Aluminum nitride crystal ingot annealing method

Abstract

The invention discloses an aluminum nitride crystal ingot annealing method which adopts an aluminum nitride crystal annealing high-temperature furnace, and in the annealing method, an aluminum nitride crystal ingot to be annealed is placed in a crucible of the high-temperature furnace, and the upper surface, the lower surface and the peripheral surface of the aluminum nitride crystal ingot are covered with an aluminum nitride material to form a wrapping state on the aluminum nitride crystal ingot; the wrapping thickness of the aluminum nitride material in each direction is 1-50mm; a doping agent can also be added into the aluminum nitride material, and the aluminum nitride crystal ingot is effectively doped in the annealing process. In the annealing process, the furnace body heating system and the temperature control system control the temperature difference from the aluminum nitride material wrapped on the outer layer to the aluminum nitride crystal ingot on the inner layer to be the forward temperature difference, temperature distribution of the periphery high temperature of the aluminum nitride crystal ingot and the low temperature of the crystal ingot is formed, and the crystal ingot annealing effect is achieved. The method can effectively eliminate residual stress in the aluminum nitride crystal ingot, reduces lattice defects, realizes effective doping in the crystal ingot, and is very suitable for preparation of high-quality aluminum nitride crystals and substrates.

Description

Technical Field

[0001] The invention relates to the technical field of semiconductor material preparation, and in particular to an aluminum nitride ingot annealing method. Background Art

[0002] As an ultra-wide bandgap semiconductor material, aluminum nitride has the advantages of high bandgap width (6.2ev), high thermal conductivity (340W (m·K), high breakdown field strength, good ultraviolet transmittance, chemical and thermal stability, etc. It is an ideal material for ultraviolet optoelectronic devices and can be widely used in deep ultraviolet LEDs, ultraviolet curing, ultraviolet detectors, etc. It has broad application prospects and is the current research focus in the field of semiconductor materials.

[0003] Since aluminum nitride single crystal substrate has extremely low dislocation density (10 2 -10 6 cm -2 ) and with AlxGa 1-x The N lattice mismatch and thermal mismatch are small, and high-quality, low-stress GaN and AlGaN films can be epitaxially grown, thereby greatly improving the performance of ultraviolet photoelectronic devices; for high-power / high-frequency power electronic devices, aluminum nitride also has excellent high-temperature stability, high thermal conductivity and high critical field strength. Therefore, aluminum nitride-based power devices can achieve higher blocking voltage, ultra-low on-resistance and faster switching frequency, and its comprehensive quality factor is about 10-15 times that of SiC and GaN-based power devices.

[0004] At present, the doping of aluminum nitride is relatively difficult. This is mainly because the band gap of aluminum nitride itself is too wide, the solid solubility of the doped acceptor is low, the activity is poor, the quantization energy is too high, and the self-compensation effect of the intrinsic donor defect is caused, which seriously restricts the development and application of aluminum nitride in optoelectronic information technology. Commonly used doping methods include liquid source diffusion doping, solid-solid diffusion doping, raw material doping, ion implantation, etc., but they are difficult to achieve effectively on aluminum nitride. Only low-concentration doping can be achieved by liquid or solid-solid diffusion. There is randomness in raw material doping, and the doping depth and uniformity are difficult to control. The use of ion implantation method causes the doping material to collide with the atoms in the wafer and lose energy, causing lattice damage and other problems. Therefore, it is necessary to seek more effective doping methods to achieve efficient conductive N-type / P-type aluminum nitride.

[0005] Annealing technology is a common method to effectively improve the internal stress and microstructure of various materials. This method can release the residual stress accumulated during the growth process, promote the rearrangement of grains, optimize the internal microstructure and reduce defects. Due to the large band gap of aluminum nitride, it is difficult to repair defects and doping with general annealing processes, so it is necessary to construct an annealing method suitable for aluminum nitride crystals. During the annealing process, aluminum nitride will produce large thermal deformation due to contact with heterogeneous support materials, which is easy to add stress and deteriorate the crystal quality. In addition, it is difficult to achieve uniform annealing treatment, impurity transmission and doping in general annealing structure assembly, resulting in uneven distribution of impurities, defects, stress, etc. in aluminum nitride ingots, affecting production yield. Therefore, how to develop an effective annealing method based on the growth characteristics of aluminum nitride crystals to improve crystal quality and achieve effective doping is a technology that is very worthy of research and development. Summary of the invention

[0006] Based on the above problems in the prior art, the purpose of the present invention is to provide an effective aluminum nitride ingot annealing method, through which the purpose of improving the quality of aluminum nitride crystals and achieving effective doping is achieved.

