A large temperature difference crystal growth furnace and a method for preparing high-quality aluminum nitride single crystal

Abstract

The present invention provides a large temperature difference crystal growth furnace, comprising: a crucible support, a crucible placed on the crucible support, a heater for heating the bottom of the crucible, an extended water-cooled wall for cooling the top of the crucible, and a heat preservation component arranged around the crucible; wherein the extended water-cooled wall extends downward from the furnace body water-cooled wall and is close to the top of the crucible, the heat preservation component is used to block the heat transfer between the extended water-cooled wall and the heater, and to keep the crucible warm, the crucible support is a movable crucible support, used to lift the crucible and move it up and down in the vertical direction and accurately control the axial position of the crucible; and also includes upper and lower temperature monitors for monitoring the temperature at the center of the upper and lower surfaces of the crucible. The extended water-cooled wall is equipped with a positioning motion system, which can realize flexible regulation of the axial temperature difference inside the crucible, broaden the growth condition window of aluminum nitride single crystals, and realize the low-temperature and high-quality aluminum nitride single crystal growth by the PVT method.

Description

Technical Field

[0001] The invention belongs to the field of crystal growth, and relates to a large temperature difference device for growing aluminum nitride single crystals and a method for preparing the aluminum nitride single crystals. Background Art

[0002] Aluminum nitride (AlN) has excellent properties such as high bandgap (6.2eV), high thermal conductivity (340W / (m·K)), high breakdown field strength (11.7MV / cm), good ultraviolet transmittance, chemical and thermal stability, etc. It is an ideal substrate for high-temperature, high-frequency, high-power electronic devices and high-Al component deep ultraviolet optoelectronic devices, such as power devices, deep ultraviolet light-emitting diodes (DUV-LEDs), ultraviolet lasers, sensors, etc. In the past, the growth of AlN bulk crystals has been explored, including hydride vapor phase epitaxy (HVPE), molecular beam epitaxy (MBE), metal organic compound vapor deposition (MOCVD), physical vapor transport (PVT), etc. Among them, the PVT method has the advantages of fast growth rate, good crystal integrity, high safety, and suitable for growing bulk high-quality substrate materials. It is considered to be the only most promising method for preparing large-size, high-quality AlN crystals.

[0003] Since there are no effective high-quality AlN substrates in nature, it is very challenging to obtain large-sized and high-quality AlN single crystals. Homoepitaxial growth and heteroepitaxial growth using SiC substrates are currently commonly used growth techniques. Homoepitaxial growth uses small-sized AlN substrates for iterative growth, and the growth cycle is long and difficult. Using SiC as a substrate for heteroepitaxial growth can quickly produce large-sized AlN single crystal ingots. However, at high temperatures, SiC is prone to surface dissociation in the early stages of growth, resulting in poor initial AlN growth quality. If the dissociation is suppressed by lowering the temperature, the growth rate will be too slow to meet industrial needs. In addition, sapphire is currently a very mature semiconductor substrate material with high crystal quality. Because sapphire tolerates too low a temperature and is easily decomposed at high temperatures, traditional PVT processes and crystal growth furnaces cannot use sapphire as a substrate for epitaxial growth.

[0004] In order to solve the above problems, the present invention proposes a large temperature difference crystal growth furnace and a method for preparing high-quality aluminum nitride single crystals. The present invention realizes a large temperature difference while lowering the substrate temperature through the internal design of a large temperature difference crystal growth furnace, ensuring that the substrate is in a low-temperature thermal environment, and does not self-dissociate, thereby not damaging the growth surface. At the same time, the crystal growth furnace realizes a large temperature difference inside the crucible to ensure that the raw materials are in a high-temperature environment, so that the AlN crystal growth has an effective material deposition rate, and the growth rate can be regulated by controlling the temperature difference, which is conducive to the initial growth of a flat two-dimensional morphology layer. The present invention realizes effective AlN growth in a low-temperature thermal environment, making it possible to inhibit epitaxial growth of sapphire or silicon carbide as a substrate, and a high-quality initial layer can be formed through low-temperature growth, which is very beneficial for subsequent high-rate growth to obtain higher-quality AlN single crystal ingots. Summary of the invention

