Silicon carbide single crystal growth method and crucible

Abstract

The invention relates to the field of silicon carbide single crystal growth, in particular to a silicon carbide single crystal growth method and a crucible. The crucible comprises a pot body, an inner heater and an outer heater, the pot body is of a circular ring shape with an opening in the top and is made of graphite, the pot body comprises an inner ring wall and an outer ring wall which are coaxially arranged and connected with each other, the inner heater is connected to the outer wall of the inner ring wall of the pot body, and the outer heater is connected to the outer wall of the outer ring wall of the pot body. According to the method, a low-temperature area with lower temperature is formed at the liquid level of the crystal growth melt, and a crucible is rotated to form carrying liquid flow flowing along the circumferential direction, so that off-axis seed crystals are in contact with the low-temperature area of the crystal growth melt, and the seed crystals are far away from the circle center of the carrying liquid flow. The step direction of the off-axis seed crystal is opposite to the liquid flow carrying direction, so that the surface of the seed crystal grows in an anti-parallel flow growth mode, and the problem that the surface of a single crystal is partitioned due to the fact that partial area of the surface of the single crystal grows in a parallel flow growth mode is solved, so that the quality of the single crystal is improved, and defects are reduced.

Description

Technical Field

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

[0002] Silicon carbide (SiC) has excellent properties such as wide bandgap, high breakdown field strength, high saturated electron drift rate and high thermal conductivity, and has important applications in new energy vehicles, photovoltaics and 5G communications. Currently, the widely used 4H-SiC single crystal is usually obtained by seed crystal growth.

[0003] At present, silicon carbide single crystals are often grown by gas phase method or liquid phase method. Among them, the liquid phase method has become a hot spot in current research due to its advantages such as low process temperature, low raw material cost, microtube healing and dislocation conversion during growth, which makes the crystal quality higher, and it is easier to grow p-type silicon carbide. In the traditional liquid phase method, a crystal growth melt containing silicon and carbon is used as a carrier of elements, and a temperature gradient with decreasing temperature from the bottom to the liquid surface is formed in the crystal growth melt. The seed crystal is rotated along the central axis to form a liquid flow. The carbon in the liquid flow is supersaturated due to cooling, and the silicon element is precipitated. The growth of silicon carbide single crystals is achieved. However, when applied to off-axis seed crystals, due to the different relative directions of the steps in different regions of the off-axis seed crystals, some areas on the surface of the seed crystal are in antiparallel flow growth mode, and other areas are in parallel flow growth mode. In the antiparallel flow area, the solute is transported to the step steps and the step surface more evenly, which can ensure that the advancement speed of the steps to the solution is relatively consistent, thereby ensuring the stability of the subsequent antiparallel flow growth mode. In the parallel flow region, the solute is more easily transported to the step surface, which makes it easier for the step to coalesce, resulting in an increase in the roughness of the crystal surface. When the crystal continues to grow, defects such as grooves and solvent inclusions will appear. Summary of the invention

[0004] The object of the present invention is to provide a silicon carbide single crystal growth method and a crucible which can suppress the partitioning of the surface of the crystal ingot.

[0005] In order to achieve the above object, the present invention provides the following technical solutions: A method for growing a silicon carbide single crystal, comprising: Adding mixed raw materials to the crucible; Heating the crucible to a heating temperature so that the mixed raw material in the crucible melts to form a crystal growth melt, and the crystal growth melt has a low temperature zone at a liquid surface with a temperature lower than the heating temperature; The crucible is controllably rotated along its central axis to form a transport liquid flow flowing in a first direction along a circumferential trajectory at the liquid surface of the crystal growth melt; Placing a plurality of off-axis silicon carbide seed crystals into the crucible, so that the seed crystals are in contact with the low-temperature zone of the crystal growth melt, the seed crystals are away from the center of the transport liquid flow, and the step direction of the seed crystals is opposite to the first direction; The seed crystal is pulled to obtain a silicon carbide single crystal.

