A splicing structure for expanding the diameter of silicon carbide seed crystal, a manufacturing method and silicon carbide crystal

Abstract

The present invention relates to the field of seed crystal technology, and in particular to a splicing structure for expanding the diameter of a silicon carbide seed crystal, a manufacturing method, and a silicon carbide crystal. The splicing structure cuts the seed crystal from three selected cutting directions, so as to keep the parts of the spliced ​​silicon carbide crystal in the same crystal direction, and performs specific angle grinding at the cutting position, which not only realizes the successful splicing of large-size seed crystals, but also eliminates the inheritance effect of cracks in the growth of silicon carbide single crystals. The splicing structure in the present invention is suitable for the expansion of substrate sizes such as 6-inch substrates to 8-inch substrates and 8-inch substrates to 12-inch substrates. The silicon carbide ingot grown after the expansion of the splicing structure is in the same crystal direction, which reduces the generation of grain boundaries, and after the angle grinding treatment, the influence of cracks at the splicing position is reduced, thereby ensuring the quality of the upper part of the crystal grown out of the ingot; and the expansion degree is large, which meets the expansion requirements of silicon carbide of various sizes.

Description

Technical Field

[0001] The present invention relates to the technical field of seed crystals, and in particular to a splicing structure for expanding the diameter of a silicon carbide seed crystal, a manufacturing method and a silicon carbide crystal. Background Art

[0002] At present, the size of conductive silicon carbide substrates is mainly 6-inch silicon carbide substrates, and they are gradually being developed towards 8-inch silicon carbide substrates; semi-insulating silicon carbide substrates are mainly 4-inch silicon carbide substrates, and they are gradually being developed towards 6-inch silicon carbide substrates. The area of ​​6-inch substrates is 2.25 times that of 4-inch substrates, and the area of ​​8-inch substrates is 4 times that of 4-inch substrates.

[0003] The multiple increase in substrate area within the same crystal preparation time leads to a significant reduction in substrate cost. At the same time, the number of chips prepared on a single substrate increases with the increase in substrate size, and the cost per chip decreases accordingly. Therefore, both conductive silicon carbide substrates and semi-insulating silicon carbide substrates are developing towards large-sized silicon carbide substrates.

[0004] Generally speaking, there are two methods for diameter expansion used in the growth of silicon carbide single crystals: one is direct diameter expansion growth through seed crystal splicing pieces, and the other is seed crystal splicing growth.

[0005] The seed crystal splicing piece is used to directly expand the diameter and then the expanded single crystal is used as the seed crystal to continue the expansion and growth, and the expansion is repeated until the target size is reached. The seed crystal splicing piece direct expansion method has a long cycle and low efficiency.

[0006] The seed crystal splicing growth method has the advantage of being time-saving. This method cuts seed crystal splicing pieces and then splices them into large-sized seed crystals for subsequent crystal growth. There are cracks at the seed crystal splicing. The presence of cracks will cause the cracks to continue in the growing single crystal, causing the subsequent single crystal to easily produce a large number of microtubes. If only the area of ​​the seed crystal after splicing is required to meet the requirements, the seed crystal splicing will increase the generation of grain boundaries in the subsequent grown crystal, deteriorate the quality of the crystal, and make it difficult to meet the substrate requirements for device preparation. Summary of the invention

[0007] In order to overcome the defect that cracks are inherited during the growth of silicon carbide single crystals, the present invention provides a splicing structure for expanding the diameter of a silicon carbide seed crystal, a manufacturing method and a silicon carbide crystal.

[0008] To achieve the above object, the present invention provides a silicon carbide seed crystal diameter expansion splicing structure, comprising:

[0009] The invention discloses a seed crystal splicing piece having a fan-shaped structure with 6 vertex angles of 60°, wherein the seed crystal splicing piece is formed by cutting 6 identical small seed chips along different crystal plane directions, the fan-shaped structure is a fan-shaped structure formed by cutting small seed chips along cutting edges of equal length, the seed crystal splicing piece having a fan-shaped structure with a vertex angle of 60° is inscribed in the small seed chip, and the entire splicing structure formed after splicing the 6 seed crystal splicing pieces having a fan-shaped structure with a vertex angle of 60° is in the same crystal plane direction.

