Sectional type crystal growth device and method

Abstract

The embodiment of the invention provides a sectional type crystal growth device and method, and relates to the technical field of silicon carbide crystal growth. The sectional type crystal growth method is applied to the sectional type crystal growth device to grow silicon carbide crystals. The sectional type crystal growth device comprises a crucible, a polycrystalline deposition assembly, a first heater and a second heater. Seed crystals are arranged at the top in the crucible, and the crucible is filled with a crystal growth raw material. The polycrystalline deposition assembly comprises a first porous graphite plate, and a first heater is used for heating a crystal growth raw material to deposit polycrystalline crystals on the first porous graphite plate, so that active enrichment and fixation of carbon impurities are realized, and direct scouring of solid carbon particles to the surfaces of seed crystals can be effectively reduced; and the second heater is used for heating the polycrystal deposited on the first porous graphite plate, sublimating the polycrystal and growing a silicon carbide crystal on the seed crystal.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of silicon carbide crystal growth, in particular to a segmented crystal growth device and method. BACKGROUND

[0002] As a new third-generation semiconductor core material, silicon carbide (SiC) has a wide band gap, a high critical breakdown field strength, a high electron mobility, and good radiation resistance and chemical stability, which makes it an important substrate wafer material widely used in various fields, such as aviation devices, new energy vehicles, rail transit, and household appliances.

[0003] During the growth of silicon carbide crystals, carbon inclusions are formed, which seriously damages the integrity of the crystal, causes local stress concentration and dislocation proliferation, and significantly affects the breakdown characteristics and reliability of the device, and is one of the important factors restricting the yield improvement of silicon carbide wafers.

[0004] In some related technologies, to inhibit the formation of carbon inclusions, the existing technology usually sets a layer of porous graphite plate as a filter structure inside the crucible, near the top of the raw material area. The large particle carbon impurities in the ascending gas flow are physically intercepted and adsorbed, which to some extent reduces the number of carbon particles entering the crystal growth zone, but the carbon particles generated by the porous graphite plate with the gas flow will still enter the crystal to become carbon inclusions, and the effect is poor. SUMMARY

[0005] The purpose of the present application includes providing a segmented crystal growth device and method which can reduce the formation of carbon inclusions during the growth of silicon carbide crystals.

[0006] Embodiments of the present application can be implemented as follows: In a first aspect, the present application provides a segmented crystal growth device, comprising: a crucible, a seed crystal is arranged at the top of the crucible, and the crucible is filled with crystal growth raw materials; a polycrystalline deposition assembly, the polycrystalline deposition assembly comprising a first porous graphite plate; a first heater, the first heater being used to heat the crystal growth raw materials to deposit a polycrystalline crystal on the first porous graphite plate; a second heater, the second heater being used to heat the polycrystalline crystal to sublimate the polycrystalline crystal, and grow a silicon carbide crystal on the seed crystal.

[0007] In an optional embodiment, a second porous graphite plate is further installed in the crucible, the second porous graphite plate being located below the first porous graphite plate, and the porosity of the second porous graphite plate being greater than the porosity of the first porous graphite plate.

[0008] In an optional embodiment, the porosity of the first porous graphite plate is 10-30%, and the porosity of the second porous graphite plate is 40-60%.

[0009] In an optional embodiment, the first porous graphite plate comprises opposite first and second sides, and the porosity of the first porous graphite plate gradually decreases along the thickness direction of the first porous graphite plate and in the direction close to the seed crystal.

[0010] In an optional embodiment, the distance between the second porous graphite plate and the first porous graphite plate in the axial direction is 30-40 mm.

[0011] In an optional embodiment, the first porous graphite plates are multiple and arranged at intervals in the axial direction, and the second heater comprises multiple heating modules, which are arranged one-to-one with the multiple first porous graphite plates.

[0012] In an optional embodiment, a flow guide cylinder is further arranged in the crucible, the seed crystal is located in the flow guide cylinder, and the flow guide cylinder is arranged above the first porous graphite plate and coaxially with the seed crystal.

