Growth device and growth method for silicon carbide single crystal

Abstract

The present application relates to the technical field of silicon carbide crystal growth, and in particular to a growth device and growth method for a silicon carbide single crystal. The growth device comprises a crucible part and a heating part. The crucible part comprises a first crucible part and a second crucible part that are coaxially arranged from top to bottom; a seed crystal accommodating part is arranged in the middle of the top of the first crucible part; the second crucible part is provided with a cavity, and the cavity is a raw material accommodating part; the outer diameter of the first crucible part is less than that of the second crucible part; and the middle of the bottom of the second crucible part is recessed towards the first crucible part to form a recess. The heating part comprises a first heating part, a second heating part and a third heating part; the first heating part is arranged in the recess in the circumferential direction, the second heating part is arranged outside the second crucible part in the circumferential direction, the third heating part is arranged outside the first crucible part in the circumferential direction, and the inner diameter of the third heating part is less than that of the second crucible part. The growth device of the present application can reduce the defects such as inclusions, dislocation density, and microtubes in the silicon carbide single crystal, and improve the internal quality of the crystal.

Description

Silicon carbide single crystal growth device and growth method

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to Chinese patent application number 202310651590.3, filed with the Patent Office of China on June 5, 2023, entitled “A Growth Device and Growth Method for Silicon Carbide Single Crystal,” the entire contents of which are incorporated by reference into this application. Technical Field

[0003] The present application belongs to the technical field of silicon carbide crystal growth, and specifically relates to a growth device and a growth method for a silicon carbide single crystal. Background Art

[0004] Physical vapor transport (PVT) is currently the main method for industrially growing silicon carbide crystals. Specifically, the gas generated by the sublimation and decomposition of silicon carbide raw materials is transported to the surface of the seed crystal for recrystallization to obtain a larger silicon carbide single crystal.

[0005] However, at high temperatures, silicon elements and silicon-rich atomic groups are more likely to escape from the raw materials, causing carbonization of the raw materials. Severely carbonized raw materials will produce carbon dust, which will follow the airflow and be deposited on the crystal growth interface to form inclusion defects. The inclusion defects will further grow into larger defects such as screw dislocations, stacking faults and microtubes, seriously affecting the crystal quality of silicon carbide. Especially when growing large-sized crystals, the radial temperature gradient of the raw materials increases with the diameter of the crucible, and the carbonization of the raw materials in the high-temperature zone tends to be serious, resulting in a further increase in the number and volume of inclusions in the crystals. In addition, when growing large-sized crystals, it is easy for the temperature gradient of the crystal to be too large, resulting in excessive internal stress in the crystal, inducing the generation of crystal defects such as dislocations, and in severe cases, the crystal may even crack.

[0006] Application Contents

[0007] The purpose of this application is to overcome the defects of inclusions, screw dislocations, stacking faults and micropipes in silicon carbide single crystals produced by the PVT method, as well as the defects of excessive internal stress in silicon carbide single crystals that induce dislocations and even crystal cracking, and to provide a growth device and growth method for silicon carbide single crystals. The growth device and growth method effectively reduce defects such as inclusions, screw dislocations, stacking faults and micropipes in silicon carbide single crystals and reduce internal stress.

[0008] To achieve the above objectives, in a first aspect, the present application provides a silicon carbide single crystal growth device, the device comprising a crucible portion and a heating portion:

[0009] The crucible portion includes a first crucible portion and a second crucible portion coaxially arranged from top to bottom, a seed crystal receiving portion is provided in the middle of the top of the first crucible portion, the second crucible portion has a cavity, and the cavity is a raw material receiving portion, the outer diameter of the first crucible portion is smaller than the outer diameter of the second crucible portion, and a groove is provided in the middle of the bottom of the second crucible portion, which is concave toward the first crucible portion;

[0010] The heating part is a graphite heating part, and the heating part includes a first heating part, a second heating part and a third heating part;

[0011] The first heating part is arranged in the groove and is arranged along the circumference of the groove. The second heating part is arranged on the outside of the second crucible part and is arranged along the circumference of the second crucible part. The third heating part is arranged on the outside of the first crucible part and is arranged along the circumference of the first crucible part. The inner diameter of the third heating part is smaller than the outer diameter of the second crucible part.

[0012] Optionally, an arc-shaped protrusion is provided in the middle of the bottom of the groove, and the arc-shaped protrusion is provided on a side facing the first crucible part.

[0013] Optionally, the ratio of the outer diameter of the second crucible part to the outer diameter of the first crucible part is in the range of 1.05 to 4.0, the ratio of the inner diameter of the second heating part to the inner diameter of the third heating part is in the range of 1.05 to 4.0, and the ratio of the diameter of the seed crystal accommodating part to the inner diameter of the third heating part is in the range of 0.26 to 0.92.

[0014] Optionally, relative to the raw material charging reference plane of the second crucible part, the upper end of the second heating part is 10mm to 50mm higher than the raw material charging reference plane; the lower end of the second heating part is 20mm to 100mm lower than the lower end of the second crucible part.

[0015] Optionally, a vertical distance between a lower end of the third heating portion and an upper end of the second heating portion is 15 mm to 60 mm;

[0016] The upper end of the third heating part is higher than the upper end of the seed crystal accommodating space of the seed crystal accommodating part. An upper furnace cover is arranged above the first crucible part. The upper end of the third heating part is connected to a third electrode, and the third electrode is movably connected to the upper furnace cover.

[0017] Optionally, a lower furnace cover is provided below the second crucible portion, a first electrode is connected to the lower end of the first heating portion, and the first electrode is movably connected to the lower furnace cover;

[0018] A support column is connected to the middle of the bottom of the groove, and the support column is connected to the side away from the first crucible. The first heating part and the support column, the bottom of the groove and the side of the groove are spaced apart, and the spacing is 15mm to 40mm.

[0019] Optionally, the cross-section of the seed crystal receiving portion is circular.

[0020] Optionally, the first crucible part and the second crucible part are cylindrical.

[0021] Optionally, when the cross section of the groove is circular, the ratio of the diameter of the arc-shaped protrusion to the diameter of the groove bottom is 0.5-1.0, and the ratio of the height of the arc-shaped protrusion to the distance from the bottom of the groove facing the first crucible part to the raw material charging reference plane is 0.15-0.5.

[0022] Optionally, the lower end of the support column is connected to the rotating motor and the lifting motor.

[0023] Optionally, a heat-insulating layer is provided on the upper side of the first crucible part, the lower side of the second crucible part, the periphery of the second heating part and the third heating part.

