JP2023123390A - Method for producing ain single crystals, ain single crystals, and apparatus for producing ain single crystals - Google Patents

Abstract

To provide: a method for producing AlN single crystals which enables less-expensive and continuous production of AlN single crystals; AlN single crystals; and an apparatus for producing AlN single crystals.SOLUTION: A method for producing AlN single crystals includes: a melt formation step for heating and melting an alloy containing Al to form a melt of the alloy; and a deposition step for depositing AlN single crystals while providing a temperature gradient to the melt by cooling a part of the melt. In the deposition step, by bringing a nitrogen-containing gas into contact with a high-temperature section of the melt and holding AlN seed crystals or a crystal growth substrate for single crystals in a low-temperature section in the melt, with nitrogen being taken into the melt in the high-temperature section, AlN single crystals are deposited on the AlN seed crystals or on the substrate in the low-temperature section, and thereby AlN single crystals continuously grow.SELECTED DRAWING: Figure 1

Description

The present invention relates to an AlN single crystal manufacturing method, an AlN single crystal, and an AlN single crystal manufacturing apparatus.

Ultraviolet light emitting elements are next-generation light sources that are expected to be used in a wide range of applications, such as sterilization light sources, high-intensity white light sources combined with phosphors, high-density information recording light sources, and resin curing light sources. This ultraviolet light emitting device is made of an AlGaN-based nitride semiconductor.

Candidates for the substrate material of this AlGaN nitride semiconductor include SiC, GaN, and AlN (aluminum nitride) because of their high lattice match with AlGaN. However, since SiC and GaN absorb light with energy higher than wavelengths of 380 nm and 365 nm, respectively, the wavelength region that can be extracted is limited. On the other hand, AlN has a wider bandgap than AlGaN and does not have the limitation of wavelength region like SiC and GaN, so it is considered to be the most excellent substrate material. However, since AlN exhibits a high dissociation pressure at high temperatures, it does not enter a molten state under normal pressure. Therefore, it is extremely difficult to produce an AlN single crystal from its own melt like a silicon single crystal.

Therefore, conventionally, manufacturing methods such as a hydride vapor phase epitaxy (HVPE) method, a liquid phase epitaxy method, a sublimation method and the like have been tried in order to produce an AlN single crystal. For example, a method of growing a group III nitride crystal by bringing a substrate into contact with a melt containing a group III element and an alkali metal under high pressure (see, for example, Patent Document 1); In addition, a method of injecting ammonia gas containing nitrogen atoms to produce group III nitride microcrystals in a melt of a group III element has been proposed (see, for example, Patent Document 2). However, these AlN single crystal production methods require high pressure and high temperature, and it has been difficult to produce a crystal that can withstand practical use in terms of size, quality and cost.

In order to solve this problem, the present inventors brought a nitrogen-containing gas into contact with the surface of an Al-containing alloy melt as a method of obtaining an inexpensive and high-quality AlN single crystal at low temperature and normal pressure. Accordingly, a liquid phase growth method for AlN single crystals is developed to grow crystals on the surface of the melt (see, for example, Patent Document 3).

Japanese Patent Application Laid-Open No. 2004-224600 JP-A-11-189498 JP 2019-194133 A

The liquid phase growth method for AlN single crystals described in Patent Document 3 can produce AlN single crystals of very good quality at low cost. The supply of nitrogen is cut off from the liquid surface where the crystals are formed. Therefore, there is room for improvement in the growth rate. In Patent Document 3, in order to continuously supply nitrogen from the melt surface, a mode is proposed in which local heating is performed by a heating laser separately from the melt formation. If the crystal can be grown continuously, the AlN single crystal can be grown stably and continuously. In particular, if it becomes possible to continuously supply nitrogen from the surface of the melt without any additional heating other than the formation of the melt, it can be expected to realize AlN single crystal growth with lower energy consumption.

The present invention has been made in view of such problems, and provides an AlN single crystal manufacturing method, an AlN single crystal, and an AlN single crystal manufacturing apparatus capable of inexpensively and continuously manufacturing an AlN single crystal. intended to

In order to achieve the above object, a method for producing an AlN single crystal according to the present invention cools a portion of an Al-containing alloy melt to provide a temperature gradient in the melt. Then, while continuing to take in nitrogen into the melt in the high-temperature part of the melt, the AlN single crystal is deposited on the AlN seed crystal or the substrate for crystal growth (hereinafter simply referred to as the growth substrate) in the low-temperature part of the melt. Crystals are precipitated to continuously grow AlN single crystals. That is, the gist and configuration of the present invention are as follows.

(1) A melt forming step of heating and melting an alloy containing Al to form a melt of the alloy, cooling a part of the melt to provide a temperature gradient in the melt, and forming an AlN single crystal and a precipitation step of precipitating the AlN single crystal, wherein the precipitation step includes bringing a nitrogen-containing gas into contact with a high temperature portion in the melt, and By holding the AlN seed crystal of the crystal or the substrate for crystal growth, the AlN single crystal is grown on the AlN seed crystal or the substrate in the low temperature portion while continuing to incorporate nitrogen into the melt in the high temperature portion. is deposited to continuously grow the AlN single crystal.

(2) The nitrogen-containing gas contains _N2 gas, and the activity of Al in the melt when the reaction for the formation of the AlN single crystal represented by the following formula (A) is in equilibrium is a ^eq _.Al , the equilibrium constant of the above formula (A) is K, the Boltzmann constant is k, the absolute temperature is T, and the partial pressure of _N2 of the nitrogen-containing gas at the time of precipitation is _pN2 , then the following formula (B) is obtained. When the value of the driving force Δμ for the growth of the AlN single crystal represented becomes ₀ , the temperature of the high temperature portion is set higher than _T0 , and the temperature of the low temperature portion is set to the above The method for producing an AlN single crystal according to (1), wherein the temperature is equal to or higher than the liquidus temperature of the alloy and lower than _T0 .
2Al(l)+ _N2 (g)→2AlN(s) (A)

(3) The method for producing an AlN single crystal according to (2), wherein the melt forming step includes a high temperature heating step of heating the high temperature portion to a temperature of T ₀ +30K or higher.

(4) The AlN unit according to (3), wherein the melt forming step includes a low temperature heating step of heating the high temperature portion to a temperature higher than T ₀ and lower than T ₀ + 30K after the high temperature heating step. Crystal production method.

