Silicon carbide crystal growth device and growth method

Abstract

The invention provides a silicon carbide crystal growth device and a growth method, and belongs to the technical field of semiconductors. The silicon carbide crystal growth device comprises a growth crucible, a crucible cover, a growth chamber, a seed crystal positioning table and a clamping groove, a crucible cover is arranged at a top opening of the growth crucible, part of the inner wall of the growth crucible is concavely arranged to form a supporting table, the supporting table is used for placing the growth chamber, and the growth chamber is used for bearing the seed crystal positioning table; a silicon carbide seed crystal is arranged on the bottom side of the seed crystal positioning table, the seed crystal positioning table is fixedly connected with the crucible cover through a clamping groove, and a cavity is formed among the seed crystal positioning table, the clamping groove and the crucible cover. By utilizing the cavity formed among the seed crystal positioning table, the clamping groove and the crucible cover, the heat conduction in the growth crucible is more uniform, the initial growth interface of the crystal is stabilized, the nearly-flat growth interface is realized, the generation of thermal stress caused by non-uniform heat is avoided, the crystal lattice slippage in the crystal is greatly inhibited, and the crystal growth efficiency is improved. And generation of growth defects such as dislocation and layer fault is reduced.

Description

Technical Field

[0001] The present invention belongs to the field of semiconductor technology, relates to the field of silicon carbide technology, and particularly relates to a silicon carbide crystal growth device and a growth method. Background Art

[0002] Silicon carbide (SiC) is a third-generation semiconductor material with a wide bandgap, high critical electric field, and high saturation mobility. It has great advantages in the fields of high-temperature, high-frequency, and high-power electronic devices, and is widely used in new energy vehicles, photovoltaic power generation, railway transportation, power systems, and other fields. Currently, the mainstream crystal growth process adopts the Physical Vapor Transport (PVT) method. This method mainly transports gas-phase components to the silicon carbide seed placed at the top of the crucible through radial and axial gradients for crystallization, thereby realizing the growth of silicon carbide single crystals. Among them, the silicon carbide seed crystal is bonded to a layer of flexible material through organic glue or photoresist, and then bonded to the graphite crucible cover. Although the conventional bonding method can fix the seed crystal on the graphite crucible cover and avoid direct contact between the seed crystal and the graphite crucible cover, due to the large difference in the thermal expansion coefficients of silicon carbide and carbon materials, and the growth temperature being above 2100 °C, even if there is a layer of flexible material between the seed crystal and the graphite crucible cover, it is impossible to offset the thermal expansion of the two, which will cause large stress in the initial growth interface of the silicon carbide crystal, resulting in lattice slip inside the crystal and the generation of growth defects such as dislocations and stacking faults.

[0003] Therefore, during the initial heating process of growing silicon carbide crystals by the PVT method, impurities in the raw materials and graphite parts used will gradually precipitate with the increase in temperature and enter the crystal along with the rising gas flow, resulting in abnormal initial growth interfaces, and further leading to the generation of dislocations and stacking faults. In addition, the entry of impurity atoms into the crystal will change the normal growth mode of the crystal, resulting in abnormal growth in the impurity region and further leading to the generation of microtubes and inclusions.

[0004] Therefore, how to solve the problem of abnormal initial growth interfaces and improve growth defects such as crystal growth dislocations, microtubes, and inclusions is an important topic that urgently needs to be studied. Summary of the Invention

[0005] Aiming at the deficiencies of the existing technology, the purpose of the present invention is to provide a silicon carbide crystal growth device and a growth method. The present invention utilizes the cavity formed between the seed crystal positioning table, the card slot, and the crucible cover, thereby making the heat conduction in the growth crucible more uniform, stabilizing the initial growth interface of the crystal, achieving a nearly flat growth interface, avoiding the generation of thermal stress caused by uneven heat, greatly suppressing lattice slip inside the crystal, and reducing the generation of growth defects such as dislocations and stacking faults.

[0006] To achieve this purpose, the present invention adopts the following technical solutions:

[0007] In a first aspect, the present invention provides a silicon carbide crystal growth apparatus, which includes a growth crucible, a crucible lid, a growth chamber, a seed crystal positioning table, and a card slot.

[0008] The crucible lid is provided at the top opening of the growth crucible. A part of the inner wall of the growth crucible is recessed to form a support platform for placing the growth chamber, and the growth chamber is used to carry the seed crystal positioning table; a silicon carbide seed crystal is provided on the bottom side of the seed crystal positioning table. The seed crystal positioning table is fixedly connected to the crucible lid through the card slot, and a cavity is formed among the seed crystal positioning table, the card slot, and the crucible lid.

[0009] The present invention utilizes the cavity formed among the seed crystal positioning table, the card slot, and the crucible lid, so that the heat conduction in the growth crucible is more uniform, stabilizes the initial growth interface of the crystal, realizes an almost flat growth interface, avoids the generation of thermal stress caused by uneven heat, greatly inhibits the lattice slip inside the crystal, and reduces the generation of growth defects such as dislocations and stacking faults.

