Silicon carbide single crystal growth device and in-situ annealing method

Abstract

The present invention belongs to the technical field of silicon carbide crystal growth, and specifically relates to a silicon carbide single crystal growth device and in-situ annealing method. The device includes a crucible portion, which includes: a crucible body for accommodating raw materials; a cover body, the edge of which extends downward to be sealed with the upper part of the crucible body, the center of the lower surface of the cover body extends downward to form an extension portion, the lower surface of the extension portion is used to mount a seed crystal, and a first annular groove is formed between the side of the extension portion and the inner side of the cover body. The upper surface of the cover body has a circumferentially arranged recessed portion, and the bottom of the circumferentially arranged recessed portion and the side of the extension portion are arranged correspondingly in the vertical direction. When used for silicon carbide single crystal growth, it can promote stress release, reduce crystal defects, and improve crystal quality.

Description

Technical Field

[0001] The present invention belongs to the technical field of silicon carbide crystal growth, and in particular relates to a silicon carbide single crystal growth device and an in-situ annealing method. Background Art

[0002] Silicon carbide is a high-quality wide-bandgap semiconductor material with advantages such as wide bandgap, high breakdown electric field, high thermal conductivity, and high saturated electron drift rate. It can meet the needs of high-temperature, high-power, low-loss, and large-diameter devices.

[0003] Physical vapor transport (PVT) is currently the main method for industrially growing silicon carbide crystals. Specifically, in a vacuum and atmospheric environment, silicon carbide polycrystalline raw materials are placed in a closed cavity formed by a graphite crucible and a crucible cover. A silicon carbide seed crystal is bonded to the inner wall of the crucible cover. A heating body outside the graphite crucible heats the silicon carbide raw materials in the graphite crucible to sublime, and the sublimated gas grows on the silicon carbide seed crystal to obtain a silicon carbide single crystal.

[0004] After silicon carbide crystal growth is complete, in-situ annealing is typically performed to prevent structural instability caused by changes in the external environment. This process releases stress within the crystal, rearranges the internal structure, and helps reduce structural inhomogeneities such as lattice distortion, vacancies, and dislocations. However, existing techniques struggle to fully release stress, and even after in-situ annealing, numerous defects such as dislocations remain in the crystal.

[0005] It should be noted that this part of the present invention only provides background technology related to the present invention and does not necessarily constitute prior art or public known technology. Summary of the Invention

[0006] The purpose of the present invention is to overcome the problems in the prior art of growing silicon carbide single crystals, such as poor in-situ annealing effect of the crystal, difficulty in fully releasing stress, and the presence of many defects such as lattice distortion, vacancies and dislocations in the crystal. A silicon carbide single crystal growth device and an in-situ annealing method are provided, which can promote stress release, reduce crystal defects and improve crystal quality when used in silicon carbide single crystal growth.

[0007] In order to achieve the above-mentioned object, in a first aspect, the present invention provides a growth device for a silicon carbide single crystal, comprising a crucible portion; the crucible portion comprises:

[0008] Crucible body, used to contain raw materials;

[0009] A cover body, the edge of which extends downward to be sealed with the upper part of the crucible body, the center of the lower surface of the cover body extends downward to form an extension portion, the lower surface of the extension portion is used to mount the seed crystal, a first annular groove is formed between the side surface of the extension portion and the inner side surface of the cover body, the upper surface of the cover body has a circumferentially arranged recess, the bottom of the circumferentially arranged recess and the side surface of the extension portion are correspondingly arranged in the vertical direction.

[0010] In some preferred embodiments, two or more recesses are spaced apart along the circumferential direction to form the circumferentially arranged recess; or the circumferentially arranged recess is a second annular groove.

[0011] In some preferred embodiments, the depth D1 of the circumferentially arranged recess accounts for 1 / 3 to 1 / 2 of the distance between the bottom of the first annular groove and the upper surface of the cover.

[0012] In some preferred embodiments, the width W1 of the circumferentially arranged recess is 0.3 mm to 1.5 mm.

[0013] In some preferred embodiments, the ratio of the center diameter of the bottom of the circumferentially arranged recess to the diameter of the extension portion is 1.0-1.2.

[0014] In some preferred embodiments, the recessed portion arranged along the circumferential direction is inclined and has a top portion away from the extending portion and a bottom portion close to the extending portion.

