An annealing apparatus and annealing method for a crystal

Abstract

The application relates to an annealing device and method of crystals, and belongs to the technical field of crystal production. The annealing device comprises: an annealing crucible for placing a plurality of crystals to be annealed, a graphite felt is coaxially arranged at the bottom of the annealing crucible, the plurality of crystals are coaxially placed on the graphite felt from bottom to top, and graphite blocks are arranged between adjacent crystals; a heat preservation layer arranged outside the annealing crucible; an induction coil for heating the annealing crucible; a liftable edge heat preservation sleeve coaxially arranged with the annealing crucible, which can extend into the interior of the annealing crucible to heat preserve the edges of the crystals; and a liftable center heat preservation column coaxially arranged with the annealing crucible, which can extend into the interior of the annealing crucible to heat preserve the center area of the crystals. The device and method can effectively realize the uniform temperature distribution of the crystals in each stage of the annealing process, greatly shorten the annealing time, improve the annealing efficiency and the quality of the crystals after annealing.

Description

Technical Field

[0001] This invention belongs to the field of crystal production technology, and particularly relates to an annealing apparatus and annealing method for crystals. Background Technology

[0002] Silicon carbide, as a typical representative of wide bandgap semiconductors, has excellent properties such as large bandgap, high breakdown field strength, high saturated electron mobility, high thermal conductivity, and good thermal and chemical stability. It is an ideal substrate material for manufacturing high-frequency, high-voltage, high-efficiency, radiation-resistant, and high-temperature resistant high-power devices and blue light-emitting diodes, making it an important and promising material for applications in new energy vehicles, high-speed rail transportation, aerospace, high-voltage smart grids, and clean energy.

[0003] The crystal quality and manufacturing cost of silicon carbide single-crystal substrates remain among the main factors limiting their large-scale application. Improving crystal quality and increasing crystal size are key to further enhancing the overall cost-effectiveness of silicon carbide single-crystal substrates. During crystal growth, the larger the crystal size, the more difficult it is to control the uniformity of the thermal field, the greater the thermal stress in the crystal, and the more difficult it is to control the crystal quality. This not only leads to a significant increase in crystal defect density but can even cause crystal cracking.

[0004] Crystal annealing is a crucial step in crystal growth. Annealing effectively releases thermal stress within the crystal, preventing cracking during slicing and improving wafer flatness and defect density. The crystal annealing process involves three basic stages: heating, isothermal control, and cooling. The direction and rate of heat transfer differ in each stage. However, existing crystal annealing equipment and methods cannot simultaneously address the varying thermal field requirements during heating, isothermal control, and cooling, resulting in inconsistent internal crystal temperature and poor annealing outcomes. While extending the temperature transition time can mitigate excessive temperature differences within the crystal at any stage, this significantly reduces production efficiency and increases energy consumption and costs.

[0005] Therefore, there is an urgent need to develop a more efficient crystal annealing apparatus and method to fundamentally improve the annealing efficiency and the quality of the annealed crystal. Summary of the Invention

[0006] To address one or more technical problems existing in the prior art, this invention provides an annealing apparatus and method for crystals. The apparatus and method of this invention can achieve in-situ control of the thermal field configuration around the crystal in the annealing crucible to meet the different thermal field requirements at different stages of the annealing process. It can effectively achieve a uniform temperature distribution in the crystal at each stage of the annealing process, while significantly shortening the annealing time, improving annealing efficiency, and enhancing the quality of the annealed crystal.

[0007] The present invention provides a crystal annealing apparatus in a first aspect, the annealing apparatus comprising: an annealing crucible for holding a plurality of crystals to be annealed, wherein a graphite felt is coaxially disposed at the bottom of the annealing crucible, and the plurality of crystals are coaxially placed on the graphite felt from bottom to top, with graphite blocks disposed between adjacent crystals; an insulation layer disposed outside the annealing crucible; an induction coil for heating the annealing crucible; a liftable edge insulation sleeve coaxially disposed with the annealing crucible, the liftable edge insulation sleeve being able to extend into the interior of the annealing crucible to insulate the edges of the crystals; and a liftable central insulation column coaxially disposed with the annealing crucible, the liftable central insulation column being able to extend into the interior of the annealing crucible to insulate the central region of the crystals.

[0008] Preferably, when the annealing device performs annealing, the annealing includes a heating stage, a constant temperature stage, and a cooling stage; in the heating stage, the bottom of the liftable edge insulation sleeve is 0-30mm above the upper surface of the uppermost crystal, and the lower surface of the liftable central insulation column is 0-10mm away from the upper surface of the uppermost crystal; in the constant temperature stage, the liftable edge insulation sleeve is fitted over the outside of the multiple crystals, and the lower surface of the liftable central insulation column is in contact with the upper surface of the uppermost crystal; in the cooling stage, the liftable edge insulation sleeve is kept fitted over the outside of the multiple crystals, while the liftable central insulation column is pulled upward at a speed of 5-60mm / h and a stroke of 80-100mm.

[0009] Preferably, the inner diameter of the liftable edge insulation sleeve is 5-20 mm larger than the diameter of the crystal; and / or the diameter of the liftable central insulation column is 0-100 mm smaller than the diameter of the crystal.

[0010] Preferably, the liftable edge insulation sleeve includes an upper sleeve section and a lower sleeve section that are interconnected. The inner diameter of the upper sleeve section is smaller than the diameter of the crystal, and the inner diameter of the lower sleeve section is larger than the diameter of the crystal. The inner diameter of the upper sleeve section is not smaller than the diameter of the liftable central insulation column. During the constant temperature stage and / or cooling stage, the lower surface of the upper sleeve section is in contact with the upper surface of the uppermost crystal.

[0011] Preferably, the liftable edge insulation sleeve is connected to a first lifting drive device for driving the liftable edge insulation sleeve to rise and fall via a first lifting rod; and / or the liftable center insulation column is connected to a second lifting drive device for driving the liftable center insulation column to rise and fall via a second lifting rod.

[0012] Preferably, the inner diameter of the annealing crucible is 10-50 mm larger than the diameter of the crystal; the diameter of the graphite felt is 0-50 mm smaller than the diameter of the crystal; and / or the diameter of the graphite block is 30-100 mm and the thickness is 5-10 mm.

[0013] Preferably, the annealing apparatus further includes a crucible support tray for supporting the annealing crucible, the crucible support tray being located below the insulation layer, and the crucible support tray being connected to a crucible rotation and lifting drive device via a crucible rotation and lifting shaft.

[0014] Preferably, the crystal is a silicon carbide crystal.

