Seed crystal connecting device and silicon carbide liquid phase growth method

Abstract

The invention relates to the technical field of preparation of silicon carbide grown by a liquid phase method, and discloses a seed crystal connecting device and a silicon carbide liquid phase growth method. The seed crystal connecting device comprises a seed crystal shaft, a seed crystal bottom support and at least one limiting piece, a threaded connection part is arranged at the axis position of one end of the seed crystal shaft, a threaded hole is formed in the center of one surface of the seed crystal bottom support, and the threaded connection part is inserted into the threaded hole; at least one cutting groove is formed in the peripheral wall of the end part, close to the threaded connection part, of the seed crystal shaft, and each cutting groove extends to penetrate through the end surface of the seed crystal shaft in the length direction of the seed crystal shaft; at least one slot is formed in one surface, facing the seed crystal shaft, of the seed crystal bottom support, each slot corresponds to one cutting groove in position, each cutting groove is communicated with the corresponding slot to form a limiting groove, and the limiting piece is inserted into the limiting groove through the cutting groove. According to the device, the inserting groove, the cutting groove and the limiting piece form a mortise and tenon joint structure, the seed crystal bottom support and the seed crystal shaft can be locked, and the condition that the bottom support is disengaged in the stirring process is avoided.

Description

Technical Field

[0001] This invention relates to the field of liquid-phase silicon carbide preparation technology, and more specifically, to a seed crystal connection device and a liquid-phase silicon carbide growth method. Background Technology

[0002] Top Seeded Solution Growth (TSSG) is an advanced method for growing high-quality, large-size single crystals. It is particularly suitable for materials like silicon carbide (SiC), which have high melting points, high vapor pressures, and numerous polymorphs. These characteristics pose significant challenges to traditional Czochralski (CZ) or physical vapor transport (PVT) methods in controlling specific crystal forms (such as 4H-SiC) and quality. The core principle of TSSG is to slowly pull a rotating seed crystal from a high-temperature Si-C solution, causing carbon and silicon atoms to epitaxially align at the solid-liquid interface according to the seed crystal's structure, gradually growing a large single crystal. (In actual production, a molten carbon flux, often made of metals like chromium, aluminum, or nickel, is added to the silicon-carbon melt, resulting in a silicon alloy that becomes highly viscous after melting at high temperatures.)

[0003] A seed crystal axis, typically made of graphite, connects the seed crystal. The rotation and vertical movement of the seed crystal axis cause the seed crystal to rotate and move vertically, as illustrated in the diagram below. Figure 1 As shown. This process will encounter the following problems in actual production: The silicon carbide growth process requires the seed crystal to rotate in both directions (alternating clockwise and counterclockwise horizontal rotation). However, currently, the connection between the seed crystal base and the seed crystal shaft is achieved by threaded tightening. Figure 2 As shown, this fixing method requires that the direction of the seed crystal rotation be consistent with the direction of the thread tightening. The opposite direction will cause the seed crystal base to separate from the seed crystal shaft (the main reason is that the viscosity of the molten silicon alloy is extremely high, and the seed crystal base will be loosened when rotating in the opposite direction).

[0004] For silicon carbide growth to be stable, the silicon melt needs to dissolve carbon to form a silicon-carbon mixture. However, the carbon flux added to the silicon melt increases its viscosity. In a conventional resistance furnace heating structure, without magnetic stirring, the melt is driven by the rotation of the seed crystal and crucible, resulting in weak fluidity and an inability to achieve a uniformly mixed melt. This leads to unstable growth and may even result in polycrystalline growth. Figure 3 As shown, Figure 3The image shows a cross-sectional view of the silicon alloy melt in the crucible after solidification. The center has a porous structure (with a higher content of aluminum and silicon), while the edges have a dense structure (with a higher content of elements such as chromium and nickel). This indicates that the silicon alloy melt was not mixed evenly, and the solidification morphology of the material was inconsistent.

[0005] In view of this, the present invention is proposed. Summary of the Invention

[0006] The purpose of this invention is to provide a seed crystal connection device and a silicon carbide liquid phase growth method, which aims to improve at least one of the problems mentioned in the background art.