[0024] In a second aspect, the present application provides a method for growing a silicon carbide single crystal using the growth apparatus of the first aspect, wherein the powers of the first heating unit, the second heating unit, and the third heating unit are P1, P2, and P3, respectively, and the growth method comprises the following steps:

[0025] Heating step: loading raw materials into the raw material receiving portion and securing the seed crystal in the seed crystal receiving portion; testing the airtightness of the furnace shell cavity formed by the upper furnace cover, the lower furnace cover, and the furnace barrel, and then evacuating the interior of the furnace shell cavity; heating the first, second, and third heating portions to a temperature of 2100° C. to 2200° C. at the top of the first crucible portion, wherein during the heating process, the relationship between P1, P2, and P3 is: P1 < P3 < P2, P2 > P1 + P3, and P1:P3 = 0.1 to 0.5;

[0026] Crystal growth step: performing a first adjustment, a second adjustment, a third adjustment and a fourth adjustment in sequence, wherein the first adjustment is to adjust the ratio of P1 and P2 so that the temperature difference between the raw material on the crucible side wall side and the raw material on the groove side of the second crucible part is less than 15°C, the second adjustment is to adjust P3 to adjust the ratio of P3 to P1+P2 so that the temperature of the upper surface of the raw material is 15°C to 80°C higher than the temperature of the lower surface of the seed crystal, the third adjustment is to adjust P3 so that the temperature difference between the seed crystal at the edge and the seed crystal in the middle is less than 20°C, and the fourth adjustment is to adjust the pressure inside the furnace shell cavity to 50Pa to 1500Pa so that the atomic groups volatilized from the raw material are crystallized and grown on the surface of the seed crystal, and the upper layer of the raw material with a preset thickness does not react;

[0027] Growth end step: perform the fifth adjustment, sixth adjustment and seventh adjustment in sequence, the fifth adjustment is to increase the pressure inside the furnace shell cavity to 2500Pa~20000Pa, the sixth adjustment is to adjust P1+P2 downward to reduce the axial temperature gradient of the silicon carbide single crystal, so that the axial temperature gradient between the lower surface of the silicon carbide single crystal and the upper surface of the silicon carbide single crystal is ≤20℃ / cm, and the seventh adjustment is to lower P1, P2 and P3 to make P1=P2=P3=0, wherein the interval between the sixth adjustment and the seventh adjustment is a preset time, and the preset time is more than 2h.

[0028] Optionally, the vacuum treatment includes, in sequence, using a mechanical pump to evacuate the furnace shell cavity so that the pressure inside is 0.1Pa to 5Pa, using a molecular pump to evacuate the furnace shell cavity so that the pressure inside is 10-2Pa to 10-4Pa, and heating the first heating part, the second heating part and the third heating part so that the temperature of the top of the first crucible part reaches 750℃ to 850℃.

[0029] Optionally, the heating step further includes, when the temperature of the top of the first crucible portion reaches 900° C. to 1100° C., adjusting and maintaining the pressure inside the furnace shell cavity to 10,000 Pa to 20,000 Pa.

[0030] Optionally, the fourth adjustment also includes an eighth adjustment, which includes: when the ratio of P1 to P2 is constant, adjusting P1+P2 upward so that the temperature difference between the upper surface of the raw material and the lower surface of the silicon carbide single crystal increases at a rate of 0.5℃ / h to 5.0℃ / h, so that the temperature of the upper surface of the raw material is 30 to 100℃ higher than the temperature of the lower surface of the silicon carbide single crystal.

[0031] Optionally, a ninth adjustment is included between the third adjustment and the fourth adjustment. The ninth adjustment is to adjust the position of the second crucible part by the lifting motor so that the temperature of the lower part of the raw material is higher than the temperature of the upper part of the raw material, and the temperature difference is controlled within 15°C.

[0032] The present application sets a groove sunken toward the first crucible part in the middle of the bottom of the second crucible part, and sets a first heating part circumferentially in the groove. During the growth of the silicon carbide single crystal, the raw material can be heated to avoid the formation of a crystallization zone in the center. Furthermore, since the highest temperature point of the graphite heater is located near the center height of the heater, through the cooperation of the first heating part and the second heating part, during the growth of the silicon carbide single crystal, part of the raw material with a preset thickness in the upper layer can be prevented from reacting.

[0033] The present application arranges a first heating portion circumferentially within the groove, and the first heating portion within the groove cooperates with the second heating portion outside the second crucible portion, so that the raw material on the groove side and the raw material on the crucible side wall side of the second crucible portion are heated more evenly. During the growth process of the silicon carbide single crystal, it can avoid heating the outside alone, which may cause the local temperature on the outside to be too high, resulting in serious carbonization of the raw material, increased carbon dust, local carbon enrichment, carbon collapse and other problems, thereby reducing defects such as inclusions, screw dislocations, stacking faults and micropipes in the silicon carbide single crystal.

[0034] The present application makes the outer diameter of the first crucible part smaller than the outer diameter of the second crucible part, and sets a third heating part on the outside of the first crucible part. During the growth process of the silicon carbide single crystal, the radial temperature gradient of the formed silicon carbide single crystal can be adjusted to prevent the generation of dislocations due to excessive internal stress, and even defects such as crystal cracking. In addition, the temperature of the edge of the crystal can be increased to reduce the probability of edge polycrystalline and polymorphic. Furthermore, the inner diameter of the third heating part is smaller than the outer diameter of the second crucible part, so that the heat emitted by the third heating part is closer to the center of the upper surface of the raw material, reducing the heating of the outer edge of the raw material, thereby preventing carbonization of the raw material edge. At the same time, since the highest temperature point of the graphite heater is located near the center height of the heater, the heating of the raw material edge by the third heating part and the second heating part will not form a severely carbonized area, but will form an unreacted area.

[0035] The present application can prevent part of the raw material with a preset thickness on the upper layer of the edge of the raw material from reacting through the cooperation of the graphite crucible structure, the second heating part and the third heating part. Through the cooperation of the first heating part and the second heating part, part of the raw material with a preset thickness on the upper layer of the middle part of the raw material will not form a crystallization zone due to local overcooling, but will form an unreacted area layer on the surface of the raw material. During the sublimation and recrystallization process of the raw material, the unreacted raw material itself acts as a filter layer to prevent carbon dust from entering the crystal growth chamber, thereby achieving the purpose of significantly reducing inclusions. During the growth of silicon carbide single crystals, the unreacted area layer formed on the surface of the raw material can be recycled and reused by removing free carbon and cleaning.

[0036] The present application provides a method for growing a silicon carbide single crystal. By limiting the relationship between the powers of the first heating unit, the second heating unit, and the third heating unit during the temperature increase step, the first adjustment, the second adjustment, the third adjustment, and the fourth adjustment are sequentially performed during the crystal growth stage. This allows a portion of the upper layer of raw material with a preset thickness to remain unreacted. The unreacted raw material serves as a filter layer to prevent carbon dust from entering the crystal growth chamber, thereby reducing defects such as inclusions, screw dislocations, stacking faults, and micropipes in the silicon carbide single crystal. After the growth is completed, the unreacted raw material can be recycled and reused after free carbon removal and cleaning. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following is a brief introduction to the drawings required for use in the embodiments. It should be understood that the following drawings only show certain embodiments of the present application 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 creative work.

[0038] FIG1 is a schematic structural diagram of an embodiment of a growth device of the present application.

[0039] FIG2 is a state distribution diagram of the raw materials after the growth completion step of Example 1 of the present application.

[0040] Description of Reference Numerals

[0041] 1-crucible part; 101-first crucible part; 102-second crucible part; 1021-groove; 1022-arc-shaped protrusion; 2-heating part; 201-first heating part; 202-second heating part; 203-third heating part; 3-seed crystal accommodating part; 4-raw material accommodating part; 5-raw material charging reference surface; 6-upper furnace cover; 7-third electrode; 8-lower furnace cover; 9-first electrode; 10-support column; 11-furnace drum; 12-second electrode; 13-rotating motor; 14-lifting motor; 15-insulation layer; 16-unreacted raw material area. DETAILED DESCRIPTION

[0042] 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.

[0043] The inventors of this application have discovered that, in the process of producing large-sized silicon carbide single crystals by physical vapor transport, carbon dust is easily deposited on the crystal growth interface, forming inclusion defects. The use of tantalum carbide powder, tantalum microporous blocks or porous graphite will significantly increase production costs or worsen the carbon / silicon element ratio. In addition, due to excessive internal stress in the silicon carbide single crystal, induced dislocations may occur, and even crystal cracking may occur.

