JP2011153055A - Method for producing nitride single crystal - Google Patents

Abstract

The present invention provides a method for producing a nitride single crystal by an ammonothermal method capable of achieving both a high growth rate and high crystal quality.
In a corrosion-resistant autoclave 3, in the presence of ammonia in a supercritical or subcritical state, at least one nitride polycrystal is used as a raw material 6 and at least one acidic mineralizer is used. In the method of producing a nitride single crystal from a nitride polycrystal by an ammonothermal method in addition to ammonia, the autoclave 3 is nitrided using a portion 9 where the nitride polycrystal is disposed and a seed crystal 7. There is a portion 10 for growing a single crystal of crystal, the temperature T1 of the portion 10 for growing a single crystal of nitride using the seed crystal 7 is 650 ° C. to 850 ° C., and a nitride polycrystal is formed. The average temperature is maintained higher than the temperature T2 of the portion 9 to be disposed, and the pressure in the corrosion-resistant autoclave 3 is maintained at 40 MPa to 250 MPa.
[Selection] Figure 1

Description

  The present invention relates to a method for producing a nitride single crystal by a solvothermal method. More specifically, the present invention provides a bulk single crystal having excellent crystallinity of a periodic table group 13 element nitride represented by gallium nitride using an acidic mineralizer in an ammonothermal method using an ammonia solvent. The present invention relates to a novel method for producing a nitride single crystal that can be obtained.

  Gallium nitride crystals are useful as materials applied to light-emitting elements such as light-emitting diodes and laser diodes. The most common manufacturing method is MOCVD (Metal-Organic Chemical Vapor) using sapphire or silicon carbide as a substrate. This is a method using vapor phase growth by the Deposition method. However, since the quality of the single crystal obtained by this method cannot be said to be sufficient depending on the application, development of a nitride single crystal substrate capable of homoepitaxial growth of these nitride single crystals is eagerly desired.

  For example, in the case of a gallium nitride single crystal, there is a self-standing single crystal substrate by HVPE (Hydride Vapor Phase Epitaxy) method, but it has not been widely used. Other methods include the high pressure method (J. Crystal Growth 178 (1977) 174) in which nitrogen and Ga are reacted at high temperature and high pressure, and the method using flux (Jpn. J. Appl. Phys. 46 (2007) L103 ), Solvothermal methods are being studied.

  The solvothermal method is a general term for crystal production methods using a solvent in a supercritical state and / or a subcritical state. Particularly, when water is used as a solvent, a hydrothermal method (hydrothermal synthesis method) and ammonia as a solvent. Is called the ammonothermal method (another-low synthesis method). The hydrothermal method is an industrial manufacturing method of artificial quartz and is widely known as one of methods for obtaining high quality crystals.

The ammonothermal method is expected as a method for producing a bulk single crystal of nitride such as gallium nitride. Using ammonia as a solvent, the temperature and pressure are adjusted to dissolve or react the raw materials, and the temperature dependence of the solubility is increased. It is used for crystal growth.
In the ammonothermal method, it is said that adding a mineralizer is effective for producing a nitride single crystal such as GaN. Mineralizers are broadly classified into acidic mineralizers that lower pH compared to the original solvent and basic mineralizers that increase pH when dissolved in ammonia. ing. Production conditions suitable for crystal growth are known to differ greatly between acidic mineralizers and basic mineralizers. For example, basic mineralizers are produced by an ammonothermal method. When used, a relatively high pressure of about 150 to 500 MPa is required, whereas in the case of an acidic mineralizer, a relatively low pressure of about 100 to 200 MPa is sufficient. In addition, the corrosion resistance required for the reaction vessel or the like differs depending on whether the acidic mineralizer is used or the basic mineralizer. As described above, in the nitride single crystal manufacturing technology by the ammonothermal method, the single crystal manufacturing technology is greatly different depending on the difference in acidity and basicity of the mineralizer used (for example, Patent Document 1). , See Patent Document 2).

  For the ammonothermal method using an acidic mineralizer, in the autoclave consisting of the lower raw material filling part and the upper growing part partitioned by a baffle plate, the lower part is filled with raw material mainly consisting of polycrystalline nitride. In addition, a technique is disclosed in which a seed crystal is arranged in the upper part and the temperature of the upper part is kept lower than that of the lower part to grow the seed crystal in the upper low-temperature region (see, for example, Patent Document 2). . Such a method is similar to the industrial production method of artificial quartz and has been considered as one of the reasons for selecting an acid mineralizer in the ammonothermal method.