[0007] This invention is implemented as follows: In a first aspect, the present invention provides a seed crystal connection device, comprising a seed crystal shaft, a seed crystal base and at least one limiting member; One end of the seed crystal shaft is provided with a threaded connection part at the shaft center position, and a threaded hole is provided at the center of one side of the seed crystal base. The threaded connection part is inserted into the threaded hole, so that the seed crystal shaft and the seed crystal base are connected by threads. At least one groove is provided on the peripheral wall of the end of the seed crystal shaft near the threaded connection part, and each groove extends along the length direction of the seed crystal shaft to the end face that penetrates the seed crystal shaft; The seed crystal base has at least one slot on the side facing the seed crystal axis. The position of each slot corresponds to a cutting groove. Each cutting groove and the corresponding slot are connected to form a limiting groove. The limiting member is inserted into the limiting groove through the cutting groove. One end of the limiting member in the limiting groove is located in the slot, and the other end is located in the cutting groove.

[0008] In an optional implementation, at least one of the following features (1) and (2) is included: (1) There are two slots, and the two slots are symmetrical about the axis of the seed crystal. (2) The limiting member is located at one end of the groove, and a strip groove is provided on the outward wall surface to facilitate its picking.

[0009] In an optional embodiment, the seed crystal connecting device further includes at least one set of stirring components; Each set of mixing components includes: The horizontal arm is attached to the seed crystal base and the two are connected. Two connecting arms are arranged opposite each other, with one end of each connecting arm connected to one end of the horizontal arm and the other end extending away from the seed crystal axis; Two agitators, each located between two connecting arms, each agitator connected to the end of one connecting arm away from the cross arm.

[0010] In an optional implementation, the cross arm is disposed on the side of the seed crystal base facing the seed crystal axis, and the cross arm is connected to the seed crystal base by multiple bolts.

[0011] In an optional implementation, the middle part of the transverse arm is annular, which fits around the seed crystal axis; Optionally, the seed crystal base is provided with a mating groove of the same shape as the horizontal arm on the side facing the seed crystal axis, and the horizontal arm is embedded in the mating groove.

[0012] In an optional embodiment, each impeller is triangular prism in shape, with one end face of the impeller connected to the inner side of the end of the connecting arm, and the other end of the impeller extending toward the opposite connecting arm. The cross-section of the agitator perpendicular to its length is an isosceles triangle, and the two walls of the agitator corresponding to the two sides of the isosceles triangle are symmetrical about the axis of the seed crystal.

[0013] In an optional implementation, the height of the isosceles triangle is 20-50 mm, and the length of the stirring paddle is less than or equal to the radius of the seed crystal. When using 6-inch seed crystals, the length of the agitator should be 30~75mm; When using 8-inch seed crystals, the length of the agitator should be 30~100mm; When using 12-inch seed crystals, the length of the agitator should be 30-150mm.

[0014] In an optional implementation, all parts in the seed crystal connection device are made of graphite.

[0015] Secondly, the present invention provides a method for liquid-phase growth of silicon carbide, wherein the seed crystal connection device as described in any of the foregoing embodiments is used to grow silicon carbide by liquid-phase pulling and stirring, and the stirring method is alternating forward and reverse rotation.

[0016] In an optional implementation, the stirring method is as follows: The stirring speed and direction are set to change periodically, with one cycle time being T, where T is 40~80s; Within one cycle, the stirring speed gradually increases from 0 to a in the forward direction, then gradually decreases to 0 in the forward direction, then gradually increases to a in the reverse direction, and then gradually decreases to 0 in the reverse direction, and so on. a is 20~100rpm.

[0017] The present invention has the following beneficial effects: The seed crystal connection device provided by the present invention utilizes a tenon and mortise structure (slot, groove and limiting member) to lock the seed crystal shaft and the seed crystal base relative to each other, so that the seed crystal base will not be unscrewed when the seed crystal shaft is reversed.

