JP2014118323A - Production method of nitride semiconductor crystal of group 13 metal in periodic table, and nitride semiconductor crystal of group 13 metal in periodic table - Google Patents

Abstract

There is provided a method capable of reducing a stacking fault generated in a crystal and efficiently producing a high-quality group 13 metal nitride semiconductor crystal having a nonpolar plane or a semipolar plane as a main surface. This is the issue.
A periodic table group 13 metal nitride semiconductor base substrate obtained by crystal growth in the presence of a solvent in a supercritical state and / or a subcritical state is used. By producing a Group 13 metal nitride semiconductor crystal, a high-quality periodic table Group 13 metal nitride semiconductor crystal having a nonpolar or semipolar surface as a main surface with very few stacking faults is efficiently produced. be able to.
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Description

  The present invention relates to a method for producing a periodic table group 13 metal nitride semiconductor crystal and a periodic table group 13 metal nitride semiconductor crystal.

  Periodic table group 13 metal nitride semiconductors typified by gallium nitride (GaN) have a large band gap, and the transition between bands is a direct transition type. It is put to practical use as a light emitting element on the relatively short wavelength side. These elements are preferably manufactured using a high-quality semiconductor substrate (free-standing substrate) made of the same material and having few dislocations and defects, and a periodic table group 13 metal nitride that can be a semiconductor substrate of this type. Research on manufacturing techniques for semiconductor crystals has been actively conducted. As a typical production method, a production method using a vapor phase growth method such as a hydride vapor phase growth method (HVPE method) or a metal organic chemical vapor deposition method (MOCVD method) is generally known. A method of manufacturing a semiconductor substrate using a so-called ammonothermal method using a contained solution has also been proposed (see Patent Document 1).

With respect to the periodic table group 13 metal nitride semiconductor substrate, a semiconductor substrate having a nonpolar surface or a semipolar surface as a main surface is required from the viewpoint of suppressing the influence of the piezoelectric field, for example, a (0001) surface or the like. A periodic table group 13 metal nitride semiconductor base substrate having a polar surface of the main surface as a main surface is grown on the main surface, and the obtained crystal is polished so that a nonpolar surface or a semipolar surface appears. It can be manufactured by cutting. However, it is difficult to efficiently manufacture a large-diameter semiconductor substrate having a nonpolar surface or a semipolar surface as a main surface by a method using a base substrate having a polar surface as a main surface. Therefore, recently, a manufacturing method in which a periodic table group 13 metal nitride semiconductor base substrate having a nonpolar plane or a semipolar plane as a main surface and crystal growth on such a main surface has attracted attention.
On the other hand, when a group 13 metal nitride semiconductor base substrate of the periodic table produced by, for example, HVPE method is used and crystal is grown on its nonpolar or semipolar surface, a large number of stacking faults are generated in the growth layer. In order to realize a high-quality periodic table group 13 metal nitride semiconductor substrate, a technique for reducing stacking faults is necessary.
As a method for reducing stacking faults, for example, a growth method has been proposed in which the difference between the impurity concentration of the GaN seed crystal substrate to be used and the impurity concentration of the GaN crystal layer to be formed is 3 × 10 ¹⁸ cm ⁻³ or less ( Patent Document 2). The effect of impurity concentration on stacking faults has not been fully clarified, but if the difference in impurity concentration between the GaN seed crystal substrate and the GaN crystal layer becomes too large, the lattice constant of the formed GaN crystal layer will change. In order to relieve the stress caused by the difference in lattice constant, the principle of stacking faults has been reported.

JP-T-2006-509710 JP 2012-066983 A

An attempt was made to obtain a periodic table group 13 metal nitride semiconductor crystal by growing a crystal on a nonpolar plane or a semipolar plane using a periodic table group 13 metal nitride semiconductor base substrate fabricated by HVPE or the like. Then, a large number of stacking faults occur in the crystal.
The present invention provides a method for efficiently producing a high-quality group 13 metal nitride semiconductor crystal having a nonpolar plane or a semipolar plane as a main surface while reducing stacking faults occurring in the crystal. The task is to do.

  As a result of intensive studies to solve the above-mentioned problems, the present inventors have conducted periodic group 13 metal nitride semiconductors obtained by crystal growth in the presence of a solvent in a supercritical state and / or a subcritical state. By using a base substrate and growing a crystal on such a main surface to produce a Group 13 metal nitride semiconductor crystal of the periodic table, the main surface has a nonpolar or semipolar surface with very few stacking faults. The inventors have found that a periodic group 13 metal nitride semiconductor crystal can be efficiently produced, and have completed the present invention.

That is, the present invention is as follows.
(1) Periodic table No. 13 including a growth step of growing a periodic table Group 13 metal nitride semiconductor crystal on a periodic table Group 13 metal nitride semiconductor base substrate having a nonpolar plane or semipolar plane as a main surface A method for producing a Group metal nitride semiconductor crystal, wherein the base substrate is a Group 13 metal nitride semiconductor crystal obtained by crystal growth in the presence of a solvent in a supercritical state and / or a subcritical state. The manufacturing method of the periodic table group 13 metal nitride semiconductor crystal characterized by the above-mentioned.
(2) The method for producing a periodic table group 13 metal nitride semiconductor crystal according to (1), wherein the base substrate is a crystal satisfying at least one of the following conditions (a) to (d).
(A) The hydrogen concentration is 1.0 × 10 ¹⁷ atoms · cm ⁻³ or more.
(B) Oxygen concentration is 1.0 * 10 < ¹⁷ > -1.0 * 10 < ²⁰ > atoms * cm < ^-3 >.
(C) Alkali metal concentration is 1.0 × 10 ¹⁷ atoms · cm ⁻³ or less.
(D) Carrier concentration is 1.0 * 10 < ¹⁷ > -1.0 * 10 < ¹⁹ > cm < ^-3 >.
(3) The method for producing a periodic table group 13 metal nitride semiconductor crystal according to (1) or (2), wherein the base substrate is a crystal having an infrared absorption peak at 3100 to 3200 cm ⁻¹ .
(4) The periodic table group 13 metal nitride semiconductor crystal according to any one of (1) to (3), wherein the base substrate is a crystal having a light absorption coefficient of ¹ to 30 cm ^{−1 at} a wavelength of 405 nm. Production method.
(5) The periodic table group 13 metal nitride semiconductor according to any one of (1) to (4), wherein the base substrate is a crystal having a light absorption coefficient of 0.5 to 5 cm ^{−1 at} a wavelength of 445 nm. Crystal production method.
(6) The periodic table group 13 metal according to any one of (1) to (5), wherein the base substrate is a crystal having a basal plane dislocation density of 1.0 × 10 ⁵ cm ⁻² or less on the main surface. A method for producing a nitride semiconductor crystal.
(7) The manufacturing method of the periodic table group 13 metal nitride semiconductor crystal according to any one of (1) to (6), wherein the base substrate is a crystal having a stacking fault density of 10 cm ⁻¹ or less.
(8) The periodic table group 13 metal nitride according to any one of (1) to (7), wherein the growth step is a step of growing a periodic table group 13 metal nitride semiconductor crystal by a vapor phase growth method. Of manufacturing a semiconductor crystal.
(9) A periodic table group 13 metal nitride semiconductor crystal produced by the method for producing a periodic table group 13 metal nitride semiconductor crystal according to any one of (1) to (8).

  ADVANTAGE OF THE INVENTION According to this invention, the periodic table group 13 metal nitride semiconductor crystal which makes a main surface a nonpolar surface or semipolar surface with very few stacking faults can be manufactured efficiently.

It is a conceptual diagram of the example of an apparatus used in order to produce the base substrate which concerns on this invention. It is a conceptual diagram of the example of an apparatus used for HVPE method. It is a conceptual diagram showing the temperature change of the growth process which concerns on this invention with time.

In explaining the details of the production method of the Group 13 metal nitride semiconductor crystal of the periodic table of the present invention, embodiments and specific examples in the gallium nitride crystal will be described, but the following contents are included unless departing from the gist of the present invention. However, the present invention is not limited to this, and can be implemented with appropriate modifications.
In the present specification, the “C plane” means a plane equivalent to the {0001} plane in a hexagonal crystal structure (wurtzite crystal structure). In the periodic table group 13 metal nitride semiconductor crystal, the C plane is a polar plane, and the + C plane corresponds to the periodic table group 13 metal plane, and in the case of gallium nitride, the Ga plane.
In the present specification, the “M plane” is a plane comprehensively represented as a {1-100} plane, specifically, a (1-100) plane, a (01-10) plane, (−1010). A plane, a (−1100) plane, a (0-110) plane, and a (10-10) plane. Such a surface is a nonpolar surface.
In the present specification, the “A plane” is a plane comprehensively represented as a {2-1-10} plane, specifically, a (2-1-10) plane and a (-12-10) plane. , (-1-120) plane, (-2110) plane, (1-210) plane, and (11-20) plane. Such a surface is a nonpolar surface.
In the present specification, the “semipolar plane” is not particularly limited as long as both the periodic table group 13 metal element and the nitrogen element exist in the crystal plane, and the abundance ratio is not 1: 1. For example, {20-21} plane, {10-11} plane, {10-12} plane, {11-21} plane, {11-22} plane, {11-23} plane, {11-24} plane, etc. Is given.
In this specification, the notation <...> Represents a collective expression of directions, and the notation [...] Represents an individual expression of directions. On the other hand, the notation {...} Represents the collective representation of the surface, and the notation (...) Represents the individual representation of the surface.
In this specification, when referring to the C, M, A, and specific index planes, a range having an off angle within 20 ° from each crystal axis measured with an accuracy within ± 0.01 °. Including the inner face. The off angle is preferably within 15 °, more preferably within 10 °.
Furthermore, the numerical range expressed using “to” in the present specification means a range including numerical values described before and after “to” as a lower limit value and an upper limit value.