(5) The holder for holding the AlN seed crystal of the single crystal or the substrate for crystal growth is provided with a cooling mechanism, and in the precipitation step, the holder is brought into contact with the melt, thereby causing the temperature gradient in the melt. The method for producing an AlN single crystal according to any one of (1) to (4), wherein

(6) The method for producing an AlN single crystal according to any one of (1) to (5), wherein the substrate for crystal growth is an AlN template substrate obtained by epitaxially growing an AlN single crystal on a sapphire single crystal.

(7) The AlN template substrate is an AlN template substrate in which a C-plane AlN single crystal is epitaxially grown on a C-plane sapphire single crystal, and the X-ray rocking curve of the (10-12) plane of the C-plane AlN single crystal is The method for producing an AlN single crystal according to (6), wherein the half width is 300 arcsec or less.

(8) The method for producing an AlN single crystal according to any one of (1) to (7), wherein the alloy containing Al is a Ni—Al alloy.

(9) A single-crystal AlN seed crystal or an AlN single crystal formed on a substrate for crystal growth, containing 8×10 ¹⁶ to 1× one or more of Fe, Ni, Cu, and Co as impurities. AlN single crystal containing 10 ²¹ /cm ³ .

(10) A single-crystal AlN seed crystal or an AlN single crystal formed on a substrate for crystal growth, the AlN single crystal containing 8×10 ¹⁶ to 1×10 ²¹ /cm ³ of Ni as an impurity.

(11) The AlN single crystal according to (9) or (10), which has a carbon concentration of 2×10 ¹⁷ cm ⁻³ or less.

(12) A reaction vessel capable of supplying a nitrogen-containing gas to the inside, a crucible capable of holding an Al-containing alloy melt, a heater for the melt, and a holder for an AlN seed crystal or a growth substrate. wherein the holder has an elevating mechanism and a cooling mechanism, and a temperature gradient can be provided between the melt and the growth substrate by bringing the holder into contact with the melt; AlN single crystal manufacturing equipment.

According to the present invention, it is possible to provide an AlN single crystal manufacturing method, an AlN single crystal, and an AlN single crystal manufacturing apparatus capable of continuously manufacturing an AlN single crystal at a low cost.

FIG. 1 is a schematic diagram showing an overview of an AlN single crystal growth apparatus according to an AlN single crystal manufacturing method according to an embodiment of the present invention. FIG. 2 is a graph showing the relationship between the driving force Δμ for AlN single crystal growth and the temperature (T) for each composition of Ni—Al alloy. FIG. 3 is a front view showing one aspect of the overall configuration of the AlN single crystal growth apparatus according to the method for producing an AlN single crystal according to the embodiment of the present invention. FIG. 4 is a front view showing another aspect of the overall configuration of the AlN single crystal growth apparatus according to the method for producing an AlN single crystal according to the embodiment of the present invention. FIG. 5 is a front view showing another aspect of the overall configuration of the AlN single crystal growth apparatus according to the method for producing an AlN single crystal according to the embodiment of the present invention. FIG. 6 is a cross-sectional SEM image of an AlN template substrate used as a substrate for crystal growth in Examples 1-5. 7 is a cross-sectional SEM image of the AlN template substrate after AlN single crystal growth in Example 1. FIG. 8 is an SEM-EDX profile of the single crystal portion grown on the AlN template substrate after AlN single crystal growth in Example 1. FIG. 9 is a cross-sectional SEM image of the AlN template substrate after AlN single crystal growth in Example 2. FIG. 10 is a cross-sectional SEM image of the AlN template substrate after AlN single crystal growth in Example 3. FIG. 11 is a cross-sectional SEM image of the AlN template substrate after AlN single crystal growth in Example 4. FIG. 12A is SIMS measurement results for N (nitrogen) and Ni (nickel) of the AlN single crystal on the AlN template in Example 2. FIG. 12B is SIMS measurement results for O (oxygen) and C (carbon) of the AlN single crystal on the AlN template in Example 2. FIG.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described with reference to the drawings. In addition, when simply describing "nitrogen" in this specification, both _N2 and N shall be meant.

(Method for producing AlN single crystal)
The method for producing an AlN single crystal according to the present embodiment includes a melt forming step of heating and melting an alloy containing Al to form an alloy melt, and cooling a part of the melt to form a temperature gradient in the melt. and a precipitation step of precipitating an AlN single crystal while providing In the precipitation step, the high-temperature portion of the melt is brought into contact with the nitrogen-containing gas, and the growth substrate is held at the low-temperature portion of the melt. While continuing to take in the AlN single crystal, the AlN single crystal is deposited on the substrate for growth in the low-temperature part, and the AlN single crystal is grown continuously.

Before describing the details of each step, an AlN single crystal manufacturing apparatus 100 applicable to the method of the present invention schematically illustrated in FIG. 1 will be described. The crucible 170 of this AlN single crystal manufacturing apparatus 100 is placed in a nitrogen-containing gas. The crucible 170 can be replenished with an Al-containing alloy, and when this alloy is heated, a melt 180 is obtained. The melt 180 can be impregnated with a holder 195 holding a substrate 190 for growth.

If the holder 195 that holds the growth substrate 190 is provided with a double-tube structure or the like, the inner tube can be provided with a cooling mechanism capable of introducing a cooling gas or a cooling liquid, and this cooling substance can be used. , a portion of the melt 180 can be cooled. By doing so, it is possible to provide a high temperature portion 181 and a low temperature portion 182 with a temperature gradient in the melt 180 . When this AlN single crystal manufacturing apparatus 100 is used, the high temperature portion 181 of the melt 180 is kept in contact with the nitrogen-containing gas, while the low temperature portion 182 of the melt 180 is impregnated with the holder 195 holding the substrate 190 for growth. can be made Note that the “nitrogen-containing gas” may be any gas that can be used as a nitrogen supply source for the melt 180, and in addition to nitrogen gas (N ₂ gas), gas containing nitrogen atoms (for example, ammonia gas, etc.) ) may be included. Hereinafter, details of the substrate for growth and each step will be sequentially described while continuing to refer to FIG.

<Substrate for growth>
The growth substrate 190 is a substrate on which an AlN single crystal can be grown, and preferably has an AlN single crystal on the substrate surface. In particular, it is preferable to use an AlN template substrate obtained by epitaxially growing an AlN single crystal on a sapphire substrate. The growth substrate 190 may be an AlN single crystal itself (single crystal AlN seed crystal) instead of the crystal growth substrate. FIG. 1 illustrates the form of the substrate.

