Silicon carbide single crystal growth device and growth method

Abstract

The present invention provides a growth device and a growth method for a silicon carbide single crystal, which belongs to the technical field of silicon carbide crystal growth. The growth device for a silicon carbide single crystal includes a crucible, a seed crystal fixing assembly, a raw material area, a graphite cylinder and a heat-insulating structure. The crucible has a first cavity located in the center and a second cavity located outside the first cavity. The top and bottom of the crucible are both recessed to form a temperature measuring groove; the seed crystal fixing assembly includes an upper fixing member arranged at the top of the first cavity and a lower fixing member arranged at the bottom of the first cavity. The space between the upper fixing member and the lower fixing member located outside the seed crystal forms a growth cavity; the raw material area is arranged in a circle in the second cavity away from the growth cavity; the graphite cylinder is arranged on the inner periphery of the raw material area, and an opening is provided on the graphite cylinder; the heat-insulating structure is arranged on the outer periphery of the crucible, and the heat-insulating structure has a through hole corresponding to the temperature measuring groove.

Description

Technical Field

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

[0002] Silicon carbide has excellent material properties such as a wide bandgap, high thermal conductivity, and high carrier mobility. It is considered to be an ideal material for making high-temperature, high-frequency, high-power and high-voltage devices. Silicon carbide single crystals are the basic material for making silicon carbide-based devices. The main methods for preparing silicon carbide single crystal ingots include high-temperature vapor deposition, liquid phase method, and physical vapor transport method (PVT method for short). The vast majority of single crystal substrates on the market are made using the PVT method. The PVT method grows high-quality crystals by sublimating the material at high temperature and then crystallizing it in a low-temperature area. During the growth of single crystals using this method, the dislocation lines of the threading dislocations (including screw dislocations and edge dislocations) in the seed crystal are basically parallel to the growth direction, causing the threading dislocations in the seed crystal to extend into the epitaxial layer, increasing the threading dislocation defect density in the formed single crystal ingot and reducing the performance and reliability of power devices made using the ingot. Summary of the Invention

[0003] The embodiments of the present invention provide a growth device and a growth method for a silicon carbide single crystal, aiming to solve the technical problem that the density of threading dislocation defects is high during the growth of existing silicon carbide single crystals using the PVT method, which reduces the performance and reliability of power devices made using the crystal ingot.

[0004] In a first aspect, an embodiment of the present invention provides a silicon carbide single crystal growth apparatus, comprising:

[0005] A crucible having a first cavity located in the center and a second cavity located outside the first cavity, wherein the first cavity and the second cavity are connected, the top surface of the second cavity is higher than the top surface of the first cavity, and the bottom surface is lower than the bottom surface of the first cavity, and the top and bottom of the crucible are both recessed to form temperature measuring grooves, and the two temperature measuring grooves are located at the top and bottom of the first cavity;

[0006] a seed crystal fixing assembly, comprising an upper fixing member disposed at the top of the first cavity and a lower fixing member disposed at the bottom of the first cavity, wherein the space surrounding the seed crystal formed by the upper fixing member and the lower fixing member forms a growth cavity, and the width of the growth cavity gradually increases as it approaches the second cavity;

[0007] a raw material area, provided in a circle in the second cavity away from the growth cavity;

[0008] A graphite cylinder is arranged on the inner periphery of the raw material area, and the graphite cylinder is provided with an opening;

[0009] The heat-insulating structure is arranged on the outer periphery of the crucible, and the heat-insulating structure has a through hole corresponding to the temperature measuring tank.

