Method and device for growing silicon carbide single crystals by liquid phase method

Abstract

The invention relates to the technical field of silicon carbide single crystal preparation, in particular to a method and a device for growing silicon carbide single crystals by a liquid phase method. The embodiment of the invention provides a method for growing a silicon carbide single crystal by a liquid phase method, which comprises the following steps of: heating and melting a material containing a solvent element in a crucible resistant to high-temperature melt corrosion to obtain a high-temperature solution in the crucible; putting a raw material block prepared from silicon carbide into the high-temperature solution so as to provide a carbon element and a silicon element in the high-temperature solution; and driving a silicon carbide seed crystal to enter the crucible by using a first rotary lifting rod, so that the silicon carbide seed crystal is in contact with the liquid level of the high-temperature solution to grow the silicon carbide single crystal. The embodiment of the invention provides a method and a device for growing silicon carbide single crystals by a liquid phase method, which can realize long-time stable growth of silicon carbide crystals.

Description

Technical Field

[0001] The present invention relates to the technical field of silicon carbide single crystal preparation, and in particular to a method and device for growing silicon carbide single crystal by a liquid phase method. Background Art

[0002] As one of the typical representatives of wide bandgap semiconductors, silicon carbide has excellent properties such as large bandgap width, high breakdown field strength, high saturated electron mobility, high thermal conductivity, good thermal stability and chemical stability. It is an ideal substrate material for making high-frequency, high-voltage, high-efficiency, radiation-resistant, high-temperature resistant high-power devices and blue light-emitting diodes, which makes it have huge application prospects in new energy vehicles, high-speed rail transit, aerospace, high-voltage smart grids and clean energy. Therefore, it has received widespread attention from academia and governments of various countries.

[0003] At present, the crystal quality and manufacturing cost of silicon carbide single crystal substrates are still one of the main factors limiting its further expansion in application. Exploring and studying methods to obtain high-quality, large-size and low-cost silicon carbide single crystal substrates is very important for fully realizing the huge application potential of silicon carbide.

[0004] The current mainstream method for growing silicon carbide single crystal substrates is physical vapor transport (PVT). Although this method has become relatively mature after decades of continuous research and development and improvement, and can currently supply a large number of silicon carbide single crystal substrates to the market, it still has some unavoidable limitations, mainly manifested in its unstable growth environment, defects that are difficult to eliminate, low yield, high cost; difficulty in diameter expansion; and difficulty in achieving continuous and effective P-type doping.

[0005] Compared with the gas phase method, the liquid phase method requires a low growth temperature and a relatively stable growth environment, which can achieve the growth of crystals in a near-equilibrium state. Not only is the growth cost relatively low, but also higher crystal quality can be achieved in theory. In addition, the liquid phase method also has good application prospects in obtaining P-type substrates and expanding crystal diameters. Therefore, the liquid phase method has received more and more attention in recent years, and related technologies have also made breakthrough progress. In the liquid phase method for growing silicon carbide single crystals, the crucible is corroded to provide a carbon source for crystal growth, which will lead to poor growth stability during the growth process due to the continuous corrosion of the crucible. In addition, during the growth process, only Si and C elements will continue to precipitate from the solution, and the C element can be continuously supplemented by corroding the crucible, but the Si element is only consumed and not supplemented during the growth process, which will cause the Si content in the high-temperature solution to continue to decrease during the growth process, thereby seriously affecting the long-term stability of crystal growth. Therefore, it is very important for the further development of the liquid phase method to develop a method that can achieve long-term stable growth of crystals. Summary of the invention

[0006] The embodiments of the present invention provide a method and device for growing a silicon carbide single crystal by a liquid phase method, which can achieve long-term stable growth of silicon carbide crystals.

[0007] In a first aspect, an embodiment of the present invention provides a method for growing a silicon carbide single crystal by a liquid phase method, comprising: placing a material containing a solvent element in a crucible resistant to high temperature melt corrosion and heating and melting it to obtain a high temperature solution in the crucible; placing a raw material block prepared from silicon carbide in the high-temperature solution to provide carbon and silicon elements to the high-temperature solution; The first rotating lifting rod is used to drive the silicon carbide seed crystal into the crucible, so that the silicon carbide seed crystal contacts the liquid surface of the high-temperature solution to grow a silicon carbide single crystal.