[0010] Preferably, the inner cavity of the growth crucible is divided into an upper growth area and a lower raw material area, and the support platform is located in the upper growth area.

[0011] Preferably, the inner diameter of the support platform is larger than the inner diameter of the lower raw material area of the growth crucible.

[0012] Preferably, the outer diameter of the growth chamber is the same as the inner diameter of the support platform.

[0013] Preferably, the material of the seed crystal positioning table is the same as that of the silicon carbide seed crystal.

[0014] Preferably, the seed crystal positioning table is bonded to the silicon carbide seed crystal.

[0015] Preferably, the surface roughness of the bonding surface where the seed crystal positioning table is connected to the silicon carbide seed crystal is less than 0.2 nm, and can be, for example, 0.18 nm, 0.5 nm, 0.12 nm, or 0.1 nm, etc.

[0016] Preferably, the thickness of the seed crystal positioning table is 5 - 20 mm, and can be, for example, 5 mm, 10 mm, 15 mm, or 20 mm, etc.

[0017] Preferably, at least the surface of the seed crystal positioning table facing away from the bonding surface is provided with a protective layer, and the material of the protective layer includes any one of carbon, tantalum carbide, or niobium carbide.

[0018] Preferably, the thickness of the card slot is 0.5 - 5 mm, and can be, for example, 0.5 mm, 1 mm, 2 mm, 3 mm, 4 mm, or 5 mm, etc.

[0019] Preferably, the inner diameter of the card slot is greater than or equal to the diameter of the silicon carbide seed crystal, and the outer diameter of the card slot is greater than or equal to the diameter of the seed crystal positioning platform.

[0020] Preferably, the material of the card slot includes any one or a combination of at least two of graphite, carbon fiber or silicon carbide.

[0021] Preferably, a heat preservation ring is arranged in the cavity formed by the growth chamber, the seed crystal positioning platform, the card slot, the crucible cover and the growth crucible.

[0022] Preferably, the material of the heat preservation ring includes any one or a combination of at least two of foam carbon, porous carbon or carbon fiber.

[0023] Preferably, the edge position of the seed crystal positioning platform is a porous structure, and the porous structure does not contact the silicon carbide seed crystal.

[0024] Preferably, in the porous structure, the pore diameter is 0.5 - 500 μm, for example, it can be 0.5 μm, 1 μm, 10 μm, 50 μm, 100 μm, 200 μm, 300 μm, 400 μm or 500 μm, etc.

[0025] Preferably, a limiting piece is arranged in the contact area between the growth chamber and the seed crystal positioning platform.

[0026] Preferably, the thickness of the limiting piece is 0.2 - 1 mm, for example, it can be 0.2 mm, 0.4 mm, 0.6 mm, 0.8 mm or 1 mm, etc.

[0027] In a second aspect, the present invention provides a method for growing a silicon carbide crystal. The growth method uses the silicon carbide crystal growth device as described in the first aspect, and includes the following steps:

[0028] Place the silicon carbide raw material in the growth crucible, place the growth chamber on the support platform, and then place the seed crystal positioning platform provided with the silicon carbide seed crystal on the growth chamber, and make the side with the silicon carbide seed crystal correspond to the silicon carbide raw material.

[0029] Place the card slot on the seed crystal positioning platform, and then cover the crucible cover, and make the crucible cover and the card slot contact.

[0030] Evacuate the air, and then heat it to make the silicon carbide crystal grow on the bottom surface of the silicon carbide seed crystal.

[0031] Preferably, before setting the silicon carbide seed crystal on the seed crystal positioning platform, first polish the surface of the seed crystal positioning platform that contacts the silicon carbide seed crystal.

[0032] Preferably, before the seed crystal positioning table is placed on the growth chamber, a limiting piece is placed in the area where the seed crystal positioning table contacts the growth chamber.

[0033] However, it is not limited to the enumerated values, and other unenumerated values within this numerical range are equally applicable.

[0034] The numerical range described in the present invention not only includes the above - cited point values, but also includes any point values between the above - mentioned numerical ranges that are not enumerated. Due to space limitations and for the sake of simplicity, the present invention does not exhaustively list the specific point values included in the range.

[0035] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0036] The present invention utilizes the cavity formed among the seed crystal positioning table, the clamping groove, and the crucible cover, so that the heat conduction in the growth crucible is more uniform, stabilizes the initial growth interface of the crystal, realizes a nearly flat growth interface, avoids the generation of thermal stress caused by uneven heat, greatly inhibits the lattice slip inside the crystal, and reduces the generation of growth defects such as dislocations and stacking faults. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 It is a schematic structural diagram of the silicon carbide crystal growth device provided in Embodiment 1 of the present invention.