[0013] In a second aspect, the present application provides a segmented crystal growth method applied to the segmented crystal growth device of any one of the preceding embodiments, and the method comprises the following steps: filling the crucible with crystal growth raw materials; arranging the first porous graphite plate in the crucible; starting the first heater to heat the crystal growth raw materials so that the crystal growth raw materials sublimate and crystallize at the first porous graphite plate to form a polycrystalline crystal body; starting the second heater to heat the polycrystalline crystal body so that the polycrystalline crystal body sublimate and grow a silicon carbide crystal at the seed crystal of the crucible.

[0014] In an optional embodiment, in the step of starting the first heater to heat the crystal growth raw materials so that the crystal growth raw materials sublimate and crystallize at the first porous graphite plate to form a polycrystalline crystal body: the temperature of the crystal growth raw materials is 2299-2301℃, and the temperature of the first porous graphite plate is 2287-2289℃.

[0015] In an optional embodiment, in the step of starting the second heater to heat the polycrystalline crystal body so that the polycrystalline crystal body sublimate and grow a silicon carbide crystal at the seed crystal of the crucible: the temperature of the crystal growth raw materials is 2365-2366℃, the temperature of the first porous graphite plate is 2349-2351℃, and the temperature of the seed crystal is 2327-2329℃.

[0016] The beneficial effects provided by the embodiment of the present application include: the embodiment of the present application provides a segmented crystal growth device and method, the segmented crystal growth method is applied to the segmented crystal growth device to grow a silicon carbide crystal, and the segmented crystal growth device comprises a crucible, a polycrystal deposition assembly, a first heater and a second heater. A seed crystal is arranged at the top in the crucible, and the crucible is filled with crystal growth raw materials. The polycrystal deposition assembly comprises a first porous graphite plate, the first heater is used for heating the crystal growth raw materials to deposit a polycrystal crystal on the first porous graphite plate, and the second heater is used for heating the polycrystal crystal deposited on the first porous graphite plate, and sublimating the polycrystal crystal to grow a silicon carbide crystal on the seed crystal. The polycrystal crystal can be deposited on the porous graphite plate in advance, active enrichment and fixation of carbon impurities can be realized, and direct erosion of solid carbon particles to the surface of the seed crystal can be effectively reduced. After the deposition of the polycrystal crystal is completed, the second heater is started to heat and sublimate the polycrystal crystal, and then a silicon carbide crystal is grown on the seed crystal. BRIEF DESCRIPTION OF DRAWINGS

[0017] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following will briefly introduce the drawings needed to be used in the embodiments. It should be understood that the following drawings only show some embodiments of the present application, and therefore should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can also be obtained without creative labor on the basis of these drawings.

[0018] Figure 1 The structure schematic diagram of the segmented crystal growth method provided by the present embodiment is shown in the following figure. Figure 2 The temperature field simulation schematic diagram of each part of the crucible provided by the present embodiment is shown in the following figure. Figure 3 The schematic diagram of some existing silicon carbide crystals under a microscope and strong light is shown in the following figure. Figure 4 The schematic diagram of the silicon carbide crystal grown by the segmented crystal growth device provided by the present embodiment under the segmented crystal growth method under strong light is shown in the following figure. Figure 5 The carrier concentration distribution diagram of some existing silicon carbide crystals is shown in the following figure. Figure 6 The carrier concentration distribution diagram of the silicon carbide crystal grown by the segmented crystal growth device provided by the present embodiment under the segmented crystal growth method is shown in the following figure.

[0019] Figure legend: 1-segmented crystal growth device; 100-crucible; 200-seed crystal; 300-first porous graphite plate; 400-second porous graphite plate; 500-flow guide cylinder; 600-first heater; 700-second heater; 2-crystal growth raw materials. DETAILED DESCRIPTION

[0020] In order to make the objects, technical solutions and advantages of the embodiments of the present application clearer, the following will clearly and completely describe the technical solutions in the embodiments of the present application with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only some but not all of the embodiments of the present application. Generally, the components of the embodiments of the present application described and shown in the drawings can be arranged and designed in various different configurations.

[0021] Therefore, the following detailed description of the embodiments of the present application provided in the drawings is not intended to limit the scope of the claimed application, but merely represents the selected embodiments of the application. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative work fall within the scope of protection of the present application.

[0022] It should be noted that: similar reference numerals and letters represent similar items in the following drawings, therefore, once an item is defined in one drawing, it does not need to be further defined and explained in subsequent drawings.

