Device for growing silicon carbide single crystals by liquid phase method

Abstract

A device for growing silicon carbide single crystals by a liquid phase method, the device comprising a growth crucible, a seed rod, an induction heating device and a material block capable of providing growth raw materials. The growth crucible comprises a crucible body and a crucible cover, the crucible body is filled with the growth raw materials, the crucible cover has an opening, and one end of the seed rod for fixing seed crystals extends into the crucible body through the opening; and the material block has a smaller density than the liquid growth raw materials, and the material block floats on a surface of the liquid growth raw materials. The device can reduce a carbon supply distance, provide a sufficient and long-term stable carbon source for a growth process of silicon carbide single crystals, greatly reduce the generation of inclusions, effectively improve the quality of single crystal growth, effectively inhibit a crucible wall from being melted through, and prevent the leakage of an auxiliary solution from affecting a temperature field and even damaging a single crystal furnace.

Description

A device for growing silicon carbide single crystal by liquid phase method Technical Field

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

[0002] As one of the third-generation semiconductor materials, silicon carbide (SiC) has the advantages of wide bandgap, high critical breakdown field strength, and high saturated electron drift rate, making it an ideal material for manufacturing high-temperature, high-frequency, high-voltage and high-power devices. It has been widely used in many fields such as rail transportation, new energy vehicles, 5G communications, aerospace, etc.

[0003] For silicon carbide single crystal growth technology, a stable carbon source supply is the core key factor of growth. Especially when using the liquid phase method for silicon carbide single crystal growth, if sufficient carbon supply cannot be guaranteed, problems such as solution encapsulation and crystal cracking will occur during crystal growth.

[0004] The technology of growing silicon carbide single crystals by liquid phase method is to transport and supply carbon elements through the combined action of convective mass transfer and diffusion mass transfer. Convective mass transfer includes the forced convection generated by the rotation of the seed crystal and the natural convection caused by the concentration difference in the growth system, while diffusion mass transfer is mainly the diffusion of carbon sources at the solid-liquid interface of crystal growth. However, as the crystal grows, the carbon element on the surface of the growth crucible is consumed, causing the carbon supply position to be farther and farther away from the growth position, and the diffusion mass transfer effect is weakened, making it difficult to ensure the sufficient supply of carbon elements required for crystal growth. Then, defects such as solution encapsulation and crystal cracking occur, affecting the quality of the crystal and causing the quality of crystal growth to deteriorate. Secondly, during long-term growth, the growth crucible (graphite crucible) as the carbon source is gradually consumed as the growth progresses, which may cause the growth crucible to melt through, and the solution flows into the furnace, thereby damaging the single crystal furnace, affecting the progress of the experiment and causing large economic losses.

[0005] Therefore, it is very necessary to provide a new device for growing silicon carbide single crystals by liquid phase method.

[0006] Summary of the Invention

[0007] To address one or more technical problems existing in the prior art, the present invention provides a device for growing silicon carbide single crystals using a liquid phase method. The device of the present invention first shortens the carbon supply distance during the liquid phase growth of silicon carbide single crystals and ensures that the carbon supply distance remains unchanged. Secondly, it can provide a sufficient and long-term stable carbon source for the silicon carbide single crystal growth process, significantly reducing the generation of inclusions and effectively improving the quality of single crystal growth. It also effectively inhibits melt penetration of the crucible wall, preventing leakage of the auxiliary solution from affecting the temperature field and even damaging the single crystal furnace. This improves the repeatability and stability of single crystal growth experiments, enables long-term growth, reduces crucible wall thickness, and saves costs.

[0008] The present invention provides a device for growing silicon carbide single crystals using a liquid phase method, the device comprising a growth crucible, a seed crystal rod fixed with a seed crystal, an induction heating device for heating, and a material block that can provide growth raw materials; the growth crucible comprises a crucible body and a crucible cover, the crucible body is filled with growth raw materials, the crucible cover has an opening, and one end of the seed crystal rod fixed with the seed crystal extends into the interior of the crucible body through the opening; the density of the material block that can provide growth raw materials is less than the density of liquid growth raw materials, and the material block that can provide growth raw materials floats on the surface of the liquid growth raw materials.

[0009] Preferably, the material block that can provide growth raw materials is a silicon carbide block.

[0010] Preferably, the material block that can provide growth raw materials is a graphite block for carbon supply.

[0011] Preferably, the carbon supply graphite block is an annular carbon supply graphite block; the annular carbon supply graphite block is arranged closely against the inner wall of the crucible body, or the outer diameter of the annular carbon supply graphite block is slightly smaller than the inner diameter of the crucible body.

[0012] Preferably, the device also includes a graphite block connector; the crucible wall of the crucible body is provided with a slot from the top downward, one end of the graphite block connector is provided with a ring, the ring is clamped in the slot, and the other end of the graphite block connector is connected to a carbon supply graphite block, the density of the carbon supply graphite block is less than the density of the liquid growth raw material, and the carbon supply graphite block floats on the liquid surface of the growth raw material.

[0013] Preferably, the graphite block connector is arranged close to the crucible wall of the crucible body; and / or the ring can move up and down in the slot.

[0014] Preferably, the graphite block connector and the ring are both made of graphite.

[0015] Preferably, one end of the seed crystal rod not fixed with the seed crystal is connected to a transmission device, and the transmission device is used to control the lifting and rotation of the seed crystal rod.

[0016] Preferably, the growth raw material comprises silicon and a metal raw material, and the metal raw material is one or more of Al, Ti, Cr, Fe, Y, Yb, Pr, La, Cu, Ce, Sn, Ge, and Co.

[0017] Preferably, the crucible wall thickness of the crucible body is 10-30 mm, and the thickness of the bottom of the crucible body is 15-40 mm; at the top of the crucible wall of the crucible body, the starting position of the slot is 2-5 mm away from the inner side of the crucible wall; the depth of the slot is 10-50 mm.

[0018] Preferably, the groove ring is provided in the crucible wall of the crucible body; the groove is an annular groove, the graphite block connector is an annular graphite block connector, and the carbon supply graphite block is an annular carbon supply graphite block.

[0019] Preferably, the thickness of the carbon supply graphite block is 10 to 30 mm, and the width of the carbon supply graphite block is 10 to 30 mm.

[0020] Preferably, two symmetrical slots are provided in the radial direction of the crucible wall of the crucible body; the number of the carbon supply graphite blocks is two; and the number of the graphite block connectors is two.

[0021] Preferably, the thickness of the carbon supply graphite block is 10-30 mm, the width of the carbon supply graphite block is 10-30 mm, and the sum of the lengths of two carbon supply graphite blocks is less than the difference between the inner diameter of the crucible body and the diameter of the seed crystal.

[0022] Preferably, a thermal insulation layer is provided between the growth crucible and the induction heating device.

[0023] Preferably, the insulation layer includes an upper insulation area located above the growth crucible, an outer insulation area located around the growth crucible, and a lower insulation area located below the growth crucible; the upper insulation area is provided with a through hole corresponding to the opening of the crucible cover, and the through hole is used for allowing the seed rod to pass through.

[0024] Preferably, the temperature field of the liquid phase method growing silicon carbide single crystal is controlled by changing the shape of the peripheral heat preservation area.

[0025] Preferably, the outer shape of the outer heat-insulating area is cylindrical, right truncated cone or inverted truncated cone.

[0026] Preferably, when the outer shape of the outer heat preservation area is a right truncated cone, the temperature gradient between the seed crystal and the liquid surface of the growth raw material is increased, thereby increasing the growth rate of the silicon carbide single crystal and improving the crystal production capacity.

[0027] Preferably, when the outer shape of the outer heat preservation area is an inverted truncated cone, the temperature gradient between the seed crystal and the liquid surface of the growth material is reduced, thereby reducing the growth rate of the silicon carbide single crystal, thereby improving the crystal quality.

[0028] Compared with the prior art, the present invention has at least the following beneficial effects:

[0029] (1) The device of the present invention includes a material block that can provide growth raw materials, preferably a graphite block for carbon supply, and the density of the graphite block for carbon supply is less than the density of the liquid growth raw material. Because the density of the graphite block for carbon supply is small, the graphite block for carbon supply can float on the liquid surface of the liquid growth raw material, and can provide a carbon source for the growth process of silicon carbide single crystals. However, the position stability of the graphite block for carbon supply is relatively poor, resulting in relatively poor stability as a carbon source supply; the present invention is preferably that the device includes a graphite block for carbon supply and a graphite block connector, and the graphite block for carbon supply can be moved up and down along the crucible wall through the graphite block connector by setting the crucible wall slot, and the graphite block for carbon supply is set to be stable. The carbon supply graphite block has good qualitative properties, and since the graphite block for carbon supply is made of graphite material, it has low density characteristics, and its density is lower than that of the growth raw material, so that it can be suspended (floating) on ​​the surface of the growth raw material solution during the long growth process, and this surface is the growth interface, thereby providing sufficient and stable carbon source for the growth of silicon carbide single crystal. Moreover, at this growth interface, as the crystal growth process is prolonged, the graphite block for carbon supply only becomes thinner at the position in contact with the liquid surface of the growth raw material solution, and other settings remain unchanged, which can ensure that the carbon supply distance remains unchanged during the long growth process of the silicon carbide single crystal, making the silicon carbide crystal growth more stable, improving the growth quality of the silicon carbide single crystal, and inhibiting the occurrence of the crucible being melted through.