[0015] The present invention provides a method for annealing crystals in a second aspect. The annealing method employs the crystal annealing apparatus described in the first aspect of the present invention. The annealing method includes a heating stage, a isothermal stage, and a cooling stage. In the heating stage: the bottom end of the liftable edge insulation sleeve is raised 0-30 mm above the upper surface of the uppermost crystal, and the lower surface of the liftable central insulation column is 0-10 mm away from the upper surface of the uppermost crystal, and then heating is performed. In the isothermal stage: the liftable edge insulation sleeve is fitted over the outside of multiple crystals, and the lower surface of the liftable central insulation column is brought into contact with the upper surface of the uppermost crystal, and then heat is maintained. In the cooling stage: the liftable central insulation column is pulled upward and the temperature is lowered.

[0016] Preferably, during the heating stage, the temperature is increased to 1700-2000℃ at a heating rate of 100-500℃ / h; during the constant temperature stage, the holding time is 5-15h; during the cooling stage, the temperature is reduced to room temperature at a cooling rate of 20-200℃ / h; and / or during the cooling stage, the lifting speed is 5-60mm / h, and the upward lifting stroke is 80-100mm.

[0017] Compared with the prior art, the present invention has at least the following beneficial effects:

[0018] (1) The annealing apparatus and annealing method of the present invention can realize the in-situ control of the thermal field configuration around the crystal in the annealing crucible to meet the different requirements of the thermal field at different stages of the annealing process. It can effectively achieve a uniform temperature distribution of the crystal at each stage of the annealing process, effectively eliminate the thermal stress inside the crystal, and at the same time significantly shorten the annealing time, improve the annealing efficiency and the quality of the crystal after annealing, thereby helping to improve the quality of silicon carbide single crystal (silicon carbide crystal) substrate.

[0019] (2) The annealing device of the present invention includes a liftable edge heat preservation sleeve and a liftable center heat preservation column. The size of the two is matched with the crystal to be annealed and the annealing crucible. The liftable edge heat preservation sleeve and the liftable center heat preservation column can achieve precise control of the heat preservation of the crystal edge and the center area respectively by in-situ lifting and lowering, so as to dynamically adjust the configuration of the thermal field around the crystal during the annealing process to adapt to the different needs of heating, constant temperature and cooling stages.

[0020] (3) The multi-stage crystal annealing method based on the annealing device of the present invention can significantly improve the quality and efficiency of crystal annealing: In the heating stage, the liftable edge insulation sleeve is appropriately raised and the liftable center insulation column is close to the crystal, which can realize rapid and uniform heating of the crystal edge and center area; In the constant temperature stage, the liftable edge insulation sleeve completely covers multiple crystals to be annealed and the liftable center insulation column is close to the surface of the uppermost crystal, which can simultaneously suppress heat dissipation of the crystal center and edge, make the crystal temperature distribution uniform, and ensure that the internal stress is fully released; In the cooling stage, while keeping the liftable edge insulation sleeve completely covering multiple crystals to be annealed, the liftable center insulation column is gradually moved up to form a heat dissipation channel between it and the uppermost crystal, which can suppress heat dissipation of the crystal edge, accelerate heat dissipation of the crystal center, and prevent the crystal edge from cooling too quickly, which would cause the crystal to crack. Attached Figure Description

[0021] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. The drawings of the present invention are provided for illustrative purposes only, and the proportions, sizes, and quantities of the parts in the drawings may not be consistent with the actual product.

[0022] Figure 1 This is a schematic diagram of the structure of the crystal annealing apparatus in some specific embodiments of the present invention;

[0023] Figure 2 This is a schematic diagram of the structure of the crystal annealing apparatus in the heating stage in some specific embodiments of the present invention.

[0024] Figure 3 This is a schematic diagram of the structure of the crystal annealing apparatus in the isothermal stage in some specific embodiments of the present invention.

[0025] Figure 4 This is a schematic diagram of the structure of the annealing device for crystals in the cooling stage in some specific embodiments of the present invention.

[0026] Figure 5 This is a diagram showing the result of edge cracks appearing in the crystal after annealing treatment according to Comparative Example 3 of the present invention.

[0027] Figure 6 This is a diagram showing the result of a central crack appearing in a crystal after annealing treatment according to Comparative Example 4 of this invention.

[0028] Figures 1 to 4 In the middle: 1: First lifting rod; 2: Second lifting rod; 3: Liftable edge insulation sleeve; 31: Upper sleeve section; 32: Lower sleeve section; 4: Insulation layer; 5: Liftable central insulation column; 6: Annealing crucible; 7: Induction coil; 8: Crystal to be annealed; 9: Graphite block; 10: Graphite felt; 11: Crucible support tray; 12: Crucible rotation lifting shaft; 13: Furnace cavity shell. Detailed Implementation

[0029] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below in conjunction with the embodiments thereof. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0030] To address the limitations of existing crystal annealing techniques, this invention provides an annealing apparatus that can effectively improve the annealing effect and efficiency. This apparatus can achieve in-situ control of the thermal field configuration around the crystal in the annealing crucible to meet the different thermal field requirements at different stages of the annealing process. Furthermore, based on the aforementioned annealing apparatus, this invention also provides a highly efficient annealing method. This method can effectively achieve a uniform temperature distribution in the crystal at each stage of the annealing process, while significantly shortening the annealing time and improving annealing efficiency and the quality of the annealed crystal.

[0031] In a first aspect, the present invention provides an annealing apparatus for crystals, for example, such as... Figure 1As shown, the annealing apparatus includes: an annealing crucible 6 for holding a plurality of crystals 8 to be annealed; a graphite felt 10 is coaxially disposed at the bottom of the annealing crucible 6; the plurality of crystals are coaxially placed on the graphite felt 10 from bottom to top, and a graphite block 9 is disposed between adjacent (two adjacent) crystals; in this invention, the upper end of the annealing crucible 6 has an opening; the annealing crucible 6 is, for example, cylindrical; the graphite felt 10 is, for example, circular; and the graphite block 9 is, for example, a circular graphite block; in this invention, Multiple crystals to be annealed may have the same or different diameters; a heat insulation layer 4 is disposed outside the annealing crucible 6; specifically, the heat insulation layer 4 wraps around the outside of the annealing crucible 6, and the upper end of the heat insulation layer 4 has an opening; an induction coil 7 is used to heat the annealing crucible 6; in this invention, the heat insulation layer 4 is coaxially arranged with the annealing crucible 6, and the induction coil 7 is located, for example, outside the heat insulation layer 4, for example, the induction coil is surrounded in the axial direction of the heat insulation layer; this invention provides heat insulation... The temperature layer, induction coil, etc., are not specifically limited, and those skilled in the art can choose them conventionally; a liftable edge insulation sleeve 3 is coaxially arranged with the annealing crucible 6, and the liftable edge insulation sleeve 3 can extend into the interior of the annealing crucible 6 to insulate the edge of the crystal; in this invention, the liftable edge insulation sleeve can, for example, extend into the interior of the annealing crucible through the opening of the insulation layer and the opening of the annealing crucible in sequence to insulate the edge of the crystal; a liftable edge insulation sleeve coaxially arranged with the annealing crucible 6... A central insulating column 5, which is liftable, extends into the interior of the annealing crucible 6 to insulate the central region of the crystal. For example, the liftable central insulating column can extend into the annealing crucible through the opening of the insulating layer and the opening of the annealing crucible to insulate the central region of the crystal. Preferably, in this invention, the inner diameter of the opening of the insulating layer is smaller than the opening of the annealing crucible, and the inner diameter of the opening of the insulating layer is clearance-fitted with the outer diameter of the liftable edge insulating sleeve. For example, ... Figure 1 As shown, the present invention does not impose specific limitations on the materials of the liftable edge insulation sleeve and the liftable center insulation column. For example, the same material as the conventional insulation layer can be used.

