Preparation method of aluminum nitride single crystal material

Abstract

The invention relates to the field of semiconductor materials, provides a preparation method of an aluminum nitride single crystal material, and solves the defects of small size, poor quality, low speed and difficulty in yield of the aluminum nitride single crystal material produced and prepared in the prior art. Comprising the following steps: 1) preparing raw materials including AlN powder and SiC seed crystals; (2) purification treatment of AlN powder; (3) preparing a TaC crucible; (4) fixing and bonding the SiC seed crystal; and 5) growing the aluminum nitride single crystal material.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor materials, and in particular to a method for preparing an aluminum nitride single crystal material. Background Art

[0002] With the rapid development of new energy, communications, rail transportation, aerospace and other fields, the semiconductor industry plays an increasingly important role. Aluminum nitride (AlN) has become a leader in the third-generation semiconductor materials due to its direct bandgap, wide bandgap, high thermal conductivity, high thermal stability, high breakdown field strength, strong radiation resistance and other characteristics. It is suitable for manufacturing high-frequency, high-temperature resistant, high-radiation resistant, high-power electronic and optoelectronic devices.

[0003] Chinese patent application number CN202210793673.1 discloses a method for preparing AlN crystal materials based on size and shape control, wherein the method uses AlN powder to prepare AlN crystals in an AlN crystal material preparation system, wherein the preparation system includes an outer crucible and an inner crucible disposed in the outer crucible, wherein the inner crucible includes a shell having an internal space and extending in a vertical direction; an upper cover, located at the upper end of the shell, and including a first surface extending in a horizontal direction; a lower cover, located at the lower end of the shell, for carrying aluminum nitride powder, and including a second surface extending in a horizontal direction; a column, disposed in the internal space of the inner crucible; a plurality of columns, and a plurality of columns are disposed at a predetermined distance between the columns; each column has a third surface extending in a horizontal direction; and multiple growths are performed through a charging step, a heating step, a growth step, and a cooling step, and an aluminum nitride seed crystal with a particle size greater than 20 mm is obtained on the third surface of the column. The homoepitaxial expansion speed of the aluminum nitride single crystal prepared by the invention is slow, the size is small, and it is difficult to mass produce.

[0004] Chinese patent application number CN202311691504.8 discloses a method for preparing an aluminum nitride single crystal composite substrate, comprising: depositing an aluminum nitride polycrystalline film layer on the surface of a substrate, annealing the aluminum nitride polycrystalline film layer to recrystallize the aluminum nitride polycrystalline film layer to form an aluminum nitride single crystal film layer, maintaining the annealing atmosphere and annealing temperature, thinning the substrate from the side of the substrate away from the aluminum nitride single crystal film layer, cooling, and obtaining an aluminum nitride single crystal composite substrate; the preparation method thins the substrate after high-temperature annealing and recrystallization to reduce the stress introduced by the thermal mismatch between the substrate and the aluminum nitride single crystal film layer during the cooling process, reduce dislocation generation, and improve the crystallization quality of the aluminum nitride single crystal film layer, and finally obtain an aluminum nitride single crystal composite substrate with high crystallization quality. However, the aluminum nitride polycrystalline film layer deposited on the substrate surface is easy to fall off, and the quality of the grown AlN crystal is poor. Summary of the invention

[0005] Therefore, in view of the above problems, the present invention provides a method for preparing aluminum nitride single crystal material to solve the defects of aluminum nitride single crystal material produced by the prior art, such as small size, poor quality, slow speed and difficulty in mass production.

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

[0007] A method for preparing an aluminum nitride single crystal material, characterized in that it comprises the following steps:

[0008] S1. Preparation of raw materials: including AlN powder and SiC seed crystal;

[0009] S2, AlN powder purification treatment: AlN powder is filled in a TaC crucible, heated to 1800°C at a heating rate of 150°C / h under a N2 protective atmosphere, kept warm for 20-24h, and naturally cooled to room temperature to obtain a primary prefabricated material; the primary prefabricated material is crushed and ground, and then filled in a TaC crucible, heated to 1900°C at a heating rate of 250°C / h under a N2 protective atmosphere, kept warm for 20-24h, and naturally cooled to room temperature to obtain a secondary prefabricated material; the secondary prefabricated material is crushed and ground, and then filled in a TaC crucible again, heated to 2000°C at a heating rate of 250°C / h under a N2 protective atmosphere, kept warm for 24-28h, and naturally cooled to room temperature to obtain a high-purity AlN raw material;