[0038] Figure 2 It is a schematic structural diagram of the silicon carbide crystal growth device provided in Embodiment 2 of the present invention.

[0039] Among them, 1 - graphite crucible cover; 2 - growth chamber; 3 - graphite growth crucible; 4 - protective layer; 5 - seed crystal positioning table; 6 - clamping groove; 7 - heat - insulating ring; 8 - silicon carbide seed crystal; 9 - limiting piece. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0040] It should be understood that in the description of the present invention, the orientation or positional relationship indicated by the terms "center", "longitudinal", "transverse", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings. It is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, so it cannot be understood as a limitation to the present invention. In addition, the terms "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, the features defined with "first", "second", etc. may explicitly or implicitly include one or more of such features. In the description of the present invention, unless otherwise specified, the meaning of "a plurality" is two or more.

[0041] It should be noted that in the description of the present invention, unless otherwise clearly specified and limited, the terms "arranged", "connected", and "coupled" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the communication inside two components. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific situations.

[0042] The technical solution of the present invention will be further described below through specific embodiments.

[0043] In a specific embodiment, the present invention provides a silicon carbide crystal growth device, and the silicon carbide crystal growth device includes a growth crucible, a crucible lid, a growth chamber, a seed crystal positioning stage, and a card slot.

[0044] The crucible lid is arranged at the top opening of the growth crucible. A support platform is recessed on a part of the inner wall of the growth crucible, and the support platform is used for placing the growth chamber, and the growth chamber is used for carrying the seed crystal positioning stage; a silicon carbide seed crystal is arranged on the bottom side of the seed crystal positioning stage, and the seed crystal positioning stage is fixedly connected to the crucible lid through the card slot, and a cavity is formed among the seed crystal positioning stage, the card slot, and the crucible lid.

[0045] The present invention utilizes the cavity formed among the seed crystal positioning stage, the card slot, and the crucible lid, so that the heat conduction in the growth crucible is more uniform, stabilizes the initial growth interface of the crystal, realizes a nearly flat growth interface, avoids the generation of thermal stress caused by uneven heat, greatly inhibits the lattice slip inside the crystal, and reduces the generation of growth defects such as dislocations and stacking faults.

[0046] Further, the inner cavity of the growth crucible is divided into an upper growth area and a lower raw material area, and the support platform is located in the upper growth area.

[0047] Further, the outer diameter of the growth crucible is 200 - 300 mm, for example, it can be 200 mm, 220 mm, 240 mm, 260 mm, 280 mm, or 300 mm, etc.

[0048] Further, the inner diameter of the support platform is larger than the inner diameter of the lower raw material area of the growth crucible.

[0049] It should be noted that the support platform is a stepped structure formed by the inner wall of the growth crucible recessing inward, and it has the effect of carrying the growth chamber.

[0050] Further, the material of the growth chamber is any one of carbon, polycrystalline silicon carbide, or single crystal silicon carbide.

[0051] Further, the growth chamber is of an annular structure. It should be noted that the hollow part of the annular structure is the transmission area for gaseous silicon carbide raw materials.

[0052] Further, the outer diameter of the growth chamber is the same as the inner diameter of the support platform.

[0053] Further, the inner diameter of the growth chamber is larger than the diameter of the silicon carbide seed crystal.

[0054] Further, the material of the seed crystal positioning platform is the same as that of the silicon carbide seed crystal.

[0055] In the present invention, the coefficient of thermal expansion of homo-bonded silicon carbide is basically the same in a high-temperature environment. Therefore, defining the material of the seed crystal positioning platform to be the same as that of the silicon carbide seed crystal helps to effectively avoid lattice slip caused by thermal stress during crystal growth, and further avoid the generation of defects such as dislocations and stacking faults.

[0056] Exemplarily, the material of the seed crystal positioning platform can be any one of single-crystal silicon carbide, polycrystalline silicon carbide, or silicon carbide ceramic.

[0057] Further, the seed crystal positioning platform is bonded to the silicon carbide seed crystal.

[0058] In the present invention, the bonded connection means that through the formation of chemical bonds or physical bonds, a strong binding force is formed between the seed crystal and the seed crystal positioning platform, which can better withstand the thermal stress during crystal growth, ensure that the seed crystal will not easily fall off or displace during crystal growth, and is beneficial to improving the success rate and quality of crystal growth; the bonded connection can form a relatively stable interface, reduce the defects and impurity aggregation at the interface, help to maintain the stability of crystal growth, and reduce the probability of crystal defects caused by interface problems; a good bonded connection can ensure that the heat transfer efficiency between the seed crystal and the seed crystal positioning platform is high and uniform, providing favorable conditions for the uniform growth of the crystal, and reducing the abnormal crystal growth caused by temperature non-uniformity.

