JP2010105903A - Method for producing group 13 metal nitride crystal and method for producing semiconductor device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for stably and continuously growing a group 13 nitride crystal such as a GaN crystal. <P>SOLUTION: The molar ratio between a nitrogen element in a liquid growing a group 13 metal nitride crystal and a group 13 metal element (N/group 13 metal) is held in the range of 3.5 to 50. The addition of the nitride may be intermittently or continuously performed into the liquid growing the group 13 metal nitride crystal, however, for achieving the more stable and continuous growth of the crystal, it is preferable that the addition of the nitride is continuously performed. The addition method of the nitride is not particularly limited, and any of the nitride in a vapor phase, the nitride in a liquid phase and the nitride in a solid phase may be added to the liquid. By adding the group 13 metal nitride such as GaN, the molar ratio between the nitrogen element and the group 13 metal element in the liquid can be adjusted as well. Further, it is possible that a solid-shaped nitride feeding compound gradually feeding a nitride into the liquid may be added without adding a nitride itself. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

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

  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 a 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 element 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. I have the same problem as 4, 5, etc.

As a technique for coping with such a problem, there is a method of creating a solution or melt in which a composite metal nitride such as Li ₃ GaN ₂ is dissolved in an ionic solvent, and growing GaN crystals in the solution or melt. It has been proposed (see Patent Document 4). In this method, the equilibrium represented by the following formula (1) is biased to the right by evaporating Li ₃ N from the solution or melt, and the growth of the GaN crystal is continuously advanced. In order to actively promote the evaporation of Li ₃ N, it is recommended that the reaction be carried out in an open system under low pressure.

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

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

  However, when the present inventors examined various methods described in Patent Document 4, it became clear that there was a problem that the shape of the obtained GaN crystal was likely to vary. In particular, it has been clarified that when a relatively thick GaN crystal is grown, the growth rate gradually decreases and it is difficult to perform stable and continuous crystal growth. It has also been clarified that there is a problem that nitrogen defects are generated in the obtained crystal and the quality of the crystal is likely to be deteriorated. For this reason, the problem which should be solved for industrial utilization remains.

  Therefore, the present inventors provide a method for stably and continuously growing a Group 13 metal nitride crystal such as a GaN crystal in order to solve such a problem of the prior art. We proceeded with the study as a purpose.

  The reason why stable and continuous crystal growth is difficult with the conventional method could not be clarified easily, but as a result of various studies, the present inventors have conducted various studies and found that nitrogen in the liquid in which the crystal grows. It was the first time that the molar ratio of the element to the Group 13 metal element was important. That is, in the conventional method, since the molar ratio of the nitrogen element and the Group 13 metal element cannot be maintained at a high value, stable and continuous crystal growth is hindered, and the quality deteriorates even when the crystal grows. I found out. Based on such an analysis, the present inventors dissolve a sufficient amount of nitrogen component in the liquid for growing the crystal, and maintain the molar ratio of the nitrogen element and the group 13 metal element at a high value. Thus, the inventors have found that crystals can be grown stably and continuously, and have provided the following present invention.

[1] When a Group 13 metal nitride crystal is grown in a liquid containing a nitrogen element and a Group 13 metal element, the molar ratio of the nitrogen element and the Group 13 metal element in the liquid (N / Group 13) A method for producing a Group 13 metal nitride crystal, wherein the metal is maintained within a range of 3.5 to 50.
[2] The group 13 according to [1], wherein a molar ratio of nitrogen element to group 13 metal element (N / group 13 metal) in the liquid is maintained within a range of 5 to 20. A method for producing a metal nitride crystal.
[3] The molar ratio of the nitrogen element and the Group 13 metal element in the liquid is controlled by suppressing evaporation of at least one of nitride and N ₂ from the liquid [1] Or the manufacturing method of the group 13 metal nitride crystal as described in [2].
[4] It is characterized by suppressing evaporation of at least one of nitride or N ₂ from the liquid by crystal growth in a state where a lid having a through hole is attached to the container containing the liquid. 3] The manufacturing method of the group 13 metal nitride crystal | crystallization of 3].
[5] Any one of [1] to [4], wherein a molar ratio of a nitrogen element and a Group 13 metal element in the liquid is controlled by dissolving nitride in the liquid. A method for producing a Group 13 metal nitride crystal as described in 1).
[6] The method according to [5], wherein a solid nitride supply compound is brought into contact with the liquid, and nitride is eluted from the solid nitride supply compound into the liquid during the crystal growth. The manufacturing method of the group 13 metal nitride crystal of description.
[7] A solid nitride supply compound is placed in contact with the liquid, and nitride is eluted from the solid nitride supply compound into the liquid during the crystal growth. [6] The method for producing a Group 13 metal nitride crystal according to [6].
[8] The solid nitride supplying compound is a solid composite metal nitride containing a Group 13 metal element and a metal element element other than Group 13, and according to [7] A method for producing a group 13 metal nitride crystal.
[9] The method for producing a Group 13 metal nitride crystal according to [8], wherein the composite metal nitride is Li ₃ GaN ₂ .
[10] The method for producing a Group 13 metal nitride crystal according to any one of [7] to [9], wherein a particle size of the solid nitride is 10 μm or more.
[11] The method for producing a Group 13 metal nitride crystal as described in any one of [5] to [10], wherein the nitride dissolved in the liquid is Li ₃ N.
[12] The molar ratio (M _N / M) of the precipitation amount (M _13N ) of Group 13 metal nitride crystals in the liquid to the amount of nitride (M _N ) added to the liquid during crystal growth _The amount of the nitride added is controlled so that _13N ) is 0.1 to 100. The group 13 metal nitride crystal according to any one of [5] to [11], Production method.
[13] A molar ratio of the precipitation rate (R _13N ) of the Group 13 metal nitride crystal in the liquid to the addition rate (R _N ) of the nitride added to the liquid during the crystal growth (R The group 13 metal nitriding according to any one of [5] to [12], wherein an amount of the nitride added is controlled so that _N / _R13N ) is 0.1 to 100 Method for producing physical crystals.
[14] Any one of [1] to [13], wherein at least one of a sodium concentration in the liquid, a potassium concentration in the liquid, or a cesium concentration in the liquid is controlled. The manufacturing method of the group 13 metal nitride crystal of description.
[15] Sodium chloride, potassium chloride, cesium chloride, sodium bromide, potassium bromide, cesium bromide, sodium iodide, potassium iodide, cesium iodide, sodium fluoride, potassium fluoride, and fluoride Any one of [1] to [14], wherein the molar ratio of the nitrogen element and the group 13 metal element in the liquid is controlled by adding at least one selected from the group consisting of cesium. A method for producing a Group 13 metal nitride crystal according to Item.
[16] The method for producing a Group 13 metal nitride crystal according to any one of [1] to [15], wherein the liquid is stirred during the crystal growth.
[17] The method for producing a Group 13 metal nitride crystal according to [16], wherein the stirring is performed by rotating a seed immersed in the liquid.
[18] The method for producing a Group 13 metal nitride crystal according to any one of [1] to [17], wherein the liquid contains a molten salt.
[19] A Group 13 metal nitride crystal according to any one of [1] to [18], wherein a Group 13 metal nitride crystal having a thickness of 10 μm or more is grown on the seed surface. Method.
[20] A method for producing a semiconductor device, comprising a step of producing a Group 13 metal nitride crystal by the production method according to any one of [1] to [19].