[0010] In combination with the first aspect, in a possible implementation, the upper fixing member and the lower fixing member both include:

[0011] a graphite sheet fixedly connected to the top wall or the bottom wall of the first cavity, the graphite sheet having a mounting hole in the middle thereof, the top surface of the graphite sheet being recessed to form a cylindrical cavity coaxial with the mounting hole, the diameter of the cavity being larger than the diameter of the mounting hole;

[0012] An insert rod, engaged with the mounting hole;

[0013] A fixed plate, fixedly connected to one end of the insertion rod facing the seed crystal;

[0014] The diameters of the fixing plate and the cavity are both smaller than the diameter of the seed crystal, and the bottom surface of the graphite sheet in the upper fixing member and the top surface of the graphite sheet in the lower fixing member enclose the growth cavity.

[0015] In combination with the first aspect, in a possible implementation, both the top wall and the bottom of the first cavity are provided with limiting rings, and the graphite sheet is snap-fitted to the inner rings of the limiting rings.

[0016] In combination with the first aspect, in a possible implementation, a diameter of the fixing disk is smaller than a diameter of the cavity.

[0017] In conjunction with the first aspect, in a possible implementation, the thermal insulation structure includes:

[0018] An outer insulation layer is wrapped around the outer periphery of the crucible, the outer insulation layer corresponds to the second cavity of the crucible, and the top and bottom of the outer insulation layer are respectively provided with temperature measuring holes corresponding to the temperature measuring tank;

[0019] The inner thermal insulation layer is respectively arranged on the side walls of the two temperature measuring tanks, and the inner diameter of the inner thermal insulation layer is smaller than the diameter of the temperature measuring hole.

[0020] In combination with the first aspect, in a possible implementation, the thickness of the inner thermal insulation layer is greater than 10 mm.

[0021] In combination with the first aspect, in a possible implementation, the wall thickness of the outer insulation layer at the top and bottom of the crucible is equal, and the ratio of the wall thickness of the insulation layer at the top of the crucible to the wall thickness of the outer periphery of the crucible is greater than 3:1.

[0022] In combination with the first aspect, in a possible implementation manner, a height ratio of the second cavity to the first cavity is 3:2 to 4:1.

[0023] The solution shown in the embodiment of the present application is compared with the prior art. The cross-sections of the first cavity and the second cavity of the crucible in the growth device for silicon carbide single crystals of the present invention are H-shaped. The heating area of ​​the entire growth device or the area directly receiving the heat radiation of the heater is the peripheral side wall of the crucible. The second cavity corresponding to the peripheral side wall has a larger electromagnetic induction or heat radiation receiving area, which is convenient for efficient heating to meet the sublimation of silicon carbide powder (raw material); and the second cavity can ensure a larger loading space, avoid the temperature increase of the cost of insulation materials caused by the expansion of the outer diameter of the crucible, and also avoid the problem of material surface crystallization caused by the larger radial thickness of the raw material; the top and bottom of the crucible are set The temperature measuring tank can ensure that the temperature measurement position is closer to the first cavity, so that the temperature measurement value can accurately reflect the axial temperature gradient of the growth cavity, which is convenient for controlling the axial temperature gradient of the growth cavity and reducing the risk of polycrystalline deposition in the growth cavity; the width of the growth cavity gradually increases in the direction close to the second cavity, which can modulate the growth cavity isotherm to have a convex shape in the middle, thereby reducing the risk of adhesion between the seed crystal and the upper or lower fixture during growth; traditional growth mainly relies on the axial temperature gradient. The seed crystal in the growth device of the present invention grows sideways, and the growth direction is perpendicular to the dislocation line of the threading dislocation in the seed crystal, which can effectively prevent the threading dislocation from extending into the growing single crystal.

[0024] In a second aspect, an embodiment of the present invention further provides a method for growing a silicon carbide single crystal, using the above-mentioned silicon carbide single crystal growth apparatus, comprising the following steps:

[0025] S10: taking an initial seed crystal, wherein the initial seed crystal has a columnar structure, and fixing the initial seed crystal between the upper fixing member and the lower fixing member;

[0026] S20: Waiting for the initial seed crystal to grow for a preset time, and forming an annular growth zone on the periphery of the initial seed crystal;

[0027] S30: removing the initial seed crystal with the growth region, and digging out the columnar growth seed crystal in the growth region;

[0028] S40: Fixing the growth seed crystal between the upper fixture and the lower fixture until a whole ingot of silicon carbide single crystal is grown.