[0030] (2) The device of the present invention is preferably the graphite block for carbon supply, which can float on the liquid surface of the growth raw material by sticking to the inner wall of the crucible for a long time and stably through the graphite block connector and the card slot. Compared with the carbon supply setting of thickening the crucible wall thickness of the graphite crucible or directly adding carbon powder or extending the graphite material into the interior of the growth raw material solution, the carbon supply method included in the device of the present invention is stable, and there is no problem of affecting the convection in the growth system, and there is no problem of affecting the quality of crystal growth due to affecting the convection, and there is no increase in cost due to increasing the wall thickness. The device of the present invention not only plays the role of providing sufficient carbon source, but also can shorten the carbon supply distance and ensure that the carbon supply distance remains unchanged, which not only ensures the carbon supply amount of diffusion mass transfer, but also does not affect the convection in the growth system. The crystal growth is more stable, and it is a very stable carbon supply device.

[0031] (3) The device of the present invention firstly shortens the carbon supply distance and ensures that the carbon supply distance remains unchanged during the liquid phase growth of silicon carbide single crystals. Secondly, it can provide sufficient and long-term stable carbon sources for the growth process of silicon carbide single crystals, greatly reducing the generation of inclusions, effectively improving the quality of single crystal growth, and at the same time effectively inhibiting the melting through of the crucible wall, especially effectively inhibiting the melting through of the crucible wall at the surface of the growth raw material solution, preventing the leakage of the auxiliary solution (growth raw material) from affecting the temperature field or even damaging the single crystal furnace, thereby improving the repeatability and stability of the single crystal growth experiment. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] The drawings of the present invention are provided for illustrative purposes only, and the proportions, sizes and quantities of the various parts in the drawings may not necessarily be consistent with the actual products.

[0033] FIG1 is a schematic structural diagram of an apparatus for growing a silicon carbide single crystal by a liquid phase method provided in some specific embodiments of the present invention;

[0034] FIG2 is a schematic structural diagram of an apparatus for growing a silicon carbide single crystal by a liquid phase method provided in some other specific embodiments of the present invention;

[0035] 3 is a schematic structural diagram of an apparatus for growing a silicon carbide single crystal by a liquid phase method provided in Example 1 of the present invention;

[0036] 4 is a schematic structural diagram of an apparatus for growing a silicon carbide single crystal by a liquid phase method provided in Example 2 of the present invention;

[0037] 5 is a schematic structural diagram of an apparatus for growing a silicon carbide single crystal by a liquid phase method provided in Example 3 of the present invention;

[0038] FIG6 is an external view of the silicon carbide single crystal obtained in Example 1 of the present invention;

[0039] FIG7 is an external view of a silicon carbide single crystal obtained in Example 2 of the present invention;

[0040] FIG8 is an external view of a silicon carbide single crystal obtained in Example 3 of the present invention;

[0041] FIG9 is a temperature gradient curve of the apparatus for growing a silicon carbide single crystal by a liquid phase method provided in Examples 1 to 3 of the present invention; in FIG9 , (a) is a temperature gradient curve of the apparatus for growing a silicon carbide single crystal by a liquid phase method provided in Example 1, (b) is a temperature gradient curve of the apparatus for growing a silicon carbide single crystal by a liquid phase method provided in Example 2, and (c) is a temperature gradient curve of the apparatus for growing a silicon carbide single crystal by a liquid phase method provided in Example 3;

[0042] 10 is a schematic diagram showing the melting through of the graphite crucible in the growth interface region after the liquid phase method for growing a silicon carbide single crystal is used in the apparatus of Comparative Example 1 of the present invention;

[0043] FIG11 is an external view of the silicon carbide single crystal obtained in Comparative Example 1 of the present invention.

[0044] In the figure: 1: growth crucible; 1-1: crucible body; 1-2: crucible cover; 2: seed crystal rod; 3: seed crystal; 4: induction coil; 5: slot; 6: graphite block for carbon supply; 7: graphite block connector; 8: ring; 9: growth raw material; 10: insulation layer; 10-1: upper insulation area; 10-2: outer insulation area; 10-3: lower insulation area. DETAILED DESCRIPTION

[0045] To make the objectives, technical solutions, and advantages of the present invention more clear, the technical solutions of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the embodiments described are part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts shall fall within the scope of protection of the present invention.

[0046] The present invention provides a device for growing silicon carbide single crystals by a liquid phase method. For example, as shown in Figure 1, the device includes a growth crucible 1, a seed rod 2 fixed with a seed crystal 3, an induction heating device for heating, and a material block that can provide growth raw materials. In the present invention, the material block that can provide growth raw materials can be, for example, a silicon carbide block, a graphite block for carbon, or other material blocks that can provide growth raw materials. The growth crucible 1 includes a crucible body 1-1 and a crucible cover 1-2. The crucible body 1-1 is filled with growth raw materials, and the crucible cover 1-2 has an opening. One end of the seed rod 2 fixed with the seed crystal 3 extends into the interior of the crucible body 1-1 through the opening. The density of the material block that can provide growth raw materials is less than the density of the liquid growth raw materials, and the material block that can provide growth raw materials floats on the surface of the liquid growth raw materials.

[0047] According to some preferred embodiments, the material block that can provide growth raw material is a silicon carbide block.

[0048] According to some preferred embodiments, the material block capable of providing growth raw materials is a graphite block for supplying carbon, for example, as shown in FIG1 .

[0049] According to some preferred embodiments, the carbon supply graphite block 6 is an annular carbon supply graphite block; the annular carbon supply graphite block is arranged close to the inner wall of the crucible body, or the outer diameter of the annular carbon supply graphite block is slightly smaller than the inner diameter of the crucible body.

[0050] According to some preferred embodiments, the device also includes a graphite block connector 7; a slot 5 is provided on the crucible wall of the crucible body 1-1 from the top downward, a ring 8 is provided at one end of the graphite block connector 7, and the ring 8 is clamped in the slot 5, and the other end of the graphite block connector 7 is connected to a carbon supply graphite block 6, the density of the carbon supply graphite block 6 is less than the density of the liquid growth raw material, and the carbon supply graphite block floats on the liquid growth raw material surface.