[0007] The present invention is achieved through the following technical solutions.

[0008] A method for annealing an aluminum nitride ingot, the annealing device used in the annealing method is a high-temperature furnace comprising at least a crucible, a furnace heating system, a temperature control system and an annealing atmosphere control system. The annealing method at least comprises: the aluminum nitride ingot to be annealed is placed in the crucible of the high-temperature furnace, and the upper, lower and peripheral surfaces of the aluminum nitride ingot are covered with aluminum nitride material to form a wrapping state of the aluminum nitride ingot, and the wrapping thickness of the aluminum nitride material in all directions reaches 1-50mm; in addition, during the annealing process, the furnace heating system and the temperature control system control the temperature difference from the outer wrapped aluminum nitride material to the inner layer of the aluminum nitride ingot to be a positive temperature difference, that is, the temperature of the aluminum nitride material is higher than the temperature of the aluminum nitride ingot.

[0009] Furthermore, a dopant is added to the aluminum nitride material. More specifically, the dopant may be Be, Mg, Zn, Li, Be3N2, Mg3N2, Zn3N2, Li3N, BeO, Be2C2, Al2OC, LiBeN, LiSi2N3, LiMgN or LiZnN material, which is used for P-type doping of the aluminum nitride crystal ingot; the dopant may also be C, Si, MgSiN2 or Si3N4 material, which is used for N-type doping of the aluminum nitride crystal ingot.

[0010] More specifically, the annealing method comprises the following steps:

[0011] S1: spreading a portion of the aluminum nitride material, i.e., the first aluminum nitride material, on the bottom of the crucible;

[0012] S2: placing an aluminum nitride ingot at a central position on the surface of the first aluminum nitride material;

[0013] S3: placing the remaining portion of the aluminum nitride material, i.e., the second aluminum nitride material, on the side and top surface of the aluminum nitride crystal ingot, and together with the first aluminum nitride material, tightly wrapping the aluminum nitride crystal ingot, and covering the crucible with a lid;

[0014] S4: placing the crucible in a high-temperature furnace, evacuating the furnace and introducing protective gas to a pressure of P1, heating the crucible to a top temperature of T1, a bottom temperature of T2, and a side temperature of T3, and keeping the temperature for a time of t1;

[0015] S5: The temperature is lowered to room temperature, annealing is completed, and the aluminum nitride ingot is taken out.

[0016] More specifically, the first aluminum nitride material and the second aluminum nitride material in steps S1 and S3 may be aluminum nitride powder, aluminum nitride ceramic fragments, or aluminum nitride crystallized fragments.

[0017] Preferably, the material of the crucible and the crucible cover in steps S1 and S3 is selected from high temperature resistant materials such as tungsten, molybdenum, tantalum, rhenium, niobium, graphite, and boron nitride or carbide.

[0018] Preferably, in step S1, the coating thickness of the first aluminum nitride material is 1-50 mm.

[0019] Preferably, the aluminum nitride ingot in step S2 has a diameter of 10-150 mm and a height of 0.5-100 mm.

[0020] Preferably, in step S3, the side wrapping thickness of the second aluminum nitride material is 1-30 mm, and the top wrapping thickness is 1-50 mm.

[0021] Preferably, in step S4, the temperature T1 of the second aluminum nitride material on the top, the temperature T2 of the first aluminum nitride material on the bottom and the temperature T3 of the second aluminum nitride material on the side are all 1200-2300°C, and are all greater than the temperature of the aluminum nitride ingot, wherein the temperature difference between the three temperatures T1, T2 and T3 is less than 20°C.

[0022] Preferably, the protective gas in step S4 can be an inert gas such as nitrogen, argon, ammonia, etc., preferably nitrogen.

[0023] Preferably, the pressure P1 in step S4 is 0.1-10 bar.

[0024] Preferably, the duration of t1 in step S4 is 1-100 hours.

[0025] The present invention achieves the following beneficial effects:

[0026] 1) In the aluminum nitride ingot annealing method of the present invention, the aluminum nitride ingot is wrapped by the aluminum nitride material, and the two are the same material with no thermal mismatch, which is beneficial to eliminate the residual stress of the aluminum nitride ingot, and no additional thermal stress is generated during annealing.