However, the single-crystal nitride growth technology based on the ammonothermal method has not yet been fully completed, and for industrial development, a faster growth rate and higher quality to increase productivity. There are many issues that must be overcome.
For example, in the case of gallium nitride, the growth rate is 30 μm / day to several microns / day in the conventionally reported ammonothermal method for nitride single crystal growth, compared with competing HVPE and flux methods. Even in a slow situation. Thus, conventionally, in the case of gallium nitride, it has been difficult to achieve both a high growth rate and smooth surface growth.

JP 2003-40699 A JP 2008-120672 A

  In view of the above technical level, the problem to be solved by the present invention is to provide a novel method for producing a nitride single crystal that can achieve both high growth rate and high crystal quality by the ammonothermal method.

In order to solve the above-mentioned problems, the inventors have intensively studied and repeated experiments. As a result, the inventors have found that the problems can be solved by the following means, and have completed the present invention.
That is, the present invention is as follows.

[1] In a corrosion-resistant autoclave, in the presence of ammonia in a supercritical or subcritical state, at least one nitride polycrystal is used as a raw material, and at least one acidic mineralizer is used as the ammonia. In addition, in the method of producing a nitride single crystal from the nitride polycrystal by an ammonothermal method,
In the autoclave, there are a portion where the nitride polycrystal is disposed and a portion where the nitride single crystal is grown using a seed crystal,
The temperature (T1) of the portion where the nitride single crystal is grown using the seed crystal is 650 ° C. to 850 ° C., and the average temperature is higher than the temperature (T2) of the portion where the nitride polycrystal is disposed. And the pressure in the corrosion-resistant autoclave is maintained at 40 MPa to 250 MPa.
A method for producing a nitride single crystal by an ammonothermal method.

  [2] The corrosion-resistant autoclave according to [1], wherein the portion where the nitride polycrystal is disposed is higher than the portion where the seed crystal is disposed and the nitride single crystal is grown. A method for producing a nitride single crystal.

  [3] The nitride polycrystal is disposed in a container provided with a plurality of holes or slit-like gaps, and at least 1 mm between the side surface of the container and the inner wall of the corrosion-resistant autoclave. The method for producing a nitride single crystal according to [1] or [2], wherein the gap is present.

  [4] The portion where the nitride polycrystal is disposed is present at a position at least 10 mm or more from the inner bottom surface of the corrosion-resistant autoclave, and the portion where the nitride polycrystal is disposed and the resistance to the nitride polycrystal. The method for producing a nitride single crystal according to the above [3], wherein the seed crystal is arranged in a space defined by the inner bottom surface of the corrosive autoclave.

  [5] The nitride single unit according to [4], wherein a partition plate is disposed between a portion where the nitride polycrystal is disposed and a portion where the nitride single crystal is grown using the seed crystal. Crystal production method.

  [6] The method for producing a nitride single crystal according to any one of [1] to [5], wherein the nitride polycrystal is produced by a vapor phase method.

  [7] A substrate made of a nitride single crystal manufactured by the method for manufacturing a nitride single crystal according to any one of 1 to 6 above.

  According to the method for producing a nitride single crystal of the present invention, it is possible to grow a nitride single crystal at a speed of 30 μm / day or more and faster than the conventional method. In addition, since the nitride single crystal obtained by the method for producing a nitride single crystal of the present invention has a flat film-like growth layer, bulk nitride capable of cutting out substrates having various orientations by the method of the present invention. A single crystal can be obtained.

It is the schematic of the manufacturing apparatus of the nitride single crystal used in the Example. It is the external appearance photograph replaced with drawing of the seed crystal (top) used in Example 1, and the single crystal obtained after the growth (bottom).

Hereinafter, the method for producing a nitride single crystal of the present invention will be described in detail.
The following description will be made based on typical embodiments of the present invention, but the present invention is not limited to these embodiments. In the present specification, the notation of the numerical ranges A to B represents a range of A to B.

  The nitride in the present invention means a nitride of a periodic table group 13 element (IUPAC, 1989) represented by gallium nitride, and not only a single metal nitride such as GaN, but also AlGaN, InGaN. And multi-component compounds such as AlInGaN. These chemical formulas only indicate the constituent elements of the nitride, and do not indicate their composition ratio.