As the AlN template substrate, it is preferable to use an AlN template substrate obtained by epitaxially growing a C-plane AlN single crystal on a C-plane sapphire single crystal. is preferably 300 arcsec or less. Furthermore, the film thickness of the C-plane AlN single crystal on the C-plane sapphire single crystal is more preferably 0.3 μm or more and 1.2 μm or less, and is half the X-ray rocking curve of the (0002) plane of the C-plane AlN single crystal. More preferably, the price range is 150 arcsec or less.

Produced by the production method of the present invention by using an AlN template substrate having an X-ray rocking curve half width of 300 arcsec or less in the (10-12) plane of a C-plane AlN single crystal grown on a C-plane sapphire single crystal. It is possible to improve the crystal quality of the AlN single crystal to be used. In addition, when the AlN template substrate is immersed in the melt to cause liquid phase growth of AlN, it is possible to suppress decomposition and disappearance of the AlN single crystal on the surface of the AlN template substrate due to etching. When the AlN in contact with the melt 180 is polycrystalline, or even when it is a single crystal, when the half-value width of the X-ray rocking curve of the (10-12) plane is greater than 300 arcsec, it is likely to decompose, and the melt 180 The AlN crystal may disappear during the immersion. Even when a single crystal AlN seed crystal is used, for the same reason, it is preferable that the half width of the X-ray rocking curve of the (10-12) plane of the AlN single crystal is 300 arcsec or less.

The sapphire substrate used for the AlN template substrate preferably has a C-plane inclined at an off angle of 0.05° or more and 0.55° or less. A C-plane SiC single crystal can also be used instead of sapphire.

As a method for manufacturing an AlN template substrate in which a C-plane AlN single crystal is epitaxially grown on a C-plane sapphire single crystal and the half width of the X-ray rocking curve of the (10-12) plane of the AlN single crystal is 300 arcsec or less, the MOCVD method is used. can be obtained by subjecting an AlN template substrate grown in a nitrogen atmosphere to a low dislocation treatment by annealing at 1823 K or higher (for example, 1873 K).

As a method for growing AlN, MOCVD using trimethylaluminum (TMA) and ammonia as raw material gases is preferable, but HVPE or sputtering can also be used.

<Melt formation process>
In the melt forming step, an alloy containing Al is heated and melted to form a melt 180 of this alloy. Although the composition of the alloy that becomes the melt 180 is not particularly limited, it is preferably composed mainly of Al and a metal element that is less likely to form a nitride than Al, and the liquidus temperature of the alloy is thermodynamically AlN is preferably lower than the temperature at which the decomposition occurs. The alloy components other than Al preferably contain at least one of Fe, Ni, Cu, Co and Si as a main component. By using the melt 180 of these alloys, an AlN single crystal can be produced efficiently, and among them, it is most preferable to use a Ni—Al alloy. Among these alloys, it is preferable to have an alloy composition in which the temperature (T ₀ ) at which the value of the driving force Δμ for the growth of the AlN single crystal becomes zero, which will be described later, is 1700 K or more and 2100 K or less, and 1750 K or more and 2000 K or less. It is more preferable to have an alloy composition between The Ni—Al alloy preferably has an Al composition of 15 mol % or more and 35 mol % or less. From the viewpoint of equipment maintenance, it is preferable not to use a highly corrosive element such as Ga as an element forming the alloy melt 180 .

The crucible 170 containing the melt 180 may be made of any material. A sintered body containing nitrogen is preferably provided on the crucible 170 itself or on the inner surface of the crucible 170 . In addition, the sintered body containing nitrogen is preferably made of AlN or a material that is thermodynamically more unstable than AlN. By using AlN or a material more thermodynamically unstable than AlN for the crucible 170 itself containing the alloy melt 180 and the inner surface of the crucible 170 , the sintered body itself is made of nitrogen (AlN can be a source of nitrogen and Al). It is also preferable to use CSZ or BN as the material of the crucible 170 . When the crucible 170 is made of CSZ or BN, a material containing Al such as AlN sintered pieces or AlN polycrystals is added in order to replenish the amount of Al in the melt 180 that decreases with crystal growth. can be done separately.

<Precipitation process>
In the precipitation step, after the melt forming step, a part of the melt 180 is cooled to provide a temperature gradient in the melt 180 while precipitating the AlN single crystal. In this precipitation step, the nitrogen-containing gas is brought into contact with the high temperature portion 181 in the melt 180 and the growth substrate 190 is held by the holder 195 at the low temperature portion 182 in the melt 180 . In this way, AlN is precipitated on the growth substrate 190 in the low temperature portion 182 while nitrogen is continuously taken into the melt 180 in the high temperature portion 181, and the AlN single crystal is continuously grown. That is, nitrogen dissolved in the alloy melt 180 is transported to the low-temperature portion 182 of the alloy melt 180 and reacted with Al in the melt 180 on the surface of the growth substrate 190 held in the low-temperature portion 182. Thus, the AlN single crystal can be grown continuously. In the present invention, while performing the melt forming step and the precipitation step in parallel, both the supply of nitrogen to the alloy melt 180 and the precipitation of AlN by the reaction between the dissolved nitrogen and Al in the alloy are simultaneously performed. can be realized, and the AlN single crystal can be grown continuously. At that time, the low temperature part 182 is cooled to a temperature at which AlN is thermodynamically stable while maintaining the high temperature part 181 in a temperature range at which AlN is thermodynamically unstable (a temperature at which AlN does not precipitate and decomposes). preferably.

<Driving Force Δμ for Growth of AlN Single Crystal>
Here, the driving force Δμ for the growth of the AlN single crystal will be explained, and a more preferable aspect of this embodiment will be explained. In the method for producing an AlN single crystal according to the present invention, Al in the melt 180 reacts with nitrogen supplied in the melt 180 to form an AlN single crystal. When the nitrogen-containing gas of the nitrogen supply source contains _N2 gas, the reaction formula at this time is shown by the following formula (1).
2Al(l)+ _N2 (g)→2AlN(s) (1)

At this time, the activity of AlN when the reaction of the above equation (1) is in equilibrium is expressed as a ^eq _{. AlN} , the activity of Al in the melt 180 is a ^eq _. Let the partial pressures of _Al and _N2 be P ^eq . Assuming that _N2 , the equilibrium constant K of the above equation (1) is represented by the following equation (2).