[0027] 2) The aluminum nitride ingot annealing method of the present invention can be doped with aluminum nitride material. The aluminum nitride ingot is tightly wrapped by aluminum nitride material on all sides, which is conducive to all-round uniform doping. Through the positive temperature gradient toward the ingot (towards the inside of the crucible) and the concentration difference of the impurity gas phase, the material exchange is more effective, and the impurities are excited to reach the Al or N atomic position at a certain temperature for effective replacement, so as to achieve the purpose of effective doping, so that the annealed aluminum nitride ingot has more stable quality when used as a substrate for electronic power devices.

[0028] 3) In the aluminum nitride ingot annealing method of the present invention, the aluminum nitride ingot is wrapped by an aluminum nitride material, and the aluminum nitride material produces a decomposed gas phase under a certain temperature and a nitrogen ambient pressure to form an Al-rich atmosphere, or under a high nitrogen ambient pressure, Al or N atoms diffuse into the interior of the aluminum nitride ingot to repair the stoichiometric ratio of AlN and repair lattice defects such as vacancies and dislocations, thereby improving the quality of the ingot.

[0029] 4) The aluminum nitride ingot annealing method of the present invention uses low-impurity and high-purity aluminum nitride material, which is beneficial to reducing unintentional impurities in the aluminum nitride ingot, thereby improving the ultraviolet transmittance of the crystal, and helping to form an aluminum nitride substrate with high ultraviolet transmittance for application in ultraviolet light-emitting electronic devices.

[0030] 5) The aluminum nitride ingot annealing method of the present invention has simple use and assembly, strong operability, low preparation cost, can be applied to large-scale industrial production, and effectively improves the mass production quality and yield of aluminum nitride ingots and aluminum nitride ingots as substrates. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 The present invention is a schematic diagram of loading aluminum nitride ingot and aluminum nitride material into a crucible when performing an aluminum nitride ingot annealing process for each embodiment of the present invention.

[0032] Wherein: 1 is a crucible, 2 is a first aluminum nitride material, 3 is an aluminum nitride ingot, 4 is a second aluminum nitride material, 5 is a crucible cover, h1 is a coating thickness of the first aluminum nitride material, h2 is a top coating thickness of the second aluminum nitride material, and d is a side coating thickness of the second aluminum nitride material.

[0033] Figure 2 Figure a in the middle shows the AlN single crystal ingot before heat treatment in Example 1. Figure 2 Figure b is a wafer image of the AlN single crystal ingot after Be-doped heat treatment in Example 1.

[0034] Figure 3Figure a in the middle is the ingot wafer before heat treatment in Example 2. Figure 3 Figure b is a wafer after heat treatment of the AlN single crystal ingot in Example 2.

[0035] Figure 4 : This is the ultraviolet absorption coefficient spectrum of the AlN wafer before and after heat treatment in Example 2.

[0036] Figure 5 XRD data of AlN wafer before and after heat treatment in Example 2; Figure 5 Figure a in the middle is the XRD rocking curve of the AlN single crystal in the (002) direction before and after heat treatment in Example 2. Figure 5 Figure b is the XRD rocking curve of the AlN single crystal (102) before and after heat treatment in Example 2. DETAILED DESCRIPTION

[0037] The present invention will be described in detail below in conjunction with the specific embodiments shown in the accompanying drawings. However, these embodiments do not limit the present invention, and any structural, methodological, or functional changes made by a person skilled in the art based on these embodiments are all within the scope of protection of the present invention.

[0038] When the aluminum nitride ingot annealing process is performed in each embodiment of the present invention, the schematic diagram of charging the aluminum nitride ingot and the aluminum nitride material in the crucible is as follows: Figure 1 As shown. As shown in the figure, the aluminum nitride ingot 3 is tightly wrapped by aluminum nitride materials on all sides, wherein the first aluminum nitride material 2 is paved on the bottom of the crucible 1, and the second aluminum nitride material 4 is paved on the surrounding side and the top of the aluminum nitride ingot 3, and the paving thickness of the first aluminum nitride material at the bottom of the crucible, that is, the wrapping thickness of the first aluminum nitride material is h1 in the figure, the top wrapping thickness of the second aluminum nitride material is h2 in the figure, and the side wrapping thickness of the second aluminum nitride material is d; the aluminum nitride ingot and aluminum nitride material are loaded in the crucible, and the crucible cover 5 is covered to form a closed annealing environment. By adjusting the key process parameter settings of temperature, air pressure, temperature difference (temperature difference between raw material and ingot), lattice defects are repaired to improve the quality of aluminum nitride ingots. At the same time, the purity of aluminum nitride raw materials is adjusted or doped into the raw materials to achieve unintentional impurities or effective doping inside the aluminum nitride ingot, and to prepare aluminum nitride ingots for different production purposes.