[0005] The purpose of the present invention is to provide a large temperature difference crystal growth furnace, in which the crucible support and the extended water-cooled wall are equipped with a positioning motion system, which can accurately adjust the axial position of the crucible and the distance between the water-cooled wall and the upper surface of the growth chamber, thereby realizing flexible regulation of the axial temperature difference inside the crucible, broadening the growth condition window of aluminum nitride single crystals, and realizing low-temperature and high-quality aluminum nitride single crystal growth by the PVT method.

[0006] To achieve the above object, the present invention adopts the following technical solutions:

[0007] The first aspect of the present invention provides a large temperature difference crystal growth furnace, comprising: a crucible support, a crucible placed on the crucible support, a heater for heating the bottom of the crucible, an extended water-cooled wall for cooling the top of the crucible, and a crucible insulation component arranged around the crucible; wherein the extended water-cooled wall extends downward from the water-cooled wall of the furnace body and is close to the top of the crucible, the crucible insulation component is used to block the heat transfer between the extended water-cooled wall and the heater, and to insulate the crucible, the crucible support is a movable crucible support, which is used to lift the crucible and move it up and down in the vertical direction and accurately control the axial position of the crucible; and also includes upper and lower temperature monitoring instruments for monitoring the temperature at the center of the upper and lower surfaces of the crucible.

[0008] Among them, the extended water-cooled wall can absorb the heat from the top of the crucible, the heater can fully heat the bottom of the crucible, and the crucible insulation component can block the heat transfer between the water-cooled wall and the heater to ensure that the high temperature at the bottom of the crucible and the low temperature at the top will not cause thermal interference with each other, and strengthen insulation while reducing power consumption. The combination of the above three components realizes a large axial temperature difference inside the crucible, so that the top of the crucible is in a completely low temperature state. At the same time, the raw material at the bottom of the crucible maintains a relatively high temperature of >1900°C, and an axial temperature difference of more than 300°C is formed between the top and bottom of the crucible. The aluminum nitride raw material decomposes at the bottom high temperature and is transmitted to the substrate surface at the top of the crucible under the drive of the large temperature difference. Through the combined effect of the large axial temperature difference and the low temperature of the substrate, it is ensured that the material has a suitable supersaturation and growth rate on the substrate surface, so as to have the ability to grow a high-quality aluminum nitride layer.

[0009] As a preferred embodiment, the extended water-cooled wall includes an extended portion, a connecting portion connecting the extended portion and the furnace water-cooled wall, and a driving portion for driving the extended portion to move up and down in a vertical direction; wherein the connecting portion is a deformable connecting portion.

[0010] The extended water-cooled wall can quickly absorb the heat on the top of the crucible, thus forming an effective low temperature on the top of the crucible.

[0011] As an optional embodiment, the structure of the heater is a woven mesh or a plate structure, the heating method is induction heating or resistance heating, and the heating form is bottom heating, side heating or combined heating.

[0012] As a preferred embodiment, the crucible heat-insulating component is made of a high-temperature resistant metal material or a ceramic material, with a thermal conductivity of less than 10 W / (m·K) and a tolerable temperature of greater than 1500°C.

[0013] As a preferred embodiment, the crucible heat-insulating component is sleeved on the side of the crucible and forms a distance with the outer side wall of the crucible, and the distance is smaller than the radius of the crucible.

[0014] As a preferred embodiment, the crucible heat-insulating component blocks the heat transfer between the extended water-cooled wall and the heater, so that a temperature difference greater than 300° C. is formed between the top and the bottom of the crucible.