[0023] In the description of the present application, it should be noted that if the terms "upper", "lower", "inner", "outer" and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, or the orientation or positional relationship when the product of the present application is used, and are only for the convenience of describing the present application and simplifying the description, and therefore cannot be understood as indicating or implying that the indicated device or element must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as limiting the present application.

[0024] In addition, if the terms "first", "second" and the like appear, they are only used to distinguish description, and cannot be understood as indicating or implying relative importance.

[0025] It should be noted that the features in the embodiments of the present application can be combined with each other without conflict.

[0026] The specific structure of the segmented crystal growth device provided by the embodiments of the present application and the corresponding technical effects brought by the specific structure will be described in detail below with reference to the patent drawings.

[0027] Please refer to Figure 1The segmented crystal growth device 1 provided by the embodiment of the present application comprises a crucible 100, a polycrystal deposition assembly, a first heater 600 and a second heater 700. The top of the crucible 100 is provided with a seed crystal 200, and the crucible 100 is filled with a crystal growth raw material 2. The polycrystal deposition assembly comprises a first porous graphite plate 300, the first heater 600 is used for heating the crystal growth raw material 2 to deposit a polycrystal crystal on the first porous graphite plate 300, and the second heater 700 is used for heating the polycrystal crystal deposited on the first porous graphite plate 300 and sublimating the polycrystal crystal to grow a silicon carbide crystal on the seed crystal 200.

[0028] It can be understood that, by using the segmented crystal growth device 1 provided by the embodiment, the polycrystal crystal can be deposited on the porous graphite plate in advance during the crystal growth process, and then the second heater 700 is started to heat and sublimate the polycrystal crystal, thereby growing the silicon carbide crystal on the seed crystal 200.

[0029] During the deposition of the polycrystal crystal, the crystal growth raw material 2 sublimates at high temperature, and not all components are volatilized in proportion (Si is more volatile than C), so that the gas phase is rich in silicon in the early stage and rich in carbon in the later stage.

[0030] When the high-temperature gas flow rises to the first porous graphite plate 300, the gas phase reaches a supersaturated state and begins to condense and crystallize because the temperature in this area is relatively low (which can be controlled by the thermal field design). During this process: carbon elements are more likely to be deposited first: because the condensation temperature of carbon is higher than that of silicon-related species (such as Si2C, SiC2, etc.), and carbon clusters (C3, C2) have high stability in low-temperature areas. The porous structure of the first porous graphite plate 300 can provide a large number of heterogeneous nucleation sites. It can be understood that the lattice matching degree of graphite and silicon carbide is high, which is beneficial to crystallization, and the pore wall increases the gas-solid contact area, which promotes carbon adsorption.

[0031] Therefore, during this process, a large number of free carbon particles, carbon-rich clusters and impure carbon phases in the raw material are “locked” in the polycrystal deposition layer formed on the surface of the first porous graphite plate 300, achieving active enrichment and fixation of carbon impurities. Moreover, the formation of the polycrystal crystal on the first porous graphite plate 300 can effectively reduce the direct erosion of solid carbon particles to the surface of the seed crystal 200.

[0032] When the polycrystal crystal on the first porous graphite plate 300 reaches a certain thickness, the second heater 700 is started to sublimate the polycrystal crystal for secondary purification. The second heater 700 locally heats the area to a temperature higher than the deposition temperature of the seed crystal 200 but lower than the temperature of the raw material area. At this time, the polycrystal crystal on the first porous graphite plate 300 sublimates, but the non-stoichiometric phase (such as carbon-rich SiC 1-xThe carbon that is less volatile remains on the graphite plate, while the near-stoichiometric SiC or Si / C equilibrium gas phase preferentially sublimates upwards to the seed crystal 200, where silicon carbide crystals grow. Thus, the Si / C ratio in the gas phase sublimated to the seed crystal 200 is close to 1:1, significantly reducing carbon supersaturation and effectively minimizing the risk of carbon precipitation and encapsulation.

[0033] Please refer to Figures 3-4 As can be seen, the silicon carbide crystals grown using the segmented crystal growth apparatus provided in this embodiment exhibit significantly fewer impurities under strong light than some existing silicon carbide crystals under strong light.