[0006] Optionally, the crucible is configured in a circular ring shape, having an inner ring wall and an outer ring wall coaxially arranged, and the inner ring wall and the outer ring wall of the crucible are heated simultaneously to form the low temperature zone between the inner ring wall and the outer ring wall.

[0007] Optionally, the rotation speed of the crucible is any value between 1 rpm and 100 rpm.

[0008] Optionally, the outer wall temperature of the outer annular wall of the crucible is a first temperature, the outer wall temperature of the inner annular wall of the crucible is a second temperature, and the difference between the first temperature and the second temperature is any value between 0°C and 5°C.

[0009] Optionally, the distance between the center of the seed crystal and the outer annular wall of the crucible is a first distance, the distance between the center of the seed crystal and the inner annular wall of the crucible is a second distance, and the ratio of the first distance to the second distance is any value in the range of 0.9 to 1.1.

[0010] Optionally, the crystal growth melt includes silicon and carbon, and also includes one or more of chromium, aluminum, iron, titanium, tin and cerium.

[0011] In a second aspect, the present invention also provides a crucible applied to the above method, comprising a pot body, an inner heater and an outer heater, the pot body being constructed in the shape of a circular ring with an open top and being constructed of graphite, the pot body comprising an inner ring wall and an outer ring wall coaxially arranged and interconnected, the inner heater being connected to the outer wall of the inner ring wall of the pot body, the outer heater being connected to the outer wall of the outer ring wall of the pot body, and the pot body being configured to controllably rotate along its central axis.

[0012] Optionally, the inner heater and the outer heater are controlled independently of each other.

[0013] Optionally, both the inner heater and the outer heater are resistive heaters.

[0014] Optionally, the crucible also includes a controller, an internal sensor and an external sensor, wherein the internal sensor and the external sensor are both temperature sensors and are electrically connected to the controller, and several of the internal sensors are arranged on the outer wall of the inner ring wall of the pot body, and several of the external sensors are arranged on the outer wall of the outer ring wall of the pot body.

[0015] According to the first aspect of the present invention, the mixed raw materials in the crucible are melted by heating the crucible, and the carbon is fully dissolved to saturation to form a crystal growth melt. Due to the loss of heat during the transfer process, the temperature of the middle part of the liquid surface in the crucible is relatively low, forming a low temperature zone. By rotating the crucible, a transport liquid flow flowing in a circumferential direction is formed. The seed crystal is contacted with the low temperature zone, and the seed crystal is kept away from the center of the transport liquid flow, so that the direction of the transport liquid flow in contact with the seed crystal is consistent, and the step direction of each region of the seed crystal is opposite to the direction of the transport liquid flow, so that each region of the seed crystal is in an antiparallel flow growth mode, which helps to improve the quality of the single crystal and reduce defects.

[0016] Furthermore, constructing the crucible into a ring shape and heating the inner and outer ring walls simultaneously helps to form a ring-shaped low-temperature zone and make the temperature distribution in the low-temperature zone uniform, which helps to uniformly grow silicon carbide single crystals on the surface of the seed crystal.

[0017] According to the second aspect of the present invention, heaters are respectively arranged on the inner walls of the inner and outer annular walls of the annular graphite pot body, so that a horizontal temperature gradient is formed by heating, and forced convection is formed at the liquid surface of the crystal growth melt in the pot body, thereby facilitating the addition of carbon to the crystal growth melt, forming a saturated solution of carbon around the inner walls of the inner and outer annular walls of the crucible, making the crystal growth melt supersaturated on the surface of the seed crystal, facilitating the precipitation of silicon carbide on the surface of the seed crystal under the action of forced convection, and facilitating the formation of single crystals.