[0018] The silicon carbide liquid phase growth method provided by the present invention uses the seed crystal connection device provided in the embodiments of the present invention to grow silicon carbide by liquid phase pulling and stirring. The stirring mode is alternating forward and reverse, which will not cause the bottom support to fall off and the melt uniformity is good. Attached Figure Description

[0019] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1 This is a schematic diagram illustrating the current working principle of the seed crystal connection device; Figure 2 This is a schematic diagram of the current connection method between the seed crystal shaft and the base support; Figure 3 This is an actual appearance diagram showing the uneven mixing of silicon alloy after stirring using the current stirring method. Figure 4 This is a schematic diagram of the seed crystal connection device provided by the present invention; Figure 5 A cross-sectional view of the seed crystal connection device provided by the present invention; Figure 6 This is a schematic diagram of the structure at the end of the seed crystal shaft; Figure 7 This is a top view of the seed crystal base; Figure 8 for Figure 7 Sectional view at point AA; Figure 9 This is a structural schematic diagram of the limiting component; Figure 10 This is a schematic diagram of the stirring assembly from a first-view perspective. Figure 11 This is a schematic diagram of the stirring assembly from a second perspective. Figure 12 These are simulation results of the natural flow of melt during the solution-based silicon carbide crystal growth process; Figure 13 This is a schematic diagram of the traditionally understood structure of an agitator during forward mixing. Figure 14 This is a schematic diagram of the traditionally understood structure of an agitator during reverse mixing. Figure 15 This is a schematic diagram of the stirring paddle of the present invention stirring in both forward and reverse directions; Figure 16 This is a schematic diagram illustrating the speed changes in three cases of variable speed forward and reverse rotation. Figures 17 to 20The images shown are, in order, the appearance of the silicon alloy after solidification following stirring in Examples 1 to 6; Figure 21 and 22 The images show the appearance of the silicon alloys after solidification following stirring in Comparative Examples 1 and 2, respectively.

[0021] Icons: 100-Seed crystal connection device; 110-Seed crystal shaft; 111-Threaded connection part; 112-Groove; 120-Seed crystal base; 121-Threaded hole; 122-Slot; 123-Matching groove; 130-Limiting component; 131-Strip groove; 140-Stirring assembly; 141-Horizontal arm; 142-Bolt; 143-Connecting arm; 144-Stirring paddle. Detailed Implementation

[0022] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0023] The features and performance of the present invention will be further described in detail below with reference to embodiments.

[0024] like Figure 4 and 5 As shown, an embodiment of the present invention provides a seed crystal connection device 100, including a seed crystal shaft 110, a seed crystal base 120 and at least one limiting member 130; like Figures 6 to 8 As shown, a threaded connection part 111 is provided at one end of the seed crystal shaft 110 at the axis center position, and a threaded hole 121 is provided at the center of one side of the seed crystal base 120. The threaded connection part 111 is inserted into the threaded hole 121, so that the seed crystal shaft 110 and the seed crystal base 120 are connected by threads. At least one groove 112 is provided on the peripheral wall of the end of the seed crystal shaft 110 near the threaded connection portion 111, and each groove 112 extends along the length direction of the seed crystal shaft 110 to penetrate the end face of the seed crystal shaft 110. The seed crystal base 120 has at least one slot 122 on the side facing the seed crystal axis 110. The position of each slot 122 corresponds to a cut 112. Each cut 112 communicates with the corresponding slot 122 to form a limiting groove. The limiting member 130 is inserted into the limiting groove through the cut 112. One end of the limiting member 130 in the limiting groove is located in the slot 122, and the other end is located in the cut 112.

[0025] The installation method of the seed crystal base 120 and the seed crystal shaft 110 is as follows: insert the threaded connection part 111 of the seed crystal shaft 110 into the threaded hole 121 of the seed crystal base 120, and screw it to connect the two. When screwed to the bottom, the slot 122 and the cut groove 112 are connected to form a limiting groove. The size of the limiting member 130 is smaller than the size of the cut groove 112. Insert the limiting member 130 into the limiting groove from the cut groove 112, and push the limiting member 130 down so that the first end of the limiting member 130 enters the slot 122 and the tail end is in the cut groove 112.

