JP2013203653A - Method for producing group iii nitride crystal, group iii nitride crystal, and group iii nitride crystal substrate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing a high-quality group III nitride crystal which has small warpage and is prevented from cracking.SOLUTION: A group III nitride seed substrate is obtained by heat-treating a single crystal made of a group III nitride crystal at 1,000°C or higher, and a group III nitride crystal film is formed on the group III nitride seed substrate to obtain a group III nitride crystal.

Description

  The present invention relates to a method for producing a high-quality group III nitride crystal with small warpage. The present invention also relates to a group III nitride crystal and a group III nitride crystal substrate manufactured by the manufacturing method.

  Group III nitride crystals are variously used as substrates for light-emitting elements such as light-emitting diodes (LEDs) and semiconductor lasers (LDs). Among these, GaN crystals are useful as substrates for blue light emitting devices such as blue light emitting diodes and blue semiconductor lasers, and active research has been conducted.

  Such a group III nitride crystal such as a GaN crystal can be obtained by crystal growth on a substrate such as sapphire by a vapor phase method or the like. However, when a group III nitride crystal is grown on the substrate, the difference in lattice constant from the substrate at the growth temperature becomes significant or distortion due to stress distribution occurs, resulting in crystal warping. There is a problem. In particular, it is known that when a group III nitride crystal grown on a dissimilar substrate such as sapphire is separated from the dissimilar substrate, warping is remarkably recognized.

Such warpage is caused by the distribution of threading dislocations in the crystal. The threading dislocations are generated at a density of 10 ¹¹ cm ⁻² at the interface between the substrate and the GaN layer. ^It decreases to ⁸ cm ^{-2, and when} it grows several hundred μm, it decreases to 10 ⁷ cm ^-2 or less, and it is pointed out that the difference in dislocation density between the crystal growth surface side and the substrate side particularly affects the warpage. (See Patent Document 1). In order to reduce such warpage, it has been shown that it is effective to remove crystals on the substrate side containing many threading dislocations or to perform heat treatment at a high temperature. Patent Document 1 describes that as a high-temperature heat treatment, a group III nitride crystal having a thickness of 150 μm is heat-treated at 1200 ° C. for 24 hours, heat-treated at 1400 ° C. for 10 minutes, or heat-treated at 1600 ° C. for 2 hours. Has been.

JP 2003-277195 A

Patent Document 1 proposes a method for reducing the warpage of a relatively thin group III nitride crystal by focusing on threading dislocations. Usually, a GaN crystal or the like is grown to a thickness of 1 mm to 2 cm in the c-axis direction. Then, the threading dislocations do not disappear rapidly as in the early stage of growth, and the threading dislocation density settles to a value of 1 × 10 ⁷ pieces / cm ² or less. However, as a result of investigations by the present inventors, it has been found that even if the threading dislocation density is attenuated, the problem of warping still cannot be solved. In general, when a group III nitride crystal is grown to a thickness of more than 1 mm, there is a problem that small cracks are likely to occur on the surface. As a result of investigations by the present inventors, it has been clarified that such a problem is related to crystal warpage. Therefore, in order to deal with such a problem, for example, adjustments such as adjusting the growth temperature of the crystal or adjusting the growth rate were tried. The problem was not solved sufficiently. Further, even when high-temperature heat treatment was performed under the conditions described in Patent Document 1, the warp of the group III nitride crystal could not be sufficiently reduced.
In view of such problems of the prior art, the present inventors have intensively studied with the object of providing a new method for producing a high-quality group III nitride crystal with small warpage and suppressed cracks. Piled up.

As a result of repeated studies by the present inventors, it has been found that the warpage of a crystal having a thickness of more than 1 mm is caused by basal plane dislocations existing in the crystal. The basal plane dislocation referred to in the present invention is different from threading dislocation as described in Patent Document 1. The threading dislocation is equivalent to about 10 ⁹ / cm ² in the GaN crystal generated along the crystal growth direction because the lattice constant is greatly different when a GaN crystal is vapor-phase grown on a heterogeneous substrate such as a sapphire substrate. This is a dislocation that propagates in the c-axis direction. On the other hand, the basal plane dislocation as referred to in the present invention is a dislocation introduced when a slip occurs on the bottom surface due to stress induction, and the propagation direction is parallel to the basal plane. (See Koji Maeda, Kunio Suzuki, Masaki Ichihara, Satoshi Nishiguchi, Kana Ono, Yutaka Mera and Shin Takeuchi, Physica B; Condensed Matter, Volumes 273-274, 1999, Pages 134-139). The inventors of the present invention have grasped a form that is transmitted while drawing an arc on the basal plane by SEM-CL observation and transmission electron microscope observation. Note that the basal plane is, for example, a (0001) plane in the case of a GaN crystal.

  Since basal plane dislocations were not described at all in Patent Document 1, the present inventors conducted extensive studies on a method for reducing warpage from a viewpoint not suggested in Patent Document 1. As a result, the present inventors have achieved a group III nitride crystal with reduced basal plane dislocations, and lowering the absolute value of the basal plane dislocation of the crystal as in the group III nitride crystal, It was found that it is extremely important to solve the problem of warpage reduction. Specifically, if a group III nitride crystal is heat-treated under specific conditions, it becomes possible to control the dislocation of the group III nitride crystal to a preferable state, thereby reducing the residual stress of the entire crystal. It has led to breakthrough results. Many basal plane dislocations remain in the crystal after heat treatment, but if the crystal is used as a seed substrate for homoepitaxial growth, introduction of new basal plane dislocations into the regrown crystal is dramatically reduced. It also led to breakthrough results. The present invention has been made based on these findings, and the contents thereof are as shown below.

