An apparatus and method for guiding the growth of silicon carbide single crystals.

Abstract

This invention relates to the field of crystal growth technology, and in particular to an apparatus and method for guiding the growth of silicon carbide single crystals. The invention provides an apparatus for guiding the growth of silicon carbide single crystals, comprising a crucible, a first rotating lifting shaft, and a turbine pump assembly. The turbine pump assembly includes a flow guide baffle, the upper part of which is connected to the first rotating lifting shaft, and the lower part of which is fitted with a seed crystal holder. Turbine blades are mounted on the flow guide baffle and uniformly distributed around the seed crystal, with the lower end of the turbine blades lower than the height of the seed crystal. This invention provides an apparatus and method for guiding the growth of silicon carbide single crystals, which can improve the stability and efficiency of solute transport in solution, and enhance the long-term growth stability of the crystal.

Description

Technical Field

[0001] This invention relates to the field of crystal growth technology, and in particular to an apparatus and method for guiding the growth of silicon carbide single crystals. Background Technology

[0002] Silicon carbide, as a typical representative of wide bandgap semiconductors, has excellent properties such as large bandgap, high breakdown field strength, high saturated electron mobility, high thermal conductivity, and good thermal and chemical stability. It is an ideal substrate material for fabricating high-frequency, high-voltage, high-efficiency, radiation-resistant, and high-temperature-resistant high-power devices and blue light-emitting diodes. This makes it a promising material for applications in new energy vehicles, high-speed rail, aerospace, high-voltage smart grids, and clean energy, and has therefore attracted widespread attention from the academic community and governments around the world.

[0003] The mainstream method for growing silicon carbide single crystal substrates is the physical vapor transport (PVT) method. Although this method has become relatively mature after decades of continuous research and improvement and can supply a large number of silicon carbide single crystal substrates to the market, it still has some unavoidable limitations. These limitations are mainly reflected in its unstable growth environment, difficulty in eliminating defects, low yield, high cost, difficulty in diameter expansion, and difficulty in achieving continuous and effective P-type doping.

[0004] Compared to the vapor-phase method, the liquid-phase growth method requires a lower growth temperature and a relatively stable growth environment, enabling crystal growth in a near-equilibrium state. This not only results in lower growth costs but also theoretically allows for higher crystal quality. Furthermore, the liquid-phase method shows promising applications in obtaining P-type substrates and crystal diameter expansion. Therefore, the liquid-phase method has received increasing attention in recent years, and related technologies have made breakthrough progress. However, current liquid-phase silicon carbide single crystal growth technology still faces some key technical bottlenecks that need to be addressed. Solute transport in liquid-phase silicon carbide single crystal growth has a crucial impact on crystal growth. The convection pattern and rate of the high-temperature solution during crystal growth play a decisive role in the solute transport path and efficiency. In existing liquid-phase silicon carbide crystal growth technologies, the convection state of the high-temperature solution is very complex, often exhibiting multiple small eddies. This severely limits the transport efficiency of solute C from the crucible sidewall to the crystal growth interface, thus limiting further improvements in crystal growth quality and rate. Summary of the Invention

[0005] To address one or more technical problems existing in the prior art, the present invention provides an apparatus and method for guiding the growth of silicon carbide single crystals, which can increase the transport efficiency of solutes in solution.

[0006] In a first aspect, the present invention provides an apparatus for guiding the growth of silicon carbide single crystals, including a crucible, a first rotating lifting shaft and a turbine liquid pump assembly;

[0007] The turbine pump kit includes a flow guide baffle. The upper part of the flow guide baffle is connected to the first rotary lifting shaft, and the lower part is equipped with a seed crystal holder with a seed crystal. Turbine blades are installed on the flow guide baffle and are evenly distributed around the seed crystal. The lower end of the turbine blades is lower than the height of the seed crystal.

[0008] Optionally, a flow guide tube is provided inside the crucible. The outer diameter of the flow guide tube is smaller than the inner diameter of the crucible. The upper end of the flow guide tube is open, and the bottom is a bottom plate with a circular hole. A conical flow guide cone is fixed on the bottom plate of the crucible. The surface of the flow guide cone is concave inward to form a flow guide surface. The flow guide cone and the circular hole at the bottom of the flow guide tube do not contact each other to form a liquid channel.

[0009] Optionally, the guide tube extends above the liquid surface, and the height of the guide tube above the liquid surface is less than the height difference between the seed crystal and the guide baffle. The inner diameter of the guide tube is greater than the diameter of the circumcircle of the plurality of turbine blades, and less than or equal to the outer diameter of the guide baffle.