[0026] The seed crystal connection device 100 provided by the present invention utilizes the tenon and mortise structure (slot 122, groove 112 and limiting member 130) to lock the seed crystal shaft 110 and the seed crystal base 120 relative to each other, so that the seed crystal base 120 will not be unscrewed when the seed crystal shaft 110 is reversed.

[0027] Furthermore, both slot 122 and groove 112 are square grooves, and the limiting member 130 is a long rectangular member.

[0028] Optionally, such as Figures 6 to 9 As shown, the groove length D1 is 5~10mm, the width L1 is 3~6mm, the groove depth H1 is 3~5mm, the seed crystal base 120 has a thickness D of 10~20mm, D>H1; the limiting component 130 has a length H of 5~15mm, a thickness L0 of 3~6mm, and a width D0 of 5~10mm; the groove 112 has a length H2≥H, a groove depth L2 of 3~6mm, and a groove width D2 of 5~10mm.

[0029] It should be noted that the above dimensions are for some implementation methods. In fact, as long as the slot 122, the cut 112 and the limiting member 130 are assembled to prevent the seed crystal base 120 from rotating relative to the seed crystal axis 110, the specific dimensions are not strictly required, and the specific tenon and mortise structure shape is also not required.

[0030] Optionally, to ensure high locking stability between the seed crystal shaft 110 and the seed crystal base 120, the number of grooves 112 is two (and the corresponding number of slots 122 and limiting members 130 is also two), with the two grooves 112 symmetrically arranged about the axis of the seed crystal shaft 110. It should be noted that in some other embodiments of the present invention, the number of slots 122 may also be greater than two.

[0031] Optionally, the limiting member 130 is located at one end of the groove 112, and a strip groove 131 is provided on its outward-facing wall surface to facilitate its handling. It should be noted that the main function of providing the strip groove 131 is to facilitate handling; in some other embodiments of the present invention, a protrusion may also be provided near the location where the strip groove 131 is provided, which can also achieve the purpose of facilitating handling.

[0032] Optionally, such as Figure 10 and Figure 11 The seed crystal connecting device 100 shown also includes at least one set of stirring components 140; Each set of stirring components 140 includes: The horizontal arm 141 is attached to the seed crystal base 120 and the two are connected. Two connecting arms 143 are arranged opposite to each other. One end of each connecting arm 143 is connected to one end of the horizontal arm 141, and the other end extends away from the seed crystal axis 110. Two agitators 144, each agitator 144 is located between two connecting arms 143, and each agitator 144 is connected to one end of a connecting arm 143 away from the cross arm 141.

[0033] A stirring component 140 is provided so that it rotates together with the seed crystal shaft 110. The stirring component 140 agitates the molten liquid below the seed crystal base 120, thereby accelerating its flow and resulting in good uniformity of the melt.

[0034] Optionally, the agitator 144 is connected to the connecting arm 143 by bolts 142.

[0035] Furthermore, to achieve a stable connection, a cross arm 141 is disposed on the side of the seed crystal base 120 facing the seed crystal axis 110, and the cross arm 141 is connected to the seed crystal base 120 by a plurality of bolts 142. For example, four bolts 142 are provided, two at each of the opposite ends of the seed crystal axis 110.

[0036] Optionally, the middle part of the transverse arm 141 is annular, which fits around the seed crystal axis 110.

[0037] Furthermore, the seed crystal base 120 is provided with a mating groove 123 with the same shape as the horizontal arm 141 on the side facing the seed crystal axis 110, and the horizontal arm 141 is embedded in the mating groove 123.

[0038] Furthermore, each stirring paddle 144 is triangular prism in shape, with one end face of the stirring paddle 144 connected to the inner side of the end of the connecting arm 143, and the other end of the stirring paddle 144 extending toward the opposite connecting arm 143. The cross-section of the impeller 144 perpendicular to its length direction is an isosceles triangle, and the two walls of the impeller 144 corresponding to the two sides of the isosceles triangle are symmetrical about the axis of the seed crystal 110.