[0032] The annealing apparatus of the present invention includes a liftable edge insulation sleeve and a liftable center insulation column. The dimensions of the two are matched with the crystal to be annealed and the annealing crucible. The liftable edge insulation sleeve and the liftable center insulation column can achieve precise control of the insulation of the crystal edge and the center area respectively by in-situ lifting, thereby dynamically adjusting the thermal field configuration around the crystal during the annealing process to adapt to the different needs of each stage of heating, isothermal and cooling.

[0033] Existing technologies have been reported to improve thermal uniformity and control the temperature distribution uniformity within the annealing furnace by relying on external heaters for zoned temperature control and fixed heat insulation plates inside the container. However, this approach does not address the dynamic control of the thermal field in localized areas of the crystal. While this method can improve macroscopic temperature uniformity, it cannot adjust the heat dissipation or heat preservation status of different parts of the crystal (especially the center and edges) as needed during the annealing process. This makes it difficult to cope with complex thermal stress evolution processes, especially when processing large-sized crystals, which can easily lead to residual stress concentration or cracking. This invention, by introducing independently liftable edge insulation sleeves and a central insulation column, achieves in-situ, regional, and dynamic control of the heat preservation status of the crystal's edge and center. This promotes uniform and rapid heating during the heating phase, maintains a highly uniform thermal environment to fully relax stress during the isothermal phase, and during the cooling phase, it suppresses heat dissipation from the crystal to the edges. By lifting the liftable central insulation column upwards, a central heat dissipation channel is formed between it and the uppermost crystal, allowing heat to dissipate from the crystal's central region, effectively preventing cracking due to excessively low temperatures at the crystal edges.

[0034] According to some preferred embodiments, when the annealing apparatus performs annealing, the annealing includes a heating stage, a isothermal stage, and a cooling stage; in the heating stage, for example, as... Figure 2 As shown, the bottom of the liftable edge insulation sleeve 3 is 0-30mm higher than the upper surface of the uppermost crystal (e.g., 0, 5, 10, 15, 20, 25, or 30mm), and the lower surface of the liftable central insulation column 5 is 0-10mm lower than the upper surface of the uppermost crystal (e.g., 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10mm). This accelerates the flow of heat from the crystal edge to the center during the crystal's heating phase, preventing heat loss from the central region and ensuring a uniform temperature distribution during heating. If the bottom of the liftable edge insulation sleeve is too high above the upper surface of the uppermost crystal, and / or the liftable... If the lower surface of the drop-type central insulation column is too far from the upper surface of the top crystal, heat dissipation will be too rapid, reducing heating efficiency. Specifically, heat is transferred from the side wall of the annealing crucible to the edge of the crystal and further to the central region of the crystal. Raising the liftable edge insulation sleeve to a suitable position above the crystal allows heat to flow quickly to the crystal for heating. Simultaneously, separating the crystals with thermally conductive graphite blocks accelerates the further flow of heat to the central region. Furthermore, the liftable central insulation column at the top of the crystal and the close contact between the bottom of the crystal and the graphite felt prevent heat loss from the central region, ensuring uniform temperature distribution during heating. During the isothermal stage, for example... Figure 3As shown, the liftable edge insulation sleeve 3 is fitted over the outside of the multiple crystals, and the lower surface of the liftable central insulation column 5 is in contact with the upper surface of the uppermost crystal. This allows for simultaneous suppression of heat dissipation from both the central region and the edges of the crystal during the isothermal stage, promoting a uniform temperature distribution within the crystal. During the cooling stage, for example... Figure 4 As shown, the adjustable edge insulation sleeve is kept on the outside of the multiple crystals, while the adjustable central insulation column is pulled upwards. This suppresses heat dissipation from the crystal edges and accelerates heat dissipation from the crystal center during the crystal cooling phase, preventing the crystal from cracking due to excessive heat dissipation from the edges. In other words, while the adjustable edge insulation sleeve remains stationary, it effectively suppresses heat dissipation from the crystal to the edges. Pulling the adjustable central insulation column upwards creates a heat dissipation channel between it and the uppermost crystal, facilitating heat dissipation from the crystal center and preventing cracking at the crystal edges. Cracking occurs due to excessively low insulation temperature. In this invention, preferably, the lifting speed is 5-60 mm / h (e.g., 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, or 60 mm / h), more preferably 5-20 mm / h (e.g., 5, 10, 15, or 20 mm / h), and the upward lifting stroke is 80-100 mm (e.g., 80, 90, or 100 mm). In this invention, the upward lifting stroke refers to the lifting until the lower surface of the liftable central insulation column is aligned with the crystal. The distance between the upper surfaces is 80-100mm. In this invention, it is preferable to slowly pull upwards at a speed of 5-60mm / h until the pulling stroke is 80-100mm. Pulling too fast, too slow, or too high is not conducive to ensuring the uniformity of radial temperature distribution during crystal cooling, thus leading to a deterioration in crystal quality. In this invention, it is preferable to slowly pull upwards at a speed of 5-60mm / h to form a heat dissipation channel with a gradually expanding channel space between the column and the uppermost crystal. This invention finds that using heat dissipation... Compared to a fixed heat dissipation channel, the dynamically expanding channel design allows for real-time matching of the changing temperature field inside the crystal by adjusting the lifting speed and stroke. This prevents thermal stress cracks in the central region caused by sudden changes in heat dissipation. The dynamically expanded heat dissipation channel prioritizes heat dissipation efficiency in the central region while maintaining a gradual decrease in edge temperature through the continuous constraint of the liftable edge insulation sleeve. Furthermore, the gradual expansion of the heat dissipation channel is more conducive to synchronizing the cooling rate differences between the crystal's interior and surface, effectively suppressing the generation of defects such as dislocations and slip, and thus improving crystal quality.