[0051] According to some specific embodiments, the present invention provides a device for growing silicon carbide single crystals by a liquid phase method. For example, as shown in FIG2 , the device includes a growth crucible 1, a seed crystal rod 2 fixed with a seed crystal 3, an induction heating device for heating (only the induction coil 4 is shown schematically in the figure), a graphite block 6 (made of graphite) for supplying carbon, and a graphite block connector 7; in the present invention, the growth crucible 1 is a graphite crucible, and the induction heating device is used to heat the growth crucible, so that the growth raw material 9 can be melted into a liquid state and the growth temperature of the silicon carbide single crystal in the growth system can be maintained; the present invention has no special requirements for the induction heating device, which is a conventional design in the field; the induction heating device includes an induction coil 4 (also referred to as a heating device). Coil), the induction coil 4 is coaxially arranged with the seed crystal rod 2, and the induction heating device heats the growth crucible by electromagnetic induction; the growth crucible 1 includes a crucible body 1-1 and a crucible cover 1-2. In the present invention, the crucible body and the crucible cover can be connected, for example, by a threaded connection. The wall thickness of the crucible body is greater than the wall thickness of the crucible cover. The outer wall of the crucible body is flush with the outer wall of the crucible cover, and the inner wall of the crucible body exceeds the inner wall of the crucible cover; the crucible body 1-1 is filled with growth raw material 9, and the crucible body 1-1 is, for example, cylindrical, and the crucible cover 1-2 has an opening, and one end of the seed crystal rod 2 fixed with the seed crystal 3 passes through the opening. The crucible body 1-1 is provided with a slot 5 on the crucible wall from the top downward, and a ring 8 is provided at one end (upper end) of the graphite block connector 7, and the ring 8 is clamped in the slot 5. The other end (lower end) of the graphite block connector 7 is connected to a carbon supply graphite block 6, and the density of the carbon supply graphite block 6 is less than the density of the liquid growth raw material 9. The carbon supply graphite block 6 is suspended (floated) on the liquid surface of the liquid growth raw material 9, that is, in the process of growing silicon carbide single crystals by the liquid phase method using the device, the carbon supply graphite block floats on the liquid surface of the liquid growth raw material, which is used to additionally increase the carbon source required for the growth of silicon carbide single crystals, that is, in the process of growing silicon carbide single crystals by the liquid phase method. , the crucible body serves as the main carbon source, and the graphite block for supplying carbon floats on the liquid surface of the growth raw material in the liquid state to continuously supply carbon for the growth of the silicon carbide single crystal as the secondary carbon source, specifically: the graphite block for supplying carbon floats on the liquid surface of the growth raw material in the liquid state and the portion of the graphite block for supplying carbon that is in contact with the liquid growth raw material is dissolved to supply carbon, while the portion of the graphite block for supplying carbon that is not in contact with the liquid growth raw material will continue to float on the liquid surface of the growth raw material in the liquid state and be continuously dissolved to continuously supply carbon; in the present invention, since the density of the graphite block for supplying carbon is less than the density of the liquid growth raw material and is supplemented by the arrangement of the graphite block connector, the ring and the slot, it is ensured that the undissolved graphite block for supplying carbon can continue to float on the liquid surface of the growth raw material in the liquid state and be continuously dissolved to supply carbon;In the present invention, the groove allows the graphite block connector to move up and down against the inner side of the crucible wall via the circular ring, thereby driving the carbon supply graphite block to move up and down against the inner side of the crucible wall. In the present invention, the carbon supply graphite block, the graphite block connector, and the circular ring can be integrally formed and connected.

[0052] The device of the present invention includes a graphite block for supplying carbon and a graphite block connector, and the graphite block for supplying carbon can be moved up and down along the crucible wall through the graphite block connector by setting the crucible wall slot. The graphite block for supplying carbon has good setting stability, and because the graphite block for supplying carbon is made of graphite material, it has low density characteristics, and its density is lower than the density of the growth raw material, so that it can float on the surface of the growth raw material solution during the long growth process, and this surface is the growth interface, thereby providing a sufficient and stable carbon source for the growth of silicon carbide single crystal. At this growth interface, as the crystal growth process extends, the graphite block for supplying carbon only becomes thinner at the position in contact with the liquid surface of the growth raw material solution, and other settings remain unchanged. It can ensure that the carbon supply distance remains unchanged during the long growth process of the silicon carbide single crystal, making the silicon carbide crystal growth more stable, improving the growth quality of the silicon carbide single crystal, and suppressing the occurrence of the crucible being melted through. The carbon supply graphite block in the device of the present invention can float on the liquid surface of the liquid growth raw material for a long time and stably along the inner wall of the crucible through the graphite block connector and the card slot. Compared with the carbon supply setting of thickening the crucible wall thickness of the graphite crucible or directly adding carbon powder or extending the graphite material into the growth raw material solution, the carbon supply method included in the device of the present invention is stable, and there is no problem of affecting the convection in the growth system, and there is no problem of affecting the quality of crystal growth due to affecting the convection. The device of the present invention not only provides a sufficient carbon source, but also can shorten the carbon supply distance and ensure that the carbon supply distance remains unchanged, will not affect the convection in the growth system, and the crystal growth is more stable. It is a very stable carbon supply device. The device of the present invention firstly shortens the carbon supply position and ensures that the carbon supply distance remains unchanged during the liquid phase growth of silicon carbide single crystals. Secondly, it can provide a sufficient and long-term stable carbon source for the silicon carbide single crystal growth process, greatly reducing the generation of inclusions, effectively improving the quality of single crystal growth, and at the same time effectively inhibiting the crucible wall from being melted through, especially effectively inhibiting the crucible wall from being melted through at the surface of the growth raw material solution, preventing the leakage of the auxiliary solution from affecting the temperature field and even damaging the single crystal furnace, thereby improving the repeatability and stability of the single crystal growth experiment.

[0053] According to some preferred embodiments, the graphite block connector 7 is arranged close to the crucible wall of the crucible body 1 - 1 ; and / or the ring 8 can move up and down in the slot 5 .

[0054] According to some preferred embodiments, the graphite block connector 7 and the ring 8 are both made of graphite.

[0055] According to some preferred embodiments, the end of the seed rod 2 to which the seed crystal 3 is not fixed is connected to a transmission device, and the transmission device is used to control the lifting and rotation of the seed rod, that is, to control the lifting and rotation of the seed crystal; in the present invention, the present invention does not make any specific limitation on the transmission device, which is a conventional design in the field and can be used to control the lifting and rotation of the seed rod; in the present invention, the device for growing silicon carbide single crystals by the liquid phase method can also include, for example, a rotating device for rotating the growth crucible; the present invention does not make any specific limitation on the setting of the rotating device, and the conventional setting in the field can be adopted.

[0056] According to some preferred embodiments, the growth raw material 9 includes silicon and a metal raw material, and the metal raw material is one or more of Al, Ti, Cr, Fe, Y, Yb, Pr, La, Cu, Ce, Sn, Ge, and Co.

[0057] The present invention does not specifically limit the parameters such as the thickness of the crucible wall of the crucible body, the thickness of the bottom of the crucible body, the depth of the slot, the width of the slot, and the size of the graphite block for carbon supply. Those skilled in the art can design them according to their needs. When designing the device for growing silicon carbide single crystals by the liquid phase method, the size of the crucible body of the graphite crucible can be first determined according to the size of the growing silicon carbide single crystal, and then the size of the crucible cover and the size of the middle opening can be determined according to the size of the crucible body to ensure that the seed crystal can enter the crucible. The crucible body and the crucible body are in a stable state. The crucible covers are all made of graphite, and a slot is set downward on the crucible wall at the top of the crucible body. The carbon-supplying graphite block can be moved up and down along the crucible wall of the crucible body through the design of the graphite block connector and the ring. For example, the wall thickness of the crucible body can be made into 10 to 30 mm. At the top of the crucible wall of the crucible body, the starting position of the slot is opened, and the distance from the inner side of the crucible wall is, for example, 2 to 5 mm. The depth of the slot is, for example, 10 to 50 mm. The bottom thickness of the crucible body is, for example, 15 to 40 mm.

[0058] According to some preferred embodiments, the crucible wall thickness of the crucible body 1-1 is 10 to 30 mm (e.g., 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29 or 30 mm), and the bottom thickness of the crucible body 1-1 is 15 to 40 mm (e.g., 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39 or 40 mm); the distance between the starting position of the slot 5 at the top of the crucible wall of the crucible body 1-1 and the inner side of the crucible wall is 2 to 5 mm (for example, 2, 2.5, 3, 3.5, 4, 4.5 or 5 mm) ; The depth of the slot 5 is 10 to 50 mm (for example, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49 or 50 mm), and preferably, in the height direction of the crucible body, the bottom of the slot is higher than the liquid level of the liquid growth material contained therein; the present invention does not specifically limit the width of the slot, for example, in the thickness direction of the crucible wall, the slot does not penetrate the thickness of the crucible wall and the starting position of the slot is 2 to 5 mm away from the inner side of the crucible wall. Preferably, The width of the card slot may be, for example, 2 to 10 mm.

[0059] According to some preferred embodiments, the slot 5 is arranged in a ring inside the crucible wall of the crucible body 1-1; the slot 5 is an annular slot, the graphite block connector 7 is an annular graphite block connector, and the carbon supply graphite block 6 is an annular carbon supply graphite block; the thickness of the carbon supply graphite block 6 is 10 to 30 mm (for example, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29 or 30 mm), and the width of the carbon supply graphite block 6 is 10 to 30 mm (for example, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29 or 30 mm).

[0060] According to some preferred embodiments, two symmetrical slots 5 are provided in the radial direction of the crucible wall of the crucible body 1-1; the number of the carbon supply graphite blocks 6 is two; the number of the graphite block connectors 7 is two; the thickness of the carbon supply graphite block 6 is 10 to 30 mm (for example, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, The width of the carbon supplying graphite block 6 is 10 to 30 mm (for example, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29 or 30 mm), and the sum of the lengths L of the two carbon supplying graphite blocks 6 is less than the difference between the inner diameter of the crucible body 1-1 and the diameter of the seed crystal 3.

