Thermal field device for growing silicon carbide crystals

Abstract

The invention discloses a thermal field device for growing silicon carbide crystals, and the thermal field device comprises a heating body, the heating body comprises a seed crystal fixing part, a guide cylinder and a convexity adjusting part, the guide cylinder and the convexity adjusting part are arranged on the lower side of the seed crystal fixing part, and the convexity adjusting part is arranged on the outer side of the guide cylinder; a silicon carbide seed crystal is arranged on one side, facing the silicon carbide crystal growth area, of the seed crystal fixing piece; the guide cylinders comprise a first guide cylinder and a second guide cylinder, the first guide cylinder is a straight cylinder, and the second guide cylinder is a conical cylinder which is obliquely expanded downwards; the convexity adjusting piece comprises a first convexity adjusting piece and a second convexity adjusting piece, the first convexity adjusting piece is a straight barrel, and the second convexity adjusting piece is a conical barrel which shrinks downwards. Through the design of the thermal field device, the growth facet of the silicon carbide crystal can be effectively removed, so that the risk of dislocation aggregation in the silicon carbide crystal can be effectively reduced, and the quality of the silicon carbide crystal is improved.

Description

Technical Field

[0001] This application belongs to the field of solution-based silicon carbide single crystal growth technology, specifically relating to a thermal field device for growing silicon carbide crystals. Background Technology

[0002] Various defects are generated during the growth of silicon carbide single crystals, including polymorphic defects, micropipes, dislocations, stacking faults, voids, and inclusions. Dislocations are point defects, mainly including screw dislocations (TSDs), basal plane dislocations (BPDs), edge dislocations (TEDs), and mixed dislocations (TMDs). Most dislocations have strong heritability, leading to a continuous decrease in crystal quality during iterative growth, ultimately failing to meet the requirements of epitaxial growth. Therefore, reducing dislocation defects in crystals has become an important research task.

[0003] According to the growth mechanism of silicon carbide crystals, most dislocation defects occur in the initial growth region of the crystal (i.e., the "growth facets"). This is mainly because the step width in the facet region is larger than that in the non-facet region, making it easier for nitrogen atoms to combine and form doped structures. Excessive nitrogen atoms occupying carbon atom positions leads to vacancies in the atomic arrangement, ultimately causing defects to accumulate in this region. Silicon carbide crystals without growth facets not only exhibit significantly improved doping uniformity but also have lower dislocation density and higher quality compared to silicon carbide crystals with growth facets.

[0004] Therefore, further improvements are needed to the existing thermal field devices for growing silicon carbide crystals. Summary of the Invention

[0005] This application aims to at least partially address one of the technical problems in related technologies. Therefore, the purpose of this application is to provide a thermal field device for growing silicon carbide crystals. Through the design of the thermal field device, this application can effectively remove the growth facets of silicon carbide crystals, thereby effectively reducing the risk of dislocation aggregation in the silicon carbide crystals and improving the quality of the silicon carbide crystals.

[0006] In one aspect of this application, a thermal field apparatus for growing silicon carbide crystals is provided. According to an embodiment of this application, the thermal field apparatus for growing silicon carbide crystals includes: A heating element includes a seed crystal fixing component, a flow guide tube, and a convexity adjusting component. The flow guide tube and the convexity adjusting component are disposed on the lower side of the seed crystal fixing component, and the convexity adjusting component is disposed on the outer side of the flow guide tube. The seed crystal fixing component and the flow guide tube together define a silicon carbide crystal growth area. A silicon carbide seed crystal is disposed on the side of the seed crystal fixing component facing the silicon carbide crystal growth area, and the flow guide tube is located on the outer edge of the silicon carbide seed crystal. The flow guide includes a first flow guide and a second flow guide, which are arranged in an annular shape. The first flow guide is a straight cylinder, and the second flow guide is a downwardly expanding conical cylinder. The convexity adjusting component includes a first convexity adjusting component and a second convexity adjusting component, which are arranged in an annular shape. The first convexity adjusting component is located outside the first flow guide, and the second convexity adjusting component is located outside the second flow guide. The first convexity adjusting component is a straight cylinder, and the second convexity adjusting component is a downwardly contracting conical cylinder.

[0007] The thermal field apparatus for growing silicon carbide crystals according to embodiments of this application effectively removes facets from the silicon carbide crystal through its design, thereby reducing the risk of dislocation aggregation and improving the quality of the silicon carbide crystal. The facetless silicon carbide crystal obtained using the thermal field apparatus of this application exhibits good resistivity uniformity, which is beneficial for downstream epitaxial process control and lays a solid foundation for the fabrication of high-quality silicon carbide devices.

[0008] In addition, the thermal field apparatus for growing silicon carbide crystals according to the above embodiments of this application may also have the following additional technical features: In some embodiments of this application, the second guide tube includes a first equal-diameter portion and an expanded-diameter portion, and the first equal-diameter portion is disposed near the seed crystal fixing member; and / or, the second convexity adjusting member includes a second equal-diameter portion and a reduced-diameter portion, and the second equal-diameter portion is disposed near the seed crystal fixing member.

[0009] In some embodiments of this application, the height of the first equal-diameter portion is 0.5mm~1mm, and the height of the expanded-diameter portion is 15mm~30mm; and / or, the difference between the maximum and minimum diameters of the expanded-diameter portion is 5mm~10mm; and / or, the height of the second equal-diameter portion is equal to the height of the first equal-diameter portion, and the height of the reduced-diameter portion is equal to the height of the expanded-diameter portion; and / or, the difference between the maximum and minimum diameters of the reduced-diameter portion is 3mm~8mm; and / or, the horizontal distance between the first guide tube and the silicon carbide seed crystal is 1mm~5mm; and / or, the horizontal distance between the second guide tube and the silicon carbide seed crystal is 1mm~5mm.