[0015] A second aspect of the present invention provides a method for preparing high-quality aluminum nitride single crystals, which comprises the following steps:

[0016] Step 1: assemble aluminum nitride raw material at the bottom of the crucible, assemble the substrate at the top of the crucible, and move the crucible to a high crucible position by means of a movable crucible support;

[0017] Step 2: The temperature is raised by a heater and high-purity nitrogen is introduced to form a large temperature difference distribution inside the crucible, so that the temperature at the substrate is less than 1800°C, the temperature at the raw material is greater than 1900°C, and the temperature difference between the two positions is greater than 300°C. A controllable low-speed deposition rate is formed on the surface of the substrate, and the temperature is kept for a period of time to form a high-quality initial layer.

[0018] A large axial temperature difference can be formed inside the crucible at the high crucible position, the raw materials are decomposed at high temperature and driven by the large temperature difference, the material is transferred to the substrate surface at the top of the crucible, and crystal growth is carried out, and the growth rate is controllable; after keeping warm for a period of time, a high-quality initial layer can be formed.

[0019] Step three, the crucible is moved to a low crucible position by the movable crucible support, the temperature at the substrate increases as the crucible position decreases, and then the deposition rate at the substrate is greatly improved to form a high-speed c-direction growth, and the temperature is kept for a period of time.

[0020] During this period, by further increasing the temperature of the substrate and the raw material, the high-speed growth of aluminum nitride single crystal can be achieved. Since a high-quality initial layer is formed at the high crucible position, the high-speed growth at the low crucible position can continue the high crystal quality and high-quality morphology of the initial layer, and finally achieve the purpose of quickly growing high-quality and large-sized single crystal ingots.

[0021] Step 4: Cooling down, and finally preparing an aluminum nitride single crystal ingot with low dislocation density and high crystal quality.

[0022] It should be noted that the above-mentioned high crucible position and low crucible position are not fixed crucible positions, but two relative concepts.

[0023] As a preferred embodiment, in step 2, the low-speed deposition rate is less than 20 μm / h.

[0024] As an optional embodiment, in step one, the substrate includes but is not limited to sapphire, silicon carbide, gallium nitride, aluminum nitride, scandium nitride, boron nitride bulk crystal materials, or a template material with epitaxial III-nitride semiconductor film, or metal materials such as tungsten, tantalum, molybdenum, tantalum carbide, etc.

[0025] As a preferred embodiment, the position parameters of the high crucible position and the low crucible position are obtained by calculating the temperature field, mass transfer field, and growth rate parameters based on numerical simulation technology, and are determined based on actual preparation experience parameters.

[0026] As a preferred embodiment, during the preparation process, different crucible position parameters are selected and the temperature is raised and lowered to control different growth rates for crystal growth.

[0027] The present invention achieves a large axial temperature difference inside the crucible while reducing the substrate temperature through the internal design of the large temperature difference crystal growth furnace, ensuring that the substrate is in a low-temperature thermal environment, does not self-dissociate, and thus does not damage the growth surface. At the same time, the large axial temperature difference inside the crucible ensures that the raw materials are in a high-temperature environment, so that the AlN crystal growth has an effective material deposition rate. Furthermore, by controlling the temperature difference, the size of the growth rate can be regulated, which is conducive to growing a flat two-dimensional morphology layer in the early stage.

[0028] The preparation method of the present invention realizes effective AlN growth in a low-temperature thermal environment, making it possible to inhibit epitaxial growth on a sapphire substrate, and can form a high-quality initial layer through low-temperature growth, which is very beneficial for subsequent high-rate growth to obtain higher-quality AlN single crystal ingots. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 It is a schematic structural diagram of an embodiment of a large temperature difference crystal growth furnace of the present invention.

[0030] Figure 2 This is a process curve diagram of preparing high-quality aluminum nitride single crystals using a large temperature difference crystal growth furnace according to an embodiment of the present invention.