[0044] In this regard, in a first aspect, the present application provides a silicon carbide single crystal growth device, the device comprising a crucible portion 1 and a heating portion 2, the crucible portion 1 comprising a first crucible portion 101 and a second crucible portion 102 coaxially arranged from top to bottom, a seed crystal receiving portion 3 being provided in the middle of the top of the first crucible portion 101, the second crucible portion 102 having a cavity, which is a raw material receiving portion 4, the outer diameter of the first crucible portion 101 being smaller than the outer diameter of the second crucible portion 102, and a groove 1021 being provided in the middle of the bottom of the second crucible portion 102, which is recessed toward the first crucible portion 101;

[0045] The heating part 2 is a graphite heating part, and the heating part 2 includes a first heating part 201, a second heating part 202 and a third heating part 203;

[0046] The first heating part 201 is arranged in the groove 1021 and is arranged circumferentially along the groove 1021. The second heating part 202 is arranged on the outside of the second crucible part 102 and is arranged circumferentially along the second crucible part 102. The third heating part 203 is arranged on the outside of the first crucible part 101 and is arranged circumferentially along the first crucible part 101. The inner diameter of the third heating part 203 is smaller than the outer diameter of the second crucible part 102.

[0047] In the present application, a groove 1021 is provided in the middle of the bottom of the second crucible part 102, which is recessed toward the first crucible part 101. A first heating part 201 is provided circumferentially along the groove 1021, and a second heating part 202 is provided circumferentially on the outer side of the second crucible part 102. This can prevent a portion of the raw material in the upper layer of a preset thickness in the middle of the raw material from forming a crystallization zone and remain unreacted, forming an unreacted raw material zone. Specifically, the first heating part 201 is used to supply heat to the interior of the raw material to avoid the formation of a crystallization zone in the center. Since the highest temperature point of the graphite heater is located near the center height of the heater, through the cooperation of the first heating part 201 and the second heating part 202, during the growth process of the silicon carbide single crystal, a portion of the raw material in the upper layer of a preset thickness in the middle of the raw material can remain unreacted. Furthermore, the outer diameter of the first crucible part 101 is smaller than the outer diameter of the second crucible part 102, and a third heating part 203 is arranged on the outer side of the first crucible part 101. The inner diameter of the third heating part 203 is smaller than the outer diameter of the second crucible part 102, so that the heat emitted by the third heating part 203 is closer to the center of the upper surface of the raw material, reducing the heating of the outer edge of the raw material, thereby preventing carbonization of the edge of the raw material. Since the highest temperature point of the graphite heater is located near the center height of the heater, not only will the upper layer of the edge of the raw material not form a severely carbonized area, but a portion of the raw material with a preset thickness on the upper layer of the edge of the raw material will not react, forming an unreacted area.

[0048] In the present application, the outer diameter of the first crucible part 101 is smaller than the outer diameter of the second crucible part 102, and a third heating part 203 is arranged on the outer side of the first crucible part 101. The inner diameter of the third heating part 203 is smaller than the outer diameter of the second crucible part 102, and the second heating part 202 is arranged circumferentially on the outer side of the second crucible part 102. A groove 1021 recessed toward the first crucible part 101 is provided in the middle of the bottom of the second crucible part 102, and the first heating part 201 is arranged circumferentially along the groove 1021, so that part of the raw material with a preset thickness on the upper layer of the raw material does not react, forming an unreacted raw material area 16. When producing silicon carbide single crystals by physical vapor transport, during the process of sublimation and recrystallization of the raw material, the unreacted area layer can filter carbon dust, prevent carbon dust from entering the crystal growth chamber, inhibit the formation of inclusion defects on the crystal growth interface, and inhibit the inclusion defects from growing into larger defects such as screw dislocations, stacking faults and micropipes, thereby improving the crystal quality. In addition, the unreacted area can be recycled after subsequent removal of free carbon and cleaning. Compared with existing technologies, the use of tantalum carbide powder, tantalum microporous blocks and porous graphite to filter carbon dust can significantly reduce costs and prevent further deterioration of the carbon / silicon element ratio balance, which affects crystal growth.

[0049] In addition, in the present application, a first heating portion 201 is circumferentially arranged inside the groove 1021, and a second heating portion 202 is circumferentially arranged outside the second crucible portion 102. The first heating portion 201 and the second heating portion 202 cooperate with each other so that the raw material on the groove side and the raw material on the crucible side wall of the second crucible portion 102 are heated more evenly, which can avoid the problems of excessively high local external temperature, increased carbon dust, local carbon enrichment and carbon collapse caused by heating the outside alone, and reduce defects such as inclusions, screw dislocations, stacking faults and micropipes in the silicon carbide single crystal. Specifically, the formation of raw material carbon collapse is that after the silicon in the raw material sublimates, a carbon skeleton is left. The uneven temperature causes the unexpected migration of silicon-rich atomic groups in the gas phase, which reacts with the carbon skeleton, causing the carbon skeleton to disappear. The upper raw material loses its support and collapses downward.

[0050] In addition, the outer diameter of the first crucible part 101 is smaller than the outer diameter of the second crucible part 102, and the third heating part 203 is provided on the outer side of the first crucible part 101. The inner diameter of the third heating part 203 is smaller than the outer diameter of the second crucible part 102. The third heating part 203 heats the top of the second crucible part 102. When the second heating part 202 heats the edge, a lower temperature can be used, which can further prevent the carbonization of the raw materials caused by the high temperature of the raw materials on the side wall of the crucible of the second crucible part 102.

[0051] In addition, the outer diameter of the first crucible part 101 is smaller than the outer diameter of the second crucible part 102, and a third heating part 203 is provided on the outer side of the first crucible part 101. During the growth of the silicon carbide single crystal, the radial temperature gradient of the silicon carbide single crystal can be adjusted to avoid induced dislocations and crystal cracking defects caused by excessive internal stress, and to avoid edge polycrystalline and polymorphic defects caused by low crystal edge temperature.

[0052] In the present application, the optional range of the cross-sectional shape of the seed crystal accommodating portion 3 is relatively wide, and it can be polygonal, square, circular, etc., preferably circular. The optional range of the cross-sectional shape of the groove 1021 set in the middle of the bottom of the second crucible portion 102 and recessed toward the first crucible portion 101 is relatively wide, and it can be polygonal, square, circular, etc., preferably circular.

[0053] 1 , the first crucible portion 101 and the second crucible portion 102 of the present application may be cylindrical. Specifically, the outer diameter of the cylindrical shape of the first crucible portion 101 is smaller than the outer diameter of the cylindrical shape of the second crucible portion 102. The first crucible portion 101 and the second crucible portion 102 may form a stepped cylindrical crucible that is interconnected. A seed crystal accommodating portion 3 with a circular cross section may be provided in the middle of the top of the first crucible portion 101. A groove 1021 with a circular cross section that is concave toward the first crucible portion 101 may be provided in the middle of the bottom of the second crucible portion 102. The cylindrical crucible wall of the second crucible portion 102 and the groove 1021 form a cavity. A raw material accommodating portion 4 is provided inside, the first heating portion 201 can be a tubular structure with a circular cross section, the first tubular heating portion 201 with a circular cross section can be circumferentially arranged inside the groove 1021 with a circular cross section, the second heating portion 202 can be a tubular structure with a circular cross section, the second tubular heating portion 202 with a circular cross section can be circumferentially arranged outside the cylindrical second crucible portion 102, the third heating portion 203 can be a tubular structure with a circular cross section, the third tubular heating portion 203 with a circular cross section can be circumferentially arranged outside the cylindrical first crucible portion 101.