[0029] Compared with the prior art, the solution shown in the embodiment of the present application is to form a growth zone on the periphery of the initial seed crystal through growth, and then a columnar growth seed crystal is dug out in the growth zone, and then the growth seed crystal is used to grow in the same way to form a whole ingot of silicon carbide single crystal. The whole ingot of silicon carbide single crystal is used as the production material of power devices, which can improve the performance and reliability of the power devices.

[0030] In conjunction with the second aspect, in a possible implementation, before step S10, the following steps are further included:

[0031] A corrosion-resistant coating is applied to the upper and lower end surfaces of the initial seed crystal. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 A schematic cross-sectional view of a silicon carbide single crystal growth apparatus provided in an embodiment of the present invention;

[0033] Figure 2 For the Figure 1 Schematic diagram of the cross-sectional structure of the CC line;

[0034] Figure 3 A schematic diagram of the regional distribution of a silicon carbide single crystal growth apparatus provided in an embodiment of the present invention;

[0035] Figure 4 This is a relationship diagram between the initial seed crystal and the growth seed crystal used in the embodiment of the present invention.

[0036] Description of reference numerals:

[0037] 10-crucible; 11-first cavity; 12-second cavity; 13-temperature measuring bath; 14-limiting ring;

[0038] 20 - upper fixing member; 21 - lower fixing member; 22 - graphite sheet; 23 - insertion rod; 24 - fixing plate; 25 - growth chamber;

[0039] 30-Raw material area;

[0040] 40-graphite cylinder;

[0041] 50-insulation structure; 51-through hole; 52-outer insulation layer; 53-inner insulation layer;

[0042] 60-initial seed crystal;

[0043] 70-Growing seed crystal. DETAILED DESCRIPTION

[0044] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present invention more clearly understood, the present invention is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0045] In the claims, description and drawings of the present invention, unless otherwise clearly defined, the use of terms such as "first", "second" or "third" is for the purpose of distinguishing different objects rather than for describing a specific order.

[0046] Unless otherwise expressly defined, the directional words in the claims, specification and the above-mentioned drawings of the present invention, such as the terms "upper", "lower", "top", "bottom", "front", "back", "inside", "outside", "center", "transverse", "longitudinal", "horizontal", "vertical", "left", "right", "clockwise", "counterclockwise", "high", "low", etc., indicating directions or positional relationships are based on the directions and positional relationships shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific direction or be constructed and operated in a specific direction, and therefore cannot be understood as limiting the specific scope of protection of the present invention.

[0047] In the claims, description and above-mentioned drawings of the present invention, unless otherwise expressly defined, the terms "fixed connection" or "fixed connection" should be understood in a broad sense, that is, any connection method without displacement relationship and relative rotation relationship between the two parties, that is, including non-detachable fixed connection, detachable fixed connection, integral connection and fixed connection through other devices or elements.

[0048] In the claims, description and drawings of the present invention, if the terms "include", "have" and their variations are used, they are intended to mean "including but not limited to".