[0034] Furthermore, carbon occupies silicon sites in SiC, forming acceptor levels (C0, C ...). si This contributes holes, leading to p-type self-doping. The structure in this embodiment can reduce the concentration of unintentionally doped carbon, improve the intrinsic purity of the crystal, and enhance the carrier concentration. Please refer to... Figures 5-6 It can be seen that the carrier concentration distribution of the silicon carbide crystal grown by the segmented crystal growth apparatus provided in this embodiment is significantly better than that of some existing silicon carbide crystals.

[0035] In detail, in this embodiment, a second porous graphite plate 400 is also installed inside the crucible 100. The second porous graphite plate 400 is located below the first porous graphite plate 300, and the porosity of the second porous graphite plate 400 is greater than that of the first porous graphite plate 300.

[0036] Understandably, by setting up the second porous graphite plate 400, large carbon impurities can be intercepted, preventing large impurities from contacting the first porous graphite plate 300. Furthermore, the second porous graphite plate 400 can also improve the uniformity of gas phase distribution.

[0037] Please refer to Figure 2 During the growth of silicon carbide crystals, the temperatures of the crystal growth raw material region 2, the second porous graphite plate 400, the first porous graphite plate 300, and the seed crystal 200 gradually decrease. In other words, the temperature at the seed crystal 200 is the lowest, so that silicon carbide crystals can be grown on the seed crystal 200.

[0038] In detail, in the embodiment, the porosity of the first porous graphite plate 300 is 10-30%, and the porosity of the second porous graphite plate 400 is 40-60%. It can be understood that the porosity of the first porous graphite plate 300 is 10-30%, which is convenient for the growth atmosphere after the sublimation of the crystal growth raw material 2 to form polycrystalline crystals on the first porous graphite plate 300. Moreover, the porosity of the second porous graphite plate 400 is 40-60%, which can intercept the large carbon particles while ensuring the passage of the sublimated gas phase and improving the uniformity of the gas phase distribution.

[0039] Optionally, in some embodiments, the first porous graphite plate 300 includes opposite first and second sides, the first side is relatively close to the seed crystal 200, that is, the first side is located on the upper side, and the porosity of the first porous graphite plate 300 gradually decreases along the thickness direction of the first porous graphite plate 300 and the direction close to the seed crystal 200. The adsorption rate of carbon particles can be improved.

[0040] Of course, the porosity of the first porous graphite plate 300 is not limited herein, and the porosity of the first porous graphite plate 300 can also be constant along the thickness direction of the first porous graphite plate 300.

[0041] In the embodiment, the distance between the second porous graphite plate 400 and the first porous graphite plate 300 in the axial direction is 30-40 mm. Thus, sufficient space is ensured for the airflow to be homogenized, the impact on the first porous graphite plate 300 is reduced, the distance is not too short to cause the particles to be carried to the upper first porous graphite plate 300 before being deposited, and the distance is not too long to cause vortexes that can cause the particles to be lifted again. Moreover, the two porous graphite plates are ensured to be in different temperature gradient regions. The second heater 700 is also provided with a space in the axial direction, so that the second heater 700 is arranged close to the first porous graphite plate 300.

[0042] Optionally, in some embodiments, the number of the first porous graphite plates 300 can be multiple and arranged at intervals in the axial direction, and the second heater 700 includes multiple heating modules, and the multiple heating modules are arranged one by one corresponding to the multiple first porous graphite plates 300.

[0043] It should be noted that the multiple in the embodiment can be understood as two or more. For example, when the number of the first porous graphite plates 300 is two, the first heater 600 can be heated to sublimate the crystal growth raw material 2, so as to deposit polycrystalline crystals on one of the first porous graphite plates 300 close to the crystal growth raw material 2, and then the heating module close to the area of the crystal growth raw material 2 on the first porous graphite plate 300 is heated, so that the polycrystalline crystals are sublimated, and the polycrystalline crystals are deposited on the first porous graphite plate 300 close to the seed crystal 200, so as to realize multi-stage deposition and further reduce the probability of the carbon particles flowing to the seed crystal 200.

[0044] In the embodiment, a flow guide cylinder 500 is further arranged in the crucible 100, the seed crystal 200 is located in the flow guide cylinder 500, the flow guide cylinder 500 is located above the first porous graphite plate 300 and coaxially arranged with the seed crystal 200, and it can be understood that, in this way, the gas phase can be relatively uniformly guided to the surface of the seed crystal 200, and the high-quality epitaxial growth is promoted.