[0061] According to some specific embodiments, for example, as shown in Figures 1 to 5, the induction heating device is arranged on the outside of the growth crucible, and the induction heating device includes an induction coil 4 coaxially arranged with the seed rod 2, and the growth crucible is placed at the center of the induction coil 4; in the present invention, when the device for growing silicon carbide single crystals by the liquid phase method is used to grow silicon carbide single crystals by the liquid phase method, the device as a whole is located in the single crystal furnace.

[0062] According to some more specific embodiments, for example, as shown in FIG2 , the device includes a growth crucible (graphite crucible) 1, the graphite crucible is used to accommodate the growth raw material 9 for growing silicon carbide single crystals by the liquid phase method and provide the main carbon source for the growth, the growth crucible includes a crucible body 1-1 and a crucible cover 1-2, the crucible body 1-1 and the crucible cover 1-2 are threadedly connected, the crucible body 1-1 is filled with the growth raw material 9, the crucible wall of the crucible body 1-1 is provided with a slot 5 from the top downward, and the crucible cover 1-2 has an opening in the middle for the seed crystal 3 1-2; an induction heating device for heating the growth crucible, the induction heating device being arranged on the outside of the growth crucible, and the induction heating device including an induction coil 4 coaxially arranged with the seed crystal rod 2, and the growth crucible being placed at the center of the induction coil 4; a graphite block connector 7 and a graphite block 6 for carbon supply, one end of the graphite block connector 7 (made of graphite) being provided with a ring 8 ( Graphite material), the ring 8 is clamped in the clamping groove 5, and the other end of the graphite block connector 7 is connected to a graphite block 6 for carbon supply, and the density of the graphite block 6 for carbon supply is less than the density of the liquid growth raw material 9. The graphite block 6 for carbon supply floats on the liquid surface of the liquid growth raw material 9, and is used to additionally increase the carbon source required for the growth of silicon carbide single crystals. The graphite block connector 7 is arranged close to the crucible wall of the crucible body 1-1, and the ring 8 can move up and down in the clamping groove 5. In the present invention, the clamping groove 5 can allow the graphite block connector 7 to move up and down along the inner side of the crucible wall through the ring 8, thereby driving the graphite block 6 for carbon supply to move up and down along the inner side of the crucible wall.

[0063] In the present invention, the graphite crucible is first used to accommodate the growth raw materials for growing silicon carbide single crystals by the liquid phase method, and secondly, it itself serves as the main carbon source for crystal growth, and a slot is set downward from the crucible wall at the top of the crucible, so that the circular ring of the graphite block connector can be sleeved in the slot and move up and down along the crucible wall. The graphite block for carbon supply is connected to the slot of the graphite crucible through the graphite block connector, the circular ring, and the graphite crucible, and is suspended inside the crucible body. The slot can allow the graphite block connector to move up and down along the inner side of the crucible wall through the circular ring, thereby driving the graphite block for carbon supply to move up and down along the inner side of the crucible wall, and because the density of the graphite block for carbon supply is less than the density of the liquid growth raw material, the graphite block for carbon supply can always float on the liquid. The liquid surface of the growth raw material provides a sufficient carbon source for the growth of silicon carbide single crystal at the growth interface; a seed crystal is bonded to the bottom of the seed crystal rod, and the seed crystal rod and the seed crystal can be bonded by epoxy resin or phenolic resin, for example, and can enter the crucible body through the opening of the crucible cover and contact with the liquid growth raw material. The top of the seed crystal rod is connected to the transmission device, and the upper end of the seed crystal rod is connected to the transmission device by, for example, a threaded connection to realize the up and down movement and rotation of the seed crystal; the growth raw material is a mixture of silicon and at least one metal raw material, which provides the silicon element required for the growth of silicon carbide single crystal by liquid phase method, and can dissolve the graphite crucible and the graphite block for carbon supply to provide carbon element for crystal growth.

[0064] In the present invention, the device for growing silicon carbide single crystals by the liquid phase method is used to grow silicon carbide single crystals by the liquid phase method. During the process of growing silicon carbide single crystals by the liquid phase method, the carbon supply distance can be shortened. Secondly, a sufficient and stable carbon source can be additionally provided, which greatly reduces the generation of inclusions and improves the quality of single crystal growth. At the same time, it effectively inhibits the melting through of the graphite crucible wall, prevents the leakage of the auxiliary solution from affecting the temperature field and even damaging the single crystal furnace, thereby improving the repeatability and stability of the single crystal growth experiment. In the present invention, the method for growing silicon carbide single crystals by the liquid phase method using the device, for example, includes the following steps:

[0065] (1) Selecting the raw material for growing silicon carbide single crystals to ensure that the density of the raw material after melting into liquid is greater than the density of the graphite block for carbon supply;

[0066] (2) The growth raw material is placed in the crucible body of the growth crucible, and the growth crucible is heated by the induction heating device to melt the growth raw material into a liquid state; specifically, after the growth raw material is placed in the crucible body, the device for growing silicon carbide single crystals by the liquid phase method is assembled, and the growth crucible is heated by the induction heating device to melt the growth raw material into a liquid state. For example, the crucible body filled with the growth raw material, the seed crystal rod fixed with the seed crystal, the induction heating device, the graphite block for supplying carbon, the graphite block connector, etc. are assembled into the device for growing silicon carbide single crystals by the liquid phase method, and the growth crucible is heated by the induction heating device to melt the growth raw material into a liquid state. The present invention does not specifically describe the assembly process of the device for growing silicon carbide single crystals by the liquid phase method, and those skilled in the art can make actual adjustments based on the structure of the device in the present invention; in the present invention, for example, the growth raw material is melted into a liquid state under a vacuum environment;

[0067] (3) The seed crystal fixed on the seed crystal rod is lowered to contact the liquid surface of the liquid growth raw material to grow a silicon carbide single crystal, thereby obtaining a silicon carbide single crystal; in the present invention, specifically, after the temperature reaches the process temperature, the seed crystal fixed on the seed crystal rod is lowered to contact the liquid surface of the liquid growth raw material. Since the temperature at the seed crystal is low, the Si and C elements in the solution can be crystallized at the seed crystal to grow a silicon carbide single crystal, thereby obtaining a silicon carbide single crystal; during the crystal growth process, the seed crystal is pulled and rotated. During the crystal growth stage, the seed crystal is set to start pulling and rotating through program settings, and the crystal growth is continued in a moving state. The pulling speed is For example, it can be 10 to 1500 μm / h, and the rotation speed can be 5 to 300 rpm. During the crystal growth process, the graphite block for carbon supply is suspended in the liquid surface of the liquid growth raw material to continuously supply carbon for the growth of the silicon carbide single crystal. Specifically, the graphite block for carbon supply is suspended in the liquid surface of the liquid growth raw material and the portion of the graphite block for carbon supply that is in contact with the liquid growth raw material is dissolved to supply carbon, while the portion of the graphite block for carbon supply that is not in contact with the liquid growth raw material will continue to be suspended in the liquid surface of the growth raw material and will continue to be dissolved to continuously supply carbon. In the present invention, after the growth is completed, it is cooled to room temperature to obtain a silicon carbide ingot (silicon carbide single crystal). The present invention does not specifically limit the parameters in the crystal growth process, and conventional silicon carbide crystal growth parameters in the field can be used.

[0068] In the present invention, a more specific method includes: a preparation stage: a. determining the single crystal growth size, and based on this, determining the size of the crucible body, crucible cover and middle opening of the graphite crucible and the graphite block for carbon supply; b. selecting the component type of the growth raw material, and calculating the density of the selected growth raw material to ensure that the density of the liquid growth raw material obtained after melting is greater than the density of the graphite block for carbon supply; c. after determining the size, the growth raw material is prepared according to the preset method and placed in the crucible body of the graphite crucible; d. placing the graphite crucible into the single crystal furnace, with one end of the seed crystal rod fixing the seed crystal and the other end connected to the transmission device. Heating stage: The single crystal furnace is evacuated and then filled with special gases such as helium, nitrogen or argon. The power is then turned on to increase the temperature, so that the induction heating device heats the graphite crucible so that the growth raw material is completely melted into a solution. Since the density of the carbon supply graphite block is lower than that of the liquid growth raw material, and through the auxiliary setting of the graphite block connector, ring and slot, it will float on the surface of the liquid growth raw material and be dissolved by it to supply carbon, and it can also ensure that the undissolved carbon supply graphite block continues to float on the liquid growth raw material surface and is continuously dissolved to supply carbon; Crystal growth stage: During the crystal growth stage, the program is set to start pulling and rotating the seed crystal, and the crystal is grown in a continuous motion state; Cooling stage: Reduce the power for cooling, and at the same time pull the crystal away from the liquid growth raw material and stop rotating. After the cooling is completed, open the single crystal furnace body, take out the graphite crucible, open the crucible cover, take out the grown crystal, and obtain a silicon carbide single crystal.