[0008] In a possible design, before placing the raw material block prepared from silicon carbide in the high-temperature solution to provide carbon and silicon elements to the high-temperature solution, the process further includes: Rotating the crucible to mix the high-temperature solution evenly; wherein the rotation speed of the crucible is 10-60 rpm; The silicon carbide seed crystal and the raw material block are rotated so that the silicon carbide seed crystal and the raw material block are heated evenly; wherein the rotation speeds of the silicon carbide seed crystal and the raw material block are both 10-60 rpm.

[0009] In a possible design, placing the raw material block prepared from silicon carbide in the high-temperature solution includes: Using the second rotating lifting rod to drive the raw material block prepared from silicon carbide to immerse in the high-temperature solution; After the first rotating lifting rod is used to drive the silicon carbide seed crystal into the crucible so that the silicon carbide seed crystal contacts the liquid surface of the high-temperature solution to grow a silicon carbide single crystal, the method further includes: The liquid level of the high-temperature solution in the crucible is monitored, and the volume of the raw material block immersed in the high-temperature solution is adjusted by using the second rotating lifting rod to keep the liquid level of the high-temperature solution unchanged.

[0010] In a possible design, placing the raw material block prepared from silicon carbide in the high-temperature solution further includes: After the high-temperature solution is evenly mixed, the raw material block is immersed in the high-temperature solution by using the second rotating lifting rod; The crucible is rotated in a first direction, and the raw material block is rotated in a second direction at a first rotation speed at the same time; wherein the first direction and the second direction are opposite.

[0011] In a possible design, after the first rotating lifting rod is used to drive the silicon carbide seed crystal into the crucible so that the silicon carbide seed crystal contacts the liquid surface of the high-temperature solution to grow a silicon carbide single crystal, the method further includes: The crucible is kept rotating in a first direction, the rotation speed of the raw material block is reduced from the first rotation speed to a second rotation speed, and the silicon carbide seed crystal is rotated in the second direction at the same time.

[0012] In a possible design, the rotation speed of the crucible is 5-30 rpm, the first rotation speed is 50-300 rpm, the second rotation speed is 10-100 rpm, and the rotation speed of the silicon carbide seed crystal is 30-200 rpm.

[0013] In one possible design, the crucible comprises a tantalum carbide crucible; or, The inner wall of the crucible is plated with a tantalum carbide corrosion-resistant coating.

[0014] In one possible design, it also includes: An insulation layer is wrapped outside the crucible, the insulation layer includes a first channel and a second channel, the first rotating lifting rod passes through the first channel, the second rotating lifting rod passes through the second channel, and the caliber of the first channel is larger than the caliber of the second channel.

[0015] In a possible design, the caliber of the first channel is 80-200 mm, and the caliber of the second channel is 20-50 mm.

[0016] In a second aspect, an embodiment of the present invention further provides a device for growing silicon carbide single crystals by a liquid phase method, which is used to implement any of the above methods, and the device includes a crucible, an insulation layer, an induction coil, a first rotating lifting rod, a second rotating lifting rod and a crucible rotating device; The crucible in the growth furnace is used to hold the high-temperature solution, the insulation layer is sleeved on the outside of the crucible to keep the crucible warm, the induction coil is used to heat the crucible, the first rotating lifting rod is used to rotate and lift the silicon carbide seed crystal, the second rotating lifting rod is used to rotate and lift the raw material block, and the crucible rotating device is used to rotate the crucible.