[0035] According to some preferred embodiments, the inner diameter of the liftable edge insulation sleeve 3 is 5-20 mm larger than the diameter of the crystal (e.g., 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19 or 20 mm), that is, the inner diameter of the liftable edge insulation sleeve 3 is 5-20 mm larger than the diameter of the crystal; and / or the diameter of the liftable central insulation column 5 is 0-100 mm smaller than the diameter of the crystal (e.g., 0, 5, 10, 20, 30, 40, 50, 60, 70, 80, 90 or 100 mm), that is, the diameter of the liftable central insulation column 5 is 0-100 mm smaller than the diameter of the crystal. Preferably, the diameter of the liftable central insulation column 5 is 0.5 to 1 times the diameter of the crystal.

[0036] According to some preferred embodiments, the liftable edge insulation sleeve 3 includes an upper sleeve section 31 and a lower sleeve section 32 that are interconnected. The inner diameter of the upper sleeve section 31 is smaller than the diameter of the crystal, and the inner diameter of the lower sleeve section 32 is larger than the diameter of the crystal, for example, the inner diameter of the lower sleeve section 32 is 5-20 mm larger than the diameter of the crystal. The inner diameter of the upper sleeve section 31 is not smaller than the diameter of the liftable central insulation column 5. In this invention, preferably, the upper sleeve section and the liftable central insulation column are in clearance fit, and / or the upper sleeve section and the liftable central insulation column have the same height. This invention does not specifically limit the height of the lower sleeve section, as long as it can completely cover multiple crystals to be annealed. During the constant temperature stage and / or cooling stage, the lower surface of the upper sleeve section is in contact with the upper surface of the uppermost crystal, for example, as shown in the figure. Figure 3 and Figure 4 As shown. In this invention, a more preferable design is a segmented, liftable edge insulation sleeve (including an upper sleeve section with a smaller inner diameter and a lower sleeve section with a larger inner diameter). Compared to a straight sleeve structure, during the isothermal stage, the upper sleeve section forms a locally enclosed space by being in close contact with the upper surface of the crystal, which can effectively suppress heat loss in the central region of the crystal. At the same time, the lower sleeve section maintains a gap with the edge of the crystal, which is more conducive to the uniform distribution of the overall temperature field of the crystal. During the cooling stage, the upper sleeve section continues to contact the upper surface of the crystal to maintain edge insulation, while the channel space formed by the liftable central insulation column gradually expands after being lifted, which is beneficial to preventing cracking of the edge due to excessive heat dissipation, and allows the central region to accelerate heat dissipation through controllable convection, which is conducive to achieving rapid and uniform cooling of the crystal.

[0037] According to some preferred embodiments, the liftable edge insulation sleeve 3 is connected to a first lifting drive device for driving the liftable edge insulation sleeve 3 to rise and fall via a first lifting rod 1; in some specific embodiments, the liftable edge insulation sleeve includes an upper sleeve section and a lower sleeve section, and the first lifting rod is disposed at the top of the upper sleeve section; and / or the liftable central insulation column 5 is connected to a second lifting drive device for driving the liftable central insulation column 5 to rise and fall via a second lifting rod 2; in this invention, the second lifting rod is disposed, for example, at the top of the liftable central insulation column; this invention does not specifically limit the first lifting rod, the first lifting drive device, the second lifting rod, and the second lifting drive device, and those skilled in the art can conventionally choose them.

[0038] According to some preferred embodiments, the inner diameter of the annealing crucible 6 is 10-50 mm larger than the diameter of the crystal (e.g., 10, 15, 20, 25, 30, 35, 40, 45, or 50 mm); the diameter of the graphite felt 10 is 0-50 mm smaller than the diameter of the crystal (e.g., 0, 5, 10, 15, 20, 25, 30, 35, 40, 45, or 50 mm); the present invention does not specifically limit the thickness of the graphite felt 10, for example, it can be 5-20 mm; and / or the diameter of the graphite block 9 is 30-100 mm (e.g., 30, 40, 50, 60, 70, 80, 90, or 100 mm), and the thickness is 5-10 mm (e.g., 5, 6, 7, 8, 9, or 10 mm); in the present invention, preferably, the diameter of the graphite block is smaller than the diameter of the graphite felt, for example, the diameter of the graphite block is 0.3-0.7 times the diameter of the graphite felt.

[0039] According to some preferred embodiments, the annealing apparatus further includes a crucible support tray 11 for supporting the annealing crucible 6. The crucible support tray 11 is located below the insulation layer 4, and the crucible support tray 11 is connected to the crucible rotation and lifting drive device via a crucible rotation and lifting shaft 12. In this invention, the crucible rotation and lifting shaft 12 passes through the furnace cavity shell 13 of the annealing furnace and is connected to the crucible support tray 11 located inside the furnace cavity shell 13.

[0040] According to some preferred embodiments, the crystal is a silicon carbide crystal.

[0041] The present invention provides a method for annealing crystals in a second aspect. The annealing method employs the crystal annealing apparatus described in the first aspect of the present invention. The annealing method includes a heating stage, a isothermal stage, and a cooling stage. In the heating stage: the bottom of the liftable edge insulation sleeve is positioned 0-30 mm above the upper surface of the uppermost crystal, and the lower surface of the liftable central insulation column is positioned 0-10 mm away from the upper surface of the uppermost crystal, followed by heating. In the isothermal stage: the liftable edge insulation sleeve is fitted over the plurality of crystals, and the lower surface of the liftable central insulation column is brought into contact with the upper surface of the uppermost crystal, followed by isothermal maintenance. In the cooling stage: the liftable central insulation column is pulled upwards and cooled. In the present invention, it is preferable to perform the cooling simultaneously by slowly pulling the liftable central insulation column upwards at a pulling speed of 5-60 mm / h to form a heat dissipation channel between it and the uppermost crystal.

[0042] The present invention provides an efficient, multi-stage annealing method based on the annealing apparatus. This annealing method can effectively achieve a uniform temperature distribution in the crystal at each stage of the annealing process, while significantly shortening the annealing time and improving the annealing efficiency and the quality of the annealed crystal.

[0043] According to some preferred embodiments, during the heating phase, the temperature is increased to 1700-2000℃ (e.g., 1700℃, 1800℃, 1900℃, or 2000℃) at a heating rate of 100-500℃ / h (e.g., 100℃ / h, 200℃ / h, 300℃ / h, 400℃ / h, or 500℃ / h); during the isothermal phase, the holding time is 5-15h (e.g., 5, 10, or 15h); and during the cooling phase, the temperature is increased at a rate of 20-200℃ / h (e.g., 20℃ / h, 50℃ / h, 100℃ / h, or 500℃ / h). The temperature is lowered to room temperature at a rate of 100-200°C / h (150°C / h or 200°C / h, preferably 100-200°C / h); in this invention, the room temperature is, for example, room temperature of 15-35°C; and / or during the cooling phase, the lifting speed is 5-60 mm / h (e.g., 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55 or 60 mm / h), more preferably 5-20 mm / h, and the upward lifting stroke is 80-100 mm (e.g., 80, 90 or 100 mm).