[0059] Further, the surface roughness of the bonding surface between the seed crystal positioning platform and the silicon carbide seed crystal is less than 0.2 nm, and can be, for example, 0.18 nm, 0.5 nm, 0.12 nm, or 0.1 nm, etc.

[0060] In the present invention, a lower surface roughness can make the contact area between the seed crystal and the seed crystal positioning platform larger and more uniform, and the connection is firm, so that it can better withstand the thermal stress generated during crystal growth, reduce the risk of seed crystal displacement or falling off due to insecure connection, and thus improve the success rate of crystal growth; at the same time, it also helps to reduce the defects and impurity aggregation at the interface, improve the uniformity of heat reception, and optimize the heat transfer efficiency.

[0061] Further, the diameter of the seed crystal positioning table is 100 - 250 mm, and it can be, for example, 100 mm, 150 mm, 200 mm, 250 mm, etc.

[0062] Further, the thickness of the seed crystal positioning table is 5 - 20 mm, and it can be, for example, 5 mm, 10 mm, 15 mm, 20 mm, etc.

[0063] Further, at least the surface of the seed crystal positioning table facing away from the bonding surface is provided with a protective layer, and the material of the protective layer includes any one of carbon, tantalum carbide, or niobium carbide.

[0064] In the present invention, the setting of the protective layer can effectively prevent the back evaporation of the seed crystal positioning table under high-temperature conditions. After the growth is completed, the crystal can be directly cut off, and the seed crystal positioning table can be reused after being processed; in addition, the presence of the protective layer makes the heating temperature of the seed crystal positioning table more uniform.

[0065] It should be noted that at least the surface of the seed crystal positioning table facing away from the bonding surface is provided with a protective layer, which means that in addition to the surface of the seed crystal positioning table facing away from the bonding surface being provided with the protective layer, the side surface of the seed crystal positioning table may also be provided with the protective layer.

[0066] Further, the thickness of the card slot is 0.5 - 5 mm, and it can be, for example, 0.5 mm, 1 mm, 2 mm, 3 mm, 4 mm, or 5 mm, etc.

[0067] In the present invention, the card slot with an appropriate thickness avoids the direct contact between the seed crystal positioning table and the crucible lid, so that a cavity with a certain volume formed between the seed crystal positioning table and the crucible lid can better improve the heat conduction uniformity in the crucible, optimize the initial interface of crystal growth, and reduce the generation of thermal stress.

[0068] Further, the inner diameter of the card slot is greater than or equal to the diameter of the silicon carbide seed crystal, and the outer diameter of the card slot is greater than or equal to the diameter of the seed crystal positioning table.

[0069] Further, if the outer diameter of the card slot is greater than the diameter of the seed crystal positioning table, the card slot has an inverted L-shaped structure and contacts the upper surface and the side surface of the seed crystal positioning table.

[0070] Further, the material of the card slot includes any one or a combination of at least two of graphite, carbon fiber, or silicon carbide.

[0071] In the present invention, defining the card slot with the above materials is beneficial to reducing thermal expansion during the growth process.

[0072] Further, a heat preservation ring is arranged in the cavity formed by the growth chamber, the seed crystal positioning table, the card slot, the crucible lid, and the growth crucible.

[0073] In the present invention, the heat-insulating ring can effectively balance the temperatures of the two side edges of the seed positioning table, and can also adsorb impurity gases in the initial growth stage, improving the growth quality of the silicon carbide crystal. In addition, the heat-insulating ring can prevent crystallization of the gas flow in the pores (when the edge position of the seed positioning table is a porous structure).

[0074] Furthermore, the material of the heat-insulating ring includes any one or a combination of at least two of foam carbon, porous carbon, or carbon fiber.

[0075] Furthermore, the edge position of the seed positioning table is a porous structure, and the porous structure does not contact the silicon carbide seed crystal.

[0076] In the present invention, the edge of the seed positioning table (i.e., the edge side in contact with the heat-insulating ring) is a porous structure, which is conducive to the deposition of impurity gases in the heat-insulating ring in the initial stage of crystal growth. On the one hand, it can prevent excessive initial impurity gases from entering the silicon carbide crystal and changing the normal crystal growth mode. On the other hand, it can avoid the disorder of the gas flow at the edge of the seed crystal and prevent ablation of the edge of the seed crystal. In addition, the purpose of defining that the porous structure does not contact the silicon carbide seed crystal is to prevent back-corrosion of the seed crystal by the gas flow during the growth process of the silicon carbide crystal.

[0077] Furthermore, in the porous structure, the pore diameter is 0.5 - 500 μm, for example, it can be 0.5 μm, 1 μm, 10 μm, 50 μm, 100 μm, 200 μm, 300 μm, 400 μm, or 500 μm, etc.

[0078] In the present invention, an appropriate pore diameter is conducive to the smooth discharge of impurity gases in the initial stage of crystal growth, improving the growth quality of the crystal.