[0010] Optionally, the lower end of the turbine blade is 5-30 mm lower than the height of the seed crystal, and the upper end of the guide tube is 5-30 mm higher than the liquid surface.

[0011] Optionally, the difference between the outer diameter of the circumscribed circle and the inner diameter of the guide tube is 1-3 mm, the distance between the outer wall of the guide tube and the inner wall of the crucible is 10-30 mm, and the minimum distance between the edge of the circular hole of the bottom plate of the guide tube and the guide cone is 10 mm.

[0012] Optionally, the crucible is located inside the furnace cavity shell, the crucible is wrapped with insulation material, an induction coil for heating is disposed between the furnace cavity shell and the insulation material, the crucible is filled with a protective atmosphere, and the crucible is placed on a support tray on which a second rotating lifting shaft is installed.

[0013] In a second aspect, embodiments of the present invention provide a method for guiding the growth of silicon carbide single crystals, based on any of the apparatuses described above, the method comprising:

[0014] S1, lower the turbine liquid pump assembly at the bottom of the first rotating lifting shaft, so that the turbine blades at the bottom of the turbine liquid pump assembly are immersed in the solution and the seed crystal at the bottom of the turbine liquid pump assembly is above the liquid surface, and rotate the turbine liquid pump assembly counterclockwise at a speed of v1 to drive the turbine blades to rotate for a duration of t1, so as to promote the solution to be mixed evenly through convection.

[0015] S2, continue to push down the first rotating lifting shaft to make the seed crystal contact the liquid surface, and rotate the turbine liquid pump assembly clockwise at a speed of v2 to drive the turbine blades to rotate for a duration of t2, so as to suppress the flow of supersaturated solution to the seed crystal and thereby dissolve the damaged layer on the surface of the seed crystal.

[0016] S3, slow growth stage, control the turbine pump rotation to slowly switch from clockwise rotation to counterclockwise rotation v3, and maintain the rotation speed v3 for time t3;

[0017] S4, accelerated growth stage: adjust the turbine liquid pump assembly to increase the turbine liquid pump speed from v3 to v5 to accelerate the solute supply rate and accelerate crystal growth;

[0018] S5, the stable growth stage, involves continuously rotating the turbine blades at a speed of v5 for a duration of t5 to achieve crystal growth.

[0019] S6, after the predetermined growth time is reached, the rotation speed of the turbine liquid pump is reduced from the counterclockwise rotation speed v5 to 0, and the turbine liquid pump assembly is pulled off the liquid surface as a whole.

[0020] Optionally, in step S1, the rotational speed v1 of the turbine liquid pump assembly is 20~50 rpm, and the time t1 is 10~30 min;

[0021] In step S2, the rotational speed v2 of the turbine pump assembly is -15 to -25 rpm, and the time t2 is 5 to 15 min.

[0022] In step S3, the rotational speed v3 of the turbine liquid pump assembly is 30~80 rpm, and the time t3 is 30~90 min;

[0023] In step S4, the target speed v5 after acceleration of the turbo pump kit is 60~150 rpm, and the acceleration time t4 is 60~180 min;

[0024] In step S5, the rotational speed v5 of the turbine liquid pump assembly is 60~150 rpm, and the time t5 is 10~200 h;

[0025] In step S6, the deceleration time t6 is 30~60 min, where the negative sign indicates clockwise rotation speed.

[0026] Optionally, before S1, there is also S0, which heats the solution to a preset temperature and rotates the turbine pump assembly clockwise to form an airflow from the edge of the seed crystal to the center region of the seed crystal;

[0027] Following S6, there is also S7, where the temperature is slowly lowered for annealing. During the annealing process, the turbine pump assembly is rotated clockwise to form an airflow from the side edge of the crystal to the central region of the crystal.

[0028] Optionally, in step S0, the rotational speed v0 of the turbine pump assembly is -30 to -60 rpm, and the time t0 is 60 to 180 min;

[0029] In step S7, the rotational speed v7 of the turbine pump assembly is -60 to -120 rpm, and the time t7 is 10 to 30 h, where the negative sign indicates clockwise rotational speed.