[0054] Optionally, an arc-shaped protrusion 1022 is provided in the middle of the bottom of the groove 1021, and the arc-shaped protrusion 1022 is provided on the side facing the first crucible part 101. Under this solution, the raw materials above the groove 1021 are heated more evenly, avoiding carbonization of the raw materials in the high temperature area and crystallization of the raw materials in the low temperature area.

[0055] In the present application, when the cross-section of the groove 1021 is circular, the ratio of the diameter of the arcuate protrusion 1022 to the diameter of the bottom of the groove 1021 can be 0.5 to 1.0, and the ratio of the height of the arcuate protrusion 1022 to the distance from the bottom of the groove 1021 facing the first crucible portion 101 to the raw material charging reference plane 5 can preferably be 0.15-0.5. Therefore, the arcuate protrusion 1022 refers to a protrusion whose height gradually decreases from the center of the protrusion to the periphery of the protrusion. The height of the arcuate protrusion 1022 refers to the distance from the bottom of the groove 1021 facing the first crucible portion 101 to the center of the protrusion. The raw material charging reference plane 5 refers to the material surface obtained after the raw material is loaded into the second crucible portion 102 according to the designed amount. Under this solution, the raw material above the groove 1021 is more evenly heated, avoiding carbonization of the raw material in the high-temperature area and crystallization of the raw material in the low-temperature area.

[0056] Optionally, the ratio of the outer diameter of the second crucible part 102 to the outer diameter of the first crucible part 101 is in the range of 1.05 to 4.0, the ratio of the inner diameter of the second heating part 202 to the inner diameter of the third heating part 203 is in the range of 1.05 to 4.0, and the ratio of the diameter of the seed crystal accommodating part 3 to the inner diameter of the third heating part 203 is in the range of 0.26 to 0.92. Under this scheme, the ratio of the outer diameter of the second crucible part 102 to the outer diameter of the first crucible part 101 is 1.05~4.0, and the ratio of the inner diameter of the second heating part 202 to the inner diameter of the third heating part 203 is 1.05~4.0, so that the heat emitted by the third heating part 203 is closer to the center of the upper surface of the raw material, reducing the heating of the outer edge of the raw material, thereby preventing carbonization at the edge of the upper surface of the raw material, and forming an unreacted zone. Furthermore, the ratio of the diameter of the seed crystal accommodating part 3 to the inner diameter of the third heating part 203 is 0.26~0.92, which is more conducive to adjusting the radial temperature gradient of the silicon carbide single crystal, avoiding induced dislocations and crystal cracking defects caused by excessive internal stress, and avoiding edge polycrystalline and polymorphic defects caused by low seed crystal edge temperature. Under this scheme, the ratio of the outer diameter of the second crucible part 102 to the outer diameter of the first crucible part 101 is not greater than 4, and the ratio of the inner diameter of the second heating part 202 to the inner diameter of the third heating part 203 is not greater than 4, which is more conducive to making the temperature of the upper layer of the raw material more uniform, thereby forming an unreacted zone with uniform thickness, avoiding the high temperature at the edge causing the unreacted zone to have a small thickness, and avoiding the low temperature in the middle causing the formation of a crystallized zone, and when producing large-sized silicon carbide single crystals, the structure of the crucible part is more reasonable; the ratio of the outer diameter of the second crucible part 102 to the outer diameter of the first crucible part 101 is The value is not less than 1.05, and the ratio of the inner diameter of the second heating part 202 to the inner diameter of the third heating part 203 is not less than 1.05, so that less heat emitted by the third heating part 203 is transmitted to the outer side of the raw material, avoiding the high temperature of the outer side resulting in a small thickness of the unreacted zone, thereby forming an unreacted raw material zone 16 with uniform thickness on the entire raw material surface, thereby reducing the deposition of carbon dust on the crystal growth surface; the ratio of the diameter of the seed crystal accommodating part 3 to the inner diameter of the third heating part 203 is not less than 0.26, which is more conducive to reducing the probability of polycrystalline and polymorphic edges of silicon carbide single crystals.

[0057] The ratio of the outer diameter of the second crucible part 102 to the outer diameter of the first crucible part 101 can be, for example, 1.1, 1.3, 1.5, 2.0, 3.0 and 4.0, the ratio of the inner diameter of the second heating part 202 to the inner diameter of the third heating part 203 can be, for example, 1.1, 1.3, 1.5, 2.0, 3.0 and 4.0, and the ratio of the diameter of the seed crystal accommodating part 3 to the inner diameter of the third heating part 203 can be, for example, 0.30, 0.40, 0.50, 0.60, 0.70, 0.80 and 0.90.

[0058] Optionally, relative to the raw material charging reference plane 5 of the second crucible portion 102, the upper end of the second heating portion 202 is positioned 10 mm to 50 mm higher than the raw material charging reference plane 5; and the lower end of the second heating portion 202 is positioned 20 mm to 100 mm lower than the lower end of the second crucible portion 102. The highest temperature point of the graphite heater is located near the center height of the heater. In this solution, the upper edge of the second heating portion 202 is higher than the raw material, and the lower edge of the second heating portion 202 is lower than the raw material. This is more conducive to reducing the difference between the upper temperature, bottom temperature, and middle temperature of the raw material, reducing the longitudinal temperature gradient of the raw material, making the longitudinal temperature gradient of the raw material more uniform, and avoiding severe carbonization of the raw material in the high temperature zone and crystallization of the raw material in the low temperature zone. Limiting the distance between the upper end of the second heating portion 202 and the raw material charging reference plane 5 to less than 50 mm is more conducive to preventing the portion of the raw material near the outside of the crucible from being carbonized.

[0059] Optionally, the vertical distance between the lower end of the third heating part 203 and the upper end of the second heating part 202 is 15 mm to 60 mm; the position of the upper end of the third heating part 203 is higher than the position of the upper end of the seed crystal accommodating space of the seed crystal accommodating part 3, and an upper furnace cover 6 is provided above the first crucible part 101, and the upper end of the third heating part 203 is connected to the third electrode 7, and the third electrode 7 is movably connected to the upper furnace cover 6. Under this scheme, the position of the upper end of the third heating part 203 is higher than the position of the upper end of the seed crystal accommodating space, which is more conducive to increasing the temperature of the crystal edge. Under the premise of large crystal size, it inhibits the formation of polycrystals and polytypes, avoids polycrystals and polytypes extending to the inner circle, increases the area of ​​high-quality crystals, and avoids the scrapping of the entire crystal; the vertical distance between the lower end of the third heating part 203 and the upper end of the second heating part 202 is 15mm~60mm, so that the heat emitted by the third heating part 203 is closer to the center of the upper surface of the raw material, reducing the heating of the outer edge of the raw material, thereby preventing carbonization of the edge of the raw material surface, and is conducive to the formation of an unreacted zone at the upper edge of the raw material; an upper furnace cover 6 is provided above the first crucible part 101, and the upper end of the third heating part 203 is connected to the third electrode 7. The third electrode 7 is movably connected to the upper furnace cover 6, which is more conducive to the disassembly and assembly of the thermal field and more conducive to avoiding uneven temperature of the crystal circumference due to heating of the electrode.