[0018] The above description is only an overview of the technical solution of the present invention. In order to more clearly understand the technical means of the present invention and implement it according to the contents of the specification, the following is a detailed description of the preferred embodiments of the present invention in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a schematic diagram of the convective mass transfer direction when growing off-axis silicon carbide single crystals by the existing liquid phase method; Figure 2 Schematic diagram of the growth mode of single crystal in antiparallel flow growth mode and parallel flow growth mode; Figure 3 This is an observation diagram of the surface of a crystal ingot grown by the existing liquid phase method; Figure 4 A schematic diagram of step heights in different regions on the surface of a crystal ingot grown by an existing liquid phase method; Figure 5 This is a flow chart of a method for growing a silicon carbide single crystal as shown in Embodiment 1 of the present invention; Figure 6 A diagram showing the position relationship between the seed crystal and the crucible shown in the first embodiment of the present invention; Figure 7 The temperature distribution at the surface of the crystal growth melt shown in the first embodiment of the present invention; Figure 8 The flow velocity distribution at the surface of the crystal growth melt shown in the first embodiment of the present invention; Fig. 9 The flow velocity distribution at the cross section of the crystal growth melt shown in the first embodiment of the present invention; Fig.10 This is a light microscopic image of a local surface of a silicon carbide single crystal obtained by the method shown in Example 1 of the present invention; Fig.11 for Fig.10 Variation of step height in the middle area.

[0020] Legend: 101-crystal growth melt, 102-seed crystal, 1-pot body, 11-inner ring wall, 12-outer ring wall, 2-inner heater, 3-outer heater. DETAILED DESCRIPTION

[0021] The technical solution of the present invention will be described clearly and completely below in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0022] In the description of the present invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship 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 orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", and "third" are used for descriptive purposes only, and cannot be understood as indicating or implying relative importance.

[0023] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0024] In addition, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0025] Liquid phase method for growing silicon carbide single crystals is a commonly used method for preparing silicon carbide single crystals. In the existing liquid phase method, a graphite crucible and the raw materials therein are heated, the raw materials are melted to form a silicon-containing solvent, and graphite is dissolved in the solvent as a solute to form a crystal growth melt, and a temperature gradient is formed in the crystal growth melt with a decreasing temperature from the bottom to the liquid surface. Since the carbon element in the graphite crucible is fully dissolved to saturation at the bottom of the crucible, the solubility of carbon decreases at the lower temperature at the liquid surface, so that the carbon in the crystal growth melt is in an oversaturated state. The seed crystal is set at the center of the crucible, and the height is flush with the liquid surface, so that the surface of the seed crystal close to the crystal growth melt is just in contact with the liquid surface. The seed crystal is rotated along the central axis, so that a liquid flow coaxial with the seed crystal is formed at the liquid surface in the melt in contact with the seed crystal, so that the carbon in the supersaturated crystal growth melt carries silicon and precipitates on the surface of the seed crystal, thereby achieving the growth of silicon carbide single crystals. As the single crystal grows, the seed crystal is pulled up to keep the lower surface of the seed crystal just in contact with the liquid surface until a silicon carbide single crystal of target thickness is obtained.

[0026] See also Figure 1 When the seed crystal is off-axis, there is a fixed step direction on the seed crystal. Since the seed crystal rotates along its axis, it drives the liquid flow in the melt, resulting in the liquid flow direction being an arc-shaped radial with the center of the seed crystal as the center. At this time, the step direction on the surface of some areas of the seed crystal is opposite to the liquid flow direction, and the growth mode of silicon carbide is an antiparallel flow growth mode. The step direction on the surface of some areas of the seed crystal is the same as the liquid flow direction, and the growth mode of silicon carbide is a parallel flow growth mode. Please refer to Figure 2 In the antiparallel flow region, the solute is transported to the step steps and the step surface more evenly, which ensures that the speed of the step advancing to the solution is relatively consistent, thereby ensuring the stability of the subsequent antiparallel flow growth mode. In the parallel flow region, the solute is more easily transported to the step surface, which makes it easier for the step to coalesce, resulting in an increase in the roughness of the crystal surface. When the crystal growth continues, defects such as grooves and solvent inclusions will appear. See Figure 3 and Figure 4 , the obtained single crystal was observed and analyzed from the microscopic and macroscopic levels, and it can be clearly seen that partitions appeared on the surface of the ingot, and the growth quality of each zone was different.