[0010] S3, preparation of TaC crucible: clean the tantalum cover and tantalum crucible with deionized water, place them in a graphite crucible after drying, fill the tantalum crucible with graphite powder until it completely covers the tantalum crucible, compact the graphite powder evenly with force, heat to 2000°C at 100°C / h under N2 atmosphere protection and keep warm for 6-8h, slowly cool to room temperature, take out and wipe the graphite powder, ultrasonically clean it with anhydrous ethanol for 15-30min, rinse it with deionized water for 3-5 times, and dry it to obtain the TaC crucible, which includes a hemispherical bottom crucible body and a crucible cover;

[0011] S4, pre-treating the TaC crucible, surface-treating the SiC seed crystals, and drying them respectively, and then fixing and bonding the dried SiC seed crystals to the crucible cover, placing the crucible body in a matching graphite crucible, and loading the high-purity AlN raw material obtained in step S2 into the crucible body, compacting while loading, until the high-purity AlN raw material is 5 mm away from the crucible opening at the top of the crucible body, stopping loading, covering the crucible cover, and covering the graphite crucible cover;

[0012] S5. Growth of aluminum nitride single crystal material: Place the graphite crucible treated in step S4 in a high-purity N2 protective atmosphere with a gas pressure of 60-70 kPa, heat it to 1850-2020°C at a heating rate of 10°C / min, keep it warm for 40 hours, cool it to 1800°C at a cooling rate of 1°C / min, and then cool it to room temperature at a cooling rate of 2°C / min to obtain the aluminum nitride single crystal material.

[0013] Furthermore, the diameter of the aluminum nitride single crystal material is 40-45 mm.

[0014] Furthermore, the thickness of the aluminum nitride single crystal material is ≧10 mm.

[0015] Furthermore, the SiC seed crystal is 4H-SiC or 6H-SiC.

[0016] Furthermore, the size of the SiC seed crystal is 2 inches.

[0017] Furthermore, the purity of the AlN powder is ≧99.8%.

[0018] Furthermore, the fixing and bonding process is as follows:

[0019] a. Cutting the flexible graphite paper into a circle having the same size as the crucible cover, and cutting the tantalum foil into a metal tantalum ring having an outer diameter having the same size as the crucible cover and an inner diameter having the same size as the SiC seed crystal;

[0020] b. Applying an adhesive to the back of the flexible graphite paper, the metal tantalum ring and the SiC seed crystal obtained in step a;

[0021] c. In a N2 atmosphere with a gas pressure of 1-1.2 atm, the temperature of the bottom of the crucible is raised to 1700-1800°C at a heating rate of 5°C / min, and kept warm for 5-8 minutes. The SiC seed crystal, the metal tantalum ring, the flexible graphite paper, and the crucible cover are bonded in a stacking order from top to bottom.

[0022] Furthermore, in step S4, the pretreatment is: ultrasonic cleaning using acetone, anhydrous ethanol and deionized water in sequence; the surface treatment is: mechanical chemical polishing of the SiC seed crystal, the surface is scratch-free and the root mean square roughness is <0.2nm, and then pickling in dilute sulfuric acid with a concentration of 10-15%.

[0023] Furthermore, the binder is the high-purity AlN raw material obtained in step S2.

[0024] By adopting the above technical solution, the beneficial effects of the present invention are:

[0025] 1. Purify AlN powder with a purity of ≥99.8% to reduce oxygen impurities and C impurities in the raw materials and improve the crystallinity of AlN powder;

[0026] 2. The TaC crucible with a hemispherical bottom is used. During the carbonization process, the stress is more evenly dispersed, and the crucible will not crack, which can increase the service life of the crucible. The utilization rate of the raw material is usually measured by the weight loss evaporation ratio. The weight loss evaporation ratio is the ratio of the weight lost by the raw material to the weight evaporated by the raw material. The smaller the weight loss evaporation ratio, the more the evaporated raw material is crystallized at the crystal. Preventing cracking can prevent the leakage of the raw material, thereby reducing the weight loss evaporation ratio, which is beneficial to the growth of AlN single crystal materials.