  Polycrystalline means that for each solid obtained in various appearances such as massive, granular, powdery, etc., a large number of fine single crystals, that is, fine crystals exist in different directions and cannot be separated. Means state. There are no particular limitations on the size of the microcrystals and the degree of orientation of the microcrystals, that is, the degree of orientation.

  In the present invention, the nitride polycrystal is used as a raw material, and any composition of the aforementioned group 13 element of the periodic table can be used, but it is not necessarily a complete nitride, and a zero-valent metal is used. May be included. For example, a multi-element nitride such as AlGaN or a mixture of AlN and GaN can be used as a raw material.

There are no particular restrictions on the method for producing the polycrystalline raw material that is used as the raw material.For example, when GaN is taken as an example, metal gallium or Ga ₂ O ₃ nitrided with ammonia, or HVPE, halide and ammonia are used. The nitride obtained by this reaction can be used as a raw material.

  In the present invention, ammonia is used as a solvent, but it is desirable that the amount of impurities contained is as small as possible. The purity of ammonia to be used is usually 99.9% or more, preferably 99.99% or more, and more preferably 99.999% or more.

  Examples of the acidic mineralizer added to ammonia as a solvent include ammonium halide. For example, as the acidic mineralizer, ammonium chloride, ammonium iodide, ammonium bromide, especially ammonium chloride is preferable.

The ammonia filling amount is adjusted so that the pressure inside the autoclave to be used is in the range of 40 MPa to 250 MPa at the selected temperature.
If the ammonia filling amount is increased, the single crystal can be grown faster, but if the pressure exceeds the upper limit of the above range, a part of the ammonia is discharged by operating the valve and the pressure range. Do not exceed.

  The higher the pressure, the faster the growth rate of the single crystal, and 40 MPa or more is sufficient as the growth rate of the single crystal. On the other hand, considering the load on the autoclave used, the pressure is 250 MPa or less. In the present invention, the pressure is preferably 40 MPa to 200 MPa, more preferably 50 MPa to 150 MPa, and still more preferably 60 MPa to 130 MPa.

  The autoclave used in the present invention is selected from those that can withstand high temperature and high pressure conditions for growing a nitride single crystal. Specifically, a Ni-based alloy, such as RENE 41, which has excellent strength characteristics at high temperatures is preferable.

  The acidic mineralizer used in the present invention has a high solubility in ammonia in a supercritical state with respect to a basic mineralizer typified by an alkali metal amide and the like, and thus can react at a low pressure. In addition, since the acidic mineralizer used in the present invention has low corrosiveness to noble metals such as platinum, if the inner surface of the autoclave is covered with these noble metals, the effects of impurities mixed in due to corrosion of the container can be minimized. Is possible. Examples of these noble metals include Pt, Au, Ir, Ru, Pd, Ag, and alloys containing these noble metals as main components. Among these, it is preferable to use Pt. Therefore, the corrosion-resistant autoclave used in the present invention may be one in which the inner surface of the autoclave is lined or coated with these noble metals.

The nitride polycrystal as a raw material can be of any shape such as a lump or powder, but these can be used as a container provided with a plurality of holes or slit-like gaps, or a cage-like container formed by a mesh. It becomes possible to arrange | position in the specific position in the autoclave to be used by putting in.
For the container holes and slit-shaped gaps, etc., it is sufficient to select a suitable hole and slit size, mesh coarseness, etc. according to the shape of the nitride polycrystal used. The polycrystalline raw material may be efficiently brought into contact with the ammonia solvent and rapidly dissolved.

  In the method for producing a nitride single crystal of the present invention, it is important to efficiently dissolve a nitride polycrystal as a raw material in supercritical ammonia. Therefore, it is preferable that a gap of at least 1 mm exists between the side surface of the container containing the raw material and the inner wall of the autoclave so that the flow of supercritical ammonia as a solvent does not stagnate inside the autoclave to be used.

  In the present invention, the lower limit of the temperature (T1) of the portion where the nitride single crystal is grown using the seed crystal may be 650 ° C. or higher, preferably 670 ° C. or higher, more preferably 690 ° C. or higher. On the other hand, the upper limit of the temperature at which the nitride single crystal is grown using the seed crystal may be 850 ° C. or less, preferably 800 ° C. or less, more preferably 750 ° C. or less, and even more preferably 720 ° C. or less. .