  According to the manufacturing method of the present invention, the Group 13 metal nitride crystal can be grown stably and continuously. In particular, a thick crystal can be produced efficiently and easily as compared with the conventional method. Further, according to the method for manufacturing a semiconductor device of the present invention, it is possible to manufacture a power IC and a semiconductor device that can handle high frequencies.

1 is a schematic cross-sectional view for explaining a reaction apparatus used in Example 1. FIG.

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

[Molar ratio of nitrogen element and Group 13 metal element]
(Molar ratio range)
In the production method of the present invention, when a Group 13 metal nitride crystal is grown in a liquid containing nitrogen and a Group 13 metal, the molar ratio of the nitrogen element to the Group 13 metal element in the liquid is set to 3.5. It is characterized by being held within a range of ˜50. The molar ratio between the nitrogen element and the group 13 metal element in the liquid is the value obtained by dividing the number of moles of nitrogen atoms present in the liquid by the number of moles of group 13 metal atoms present in the liquid. It means (number of moles of N atom / number of moles of group 13 metal atom). The number of moles of nitrogen atom and group 13 metal atom here is not only the number of moles of atoms present in the liquid as atomic nitrogen or atomic group 13 metal, but also the number of nitrogen atoms or group 13 metal atoms. The number of moles of nitrogen atoms and group 13 metal atoms constituting molecules, ions, complexes and complex ions containing group metal atoms are also included.

  The molar ratio of the nitrogen element and the Group 13 metal element is preferably 4-30, more preferably 5-20, and even more preferably 7-18. When the molar ratio of the nitrogen element to the group 13 metal element is more than 50, the group 13 metal nitride crystal is re-dissolved in the solution (meltback), the crystal growth rate is slowed, and the crystal surface is roughened. The problem that it ends up is easy to occur. Moreover, when the molar ratio of the nitrogen element and the Group 13 metal element is less than 3.5, the growth rate of the Group 13 metal nitride crystal is slow and the size of the obtained crystal is reduced. Is likely to occur.

Note that the Group 13 metal that is the object of the calculation of the molar ratio is the Group 13 metal of the Group 13 metal nitride crystal to be crystal-grown. Therefore, when a GaN crystal is to be grown, the molar ratio is N / Ga, and other group 13 metal elements are not considered.
In order to maintain the molar ratio of the nitrogen element and the Group 13 metal element in the range of 3.5 to 50, various methods can be employed. A typical method will be described below. These methods are preferably employed in combination as appropriate.

(Controlling the molar ratio with the lid)
For example, the molar ratio of the nitrogen element and the Group 13 metal element can be controlled by suppressing evaporation of at least one of nitride and N ₂ from the liquid for growing the Group 13 metal nitride crystal. When growing crystals in an open system in which nitride and N ₂ freely evaporate from the liquid, since nitride and N ₂ evaporate one after another from the liquid, the nitrogen element and the group 13 metal element in the liquid The molar ratio gradually decreases. For this reason, the crystal growth rate decreases with the passage of time, and the crystal growth is eventually stopped. In order to avoid such an adverse effect caused by a decrease in the molar ratio of the nitrogen element to the group 13 metal element, a method of suppressing evaporation of at least one of nitride or N ₂ from the liquid by various means is preferably employed. can do.

Specifically, a method of covering the reaction vessel containing the liquid can be mentioned. The lid here has an action of suppressing the evaporation of nitride and N ₂ from the liquid by limiting the volume occupied by the gas phase in the reaction vessel. The lid may be provided with a through hole, and the through hole may be always open or openable. When the through-hole is always opened, the amount of nitride and N ₂ released outside the reaction vessel through the through-hole is appropriately balanced with the amount of nitride and N ₂ evaporated from the liquid to the gas phase in the reaction vessel. It is preferable to adjust the size of the hole so that it does.
The cross-sectional area through which the through hole can be vented can be, for example, 0.1 to ²⁰⁰ mm ² , preferably 1 to 50 mm ^2, and more preferably ² to 20 mm ² . When opening and closing the through hole, the through hole is closed when the molar ratio of the nitrogen element and the Group 13 metal element in the liquid decreases, and the molar ratio of the nitrogen element and the Group 13 metal element in the liquid increases. It is preferable to control so as to open a through hole. Such control can be automatically performed based on monitoring results and empirical rules of the molar ratio of the nitrogen element to the group 13 metal element in the solution. Moreover, as another aspect, it is also possible to control by changing the hole diameter of the through hole. That is, when the molar ratio between the nitrogen element and the Group 13 metal element in the liquid decreases, the hole diameter of the through hole is reduced, and when the molar ratio between the nitrogen element and the Group 13 metal element in the liquid increases, the through hole Can be controlled to widen. As yet another aspect, there is a method of controlling the number of open / closed through holes provided in the lid. That is, when the molar ratio between the nitrogen element in the liquid and the Group 13 metal element is decreased, the number of through holes to be closed is increased, and the molar ratio between the nitrogen element and the Group 13 metal element in the liquid is increased. It is possible to control to increase the number of through-holes to be opened.