[0027] 3. The SiC seed crystal, the metal tantalum ring, the flexible graphite paper and the crucible cover are bonded in the order of stacking from top to bottom. The metal tantalum ring can alleviate the decomposition of the edge of the SiC seed crystal, which is beneficial to maintain the size of the SiC seed crystal, prevent the flexible graphite paper from reacting with Al vapor, and prevent the SiC seed crystal from falling off. High-purity AlN raw material is used as a binder. When the temperature is increased to 1700-1800° C., the binder sublimates and deposits to form a polycrystalline bonding layer, thereby achieving fixed bonding of the SiC seed crystal on the crucible cover;

[0028] 4. Surface treatment of the SiC seed crystal is performed by mechanical chemical polishing to ensure that the surface of the SiC seed crystal is scratch-free and has a root mean square roughness of less than 0.2 nm, thereby obtaining a high-quality substrate;

[0029] 5. During the growth process of aluminum nitride single crystal material, the cooling rate is 1°C / min. Before it is cooled to 1800°C, the temperature of the crystallization zone is kept higher than the temperature of the sublimation zone to inhibit nucleation on the surface of the SiC seed crystal substrate and secondary crystallization on the surface of the AlN crystal during the cooling stage. DETAILED DESCRIPTION

[0030] Example 1

[0031] A method for preparing an aluminum nitride single crystal material, characterized in that it comprises the following steps:

[0032] (1) Preparation of raw materials: including AlN powder with a purity of ≥99.8% and 6H-SiC seed crystals with a size of 2 inches;

[0033] (2) AlN powder purification treatment: AlN powder is loaded into a TaC crucible, heated to 1800°C at a heating rate of 150°C / h under a N2 protective atmosphere, kept warm for 24 hours, and naturally cooled to room temperature to obtain a primary preform; the primary preform is crushed and ground, then loaded into a TaC crucible, heated to 1900°C at a heating rate of 250°C / h under a N2 protective atmosphere, kept warm for 24 hours, and naturally cooled to room temperature to obtain a secondary preform; the secondary preform is crushed and ground, loaded into a TaC crucible again, heated to 2000°C at a heating rate of 250°C / h under a N2 protective atmosphere, kept warm for 28 hours, and naturally cooled to room temperature to obtain a high-purity AlN raw material;

[0034] (3) Preparation of TaC crucible: The tantalum cover and the tantalum crucible are cleaned with deionized water, dried and placed in a graphite crucible, and the graphite powder is filled until the tantalum crucible is completely covered, and the graphite powder is evenly compacted with force, and the temperature is raised to 2000°C at 100°C / h under N2 atmosphere protection and kept at this temperature for 8h, and then slowly cooled to room temperature, and the graphite powder is taken out and wiped clean, and ultrasonically cleaned with anhydrous ethanol for 30min, and then rinsed with deionized water for 3 times, and dried to obtain the TaC crucible, which includes a hemispherical bottom crucible body and a crucible cover;

[0035] (4) Fixed bonding of SiC seed crystal

[0036] (4-1) pre-treating the TaC crucible, ultrasonically cleaning it with acetone, anhydrous ethanol and deionized water in sequence, and drying it; surface treating the SiC seed crystal, mechanically chemically polishing the SiC seed crystal to obtain a SiC seed crystal with no scratches on the surface and a root mean square roughness of less than 0.2 nm, and then pickling it in dilute sulfuric acid with a concentration of 10%, and drying it;

[0037] (4-2) cutting the flexible graphite paper into a circle having the same size as the crucible cover, and cutting the tantalum foil into a metal tantalum ring having an outer diameter having the same size as the crucible cover and an inner diameter having the same size as the SiC seed crystal;

[0038] (4-3) applying the high-purity AlN raw material to the back of the flexible graphite paper, the metal tantalum ring and the SiC seed crystal obtained in step (4-2);

[0039] (4-4) In a N2 atmosphere with a gas pressure of 1 atm, the bottom of the crucible body was heated to 1700°C at a heating rate of 5°C / min, and kept at this temperature for 5 min, and the SiC seed crystal, the metal tantalum ring, the flexible graphite paper, and the crucible cover were bonded in a stacking order from top to bottom;

[0040] (4-5) placing the crucible body in a matching graphite crucible, loading the high-purity AlN raw material obtained in step (2) into the crucible body, compacting while loading, until the high-purity AlN raw material is 5 mm away from the crucible opening at the top of the crucible body, stopping loading, covering the crucible cover bonded and fixed in step (4-4), and covering with a graphite crucible cover;

[0041] (5) Growth of aluminum nitride single crystal material: The graphite crucible treated in step S4 was placed in a high-purity N2 protective atmosphere with a gas pressure of 60 kPa, heated to 1850°C at a heating rate of 10°C / min, kept at that temperature for 40 hours, cooled to 1800°C at a cooling rate of 1°C / min, and then cooled to room temperature at a cooling rate of 2°C / min to obtain the aluminum nitride single crystal material with a diameter of 45 mm and a thickness of 10 mm.