[0049] Please also refer to Figures 1 to 3 The silicon carbide single crystal growth device provided by the present invention is now described. The silicon carbide single crystal growth device includes a crucible 10, a seed crystal fixing assembly, a raw material area 30, a graphite cylinder 40, and a heat-insulating structure 50. The crucible 10 has a first cavity 11 located in the center and a second cavity 12 located on the periphery of the first cavity 11. The first cavity 11 and the second cavity 12 are connected. The top surface of the second cavity 12 is higher than the top surface of the first cavity 11, and the bottom surface is lower than the bottom surface of the first cavity 11. The top and bottom of the crucible 10 are both recessed to form temperature measuring grooves 13. The two temperature measuring grooves 13 are located at the top and bottom of the first cavity 11; the seed crystal fixing assembly It includes an upper fixing part 20 arranged at the top of the first cavity 11 and a lower fixing part 21 arranged at the bottom of the first cavity 11. The upper fixing part 20 and the lower fixing part 21 are located in the space around the seed crystal to form a growth cavity 25, and the width of the growth cavity 25 gradually increases along the direction approaching the second cavity 12; the raw material area 30 is arranged in a circle in the second cavity 12 away from the growth cavity 25; the graphite cylinder 40 is arranged on the inner periphery of the raw material area 30, and the graphite cylinder 40 is provided with an opening; the heat preservation structure 50 is arranged on the outer periphery of the crucible 10, and the heat preservation structure 50 has a through hole 51 corresponding to the temperature measuring tank 13.

[0050] The specific growth process of the silicon carbide single crystal growth device provided in this embodiment is: the seed crystal is fixed between the upper fixing member 20 and the lower fixing member 21, and the crucible 10 is heated by arranging a heater on the periphery of the growth device of this embodiment. During the heating process, the raw materials sublime to produce gaseous substances including Si, Si2C, SiC2, etc. These gaseous substances pass through the graphite cylinder 40 and are driven by the temperature gradient to be transferred to the seed crystal with lower temperature, and grow into a silicon carbide single crystal through a solid-gas-solid reaction.

[0051] It should be noted that the crucible 10 can be heated by induction or resistance heating.

[0052] Compared with the prior art, the cross-section of the first cavity 11 and the second cavity 12 of the crucible 10 in the silicon carbide single crystal growth device of the present invention is H-shaped, and the heating area of ​​the entire growth device or the area directly receiving the heat radiation of the heater is the outer peripheral side wall of the crucible 10. The second cavity 12 corresponding to the outer peripheral side wall has a larger local electromagnetic induction or heat radiation receiving area, which is convenient for efficient heating to meet the sublimation of silicon carbide powder (raw material); and the second cavity 12 can ensure a larger loading space, avoid the temperature increase of the insulation material and the like caused by the expansion of the outer diameter of the crucible 10, and also avoid the problem of crystallization of the material surface caused by the larger radial thickness of the raw material; the top and bottom of the crucible 10 are provided with temperature measuring grooves 13, which can ensure the position of temperature measurement The device is located closer to the first cavity 11, so that the temperature measurement value can accurately reflect the axial temperature gradient of the growth cavity 25, which is convenient for controlling the axial temperature gradient of the growth cavity 25 and reducing the risk of polycrystalline deposition in the growth cavity 25; the width of the growth cavity 25 in the direction close to the second cavity 12 gradually increases, and the isotherm of the growth cavity 25 can be modulated to have a convex shape in the middle, thereby reducing the risk of adhesion between the seed crystal and the upper fixture 20 or the lower fixture 21 during growth; traditional growth mainly relies on the difference in axial temperature gradient. The seed crystal in the growth device of the present invention grows sideways, and the growth direction is perpendicular to the dislocation line of the threading dislocation in the seed crystal, thereby avoiding the replication of the threading dislocation and effectively preventing the threading dislocation from extending into the growing single crystal.

[0053] In some embodiments, a specific implementation of the upper fixing member 20 and the lower fixing member 21 can be as follows: Figure 1 and Figure 3 The structure shown. Figure 1 and Figure 3 The upper fixing member 20 and the lower fixing member 21 each include a graphite sheet 22, an insertion rod 23, and a fixing plate 24. The graphite sheet 22 is fixed to the top wall or bottom wall of the first cavity 11. The middle portion of the graphite sheet 22 has a mounting hole. The top surface of the graphite sheet 22 is recessed to form a cylindrical cavity coaxial with the mounting hole. The diameter of the cavity is larger than the diameter of the mounting hole. The insertion rod 23 cooperates with the mounting hole. The fixing plate 24 is fixed to the end of the insertion rod 23 facing the seed crystal.