1. Method for Producing Periodic Table Group 13 Metal Nitride Semiconductor Crystal The method for producing Periodic Table Group 13 metal nitride semiconductor crystal of the present invention (hereinafter sometimes abbreviated as “production method of the present invention”) is nonpolar. It is a manufacturing method including a growth step of growing a periodic table group 13 metal nitride semiconductor crystal on a periodic table group 13 metal nitride semiconductor base substrate having a plane or semipolar plane as a main surface. Then, a periodic table group 13 metal nitride obtained by crystal growth of a base substrate (hereinafter sometimes abbreviated as “the base substrate according to the present invention”) in the presence of a solvent in a supercritical state and / or a subcritical state. It is a feature semiconductor crystal.
As described above, in the method of growing a crystal on a nonpolar plane or a semipolar plane using a periodic table group 13 metal nitride semiconductor base substrate produced by the HVPE method or the like, a large number of growth layers are formed on the formed growth layer. There is a problem that stacking faults occur. According to a study by the present inventors, the strain remaining in the base substrate contributes to the stress generated in the growth layer, and a stacking fault occurs in the growth layer due to the action of relieving the stress. It is thought that it will end up. Therefore, it is considered that stacking faults generated in the growth layer can be reduced by using a base substrate having a small residual strain. Then, the present inventors use a so-called ammonothermal method in which crystals are grown in the presence of a solvent in a supercritical state and / or a subcritical state, whereby a periodic table group 13 metal nitride semiconductor crystal having a small residual strain is obtained. It was also found that by using such a crystal as a base substrate, a periodic table group 13 metal nitride semiconductor crystal with extremely few stacking faults can be produced.
Since the ammonothermal method is a crystal growth under a state close to equilibrium due to dissolution and precipitation of raw materials, it is a low-distortion and high-quality periodic table as compared with the HVPE method in which a crystal is grown by a chemical reaction.
It is considered that a Group 3 metal nitride semiconductor crystal is obtained. The residual strain in the crystal can be grasped by the dislocation density and the expansion / contraction of the lattice spacing. For example, the inventors confirmed that the residual strain in the crystal increases as the expansion / contraction of the lattice spacing increases. ing. A crystal having a nonpolar plane or a semipolar plane as a principal plane obtained by the ammonothermal method also has expansion / contraction (Δd / d _ave ) for the lattice spacing in the a-axis direction and / or c-axis direction. | 5.0 × 10 ⁻⁶ | or less, which is smaller by an order of magnitude than crystals obtained by the HVPE method (Δd / d _ave = | 1.0 to 5.0 × 10 ⁻⁵ |). The inventors have confirmed (in terms of dislocation density, the number of crystals obtained by the ammonothermal method is 5 × 10 ⁴ pieces / cm ² or less, whereas the number of crystals obtained by the HVPE method is 1 × 10 6. ⁶ to 10 × 10 ⁶ / cm ² ). That is, the ammonothermal method can obtain a high-quality periodic table group 13 metal nitride semiconductor crystal with lower distortion than the HVPE method or the like.
In the present invention, the “main surface” means the widest surface among the surfaces existing on the crystal such as the base substrate and the formed growth layer, and means the surface on which crystal growth should proceed.
In addition, the “supercritical state” solvent means that the solvent is in a supercritical fluid state under a condition where the solvent exceeds a critical point (critical temperature and / or critical pressure). A supercritical fluid generally has a low viscosity, excellent diffusibility, and has a solvating power similar to that of a liquid.
Further, the “subcritical solvent” means that the solvent is in a liquid state having a density substantially equal to the critical density under conditions near the critical temperature.
The base substrate according to the present invention is “a periodic table group 13 metal nitride semiconductor crystal obtained by crystal growth in the presence of a solvent in a supercritical state and / or a subcritical state”. And / or a crystal growth apparatus capable of setting a critical pressure, and means a crystal obtained by crystal growth under a condition that a solvent is in a supercritical state and / or a subcritical state.
In addition, “a periodic table group 13 metal nitride semiconductor crystal obtained by crystal growth in the presence of a solvent in a supercritical state and / or a subcritical state” is an underlayer that exhibits an excellent effect other than the reduction of stacking faults. The inventors of the present invention have made it clear that it becomes a substrate. For example, when a gallium nitride crystal is grown with a polar surface as the main surface, facet growth is generally performed using a template substrate having a line or dot pattern asperity or mask as a base substrate. In this case, crystallinity unevenness corresponding to the pattern occurs, and it is difficult to obtain a uniform and high-quality crystal. However, by using “group 13 metal nitride semiconductor crystal of the periodic table obtained by crystal growth in the presence of a solvent in a supercritical state and / or a subcritical state” as a base substrate, a uniform and high quality crystal is obtained. We have made it clear that this is possible. That is, “a periodic table group 13 metal nitride semiconductor including a growth step of growing a periodic table group 13 metal nitride semiconductor crystal on a periodic table group 13 metal nitride semiconductor base substrate whose main surface is a polar surface” A method for producing a crystal, wherein the base substrate is a periodic table group 13 metal nitride semiconductor crystal obtained by crystal growth in the presence of a solvent in a supercritical state and / or a subcritical state. It can be said that the “manufacturing method of Group 13 metal nitride semiconductor crystal of the periodic table” is an effective manufacturing method for the problem of obtaining a high-quality crystal without unevenness in crystallinity.

1-1. Base substrate 1-1-1. Characteristics of Underlying Substrate As long as the underlying substrate according to the present invention is a periodic table group 13 metal nitride semiconductor crystal, the specific type is not particularly limited, and one type of periodic table group 13 metal such as GaN, AlN, InN, etc. May be a mixed crystal containing two or more Group 13 metals of the periodic table such as GaInN and AlGaN as constituent elements. However, it is preferable to select the base substrate so that the base substrate and the growth layer satisfy the lattice mismatch condition expressed by the following formula. The degree of lattice mismatch means a theoretical value calculated from the lattice constant of a complete crystal.
2 | a ₁ −a ₂ | / [a ₁ + a ₂ ] ≦ 1 × 10 ⁻³
(Wherein a ₁ is the lattice constant of the underlying substrate and the lattice constant of the crystal axis perpendicular to the growth direction of the growth layer, and a ₂ is the lattice constant of the growth layer and the crystal axis of the growth axis perpendicular to the growth direction) Represents the lattice constant.)
The degree of lattice mismatch between the base substrate and the growth layer is more preferably 5 × 10 ⁻⁴ or less, further preferably 1 × 10 ⁻⁴ or less, and particularly preferably 1 × 10 ⁻⁵ or less. It should be noted that the growth direction is a direction mainly growing in the growth of the entire crystal and corresponds to the thickness direction of the crystal.

The shape of the base substrate according to the present invention is not particularly limited, and a substrate having a disk shape, a polygonal plate shape, a rectangular parallelepiped shape, or the like can be appropriately employed according to the purpose. However, the maximum area of the base substrate is 1 cm ² or more, preferably 2 cm ² or more, more preferably 5 cm ² or more from the viewpoint of efficiently producing a large wafer (semiconductor substrate) by taking advantage of the manufacturing method of the present invention. More preferably, it is 10 cm ² or more.

  The base substrate according to the present invention has a nonpolar plane or a semipolar plane as a main plane, but the specific plane orientation is not particularly limited as long as it is a nonpolar plane or a semipolar plane. However, since a growth layer particularly suitable as a substrate of a device or the like can be formed, the C plane, that is, a plane inclined by 20 ° or more and 90 ° or less from the (0001) plane is preferable, and 42 ° or more from the (0001) plane, A plane inclined by 90 ° or less is more preferable. The semipolar plane is a plane inclined from the C plane, that is, the (0001) plane, and means a plane in which the abundance ratio of the Group 13 metal element and the nitrogen element is not 1: 1. Specifically, (10-11) plane, (10-1-1) plane, (20-21) plane, (20-2-1) plane, (10-12) plane, (10-1-2) A surface etc. can be mentioned. The crystal plane includes a plane within a range having an off angle within 20 ° from each crystal axis measured with an accuracy within ± 0.01 °, and preferably the off angle is within 15 °. More preferably, it is within 10 °.

The manufacturing method of the present invention is not limited to an embodiment in which a single periodic table group 13 metal nitride semiconductor crystal is used as a base substrate, and a plurality of periodic table group 13 metal nitride semiconductor crystals are arranged as a base substrate. (Hereinafter, each crystal when a plurality of periodic table Group 13 metal nitride semiconductor crystals are arranged and used as a base substrate may be abbreviated as “base crystal”.) Even when a large substrate cannot be prepared as a base substrate, a large-area main surface can be formed by arranging the plane orientations of the main surfaces of a plurality of base crystals as nonpolar surfaces or semipolar surfaces.
The arrangement method of the base crystal is not particularly limited as long as it is arranged so that a periodic table group 13 metal nitride semiconductor crystal having a nonpolar plane or a semipolar plane as a main surface is formed, and is well known. These methods can be adopted as appropriate. For example, they may be arranged so that the plane orientations of the base crystals are aligned or different. Further, adjacent base crystals may or may not be in contact with each other. Furthermore, the plurality of base crystals do not have to be arranged on the same plane, and may be arranged so as to overlap on the plane. However, it is preferable to align the crossing direction of the main surface and the polar surface of the base crystal so that the distribution of the crossing direction between the main surface and the polar surface of the base crystal is within ± 5 °. It is more preferable that they are aligned so that they are within ± 3 °, more preferably they are aligned so that they are within ± 1 °, and it is particularly preferable that they are aligned so that they are within ± 0.5 °.

  If the base substrate according to the present invention is a periodic table group 13 metal nitride semiconductor crystal obtained by crystal growth in the presence of a solvent in a supercritical state and / or a subcritical state, other conditions such as physical properties are particularly Although not limited, suitable physical properties will be described below. As described above, it is possible to obtain a high-quality periodic table group 13 metal nitride semiconductor crystal with low strain by the ammonothermal method. However, by optimizing the following physical properties, the residual strain can be further reduced. The present inventors have revealed that it is possible to grow a few Group 13 metal nitride semiconductor crystals of the periodic table (for example, light elements and point defects have an effect of relaxing the stress and suppressing the generation of strain). .)

(Extension / contraction of lattice spacing)
In the base substrate according to the present invention, the expansion and contraction (Δd / d _ave ) of the lattice spacing is preferably | 1.0 × 10 ⁻⁵ or less, and | 5.0 × 10 ⁻⁶ or less. Is more preferable, and | 2.0 × 10 ⁻⁶ | or less is more preferable. As described above, it is considered that the residual strain in the crystal can be reduced by reducing the expansion and contraction of the lattice spacing.
In addition, the expansion / contraction (Δd / d _ave ) of the lattice spacing is a multipoint measurement of the lattice spacing (Δd) of the (30-30) plane or (3-2-10) plane in one direction of the a-axis or c-axis. To calculate. At this time, the measurement range is preferably 4 mm or more, the number of measurement points is preferably 10 points or more, and each measurement point is preferably at a constant interval. Δd is the lattice spacing, d _ave is the average value of all lattice spacings Δd in the measurement range, and Δd / d _ave is the maximum value calculated from Δd and d _ave by | 1-d / d _ave | is there.

(Dislocation density)
The base substrate according to the present invention preferably has a dislocation density of 5 × 10 ⁴ pieces cm ⁻² or less, more preferably 1.0 × 10 ³ pieces cm ⁻² or less, and 1.0 × 10 6. More preferably, it is ² cm ⁻¹ or less. As described above, it is considered that residual strain in the crystal can be reduced by reducing the dislocation density.
The dislocation density means the number of all types of dislocations such as basal plane dislocations and stacking faults converted to a value per unit area (cm ² ). The dislocation density can be measured by using a method in which the main surface of the base substrate is observed with TEM (transmission electron microscopy), SEM-CL (cathode luminescence method), and surface pits by etching are observed with an AFM or an optical microscope. it can.

(Light element concentration)
The base substrate according to the present invention is preferably a crystal containing a light element. The “light element” means a nonmetallic element belonging to the first period or the second period of the periodic table in the present invention. Specifically, hydrogen (H), carbon (C), nitrogen (N), oxygen (O ) And fluorine (F). As described above, the light element has an effect of reducing the strain generated in the crystal, and it is considered that the generation of stacking faults due to the strain can be suppressed.
The concentration of the light element contained in the base substrate is not particularly limited, but is preferably 1.0 × 10 ¹⁷ atoms · cm ⁻³ or more, more preferably 2.0 × 10 ¹⁷ atoms · cm ⁻³ or more, more preferably 1.0 × 10 ¹⁸ atoms · cm ⁻³ or more, more preferably 2.0 × 10 ¹⁸ atoms · cm ⁻³ or more, particularly preferably 5.0 × 10 ¹⁸ atoms · cm ⁻³ or more, preferably 1.0 × 10 ²⁰ atoms · cm ⁻³ or less, more preferably 5.0 × 10 ¹⁹ atoms · cm ⁻³ or less.
Among light elements, the hydrogen concentration is preferably 1.0 × 10 ¹⁷ atoms · cm ⁻³ or more, more preferably 2.0 × 10 ¹⁷ atoms · cm ⁻³ or more, and even more preferably 5.0 × 10 ¹⁷ atoms / cm ^3. · Cm ⁻³ or more, more preferably 1.0 × 10 ¹⁸ atoms · cm ⁻³ or more, preferably 1.0 × 10 ²⁰ atoms · cm ⁻³ or less, more preferably 5.0 × 10 ¹⁹ atoms. ^-It is cm- ³ or less.
The oxygen concentration is preferably 1.0 × ¹⁰ 17 atoms · ^{cm -3} or more, more preferably 2.5 × ¹⁰ 17 atoms · ^{cm -3} or more, more preferably 5.0 × ¹⁰ 17 atoms · cm ^{- 3} or more, preferably 1.0 × 10 ²⁰ atoms · cm ⁻³ or less, more preferably 5.0 × 10 ¹⁹ atoms · cm ⁻³ or less.
Fluorine may or may not be contained, but when it is contained, the concentration is preferably 5.0 × 10 ¹⁶ atoms · cm ⁻³ or more, more preferably 1.0 × 10 6. ^{It is 17} atoms · cm ⁻³ or more, more preferably 5.0 × 10 ¹⁷ atoms · cm ⁻³ or more, and preferably 5.0 × 10 ¹⁸ atoms · cm ⁻³ or less. Within the above range, it becomes easy to produce a periodic table group 13 metal nitride semiconductor crystal with few stacking faults.
The light element concentration can be measured by SIMS (secondary ion mass spectrometer) or GDMS (glow discharge mass spectrometry).