[0015] Preferably, the inclination angle of the recessed portion arranged along the circumferential direction relative to the vertical direction is 2° to 8°.

[0016] In a second aspect, the present invention provides an in-situ annealing method for a silicon carbide single crystal using the growth device described in the first aspect, which sequentially includes: a high-temperature stress release stage, a pressure increase and temperature reduction stage, and a furnace cooling stage. The high-temperature stress release stage includes: introducing an inert gas into the furnace shell cavity to increase the pressure in the furnace shell cavity to 30,000 Pa~49,000 Pa, cooling the crucible part to 1800°C~2000°C, and then keeping it warm for 5h~10h.

[0017] In some preferred embodiments, during the high-temperature stress release stage, the conditions for introducing the inert gas include: a nitrogen flow rate of 0.15 L / h to 0.24 L / h, and an argon flow rate of 0.30 L / h to 0.44 L / h.

[0018] In some preferred embodiments, the pressure increasing and temperature decreasing stage includes: introducing an inert gas into the furnace shell cavity to increase the pressure in the furnace shell cavity to 50,000 Pa~70,000 Pa, cooling the crucible part to 800°C~900°C and then keeping it warm for 3h~5h.

[0019] During the growth of a silicon carbide single crystal, some sublimated gas reaches the edge of the seed crystal and condenses to form polycrystals, which typically wrap around the edge of the crystal. The inventors have discovered that during in-situ annealing of the crystal, the silicon carbide crystal and the edge polycrystals bond together. Due to their different thermal expansion coefficients, they constrain each other during annealing temperature changes. The polycrystals wrapped around the edge of the crystal affect the release of residual stress within the crystal and the reduction of structural defects in the crystal. In the silicon carbide single crystal growth apparatus of the present invention, the center of the lower surface of the cover extends downward to form an extension portion for mounting the seed crystal. The upper surface of the cover has a circumferentially arranged recess. During in-situ annealing, the cover is susceptible to cracking at the circumferentially arranged recess due to the stress within the crystal. Because the bottom of the circumferentially arranged recess and the side surfaces of the extension correspond in the vertical direction, cracking of the cover easily loosens or even causes the polycrystals wrapped around the edge of the crystal to fall off. This eliminates the effect of the edge polycrystals on stress release and structural rearrangement during the annealing process of the silicon carbide crystal. In-situ annealing can fully release stress, significantly reduce crystal defects, and improve crystal quality. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments. It should be understood that the following drawings only illustrate certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other relevant drawings can be obtained based on these drawings without paying any creative work.

[0021] Figure 1 It is a structural schematic diagram of a specific embodiment of the silicon carbide single crystal growth device of the present invention.

[0022] Figure 2 yes Figure 1 Schematic diagram of the structure of the middle cover body.

[0023] Figure 3 yes Figure 2 A partial enlarged view of part I in the middle.

[0024] Figure 4 It is a cross-sectional view of a specific embodiment of the cover of the present invention.

[0025] Figure 5 This is a dislocation density diagram of the silicon carbide single crystal after in-situ annealing in Example 1 of the present invention.

[0026] Figure 6 This is a dislocation density diagram of the silicon carbide single crystal after in-situ annealing in Example 5 of the present invention.

[0027] Figure 7This is a dislocation density diagram of the silicon carbide single crystal after in-situ annealing in Comparative Example 1 of the present invention.

[0028] Description of Reference Numerals

[0029] 1. Crucible body; 2. Cover; 201. Extension portion; 202. First annular groove; 203. Concave portion arranged along the circumferential direction. DETAILED DESCRIPTION

[0030] The endpoints of the ranges and any values disclosed herein are not limited to the precise ranges or values, and these ranges or values should be understood to include values close to these ranges or values. For numerical ranges, the endpoints of each range, the endpoints of each range and individual point values, and the individual point values can be combined with each other to obtain one or more new numerical ranges, which should be considered to be specifically disclosed herein.

[0031] In this document, unless otherwise specified, directional terms such as "upper" and "lower" are generally understood in conjunction with the directions shown in the drawings and actual applications, and "inside" and "outside" refer to the inside and outside of the outline of a component.

[0032] In the description of the present invention, it should be understood that the terms "center", "lateral", "width", "thickness", "up", "down", "vertical", "top", "bottom", "inside", "outside", "radial", "circumferential", etc., indicating the orientation or position relationship, are based on the orientation or position relationship shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operate in a specific orientation, and therefore cannot be understood as a limitation on the present invention.