[1] A step of obtaining a group III nitride seed substrate by subjecting a single crystal composed of a group III nitride crystal to heat treatment at 1000 ° C. or higher;
Forming a group III nitride crystal film on the group III nitride seed substrate to obtain a group III nitride crystal;
And a method for producing a group III nitride crystal.
[2] The method for producing a group III nitride crystal according to [1], wherein a group III nitride crystal film having a thickness of 500 μm or more is formed on the group III nitride seed substrate.
[3] The method for producing a group III nitride crystal according to [1], wherein a group III nitride crystal film having a thickness of more than 1 mm is formed on the group III nitride seed substrate.
[4] The III according to any one of [1] to [3], wherein a standard deviation of a phase difference by a photoelastic method within a diameter of 50 mm from a center of the group III nitride seed substrate is less than 0.1 nm. A method for producing a group nitride crystal.
[5] The group III nitride crystal according to any one of [1] to [4], wherein a basal plane dislocation density of the group III nitride seed substrate is 1 × 10 ⁶ to 1 × 10 ⁹ pieces / cm ^2. Manufacturing method.
[6] The method for producing a group III nitride crystal according to any one of [1] to [5], wherein a β-type basal plane dislocation in the basal plane dislocation of the group III nitride seed substrate exceeds 50%. .
[7] The group III nitride crystal film formed on the group III nitride seed substrate has a basal plane dislocation density in the range of 1 × 10 ³ to 1 × 10 ⁶ pieces / cm ² [1] to [ [6] The method for producing a Group III nitride crystal according to any one of [6].
[8] The group III according to any one of [1] to [7], further including a step of removing at least a part of a seed substrate of the group III nitride crystal obtained after the group III nitride crystal film is formed. A method for producing a nitride crystal.
[9] The method for producing a group III nitride crystal according to [8], wherein the group III nitride crystal film obtained after the removal has a basal plane dislocation density of 1 × 10 ³ to 1 × 10 ⁶ pieces / cm ² .
[10] Any one of [1] to [9], further including a step of obtaining a group III nitride free-standing crystal by removing a seed substrate of the group III nitride crystal obtained after the group III nitride crystal film is formed. A method for producing a group III nitride crystal according to item.
[11] The method for producing a group III nitride crystal according to [10], wherein the thickness of the group III nitride free-standing crystal is more than 1 mm.
[12] A group III nitride crystal produced by the production method according to any one of [1] to [11].
[13] A group III nitride crystal substrate comprising the group III nitride crystal according to [12].

  According to the production method of the present invention, a group III nitride crystal film having a reduced basal plane dislocation density can be formed, and as a result, a group III nitride crystal with small warpage can be produced. In the manufacturing method of the present invention, the group III nitride crystal film obtained by regrowth is obtained by regrowth of the group III nitride crystal film on the same group III nitride seed substrate having the same crystal structure with reduced residual stress. The film has excellent crystal quality because surface cracks are suppressed and the basal plane dislocation density is low. These excellent effects of the present invention can be obtained by an extremely simple method of heat treatment under specific conditions.

It is sectional drawing which shows an example of a crystal manufacturing apparatus. It is sectional drawing which shows an example of the heat processing apparatus. It is the side view (a) and top view (b) explaining the aspect which cut | disconnects the crystal sample fixed on the base with a wire. It is a side view explaining the aspect which cut | disconnects a crystal sample, rocking a wire. 3 is a photoelastic test result of the seed substrate of Example 1. FIG. 3 is a photoelastic test result of a seed substrate of Comparative Example 1. FIG.

  Hereinafter, the contents of the present invention will be described in detail. The description of the constituent elements described below may be made based on typical embodiments and specific examples of the present invention, but the present invention is not limited to such embodiments and specific examples. For example, a GaN crystal may be described as a representative example of a group III nitride crystal, but the present invention is not limited to the GaN crystal and the manufacturing method thereof. In the present specification, a numerical range represented by using “to” means a range including numerical values described before and after “to” as a lower limit value and an upper limit value.

In the present specification, the “C plane” or “basal plane” is a plane equivalent to the {0001} plane in a hexagonal crystal structure (wurtzite type crystal structure). In a group III nitride crystal, the + C plane is a group III plane, and in gallium nitride, it corresponds to a Ga plane.
In this specification, the “M plane” means a {1-100} plane, {01-10} plane, {1-100} plane, {−1100} plane, {0-110} plane, or {10 -10} planes, which are comprehensively expressed as (1-100) plane, (01-10) plane, (-1010) plane, (-1100) plane, (0-110) Plane, and (10-10) plane. Further, in this specification, the “A plane” means {2-1-10} plane, {-12-10} plane, {-1-120} plane, {-2110} plane, {1-210} plane. Or a plane that is comprehensively represented as a {11-20} plane, specifically, a (2-1-10) plane, a (-12-10) plane, a (-1-120) plane, (- 2110) plane, (1-210) plane, and (11-20) plane.

[Production Method of Group III Nitride Crystal]
(Basic configuration)
The method for producing a group III nitride crystal of the present invention includes the following steps (1) and (2). The manufacturing method of the present invention includes the step of performing the heat treatment step (1) and then performing the processing step (2) at least once, and includes the steps (1) and (2). May be repeated. Moreover, the manufacturing method of this invention includes processes other than (1) and (2) before the process of (1), between the processes of (1) and (2), and after the process of (2). It may be.
(1) A first step of obtaining a group III nitride seed substrate by subjecting a single crystal composed of a group III nitride crystal to heat treatment at 1000 ° C. or higher.
(2) A second step of obtaining a group III nitride crystal by forming a group III nitride crystal film on the group III nitride seed substrate.

(Heat treatment)
In the first step of the production method of the present invention, a single crystal composed of a group III nitride crystal is heat-treated at 1000 ° C. or higher. Preferably, the heat treatment is performed at a temperature equal to or higher than the temperature at which the single crystal is grown. Specifically, the heat treatment temperature is preferably 1100 ° C. or higher, more preferably 1200 ° C. or higher. More preferably, the temperature is higher than or equal to ° C. Further, the temperature of the heat treatment is preferably 2200 ° C. or less, more preferably 1700 ° C. or less, and further preferably 1500 ° C. or less. According to the present invention, by performing the heat treatment at 1000 ° C. or higher, the basal plane dislocations dispersed and present in the single crystal move, and the basal plane dislocations are locally concentrated. As a result, a group III nitride seed substrate with reduced residual stress can be obtained, and in the subsequent second step, basal plane dislocations are not propagated from the seed substrate or new basal plane dislocations are not generated. It becomes possible to form a group III nitride crystal film, and it is possible to grow a group III nitride crystal film having small warpage and excellent quality.

The heat treatment at 1000 ° C. or higher may be performed only once or a plurality of times in the production method of the present invention. In the case of performing a plurality of times, it means that the heat treatment is once performed at 1000 ° C. or more, then the temperature is lowered to 1000 or less, the temperature is again raised to 1000 ° C. or more, and the heat treatment is performed once or more. The total time for heat treatment at 1000 ° C. or more is preferably 0.5 hours or more, more preferably 3 hours or more, and further preferably 6 hours or more. In addition, the total time for heat treatment at 1000 ° C. or higher is preferably within 10,000 hours, more preferably within 100 hours, and even more preferably within 10 hours.
For example, when a heat treatment temperature in the range of 1275 to 1375 ° C. is employed, the heat treatment is preferably 0.25 to 24 hours, and more preferably 1.0 to 10 hours. Moreover, when employ | adopting the heat processing temperature within the range of 1150-1250 degreeC, it is preferable to heat-process for 1.0 to 200 hours, and it is more preferable to heat-process for 24 to 100 hours.