[0017] Compared with the prior art, the present invention has at least the following beneficial effects: Using silicon carbide raw material blocks to provide Si and C elements for crystal growth can ensure that the concentrations of Si and C elements in the solution remain unchanged during the long-term growth of the crystal, which is conducive to long-term stable growth. Specifically, the carbon source and silicon source required for the growth of silicon carbide single crystals come from the raw material blocks. The raw material blocks are immersed in a high-temperature solution. The high-temperature solution will dissolve the raw material blocks and obtain carbon and silicon elements in the high-temperature solution. As silicon carbide grows, the carbon and silicon elements in the solution are consumed. At the other end, the raw material blocks are also continuously dissolved to compensate for the carbon and silicon elements in the high-temperature solution, and finally achieve long-term stable growth of silicon carbide. In addition, since the carbon element in the growth raw material of silicon carbide single crystals comes from the raw material blocks, there is no need for the crucible itself to provide a carbon source. In order to ensure the stable growth of silicon carbide single crystals, a crucible resistant to high-temperature melt corrosion is selected. In this way, after a long period of growth, there is no need to replace the crucible, and only a simple replenishment of the raw material blocks is required. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0019] Figure 1 It is a structural schematic diagram of a method and device for growing a silicon carbide single crystal by a liquid phase method provided in an embodiment of the present invention; Figure 2 is an optical photograph of a high-quality silicon carbide single crystal provided by Example 1 of the present invention; Figure 3 This is a cross-sectional optical photograph of the crucible after the growth is completed in Comparative Example 1 of the present invention, and a part of the side wall of the crucible has been dissolved by the flux; Figure 4 This is the silicon carbide crystal growth result provided in Comparative Example 3 of the present invention. An obvious necking phenomenon occurs in the later stage of crystal growth.

[0020] In the figure: 1-controller; 2-signal transmission line; 3-first drive device; 4-second drive device; 5-laser rangefinder; 6-second rotating lifting rod; 7-first rotating lifting rod; 8-insulating layer; 9-growth furnace; 10-crucible; 11-induction coil; 12-raw material block; 13-seed crystal tray; 14-silicon carbide seed crystal; 15-high temperature solution; 16-crucible support tray; 17-crucible rotating device. DETAILED DESCRIPTION

[0021] In order to make the purpose, 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 in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0022] In the description of the embodiments of the present invention, unless otherwise clearly specified and limited, the terms "first" and "second" are used for descriptive purposes only and cannot be understood as indicating or implying relative importance; unless otherwise specified or explained, the term "multiple" refers to two or more; the terms "connected" and "fixed" should be understood in a broad sense, for example, "connected" can be a fixed connection, a detachable connection, an integral connection, or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0023] In the description of this specification, it should be understood that the directional words such as "upper" and "lower" described in the embodiments of the present invention are described at the angles shown in the drawings and should not be understood as limiting the embodiments of the present invention. In addition, in the context, it should also be understood that when it is mentioned that an element is connected to another element "upper" or "lower", it can not only be directly connected to another element "upper" or "lower", but also indirectly connected to another element "upper" or "lower" through an intermediate element.

[0024] like Figure 1 As shown, an embodiment of the present invention provides a method for growing a silicon carbide single crystal by a liquid phase method, comprising: The material containing the solvent element is placed in a crucible 10 resistant to high temperature melt corrosion and heated to melt, thereby obtaining a high temperature solution 15 in the crucible 10; Placing a raw material block 12 made of silicon carbide in a high-temperature solution 15 to provide carbon and silicon elements to the high-temperature solution 15; The first rotating lifting rod 7 is used to drive the silicon carbide seed crystal 14 into the crucible 10, so that the silicon carbide seed crystal 14 contacts the liquid surface of the high-temperature solution 15 to grow a silicon carbide single crystal.

[0025] By using the silicon carbide raw material block 12 to provide Si and C elements for crystal growth, it can be ensured that the concentrations of Si and C elements in the solution remain unchanged during the long-term growth of the crystal, which is conducive to long-term stable growth. Specifically, the carbon source and silicon source required for the growth of silicon carbide single crystals come from the raw material block 12. The raw material block 12 is immersed in a high-temperature solution 15. The high-temperature solution 15 will dissolve the raw material block 12, and obtain carbon and silicon elements in the high-temperature solution 15. As the silicon carbide grows, the carbon and silicon elements in the solution are consumed. At the other end, the raw material block 12 is also continuously dissolved, and the carbon and silicon elements are compensated to the high-temperature solution 15, and finally the long-term stable growth of silicon carbide is achieved. In addition, since the carbon element in the growth raw material of the silicon carbide single crystal comes from the raw material block 12, there is no need for the crucible 10 itself to provide a carbon source. In order to ensure the stable growth of the silicon carbide single crystal, a crucible 10 resistant to high-temperature melt corrosion is selected. In this way, after a long period of growth, there is no need to replace the crucible 10, and only a simple replenishment of the raw material block 12 is required.