[0027] See also Figure 5 The silicon carbide single crystal growth method shown in a preferred embodiment of the present application includes: S1. Add mixed raw materials into the crucible.

[0028] S2. The crucible is heated to a heating temperature so that the mixed raw materials in the crucible are melted to form a crystal growth melt, and the surface of the crystal growth melt has a low temperature zone whose temperature is lower than the heating temperature.

[0029] S3. The crucible is controlled to rotate along its central axis to form a transport liquid flow flowing in a first direction along a circular trajectory at the liquid surface of the crystal growth melt.

[0030] S4. Place a number of off-axis silicon carbide seed crystals into the crucible so that the seed crystals are in contact with the low-temperature zone of the crystal growth melt, the seed crystals are away from the center of the conveying liquid flow, and the step direction of the seed crystals is opposite to the first direction.

[0031] S5. Pull up the seed crystal to obtain a silicon carbide single crystal.

[0032] The mixed raw materials in the crucible are melted by heating, and the carbon is fully dissolved to saturation to form a crystal growth melt. Due to the loss of heat during the transfer process, the temperature in the middle of the liquid surface in the crucible is low, forming a low temperature zone. By rotating the crucible, a transport liquid flow flowing in a circumferential direction is formed. The surface of the seed crystal is contacted with the low temperature zone, and the seed crystal is kept away from the center of the transport liquid flow, so that the direction of the transport liquid flow in contact with the seed crystal is consistent, and the step direction of each region of the seed crystal is opposite to the direction of the transport liquid flow, so that each region of the seed crystal is in an antiparallel flow growth mode, which helps to improve the quality of the single crystal and reduce defects.

[0033] In some embodiments, the crucible is configured in a circular ring shape, having a coaxially arranged inner ring wall and an outer ring wall. The inner ring wall and the outer ring wall of the crucible are heated simultaneously to form a low-temperature zone between the inner ring wall and the outer ring wall, which helps to make the temperature in the low-temperature zone uniform, and further helps to uniformly grow silicon carbide single crystals on the surface of the seed crystal.

[0034] In some embodiments, the rotation speed of the crucible is any value between 1rpm and 100rpm, for example, it can be any value between 1rpm, 10rpm, 30rpm, 50rpm, 80rpm and 100rpm. Limiting the rotation speed of the crucible helps to suppress the influence of the centrifugal force generated by rapid rotation on the stability of the liquid level and ensure the generation of the transport liquid flow.

[0035] In some embodiments, the outer wall temperature of the outer ring wall of the crucible is a first temperature, the outer wall temperature of the inner ring wall of the crucible is a second temperature, and the difference between the first temperature and the second temperature is any value between 0°C and 5°C, for example, it can be any value between 0°C, 1°C, 2°C, 3°C, 4°C and 5°C, which helps to improve the temperature uniformity in the annular low-temperature zone.

[0036] In some embodiments, the distance between the center of the seed crystal and the outer annular wall of the crucible is a first distance, and the distance between the center of the seed crystal and the inner annular wall of the crucible is a second distance. The ratio of the first distance to the second distance is any value between 0.9 and 1.1, for example, it can be any value between 0.9, 0.95, 1.05 and 1.1, which helps to ensure that the surface temperature of the seed crystal in contact with the crystal growth melt is uniform, and helps to make the single crystal grow uniformly.

[0037] In some embodiments, the crystal growth melt includes silicon and carbon, and also includes one or more of chromium, aluminum, iron, titanium, tin and cerium. Among them, chromium as a co-solvent helps to increase the solubility of carbon, thereby increasing the growth rate of liquid phase silicon carbide single crystals, and the addition of aluminum helps to stabilize the growth of silicon carbide crystal form 4H and is conducive to the growth of p-type silicon carbide.