[0044] This invention employs a unique dynamic insulation design to precisely control the thermal environment of the crystal during each annealing stage—heating, isothermal, and cooling—achieving rapid heating and cooling, significantly shortening the annealing time. During the heating stage, by adjusting the liftable edge insulation sleeve and the liftable central insulation column to maintain a specific close distance from the crystal's upper surface, direct obstruction of the crystal's heating is avoided while maintaining necessary radiative heat reflection, allowing heat to penetrate the crystal more evenly and rapidly. Therefore, a heating rate of 100~500℃ / h can be achieved for rapid heating. During the isothermal stage, ... The liftable edge insulation sleeve is completely fitted over the outside of the crystal, and the liftable central insulation column is in contact with the upper surface of the crystal, creating a highly sealed and uniform insulation environment. This effectively suppresses heat loss, allowing for sufficient relaxation and stress relief within a short period of 5 to 15 hours. During the cooling phase, the liftable central insulation column is slowly lifted, increasing the heat dissipation area and path on the upper surface of the crystal. At the same time, the liftable edge insulation sleeve continues to be fitted over the outside of the crystal, preventing the edges from cooling too quickly. This allows the cooling rate to reach 20 to 200°C / h for controlled rapid cooling. In contrast, existing conventional annealing equipment, due to its fixed insulation structure, typically employs an extremely slow temperature change rate (for example, the heating rate is usually no more than 50℃ / h, while the cooling rate is generally only 10~50℃ / h) to avoid cracking or defects caused by excessive temperature differences between the inside and outside of the crystal during heating or cooling. Although this can control thermal stress to some extent, it inevitably leads to a significant extension of the annealing cycle, low annealing efficiency, and high energy consumption and cost.

[0045] According to some specific embodiments, the annealing method includes the following steps:

[0046] (1) The annealing apparatus for assembling the crystal, specifically, for example: preparing an annealing crucible, the annealing crucible being an open crucible, the inner diameter of the annealing crucible being 10-50 mm larger than the diameter of the crystal to be annealed; placing a layer of circular graphite felt coaxially at the bottom of the annealing crucible, the diameter of the circular graphite felt being 0-50 mm smaller than the diameter of the crystal; placing multiple crystals to be annealed coaxially on the circular graphite felt from bottom to top, and separating the crystals from each other with circular graphite blocks, the thickness of the circular graphite blocks being 5-10 mm and the diameter being 30-100 mm; placing a liftable edge insulation sleeve and a liftable center insulation column into the annealing crucible, the liftable edge insulation sleeve and the center insulation column being placed into the annealing crucible, the liftable edge insulation sleeve and the center insulation column being placed into the annealing crucible; ... The inner diameter of the edge insulation sleeve is 5-20 mm larger than the outer diameter of the crystal, and the diameter of the liftable central insulation column is 0-100 mm smaller than the diameter of the crystal. The liftable edge insulation sleeve is equipped with a first lifting rod, and the liftable central insulation column is equipped with a second lifting rod. An insulation layer is installed on the outside of the annealing crucible. The assembled annealing crucible, along with the insulation layer, is placed on a crucible support tray inside the furnace cavity shell of the annealing furnace. The crucible support tray is connected to a crucible rotation and lifting drive device via a crucible rotation and lifting shaft passing through the furnace cavity shell. The position of the annealing crucible is adjusted to be inside the induction coil by the crucible rotation and lifting drive device.

[0047] (2) Close the furnace chamber of the annealing furnace and perform vacuum treatment on the furnace chamber. When the gas pressure in the furnace chamber is less than or equal to 1×10 -4 After Pa, inert protective gas (nitrogen and / or argon) is introduced into the furnace cavity until the pressure reaches 3 × 10⁻⁶. 4 Pa ~ 4 × 10 4 Pa.

[0048] (3) Perform annealing treatment, which includes the following three stages:

[0049] Heating stage: Adjust the position of the liftable edge insulation sleeve so that the bottom of the liftable edge insulation sleeve is 0-30mm higher than the upper surface of the top crystal, and adjust the lower surface of the liftable central insulation column to be 0-10mm away from the upper surface of the top crystal. Then, heat the crystal rapidly to 1800℃ at a heating rate of 100-500℃ / h by induction coil heating.

[0050] Constant temperature stage: Lower the liftable edge insulation sleeve to cover the outside of the multiple crystals, that is, completely cover the crystals, and make the lower surface of the liftable central insulation column in complete contact with the upper surface of the uppermost crystal. Keep the heating power of the induction coil unchanged and maintain constant temperature for 5~15 hours to allow the internal stress in the crystals to be fully released.

[0051] Cooling stage: Keep the position of the liftable edge insulation sleeve unchanged, slowly lift the liftable central insulation column upward to accelerate the heat dissipation rate of the crystal center area, and cool the crystal to room temperature at a cooling rate of 20~200℃ / h by controlling the heating power of the induction coil (e.g., reducing the heating power).

[0052] (4) Fill the furnace chamber of the annealing furnace with an inert protective gas to one atmosphere, open the furnace chamber, take out the annealing crucible, and take out the annealed crystal.

[0053] The present invention will be further described below by way of examples, but the scope of protection of the present invention is not limited to these embodiments.

[0054] Example 1

[0055] This embodiment provides an annealing apparatus for crystals, for example, such as... Figures 1 to 4 As shown, the annealing apparatus includes:

[0056] An annealing crucible for holding multiple crystals to be annealed, wherein a circular graphite felt is coaxially arranged at the bottom of the annealing crucible, and multiple crystals are placed coaxially on the circular graphite felt from bottom to top, with a circular graphite block placed between adjacent crystals. The upper end of the annealing crucible has an opening, wherein each crystal has a diameter of 150 mm, the inner diameter of the annealing crucible is 20 mm larger than the diameter of the crystal, the diameter of the circular graphite felt is 30 mm smaller than the diameter of the crystal and the thickness is 5 mm, and the diameter of the circular graphite block is 50 mm and the thickness is 5 mm.

[0057] An insulation layer is disposed outside the annealing crucible, the insulation layer wraps around the outside of the annealing crucible, and the upper end of the insulation layer has an opening.