(Control of molar ratio by adding nitride)
As another method for maintaining the molar ratio of the nitrogen element and the Group 13 metal element in the range of 3.5 to 50, there is also a method of adding nitride to the liquid for growing the Group 13 metal nitride crystal. It can preferably be employed. This method is preferably employed in combination with the above control of the molar ratio by the lid. Examples of the nitride herein include Li ₃ N, Ca ₃ N ₂ , Mg ₃ N ₂ , Ba ₃ N ₂ , Li ₃ GaN ₂ and GaN, and Li ₃ N is preferable.

The addition of nitride may be performed intermittently or continuously in the liquid for growing the Group 13 metal nitride crystal. In order to realize more stable and continuous crystal growth, it is preferable to continuously add nitride. The method for adding the nitride is not particularly limited, and any of vapor phase nitride, liquid phase nitride, and solid phase nitride may be added to the liquid. When adding a solid phase nitride, it is possible to use a nitride that dissolves quickly in the liquid, such as Li ₃ N, or a nitride that dissolves gradually, such as GaN. May be used in combination to adjust the nitrogen supply rate into the liquid. If a Group 13 metal nitride such as GaN is added, the molar ratio of the nitrogen element and the Group 13 metal element in the liquid can also be adjusted. Further, a solid nitride supply compound capable of gradually supplying nitride into the liquid may be added to the liquid without adding the nitride itself. Further, a liquid or a solid containing nitride may be added.

When using a solid nitride supply compound capable of gradually supplying nitride into the liquid, it is preferable that the liquid and the solid nitride supply compound are in contact with each other before starting crystal growth. . Although the aspect of contact is not particularly limited, for example, an aspect in which part or all of the solid nitride supply compound is immersed in the liquid can be exemplified. Specifically, an aspect in which a solid nitride supply compound is present below the liquid and an aspect in which the particles of the nitride supply compound are dispersed in the liquid can be exemplified. It is preferable to use a solid nitride supply compound having a certain particle size when contacting with the liquid because the nitride can be gradually released into the liquid. The particle size is preferably 10 μm to 10 cm, more preferably 20 μm to 5 cm, and even more preferably 100 μm to 1 cm. If the particle size is 10 μm or more, all of the nitride elutes from the solid nitride supply compound in a short time, or the solid nitride supply compound rises and adheres to the seed surface by convection in the liquid. There is a tendency that problems such as inhibition of crystal growth and mixing of impurities into the crystal hardly occur. In addition, it is also possible to control the amount of nitride released over time by giving the particle size a distribution or giving a shape to the device. Furthermore, it is possible to add both a solid nitride supply compound and a nitride, and particularly when the amount of the solid nitride supply compound added is small, by adding a combination of nitrides in the liquid It is easier to adjust the molar ratio of the nitrogen element and the Group 13 metal element. As such a solid nitride supply compound, a solid composite metal nitride containing a Group 13 metal element and a metal element other than Group 13 is particularly preferred. For example, Li ₃ GaN ₂ , Ca ₃ Ga ₂ Composite nitrides of alkali metals or alkaline earth metals such as N ₄ , Ba ₃ Ga ₂ N ₄ , Mg ₃ GaN ₃ , and CaGaN and Group 13 metals, and the above composite nitrides and Li ₃ N, Ca ₃ N ₂ , Ba ₃ N ₂ , Mg ₃ N ₂ , a sintered body with a nitride such as GaN, and the like, and a sintered body of Li ₃ GaN ₂ and Li ₃ N is particularly preferable. By using a sintered body having a particle size of 10 μm or more, the release rate of Li ₃ N from the sintered body into the solution is suppressed, and Li ₃ N can be gradually dissolved in the solution during crystal growth.

The composite metal 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. After mixing with a body (for example, Li ₃ N, Ca ₃ N ₂ ), it can be obtained by a method such as raising the temperature and causing a solid phase reaction. Preferred examples of 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 metal nitrides include composites of alkali metals or alkaline earth metals such as Li ₃ GaN ₂ , Ca ₃ Ga ₂ N ₄ , Ba ₃ Ga ₂ N ₄ , Mg ₃ GaN ₃ , CaGaN, and Group 13 metals. A metal nitride can be mentioned, and Li ₃ GaN ₂ is more preferable. When Li ₃ GaN ₂ is used, the content of Li ₃ N is adjusted in advance by removing impurities Li ₃ N contained in Li ₃ GaN ₂ or by adding Li ₃ N on the contrary. It is preferable. In the present invention, two or more kinds of composite metal nitrides may be used.