[0039] The simulation results of the flow direction distribution of the alloy melt during crystal growth due to natural convection are as follows: Figure 12As shown, the flow direction of the molten metal at the edge is downward, but the natural convection direction of most of the molten metal outside the edge is upward. To increase the uniformity of the molten metal, the stirring structure should drive the melt flow in the same direction as the natural convection direction of the molten metal; this is a basic principle.

[0040] To maintain high-speed rotation and prevent the stirring structure from colliding with the crucible sidewall, the designed stirring structure must maintain a certain distance from the crucible sidewall, at least 5mm. Therefore, the function of the stirring structure is to lift the molten liquid upwards. Traditionally, the structure of the stirring paddle is considered similar to a ship's oar. Figure 13 As shown, when the stirring paddle rotates in the same direction as the molten liquid flow, it lifts the molten liquid upwards, achieving the stirring purpose. However, thorough stirring requires back-and-forth motion. Therefore, when the same structure rotates in opposite directions, it will push the molten liquid downwards, weakening natural convection and failing to enhance the stirring effect. Figure 14 As shown.

[0041] The stirring paddle of this invention is designed with an isosceles triangular cross-section, which allows it to lift the molten liquid upwards in both forward and reverse rotation. Special attention should be paid to the installation of the stirring paddle, ensuring the triangle... Figure 15 The cone shown is placed upwards; if the triangle is placed upside down, it will inhibit the natural convection of the melt.

[0042] Specifically, the length of the horizontal arm 141 does not exceed the diameter of the crucible, which is generally between 250 and 300 mm. The connecting arm 143 is vertically positioned, and its length ensures that the stirring paddle 144 can be immersed in the molten metal, ensuring that the seed crystal can contact the molten metal while the stirrer does not touch the bottom of the crucible. It is necessary to ensure that h3-D (base thickness) ≤ L (molten metal depth).

[0043] Furthermore, the height h1 of the isosceles triangle is 20~50mm, and the length of the agitator 144 is less than or equal to the radius of the seed crystal; when using a 6-inch seed crystal, the length R of the agitator 144 is 30~75mm; when using an 8-inch seed crystal, the length R of the agitator 144 is 30~100mm; when using a 12-inch seed crystal, the length R of the agitator 144 is 30~150mm.

[0044] This invention provides a method for liquid-phase growth of silicon carbide. The method utilizes a seed crystal connection device 100 provided in this invention to perform liquid-phase growth of silicon carbide pulling and stirring, with alternating forward and reverse rotation. Because this growth method employs the device provided in this invention for liquid-phase growth of silicon carbide pulling and stirring, the melt uniformity is good, resulting in high-quality liquid-phase grown silicon carbide. Alternating forward and reverse rotation improves melt uniformity; for example, forward rotation corresponds to clockwise rotation from a top-view angle, while reverse rotation corresponds to counterclockwise rotation from a top-view angle.

[0045] Specifically, the stirring method is as follows: Set the stirring speed and direction to change periodically, such as Figure 16 As shown, one cycle time is T, where T is 40~80s (e.g., 40s, 60s or 80s). Within one cycle, the stirring speed gradually increases from 0 to a in the forward direction, then gradually decreases to 0 in the forward direction, then gradually increases to a in the reverse direction, and then gradually decreases to 0 in the reverse direction, and so on; a is 30~50 rpm (e.g. 30 rpm, 40 rpm or 50 rpm).

[0046] Preferably, the speed acceleration value remains constant during the process of increasing or decreasing the speed, i.e., as shown in the figure. Figure 12 The rotational speed and time show a broken line shape.

[0047] Rapidly changing forward and reverse mixing can increase the mixing effect and make the mixture more even. For example... Figure 16 As shown in the figure, three stirring schemes are given, with different rotation speeds and accelerations for different situations. Excessive rotation speed will cause the liquid to overflow from the crucible, and the rotation speed should not exceed 50 revolutions per minute (rpm).

[0048] Example 1 The seed crystal connection device 100 provided in this embodiment is as follows: Figures 4-9 As shown.