[0079] Furthermore, a limiting piece is provided in the contact area between the growth chamber and the seed positioning table. Exemplarily, the material of the limiting piece is graphite, etc.

[0080] In the present invention, the density of the limiting piece is set to leave an exhaust by increasing the limit, which is conducive to the deposition of impurity gases in the initial stage of crystal growth in the gap between the inverted L-shaped structure and the crucible, thereby preventing excessive initial impurity gases from entering the silicon carbide crystal and changing the normal crystal growth mode.

[0081] Furthermore, the thickness of the limiting piece is 0.2 - 1 mm, for example, it can be 0.2 mm, 0.4 mm, 0.6 mm, 0.8 mm, or 1 mm, etc.

[0082] In the present invention, a limiting piece with an appropriate thickness is conducive to the smooth discharge of impurity gases in the initial stage of crystal growth, improving the growth quality of the crystal.

[0083] In another specific embodiment, the present invention provides a method for growing a silicon carbide crystal. The growth method uses the silicon carbide crystal growth apparatus as described above and includes the following steps:

[0084] Place the silicon carbide raw material in the growth crucible, place the growth chamber on the support table, and then place the seed crystal positioning table provided with the silicon carbide seed crystal on the growth chamber, and make the side with the silicon carbide seed crystal correspond to the silicon carbide raw material.

[0085] Place a clamping groove on the seed crystal positioning table, then cover the crucible lid, and make the crucible lid contact the clamping groove.

[0086] Vacuumize, and then heat to cause the silicon carbide crystal to grow on the bottom surface of the silicon carbide seed crystal.

[0087] Further, before setting the silicon carbide seed crystal on the seed crystal positioning table, polish the surface of the seed crystal positioning table that contacts the silicon carbide seed crystal.

[0088] Further, before placing the seed crystal positioning table on the growth chamber, place a limit piece in the area where the seed crystal positioning table contacts the growth chamber.

[0089] Further, after the vacuumization, the vacuum degree in the furnace where the crucible is located is less than 10 -1 Pa, for example, it can be 5×10 - 2 Pa, 1×10 -2 Pa, 5×10 -3 Pa, 1×10 -3 Pa, 5×10 -4 Pa or 1×10 -4 Pa, etc.

[0090] Further, the heating rate of the heating is 0.2 - 1 °C / min, for example, it can be 0.2 °C / min, 0.4 °C / min, 0.6 °C / min, 0.8 °C / min or 1 °C / min, etc.

[0091] Further, the growth temperature is 2200 - 2300 °C, for example, it can be 2200 °C, 2250 °C or 2300 °C, etc.

[0092] Further, the growth time is 80 - 200 h, for example, it can be 80 h, 100 h, 120 h, 140 h, 160 h, 180 h or 200 h, etc.

[0093] Further, after the growth is completed, stop heating, then fill with a protective gas. After cooling to room temperature, take out the seed crystal positioning table on which the silicon carbide crystal has grown, and then use a single-wire cutting machine to separate the silicon carbide crystal.

[0094] Example 1

[0095] This embodiment provides a silicon carbide crystal growth device, and its structural schematic diagram is as shown in Figure 1 Figure. The silicon carbide crystal growth device includes a graphite growth crucible 1, a graphite crucible lid 3, a growth chamber 2, a seed crystal positioning stage 5, and a slot 6.

[0096] At the top opening of the graphite growth crucible 1, a graphite crucible lid 3 is provided. A support platform is recessed on a part of the inner wall of the graphite growth crucible 1. The support platform is used to place the growth chamber 2 made of polycrystalline silicon carbide. The growth chamber 2 is of an annular structure and is used to carry the seed crystal positioning stage 5. A silicon carbide seed crystal 8 is bonded to the bottom side of the seed crystal positioning stage 5. The seed crystal positioning stage 5 is fixedly connected to the graphite crucible lid 3 through the slot 6, and a cavity is formed among the seed crystal positioning stage 5, the slot 6, and the graphite crucible lid 3.

[0097] The outer diameter of the graphite growth crucible 1 is 250 mm. The inner cavity of the graphite growth crucible 1 is divided into an upper growth area and a lower raw material area. The support platform is located in the upper growth area. The inner diameter of the support platform is larger than the inner diameter of the lower raw material area of the graphite growth crucible 1. The outer diameter of the growth chamber 2 is the same as the inner diameter of the support platform, and the inner diameter is larger than the diameter of the silicon carbide seed crystal 8. The material of the seed crystal positioning stage 5 is the same as that of the silicon carbide seed crystal 8, both being single crystal silicon carbide. The surface roughness of the bonding surface where the seed crystal positioning stage 5 is bonded to the silicon carbide seed crystal 8 is 0.1 nm. The diameter of the seed crystal positioning stage 5 is 200 mm, and the thickness of the seed crystal positioning stage 5 is 10 mm. A protective layer 4 is provided on the surface of the seed crystal positioning stage 5 that faces away from the bonding surface. The material of the protective layer 4 is tantalum carbide. The thickness of the slot 6 is 2 mm. The inner diameter of the slot 6 is equal to the diameter of the silicon carbide seed crystal 8, the outer diameter of the slot 6 is equal to the diameter of the seed crystal positioning stage 5, and the material of the slot 6 is graphite. A thermal insulation ring 7 is arranged in the cavity formed by the growth chamber 2, the seed crystal positioning stage 5, the slot 6, the graphite crucible lid 3, and the graphite growth crucible 1. The material of the thermal insulation ring 7 is carbon foam. The edge position where the seed crystal positioning stage 5 contacts the thermal insulation ring 7 is a porous structure, and the porous structure does not contact the silicon carbide seed crystal 8. In the porous structure, the pore diameter is 100 μm.