[0069] According to some preferred embodiments, the device for growing silicon carbide single crystals by the liquid phase method further includes a thermal insulation layer arranged between the growth crucible and the induction heating device, that is, a thermal insulation layer 10 is arranged between the growth crucible and the induction heating device, for example, as shown in Figures 3 to 5; specifically, the thermal insulation layer 10 is located between the growth crucible 1 and the induction coil 4 included in the induction heating device; the induction coil of the induction heating device is located outside the growth crucible and is coaxially arranged with the seed rod; the thermal insulation layer is, for example, graphite felt, which is laid in layers on the outside of the growth crucible and is located between the growth crucible and the heating coil, and the growth crucible is placed on the induction crucible. The central position of the induction coil of the heating device should be selected. In the present invention, the graphite felt used for insulation can be selected from hard graphite felt or soft graphite felt. When soft graphite felt is selected, its thickness can be, for example, an integer value between 2 and 15 mm. In the present invention, hard graphite felt or soft graphite felt is laid in layers to form the insulation layer. Preferably, soft graphite felt is laid in layers to form the insulation layer. The present invention does not make any specific limitation on the soft graphite felt, and products that can be directly purchased on the market can be used. The present invention does not make any specific limitation on the size of the central area of ​​the induction coil, and those skilled in the art can design it as needed. For example, the diameter of the central area of ​​the induction coil can be 350 to 500 mm.

[0070] In the present invention, the entire device is placed in a single crystal furnace, and the provision of the thermal insulation layer is beneficial for stabilizing the temperature field, thereby improving the quality of the crystal.

[0071] According to some preferred embodiments, the growth crucible 1 is made of graphite, and the graphite is high-purity graphite, and the purity of the graphite is not less than 99.95%. In the present invention, unless otherwise specified, the graphite material refers to graphite with a purity of not less than 99.95%. Unless otherwise specified, the graphite has a density of 1.70 to 2.00 g / cm 3 of graphite.

[0072] According to some preferred embodiments, the insulation layer 10 includes an upper insulation area 10-1 located above the growth crucible 1, an outer insulation area 10-2 located around the growth crucible 1, and a lower insulation area 10-3 located below the growth crucible 1; the upper insulation area is provided with a through hole corresponding to the opening of the crucible cover, and the through hole is used for the seed rod to pass through; specifically, the insulation layer 10 includes an upper insulation area 10-1 located above the growth crucible 1 and between the induction coil 4, an outer insulation area 10-2 located around the growth crucible 1 and between the induction coil 4 The outer insulation area 10-2 and the lower insulation area 10-3 located below the growth crucible 1 and between the induction coil 4; the outer diameter of the outer insulation area 10-2 can be, for example, an integer value between 130 and 480 mm, and the specific setting depends on the temperature field requirements. The upper insulation area 10-1 is provided with a through hole corresponding to the opening of the crucible cover 1-2, and the through hole is used for allowing the seed rod 2 to pass through. For example, the through hole is used for allowing the end of the seed rod 2 not fixed with the seed crystal 3 to pass through. The aperture of the through hole can be, for example, an integer value between 20 and 150 mm.

[0073] In the process of growing silicon carbide single crystals by the liquid phase method, the control of the temperature field is of vital importance. A stable temperature field can effectively ensure that the environment for long-term crystal growth is relatively stable and can improve the repeatability of the experiment. In addition, the change of the temperature field will also provide more selectivity for the growth of silicon carbide single crystals, or focus on growth quality or growth rate, etc. Therefore, in addition to being able to shorten the carbon supply distance and ensure that the carbon supply distance remains unchanged, and being able to provide sufficient and long-term stable carbon sources for the growth process of silicon carbide single crystals, the device of the present invention having a diversified, variable, and convenient adjustable stable temperature field is also of great significance. For example, the growth rate of silicon carbide single crystals can be changed as needed while ensuring the growth quality of silicon carbide single crystals. However, the prior art devices for growing silicon carbide single crystals by the liquid phase method are difficult to achieve stable temperature field regulation.

[0074] According to some preferred embodiments, the temperature field of the liquid-phase grown silicon carbide single crystal is controlled by changing the shape of the outer insulation area 10-2. The present invention finds that by changing the shape of the outer insulation area in this way, not only the device can be manufactured conveniently and the repeatability of production can be guaranteed to a large extent, but also the yield of the silicon carbide single crystal can be improved and the plasticity of the device can be increased. By changing the shape of the insulation layer, the stable change of the temperature field can be controlled. Changing the shape of the outer insulation area to control the temperature field of the liquid-phase grown silicon carbide single crystal is a new control method. This method can perform diversified regulation on the temperature field of the growth of silicon carbide single crystal, providing more possibilities for the growth of silicon carbide single crystal.

[0075] According to some preferred embodiments, the outer shape of the peripheral heat insulation area 10-2 is cylindrical, right truncated cone or inverted truncated cone; in some embodiments, the outer shape of the peripheral heat insulation area 10-2 is cylindrical, for example, as shown in Figure 3; in some embodiments, the outer shape of the peripheral heat insulation area 10-2 is right truncated cone, for example, as shown in Figure 4; in some embodiments, the outer shape of the peripheral heat insulation area 10-2 is inverted truncated cone, for example, as shown in Figure 5.

[0076] According to some preferred embodiments, when the outer shape of the outer heat preservation area 10-2 is a right truncated cone, for example, as shown in Figure 4, the temperature gradient between the seed crystal and the liquid surface of the growth raw material is increased, thereby increasing the growth rate of the silicon carbide single crystal, thereby enabling crystal production capacity; for example, when the device is not used, the range of crystal growth rate is small when the temperature is constant. After selecting this device, the growth rate range can be expanded to 15-280μm / h, providing more possibilities for crystal growth; when the outer shape of the outer heat preservation area 10-2 is an inverted truncated cone, for example, as shown in Figure 5, the temperature gradient between the seed crystal and the liquid surface of the growth raw material is reduced, thereby reducing the growth rate of the silicon carbide single crystal, thereby enabling a more sufficient carbon source supply and improving the crystal quality.

[0077] It is particularly noted that the temperature field includes the temperature gradient, temperature, specific temperature distribution, etc. The stability of the temperature field can be the stability of a large temperature gradient. The stability mainly lies in maintaining this state. From the beginning to the end, it is a large temperature gradient or a small temperature gradient, which can be said to be a stable temperature field. In the present invention, the temperature field temperature gradient change can be controlled and changed, and it does not change in the middle of growth. For the present invention, after determining the shape of the outer insulation area, the gradient change of the temperature field is determined before the growth of the silicon carbide single crystal, and then the entire growth process is in a balanced state.