(Alkali metal concentration)
The base substrate according to the present invention is preferably a crystal having a low alkali metal concentration. Alkali metals exhibit metal bonding properties and react with halogens in addition to hydrogen (H) and oxygen (O), and thus are considered to adversely affect the effects of light elements.
The alkali metal concentration contained in the base substrate is not particularly limited, but is preferably 1.0 × 10 ¹⁷ atoms · cm ⁻³ or less, more preferably 1.0 × 10 ¹⁶ atoms · cm ⁻³ or less, and further preferably 1 0.0 × 10 ¹⁵ atoms · cm ⁻³ or less. Within the above range, it becomes easy to produce a periodic table group 13 metal nitride semiconductor crystal with few stacking faults.
The alkali metal concentration can be measured by SIMS (secondary ion mass spectrometry) or GDMS (glow discharge mass spectrometry).

(Carrier concentration)
The carrier concentration of the base substrate according to the present invention is not particularly limited, and may be a conductive type or a semi-insulating type.

(Infrared absorption peak)
The base substrate according to the present invention is preferably a crystal having an infrared absorption peak at 3100 to 3200 cm ⁻¹ . In “3100-3200 cm ⁻¹ ”, it is considered that a peak due to the N—H bond in the crystal appears. Although the detailed mechanism is not clear, it is thought that the presence of the N—H bond suggests that a point defect exists in the crystal. This point defect tends to easily incorporate light elements, and the effect of the incorporated light elements makes it easy to produce a periodic table group 13 metal nitride semiconductor crystal with few stacking faults.
Although infrared specific type of absorption peak is not particularly limited, 3150 is considered as a peak caused by the N-H bonds in the crystal ^{± 1.5cm -1, 3164 ± 1.5cm -1} , 3175 ± 1.5cm -1 , 3188 ± 1.5 cm ⁻¹ is preferable.
The infrared absorption peak can be measured by transmitting infrared light through a substrate having both the main surface and the back surface subjected to CMP using a Fourier transform infrared spectrophotometer (FT-IR).

(Light absorption coefficient)
The base substrate according to the present invention preferably has a light absorption coefficient of 1.0 to 30 cm ^{−1 at} a wavelength of 405 nm and / or a light absorption coefficient of 0.5 to 5 cm ⁻¹ at a wavelength of 445 nm. Although the detailed mechanism is not clear, it is considered that the light absorption coefficient is related to the impurity concentration and point defect density in the crystal. If the light absorption coefficient is in the above range, the impurity concentration and point defect density are suitable. It is considered to be in the range. The specific numerical value of the light absorption coefficient at a wavelength of 405 nm is not particularly limited, but is preferably 1.5 cm ⁻¹ or more, more preferably 2.0 cm ⁻¹ or more, preferably 20 cm ⁻¹ or less, more preferably 15 cm. ^-1 or less. On the other hand, the absorption coefficient of light is also not particularly limited in the wavelength 445 nm, preferably 0.6 cm ^-1 or more, more preferably 0.7 cm ^-1 or more, preferably 4.5 cm ^-1 or less, more preferably 4. 2 cm ⁻¹ or less.
The light absorption coefficient can be determined from the Lambert-Beer rule by evaluating the absorption characteristics when 405 nm and 445 nm laser beams are respectively irradiated into the integrating sphere. By measuring in an integrating sphere, loss factors other than absorption can be eliminated.

(Basal plane dislocation)
The base substrate according to the present invention is preferably a crystal having a low basal plane dislocation density on the main surface. Some stacking faults are thought to occur starting from basal plane dislocations, and it is easy to manufacture a periodic table group 13 metal nitride semiconductor crystal with few stacking faults when the base substrate has a low basal plane dislocation density. Become. Although the specific basal plane dislocation density is not particularly limited, it is preferably 1.0 × 10 ⁵ cm ⁻² or less, more preferably 1.0 × 10 ⁴ cm ⁻² or less, and further preferably 1.0 × 10 ³ cm. ^-2 or less, most preferably 0 cm ^-2 .
The “basal plane dislocation density on the main surface” represents a value obtained by converting the number of basal plane dislocations when the main surface is observed into a value per unit area (cm ² ). The basal plane dislocation can be measured by using a transmission electron microscope method (TEM method), a cathodoluminescence method (SEM-CL method), and a method of observing surface pits by etching with an AFM, an optical microscope, or the like.

(Stacking fault density)
The base substrate according to the present invention is preferably a crystal having a low stacking fault density. It is considered that the stacking fault of the base substrate propagates to the growth layer. When the base substrate has a low basal plane dislocation density, it becomes easy to manufacture a periodic table group 13 metal nitride semiconductor crystal with few stacking faults. The specific stacking fault density is not particularly limited, but is preferably 10 cm ⁻¹ or less, more preferably 5 cm ⁻¹ or less, and even more preferably 1 cm ⁻¹ or less.
The stacking fault density can be measured by a cathodoluminescence method (SEM-CL method) or can be estimated by a low temperature PL measurement.

1-1-2. Manufacturing method of base substrate The base substrate according to the present invention is a periodic table group 13 metal nitride obtained by using a so-called ammonothermal method in which crystal growth is performed in the presence of a solvent in a supercritical state and / or a subcritical state. Although it is a physical semiconductor crystal, detailed growth conditions such as an apparatus, a raw material, and a solvent used for crystal growth are not particularly limited. Hereinafter, specific conditions will be described with reference to the apparatus of FIG. 1, but the present invention is not limited to such an embodiment, and can be implemented by appropriately adopting known configurations.

The apparatus shown in FIG. 1 (a) is an apparatus including a reaction vessel 20 as an inner cylinder in a pressure-resistant vessel (autoclave) 1, and in a production method using such an apparatus, seed crystals, solvents, raw materials, A mineralizer that increases the solubility of the raw material is used. The inside of the reaction vessel 20 has a structure divided into a raw material melting region 9 for melting the raw material and a crystal growth region 6 for crystal growth, and includes a baffle plate 5 that partitions the two regions. Yes. For example, the raw material melting region 9 can be loaded with the raw material 8 and a mineralizer, and the seed crystal 7 can be installed in the crystal growth region 6 by suspending it on a wire. Further, it is possible to fill with ammonia while filling the nitrogen gas from the nitrogen cylinder 13 through the valve 10 or confirming the flow rate with the mass flow meter 14 from the ammonia cylinder 12. In addition, the vacuum pump 11 can perform necessary pressure reduction.
In addition, as in the apparatus shown in FIG. 1B, a seed crystal and a raw material containing a Group 13 metal element of the periodic table are directly placed in the pressure-resistant vessel, and a nitrogen-containing solvent is filled. May be.
“Amonothermal method” is a method for producing a desired material using a dissolution-precipitation reaction of raw materials using a solvent containing nitrogen such as an ammonia solvent in a supercritical state and / or a subcritical state. is there. When the ammonothermal method is applied to crystal growth, a supersaturated state is generated due to a temperature difference using the temperature dependence of the raw material solubility in an ammonia solvent to precipitate crystals. Crystal growth by the ammonothermal method is a reaction in a high-temperature and high-pressure supercritical ammonia environment, and the solubility of the Group 13 metal nitride in the periodic table in pure ammonia in a supercritical state is extremely small. Usually, a mineralizer is preferably used to improve the crystal growth and promote crystal growth. According to the method for producing a periodic table group 13 metal nitride semiconductor crystal of the present invention, the temperature and pressure in a reaction vessel containing a seed crystal, a nitrogen-containing solvent, a raw material, and a mineralizer are supercritical. It is preferable to include a step of growing a group 13 metal nitride semiconductor crystal of the periodic table on the surface of the seed crystal by controlling to be in a state and / or a subcritical state.

Hereinafter, a specific procedure in the case of using the apparatus shown in FIG.
(1) Materials such as seed crystals, solvents, raw materials, and mineralizers are introduced into the reaction vessel, and the reaction vessel is sealed.
Specific operations and procedures for introducing materials such as seed crystals, solvents, raw materials, and mineralizers into the reaction vessel are not particularly limited, and publicly known methods may be adopted as appropriate depending on the type of materials and the structure of the apparatus. Can do. For example, when the material is a gas at normal temperature and pressure, it can be introduced by cooling the reaction vessel and liquefying the material in the reaction vessel. When ammonia (NH ₃ ) is used as a solvent, it can be introduced (filled) as a liquid by cooling the reaction vessel with a dry ice ethanol solvent or the like and then blowing ammonia gas into the reaction vessel.
Before or after introducing the material, the inside of the reaction vessel is evacuated, and further, when introducing the material, an inert gas such as nitrogen gas (N ₂ ) is circulated to mix impurities. It is preferable to take measures to suppress. Moreover, it is preferable to employ | adopt the thing made from a noble metal excellent in corrosion resistance as jigs, such as a wire for installing a seed crystal.
The method for sealing the reaction vessel is not particularly limited as long as it can withstand the pressure conditions for crystal growth, but it is usually sealed and sealed, for example, by welding the inlet.
(2) The reaction container is loaded into a pressure-resistant container, and a solvent is filled in the space between the pressure-resistant container and the reaction container, and the pressure-resistant container is sealed.
As shown in FIG. 1, in the case of an apparatus in which a reaction vessel is loaded in a pressure-resistant vessel, a pressure difference is generated between the inside and outside of the reaction vessel due to an increase in pressure inside the reaction vessel. Therefore, it is preferable to fill the space between the pressure-resistant vessel and the reaction vessel with a solvent from the viewpoint of suppressing the reaction vessel from bursting during crystal growth. In addition, it is preferable that the filling amount of the solvent is appropriately adjusted in consideration of the effective volume of the void for the purpose of reducing the pressure difference.
(3) The pressure-resistant container is heated to a set temperature to advance crystal growth.
A method for heating the pressure-resistant container is not particularly limited, and a method for heating the pressure-resistant container in an electric furnace is mentioned. Further, as described above, when crystal growth is performed by setting a temperature difference between the raw material melting region and the crystal growth region, a method of using an electric furnace including a plurality of heaters can be used.
(4) The temperature of the pressure-resistant vessel is lowered, the pressure-resistant vessel and the reaction vessel are opened, and the periodic table group 13 metal nitride semiconductor crystal is recovered.