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

In the liquid for growing the Group 13 metal nitride crystal, as described above, a liquid or a solid containing a nitride can also be added. For example, instead of adding Li ₃ N as a nitride to the liquid as a nitride, a solid containing Li ₃ N can be added according to the following method. First, Li ₃ N is added to LiCl, and the resulting mixture is heated to a melting point or higher to prepare a mixed solution in which Li ₃ N is melted in LiCl. The mixed solution is cooled to a mixed solid, and the mixed solid is added to the liquid. When the amount of Li ₃ N to be added is small (for example, 1 mg or less), it is difficult to measure and add a weight of 1 mg or less by the method of adding Li ₃ N alone, so that accurate addition becomes difficult. However, in the method of adding the above-mentioned mixed solid containing Li ₃ N and LiCl, for example, 1 mg of Li ₃ N and 1 g of LiCl are mixed and dissolved, and the Li ₃ N concentration in the mixed solid prepared by cooling is 0. Therefore, when 0.1 mg of Li ₃ N is added to the solution, 100 mg of mixed solid may be added, and there is an advantage that precise control of the addition amount is facilitated.

When adding nitrides or nitride supply compounds, prevent oxygen or moisture from entering the reaction system and the gas phase entrained in the reaction system during the addition to prevent oxygen or moisture from entering the reaction system. It is preferable to operate as follows.
In addition, in order to determine the addition amount of nitride or nitride supply compound, the nitrogen concentration in the liquid is measured, or the molar ratio of the nitrogen element to the group 13 metal element in the liquid is analyzed. It is particularly preferable to feed back the result to the added amount. In order to analyze the molar ratio in the liquid, the molar ratio in the liquid can be calculated by a technique of sampling the liquid during crystal growth and analyzing the composition, or by an electrochemical or optical technique. In analyzing these molar ratios, it is preferable to prevent oxygen and moisture from being mixed into the reaction system.

(Control of molar ratio by Na concentration etc.)
As another method for maintaining the molar ratio of the nitrogen element and the Group 13 metal element within the range of 3.5 to 50, there is also a method of controlling the Na concentration in the liquid for growing the Group 13 metal nitride crystal. preferable. This method is also preferably employed in combination with the control of the molar ratio by the lid and the control by addition of nitride. In order to analyze the composition of the molar ratio in the liquid, any elemental analysis method can be used. For example, the ICP-AES method is preferable for the analysis of Ga concentration, and ion chromatography is used for the analysis of N and Na concentrations. The method is preferred.

  According to the study by the present inventors, the Na concentration in the liquid for growing the Group 13 metal nitride crystal decreases with the passage of time, and in conjunction with this, the moles of the nitrogen element and the Group 13 metal element in the liquid are reduced. It is clear that the ratio also tends to decrease. Therefore, it is preferable to maintain the Na concentration in advance by increasing the Na concentration in the liquid before the start of crystal growth, or by adding Na or a Na compound intermittently or continuously during the crystal growth. At this time, Na or a Na compound can be added to the solution in any of a gas phase, a liquid phase, and a solid phase. Examples of the Na compound include sodium chloride, sodium bromide, sodium iodide, sodium fluoride and the like. The concentration of Na in the liquid is preferably maintained at 0.1 to 35% by weight, more preferably maintained at 0.5 to 10% by weight, and further preferably maintained at 1.5 to 8% by weight. preferable.

  It is also possible to control the molar ratio by K concentration or Cs concentration instead of Na concentration. For example, potassium chloride, potassium bromide, potassium iodide, and potassium fluoride can be used as the K compound, and cesium chloride, cesium bromide, cesium iodide, and cesium fluoride can be used as the Cs compound. In this invention, it is preferable to adjust with Na density | concentration and K density | concentration, and it is more preferable to adjust with Na density | concentration.

(Control of the amount of nitride in the liquid)
In the present invention, by appropriately combining the above methods, the molar ratio of the nitrogen element and the Group 13 metal element in the liquid for crystal growth is maintained within the range of 3.5 to 50, but more stable and continuous. In order to achieve effective crystal growth, it is particularly preferable to minimize the variation in the amount of nitride in the liquid.

For that purpose, the molar ratio (M _N / M) of the precipitation amount (M _13N ) of the Group 13 metal nitride crystal in the liquid to the amount of nitride (M _N ) added to the liquid during the crystal growth. It is preferable to control the addition amount of the nitride so that M _13N ) is 0.1-100. The molar ratio (M _N / M _13N ) is more preferably controlled to be 1.1 to 10, and further preferably controlled to be 1.5 to 3.0. Also, the relative addition rate of the crystal growth nitride to be added to the solution in (R _N), on a molar basis of the speed ratio (R _N of the deposition rate of the Group 13 metal nitride crystal in the liquid in the (R _13N) / R _13N ) is preferably controlled so that the added amount of the nitride is 0.1-100. The speed ratio (R _N / R _13N ) is more preferably controlled to be 1.1 to 10, and further preferably controlled to be 1.5 to 3.0.

(Stirring)
Further, in order to realize more stable and continuous crystal growth, it is preferable to stir the liquid for crystal growth. By stirring, the concentration unevenness in the liquid can be eliminated and the reaction efficiency can be increased. Stirring can be performed by rotating a stirrer provided in the reaction vessel or by rotating a seed. When the seed is rotated, the rotation speed is usually 0.1 to 100 rpm, preferably 0.5 to 80 rpm, and more preferably 5 to 50 rpm. In the conventional method, the molar ratio between the nitrogen element and the Group 13 metal element in the liquid is further reduced by stirring, and the reaction efficiency is lowered. However, in the method of the present invention, it is more stable by stirring. Continuous crystal growth can be realized.

[Liquid containing nitrogen and Group 13 metal]
In the production method of the present invention, a Group 13 metal nitride crystal is grown in a liquid containing nitrogen and a Group 13 metal. The Group 13 metal contained in the liquid used here is a Group 13 metal constituting the crystal to be crystal-grown. The liquid used in the present invention is a solution or a melt, and preferably contains an ionic solvent.

(Ionic solvent)
As the ionic solvent, a solvent having the following functions (A) to (D) is preferably selected. In addition, when not using composite metal nitride, it is preferable to select what has the function of (B) and (C).
(A) A function of dissolving a composite metal nitride to create a solution.
(B) A function of dissolving the generated Group 13 metal nitride crystal.
(C) The function of promoting the precipitation of Group 13 metal nitride crystals from the liquid.
(D) A function of dissolving nitrides of metal elements other than Group 13 contained in the composite metal nitride.