[0049] The seed crystal base 120 has a diameter of 150mm and a thickness D of 15mm; The slot D1 of slot 122 is 8mm long, the slot L1 is 6mm wide, and the slot H1 is 5mm deep; The groove 112 on the seed crystal axis 110 has a groove depth L2 of 6 mm, a length H2 of 15 mm, and a width D2 of 8 mm; The limiting component 130 has a length H of 10mm, a thickness L0 of 6mm, and a width D0 of 8mm.

[0050] The bottom of the agitator 144 and the horizontal arm 141 have an h3 of 60 mm. The length R of the agitator 144 is 50 mm. The cross section of the agitator 144 is an isosceles triangle with a base length L3 of 40 mm and a height h1 of 20 mm. The bottom end face of the connecting arm 143 is flush with the end face of the agitator 144.

[0051] When the seed crystal connecting device 100 is working, the inner diameter of the crucible is 300mm, the molten liquid depth is 50mm, and the seed crystal size is 150mm.

[0052] When stirring, follow Figure 16 The stirring process, as shown in Case 1, involves forward and reverse rotation speed changes.

[0053] Example 2 This embodiment is basically the same as Embodiment 1, except that: according to Figure 16The stirring process, as shown in Case 2, involves forward and reverse rotation speed changes.

[0054] Example 3 This embodiment is basically the same as Embodiment 1, except that: according to Figure 16 The stirring process, as shown in Case 3, involves forward and reverse rotation speed changes.

[0055] Example 4 This embodiment is basically the same as embodiment 1, except that the structure of the stirring paddle 144 in this embodiment is different from that in embodiment 1. In this embodiment, the stirring paddle 144 is plate-shaped and its height is the same as that of the stirring paddle 144 in embodiment 1.

[0056] Comparative Example 1 This embodiment is basically the same as embodiment 1, except that the seed crystal connecting device 100 is not equipped with a stirring component 140.

[0057] Comparative Example 2 This comparative example is basically the same as Example 1, except that it rotates in one direction at a speed of 50 rpm.

[0058] Experimental Example The liquid-phase silicon carbide growth experiment was carried out according to the methods provided in the various embodiments and comparative examples. The specific operation method is as follows: In the melting process, the stirring structure is suspended above the raw material and heated to 1900℃ until the material is completely melted. The stirring paddle is then slowly rotated unidirectionally at 15 rpm, while the stirring mechanism is slowly lowered at a speed of 80 mm / h. When the stirring structure is completely immersed in the melt and the seed crystal has not yet come into contact with the melt, the entire system is rotated forward and backward according to the process of this invention for 1 hour to ensure uniform stirring. Afterward, the entire system is slowly lowered at a speed of 50 mm / h. Once the seed crystal comes into contact with the melt, the crystal growth process begins. During crystal growth, the melt is also stirred by the stirring mechanism.

[0059] After crystal growth, the molten silicon alloy in the crucible was allowed to solidify slowly, and images of the solidified surface were taken. The images of the solidified silicon melt after stirring in Examples 1-6 are shown below. Figures 17-20 As shown, the apparent appearance of the molten silicon in Comparative Examples 1 and 2 after solidification is as follows. Figure 21 , 22 As shown in the figure, the silicon alloy mixing uniformity is significantly better in each embodiment compared to the comparative example; Comparing Examples 1 to 3, it can be seen from the figure that Example 1 has significantly improved uniformity compared to Comparative Example 2, but still has local non-uniformity compared to Examples 2 and 3. This may be because the stirring cycle is too short and the rate change is too large. Comparing Example 4 with Example 1, the stirring effect of Example 4 is worse than that of Example 1, indicating that the isosceles triangular prism-shaped stirring paddle 144 of the present invention has a better stirring effect than the ordinary plate-shaped stirring paddle 144 due to its bidirectional reciprocating rotation. The seed crystal connection device provided by the present invention utilizes a tenon and mortise structure (slot 122, groove 112 and limiting member 130) to lock the seed crystal shaft 110 and the seed crystal base 120 relative to each other, so that the seed crystal base 120 will not be unscrewed when the seed crystal shaft 110 is reversed.