[0031] Figure 3 The graph is a graph showing the influence of the distance between the extended water-cooled wall and the upper part of the crucible on the power of the large temperature difference furnace and the temperature difference between the source crystals in the large temperature difference crystal growth furnace according to an embodiment of the present invention.

[0032] Figure 4 The thermal field comparison diagram is with and without the crucible insulation component installed.

[0033] Figure 5 It is a curve diagram showing the relationship between the spacing between the heat-insulating parts on the side of the crucible and the temperature difference between the source crystals.

[0034] Figure 6 This is a curve chart showing the effect of crucible position on the temperature difference between source crystals, heating power, and crystal growth rate.

[0035] Figure 7 The present invention provides HRXRD rocking curves of the AlN single crystal prepared by the method of the present invention at the (0002) and (10-12) diffraction planes.

[0036] Wherein: 1-inserted water-cooled wall, 2-tungsten mesh heater, 3-zirconia ceramic, 4-tungsten screen, 5-movable crucible support, 6-crucible system, 7-water-cooled wall, 11-inserted part, 12-connecting part, 41-upper tungsten screen, 42-side tungsten screen, 43-lower tungsten screen, 61-crucible body, 62-aluminum nitride raw material, 63-sapphire substrate. DETAILED DESCRIPTION

[0037] In order to further understand the present invention, preferred embodiments of the present invention are described below in conjunction with examples. However, it should be understood that these descriptions are only for further illustrating the features and advantages of the present invention, rather than limiting the claims of the present invention.

[0038] In an embodiment, the internal structure of a large temperature difference crystal growth furnace can be referred to as Figure 1 The large temperature difference crystal growth furnace is mainly composed of an extended water-cooled wall 1, a tungsten mesh heater 2, zirconia ceramics 3, a tungsten insulation screen 4, a movable crucible support 5, a crucible system 6 and a cooling wall 7.

[0039] The movable crucible support 5 is used to lift the crucible system 6 to move up and down in the vertical direction, and can accurately control the axial position of the crucible. In this embodiment, it includes a telescopic shaft and a top platform for placing the crucible at the top of the telescopic shaft. It can also be other structures, which are not specifically limited here.

[0040] In this embodiment, the extended water-cooled wall 1 includes an extended portion 11 and a connecting portion 12 connecting the extended portion 11 and the furnace water-cooled wall 7, and a driving portion (not shown) for driving the extended portion 11 to move up and down in the vertical direction. Among them, the connecting portion 12 is a deformable metal connecting portion, such as a structure similar to a metal bellows, which can be extended and retracted in the vertical direction and simultaneously transport cooling water to the extended portion 11. The extended portion 11 is a double-layer steel plate structure, with circulating cooling water passing through the middle, and the distance between the bottom wall and the top surface of the crucible is greater than 0.1mm. The smaller the distance between the bottom wall and the top surface of the crucible, the better the cooling effect, otherwise the cooling effect is reduced. Therefore, by adjusting the distance between the bottom wall of the extended portion and the top surface of the crucible, the temperature of the top area of ​​the crucible can be adjusted. In this embodiment, the driving portion can be a mechanical or magnetostrictive mechanism for driving the extended portion 11 to move up and down in the vertical direction, which is not specifically limited here.

[0041] In this embodiment, the heater is a tungsten mesh heater 2, which is used to heat the bottom of the crucible. In other embodiments, it can also be a flat plate structure, the heating method is induction heating or resistance heating, and the heating form is bottom heating, side heating or combined heating.

[0042] In this embodiment, the large temperature difference crystal growth furnace also includes upper and lower temperature monitors (not shown in the figure) for monitoring the temperature at the center of the upper and lower surfaces of the crucible. In this embodiment, the crucible heat-insulating component is made of zirconia ceramic 3, but is not limited to zirconia ceramic 3. In other embodiments, it can be made of other low thermal conductivity, high temperature resistant materials. The crucible system 6 is composed of a crucible body 61, an aluminum nitride raw material 62 and a sapphire substrate 63.