In order to exhibit the function of (A), for example, an ionic solvent containing a metal element other than Group 13 contained in the composite metal nitride can be used. This is because if the ionic solvent contains ions of the same type as the ions contained in the composite metal nitride, the ion affinity is high and the composite metal nitride is easily dissolved. In this regard, for example, when Li ₃ GaN ₂ is used as the composite metal 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 exhibit the function (B), for example, when Li ₃ GaN ₂ is used as the composite metal 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 metal nitride, Li ₃ N is generated as a by-product by the reaction of the present invention, and a mixed ionic solvent of LiCl and Li ₃ N in the system In order to use the function of (B) more effectively, a mixed ion solvent containing LiCl and Li ₃ N is used in advance, and the composite metal nitride is dissolved in this. It is suitably performed.

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 metal nitride is dissolved in an ionic solvent, there are methods such as lowering the liquid temperature or adding a temperature difference to the solution or melt. As mentioned above, 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 not containing a group 13 metal element contained in the composite metal 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 metal 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.

The contents of the function (D) are as follows. When the Group 13 metal nitride is generated from the composite metal nitride, a nitride of an element other than the Group 13 metal contained in the composite metal 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 metal nitride.
In order to exert the function (D), for example, when Li ₃ GaN ₂ is used as the composite metal nitride, it is preferable to use LiCl that dissolves the by-product Li ₃ N as a solvent.

(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 on the seed, but preferably has a strong chemical affinity with a metal nitride other than the Group 13 metal element in the composite metal 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.

  Also, a mixture of a plurality of salts can be used as described above in order to control the solubility of the composite metal 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. Li ₃ N, Ca ₃ N ₂ or the like is preferably used as the metal nitride other than the Group 13 metal element.

[seed]
In the production method of the present invention, it is preferable to grow a Group 13 metal nitride crystal on the seed. The seed used may be a Group 13 metal nitride crystal or a different substrate such as sapphire, SiC, ZnO or the like. Preference is given to using a Group 13 metal nitride crystal or substrate as the seed. 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 substrates in vapor phase growth methods such as GaAs can also be used. 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.
According to the manufacturing method of the present invention, for example, a Group 13 metal nitride crystal having a thickness of 10 μm or more can be grown on a seed. Further, a Group 13 metal nitride crystal having an arbitrary thickness such as 30 μm or more, 70 μm or more, or 140 μm or more can be grown.

[Reaction vessel]
The reaction vessel used in the present invention is preferably a reaction vessel mainly composed of a thermally and chemically stable oxide. The main component here means a component that occupies 90% by weight or more of the oxide component contained in the material constituting the wall in contact with the solution or melt in the reaction vessel, preferably the solution or melt in the reaction vessel. It is a component that occupies 95% by weight or more in the oxide component contained in the material constituting the wall surface in contact with the liquid. When the reaction vessel is made of a uniform material, it is equal to a component occupying 90% by weight or more, preferably 95% by weight or more in the oxide component contained in the material constituting the entire reaction vessel. Moreover, it is preferable that an oxide here is an oxide containing periodic table 2nd-3rd group metal elements, such as Mg, Ca, Al, Ti, Y, Ce, La. More preferably, 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. are 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.

  The temperature at which the Group 13 metal nitride crystal is grown in the reaction vessel is usually 200 to 1000 ° C., preferably 400 to 850 ° C., more preferably 600 to 800 ° C. The pressure in the reaction vessel when growing 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.

[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 adjustment examples, production examples, examples and comparative examples. First, an adjustment example specifically explaining the control method of the N / Ga ratio is given, followed by a production example specifically explaining the synthesis method of the composite nitride and the sintered body, and then a method for producing a gallium nitride crystal. Specific examples and comparative examples will be given. 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 present application, the N / Ga ratio means a value obtained by dividing the number of moles of N atoms contained in the liquid by the number of moles of Ga atoms contained in the liquid.

[Control method of N / Ga ratio]
(Adjustment example 1)
A first crucible made of Y ₂ O ₃ containing 5 g of LiCl and 0.5 g of Li ₃ GaN ₂ in a quartz reaction tube, and a _second Y ₂ O ₃ made of Y ₂ O ₃ containing 1.75 g of NaCl and 3.25 g of LiCl. The crucibles were placed side by side. Each crucible was not covered, and a quartz reaction tube was covered with a reaction tube lid. Thereafter, the quartz reaction tube was placed in an electric furnace, and the inside of the reaction tube was evacuated and replaced with nitrogen. In a nitrogen stream of 100 ml / min, temperature increase by an electric furnace was started, and after reaching 745 ° C., the temperature was maintained for 138 hours. NaCl moved from the second crucible to the first crucible via the gas phase, the Na concentration in the first crucible was 0.80 wt%, and the N / Ga ratio was 4.4.

(Adjustment example 2)
The same method as in Reference Example 1 was carried out except that the holding time at 745 ° C. was changed to 235 hours. As a result, the Na concentration in the first crucible was 1.26% by weight, and the N / Ga ratio was 5.1.
The N / Ga ratio can be controlled to a desired value according to the methods of Preparation Example 1 and Preparation Example 2 described above.