[0060] In a preferred embodiment, a stirring component connected to the seed crystal base is provided, which can better stir the silicon liquid during the rotation of the seed crystal shaft, resulting in better uniformity of silicon alloy mixing.

[0061] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A seed crystal connection device, characterized in that, Includes a seed crystal shaft, a seed crystal base, and at least one limiting component; One end of the seed crystal shaft is provided with a threaded connection part at the shaft center position, and a threaded hole is provided at the center of one side of the seed crystal base. The threaded connection part is inserted into the threaded hole, so that the seed crystal shaft and the seed crystal base are connected by threads. At least one groove is provided on the peripheral wall of the end of the seed crystal shaft near the threaded connection portion, and each groove extends along the length direction of the seed crystal shaft to penetrate the end face of the seed crystal shaft. The seed crystal base is provided with at least one slot on the side facing the seed crystal axis. The position of each slot corresponds to one of the cutting grooves. Each cutting groove and the corresponding slot are connected to form a limiting groove. The limiting member is inserted into the limiting groove through the cutting groove. One end of the limiting member in the limiting groove is located in the slot, and the other end is located in the cutting groove.

2. The seed crystal connection device according to claim 1, characterized in that, Includes at least one of the following features (1) and (2): (1) The number of the cutting grooves is 2, and the two cutting grooves are symmetrically arranged about the axis of the seed crystal axis; (2) The limiting member is located at one end of the groove, and a strip groove is provided on the outward wall surface to facilitate its picking.

3. The seed crystal connection device according to claim 1, characterized in that, The seed crystal connecting device also includes at least one set of stirring components; Each set of stirring components includes: A horizontal arm is attached to and connected to the seed crystal base. Two connecting arms are arranged opposite each other, with one end of each connecting arm connected to one end of the cross arm and the other end extending away from the seed crystal axis; Two agitators, each agitator being located between the two connecting arms, each agitator being connected to one end of one connecting arm away from the cross arm.

4. The seed crystal connection device according to claim 3, characterized in that, The cross arm is disposed on the side of the seed crystal base facing the seed crystal axis, and the cross arm is connected to the seed crystal base by multiple bolts.

5. The seed crystal connection device according to claim 4, characterized in that, The middle part of the horizontal arm is an annular shape, which fits around the seed crystal axis; Optionally, the seed crystal base is provided with a mating groove of the same shape as the horizontal arm on the side facing the seed crystal axis, and the horizontal arm is embedded in the mating groove.

6. The seed crystal connection device according to claim 3, characterized in that, Each of the stirring paddles is triangular prism in shape, with one end face of the stirring paddle connected to the inner side of the end of the connecting arm, and the other end of the stirring paddle extending toward the opposite connecting arm. The shape of the cross section of the stirring paddle perpendicular to its length direction is an isosceles triangle, and the two walls of the stirring paddle corresponding to the two legs of the isosceles triangle are symmetrical about the axis of the seed crystal.

7. The seed crystal connection device according to claim 6, characterized in that, The height of the isosceles triangle is 20~50mm, and the length of the stirring paddle is less than or equal to the radius of the seed crystal; When using 6-inch seed crystals, the length of the stirring paddle is 30~75mm; When using 8-inch seed crystals, the length of the stirring paddle is 30~100mm; When using 12-inch seed crystals, the length of the stirring paddle is 30~150mm.

8. The seed crystal connection device according to any one of claims 1 to 7, characterized in that, All parts in the seed crystal connecting device are made of graphite.

9. A method for liquid-phase growth of silicon carbide, characterized in that, The liquid phase growth of silicon carbide is performed using the seed crystal connection device as described in any one of claims 1 to 8, and the stirring method is alternating between forward and reverse rotation.

10. The silicon carbide liquid phase growth method according to claim 9, characterized in that, The stirring method is as follows: The stirring speed and direction are set to change periodically, with one cycle time being T, where T is 40~80s; Within one cycle, the stirring speed gradually increases from 0 to a in the forward direction, then gradually decreases to 0 in the forward direction, then gradually increases to a in the reverse direction, and then gradually decreases to 0 in the reverse direction, and so on. a is 20~100rpm.

Images