Silicon carbide single crystal growth device and method for improving powder utilization rate

Abstract

The invention provides a silicon carbide single crystal growth device and method for improving the powder utilization rate, the silicon carbide single crystal growth device comprises a heating barrel, a crucible and a heat conduction assembly, the heating barrel comprises an upper cover and a barrel body which are matched with each other, the crucible is contained in the barrel body, a through hole is formed in the bottom of the crucible, a heat conduction rod is arranged at the bottom of the barrel body, and the heat conduction rod extends into the crucible; the crucible comprises a crucible cover and a crucible body which are matched with each other, silicon carbide seed crystals are arranged at the lower end of the crucible cover, silicon carbide powder is arranged in the crucible body, a heat conduction assembly is arranged in the charging area and comprises a heat conduction tower and a heat conduction ring, a hollow structure is arranged in the heat conduction tower, and the heat conduction tower is connected to the outer side of the heat conduction rod in a sleeving mode. A plurality of layers of heat conduction rings are arranged on the heat conduction tower, and the heat conduction rings extend outwards to act on different areas of the charging area. The heating barrel and the heat conduction structure are introduced in the silicon carbide single crystal growth process, the powder utilization rate is increased, the sealing performance of the growth structure is improved, and efficient utilization of powder in the growth process is achieved.

Description

Technical Field

[0001] The invention belongs to the technical field of semiconductors, and in particular relates to a silicon carbide single crystal growth device and method for improving powder material utilization. Background Art

[0002] The statements in this section merely provide background information related to the present invention and do not necessarily constitute prior art.

[0003] As a third-generation semiconductor material, silicon carbide has great application potential in rail transit, electric vehicles, high-voltage power transmission and transformation, photovoltaics, chips and other fields due to its many characteristics such as large bandgap, strong critical breakdown field, high thermal conductivity, and high saturation drift velocity.

[0004] The main growth method of silicon carbide single crystals is the physical vapor transport (PVT) method. In this process, silicon carbide powder is placed at the bottom of the crucible and silicon carbide seed crystals are placed at the top of the crucible. The powder at the bottom of the crucible sublimates due to its high temperature, and is transported to the silicon carbide seed crystals at the top of the crucible with a lower temperature under the driving force of the temperature gradient for deposition and growth. Among them, induction heating is a commonly used heating mode for growing silicon carbide single crystals by the PVT method due to its low power consumption. However, in induction heating, the crucible wall acts as a heating element. Due to the skin effect, the temperature of the crucible wall is significantly higher than that of the center, resulting in an obvious radial temperature gradient in the crucible. The growth of large-diameter silicon carbide single crystals requires a large-diameter crucible as a reaction vessel and heating element. The increase in the diameter of the crucible further exacerbates the radial temperature gradient inside the crucible.

[0005] When silicon carbide single crystals grow, the temperature at the bottom of the powder is high and the temperature at the seed crystal is low. When the axial temperature gradient in the powder becomes larger, it is very easy for the gas phase components to crystallize at the top of the powder, which hinders the transport of the growing gas phase components to the seed crystal and causes a serious reduction in the powder utilization rate. In addition, after sublimation and decomposition, a part of the residual carbon will remain at the bottom of the crucible, affecting the heat transfer from the bottom of the crucible to the surface of the powder. If the radial temperature gradient is too large, the powder on the side wall will move toward the center after sublimation, which may also cause the center of the powder to recrystallize, thereby affecting the utilization efficiency of the powder and reducing the growth rate.

[0006] At the same time, during the PVT growth process, since the graphite crucible itself has pores and its structure cannot be completely sealed, the silicon carbide powder decomposes and sublimates when heated. The sublimated components will not only be deposited at the seed crystal position to achieve crystal growth, but will also leak from the crucible structure through gaps and cracks, thereby corroding the insulation structure and even the growth furnace structure, which will affect the service life of the insulation, crucible and even the furnace, and increase the cost of use.

[0007] Prior art CN118461121A discloses that multiple induction components are arranged in the crucible body, and silicon carbide powder is inductively heated by the induction components to reduce the temperature gradient in the powder and improve the temperature uniformity of the powder in the crucible. However, due to the skin effect and the induction heating conversion efficiency, multiple induction components inside the crucible cannot be effectively heated, and the powder utilization rate cannot be effectively improved. Prior art CN216688415U discloses that accessories are inserted into the center of the powder source in the crucible to increase the surface area of ​​the powder source sublimation and increase the sublimation rate of the central powder source. However, since the silicon carbide powder sublimated at the bottom will recrystallize on the accessories with lower temperature, the utilization rate of the powder cannot be effectively improved. Prior art CN221918323U discloses that a double layer of porous graphite is placed inside the crucible, and the temperature field is adjusted by the porous graphite to improve the utilization rate of the powder, but the axial and radial temperature gradients of the powder are both large, which will hinder the efficient utilization of the powder. Summary of the invention

[0008] In order to solve the problems of low powder utilization during the growth process under the above-mentioned crucible structure and the leakage of silicon carbide gas phase components affecting the service life of the growth components, the present invention proposes a silicon carbide single crystal growth device and method for improving the powder utilization rate. The present invention introduces a heating barrel and a heat-conducting structure during the silicon carbide single crystal growth process, thereby improving the powder utilization rate, enhancing the sealing of the growth structure, achieving efficient utilization of powder during the growth process, and extending the service life of the growth device and reducing costs.