While the heat treatment is performed at a temperature of 1000 ° C. or higher, the temperature may be kept constant, or may be changed within a range of 1000 ° C. or higher depending on time. Usually, it is preferable from the viewpoint of energy efficiency that the temperature is raised to a specific temperature, held at the specific temperature for a certain period of time, and then lowered to 1000 ° C. or lower. The speed at which the temperature is raised to a specific temperature is not particularly limited, but is usually preferably 10 ° C./hour or more, and more preferably 100 ° C./hour or more.
In the first step of the production method of the present invention, the heat treatment is performed under such conditions that a film is formed on the surface of the group III nitride crystal by performing heat treatment on the group III nitride crystal single crystal. It is preferable to carry out. It is preferable that a film made of a compound containing a group III element is formed on the single crystal by heat treatment. Such a film can be easily obtained by performing an XRD analysis or analyzing a cleaning solution after washing with nitric acid. Can be confirmed. The type of the film made of a compound containing a group III element is not particularly limited as long as it contains a group III element. For example, a group III metal, a group III oxide, a group III hydroxide, an oxyhydroxide, etc. can be mentioned, and a mixture thereof may also be used. Specifically, when the group III element is Ga, gallium metal, gallium oxide, and gallium oxyhydroxide can be exemplified. After carrying out the first step of the present invention, a film containing gallium metal, gallium oxide and gallium oxyhydroxide is usually formed and the outermost surface becomes black, so that the film formation can be confirmed visually. .
A film made of a compound containing a group III element may be formed directly on a single crystal made of a group III nitride crystal, or after forming another layer as an intermediate layer on the single crystal, Although it may be formed above, it is preferably formed directly on the single crystal because the effect of the present invention is more remarkable.

(Heat treatment equipment)
The apparatus for performing the heat treatment is not particularly limited as long as it can hold a single crystal composed of a group III nitride crystal and can withstand heat treatment at 1000 ° C. or higher. For example, as shown in FIG. 2, an apparatus is provided in which a single crystal (for example, GaN crystal) 201 made of a group III nitride crystal is installed in an alumina tube 200 and can be heated using a heater 202. It can be illustrated. This apparatus is provided with a gas introduction pipe 203 and a gas discharge pipe 204 so that the gas can be heated while being circulated. Examples of the gas to be circulated include ammonia / nitrogen mixed gas.

(Single crystal consisting of Group III nitride crystal)
The single crystal used in the first step of the present invention is a single crystal composed of a group III nitride crystal. Specifically, gallium nitride, aluminum nitride, indium nitride, or a mixed crystal thereof can be given. For example, a single crystal composed of a group III nitride crystal obtained by growing a group III nitride crystal on a sapphire substrate by a vapor phase method and then removing the sapphire substrate can be used. Not limited. Since the manufacturing method of the present invention can be used for manufacturing a large group III nitride crystal, a large single crystal used in the first step can be used. For example, a single crystal made of a large group III nitride crystal of, for example, 3 inches or more can be used.
The plane orientation of the main surface of the single crystal used in the first step of the present invention is not particularly limited. The main surface here means the surface having the largest area in the crystal, and refers to the surface on which the group III nitride crystal film is grown in the second step. The main surface may be a polar surface, a nonpolar surface, or a semipolar surface. For example, the C surface can be cited as a preferred main surface.

(Seed substrate)
A group III nitride seed substrate can be obtained from the crystal after the heat treatment in the first step. After performing the heat treatment, a process usually performed to obtain a seed substrate can be appropriately performed. For example, a method used for normal seed substrate production is selected and used, such as peripheral processing for processing the heat-treated crystal into a wafer-shaped circle, slicing for adjusting the wafer thickness, and chemical polishing for adjusting the surface state. Thus, a group III nitride seed substrate can be obtained. Examples of the outer shape processing include dicing, outer periphery polishing, and a method of cutting with a wire. In addition, the process for obtaining these seed substrates may be performed before the heat treatment, and the seed substrate may be obtained by performing a heat treatment after making the substrate state.
The obtained group III nitride seed substrate has a feature that the residual stress is smaller than that of the seed substrate manufactured without performing the heat treatment in the first step.
As a result of detailed microscopic observation of a conventional single crystal composed of a group III nitride crystal, the present inventors are dotted with regions having a dislocation density as high as 1 × 10 ⁸ cm ^{−2 on} the outer periphery of the crystal. Was confirmed. It was also confirmed that dislocations of the same kind were widely distributed although the density was as low as 10 ⁶ cm ⁻² to 10 ⁷ cm ⁻² up to the crystal center. As described above, the present inventors have found that the basal plane dislocations locally concentrated on the outer peripheral portion leads to weakening of the outer peripheral portion, and are uniformly dispersed in the central portion with respect to the local concentration of the outer peripheral portion. It has been found that this state contributes to the residual stress distributed throughout the crystal. Then, the distribution of basal plane dislocations can be controlled by heat treatment, thereby succeeding in reducing the residual stress in the crystal.
Specifically, when a single crystal composed of a group III nitride crystal is heat-treated at 1000 ° C. or higher according to the manufacturing method of the present invention, basal plane dislocations (isolated dislocations) isolated in the center are accumulated in the same plane. Succeeded in doing. As a result, a large number of basal plane dislocation aggregates in which basal plane dislocations are arranged at intervals of 50 nm to 500 nm are observed at the center of the crystal. For example, it is possible to increase the number of basal plane dislocation aggregates in the center by 2 to 10 times by heat-treating a group III nitride crystal such as a GaN crystal according to the production method of the present invention. By accumulating dislocations in the basal plane dislocation aggregate in the center of the crystal in this way, the number of isolated dislocations is reduced in other regions. Specifically, the dislocation accumulation degree (A / B) represented by the ratio of the number density (A) of basal plane dislocation aggregates observed in the M plane and the number density (B) of isolated dislocations is preferably 1%. Or more, more preferably 2% or more, and further preferably 3% or more. As a result, the residual stress existing over the entire crystal is reduced, and it is difficult for relatively large cracks to be generated due to damage such as small cracks generated in the outer peripheral portion having low brittleness. Such accumulation of basal plane dislocations is considered to be the result of the basal plane dislocations exhibiting the most stable arrangement in the form of assisting the driving force that reduces the residual stress inside the crystal.
For this reason, if the seed substrate obtained in the first step is used, a group III nitride crystal film having excellent properties in the second step to be performed next can be grown. Hereinafter, the residual stress, the basal plane dislocation density, and the α and β dislocations of the basal plane dislocation will be described in order.