Here, since AlN is a substantially pure solid, the activity a ^eq _.AlN of AlN is 1. In addition, the driving force Δμ for the growth of the AlN single crystal is the chemical potential of N ₂ in the atmosphere, where PN ₂ is the partial pressure of N ₂ in the atmosphere, and N ₂ and is expressed by the following equation (3). Furthermore, by using the equilibrium relationship of the above equation (2), the driving force Δμ for the growth of the AlN single crystal can finally be expressed by the following equation (4). In the formulas (3) and (4), k represents Boltzmann's constant and T represents absolute temperature.

From the above equation (4), the driving force Δμ for the growth of the AlN single crystal in the melt 180 is the N ₂ partial pressure PN ₂ in the atmosphere, the equilibrium constant K, the Boltzmann constant k, the absolute temperature T and in the melt 180 is represented by the Al activity a ^eq _.Al . From this, the driving force Δμ for AlN single crystal growth in the melt 180 can be controlled by the N ₂ partial pressure in the atmosphere, the temperature, and the alloy composition of the melt 180 . The temperature at which the value of the driving force Δμ for AlN single crystal growth becomes zero is defined as T ₀ . At this time, the temperature of the high-temperature portion 181 (hereinafter referred to as T1) in the melt 180 is higher than _T0 , and the temperature of the low-temperature portion 182 (hereinafter referred to as T2) is the liquid of the alloy forming the melt 180. It is preferably higher than the phase wire temperature and lower than _T0 . The temperature T1 of the high-temperature portion 181 of the melt 180 is kept at a temperature at which Δμ becomes negative (that is, T1>T ₀ ), and the high-temperature portion 181 is brought into contact with N ₂ gas. You can definitely dissolve it. In addition, the higher the temperature of the alloy melt 180, the more nitrogen can be dissolved _in the alloy melt. It is preferable to include steps.

As an example, a case where the melt 180 is obtained from a Ni—Al alloy containing Al and Ni as main components will be described. Here, the activity of Al in the melt 180 a ^eq. Regarding _Al , composition dependence of Al activity in Ni—Al at a temperature of 1873 K was reported in Desai PD. Thermodynamic properties of selected binary aluminum alloy systems. J Phys Chem Ref data. 1987;16:109-24. and its composition-dependent data can be used. Further, assuming that Ni--Al is a regular solution, the activity of Al in Ni--Al at temperatures other than 1873K can be obtained. When the partial pressure PN ₂ of N ₂ in the atmosphere is 1 bar, the relationship between the driving force Δμ for AlN single crystal growth and the temperature (T) for each composition of the Ni—Al alloy is obtained from the above equation (4). be able to. FIG. 2 shows the relationship in each alloy composition obtained in this manner. In addition, the end point on the low temperature side of the line corresponding to each alloy composition shown in FIG. 2 indicates the temperature of the liquidus line in that alloy composition. Adachi M, Sato A, Hamaya S, Ohtsuka M, Fukuyama H. Containerless measurements of the liquid-state density of Ni-Al alloys for use as turvine blade materials. SN Appl Sci. 2019;1: Data from 18-1-7 can be used.

In each alloy composition, the temperature at which the driving force for the growth of the AlN single crystal Δμ=0 is the temperature at which the reaction of the equation (1) is balanced. decomposes. As can be seen from FIG. 2, in each alloy composition, by controlling the temperature of the melt 180, the value of the driving force Δμ for AlN single crystal growth can be adjusted, and whether AlN is precipitated (Δμ>0) or not. , AlN is decomposed (Δμ<0). For example, when the melt 180 has an alloy composition of Ni-20 mol % Al, the value of _T0 is 1832K. In this case, since Δμ becomes negative at temperatures higher than 1832K, AlN decomposes in the melt 180, whereas at temperatures lower than 1832K, Δμ becomes positive and AlN precipitates. When the nitrogen-containing gas of the nitrogen supply source contains _N2 gas, the nitrogen-containing gas is brought into contact with the melt while maintaining the high-temperature portion 181 of the melt 180 at a temperature higher than the temperature at which Δμ=0. Since nitrogen dissolves in the alloy melt 180 without precipitating AlN single crystals on the contact surface between the liquid 180 and the gas, nitrogen can be continuously supplied into the melt 180 . In another example, the value of T ₀ is 1998K when the alloy melt 180 has an alloy composition of Ni-30 mol % Al. As for the composition of the alloy that becomes the melt 180, it is preferable to select such a composition that the value of _T0 is 1700 or more and 2000K or less.

It is preferable to hold the growth substrate 190 on the low temperature portion 182 while maintaining the low temperature portion 182 of the melt 180 at a temperature lower than the temperature at which Δμ=0. In this way, nitrogen dissolved in the alloy in the high temperature portion 181 reacts with Al in the alloy melt 180 on the surface of the substrate 190 for growth held in the low temperature portion 182, and the AlN single crystal is more stably formed. can be grown continuously.

More specific description will be given. Since a temperature gradient is provided in the melt 180, nitrogen is supplied into the melt 180 because Δμ<0 in the high temperature portion 181 (T1). Simultaneously with this supply of nitrogen, the low temperature section 182 (T2) becomes supersaturated with nitrogen because Δμ>0. In this way, the AlN single crystal can be grown continuously more reliably. Further, the surface temperature of the growth substrate 190 held in the low-temperature part 182 is preferably maintained at a temperature at which at least the AlN single crystal of the growth substrate 190 is not decomposed. is immersed in a high-temperature melt 180 at which Δμ<0, the surface of the AlN single crystal is preferably lowered to a low temperature at which Δμ>0 before the AlN single crystal serving as the starting point for crystal growth disappears. . Therefore, it is preferable to heat the high temperature portion 181 to a temperature higher than T ₀ and lower than T ₀ +30K. Furthermore, before the growth substrate 190 is immersed in the melt 180, the temperature of the high-temperature portion 181 is heated to T ₀ +30 K or higher to dissolve more nitrogen in the melt 180, and then the temperature of the high-temperature portion 181 increases. is higher than T ₀ and less than T ₀ +30K, the AlN single crystal can be grown more efficiently while retaining the AlN single crystal that serves as the starting point of crystal growth.

Thus, the method for producing an AlN single crystal according to the embodiment of the present invention can continue to take in nitrogen from the high temperature portion 181 while providing a temperature gradient in the alloy melt 180 by cooling. By appropriately selecting the alloy type, composition, atmosphere, _N2 partial pressure, etc., it is possible to continuously produce AlN single crystals at a lower temperature and lower cost than the sublimation method.