[0033] In the present invention, unless otherwise expressly specified or limited, terms such as "mounted" and "connected" should be interpreted broadly. For example, they may refer to fixed or detachable connections, or integration; mechanical or electrical connections; direct or indirect connections through an intermediate medium; and internal communication between two components or interaction between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on specific circumstances.

[0034] In the present invention, unless otherwise expressly specified or limited, when a first feature is "above" or "below" a second feature, it may mean that the first and second features are in direct contact, or that the first and second features are in indirect contact through an intermediary. Furthermore, when a first feature is "above," "above," or "above" a second feature, it may mean that the first feature is directly above or diagonally above the second feature, or simply means that the first feature is at a higher level than the second feature. When a first feature is "below," "below," or "below" a second feature, it may mean that the first feature is directly below or diagonally below the second feature, or simply means that the first feature is at a lower level than the second feature.

[0035] The inventors of the present invention have discovered that during the growth of silicon carbide single crystals, part of the sublimated gas reaches the edge of the seed crystal and condenses to form polycrystals. The polycrystals usually wrap around the edge of the crystal. During the in-situ annealing of the crystal, the silicon carbide crystal and the edge polycrystals will bond to each other into one. Due to the inconsistency of their respective thermal expansion coefficients, the two restrict each other during the annealing temperature change process. The polycrystals wrapped around the edge of the crystal affect the release of residual stress inside the crystal and the reduction of structural defects in the crystal.

[0036] On this first aspect, see Figures 1 to 4 The present invention provides a silicon carbide single crystal growth device, comprising a crucible portion: the crucible portion comprises:

[0037] Crucible body 1, used for containing raw materials;

[0038] The cover body 2 has an edge that extends downward to be sealed with the upper portion of the crucible body 1, and the center of the lower surface of the cover body 2 extends downward to form an extension portion 201, and the lower surface of the extension portion 201 is used to mount a seed crystal. A first annular groove 202 is formed between the side surface of the extension portion 201 and the inner side surface of the cover body 2, and the upper surface of the cover body 2 has a circumferentially arranged recess 203, and the bottom of the circumferentially arranged recess 203 and the side surface of the extension portion 201 are correspondingly arranged in the vertical direction.

[0039] The growth device of silicon carbide single crystal of the present invention comprises a crucible part including a crucible body and a cover body, the edge of the cover body extends downward to be sealed and connected with the upper part of the crucible body, the center of the lower surface of the cover body extends downward to form an extension part, the lower surface of the extension part is used to install the seed crystal, and a first annular groove is formed between the side surface of the extension part and the inner side surface of the cover body. During the growth process of the silicon carbide single crystal, part of the sublimated gas reaches the edge of the seed crystal and condenses to produce polycrystals, which will fill the first annular groove and wrap the edge of the silicon carbide crystal. The present invention provides a circumferentially arranged recess on the upper surface of the cover body, and the bottom of the circumferentially arranged recess and the side surface of the extension part are correspondingly arranged in the vertical direction. During the in-situ annealing process of the crystal In the process, the stress in the crystal will be transmitted to the cover body. Under the action of the stress in the crystal, the cover body is prone to cracking at the recessed portion arranged along the circumference. By cracking at the recessed portion arranged along the circumference, on the one hand, the stress is directly released. On the other hand, since the bottom of the recessed portion arranged along the circumference and the side of the extension portion are arranged correspondingly in the vertical direction, the cover body is prone to loosening or falling off the polycrystals wrapped around the edge of the crystal, reducing the restriction of the edge polycrystals on the circumference of the crystal, reducing the external force wrapping of the edge polycrystals on the crystal, reducing the edge external force confinement during the crystal annealing process, eliminating the influence of the edge polycrystals on the stress release and internal structure rearrangement during the annealing process of the silicon carbide crystal, and promoting stress release and internal structure rearrangement.

[0040] During the in-situ annealing process, the present invention can fully release stress by cracking at the concave portion of the crucible cover, fully optimize and stabilize the crystal structure, significantly reduce structural heterogeneity in the crystal, reduce crystal defects such as lattice distortion, vacancies and dislocations, reduce the dislocation density inside the silicon carbide crystal, improve the crystallinity and internal structural integrity of the crystal, and improve the mechanical strength, thermal conductivity and chemical stability of the crystal.