[0030] Compared with the prior art, the present invention has at least the following beneficial effects:

[0031] 1. In this embodiment, the device and process provided by the present invention can effectively drive the high-temperature solution in the crucible to undergo orderly convection circulation. Specifically, this circulation includes three main processes: the undersaturated high-temperature solution with silicon carbide precipitated at the solid-liquid interface is promptly discharged to the side wall of the crucible by a turbine-liquid pump; the undersaturated high-temperature solution discharged to the side wall of the crucible undergoes carbon dissolution and reaches saturation; and the saturated high-temperature solution flows upward to the lower-temperature crystal growth interface under the guidance of a guide cone, reaches a supersaturated state, and precipitates silicon carbide to achieve crystal growth. Driven by the turbine-liquid pump, the above three processes continuously circulate, achieving efficient and rapid transport of solute C from the inner wall of the crucible to the crystal growth interface, effectively improving the uniformity of solute distribution and temperature distribution at the crystal growth interface, and enabling rapid growth of large-size, high-quality silicon carbide single crystals. It should be noted that the seed crystal located in the middle is in contact with the liquid surface, which can limit the fluctuation of the liquid surface to a certain extent, resulting in large fluctuations in the liquid surface around the seed crystal, increasing convection, and making the liquid surface at the seed crystal relatively stable, which is beneficial to the growth effect.

[0032] 2. In this embodiment, the device and process provided by the present invention can effectively eliminate local small eddies inside the high-temperature solution during crystal growth, avoid severe local preferential corrosion of the crucible leading to leakage, and improve the long-term stability of crystal growth.

[0033] 3. In this embodiment, the device and process provided by the present invention can also achieve the following excellent effects: 1) It can effectively suppress the corrosion and damage of the seed crystal surface by metal vapor before growth, and improve the quality of the crystal in the early stage of growth; in the early stage of growth, the seed crystal can be reversed by controlling the turbine to achieve seed crystal re-dissolution, thereby improving the quality of crystal growth; 2) It can realize the regulation of the radial temperature gradient of the crystal during the in-situ annealing process, thereby effectively reducing the internal thermal stress of the crystal, preventing stress cracking during the cooling process of the crystal, and reducing the dislocation density. Attached Figure Description

[0034] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0035] Figure 1 This is a schematic diagram of the structure of a device for guiding the growth of silicon carbide single crystals provided by the present invention;

[0036] Figure 2 This is a schematic diagram of a crystal growth process in a specific embodiment of the present invention;

[0037] Figure 3 This is an optical photograph of the 6-inch silicon carbide crystal grown in Embodiment 1 of the present invention;

[0038] Figure 4 This is an optical photograph of the crucible cross-section after growth in Embodiment 1 of the present invention;

[0039] Figure 5 This is an optical photograph of the 6-inch silicon carbide crystal grown in Comparative Example 1 of the present invention.

[0040] Figure 6 This is an optical photograph of the crucible cross-section after growth in Comparative Example 1 of the present invention;

[0041] Figure 7 This is an optical photograph of the 6-inch silicon carbide crystal grown in Comparative Example 2 of the present invention;

[0042] Figure 8 This is an optical photograph of the 6-inch silicon carbide crystal grown in Comparative Example 3 of this invention.

[0043] In the picture:

[0044] 1-First rotary lifting shaft; 2-Furnace cavity shell; 3-Insulation material; 4-Crucible; 5-Protective atmosphere; 6-Turbine liquid pump kit (6-1: Flow guide baffle; 6-2: Turbine blade; 6-3: Seed crystal holder; 6-4: Seed crystal); 7-Induction coil; 8-Flow guide cylinder; 9-Solution; 10-Flow guide cone; 11-Support tray; 12-Second rotary lifting shaft. Detailed Implementation

[0045] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are some embodiments of the present invention, but not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0046] In the description of the embodiments of the present invention, unless otherwise expressly specified and limited, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance; unless otherwise specified or stated, the term "multiple sets" refers to two or more sets; the terms "connection," "fixed," etc., should be interpreted broadly. For example, "connection" can be a fixed connection, a detachable connection, an integral connection, or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium. The terms "comprising," "including," or any other variations thereof are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes the element. Those skilled in the art can understand the specific meaning of the above terms in the present invention according to the specific circumstances.

[0047] In this specification, it should be understood that the directional terms such as "upper" and "lower" used in the description of the embodiments of the present invention are used to describe the angles shown in the accompanying drawings and should not be construed as limiting the embodiments of the present invention. Furthermore, in the context, it should also be understood that when it is mentioned that one element is connected "upper" or "lower" to another element, it can be directly connected to the other element "upper" or "lower," or indirectly connected to the other element "upper" or "lower" through an intermediate element.

[0048] like Figure 1 As shown, the present invention provides an apparatus for guiding the growth of silicon carbide single crystals, including a crucible 4, a first rotating lifting shaft 1, and a turbine liquid pump assembly 6;

[0049] The turbine pump kit 6 includes a flow guide baffle 6-1. The upper part of the flow guide baffle 6-1 is connected to the first rotary lifting shaft 1, and the lower part is equipped with a seed crystal holder 6-3 with a seed crystal 6-4. Turbine blades 6-2 are installed on the flow guide baffle 6-1 and are evenly distributed around the seed crystal 6-4. The height of the lower end of the turbine blades 6-2 is lower than the height of the seed crystal 6-4.