[0098] This embodiment also provides a method for growing silicon carbide crystals. This growth method uses the silicon carbide crystal growth device described above and includes the following steps:

[0099] (1) Polish one side surface of the seed crystal positioning stage, then bond it with the silicon carbide seed crystal on the polished surface, and then deposit a protective layer on the back of the seed crystal positioning stage that faces away from the polished surface.

[0100] (2) Load the silicon carbide raw materials into the lower raw material area of the graphite growth crucible, place the growth chamber above the support platform of the graphite growth crucible, then place the seed crystal positioning table processed in step (1) in the center on the growth chamber. Next, place a heat preservation ring on the growth chamber between the seed crystal positioning table and the graphite growth crucible, place a clamping groove above the seed crystal positioning table, and finally screw the graphite crucible cover and the graphite growth crucible tightly so that the upper end of the clamping groove is in close contact with the crucible cover.

[0101] (3) Place the entire crucible obtained in step (2) into the growth furnace, evacuate to 1×10 -2 Pa, then turn on the heating power supply and heat it up to 2200 °C at a heating rate of 0.5 °C / min for 140 h of crystal growth.

[0102] (4) After the growth is completed, turn off the heating power supply, fill it with nitrogen gas, and cool it to room temperature of 25 °C. Take out the seed crystal positioning table with the silicon carbide crystal grown on it, and then use a single-wire cutting machine to separate the seed crystal positioning table and the silicon carbide crystal.

[0103] Example 2

[0104] This example provides a silicon carbide crystal growth device, and its structural schematic diagram is as Figure 2 shown. The silicon carbide crystal growth device includes a graphite growth crucible 1, a graphite crucible cover 3, a growth chamber 2, a seed crystal positioning table 5, and a clamping groove 6.

[0105] A graphite crucible cover 3 is provided at the top opening of the graphite growth crucible 1. A support platform is recessed on a part of the inner wall of the graphite growth crucible 1 for placing the growth chamber 2 made of single-crystal silicon carbide. The growth chamber 2 is of an annular structure for carrying the seed crystal positioning table 5; a silicon carbide seed crystal 8 is bonded to the bottom side of the seed crystal positioning table 5. The seed crystal positioning table 5 is fixedly connected to the graphite crucible cover 3 through the clamping groove 6, and a cavity is formed among the seed crystal positioning table 5, the clamping groove 6, and the graphite crucible cover 3.

[0106] The outer diameter of the graphite growth crucible 1 is 300 mm; the inner cavity of the graphite growth crucible 1 is divided into an upper growth area and a lower raw material area. The support platform is located in the upper growth area. The inner diameter of the support platform is larger than the inner diameter of the lower raw material area of the graphite growth crucible 1. The outer diameter of the growth chamber 2 is the same as the inner diameter of the support platform, and the inner diameter is larger than the diameter of the silicon carbide seed crystal 8; the material of the seed crystal positioning platform 5 is the same as that of the silicon carbide seed crystal 8, both are polycrystalline silicon carbide; the surface roughness of the bonding surface where the seed crystal positioning platform 5 is bonded to the silicon carbide seed crystal 8 is 0.1 nm; the diameter of the seed crystal positioning platform 5 is 250 mm, and the thickness of the seed crystal positioning platform 5 is 20 mm; a protective layer 4 is provided on the surface of the seed crystal positioning platform 5 facing away from the bonding surface and on the side surface of the seed crystal positioning platform 5. The material of the protective layer 4 is niobium carbide; the thickness of the card slot 6 is 5 mm. The inner diameter of the card slot 6 is larger than the diameter of the silicon carbide seed crystal 8. The outer diameter of the card slot 6 is larger than the diameter of the seed crystal positioning platform 5. The card slot 6 has an inverted L-shaped structure and is in contact with the upper surface and the side surface of the seed crystal positioning platform 5. The material of the card slot 6 is carbon fiber; a limiting piece 9 is provided in the contact area between the growth chamber 2 and the seed crystal positioning platform 5. The thickness of the limiting piece 9 is 0.5 mm.

