive sputtering. The method usually used when synthesizing a composite nitride in which X is N is a method in which an alloy of a Group 13 metal and a metal element other than Group 13 is made and dissolved while raising the temperature in a nitrogen atmosphere. Yes, it can be easily synthesized. 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. Moreover, although it is inferior in economic efficiency, after mixing fine powder of Group 13 metal nitride crystal and nitride of elements other than Group 13 metal (for example, Li ₃ N, Ca ₃ N ₂ ), solid phase reaction at high temperature Can also be synthesized. 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. It may be an amorphous substance deviating from the stoichiometric composition generated above. Depending on the type of composite nitride, the reaction may be more likely to proceed if a slightly larger amount of the B metal component is included during synthesis. 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 the dry process, it is possible to easily produce even a nitride that is difficult to synthesize chemically.
In the present invention, two or more kinds of compounds ABX may be used.

(Synthesis of Li ₃ GaN ₂ )
Li ₃ GaN ₂ is produced by reacting GaN and Li ₃ N at about 700 ° C. (Method A), or by heat-treating a Ga—Li alloy at 600 to 800 ° C. in a nitrogen atmosphere (Method B). be able to. 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 amorphous film of Li—N and Ga—Li—N, which is formed as 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 yttrium oxide, magnesium oxide, and calcium oxide 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 .

On the other hand, there is a problem with the above synthesis method of Li ₃ GaN ₂ . That is, when the raw material is used at a composition ratio of Li ₃ N: GaN = 1.00 which is a stoichiometric ratio in Method A, or an alloy having a composition ratio of Li / Ga = 3.0 is used in Method B above, Since the Li-containing component in Li ₃ GaN ₂ is vaporized and lost, there is a problem that high-purity Li ₃ GaN ₂ cannot be synthesized. In order to solve this problem, it is necessary to use an alloy having an excess of Li ₃ N with respect to GaN or a ratio exceeding Li / Ga = 3.0. However, when Li ₃ GaN ₂ is synthesized with such a Li-excess composition ratio, there is a problem that Li ₃ N is contained as an impurity. If Li ₃ N is contained as an impurity in Li ₃ GaN ₂ , the produced GaN or seed GaN reacts with Li ₃ N to dissolve (melt back) and disappear.
In order to solve this problem, it is preferable to adopt the following method 1) or 2) in the present invention.
1) Method of removing impurities Li ₃ N in Li ₃ GaN ₂ before introducing seeds during crystal growth 2) After synthesizing Li ₃ GaN ₂ , Li ₃ N is removed before being used for crystal growth As a specific example of the technique 1), there is a technique in which excess Li ₃ N is removed or decomposed out of the system by evaporation, reaction with HCl, or the like before seeding. As a specific example of 2), there is a method in which Li ₃ GaN ₂ is synthesized and held under a high temperature vacuum such as 600 ° C. to remove excess Li ₃ N. The holding time is preferably 0.1 to 100 hours, more preferably 0.1 to 10 hours, and further preferably 0.5 to 5 hours.

If a solution is prepared in a state where Li ₃ N is present in excess of the stoichiometric composition of Li ₃ GaN _2, the GaN concentration becomes low, which is not preferable for crystal growth. Accordingly, in the present invention, Li ₃ when the N component using Li ₃ GaN ₂ containing slightly more from the stoichiometric composition, the ionic solvent (e.g. LiCl or mixed ionic solvent such as LiCl-NaCl containing Li ) And removing the excess Li ₃ N solute component from this solution to control the Li ₃ N concentration, thereby promoting the crystal growth of GaN. For the method of removing the li ₃ N, it can be appropriately selected and used the method described above.

(Additives other than BX)
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, it is preferable to use Li ₃ N, Ca ₃ N ₂ , Sr ₃ N ₂ , Ba ₃ N ₂ or the like.
Further, when doping a substance other than the Group 13 metal into the crystal, it is dissolved in a molten salt in the form of a nitride such as Mg ₃ N ₂ or Mg ₃ GaN ₃ or as a part of the solvent. For example, MgCl ₂ or the like may be added.