[0043] In this embodiment, the outer insulation component adopts a tungsten insulation screen 4, which is composed of an upper screen 41, a side screen 42, and a lower screen 43, but is not limited to the tungsten insulation screen 4. In other embodiments, it can be other high-temperature resistant metal or ceramic insulation materials or a combination.

[0044] In this embodiment, a sapphire substrate sheet 63 is used as the substrate, but the substrate used is not limited to sapphire. In other embodiments, it can also be composed of bulk substrate materials such as sapphire, silicon carbide, gallium nitride, aluminum nitride, or a template material with an epitaxial III-nitride semiconductor film.

[0045] The above-mentioned large temperature difference crystal growth furnace is used to perform epitaxial growth of aluminum nitride single crystal with the sapphire substrate 63 as the substrate. The growth process is shown in the process curve diagram ( Figure 2 ) is shown. The detailed method for preparing high-quality aluminum nitride single crystals is as follows.

[0046] Preparation stage: assembling aluminum nitride raw material 62 at the bottom of crucible body 61, assembling sapphire substrate sheet 63 at the top of crucible body 61, and moving the crucible system 6 to the high crucible position by means of movable crucible support 5;

[0047] Stage 1: Heating. High-purity nitrogen is used with a pressure between 20-100 kPa. Heat the bottom of the crucible 61 from room temperature to T2>1950°C through heater 2, and heat the substrate from room temperature to T1<1700°C, so that the temperature difference (T2-T1) between the bottom and top of the crucible 61 is greater than 300°C, forming a large temperature difference thermal environment;

[0048] Stage 2: low-temperature insulation. The raw material decomposes at high temperature and is driven by a large temperature difference to be transferred to the surface of the sapphire 63 at the top of the crucible. Since the sapphire substrate is in a low-temperature environment, no or very little surface self-decomposition occurs, thereby ensuring that the substrate surface is not damaged by high temperature in the early stages of growth, maintaining high-quality surface morphology and orientation. On the basis of this high-quality substrate, due to the high-temperature sublimation of the bottom of the raw material 62 and the large temperature difference drive, sufficient material components are provided to the substrate surface, thereby achieving effective crystal growth at a growth rate of 0.5-10μm / h. During this period, the insulation can be maintained for 10-20 hours, and the insulation time is not limited. The time can be set according to the actual rate and the predetermined crystal thickness to form a high-quality initial layer;

[0049] Stage 3: Lowering the crucible position. Move the crucible system 6 to the lower crucible position through the movable crucible support 5, and try to keep the upper and lower temperatures stable during the movement;

[0050] Stage 4: Raise the temperature. The bottom of the crucible 61 is heated to T4>2100°C by heater 2, and the temperature of the substrate is heated to T3>2000°C. The temperature difference between the bottom and top of the crucible 61 is reduced, forming a high-temperature growth environment.

[0051] Stage 5: High-temperature insulation. The low crucible position realizes traditional high-temperature and high-speed PVT growth, with a growth rate of 50-200μm / h, and can be kept warm for 50-100h. The insulation time is not limited and can be set according to the actual rate and the predetermined final crystal thickness. During this period, based on the high-quality initial layer formed at the high crucible position, the high crystal quality and high-quality morphology of the initial layer can be continued during the high-speed growth process at the low crucible position, and high-quality and large-sized single crystal ingots can be grown quickly, ultimately forming high-quality aluminum nitride single crystal ingots;

[0052] Stage 6: Cooling. Finally, an aluminum nitride single crystal ingot with low dislocation density and high crystal quality is prepared and taken out.