[0009] According to some embodiments, the present invention adopts the following technical solutions:

[0010] In a first aspect, the present invention provides a silicon carbide single crystal growth device that improves powder utilization, which is used to increase the airtightness of the growth system and extend the service life of the growth crucible, insulation and single crystal furnace.

[0011] A silicon carbide single crystal growth device for improving powder utilization rate, comprising a heating barrel, a crucible and a heat-conducting component, wherein the heating barrel comprises an upper cover and a barrel body adapted to each other, the crucible is accommodated inside the barrel body, a through hole is provided at the bottom of the crucible, and a heat-conducting rod is provided at the bottom of the barrel body, and the heat-conducting rod extends upward to the inside of the crucible through the through hole;

[0012] The crucible comprises a matching crucible cover and a crucible body, the lower end of the crucible cover is provided with a silicon carbide seed crystal, the lower part of the crucible body is a loading area, the loading area carries silicon carbide powder, and the area between the silicon carbide seed crystal and the surface of the silicon carbide powder is a growth cavity;

[0013] A heat-conducting component is arranged in the loading area, and the heat-conducting component includes a heat-conducting tower and a heat-conducting ring. A hollow structure is arranged inside the heat-conducting tower, and the heat-conducting tower is sleeved on the outside of the heat-conducting rod. Several layers of heat-conducting rings are arranged on the heat-conducting tower, and the heat-conducting rings extend outward to act on different areas of the loading area.

[0014] As an optional embodiment, the heating barrel and the heat-conducting rod are made of graphite, and the heat-conducting tower and the heat-conducting ring are made of at least one of graphite, metal carbide or metal.

[0015] As a further limited embodiment, the graphite material includes at least one of isostatic graphite and extruded graphite, the metal carbide material includes at least one of tantalum carbide and niobium carbide, and the metal material includes at least one of tantalum and niobium.

[0016] As an optional implementation, the wall thickness of the heating barrel is consistent with the wall thickness of the crucible, the inner diameter of the heating barrel is matched with the outer diameter of the crucible, and the height of the heating barrel is 120% to 200% of the height of the crucible.

[0017] As an optional implementation, the diameter and height of the crucible are adjusted according to the required size of the grown crystal.

[0018] As an optional implementation manner, the height of the charging area is 30% to 60% of the height of the crucible, and the growth chamber is 40% to 70% of the height of the crucible.

[0019] As an optional embodiment, the height of the heat conductive rod is less than the height of the loading area, the diameter of the heat conductive rod is 5% to 15% of the diameter of the crucible, and the diameter of the hollow structure inside the heat conductive tower is 10% to 20% of the diameter of the crucible; the total height of the heat conductive tower is consistent with the height of the loading area and is higher than the height of the heat conductive rod.

[0020] As an optional implementation, the heat-conducting tower includes several layers, and the side of each layer in contact with the silicon carbide material is a variable diameter structure, and the diameter increases from top to bottom.

[0021] Preferably, the variable diameter structure is in the shape of a truncated cone.

[0022] As a further limited implementation, the top diameter of the heat conducting tower is 10% to 20% of the diameter of the crucible, and the bottom diameter of the heat conducting tower is 15% to 30% of the diameter of the crucible, which is consistent with the size of the central hole at the bottom of the crucible.

[0023] As an optional embodiment, the heat-conducting ring includes an inner ring, an outer ring and spokes, the diameter of the inner ring is set according to the number of layers of the heat-conducting tower or the diameter of the position where the heat-conducting tower is installed, and the diameter of the outer ring is 80% to 90% of the diameter of the charging area;

[0024] The inner ring and the outer ring are connected by a plurality of spokes arranged circumferentially.

[0025] The inner ring, outer ring and spokes are all made of heat-conducting materials, and the diameters of the inner ring, outer ring and the number of spokes can be flexibly set according to heat conduction requirements.

[0026] As an optional embodiment, the silicon carbide single crystal growth device further includes a heating system arranged outside the heating barrel, and the space between the heating barrel and the heating system is filled with a heat-insulating material.

[0027] In a second aspect, the present invention provides a method for growing a silicon carbide single crystal, using the above silicon carbide single crystal growth apparatus.