(Residual stress)
The group III nitride seed substrate obtained by performing the heat treatment in the first step has a small residual stress. Specifically, as described above, the basal plane dislocations are locally concentrated and the group III nitride seed substrate is relieved of internal stress. The internal stress (residual stress) remaining in the crystal can be grasped by the residual strain, and the residual strain can be measured by, for example, a phase difference by a photoelastic method. Measurement of the residual strain amount by the photoelastic method is performed using the following relational expression (see APPL. Phys. Lett. 47 (1985) pp. 365-367). Residual strain amount, the absolute value of the difference between the strain S _r and tangential strain S _t in the radial direction of the crystal | S _r -S _t | a but, because it takes the value is a function of the phase difference [delta], crystalline The residual strain distribution can be relatively grasped by the phase difference δ distribution.

(Λ is the wavelength of light used for measurement, d is the thickness of the substrate used for measurement, n ₀ is the refractive index, δ is the phase difference caused by the birefringence of the sample, φ is the main vibration azimuth, p ₁₁ , p ₁₂ , p ₄₄ represents a photoelastic constant.)

  The group III nitride seed substrate obtained by performing the heat treatment in the first step preferably has a standard deviation of the phase difference δ by the photoelastic method of less than 0.1 nm, for example, within a diameter of 50 mm from the center. More preferably, it is less than 0.09 nm. The center here means the center of a circle when the group III nitride seed substrate is disk-shaped, and the center of gravity when it is non-disk-shaped. If the standard deviation is within the above range, it is preferable because cracks during processing and molding are less likely to occur. As the phase difference distribution, if a portion where the value of the phase difference δ is high or low is localized in the plane of the crystal, the residual strain is also unevenly distributed at a specific portion of the crystal. Therefore, the group III nitride seed substrate used in the present invention preferably has a phase difference uniformly dispersed in the plane.

(Basal plane dislocation density)
The group III nitride seed substrate obtained by performing the heat treatment in the first step preferably has a basal plane dislocation density of 1 × 10 ⁹ pieces / cm ² or less, preferably 1 × 10 ⁷ pieces / cm ² or less. More preferably, the number of particles / cm ² or less. The lower limit is not particularly limited, but is usually about 1 × 10 ³ pieces / cm ² or more. Although the basal plane dislocation moves due to the heat treatment in the first step, the basal plane dislocation density of the entire crystal does not change greatly. In rare cases, α-type basal plane dislocations and β-type basal plane dislocations, which will be described later, move and cancel each other, and dislocations may disappear. It is considered that the basal plane dislocation density in the single crystal composed of the previous group III nitride crystal and the basal plane dislocation density of the group III nitride seed substrate are comparable.

  The basal plane dislocation density in the present invention means a value calculated by the following calculation formula.

(Ρ is the basal plane dislocation density, N is the number of measured basal plane dislocations, A is the cross-sectional area of the portion where the number of basal plane dislocations is measured. | Δρ | is the α-type basal plane dislocation density and the β-type basis. (The absolute value of the difference in the plane dislocation density, ρα represents the α-type basal plane dislocation density, and ρβ represents the β-type basal plane dislocation density.)

The number N of basal plane dislocations is measured by using, for example, a transmission electron microscope method (TEM method), a cathodoluminescence method (SEM-CL method), or a method of observing surface pits by etching with an AFM or an optical microscope. can do. These methods have different observable fields of view. In the TEM method, the dislocation density is mainly 5 × 10 ⁷ cm ⁻² or more, and in the SEM-CL method, the dislocation density is mainly 1 × 10 ⁵ cm ⁻² or more. The method of observing the surface pits by etching with an AFM, an optical microscope or the like is suitable when the dislocation density is mainly 1 × 10 ³ to 1 × 10 ⁶ cm ⁻² . In the present invention, it is particularly preferable to measure using the SEM-CL method. In the observation of the basal plane dislocation using the SEM-CL method, the basal plane dislocation can be confirmed as a dark line when observed from the C plane. When observed from a surface orthogonal to the C surface such as a prism surface, it can be observed as a dark spot. In order to differentiate between dark lines and dark spots, it is desirable to make a determination in view of an aspect ratio obtained from image measurement. The value is preferably 2.0 or less, more preferably 1.5 or less, and particularly preferably 1.2 or less. Based on the determination of the aspect ratio, dark spots observed from the (10-10) plane can be identified as basal plane dislocations, and dark lines can be identified as threading dislocations. Note that observation from a semipolar plane is not appropriate because it is difficult to distinguish dark lines and dark spots. Specific measurement conditions when using the SEM-CL method are also not particularly limited, but the acceleration voltage is usually preferably 3 to 5 kV and particularly preferably 3 kV.

The number N of basal plane dislocations can be measured by the method as described above, but the measured value varies depending on the direction from which the crystal is observed, and the cross-sectional area A is also derived from the surface to be observed. Is the value to be Therefore, the value of the basal plane dislocation density ρ can also vary depending on the direction from which the crystal is observed. Therefore, in the present invention, the group III nitride semiconductor crystal is specified by utilizing the value of the basal plane dislocation density ρ particularly when the {10-10} plane is observed. That is, in the present specification, when simply referred to as “basal plane dislocation density (ρ)”, the number N of basal plane dislocations observed mainly as points when the M plane intersecting the basal plane is observed is measured. It is assumed that this is converted into a value per unit area (cm ² ). Further, the specific value of the cross-sectional area A for calculating the basal plane dislocation density ρ is not particularly limited, but it is usually 100 μm ² or more, preferably 250 μm ² or more, more preferably 10,000 μm ² or more. preferable. Within the above range, the value of the basal plane dislocation density can be calculated with good reproducibility. The cross-sectional area A is preferably a rectangular area close to a rectangle or a square.

  In the present invention, in specifying the group III nitride semiconductor crystal, the number of basal plane dislocations when the {10-10} plane is observed is used. It is preferable to measure after forming the crystal so that it appears on the crystal surface and the basal plane dislocations can be easily observed. Specifically, it is preferable to perform cutting or slicing so that the {10-10} plane appears on the crystal surface, and further polishing the surface by lapping with diamond slurry and chemical mechanical polishing (CMP).