Furthermore, in the present invention, the temperature (T1) of the portion where the nitride single crystal is grown using the seed crystal is set higher than the temperature (T2) of the portion where the nitride polycrystal is disposed. (T1> T2).
For example, the temperature difference (T1−T2) between the temperature (T1) of the portion where the nitride single crystal is grown using the seed crystal and the temperature (T2) of the portion where the nitride polycrystal is disposed is 150 ° C. to 1 ° C. It can be set to ° C. Increasing this temperature difference tends to increase the crystal growth rate, but decreasing the temperature difference tends to improve the quality of the crystal.
Therefore, the temperature difference (T1-T2) is preferably 100 ° C. to 5 ° C., and more preferably 90 ° C. to 10 ° C., from the viewpoints of crystal growth rate (crystal precipitation) and crystal quality.

  In the present invention, as long as this temperature condition is satisfied, a single crystal precipitation site may be mixed in a part of the nitride polycrystal as a raw material. For example, if a seed crystal is placed in a mesh-like container together with a polycrystalline raw material while maintaining a space where the crystal can be grown on the surface thereof, the growth of a nitride single crystal at a location very close to the raw material supply source It is possible to achieve a high growth rate.

  In the present invention, a vertical autoclave can also be used. In this case, the portion where the nitride polycrystal is arranged is higher in the vertical direction than the portion where the nitride single crystal is grown using the seed crystal. It becomes possible to precipitate a single crystal more efficiently by arrange | positioning to. Because of this positional relationship, the space defined by the portion where the nitride polycrystal is arranged and the inner bottom surface of the autoclave is used as a region for growing the nitride single crystal using the seed crystal, and the nitride This is because a single crystal that falls into the region by gravity from the portion where the polycrystal is disposed or precipitates in the space can be efficiently grown in the space.

  Since the precipitated single crystal is preferably prevented from polycrystallization due to coalescence with other single crystal grains as much as possible, the portion where the nitride polycrystal is disposed should be at least 10 mm above the bottom of the autoclave. Is preferred. As an upper limit of the height of the portion where the nitride polycrystal is arranged from the bottom surface of the autoclave, for example, the height from the bottom surface can be 125 mm or less, but a space as a crystal precipitation region is ensured. As long as the height from the bottom of the autoclave is 10 mm or more, it may be 50% vol or less of the entire space in the autoclave.

  In the conventional arrangement using the acidic mineralizer (polycrystalline raw material at the bottom of the autoclave and seed crystal at the top), no crystal growth on the seed crystal is observed in the temperature range disclosed in the present invention.

  In the present invention, a seed crystal is used, but it is preferable to select a material having a crystal system that matches or matches the target nitride single crystal, a lattice constant, and a crystal lattice size parameter. For example, in the case of gallium nitride, A nitride single crystal such as aluminum nitride, a single crystal of zinc oxide, a single crystal of silicon carbide, or the like can be used. More preferably, a gallium nitride single crystal is used. The seed crystal manufacturing method is not particularly limited. For example, in the case of gallium nitride, a single crystal substrate or template substrate by MOCVD method or HVPE method, a free-standing substrate obtained by a high-pressure method, or free-standing GaN produced by a flux method Crystals can be used. In the ammonothermal method, nitride single crystal grains obtained by spontaneous nucleation can be used as they are or after being cut.

Hereinafter, the features of the present invention will be specifically described with reference to Examples and Comparative Examples.
The materials, amounts used, ratios, processing details, and processing procedures shown in the following examples can be changed within the scope of the present invention. Accordingly, the scope of the present invention should not be construed as being limited by the following examples.

  In addition, since it is very difficult to measure the internal temperature of the autoclave in the supercritical state, the empty autoclave lid is closed, the valve is removed, the heater is set, and the heater is controlled under the same conditions as during the reaction. The value of each part of the inner wall of the autoclave measured using a thermocouple inserted through a conduit was taken as the internal temperature of the autoclave in the supercritical state.