[0039] The aluminum nitride ingot annealing method of the present invention is further described below through specific embodiments.

[0040] Example 1

[0041] The specific annealing process of the aluminum nitride ingot in this embodiment is as follows.

[0042] S1: Select aluminum nitride crystallized fragments uniformly doped with Be as aluminum nitride material, divide the aluminum nitride material into two parts, namely, a first aluminum nitride material 2 and a second aluminum nitride material 4, and spread the first aluminum nitride material 2 on the bottom of the tungsten crucible 1. The paving thickness of the first aluminum nitride material, i.e., the wrapping thickness of the first aluminum nitride material, is Figure 1 In the embodiment, h1 is 30 mm, that is, the distance between the upper surface of the first aluminum nitride material laid flat and the bottom of the crucible is 30 mm.

[0043] S2: placing an aluminum nitride crystal ingot 3 with a diameter of 40 mm and a height of 20 mm at the center of the upper surface of the first aluminum nitride material 2 .

[0044] S3: The second aluminum nitride material 4 is put into the side and top of the aluminum nitride crystal ingot 3 to form a tight wrap around the aluminum nitride crystal ingot 3. After the loading is completed, the second aluminum nitride material 4 wraps the top of the aluminum nitride crystal ingot 3 with a thickness of Figure 1 h2 in the figure, the thickness of the second aluminum nitride material 4 wrapping the side of the aluminum nitride crystal ingot 3 is Figure 1 d in the figure, and the tungsten crucible cover 5 is covered to seal the container. In this embodiment, h2 and d are 20 mm and 30 mm respectively. After repeated tests, the inventors used different crucibles to control the side wrapping thickness of the second aluminum nitride material to meet 1-30 mm and the top wrapping thickness to meet 1-50 mm, and the effect equivalent to that of this embodiment can be achieved.

[0045] S4: Place the loaded crucible into a high temperature furnace and evacuate the crucible to a vacuum of 1×10 -4 Below pa, turn on the heater for heating, and at the same time introduce nitrogen to 10 bar, raise the temperature to the outer wall temperature of the crucible at the measuring point: the top temperature is 2290℃, the bottom temperature is 2285℃, and the middle temperature of the side is 2300℃, and keep warm for 100 hours.

[0046] S5: Cool down to room temperature and take out the annealed aluminum nitride ingot.

[0047] Example 2

[0048] The specific annealing process of the aluminum nitride ingot in this embodiment is as follows.

[0049] S1: Select high-purity aluminum nitride crystallized fragments as aluminum nitride material, divide the aluminum nitride material into two parts, namely a first aluminum nitride material 2 and a second aluminum nitride material 4, and spread the first aluminum nitride material 2 on the bottom of the rhenium crucible 1, with a paving thickness h1 of 50 mm.

[0050] S2: placing an aluminum nitride crystal ingot 3 with a diameter of 100 mm and a height of 40 mm at the center of the upper surface of the first aluminum nitride material 2 .

[0051] S3: The second aluminum nitride material 4 is put into the side and top of the aluminum nitride crystal ingot 3 to form a tight package around the aluminum nitride crystal ingot 3, and the rhenium crucible cover 5 is covered to seal the container. In this embodiment, the top package thickness h2 and the side package thickness d are 30 mm and 50 mm respectively.

[0052] S4: Place the sealed crucible in a high temperature furnace and evacuate the vacuum to 1×10 -4 Below pa, turn on the heater for heating, and at the same time introduce argon to 15 bar, raise the temperature to the outer wall temperature of the crucible: the top temperature T1 is 1920℃, the bottom temperature T2 is 1915℃, and the middle temperature of the side T3 is 1906℃, and keep warm for 20 hours.

[0053] S5: Cool down to room temperature and take out the annealed aluminum nitride ingot.