[0041] The cover of the present invention cracks at the recessed portion arranged along the circumferential direction, and the polycrystal wrapped around the edge of the crystal becomes loose or falls off. On the one hand, it promotes the full release of stress of the crystal and improves the quality of the crystal. On the other hand, it just realizes the automatic separation of silicon carbide single crystal and polycrystal to obtain the target product silicon carbide single crystal, avoiding the destruction of the structure of the silicon carbide single crystal and the influence of the crystal quality during the subsequent mechanical separation of the silicon carbide single crystal and polycrystal.

[0042] The present invention does not limit the form of the recess. In some preferred embodiments of the present invention, two or more recesses are arranged at intervals along the circumference to form the recess 203 arranged along the circumference; or the recess 203 arranged along the circumference is a second annular groove. Under this preferred embodiment, it is more conducive to the cover body to crack at the recess arranged along the circumference under the action of stress in the crystal, fully releasing the stress in the crystal and reducing the dislocation density inside the silicon carbide crystal. When two or more recesses are arranged at intervals along the circumference to form a recess arranged along the circumference, the present invention does not limit the number and shape of the recesses. The recesses can be circular or arc-shaped, etc., and the distribution of the recesses can be around a ring. For example, they can be multiple holes arranged along the ring with intervals between them.

[0043] In some preferred embodiments of the present invention, the depth D1 of the circumferentially disposed recess 203 relative to the distance between the bottom of the first annular groove 202 and the upper surface of the cover 2 is 1 / 3 to 1 / 2. In this preferred embodiment, the depth D1 of the recess is no less than 1 / 3 of the distance between the bottom of the first annular groove and the upper surface of the cover, which is more conducive to the cover cracking at the circumferentially disposed recess under the action of internal stress in the crystal, promoting the full release of residual stress in the crystal during annealing, rearranging the internal structure, and reducing the dislocation density inside the silicon carbide crystal. The depth D1 is no more than 1 / 2, which is more conducive to improving the strength of the crucible cover and preventing the crucible cover from breaking during processes such as crystal growth. If the depth is too deep, the overall strength of the crucible cover will be reduced, which will increase the risk of the crucible cover breaking during processes such as crystal growth. If the depth is too small, it is not conducive to the full release of residual stress in the crystal during annealing, which is not conducive to reducing the dislocation density inside the silicon carbide crystal. The depth of the recess in the present invention refers to the vertical distance between the top and bottom of the recess.

[0044] In some preferred embodiments, the width W1 of the circumferential recess 203 is 0.3 mm to 1.5 mm. In this preferred embodiment, the width of the recess is not less than 0.3 mm, which is more conducive to the cover body cracking at the circumferential recess under the action of stress in the crystal, promoting stress release and internal structure rearrangement. The width of the recess is not more than 1.5 mm, which is more conducive to improving the strength of the crucible cover, preventing the crucible cover from breaking during crystal growth, controlling the temperature difference between the circumferential recess and the two sides of the recess, controlling the temperature distribution on the crystal side, and improving the crystal quality. If the recess width is too large, the overall strength of the crucible cover will be reduced, which will increase the risk of the crucible cover breaking during crystal growth. If the recess width is too large, it may also cause problems such as an increase in the temperature difference between the recess and the two sides of the recess, which is not conducive to temperature control on the upper part of the seed crystal. If the recess width is too small, it is not conducive to the full release of residual stress inside the crystal during annealing, which is not conducive to reducing the dislocation density inside the silicon carbide crystal. For a circumferentially arranged recess formed by two or more recesses spaced apart, the width of the recess refers to the distance from one side of the recess to the other in the radial direction of the cover. For a circumferentially arranged recess in the form of a second annular groove, the width of the recess refers to the distance between opposite sides of the second annular groove.