(Seed crystal)
The seed crystal is not particularly limited as long as it is a known one used for crystal growth of Group 13 metal nitride semiconductor crystals of the periodic table. Gallium nitride (GaN), indium gallium nitride (InGaN), aluminum gallium nitride In addition to using the same type of target periodic table group 13 metal nitride semiconductor crystals such as (AlGaN), metal oxides such as sapphire (Al ₂ O ₃ ) and zinc oxide (ZnO), silicon carbide (SiC) Silicon-containing materials such as silicon (Si), arsenic gallium (GaAs), or the like can be used. Provided that it is a seed crystal having a lattice constant, a crystal lattice size parameter consistent with or suitable for the desired Group 13 metal nitride semiconductor crystal, or heteroepitaxy (ie, the crystallographic position of some atoms). It is preferable to use a seed crystal composed of a single crystal material piece or a polycrystalline material piece arranged so as to guarantee the same).

The seed crystal can be determined in consideration of the solubility in the solvent and the reactivity with the mineralizer. For example, as a seed crystal of gallium nitride (GaN), a single crystal obtained by epitaxial growth on a heterogeneous substrate such as sapphire by MOCVD method or HVPE method, and then separated from metal gallium (Ga) to sodium (Na) or A single crystal obtained by crystal growth using lithium (Li) as a flux, a single crystal obtained by homo / heteroepitaxial growth obtained by using the LPE method,
Single crystals produced by the ammonothermal method and crystals obtained by cutting them can be used.

The plane orientation of the main surface of the seed crystal is not particularly limited, but from the viewpoint of efficiently producing a periodic table group 13 metal nitride semiconductor base substrate having a nonpolar plane or a semipolar plane as a main plane, the intended periodic table It is preferable to select a seed crystal having a nonpolar plane or a semipolar plane as a main plane in accordance with the Group 13 metal nitride semiconductor crystal. In addition, (1) From the viewpoint of suppressing residual strain in the base substrate, it is preferable to use, as a seed crystal, a crystal grown by an ammonothermal method so as to widen a crystal plane corresponding to the main surface of the base substrate. . Further, (2) when the crystal is grown on the seed crystal, it is possible to obtain a base substrate in which residual strain is suppressed by growing the crystal face corresponding to the main surface of the base substrate.
As a specific growth method for expanding the crystal plane corresponding to the main surface of the base substrate, (i) lateral growth is performed from the side surface of the crystal whose main surface is substantially the same crystal plane as the main surface of the base substrate. (Ii) a method of growing from a main surface of a crystal whose main surface is a crystal surface different from the main surface of the base substrate, and (iii) a crystal whose main surface is a crystal surface different from the main surface of the base substrate Examples include growing from the side. More specifically, (i) as a method of laterally growing from the side surface of the crystal whose main surface is substantially the same crystal surface as the main surface of the base substrate, a seed having a plurality of growth start surfaces (side surfaces), for example, V-shaped seeds, U-shaped seeds, R-shaped seeds, L-shaped seeds, O-shaped seeds, a method using a seed having one or more holes, and a guide to surround a region where crystals are to be grown The method of providing is mentioned. Further, (ii) a method of growing from a main surface of a crystal having a crystal surface different from the main surface of the base substrate as a main surface includes a method of growing from a seed in which a part of the main surface is covered with a mask, And a method of growing from a seed in which a side surface of a plate-like member is adhered to a part of the plate. Further, (iii) as a method of growing from the side surface of the crystal having a crystal plane different from the main surface of the base substrate as the main surface, as shown in FIG. 4 of International Publication No. 2008/143166, The method of growing so that it may extend in the normal direction is mentioned.

(solvent)
As the solvent, a solvent containing nitrogen is used. Examples of the solvent containing nitrogen include a solvent that does not impair the stability of the group 13 metal nitride semiconductor crystal to be grown. Specifically, ammonia (NH ₃ ), hydrazine (N ₂ H ₄ ), urea (CH ₄ N ₂ O), amines (eg, primary amines such as methylamine, secondary amines such as dimethylamine, tertiary amines such as trimethylamine, ethylenediamine, etc. Diamine) and melamine. These solvents may be used alone or in combination.

The solvent preferably has as little impurities as possible such as water (H ₂ O) and oxygen (O ₂ ), and the content thereof is preferably 1000 ppm or less, more preferably 10 ppm or less, and even more preferably 0.1 ppm or less. . When ammonia (NH ₃ ) is used as a solvent, the purity is usually 99.9% or more, preferably 99.99% or more, more preferably 99.999% or more, and particularly preferably 99.9999% or more.

(material)
As a raw material, a compound containing an element constituting a target periodic table group 13 metal nitride semiconductor base substrate is used. For example, a periodic table group 13 metal nitride semiconductor polycrystalline raw material (hereinafter sometimes abbreviated as "polycrystalline raw material") and / or a metal of the periodic table group 13 element, preferably gallium nitride and / or gallium. It is. The polycrystalline raw material does not need to be a complete nitride, and may contain a metal component in which the Group 13 element of the periodic table is in a metal state (zero valence) depending on conditions. For example, the crystal is gallium nitride. In some cases, a mixture of gallium nitride and metal gallium may be mentioned.

  When a polycrystalline raw material is used as a raw material, its production method is not particularly limited, but a material produced by reacting a metal or its oxide or hydroxide with ammonia in a reaction vessel in which ammonia gas is circulated is used. be able to. In addition, as a metal compound raw material having higher reactivity, a compound having a covalent MN bond such as a halide, an amide compound, an imide compound, or galazan can be used. Furthermore, a nitride polycrystal produced by reacting a metal such as Ga with nitrogen at a high temperature and a high pressure can also be used.

Although it has been described above that the base substrate according to the present invention is preferably a crystal containing a light element, the impurity concentration contained in the base substrate can be controlled by, for example, the concentration of impurities contained in the raw material (note that It is also possible to control by adding a predetermined impurity to a mineralizer or a solvent (which includes an impurity in a gas). Therefore, from the viewpoint of setting the light element concentration of the base substrate, for example, the oxygen (O) concentration in a suitable range, the oxygen concentration contained in the raw material polycrystal is usually 5 × 10 ²⁰ atoms · cm ⁻³ or less, preferably 1 × 10 ²⁰ atoms · cm ⁻³ or less, particularly preferably 5 × 10 ¹⁹ atoms · cm ⁻³ or less.

(Mineralizer)
The mineralizer is not particularly limited as long as it is a known one used for crystal growth of Group 13 metal nitride semiconductor crystals of the periodic table, and a mineralizer containing a halogen element or a mineralizer containing an alkali metal. Can be used. However, as described above, the base substrate according to the present invention is preferably a crystal having a low alkali metal concentration, and a mineralizer containing a halogen element is preferably used.

  One type of halogen element contained in the mineralizer may be used, or two or more types may be combined. When two or more types are combined, it may be a combination of two elements such as chlorine and fluorine, bromine and fluorine, iodine and fluorine, or 3 such as chlorine and bromine and fluorine, chlorine and iodine and fluorine, bromine and iodine and fluorine. It may be a combination of elements, or a combination of four elements such as chlorine, bromine, iodine and fluorine.

  Specific examples of mineralizers containing halogen elements include ammonium halide, hydrogen halide, ammonium hexahalosilicate, and hydrocarbyl ammonium fluoride, tetramethylammonium halide, tetraethylammonium halide, benzyltrimethylammonium halide, halogen Illustrative examples include alkylammonium salts such as dipropylammonium halide and isopropylammonium halide, alkyl metal halides such as sodium alkyl fluoride, alkaline earth metal halides and metal halides. Of these, an additive (mineralizing agent) containing a halogen element is preferably an alkali halide, an alkaline earth metal halide, a metal halide, an ammonium halide, or a hydrogen halide, more preferably a halogenated. Alkali, ammonium halide, Group 13 metal halide and hydrogen halide are particularly preferred, and ammonium halide, gallium halide and hydrogen halide are particularly preferred.

A mineralizer that does not contain a halogen element can be used together with a mineralizer that contains a halogen element. For example, it can be used in combination with an alkali metal amide such as NaNH ₂ , KNH _2, or LiNH ₂ . When a halogen element-containing mineralizer such as ammonium halide and a mineralizer containing an alkali metal element or an alkaline earth metal element are used in combination, it is preferable to increase the amount of the halogen element-containing mineralizer. Specifically, the mineralizer containing an alkali metal element or alkaline earth metal element is preferably 50 to 0.01 parts by mass with respect to 100 parts by mass of the halogen element-containing mineralizer. It is more preferable to set it as 1 mass part, and it is further more preferable to set it as 5-0.2 mass part. By adding a mineralizer containing an alkali metal element or an alkaline earth metal element, it is possible to further increase the m-axis crystal growth rate ratio (m-axis / c-axis) with respect to the crystal growth rate in the c-axis direction. is there.

  It is preferable to use the mineralizer after purification and drying. The purity of the mineralizer is usually 95% or more, preferably 99% or more, more preferably 99.99% or more. Note that aluminum halide, phosphorus halide, silicon halide, germanium halide, zinc halide, arsenic halide, tin halide, antimony halide, bismuth halide, and the like may be present in the reaction vessel.

(Reaction vessel)
The apparatus shown in (a) of FIG. 1 is an apparatus provided with a reaction vessel as an inner cylinder in a pressure-resistant vessel. Such a reaction vessel is selected from those capable of withstanding high-temperature and high-pressure conditions during crystal growth. The “reaction vessel” means a vessel for producing a periodic table group 13 metal nitride semiconductor crystal in a state where a solvent in a supercritical state and / or a subcritical state can be in direct contact with the inner wall surface thereof. In the case of the apparatus shown in FIG. 1B, the pressure-resistant vessel corresponds to the “reaction vessel”.
The reaction vessel is formed from the outside of the reaction vessel as described in JP-T-2003-511326 (International Publication No. 01/024921 pamphlet) and JP-T-2007-509507 (International Publication No. 2005/043638 pamphlet). It may be provided with a mechanism for adjusting the pressure applied to the reaction vessel and its contents, or may be an autoclave not having such a mechanism.
The reaction vessel is preferably composed of a material having pressure resistance and corrosion resistance, and particularly Ni-based alloy having excellent corrosion resistance against solvents such as ammonia, Stellite (registered trademark of Deloro Stellite Company, Inc.), etc. It is preferable to use a Co-based alloy. More preferably, it is a Ni-based alloy. Specifically, Inconel 625 (Inconel is a registered trademark of Huntington Alloys Canada Limited, the same applies hereinafter), Nimonic 90 (Nimonic is a registered trademark of Special Metals Wiggin Limited, the same applies hereinafter), RENE41 (Teledyne). Allvac, Inc.), Inconel 718 (Inconel is a registered trademark of Huntington Alloys Canada Limited), Hastelloy (registered trademark of Haynes International, Inc.), Waspaloy (registered trademark of United Technologies, Inc.).
The composition ratio of these alloys depends on the temperature and pressure conditions of the solvent in the system, and the reactivity with mineralizers and their reactants contained in the system and / or the oxidizing power / reducing power, pH conditions, What is necessary is just to select suitably. Although the alloys used in these pressure resistant reaction vessels have high corrosion resistance, they do not have such high corrosion resistance that they have no influence on the crystal quality. In these alloys, in a supercritical solvent atmosphere, particularly in a more severe corrosive environment containing a mineralizer, components such as Ni, Cr, and Fe are dissolved in the solution and taken into the crystal. Therefore, in the present invention, in order to suppress inner surface corrosion of these pressure resistant containers, a method of directly lining or coating the inner surface with a material having further excellent corrosion resistance, or a capsule made of a material having further excellent corrosion resistance is disposed in the pressure resistant container. It is preferable to form the reaction vessel by a method for the above.