Example 1
GaN single crystal grains were fabricated by the ammonothermal method using GaN polycrystals produced by the vapor phase method as raw materials. From the gallium nitride single crystal produced by spontaneous nucleation, grains with a self-shape of about 4 mm in length and 0.7 mm in thickness were used as seed crystals.
The autoclave is made of platinum or a platinum-based alloy with an inner lining made of RENE41 (inner diameter 8 mm, length 250 mm, inner volume approx. 12.5 mL), and the seed crystal is platinum wire And hung at a position 25 mm from the bottom of the autoclave.
Cylindrical container (outside dimension 5.5mm, height 100mm, width 0.5mm on the side) made by processing 0.3g-thick platinum plate of 5.0g of GaN polycrystal (size 1mm-5mm) manufactured by vapor phase method 6 mm x 80 mm long slits and 5 φ0.5 mm holes on the bottom). The cylindrical container was filled with filled polycrystals. The container was set in an autoclave in which seed crystals were set so that a gap of 50 mm was maintained from the bottom, and then 0.426 g of 99.99% pure ammonium chloride was added, and the autoclave lid was closed. The vessel was connected to a vacuum pump and the interior was evacuated. Using a turbo molecular pump, exhaust was performed until the pressure directly above the pump reached 1.0 × 10 ⁻⁴ Pa or less. Thereafter, the autoclave was cooled using dry ice / refrigerant, and 5.0 g of 99.999% purity ammonia was charged without touching the outside air, and the valve was closed. (Ammonia amount was converted to ammonia density at -33 ° C and corresponded to 59% of the autoclave internal volume.)

Next, the autoclave was set on a heater, and the autoclave was heated. The average temperature of the polycrystalline arrangement site is 660 ° C (681 ° C, 663 ° C, 645 ° C, 646 ° C, 644 ° C at regular intervals), and the average temperature of the single crystal precipitation site is 697 ° C (698 ° C, 699 at regular intervals) And 694 ° C.). At this time, the pressure was 125 MPa.
After maintaining in this state for 168 hours, it was allowed to cool naturally and the internal ammonia was discharged. The seed crystal grew from its original shape, and became 6.1 mm long and 1.1 mm thick. The growth rate at this time was estimated to be 300 μm / day in the length direction and 57 μm / day in the thickness direction.
The obtained crystal grains were placed on a Si non-reflective plate and subjected to X-ray diffraction measurement. As a result, diffraction from only the m-plane was obtained, indicating that it was a single crystal.

(Example 2)
The amount of ammonia to be charged is 4.2 g, the charge amount is about 50% of the container in terms of density at −33 ° C., the acid mineralizer is reduced to 0.357 g, and the reaction time is lengthened, It implemented on the conditions similar to Example 1. FIG. Due to the difference in filling rate, the holding pressure became 70 MPa. After holding for 480 hours, it was allowed to cool naturally and the ammonia inside was discharged. The seed crystal has grown from its original state and has a length of 7.2 mm and a thickness of 1.7 mm. The growth rate at this time was estimated to be 160 μm / day in the length direction and 50 μm / day in the thickness direction.
The obtained crystal grains were confirmed to be hexagonal GaN by X-ray diffraction. In addition, as a result of X-ray diffraction measurement by placing one well-formed crystal grain on a Si non-reflective plate, diffraction was obtained only from the m-plane, indicating that it was a single crystal.

(Example 3)
The 1.7 mm thick crystal grains obtained in Example 2 were cut perpendicular to the length direction to obtain a GaN single crystal substrate having an opposite side of about 1.5 mm and a thickness of 0.5 mm. This was used as a seed crystal and grown under the same conditions as in Example 1. The crystal grew from its original state, growing to a thickness of 0.9 mm and an opposite side of 1.8 mm. The growth rate at this time was estimated to be 57 μm / day in the thickness direction (c-axis direction) and 43 μm / day in the coping direction (m-axis direction).

(Comparative Example 1)
GaN single crystal grains were fabricated by the ammonothermal method using GaN polycrystals produced by the vapor phase method as raw materials. From a gallium nitride single crystal produced by spontaneous nucleation, grains with a self-shape of 4 mm in length and 0.7 mm in thickness were used as seed crystals.
The autoclave is made of platinum or a platinum-based alloy with an inner lining made of RENE41 (inner diameter 8 mm, length 250 mm, inner volume approx. 12.5 mL), and the seed crystal is platinum wire And hung at a position 25 mm from the bottom of the autoclave.
Cylindrical container (outside dimension 5.5mm, height 100mm, width 0.5mm on the side) made by processing 0.3g-thick platinum plate of 5.0g of GaN polycrystal (size 1mm-5mm) manufactured by vapor phase method 6 mm x 80 mm long slits and 5 φ0.5 mm holes on the bottom). The cylindrical container was filled with filled polycrystals. The container was set in an autoclave in which seed crystals were set so that a gap of 50 mm was maintained from the bottom, and then 0.426 g of 99.99% pure ammonium chloride was added, and the autoclave lid was closed. The vessel was connected to a vacuum pump and the interior was evacuated.