[0042] Example 2

[0043] A method for preparing an aluminum nitride single crystal material, characterized in that it comprises the following steps:

[0044] (1) Preparation of raw materials: including AlN powder with a purity of ≥99.8% and 6H-SiC seed crystals with a size of 2 inches;

[0045] (2) AlN powder purification treatment: AlN powder is loaded into a TaC crucible, heated to 1800°C at a heating rate of 150°C / h under a N2 protective atmosphere, kept warm for 20 hours, and naturally cooled to room temperature to obtain a primary preform; the primary preform is crushed and ground, then loaded into a TaC crucible, heated to 1900°C at a heating rate of 250°C / h under a N2 protective atmosphere, kept warm for 20 hours, and naturally cooled to room temperature to obtain a secondary preform; the secondary preform is crushed and ground, loaded into a TaC crucible again, heated to 2000°C at a heating rate of 250°C / h under a N2 protective atmosphere, kept warm for 24 hours, and naturally cooled to room temperature to obtain a high-purity AlN raw material;

[0046] (3) Preparation of TaC crucible: The tantalum cover and the tantalum crucible are cleaned with deionized water, dried and placed in a graphite crucible, and the graphite powder is filled until the tantalum crucible is completely covered, and the graphite powder is evenly compacted with force, and the temperature is raised to 2000°C at 100°C / h under N2 atmosphere protection and kept for 6h, and then slowly cooled to room temperature, and the graphite powder is taken out and wiped clean, and ultrasonically cleaned with anhydrous ethanol for 20min, and then rinsed with deionized water for 3 times, and dried to obtain the TaC crucible, which includes a hemispherical bottom crucible body and a crucible cover;

[0047] (4) Fixed bonding of SiC seed crystal

[0048] (4-1) pre-treating the TaC crucible, ultrasonically cleaning it with acetone, anhydrous ethanol and deionized water in sequence, and drying it; surface treating the SiC seed crystal, mechanically chemically polishing the SiC seed crystal to obtain a SiC seed crystal with no scratches on the surface and a root mean square roughness of less than 0.2 nm, and then pickling it in dilute sulfuric acid with a concentration of 10%, and drying it;

[0049] (4-2) cutting the flexible graphite paper into a circle having the same size as the crucible cover, and cutting the tantalum foil into a metal tantalum ring having an outer diameter having the same size as the crucible cover and an inner diameter having the same size as the SiC seed crystal;

[0050] (4-3) applying the high-purity AlN raw material to the back of the flexible graphite paper, the metal tantalum ring and the SiC seed crystal obtained in step (4-2);

[0051] (4-4) In a N2 atmosphere with a gas pressure of 1.1 atm, the bottom of the crucible was heated to 1750°C at a heating rate of 5°C / min, and kept at this temperature for 6 min, and the SiC seed crystal, the metal tantalum ring, the flexible graphite paper, and the crucible cover were bonded in a stacking order from top to bottom;

[0052] (4-5) placing the crucible body in a matching graphite crucible, and loading the high-purity AlN raw material obtained in step (2) into the crucible body, compacting while loading, until the high-purity AlN raw material is 5 mm away from the crucible opening at the top of the crucible body, stopping loading, covering the crucible cover, and covering the graphite crucible cover;

[0053] (5) Growth of aluminum nitride single crystal material: The graphite crucible treated in step S4 was placed in a high-purity N2 protective atmosphere with a gas pressure of 65 kPa, heated to 1900°C at a heating rate of 10°C / min, kept at that temperature for 40 hours, cooled to 1800°C at a cooling rate of 1°C / min, and then cooled to room temperature at a cooling rate of 2°C / min to obtain the aluminum nitride single crystal material with a diameter of 40 mm and a thickness of 10 mm.