[Synthesis of composite nitride and sintered body]
(Production Example 1)
In an argon box having an oxygen concentration of 10 ppm and a dew point of −70 ° C., 6.5 g of metal gallium and 2.1 g of metal lithium were placed in a Y ₂ O ₃ boat, and the boat was placed in a quartz reaction tube with a valve. The valve was closed so that the boat contents did not come into contact with oxygen and moisture, and then the quartz reaction tube was taken out of the argon box and installed in an electric furnace. The quartz reaction tube was connected to the gas line through a valve, and the temperature was raised from room temperature to 1 hour until the temperature of the boat portion reached 700 ° C. while circulating 100 Nml / min of argon through the quartz reaction tube. Hold at 1 ° C. for 1 hour. Thereafter, the flow gas was switched to 100 ml / min of nitrogen, and nitriding was performed at 700 ° C. for 10 hours. After closing the valve, the quartz reaction tube was returned to the argon box, the solid product was taken out from the boat, and pulverized to a predetermined size with a mortar. It was confirmed that the solid product obtained by XRD measurement was a composite nitride Li ₃ GaN ₂ .

(Production Example 2)
A composite nitride was synthesized in the same manner as in Production Example 1 except that 5.4 g of metal gallium was used. It was confirmed that the solid product obtained by XRD measurement was a sintered body of composite nitrides Li ₃ GaN ₂ and Li ₃ N. Further, as a result of analyzing the Ga concentration and N concentration in the sintered body by ICP-AES method and ion chromatography method, it was found that 1 mg of this sintered body contained 70 mg of Li ₃ N.

[Method of producing gallium nitride crystal]
Example 1
A GaN crystal was grown using the reaction vessel shown in FIG.
In an argon box having an oxygen concentration of 10 ppm and a dew point of −70 ° C., a Y ₂ O ₃ crucible (5) having an outer diameter of 31 mm, an inner diameter of 25 mm, and a height of 200 mm is filled with 9.7 g of LiCl and 0.3 g of NaCl. production example 1 synthesized in particle size 2mm or more _{Li 3 GaN 2 (7) (} Li did not pass through the 2mm sieve ₃ GaN _2: hereinafter the same) was placed 1.0 g Y ₂ O ₃ manufactured by lid (11 ), And the crucible (5) was placed in the quartz reaction tube (4) and the reaction tube was covered. Further, a GaN seed (6) (surface index (10-1-1)) having a length of 3 mm, a width of 15 mm, and a thickness of 300 μm is held by a Ta wire, and the other end of the wire is a tungsten seed holding rod for stirring having a diameter of 3 mm. It was attached to (8). The GaN seed (6) attached to the tip of the seed holding rod (8) is inserted into the quartz reaction tube (4) through the insertion mechanism provided in the reaction tube lid, and further provided on the crucible lid (11). It was inserted through a through-hole (10) having a diameter of 8 mm. At this time, the GaN seed was held directly under the reaction tube lid so as not to contact the mixture in the crucible. In the reaction apparatus used in Example 1, the inside and outside of the crucible are ventilated through the gap between the through hole (10) provided in the crucible lid and the seed holding rod (8). Compared to the case without it, it is greatly limited. Further, the insertion mechanism in which the seed holding rod (8) is inserted into the quartz reaction tube (4) is not breathable. The quartz reaction tube (4) was sealed by closing the valves of the gas introduction port (1) and the gas exhaust port (2) provided on the lid of the quartz reaction tube.

Place the quartz reaction tube (4) in the electric furnace (3), evacuate the quartz reaction tube (4), and then open the valves for the gas inlet (1) and the gas outlet (2). The operation of substituting with nitrogen was repeated twice. Then, the temperature increase by the electric furnace (3) was started in a nitrogen stream of 100 ml / min. One hour after the start of heating, the temperature in the crucible reached 745 ° C., and LiCl—NaCl became a molten salt. The temperature was further maintained at 745 ° C. for 90 hours, and excess Li ₃ N was removed to adjust the N / Ga ratio in the crucible. Thereafter, the temperature is lowered to 720 ° C., the GaN seed is immersed in the molten salt (9) by lowering the seed holding rod (8), and the GaN seed (6) is rotated at 20 rpm by turning the seed holding rod (8). Crystals were grown at 720 ° C. for 210 hours while rotating. After 210 hours, the seed holding rod (8) was pulled up to take out the GaN seed (6) from the molten salt (9), and the quartz reaction tube (4) was cooled to room temperature. After cooling, the crucible (5) was taken out in an argon box, and a part of the solidified molten salt was sampled for analysis to confirm that the N / Ga ratio was 11. The molten salt at the time when the GaN seed was immersed in the molten salt and crystal growth was started was sampled, and the molar ratio in the salt was compositionally analyzed. The N / Ga ratio was 9.2. After the remaining crucible contents and sheet were removed by dissolving the salt with water, the seed and the GaN single crystal (spontaneous nucleation GaN crystal) precipitated in the salt were taken out.

  As a result of measuring the seed thickness with a film thickness meter, it was confirmed that the seed thickness increased by 140 μm because GaN grew on the seed. The GaN grown on the seed was colorless and transparent. The ratio of the increase in the weight of the spontaneous nucleation GaN crystal and the seed weight was 3: 1.

(Example 2)
The same method as in Example 1 was performed except that the GaN seed was not rotated. As a result of sampling in the same manner as in Example 1, the N / Ga ratio in the molten salt at the start of crystal growth was 10, and the N / Ga ratio in the molten salt after crystal growth at 720 ° C. for 60 hours was 12. Yes, the N / Ga ratio in the molten salt after crystal growth at 720 ° C. for 200 hours was 9.0. Moreover, when the seed thickness after crystal growth at 720 ° C. for 200 hours was measured with a film thickness meter, the film thickness increased by 70 μm. The GaN grown on the seed was colorless and transparent.

(Example 3)
The same method as in Example 1 was carried out except that the amount of Li ₃ GaN ₂ placed in the crucible was changed to 0.25 g and 21 mg of Li ₃ N was also added. As a result of sampling in the same manner as in Example 1, the N / Ga ratio in the molten salt at the start of crystal growth was 10. The N / Ga ratio in the molten salt after crystal growth at 720 ° C. for 210 hours was 9. 3. Further, as a result of measuring the seed thickness with a film thickness meter, the seed thickness increased by 16 μm. The GaN grown on the seed was colorless and transparent.