In addition, if the AlN single crystal is grown continuously in the precipitation step, the Al in the melt 180 is consumed, so the alloy composition of the melt 180 may change. For example, when the Al ratio in a Ni—Al alloy decreases, the temperature T ₀ in the composition decreases. Since the absolute value of Δμ decreases in the portion 182, AlN is more difficult to precipitate, and since the absolute value of Δμ increases in the high-temperature portion 181, more nitrogen is supplied from the gas phase to the liquid phase. Therefore, it is preferable to adjust the temperature of the melt 180 during the precipitation process so that the temperature of the melt 180 follows the change in the composition of the melt 180 . The heating conditions for the entire melt 180 may be adjusted, the temperatures of both the low-temperature portion 182 and the high-temperature portion 181 may be lowered, or only the temperature of the low-temperature portion 182 may be lowered. The temperature of the high-temperature portion 181 may be partially raised, or a combination thereof is also preferred. In addition, in order to compensate for the balance between the consumption of nitrogen in the melt and the supply of nitrogen to the melt when the AlN single crystal is continuously grown, the gas phase in the high temperature part 181 is changed from the liquid phase to the liquid phase. The _N2 partial pressure in the gas phase portion may be increased during the deposition process in order to efficiently supply nitrogen to .

Next, an example of an AlN single crystal growth apparatus applicable to the AlN single crystal manufacturing method according to the embodiment of the present invention will be described in further detail. In the following, when the last two digits of the reference numerals are the same as those of the above-described configuration, the redundant description will be omitted for the sake of simplicity. The configuration of the AlN single crystal growth apparatus described below is merely an example, and is not limited.

<AlN Single Crystal Growth Apparatus>
Please refer to FIG. The AlN single crystal manufacturing apparatus used in the present invention includes a reaction vessel 210 capable of supplying a nitrogen-containing gas to the interior thereof, and a crucible 270 stored inside the reaction vessel 210 and capable of holding an Al-containing alloy melt 280. , a heating device capable of heating the melt 280 by heating the crucible 270, and a holder 295 extending from above the liquid surface of the melt 280 to below the liquid surface. An AlN seed crystal or a substrate 290 for crystal growth is attached to the holder 295 . Here, the holder 295 is provided with an elevating mechanism and a cooling mechanism. It becomes possible to provide a temperature gradient between the substrate 290 of the .

FIG. 3 shows an example of an AlN single crystal growth apparatus according to an embodiment of the present invention. AlN single crystal growth apparatus 200 includes reaction vessel 210 , high frequency coil 220 , susceptor 230 , heat insulator 240 , gas supply pipe 250 and gas exhaust pipe 255 . The susceptor 230 accommodates the crucible 270 inside and is provided inside the reaction vessel 210 so as to cover the side surface of the accommodated crucible 270 . By energizing the high-frequency coil 220 , the susceptor 230 is heated and the crucible 270 can be heated. The crucible 270 may be made of any material that can hold the alloy melt 280, such as AlN and CSZ (calcia stabilized zirconia). A heat insulating material 240 is provided inside the reaction vessel 210 so as to cover the susceptor 230 and the crucible 270 . The gas supply pipe 250 is provided so as to be able to supply the atmosphere gas inside the reaction vessel 210 , and the gas exhaust pipe 255 is provided so as to be able to discharge the atmosphere gas inside the reaction vessel 210 .

The AlN single crystal growth apparatus 200 is provided with a holder 295 for a growth substrate 290 extending from the top of the reaction vessel 210 to the inside of the crucible 270 . By raising and lowering the growth substrate 290 attached to the lower end of the holder 295, the growth substrate 290 can be immersed in the melt 280, and the growth substrate 290 can be pulled up from the melt 280 and recovered. In order to cool part of the melt 280, the holder 295 preferably has a cooling mechanism, and the holder 295 preferably has a double-tube structure. By introducing a cooling gas or cooling liquid into the tube inside the holder 295 , the temperature of the holder 295 and its surroundings can be lowered, and a temperature gradient can be provided in the melt 280 . Moreover, in order to cool a part of the melt 280 and give a temperature gradient to the melt 280, it is possible to adopt a structure other than the double pipe structure. For example, a material with high heat dissipation may be used inside the holder 295, or the shape of the crucible 270, the placement of the high-frequency coil 220, the heat insulating material 240, or the like or output adjustment may be used to place the melt 280 at a desired position. A temperature gradient may be formed.

In FIG. 3, since the growth substrate 290 is arranged on the side surface of the holder 295 (horizontal to the axial direction of the holder), the crystal growth is perpendicular to the axial direction of the holder 295 . The growth substrate 290 does not have to be arranged perpendicular to the axial direction as shown in FIG. A growth substrate 390 may be placed to allow crystal growth in the same direction as the axial direction. In addition, by applying the VGF method (vertical temperature gradient solidification method), as shown in FIG. You can let me.

<AlN single crystal>
The AlN single crystal of the present invention formed on a single crystal AlN seed crystal or a substrate for crystal growth contains 8×10 ¹⁶ to 1×10 of any one or more of Fe, Ni, Cu and Co as impurities. ²¹ /cm ³ and preferably 1.5×10 ¹⁷ /cm ³ or more. Here, the concentration of impurities contained in the AlN single crystal refers to the half thickness range centering on the center of the region corresponding to the thickness range of the AlN single crystal in the SIMS analysis profile (that is, the thickness of the AlN single crystal 1/2 thickness range of the central portion excluding the 1/4 thickness of both end portions in the depth direction). These impurities are contained because the melt (alloy components other than Al contain at least one of Fe, Ni, Cu, and Co as a main component) contains these elements. be. In particular, the AlN single crystal preferably contains 8×10 ¹⁶ to 1×10 ²¹ /cm ³ of Ni as an impurity, more preferably 1.5×10 ¹⁷ /cm ^{3 or} more.

The carbon concentration in the AlN single crystal obtained by the present invention is preferably 2×10 ¹⁷ cm ⁻³ or less. This is because a carbon concentration of 2×10 ¹⁷ cm ⁻³ or less is likely to provide a high transmittance.

Hereinafter, the method for producing an AlN single crystal according to the present invention will be described in detail using examples.