(seed)
In the present invention, when the compound AX is crystal-grown, 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 seeds of group 13 metal nitrides such as vapor grown GaN, InGaN, and AlGaN. In addition, metal oxides such as sapphire, silica, ZnO, and BeO, silicon-containing materials such as SiC and Si, and materials used as 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, a bulk crystal can be produced by first growing in a seed portion and then performing crystal growth in the vertical direction while also performing crystal growth in the horizontal direction.
Also, when using wurtzite GaN or the like having a polar face as a seed, epitaxial growth in molten salt on the N polar face increases the fan-shaped growth area, and produces a large area crystal from a small seed. Is preferable.
In order to prevent the meltback and efficiently grow the crystal, the seed surface roughness (Ra) is preferably 5 nm or less, more preferably 1 nm or less, and further preferably 0.5 nm or less. .

(Reaction atmosphere)
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 the reaction vessel containing a solution in which Li ₃ GaN ₂ is dissolved in a molten salt.

(Reaction temperature and pressure)
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, since the composite nitride is used by being dissolved in a molten salt, it can be used at a temperature lower than the melting point of the composite nitride.
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.

(Container material)
It is preferable that the reaction vessel and the part for crystal growth that are in contact with the solution used in the present invention are mainly composed of a thermally and chemically stable oxide. Table 1 below shows the standard production energy (Ihsan Barin: Thermochemical dada of pure substances (VCH)) of each oxide, and the more negative, the more chemically stable.

The main component here means a component occupying 90% by weight or more in the oxide component contained in the material constituting the wall surface (inner wall) in contact with the solution or melt in the reaction vessel, preferably in the reaction vessel It is a component occupying 95% by weight or more in the oxide component contained in the material constituting the wall surface that comes into contact with the solution or melt. 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.

(Specific manufacturing method)
Next, the manufacturing method of the present invention will be described more specifically with reference to the drawings. FIGS. 1-3 and 17-18 show the structural example of the manufacturing apparatus for the group 13 metal nitride crystal growth used when implementing this invention, FIG.4, FIG.5, FIG.11, FIG. 12, FIG. 15 and FIG. 16 are diagrams showing the apparatus used in the embodiment of the present 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 salt purification equipment)
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 process of growing a Group 13 metal nitride crystal according to the present invention will be specifically described. Here, a case where a composite nitride Li ₃ GaN ₂ composed of a metal element of Group 13 and a metal element other than Group 13 is used as a raw material and a molten salt containing LiCl purified by the apparatus of FIG. 6 is used as a molten salt is used. Let's take an example. The following description can also be applied when other materials are selected.

(Manufacturing with the apparatus of FIG. 1)
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. The dissolved Li ₃ GaN ₂ composite nitride is considered to dissolve while forming a complex salt with LiCl as a solvent. In this state, it reaches the surface of the GaN crystal 1, and the GaN crystal grows by the reaction of the formula (A). 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. However, in order to grow a large bulk crystal, it is preferable to place Ga metal behind the GaN crystal 1 as shown in FIG. Li ₃ N whose concentration has increased in the vicinity of the crystal growth portion becomes a GaLi alloy by reaction with Ga metal, and at the same time, GaN and Li ₃ GaN ₂ are generated in the vicinity of the GaLi alloy surface. 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. Further, if the dissolved portion of Li ₃ GaN ₂ is set to a high temperature and the crystal growth portion is set to a low temperature, there is an advantage that the crystallization speed increases.