[0026] In this embodiment, the element composition of the raw material block satisfies the molar ratio Si:C=1:1, and the shape is cylindrical or prismatic. It can be a single crystal silicon carbide block with poor crystal quality, a polycrystalline silicon carbide block, or a block after uniformly mixing and sintering silicon and carbon.

[0027] In some embodiments of the present invention, the elemental composition of the solvent raw material is Si + transition metal elements (including Cr, Fe, Ni, Ti, Al, Mn, Co, Sc, etc.) + rare earth elements (including Y, Ce, Pr, etc.).

[0028] In some embodiments of the present invention, before placing the raw material block 12 prepared from silicon carbide in the high-temperature solution 15 to provide carbon and silicon elements to the high-temperature solution 15, the method further includes: Rotate the crucible 10 to mix the high-temperature solution evenly; wherein the rotation speed of the crucible 10 is 10-60 rpm; The silicon carbide seed crystal 14 and the raw material block 12 are rotated so that the silicon carbide seed crystal 14 and the raw material block 12 are heated evenly; wherein the rotation speeds of the silicon carbide seed crystal 14 and the raw material block 12 are both 10-60 rpm.

[0029] In this embodiment, the crucible is rotated to rotate the molten high temperature solution, thereby mixing the components inside. When the silicon carbide seed crystal 14 and the raw material block 12 are not immersed in the high temperature solution, they are rotated first to preheat them evenly.

[0030] In some embodiments of the present invention, placing a raw material block 12 made of silicon carbide in a high-temperature solution 15 comprises: The second rotating lifting rod 6 drives the raw material block 12 made of silicon carbide to be immersed in the high-temperature solution 15; After the first rotating lifting rod 7 is used to drive the silicon carbide seed crystal 14 into the crucible 10 so that the silicon carbide seed crystal 14 contacts the liquid surface of the high-temperature solution 15 to grow a silicon carbide single crystal, the method further includes: The liquid level of the high-temperature solution 15 in the crucible 10 is monitored, and the volume of the raw material block 12 immersed in the high-temperature solution 15 is adjusted by using the second rotating lifting rod 6 to keep the liquid level of the high-temperature solution 15 unchanged.

[0031] In this embodiment, the depth of the raw material block 12 immersed in the high-temperature solution 15 can be controlled to control the height of the liquid level during the crystal growth process. Combined with the liquid level monitoring and feedback device, the liquid level can be kept stable during the long-term growth process, which is very beneficial for the growth of high-quality crystals. Specifically, the laser rangefinder 5 can be used to detect the liquid level of the high-temperature solvent. The laser rangefinder 5 is connected to the control device through a signal transmission line 2. The laser rangefinder 5 feeds back the collected liquid level information to the controller 1, and the controller 1 controls the second rotating lifting rod 6 to rise and fall to keep the height of the high-temperature solution 15 unchanged. It should be noted that the laser rangefinder 5 can be set outside the thermal insulation layer 8. In order to facilitate the laser rangefinder 5 to measure the liquid level position of the high-temperature solution 15, a light-transmitting hole can be set on the thermal insulation layer 8 to facilitate the laser to pass through the thermal insulation layer 8 to reach the liquid surface of the high-temperature solution 15.

[0032] In this embodiment, the controller 1 can control the lifting and rotation of the first rotating lifting rod 7 and the second rotating lifting rod 6 through the first driving device 3 and the second driving device 4 respectively.