The temperature condition is not particularly limited, but the temperature in the reaction vessel is preferably 500 ° C. or higher, more preferably 515 ° C. or higher, further preferably 530 ° C. or higher, preferably 700 ° C. or lower, more preferably 650 ° C. or lower, More preferably, it is 630 degrees C or less.
Moreover, when setting so that a temperature difference may arise between a raw material melt | dissolution area | region and a crystal growth area | region, it is preferable that the temperature of a raw material melt | dissolution area | region is higher than the temperature of a crystal growth area | region. The temperature difference (| ΔT |) between the raw material dissolution region and the crystal growth region is preferably 5 ° C. or higher, more preferably 10 ° C. or higher, preferably 100 ° C. or lower, more preferably 80 ° C. or lower. The optimum temperature and pressure in the reaction vessel can be appropriately determined depending on the type and amount of mineralizer and additive used during crystal growth.
Note that the temperature in the reaction vessel is a thermocouple provided in contact with the outer surface of the reaction vessel, and / or
Alternatively, it can be measured by a thermocouple inserted into a hole having a certain depth from the outer surface, and converted into the internal temperature of the reaction vessel and estimated. The average value of the temperatures measured with these thermocouples is taken as the average temperature. Usually, the average value of the temperature of the raw material melting region and the temperature of the crystal growth region is defined as the average temperature, and the temperature in the reaction vessel.

  The growth of the periodic table group 13 metal nitride semiconductor in the reaction vessel is performed by heating and heating the reaction vessel using an electric furnace or the like having a thermocouple, so that the reaction vessel is subcritical in a solvent such as ammonia. Alternatively, it is carried out by maintaining a supercritical state. The heating method and the rate of temperature increase to a predetermined reaction temperature are not particularly limited, but are usually performed over several hours to several days. If necessary, the temperature can be raised in multiple stages or the temperature raising speed can be changed in the temperature range. It can also be heated while being partially cooled.

  Under supercritical conditions, a sufficient growth rate of Group 13 metal nitride semiconductor crystals of the periodic table can be obtained. The reaction time depends in particular on the reactivity of the mineralizer and the thermodynamic parameters, ie temperature and pressure values. The pressure during the synthesis or growth of the Group 13 metal nitride semiconductor crystal of the periodic table is preferably 120 MPa or more, more preferably 150 MPa or more, and further preferably 180 MPa or more. Also, it is preferably 700 MPa or less, more preferably 500 MPa or less, further preferably 350 MPa or less, and particularly preferably 300 MPa or less.

  The reaction time after reaching the prescribed temperature depends on the type of nitride crystal, the raw material, the type of mineralizer, and the size and amount of the crystal to be produced, but it is usually several hours to several hundred days. Can do. During the reaction, the reaction temperature may be constant, or the temperature may be gradually raised or lowered.

  In the case of producing gallium nitride, JP 2009-263229 A can be preferably referred to for details of materials, production conditions, production apparatuses, and processes other than those described above. The entire disclosure of this publication is incorporated herein by reference.

1-2. Growth process 1-2-1. Growth Method and Structure of Crystal Growth Apparatus The manufacturing method of the present invention includes a growth process for growing a group 13 metal nitride semiconductor crystal of the periodic table (hereinafter sometimes abbreviated as “growth process according to the present invention”). However, the specific growth method in the growth process is not particularly limited, and hydride vapor phase growth method (HVPE method), metal organic chemical vapor deposition method (MOCVD method), metal organic chloride vapor phase growth method (MOC method), etc. Alternatively, a liquid phase growth method such as a vapor phase growth method or a flux method, or a known growth method such as the above-described ammonothermal method can be employed. Among these, the HVPE method, the flux method, and the ammonothermal method are preferable, and the HVPE method is particularly preferable from the viewpoint of a high growth rate.
Hereinafter, in describing the details of the growth process according to the present invention, the configuration of the crystal growth apparatus in the case of producing a GaN crystal by the HVPE method will be described with a specific example, but is not limited to the following modes. . When the ammonothermal method is employed, the method described in “1-1-2. Method for manufacturing base substrate” can be performed as the growth step.

  The crystal growth apparatus shown in FIG. 2 is a general apparatus used in the HVPE method, and contains a reactor (reaction vessel) 100, a susceptor 108 for placing a base substrate, a periodic table group 13 metal source, and the like. A reservoir 106, introduction pipes 101 to 105 for introducing gas into the reactor, an exhaust pipe 108 for exhausting, and a heater 107 for heating the reactor are provided. In addition, you may change suitably the number of introduction pipes according to the kind of gas to be used.

  Quartz, sintered boron nitride, stainless steel and the like are used as the material of the reactor, and quartz is particularly preferable. The material of the susceptor is preferably carbon, and in particular, the one whose surface is coated with SiC is preferable.

Gas types used in the growth process (in the case of the HVPE method) according to the present invention are gallium chloride (GaCl) as a gallium source (group 13 metal raw material), ammonia (NH ₃ ) as a nitrogen raw material, carrier gas, and separate. A gas, a dopant, etc. are mentioned. Gallium chloride (GaCl) serving as a gallium source is generated by, for example, putting gallium (Ga) in the reservoir 106 and supplying a gas that reacts with gallium (Ga) such as hydrogen chloride (HCl) from the introduction tube 103. Can be supplied. In addition to gallium (Ga), aluminum (Al), indium (In), or the like can be placed in the reservoir 106 depending on the purpose. Further, a carrier gas may be supplied from the introduction pipe 103 together with hydrogen chloride (HCl). As the carrier gas, hydrogen gas (H ₂ ), nitrogen gas (N ₂ ), helium gas (He), neon gas (Ne). , Argon gas (Ar), or a mixed gas thereof. Ammonia gas (NH ₃ ), carrier gas, separate gas, dopant, and the like, which are nitrogen raw materials, can be supplied from the introduction pipes 101, 102, 104, and 105. Examples of the separate gas include hydrogen gas (H ₂ ) and nitrogen gas. (N ₂ ), helium gas (He), neon gas (Ne), argon gas (Ar), or a mixed gas thereof is used as a dopant gas, such as oxygen (O ₂ ), water (H ₂ O), silane gas (SiH ₄ ). ), Hydrogen sulfide (H ₂ S), and the like.

  The exhaust pipe 109 may exist at any position on the top surface, bottom surface, and side surface of the inner wall of the reactor 100, but is preferably located below the crystal growth end from the viewpoint of dust removal, and as shown in FIG. It is more preferable that it is installed.

1-2-2. Growth Conditions Hereinafter, the growth conditions for producing a GaN crystal by the HVPE method will be described with specific examples.
When producing a GaN crystal by the HVPE method, the temperature condition is usually set in the range of 900 to 1200 ° C. (The temperature condition is intended to mean the temperature in the vicinity of the surface of the base substrate where crystal growth proceeds. Strictly speaking, it means the temperature of the susceptor on which the base substrate is placed, and is hereinafter abbreviated as “temperature of the growth part”). Therefore, it is necessary to raise the temperature of the growth part, but the state in which the temperature of the growth part is raised in the growth process is abbreviated as “heating process”. In addition, the state set as the main condition for advancing crystal growth is abbreviated as “main growth process”. Further, the state in which the temperature of the growth portion is raised while simultaneously supplying both the Group 13 metal raw material and the nitrogen raw material is abbreviated as “temperature rising growth process” (actually crystalline It doesn't matter whether growth is progressing or not). The “temperature rising process” means a state in which the temperature of the growth part is raised without simultaneously supplying both the group 13 metal material and the nitrogen material. "And shall be used separately.
As the growth process according to the present invention, for example,
(A) Growth process including temperature rising process and main growth process (not including temperature rising growth process),
(B) There are growth processes including a temperature rising process, a temperature rising growth process, and a main growth process (see FIGS. 3A and 3B). , And a growth process including this growth process is a particularly preferable embodiment.
By including the temperature rising growth process, the amount of impurities adhering to the surface of the base substrate is reduced to suppress the decrease in surface energy, and the base substrate temperature at the start of growth is set to a relatively low temperature to achieve two-dimensional growth. As a result, the occurrence of stacking faults can be more effectively suppressed. Hereinafter, the main growth process, the temperature rising process, and the temperature rising growth process will be described in detail. Note that the temperature of the growth part set in the main growth process is abbreviated as temperature T2, and the temperature of the growth part reached in the temperature rising process when both the temperature rising process and the temperature rising growth process are included is expressed as temperature. It will be expressed as T1.

(This growth process)
The temperature T2 of the growth part set in this growth process is usually 900 ° C. or higher, preferably 920 ° C. or higher, more preferably 940 ° C. or higher, and usually 1200 ° C. or lower, preferably 1100 ° C. or lower, more preferably 1050 ° C. or lower. More preferably, it is 1020 ° C. or lower. If it is the above ranges, a good periodic table group 13 metal nitride semiconductor crystal can be grown efficiently.
The pressure during this growth process (pressure in the reactor) is usually 10 kPa or more, preferably 30 kPa or more, more preferably 50 kPa or more, and usually 200 kPa or less, preferably 150 kPa or less, more preferably 120 kPa or less.

The supply amount of the periodic table group 13 metal raw material in this growth process is usually 1.20 × 10 ² Pa or more as a partial pressure of GaCl at a growth portion pressure of 1.01 × 10 ⁵ Pa when using GaCl. Preferably it is 1.60 × 10 ² Pa or more, more preferably 2.00 × 10 ² Pa, usually 9.00 × 10 ² Pa or less, preferably 7.00 × 10 ² Pa or less, more preferably 5. It is 00 × 10 ² Pa or less.
When NH ₃ is used as the nitrogen raw material, the partial pressure of NH _{3 at} the growth portion pressure of 1.01 × 10 ⁵ Pa is usually 3.5 × 10 ³ Pa or more, preferably 6.2 × 10 ³ Pa or more, More preferably, it is 9.3 × 10 ³ Pa, usually 2.7 × 10 ⁴ Pa or less, preferably pressure 2.0 × 10 ⁴ Pa or less, more preferably 1.2 × 10 ⁴ Pa or less.
When hydrogen (H ₂ ) is used as the carrier gas, the partial pressure of H _{2 at} the growth portion pressure of 1.01 × 10 ⁵ Pa is 1.00 × 10 ³ Pa or more, preferably 5.00 × 10 ³ Pa. Above, more preferably 1.00 × 10 ⁴ Pa or more.

Regarding the atmospheric gas in this growth process, it is preferable that 40% by volume or more of the total gas flow rate is an inert gas species such as nitrogen, and 70% by volume or more of the total gas flow rate is an inert gas species. Preferably, 90% by volume or more is an inert gas species.
The concentration of the inert gas species may be constant during the growth process or may be changed during the growth process. However, when changing the concentration of the inert gas species, the change time is preferably 1 second or longer, more preferably 1 minute or longer, and even more preferably 1 hour or longer. The change may be made by changing all gas types at the same time or sequentially for each gas type. In addition, the gas species may be constant without changing during the growth process, or may be changed. For example, N ₂ is used as an inert gas at the initial stage of growth, and Ar is used as an inert gas in this growth. There are cases.

(Heating process)
In the case of the growth process including the temperature rising process and the main growth process (not including the temperature rising growth process), the temperature of the growth part reached in the temperature rising process is synonymous with the temperature T2 of the growth part set in the above-described main growth process. It is.
On the other hand, in the case of the growth process including (b) the temperature rising process, the temperature rising growth process, and the main growth process, the temperature T1 of the growth portion reached in the temperature rising process is usually 700 ° C. or higher, preferably 750 ° C. or higher. Preferably it is 790 degreeC or more, More preferably, it is 830 degreeC or more, Usually, it is 950 degrees C or less, Preferably it is 940 degrees C or less, More preferably, it is 910 degrees C or less, More preferably, it is 870 degrees C or less. Within the above range, formation of periodic table group 13 metal nitride semiconductor crystals with poor crystallinity and adhesion of impurities can be suppressed, and the generation of stacking faults can be more effectively suppressed.