[0045] In some preferred embodiments of the present invention, the ratio of the center diameter of the bottom of the circumferentially arranged recess 203 to the diameter of the extension 201 is 1.0~1.2. For the circumferentially arranged recess formed by two or more recesses with a gap between them, find the middle point in the width direction on the bottom of each recess, and connect each middle point in the width direction in sequence to form a ring, and the distance between the two relative points of the ring is the center diameter of the bottom of the circumferentially arranged recess. Under this preferred embodiment, the ratio of the center diameter of the bottom of the circumferentially arranged recess to the diameter of the extension is not less than 1.0, the ratio of the center diameter of the bottom of the circumferentially arranged recess to the diameter of the extension is not greater than 1.2, the center diameter of the bottom of the circumferentially arranged recess is equal to or slightly greater than the crystal diameter, and the radial center position of the bottom of the circumferentially arranged recess is located outside the crystal or flush with the crystal along the long line. During the in-situ annealing process, the cover is more likely to crack under the action of stress in the crystal, and it is more likely to loosen or fall off the polycrystal wrapped around the edge of the crystal through the cracking of the cover, reducing the crystal The external force at the edge during the annealing process is confined, which promotes stress release and internal structure rearrangement, stabilizes the crystal structure, and improves the crystal quality; the center diameter of the annular groove is small, which reduces the probability of the graphite cover cracking under the action of stress in the crystal, and the stress release effect is suppressed to a certain extent, reducing the stress release ability of the crystal, which is not conducive to the stability of the crystal structure and quality improvement; the center diameter of the annular groove is large, and the groove is far away from the crystal, which reduces the probability of the graphite cover cracking under the action of stress in the crystal, seriously affecting the elimination or reduction of external force wrapping on the crystal edge, which is not conducive to the stability of the crystal structure and quality improvement.

[0046] In some preferred embodiments of the present invention, the circumferentially disposed recess 203 is inclined, having a top portion away from the extension portion 201 and a bottom portion close to the extension portion 201. In this preferred embodiment, the use of the inclined circumferentially disposed recess facilitates cracking of the cover at the circumferentially disposed recess under the action of stress within the crystal during in-situ annealing, loosening or falling off the polycrystal wrapped around the edge of the crystal, reducing edge force confinement during crystal annealing, promoting stress release and internal structural rearrangement, stabilizing the crystal structure, and improving crystal quality.

[0047] Preferably, the circumferential recesses 203 are inclined at an angle of 2° to 8° relative to the vertical direction. This preferred solution is more conducive to in-situ annealing, where the cover body cracks at the circumferential recesses under the action of stress within the crystal, causing the polycrystalline wrapped around the edge of the crystal to loosen or fall off.

[0048] In some preferred embodiments of the present invention, a layer of graphite paper is bonded to the lower surface of the extension portion to provide a buffering effect for lateral displacement changes, which is more conducive to fully releasing stress during the in-situ annealing stage and reducing crystal defects such as lattice distortion, vacancies and dislocations.

[0049] In a second aspect, the present invention provides an in-situ annealing method for a silicon carbide single crystal using the growth apparatus described in the first aspect, the method sequentially comprising: a high-temperature stress release stage, a pressure increase and temperature reduction stage, and a furnace cooling stage. The high-temperature stress release stage comprises: introducing an inert gas into a furnace shell cavity to increase the pressure within the furnace shell cavity to 30,000 Pa to 49,000 Pa, cooling the crucible portion to 1800°C to 2000°C, and then maintaining the temperature for 5 to 10 hours. During the high-temperature stress release stage, the inert gas introduction conditions include: a nitrogen flow rate of 0.15 L / h to 0.24 L / h, and an argon flow rate of 0.30 L / h to 0.44 L / h.

[0050] Under this scheme, the pressure in the furnace shell cavity is raised to 30000Pa~49000Pa at the initial stage of in-situ annealing, the temperature of the crucible is reduced to 1800℃~2000℃ and then kept warm for 5h~10h. The conditions for introducing inert gas include: nitrogen flow rate of 0.15L / h~0.24L / h, argon flow rate of 0.30L / h~0.44L / h, the stress of the crystal is quickly released, which is more conducive to promoting the cover to be arranged along the circumference. The recessed parts provided along the circumference crack, which promotes the polycrystals wrapped around the edge of the crystal to loosen or fall off. In the early stage of in-situ annealing, the stress in the crystal is large and is more easily transferred to the recessed parts provided along the circumference. The recessed parts are prone to cracking. In the early stage of in-situ annealing, the cover body is cracked at the recessed parts provided along the circumference and the polycrystals wrapped around the edge of the crystal are loosened or fall off. Early elimination or reduction of external force wrapping can promote stress release and rearrangement of the internal structure of the crystal to the greatest extent, reduce crystal defects and improve crystal quality.