  The basal plane dislocation in the present invention is not particularly limited in the direction and length of the dislocation line as long as it is perpendicular to the c-axis as described above. That is, the basal plane dislocations protruding in one M plane do not necessarily match the total number of all basal plane dislocations. That is, there are three crystallographically equivalent M-planes, and one of the M-planes is observed, so that the basal plane dislocation that propagates parallel to the M-plane and basal plane of this observation plane is observed in principle. Can not. Therefore, the number of basal plane dislocations described by the inventors is not the total number of basal plane dislocations but the basal plane dislocation density divided by an arbitrary observation cross-sectional area.

(Α and β dislocations of basal plane dislocations)
The group III nitride seed substrate obtained by performing the heat treatment in the first step preferably has a β-type basal plane dislocation accounted for more than 50% in the basal plane dislocation. The β-type basal plane dislocation (β-dislocation) in the basal plane dislocation is more preferably more than 50% and 95% or less. According to the study by the present inventors, it has been found that if either α-dislocation or β-dislocation exists as a basal plane dislocation, the warp tends to occur. A crystal having a large warp generally has a high residual stress in general, but the group III nitride seed crystal used in the present invention, as described above, has a residual stress even when it contains a large amount of β-dislocations. Is reduced.

  The definition of α-dislocation and β-dislocation of basal plane dislocations is described in detail in Chapter 6 of “Dislocation Dynamics and Plasticity” by Taira Suzuki. In the group III-V nitride semiconductor crystal, there are two types of basal plane dislocations reflecting the polarity of the crystal. They are called α-dislocation and β-dislocation, respectively, depending on whether the atoms on the excess atomic face of the edge-shaped basal plane dislocation are group III atoms or group V atoms. Furthermore, in the basal plane dislocation of the blade type, the sign of distortion becomes asymmetric in the sliding direction and the vertical direction. In the case of wurtzite type crystals, the edge-type basal plane dislocations also have a distinction between α-dislocations and β-dislocations, and there are two possibilities: glide set and shuffle set. If the dislocation is a glide set, the types of atoms at the end of the excess atomic plane of the defined α-dislocation and β-dislocation are inverted. However, when the basal plane dislocation bargas vectors are the same, the strain distribution in the vertical direction is the same as the sliding direction parallel to the basal plane, regardless of whether the shuffle set or the glide set is used.

  That is, if the strain distribution of the basal plane dislocation is measured, α and β of the basal plane dislocation can be identified. That is, when the distance between the M plane and the A plane is widened in the −c axis direction with respect to the basal plane dislocation core, and the distance between the M plane and the A plane is narrowed in the + c density direction, it is an α dislocation. The β-dislocation is reversed from the strain polarity of the α-dislocation. In order to discriminate between α and β as described above, in the present invention, it is particularly preferable to perform analysis using a transmission electron microscope (TEM). Specific measurement conditions in the case of using the TEM method are not particularly limited, but the measurement is preferably performed with a general-purpose TEM having an acceleration voltage of usually 100 kV to 300 kV, and particularly preferably measured with an ultrahigh acceleration voltage exceeding 500 kV. The optimum thickness for the thinning process of the sample for such observation is preferably 3 nm or more, more preferably 10 nm or more, and more preferably 50 nm or more. The upper limit of the thinning process is not particularly clear, but is preferably 2.0 μm or less, more preferably 1.7 μm or less, and even more preferably 1.2 μm or less. The measurement area with TEM is preferably 10 μm × 10 μm or more, preferably 50 μm × 50 μm or more, and more preferably 100 μm × 500 μm or more.

(Growth of group III nitride crystal film)
In the manufacturing method of the present invention, the second step of forming a group III nitride crystal film on the group III nitride seed substrate produced in the first step is performed. As a method for growing a group III nitride crystal film in the present invention, for example, a vapor phase method such as a hydride vapor phase epitaxy (HVPE) method, a metal organic chemical vapor deposition (MOCVD) method, or a sublimation method may be employed. The HVPE method can be preferably used. In the following, as an example of a preferable manufacturing apparatus, an HVPE manufacturing apparatus will be described with reference to FIG.

1) Basic Structure The manufacturing apparatus of FIG. 1 includes a susceptor 108 on which a seed substrate 110 is placed and a reservoir 106 into which a raw material of a group III nitride crystal film to be grown is placed. In addition, introduction pipes 101 to 104 for introducing gas into the reactor 100 and an exhaust pipe 109 for exhausting are installed. Further, a heater 107 for heating the reactor 100 from the side surface is installed.

2) Reactor material, gas type of ambient gas As the material of the reactor 100, quartz, sintered boron nitride, stainless steel, or the like is used. A preferred material is quartz. The reactor 100 is filled with atmospheric gas in advance before starting the reaction. Examples of the atmospheric gas (carrier gas) include inert gases such as hydrogen, nitrogen, He, Ne, and Ar. These gases may be mixed and used.

3) Material and shape of susceptor, distance from growth surface to susceptor The material of the susceptor 108 is preferably carbon, and more preferably the surface is coated with SiC. The shape of the susceptor 108 is not particularly limited as long as the seed substrate used in the present invention can be placed, but it is preferable that no structure exists near the crystal growth surface when the crystal is grown. If there is a structure that can grow in the vicinity of the crystal growth surface, a polycrystal adheres to the structure, and HCl gas is generated as a product to adversely affect the crystal to be grown. The contact surface between the seed substrate 110 and the susceptor 108 is preferably separated from the main surface (crystal growth surface) of the seed substrate by 1 mm or more, more preferably 3 mm or more, and further preferably 5 mm or more. .

4) Reservoir The reservoir 106 is charged with the raw material of the group III nitride semiconductor to be grown. Specifically, the raw material which becomes a group III source is put. Examples of the raw material to be a group III source include Ga, Al, and In. A gas that reacts with the raw material put in the reservoir 106 is supplied from an introduction pipe 103 for introducing the gas into the reservoir 106. For example, when a raw material that is a group III source is put in the reservoir 106, HCl gas can be supplied from the introduction pipe 103. At this time, the carrier gas may be supplied from the introduction pipe 103 together with the HCl gas. Examples of the carrier gas include hydrogen, nitrogen, an inert gas such as He, Ne, and Ar. These gases may be mixed and used.