(Example 1)
First, an AlN template substrate was produced. The AlN single crystal on the surface of the AlN template substrate was formed on a C-plane sapphire substrate having a diameter of 2 inches and a thickness of 430 μm (off angle in the M-plane direction of 0.11°) by MOCVD using trimethylaluminum (TMA) and ammonia as raw material gases. formed by At this time, the growth temperature was 1613 K, the growth pressure was 13.3 mbar, and a C-plane AlN single crystal was grown to a thickness of 0.5 μm on the C-plane sapphire substrate. Further, after the AlN single crystal was grown by the above-mentioned MOCVD method, it was annealed at 1873K for 4 hours in a nitrogen atmosphere to reduce dislocations. When the half width of the X-ray rocking curve of the (10-12) plane of the AlN single crystal on the surface of the prepared AlN template substrate was measured, it was 265 arcsec. The half width of the X-ray rocking curve of the (0002) plane of the AlN single crystal measured in the same manner was 49 arcsec.

Then, in an apparatus having a structure similar to that of the AlN single crystal growth apparatus described above with reference to FIG. The inside of the reaction vessel was replaced with N ₂ by supplying N ₂ gas from the gas supply pipe, and the reaction vessel was set to a 1 bar N ₂ gas atmosphere. As a substrate for crystal growth, the AlN template substrate having the AlN single crystal with a thickness of 0.5 μm was used, and this template substrate was placed on the side of a double-tube structure holder equipped with a cooling mechanism. Next, in a state in which a double-tube holder holding the AlN template substrate is held so as not to come into contact with the melt, a high-frequency coil is energized to heat the susceptor, thereby reducing the interface between the crucible and the alloy melt. The alloy melt was heated to a temperature of 1852K. The liquidus temperature of Ni-20mol%Al alloy is 1669K. At this time, the upper surface temperature of the high temperature portion of the melt is 1852K, and the value of T ₀ of the Ni-20mol%Al alloy is 1832K, so the temperature T1 of the high temperature portion is T ₀ +20K. During the heating of the alloy melt, a cooling gas was kept flowing through the tube inside the holder so as not to decompose the AlN of the AlN template substrate. Then, while cooling by introducing Ar gas as a cooling gas into the inner tube of the holder at a flow rate of 10 L / min into the inner tube, the holder is immersed in the alloy melt while maintaining the temperature T1 of the high temperature part. The periphery of the holder was kept at a low temperature portion and held for 7 hours to deposit AlN on the AlN template substrate. After that, the holder was pulled out from the alloy melt and cooled to room temperature.

A cross-sectional SEM image of the AlN template substrate before precipitation of AlN is shown in FIG. 6, and a cross-sectional SEM image of the AlN template substrate after precipitation of AlN is shown in FIG. SEM-EDX profile of the precipitated crystal is shown in FIG. The peaks appearing at 0.28 keV and 2.12 keV in the SEM-EDX profile of FIG. 8 represent the carbon contaminant of the sample and the gold coating agent during SEM observation, respectively, and the grown (precipitated) crystal It is not the origin peak. It was confirmed from FIG. 7 that there was a film with a thickness of 4.2 μm on the sapphire, and from FIG. 8 it was confirmed that the film was AlN crystal. In addition, as in Patent Document 3, an inverse pole figure crystal orientation map (not shown) by electron beam backscatter diffraction (EBSD) in each of the ND, TD, and RD directions for a grown (precipitated) AlN crystal. , it was confirmed that the grown (precipitated) AlN crystal was a single crystal. Since the film thickness of the AlN single crystal of the AlN template substrate before crystal growth (precipitation growth) was 0.5 μm, it was found that the AlN single crystal film grew to a thickness of 3.7 μm in this example.

(Example 2)
AlN was precipitated on the AlN template substrate under the same conditions as in Example 1, except that a high-temperature heating step of preheating at a high temperature was performed before the precipitation step. In the high-temperature heating step, before the holder is immersed in the alloy melt, the alloy melt is heated in advance so that the temperature of the interface between the crucible and the alloy melt reaches 1886 K and is held for 1 hour. The temperature of the interface of the alloy melt was cooled to 1852K. The upper surface temperature of the hot part of the melt is 1852K, the temperature T1 of the hot part is T ₀ +20K, and the temperature of the high temperature heating step is T ₀ +54K.

FIG. 9 shows a cross-sectional SEM image of the AlN template substrate after AlN has precipitated. From FIG. 9, it was confirmed that there was an 8.0 μm AlN single crystal on sapphire. Since the film thickness of the AlN single crystal of the AlN template substrate before growth (precipitation growth) was 0.5 μm, it was found that the film of the AlN single crystal grew to a thickness of 7.5 μm in this example.

From Example 1, it was confirmed that the AlN single crystal grew continuously on the AlN template substrate. Further, by comparing Example 1 and Example 2, it was found that by heating the interface between the crucible and the alloy melt to a high temperature in advance before the holder was immersed in the alloy melt, the AlN template substrate was formed. It has been found that the amount of AlN single crystal grown can be increased.

(Example 3)
AlN was deposited on the AlN template substrate under the same conditions as in Example 2, except that the holding time after the holder was immersed in the alloy melt was 1 hour. After that, the holder was pulled out from the alloy melt and cooled to room temperature.

FIG. 10 shows a cross-sectional SEM image of the AlN template substrate after AlN has precipitated. From FIG. 10, it was confirmed that there was an AlN single crystal film with a thickness of 0.7 μm on the sapphire and island-shaped AlN single crystals with a height of 0.8 μm thereon. Since the film thickness of the AlN single crystal of the AlN template substrate before growth (precipitation growth) was 0.5 μm, in Example 3, the AlN single crystal film grew (precipitation growth) to 0.2 μm, and It was found that island-like AlN single crystals were grown on the substrate.

Comparing FIGS. 9 and 10, when the holding time after immersing the holder in the alloy melt is 1 hour, island-like AlN single crystals grow (precipitation growth) on the surface. When the holding time was 7 hours, no island-shaped AlN single crystals were observed, and only film-shaped AlN single crystals were observed. From this, it is considered that island-like AlN single crystals are precipitated at the initial stage of growth (precipitation growth), and then they coalesce to precipitate (grow) film-like AlN single crystals.

(Example 4)
An AlN single crystal was grown (precipitation growth) on an AlN template substrate in the same manner as in Example 1, except that a crucible made of CSZ (ZrO ₂ -4.5 mass% CaO) was used. FIG. 11 shows a cross-sectional SEM image of the AlN template substrate after AlN has precipitated. From FIG. 11, it was confirmed that there was a film with a thickness of 8.8 μm on the sapphire. Since the film thickness of the AlN single crystal of the AlN template substrate before single crystal growth (precipitation growth) was 0.5 μm, it was found that the AlN single crystal film grew to 8.3 μm in this example. .