[0010] Optionally, the small seed chips are formed by cutting along the most densely packed crystal planes in the longitudinal direction.

[0011] Optionally, the seed crystal splicing pieces are respectively the first seed crystal splicing piece to the sixth seed crystal splicing piece, and the crystal planes of the first seed crystal splicing piece to the sixth seed crystal splicing piece have three crystal plane cutting directions, which are respectively the first crystal plane cutting direction, the second crystal plane cutting direction, and the third crystal plane cutting direction, and the cutting edges of adjacent seed crystal splicing pieces have the same crystal plane cutting direction.

[0012] Optionally, the first seed crystal splicing piece has a first crystal plane cutting direction and a second crystal plane cutting direction, the second seed crystal splicing piece has a second crystal plane cutting direction and a third crystal plane cutting direction; the third seed crystal splicing piece has a third crystal plane cutting direction and a first crystal plane cutting direction; the fourth seed crystal splicing piece has a first crystal plane cutting direction and a second crystal plane cutting direction; the fifth seed crystal splicing piece has a second crystal plane cutting direction and a third crystal plane cutting direction; the sixth seed crystal splicing piece has a third crystal plane cutting direction and a first crystal plane cutting direction.

[0013] Optionally, the cutting edges of the seed crystal splicing pieces have a grinding structure, and the two cutting edges of each seed crystal splicing piece are both ground upward at one side and ground downward at the other side, and the angles of the upward grinding angle and the downward grinding angle are equal. The cutting edges of adjacent seed crystal splicing pieces have one upward grinding angle and the other downward grinding angle, and the upward grinding angle fits the downward grinding angle.

[0014] A silicon carbide crystal comprises: a splicing structure of the silicon carbide seed crystal with an expanded diameter as described above and a silicon carbide crystal structure grown on the surface of the splicing structure, wherein the silicon carbide crystal structure is an integral structure.

[0015] Optionally, the lengths of the cutting edges of the first to sixth seed crystal splicing pieces are equal, the length of the cutting edge of the seed crystal splicing piece is the radius of the silicon carbide crystal, the diameter of the small seed crystal piece is the diameter of the seed crystal splicing piece, and the diameter of the silicon carbide crystal is 1 / 2 of the diameter of the small seed crystal piece. times.

[0016] A method for manufacturing a splicing structure of a silicon carbide seed crystal with an expanded diameter, comprising:

[0017] Provide 6 identical small seed wafers;

[0018] Cutting the six small seed crystal pieces along a specific crystal plane cutting direction into six seed crystal splicing pieces with a fan-shaped structure and equal cutting edges, wherein the seed crystal splicing pieces are inscribed in the small seed crystal pieces;

[0019] Grinding the cutting edge of the seed crystal splicing sheet so that the cutting edge has an inclined structure;

[0020] The seed crystal splicing pieces after the grinding process are spliced ​​to form a splicing structure with an enlarged seed crystal diameter, wherein the diameter of the splicing structure is 1 / 2 of the diameter of the small seed crystal piece. times;

[0021] The spliced ​​structure is placed in a single crystal growth furnace for growth to form a crystal.

[0022] Optionally, it is characterized in that the two cutting edges of each seed crystal splicing piece are ground by an angle grinding process so that one side of the seed crystal splicing piece has an upward grinding angle and the other side has a downward grinding angle, and the angles of the upward grinding angle and the downward grinding angle are equal, so that the upward grinding angle and the downward grinding angle of the cutting edges of every two adjacent seed crystal splicing pieces are in line with each other.

[0023] Optionally, the angle grinding process is performed using a frustum-type diamond wheel angle grinding device.

[0024] In summary, the advantages and beneficial effects of the present invention are:

[0025] The present invention provides a splicing structure, a manufacturing method and a silicon carbide crystal for expanding the diameter of a silicon carbide seed crystal. The splicing structure improves the cutting and splicing process of the seed crystal, cuts the seed crystal from three selected cutting directions, thereby keeping the parts of the spliced ​​silicon carbide crystal in the same crystal direction, and performs specific grinding at the cutting position, which not only realizes the successful splicing of large-size seed crystals, but also eliminates the inheritance effect of cracks in the growth of silicon carbide single crystals. The splicing structure in the present invention is suitable for expanding the diameter of a 6-inch substrate to an 8-inch substrate, an 8-inch substrate to a 12-inch substrate, and other substrate sizes.