5) Nitrogen source (ammonia), separate gas, dopant gas From the introduction pipe 104, a raw material gas serving as a nitrogen source is supplied. Usually, NH ₃ is supplied. A carrier gas is supplied from the introduction pipe 101. As the carrier gas, the same carrier gas supplied from the introduction pipe 103 can be exemplified. This carrier gas also has an effect of suppressing the reaction in the gas phase between the source gases and preventing the polycrystal from adhering to the nozzle tip. A dopant gas can also be supplied from the introduction pipe 102. For example, an n-type dopant gas such as SiH ₄ , SiH ₂ Cl ₂ , or H ₂ S can be supplied.

6) Gas introduction method The gases supplied from the introduction pipes 101 to 104 may be exchanged with each other and supplied from another introduction pipe. In addition, the source gas and the carrier gas serving as a nitrogen source may be mixed and supplied from the same introduction pipe. Further, a carrier gas may be mixed from another introduction pipe. These supply modes can be appropriately determined according to the size and shape of the reactor 100, the reactivity of the raw materials, the target crystal growth rate, and the like.

7) Location of Exhaust Pipe The gas exhaust pipe 109 can be installed on the top, bottom, and side surfaces of the reactor inner wall. From the viewpoint of dust removal, it is preferably located below the crystal growth end, and more preferably a gas exhaust pipe 109 is installed on the bottom of the reactor as shown in FIG.

8) Crystal Growth Conditions Crystal growth using the above production apparatus is preferably performed at 950 ° C. or higher, more preferably at 970 ° C. or higher, and further preferably at 980 ° C. or higher. Moreover, it is preferable to carry out at 1120 degrees C or less, It is more preferable to carry out at 1100 degrees C or less, It is further more preferable to carry out at 1090 degrees C or less. The temperature drop during crystal growth is preferably controlled within 60 ° C, more preferably controlled within 40 ° C, and even more preferably controlled within 20 ° C. The pressure in the reactor is preferably 10 kPa or more, more preferably 30 kPa or more, and further preferably 50 kPa or more. Moreover, it is preferable to set it as 200 kPa or less, It is more preferable to set it as 150 kPa or less, It is further more preferable to set it as 120 kPa or less.

(Crystal processing)
By processing the crystal produced by the production method of the present invention, a group III nitride crystal substrate or the like can be produced. In order to obtain a group III nitride crystal substrate having a desired shape, it is preferable to appropriately perform slicing, outer shape processing, surface polishing and the like on the obtained group III nitride crystal. Any one of these methods may be selected and used, or may be used in combination. When used in combination, for example, slicing, contour processing, and surface polishing can be performed in this order. If it demonstrates in detail about each process, a slice can be performed by cut | disconnecting with a wire, for example. Examples of surface polishing include a method of polishing the surface using abrasive grains such as diamond abrasive grains, CMP (chemical mechanical polishing), damage layer etching by RIE after mechanical polishing, and the like. By appropriately combining these methods, for example, a base substrate, a nonpolar substrate, and a semipolar substrate can be provided at low cost.

[Group III nitride crystals]
(Feature)
The group III nitride crystal produced by the production method of the present invention is characterized by small warpage, suppressed surface cracks, and excellent crystal quality. In particular, in the production method of the present invention, although the crystal is grown on a seed substrate having warpage, the warp of the obtained group III nitride crystal is remarkably suppressed. According to the present invention, it is possible to obtain a crystal having a radius of curvature of 3.0 m or more, preferably it is possible to obtain a crystal of 3.5 m or more, and more preferably a crystal of 4.0 m or more. It is also possible. Further, the surface crack is remarkably reduced as compared with the group III nitride crystal produced by crystal growth without performing the heat treatment in the first step of the present invention.
In addition, the group III nitride crystal film formed on the group III nitride seed substrate has an extremely low basal plane dislocation density and excellent crystal quality. Specifically, the basal plane dislocation density of the group III nitride crystal film preferably has a range of 1 × 10 ³ to 1 × 10 ⁶ pieces / cm ² , more preferably 5 × 10 ⁵ pieces / cm ^2. It has the following range. The group III nitride crystal film formed in the vicinity of the outer periphery of the group III nitride seed substrate may facet growth, and the basal plane dislocation density exceeds 1 × 10 ⁶ pieces / cm ² in such a place. There is also. Therefore, by removing a part of such a region of the group III nitride crystal film, the group III nitride crystal substrate having a basal plane dislocation density of 1 × 10 ³ to 1 × 10 ⁶ pieces / cm ² as a whole. It is preferable to obtain

  In the production method of the present invention, if the first step is performed using a single crystal made of a large group III nitride crystal, the large group III nitride crystal can be easily manufactured. For example, a large group III nitride crystal of 3 inches or more can be used. In addition, according to the production method of the present invention, a thick Group III nitride crystal can be produced particularly preferably. For example, a group III nitride crystal having a thickness of 500 μm or more can be produced, a group III nitride crystal exceeding 1 mm can be produced, and a group III nitride crystal exceeding 2 mm or 3 mm is also preferably produced. be able to. In the conventional manufacturing method, a thick group III nitride crystal having a thickness of more than 1 mm, which has a small warpage and suppresses surface cracks and is excellent in crystal quality, cannot be easily provided. According to this manufacturing method, it can be provided very simply and easily.

According to the production method of the present invention, when the α-type basal plane dislocation density of the whole crystal is ρα and the β-type basal plane dislocation density is ρβ, the absolute value of ρα−ρβ = Δρ is 1 × 10 ⁷ pieces / cm ^2. It is possible to obtain the following group III nitride crystals. According to the production method of the present invention, a group III nitride crystal having an absolute value of Δρ of 1 × 10 ⁶ pieces / cm ² or less can be more preferably obtained, and an absolute value of Δρ is 1 × 10 ⁴ pieces / cm 2. It is also possible to obtain a group III nitride crystal having ² or less. In addition, a group III nitride crystal having ρα of 1 × 10 ⁴ pieces / cm ² or less and a group III nitride crystal having ρβ of 1 × 10 ⁴ pieces / cm ² or less can be obtained. When the obtained crystal satisfies such a relationship, it is possible to obtain a crystal with less warpage and no cracks. In addition, according to the production method of the present invention, a group III nitride crystal having a threading dislocation density of 10 ⁶ to 10 ⁸ pieces / cm ² can be obtained.