Also in the results of Example 4, it was confirmed that an AlN single crystal was grown on the AlN template substrate, as in Examples 1-3. In the results of Examples 1 to 3, it is believed that the AlN single crystal was precipitated on the AlN template substrate due to the nitrogen in the crucible and atmosphere being dissolved in the melt. It has been confirmed that an AlN single crystal can be produced only by supplying nitrogen from .

As described above, in the method for producing an AlN single crystal according to the embodiment of the present invention, by heating the high-temperature portion of the alloy melt to a temperature range in which Δμ is negative, the type and composition of the alloy are continuously , atmosphere, and N ₂ partial pressure, AlN single crystals can be produced at a lower temperature and at a lower cost than the sublimation method.

FIG. 12A shows SIMS analysis results for Ni (nickel) of the AlN single crystal of Example 2, and SIMS analysis results for O (oxygen) and C (carbon) are shown in FIG. 12B. SIMS analysis was performed under the following conditions. Ni analysis was carried out using a SIMS measurement device (CAMECA IMS-7f) with a primary ion species of O ²⁺ , a primary acceleration voltage of 8.0 kV, and a detection area of 30 μm in diameter. The C, O, and B analysis was performed using a SIMS measurement device (CAMECA IMS-6f) with Cs ⁺ as the primary ion species, a primary acceleration voltage of 15.0 kV, and a detection area of 30 μm in diameter. In addition, quantification was performed using an AlN standard sample.

From the SIMS analysis results shown in FIG. 12A, the region from the position where the Ni concentration sharply drops to the position where the N (secondary ion intensity) drops sharply indicates an AlN single crystal grown by MOCVD on the AlN template substrate. The Ni concentration in that region was about 5×10 ¹⁶ cm ⁻³ . On the other hand, the shallow region below the position where the Ni concentration drops sharply is considered to be the region showing the AlN single crystal grown in the Ni-20 mol% Al alloy, and the Ni concentration value in this region is 1.5 × 10. It is within the range of ¹⁷ cm ⁻³ to 3×10 ¹⁸ cm ⁻³ , and the thickness range of the center portion 1/2 excluding the thickness of both end portions 1/4 in the thickness direction of the AlN single crystal (hereinafter referred to as “ The average value of the thickness of the AlN single crystal is 2×10 ¹⁷ cm ⁻³ in the half-thickness range at the center of the thickness of the AlN single crystal. From this result, it was confirmed that the AlN single crystal of the present invention grown in a Ni-20 mol % Al alloy contained a large amount of Ni as an impurity.

Similarly, as a result of SIMS analysis of Ni (nickel) and Zr (zirconium) of the AlN single crystal of Example 4, in Example 4, Ni of the AlN single crystal grown in the Ni-20 mol% Al alloy The concentration was 1×10 ¹⁸ cm ⁻³ on average in the half-thickness range at the center of the thickness of the AlN single crystal, which was even higher than in Example 2. Zr was below the detection limit.

From the above, it was found that the AlN single crystal produced by the production method of the present invention contains a large amount of alloy components other than Al, which form an alloy containing Al, as impurities. Ni can also be expected to act as p-type conduction in the AlN single crystal.

Further, from the SIMS analysis results shown in FIGS. 12A and 12B, in the region considered to be the AlN layer of the AlN template substrate manufactured by the MOCVD method, both the oxygen and carbon concentrations are high. The carbon concentration of the grown AlN layer is about 4×10 ¹⁷ cm ⁻³ , whereas the carbon concentration of the AlN single crystal grown in the Ni-20 mol % Al alloy is the thickness at the center of the AlN single crystal thickness. The average value of the half range was 1.3×10 ¹⁷ cm ⁻³ .

AlN single crystals produced by sublimation or MOCVD were said to have lower transmittance in the deep ultraviolet region due to the inclusion of carbon. It has also been found that, in the AlN single crystal of the present invention described above, it is possible to suppress the contamination of the carbon concentration that lowers the transmittance of the crystal.

According to the present invention, it is possible to provide an AlN single crystal manufacturing method, an AlN single crystal, and an AlN single crystal manufacturing apparatus capable of continuously manufacturing an AlN single crystal at a low cost.

100 AlN Single Crystal Manufacturing Apparatus 170 Crucible 180 Melt 181 High Temperature Section 182 Low Temperature Section 190 Growth Substrate 195 Holder

(2) The nitrogen-containing gas contains _N2 gas, and the activity of Al in the melt when the reaction for the formation of the AlN single crystal represented by the following formula (A) is in equilibrium is a ^eq _.Al , the equilibrium constant of the formula (A) is K, the Boltzmann constant is k, the absolute temperature is T, and the partial pressure of _N2 of the nitrogen-containing gas at the time of precipitation _is PN2 , the following formula (B) is obtained. When the value of the driving force Δμ for the growth of the AlN single crystal represented becomes ₀ , the temperature of the high temperature portion is set higher than _T0 , and the temperature of the low temperature portion is set to the above The method for producing an AlN single crystal according to (1), wherein the temperature is equal to or higher than the liquidus temperature of the alloy and lower than _T0 .
2Al(l)+ _N2 (g)→2AlN(s) (A)

At this time, the activity of AlN when the reaction of the above equation (1) is in equilibrium is expressed as a ^eq _{. AlN} , the activity of Al in the melt 180 is a ^eq _. Let the partial pressures of _Al and _N2 be P ^eq . Assuming that _N2 , the equilibrium constant K of the above equation (1) is represented by the following equation (2).

Here, since AlN is a substantially pure solid, the activity a ^eq _.AlN of AlN is 1. In addition, the driving force Δμ for the growth of the AlN single crystal is the chemical potential of N ₂ in the atmosphere, where P _N2 is the partial pressure of N ₂ in the atmosphere, and N ₂ and is expressed by the following formula (3). Furthermore, by using the equilibrium relationship of the above equation (2), the driving force Δμ for the growth of the AlN single crystal can finally be expressed by the following equation (4). In the formulas (3) and (4), k represents Boltzmann's constant and T represents absolute temperature.