[0010] In some embodiments of this application, the expanded diameter portion has a plurality of first air channels that penetrate the second guide tube in a vertical direction distributed on the expanded diameter wall; the seed crystal fixing member has a plurality of second air channels that penetrate the seed crystal fixing member in a vertical direction distributed on the side near the second guide tube, and the first air channels and the second air channels are connected in a vertical direction.

[0011] In some embodiments of the present application, the inner diameter of the first air duct is 2 mm to 5 mm; and / or, the inner diameter of the second air duct is 2 mm to 5 mm.

[0012] In some embodiments of the present application, the heating element further includes an inclined graphite member, the inclined graphite member is disposed on a side of the seed crystal fixing member away from the silicon carbide seed crystal, and along the horizontal direction from the first flow guiding cylinder to the second flow guiding cylinder, the thickness of the inclined graphite member decreases in sequence, and the inclined graphite member does not block the second air duct.

[0013] In some embodiments of the present application, the maximum thickness of the inclined graphite member is h1, and the minimum thickness is h2, satisfying: 0 mm < h2 ≤ 1, 1 mm ≤ h1 ≤ 6 mm, 1 mm ≤ h2 - h1 ≤ 5 mm.

[0014] In some embodiments of the present application, the heating element further includes a filter member, an inner crucible, a porous graphite barrel, and an outer crucible. The filter member is disposed on the lower side of the flow guiding cylinder and on the upper side of the inner crucible. The porous graphite barrel is disposed inside the inner crucible, and the outer crucible is disposed outside the inner crucible; along the horizontal direction, one side of the porous graphite barrel close to the first flow guiding cylinder is in contact with the inner wall of the inner crucible, and a sandwich region is formed between one side of the porous graphite barrel away from the first flow guiding cylinder and the inner crucible. The porous graphite barrel is used for placing the first silicon carbide powder material, and the sandwich region is used for placing the second silicon carbide powder material. The loading height of the first silicon carbide powder material is lower than the loading height of the second silicon carbide powder material.

[0015] In some embodiments of the present application, the inner diameter difference between the inner crucible and the porous graphite barrel is 5 mm to 10 mm; and / or, the width of the sandwich region is equal to the difference between the maximum diameter and the minimum diameter of the diameter-expanded portion; and / or, the difference between the loading height of the second silicon carbide powder material and the loading height of the first silicon carbide powder material is 5 mm to 15 mm; and / or, a first crystal form stabilizer barrel is disposed at the bottom of the inner crucible, and a plurality of second crystal form stabilizer barrels are disposed in the sandwich region. The plurality of second crystal form stabilizer barrels are uniformly distributed in the vertical direction, and the number of the second crystal form stabilizer barrels is greater than the number of the first crystal form stabilizer barrels.

[0016] In some embodiments of this application, the thermal field device further includes a heat insulation body, which includes an upper heat insulation felt, a side heat insulation felt, and a lower heat insulation felt. The upper heat insulation felt is disposed on the upper part of the thermal field device, the side heat insulation felt is disposed on the outer side of the thermal field device, and the lower heat insulation felt is disposed on the bottom of the thermal field device. The inner diameter of the upper heat insulation felt is a stepped structure that is wider at the top and narrower at the bottom, and the wide inner diameter of the upper heat insulation felt is consistent with the outer diameter of the guide tube, and the narrow inner diameter of the upper heat insulation felt is equal to the maximum inner diameter of the guide tube. And / or, the silicon carbide seed crystal is a seed crystal with growth facets, and the region with growth facets is close to the side where the second guide tube is located.

[0017] Additional aspects and advantages of this application will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of this application. Attached Figure Description

[0018] The above and / or additional aspects and advantages of this application will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, in which: Figure 1 This is a schematic diagram of the thermal field device for growing silicon carbide crystals according to an embodiment of this application; Figure 2 This is a schematic diagram of a silicon carbide seed crystal according to an embodiment of this application; Figure 3 This is a schematic diagram of the structure of the graphite component according to an embodiment of this application; Figure 4 This is a top view of the assembly of the flow guide tube and the seed crystal according to an embodiment of this application; Figure 5 This is a schematic diagram of the convexity adjustment component according to an embodiment of this application; Figure 6 A top view of the assembly of the inner crucible and porous graphite barrel according to an embodiment of this application; Figure 7 This is a resistivity mapping diagram of silicon carbide substrate A in Embodiment 1 of this application; Figure 8 This is a dislocation data diagram of silicon carbide substrate A in Embodiment 1 of this application.

[0019] Figure label: 1-Silicon carbide seed crystal, 1-1-Non-small facet region, 1-2-Small facet region, 1-2-1-Growth small facet, 2-Convexity adjustment component, 2-1-First convexity adjustment component, 2-2-Second convexity adjustment component, 3-Guide cylinder, 3-1-First guide cylinder, 3-2-Second guide cylinder, 3-2-1-First air passage, 4-Filter component, 5-Inner crucible, 6-Upper insulation felt, 7-Graphite component, 8-Seed crystal fixing component, 9-Side insulation felt, 10-Second crystal stabilizer container, 11-Outer crucible, 12-Porous graphite container, 13-Lower insulation felt, 14-First crystal stabilizer container, 15-First silicon carbide powder, 16-Second silicon carbide powder. Detailed Implementation

[0020] The embodiments of this application are described in detail below. Examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain this application, and should not be construed as limiting this application.

[0021] In the description of this application, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "axial", "radial", "circumferential", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the elements referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application.