[0026] The silicon carbide ingot grown after diameter expansion by using the splicing structure is in the same crystal direction, reducing the generation of grain boundaries; and after angle grinding, the influence of cracks at the splicing is reduced, ensuring the quality of the upper part of the crystal grown in the ingot; and the diameter expansion degree is large, meeting the diameter expansion requirements of silicon carbide of various sizes. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1The figure shows a schematic structural diagram of a seed crystal splicing sheet in the crystal plane direction of a splicing structure of a silicon carbide seed crystal with an expanded diameter in an embodiment of the present invention;

[0028] Figure 2 The figure shows a cross-sectional view of the joint of the seed crystal splicing pieces after the angle is ground in a splicing structure of a silicon carbide seed crystal expansion in an embodiment of the present invention;

[0029] Figure 3 The figure shows a schematic diagram of the crystal plane direction structure of a silicon carbide crystal in an embodiment of the present invention;

[0030] Figure 4 It is a schematic diagram of a process of manufacturing a splicing structure of a silicon carbide seed crystal with an expanded diameter according to an embodiment of the present invention;

[0031] Figure 5 The figure shows a schematic diagram of the cutting direction of a seed crystal splicing piece of a splicing structure with an expanded diameter of a silicon carbide seed crystal in an embodiment of the present invention;

[0032] Figure 6 It is a schematic diagram of an angle grinding device for a method of manufacturing a splicing structure with a silicon carbide seed crystal expansion in an embodiment of the present invention;

[0033] Figure 7 It is a schematic diagram of the angle grinding process of a method for manufacturing a splicing structure with an expanded diameter of a silicon carbide seed crystal in an embodiment of the present invention. DETAILED DESCRIPTION

[0034] In order to facilitate understanding by those skilled in the art, the present invention will be further described in detail below with reference to specific embodiments.

[0035] The embodiment of the present invention provides a splicing structure for expanding the diameter of a silicon carbide seed crystal, please refer to Figure 1 ,include:

[0036] The invention discloses 6 seed crystal splicing pieces, wherein the seed crystal splicing pieces are formed by cutting 6 identical small seed crystal pieces along different crystal plane directions, the seed crystal splicing piece is inscribed in the small seed crystal pieces, the seed crystal splicing piece has a fan shape, the top angle of the seed crystal splicing piece is 60°, the side lengths of the cut edges of the 6 seed crystal splicing pieces are equal, and the entire splicing structure formed after the 6 seed crystal splicing pieces are spliced ​​together is in the same crystal plane direction.

[0037] Specifically, in the embodiment of the present invention, the small seed crystal pieces are formed by cutting along the most densely packed crystal planes in the longitudinal direction.

[0038] The crystal plane of the longitudinal most densely packed plane has the least unsaturated bonds and the lowest surface energy, and is therefore the most stable, thus reducing the adsorption of impurities and the generation of polycrystals during growth.

[0039] The determination of the most densely packed crystal plane facilitates the determination of the cutting direction, while ensuring that the seed crystal splicing pieces are in the same crystal plane direction, thereby avoiding the occurrence of large grain boundaries at the splicing locations of the subsequently grown silicon carbide crystals.

[0040] The six seed crystal splicing pieces are cut into a fan-shaped structure with a vertex angle of 60°, and the vertex angle serves as the central angle of the splicing structure.

[0041] In an embodiment of the present invention, the six seed crystal splicing pieces are respectively the first seed crystal splicing piece 10 to the sixth seed crystal splicing piece 60, and the crystal planes of the first seed crystal splicing piece 10 to the sixth seed crystal splicing piece 60 have three crystal plane cutting directions, which are respectively the first crystal plane cutting direction 100, the second crystal plane cutting direction 200, and the third crystal plane cutting direction 300, and the cutting edges of adjacent seed crystal splicing pieces have the same crystal plane cutting direction.

[0042] The three cutting directions in the process of cutting the small seed pieces into the seed crystal splicing pieces are in the same crystal plane direction, so that the parts of the splicing structure formed after the seed crystal splicing pieces are in the same crystal plane direction, avoiding the generation of grain boundaries of the subsequently grown silicon carbide crystals.