From the above equation (4), the driving force Δμ for the growth of the AlN single crystal in the melt 180 is the N ₂ partial pressure P _N2 in the atmosphere, the equilibrium constant K, the Boltzmann constant k, the absolute temperature T and in the melt 180 is represented by the Al activity a ^eq _.Al . From this, the driving force Δμ for AlN single crystal growth in the melt 180 can be controlled by the N ₂ partial pressure in the atmosphere, the temperature, and the alloy composition of the melt 180 . The temperature at which the value of the driving force Δμ for AlN single crystal growth becomes zero is defined as T ₀ . At this time, the temperature of the high-temperature portion 181 (hereinafter referred to as T1) in the melt 180 is higher than _T0 , and the temperature of the low-temperature portion 182 (hereinafter referred to as T2) is the liquid of the alloy forming the melt 180. It is preferably higher than the phase wire temperature and lower than _T0 . The temperature T1 of the high-temperature portion 181 of the melt 180 is kept at a temperature at which Δμ becomes negative (that is, T1>T ₀ ), and the high-temperature portion 181 is brought into contact with N ₂ gas. You can definitely dissolve it. In addition, the higher the temperature of the alloy melt 180, the more nitrogen can be dissolved _in the alloy melt. It is preferable to include steps.

As an example, a case where the melt 180 is obtained from a Ni—Al alloy containing Al and Ni as main components will be described. Here, the activity of Al in the melt 180 a ^eq. Regarding _Al , composition dependence of Al activity in Ni—Al at a temperature of 1873 K was reported in Desai PD. Thermodynamic properties of selected binary aluminum alloy systems. J Phys Chem Ref data. 1987;16:109-24. and its composition-dependent data can be used. Further, assuming that Ni--Al is a regular solution, the activity of Al in Ni--Al at temperatures other than 1873K can be obtained. When the partial pressure P _N2 of N ₂ in the atmosphere is 1 bar, the relationship between the driving force Δμ for AlN single crystal growth and the temperature (T) for each composition of the Ni—Al alloy is obtained from the above equation (4). be able to. FIG. 2 shows the relationship in each alloy composition obtained in this manner. In addition, the end point on the low temperature side of the line corresponding to each alloy composition shown in FIG. 2 indicates the temperature of the liquidus line in that alloy composition. Adachi M, Sato A, Hamaya S, Ohtsuka M, Fukuyama H. Containerless measurements of the liquid-state density of Ni-Al alloys for use as turvine blade materials. SN Appl Sci. 2019;1: Data from 18-1-7 can be used.

Claims (12)

a melt forming step of heating and melting an alloy containing Al to form a melt of the alloy;
a precipitation step of precipitating an AlN single crystal while cooling a part of the melt to provide a temperature gradient in the melt;
A method for producing an AlN single crystal comprising
In the precipitation step, a nitrogen-containing gas is brought into contact with a high-temperature portion in the melt, and a single-crystal AlN seed crystal or a substrate for crystal growth is held at a low-temperature portion in the melt, so that the high-temperature The AlN single crystal is precipitated on the AlN seed crystal or the substrate in the low temperature portion while continuing to take in nitrogen into the melt in the low temperature portion, thereby continuously growing the AlN single crystal. AlN single crystal manufacturing method. the nitrogen-containing gas comprises _N2 gas;
Al is the activity of Al in the melt when the reaction for forming the AlN single crystal represented by the following formula (A) ^is in equilibrium, K is the equilibrium constant _of the formula (A), Let k be the Boltzmann constant, T be the absolute temperature, and _pN2 be the partial pressure of _N2 of the nitrogen-containing gas during precipitation,
When the value of the driving force Δμ for growth of the AlN single crystal represented by the following formula (B) is ₀ , the temperature of the high temperature portion is higher than _T0 , and the 2. The method for producing an AlN single crystal according to claim 1, wherein the temperature of the low temperature portion is set to a temperature equal to or higher than the liquidus temperature of the alloy and lower than _T0 .
2Al(l)+ _N2 (g)→2AlN(s) (A)

3. The method for producing an AlN single crystal according to claim 2, wherein said melt forming step includes a high temperature heating step of heating said high temperature portion to a temperature of _T0 +30K or higher. 4. The production of the AlN single crystal according to claim 3, wherein the melt-forming step includes a low-temperature heating step of heating the high-temperature portion to a temperature higher than _T0 and lower than _T0 +30K after the high-temperature heating step. Method. a holder for holding the AlN seed crystal of the single crystal or the substrate for crystal growth has a cooling mechanism;
The method for producing an AlN single crystal according to any one of claims 1 to 4, wherein in the precipitation step, the melt is provided with the temperature gradient by bringing the holder into contact with the melt. The method for producing an AlN single crystal according to any one of claims 1 to 4, wherein the substrate for crystal growth is an AlN template substrate obtained by epitaxially growing an AlN single crystal on a sapphire single crystal. The AlN template substrate is an AlN template substrate obtained by epitaxially growing a C-plane AlN single crystal on a C-plane sapphire single crystal, and the half width of the X-ray rocking curve of the (10-12) plane of the C-plane AlN single crystal is 7. The method for producing an AlN single crystal according to claim 6, wherein the time is 300 arcsec or less. The method for producing an AlN single crystal according to claim 1, wherein the alloy containing Al is a Ni—Al alloy. A single-crystal AlN seed crystal or an AlN single crystal formed on a substrate for crystal growth, containing at least one of Fe, Ni, Cu, and Co as an impurity in an amount of 8×10 ¹⁶ to 1×10 ²¹ / AlN single crystal containing cm ³ . 10. The AlN single crystal according to claim 9, which is a single crystal AlN seed crystal or an AlN single crystal formed on a substrate for crystal growth, and contains 8×10 ¹⁶ to 1×10 ²¹ /cm ³ of Ni as an impurity. AlN single crystal. 11. The AlN single crystal according to claim 9, having a carbon concentration of 2×10 ¹⁷ cm ⁻³ or less. a reaction vessel into which a nitrogen-containing gas can be supplied;
a crucible stored inside the reaction vessel and capable of holding a melt of an alloy containing Al;
a heating device capable of heating the melt by heating the crucible;
a holder extending from above the melt surface to below the melt surface;
An AlN seed crystal or a substrate for crystal growth is attached to the holder,
The holder is provided with a lifting mechanism and a cooling mechanism,
A temperature gradient can be provided between the melt and the AlN seed crystal or the substrate for crystal growth by using the cooling mechanism while bringing the holder into contact with the melt using the elevating mechanism. Na,
AlN single crystal manufacturing equipment.

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