[0051] Preferably, the pressure-increasing and temperature-reducing stage includes: introducing an inert gas into the furnace shell cavity to increase the pressure within the furnace shell cavity to 50,000 Pa to 70,000 Pa, cooling the crucible portion to 800°C to 900°C, and then maintaining the temperature for 3 to 5 hours. The inert gas preferably includes nitrogen and argon, with the nitrogen flow rate being 0.25 L / h to 0.35 L / h and the argon flow rate being 0.45 L / h to 0.55 L / h. This preferred embodiment is more conducive to fully promoting stress release and rearrangement of the crystal internal structure, reducing crystal defects, and improving crystal quality.

[0052] In some preferred embodiments, the duration of the furnace cooling stage is 10 h to 15 h.

[0053] The present invention will be further described in detail below with reference to specific embodiments.

[0054] Example 1

[0055] A silicon carbide single crystal growth device includes a crucible portion, the crucible portion including a crucible body 1 for accommodating a raw material, an edge of which extends downward to a cover 2 sealedly connected to the upper portion of the crucible body 1, the center of the lower surface of the cover 2 extending downward to form an extension portion 201, the lower surface of the extension portion 201 is used to mount a seed crystal, a first annular groove 202 is formed between the side surface of the extension portion 201 and the inner side surface of the cover 2, the upper surface of the cover has a circumferentially arranged recess 203 in the form of a second annular groove, the depth D1 of the second annular groove relative to the distance between the bottom of the first annular groove and the upper surface of the cover 2 is 0.4, the width W1 of the second annular groove is 1 mm, the second annular groove is inclined, with a top away from the extension portion 201 and a bottom close to the extension portion 201, the inclination angle of the second annular groove relative to the vertical direction is 5°, the bottom of the second annular groove and the side surface of the extension portion 201 are arranged correspondingly in the vertical direction, and the ratio of the center diameter of the bottom of the second annular groove to the diameter of the extension portion 201 is 1.05.

[0056] A method for in-situ annealing of a silicon carbide single crystal comprises, in sequence, a high-temperature stress release stage, a pressure increase and temperature reduction stage, and a furnace cooling stage. During the high-temperature stress release stage, nitrogen and argon are introduced into the furnace shell cavity of a silicon carbide growth furnace to increase the pressure within the furnace shell cavity to 40,000 Pa. Simultaneously, the temperature is lowered to 1,900°C, where the crucible temperature is maintained for 8 hours. The nitrogen flow rate is 0.2 L / h, and the argon flow rate is 0.4 L / h. During the pressure increase and temperature reduction stage, nitrogen and argon are introduced into the furnace shell cavity to increase the pressure within the furnace shell cavity to 60,000 Pa. Simultaneously, the temperature is lowered to 850°C, where the crucible temperature is maintained for 4 hours. The nitrogen flow rate is 0.3 L / h, and the argon flow rate is 0.5 L / h. During the furnace cooling stage, ventilation and exhaust within the furnace shell cavity are stopped, the heating power is turned off, and the crucible temperature is allowed to cool naturally to room temperature. The cracking rate of the cover is 71%. The cracking of the cover makes the polycrystalline wrapped around the edge of the crystal loose and fall off. The annealing of the cracked cover makes the dislocation density of the silicon carbide crystal greatly reduced. The dislocation density is shown in Figure 5 , the dislocation density is low, and the stress of the crystal is fully released. The dislocation density is obtained by testing with a dislocation detector after section corrosion. The cracking rate of the cover is the ratio of the number of graphite cover cracks in the limited group annealing test to the total number of groups. Figure 5 、 Figure 6 、 Figure 7In the figure, each figure includes 4 sub-figures, which respectively represent the dislocation density detection results of total dislocation (SUM), threading screw dislocation (TSD), threading ductile dislocation (TED) and basis plane dislocation (BPD). The numbers in the upper left corner of the four sub-figures represent the number of corresponding dislocations in the silicon carbide single crystal sample. The grayscale levels of the grids in the sub-figures are different, and different grayscale levels represent the dislocation density level of the grid. The corresponding relationship between grayscale level and dislocation density level can be seen in the legend in the lower right corner of each sub-figure.