[0054] Example 3

[0055] A method for preparing an aluminum nitride single crystal material, characterized in that it comprises the following steps:

[0056] (1) Preparation of raw materials: including AlN powder with a purity of ≥99.8% and 6H-SiC seed crystals with a size of 2 inches;

[0057] (2) AlN powder purification treatment: AlN powder is loaded into a TaC crucible, heated to 1800°C at a heating rate of 150°C / h under a N2 protective atmosphere, kept warm for 22 hours, and naturally cooled to room temperature to obtain a primary preform; the primary preform is crushed and ground, then loaded into a TaC crucible, heated to 1900°C at a heating rate of 250°C / h under a N2 protective atmosphere, kept warm for 22 hours, and naturally cooled to room temperature to obtain a secondary preform; the secondary preform is crushed and ground, loaded into a TaC crucible again, heated to 2000°C at a heating rate of 250°C / h under a N2 protective atmosphere, kept warm for 26 hours, and naturally cooled to room temperature to obtain a high-purity AlN raw material;

[0058] (3) Preparation of TaC crucible: The tantalum cover and the tantalum crucible were cleaned with deionized water, dried and placed in a graphite crucible, and the graphite powder was filled until the tantalum crucible was completely covered. The graphite powder was evenly compacted with force, and the temperature was raised to 2000°C at 100°C / h under N2 atmosphere protection and kept for 7h, and then slowly cooled to room temperature, and the graphite powder was taken out and wiped clean, and ultrasonically cleaned with anhydrous ethanol for 15min, and then rinsed with deionized water for 3 times, and dried to obtain the TaC crucible, which includes a hemispherical bottom crucible body and a crucible cover;

[0059] (4) Fixed bonding of SiC seed crystal

[0060] (4-1) pre-treating the TaC crucible, ultrasonically cleaning it with acetone, anhydrous ethanol and deionized water in sequence, and drying it; surface treating the SiC seed crystal, mechanically and chemically polishing the SiC seed crystal to obtain a SiC seed crystal with no scratches on the surface and a root mean square roughness of less than 0.2 nm, and then pickling it in dilute sulfuric acid with a concentration of 15%, and drying it;

[0061] (4-2) cutting the flexible graphite paper into a circle having the same size as the crucible cover, and cutting the tantalum foil into a metal tantalum ring having an outer diameter having the same size as the crucible cover and an inner diameter having the same size as the SiC seed crystal;

[0062] (4-3) applying the high-purity AlN raw material to the back of the flexible graphite paper, the metal tantalum ring and the SiC seed crystal obtained in step (4-2);

[0063] (4-4) In a N2 atmosphere with a gas pressure of 1.2 atm, the bottom of the crucible was heated to 1800°C at a heating rate of 5°C / min, and kept at this temperature for 8 min, and the SiC seed crystal, the metal tantalum ring, the flexible graphite paper, and the crucible cover were bonded in a stacking order from top to bottom;

[0064] (4-5) placing the crucible body in a matching graphite crucible, and loading the high-purity AlN raw material obtained in step (2) into the crucible body, compacting while loading, until the high-purity AlN raw material is 5 mm away from the crucible opening at the top of the crucible body, stopping loading, covering the crucible cover, and covering the graphite crucible cover;

[0065] (5) Growth of aluminum nitride single crystal material: The graphite crucible treated in step S4 was placed in a high-purity N2 protective atmosphere with a gas pressure of 70 kPa, heated to 2000°C at a heating rate of 10°C / min, kept at that temperature for 40 hours, cooled to 1800°C at a cooling rate of 1°C / min, and then cooled to room temperature at a cooling rate of 2°C / min to obtain the aluminum nitride single crystal material with a diameter of 45 mm and a thickness of 10 mm.

[0066] Although the present invention has been specifically shown and described in conjunction with the preferred embodiments, it should be understood by those skilled in the art that various changes may be made to the present invention in form and details without departing from the spirit and scope of the present invention as defined by the appended claims, all of which are within the scope of protection of the present invention.