[0022] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this application, "multiple" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0023] In this application, unless otherwise expressly specified and limited, terms such as "installation," "connection," "joining," and "fixing" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components, unless otherwise expressly limited. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0024] In this application, unless otherwise expressly specified and limited, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature is in indirect contact with the second feature through an intermediate medium. Furthermore, "above," "on top of," and "over" the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0025] In one aspect of this application, a thermal field apparatus for growing silicon carbide crystals is provided. According to an embodiment of this application, refer to the accompanying drawings. Figure 1 ~Appendix Figure 6 The aforementioned thermal field device for growing silicon carbide crystals includes: a heating element (e.g., some graphite components inside the thermal field device), the heating element including a seed crystal fixing component 8 (e.g., a graphite cover), a flow guide tube 3, and a convexity adjustment component 2. The flow guide tube 3 and the convexity adjustment component 2 are disposed on the lower side of the seed crystal fixing component 8, and the convexity adjustment component 2 is disposed on the outer side of the flow guide tube 3; the seed crystal fixing component 8 and the flow guide tube 3 together define a silicon carbide crystal growth area, a silicon carbide seed crystal 1 is disposed on the side of the seed crystal fixing component 8 facing the silicon carbide crystal growth area, and the flow guide tube 3 is located on the outer edge of the silicon carbide seed crystal 1; wherein, the flow guide tube 3 includes a first flow guide tube 3-1 and a second flow guide tube 3-2, the first The first guide tube 3-1 and the second guide tube 3-2 form an annular ring. The first guide tube 3-1 is a straight tube (e.g., a semi-circular straight tube), and the second guide tube 3-2 is a downwardly expanding conical tube. The convexity adjusting member 2 includes a first convexity adjusting member 2-1 and a second convexity adjusting member 2-2, which form an annular ring. The first convexity adjusting member 2-1 is located outside the first guide tube 3-1, and the second convexity adjusting member 2-2 is located outside the second guide tube 3-2. The first convexity adjusting member 2-1 is a straight tube (e.g., a semi-circular straight tube), and the second convexity adjusting member 2-2 is a downwardly contracting conical tube. Therefore, this application, through the design of the thermal field device, can effectively remove the growth facets of silicon carbide crystals, thereby effectively reducing the risk of dislocation aggregation in silicon carbide crystals and improving the quality of silicon carbide crystals. The silicon carbide crystal without facets obtained using the thermal field device of this application has good resistivity uniformity, which is beneficial to the process control of downstream epitaxial ends and lays a solid foundation for the preparation of high-quality silicon carbide devices.

[0026] The following is a detailed description of the beneficial effects that the thermal field device for growing silicon carbide crystals proposed in this application can achieve: This application utilizes a downwardly expanding second guide tube 3-2 to radially increase the diameter of the silicon carbide crystal, pushing the growth facets of the silicon carbide crystal to the edge region until they disappear. Simultaneously, a downwardly contracting second convexity adjustment member 2-2 can be used to regulate the temperature at the edge of the silicon carbide crystal, thereby effectively controlling the growth at the crystal edge and ultimately achieving the goal of adjusting the crystal convexity. Furthermore, the contracted portion of the second convexity adjustment member 2-2 corresponds to the expansion portion of the silicon carbide crystal. This design aims to gradually increase the thickness of the second convexity adjustment member 2-2, improving the heating efficiency of its contracted portion, effectively increasing the crystal growth temperature in the expansion region of the silicon carbide crystal, thus facilitating a higher crystal growth rate in this region. Therefore, this application, through the design of the thermal field device, can effectively remove the growth facets of the silicon carbide crystal, thereby effectively reducing the risk of dislocation aggregation in the silicon carbide crystal and improving its quality. The silicon carbide crystal without facets obtained using the thermal field device of this application exhibits good resistivity uniformity, which is beneficial for downstream epitaxial process control and lays a solid foundation for the fabrication of high-quality silicon carbide devices. It should be noted that defects in silicon carbide substrates generally occur in the transition region between facets and non-facets, as well as in the facet region itself. This application, by removing facets from the silicon carbide crystal, effectively removes these defects as well, thus improving the quality of the silicon carbide crystal.

[0027] Understandably, during the oblique expansion growth process of silicon carbide crystals, the facets grow towards the edges. The growth of silicon carbide crystals in the edge region is slower during this process, while the growth in the central region is relatively faster. This leads to excessive crystal convexity, causing an imbalance between central and edge growth and resulting in crystal defects. The second convexity adjustment component 2-2 can increase the edge temperature and thus improve the edge growth rate, effectively regulating the uniformity of the growth rate and improving the product quality of the silicon carbide crystals.

[0028] It should be noted that the appendix Figure 1 The X direction marked in the diagram is the horizontal direction of the thermal field device, and the Y direction is the vertical direction of the thermal field device.

[0029] Specifically, the silicon carbide crystal without facets obtained using the thermal field device of this application has a resistivity uniformity of 0.5%~2% and a total dislocation density of 1000 ea / cm. 2 Within.

[0030] According to some specific embodiments of this application, refer to the appendix. Figure 2The aforementioned silicon carbide seed crystal 1 is a seed crystal with a growth facet 1-2-1, and the region with the growth facet 1-2-1 is close to the side where the second guide cylinder 3-2 is located. The aforementioned silicon carbide seed crystal includes a facet region 1-2 and a non-facet region 1-1, with the growth facet 1-2-1 located in the facet region 1-2. The second guide cylinder 3-2 and the second convexity adjustment component 2-2 correspond to the facet region 1-2 of the silicon carbide seed crystal.