[0107] This embodiment also provides a method for growing silicon carbide crystals. The growth method uses the above silicon carbide crystal growth device and includes the following steps:

[0108] (1) Polish one side surface of the seed crystal positioning platform, then bond it with the silicon carbide seed crystal on the polished surface, and then deposit a protective layer on the back of the seed crystal positioning platform facing away from the polished surface.

[0109] (2) Load the silicon carbide raw material into the lower raw material area of the graphite growth crucible, place the growth chamber above the support platform of the graphite growth crucible, then place the limiting piece, and then place the seed crystal positioning platform processed in step (1) in the center on the growth chamber, and the seed crystal positioning platform and the growth chamber are connected through the limiting piece.

[0110] Then place the card slot above and on the side of the seed crystal positioning platform, and finally tighten the graphite crucible cover and the graphite growth crucible so that the upper end of the card slot is in close contact with the crucible cover.

[0111] (3) Place the entire crucible obtained in step (2) in a growth furnace, evacuate to 1×10 -2 Pa, then turn on the heating power supply, and heat it up to 2200 °C at a heating rate of 0.5 °C / min for 140 h of crystal growth.

[0112] (4) After the growth is completed, turn off the heating power supply, fill it with nitrogen gas, and cool it to room temperature of 25 °C. Take out the seed crystal positioning platform with the grown silicon carbide crystal, and then use a single-wire cutting machine to separate the seed crystal positioning platform and the silicon carbide crystal.

[0113] Example 3

[0114] The difference between this embodiment and Embodiment 1 is that the seed crystal positioning table is adhesively connected to the silicon carbide seed crystal.

[0115] The remaining devices and parameters are the same as those in Embodiment 1.

[0116] Embodiment 4

[0117] The difference between this embodiment and Embodiment 1 is that no protective layer is provided.

[0118] The remaining devices and parameters are the same as those in Embodiment 1.

[0119] Embodiment 5

[0120] The difference between this embodiment and Embodiment 1 is that the thickness of the card slot is 0.1 mm.

[0121] The remaining devices and parameters are the same as those in Embodiment 1.

[0122] Embodiment 6

[0123] The difference between this embodiment and Embodiment 1 is that the thickness of the card slot is 8 mm.

[0124] The remaining devices and parameters are the same as those in Embodiment 1.

[0125] Embodiment 7

[0126] The difference between this embodiment and Embodiment 1 is that no heat preservation ring is provided.

[0127] The remaining devices and parameters are the same as those in Embodiment 1.

[0128] Embodiment 8

[0129] The difference between this embodiment and Embodiment 1 is that the seed crystal positioning table has a non-porous structure.

[0130] The remaining devices and parameters are the same as those in Embodiment 1.

[0131] Embodiment 9

[0132] The difference between this embodiment and Embodiment 2 is that no limiting piece is provided.

[0133] The remaining devices and parameters are the same as those in Embodiment 2.

[0134] Comparative Example 1

[0135] The difference between this comparative example and Embodiment 1 is that no card slot is provided, so that the seed crystal positioning table and the graphite crucible cover are in close contact.

[0136] The remaining devices and parameters are the same as those in Embodiment 1.

[0137] Analysis

[0138] As can be seen from the comparison between Example 1 and Example 3, if the seed crystal positioning table is adhesively connected to the silicon carbide seed crystal, the bonding force between the seed crystal and the seed crystal positioning table is weak and it is not easy to withstand the thermal stress during crystal growth, which may cause the seed crystal to fall off or displace during crystal growth, resulting in poor crystal growth quality.

[0139] As can be seen from the comparison between Example 1 and Example 4, if the protective layer is not provided, it is easy to cause back-corrosion of the seed crystal positioning table during growth, resulting in uneven heating of the seed crystal surface, and further causing thermal stress inside the crystal, which is not conducive to the growth of silicon carbide crystals.

[0140] As can be seen from the comparison between Example 1 and Examples 5-6, if the thickness of the card slot is too small, the enclosed cavity is small, and the seed crystal positioning table is greatly affected by the graphite crucible cover, which is not conducive to the formation of the gas layer and results in uneven heating; if the thickness of the card slot is too large, it is not conducive to the uniform conduction of heat of the seed crystal positioning table, resulting in uneven heating of the seed crystal.

[0141] As can be seen from the comparison between Example 1 and Example 7, if the heat preservation ring is not provided, the temperatures at both side edges of the seed crystal positioning table are uneven, and the impurity gases in the initial stage of crystal growth cannot be fully removed, affecting the crystal growth quality. In addition, crystallization occurs in the pores of the porous structure, resulting in the entry of initial impurities into the crystal and the formation of defects.

[0142] As can be seen from the comparison between Example 1 and Example 8, if the seed crystal positioning table is a non-porous structure, it is difficult to smoothly remove the impurity gases in the initial stage of crystal growth, making the crystal growth irregular and of poor quality.