[0078] When designing the devices in some preferred embodiments of the present invention, the size of the graphite felt for insulation is first determined according to the size of the growth crucible and the induction coil, so that the outer diameter of the insulation layer is slightly smaller than the size of the central area of ​​the induction coil, for example, 20 to 60 mm smaller than the diameter of the central area of ​​the induction coil; then the number of lower layers of graphite felt is determined according to the height of the induction coil and the position of the growth crucible (the overall induction heating degree is higher when the growth crucible is in the middle position in the height direction of the induction coil; when the growth crucible is in the lower area of ​​the induction coil, the high temperature line of the growth environment moves upward, and the crystal growth rate is slower; when the growth crucible is in the upper area of ​​the induction coil, the high temperature line of the growth environment moves downward, and the crystal growth rate is faster); after the relative position of the growth crucible and the induction coil is determined, for example, the growth crucible is determined. After the long crucible is located in the middle position of the induction coil, specifically, for example, it is determined that the growth crucible is in the middle position of the radial direction and the height direction of the induction coil, so as to determine the number of layers of graphite felt in the lower insulation area, and according to experimental needs, the placement of the graphite felt in the outer part of the growth crucible is further adjusted. In the present invention, the graphite felt is placed in a layered manner so that the outer insulation area of ​​the growth crucible has different shapes. The outer diameter of the graphite felt in the outer insulation area is 20 to 60 mm smaller than the diameter of the central area of ​​the induction coil, and the inner diameter is the same as the outer diameter of the growth crucible. The outer diameter of the graphite felt in the outer insulation area can be the same or different. The area with a larger outer diameter has a stronger insulation capacity, and the area with a smaller outer diameter has a better heat dissipation capacity. The outer diameter of the graphite felt in the outer insulation area can be the same or different. The area with a larger outer diameter has a stronger insulation capacity, and the area with a smaller outer diameter has a better heat dissipation capacity. The outer diameter of the graphite felt in the outer insulation area can be determined according to experimental needs. The outer diameter of the graphite felt in the position, when the outer diameter of the graphite felt is the same from top to bottom, that is, the outer diameter of the outer insulation area is the same from top to bottom, then the outer shape of the outer insulation area is cylindrical, when the outer diameter of the graphite felt increases from top to bottom, that is, the outer diameter of the outer insulation area increases from top to bottom, that is, the outer shape of the outer insulation area is a right truncated cone. At this time, since the outer diameter of the outer insulation area increases from top to bottom, the insulation capacity of the outer insulation area can be increased from top to bottom, thereby increasing the temperature gradient between the seed crystal and the liquid surface of the growth raw material, thereby increasing the growth rate of the silicon carbide single crystal, thereby increasing the crystal production capacity; when the outer diameter of the graphite felt decreases from top to bottom, that is, the outer diameter of the outer insulation area The outer diameter of the outer heat-insulating region decreases from top to bottom, that is, the outer shape of the outer heat-insulating region is an inverted truncated cone. At this time, since the outer diameter of the outer heat-insulating region decreases from top to bottom, the heat-insulating capacity of the outer heat-insulating region decreases from top to bottom, thereby reducing the temperature gradient between the seed crystal and the liquid surface of the growth raw material, thereby reducing the growth rate of the silicon carbide single crystal, thereby obtaining a more sufficient carbon source supply and improving the crystal quality; the growth raw material is placed in the growth crucible, and the seed crystal rod connected with the seed crystal is placed in the crucible body; the upper graphite felt is placed according to the set temperature field, the outer diameter of this part of the graphite felt (upper heat-insulating region) is smaller than the diameter of the central region of the induction coil by 20 to 60 mm, and a through hole larger than the outer diameter of the seed crystal rod is provided in the center to allow the seed crystal rod to pass through;The seed crystal rod is connected to a transmission device, which can drive the seed crystal to move up and down (lift and lower) and rotate; when the preferred device is used to grow silicon carbide single crystals by the liquid phase method, after pretreatment such as vacuum, the induction coil power is turned on for heating; after the set time, the growth material is melted, and the seed crystal is lowered through the transmission device connected to the seed crystal rod until the seed crystal contacts the liquid surface of the growth material, and single crystal growth begins; after the growth is completed, the temperature is lowered to room temperature, and the grown single crystal is taken out, which is a silicon carbide single crystal. Using the device for growing silicon carbide single crystals by the liquid phase method as shown in Figures 4 and 5 of the present invention to grow single crystals can increase the temperature field change of the growth system, such as increasing the temperature gradient to increase the crystal growth rate and increase production capacity (as shown in Figure 4), or reducing the temperature gradient to reduce the crystal growth rate, thereby obtaining a more sufficient carbon source supply and improving crystal quality (as shown in Figure 5). ;

[0079] The present invention will be further described below by way of examples, but the protection scope of the present invention is not limited to these examples.

[0080] Example 1

[0081] This embodiment provides a device for growing a silicon carbide single crystal using a liquid phase method, a schematic structural diagram of which is shown in FIG3 ; the device comprises:

[0082] A growth crucible (graphite crucible) is used to accommodate the growth raw materials for growing silicon carbide single crystals by the liquid phase method and provide the main carbon source (main carbon source) for growth. The growth crucible is cylindrical and includes a crucible body and a crucible cover. The crucible body and the crucible cover are threadedly connected. The crucible body is filled with growth raw materials. The crucible wall of the crucible body is provided with a slot from the top downward. Specifically, two symmetrical slots are provided in the radial direction of the crucible wall of the crucible body. The crucible cover has an opening in the middle for seed crystals to enter.

[0083] A seed crystal rod, one end of which is fixed with a seed crystal, and the other end is connected to a transmission device, which can control the lifting and rotation of the seed crystal; the end of the seed crystal rod used to fix the seed crystal (silicon carbide seed crystal) extends into the interior of the crucible body through the opening of the crucible cover.

[0084] An induction heating device for heating a growth crucible comprises an induction coil coaxially arranged with the seed crystal rod.

[0085] A graphite block connector and a graphite block for carbon supply, the number of the graphite blocks for carbon supply (graphite material) is two, and the number of the graphite block connectors is two; a circular ring (graphite material) is provided at one end of the graphite block connector (graphite material), the circular ring is clamped in the clamping groove, and the other end of the graphite block connector is connected to the graphite block for carbon supply, the density of the graphite block for carbon supply is less than the density of the liquid growth raw material, the graphite block for carbon supply is suspended in the liquid surface of the liquid growth raw material, and is used to additionally increase the carbon source required for the growth of silicon carbide single crystals, the graphite block connector is arranged close to the crucible wall of the crucible body, the circular ring can move up and down in the clamping groove, and the clamping groove can allow the graphite block connector to move up and down close to the inner side of the crucible wall through the circular ring, thereby driving the graphite block for carbon supply to move up and down close to the inner side of the crucible wall.

[0086] The graphite crucible used in this embodiment has an inner diameter of 150 mm, an outer diameter of 185 mm, and a height of 100 mm; the silicon carbide seed crystal is 4H-SiC grown by the PVT method, with a diameter of 100 mm and a thickness of 0.5 mm; the starting position of the slot is opened at the top of the crucible wall of the crucible body, and the distance from the inner side of the crucible wall to the starting position is 4 mm, the depth of the slot is 35 mm, the thickness of the carbon supply graphite block is 20 mm, the width of the carbon supply graphite block is 20 mm, the length of the carbon supply graphite block is 15 mm, and the sum of the lengths of the two carbon supply graphite blocks is 30 mm.

[0087] The device for growing silicon carbide single crystals by the liquid phase method in this embodiment also includes a thermal insulation layer arranged between the growth crucible and the induction coil; the thermal insulation layer is made of graphite soft felt, which is laid in layers on the outside of the growth crucible and is located between the growth crucible and the induction coil, and the growth crucible is placed at the center position inside the induction coil of the induction heating device, and the induction coil is coaxially arranged with the seed rod; the thermal insulation layer includes an upper thermal insulation area located above the growth crucible and between the induction coil, an outer thermal insulation area located around the growth crucible and between the induction coil, and a lower thermal insulation area located below the growth crucible and between the induction coil. The upper heat preservation area is provided with a through hole corresponding to the opening of the crucible cover, and the through hole is used for allowing the seed rod to pass through. The outer diameter of the upper heat preservation area is smaller than the diameter of the central area of ​​the induction coil by 40 mm, and the outer diameter of the lower heat preservation area is also smaller than the diameter of the central area of ​​the induction coil by 40 mm; the growth crucible is located in the middle position of the induction coil in the radial direction and the height direction. The outer heat preservation area is cylindrical, and the outer diameter of the outer heat preservation area is equal from top to bottom. The outer diameter of the outer heat preservation area is smaller than the diameter of the central area of ​​the induction coil by 40 mm, and the inner diameter is the same as the outer diameter of the growth crucible; the diameter of the central area of ​​the induction coil is 420 mm.

[0088] The device for growing a silicon carbide single crystal by the liquid phase method in this embodiment is used to grow a silicon carbide single crystal by the liquid phase method, including the following steps:

[0089] ① Select the growth material for growing silicon carbide single crystals, ensuring that the density of the growth material after melting into a liquid state is greater than the density of the graphite block for carbon supply; the growth material used in this embodiment is a mixture of Si, Cr and Al, and the mass percentages of these three components in the growth material are Si: 50%, Cr: 40%, and Al: 10%.

[0090] ②Put the mixed growth materials into the crucible body of the graphite crucible, and use a molecular pump to evacuate the graphite crucible to 2×10 -4 After the pressure drops below Pa, 0.8 atm Ar gas is introduced as a protective gas and the graphite crucible is heated by an induction heating device to completely melt the growth raw materials into a liquid state.

[0091] ③ After the temperature reaches the process temperature of 1800℃, the seed crystal fixed on the seed crystal rod is lowered to contact the liquid surface of the liquid growth raw material. Due to the low temperature at the seed crystal, the Si and C elements in the solution can be crystallized at the seed crystal, and the silicon carbide single crystal is grown, thereby obtaining a silicon carbide single crystal; during the crystal growth process, the seed crystal is pulled and rotated, slowly pulling the silicon carbide seed crystal at a speed of 0.02mm / h, rotating the silicon carbide seed crystal at a speed of 40rpm, and rotating the silicon carbide seed crystal at a speed of 20rpm. The graphite crucible is rotated in the opposite direction; during the crystal growth process, the graphite crucible provides a carbon source for growing a silicon carbide single crystal as a primary carbon source, and a carbon supply graphite block floats on the liquid surface of the liquid growth raw material to continuously supply carbon for the growth of the silicon carbide single crystal as a secondary carbon source; after the entire crystal growth process lasts for 60 hours, the silicon carbide seed crystal is pulled upward at a speed of 3 mm / h to separate the growing silicon carbide single crystal from the liquid surface of the growth raw material and stop rotating, and then slowly cool to room temperature, that is, the entire liquid phase silicon carbide crystal growth process is completed to obtain a silicon carbide single crystal.