[0031] According to further specific embodiments of this application, refer to the appendix. Figure 1 The aforementioned second guide tube 3-2 includes a first equal diameter section (straight tube design) and an expanded diameter section (conical design). The first equal diameter section is located near the seed crystal fixing member 8. The expanded diameter section can effectively radially expand the diameter of the silicon carbide crystal, driving the growth facet of the silicon carbide crystal to the edge region of the silicon carbide crystal until it disappears, thereby improving the quality of the silicon carbide crystal.

[0032] According to some further specific embodiments of this application, refer to the appendix. Figure 1 and attached Figure 5 The aforementioned second convexity adjustment member 2-2 includes a second equal diameter portion and a reduced diameter portion. The second equal diameter portion is located near the seed crystal fixing member 8, and the reduced diameter portion corresponds to the diameter expansion growth portion of the silicon carbide crystal. The purpose of this design is to improve the heating efficiency of its reduced diameter portion by gradually increasing the thickness of the second convexity adjustment member 2-2, which can effectively increase the crystal growth temperature of the diameter expansion growth region of the silicon carbide crystal, thereby helping to improve the crystal growth rate in this region.

[0033] According to some specific embodiments of this application, the height of the first equal-diameter portion is slightly greater than the thickness of the silicon carbide seed crystal. The height of the first equal-diameter portion is specifically 0.5mm to 1mm (e.g., 0.5mm, 0.6mm, 0.7mm, 0.8mm, 0.9mm, 1mm, etc.), and the height of the diameter-expanding portion is 15mm to 30mm (e.g., 15mm, 16mm, 18mm, 20mm, 22mm, 24mm, 26mm, 28mm, 30mm, etc.), preferably 15mm to 25mm. This further ensures the radial expansion of the silicon carbide crystal diameter, pushing the growth facets of the silicon carbide crystal to the edge region of the silicon carbide crystal until they disappear, thereby further improving the quality of the silicon carbide crystal.

[0034] According to some specific embodiments of this application, the difference between the maximum diameter and the minimum diameter of the expanded portion is 5mm to 10mm (for example, it can be 5mm, 6mm, 7mm, 8mm, 9mm, 10mm, etc.), preferably 6mm to 8mm. This ensures effective expansion of the silicon carbide crystal while preventing imbalance of axial and radial temperature gradients that could lead to crystal phase transformation.

[0035] According to some specific embodiments of this application, the height of the second equal diameter portion is equal to the height of the first equal diameter portion, and the height of the reduced diameter portion is equal to the height of the expanded diameter portion, which can further ensure the effective expansion of the silicon carbide crystal, thereby further improving the quality of the silicon carbide crystal.

[0036] According to some specific embodiments of this application, the diameter of the second equal diameter portion of the second convexity adjustment member 2-2 is greater than the diameter of the reduced diameter portion, and the difference between the maximum diameter and the minimum diameter of the reduced diameter portion is 3mm to 8mm (for example, it can be 3mm, 4mm, 5mm, 6mm, 7mm, 8mm, etc.), preferably 4mm to 6mm. This can effectively prevent the difference in heating efficiency from being too large, thus preventing crystal polymorphism.

[0037] According to some specific embodiments of this application, the horizontal distance between the first guide tube 3-1 and the silicon carbide seed crystal is 1mm to 5mm (e.g., 1mm, 2mm, 3mm, 4mm, 5mm, etc.), preferably 1mm to 3mm; and / or, the horizontal distance between the second guide tube 3-2 and the silicon carbide seed crystal is 1mm to 5mm (e.g., 1mm, 2mm, 3mm, 4mm, 5mm, etc.), preferably 1mm to 3mm. Therefore, this design can effectively suppress the growth of edge polycrystalline material. As some specific embodiments, the horizontal distance between the first guide tube 3-1 and the silicon carbide seed crystal is equal to the horizontal distance between the second guide tube 3 and the silicon carbide seed crystal.

[0038] According to some further specific embodiments of this application, refer to the appendix. Figure 4 The expansion wall of the aforementioned diameter-expanding section has multiple first air channels 3-2-1 that penetrate the second guide tube 3-2 vertically. The seed crystal fixing member 8 has multiple second air channels that penetrate the seed crystal fixing member 8 vertically on the side near the second guide tube 3-2, and the first air channels 3-2-1 and second air channels are connected vertically. Thus, the first air channels 3-2-1 and second air channels can effectively discharge the supersaturated gas generated in the crystal growth region, preventing polycrystalline growth at the crystal edge. Simultaneously, the first air channels 3-2-1 are only provided on the expansion wall of the diameter-expanding section, and the second air channels are only provided on the side of the seed crystal fixing member 8 near the second guide tube 3-2. The purpose is to guide the crystal growth nucleation region outwards during crystal growth, thereby "driving" the small faces away from the crystal edge, thus further improving the quality of the silicon carbide crystal. In some specific embodiments, the number of second air channels is generally ≥2, and they are evenly distributed in this area. In some specific embodiments, the first air passage and the second air passage correspond one-to-one and are assembled to form an exhaust channel.

[0039] According to some further specific embodiments of the present application, the inner diameter of the first air duct is 2 mm to 5 mm (for example, it can be 2 mm, 3 mm, 4 mm, 5 mm, etc.), preferably 2 mm to 4 mm; and / or, the inner diameter of the second air duct is 2 mm to 5 mm (for example, it can be 2 mm, 3 mm, 4 mm, 5 mm, etc.), preferably 2 mm to 4 mm. Thus, it can be further ensured that the supersaturated gas generated in the crystal growth region is discharged, preventing polycrystal growth at the crystal edge. As some specific embodiments, the inner diameters of the first air duct and the second air duct are equal.