[0043] The included angles of the three cutting directions are all 60°. This cutting angle maximizes the utilization rate of the small seed wafer and realizes the splicing structure of the largest size.

[0044] The sum of the degrees of the six seed crystal splicing pieces with a vertex angle of 60° is 360°, and the spliced ​​structure is a circular splicing structure, which facilitates the formation of the silicon carbide circular structure.

[0045] The 60-degree cutting angle maximizes the utilization rate of the small seed chips, enabling the direct expansion of an 8-inch silicon carbide crystal into a 12-inch silicon carbide crystal, while ensuring that the hexagonal crystal system small seed chips are cut with the most densely packed surface.

[0046] In the embodiment of the present invention, the first seed crystal splicing piece 10 has a first crystal plane cutting direction 100 and a second crystal plane cutting direction 200, the second seed crystal splicing piece 20 has a second crystal plane cutting direction 200 and a third crystal plane cutting direction 300; the third seed crystal splicing piece 30 has a third crystal plane cutting direction 300 and a first crystal plane cutting direction 100; the fourth seed crystal splicing piece 40 has a first crystal plane cutting direction 100 and a second crystal plane cutting direction 200; the fifth seed crystal splicing piece 50 has a second crystal plane cutting direction 200 and a third crystal plane cutting direction 300; the sixth seed crystal splicing piece 60 has a third crystal plane cutting direction 300 and a first crystal plane cutting direction 100.

[0047] After the seed crystal splicing pieces are spliced ​​together, the splicing structure is formed, thereby achieving the diameter expansion of the silicon carbide seed crystal.

[0048] In an embodiment of the present invention, the cutting edge of the seed crystal splicing piece has a grinding structure.

[0049] In the embodiment of the present invention, the cut seed crystal splicing pieces are subjected to angle grinding, and the two cutting edges of each seed crystal splicing piece are ground upward at an angle of 400 on one side and ground downward at an angle of 500 on the other side, and the angles of the upward grinding angle 400 and the downward grinding angle 500 are equal.

[0050] In the embodiment of the present invention, please refer to Figure 2 The cutting edges of the adjacent seed crystal splicing pieces are the connecting parts of the splicing structure. The cutting edges of the two seed crystal splicing pieces at the connecting parts have an upward grinding angle of 400 and a downward grinding angle of 500. The upward grinding angle 400 fits the downward grinding angle 500.

[0051] In the embodiment of the present invention, the first crystal plane cutting direction 100 of the first seed crystal splicing piece 10 has an upward grinding angle 400, and the second crystal plane cutting direction 200 has a downward grinding angle 500, the second crystal plane cutting direction 200 of the second seed crystal splicing piece 20 has an upward grinding angle 400, and the third crystal plane cutting direction 300 has a downward grinding angle 500; the third crystal plane cutting direction 300 of the third seed crystal splicing piece 30 has an upward grinding angle 400, and the first crystal plane cutting direction 100 has a downward grinding angle Angle 500; the fourth seed crystal splicing piece 40 has an upward grinding angle 400 in the first crystal cutting plane direction 100, and a downward grinding angle 500 in the second crystal cutting direction 200; the fifth seed crystal splicing piece 50 has an upward grinding angle 400 in the second crystal cutting direction 200, and a downward grinding angle 500 in the third crystal cutting direction 300; the sixth seed crystal splicing piece 60 has an upward grinding angle 400 in the third crystal cutting direction 300, and a downward grinding angle 500 in the first crystal cutting direction 100.

[0052] The cracks between the seed crystal splicing pieces after the angle grinding treatment are tilted in the inheritance direction, and the joints of the adjacent seed crystal splicing pieces are also tilted. The atomic accumulation during the growth of the single crystal will accumulate along the tilted direction, thereby changing the crack inheritance direction, eliminating the influence of the cracks on the growth of the silicon carbide crystal, reducing the length of the cracks in the axial direction of the ingot during the growth of the silicon carbide crystal, and increasing the volume of the silicon carbide single crystal with good quality grown, thereby ensuring the quality of the subsequent ingot area.

[0053] In the embodiment of the present invention, the spliced ​​structure is placed in a single crystal growth furnace for growth to form silicon carbide crystals.