[0054] Example 3

[0055] The specific annealing process of the aluminum nitride ingot in this embodiment is as follows.

[0056] S1: Select aluminum nitride crystallized fragments uniformly doped with C powder as aluminum nitride material, divide the aluminum nitride material into two parts, namely a first aluminum nitride material 2 and a second aluminum nitride material 4, and spread the first aluminum nitride material 2 on the bottom of the graphite crucible 1, with a paving thickness h1 of 5 mm.

[0057] S2: placing an aluminum nitride crystal ingot 3 with a diameter of 40 mm and a height of 10 mm at the center of the upper surface of the first aluminum nitride material 2 .

[0058] S3: The second aluminum nitride material 4 is put into the side and top of the aluminum nitride crystal ingot 3 to form a tight package around the aluminum nitride crystal ingot 3, and the graphite crucible cover 5 is covered to seal the container. In this embodiment, the top package thickness h2 and the side package thickness d are 5 and 10 mm respectively.

[0059] S4: Place the sealed crucible in a high temperature furnace and evacuate the vacuum to 1×10 -4 Below pa, turn on the heater for heating, and at the same time introduce ammonia to 1 bar, raise the temperature to the temperature of the outer wall of the crucible: the top temperature T1 is 1300℃, the bottom temperature T2 is 1310℃, and the middle temperature of the side T3 is 1306℃, and keep warm for 40 hours.

[0060] S5: Cool down to room temperature and take out the annealed aluminum nitride ingot.

[0061] The above embodiments are only used to help understand the method and core idea of ​​the present invention. It should be noted that, for those skilled in the art, several improvements and modifications can be made to the present invention without departing from the principles of the present invention, and these improvements and modifications also fall within the scope of protection of the claims of the present invention.

[0062] Application Example 1

[0063] The uniformly Be-doped ingot prepared in Example 1 is as follows: Figure 2 The element contents in the ingot before and after Be doping are shown in Table 1. The Si and Be element contents in the ingot before and after heat treatment were detected by GDMS, and the C and O element contents in the ingot before and after heat treatment were detected by EGA. It can be found that by adding Be powder to the raw material, an AlN single crystal ingot containing Be can be prepared after high-temperature heat treatment in Example 1, and the chip contains Be element, realizing P-type doping of the AlN ingot.

[0064] Table 1

[0065]

[0066] Application Example 2

[0067] The AlN ingot is subjected to high temperature heat treatment in Example 2 to further remove impurities in the ingot, such as Figure 3 Figure a in the middle is a cut wafer image of the crystal ingot before heat treatment. Figure 3 Figure b in the middle is a picture of the cut wafer of the crystal ingot after heat treatment. Table 2 below shows the impurity content in the crystal ingot before and after heat treatment. The Si element content in the crystal ingot before and after heat treatment is detected by GDMS, and the C and O element content in the crystal ingot before and after heat treatment is detected by EGA. The impurities in the wafer are reduced after heat treatment. Figure 5 Figure a in the middle is the XRD rocking curve of the AlN single crystal in the (002) direction before and after heat treatment in Example 2. Figure 5 Figure b is the XRD rocking curve of the AlN single crystal (102) direction before and after heat treatment in Example 2. After heat treatment, the half-width (FWHM) values ​​of the single crystal are reduced, the FWHM value of (002) direction is reduced from 165 arcsec to 86 arcsec, and the FWHM value of (102) direction is reduced from 86 arcsec to 18 arcsec, and the quality of the ingot is significantly improved.

[0068] Table 2

[0069] Sample element detection <![CDATA[Si / at·cm -3 ]]> <![CDATA[O / at·cm -3 ]]> <![CDATA[C / at·cm -3 ]]> Example 2 Before heat treatment of ingot <![CDATA[1.5×10 17 ]]> <![CDATA[2.1×10 19 ]]> <![CDATA[4.3×10 18 ]]> Example 2 After heat treatment of the ingot <![CDATA[7.9×10 16 ]]> <![CDATA[2.8×10 18 ]]> <![CDATA[1.0×10 18 ]]>

[0070] The raw materials are high-purity raw materials. The AlN single crystal ingot prepared by the present invention has the characteristics of low impurity content, high ultraviolet transmittance and high structural quality. For example, the ultraviolet absorption coefficient spectrum of the AlN wafer before and after heat treatment in Example 2 was detected by a visible light-ultraviolet spectrophotometer (the results are shown in Figure 4 ), the heat-treated wafer has a lower absorption coefficient in deep ultraviolet (265nm band), indicating better ultraviolet transmittance. These data confirm that the AlN ingot after heat treatment of the present invention has extremely high purity and is an excellent material basis for the development of high-end ultraviolet electronic devices.