[0058] An induction coil for heating the annealing crucible; the insulation layer is coaxially arranged with the annealing crucible, and the induction coil is located outside the insulation layer and surrounds the insulation layer in the axial direction.

[0059] A liftable edge insulation sleeve is coaxially arranged with the annealing crucible. The liftable edge insulation sleeve can extend into the interior of the annealing crucible through the opening of the insulation layer and the opening of the annealing crucible to insulate the edge of the crystal. The liftable edge insulation sleeve is connected to a first lifting drive device for driving the liftable edge insulation sleeve to move up and down via a first lifting rod. The inner diameter of the opening of the insulation layer is smaller than the opening of the annealing crucible, and the inner diameter of the opening of the insulation layer is clearance-fitted with the outer diameter of the liftable edge insulation sleeve.

[0060] A liftable central heat-insulating column is coaxially arranged with the annealing crucible. The liftable central heat-insulating column can extend into the interior of the annealing crucible through the opening of the heat-insulating layer and the opening of the annealing crucible to heat the central region of the crystal. The liftable central heat-insulating column is connected to a second lifting drive device for driving the liftable central heat-insulating column to move up and down through a second lifting rod.

[0061] A crucible support tray is used to support the annealing crucible. The crucible support tray is located below the insulation layer and is connected to the crucible rotation and lifting drive device via a crucible rotation and lifting shaft.

[0062] The adjustable edge insulation sleeve includes an upper sleeve section and a lower sleeve section that are interconnected. The inner diameter of the upper sleeve section is smaller than the diameter of the crystal, and the inner diameter of the lower sleeve section is 5mm larger than the diameter of the crystal. The diameter of the adjustable central insulation column is 40mm smaller than the diameter of the crystal. The upper sleeve section and the adjustable central insulation column are clearance-fitted, and the upper sleeve section and the adjustable central insulation column have the same height.

[0063] This embodiment also provides a method for annealing crystals, which is performed using the annealing apparatus described in this embodiment. The annealing method includes the following steps:

[0064] (1) Annealing apparatus for assembling the crystal.

[0065] (2) Close the furnace chamber of the annealing furnace and perform vacuum treatment on the furnace chamber. When the gas pressure in the furnace chamber is less than or equal to 1×10 -4 After Pa, inert protective gas (argon) is introduced into the furnace cavity until the pressure reaches 30000 Pa.

[0066] (3) Perform annealing treatment, which includes the following three stages:

[0067] Heating stage: Adjust the position of the liftable edge insulation sleeve so that the bottom of the liftable edge insulation sleeve is 1mm higher than the upper surface of the top crystal, and adjust the lower surface of the liftable central insulation column to be 1mm away from the upper surface of the top crystal. Then, heat the crystal rapidly to 1800℃ at a heating rate of 200℃ / h by induction coil heating.

[0068] Constant temperature stage: The liftable edge insulation sleeve is lowered to cover the outside of the multiple crystals, and the lower surface of the liftable central insulation column is in complete contact with the upper surface of the uppermost crystal. The heating power of the induction coil is kept constant, and the temperature is maintained for 5 hours to allow the internal stress in the crystal to be fully released. During the constant temperature stage, the lower surface of the upper sleeve section is in contact with the upper surface of the uppermost crystal.

[0069] Cooling stage: Keep the position of the liftable edge insulation sleeve unchanged, slowly lift the liftable center insulation column upward to form a heat dissipation channel with gradually expanding channel space between it and the uppermost crystal, the lifting speed is 10mm / h, and stop lifting after lifting 100mm; and cool the crystal to room temperature at a cooling rate of 150℃ / h by controlling the heating power of the induction coil.

[0070] (4) Fill the furnace chamber of the annealing furnace with an inert protective gas to one atmosphere, open the furnace chamber, take out the annealing crucible, and take out the annealed crystal.

[0071] Table 1 shows the comparison results of key quality indicators of the crystal before and after annealing using the annealing apparatus and method described in this embodiment. As can be seen from Table 1, the crystallization quality of the crystal is significantly improved after annealing, and the full width at half maximum (FWHM) of the X-ray diffraction rocking curve of the crystal is significantly reduced by several times. This indicates that the annealing apparatus and method provided by this invention can greatly improve the quality of the crystal.

[0072] Table 1: Comparison of crystal quality before and after annealing in Example 1.

[0073]

[0074] Example 2

[0075] Example 2 is basically the same as Example 1, except that:

[0076] (3) Perform annealing treatment, which includes the following three stages:

[0077] Heating stage: Adjust the position of the liftable edge insulation sleeve so that the bottom of the liftable edge insulation sleeve is 1mm higher than the upper surface of the top crystal, and adjust the lower surface of the liftable central insulation column to be 1mm away from the upper surface of the top crystal; then heat the crystal rapidly to 1800℃ at a heating rate of 50℃ / h by induction coil heating.

[0078] Constant temperature stage: The liftable edge insulation sleeve is lowered to cover the outside of the multiple crystals, and the lower surface of the liftable central insulation column is in complete contact with the upper surface of the uppermost crystal. The heating power of the induction coil is kept constant, and the temperature is maintained for 5 hours to allow the internal stress in the crystal to be fully released. During the constant temperature stage, the lower surface of the upper sleeve section is in contact with the upper surface of the uppermost crystal.

[0079] Cooling stage: Keep the position of the liftable edge insulation sleeve unchanged, slowly lift the liftable center insulation column upward to form a heat dissipation channel with gradually expanding channel space between it and the uppermost crystal, the lifting speed is 10mm / h, and stop lifting after lifting 100mm; and cool the crystal to room temperature at a cooling rate of 20℃ / h by controlling the heating power of the induction coil.

[0080] Table 2 shows the comparison results of key quality indicators of the crystal before and after annealing using the annealing apparatus and method described in this embodiment. As can be seen from the results in Table 2, the crystal quality of the crystal is significantly improved after annealing, and the full width at half maximum (FWHM) of the X-ray diffraction rocking curve of the crystal is significantly reduced by several times. Furthermore, the improvement in crystal quality is comparable to that in Example 1, indicating that the annealing apparatus and method of this invention, which can increase the heating and cooling rates, do not sacrifice crystal quality.

[0081] Table 2: Comparison of crystal quality before and after annealing in Example 2.

[0082]

[0083] Comparative Example 1

[0084] Comparative Example 1 is basically the same as Example 1, except that:

[0085] (3) Perform annealing treatment, which includes the following three stages:

[0086] Heating stage: Adjust the position of the liftable edge insulation sleeve so that the bottom of the liftable edge insulation sleeve is 1mm higher than the upper surface of the top crystal, and adjust the lower surface of the liftable central insulation column to be 1mm away from the upper surface of the top crystal; then heat the crystal rapidly to 1800℃ at a heating rate of 200℃ / h by induction coil heating.