[0054] In an embodiment of the present invention, a silicon carbide crystal is provided, comprising the above-mentioned splicing structure of the silicon carbide seed crystal with an expanded diameter and a silicon carbide crystal structure grown on the surface of the splicing structure, wherein the silicon carbide crystal structure is an integral structure.

[0055] In the embodiment of the present invention, please refer to Figure 3 The lengths of the cutting edges of the first to sixth seed crystal splicing pieces are equal, the length of the cutting edge of the seed crystal splicing piece is the radius of the silicon carbide crystal, the diameter of the small seed crystal piece is the diameter of the seed crystal splicing piece, and the diameter of the silicon carbide crystal is 1 / 2 of the diameter of the small seed crystal piece. times.

[0056] The splicing structure completed by splicing the seed crystal splicing pieces obtains a large-sized silicon carbide seed crystal, realizes the diameter expansion of the silicon carbide seed crystal, and makes the diameter of the silicon carbide crystal expand. times, increasing the size of the silicon carbide crystal.

[0057] In the embodiment of the present invention, please refer to Figure 4 , a method for manufacturing a splicing structure of a silicon carbide seed crystal with an expanded diameter, comprising:

[0058] Step S10, providing 6 identical small seed wafers;

[0059] Step S20, cutting the six small seed crystal sheets along a specific crystal plane cutting direction into six seed crystal splicing sheets with a fan-shaped structure and equal cutting edges with a vertex angle of 60°, wherein the seed crystal splicing sheets are inscribed in the small seed crystal sheets;

[0060] Step S30, grinding the cut edge of the seed crystal splicing sheet so that the cut edge has an inclined structure;

[0061] Step S40, splicing the seed crystal splicing pieces after the angle grinding process to form a splicing structure with an enlarged seed crystal diameter, wherein the diameter of the splicing structure is 1 / 2 of the diameter of the small seed crystal piece. times;

[0062] Step S50, placing the spliced ​​structure into a single crystal growth furnace for growth to form a silicon carbide crystal.

[0063] Specifically, step S10 is performed to provide 6 identical small seed wafers.

[0064] In the embodiment of the present invention, the small seed crystal pieces are formed by cutting along the most densely packed crystal planes in the longitudinal direction.

[0065] The crystal plane of the longitudinal most densely packed plane has the least unsaturated bonds and the lowest surface energy, and is therefore the most stable, thus reducing the adsorption of impurities and the generation of polycrystals during growth.

[0066] Execute step S20, cut the six small seed crystal pieces along a specific crystal plane cutting direction to form six seed crystal splicing pieces with a fan-shaped structure and equal cutting edges with a vertex angle of 60°, wherein the seed crystal splicing pieces are inscribed in the small seed crystal pieces.

[0067] In the embodiment of the present invention, the specific crystal plane cutting directions are respectively the first to third crystal plane cutting directions, the first crystal plane cutting direction 100 is (-12-10), the second crystal plane cutting direction 200 is (-2110), and the third crystal plane cutting direction 300 is (11-20).

[0068] The cutting direction is the same crystal plane direction, so that the parts of the spliced ​​structure formed after the seed crystal splicing pieces are spliced ​​are in the same crystal plane direction, avoiding the generation of grain boundaries of the subsequently grown silicon carbide crystals.

[0069] In the embodiment of the present invention, please refer to Figure 5 The first seed crystal splicing piece 10 has a cutting direction of (-12-10) and a cutting direction of (-2110), the second seed crystal splicing piece 20 has a cutting direction of (-2110) and a cutting direction of (11-20); the third seed crystal splicing piece 30 has a cutting direction of (11-20) and a cutting direction of (-12-10); the fourth seed crystal splicing piece 40 has a cutting direction of (-12-10) and a cutting direction of (-2110); the fifth seed crystal splicing piece 50 has a cutting direction of (-2110) and a cutting direction of (11-20); the sixth seed crystal splicing piece 60 has a cutting direction of (11-20) and a cutting direction of (-12-10).

[0070] Step S30 is executed to grind the cut edge of the seed crystal splicing sheet so that the cut edge has an inclined structure.