[0057] Example 2

[0058] The same procedures were followed as in Example 1, except that the second annular groove of Example 1 was replaced with two or more recessed portions spaced apart in a circular pattern. All other aspects remained unchanged. The lid cracking rate was 69%. The lid cracking significantly loosened and detached the polycrystals encased at the edges of the crystal. Annealing of the lid cracking significantly reduced the dislocation density of the silicon carbide crystal, resulting in a low dislocation density and sufficient stress relief in the crystal.

[0059] Example 3

[0060] The same procedure as in Example 1 was followed, except that the depth D1 of the second annular groove relative to the distance between the bottom of the first annular groove and the upper surface of the cover was 0.2, while all other parameters remained unchanged. The cover cracking rate was 37%. The cracking of the cover caused the polycrystals wrapped around the crystal edges to loosen and fall off significantly. Annealing of the cracked cover significantly reduced the dislocation density of the silicon carbide crystals, resulting in a low dislocation density and sufficient stress relief in the crystals.

[0061] Example 4

[0062] The same procedure was followed as in Example 1, except that the width W1 of the second annular groove was 0.2 mm. All other parameters remained unchanged. The lid cracking rate was 41%. The lid cracking caused the polycrystals wrapped around the crystal edges to loosen and fall off significantly. Annealing of the lid cracking significantly reduced the dislocation density of the silicon carbide crystals, resulting in a low dislocation density and sufficient stress relief in the crystals.

[0063] Example 5

[0064] The same method as in Example 1 was used, except that the ratio of the center diameter of the bottom of the circumferentially arranged recess to the diameter of the extension was 0.95. Other parameters remained unchanged. The cracking rate of the cover was 62%. The annealing of the cracked cover loosened the polycrystals wrapped around the crystal edge. The annealing of the cracked cover also significantly improved the dislocation density of the silicon carbide crystal. The dislocation density is shown in Table 1. Figure 6 , the dislocation density is medium, and a small amount of residual stress remains in the crystal after annealing.

[0065] Example 6

[0066] The same procedures were followed as in Example 1, except that the ratio of the center diameter of the bottom of the circumferential recess to the diameter of the extension was 1.25. All other conditions remained unchanged. The lid cracking rate was 65%. Annealing of the lid cracking loosened the polycrystals wrapped around the crystal edges. Annealing of the lid cracking significantly improved the dislocation density of the silicon carbide crystal, resulting in a moderate dislocation density. A small amount of residual stress remained in the crystal after annealing.

[0067] Example 7

[0068] The same procedure was followed as in Example 1, except that the second annular groove was vertically positioned. All other parameters remained unchanged. The lid cracking rate was 62%. The lid cracking significantly loosened and detached the polycrystals encased at the edges of the crystals. Annealing of the lid cracking significantly reduced the dislocation density of the silicon carbide crystals, resulting in a low dislocation density and sufficient stress relief in the crystals.

[0069] Example 8

[0070] The method was carried out in accordance with Example 1, except that, during the high-temperature stress release stage in the in-situ annealing method, nitrogen and argon were introduced into the shell cavity of the silicon carbide growth furnace to increase the pressure in the shell cavity to 25,000 Pa. At the same time, the temperature of the crucible was reduced to 2,100°C and kept warm for 12 hours. The nitrogen flow rate was 0.3 L / h and the argon flow rate was 0.5 L / h. Other factors remained unchanged. The cracking rate of the cover was 47%. The cracking of the cover caused the polycrystal wrapped around the edge of the crystal to become loose and fall off. The annealing of the cracked cover significantly improved the dislocation density of the silicon carbide crystal, which was medium. A small amount of residual stress remained in the crystal after annealing.

[0071] Comparative Example 1

[0072] The same method was used as in Example 1, except that the upper surface of the cover was not provided with a circumferential recess. Other aspects remained unchanged. The cracking rate of the cover was 13%. During the annealing process, the polycrystalline wrapped around the edge of the crystal did not loosen or fall off significantly. Annealing could not effectively improve the dislocation density of the silicon carbide crystal. The dislocation density can be found in Figure 7 , the dislocation density is high, and there is more residual stress in the crystal after annealing.