(Manufacturing with the apparatus of FIG. 16)
FIG. 16 is a schematic diagram of a typical manufacturing apparatus used when carrying out the present invention. First, purified LiCl and NaCl salt 6 are put in a reaction vessel 14 of yttrium oxide or silicon carbide, and dissolved at 650 to 780 ° C. Li ₃ GaN ₂ composite nitride 8 prepared in advance is placed at the bottom of the reaction vessel 14 and dissolved in the molten salt 6. The heater 27 is installed under the composite nitride 8, and the Li ₃ GaN ₂ solution dissolved in LiCl as a solvent is heated to become an upward flow as indicated by an arrow. Thermal convection by heating is characterized by high efficiency of dissolving the raw material in the solution because the solution can be forced to pass through the gaps of the composite compound ABX in the form of a lump, granule or powder. Further, the upward flow generated by the heating is generally laminar and does not spread so much, and therefore the solute concentration of Li ₃ GaN ₂ increases without decreasing. Li ₃ GaN ₂ is considered to dissolve while forming a complex salt with LiCl as a solvent. In this state, it reaches the surface of the GaN crystal 1, and the GaN crystal grows by the reaction of the formula (A). ₃ the concentration of N is increased at its periphery. 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 is gently passed through the substrate 2 and the substrate holding mechanism 3. It is preferred to exercise in solution. The solution with the increased Li ₃ N concentration spreads outward from the crystal, and while the concentration of the solute itself decreases, a part of the solution moves toward the gas-liquid interface where Li ₃ N evaporates or reacts with HCl. A part of the gas flows down the wall of the reaction vessel and circulates again to a portion where Li ₃ GaN ₂ 8 which is a raw material for crystal growth is present. The upper and lower circulation flows are mixed at a portion where they intersect with each other, and the solution in which Li ₃ N is reduced at the upper portion also partially merges with the lower circulation flow. In addition, since the solution with increased Li ₃ N solute component concentration released by crystal growth creates a downward flow along the wall of the container, the GaN crystal is less likely to precipitate on the wall due to the reaction of formula (A). There is also. In order to grow a large bulk crystal, when 0.1 to 50% of NaCl is added to LiCl as a solvent, the evaporation of Li ₃ N is promoted, and the GaN crystal 1 is continuously grown. In addition, a carrier gas mixed with a very small amount of HCl is introduced into the reactor from the carrier gas inlet shown by 10 to decompose the Li ₃ N component solute on the surface of the solution. Can be freely controlled by the gas flow rate. Further, when the crystal is grown largely, the crystal rotation holding mechanism 3 is pulled upward as the crystal grows so that the distance between the crystal growth surface and the Li ₃ GaN ₂ raw material becomes substantially constant. Good.

(Manufacturing with the apparatus of FIG. 17)
The apparatus shown in FIG. 17 is almost the same as the schematic diagram of the manufacturing apparatus shown in FIG. 16, but a large number of substrates can be placed in the crystal apparatus at the same time by standing the substrates in the vertical direction, which is relatively small. It is an apparatus suitable for efficiently producing a substrate of a size. First, the purified LiCl salt 6 is put in a reaction vessel 14 of yttrium oxide or silicon carbide and dissolved at 650 to 780 ° C. Li ₃ GaN ₂ composite nitride 8 prepared in advance is placed at the bottom of the reaction vessel 14 and dissolved in the molten salt 6. The heater 27 is installed under the composite nitride 8, and the Li ₃ GaN ₂ solution dissolved in LiCl as a solvent is heated to become an upward flow as indicated by an arrow. The GaN crystal 1 is preferably moved gently in the solution through the substrate holding mechanism 3. The difference from the manufacturing apparatus shown in FIG. 16 is that, in a large container in which many crystal substrates are placed, it is difficult to create a circulation flow of the entire bath only by thermal convection. Therefore, a partition wall 29 is installed in the container. However, it is preferable to create a circulating flow by the stirring blade 28. The solution having an increased Li ₃ N concentration after crystal growth is decomposed by evaporating on the surface of the liquid surface or by reacting with HCl. The solution with the reduced Li ₃ N concentration returns to the portion of the Li ₃ GaN ₂ raw material 8 along a large circulating flow. In this case as well, in order to grow a large bulk crystal, if 0.1 to 50% of NaCl is added to LiCl as a solvent, the evaporation of Li ₃ N is promoted, and the GaN crystal 1 is continuously formed. grow up. In addition, when a carrier gas mixed with a very small amount of HCl is introduced into the reactor from the carrier gas inlet shown by 10 and the Li ₃ N component solute is decomposed on the surface of the solution, the gas flows the crystal growth rate. It can be controlled freely by the flow rate. You may arrange | position A metals, such as Ga, in a part of circulation flow of a solution.