[0071] In an embodiment of the present invention, the two cutting edges of each seed crystal splicing piece are ground through an angle grinding process so that one side of the seed crystal splicing piece has an upward grinding angle and the other side has a downward grinding angle, and the angles of the upward grinding angle and the downward grinding angle are equal, so that the upward grinding angle and the downward grinding angle of the cutting edges of every two adjacent seed crystal splicing pieces are in line with each other.

[0072] In the embodiment of the present invention, please refer to Figure 6 The angle grinding process is performed using a frustum-type diamond wheel angle grinding device.

[0073] In the embodiment of the present invention, the frustoconical diamond grinding wheel comprises: a diamond grinding wheel 700 and a central through hole 600. The diamond grinding wheel 700 comprises a base 710 and an outer abrasive layer 720. The central through hole 600 has a connecting shaft inside, which enables the frustoconical diamond grinding wheel 700 to rotate; the base 710 is made of alloy and serves as a carrier of the outer abrasive layer 720; the outer abrasive layer 720 is located on the surface of the base 710, and the components of the outer abrasive layer 720 include diamond and a binder.

[0074] In the embodiment of the present invention, the mesh number of the diamond should be less than 1000 mesh, so that the cutting edge of the small seed crystal sheet can be polished flat and smooth.

[0075] In the embodiment of the present invention, the grinding angle of the small seed wafer is used as the angle for manufacturing the frustoconical diamond grinding wheel, and the angle of the frustoconical diamond grinding wheel is the angle of the side surface of the diamond grinding wheel 700 .

[0076] In the embodiment of the present invention, the present invention takes the first seed crystal splicing sheet 10 as an example, please refer to Figure 7 The angle grinding process includes: fixing the cut first seed crystal splicing piece 10, and using the high-speed rotating frustum-shaped diamond grinding wheel to grind the cutting edge position of the first seed crystal splicing piece 10 back and forth, so that the angle of the cutting edge of the first seed crystal splicing piece 10 is the same as the angle of the frustum-shaped diamond grinding wheel.

[0077] In the embodiment of the present invention, the first seed crystal splicing sheet 10 is fixed by a vacuum suction cup.

[0078] In the embodiment of the present invention, during the angle grinding process, cold water spraying is used to reduce the temperature of the contact surface to avoid excessive temperature affecting the material structure of the seed crystal splicing sheet, thereby achieving a better angle grinding effect.

[0079] In other embodiments of the present invention, the angle grinding device is other suitable equipment, and the angle grinding angle is determined by the angle grinding device.

[0080] Step S40 is executed to splice the seed crystal splicing pieces after the angle grinding process to form a splicing structure.

[0081] Execute step S50 to place the spliced ​​structure into a single crystal growth furnace for growth to form a silicon carbide crystal.

[0082] The above-mentioned diameter expansion method can be repeated multiple times, and the silicon carbide crystal obtained by the diameter expansion can be used as a seed crystal and then directly grown to obtain a higher quality ingot.

[0083] Finally, it is to be noted that any modification or equivalent replacement of part or all of the technical features based on the device structure of the present invention and the technical solution of the described embodiment, which does not deviate from the essence of the corresponding technical solution of the present invention, belongs to the patent scope of the device structure of the present invention and the described implementation scheme.