[0050] In this embodiment, the turbine blades 6-2, distributed around the seed crystal 6-4 and with their lower ends lower than the height of the seed crystal 6-4, can increase the convection of the solution 9 by rotating when the seed crystal 6-4 is just in contact with the liquid surface, thereby increasing the solute transport efficiency. It should be noted that the seed crystal 6-4, located in the middle and just in contact with the liquid surface, can limit the fluctuations of the liquid surface to a certain extent, resulting in larger fluctuations around the seed crystal 6-4, increasing convection, and making the liquid surface at the seed crystal 6-4 more stable, which is beneficial to the growth effect.

[0051] In some embodiments of the present invention, a flow guide tube 8 is provided inside the crucible 4. The outer diameter of the flow guide tube 8 is smaller than the inner diameter of the crucible 4. The upper end of the flow guide tube 8 is open, and the bottom is a bottom plate with a circular hole. A conical flow guide cone 10 is fixed on the bottom plate of the crucible 4. The surface of the flow guide cone 10 is recessed inward to form a flow guide surface. The flow guide cone 10 and the circular hole at the bottom of the flow guide tube 8 do not contact each other to form a liquid channel.

[0052] To further enhance the convection effect, a guide tube 8 and a guide cone 10 are installed inside the crucible 4. As silicon carbide precipitates at the solid-liquid interface of the seed crystal 6-4, the high-temperature solution 9 at the solid-liquid interface becomes undersaturated. Under the action of the turbine blades 6-2, the undersaturated solution 9 is drawn into the channel formed by the turbine blades and the top guide baffle 6-1, and finally, under the action of centrifugal force, it is thrown out of the channel to both sides and enters the space formed between the inner wall of the crucible 4 and the outer wall of the guide tube 8. The crucible 4 is made of graphite, and the undersaturated solution 9 dissolves the carbon on the inner wall of the crucible 4, re-saturating it. It should be noted that the space between the inner wall of the crucible 4 and the outer wall of the guide tube 8 is relatively narrow, meaning that a small amount of undersaturated solution 9 in the space can quickly dissolve the carbon elements on the inner wall of the crucible 4 to achieve saturation. Solution 9 is thrown from inside the guide tube 8 to the outside, creating a pressure difference between the inside and outside of the guide tube 8 at the bottom of the crucible 4. This pressure difference causes the solution 9, which has been saturated with dissolved carbon again, to re-enter the guide tube 8 through the circular hole on the bottom plate. During this process, the guide cone 10 guides the saturated solution 9 that has re-entered the guide tube 8, directing it upwards and quickly reaching the solid-liquid interface at the bottom of the seed crystal 6-4, where silicon carbide crystallizes and grows. This cycle continues, allowing the undersaturated solution 9 to be quickly discharged from the solid-liquid interface and the saturated solution 9 to be quickly replenished at the solid-liquid interface, thus increasing the transport of solute.

[0053] It should be noted that the guide tube 8 can be fixed in a preset position by means of a bracket or support rod or other device.

[0054] In some embodiments of the present invention, the guide tube 8 is higher than the liquid surface, and the height of the guide tube 8 above the liquid surface is less than the height difference between the seed crystal 6-4 and the guide baffle 6-1. The inner diameter of the guide tube 8 is greater than the diameter of the circumcircle of the plurality of turbine blades 6-2, and less than or equal to the outer diameter of the guide baffle 6-1.

[0055] In this embodiment, the guide tube 8 is higher than the liquid surface of the solution 9, separating the solution 9 so that the solution 9 outside the guide tube 8 can only re-enter the guide tube 8 from the bottom along a preset path. The height of the guide tube 8 above the liquid surface is less than the height difference between the seed crystal 6-4 and the guide baffle 6-1. The inner diameter of the guide tube 8 is greater than the diameter of the circumcircle of the multiple turbine blades 6-2, and less than or equal to the outer diameter of the guide baffle 6-1. That is, when growing silicon carbide single crystals, a gap is formed between the guide tube 8 and the guide baffle 6-1, which facilitates the turbine to throw the undersaturated solution 9 out of the gap.

[0056] In some embodiments of the present invention, the lower end of the turbine blade 6-2 is 5-30 mm lower than the height of the seed crystal 6-4, and the upper end of the guide tube 8 is 5-30 mm higher than the liquid surface.