In the reaction of the formula (A), by removing the Li ₃ N solute component, the GaN crystal grows on the seed. The crystal growth mode is film-like or mirror-like in a portion close to equilibrium. As it grows away from the equilibrium, it becomes a mode in which columnar crystals are grown rather than a smooth film, and further away from the equilibrium, GaN powder crystals are deposited on the seeds. An industrially valuable crystal is a crystal that grows in the form of a film. In order to keep this condition stable during the growth time, the removal rate of the Li ₃ N solute component is monitored or appropriately during the growth time. The removal rate is preferably controlled while sampling the solution and monitoring the Li ₃ N solute concentration.
When 0.1 to 50% of NaCl is added to LiCl, the Li ₃ N solute component tends to spontaneously evaporate over time as compared to Li ₃ N generated by the reaction of formula (A). In the formula (A), in order to control the range of the film-like crystal growth, the upper part of the crucible is obtained based on the data of the deposited Li ₃ N film thickness monitor at the upper part of the crucible over time. The lid is gradually tightened to reduce the amount of evaporation, and the solute components in the solution are controlled to be constant so that film growth is possible.
When the solvent is only LiCl, Li ₃ N generated in the reaction of the formula (A) is dissolved in the solvent without limitation, and Li ₃ N does not evaporate. The crystal growth stops. For such a system, a carrier gas mixed with a very small amount of HCl is introduced into the reactor from the carrier gas inlet indicated by 10 to crystallize the Li ₃ N component solute on the solution surface. Growth begins. The amount of gas to be introduced may be controlled while monitoring the amount of cracked gas (H ₂ or N ₂ ) generated in the cracking reaction.

(Manufacturing with the apparatus of FIG. 18)
The apparatus shown in FIG. 18 is similar to the schematic diagram of the manufacturing apparatus shown in FIG. 17, but separates the region where the Li ₃ GaN ₂ raw material 8 is melted from the crystal growth region. To increase the dissolution rate. In this case, this region is sealed so as not to be a crystal precipitation condition, and the Li ₃ N solute component is prevented from evaporating and decomposing, and the solution in which the solute is dissolved is conveyed toward the crystal growth region, Crystal growth is performed on the same principle as the manufacturing apparatus shown in FIG.

(Manufacturing with the apparatus of FIG. 2)
FIG. 2 is another vertical type crystal growth apparatus suitable for carrying out the present invention. A 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 net 9 is put on and the seed 2 attached to the tip of the substrate support rod 3 having a rotation function is placed on the bottom of the reaction vessel 14 and placed on the top, the GaN crystal is dissolved from the solution or melt in which Li ₃ GaN ₂ is dissolved. Folding occurs 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.

(Manufacturing with the apparatus of FIG. 3)
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. Thus, 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 formula (A), since dissolution and 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. According to the manufacturing method of the present invention, it is possible to manufacture a power IC, a semiconductor device capable of handling high frequencies, and the like.

The features of the present invention will be described more specifically with reference to 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.
In the examples, LiCl and NaCl used as crystal growth solvents were purified according to the above description using the apparatus shown in FIG.

(Production Example 1) Compound Nitride Synthesis Example 1
Polycrystalline gallium nitride and a lithium nitride reagent (manufactured by Mitsuwa Chemical Co., Ltd.) were mixed at a molar ratio of Li ₃ N / GaN = 1.05 using a mortar, and about 2 g of the resulting mixture was added to a Y ₂ O ₃ reaction vessel ( The composite nitride was prepared by firing in a crucible) and firing under a nitrogen flow of 60 ml / min. When firing, the temperature was raised from room temperature to 700 ° C. over 1 hour, held at 700 ° C. for 20 hours, and then the electric furnace power source was turned off and allowed to cool naturally. 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. The obtained Li ₃ GaN ₂ was used in Examples 2 to 6 below.

(Production Example 2) Compound nitride synthesis example 2
According to the same manner as in Preparation Example 1 except for changing the Li ₃ N / GaN ratio 1.07, were synthesized Li ₃ GaN ₂ held in 700 ° C. 20 hours. The obtained Li ₃ GaN ₂ was used in No. 71 of Example 7 below.

(Production Example 3) Composite nitride synthesis example 3
Li ₃ GaN ₂ was synthesized by holding at 700 ° C. for 20 hours according to Production Example 2, and then evacuated at 630 ° C. for 2 hours to remove excess Li ₃ N. It was confirmed by XRD that redness disappeared from Li ₃ GaN _{2 and} that excess Li ₃ N was removed. The obtained Li ₃ GaN ₂ was used in No. 72 of Example 7 below.