[0060] Optionally, a lower furnace cover 8 is provided below the second crucible portion 102, a first electrode 9 is connected to the lower end of the first heating portion 201, and the first electrode 9 is movably connected to the lower furnace cover 8; a support column 10 is connected to the middle of the bottom of the groove 1021, and the support column 10 is connected to the side facing away from the first crucible portion 101. The first heating portion 201 and the support column 10, the bottom of the groove 1021, and the side of the groove 1021 are spaced apart, and the spacing is 15mm to 40mm. Under this solution, a lower furnace cover 8 is provided below the second crucible portion 102, the lower end of the first heating portion 201 is connected to the first electrode 9, and the first electrode 9 is movably connected to the lower furnace cover 8, which is more conducive to thermal field disassembly and assembly, and is more conducive to avoiding uneven circumferential temperature at the bottom of the raw material due to heating of the electrode. The first heating part 201 is spaced apart from the support column 10, the bottom of the groove 1021 and the side of the groove 1021, and the interval of the spacing is 15mm to 40mm, which is more conducive to preventing the conductive carbon powder and silicon powder from escaping from the graphite parts and raw materials, causing the first heating part 201 to ignite with the support column 10 or the groove 1021.

[0061] Optionally, the first electrode 9 is movably connected to the lower furnace cover 8, the third electrode 7 is movably connected to the upper furnace cover 6, the lower end of the second heating part 202 is connected to the second electrode 12, and the second electrode 12 is movably connected to the lower furnace cover 8. By making the electrodes movably connected to the furnace cover, under this scheme, the positions of the first heating part 201, the second heating part 202 and the third heating part 203 can be fine-tuned. By fine-tuning the position of the heating part 2, it is more conducive to ensuring that part of the raw material with uniform thickness on the surface of the raw material does not react.

[0062] Optionally, the lower end of the support column 10 is connected to the rotating motor 13 and the lifting motor 14. The crucible part 1 is driven to rotate by the rotating motor 13, which is more conducive to compensating for the uneven temperature distribution of the raw material in the circumferential direction. The lifting motor 14 can fine-tune the longitudinal position of the crucible part 1, which is more conducive to fine-tuning the longitudinal temperature gradient of the raw material, and is more conducive to coordinating the power ratio of the first heating part 201 and the second heating part 202 to fine-tune the radial temperature gradient of the raw material.

[0063] Optionally, a heat-insulating layer 15 is provided on the upper side of the first crucible part 101 , the lower side of the second crucible part 102 , and the peripheries of the second heating part 202 and the third heating part 203 .

[0064] In a second aspect, the present application provides a method for growing a silicon carbide single crystal using the growth apparatus of the first aspect, wherein the powers of the first heating unit 201, the second heating unit 202, and the third heating unit 203 are P1, P2, and P3, respectively, and the growth method comprises the following steps:

[0065] Heating step: loading raw materials into the raw material receiving portion 4 and mounting and fixing the seed crystal in the seed crystal receiving portion 3; testing the airtightness of the furnace shell cavity surrounded by the upper furnace cover 6, the lower furnace cover 8, and the furnace barrel 11, and then evacuating the interior of the furnace shell cavity; heating the first heating portion 201, the second heating portion 202, and the third heating portion 203 to raise the temperature of the top of the first crucible portion 101 to 2100-2200° C., wherein, during the heating process, the relationship between P1, P2, and P3 is: P1<P3<P2, P2>P1+P3, and P1:P3=0.1-0.5;

[0066] Crystal growth step: performing a first adjustment, a second adjustment, a third adjustment, and a fourth adjustment in sequence, wherein the first adjustment is to adjust the ratio of P1 and P2 so that the temperature difference between the raw material on the crucible side wall of the second crucible part 102 and the raw material on the groove 1021 side is less than 15°C, the second adjustment is to adjust P3 to adjust the ratio of P3 to P1+P2 so that the temperature of the upper surface of the raw material is 15°C to 80°C higher than the temperature of the lower surface of the seed crystal, the third adjustment is to adjust P3 so that the temperature difference between the seed crystal at the edge and the seed crystal in the middle is less than 20°C, and the fourth adjustment is to adjust the pressure inside the furnace shell cavity to 50Pa to 1500Pa so that the atomic groups volatilized from the raw material are crystallized and grown on the surface of the seed crystal, and the upper layer of the raw material with a preset thickness does not react;

[0067] Growth end step: perform the fifth adjustment, sixth adjustment and seventh adjustment in sequence, the fifth adjustment is to increase the pressure inside the furnace shell cavity to 2500Pa~20000Pa, the sixth adjustment is to adjust P1+P2 downward to reduce the axial temperature gradient of the silicon carbide single crystal, so that the axial temperature gradient between the lower surface of the silicon carbide single crystal and the upper surface of the silicon carbide single crystal is ≤20℃ / cm, and the seventh adjustment is to slowly lower P1, P2 and P3 to make P1=P2=P3=0, wherein the interval between the sixth adjustment and the seventh adjustment is a preset time, and the preset time is more than 2h.

[0068] In the present application, the lower surface of the silicon carbide single crystal refers to the surface close to the second crucible part 102 , and the upper surface of the silicon carbide single crystal refers to the surface away from the second crucible part 102 .

[0069] In the present application, in the heating step, the power of the first heating part 201, the second heating part 202 and the third heating part 203 are limited. In the crystal growth stage, the first adjustment, the second adjustment, the third adjustment and the fourth adjustment are performed in sequence, which is more conducive to ensuring that part of the raw materials with uniform thickness on the upper layer of the raw materials do not react. At the end of the growth stage, after the pressure inside the furnace shell cavity increases to 2500Pa~20000Pa, P1+P2 is first adjusted downward to reduce the axial temperature gradient between the lower surface of the silicon carbide single crystal and the upper surface of the silicon carbide single crystal, keep P1, P2, and P3 constant, and perform in-situ annealing, which is more conducive to reducing the internal stress of the crystal.

[0070] Specifically, in the heating step, by making P1<P3<P2, P1 is minimum, and P2 is maximum, it is more conducive to avoiding high temperature in the central area and possible central overheating caused by adjusting power, rotating crucible, and lifting crucible. Furthermore, making P2>P1+P3, the three heaters are adjusted within their respective controllable ranges, which is more conducive to controlling the formation of temperature gradient in the furnace and forming a uniform unreacted zone on the surface of the material. Furthermore, P1:P3=0.1~0.5, which is more conducive to preventing part of the raw material with a preset thickness in the upper layer in the middle of the raw material from reacting.

[0071] Specifically, by first performing the first adjustment to adjust the ratio of P1 and P2, and then performing the second adjustment to adjust P3 to adjust the ratio of P3 to P1+P2, (P1+P2) determines the temperature of the lower part, and P3 determines the temperature of the upper part. After the ratio of P1 and P2 is adjusted, (P1+P2) can be regarded as a variable, and the longitudinal temperature gradient only needs to adjust the ratio of (P1+P2) to P3.

[0072] Specifically, at the end of the growth stage, the pressure inside the furnace shell cavity is increased to 2500Pa~20000Pa, which is more conducive to quickly reducing the volatilization rate of the raw materials and inhibiting the continued growth of the crystal. First, P1+P2 is adjusted downward to reduce the axial temperature gradient between the lower surface of the silicon carbide single crystal and the upper surface of the silicon carbide single crystal, and keep P1, P2, and P3 constant. By keeping P1, P2, and P3 constant, it is more conducive to reducing crystal stress.

[0073] Optionally, a ninth adjustment is included between the third adjustment and the fourth adjustment. The ninth adjustment is to fine-tune the position of the second crucible part (102) through the lifting motor so that the temperature of the lower part of the raw material is higher than the temperature of the upper part of the raw material, and the temperature difference is controlled within 15°C, which is more conducive to promoting the volatilization of the silicon carbide raw material.