[0054] The diameters of the fixing plate 24 and the cavity are both smaller than the diameter of the seed crystal. The bottom surface of the graphite sheet 22 in the upper fixing member 20 and the top surface of the graphite sheet 22 in the lower fixing member 21 enclose a growth cavity 25 .

[0055] The mounting hole in the upper fixing member 20 is located between the top wall of the first cavity 11 and the cavity, and the mounting hole in the lower fixing member 21 is located between the bottom wall of the first cavity 11 and the cavity. Since the mounting hole has a certain depth, by inserting the insertion rod 23 into the mounting hole, the spacing between the two fixing plates 24 can be adjusted when the seed crystal is loaded between the two fixing plates 24, thereby ensuring that the error in the axial size of the seed crystal is adapted.

[0056] In a specific implementation, the fixed disk 24 and the insertion rod 23 are an integrated structure, and the fixed disk 24, the insertion rod 23, and the graphite sheet 22 are all made of isostatically pressed graphite. The fixed disk 24 is used to install the seed crystal, and the upper and lower end faces of the seed crystal after installation are fixed on the fixed disk 24, which can prevent the upper and lower end faces of the seed crystal from growing.

[0057] In some embodiments, an improved embodiment of the first cavity 11 can be as follows: Figures 1 to 3 See the structure shown. Figures 1 to 3 The top and bottom of the first cavity 11 are both provided with retaining rings 14, and the graphite sheet 22 is snap-fitted to the inner rings of the retaining rings 14. After installation, the retaining rings 14 retain the graphite sheet 22 in place, preventing it from sliding and changing position. This ensures that the graphite sheet 22 is located in the center of the first cavity 11, and also ensures that the seed crystal is located in the center of the first cavity 11. This ensures that the distance between the outer periphery of the seed crystal and the raw material area 30 remains consistent, thereby improving the growth quality of the seed crystal.

[0058] In some embodiments, an improved embodiment of the upper fixing member 20 and the lower fixing member 21 can be as follows: Figure 1 and Figure 3 See the structure shown. Figure 1 and Figure 3 The diameter of the fixed disk 24 is smaller than the diameter of the cavity. A gap is formed between the outer circumference of the fixed disk 24 and the inner circumference of the cavity to ensure that the cavity and the growth chamber 25 are connected, forming an escape channel. During the seed crystal growth process, the growth material on the outer circumference of the seed crystal not only grows in the radial direction of the seed crystal, but also partially enters the escape channel, ensuring the growth quality of the outer circumference of the seed crystal near the top and bottom edges.

[0059] In some embodiments, a specific embodiment of the thermal insulation structure 50 can be as follows: Figure 1 See the structure shown. Figure 1The insulation structure 50 includes an outer insulation layer 52 and an inner insulation layer 53. The outer insulation layer 52 is wrapped around the outer periphery of the crucible 10 and corresponds to the second cavity 12 of the crucible 10. The top and bottom of the outer insulation layer 52 are respectively provided with temperature measuring holes corresponding to the temperature measuring grooves 13; the inner insulation layer 53 is respectively provided on the side walls of the two temperature measuring grooves 13, and the inner diameter of the inner insulation layer 53 is smaller than the diameter of the temperature measuring holes. By dividing the insulation structure 50 into the outer insulation layer 52 and the inner insulation layer 53, the temperature gradient between the raw material area 30 and the growth chamber 25 can be optimized by adjusting the thickness of the inner insulation layer 53. For details, see Figure 2 By adjusting the thickness of the inner insulation layer 53, the radial temperature gradient in region A can be reduced, thereby reducing the risk of crystallization in region a; the axial temperature gradient in region B can also be reduced, thereby reducing the risk of crystallization in region b; the radial temperature gradient in the growth chamber 25 is increased, thereby increasing the growth momentum of the seed crystal in the growth chamber 25.