[0057] In some embodiments of the present invention, the difference between the outer diameter of the circumscribed circle and the inner diameter of the guide tube 8 is 1-3 mm, the distance between the outer wall of the guide tube 8 and the inner wall of the crucible 4 is 10-30 mm, and the minimum distance between the edge of the circular hole of the bottom plate of the guide tube 8 and the guide cone 10 is 10 mm.

[0058] In some embodiments of the present invention, the crucible 4 is located inside the furnace cavity shell 2, the crucible 4 is wrapped with heat-insulating material 3, an induction coil 7 for heating is disposed between the furnace cavity shell 2 and the heat-insulating material 3, the crucible 4 is filled with a protective atmosphere 5, and the crucible 4 is placed on a support tray 11 on which a second rotating lifting shaft 12 is installed.

[0059] This invention provides a method for guiding the growth of silicon carbide single crystals, based on any of the above-described apparatus, the method comprising:

[0060] S1, lower the turbine liquid pump assembly at the bottom of the first rotating lifting shaft, so that the turbine blades at the bottom of the turbine liquid pump assembly are immersed in the solution and the seed crystal at the bottom of the turbine liquid pump assembly is above the liquid surface, and rotate the turbine liquid pump assembly counterclockwise at a speed of v1 to drive the turbine blades to rotate for a duration of t1, so as to promote the solution to be mixed evenly through convection.

[0061] S2, continue to push down the first rotating lifting shaft to make the seed crystal contact the liquid surface, and rotate the turbine liquid pump kit clockwise at a speed of v2 to drive the turbine blades to rotate for a duration of t2, so as to suppress the flow of supersaturated solution to the seed crystal, thereby dissolving the damaged layer on the surface of the seed crystal, completing the reverse dissolution of the surface of the seed crystal 6-4, and obtaining a perfect solid-liquid initial growth interface.

[0062] S3, the slow growth stage, controls the rotation of the turbine liquid pump to slowly switch from clockwise rotation to counterclockwise rotation v3, and maintains the rotation speed v3 for time t3, thereby driving the high temperature solution 9 to circulate in an orderly manner in the crucible 4, so that the crystal begins to grow. In the early stage of crystal growth, the turbine liquid pump is controlled to rotate counterclockwise at a low speed. The low growth rate can ensure that high crystal quality is obtained in the early stage of growth, laying the foundation for high-quality crystal growth in the later stage.

[0063] S4, accelerated growth stage: adjust the turbine liquid pump assembly to increase the turbine liquid pump speed from v3 to v5 to accelerate the solute supply rate and accelerate crystal growth;

[0064] S5, the stable growth stage, involves continuously rotating the turbine blades at a speed of v5 for a duration of t5 to achieve crystal growth.

[0065] S6, after the predetermined growth time is reached, the rotation speed of the turbine liquid pump is reduced from the counterclockwise rotation speed v5 to 0, and the turbine liquid pump assembly is pulled off the liquid surface as a whole.

[0066] In some embodiments of the present invention

[0067] In step S1, the rotational speed v1 of the turbine liquid pump assembly is 20~50 rpm, and the time t1 is 10~30 min;

[0068] In step S2, the rotational speed v2 of the turbine pump assembly is -15 to -25 rpm, and the time t2 is 5 to 15 min.

[0069] In step S3, the rotational speed v3 of the turbine liquid pump assembly is 30~80 rpm, and the time t3 is 30~90 min;

[0070] In step S4, the target speed v5 after acceleration of the turbo pump kit is 60~150 rpm, and the acceleration time t4 is 60~180 min;

[0071] In step S5, the rotational speed v5 of the turbine liquid pump assembly is 60~150 rpm, and the time t5 is 10~200 h;

[0072] In step S6, the deceleration time t6 is 30~60 min, where the negative sign indicates clockwise rotation speed.

[0073] In some embodiments of the present invention, before S1, S0 is also included, in which the solution 9 is heated to a preset temperature and the turbine liquid pump kit 6 is rotated clockwise to form an airflow from the edge of the seed crystal 6-4 to the center region of the seed crystal 6-4. On the one hand, this can effectively suppress the deposition of metal vapor on the surface of the seed crystal 6-4, which can damage the surface quality of the seed crystal 6-4; on the other hand, it can reduce the temperature field in the edge region and the center region of the seed crystal 6-4, making the seed crystal 6-4 more uniformly heated and reducing the thermal stress in the seed crystal 6-4.

[0074] After S6, there is also S7. After the crystal growth is completed, the temperature is slowly reduced for annealing. During the annealing process, the turbine liquid pump kit 6 is rotated clockwise to form an airflow from the side edge of the crystal to the center region of the crystal, which reduces the temperature field in the center and edge regions of the crystal, reduces the internal stress of the crystal, prevents stress cracking of the crystal during the cooling process, and reduces the defect density in the crystal.