[0038] See also Figure 6 The present invention also applies to protect a crucible, including a pot body, an inner heater and an outer heater. The pot body is constructed in a circular ring shape with an open top and is made of graphite. The pot body includes an inner ring wall and an outer ring wall that are coaxially arranged and interconnected. The inner heater is connected to the outer wall of the inner ring wall of the pot body, and the outer heater is connected to the outer wall of the outer ring wall of the pot body. The pot body is configured to rotate controllably along its central axis.

[0039] By arranging heaters on the inner walls of the inner ring wall and the outer ring wall of the annular graphite pot body respectively, it is convenient to form a horizontal temperature gradient by heating, and it is convenient to form forced convection at the liquid surface of the crystal growth melt in the pot body, so as to facilitate the addition of carbon to the crystal growth melt, and form a saturated solution of carbon around the inner walls of the inner ring wall and the outer ring wall of the crucible, so that the crystal growth melt is supersaturated on the surface of the seed crystal, which makes it convenient for silicon carbide to precipitate on the surface of the seed crystal under the action of forced convection, and is conducive to the formation of single crystals.

[0040] In some embodiments, the inner heater and the outer heater are controlled independently of each other, so as to match the different surface areas of the inner and outer annular walls and select different powers, thereby making the temperatures of the inner and outer annular walls similar.

[0041] In some embodiments, both the inner heater and the outer heater are resistive heaters.

[0042] In some embodiments, the crucible further includes a controller, an inner sensor and an outer sensor, both of which are temperature sensors and are electrically connected to the controller, and a plurality of inner sensors are disposed on the outer wall of the inner ring wall of the pot body, and a plurality of outer sensors are disposed on the outer wall of the outer ring wall of the pot body. The temperature sensors are provided to help ensure that the temperatures of the inner ring wall and the outer ring wall are similar.

[0043] Please refer to the following examples for details.

[0044] Embodiment 1: See also Figure 5 The silicon carbide single crystal growth method shown in a preferred embodiment of the present application includes: S1. Add mixed raw materials into the crucible.

[0045] S2, heating the crucible to a heating temperature, so that the mixed raw materials in the crucible are melted to form a crystal growth melt 101, and the crystal growth melt 101 has a low temperature zone at a liquid surface with a temperature lower than the heating temperature.

[0046] S3. The crucible is controlled to rotate along its central axis to form a transport liquid flow flowing in a first direction along a circular trajectory at the liquid surface of the crystal growth melt 101 .

[0047] S4. Place a number of off-axis silicon carbide seed crystals 102 into the crucible so that the seed crystals 102 are in contact with the low temperature zone of the crystal growth melt 101, the seed crystals 102 are away from the center of the transport liquid flow, and the step direction of the seed crystals 102 is opposite to the first direction.

[0048] S5. Pull up the seed crystal 102 to obtain a silicon carbide single crystal.

[0049] In step S1, the molar ratio of elemental silicon, elemental chromium and elemental aluminum in the mixed raw material is 53:40:7, see Figure 6 The crucible includes a pot body 1, an inner heater 2 and an outer heater 3. The pot body 1 is made of graphite and is constructed in a circular ring shape with an open top. The pot body 1 includes an inner ring wall 11 and an outer ring wall 12 that are circular and coaxially arranged. The outer ring wall 12 is sleeved on the outer side of the inner ring wall 11, and the bottoms of the two are connected through the pot bottom. In this embodiment, the diameter of the outer ring wall 12 is twice that of the inner ring wall 11. The inner heater 2 and the outer heater 3 are both resistance heaters and are independently controlled. The inner heater 2 is connected to the outer wall of the inner ring wall 11 of the pot body 1, and the outer heater 3 is connected to the outer wall of the outer ring wall 12 of the pot body 1. In this embodiment, the crucible also includes a controller, an inner sensor and an outer sensor. The inner sensor and the outer sensor are both tungsten-rhenium thermocouples and are electrically connected to the controller, and are used to sense the temperature of the outer walls of the inner ring wall 11 and the outer ring wall 12, respectively. The chamber where the crucible is located is evacuated and argon gas is introduced for protection.