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

(Crystal growth)
A template substrate having a C-plane of GaN grown by MOCVD on a sapphire substrate having a diameter of 76 mmΦ as a main surface is prepared, and this is used as a base substrate 110 on a carbon substrate holder 108 coated with SiC having a diameter of 85 mm and a thickness of 20 mm. Placed in the reactor 100 of the HVPE apparatus (see FIG. 1). After the reactor 100 was heated to 1020 ° C., HCl gas was supplied through the introduction pipe 103, and GaCl gas G 3 generated by reacting with Ga in the reservoir 106 was supplied into the reactor through the introduction pipe 104. In such a GaN layer growth step on the base substrate 110, the reactor temperature of 1020 ° C. is maintained for 29 hours, the growth pressure is 1.01 × 10 ⁵ Pa, and the partial pressure of the GaCl gas G3 is 6.52. × and 10 ² Pa, the partial pressure of NH ₃ gas G4 and 7.54 × 10 ³ Pa, and the partial pressure of hydrogen chloride (HCl) and 3.55 × 10 ¹ Pa. After the completion of the GaN layer growth step, the temperature in the reactor was lowered to room temperature to obtain a GaN crystal that was a group III nitride crystal. The obtained GaN crystal was grown with the C-plane as the growth surface, the surface state of the growth surface was a mirror surface, and the thickness measured with a stylus type film thickness meter was 3.5 mm. The obtained GaN crystal was subjected to the following heat treatment (high temperature corrosion annealing) without performing pretreatment such as cleaning, etching, and cap.

(Heat treatment)
As shown in FIG. 2, the heat treatment is performed by installing a GaN crystal 201 in an alumina tube (Al ₂ O ₃ 99.7%) 200 and introducing an ammonia / nitrogen mixed gas from a gas introduction tube 203 at a flow rate of 200 ml / min. While carrying out. Ammonia / nitrogen mixed gas (NH ₃ 8.5% + N ₂ 91.5%) is 45 days or more until a uniform mixed gas is obtained after mixing ammonia gas and nitrogen gas in a 4.9 MPa 47-liter cylinder. Used after standing. When raising the temperature, the heater 202 was used to raise the temperature from room temperature to 600 ° C. at 300 ° C./hour and from 600 ° C. to 1300 ° C. at 250 ° C./hour. Thereafter, the GaN crystal was heat-treated at 1300 ° C. for 6 hours. Then, it cooled from 1300 degreeC to 600 degreeC at 100 degreeC / hour. The crystal surface after the heat treatment is black, and as a result of identification by XRD, it has been found that gallium hydroxide, gallium oxide, and gallium metal are mixed. From this, it was confirmed that the hydrolysis reaction of the GaN crystal was caused by the water molecules generated by the reaction between ammonia and the alumina of the core tube member.

By immersing the heat-treated crystal in nitric acid (99.9%) at 120 ° C., Ga metal was removed, and a crystal sample in which cream-like gallium hydroxide and white gallium oxide were present on the crystal surface was obtained. .
In addition to the crystal sample (Example 1) subjected to the heat treatment thus obtained, a comparative crystal sample (Comparative Example 1) obtained in the same manner as in Example 1 except that the heat treatment was not performed was also obtained.

(Preparation of seed substrate)
In order to obtain a seed substrate from the obtained crystal sample, the following procedure is used for the outer periphery processing for processing the crystal into a wafer-shaped circle, the slicing processing for adjusting the wafer thickness, and the chemical polishing for making the surface state suitable for the test. It carried out according to.

  As a grinding wheel for crystal grinding, a grinding stone having an average grain diameter of 25 μm and vitrified as a bonding agent was used, and the grinding wheel processing surface was arranged to be perpendicular to the (0001) plane of the crystal. The grindstone rotation speed was 2500 m / min, and the crystal rotation speed was 5 mm / sec. Moreover, it controlled so that a grindstone processing surface might approach 0.02-0.04 mm crystal center per rotation of a crystal | crystallization. The outer periphery of the crystal sample was processed under the above conditions.

  A crystal having a disk-shaped (0001) plane as a main surface with a diameter of 50 mm and a thickness of 3.5 mm obtained by peripheral processing was fixed on the pedestal 2 using an epoxy adhesive as shown in FIG. Here, FIG. 3A is a front view, and FIG. 3B is a side view. As a crystal cutting wire W, an apparatus was prepared in which 70 wires electrodeposited with diamond abrasive grains having an average particle size of 12 to 25 μm were arranged in parallel, and 6 of them were made to contribute to the cutting of the crystal sample. As shown in FIG. 4A, the wires W arranged in parallel travel when the roller R1 and the roller R2 rotate in the same direction, and the two rollers R1 and R2 are as shown in FIG. 4B. It was controlled to swing by moving up and down alternately. During operation, the midpoint of the wire linear portion formed between the roller R1 and the roller R2 was set not to swing. The maximum swing angle φ of the swing was 10 °, the maximum traveling speed of the wire was 330 m / min, and the swing cycle of the wire was controlled to 800 times / min. The crystal sample was sliced under the above conditions.

  The C-plane front and back of the crystal obtained by slicing is subjected to chemical mechanical polishing until the surface is suitable for photoelasticity testing and SEM-CL observation, and has a uniform thickness of 400 mm ± 0.05 mm It was.

(Evaluation of curvature radius)
When the curvature of the C-plane of the seed substrate (Example 1) prepared from the heat-treated crystal sample was measured, the radius of curvature measured perpendicular to the m-axis was 1.5 m, and the curvature measured in parallel with the m-axis was 1.3 m. Met. On the other hand, when the curvature of the C-plane of the seed substrate (Comparative Example 1) prepared from the comparative crystal sample that was not heat-treated was measured, the radius of curvature measured perpendicular to the m-axis was 2.5 m and measured parallel to the m-axis. The curvature radius was 2.3 m.
From the above facts, it can be seen that the presence or absence of heat treatment for crystals grown to a thickness of more than 1 mm does not help improve the curvature.

(Evaluation of residual strain distribution by photoelasticity (photoelasticity test))
In order to observe the internal stress in the seed substrate of Example 1 and Comparative Example 1, the residual strain in the crystal was measured by the photoelastic method. The residual strain was measured using a GaN wafer residual strain measuring device manufactured by Japan Laser Corporation. The results of the phase difference distribution of Example 1 and Comparative Example 1 are shown in FIGS. 5 and 6, respectively.
As shown in FIG. 6, in the seed substrate of Comparative Example 1, it can be seen that the phase difference distribution is localized in a rotationally symmetric manner, and the distortion is also localized. In the seed substrate of Example 1, localization of the phase difference distribution as in Comparative Example 1 is not recognized, and it is clear that the seed substrate is uniformly dispersed. The above results indicate that the residual stress in the crystal is drastically reduced by performing the heat treatment. Such a decrease in residual stress in Example 1 is considered to be due to localization of basal plane dislocations contained in the seed substrate by heat treatment. The dislocation integration degree (A / B) represented by the ratio of the number density (A) of basal plane dislocation aggregates observed on the M-plane of the seed substrate of Example 1 and the number density (B) of isolated dislocations is In all of the crystals, the ratio was 3% or more.