(Example 1)
In the apparatus of FIG. 2, 0.3 g of GaN powder, 5.2 g of LiCl, and Li ₃ N are added in amounts shown in Table 2, and the temperature is raised from room temperature to 760 ° C. in 1 hour in a nitrogen atmosphere. Held for hours. Table 2 shows the results of analyzing the Ga concentration in the solution after holding for 20 hours and the presence or absence of GaN crystal growth in the solution. The optical micrograph, SEM photograph, and XRD pattern of the obtained GaN crystal are shown in FIGS.

In No. 11 in which Li ₃ N was not added, GaN was not dissolved in the solution, and growth of a single crystal of GaN could not be confirmed. On the other hand, in Nos. 12 to 15 to which Li ₃ N was added, GaN was dissolved in the solution, and it was confirmed that a single crystal of GaN grew by performing crystal growth using this solution. It was. It was also found that the growth rate and size of the GaN single crystal can be controlled by adjusting the amount of Li ₃ N added.

(Example 2)
Using a device in which 0.52 g of Li ₃ GaN ₂ synthesized in Production Example 1 was added to a solvent in which 3.4 g of LiCl and 1.8 g of NaCl were mixed, and the lid was removed so that Li ₃ N could be evaporated. The temperature was raised to 760 ° C. in an N ₂ atmosphere over 1 hour. Thereafter, 390 mg of GaN seed was added at the timing shown in Table 3, and after 10 hours holding, the seed was taken out and the change was confirmed. The results are shown in Table 3. The SEM photograph of the obtained GaN crystal and the rocking curve measurement result of the (002) diffraction peak of X-ray diffraction are shown in FIGS.

In No. 21 in which the GaN seed was added to the solution before the evaporation of excess Li ₃ N was completed, meltback was observed in which the GaN seed was dissolved by excess Li ₃ N, and the seed weight was reduced. On the other hand, in No. 22 in which the GaN seed was introduced after evaporating excess Li ₃ N, no meltback was observed, and a GaN growth layer was formed on the seed surface. It has been clarified that the growth rate and size of the GaN single crystal can be controlled by adjusting the evaporation amount of Li ₃ N.

(Example 3)
In the apparatus shown in FIG. 2, 0.33 g of Li ₃ GaN ₂ synthesized in Production Example 1, 0.03 g of Li ₃ N, and LiCl and NaCl are added in amounts shown in Table 4, respectively, and room temperature is obtained in an N ₂ atmosphere. Then, the temperature was raised to 760 ° C. over 1 hour, and crystal growth was attempted at 760 ° C. for 20 hours while evaporating Li ₃ N. Table 4 shows the amount of GaN single crystals produced.

In No. 31, since Li ₃ N could not be removed from the system, formation of a GaN single crystal was not observed. On the other hand, in No. 32 and No. 33, it was possible to perform crystal growth while evaporating Li ₃ N from the system, and a GaN single crystal was formed. At this time, it became clear that the growth rate and size of the GaN single crystal can be controlled by adjusting the addition amounts of LiCl and NaCl.

Example 4
In the apparatus of FIG. 12, 0.52 g of Li ₃ GaN ₂ synthesized in Production Example 1 and 5.2 g of LiCl were added, and Ar gas containing HCl in the amount shown in Table 5 was circulated at a rate of 50 ml / min. The temperature was raised to 760 ° C. over 1 hour in a fresh atmosphere and kept at 760 ° C. for 8 hours. Table 5 shows the amount of GaN single crystal produced.

In No. 42 in which Li ₃ N in the solution was removed by containing HCl in Ar gas, a GaN single crystal was formed. It has been clarified that the growth rate and size of a single crystal of GaN can be controlled by flowing a gas reactive with Li ₃ N.

(Example 5)
16, 0.52 g of Li ₃ GaN ₂ synthesized in Production Example 1, 6.8 g of LiCl, and 3.6 g of NaCl are added, and the temperature is raised to 760 ° C. in a nitrogen atmosphere over 1 hour. The GaN crystal was grown for 8 hours. At this time, in No. 52, only the bottom portion was heated to 770 ° C. with a heater, and the other portions were set to 760 ° C., and the crystal was grown in a state where a heat distribution was formed in the crucible. Table 6 shows the amount of GaN single crystal produced.

In No. 52, by heating the bottom with a heater, an upward flow passing through the gap of Li ₃ GaN ₂ was formed in the solution by thermal convection, and as a result, more GaN single crystals were generated. It has been clarified that by causing convection, the dissolution rate of Li ₃ GaN ₂ increases, and as a result, the growth rate and size of the GaN single crystal can be controlled.