[0092] After the device in this embodiment was used to grow silicon carbide single crystals by liquid phase method for 60 hours, there was no phenomenon of melting through of the graphite crucible, and there was no phenomenon of melting through of the crucible wall at the liquid level of the growth raw material.

[0093] The device in this embodiment is used to grow silicon carbide single crystals by liquid phase method, and the single crystal growth rate is 100 μm / h. The device in this embodiment is used to grow silicon carbide single crystals by liquid phase method, and the growth rate is moderate. The surface of the obtained silicon carbide single crystal is smooth and flat, and the quality is good. The appearance of the silicon carbide single crystal obtained in this embodiment is shown in Figure 6.

[0094] Example 2

[0095] Example 2 is basically the same as Example 1, except that:

[0096] The apparatus for growing silicon carbide single crystals by a liquid phase method used in this embodiment has a different shape of the insulation layer than the apparatus for growing silicon carbide single crystals by a liquid phase method in Example 1. The schematic structural diagram of the apparatus for growing silicon carbide single crystals by a liquid phase method in this embodiment is shown in FIG4 . The specific difference lies in: the shape of the peripheral insulation region is different; in this embodiment, the peripheral insulation region is a right truncated cone, the inner diameter of the peripheral insulation region is equal to the outer diameter of the growth crucible, and the outer diameter of the peripheral insulation region increases from top to bottom, so that the insulation capacity of the peripheral insulation region increases from top to bottom, thereby increasing the temperature gradient between the seed crystal and the liquid surface of the growth material, thereby increasing the growth rate of the silicon carbide single crystal, and thus improving the crystal production capacity; in this embodiment, the top outer diameter of the peripheral insulation region is greater than the outer diameter of the growth crucible by 40 mm, and the bottom outer diameter of the peripheral insulation region is less than the 40 mm diameter of the central region of the induction coil, which has a diameter of 420 mm.

[0097] After the device in this embodiment was used to grow silicon carbide single crystals by liquid phase method for 60 hours, there was no phenomenon of melting through of the graphite crucible, and there was no phenomenon of melting through of the crucible wall at the liquid level of the growth raw material.

[0098] The device in this embodiment is used to grow silicon carbide single crystals by liquid phase method, and the single crystal growth rate is 140μm / h; the device in this embodiment is used to grow silicon carbide single crystals by liquid phase method, and the growth rate is fast, which can improve the crystal production capacity, and the overall quality of the crystal is moderate. However, compared with the device in Example 1, it will still cause the smoothness and flatness of the crystal surface to decrease, and relatively more small grooves and step bunching will appear, which will affect the crystal quality to a certain extent. The appearance of the silicon carbide single crystal obtained in this embodiment is shown in Figure 7.

[0099] Example 3

[0100] Example 3 is basically the same as Example 1, except that:

[0101] The apparatus for growing silicon carbide single crystals by a liquid phase method employed in this embodiment has a different shape of the insulation layer than that employed in the apparatus for growing silicon carbide single crystals by a liquid phase method in Example 1. A schematic structural diagram of the apparatus for growing silicon carbide single crystals by a liquid phase method in this embodiment is shown in FIG5 . Specifically, the difference lies in the different shape of the peripheral insulation region. In this embodiment, the peripheral insulation region is in the shape of an inverted truncated cone, and the inner diameter of the peripheral insulation region is equal to the outer diameter of the growth crucible. The outer diameter of the peripheral insulation region decreases from top to bottom, thereby decreasing the insulation capacity of the peripheral insulation region from top to bottom. This reduces the temperature gradient between the seed crystal and the liquid surface of the growth material, thereby reducing the growth rate of the silicon carbide single crystal, thereby obtaining a more sufficient carbon source supply and improving the crystal quality. In this embodiment, the outer diameter of the top of the peripheral insulation region is less than the diameter of the central region of the induction coil by 40 mm, and the outer diameter of the bottom of the peripheral insulation region is greater than the outer diameter of the growth crucible by 40 mm. The diameter of the central region of the induction coil is 420 mm.

[0102] After the device in this embodiment was used to grow silicon carbide single crystals by liquid phase method for 60 hours, there was no phenomenon of melting through of the graphite crucible, and there was no phenomenon of melting through of the crucible wall at the liquid level of the growth raw material.

[0103] The device in this embodiment is used to grow silicon carbide single crystals by the liquid phase method, and the single crystal growth rate is 60μm / h; the device in this embodiment is used to grow silicon carbide single crystals by the liquid phase method, and the growth rate is slow. The surface of the obtained silicon carbide single crystal is very smooth and flat, the quality is very good, and there are no macroscopically visible defects. Compared with the device in Example 1, the quality of the silicon carbide single crystal obtained in this embodiment is further improved. The appearance of the silicon carbide single crystal obtained in this embodiment is shown in Figure 8.

[0104] The present invention also assembles and heats the devices in Examples 1 to 3 without placing the growth raw materials, and conducts a temperature gradient test. The test method is as follows: the temperature measuring point is located on the back of the seed crystal, and the seed crystal is moved to a position 1 cm from the bottom of the crucible body by a transmission device. The stable temperature here is obtained by the temperature measuring equipment, and the temperature at this point is controlled to be 1800°C. After that, the seed crystal is moved to obtain the temperature values ​​at 2cm-3cm-4cm-5cm-6cm, respectively. The temperature gradient curves under the temperature field of each embodiment are obtained by graphical calculation, and the results are shown in Figure 9. It can be concluded from the results of Figure 9 that the temperature gradient under the temperature field of Example 1 is about 20°C / cm, the temperature gradient under the temperature field of Example 2 is about 28°C / cm, and the temperature gradient under the temperature field of Example 3 is about 14°C / cm. When the temperature gradient increases, the crystal growth rate accelerates and the crystal quality is relatively poor. When the temperature gradient decreases, the crystal growth rate decreases, but the crystal quality is significantly improved.

[0105] Comparative Example 1

[0106] The device for growing silicon carbide single crystals by the liquid phase method used in this comparative example does not include a graphite block for supplying carbon, a graphite block connector, and a ring, and the crucible wall of the growth crucible does not have a slot, that is, the device in this comparative example includes:

[0107] A growth crucible (graphite crucible) is used to accommodate the growth raw materials for growing silicon carbide single crystals by the liquid phase method and provide a carbon source for growth. The growth crucible includes a crucible body and a crucible cover. The crucible body and the crucible cover are threadedly connected. The crucible body contains the growth raw materials, and the crucible cover has an opening in the middle for seed crystals to enter.

[0108] A seed crystal rod, one end of which is fixed with a seed crystal, and the other end is connected to a transmission device, which can control the lifting and rotation of the seed crystal; the end of the seed crystal rod used to fix the seed crystal (silicon carbide seed crystal) extends into the interior of the crucible body through the opening of the crucible cover.

[0109] An induction heating device is used to heat the growth crucible, and the induction heating device includes an induction coil coaxially arranged with the seed rod.

[0110] An insulation layer is provided between the growth crucible and the induction coil. The insulation layer is made of graphite felt. The size of the graphite felt is determined based on the growth crucible. The graphite felt is processed based on the size, wrapping the growth crucible as an insulation layer. In this comparative example, the insulation layer is integrally formed from the graphite felt. The growth crucible and insulation layer are placed in a furnace, with the growth crucible positioned at the center of the induction coil (both radially and vertically). The outer diameter of the insulation layer is slightly smaller than the center of the induction coil, and is 40 mm smaller than the diameter of the center of the induction coil. The graphite crucible used in this comparative example has an inner diameter of 150 mm, an outer diameter of 185 mm, and a height of 100 mm. The silicon carbide seed crystal is 4H-SiC grown using a PVT method, with a diameter of 100 mm and a thickness of 0.5 mm.

[0111] The liquid phase method for growing silicon carbide single crystals using the device for growing silicon carbide single crystals in this comparative example comprises the following steps:

[0112] ① Selecting a growth material for growing silicon carbide single crystal. The growth material used in this comparative example is a mixture of Si, Cr and Al. In the growth material, the mass percentages of these three components are Si: 50%, Cr: 40%, and Al: 10%.