[0075] In some embodiments of the present invention, in step S0, the rotational speed v0 of the turbine liquid pump assembly 6 is -30 to -60 rpm, and the time t0 is 60 to 180 min;

[0076] In step S7, the rotational speed v7 of the turbine pump kit 6 is -60 to -120 rpm, and the time t7 is 10 to 30 h, where the negative sign indicates clockwise rotational speed.

[0077] Example 1

[0078] This embodiment uses the apparatus provided by the present invention for rapidly growing high-quality silicon carbide single crystals. Figure 1 ) and process methods ( Figure 2 The growth of 6-inch silicon carbide single crystals includes the following steps:

[0079] (1) Install the guide sleeve and the guide cone into the graphite crucible respectively;

[0080] (2) The fluxing raw materials are loaded into the graphite crucible according to the following ratio: Si:Cr:Fe:Mn=60:20:10:10, and the total mass of the raw materials is 20kg.

[0081] (3) A silicon carbide seed crystal with a diameter of 150 mm is bonded to a seed crystal holder with turbine blades;

[0082] (4) Place the crucible and seed crystal-related components into the single crystal growth furnace, and place insulation material around the crucible;

[0083] (5) Connect the seed crystal holder with the seed crystal installed to the seed crystal rotating lifting shaft of the equipment, while ensuring that the position of the turbine blade is 30mm higher than the raw material surface;

[0084] (6) Close the furnace chamber and perform vacuum treatment on the furnace chamber. When the furnace chamber pressure is less than or equal to 1E-4Pa, fill the furnace chamber with protective gas.

[0085] (7) Heat the crucible to completely liquefy the fluxing agent in the crucible and let it stand for 30 minutes;

[0086] (8) During the heating process, the turbine is rotated clockwise at a speed of -60 rpm to form an airflow from the edge of the seed crystal to the center of the seed crystal. On the one hand, this can effectively suppress the deposition of metal vapor on the surface of the seed crystal, which can damage the surface quality of the seed crystal. On the other hand, it can reduce the temperature field in the edge and center regions of the seed crystal, making the seed crystal more uniformly heated and reducing the thermal stress in the seed crystal.

[0087] (9) Slowly push down the first rotating lifting shaft and precisely control the height of the push down, so that the turbine blades around the seed crystal holder are immersed in the high temperature melt at the same time, the seed crystal does not come into contact with the high temperature solution.

[0088] (10) The rotation direction of the turbine liquid pump is changed to counterclockwise rotation at a speed of 50 rpm. Under the condition that the seed crystal does not come into contact with the high temperature solution, the high temperature solution is driven to circulate in the crucible in a directional manner, so that the high temperature solution in the crucible is fully mixed and uniform.

[0089] (11) Continue to push down the first rotating lifting shaft so that the silicon carbide seed crystal is in complete contact with the high temperature solution;

[0090] (12) The rotation direction of the turbine liquid pump is switched to clockwise rotation at a speed of -20 rpm to suppress the flow of supersaturated solution to the seed crystal, complete the reverse dissolution of the seed crystal surface, and obtain a perfect solid-liquid initial growth interface.

[0091] (13) After the seed crystal surface is dissolved, slowly adjust the speed of the turbine liquid pump to rotate counterclockwise, with a target speed of 30 rpm, so that the high temperature solution can be driven to circulate in an orderly manner in the crucible, so that the crystal can begin to grow.

[0092] (14) In the early stage of crystal growth, the turbine liquid pump is controlled to rotate counterclockwise at a low speed of 30 rpm to ensure high crystal quality in the early stage of growth with a low growth rate, laying the foundation for high-quality crystal growth in the later stage.

[0093] (15) After the crystal growth is stable, gradually increase the speed of the turbine pump, with a target speed of 120 rpm, in order to increase the crystal growth rate.

[0094] (16) After the predetermined growth time is reached, the turbine liquid pump and the crystal are slowly pulled away from the liquid surface. After the crystal growth is completed;

[0095] (17) After the crystal growth is completed, the crystal is slowly cooled down to perform in-situ annealing. During the annealing process, the turbine is rotated clockwise at a speed of -100 rpm to form an airflow from the side edge of the crystal to the center region of the crystal, which reduces the temperature field in the center and edge regions of the crystal, reduces the internal stress of the crystal, prevents stress cracking of the crystal during the cooling process, and reduces the defect density in the crystal.

[0096] (18) After the crystal has cooled to room temperature, open the furnace chamber and remove the crystal from the seed crystal holder.