[0087] Constant temperature stage: The liftable edge insulation sleeve is lowered to cover the outside of the multiple crystals, and the lower surface of the liftable central insulation column is in complete contact with the upper surface of the uppermost crystal. The heating power of the induction coil is kept constant, and the temperature is maintained for 5 hours to allow the internal stress in the crystal to be fully released. During the constant temperature stage, the lower surface of the upper sleeve section is in contact with the upper surface of the uppermost crystal.

[0088] Cooling stage: Keep the position of the liftable edge insulation sleeve unchanged, and quickly lift the liftable center insulation column upward at a speed of 120mm / h until the distance between the lower surface of the liftable center insulation column and the upper surface of the crystal is 120mm. Then, by controlling the heating power of the induction coil, the crystal is cooled to room temperature at a cooling rate of 150℃ / h.

[0089] The comparison results of key quality indicators of the crystals before and after annealing using the annealing apparatus and annealing method in this comparative example are shown in Table 3. The results in Table 3 show that the crystallization quality of the crystals improved after annealing. However, the decrease in the full width at half maximum (FWHM) of the X-ray diffraction rocking curve of the crystals was significantly smaller than that in Example 1. This indicates that if the speed and height of the liftable central heat-insulating column are too fast and too large during the cooling stage of the annealing apparatus and annealing method of this invention, the annealing effect of the crystals will be significantly worsened, and the improvement in crystal quality after annealing will not be ideal.

[0090] Table 3: Comparison of crystal quality before and after annealing in Comparative Example 1.

[0091]

[0092] Comparative Example 2

[0093] Comparative Example 2 is basically the same as Example 1, except that:

[0094] When assembling the annealing device in step (1), no liftable edge insulation sleeve or liftable center insulation column is set, and multiple crystals are placed coaxially on the circular graphite felt from bottom to top. No circular graphite blocks are set between adjacent crystals, and they are directly stacked together.

[0095] In step (3), the annealing process involves heating the crystal to 1800°C at a heating rate of 200°C / h using an induction coil and holding it at that temperature for 5 hours. Then, the crystal is cooled to room temperature at a cooling rate of 150°C / h by controlling the heating power of the induction coil.

[0096] Table 4 shows the comparison results of key quality indicators of the crystals before and after annealing using the annealing apparatus and method described in this comparative example. As can be seen from Table 4, the improvement in crystal quality after annealing is minimal. The full width at half maximum (FWHM) of the X-ray diffraction rocking curve of the annealed crystal is still greater than 100 arcsec, indicating that the residual stress in the crystal is still very high, resulting in poor crystal quality. This demonstrates that under the same annealing temperature variation rate process, it is difficult to achieve the desired annealing effect without using the apparatus and method provided by this invention.

[0097] Table 4: Comparison of crystal quality before and after annealing in Comparative Example 2.

[0098]

[0099] Comparative Example 3

[0100] Comparative Example 3 is basically the same as Example 1, except that:

[0101] When assembling the annealing device in step (1), the liftable edge insulation sleeve is not installed.

[0102] When performing annealing in step (3), the annealing process is as follows: the lower surface of the liftable central heat-insulating column is brought into complete contact with the upper surface of the uppermost crystal, and then the crystal is rapidly heated to 1800℃ at a heating rate of 200℃ / h and held at that temperature for 5h by heating with an induction coil, while keeping the position of the liftable central heat-insulating column unchanged, and then the crystal is cooled to room temperature at a cooling rate of 150℃ / h by controlling the heating power of the induction coil.

[0103] After annealing in this comparative example, the crystal showed edge cracking, such as... Figure 5 As shown, this is mainly due to the excessively fast heat dissipation rate in the crystal edge region during the cooling process, which causes the crystal edge region to shrink rapidly relative to the central region, leading to cracking in the crystal edge region.

[0104] Comparative Example 4

[0105] Comparative Example 4 is basically the same as Example 1, except that:

[0106] When assembling the annealing device in step (1), a liftable central insulation column is not installed.

[0107] In step (3), the annealing process includes lowering the liftable edge insulation sleeve to cover the outside of the multiple crystals, then heating the crystals rapidly to 1800°C at a heating rate of 200°C / h and holding them at that temperature for 5 hours by using an induction coil, and then cooling the crystals to room temperature at a cooling rate of 150°C / h by controlling the heating power of the induction coil. Throughout the annealing process, the lower surface of the upper sleeve section is in contact with the upper surface of the uppermost crystal.

[0108] The crystal after annealing in this comparative example: a central crack appeared in the crystal center, as shown in the example. Figure 6 As shown, this is mainly due to the excessively rapid heat dissipation rate in the central region of the crystal during the cooling process, causing the central region to shrink rapidly relative to the edge region, resulting in cracking in the central region of the crystal.

[0109] As can be seen from the results of Examples 1, 2, 3, and 4, the present invention, through the coordinated lifting and lowering adjustment of the adjustable edge insulation sleeve and the adjustable central insulation column, as well as the setting of graphite blocks between crystals, dynamically controls the uniformity of crystal temperature distribution in each stage of annealing, thereby significantly improving the quality of annealed crystals. If the adjustable edge insulation sleeve or the adjustable central insulation column is not set, and the operation of the adjustable edge insulation sleeve and the adjustable central insulation column is not performed in conjunction during the annealing stage, the phased balance of the temperature field will be disrupted, and the crystal annealing effect will be worse than that of Comparative Example 2, which did not set the adjustable edge insulation sleeve, the adjustable central insulation column, and the graphite blocks.

[0110] Comparative Example 5

[0111] Comparative Example 5 is basically the same as Example 1, except that:

[0112] In step (3), the annealing process includes: lowering the liftable edge insulation sleeve to cover the outside of the multiple crystals, and making the lower surface of the liftable center insulation column fully contact the upper surface of the uppermost crystal. During the entire annealing stage, the lower surface of the upper sleeve section is in contact with the upper surface of the uppermost crystal. Then, while maintaining the same power of the induction coil as in Example 1, the crystal is heated to 1800°C by the induction coil and kept at that temperature for 5 hours. Then, while maintaining the same heating power of the induction coil as in Example 1, the crystal is cooled to room temperature.

[0113] When annealing was performed in this comparative example, the crystal was covered with insulation felt on all sides, resulting in very slow heating and cooling rates. Under the same power setting, the heating and cooling time increased by about 2 times, leading to very low annealing efficiency.

[0114] Comparative Example 6

[0115] Comparative Example 6 is basically the same as Example 1, except that:

[0116] In step (1), when assembling the annealing device, multiple crystals are placed coaxially on the circular graphite felt from bottom to top, and no circular graphite blocks are set between adjacent crystals; they are directly stacked together.