[0050] In step S2, the inner heater 2 and the outer heater 3 are turned on at the same time, wherein the heating power of the inner heater 2 is 8kW, and the heating power of the outer heater 3 is 32kW, which are matched with the diameters of the inner annular wall 11 and the outer annular wall 12. In this embodiment, the heating temperature is 1822°C. After the inner sensor and the outer sensor show that the temperature has reached 1822°C, the heating power is reduced and controlled by the controller so that the temperature of the outer walls of the inner annular wall 11 and the outer annular wall 12 are maintained in the range of 1820°C to 1824°C. At this time, the mixed raw materials are melted to form a solvent containing silicon, and the inner wall of the graphite pot body 1 is corroded by the solvent to form a long crystal melt 101. Since heat is lost during the transfer process, an annular low-temperature zone is formed in the middle of the liquid surface between the inner annular wall 11 and the outer annular wall 12. Please refer to Figure 7 , the temperature distribution of the crystal growth melt 101 is calculated using simulation software. It can be seen that there is a temperature gradient at the liquid surface of the crystal growth melt 101, the maximum temperature difference reaches 16.9°C, and the temperature in the low temperature zone is relatively uniform.

[0051] In step S3, four seed crystals 102 are lowered so that each seed crystal 102 is in contact with the low temperature zone of the crystal growth melt 101, the distance between the center of each seed crystal 102 and the inner ring wall 11 and the outer ring wall 12 of the pot body 1 is equal, and each seed crystal 102 is evenly arranged along the circumference. The crucible is driven by an external power device to rotate along the central axis at a speed of 70 rpm to form a transport liquid flow in a counterclockwise direction. See Figure 8 , the flow velocity distribution at the surface of the crystal growth melt 101 is calculated using simulation software, and it can be seen that the direction of the fluid in contact with the surface of the seed crystal 102 is highly consistent. By setting the seed crystal 102 in a fixed direction, it can be ensured that the step direction of the seed crystal 102 is opposite to the direction of the contacting fluid. The flow velocity of the crystal growth melt 101 in contact with each seed crystal 102 is basically the same, showing good flow uniformity.

[0052] See also Fig. 9 The simulation software is used to calculate the flow velocity distribution of the cross-section of the crystal growth melt 101. The crystal growth melt 101 is affected by the forced convection caused by the rotation of the crucible, the buoyancy flow and the Marangoni convection. The liquid flow in the crystal growth melt 101 is transported from the bottom corner of the outer ring wall 12 to the surface of the seed crystal 102, and then gradually transported along the surface of the seed crystal 102 to the inner ring wall 11, and after reaching the inner ring wall 11, it is transported downward along the inner wall of the inner ring wall 11 and transported back to the outer ring wall 12 through the bottom of the crucible.

[0053] Combination Figure 7 , Figure 8 and Fig. 9 It can be seen that when the liquid flow in the crystal growth melt 101 flows, the carbon in the crucible is corroded at the inner walls of the inner annular wall 11 and the outer annular wall 12 where the temperature is higher, and supersaturation is reached on the surface of the seed crystal 102 where the temperature is lower, and an antiparallel flow growth mode is realized on the surface of the entire seed crystal 102, so that carbon carries silicon to precipitate, thereby forming a silicon carbide single crystal with fewer surface defects, and the growth rate of each seed crystal 102 is equal.

[0054] In step S5, each seed crystal 102 is pulled synchronously so that the lower surface of the seed crystal 102 is always in contact with the liquid surface. After the thickness of the ingot reaches a preset value, the ingot is separated from the crystal growth melt 101 to obtain a silicon carbide single crystal. The surface of the ingot obtained in this embodiment is relatively flat and consistent, and there is no zoning phenomenon. Please refer to Fig.10 and Fig.11 , an optical microscope was used to observe a local area on the surface of the ingot, and the observation area was a non-feature area, and the change in step height in this area was detected. It can be seen that the step distribution is relatively uniform, that is, the ingot was grown in an antiparallel flow growth mode.