Claims

1. An annealing method for aluminum nitride ingots, wherein the annealing device used in the annealing method comprises at least a high-temperature furnace including a crucible, a furnace heating system, a temperature control system, and an annealing atmosphere control system; characterized in that: The annealing method at least includes: during annealing, the aluminum nitride ingot to be annealed is placed in the crucible of the high-temperature furnace, and the upper, lower and peripheral surfaces of the aluminum nitride ingot are covered with aluminum nitride material to form a wrapped state of the aluminum nitride ingot, and the wrapping thickness of the aluminum nitride material in all directions reaches 1-50mm; in addition, during the annealing process, the furnace body heating system and the temperature control system control the temperature difference from the outer layer of the aluminum nitride material to the inner layer of the aluminum nitride ingot to be a positive temperature difference, that is, the temperature of the aluminum nitride material is higher than the temperature of the aluminum nitride ingot.

2. The method for annealing an aluminum nitride ingot according to claim 1, characterized in that: The annealing method comprises the following steps: S1, spreading a portion of the aluminum nitride material, i.e., the first aluminum nitride material, on the bottom of the crucible; S2, placing an aluminum nitride ingot at a central position on the surface of the first aluminum nitride material; S3, placing the remaining portion of the aluminum nitride material, i.e., the second aluminum nitride material, on the side and top surface of the aluminum nitride crystal ingot, and together with the first aluminum nitride material, tightly wrapping the aluminum nitride crystal ingot, and covering the crucible with a lid; S4, placing the crucible in a high-temperature furnace, evacuating the furnace and introducing protective gas to a pressure of P1, heating the crucible to a top temperature of T1, a bottom temperature of T2, and a side temperature of T3, and keeping the temperature for a time period of t1; S5, the temperature is lowered to room temperature, the annealing is completed, and the aluminum nitride ingot is taken out.

3. The annealing method of an aluminum nitride ingot according to claim 1 or 2, characterized in that: Dopants are added into the aluminum nitride material.

4. The method for annealing an aluminum nitride ingot according to claim 3, characterized in that: The dopant is Be, Mg, Zn, Li, Be3N2, Mg3N2, Zn3N2, Li3N, BeO, Be2C2, Al2OC, LiBeN, LiSi2N3, LiMgN or LiZnN, which is used for P-type doping of the aluminum nitride ingot; or, the dopant is C, Si, MgSiN2 or Si3N4, which is used for N-type doping of the aluminum nitride ingot.

5. The method for annealing an aluminum nitride ingot according to claim 2, characterized in that: In steps S1 and S3, the first aluminum nitride material and the second aluminum nitride material are aluminum nitride powder, aluminum nitride ceramic fragments or aluminum nitride crystallized fragments.

6. The method for annealing an aluminum nitride ingot according to claim 2, characterized in that: In step S1, the wrapping thickness of the first aluminum nitride material is 1-50 mm; in step S3, the side wrapping thickness of the second aluminum nitride material is 1-30 mm, and the top wrapping thickness is 1-50 mm.

7. The method for annealing an aluminum nitride ingot according to claim 2, characterized in that: The aluminum nitride ingot in step S2 has a diameter of 10-150 mm and a height of 0.5-100 mm.

8. The method for annealing an aluminum nitride ingot according to claim 2, characterized in that: In step S4, the temperature T1 of the second aluminum nitride material at the top, the temperature T2 of the first aluminum nitride material at the bottom and the temperature T3 of the second aluminum nitride material at the side are all 1200-2300°C, and are all greater than the temperature of the aluminum nitride ingot, wherein the temperature difference between the three temperatures T1, T2 and T3 is less than 20°C.

9. The method for annealing an aluminum nitride ingot according to claim 2, characterized in that: The protective gas in step S4 is nitrogen, argon or ammonia.

10. The method for annealing an aluminum nitride ingot according to claim 2, characterized in that: In step S4, the pressure P1 is 0.1-10 bar, and the duration t1 is 1-100 h.

Images