[0053] In a preferred embodiment, numerical simulation technology is used to simulate and optimize the large temperature difference thermal environment in the second stage, so as to determine the optimal thermal field structure. Among them, the distance between the extended water-cooled wall 1 and the top of the crucible body 61 and the shape of the zirconia ceramic 3 have the greatest influence on the formation of the large temperature difference. The substrate temperature is simulated and controlled to be 1650°C. The simulation results (reference Figure 3 ) shows that when the distance between the top 61 of the crucible body and the water-cooled wall 1 is 20 mm, the axial temperature difference in the growth chamber is the minimum. The axial temperature difference increases exponentially with the decrease of the distance, indicating that reducing the distance between the top 61 of the crucible body and the water-cooled wall 1 can effectively increase the temperature difference inside the crucible system 6. However, the output power of the heater 3 also increases rapidly with the decrease of the distance, indicating that in order to obtain a larger temperature difference, the power output and loss need to be increased. Considering the influence of the above factors, the best choice is that the distance between the top 61 of the crucible body and the water-cooled wall 1 is 0.5-2 mm.

[0054] The zirconia ceramic 3 plays a key role in forming a large temperature difference inside the crucible system 6 at low temperature. It can block the heat transfer between the heater 2 and the extended water-cooled wall 1, so that the heater 2 and the water-cooled wall 1 can fully act on the bottom heating and top heat absorption of the crucible system 6 respectively, thereby forming a large temperature difference.

[0055] refer to Figure 4 The thermal field simulation results with and without the placement of zirconia ceramics 3 show that the thermal field of the placement of zirconia ceramics 3 ( Figure 4 Left side) to obtain a larger temperature difference inside the crucible system 6 than the temperature field of the non-zirconia ceramic 3 ( Figure 4 The right side) is about 200℃ higher, which is enough to show the importance of zirconia ceramic 3 in forming a large temperature difference and the effectiveness of thermal field design. Further, the effect of the distance between zirconia ceramic 3 and the crucible on the temperature difference is analyzed. Figure 5The simulation results show that as the spacing increases, the temperature difference decreases almost linearly. The above shows that the closer the zirconia ceramic 3 and the crucible system 6 are, the better the heat preservation effect on the side of the crucible and the more effective the heat transfer between the barrier heater 2 and the extended water-cooled wall 1, thus forming the expected large temperature difference effect.

[0056] The different axial positions of the crucible system 6 in the thermal field have a great influence on its internal temperature difference and temperature distribution. In order to find the most suitable crucible position with large temperature difference, numerical simulation technology is used for preliminary exploration. Figure 5 As the crucible position moves downward, the temperature difference decreases almost linearly, and the power also decreases. This is because the crucible system 6 gradually approaches the central area of ​​effective heating by the heater 3, resulting in a gradual decrease in the temperature difference and a decrease in power demand. In order to ensure that the temperature difference is greater than 300°C, the crucible system 6 is selected to be above -20°C.

[0057] Based on the above simulation results and optimized process design, high-quality aluminum nitride single crystals are grown on the sapphire substrate 63. In the later stage of aluminum nitride single crystal growth, it grows in the c direction at a high speed. In order to obtain a thicker ingot, the ingot is cut / grinded / chemical mechanical polished to finally form a polished wafer with low roughness. Through high-resolution XRD rocking curve detection, the half-height width of the (0002) diffraction surface of the wafer is 193 arc seconds, and the half-height width of the (10-12) diffraction surface is 149 arc seconds, indicating that the crystal quality of the wafer has reached a high quality level.

[0058] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modification, equivalent substitution, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention. Any reference numeral in a claim shall not be regarded as limiting the claim involved.

[0059] In addition, it should be understood that although the present specification is described according to implementation modes, not every implementation mode contains only one independent technical solution. This description of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment may also be appropriately combined to form other implementation modes that can be understood by those skilled in the art.