[0060] By controlling the temperature gradients in the A region, the B region, and the growth chamber 25 , unnecessary polycrystalline deposition can be avoided, and effective component transport and normal growth of the seed crystal can be achieved.

[0061] Optionally, both the outer insulation layer 52 and the inner insulation layer 53 may be made of insulation carbon felt.

[0062] Specifically, the thicker the inner thermal insulation layer 53 is, the greater the temperature gradient in the axial direction of the growth chamber 25 is. Therefore, the thickness of the inner thermal insulation layer 53 is controlled to be above 10 mm.

[0063] In some embodiments, a specific design standard for the above-mentioned insulation structure 50 is: the wall thickness of the outer insulation layer 52 located at the top and bottom of the crucible 10 is equal, and the ratio of the wall thickness of the insulation layer located at the top of the crucible 10 to the wall thickness of the outer periphery of the crucible 10 is greater than 3:1.

[0064] By adjusting the thickness of the outer insulation layer 52 at the top and bottom of the crucible 10, combined with the thickness of the inner insulation layer 53, the axial temperature gradient within the crucible 10 can be adjusted, thereby controlling the probability of the seed crystal adhering to the side wall of the growth chamber 25. The axial temperature gradient in the center region of the seed crystal is kept as close to zero as possible to ensure axial symmetry during the crystal growth process and to reduce adhesion between the well body and the inner wall of the growth chamber 25. The axial temperature gradient in the region where the seed crystal is located is adjusted by controlling the deviation of the measured temperatures in the upper and lower temperature measuring tanks 13 to be less than 10°C, within a temperature range of 1800°C to 2150°C.

[0065] At the same time, the axial temperature gradient of the growth chamber 25 is also related to the opening angle of the growth chamber 25. The top surface of the growth chamber 25 (i.e., the bottom surface of the graphite sheet 22 in the upper fixture 20) gradually tilts upward in the direction approaching the second cavity 12, and the bottom surface of the growth chamber 25 (i.e., the top surface of the graphite sheet 22 in the lower fixture 21) gradually tilts downward in the direction approaching the second cavity 12. The angle between the top and bottom surfaces of the growth chamber 25 is the opening angle. An opening angle that is too large or too small is not conducive to suppressing the occurrence of polycrystalline adhesion. Therefore, the opening angle should be controlled between 5° and 20°.

[0066] By adjusting the thickness of the outer insulation layer 52 located at the outer peripheral part of the crucible 10, the radial temperature gradient in the crucible 10 can be adjusted, thereby controlling the growth of the seed crystal in the radial direction. The radial temperature gradient in the crucible 10 involves the radial temperature gradient of the growth chamber 25 and the raw material area 30. The radial temperature gradient is the driving force for the growth of the seed crystal. The temperature difference between the outer peripheral surface of the seed crystal and the surface of the raw material is between 20°C and 60°C.

[0067] In some embodiments, a specific design standard for the crucible 10 is that the height ratio of the second cavity 12 to the first cavity 11 is 3:2 to 4:1. The exterior and interior of the crucible 10 are both H-shaped. This defined height ratio facilitates system deheating, raw material loading, and temperature gradient control, thus promoting proper single crystal growth.

[0068] Based on the same inventive concept, see Figure 4 The present invention also provides a silicon carbide single crystal growth device, which includes the following steps:

[0069] S10: Take an initial seed crystal 60, which is a columnar structure, and fix the initial seed crystal 60 between the upper fixing member 20 and the lower fixing member 21;

[0070] S20: Waiting for the initial seed crystal 60 to grow for a preset time, forming an annular growth zone around the initial seed crystal 60;

[0071] S30: removing the initial seed crystal 60 with the growth zone, and digging out the columnar growth seed crystal 70 in the growth zone;

[0072] S40: Fixing the growth seed crystal 70 between the upper fixture 20 and the lower fixture 21 until a whole ingot of silicon carbide single crystal is grown.