[0074] Optionally, the vacuuming process sequentially includes using a mechanical pump to evacuate the furnace shell cavity to a pressure of 0.1 Pa to 5 Pa, using a molecular pump to evacuate the furnace shell cavity to a pressure of 10-2 Pa to 10-4 Pa, and heating the first heating unit 201, the second heating unit 202, and the third heating unit 203 to raise the temperature of the top of the first crucible part 101 to 750°C to 850°C. Under this solution, by sequentially evacuating the furnace shell cavity with a mechanical pump, evacuating the furnace shell cavity with a molecular pump, and heating the furnace shell cavity with the three heating units to raise the temperature of the top of the first crucible part 101 to 750°C to 850°C, oxygen and moisture inside the furnace shell cavity, as well as moisture adsorbed by various components, are more effectively removed, thereby preventing oxidation of raw materials and thermal field materials.

[0075] Optionally, the heating step further includes, when the temperature of the top of the first crucible portion 101 reaches 900°C to 1100°C, adjusting and maintaining the pressure inside the furnace shell cavity at 10,000 Pa to 20,000 Pa. In this solution, by increasing the pressure when the temperature of the top of the first crucible portion reaches 900°C to 1100°C and then continuing to increase the temperature to 2100°C to 2200°C, atomic radicals volatilized from the raw materials are prevented from depositing on the seed crystal before the temperature reaches a temperature suitable for single crystal growth, thereby further improving the quality of crystal growth.

[0076] Optionally, an eighth adjustment is also included after the fourth adjustment, comprising: while maintaining a constant ratio of P1 to P2, upwardly adjusting P1+P2 so that the temperature difference between the upper surface of the raw material and the lower surface of the silicon carbide single crystal increases at a rate of 0.5°C / h to 5.0°C / h, and so that the temperature of the upper surface of the raw material is 30°C to 100°C higher than the temperature of the lower surface of the silicon carbide single crystal. The reaction and volatilization of the raw materials is continuous. Under this scheme, gradually increasing the temperature can accelerate the volatilization of the remaining raw materials, so that the sublimation rate of the raw materials does not decrease rapidly due to the extension of the crystal growth time, thereby maintaining a relatively stable crystal growth rate and further improving the crystal quality.

[0077] Example 1:

[0078] 1 , the silicon carbide single crystal growth device of this example includes a crucible portion 1 and a heating portion 2. The crucible portion 1 includes a cylindrical first crucible portion 101 and a second crucible portion 102 coaxially arranged from top to bottom. The bottom of the first crucible portion 101 is connected to the top of the second crucible portion 102. The ratio of the outer diameter of the second crucible portion 102 to the outer diameter of the first crucible portion 101 is 1.5. A seed crystal accommodating portion 3 with a circular cross section is provided in the middle of the top of the first crucible portion 101. A groove 1021 with a circular cross section that is concave toward the first crucible portion 101 is provided in the middle of the bottom of the second crucible portion 102. The ratio of the depth of the groove 1021 to the distance from the raw material charging reference surface 5 to the bottom of the second crucible portion 102 is 0.85. The groove 1021 The ratio of the diameter of the second crucible part 102 to the outer diameter of the second crucible part 102 is 0.45, and an arc-shaped protrusion 1022 is provided in the middle of the side of the bottom of the groove 1021 facing the first crucible part 101. The ratio of the diameter of the arc-shaped protrusion 1022 to the diameter of the bottom of the groove is 0.9, and the ratio of the height of the arc-shaped protrusion 1022 to the distance from the side of the bottom of the groove 1021 facing the first crucible part 101 to the raw material charging reference surface 5 is 0.5. The cavity formed by the cylindrical crucible wall of the second crucible part 102 and the groove 1021 is the raw material accommodating part 4. The middle of the side of the bottom of the groove 1021 facing away from the first crucible 101 is connected to the support column 10, and the lower end of the support column 10 is connected to the rotating motor 13 and the lifting motor 14. The interior of the groove 1021 is provided with a cross-sectional area 4 along the circumferential direction. The first heating portion 201 is annular in shape, and the first heating portion 201 is spaced 20 mm apart from the support column 10, the bottom of the groove 1021, and the side of the groove 1021. A second heating portion 202 with an annular cross section is circumferentially provided on the outer side of the second crucible portion 102. A third heating portion 203 with an annular cross section is circumferentially provided on the outer side of the first crucible portion 101. The ratio of the outer diameter of the second crucible portion 102 to the inner diameter of the third heating portion 203 is 1.2, the ratio of the inner diameter of the second heating portion 202 to the inner diameter of the third heating portion is 1.3, the ratio of the diameter of the seed crystal accommodating portion to the inner diameter of the third heating portion is 0.6, and relative to the raw material charging reference surface 5 of the second crucible portion 102, the position of the upper end of the second heating portion 202 is lower than the raw material charging reference surface 5 is 25 mm higher than the position of the lower end of the second crucible part 102, the lower end of the second heating part 202 is 50 mm lower than the lower end of the second crucible part 102, the vertical distance between the lower end of the third heating part 203 and the upper end of the second heating part 202 is 40 mm, and the upper end of the third heating part 203 is 100 mm higher than the upper end of the accommodating space of the seed crystal accommodating part 3. An upper furnace cover 6 is arranged above the first crucible part 101, and a lower furnace cover 8 is arranged below the second crucible part 102. The lower end of the first heating part 201 is connected to the first electrode 9, the lower end of the second heating part 202 is connected to the second electrode 12, and the upper end of the third heating part 203 is connected to the third electrode 7. The first electrode 9 and the second electrode 12 are movably connected to the lower furnace cover 8, and the third electrode 7 is movably connected to the upper furnace cover 6.

[0079] The method for growing a silicon carbide single crystal includes: a heating step: after installing the heat field structure, loading the raw material into the raw material receiving portion 4, loading the raw material to the raw material charging reference surface 5, fixing the seed crystal in the seed crystal receiving portion 3, detecting the air tightness of the furnace shell cavity surrounded by the upper furnace cover 6, the lower furnace cover 8 and the furnace barrel 11, vacuuming the furnace shell cavity with a mechanical pump to a pressure of 0.1Pa-5Pa, and continuing to vacuumize the furnace shell cavity with a molecular pump to a pressure of 10-2Pa-10-4Pa, turning on the rotating motor 13, and heating the first crucible portion 1 through the first heating portion 201, the second heating portion 202 and the third heating portion 203. 01 reaches a top temperature of 800° C., and then a mixed gas including nitrogen / hydrogen and an inert gas is injected into the furnace shell cavity. When the temperature of the top of the first crucible part 101 reaches 1000° C., the pressure inside the furnace shell cavity is adjusted to be maintained in the range of 10000 Pa to 20000 Pa, so that the temperature of the top of the first crucible part 101 is increased to 2100-2200° C. During the temperature increase step, the power P1 of the first heating part 201, the power P2 of the second heating part 202, and the power P3 of the third heating part 203 are maintained to meet the following conditions: P1<P3<P2, P2>P1+P3, and P1:P3=0.3;

[0080] Crystal growth step: perform the first adjustment, adjust P1 / P2, so that the temperature difference between the raw material on the crucible side wall of the second crucible part 102 and the raw material on the groove 1021 side is less than 10°C, perform the second adjustment, adjust P3 to adjust P3 / P1+P2, so that the temperature of the upper surface of the raw material is 15°C to 80°C higher than the temperature of the lower surface of the seed crystal, perform the third adjustment, adjust P3, so that the temperature difference between the edge of the seed crystal and the center of the seed crystal is less than 10°C, check the temperature difference between the upper surface of the raw material and the lower surface of the seed crystal, perform the ninth adjustment, and use the lifting motor 14 to fine-tune The crucible portion 1 is positioned so that the temperature of the lower portion of the raw material is less than 15°C higher than the temperature of the upper portion of the raw material. A fourth adjustment is performed to slowly reduce the pressure in the furnace shell cavity so that the pressure inside the furnace shell cavity is maintained at 50 Pa to 1500 Pa. An eighth adjustment is performed to adjust P1+P2 upward while keeping the ratio of P1 to P2 constant so that the temperature difference between the upper surface of the raw material and the lower surface of the silicon carbide single crystal increases at a rate of 0.5°C / h to 5.0°C / h, so that the temperature of the upper surface of the raw material is 30 to 100°C higher than the temperature of the lower surface of the silicon carbide single crystal.