Claims

1. A method for preparing high-quality aluminum nitride single crystals, based on a large temperature difference crystal growth furnace for preparing aluminum nitride single crystals, characterized in that: The large temperature difference crystal growth furnace comprises: a crucible support, a crucible placed on the crucible support, a heater for heating the bottom of the crucible, an extended water-cooled wall for cooling the top of the crucible, and a crucible insulation component arranged around the crucible; wherein the extended water-cooled wall extends downward from the water-cooled wall of the furnace body and is close to the top of the crucible, the crucible insulation component is used to block the heat transfer between the extended water-cooled wall and the heater, and to keep the crucible warm, the crucible support is a movable crucible support, used to lift the crucible and move it up and down in the vertical direction and accurately control the axial position of the crucible; and also includes upper and lower temperature monitors for monitoring the temperature at the center of the upper and lower surfaces of the crucible; The preparation method comprises the following steps: Step 1: assemble aluminum nitride raw material at the bottom of the crucible, assemble the substrate at the top of the crucible, and move the crucible to a high crucible position by means of a movable crucible support; Step 2: The temperature is raised by a heater and high-purity nitrogen is introduced to form a large temperature difference distribution inside the crucible, so that the temperature at the substrate is less than 1800° C., the temperature at the raw material is greater than 1900° C., and the temperature difference between the two positions is greater than 300° C., a controllable low-speed deposition rate is formed on the surface of the substrate, and the temperature is kept for a period of time to form a high-quality initial layer; Step 3, the crucible is moved to a low crucible position by the movable crucible support, the temperature at the substrate increases as the crucible position decreases, and then the deposition rate at the substrate is greatly increased to form a high-speed c-direction growth, and the temperature is kept for a period of time; Step 4: Cool down and take out the prepared aluminum nitride single crystal ingot.

2. The method for preparing high-quality aluminum nitride single crystal according to claim 1, characterized in that: The intrusion-type water-cooled wall comprises an intrusion portion, a connection portion connecting the intrusion portion and the furnace water-cooled wall, and a driving portion for driving the intrusion portion to move up and down in a vertical direction; wherein the connection portion is a deformable connection portion.

3. The method for preparing high-quality aluminum nitride single crystal according to claim 1, characterized in that: The structure of the heater is a woven mesh or a plate structure, the heating method is induction heating or resistance heating, and the heating form is bottom heating, side heating or combined heating.

4. The method for preparing high-quality aluminum nitride single crystal according to claim 1, characterized in that: The crucible heat-insulating component is made of a high-temperature resistant metal material or a ceramic material, has a thermal conductivity of less than 10 W / (m·K), and can withstand a temperature greater than 1500°C.

5. The method for preparing high-quality aluminum nitride single crystal according to claim 4, characterized in that: The crucible heat-insulating component is sleeved on the side of the crucible and forms a distance with the outer side wall of the crucible, and the distance is smaller than the radius of the crucible.

6. The method for preparing high-quality aluminum nitride single crystal according to claim 1, 4 or 5, characterized in that: The crucible heat-insulating component blocks the heat transfer between the extended water-cooled wall and the heater, so that a temperature difference greater than 300° C. is formed between the top and the bottom of the crucible.

7. The method for preparing high-quality aluminum nitride single crystal according to claim 1, characterized in that: In step 2, the low-speed deposition rate is less than 20 μm / h.

8. The method for preparing high-quality aluminum nitride single crystal according to claim 1, characterized in that: In step 1, the substrate includes but is not limited to sapphire, silicon carbide, gallium nitride, aluminum nitride, scandium nitride, boron nitride bulk crystal materials, or a template material with epitaxial III-nitride semiconductor film, or tungsten, tantalum, molybdenum, tantalum carbide metal materials.

9. The method for preparing high-quality aluminum nitride single crystal according to any one of claims 7 to 8, characterized in that: The position parameters of the high crucible position and the low crucible position are obtained by calculating the temperature field, mass transfer field, and growth rate parameters based on numerical simulation technology, and are determined based on actual preparation experience parameters; During the preparation process, different growth rates are controlled by selecting different crucible position parameters and adjusting the temperature.

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