Using a turbo molecular pump, exhaust was performed until the pressure directly above the pump reached 1.0 × 10 ⁻⁴ Pa or less. Thereafter, the autoclave was cooled using dry ice / refrigerant, and 5.0 g of 99.999% purity ammonia was charged without touching the outside air, and the valve was closed. (Ammonia amount was converted to ammonia density at -33 ° C and corresponded to 59% of the autoclave internal volume.)
Next, the autoclave was set in a heater, and the container was heated. The average temperature of the polycrystal arrangement site is 638 ° C (620 ° C, 633 ° C, 645 ° C, 650 ° C, 644 ° C at regular intervals), and the average temperature at the position corresponding to the single crystal precipitation site where the seed crystals are arranged is 600 It was kept at ℃ (590 ° C, 602 ° C, 610 ° C at regular intervals). At this time, the pressure was 96 MPa. After maintaining in this state for 168 hours, it was allowed to cool naturally and the internal ammonia was discharged. When the inside of the autoclave was confirmed, all the set seed crystals were dissolved and disappeared.

(Comparative Example 2)
The amount of ammonia to be charged is 2.5 g, approximately 30% of the container in terms of ammonia density at −33 ° C., and the same conditions as in Example 1 except that the mineralizer ammonium chloride is reduced to 0.213 g. It carried out in. Due to the difference in filling rate, the holding pressure was 27 MPa. After holding for 168 hours, it was allowed to cool naturally and the ammonia inside was discharged. When the inside of the autoclave was confirmed, the set seed crystal and polycrystalline raw material remained almost as they were, and no crystal growth occurred.

  According to the method for producing a nitride single crystal of the present invention, it is possible to grow a nitride single crystal at a speed of 30 μm / day or more and faster than the conventional method. Further, since the nitride single crystal obtained by the method for producing a nitride single crystal of the present invention has a flat film-like growth layer, according to the present invention, a bulk nitride single crystal capable of cutting out substrates of various orientations can be obtained. Obtainable.

1 Pressure gauge 2 Valve 3 Autoclave 4 Conduit 5 Raw material container 6 Nitride polycrystalline raw material 7 Seed crystal 8 Electric furnace (heater)
9 Nitride polycrystal arrangement site 10 Nitride single crystal growth site

Claims (7)

In a corrosion-resistant autoclave, in the presence of ammonia in a supercritical or subcritical state, at least one nitride polycrystal is used as a raw material, and at least one acidic mineralizer is added to the ammonia. In the method for producing a nitride single crystal from the nitride polycrystal by an ammonothermal method,
In the autoclave, there are a portion where the nitride polycrystal is disposed and a portion where the nitride single crystal is grown using a seed crystal,
The temperature (T1) of the portion where the nitride single crystal is grown using the seed crystal is 650 ° C. to 850 ° C., and the average temperature is higher than the temperature (T2) of the portion where the nitride polycrystal is disposed. And the pressure in the corrosion-resistant autoclave is maintained at 40 MPa to 250 MPa.
A method for producing a nitride single crystal by an ammonothermal method.   The nitride single crystal according to claim 1, wherein the corrosion-resistant autoclave is present at a position where the portion where the nitride polycrystal is arranged is higher than the portion where the seed crystal is arranged and the nitride single crystal is grown. Manufacturing method.   The nitride polycrystal is disposed in a container provided with a plurality of holes or slit-shaped gaps, and a gap of at least 1 mm is provided between the side surface of the container and the inner wall of the corrosion-resistant autoclave. The manufacturing method of the nitride single crystal of Claim 1 or 2 with which exists.   The portion where the nitride polycrystal is disposed is present at a height of at least 10 mm or more from the inner bottom surface of the corrosion-resistant autoclave, and the portion where the nitride polycrystal is disposed and the corrosion-resistant autoclave The method for producing a nitride single crystal according to claim 3, wherein the seed crystal is arranged in a space defined by the inner bottom surface.   The method for producing a nitride single crystal according to claim 4, wherein a partition plate is disposed between a portion where the nitride polycrystal is disposed and a portion where the nitride single crystal is grown using the seed crystal. .   The method for producing a nitride single crystal according to any one of claims 1 to 5, wherein the nitride polycrystal is produced by a vapor phase method.   The board | substrate which consists of a nitride single crystal manufactured by the manufacturing method of the nitride single crystal of any one of Claims 1-6.