Example 4
The same method as in Example 1 was performed except that the amount of Li ₃ GaN ₂ placed in the crucible was changed to 0.5 g. As a result of sampling in the same manner as in Example 1, the N / Ga ratio in the molten salt at the start of crystal growth was 9.1, and the N / Ga ratio in the salt after crystal growth at 720 ° C. for 200 hours was 13 Met. Moreover, when the seed thickness after crystal growth at 720 ° C. for 200 hours was measured with a film thickness meter, the film thickness increased by 30 μm. The GaN grown on the seed was colorless and transparent.

(Example 5)
Using 1 g of Li ₃ GaN ₂ —Li ₃ N sintered body synthesized by the method shown in Production Example 2, the surface index of the GaN seed was set to (10−10), and excess Li ₃ N was removed to remove the excess Li ₃ N. The same method as in Example 2 except that the holding time for adjusting the N / Ga ratio was 70 hours, the GaN seed was immersed in the molten salt while maintaining the temperature at 745 ° C., and was grown at 745 ° C. for 130 hours. It carried out in. As a result of sampling in the same manner as in Example 1, the N / Ga ratio in the molten salt at the start of crystal growth was 46. Since Li ₃ N was gradually released from the sintered body into the solution, the crystal was grown for 50 hours. The N / Ga ratio in the later solution was as high as 17. Further, when the seed thickness after crystal growth for 130 hours was measured with a film thickness meter, the film thickness increased by 70 μm.

(Example 6)
The surface index of the GaN seed is (10-10), the holding time for adjusting the N / Ga ratio in the crucible by removing excess Li ₃ N is 50 hours, and the GaN seed is immersed in the molten salt. This was carried out in the same manner as in Example 4 except that the crystal was grown for 100 hours. The N / Ga ratio in the salt after crystal growth at 720 ° C. for 100 hours was 6.0, and the seed thickness after crystal growth at 720 ° C. for 100 hours was measured with a film thickness meter. Increased by 33 μm.

(Example 7)
The surface index of the GaN seed was set to (10-10), and the same method as in Example 1 was used except that 1 mg of Li ₃ N was added every 8 hours after the GaN seed was immersed in the molten salt and the crystal was grown for 195 hours. Carried out. The N / Ga ratio in the salt after crystal growth at 745 ° C. for 195 hours was 14.0, and the seed thickness after crystal growth at 745 ° C. for 195 hours was measured with a film thickness meter. Increased by 35 μm. In addition to the GaN seed with an increased film thickness, spontaneous nucleation crystals were formed in the solution, and the total weight of GaN produced in this example was 45 mg. Since the total amount of Li ₃ N added is 24 mg, and the amount of Li ₃ N dissolved in the solution from Li ₃ GaN ₂ with the formation of GaN is 19 mg, M _N / M _13N and R _N / R _13N are 2.3.

(Comparative Example 1)
The same method as in Example 1 was performed except that a Y ₂ O ₃ lid for crucible was not used. As a result of sampling in the same manner as in Example 1, the N / Ga ratio in the molten salt at the start of crystal growth was 7.0, and the N / Ga ratio in the molten salt after crystal growth at 720 ° C. for 210 hours was 2.7. Moreover, as a result of measuring the seed thickness with a film thickness meter, no increase in the seed thickness was observed.

(Comparative Example 2)
The same method as in Example 3 was performed except that Li ₃ N was not added. The N concentration and the Ga concentration in the molten salt after holding the GaN seed at 720 ° C. for 210 hours were below the measurement limit, and the N / Ga ratio could not be obtained. Moreover, as a result of measuring the seed thickness with a film thickness meter, no increase in the seed thickness was observed.

(Comparative Example 3)
Li ₃ GaN ₂ synthesized in Production Example 1 was pulverized to obtain particles that passed through a 10 μm sieve. The same method as in Example 1 was performed except that Li ₃ GaN ₂ having a particle size of less than 10 μm was used. As a result of sampling in the same manner as in Example 1, the N / Ga ratio in the molten salt at the start of crystal growth was 7.1, and the N / Ga ratio in the molten salt after holding the GaN seed at 720 ° C. for 210 hours. Was 2.5. Moreover, as a result of measuring the seed thickness with a film thickness meter, no increase in the seed thickness was observed.

(Comparative Example 4)
The same method as in Example 1 except that Li ₃ GaN ₂ with a particle size of less than 10 μm was used, a Y ₂ O ₃ lid for crucible was not used, and the GaN seed was not rotated. Carried out. As a result of sampling in the same manner as in Example 1, the N / Ga ratio in the molten salt at the start of crystal growth was 7.8, and the N / Ga ratio in the molten salt after crystal growth at 720 ° C. for 20 hours was 3.4. Further, when the seed thickness after crystal growth at 720 ° C. for 20 hours was measured with a film thickness meter, the film thickness increased only by 2 μm. Furthermore, even if kept at 720 ° C. for a long time, almost no crystal growth was observed.

(Comparative Example 5)
10 g of LiCl and ₃₀ mg of Li ₃ N are charged into the crucible, and the GaN seed is also charged before the temperature rises (this corresponds to zero time for adjusting the N / Ga ratio in the crucible by removing Li ₃ N). And the same method as in Example 2 except that the crystal growth time was changed. When a part of the molten salt was sampled for analysis immediately after reaching 745 ° C. (30 minutes later), the N / Ga ratio in the molten salt was 52.2. When the GaN seed was taken out of the solution after 2 hours and observed for change, the GaN seed was immersed in the molten salt with a high N / Ga ratio of 52.2, so the surface melted back and no growth was seen. The weight was also reduced by 5%.

In addition to the comparative example described above, even when the lid is completely covered so as not to evaporate Li ₃ N from the reaction mixture, the crystal growth of GaN as described in Comparative Example 2 of JP-A-2007-84422 Is not allowed at all.