[0033] In some embodiments of the present invention, placing the raw material block 12 prepared from silicon carbide in the high-temperature solution 15 further includes: After the high-temperature solution is evenly mixed, the raw material block is immersed in the high-temperature solution by using the second rotating lifting rod; The crucible 10 is rotated in a first direction, and the raw material block 12 is rotated in a second direction at a first rotation speed, wherein the first direction and the second direction are opposite.

[0034] In this embodiment, the raw material block 12 is first immersed in a high-temperature solution, and the crucible 10 and the raw material block are rotated in the opposite direction, so that the Si and C elements in the raw material block are quickly dissolved into the high-temperature solution to reach saturation.

[0035] In some embodiments of the present invention, after the first rotating lifting rod 7 is used to drive the silicon carbide seed crystal 14 into the crucible 10 so that the silicon carbide seed crystal 14 contacts the liquid surface of the high-temperature solution 15 to grow a silicon carbide single crystal, the method further includes: The crucible is kept rotating in the first direction, the rotation speed of the raw material block is reduced from the first rotation speed to the second rotation speed, and the silicon carbide seed crystal 14 is rotated in the second direction at the same time.

[0036] In this embodiment, the high temperature solution 15 in the crucible 10 is a solvent for crystal growth, which can dissolve and transfer Si and C elements and precipitate SiC at the low temperature end; during the growth process, the raw material block 12 rotates in the high temperature solution 15, which can promote the high temperature solution 15 to dissolve Si and C elements from the raw material block 12. The Si and C elements dissolved in the high temperature solution 15 will be transferred to the relatively low temperature silicon carbide seed crystal 14 end under the combined use of the rotation of the crucible 10 and the convection and solute diffusion of the high temperature solution 15. The Si and C elements are continuously precipitated and deposited in the form of SiC on the silicon carbide seed crystal 14 to achieve continuous growth of the crystal. Among them, the convection of the high temperature solution 15 is achieved by counter-rotating the crucible 10 and the raw material block 12.

[0037] It is understandable that during the growth stage of silicon carbide single crystal, the Si and C elements in the high-temperature solution reach a dynamic balance, and the rotation speed requirement for the raw material block is reduced. Therefore, the rotation speed of the raw material block is slowed down.

[0038] In some embodiments of the present invention, the rotation speed of the crucible 10 is 5-30 rpm, the first rotation speed is 50-300 rpm, the second rotation speed is 10-100 rpm, and the rotation speed of the silicon carbide seed crystal 14 is 30-200 rpm.

[0039] In this embodiment, during the growth process, the dissolution rate of the raw material block 12 and the growth rate of the silicon carbide single crystal can be regulated by controlling the rotation speed of the silicon carbide seed crystal 14, the rotation speed of the raw material block 12 and the rotation speed of the crucible 10, so that the dissolution of the raw material block and the growth of silicon carbide reach a dynamic balance. It has been verified through experiments that when the rotation speeds of the crucible 10, the silicon carbide seed crystal 14 and the raw material block 12 are within the above range, the growth quality is the highest.

[0040] In some embodiments of the present invention, the crucible 10 comprises a tantalum carbide crucible 10 .

[0041] or, The inner wall of the crucible 10 is plated with a tantalum carbide corrosion-resistant coating.

[0042] In some embodiments of the present invention, it further includes: The crucible 10 is wrapped with an insulating layer 8, which includes a first channel and a second channel. The first rotating lifting rod 7 passes through the first channel, and the second rotating lifting rod 6 passes through the second channel. The diameter of the first channel is larger than that of the second channel.

[0043] In this embodiment, the first channel opening of the insulation layer 8 at the top of the silicon carbide seed crystal 14 has a large diameter, and the second channel opening of the insulation layer 8 at the top of the raw material block 12 has a small diameter. Therefore, the temperature at the silicon carbide seed crystal 14 can be lower than the temperature at the raw material block 12, so that the raw materials are dissolved in the growth process to provide Si and C elements, and the Si and C elements migrate to the silicon carbide seed crystal 14 to precipitate and grow.

[0044] In some embodiments of the present invention, the caliber of the first channel is 80-200 mm, and the caliber of the second channel is 20-50 mm.

[0045] In this embodiment, when the diameters of the first channel and the second channel are within the above range, the growth effect of the silicon carbide single crystal is optimal.