[0040] According to some further specific embodiments of the present application, referring to the attached Figure 1 and the attached Figure 3 , the heating element further includes an inclined graphite member 7 (for example, an inclined graphite plate), and the inclined graphite member 7 is arranged on the side of the seed crystal fixing member 8 away from the silicon carbide seed crystal. Along the horizontal direction from the first guide cylinder 3-1 to the second guide cylinder 3-2, the thickness of the inclined graphite member 7 gradually decreases, and the inclined graphite member 7 does not block the second air duct. That is, the thin side of the inclined graphite member 7 corresponds to the diameter-expanded region, and the other side is the thick side. As graphite, the inclined graphite member 7 will generate heat by itself during heating, making the temperature at the position of the thick plate high and the temperature at the position of the thin plate relatively low. Thus, the diameter-expanded part corresponding to the thin plate has a larger axial temperature gradient, and there is also a temperature difference between the seed crystal and the diameter-expanded region in the radial direction, which is beneficial to the growth of the diameter-expanded part, and thus drives the growth facet of the silicon carbide crystal to the edge region of the silicon carbide crystal.

[0041] According to some further specific embodiments of the present application, the highest thickness of the inclined graphite member 7 is h1, and the lowest thickness is h2, satisfying: 0 mm < h2 ≤ 1, 1 mm ≤ h1 ≤ 6 mm, 1 mm ≤ h2 - h1 ≤ 5 mm. Thus, it can be further ensured that the diameter-expanded part corresponding to the thin plate has a larger axial temperature gradient, and there is also a temperature difference between the seed crystal and the diameter-expanded region in the radial direction, which is further beneficial to the growth of the diameter-expanded part, and thus drives the growth facet of the silicon carbide crystal to the edge region of the silicon carbide crystal.

[0042] According to some further specific embodiments of the present application, referring to the attached Figure 1 and the attached Figure 6The aforementioned heating element also includes a filter element 4 (e.g., a filter plate), an inner crucible 5, a porous graphite barrel 12, and an outer crucible 11. The filter element 4 is disposed below the flow guide cylinder 3 and above the inner crucible 5. The porous graphite barrel 12 is disposed inside the inner crucible 5, and the outer crucible 11 is disposed outside the inner crucible 5. Horizontally, the side of the porous graphite barrel 12 closest to the first flow guide cylinder 3-1 is fitted against the inner wall of the inner crucible 5, and the side of the porous graphite barrel 12 furthest from the first flow guide cylinder 3-1 forms an interlayer region with the inner crucible 5. The porous graphite barrel 12 is used to hold the first silicon carbide powder 15, and the interlayer region is used to hold the second silicon carbide powder 16. The loading height of the first silicon carbide powder 15 is lower than the loading height of the second silicon carbide powder 16. The first silicon carbide powder 15 mainly provides raw materials for the growth of the seed crystal region, and the second silicon carbide powder 16 mainly provides raw materials for the growth of the diameter expansion section. The loading height of the first silicon carbide powder 15 is lower than that of the second silicon carbide powder 16. Its main purpose is to provide sufficient raw materials for the growth of the crystal in the diameter expansion section, and to prevent the growth of the crystal in the diameter expansion section from being inconsistent with the growth of the crystal in the seed crystal region, resulting in problems such as polymorphism and impurities.

[0043] In the embodiments of this application, the seed crystal fixing member 8, the guide tube 3 and the filter member 4 together define the crystal growth area, and the filter member 4, the inner crucible 5 and the porous graphite barrel 12 together define the raw material area.

[0044] As some specific embodiments of this application, the bottom of the outer crucible 11 is designed with a stepped shape to position the inner crucible 5, and the inner diameter of the outer crucible 11 is slightly smaller than the outer diameter of the guide tube 3.

[0045] As some specific embodiments of this application, the bottom of the inner crucible 5 is also designed with a groove for positioning the porous graphite barrel 12; the inner diameter of the porous graphite barrel 12 is similar to the diameter of the seed crystal, and is in a straight line with the edge of the seed crystal in the vertical direction; the inner diameter of the inner crucible 5 is consistent with the maximum outer diameter of the guide tube 3, and is in a straight line with the edge of the inner diameter of the guide tube 3 in the vertical direction.

[0046] As some specific embodiments of this application, the filter element 4 (e.g., a filter plate) rests on top of the porous graphite barrel 12, and its edge is precisely caught on the inner side of the inner crucible 5 wall.

[0047] According to some specific embodiments of this application, the inner diameter difference between the inner crucible 5 and the porous graphite barrel 12 is 5mm to 10mm (for example, it can be 5mm, 6mm, 7mm, 8mm, 9mm, 10mm, etc.), preferably 6mm to 8mm. The inner diameter difference between the inner crucible 5 and the porous graphite barrel 12 (i.e., the width of the interlayer region) is consistent with the difference between the maximum and minimum diameters of the expanded diameter portion of the second guide tube 3-2, and this region corresponds exactly to the region of crystal expansion.

[0048] According to some specific embodiments of this application, the difference between the loading height of the second silicon carbide powder and the loading height of the first silicon carbide powder is 5mm to 15mm (for example, it can be 5mm, 6mm, 8mm, 10mm, 12mm, or 15mm), preferably 10mm to 15mm. This can further ensure that sufficient raw materials are provided for the growth of the crystal in the diameter-expanding part, and prevent the growth of the crystal in the diameter-expanding part from being inconsistent with the growth of the crystal in the seed crystal region, resulting in problems such as polymorphism and impurities.