Claims

1. A method for preparing aluminum nitride single crystal material, characterized in that: The following steps are involved: S1. Preparation of raw materials: including AlN powder and SiC seed crystal; S2, AlN powder purification treatment: AlN powder is filled in a TaC crucible, heated to 1800°C at a heating rate of 150°C / h under a N2 protective atmosphere, kept warm for 20-24h, and naturally cooled to room temperature to obtain a primary prefabricated material; the primary prefabricated material is crushed and ground, and then filled in a TaC crucible, heated to 1900°C at a heating rate of 250°C / h under a N2 protective atmosphere, kept warm for 20-24h, and naturally cooled to room temperature to obtain a secondary prefabricated material; the secondary prefabricated material is crushed and ground, and then filled in a TaC crucible again, heated to 2000°C at a heating rate of 250°C / h under a N2 protective atmosphere, kept warm for 24-28h, and naturally cooled to room temperature to obtain a high-purity AlN raw material; S3, preparation of TaC crucible: clean the tantalum cover and tantalum crucible with deionized water, place them in a graphite crucible after drying, fill the tantalum crucible with graphite powder until it completely covers the tantalum crucible, compact the graphite powder evenly with force, heat to 2000°C at 100°C / h under N2 atmosphere protection and keep warm for 6-8h, slowly cool to room temperature, take out and wipe the graphite powder, ultrasonically clean it with anhydrous ethanol for 15-30min, rinse it with deionized water for 3-5 times, and dry it to obtain the TaC crucible, which includes a hemispherical bottom crucible body and a crucible cover; S4, pre-treating the TaC crucible, surface-treating the SiC seed crystals, and drying them respectively, and then fixing and bonding the dried SiC seed crystals to the crucible cover, placing the crucible body in a matching graphite crucible, and loading the high-purity AlN raw material obtained in step S2 into the crucible body, compacting while loading, until the high-purity AlN raw material is 5 mm away from the crucible opening at the top of the crucible body, stopping loading, covering the crucible cover, and covering the graphite crucible cover; S5. Growth of aluminum nitride single crystal material: Place the graphite crucible treated in step S4 in a high-purity N2 protective atmosphere with a gas pressure of 60-70 kPa, heat it to 1850-2020°C at a heating rate of 10°C / min, keep it warm for 40 hours, cool it to 1800°C at a cooling rate of 1°C / min, and then cool it to room temperature at a cooling rate of 2°C / min to obtain the aluminum nitride single crystal material.

2. The method for preparing an aluminum nitride single crystal material according to claim 1, characterized in that: The diameter of the aluminum nitride single crystal material is 40-45 mm.

3. The method for preparing an aluminum nitride single crystal material according to claim 1, characterized in that: The thickness of the aluminum nitride single crystal material is ≧10 mm.

4. The method for preparing an aluminum nitride single crystal material according to claim 1, characterized in that: The SiC seed crystal is 4H-SiC or 6H-SiC.

5. The method for preparing an aluminum nitride single crystal material according to claim 1, characterized in that: The size of the SiC seed crystal is 2 inches.

6. The method for preparing an aluminum nitride single crystal material according to claim 1, characterized in that: The purity of AlN powder is ≥99.8%.

7. The method for preparing an aluminum nitride single crystal material according to claim 1, characterized in that: The process of fixing and bonding is as follows: a. Cutting the flexible graphite paper into a circle having the same size as the crucible cover, and cutting the tantalum foil into a metal tantalum ring having an outer diameter having the same size as the crucible cover and an inner diameter having the same size as the SiC seed crystal; b. Applying an adhesive to the back of the flexible graphite paper, the metal tantalum ring and the SiC seed crystal obtained in step a; c. In a N2 atmosphere with a gas pressure of 1-1.2 atm, the temperature of the bottom of the crucible is raised to 1700-1800°C at a heating rate of 5°C / min, and kept warm for 5-8 minutes. The SiC seed crystal, the metal tantalum ring, the flexible graphite paper, and the crucible cover are bonded in a stacking order from top to bottom.

8. The method for preparing an aluminum nitride single crystal material according to claim 1, characterized in that: In step S4, the pretreatment is: ultrasonic cleaning using acetone, anhydrous ethanol and deionized water in sequence; the surface treatment is: mechanical chemical polishing of the SiC seed crystal to obtain a SiC seed crystal with no scratches on the surface and a root mean square roughness of <0.2nm, and then pickling in dilute sulfuric acid with a concentration of 10-15%.

9. The method for preparing an aluminum nitride single crystal material according to claim 7, characterized in that: The binder is the high-purity AlN raw material obtained in step S2.