[0117] When performing annealing (3), the annealing process includes the following three stages:

[0118] Heating stage: Adjust the position of the liftable edge insulation sleeve so that the bottom of the liftable edge insulation sleeve is 1mm higher than the upper surface of the top crystal, and adjust the lower surface of the liftable central insulation column to be 1mm away from the upper surface of the top crystal; while keeping the power of the induction coil the same as in Example 1, heat the crystal to 1800℃ by induction coil heating.

[0119] Constant temperature stage: The liftable edge insulation sleeve is lowered to cover the outside of the multiple crystals, and the lower surface of the liftable central insulation column is in complete contact with the upper surface of the uppermost crystal. The heating power of the induction coil is kept constant and the temperature is maintained for 5 hours. During the constant temperature stage, the lower surface of the upper sleeve section is in contact with the upper surface of the uppermost crystal.

[0120] Cooling stage: Keep the position of the liftable edge insulation sleeve unchanged, slowly lift the liftable center insulation column upward at a speed of 10mm / h, and stop lifting after lifting 100mm; while keeping the power of the induction coil the same as in Example 1, cool the crystal to room temperature.

[0121] Table 5 shows the comparison results of key quality indicators of the crystals before and after annealing using the annealing apparatus and method described in this comparative example. The results of this comparative example indicate that if the crystals are not separated by graphite blocks, the heat flow in the central region of the crystal will be impeded, resulting in a large temperature field between the crystal edge and the central region during heating and cooling. This also leads to increased internal stress remaining after annealing, thus resulting in poor annealing effect.

[0122] Table 5: Comparison of crystal quality before and after annealing in Comparative Example 6.

[0123]

[0124] In the description of this invention, it should be noted that the terms "inner", "outer", "upper", "lower", "central area", "edge", etc., indicating the orientation or positional relationship are based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this invention and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this invention.

[0125] In the description of this invention, it should also be noted that, unless otherwise explicitly specified and limited, the term "connection" should be interpreted broadly. For example, it can refer to a fixed connection, a detachable connection, or an integral connection; it can be a direct connection, an indirect connection through an intermediate medium, or an electrical connection, etc. Those skilled in the art can understand the specific meaning of this term in this invention depending on the specific circumstances.

[0126] The parts of this invention not described in detail are techniques known to those skilled in the art.

[0127] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. An annealing apparatus for crystals, characterized in that, The annealing apparatus includes: An annealing crucible for holding multiple crystals to be annealed, wherein a graphite felt is coaxially arranged at the bottom of the annealing crucible, and multiple crystals are coaxially placed on the graphite felt from bottom to top, with graphite blocks arranged between adjacent crystals; A heat insulation layer is provided on the outside of the annealing crucible; An induction coil used for heating the annealing crucible; A liftable edge insulation sleeve is coaxially arranged with the annealing crucible. The liftable edge insulation sleeve can extend into the interior of the annealing crucible to insulate the edge of the crystal. A liftable central heat-insulating column is coaxially arranged with the annealing crucible. The liftable central heat-insulating column can extend into the interior of the annealing crucible to keep the central region of the crystal warm. When the annealing apparatus performs annealing, the annealing includes a heating stage, a constant temperature stage, and a cooling stage; During the heating stage, the bottom of the liftable edge insulation sleeve is 0-30mm higher than the upper surface of the uppermost crystal, and the lower surface of the liftable central insulation column is 0-10mm away from the upper surface of the uppermost crystal. During the constant temperature stage, the liftable edge insulation sleeve is fitted over the outside of the multiple crystals, and the lower surface of the liftable central insulation column is in contact with the upper surface of the uppermost crystal. During the cooling phase, the liftable edge insulation sleeve is kept on the outside of the multiple crystals, while the liftable central insulation column is pulled upward at a speed of 5~60mm / h and a stroke of 80~100mm. The liftable edge insulation sleeve includes an upper sleeve section and a lower sleeve section that are connected to each other. The inner diameter of the upper sleeve section is smaller than the diameter of the crystal, and the inner diameter of the lower sleeve section is larger than the diameter of the crystal. The inner diameter of the upper sleeve section is not less than the diameter of the liftable central insulation column; the upper sleeve section and the liftable central insulation column are clearance-fitted, and the upper sleeve section and the liftable central insulation column have the same height. During the isothermal and cooling phases, the lower surface of the upper sleeve section comes into contact with the upper surface of the uppermost crystal.

2. The annealing apparatus according to claim 1, characterized in that: The diameter of the liftable central insulation column is 0-100mm smaller than the diameter of the crystal.

3. The annealing apparatus according to claim 1, characterized in that: The liftable edge insulation sleeve is connected to a first lifting drive device for driving the liftable edge insulation sleeve to rise and fall via a first lifting rod; and / or The liftable central insulation column is connected to a second lifting drive device for driving the liftable central insulation column to rise and fall via a second lifting rod.

4. The annealing apparatus according to claim 1, characterized in that: The inner diameter of the annealing crucible is 10-50 mm larger than the diameter of the crystal; The diameter of the graphite felt is smaller than the diameter of the crystal by 0-50 mm; and / or The graphite block has a diameter of 30-100 mm and a thickness of 5-10 mm.

5. The annealing apparatus according to claim 1, characterized in that: The annealing apparatus further includes a crucible support tray for supporting the annealing crucible. The crucible support tray is located below the insulation layer and is connected to a crucible rotation and lifting drive device via a crucible rotation and lifting shaft.

6. The annealing apparatus according to any one of claims 1 to 5, characterized in that: The crystal is a silicon carbide crystal.

7. An annealing method for a crystal, characterized in that, The annealing method is performed using the annealing apparatus for crystals according to any one of claims 1 to 6, and the annealing method includes a heating stage, a isothermal stage, and a cooling stage; During the heating stage: the bottom of the liftable edge insulation sleeve is 0-30mm higher than the upper surface of the uppermost crystal, and the lower surface of the liftable center insulation column is 0-10mm away from the upper surface of the uppermost crystal, and then the heating is carried out. During the constant temperature stage: the liftable edge insulation sleeve is placed over the outside of the multiple crystals, and the lower surface of the liftable central insulation column is brought into contact with the upper surface of the uppermost crystal, and then insulation is performed. During the cooling stage: the liftable central insulation column is pulled upwards to cool it down. The pulling speed is 5~60mm / h and the upward pulling stroke is 80~100mm.

8. The method according to claim 7, characterized in that: During the heating phase, the temperature is increased to 1700-2000℃ at a heating rate of 100-500℃ / h. During the constant temperature stage, the heat preservation time is 5~15 hours; During the cooling phase, the temperature is reduced to room temperature at a rate of 20~200℃ / h.

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