(Example 6)
In a crucible made of Y ₂ O _{3 having} an inner diameter of 25 mm, 0.52 g of Li ₃ GaN ₂ synthesized in Production Example 1, 6.8 g of LiCl, and 3.6 g of NaCl were charged. Two 5 mm square stirring blades are installed in the center of the crucible. The temperature was raised from room temperature to 760 ° C. in a nitrogen atmosphere over 1 hour and held for 20 hours to grow GaN crystals. At this time, in No. 62, after reaching 760 ° C., the stirring blade was rotated at 20 rpm, and the solution was held for 20 hours while stirring. Table 7 shows the amount of GaN single crystal produced.

In No. 62, a flow through the gap of Li ₃ GaN ₂ was formed in the solution by stirring, and as a result, more GaN single crystals were produced. It has become clear that the growth rate and size of GaN single crystals can be controlled by forming a solution flow by mechanical means.

(Example 7)
In the apparatus of FIG. 11, 0.52 g of Li ₃ GaN _{2 of the} type shown in Table 8, 6.8 g of LiCl, and 3.6 of NaCl are added, and the temperature is raised to 760 ° C. over 1 hour in a nitrogen atmosphere. As soon as the temperature reached 760 ° C., seeds were added and held for 12 hours to grow GaN crystals.

In No. 71, meltback occurred due to excess Li ₃ N, and the weight of the seed decreased. On the other hand, in No. 72 using Li ₃ GaN _{2 from} which excess Li ₃ N was removed, a GaN single crystal was formed. It has been clarified that the growth rate and size of a single crystal of GaN can be improved by crystal growth using Li ₃ GaN _{2 from} which excess Li ₃ N has been removed in advance.

  According to the present invention, a high-quality compound crystal can be produced at a low pressure of 10 MPa or less or normal pressure. For this reason, it is possible to control the crystal growth speed, quality, and crystal size while solving the problems of conventional multi-nuclear generation under high pressure and reduction of nitrogen concentration in the liquid under low pressure. In addition, according to the present invention, a compound crystal having a size sufficient for application to a semiconductor device can be produced using a relatively inexpensive container. 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 for this invention. It is a schematic explanatory drawing which shows the suitable crystal growth apparatus (the 2) used for this invention. It is a schematic explanatory drawing which shows the suitable crystal growth apparatus (the 3) used for 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. ₃ is an XRD pattern of a Li ₃ GaN ₂ crystal obtained in Production Example 1. FIG. 2 is an optical micrograph of a GaN crystal obtained in Example 1. 2 is a SEM photograph of the GaN crystal obtained in Example 1. 2 is an XRD pattern of a GaN crystal obtained in Example 1. FIG. 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 2. 4 is a measurement result of an X-ray rocking curve of a GaN crystal obtained in Example 2. It is a schematic explanatory drawing which shows the crystal growth apparatus (the 5) used in the Example. It is a schematic explanatory drawing which shows the crystal growth apparatus (the 6) used in the Example. It is a schematic explanatory drawing which shows the suitable crystal growth apparatus (the 4) used for this invention. The left figure is a front view of the apparatus, and the right figure is a left side view of the apparatus. It is a schematic explanatory drawing which shows the suitable crystal growth apparatus (the 5) used for this invention. The left figure is a front view of the apparatus, and the right figure is a left side view of the apparatus.

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 27 Heater 28 Stirring Feather 29 Bulkhead

Claims (28)