The rate of temperature rise in the temperature raising process is usually 5 ° C./min or more, preferably 8 ° C./min or more, more preferably 12 ° C./min or more, and usually 20 ° C./min or less, preferably 25 ° C./min or less. More preferably, it is 30 ° C./min or less. Within the above range, formation of periodic table group 13 metal nitride semiconductor crystals with poor crystallinity and adhesion of impurities can be suppressed, and the generation of stacking faults can be more effectively suppressed.

There are no particular limitations on the type of atmospheric gas in the temperature raising process, but hydrogen (H ₂ ), ammonia (NH ₃ ), nitrogen (N ₂ ), helium (He), neon (Ne), argon (Ar), etc. An active gas species or a mixed gas thereof may be used. Among these, hydrogen _(H 2), ammonia _(NH 3), preferably contains a nitrogen _{(N 2),} more preferably ammonia (NH ₃₎ and nitrogen _{(N 2).}
The concentration of each gas in the atmospheric gas is not particularly limited, but the concentration of the inert gas species is usually 10% by volume or more, preferably 20% by volume or more, more preferably 30% by volume or more. The concentration of hydrogen (H ₂ ) is usually 1% by volume or more, preferably 5% by volume or more, more preferably 8% by volume or more, and usually 90% by volume or less, preferably 80% by volume or less, more preferably 70%. % Volume% or less. The concentration of ammonia (NH ₃ ) is usually 5% by volume or more, preferably 10% by volume or more, more preferably 15% by volume or more.
Further, the temperature raising process may be performed in a closed system or in a circulation system that sequentially introduces atmospheric gas, but from the viewpoint of easily controlling the conditions of the atmospheric gas, the circulation in which atmospheric gas is sequentially introduced. It is preferred to be carried out in a system.

  There may be a holding process in which the set conditions are held for a short time until the temperature conditions in the reactor are stabilized during the period from the temperature rising process to the temperature rising growth process or the main growth process. Good. For example, after the temperature T1 is reached, before the transition to the temperature rising growth process, that is, before the simultaneous supply of both raw materials of Group 13 metal raw material and nitrogen raw material starts, a holding process is included ( Hereinafter, after reaching the temperature T1, a predetermined time until both the Group 13 raw material and the nitrogen raw material are supplied may be abbreviated as “time M1”. The time M1 is preferably as short as possible from the viewpoint of reducing the adhesion of impurities, but it may take time for the temperature in the reactor to stabilize depending on the structure of the manufacturing apparatus and the like. Therefore, the specific time of M1 should be appropriately set according to the structure of the manufacturing apparatus and the like, but is usually 60 minutes or less, preferably 30 minutes or less, more preferably 10 or less. If it is in the said range, the adhesion amount of an impurity can be reduced and generation | occurrence | production of a stacking fault can be suppressed more effectively.

(Temperature growth process)
The temperature rising rate up to T2 in the temperature rising growth process is usually 5 ° C./min or more, preferably 8 ° C./min or more, more preferably 11 ° C./min or more, and usually 30 ° C./min or less, preferably 27 ° C. / Min or less, more preferably 24 ° C./min or less. Within the above range, formation of periodic table group 13 metal nitride semiconductor crystals with poor crystallinity and adhesion of impurities can be suppressed, and the generation of stacking faults can be more effectively suppressed.

The supply amount of the periodic table group 13 metal raw material and the nitrogen raw material in the temperature raising process is not particularly limited, but when using GaCl as the periodic table group 13 metal raw material, GaCl at a growth portion pressure of 1.01 × 10 ⁵ Pa is used. Is usually 1.20 × 10 ² Pa or more, preferably 1.60 × 10 ² Pa or more, more preferably 2.00 × 10 ² Pa, and usually 9.00 × 10 ² Pa or less, preferably Is 7.00 × 10 ² Pa or less, more preferably 5.00 × 10 ² Pa or less.
When NH ₃ is used as a nitrogen raw material, the partial pressure of NH _{3 at} a growth portion pressure of 1.01 × 10 ⁵ Pa is usually 3.5 × 10 ³ Pa or more, preferably 6.2 × 10 ³ Pa or more, More preferably, it is 9.3 × 10 ³ Pa, usually 2.7 × 10 ⁴ Pa or less, preferably pressure 2.0 × 10 ⁴ Pa or less, more preferably 1.2 × 10 ⁴ Pa or less.
When hydrogen (H ₂ ) is used as the carrier gas, the partial pressure of H _{2 at} the growth portion pressure of 1.01 × 10 ⁵ Pa is 1.00 × 10 ³ Pa or more, preferably 5.00 × 10 ³ Pa. Above, more preferably 1.00 × 10 ⁴ Pa or more. Within the above range, the crystal growth rate in the temperature rising growth process can be controlled to an appropriate range, and the generation of stacking faults can be more effectively suppressed.

Regarding the atmospheric gas in the temperature rising growth process, 40% by volume or more of the total gas flow rate is preferably an inert gas species such as nitrogen. Note that 70% by volume or more of the entire gas flow rate is preferably an inert gas species, and 90% by volume or more is more preferably an inert gas species. The concentration of the inert gas species at the total gas flow rate can be calculated from the sum of the flow rates of all the inert gas species circulated through the reaction apparatus with respect to the sum of the flow rates of all the gases circulated through the reaction apparatus. Specific types of the inert gas species are not particularly limited, and examples include nitrogen (N ₂ ), helium (He), neon (Ne), and argon (Ar).

  When introducing the gas in the growth process, the time required for each gas to reach a predetermined gas partial pressure (gas flow rate) (hereinafter referred to as gas introduction time) is set to a relatively short time, so that the surface of the initial growth layer Even when the thickness of the group 13 nitride layer is increased after affecting the morphology and growth mode, the generation of anisotropic strain between the growth direction and the growth surface is suppressed, and stacking faults are increased. -It is preferable because propagation can be suppressed. Specifically, it is preferably 10 minutes or less, more preferably 5 minutes or less, and even more preferably 2 minutes or less. In particular, it is preferable to use a carrier gas containing hydrogen gas in the growth step because the above-described effects can be easily obtained.

  The growth process according to the present invention is preferably performed while rotating the base substrate. Although the rotational speed of a base substrate is not specifically limited, It is preferable that it is 1-50 rpm, and it is more preferable that it is 5-20 rpm.

  The growth rate of the growth step according to the present invention is usually in the range of 80 μm / h to 300 μm / h, preferably 100 μm / h or more, more preferably 120 μm / h or more, and particularly preferably 150 μm / h or more.

  The thickness of the growth layer grown in the growth process according to the present invention can be appropriately set according to the size of the periodic table group 13 metal nitride semiconductor crystal to be finally obtained, but the thickness of the growth layer increases as the thickness grows. The effects of the invention can be used more suitably. The specific thickness is usually 100 μm or more, preferably 1 mm or more, more preferably 3 mm or more, further preferably 10 mm or more, and is usually 51 mm or less, preferably 24 mm or less, more preferably 14 mm or less. The “thickness” means a thickness in a direction perpendicular to the main surface of the base substrate.

  In addition to the growth step described above, the production method of the present invention may include a known treatment step such as a separation step of separating the obtained crystal from the base substrate, other slicing steps, and a surface polishing step. Specific examples of the slicing step include wire slicing and inner peripheral edge slicing. The surface polishing step includes, for example, an operation of polishing the surface using abrasive grains such as diamond and colloidal silica, and CMP (chemical mechanical polishing). ), An operation of etching the damaged layer by RIE after mechanical polishing. The plane orientation for slicing can be appropriately set according to the purpose, but is usually within ± 90 °, preferably within ± 60 °, more preferably ± with respect to each of the C-plane, A-plane, and M-plane. It is within 30 °.

  The type of the periodic table group 13 metal nitride semiconductor crystal targeted by the production method of the present invention is not particularly limited as long as it is a nitride crystal containing a periodic table group 13 metal as a constituent element, but GaN, AlN, In addition to nitrides containing one kind of periodic table group 13 metal such as InN as constituent elements, mixed crystals containing two or more kinds of periodic table group 13 metals such as GaInN and AlGaN as constituent elements may also be mentioned.

  The periodic table group 13 metal nitride semiconductor crystal produced by the production method of the present invention can be used for various applications. In particular, a semiconductor device such as an electronic device as a semiconductor substrate for manufacturing a relatively short wavelength side light emitting element such as an ultraviolet to blue light emitting diode or a semiconductor laser, and a green to red light emitting element on a relatively long wavelength side It is also useful as a semiconductor substrate.

2. Periodic Table Group 13 Metal Nitride Semiconductor Crystal By the manufacturing method of the present invention described above, a periodic table Group 13 metal nitride semiconductor crystal whose main surface is a nonpolar or semipolar surface with very few stacking faults is efficiently manufactured. However, the specific stacking fault density of the periodic table group 13 metal nitride semiconductor crystal manufactured by the manufacturing method of the present invention is not particularly limited. However, according to the production method of the present invention, a periodic table group 13 metal nitride semiconductor crystal of usually 10 cm ⁻¹ or less, preferably 8 cm ⁻¹ or less, more preferably 5 cm ⁻¹ or less can be obtained.

Further, other physical properties of the periodic table group 13 metal nitride semiconductor crystal manufactured by the manufacturing method of the present invention are not particularly limited, but preferable physical properties will be described below.
(Carrier concentration)
In the case of a GaN crystal, the carrier concentration of the periodic table group 13 metal nitride semiconductor crystal is usually 5.0 × 10 ¹⁷ cm ⁻³ or more, preferably 9.0 × 10 ¹⁷ cm ⁻³ or more, and usually 1 × It is 10 ¹⁹ cm ⁻³ or less, preferably 8.0 × 10 ¹⁸ cm ⁻³ or less.

(Impurity concentration)
The hydrogen concentration of the periodic table group 13 metal nitride semiconductor crystal is usually 1.0 × 10 ¹⁶ atoms · cm ⁻³ or more, preferably 5.0 × 10 ¹⁶ atoms · cm ⁻³ or more, and usually 1.0 × 10 ²⁰ atoms · cm ⁻³ or less, preferably 5.0 × 10 ¹⁹ atoms · cm ⁻³ or less, more preferably 3.0 × 10 ¹⁹ atoms · cm ⁻³ or less, more preferably 5.0 × 10 ¹⁸ atoms · cm ⁻³ or less, particularly preferably 1.0 × 10 ¹⁸ atoms · cm ⁻³ or less. In particular, a crystal of 1.0 × 10 ¹⁸ atoms · cm ⁻³ or less can be obtained by employing a vapor phase growth method as a growth method in the growth process. If it is not more than the above upper limit value, it tends to be excellent in light emission characteristics and electrical characteristics, and can be suitably used as a base substrate for forming light emitting devices such as light emitting elements or as a base substrate for forming power devices such as transistors.
The oxygen concentration of the periodic table group 13 metal nitride semiconductor crystal is usually 1.0 × 10 ¹⁷ atoms · cm ⁻³ or more, preferably 2.5 × 10 ¹⁷ atoms · cm ⁻³ or more, more preferably 5.0. × 10 ¹⁷ atoms · cm ⁻³ or more, usually 1.0 × 10 ²⁰ atoms · cm ⁻³ or less, preferably 5.0 × 10 ¹⁹ atoms · cm ⁻³ or less, more preferably 3.0 × 10 ¹⁹ atoms · cm ⁻³ or less.
The halogen concentration of the periodic table group 13 metal nitride semiconductor crystal is usually 5.0 × 10 ¹⁸ atoms · cm ⁻³ or less, preferably 3.0 × 10 ¹⁸ atoms · cm ⁻³ or less, more preferably 1.0. × 10 ¹⁸ atoms · cm ⁻³ or less, more preferably 1.0 × 10 ¹⁷ atoms · cm ⁻³ or less, and particularly preferably 5.0 × 10 ¹⁶ atoms · cm ⁻³ or less. In particular, by adopting a vapor phase growth method as a growth method in the growth process, a crystal of 5.0 × 10 ¹⁶ atoms · cm ⁻³ or less can be obtained. If it is not more than the above upper limit value, it tends to be excellent in light emission characteristics and electrical characteristics, and can be suitably used as a base substrate for forming light emitting devices such as light emitting elements or as a base substrate for forming power devices such as transistors.
The alkali metal concentration of the periodic table group 13 metal nitride semiconductor crystal is usually 1.0 × 10 ¹⁷ atoms · cm ⁻³ or less, preferably 1.0 × 10 ¹⁶ atoms · cm ⁻³ or less, more preferably 1. 0 × 10 ¹⁵ atoms · cm ⁻³ or less.
The transition metal concentration of the group 13 metal nitride semiconductor crystal of the periodic table is usually 1.0 × 10 ¹⁷ atoms · cm ⁻³ or less, preferably 1.0 × 10 ¹⁶ atoms · cm ⁻³ or less, more preferably 1. 0 × 10 ¹⁵ atoms · cm ⁻³ or less.