[0073] Compared with the prior art, the silicon carbide single crystal growth method provided in this embodiment is to grow an initial seed crystal 60 to form a growth zone on its periphery, then dig out a columnar growth seed crystal 70 in the growth zone, and then use the growth seed crystal 70 to grow a whole ingot of silicon carbide single crystal in the same way. The whole ingot of silicon carbide single crystal can be used as a production material for power devices, which can improve the performance and reliability of power devices.

[0074] It should be noted that the initial seed crystal 60 selected in this invention is short cylindrical. The short cylindrical seed crystal has two flat end faces and a cylindrical surface on the outer periphery. The upper and lower end faces are the installation and fixing surfaces of the seed crystal, and the cylindrical surface is a polished surface, which is used for the subsequent growth process of the crystal to grow along the radial direction of the short cylindrical seed crystal.

[0075] A too low seed crystal height will cause the growth chamber 25 to be too flat, which is not conducive to maintaining a stable growth interface. When growing crystals of the same diameter, a too large seed crystal height will require too much raw material loading. In this embodiment, the height of the short cylindrical seed crystal is between 5-15 mm.

[0076] In some embodiments, an improved implementation of the above-mentioned silicon carbide single crystal growth method is:

[0077] Before step S10, it also includes:

[0078] A corrosion-resistant coating is applied to the upper and lower end surfaces of the initial seed crystal 60 .

[0079] Since the upper and lower end surfaces of the initial seed crystal 60 are installation and fixing surfaces, coating the dense corrosion-resistant coating can prevent the sublimation negative growth from occurring on the two end surfaces of the initial seed crystal 60 .

[0080] As an example, a specific step of the silicon carbide single crystal growth method provided in an embodiment of the present application is:

[0081] It is mainly used in the field of growing 4-H silicon carbide crystals no smaller than 6 inches.

[0082] (1) In the first step of non-carbon surface growth, the height ratio of the second cavity 12 to the first cavity 11 of the selected H-type isostatically pressed graphite crucible 10 is 2. Silicon carbide powder is placed in the raw material area 30 of the H-type isostatically pressed graphite crucible 10 with a loading amount of 2000 g.

[0083] (2) A seed crystal is placed between the upper fixing member 20 and the lower fixing member 21 of an H-type isostatically pressed graphite crucible 10. The seed crystal has a thickness of 7 mm and a diameter of 30 mm. The opening angle of the growth chamber 25 is 10°.

[0084] (3) The thickness of the inner insulation layer 53 is selected to be 20 mm, and the thickness of the outer insulation layer 52 at the top of the crucible 10 and the thickness at the outer peripheral surface of the crucible 10 are in a ratio of 4:1. The thermal field assembly is completed.

[0085] (4) In the crystal growth stage, the process gas is purified argon with a pressure of 2000 Pa; the upper and lower temperature measurements are controlled at around 2100°C, with a difference of less than 10°C.

[0086] (5) After the first step of non-carbon surface growth is completed, a 30 mm diameter area is taken from the non-carbon surface growth area of ​​the obtained crystal ingot to be processed into a seed crystal for the second step of non-carbon surface growth. The seed crystal thickness is 7 mm.

[0087] (6) Repeat steps (1) to (4) to obtain a silicon carbide single crystal grown on the non-carbon surface of the entire ingot.