(Evaluation of homoepitaxial growth)
Using the + C plane of the seed substrate of Example 1 as the regrowth plane, the temperature of the reactor is set to 1030 ° C., and the partial pressures of the GaCl gas that is a Group III material and the NH ₃ gas that is a Group V material are 7.00 × 10 respectively. ^The GaN film was grown under the same conditions as the crystal growth before the heat treatment except that the pressure was ² Pa, 8.21 × 10 ³ Pa, and the crystal growth time was changed to 24 hours. As a result, a GaN single crystal having a thickness in the c-axis direction of 1.6 mm could be obtained without cracks.
For the seed substrate of Comparative Example 1 that was not heat-treated in the same manner, when a GaN film was grown, cracks were introduced at the initial stage of regrowth, and a crack-free GaN single crystal could not be obtained. It was.

(Evaluation of basal plane dislocation density and radius of curvature)
For a GaN single crystal (Example 1) obtained by homoepitaxial growth (re-growth) as a seed substrate subjected to heat treatment, the basal plane dislocation density was determined using SEM-CL for the M-plane cross section after facing the M-plane. It was measured. As a result, the basal plane dislocation density is 1.11 × 10 ⁴ pieces / cm ² near the outermost surface of crystal growth, and 1.12 × 10 ⁵ pieces / cm ² near the interface on the seed substrate side of the GaN film. Met. The crystal growth side surface of the seed substrate was 4.57 × 10 ⁶ pieces / cm ² . Although the basal plane dislocation of the order of 10 ⁶ pieces / cm ² is observed in the seed substrate subjected to the heat treatment, it becomes the order of 10 ⁵ pieces / cm ^{2 in the} vicinity of the regrowth interface of the GaN film grown on the seed substrate. It was confirmed that the basal plane dislocation density rapidly decreased to the order of 10 ⁴ / cm ² near the surface of the regrown crystal of the GaN film regrown 6 mm.
When the curvature radius of the C plane of the obtained GaN crystal was measured, the curvature radius measured perpendicular to the m-axis was 4.2 m, and the curvature measured in parallel with the m-axis was 3.7 m. This indicates that the warpage of the obtained GaN crystal is considerably reduced as compared with the seed substrate.

(Removal of seed substrate and evaluation of curvature radius)
Processing was performed to remove the seed substrate of the obtained GaN crystal over a thickness of 400 μm. Specifically, the −C face side was shaved off by 350 μm by mechanical polishing, and then the remaining 50 μm was removed by KOH cleaning to obtain a seed substrate-removed GaN crystal.
When the radius of curvature of the C plane of the obtained GaN crystal with the seed substrate removed was measured, the radius of curvature measured perpendicular to the m-axis was 4.8 m, and the curvature measured in parallel with the m-axis was 4.0 m. This result shows that the warpage of the regrown GaN crystal can be further reduced by removing at least a part of the seed substrate.

  According to the production method of the present invention, it is possible to easily produce a group III nitride crystal having small warpage and suppressing surface cracks and having excellent crystal quality. Therefore, according to the present invention, a single crystal gallium nitride (GaN) substrate that can be used as a substrate of a blue light emitting element such as a blue light emitting diode (LED) or a blue semiconductor laser (LD) made of a group III nitride semiconductor is easily provided. Is possible. The present invention can be widely applied to a method for growing a single crystal gallium nitride substrate (GaN) and a method for manufacturing a single crystal gallium nitride substrate (GaN). Therefore, the present invention has high industrial applicability.

1 Crystal sample 2 Base W Wire φ Maximum swing angle R1, R2 Roller 100 Reactor 101-104 Gas introduction pipe 106 Group III material reservoir 107 Heater 108 Susceptor 109 Exhaust pipe 110 Seed substrate 200 Alumina pipe 201 Crystal 202 Heater 203 Gas inlet pipe 204 Gas outlet pipe

Claims (13)

A step of obtaining a group III nitride seed substrate by subjecting a single crystal comprising a group III nitride crystal to heat treatment at 1000 ° C. or higher;
Forming a group III nitride crystal film on the group III nitride seed substrate to obtain a group III nitride crystal;
And a method for producing a group III nitride crystal.   2. The method for producing a group III nitride crystal according to claim 1, wherein a group III nitride crystal film having a thickness of 500 μm or more is formed on the group III nitride seed substrate.   2. The method for producing a group III nitride crystal according to claim 1, wherein a group III nitride crystal film having a thickness of more than 1 mm is formed on the group III nitride seed substrate.   The group deviation of the group III nitride crystal according to any one of claims 1 to 3, wherein a standard deviation of a phase difference by a photoelastic method within a diameter of 50 mm from a center of the group III nitride seed substrate is less than 0.1 nm. Production method. 5. The method for producing a group III nitride crystal according to claim 1, wherein the group III nitride seed substrate has a basal plane dislocation density of 1 × 10 ⁶ to 1 × 10 ⁹ pieces / cm ² .   The method for producing a group III nitride crystal according to any one of claims 1 to 5, wherein β-type basal plane dislocations occupied in basal plane dislocations of the group III nitride seed substrate are more than 50%. 7. The basal plane dislocation density of the group III nitride crystal film formed on the group III nitride seed substrate has a range of 1 × 10 ³ to 1 × 10 ⁶ pieces / cm ² . A method for producing a group III nitride crystal according to item 1.   The production of a group III nitride crystal according to any one of claims 1 to 7, further comprising a step of removing at least a part of a seed substrate of the group III nitride crystal obtained after the group III nitride crystal film is formed. Method. 9. The method for producing a group III nitride crystal according to claim 8, wherein a basal plane dislocation density of the group III nitride crystal film obtained after the removal is 1 × 10 ³ to 1 × 10 ⁶ pieces / cm ² .   10. The III according to claim 1, further comprising a step of obtaining a group III nitride free-standing crystal by removing a seed substrate of the group III nitride crystal obtained after the group III nitride crystal film is formed. A method for producing a group nitride crystal.   The method for producing a group III nitride crystal according to claim 10, wherein the thickness of the group III nitride free-standing crystal is more than 1 mm.   The group III nitride crystal manufactured by the manufacturing method of any one of Claims 1-11.   A group III nitride crystal substrate comprising the group III nitride crystal according to claim 12.