Claims

1. A splicing structure for expanding the diameter of a silicon carbide seed crystal, characterized in that: include: A seed crystal splicing piece with 6 fan-shaped structures with vertex angles of 60°, the seed crystal splicing piece is formed by cutting 6 completely identical small seed chips along different crystal plane directions, the fan-shaped structure is a fan-shaped structure formed by cutting small seed chips along cutting edges of equal length, the seed crystal splicing piece with a fan-shaped structure with a vertex angle of 60° is inscribed inwardly with the small seed chips, and the entire splicing structure formed after splicing the 6 fan-shaped seed crystal splicing pieces with vertex angles of 60° has the same crystal plane direction, wherein the seed crystal splicing pieces are respectively the first seed crystal splicing piece to the sixth seed crystal splicing piece, the crystal planes of the first seed crystal splicing piece to the sixth seed crystal splicing piece have three crystal plane cutting directions, the crystal plane cutting directions are respectively the first crystal plane cutting direction, the second crystal plane cutting direction, and the third crystal plane cutting direction, the cutting edges of adjacent seed crystal splicing pieces have the same crystal plane cutting direction, and the first seed crystal splicing piece The piece has a first crystal plane cutting direction and a second crystal plane cutting direction, the second seed crystal splicing piece has a second crystal plane cutting direction and a third crystal plane cutting direction, the third seed crystal splicing piece has a third crystal plane cutting direction and a first crystal plane cutting direction, the fourth seed crystal splicing piece has a first crystal plane cutting direction and a second crystal plane cutting direction, the fifth seed crystal splicing piece has a second crystal plane cutting direction and a third crystal plane cutting direction, and the sixth seed crystal splicing piece has a third crystal plane cutting direction and a first crystal plane cutting direction; the cutting edges of the seed crystal splicing pieces have an angle grinding structure, and the two cutting edges of each of the seed crystal splicing pieces are both one side ground upward and the other side ground downward, and the angle of the upward grinding angle is equal to the angle of the downward grinding angle, and the cutting edges of the adjacent seed crystal splicing pieces are one upward grinding angle and the other downward grinding angle, and the upward grinding angle is in contact with the downward grinding angle.

2. A silicon carbide seed crystal expansion splicing structure as claimed in claim 1, characterized in that: The small seed pieces are formed by cutting along the most densely packed crystal planes in the longitudinal direction.

3. A silicon carbide crystal, characterized in that: include: The silicon carbide seed crystal expansion splicing structure as described in any one of claims 1 to 2 and the silicon carbide crystal structure grown on the surface of the splicing structure.

4. A silicon carbide crystal according to claim 3, characterized in that: The lengths of the cutting edges of the first to sixth seed crystal splicing pieces are equal, the length of the cutting edges of the seed crystal splicing pieces is the radius of the silicon carbide crystal, and the diameter of the small seed crystal piece is the diameter of the seed crystal splicing piece.

5. A method for manufacturing a splicing structure of a silicon carbide seed crystal with an expanded diameter as claimed in any one of claims 1 to 2, characterized in that: include: Provide 6 identical small seed wafers; Cut the six small seed crystal pieces along a specific crystal plane cutting direction to form six seed crystal splicing pieces with a fan-shaped structure and equal cutting edges, wherein the seed crystal splicing piece is inscribed in the small seed crystal piece, wherein the specific crystal plane cutting directions are the first to third crystal plane cutting directions, the first crystal plane cutting direction is (-12-10), the second crystal plane cutting direction is (-2110), and the third crystal plane cutting direction is (11-20); Grinding the cutting edge of the seed crystal splicing sheet so that the cutting edge has an inclined structure; The seed crystal splicing pieces after the angle grinding process are spliced ​​together to form a splicing structure with an expanded seed crystal diameter.

6. The method for manufacturing a silicon carbide seed crystal expansion splicing structure according to claim 5, characterized in that: The two cutting edges of each seed crystal splicing piece are ground through the grinding process so that one side of the seed crystal splicing piece has an upward grinding angle and the other side has a downward grinding angle, and the angles of the upward grinding angle and the downward grinding angle are equal, so that the upward grinding angle and the downward grinding angle of the cutting edges of every two adjacent seed crystal splicing pieces are in line with each other.

7. The method for manufacturing a silicon carbide seed crystal expansion splicing structure according to claim 6, characterized in that: The angle grinding process is performed by using a frustum-type diamond wheel angle grinding device.

8. A method for preparing silicon carbide crystal according to any one of claims 3 to 4, characterized in that: include: Provide 6 identical small seed wafers; Cut the six small seed crystal pieces along a specific crystal plane cutting direction to form six seed crystal splicing pieces with a fan-shaped structure and equal cutting edges, wherein the seed crystal splicing piece is inscribed in the small seed crystal piece, wherein the specific crystal plane cutting directions are the first to third crystal plane cutting directions, the first crystal plane cutting direction is (-12-10), the second crystal plane cutting direction is (-2110), and the third crystal plane cutting direction is (11-20); Grinding the cutting edge of the seed crystal splicing sheet so that the cutting edge has an inclined structure; Splicing the seed crystal splicing pieces after the angle grinding process to form a splicing structure with an expanded seed crystal diameter; The spliced ​​structure is placed in a single crystal growth furnace for growth to form a crystal.

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