[0055] The beneficial effect of the present invention is that it can effectively prevent the occurrence of zoning on the surface of the silicon carbide single crystal obtained by off-axis seed crystal growth, and the presence of defects such as grooves and solvent inclusions in some areas. In addition, the method can simultaneously grow multiple seed crystals, which helps to improve efficiency and reduce costs.

[0056] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0057] The above-mentioned embodiments only express several implementation methods of the present invention, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims

1. A method for growing a silicon carbide single crystal, characterized in that: include: Adding mixed raw materials to the crucible; The crucible is heated to a heating temperature, so that the mixed raw material in the crucible is melted to form a crystal growth melt (101), and the crystal growth melt (101) has a low temperature zone at a liquid surface with a temperature lower than the heating temperature; The crucible is controlled to rotate along its central axis to form a transport liquid flow flowing in a first direction along a circumferential trajectory at the liquid surface of the crystal growth melt (101); Placing a plurality of off-axis silicon carbide seed crystals (102) into the crucible, so that the seed crystals (102) are in contact with the low-temperature zone of the crystal growth melt (101), the seed crystals (102) are away from the center of the transport liquid flow, and the step direction of the seed crystals (102) is opposite to the first direction; The seed crystal (102) is pulled to obtain a silicon carbide single crystal.

2. The method according to claim 1, characterized in that The crucible is constructed in a circular ring shape and has an inner ring wall (11) and an outer ring wall (12) arranged coaxially. The inner ring wall (11) and the outer ring wall (12) of the crucible are heated simultaneously to form the low-temperature zone between the inner ring wall (11) and the outer ring wall (12).

3. The method according to claim 2, characterized in that The rotation speed of the crucible is any value between 1 rpm and 100 rpm.

4. The method according to claim 3, characterized in that The outer wall temperature of the outer annular wall (12) of the crucible is a first temperature, the outer wall temperature of the inner annular wall (11) of the crucible is a second temperature, and the difference between the first temperature and the second temperature is any value within a range of 0°C to 5°C.

5. The method according to claim 4, characterized in that The distance between the center of the seed crystal (102) and the outer annular wall (12) of the crucible is a first distance, the distance between the center of the seed crystal (102) and the inner annular wall (11) of the crucible is a second distance, and the ratio of the first distance to the second distance is any value between 0.9 and 1.

1.

6. The method according to claim 1, characterized in that The crystal growth melt (101) includes silicon and carbon, and also includes one or more of chromium, aluminum, iron, titanium, tin and cerium.

7. A crucible for implementing the silicon carbide single crystal growth method according to any one of claims 1 to 6, characterized in that: The invention comprises a pot body (1), an inner heater (2) and an outer heater (3); the pot body (1) is constructed in the shape of a circular ring with an open top and is made of graphite; the pot body (1) comprises an inner ring wall (11) and an outer ring wall (12) which are coaxially arranged and connected to each other; the inner heater (2) is connected to the outer wall of the inner ring wall (11) of the pot body (1); the outer heater (3) is connected to the outer wall of the outer ring wall (12) of the pot body (1); and the pot body (1) is configured to controllably rotate along its central axis.

8. The crucible according to claim 7, characterized in that The inner heater (2) and the outer heater (3) are controlled independently of each other.

9. The crucible according to claim 7, characterized in that The inner heater (2) and the outer heater (3) are both resistance heaters.

10. The crucible according to claim 7, characterized in that It also includes a controller, an internal sensor and an external sensor, wherein the internal sensor and the external sensor are both temperature sensors and are electrically connected to the controller, and a plurality of the internal sensors are arranged on the outer wall of the inner ring wall (11) of the pot body (1), and a plurality of the external sensors are arranged on the outer wall of the outer ring wall (12) of the pot body (1).

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