[0113] ②Put the mixed growth materials into the crucible body of the graphite crucible, and use a molecular pump to evacuate the graphite crucible to 2×10 -4After the pressure drops below Pa, 0.8 atm Ar gas is introduced as a protective gas and the graphite crucible is heated by an induction heating device to completely melt the growth raw materials into a liquid state.

[0114] ③ After the temperature reaches the process temperature of 1800℃, the seed crystal fixed on the seed crystal rod is lowered to contact the liquid surface of the liquid growth raw material. Due to the low temperature at the seed crystal, the Si and C elements in the solution can be crystallized at the seed crystal, and the silicon carbide single crystal is grown, thereby obtaining a silicon carbide single crystal; during the crystal growth process, the seed crystal is pulled and the seed crystal is rotated, the silicon carbide seed crystal is slowly pulled at a speed of 0.02mm / h, the silicon carbide seed crystal is rotated at a speed of 40rpm, and the graphite crucible is rotated in the opposite direction at a speed of 20rpm; after the entire crystal growth process lasts for 60h, the silicon carbide seed crystal is pulled upward at a speed of 3mm / h, the grown silicon carbide single crystal is separated from the liquid surface of the growth raw material and stops rotating, and slowly cooled to room temperature, that is, the entire liquid phase silicon carbide crystal growth process is completed, and a silicon carbide single crystal is obtained.

[0115] Comparative Example 1 uses a commonly used liquid-phase method for growing silicon carbide single crystals. After determining the size of the growth crucible, the device in this comparative example uses this as a benchmark for its insulation and temperature field. Once prepared, it cannot be modified and can only be determined by adjusting the temperature and the position of the heated body in the induction coil. This poor flexibility limits the research and development capabilities of liquid-phase crystal growth. Moreover, because the device uses a standard graphite crucible for silicon carbide single crystal growth, as growth progresses, the carbon in the crucible's easily carbon-soluble region is dissolved and transported due to the dual effects of convection and diffusion, allowing the crystal to continue growing. The easily carbon-soluble region includes the high-temperature region and the growth interface region that is conducive to diffusion. After the crucible dissolves in the growth interface region, the distance between the single crystal growth surface and the carbon source becomes farther, resulting in insufficient carbon supply and defects such as solution wrapping. What's more, the crucible in the growth liquid surface area is dissolved, causing the solution to leak out, affecting the temperature field and having a certain probability of flowing into the single crystal furnace, causing damage to the equipment.

[0116] When the apparatus in this comparative example was used to grow a silicon carbide single crystal for 60 hours, the growth interface region of the growth crucible (graphite crucible) was obviously melted through, as shown in FIG10 .

[0117] The device in this comparative example was used to grow silicon carbide single crystals by the liquid phase method, and the single crystal growth rate was 92μm / h; the device in this comparative example was used to grow silicon carbide single crystals by the liquid phase method, and the growth rate was moderate, but due to insufficient diffusion and mass transfer, the crystal lacked carbon, resulting in many large grooves on the surface and poor quality. The appearance of the silicon carbide single crystal obtained in this comparative example is shown in Figure 11.

[0118] In the description of the present invention, it should be noted that the terms "upper", "lower", "above", "below", "top", "bottom", "inside", etc., indicating the orientation or position relationship, are based on the orientation or position relationship shown in Figures 1 to 5. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operate in a specific orientation. Therefore, they cannot be understood as limiting the present invention.

[0119] It should also be noted that, in the description of the present invention, unless otherwise expressly specified or limited, the term "connection" should be understood in a broad sense. For example, it can mean a fixed connection, a detachable connection, or an integral connection; it can mean a direct connection or an indirect connection through an intermediate medium. Those skilled in the art will understand the specific meaning of this term in the present invention depending on the specific circumstances.

[0120] Parts of the present invention that are not described in detail are well known to those skilled in the art.

[0121] 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 various embodiments of the present invention.

Claims

1. A device for growing silicon carbide single crystals by a liquid phase method, characterized in that: The device comprises a growth crucible, a seed crystal rod fixed with a seed crystal, an induction heating device for heating, and a material block capable of providing growth raw materials; The growth crucible comprises a crucible body and a crucible cover, wherein the crucible body contains growth raw materials, and the crucible cover has an opening, and one end of the seed crystal rod fixed with the seed crystal extends into the interior of the crucible body through the opening; The density of the material block that can provide growth raw materials is lower than the density of the liquid growth raw materials, and the material block that can provide growth raw materials floats on the surface of the liquid growth raw materials.

2. The device according to claim 1, characterized in that: The material block that can provide growth raw materials is a silicon carbide block.

3. The device according to claim 1, characterized in that: The material block that can provide growth raw materials is a graphite block for supplying carbon.

4. The device according to claim 3, characterized in that: The carbon supply graphite block is an annular carbon supply graphite block; The annular graphite block for carbon supply is arranged closely to the inner wall of the crucible body, or the outer diameter of the annular graphite block for carbon supply is slightly smaller than the inner diameter of the crucible body.

5. The device according to claim 3, characterized in that: The device also includes a graphite block connector; The crucible wall of the crucible body is provided with a slot from the top downwards, a ring is provided at one end of the graphite block connector, the ring is clamped in the slot, and a carbon supply graphite block is connected to the other end of the graphite block connector. The density of the carbon supply graphite block is less than the density of the liquid growth raw material, and the carbon supply graphite block floats on the liquid growth raw material surface.

6. The device according to claim 5, characterized in that: The graphite block connector is arranged close to the crucible wall of the crucible body; and / or The ring can move up and down in the slot.

7. The device according to claim 5, characterized in that: The graphite block connector and the ring are both made of graphite.

8. The device according to claim 1, characterized in that: One end of the seed crystal rod not fixed with the seed crystal is connected to a transmission device, and the transmission device is used to control the lifting and rotation of the seed crystal rod.

9. The device according to claim 1, characterized in that: The growth raw materials include silicon and metal raw materials, and the metal raw materials are one or more of Al, Ti, Cr, Fe, Y, Yb, Pr, La, Cu, Ce, Sn, Ge, and Co.

10. The device according to claim 5, characterized in that: The crucible wall thickness of the crucible body is 10 to 30 mm, and the bottom thickness of the crucible body is 15 to 40 mm; The starting position of the slot is provided at the top of the crucible wall of the crucible body, and the distance from the inner side of the crucible wall to the slot is 2 to 5 mm; The depth of the card slot is 10 to 50 mm.

11. The device according to claim 5, characterized in that: The groove ring is arranged in the crucible wall of the crucible body; The clamping groove is an annular clamping groove, the graphite block connecting piece is an annular graphite block connecting piece, and the carbon supplying graphite block is an annular graphite block for carbon supplying.

12. The device according to claim 11, characterized in that: The thickness of the carbon supplying graphite block is 10 to 30 mm, and the width of the carbon supplying graphite block is 10 to 30 mm.

13. The device according to claim 5, characterized in that: Two symmetrical slots are provided in the radial direction of the crucible wall of the crucible body; The number of graphite blocks for carbon supply is two; The number of the graphite block connecting pieces is two.

14. The device according to claim 13, characterized in that: The thickness of the carbon supply graphite block is 10 to 30 mm, the width of the carbon supply graphite block is 10 to 30 mm, and the sum of the lengths of the two carbon supply graphite blocks is less than the length of the crucible body. The difference between the diameter of the crystal and the diameter of the seed crystal.

15. The device according to any one of claims 1 to 14, characterized in that: A heat-insulating layer is arranged between the growth crucible and the induction heating device.

16. The device according to claim 15, characterized in that: The insulation layer includes an upper insulation region located above the growth crucible, a peripheral insulation region located around the growth crucible, and a lower insulation region located below the growth crucible; The upper heat preservation area is provided with a through hole corresponding to the opening of the crucible cover, and the through hole is used for the seed crystal rod to pass through.

17. The device according to claim 16, characterized in that: The temperature field of the liquid phase method growing silicon carbide single crystal is controlled by changing the shape of the peripheral heat preservation area.

18. The device according to claim 16, characterized in that: The outer shape of the outer heat preservation area is cylindrical, regular truncated cone or inverted truncated cone.

19. The device according to claim 18, characterized in that: When the outer shape of the outer heat preservation area is a right truncated cone, the temperature gradient between the seed crystal and the liquid surface of the growth raw material is increased, thereby increasing the growth rate of the silicon carbide single crystal, thereby improving the crystal production capacity.

20. The device according to claim 18, characterized in that: When the outer shape of the outer heat preservation area is an inverted truncated cone, the temperature gradient between the seed crystal and the liquid surface of the growth material is reduced, thereby reducing the growth rate of the silicon carbide single crystal, thereby improving the crystal quality.

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