[0097] This embodiment successfully grew a high-quality 6-inch silicon carbide crystal. A front optical photograph of the crystal can be found here. Figure 3 The crystal growth surface is very smooth and bright, without defects such as metal inclusions and cracks, indicating excellent crystal crystallization quality; the crystal growth surface has very small convexity, indicating that the radial temperature distribution during crystal growth is very uniform; the crystal growth rate is about 300 μm / h, which is significantly higher than the current general level. Figure 4 The image shows a longitudinal section optical photograph of the graphite crucible after crystal growth. It can be seen that the sidewall corrosion of the crucible is relatively uniform, and there is no severe localized preferential corrosion.

[0098] The results of this embodiment demonstrate that the growth apparatus and growth process provided by the present invention can effectively achieve rapid growth of high-quality silicon carbide single crystals, make the temperature and solute concentration distribution at the solid-liquid interface more uniform, suppress severe localized preferential corrosion of the crucible during the growth process, and reduce crystal thermal stress to prevent crystal stress cracking.

[0099] Comparative Example 1

[0100] The basic crystal growth process used in this comparative example is consistent with that in Example 1: the same flux ratio and total mass, the same size crucible and silicon carbide seed crystal, and the same growth temperature. The difference is that the turbine liquid pump device and the growth process based on the turbine liquid pump device provided by this invention were not used.

[0101] Figure 5 This is a front-facing optical photograph of the 6-inch silicon carbide crystal grown in this comparative example. It is clearly visible that only the central local area of ​​the crystal exhibits good growth quality and a bright surface, while the edge region of the crystal has numerous groove-like defects accompanied by metallic inclusions. This is due to the excessively high temperature and low solute concentration in the edge region, resulting in a severe shortage of solute supply and causing numerous defects. Furthermore, the crystal growth rate is also very low, only about 100 μm / h. Figure 6The image shows a longitudinal cross-sectional optical photograph of the graphite crucible after growth in this comparative example. It can be seen that very severe localized preferential corrosion occurred on the side of the crucible. Only the crucible in the liquid surface area was extensively corroded and dissolved through, while the area below the liquid surface was basically uncorroded. This is because there are local eddies in the liquid surface area, which leads to severe localized corrosion of the liquid surface. This is very detrimental to the long-term stable growth of crystals.

[0102] The comparative results further demonstrate that the growth apparatus and growth process provided by the present invention can effectively achieve rapid growth of high-quality silicon carbide single crystals, can make the temperature and solute concentration distribution at the solid-liquid interface more uniform, and can suppress severe localized preferential corrosion of the crucible during the growth process.

[0103] Comparative Example 2

[0104] The only difference between this comparative example and Example 1 is that the in-situ clockwise rotating turbine pump provided by this invention was not used in the in-situ annealing process after crystal growth. All other crystal growth processes are completely consistent with Example 1.

[0105] Figure 7 The 6-inch silicon carbide crystal grown in Comparative Example 2 shows that the crystal surface is generally flat and smooth, but there are multiple cracks in the central area of ​​the crystal. This is because the temperature in the central area is too low during the in-situ annealing cooling process, resulting in excessive shrinkage in the central area and cracking.

[0106] This comparative example further demonstrates that the growth apparatus and growth process provided by the present invention can effectively reduce the thermal stress of the crystal and prevent stress cracking of the crystal during the cooling process.

[0107] Comparative Example 3

[0108] The steps of Comparative Example 3 are the same as those of Example 1, but the flow guide tube and flow guide cone are not provided on the device.

[0109] Optical photographs of the crystals grown in this comparative example are attached. Figure 8 The lack of a flow guide tube and flow cone resulted in extremely unstable solution convection, which not only did not significantly improve solute transport efficiency but also led to highly unstable crystal interfaces. Numerous disordered groove-like defects developed within the crystal, accompanied by the local growth of polycrystalline grains, resulting in very poor crystal quality.

[0110] This comparative example fully demonstrates the necessity of the guide tube and guide cone in the device provided by the present invention. Without the guide tube and guide cone, the ideal growth result cannot be achieved.