[0073] Comparing Example 1 with Examples 3 and 4, the depth D1 of the circumferential recess 203 is no less than 1 / 3 of the distance between the bottom of the first annular groove 202 and the upper surface of the cover 2, and the width W1 of the circumferential recess 203 is no less than 0.3 mm. This facilitates cracking of the cover at the circumferential recess under the action of intracrystalline stress, thereby improving the cover cracking rate. Comparing Example 1 with Examples 5 and 6, the ratio of the center diameter of the bottom of the circumferential recess 203 to the diameter of the extension 201 is 1.0 to 1.2, making the cover more likely to crack under the action of intracrystalline stress. This cracking of the cover makes it more likely to loosen or fall off the polycrystal wrapped around the edge of the crystal, thereby improving the stress relief effect and reducing crystal defects. Comparing Example 1 with Example 7, the circumferential recess 203 is tilted, which facilitates cracking of the cover at the circumferential recess under the action of intracrystalline stress, thereby improving the cover cracking rate. Comparing Example 1 and Example 8, the high-temperature stress release stage of the annealing process, under unique process conditions, is more conducive to promoting the cracking of the cover at the recessed portion arranged along the circumferential direction, increasing the cracking rate of the cover, improving the stress release effect and reducing the crystal defects.

[0074] In comparison with the embodiment and the comparative example, a circumferentially arranged recess is provided on the upper surface of the cover body, and the bottom of the circumferentially arranged recess 203 and the side surface of the extension portion 201 are arranged correspondingly in the vertical direction. The annealing process can greatly promote stress release, promote the rearrangement of the internal structure of the crystal, and improve the quality of the crystal.

[0075] The preferred embodiments of the present invention have been described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, various simple variations of the technical solution of the present invention may be made, including combining the various technical features in any other appropriate manner. These simple variations and combinations should also be regarded as disclosed in the present invention and fall within the scope of protection of the present invention.

Claims

1. A silicon carbide single crystal growth device, comprising a crucible portion, characterized in that: The crucible portion comprises: Crucible body (1), used for containing raw materials; A cover body (2), wherein the edge of the cover body (2) extends downward to be sealed with the upper part of the crucible body (1), the center of the lower surface of the cover body (2) extends downward to form an extension portion (201), the lower surface of the extension portion (201) is used to mount a seed crystal, a first annular groove (202) is formed between the side surface of the extension portion (201) and the inner side surface of the cover body (2), the upper surface of the cover body (2) has a circumferentially arranged recess (203), and the bottom of the circumferentially arranged recess (203) and the side surface of the extension portion (201) are correspondingly arranged in the vertical direction; The depth D1 of the circumferentially arranged recess (203) accounts for 1 / 3 to 1 / 2 of the distance between the bottom of the first annular groove (202) and the upper surface of the cover body (2); The width W1 of the recess (203) arranged along the circumferential direction is 0.3 mm to 1.5 mm; The ratio of the center diameter of the bottom of the circumferentially arranged recess (203) to the diameter of the extension portion (201) is 1.0 to 1.2; The growth device is used for in-situ annealing of silicon carbide single crystals.

2. The growth device according to claim 1, characterized in that Two or more recesses are spaced apart along the circumferential direction to form the recess (203) arranged along the circumferential direction; or the recess (203) arranged along the circumferential direction is a second annular groove.

3. The growth device according to claim 1, characterized in that The recessed portion (203) arranged along the circumferential direction is arranged at an angle, and has a top portion away from the extension portion (201) and a bottom portion close to the extension portion (201).

4. The growth device according to claim 3, characterized in that The inclination angle of the recess (203) arranged along the circumferential direction relative to the vertical direction is 2° to 8°.

5. An in-situ annealing method for a silicon carbide single crystal using the growth apparatus according to any one of claims 1 to 4, characterized in that: Including in order: The high-temperature stress release stage, the pressure increase and temperature reduction stage and the furnace cooling stage include: introducing inert gas into the furnace shell cavity to increase the pressure in the furnace shell cavity to 30,000 Pa ~ 49,000 Pa, cooling the crucible part to 1800 ° C ~ 2000 ° C and then keeping it warm for 5h ~ 10h.

6. The annealing method according to claim 5, characterized in that During the high-temperature stress release stage, the conditions for introducing the inert gas include: a nitrogen flow rate of 0.15 L / h to 0.24 L / h, and an argon flow rate of 0.30 L / h to 0.44 L / h.

7. The annealing method according to claim 5, characterized in that The pressure increasing and temperature decreasing stage includes: introducing inert gas into the furnace shell cavity to increase the pressure in the furnace shell cavity to 50000Pa~70000Pa, cooling the crucible part to 800℃~900℃ and then keeping it warm for 3h~5h.

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