A method for controlling a crystal growth rate when a compound AX is crystal-grown in a solution in which the compound ABX is dissolved in an ionic solvent,
A crystal growth rate control method comprising controlling the crystal growth rate of a compound AX by adjusting the concentration of a solute component BX in a solution in a crystal growth field.
[B is a Group 1 metal element or a Group 2 metal element,
The A is a Group 13 metal element and the X is a Group 15 element, the A is a Group 12 metal element and the X is a Group 16 element, or the A is a Group It is a group 14 element and said X is a carbon element. ]   The crystal growth rate control method according to claim 1, wherein the concentration of the solute component BX in the solution in the crystal growth field is lowered by removing the solute component BX from the crystal growth field.   The crystal growth rate control method according to claim 1, wherein the concentration of the solute component BX in the solution in the crystal growth field is lowered by evaporating and removing the solute component BX from the solution.   The metal A and the solute component BX are reacted in the solution, or the gas phase substance G that reacts with the solute component BX and the solute component BX are reacted in the solution or at the interface between the solution and the gas phase. The crystal growth rate control method according to claim 1, wherein the concentration of the solute component BX in the solution in the crystal growth field is lowered.   The crystal growth rate according to any one of claims 1 to 4, wherein the concentration of the solute component BX in the solution in the crystal growth field is adjusted by causing the flow of the solution in the crystal growth field. Control method.   6. The crystal growth rate control method according to claim 5, wherein the flow of the solution is generated by mechanical means.   The crystal growth rate control method according to claim 6, wherein the flow of the solution is generated by rotating a seed.   The crystal growth rate control method according to claim 5, wherein the flow of the solution is generated by local heating of a reaction vessel.   The crystal growth rate control according to any one of claims 1 to 8, wherein continuous crystal growth is performed while maintaining a distance between a crystal growth field of compound AX and a dissolved portion of compound ABX substantially constant. Method.   10. A partition wall for limiting a solution flow rate between the two regions is provided between a region where the compound ABX is continuously dissolved and a region where crystal growth of the compound AX is performed. The crystal growth rate control method according to any one of the above.   The crystal growth rate control method according to claim 10, wherein the solute component BX is removed only in a region where the crystal growth of the compound AX is performed. The crystal growth rate control method according to claim 1, comprising the following steps (1) to (6).
(1) Step of dissolving compound ABX in an ionic solvent (2) Step of transporting a solution containing a solute in which the compound is dissolved to a crystal growth field of compound AX,
(3) Step of crystal growth of compound AX in the crystal growth field (4) Step of transporting the solution of the crystal growth field to a field for reducing the solute component BX (5) Solute in the solution in a field for reducing the solute component BX Step (6) of reducing the concentration of the component BX Transporting the solution having the reduced concentration of the solute component BX for use in the step (1), (2) or (3)   13. The method for producing a compound crystal according to claim 12, wherein the transport of (2) is performed in a laminar flow channel, and the channel is expanded after the crystal growth of (3).   The method for producing a compound crystal according to claim 12 or 13, wherein the transport direction (2) and the crystal growth surface of the crystal growth field are substantially orthogonal to each other.   14. The method for producing a compound crystal according to claim 12, wherein the transport direction (2) and the crystal growth surface of the crystal growth field are substantially parallel.   The B constituting the solute component BX is at least one element selected from the group consisting of a Group 1 metal element and a Group 2 metal element. Crystal growth rate control method.   The crystal growth rate control method according to any one of claims 1 to 16, wherein the ionic solvent is one kind or plural kinds of metal halides.   The crystal growth rate control method according to claim 1, wherein the removal amount of the solute component BX is controlled by adjusting the composition of the ionic solvent.   The crystal growth rate control method according to claim 1, wherein a crystal doped with the element is grown by dissolving a doping element in the solution.   The crystal growth rate control method according to claim 19, wherein the solution is adjusted using a solvent containing a doping element.   21. The crystal growth rate control method according to any one of claims 1 to 20, wherein the solute component BX is removed from the compound ABX and used for the crystal growth after being brought close to the stoichiometric composition of ABX.   The crystal growth rate control method according to claim 21, wherein the solute component BX is removed from the compound ABX before the compound ABX is dissolved in the ionic solvent.   23. The crystal growth of the compound AX is performed in a reaction vessel having an inner wall mainly composed of an oxide having a standard production energy of −930 kJ / mol or less at 1000K. The crystal growth rate control method described in 1.   The compound ABX is prepared in a reaction vessel having an inner wall mainly composed of an oxide having a standard generation energy of -930 kJ / mol or less at 1000 K, according to any one of claims 1 to 22. The crystal growth rate control method as described.   The crystal growth rate control method according to claim 23 or 24, wherein an inner wall of the reaction vessel contains silicon carbide as a main component.   A method for producing a compound crystal comprising the step according to any one of claims 1 to 25.   A compound crystal grown by the crystal growth method according to claim 26.   27. A method of manufacturing a semiconductor device, comprising a step of manufacturing a compound crystal by the crystal growth method according to claim 26.