[0045] The embodiment of the present application further provides a segmented crystal growth method, which is applied to the segmented crystal growth device 1 and comprises the following steps. The first porous graphite plate 300 is arranged in the crucible 100.

[0046] The first heater 600 is started to heat the crystal growth raw material 2 so that the crystal growth raw material 2 is sublimated and crystallized at the first porous graphite plate 300 to form a polycrystalline crystal body.

[0047] Then, the second heater 700 is started to heat the polycrystalline crystal body, so that the polycrystalline crystal body is sublimated, and a silicon carbide crystal is grown at the seed crystal 200 of the crucible 100.

[0048] It can be understood that, in the process of depositing the polycrystalline crystal body, when the high-temperature gas flow rises to the first porous graphite plate 300, the gas phase reaches a supersaturated state and begins to condense and crystallize due to the relatively low temperature in this area (which can be controlled by the thermal field design). In this process: carbon elements are more likely to be deposited preferentially: because the condensation temperature of carbon is higher than that of silicon-related species (such as Si2C, SiC2, etc.), and carbon clusters (C3, C2) have high stability in low-temperature areas. The porous structure of the first porous graphite plate 300 can provide a large number of heterogeneous nucleation sites. It can be understood that the graphite has high lattice matching degree with the silicon carbide, which is beneficial to crystallization, and the pore wall increases the gas-solid contact area, which promotes carbon adsorption. Therefore, in this process, a large number of free carbon particles, carbon-rich clusters and impure carbon phases in the raw material are “locked” in the polycrystalline deposition layer formed on the surface of the first porous graphite plate 300, realizing active enrichment and fixation of carbon impurities. And the polycrystalline crystal body formed on the first porous graphite plate 300 can effectively reduce the direct erosion of solid carbon particles to the surface of the seed crystal 200.

[0049] In detail, before the first porous graphite plate 300 is arranged in the crucible 100, a second porous graphite plate 400 is further arranged in the crucible 100. Therefore, after the first heater 600 is started, the sublimated gas phase will first pass through the second porous graphite plate 400, and part of the large-particle carbon particles will be adsorbed by the second porous graphite plate 400.

[0050] It should be noted that, after starting the first heater 600, the temperature of the position of the long crystal raw material 2 is 2299-2301℃, the temperature of the second porous graphite plate 400 is 2294-2296℃, and the temperature of the first porous graphite plate 300 is 2287-2289℃ in the step of heating the long crystal raw material 2 to sublimate the long crystal raw material 2 and crystallize the polycrystalline crystal at the first porous graphite plate 300.

[0051] Thus, the temperature of the first porous graphite plate 300 is relatively low to facilitate the deposition of the polycrystalline crystal on the first porous graphite plate 300.

[0052] In detail, the second heater 700 is started to heat the polycrystalline crystal to sublimate the polycrystalline crystal and grow the silicon carbide crystal at the seed crystal 200 of the crucible 100 in the step. The temperature of the position of the long crystal raw material 2 is 2365-2366℃, the temperature of the second porous graphite plate 400 is 2362-2364℃, the temperature of the first porous graphite plate 300 is 2349-2351℃, and the temperature of the seed crystal 200 is 2327-2329℃. Thus, the deposition of the silicon carbide crystal at the seed crystal 200 is facilitated.

[0053] In summary, the embodiment of the present application provides a segmented crystal growth device 1 and method. The segmented crystal growth method is applied to the segmented crystal growth device 1 to grow the silicon carbide crystal. The segmented crystal growth device 1 comprises a crucible 100, a polycrystalline deposition assembly, a first heater 600, and a second heater 700. The top of the crucible 100 is provided with a seed crystal 200, and the crucible 100 is filled with a long crystal raw material 2. The polycrystalline deposition assembly comprises a first porous graphite plate 300. The first heater 600 is used to heat the long crystal raw material 2 to deposit a polycrystalline crystal on the first porous graphite plate 300. The second heater 700 is used to heat the polycrystalline crystal deposited on the first porous graphite plate 300, sublimate the polycrystalline crystal, and grow the silicon carbide crystal on the seed crystal 200. The polycrystalline crystal can be deposited on the porous graphite plate in advance to actively enrich and fix the carbon impurities, which can effectively reduce the direct flushing of solid carbon particles to the surface of the seed crystal 200. After the deposition of the polycrystalline crystal is completed, the second heater 700 is started to heat and sublimate the polycrystalline crystal, and then grow the silicon carbide crystal on the seed crystal 200.