  As is clear from the above results, in Examples 1 to 7 where the GaN crystal was grown in a state where the N / Ga ratio in the molten salt was maintained between 3.5 and 50, the film thickness of the GaN seed was greatly increased. It was confirmed that the GaN crystal was efficiently grown. On the other hand, the GaN seed is held in the molten salt whose N / Ga ratio is out of the range of 3.5 to 50, or the N / Ga ratio is lowered during the crystal growth and is in the range of 3.5 to 50. When the GaN seed was held in the molten salt in an environment that would be outside, GaN crystal growth was not observed or even if crystal growth was observed (Comparative Examples 1 to 5) . From the above, it was confirmed that the GaN crystal can be efficiently grown by growing the GaN crystal in a state where the N / Ga ratio in the molten salt is maintained between 3.5 and 50 according to the present invention.

  According to the production method of the present invention, a Group 13 metal nitride crystal can be produced stably and continuously. In addition, the crystals obtained have a uniform shape and are less susceptible to unevenness due to conditions. In addition, according to the present invention, since a compound crystal having a size sufficient for application to a semiconductor device can be produced using a relatively inexpensive container, the industrial applicability is high.

DESCRIPTION OF SYMBOLS 1 Gas introduction port 2 Gas exhaust port 3 Electric furnace 4 Quartz reaction tube 5 Crucible 6 Seed 7 Nitride supply compound 8 Seed holding rod 9 Solvent (molten salt)
10 Through-hole 11 Crucible lid

Claims (20)

  When a Group 13 metal nitride crystal is grown in a liquid containing a nitrogen element and a Group 13 metal element, the molar ratio (N / Group 13 metal) of the nitrogen element and the Group 13 metal element in the liquid is determined. A method for producing a Group 13 metal nitride crystal, characterized by being held within a range of 3.5 to 50.   2. The Group 13 metal nitride according to claim 1, wherein a molar ratio (N / Group 13 metal) of a nitrogen element and a Group 13 metal element in the liquid is maintained within a range of 5 to 20. 3. Crystal production method. _3. The molar ratio of nitrogen element and group 13 metal element in the liquid is controlled by suppressing evaporation of at least one of nitride and N ₂ from the liquid. The manufacturing method of the group 13 metal nitride crystal of description. 4. The method according to claim 3, wherein crystal growth is performed in a state where a lid having a through-hole is attached to the container in which the liquid is placed, thereby suppressing evaporation of at least one of nitride and N ₂ from the liquid. The manufacturing method of the group 13 metal nitride crystal of description.   The thirteenth aspect according to any one of claims 1 to 4, wherein a molar ratio of a nitrogen element and a group 13 metal element in the liquid is controlled by dissolving nitride in the liquid. Group metal nitride crystal manufacturing method.   6. The method for producing a Group 13 metal nitride crystal according to claim 5, wherein the nitride is continuously dissolved in the liquid during the growth of the Group 13 metal nitride crystal.   7. The method according to claim 6, wherein a solid nitride supply compound is brought into contact with the liquid to elute nitride from the solid nitride supply compound into the liquid during the crystal growth. A method for producing a group 13 metal nitride crystal.   8. The Group 13 metal nitride according to claim 7, wherein the solid nitride supply compound is a solid composite metal nitride containing a Group 13 metal element and a metal element other than the Group 13 metal element. Method for producing physical crystals. The method for producing a Group 13 metal nitride crystal according to claim 8, wherein the composite metal nitride is Li ₃ GaN ₂ .   The method for producing a Group 13 metal nitride crystal according to any one of claims 7 to 9, wherein the particle size of the solid nitride supply compound is 10 µm or more. Process for producing a Group 13 metal nitride crystal according to any one of claims 5-10, wherein the nitride is dissolved in said solution is a Li ₃ N. The molar ratio (M _N / M _13N ) of the precipitation amount (M _13N ) of the group 13 metal nitride crystal in the liquid to the amount of nitride (M _N ) added to the liquid during the crystal growth is The method for producing a Group 13 metal nitride crystal according to any one of Claims 5 to 11, wherein the amount of the nitride added is controlled to be 0.1 to 100. A molar ratio (R _N / R) of the precipitation rate (R _13N ) of the Group 13 metal nitride crystal in the liquid to the addition rate (R _N ) of the nitride added to the liquid during the crystal growth. _The method for producing a Group 13 metal nitride crystal according to any one of claims 5 to 12, wherein the amount of the nitride added is controlled so that _13N ) is 0.1 to 100. .   The group 13 according to any one of claims 1 to 13, wherein at least one of a sodium concentration in the liquid, a potassium concentration in the liquid, or a cesium concentration in the liquid is controlled. A method for producing a metal nitride crystal.   The liquid comprises sodium chloride, potassium chloride, cesium chloride, sodium bromide, potassium bromide, cesium bromide, sodium iodide, potassium iodide, cesium iodide, sodium fluoride, potassium fluoride, and cesium fluoride. The molar ratio of the nitrogen element and the group 13 metal element in the liquid is controlled by adding at least one selected from the group, The first aspect according to any one of claims 1 to 14, A method for producing a group 13 metal nitride crystal.   The method for producing a Group 13 metal nitride crystal according to any one of claims 1 to 15, wherein the liquid is stirred during the crystal growth.   The method for producing a Group 13 metal nitride crystal according to claim 16, wherein the stirring is performed by rotating a seed immersed in the liquid.   The method for producing a Group 13 metal nitride crystal according to any one of claims 1 to 17, wherein the liquid contains a molten salt.   19. The method for producing a Group 13 metal nitride crystal according to claim 1, wherein a Group 13 metal nitride crystal having a thickness of 10 [mu] m or more is grown on the seed surface.   A method for manufacturing a semiconductor device, comprising a step of manufacturing a Group 13 metal nitride crystal by the manufacturing method according to claim 1.

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