[0049] According to some further specific embodiments of this application, refer to the appendix. Figure 1 A first crystal stabilizer container 14 is provided at the bottom of the inner crucible 5, and multiple second crystal stabilizer containers 10 are provided in the interlayer region (corresponding to the diameter expansion region). These second crystal stabilizer containers 10 are evenly distributed vertically, and the number of second crystal stabilizer containers 10 is greater than the number of first crystal stabilizer containers 14. Both the first crystal stabilizer containers 14 and the second crystal stabilizer containers 10 are used to contain crystal stabilizers. The main function of the crystal stabilizer is to ensure the normal growth of silicon carbide crystals and avoid problems such as polymorphism and impurities. Increasing the distribution of crystal stabilizers in the silicon carbide powder corresponding to the diameter expansion region aims to prevent polymorphism and phase transition problems during crystal growth in the diameter expansion region. It should be noted that the phase transition probability of crystals in the diameter expansion region is generally higher than that in the constant diameter region.

[0050] As some specific examples, the crystal stabilizer is a cerium compound, typically cerium silicide or cerium oxide, with a purity ≥99.99%.

[0051] In some specific embodiments, a first crystal stabilizer container containing a crystal stabilizer can be set at the bottom center of the inner crucible 5, and the number of second crystal stabilizer containers in the interlayer region (corresponding to the diameter expansion region) is greater than or equal to 2, and they are evenly distributed in the vertical direction.

[0052] According to some specific embodiments of this application, the total loading mass of crystal stabilizer in all crystal stabilizer containers is 0.05%-0.2% of the total mass of all silicon carbide powder, for example, it can be 0.05%, 0.08%, 0.1%, 0.12%, 0.15%, 0.18%, 0.2%, etc. Further, the total loading mass of crystal stabilizer in the second silicon carbide powder is 0.1%-0.2% of the total mass of the second silicon carbide powder, for example, it can be 0.1%, 0.12%, 0.14%, 0.16%, 0.18%, 0.2%, etc., increasing the amount of crystal stabilizer per unit area in the expanded diameter region of the powder, with the aim of preventing polymorphism, phase transition, and other problems in the expanded diameter region.

[0053] In the embodiments of this application, the raw materials used in the crystal growth process include silicon carbide seed crystals, silicon carbide powder, and a crystal form stabilizer. The silicon carbide seed crystal is located in the crystal growth region and is fixed to the side of the seed crystal fixing component 8 (e.g., a graphite cap) facing the crystal growth region by adhesive bonding. The filling of the silicon carbide powder is divided into two parts: the first silicon carbide powder is located inside the porous graphite barrel 12, and the second silicon carbide powder is located in the interlayer region formed by the porous graphite barrel 12 and the inner crucible 5. The crystal form stabilizer is loaded in a small barrel, which is buried inside the first and second silicon carbide powders.

[0054] According to some further specific embodiments of this application, refer to the appendix. Figure 1 The aforementioned thermal field device also includes an insulation body, comprising an upper insulation felt 6, side insulation felts 9, and a lower insulation felt 13. The upper insulation felt 6 is positioned at the top of the thermal field device, the side insulation felts 9 are positioned on the outer side of the thermal field device, and the lower insulation felt 13 is positioned at the bottom of the thermal field device. The outer diameter of the upper insulation felt 6 is the same as the outer diameter of the graphite cap, and the inner diameter of the upper insulation felt 6 has a stepped structure that is wider at the top and narrower at the bottom. The wider inner diameter of the upper insulation felt 6 is the same as the outer diameter of the guide tube 3 and they are aligned vertically. The narrower inner diameter of the upper insulation felt 6 is equal to the maximum inner diameter of the guide tube 3. The upper insulation felt 6, side insulation felts 9, and lower insulation felt 13 work together to wrap around the heating element, preventing the heat field from dissipating and achieving a good insulation effect. The stepped structure of the upper insulation felt 6, which is wider at the top and narrower at the bottom, is mainly designed to create a suitable radial temperature gradient, allowing the crystal to effectively expand its diameter and pushing the small facets of the crystal to the edge region of the crystal.

[0055] The embodiments of this application are described in detail below. It should be noted that the embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application. In addition, unless otherwise specified, all reagents used in the following embodiments are commercially available or can be synthesized according to the methods described herein or known methods. For reaction conditions not listed, they are also readily available to those skilled in the art.