[0111] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. An apparatus for guiding the growth of silicon carbide single crystals, characterized in that, Includes a crucible, a first rotary lifting shaft, and a turbine liquid pump assembly; The turbine pump kit includes a flow guide baffle, the upper part of which is connected to the first rotary lifting shaft, and the lower part is equipped with a seed crystal holder with a seed crystal. Turbine blades are mounted on the flow guide baffle and are evenly distributed around the seed crystal. The lower end of the turbine blades is lower than the height of the seed crystal. The crucible is equipped with a flow guide tube inside. The outer diameter of the flow guide tube is smaller than the inner diameter of the crucible. The upper end of the flow guide tube is open, and the bottom is a bottom plate with a circular hole. A conical flow guide cone is fixed to the bottom plate of the crucible. The surface of the flow guide cone is concave inward to form a flow guide surface. The flow guide cone and the circular hole at the bottom of the flow guide tube are not in contact to form a liquid channel. The guide tube is above the liquid surface, and the height of the guide tube above the liquid surface is less than the height difference between the seed crystal and the guide baffle. The inner diameter of the guide tube is greater than the diameter of the circumcircle of the plurality of turbine blades, and less than or equal to the outer diameter of the guide baffle. The lower end of the turbine blade is 5-30 mm lower than the height of the seed crystal, and the upper end of the guide tube is 5-30 mm higher than the liquid surface. The difference between the outer diameter of the circumscribed circle and the inner diameter of the guide tube is 1-3 mm, the distance between the outer wall of the guide tube and the inner wall of the crucible is 10-30 mm, and the minimum distance between the edge of the circular hole at the bottom of the guide tube and the guide cone is 10 mm.

2. The apparatus according to claim 1, characterized in that, The crucible is located inside the furnace cavity shell, and the outside of the crucible is wrapped with heat-insulating material. An induction coil for heating is arranged between the furnace cavity shell and the heat-insulating material. The crucible is filled with a protective atmosphere and is placed on a support tray on which a second rotating lifting shaft is installed.

3. A method for guiding the growth of silicon carbide single crystals, characterized in that, Based on the apparatus according to any one of claims 1-2, the method comprises: S1, lower the turbine liquid pump assembly at the bottom of the first rotating lifting shaft, so that the turbine blades at the bottom of the turbine liquid pump assembly are immersed in the solution and the seed crystal at the bottom of the turbine liquid pump assembly is above the liquid surface, and rotate the turbine liquid pump assembly counterclockwise at a speed of v1 to drive the turbine blades to rotate for a duration of t1, so as to promote the solution to be mixed evenly through convection. S2, continue to push down the first rotating lifting shaft to make the seed crystal contact the liquid surface, and rotate the turbine liquid pump assembly clockwise at a speed of v2 to drive the turbine blades to rotate for a duration of t2, so as to suppress the flow of supersaturated solution to the seed crystal and thereby dissolve the damaged layer on the surface of the seed crystal. S3, slow growth stage, control the turbine pump rotation to slowly switch from clockwise rotation to counterclockwise rotation v3, and maintain the rotation speed v3 for time t3; S4, accelerated growth stage: adjust the turbine liquid pump assembly to increase the turbine liquid pump speed from v3 to v5 to accelerate the solute supply rate and accelerate crystal growth; S5, the stable growth stage, involves continuously rotating the turbine blades at a speed of v5 for a duration of t5 to achieve crystal growth. S6, after the predetermined growth time is reached, the rotation speed of the turbine liquid pump is reduced from the counterclockwise rotation speed v5 to 0, and the turbine liquid pump assembly is pulled off the liquid surface as a whole.

4. The method according to claim 3, characterized in that, In step S1, the rotational speed v1 of the turbine liquid pump assembly is 20~50 rpm, and the time t1 is 10~30 min; In step S2, the rotational speed v2 of the turbine pump assembly is -15 to -25 rpm, and the time t2 is 5 to 15 min. In step S3, the rotational speed v3 of the turbine liquid pump assembly is 30~80 rpm, and the time t3 is 30~90 min; In step S4, the target speed v5 after acceleration of the turbo pump kit is 60~150 rpm, and the acceleration time t4 is 60~180 min; In step S5, the rotational speed v5 of the turbine liquid pump assembly is 60~150 rpm, and the time t5 is 10~200 h; In step S6, the deceleration time t6 is 30~60 min, where the negative sign indicates clockwise rotation speed.

5. The method according to claim 3, characterized in that, Before S1, there is also S0, which heats the solution to a preset temperature and rotates the turbine pump assembly clockwise to form an airflow from the edge of the seed crystal to the center region of the seed crystal; Following S6, there is also S7, where the temperature is slowly lowered for annealing. During the annealing process, the turbine pump assembly is rotated clockwise to form an airflow from the side edge of the crystal to the central region of the crystal.

6. The method according to claim 5, characterized in that, In step S0, the rotational speed v0 of the turbine pump assembly is -30 to -60 rpm, and the time t0 is 60 to 180 min; In step S7, the rotational speed v7 of the turbine pump assembly is -60 to -120 rpm, and the time t7 is 10 to 30 h, where the negative sign indicates clockwise rotational speed.

Images