[0046] The embodiment of the present invention further provides a device for growing silicon carbide single crystal by liquid phase method, which is used to implement any of the above methods, and the device includes a crucible 10, a heat preservation layer 8, an induction coil, a first rotating lifting rod 7, a second rotating lifting rod 6 and a crucible rotating device 17; The crucible 10 in the growth furnace 9 is used to hold a high-temperature solution 15, the insulation layer 8 is sleeved on the outside of the crucible 10 to keep the crucible 10 warm, the induction coil is used to heat the crucible 10, the first rotating lifting rod 7 is used to rotate and lift the silicon carbide seed crystal 14, the second rotating lifting rod 6 is used to rotate and lift the raw material block 12, and the crucible rotating device 17 is used to rotate the crucible 10.

[0047] In this embodiment, the first rotating lifting rod 7 is connected to the silicon carbide seed crystal 14 via the seed crystal holder 13. The growth crucible 10 is placed on the crucible support tray 16.

[0048] The embodiment of the present invention also provides a method for preparing a silicon carbide single crystal by a liquid phase method, comprising: 1) loading the solvent raw material into a crucible 10 resistant to high temperature melt corrosion; 2) placing the crucible 10 into the growth furnace 9, fixing the silicon carbide seed crystal 14 and the silicon carbide raw material block 12 on the first and second rotating lifting and lowering rods at the top of the device, respectively, and ensuring that the raw material block 12 and the silicon carbide seed crystal 14 are not in contact with the material surface at this time; 3) After the insulation layer 8 is configured, the furnace chamber is closed, the furnace chamber is subjected to high vacuum treatment, and then the growth protective atmosphere is configured; 4) heating the crucible 10 to 1800° C. to completely liquefy the solvent raw material in the crucible 10, and rotating the crucible 10 at a speed of 10 rpm to completely homogenize the high-temperature solvent; 5) Control the second rotating lifting rod 6 to slowly descend, and immerse the raw material block 12 in the high-temperature solution 15 until the liquid level reaches a preset height, and at the same time control the raw material to rotate at a speed of 60 rpm, the rotation direction is opposite to the crucible 10, so as to accelerate the solution of the silicon carbide raw material block 12; 6) After the high-temperature solution 15 dissolves the raw material block 12 to saturation, the height of the raw material block 12 is adjusted so that the liquid level returns to a preset height; 7) Second, the first rotating lifting rod is controlled to slowly lower the silicon carbide seed crystal 14 and contact the liquid surface, and crystal growth begins; 8) During the crystal growth process, the silicon carbide seed crystal 14 is controlled to rotate periodically and pulled at a certain pulling speed; 9) During the growth process, the laser rangefinder located at the top of the device monitors the height data of the liquid level in real time and feeds back the data to the controller 1. The controller 1 calculates according to the data fed back by the laser rangefinder 5 and sends an adjustment signal to the second drive device 4, and adjusts the depth of the raw material being immersed in the high-temperature solution 15 in real time in situ to ensure that the height of the liquid level remains unchanged during the growth process; 10) After the growth is completed, the crystal and the raw material block 12 are pulled away from the liquid surface and slowly cooled; 11) After the temperature reaches room temperature, remove the crystal.

[0049] In order to more clearly illustrate the technical solutions and advantages of the present invention, several embodiments are described in detail below. Example 1

[0050] This embodiment adopts the device and method for growing silicon carbide crystals by liquid phase method provided by the present invention to grow silicon carbide single crystals, including the following steps: The solvent raw material is loaded into a crucible resistant to high temperature melt corrosion, wherein the composition and ratio of the solvent raw material is Cr:Fe:Ti=60:20:20, and the total mass is 15 kg; the high temperature and corrosion resistant crucible is a graphite crucible with a tantalum carbide coating on the inner wall.