(Light absorption coefficient)
The light absorption coefficient of the periodic table group 13 metal nitride semiconductor crystal at a wavelength of 405 nm is usually 5 cm ⁻¹ or less, preferably 3 cm ⁻¹ or less, and usually 0.01 cm ⁻¹ or more, preferably 0.1 cm ^−1. That's it.
The light absorption coefficient of the periodic table group 13 metal nitride semiconductor crystal at a wavelength of 455 nm is usually 3 cm ⁻¹ or less, preferably 2 cm ⁻¹ or less, and usually 0.01 cm ⁻¹ or more, preferably 0.1 cm ^−1. That's it

(Half width of rocking curve of X-ray diffraction peak)
The full width at half maximum of the rocking curve of the (100) diffraction peak of the X-ray diffraction of the Group 13 metal nitride semiconductor crystal of the periodic table is usually 50 arcsec or less, preferably 40 arcsec or less, more preferably 35 arcsec or less, and further preferably 30 arcsec.

(curvature radius)
The curvature radius of the periodic table group 13 metal nitride semiconductor crystal is usually 5 m or more, preferably 7 m or more, more preferably 10 m or more, and usually 100 m or less.

(Stacking fault density)
The stacking fault density of the periodic table group 13 metal nitride semiconductor crystal is usually 10 cm ⁻¹ or less, preferably 5 cm ⁻¹ or less, more preferably 1 cm ⁻¹ or less.
The stacking fault density can be measured by a cathodoluminescence method (SEM-CL method) or can be estimated by a low temperature PL measurement.

  Hereinafter, the present invention will be described more specifically with reference to Examples and Comparative Examples, but can be appropriately changed without departing from the gist of the present invention. Accordingly, the scope of the present invention should not be construed as being limited by the specific examples shown below.

<Example 1>
[Preparation of base substrate]
In this example, a nitride crystal was grown using a reactor as shown in FIG.
(1) Using the nickel-based alloy autoclave 1 as a pressure vessel, Pt-Ir capsules 20 were used as reaction vessels to perform crystal growth for obtaining a base substrate.
Polycrystalline GaN particles were placed in the capsule lower region (raw material dissolution region 9) as the raw material 8, and high-purity NH ₄ F was charged into the capsule as a mineralizer. Further, a platinum baffle plate 5 was installed between the lower raw material dissolution region 9 and the upper crystal growth region 6. A C-plane substrate having a diameter of 50 mm obtained by the HVPE method was suspended as a seed crystal 7 using a platinum wire and a seed support frame, and was placed in the crystal growth region 6 above the capsule. A part of the CMP-finished region was exposed on the main surface (-C plane) surface of the seed crystal 7, and the crystal was grown so that the M-plane was expanded by lateral growth.
(2) After a cap made of Pt—Ir was connected to the upper part of the capsule 20 by welding, the lower part of the capsule was cooled with liquid nitrogen, and the valve was opened and filled with HI without touching the outside air. The capsule was then connected to an NH ₃ gas line and filled with NH ₃ without touching the outside air. Based on the flow rate control, NH ₃ was filled as a liquid corresponding to about 55% of the effective volume of the capsule (in terms of NH ₃ density at −33 ° C.), and then the valve was closed again. Thereafter, the tube at the top of the cap was sealed with a welder. Note that the concentration of F introduced into the capsule is 0 with respect to NH ₃ .
. 5 mol% and I concentration were 2.0 mol%.
(3) The capsule was inserted into the autoclave and the autoclave was sealed.
(4) Open the valve, vacuum deaerate, cool the autoclave 1 with dry ice methanol solvent while maintaining the vacuum state, and fill the autoclave 1 with NH ₃ through the NH ₃ cylinder 12 without touching the outside air did. The NH ₃ effective volume of the autoclave 1 - after (converted at NH ₃ density of -33 ° C.) filling the corresponding liquid to approximately 56% of (autoclave volume filling volume), closed valve 10 again.
(5) The autoclave 1 was stored in an electric furnace composed of a plurality of heaters. The temperature was raised while controlling the autoclave outer surface temperature so that the average temperature inside the autoclave was 600 ° C. and the internal temperature difference was 20 ° C. After reaching the set temperature, the temperature was maintained for 30 days. The pressure in the autoclave was 215 MPa. Further, the variation in the control temperature of the outer surface of the autoclave during the holding was ± 0.3 ° C. or less.
(6) While the autoclave 1 was cooled, the valve 10 attached to the autoclave was opened, and NH ₃ in the autoclave was removed. At this time, the capsule was divided using the pressure difference between the autoclave and the capsule, and NH ₃ filled in the capsule was also removed.
(7) The autoclave 1 was weighed to confirm the discharge of NH ₃ , the autoclave lid was opened, the capsule 20 was taken out, and the crystals inside were taken out. A gallium nitride crystal was grown on the seed crystal, and the c-axis thickness was 7 mm.
From the gallium nitride crystal, a plurality of gallium nitride wafers having the M surface as the main surface along the C axis could be cut out. The wafer was etched on the front and back sides and four side surfaces of the M main surface to remove damage, and the front and back surfaces of the M main surface were mirror-polished. The obtained double-side polished crystal was subjected to X-ray diffraction measurement, and it was confirmed that the crystal system was hexagonal and cubic GaN was not contained. Subsequently, other physical properties were analyzed and evaluated. The results are listed in Table 1.

[Growth process for homo-growth on the main surface of the underlying substrate]
A wafer having a long side of 35 mm × short side of 7 mm and a thickness of 330 μm, which is prepared as described above, is a base substrate. The mineralizer is an F concentration of 0.5 mol%, an I concentration of 1.5 mol%, and the number of growing days. Was 20 days. The base substrate was subjected to CMP finishing on the entire main surface (M surface) in order to perform homo-growth in the M surface direction. Other than that, crystal growth was performed in the same manner as in [Preparation of base substrate] described above.
When the extracted crystal was observed, a gallium nitride crystal having an M plane as a main surface was grown, and the size was c-axis 10 mm × a-axis 40 mm × m-axis 6 mm.
Subsequently, a plurality of the obtained gallium nitride crystals were cut out as the M main surface, the front and back surfaces and the four side surfaces of the M main surface were etched to remove damage, and the front and back surfaces of the M main surface were mirror-polished. The obtained double-side polished crystal was subjected to X-ray diffraction measurement, and it was confirmed that the crystal system was hexagonal and cubic GaN was not contained. Subsequently, other physical properties were analyzed and evaluated. The results are listed in Table 2. An M-plane crystal free from stacking faults was obtained.

<Example 2>
[Growth process for homo-growth on the main surface of the underlying substrate]
Example 1 except that the M-plane substrate obtained in “Step of homo-growing on the main surface of the base substrate” was used as the base substrate, and the mineralizer was made an F concentration of 0.5 mol% and an I concentration of 1.5 mol%. Crystal growth was performed in the same manner as in [Preparation of base substrate] described above.
When the extracted crystal was observed, a gallium nitride crystal having an M plane as a main surface was grown, and the size was c-axis 10 mm × a-axis 40 mm × m-axis 6 mm.
Subsequently, the obtained gallium nitride crystal was mirror-polished in the same manner as in Example 1 on both sides of the M main surface. The obtained double-side polished crystal was subjected to X-ray diffraction measurement, and it was confirmed that the crystal system was hexagonal and cubic GaN was not contained. Subsequently, other physical properties were analyzed and evaluated. The results are listed in Table 2. An M-plane crystal free from stacking faults was obtained.

<Example 3>
[Growth process for homo-growth on the main surface of the underlying substrate]
A single crystal GaN having a long side of 17 mm × a short side of 8 mm and a thickness of 330 μm obtained in Example 1 “Process for Homo Growth on the Main Surface of the Base Substrate” was prepared as a base substrate. The main surface of the base substrate is a surface having an off angle of −2 ° in the [0001] direction and 0 ° in the [-12-10] direction from the (10-10) plane.
Using the HVPE apparatus as shown in FIG. 2, the prepared single crystal GaN base substrate was placed on the susceptor 108 (substrate holder 110), the temperature of the reaction chamber was raised to 850 ° C., and held for 15 minutes. Thereafter, GaCl which is a Group 13 metal raw material and NH ₃ which is a nitrogen raw material are supplied from the main surface direction, and the temperature is raised to a growth temperature of 950 ° C. (temperature increase rate: 21 ° C./min). After reaching, GaN was grown for 30 hours. In this growth process, the growth pressure is 1.01 × 10 ⁵ Pa, the partial pressure of GaCl gas is 3.54 × 10 ² Pa, the partial pressure of NH ₃ gas is 1.13 × 10 ⁴ Pa, The ratio of inert gas (N ₂ ) in the gas flow rate was 48% by volume. After the growth process was completed, the temperature was lowered to room temperature to obtain a GaN crystal.

The film thickness in the m-axis direction of the obtained GaN single crystal was about 0.8 mm.
The dislocation density of the obtained GaN crystal was evaluated by cathodoluminescence (CL) observation in a 3 kV, 100 pA, 1000-fold field in an as-grown state. It was 9.4 * 10 ^{< 5} > cm ^<-2 > when the dislocation within a crystal | crystallization was computed from the dark spot density by CL observation.
Next, the stacking fault density of the obtained GaN bulk crystal was evaluated by low-temperature cathodoluminescence (LTCL) observation in an as-grown state at 5 kV, 500 pA, and 200-fold field of view. The horizontal line existing in the direction parallel to the C-plane of the LTCL observation image is a stacking fault, but was not observed. Subsequently, other physical properties were analyzed and evaluated. The results are listed in Table 2. An M-plane crystal free from stacking faults was obtained.