[0081] Growth end step: perform the fifth adjustment to increase the pressure inside the furnace shell cavity to 2500Pa~20000Pa, perform the sixth adjustment to adjust P1+P2 downward so that the axial temperature gradient between the lower surface of the silicon carbide single crystal and the upper surface of the silicon carbide single crystal is less than 20℃ / cm, and maintain for 3h, perform the seventh adjustment to lower P1, P2 and P3 so that P1=P2=P3=0.

[0082] Example 2

[0083] The process is carried out in accordance with Example 1, except that no arc-shaped protrusion 1022 is provided on the side of the bottom of the groove 1021 facing the first crucible part 101 .

[0084] Example 3

[0085] The process was carried out in accordance with Example 1, except that the ratio of the outer diameter of the second crucible portion 102 to the outer diameter of the first crucible portion 101 was 1.02, the ratio of the inner diameter of the second heating portion 202 to the inner diameter of the third heating portion 203 was 1.02, and the ratio of the outer diameter of the second crucible portion 102 to the inner diameter of the third heating portion 203 was 1.01.

[0086] Example 4

[0087] The process is carried out in accordance with Example 1, except that the ratio of the outer diameter of the second crucible portion 102 to the outer diameter of the first crucible portion 101 is 4.2, the ratio of the inner diameter of the second heating portion 202 to the inner diameter of the third heating portion 203 is 4.2, and the ratio of the outer diameter of the second crucible portion 102 to the inner diameter of the third heating portion 203 is 4.

[0088] Example 5

[0089] The process is carried out in accordance with Example 1, except that the ratio of the diameter of the seed crystal receiving portion 3 to the inner diameter of the third heating portion 203 is 0.24.

[0090] Example 6

[0091] The process is carried out in accordance with Example 1, except that, relative to the raw material charging reference plane 5 of the second crucible part 102 , the position of the upper end of the second heating part 202 is 5 mm higher than the position of the raw material charging reference plane 5 , and the position of the lower end of the second heating part 202 is 5 mm lower than the position of the lower end of the second crucible part 102 .

[0092] Example 7

[0093] The process was carried out in accordance with Example 1, except that the vertical distance between the lower end of the third heating portion 203 and the upper end of the second heating portion 202 was 10 mm.

[0094] Comparative Example 1

[0095] The process is carried out in accordance with Example 1, except that the groove 1021 with a circular cross-section that is concave toward the first crucible part 101 is not provided in the middle of the bottom of the second crucible part 102, and the first heating part 201 is not provided. In the method for growing a silicon carbide single crystal, in the heating step, the second heating part 202 and the third heating part 203 are heated, and the power P2 of the second heating part 202 and the power P3 of the third heating part 203 meet and maintain P3<P2. In the crystal growth step, the first adjustment is not performed, the second adjustment is to adjust P3 to adjust P3 / P2, the eighth adjustment is to adjust P2 upwards, and in the growth end step, the sixth adjustment adjusts P2 downwards and maintains for 3h.

[0096] Comparative Example 2

[0097] The process is carried out in accordance with Example 1, except that the outer diameter of the first crucible is the same as that of the second crucible, and the inner diameter of the second heating portion is the same as that of the third heating portion. The ratio of the outer diameter of the second crucible 102 to the inner diameter of the third heating portion 203 is 0.95.

[0098] The edge polycrystals and polytypes, inclusions, dislocation density, and micropipes of the silicon carbide single crystals of Examples 1-7 and Comparative Examples 1-2 were tested. The specific testing methods included visually observing the polycrystals and polytypes under white light or under ultraviolet light; observing the surface of the polished crystals with a microscope to detect the number of inclusions; microscopically observing the shape and number of etch pits after etching the wafer surface, and detecting the dislocation density and number of micropipes on the wafer; and determining whether the raw materials had reacted based on their surface color. Crystallization was determined based on whether the raw materials agglomerated and whether new crystals formed on the surface of the raw materials. The test results are shown in Table 1. The morphological distribution of the raw materials after the growth completion step of Examples 1-7 and Comparative Examples 1-2 was tested by visually observing the appearance, color, and shape of the raw materials.

[0099] Table 1

[0100] Lattice distortion near the inclusions will further increase the probability of dislocations and micropipes. By comparing Example 1-7 with Comparative Example 1-2, the relative positions and sizes of the heating part and the crucible part are reasonably designed, and combined with a reasonable process flow, so that during the crystal growth process, there is always a layer of raw material on the surface of the raw material that does not participate in the reaction, which can prevent the carbon dust below from floating to the crystal growth surface with the airflow to form inclusions, reduce the density of dislocations and micropipes, and improve the internal quality of the crystal; controlling the relative diameters of the seed crystal receiving part and the third heating part can make it easier to obtain crystals without polycrystalline or polymorphic edges.

[0101] The preferred embodiments of the present application are described in detail above, but the present application is not limited thereto. Within the technical concept of the present application, various simple modifications can be made to the technical solution of the present application, including combining the various technical features in any other appropriate manner. These simple modifications and combinations should also be regarded as the contents disclosed in the present application and fall within the scope of protection of the present application. Industrial Applicability

[0102] The silicon carbide single crystal growth device provided in the present application overcomes the defects of inclusions, screw dislocations, stacking faults and micropipes present in silicon carbide single crystals produced by the PVT method, as well as the defects of excessive internal stress in silicon carbide single crystals that induce dislocations and even crystal cracking. It can effectively reduce defects such as inclusions, screw dislocations, stacking faults and micropipes in silicon carbide single crystals and reduce internal stress.

[0103] The method for growing silicon carbide single crystals provided in the present application can prevent a portion of the raw material with a preset thickness on the upper layer of the raw material from reacting. The unreacted raw material serves as a filter layer to prevent carbon dust from entering the crystal growth chamber, thereby reducing defects such as inclusions, screw dislocations, stacking faults and microtubes in the silicon carbide single crystal. After the growth is completed, the unreacted raw material can be recycled and reused after removing free carbon and cleaning.

Claims

1. A silicon carbide single crystal growth device, comprising a crucible portion (1) and a heating portion (2), It is characterized in that The crucible part (1) comprises a first crucible part (101) and a second crucible part (102) which are coaxially arranged from top to bottom; a seed crystal receiving part (3) is arranged in the middle of the top of the first crucible part (101); the second crucible part (102) has a cavity, which is a raw material receiving part (4); the outer diameter of the first crucible part (101) is smaller than the outer diameter of the second crucible part (102); and a groove (1021) which is recessed toward the first crucible part (101) is arranged in the middle of the bottom of the second crucible part (102); The heating part (2) is a graphite heating part, and the heating part (2) comprises a first heating part (201), a second heating part (202) and a third heating part (203); The first heating part (201) is arranged in the groove (1021) and is arranged along the circumference of the groove (1021); the second heating part (202) is arranged on the outer side of the second crucible part (102) and is arranged along the circumference of the second crucible part (102); the third heating part (203) is arranged on the outer side of the first crucible part (101) and is arranged along the circumference of the first crucible part (101); the inner diameter of the third heating part (203) is smaller than the outer diameter of the second crucible part (102).