[0051] The crucible is placed in a growth furnace, and the silicon carbide seed crystal and the silicon carbide raw material block are respectively fixed on the first and second rotating lifting and lowering rods at the top of the device, and it is ensured that the raw material block and the silicon carbide seed crystal do not contact the material surface at this time; After the insulation layer is configured, the furnace chamber is closed, the furnace chamber is subjected to high vacuum treatment, and then the growth protection atmosphere is configured; Heat the crucible to 1800°C to completely liquefy the solvent raw materials in the crucible, and rotate the crucible at a speed of 10 rpm to completely homogenize the high-temperature solvent; Control the second rotating lifting rod to slowly descend, and immerse the raw material block in the high-temperature solution until the liquid level reaches a preset height, and at the same time control the raw material to rotate at a speed of 60 rpm, the rotation direction is opposite to the crucible, so as to speed up the solution of the silicon carbide raw material block; After the high-temperature solution dissolves the raw material block to saturation, adjust the height of the raw material block so that the liquid level returns to the preset height; secondly, controlling the first rotating lifting rod to make the silicon carbide seed crystal slowly descend and contact with the liquid surface, and the crystal growth starts; During the crystal growth process, the silicon carbide seed crystal is controlled to rotate periodically and pulled at a certain pulling speed; During the growth process, the laser rangefinder located at the top of the equipment monitors the height data of the liquid level in real time and feeds back to the controller. The controller calculates according to the data fed back by the laser rangefinder and sends an adjustment signal to the second drive device, and adjusts the depth of the raw material immersed in the high-temperature solution in real time in situ to ensure that the height of the liquid level remains unchanged during the growth process. After the growth is completed, the crystals and raw material blocks are pulled away from the liquid surface and slowly cooled; After the temperature reaches room temperature, remove the crystal.

[0052] Figure 2 This is a photo of the silicon carbide crystal produced in this embodiment. The crystal surface is bright and the crystal quality is very high. The growth rate is 300 μm / h and the growth thickness is 20 mm. It proves that the device and method provided by the present invention can effectively improve the stability of long-term rapid growth of crystals and obtain high-quality silicon carbide crystals.

[0053] Comparative Example 1 The process parameters of this comparative example are basically the same as those of Example 1, except that the device of the present invention is not used.

[0054] In this comparative example, the growth crucible is severely corroded. Figure 3 As shown, the side wall of the crucible has been dissolved. In addition, a large number of groove defects appear in the late stage of crystal growth, and the time growth stability is poor. The comparison shows that in the absence of the device provided by the present invention, the growth process stability is poor by corroding the crucible to provide raw materials for crystal growth, which is very unfavorable for the long-term growth of crystals.

[0055] Comparative Example 2 The process parameters of this comparative example are basically the same as those of Example 1, except that the crucible is not rotated during the growth process.

[0056] In this comparative example, the crystal growth rate is 60 μm / h, there are a few grooves on the crystal surface, and the crystal quality is poor. The comparison shows that when the crucible is not rotated, the solute transmission rate is low, resulting in insufficient solute supply during the growth process, which in turn leads to a low crystal growth rate and poor crystal quality.

[0057] Comparative Example 3 The process parameters of this comparative example are basically the same as those of Example 1, except that no liquid level control technology is used.

[0058] Figure 4The optical photograph of the silicon carbide crystal grown in this comparative example shows that serious necking phenomenon occurs in the late stage of crystal growth, and there are some obvious defects on the surface of the crystal, indicating that the crystal quality is poor. The comparison shows that without using the liquid level control technology provided by the present invention, the liquid level will continue to decrease as the crystal grows, causing the meniscus height to continue to increase during the crystal growth process, which will not only cause crystal necking, but also affect the stability of the crystal interface, thereby causing the crystal quality to deteriorate.

[0059] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for growing a silicon carbide single crystal by a liquid phase method, characterized in that: include: placing a material containing a solvent element in a crucible (10) resistant to corrosion by a high temperature melt and heating and melting it to obtain a high temperature solution (15) in the crucible (10); Placing a raw material block (12) made of silicon carbide in the high-temperature solution (15) to provide carbon and silicon elements to the high-temperature solution (15); The first rotating lifting rod (7) is used to drive the silicon carbide seed crystal (14) into the crucible (10), so that the silicon carbide seed crystal (14) contacts the liquid surface of the high-temperature solution (15) to grow a silicon carbide single crystal.