[0088] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A silicon carbide single crystal growth device, characterized in that: include: A crucible having a first cavity located in the center and a second cavity located outside the first cavity, wherein the first cavity and the second cavity are connected, the top surface of the second cavity is higher than the top surface of the first cavity, and the bottom surface is lower than the bottom surface of the first cavity, the top and bottom of the crucible are both recessed to form temperature measuring grooves, and the two temperature measuring grooves are located at the top and bottom of the first cavity, and the cross-section of the first cavity and the second cavity is H-shaped; A seed crystal fixing assembly, comprising an upper fixing member disposed at the top of the first cavity and a lower fixing member disposed at the bottom of the first cavity, wherein the upper fixing member and the lower fixing member are located in a space surrounding the seed crystal to form a growth cavity, wherein the width of the growth cavity gradually increases in a direction approaching the second cavity, and the seed crystal grows laterally, with the growth direction being perpendicular to the dislocation line of the threading dislocation in the seed crystal; a raw material area, provided in a circle in the second cavity away from the growth cavity; A graphite cylinder is arranged on the inner periphery of the raw material area, and the graphite cylinder is provided with an opening; A heat-insulating structure is provided on the outer periphery of the crucible, and the heat-insulating structure has a through hole corresponding to the temperature measuring tank; The upper fixing member and the lower fixing member both include: a graphite sheet fixedly connected to the top wall or the bottom wall of the first cavity, the graphite sheet having a mounting hole in the middle thereof, the top surface of the graphite sheet being recessed to form a cylindrical cavity coaxial with the mounting hole, the diameter of the cavity being larger than the diameter of the mounting hole; An insert rod, engaged with the mounting hole; A fixed plate, fixedly connected to one end of the insertion rod facing the seed crystal; The diameters of the fixing plate and the cavity are both smaller than the diameter of the seed crystal, and the bottom surface of the graphite sheet in the upper fixing member and the top surface of the graphite sheet in the lower fixing member enclose the growth cavity; The thermal insulation structure comprises: An outer insulation layer is wrapped around the outer periphery of the crucible, the outer insulation layer corresponds to the second cavity of the crucible, and the top and bottom of the outer insulation layer are respectively provided with temperature measuring holes corresponding to the temperature measuring tank; An inner thermal insulation layer is respectively provided on the side walls of the two temperature measuring tanks, and the inner diameter of the inner thermal insulation layer is smaller than the diameter of the temperature measuring hole; The axial temperature gradient in the crucible is adjusted by adjusting the thickness of the outer insulation layer at the top and bottom of the crucible and combining the adjustment of the thickness of the inner insulation layer.

2. The silicon carbide single crystal growth apparatus according to claim 1, wherein The top wall and the bottom of the first cavity are both provided with limiting rings, and the graphite sheet is snap-fitted to the inner rings of the limiting rings.

3. The silicon carbide single crystal growth apparatus according to claim 1, wherein The diameter of the fixing disk is smaller than the diameter of the cavity.

4. The silicon carbide single crystal growth apparatus according to claim 1, wherein The thickness of the inner thermal insulation layer is greater than 10 mm.

5. The silicon carbide single crystal growth apparatus according to claim 1, wherein The wall thickness of the outer insulation layer at the top and bottom of the crucible is equal, and the ratio of the wall thickness of the insulation layer at the top of the crucible to the wall thickness of the insulation layer at the periphery of the crucible is greater than 3:

1.

6. The silicon carbide single crystal growth apparatus according to claim 1, wherein: The height ratio of the second cavity to the first cavity is 3:2 to 4:

1.

7. A method for growing a silicon carbide single crystal, characterized in that: The silicon carbide single crystal growth device according to any one of claims 1 to 6 comprises the following steps: S10: taking an initial seed crystal, wherein the initial seed crystal has a columnar structure, and fixing the initial seed crystal between the upper fixing member and the lower fixing member; S20: Waiting for the initial seed crystal to grow for a preset time, and forming an annular growth zone on the periphery of the initial seed crystal; S30: removing the initial seed crystal with the growth region, and digging out the columnar growth seed crystal in the growth region; S40: Fixing the growth seed crystal between the upper fixture and the lower fixture until a whole ingot of silicon carbide single crystal is grown.

8. The method for growing a silicon carbide single crystal according to claim 7, wherein: The step S10 also includes: A corrosion-resistant coating is applied to the upper and lower end surfaces of the initial seed crystal.

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