<Comparative Example 1>
[Preparation of base substrate]
A non-doped GaN template having a C-plane principal surface is prepared by growing gallium nitride (GaN) on a sapphire substrate by metal organic chemical deposition (MOCVD), and a Si ₃ N ₄ mask is formed on the template. A C-plane-GaN layer was grown by epitaxial lateral overgrowth through the mask opening to prepare a seed substrate.
Next, the HVPE apparatus as shown in FIG. 2 was used to place the seed substrate on the susceptor 108 so that the C-plane-GaN layer of the seed substrate was exposed on the upper surface. At this time, the distance between the tip of the gas introduction tube 104 and the base substrate was 9 cm. Thereafter, the temperature of the reaction chamber was raised to 1010 ° C. to grow a GaN single crystal. In this growth step, the growth pressure was 1.01 × 10 ⁵ Pa, the partial pressure of GaCl gas was 6.55 × 10 ² Pa, and the partial pressure of NH ₃ gas was 7.58 × 10 ³ Pa. The growth time was 64 hours.
After the growth was completed, the temperature was lowered to room temperature to obtain a GaN single crystal. A GaN single crystal having a thickness of 8.3 mm and a principal surface being a C plane (hereinafter referred to as C plane-GaN single crystal) was obtained on the seed substrate. When the growth rate was calculated from the thickness of the C-plane GaN single crystal and the growth time, it was 130 μm / h.

From the obtained crystal, as the main surface, -2 ° in the [0001] direction from the (10-10) plane,
Slicing was performed so that a surface having an off angle of 0 ° in the [-12-10] direction was obtained to obtain a plurality of small-sized substrates. Among these, a single crystal GaN (self-supporting) having a square of 50 mm long side × 5 mm short side and a thickness of 330 μm was prepared as a base substrate.
The obtained double-side polished crystal was subjected to X-ray diffraction measurement, and it was confirmed that the crystal system was hexagonal and cubic GaN was not contained. Subsequently, other physical properties were analyzed and evaluated. The results are listed in Table 1.

[Growth process for homo-growth on the main surface of the underlying substrate]
The obtained base substrate was placed on the susceptor 108 (substrate holder 110) of the HVPE apparatus as shown in FIG. 2, and the temperature of the reaction chamber was raised to 850 ° C. and held for 15 minutes. Thereafter, GaCl which is a Group 13 metal raw material and NH ₃ which is a nitrogen raw material are supplied from the main surface direction, and the temperature is raised to a growth temperature of 950 ° C. (temperature increase rate: 21 ° C./min). After reaching, GaN was grown for 30 hours. In this growth process, the growth pressure is set to 1.01 × 10 ⁵ Pa, the partial pressure of GaCl gas is set to 3.54 × 10 ² Pa, the partial pressure of NH ₃ gas is set to 1.13 × 10 ⁴ Pa, and the entire gas is supplied. The ratio of inert gas (N ₂ ) in the flow rate was 48% by volume. After the growth process was completed, the temperature was lowered to room temperature to obtain a GaN crystal.

The film thickness in the m-axis direction of the obtained GaN single crystal was about 0.8 mm.
The dislocation density of the obtained GaN crystal was evaluated by cathodoluminescence (CL) observation in a 3 kV, 100 pA, 1000-fold field in an as-grown state. It was 1.5 * 10 ^{< 6} > cm ^<-2> when the dislocation in a crystal | crystallization was computed from the dark spot density by CL observation.
Next, the stacking fault density of the obtained GaN bulk crystal was evaluated by low-temperature cathodoluminescence (LTCL) observation in an as-grown state at 5 kV, 500 pA, and 200-fold field of view.
The horizontal line existing in the direction parallel to the C-plane of the LTCL observation image was a stacking fault, and the stacking fault density was 1.5 × 10 ² cm ⁻¹ .

<Comparative example 2>
[Preparation of base substrate]
From the crystal obtained by the same method as [Preparation of base substrate] in Comparative Example 1, the main surface is 0 ° in the [0001] direction and 0 ° in the [-12-10] direction from the (10-10) plane. Slicing was performed so that the surface had an off angle, and a plurality of small-sized substrates were obtained. Subsequently, the front and back and the four side surfaces of the M main surface were etched to remove damage, and the front and back of the M main surface were mirror-polished. The obtained double-side polished crystal was subjected to X-ray diffraction measurement, and it was confirmed that the crystal system was hexagonal and cubic GaN was not contained. Subsequently, other physical properties were analyzed and evaluated. The results are listed in Table 1.

[Growth process for homo-growth on the main surface of the underlying substrate]
Single-crystal GaN having a long side of 20 mm × short side of 10 mm square and a thickness of 330 μm is used as the base substrate 7 from the base substrate manufactured as described above, and the mineralizer is F concentration 0.2 mol% and I concentration. Crystal growth was performed in the same manner as in [Preparation of base substrate] in Example 1 except that 1.5 mol% and the number of days for growth were set to 9.1 days.
When the extracted crystal was observed, a gallium nitride crystal having an M-plane as a main surface was grown, and the size was c-axis 11 mm × a-axis 20 mm × m-axis 1.8 mm.
Subsequently, a plurality of the obtained gallium nitride crystals were cut out as an m main surface, the front and back surfaces and the four side surfaces of the M main surface were etched to remove damage, and the front and back surfaces of the M main surface were mirror-polished. X-ray diffraction measurement was performed on the obtained double-side polished substrate, and it was confirmed that the crystal system was hexagonal and cubic GaN was not included. Subsequently, other physical properties were analyzed and evaluated. The results are listed in Table 2. The stacking fault density was 1.0 × 10 ² cm ⁻¹ .

<Comparative Example 3>
[Preparation of base substrate]
From the crystal obtained in the [growth step of homo-growing on the main surface of the base substrate] of Comparative Example 1, as the main surface, 0 ° in the [0001] direction from the (10-10) plane, [-12-10] Slicing was performed so that a surface having an off angle of 0 ° in the direction was obtained, thereby obtaining a plurality of small piece substrates. Subsequently, the front and back and the four side surfaces of the M main surface were etched to remove damage, and the front and back of the M main surface were mirror-polished. X-ray diffraction measurement was performed on the obtained double-side polished substrate, and it was confirmed that the crystal system was hexagonal and cubic GaN was not included. Subsequently, other physical properties were analyzed and evaluated. The results are listed in Table 1.

[Growth process for homo-growth on the main surface of the underlying substrate]
A single crystal GaN having a long side of 14 mm × a short side of 10 mm and a single crystal GaN having a thickness of 330 μm is used as the base substrate 7 from the base substrate manufactured as described above, and the mineralizer is F concentration 0.5 mol% and I concentration. Crystal growth was performed in the same manner as in [Preparation of base substrate] in Example 1, except that 1.5 mol% and the number of days for growth were 12 days.
When the extracted crystal was observed, a gallium nitride crystal having an M-plane as a main surface was grown, and the size was c-axis 10 mm × a-axis 14 mm × m-axis 2 mm.
Subsequently, a plurality of the obtained gallium nitride crystals were cut out as the M main surface, the front and back surfaces and the four side surfaces of the M main surface were etched to remove damage, and the front and back surfaces of the m main surface were mirror-polished. The obtained double-side polished crystal was subjected to X-ray diffraction measurement, and it was confirmed that the crystal system was hexagonal and cubic GaN was not contained. Subsequently, other physical properties were analyzed and evaluated. The results are listed in Table 2. The stacking fault density was 1.5 × 10 ² cm ⁻¹ .

<Reference Example 1>
Expansion and contraction Δd / d _ave of the lattice spacing of the M-plane substrate cut out from the M-plane crystal obtained by the same method as in Example 1 (M-plane substrate made by the same method as the base substrate used in Examples 2 and 3) Was 2.0 × 10 ⁻⁶ , and the dislocation density in the M-plane principal surface was 0 to 1 × 10 ³ pieces / cm ² . Note that the lattice spacing (Δd) is measured by measuring the (30-30) plane using XRD, the measurement range is 4 mm in the c-axis direction, the measurement interval is 0.1 mm, and the lattice spacing is calculated from 40 points in total. Expansion (Δd / d _ave ) was calculated. The dislocation density was measured by SEM-CL.

<Reference Example 2>
The expansion and contraction Δd / d _ave of the lattice spacing of the M-plane substrate made by the same method as the base substrate used in Comparative Examples 1 and 2 is 3.0 × 10 ⁻⁵ , and the dislocation density in the M-plane main surface is 1 to 5 ×. 10 ⁶ pieces / cm ² . Note that the lattice spacing (Δd) is measured by measuring the (30-30) plane using XRD, the measurement range is 4 mm in the c-axis direction, the measurement interval is 0.1 mm, and the lattice spacing is calculated from 40 points in total. Expansion (Δd / d _ave ) was calculated. The dislocation density was measured by SEM-CL.

1 Pressure resistant container (autoclave)
2 pressure vessel internal 3 lining 4 lining the inner surface 5 baffle plate 6 crystal growth region 7 seed crystal 8 material 9 Raw material region 10 valve 11 vacuum pump 12 ammonia (NH ₃₎ gas cylinder 13 of nitrogen _{(N 2)} gas cylinder 14 mass flow meters 20 Reaction vessel 21 100 inside reaction vessel Reactor (reaction vessel)
101 to 105 Introduction pipe 106 Reservoir 107 Heater 108 Susceptor 109 Exhaust pipe 110 Substrate holder

Claims (9)

A periodic table group 13 metal nitride semiconductor including a growth step of growing a periodic table group 13 metal nitride semiconductor crystal on a periodic table group 13 metal nitride semiconductor base substrate having a nonpolar plane or a semipolar plane as a main surface A method for producing a semiconductor crystal comprising:
The periodic substrate group 13 metal nitride semiconductor crystal, wherein the base substrate is a periodic table group 13 metal nitride semiconductor crystal obtained by crystal growth in the presence of a solvent in a supercritical state and / or a subcritical state. Of manufacturing a semiconductor crystal. 2. The method for producing a periodic table group 13 metal nitride semiconductor crystal according to claim 1, wherein the base substrate is a crystal satisfying at least one of the following conditions (a) to (d).
(A) The hydrogen concentration is 1.0 × 10 ¹⁷ atoms · cm ⁻³ or more.
(B) Oxygen concentration is 1.0 * 10 < ¹⁷ > -1.0 * 10 < ²⁰ > atoms * cm < ^-3 >.
(C) Alkali metal concentration is 1.0 × 10 ¹⁷ atoms · cm ⁻³ or less.
(D) Carrier concentration is 1.0 * 10 < ¹⁷ > -1.0 * 10 < ¹⁹ > cm < ^-3 >. The manufacturing method of the periodic table group 13 metal nitride semiconductor crystal of Claim 1 or 2 whose said base substrate is a crystal | crystallization which has an infrared absorption peak in 3100-3200cm < ^-1 >. The production of the periodic table group 13 metal nitride semiconductor crystal according to any one of claims 1 to 3, wherein the base substrate is a crystal having a light absorption coefficient of 1.0 to 30 cm ^{-1 at} a wavelength of 405 nm. Method. The production of the periodic table group 13 metal nitride semiconductor crystal according to any one of claims 1 to 4, wherein the base substrate is a crystal having a light absorption coefficient of 0.5 to 5 cm ^{-1 at} a wavelength of 445 nm. Method. 6. The periodic table group 13 metal nitride semiconductor according to claim 1, wherein the base substrate is a crystal having a basal plane dislocation density of 1.0 × 10 ⁵ cm ⁻² or less on a main surface. Crystal production method. The method for producing a periodic table group 13 metal nitride semiconductor crystal according to claim ¹ , wherein the base substrate is a crystal having a stacking fault density of 10 cm ⁻¹ or less. The periodic table group 13 metal nitride semiconductor crystal according to any one of claims 1 to 7, wherein the growth step is a step of growing a periodic table group 13 metal nitride semiconductor crystal by a vapor phase growth method. Manufacturing method. A periodic table group 13 metal nitride semiconductor crystal produced by the method for producing a periodic table group 13 metal nitride semiconductor crystal according to any one of claims 1 to 8.