2. The method according to claim 1, characterized in that Before placing the raw material block (12) prepared from silicon carbide in the high-temperature solution (15) to provide carbon and silicon elements to the high-temperature solution (15), the method further comprises: Rotating the crucible (10) to mix the high-temperature solution evenly; wherein the rotation speed of the crucible (10) is 10-60 rpm; The silicon carbide seed crystal (14) and the raw material block (12) are rotated so that the silicon carbide seed crystal (14) and the raw material block (12) are heated evenly; wherein the rotation speeds of the silicon carbide seed crystal (14) and the raw material block (12) are both 10 to 60 rpm.

3. The method according to claim 1, characterized in that Placing the raw material block (12) prepared from silicon carbide in the high-temperature solution (15) comprises: Using a second rotating lifting rod (6) to drive a raw material block (12) made of silicon carbide to be immersed in the high-temperature solution (15); After the first rotating lifting rod (7) is used to drive the silicon carbide seed crystal (14) into the crucible (10), so that the silicon carbide seed crystal (14) contacts the liquid surface of the high-temperature solution (15) to grow a silicon carbide single crystal, the method further comprises: The liquid level of the high-temperature solution (15) in the crucible (10) is monitored, and the volume of the raw material block (12) immersed in the high-temperature solution (15) is adjusted by using the second rotating lifting rod (6) to keep the liquid level of the high-temperature solution (15) unchanged.

4. The method according to claim 3, characterized in that Also includes: After the high-temperature solution is evenly mixed, the raw material block is immersed in the high-temperature solution by using the second rotating lifting rod; The crucible (10) is rotated in a first direction, and the raw material block (12) is simultaneously rotated in a second direction at a first rotation speed; wherein the first direction and the second direction are opposite.

5. The method according to claim 3, characterized in that: After the first rotating lifting rod (7) is used to drive the silicon carbide seed crystal (14) into the crucible (10), so that the silicon carbide seed crystal (14) contacts the liquid surface of the high-temperature solution (15) to grow a silicon carbide single crystal, the method further comprises: The crucible is kept rotating in a first direction, the rotation speed of the raw material block is reduced from the first rotation speed to a second rotation speed, and the silicon carbide seed crystal (14) is rotated in the second direction at the same time.

6. The method according to claim 5, characterized in that The rotation speed of the crucible (10) is 5-30 rpm, the first rotation speed is 50-300 rpm, the second rotation speed is 10-100 rpm, and the rotation speed of the silicon carbide seed crystal (14) is 30-200 rpm.

7. The method according to claim 1, characterized in that The crucible (10) comprises a tantalum carbide crucible (10); or, The inner wall of the crucible (10) is plated with a tantalum carbide corrosion-resistant coating.

8. The method according to claim 1, characterized in that: Also includes: An insulating layer (8) is wrapped around the outside of the crucible (10), the insulating layer (8) comprising a first channel and a second channel, the first rotating lifting rod (7) passes through the first channel, the second rotating lifting rod (6) passes through the second channel, and the caliber of the first channel is larger than the caliber of the second channel.

9. The method according to claim 8, characterized in that The caliber of the first channel is 80-200 mm, and the caliber of the second channel is 20-50 mm.

10. A device for growing silicon carbide single crystal by liquid phase method, characterized in that: Used to implement any of the methods described in claims 1 to 9, the device comprising a crucible (10), a heat-insulating layer (8), an induction coil (11), a first rotating lifting rod (7), a second rotating lifting rod (6) and a crucible rotating device (17); The crucible (10) in the growth furnace (9) is used to contain the high-temperature solution (15); the heat-insulating layer (8) is sleeved on the outside of the crucible (10) to keep the crucible (10) warm; the induction coil (11) is used to heat the crucible (10); the first rotating lifting rod (7) is used to rotate and lift the silicon carbide seed crystal (14); the second rotating lifting rod (6) is used to rotate and lift the raw material block (12); and the crucible rotating device (17) is used to rotate the crucible (10).

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