[0143] As can be seen from the comparison between Example 2 and Example 9, if the limiting piece is not provided, too many impurity gases in the initial stage of growth enter the silicon carbide crystal, changing the normal crystal growth mode and resulting in poor crystal growth quality.

[0144] As can be seen from the comparison between Example 1 and Comparative Example 1, if the card slot is not provided and the seed crystal positioning table is in close contact with the graphite crucible cover, the seed crystal positioning table is unevenly heated, resulting in local thermal stress in the crystal during the growth of the silicon carbide crystal and causing poor crystal quality.

[0145] The applicant declares that the above description is only the specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention fall within the protection scope and the disclosure scope of the present invention.

Claims

1. A silicon carbide crystal growth apparatus, characterized in that, The silicon carbide crystal growth apparatus includes a growth crucible, a crucible lid, a growth chamber, a seed crystal positioning stage, and a card slot; At the top opening of the growth crucible, the crucible lid is provided. A support platform is recessed on a part of the inner wall of the growth crucible. The support platform is used to place the growth chamber, and the growth chamber is used to carry the seed crystal positioning stage. A silicon carbide seed crystal is provided on the bottom side of the seed crystal positioning stage. The seed crystal positioning stage is fixedly connected to the crucible lid through the card slot, and a cavity is formed between the seed crystal positioning stage, the card slot, and the crucible lid.

2. The silicon carbide crystal growth apparatus according to claim 1, characterized in that, The inner cavity of the growth crucible is divided into an upper growth area and a lower raw material area, and the support platform is located in the upper growth area; and / or, the inner diameter of the support platform is greater than the inner diameter of the lower raw material area of the growth crucible; and / or, the growth chamber is an annular structure; and / or, the outer diameter of the growth chamber is the same as the inner diameter of the support platform.

3. The silicon carbide crystal growth apparatus according to claim 1, wherein The material of the seed crystal positioning stage is the same as the material of the silicon carbide seed crystal; and / or, the seed crystal positioning stage is bonded to the silicon carbide seed crystal; and / or, the surface roughness of the bonding surface where the seed crystal positioning stage is connected to the silicon carbide seed crystal is less than 0.2 nm.

4. The silicon carbide crystal growth device according to claim 3, characterized in that, The thickness of the seed crystal positioning stage is 5 - 20 mm; and / or, at least the surface of the seed crystal positioning stage that faces away from the bonding surface is provided with a protective layer, and the material of the protective layer includes any one of carbon, tantalum carbide, or niobium carbide.

5. The silicon carbide crystal growth device according to claim 1, wherein, The thickness of the card slot is 0.5 - 5 mm; and / or, the inner diameter of the card slot is greater than or equal to the diameter of the silicon carbide seed crystal, and the outer diameter of the card slot is greater than or equal to the diameter of the seed crystal positioning stage; and / or, the material of the card slot includes any one or a combination of at least two of graphite, carbon fiber, or silicon carbide.

6. The silicon carbide crystal growth apparatus according to claim 1, characterized in that A heat preservation ring is arranged in the cavity formed by the growth chamber, the seed crystal positioning stage, the card slot, the crucible lid, and the growth crucible; and / or, the material of the heat preservation ring includes any one or a combination of at least two of foam carbon, porous carbon, or carbon fiber.

7. The silicon carbide crystal growth device according to claim 1, characterized in that, The edge position of the seed crystal positioning stage is a porous structure, and the porous structure does not contact the silicon carbide seed crystal; and / or, in the porous structure, the pore diameter is 0.5 - 500 μm.

8. The silicon carbide crystal growth device according to claim 1, characterized in that, A limiting piece is arranged in the contact area between the growth chamber and the seed crystal positioning stage; and / or, the thickness of the limiting piece is 0.2 - 1 mm.

9. A method for growing a silicon carbide crystal, characterized in that, The growth method uses the silicon carbide crystal growth apparatus according to any one of claims 1 - 8, and includes the following steps: Place the silicon carbide raw material in the growth crucible, place the growth chamber on the support platform, and then place the seed crystal positioning stage provided with the silicon carbide seed crystal on the growth chamber, and make the side with the silicon carbide seed crystal correspond to the silicon carbide raw material; Place the card slot on the seed crystal positioning stage, then cover the crucible lid, and make the crucible lid and the card slot contact; Vacuumize, and then heat to make the silicon carbide crystal grow on the bottom surface of the silicon carbide seed crystal.

10. The method for growing a silicon carbide crystal according to claim 9, characterized in that, Before setting the silicon carbide seed crystal on the seed crystal positioning stage, polish the surface of the seed crystal positioning stage that contacts the silicon carbide seed crystal first; And / or, before the seed crystal positioning stage is placed on the growth chamber, a limit piece is placed in the area where the seed crystal positioning stage contacts the growth chamber.

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