[0054] The above description is only a specific embodiment of the present application, but the protection scope of the present application is not limited thereto. Any changes or replacements within the technical range disclosed by the present application can be easily thought by those skilled in the art, which should be covered within the protection scope of the present application.

Claims

1. A segmented crystal growth apparatus, characterized in that, include: A crucible (100) is provided with a seed crystal (200) at the top and is filled with crystal growth material (2). A polycrystalline deposition assembly, the polycrystalline deposition assembly comprising a first porous graphite plate (300). A first heater (600) is used to heat the crystal growth material (2) to deposit polycrystalline crystals on the first porous graphite plate (300); A second heater (700) is used to heat the polycrystalline material to sublimate the polycrystalline material and grow silicon carbide crystals on the seed crystal (200).

2. The segmented crystal growth apparatus according to claim 1, characterized in that: The crucible (100) is also equipped with a second porous graphite plate (400), which is located below the first porous graphite plate (300). The porosity of the second porous graphite plate (400) is greater than that of the first porous graphite plate (300).

3. The segmented crystal growth apparatus according to claim 2, characterized in that: The porosity of the first porous graphite plate (300) is 10~30%, and the porosity of the second porous graphite plate (400) is 40~60%.

4. The segmented crystal growth apparatus according to claim 3, characterized in that: The first porous graphite plate (300) includes a first side and a second side opposite to each other. The first side is relatively close to the seed crystal (200). Along the thickness direction of the first porous graphite plate (300) and in the direction close to the seed crystal (200), the porosity of the first porous graphite plate (300) gradually decreases.

5. The segmented crystal growth apparatus according to claim 2, characterized in that: The axial distance between the second porous graphite plate (400) and the first porous graphite plate (300) is 30~40mm.

6. The segmented crystal growth apparatus according to claim 1, characterized in that: The number of the first porous graphite plates (300) is multiple and they are arranged at intervals along the axial direction of the crucible (100). The second heater (700) includes multiple heating modules, and the multiple heating modules are arranged in a one-to-one correspondence with the multiple first porous graphite plates (300).

7. The segmented crystal growth apparatus according to claim 1, characterized in that: The crucible (100) is also provided with a flow guide tube (500), the seed crystal (200) is located inside the flow guide tube (500), the flow guide tube (500) is located above the first porous graphite plate (300) and is coaxially arranged with the seed crystal (200).

8. A segmented crystal growth method, applied to the segmented crystal growth apparatus according to any one of claims 1-7, characterized in that, The method includes: Fill the crucible (100) with the crystal growth material (2); A first porous graphite plate (300) is provided inside the crucible (100); The first heater (600) is activated to heat the crystal growth material (2) so that the crystal growth material (2) sublimates and crystallizes at the first porous graphite plate (300) to form a polycrystalline body; The second heater (700) is activated to heat the polycrystalline material to sublimate it and grow silicon carbide crystals at the seed crystal (200) of the crucible (100).

9. The segmented crystal growth method according to claim 8, characterized in that, In the step of activating the first heater (600) to heat the crystal growth material (2) so that the crystal growth material (2) sublimates and crystallizes at the first porous graphite plate (300) to form a polycrystalline body: The temperature at the location of the crystal growth material (2) is set to 2299~2301℃, and the temperature of the first porous graphite plate (300) is set to 2287~2289℃.

10. The segmented crystal growth method according to claim 8, characterized in that, In the step of activating the second heater (700) to heat the polycrystalline material, causing the polycrystalline material to sublimate, and growing silicon carbide crystals at the seed crystal (200) of the crucible (100): The temperature at the location of the crystal growth material (2) is set to 2365~2366℃, the temperature of the first porous graphite plate (300) is set to 2349~2351℃, and the temperature at the location of the seed crystal (200) is set to 2327~2329℃.

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