[0056] Example 1 This embodiment provides a thermal field device for growing facetless silicon carbide crystals, see attached figure. Figure 1The thermal field mainly consists of an insulation body and a heating element. The insulation body refers to insulation felt, which includes an upper insulation felt, side insulation felt, and a lower insulation felt. These three insulation felts work together to wrap around the heating element, preventing heat dissipation and providing good insulation. The heating element refers to a series of graphite components inside the thermal field, which, from top to bottom, mainly include an inclined graphite plate, a graphite cover, a flow guide tube, a convexity adjustment component, a filter plate, an outer crucible, an inner crucible, a small bucket, and a porous graphite bucket. The flow guide tube and the convexity adjustment component are located below the graphite cover, with the convexity adjustment component located outside the flow guide tube. The graphite cover, flow guide tube, and filter plate together define the crystal growth area, while the filter plate, inner crucible, and porous graphite bucket together define the raw material area. The seed crystal used in this invention is a seed crystal with growth facets. The seed crystal can be divided into facet regions and non-facet regions according to the location of the facets. The seed crystal is fixed to the center of the graphite cap by bonding. Three second air channels, each with a diameter of 3 mm, are evenly distributed in the graphite cap region corresponding to the facet regions of the seed crystal. The guide tube is located on the outer edge of the seed crystal. The design of the guide tube for the facet regions and non-facet regions is different. The first guide tube for the non-facet regions is a semi-circular straight tube. The second guide tube for the facet regions is different. The part of the second guide tube closer to the seed crystal is a straight tube, while the part farther away from the seed crystal is a tapered design that expands outwards. The gap between the first and second guide tubes and the seed crystal is the same, 3 mm. The height of the constant diameter section of the second guide tube is 0.7 mm, and the height of the expanded diameter section is 20 mm. The difference between the maximum and minimum diameter of the expanded diameter section of the second guide tube is 6 mm. The outer diameter of the upper insulation felt is the same as that of the graphite cap, while the inner diameter has a stepped design that is wider at the top and narrower at the bottom. Specifically, the wider inner diameter of the upper insulation felt matches the outer diameter of the guide tube and they are aligned vertically. The narrower inner diameter of the upper insulation felt matches the maximum diameter formed by the first and second guide tubes. The diameter of the oblique graphite plate is R1, which is larger than the diameter of the seed crystal but smaller than the distance between the second gas channel and the opposite side of the seed crystal. The maximum thickness of the oblique graphite plate is h1, and the minimum thickness is h2; h2 is 0.5 mm, and h1 is 3 mm. Convexity adjustment components are distributed within the interlayer formed by the outer crucible and the guide tubes. Similar to the guide tubes, the convexity adjustment components are also divided into a first convexity adjustment component and a second convexity adjustment component. The first convexity adjustment component is a semi-circular straight cylinder; the second convexity adjustment component is divided into a constant-diameter section and a reduced-diameter section. The height of the constant-diameter section is 0.7 mm, and the height of the reduced-diameter section is 20 mm; the difference between the maximum and minimum diameters of the reduced-diameter section is 5 mm.The bottom of the outer crucible has a stepped design to position the inner crucible, and the inner diameter of the outer crucible is slightly smaller than the outer diameter of the flow guide tube. The bottom of the inner crucible also has a groove design to position the porous graphite barrel. The inner diameter of the porous graphite barrel is similar to the diameter of the seed crystal and is vertically aligned with the edge of the seed crystal. The inner diameter of the inner crucible is the same as the maximum outer diameter of the flow guide tube and is vertically aligned with the edge of the inner diameter of the flow guide tube. The difference in inner diameter between the inner crucible and the porous graphite barrel is 6mm. The filter plate rests on top of the porous graphite barrel, and its edge fits precisely into the inner wall of the inner crucible. A porous graphite barrel is positioned inside the inner crucible, and an outer crucible is positioned outside the inner crucible. Horizontally, the side of the porous graphite barrel closest to the first guide tube is fitted against the inner wall of the inner crucible, while the side of the porous graphite barrel furthest from the first guide tube forms a sandwich zone with the inner crucible. The porous graphite barrel holds the first silicon carbide powder, and the sandwich zone holds the second silicon carbide powder. The loading height of the second silicon carbide powder is greater than that of the first silicon carbide powder, with a height difference of 10 mm. The crystal stabilizer is cerium silicide with a purity of 99.99%. In this embodiment, the total silicon carbide powder loading is 4 kg, with 2.5 kg of the first silicon carbide powder and 1.5 kg of the second silicon carbide powder. The total mass of the crystal stabilizer in the small barrels is 4 g, with three small barrels containing the second silicon carbide powder, each containing a total of 3 g of crystal stabilizer.

[0057] The assembled thermal field device was placed in a crystal growth furnace for crystal growth at a temperature of 2200℃ and a pressure of 4 mbar for 150 hours. The resulting crystal, known as crystal A, was then processed by slicing, grinding, polishing, and cleaning to obtain a silicon carbide substrate.

[0058] The resistivity uniformity and dislocation data of the silicon carbide substrate were tested, and the results are as follows: Figure 7 and Figure 8 As shown. Figure 7 The resistivity mapping diagram of the silicon carbide substrate shows that its resistivity is 0.021-0.022 Ω·cm and its uniformity is 1.6%. Figure 8 This is a dislocation data diagram of a silicon carbide substrate, in which... Figure 8 In this context, 'a' represents the total dislocation density (EPD) of the silicon carbide substrate. Figure 8 In the diagram, 'b' represents the spiral dislocation density (TSD) plot of the silicon carbide substrate. Figure 8 In this context, 'c' represents the edge dislocation density (TED) of the silicon carbide substrate. Figure 8 In the diagram, 'd' represents the basal plane dislocation density (BPD) plot of the silicon carbide substrate. From... Figure 8 As can be seen from this, its spiral dislocation density (TSD) is 0 ea / cm. 2 The basal dislocation density (BPD) is 122 ea / cm. 2The edge dislocation density (TED) is 731 ea / cm. 2 The total dislocation density (EPD) is 854 ea / cm. 2 It can be seen that the dislocation data of crystal A is good and the resistivity is relatively uniform, indicating that its quality is good.

[0059] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0060] Although embodiments of this application have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting this application. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of this application.