2. The growth device according to claim 1, It is characterized in that An arc-shaped protrusion (1022) is arranged in the middle of the bottom of the groove (1021), and the arc-shaped protrusion (1022) is arranged on a side facing the first crucible part (101).

3. The growth device according to claim 1, It is characterized in that The ratio of the outer diameter of the second crucible part (102) to the outer diameter of the first crucible part (101) is in the range of 1.05 to 4.0, the ratio of the inner diameter of the second heating part (202) to the inner diameter of the third heating part (203) is in the range of 1.05 to 4.0, and the ratio of the diameter of the seed crystal accommodating part (3) to the inner diameter of the third heating part (203) is in the range of 0.26 to 0.

92.

4. The growth device according to claim 1, It is characterized in that Relative to the raw material charging reference plane (5) of the second crucible part (102), the position of the upper end of the second heating part (202) is 10 mm to 50 mm higher than the position of the raw material charging reference plane (5); the position of the lower end of the second heating part (202) is 20 mm to 100 mm lower than the position of the lower end of the second crucible part (102).

5. The growing device according to claim 4, It is characterized in that The vertical distance between the lower end of the third heating part (203) and the upper end of the second heating part (202) is 15 mm to 60 mm; The position of the upper end of the third heating part (203) is higher than the position of the upper end of the seed crystal accommodating space of the seed crystal accommodating part (3); an upper furnace cover (6) is arranged above the first crucible part (101); the upper end of the third heating part (203) is connected to a third electrode (7); and the third electrode (7) is movably connected to the upper furnace cover (6).

6. The growing device according to claim 1, It is characterized in that A lower furnace cover (8) is provided below the second crucible part (102); a first electrode (9) is connected to the lower end of the first heating part (201); and the first electrode (9) is movably connected to the lower furnace cover (8); A support column (10) is connected in the middle of the bottom of the groove (1021), and the support column (10) is connected to the side away from the first crucible part (101). The first heating part (201) is spaced apart from the support column (10), the bottom of the groove (1021) and the side of the groove (1021), and the interval of the spacing is 15 mm to 40 mm.

7. The growing device according to claim 1, It is characterized in that The cross-sectional shape of the seed crystal accommodating portion (3) is circular.

8. The growing device according to claim 1, It is characterized in that The first crucible part (101) and the second crucible part (102) are cylindrical.

9. The growing device according to claim 2, It is characterized in that When the cross section of the groove (1021) is circular, the ratio of the diameter of the arc-shaped protrusion (1022) to the bottom diameter of the groove (1021) is 0.5-1.0, and the ratio of the height of the arc-shaped protrusion (1022) to the distance from the bottom of the groove (1021) facing the first crucible part (101) to the raw material charging reference plane (5) is 0.15-0.

5.

10. The growing device according to claim 6, It is characterized in that The lower end of the support column (10) is connected to a rotating motor (13) and a lifting motor (14).

11. The growing device according to claim 1, It is characterized in that A heat-insulating layer (15) is provided on the upper side of the first crucible part (101), the lower side of the second crucible part (102), the second heating part (202) and the periphery of the third heating part (203).

12. A method for growing a silicon carbide single crystal using the growth apparatus according to any one of claims 1 to 11, It is characterized in that The powers of the first heating unit (201), the second heating unit (202) and the third heating unit (203) are P1, P2 and P3 respectively, and the growth method comprises the following steps: The heating step comprises: loading the raw material into the raw material receiving part (4), and installing and fixing the seed crystal in the seed crystal receiving part (3); after detecting the air tightness of the furnace shell cavity surrounded by the upper furnace cover (6), the lower furnace cover (8) and the furnace barrel (11), the interior of the furnace shell cavity is evacuated; heating the first heating part (201), the second heating part (202) and the third heating part (203) to make the temperature of the top of the first crucible part (101) reach 2100° C. to 2200° C., wherein during the heating process, the relationship between P1, P2 and P3 is: P1<P3<P2, P2>P1+P3, P1∶P3=0.1~0.5; Crystal growth step: performing a first adjustment, a second adjustment, a third adjustment and a fourth adjustment in sequence, wherein the first adjustment is to adjust the ratio of P1 and P2 so that the temperature difference between the raw material on the crucible side wall of the second crucible part (102) and the raw material on the groove (1021) side is less than 15°C, the second adjustment is to adjust P3 to adjust the ratio of P3 to P1+P2 so that the temperature of the upper surface of the raw material is 15°C to 80°C higher than the temperature of the lower surface of the seed crystal, the third adjustment is to adjust P3 so that the temperature difference between the seed crystal at the edge and the seed crystal in the middle is less than 20°C, and the fourth adjustment is to adjust the pressure inside the furnace shell cavity to 50Pa to 1500Pa so that the atomic groups volatilized from the raw material are crystallized and grown on the surface of the seed crystal, and the upper layer of the raw material with a preset thickness does not react; Growth end step: perform the fifth adjustment, the sixth adjustment and the seventh adjustment in sequence, wherein the fifth adjustment is to increase the pressure inside the furnace shell cavity to 2500Pa~20000Pa, the sixth adjustment is to adjust P1+P2 downward to reduce the axial temperature gradient of the silicon carbide single crystal, so that the axial temperature gradient between the lower surface of the silicon carbide single crystal and the upper surface of the silicon carbide single crystal is ≤20℃ / cm, and the seventh adjustment is to lower P1, P2 and P3 to make P1=P2=P3=0, wherein a preset time is separated from the sixth adjustment and the seventh adjustment, and the preset time is more than 2h.

13. The growth method according to claim 12, It is characterized in that The vacuum treatment includes, in sequence, using a mechanical pump to evacuate the furnace shell cavity so that the pressure inside the furnace shell cavity is 0.1Pa to 5Pa, using a molecular pump to evacuate the furnace shell cavity so that the pressure inside the furnace shell cavity is 10-2Pa to 10-4Pa, and heating the first heating part (201), the second heating part (202) and the third heating part (203) so that the temperature of the top of the first crucible part (101) reaches 750°C to 850°C.

14. The growth method according to claim 12, It is characterized in that The temperature raising step further comprises, when the temperature of the top of the first crucible part (101) reaches 900°C to 1100°C, adjusting and maintaining the pressure inside the furnace shell cavity to 10000Pa to 20000Pa.

15. The growth method according to claim 12, It is characterized in that The fourth adjustment also includes an eighth adjustment, and the eighth adjustment includes: when the ratio of P1 to P2 is constant, P1+P2 is adjusted upward so that the temperature difference between the upper surface of the raw material and the lower surface of the silicon carbide single crystal increases at a rate of 0.5°C / h to 5.0°C / h, so that the temperature of the upper surface of the raw material is 30°C to 100°C higher than the temperature of the lower surface of the silicon carbide single crystal.

16. The growth method according to claim 12, It is characterized in that A ninth adjustment is included between the third adjustment and the fourth adjustment. The ninth adjustment is to adjust the position of the second crucible part (102) by a lifting motor so that the temperature of the lower part of the raw material is higher than the temperature of the upper part of the raw material, and the temperature difference is controlled within 15°C.

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