Claims

1. A hot zone apparatus for growing silicon carbide crystals, comprising: The heating body comprises a seed crystal fixing member, a flow guide cylinder and a convexity adjusting member, the flow guide cylinder and the convexity adjusting member are arranged on the lower side of the seed crystal fixing member, and the convexity adjusting member is arranged on the outer side of the flow guide cylinder; the seed crystal fixing member and the flow guide cylinder jointly define a silicon carbide crystal growth zone, the seed crystal fixing member is provided with a silicon carbide seed crystal on the side facing the silicon carbide crystal growth zone, and the flow guide cylinder is located outside the edge of the silicon carbide seed crystal. The flow guide cylinder comprises a first flow guide cylinder and a second flow guide cylinder, the first flow guide cylinder and the second flow guide cylinder enclose an annular shape, the first flow guide cylinder is a straight cylinder, and the second flow guide cylinder is a downwardly inclined tapered cylinder; the convexity adjusting member comprises a first convexity adjusting member and a second convexity adjusting member, the first convexity adjusting member and the second convexity adjusting member enclose an annular shape, the first convexity adjusting member is arranged on the outer side of the first flow guide cylinder, the second convexity adjusting member is arranged on the outer side of the second flow guide cylinder, the first convexity adjusting member is a straight cylinder, and the second convexity adjusting member is a downwardly contracted tapered cylinder. The second flow guide cylinder comprises a first constant-diameter portion and a diameter-expanding portion, and the first constant-diameter portion is arranged close to the seed crystal fixing member; 2. The thermal field apparatus for growing silicon carbide crystals of claim 1 wherein, And / or, the second convexity adjusting member comprises a second constant-diameter portion and a diameter-contracting portion, and the second constant-diameter portion is arranged close to the seed crystal fixing member. The height of the first constant-diameter portion is 0.5mm-1mm, and the height of the diameter-expanding portion is 15mm-30mm; 3. The thermal field apparatus for growing silicon carbide crystals of claim 2 wherein, And / or, the maximum diameter and the minimum diameter of the diameter-expanding portion differ by 5mm-10mm; And / or, the height of the second constant-diameter portion is equal to the height of the first constant-diameter portion, and the height of the diameter-contracting portion is equal to the height of the diameter-expanding portion; And / or, the maximum diameter and the minimum diameter of the diameter-contracting portion differ by 3mm-8mm; And / or, the horizontal distance between the first flow guide cylinder and the silicon carbide seed crystal is 1mm-5mm; And / or, the horizontal distance between the second flow guide cylinder and the silicon carbide seed crystal is 1mm-5mm. A plurality of first air passages penetrating the second flow guide cylinder in the vertical direction are distributed on the diameter-expanding wall of the diameter-expanding portion; 4. The thermal field apparatus for growing silicon carbide crystals of claim 2 wherein, A plurality of second air passages penetrating the seed crystal fixing member in the vertical direction are distributed on the side of the seed crystal fixing member close to the second flow guide cylinder, and the first air passages and the second air passages are connected in the vertical direction. The inner diameter of the first air passage is 2mm-5mm; 5. The thermal field apparatus for growing silicon carbide crystals of claim 4 wherein, And / or, the inner diameter of the second air passage is 2mm-5mm. The heating body further comprises an inclined graphite member, the inclined graphite member is arranged on the side of the seed crystal fixing member away from the silicon carbide seed crystal, along the horizontal direction from the first flow guide cylinder to the second flow guide cylinder, the thickness of the inclined graphite member decreases in turn, and the inclined graphite member does not block the second air passage.

6. The thermal field apparatus for growing silicon carbide crystals of claim 4 wherein, The maximum thickness of the inclined graphite member is h1, the minimum thickness is h2, and 0mm<h2≤1, 1mm≤h1≤6mm, and 1mm≤h2-h1≤5mm.

7. The thermal field apparatus for growing silicon carbide crystals of claim 6 wherein, ​ 8. The thermal field assembly for growing a silicon carbide crystal according to any one of claims 2 to 7, wherein The heating body further comprises a filter, an inner crucible, a porous graphite barrel and an outer crucible, the filter is arranged on the lower side of the flow guide cylinder and on the upper side of the inner crucible, the porous graphite barrel is arranged on the inner side of the inner crucible, and the outer crucible is arranged on the outer side of the inner crucible; in the horizontal direction, one side of the porous graphite barrel close to the first flow guide cylinder is arranged in close contact with the inner wall of the inner crucible, and the other side of the porous graphite barrel away from the first flow guide cylinder forms a sandwich area with the inner crucible, the porous graphite barrel is used for placing first silicon carbide powder, and the sandwich area is used for placing second silicon carbide powder, and the filling height of the first silicon carbide powder is lower than that of the second silicon carbide powder.

9. The thermal field apparatus for growing silicon carbide crystals of claim 8 wherein, The difference between the inner diameters of the inner crucible and the porous graphite barrel is 5mm-10mm; And / or, the width of the sandwich area is equal to the difference between the maximum diameter and the minimum diameter of the expanded diameter part; And / or, the difference between the filling height of the second silicon carbide powder and the filling height of the first silicon carbide powder is 5mm-15mm; And / or, the bottom of the inner crucible is provided with a first crystal form stabilizer barrel, and the sandwich area is provided with a plurality of second crystal form stabilizer barrels, the plurality of second crystal form stabilizer barrels are uniformly distributed in the vertical direction, and the number of the second crystal form stabilizer barrels is greater than that of the first crystal form stabilizer barrels.

10. The thermal field assembly for growing a silicon carbide crystal according to any one of claims 1 to 7, wherein The thermal field device further comprises an insulation body, the insulation body comprises an upper insulation felt, a side insulation felt and a lower insulation felt, the upper insulation felt is arranged on the upper part of the thermal field device, the side insulation felt is arranged on the outer side of the thermal field device, and the lower insulation felt is arranged on the bottom of the thermal field device; The inner diameter of the upper insulation felt is a stepped structure with the upper part being wide and the lower part being narrow, the wide inner diameter of the upper insulation felt is consistent with the outer diameter of the flow guide cylinder, and the narrow inner diameter of the upper insulation felt is equal to the maximum inner diameter of the flow guide cylinder; And / or, the silicon carbide seed crystal is a seed crystal with growth facets, and the region with growth facets is close to the side where the second flow guide cylinder is located.

Images