[0028] A method for growing a silicon carbide single crystal comprises the following steps:

[0029] The heat-conducting tower and the hole at the bottom of the crucible are sealed by threaded connection, and then the crucible is placed in the heating barrel so that the heat-conducting rod is embedded in the cylindrical hole inside the heat-conducting tower;

[0030] Spread silicon carbide powder evenly on the bottom of the graphite crucible, with the height of the powder being level with the height of the heat-conducting tower. Place the heat-conducting ring on the surface of the powder or bury it in the powder according to the shape of the heat-conducting tower and the inner diameter of the inner ring of the heat-conducting ring, and insert the inner ring of the heat-conducting ring into the heat-conducting tower. Fix the silicon carbide seed crystal on the upper cover of the crucible.

[0031] Put the heating barrel together with the graphite crucible into the growth device, seal the growth device, and evacuate the inside of the device;

[0032] The inside of the growth device after vacuum treatment is heated, and a carrier gas is filled into the inside of the growth device. After the heating reaches the expected temperature, the temperature is maintained constant to allow the silicon carbide powder to sublime, and the sublimated powder is transported to the surface of the silicon carbide seed crystal to achieve crystal growth;

[0033] When the crystal growth is completed, the temperature inside the growth device is lowered, and a carrier gas is filled into the growth device to allow the crystal to cool naturally to obtain a silicon carbide single crystal.

[0034] Compared with the prior art, the present invention has the following beneficial effects:

[0035] The present invention innovatively introduces a heating barrel and a heat-conducting structure during the growth process of silicon carbide single crystals. The heating barrel is heated by induction heating. The heating barrel made of graphite conducts or radiates the heat generated by the induction to the crucible wall and the heat-conducting rod extending into the crucible, thereby heating the heating tower and the heating ring, thereby adjusting the temperature field of the loading area in the crucible and effectively improving the powder utilization rate.

[0036] The inner diameter and the number of spokes of the heat-conducting ring of the present invention can be adjusted according to the situation to achieve efficient utilization of silicon carbide powder. After the powder at the bottom of the crucible is sublimated, loose graphitized residues will be formed at the bottom of the crucible, and part of the sublimated silicon carbide components will grow into crystals at the top along the temperature gradient and the carrier gas, and the other part will be recrystallized into silicon carbide polycrystals on the heat-conducting ring, increasing the weight of the heat-conducting ring. When the graphitized residue cannot support the heat-conducting ring and the silicon carbide polycrystals crystallized thereon, the heat-conducting ring slowly moves along the heat-conducting tower to the bottom of the crucible, realizing the automatic transfer of powder from the low temperature zone to the high temperature zone. The heat-conducting tower of the present invention can be a truncated cone structure, and the heat-conducting ring gradually approaches the high temperature position during the descent process, and the heat transfer efficiency is gradually improved, so as to fully heat the remaining powder and the recrystallized silicon carbide polycrystals, thereby solving the problem that the crystallization of powder in the traditional crucible affects the crystal growth.

[0037] The heating barrel in the present invention is designed as a closed design, which ensures the sealing of the growth crucible chamber, can effectively prevent the leakage of silicon carbide components during the growth process from affecting the insulation structure and even the single crystal growth furnace, extend the service life of the graphite components, and significantly reduce the complexity of crystal growth process adjustment and the growth cost of silicon carbide single crystals.

[0038] Compared with the structure that only uses a heating barrel to heat the crucible, the present invention can directly heat the inside of the powder by introducing a heat-conducting component, avoid the problem of crystallization in the center of the powder, effectively improve the heat transfer efficiency, reduce power loss, and greatly reduce production costs.

[0039] The various structures of the present invention are compatible with the current growth process, and the sizes of different components can be adjusted and adapted accordingly according to the existing silicon carbide growth equipment, so as to facilitate promotion and use.

[0040] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, preferred embodiments are given below and described in detail with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] The accompanying drawings in the specification, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0042] Figure 1 The following is a schematic diagram of a silicon carbide single crystal growth device in an embodiment, wherein (a) is a schematic diagram of the initial growth state, and (b) is a schematic diagram of the state during the growth process.

[0043] Figure 2 is a three-dimensional disassembled diagram of a silicon carbide crystal growth device in an embodiment;

[0044] Figure 3 The figure is a temperature field distribution diagram of a graphite crucible for growing a silicon carbide single crystal obtained by numerical simulation in an embodiment.

[0045] Figure 4 is a temperature field diagram in a graphite crucible for growth of a silicon carbide single crystal obtained by numerical simulation in an embodiment;

[0046] Figure 5 It is a temperature field diagram inside a graphite crucible powder for growing a silicon carbide single crystal obtained by numerical simulation in another embodiment.

[0047] Among them, 1 is the upper cover of the heating barrel, 2 is the heating barrel body, 3 is the upper cover of the crucible, 4 is the silicon carbide seed crystal, 5 is the crucible body, 6 is the heat conduction tower, 7 is the heat conduction ring, 8 is the heat conduction rod, 9 is the growth chamber, and 10 is the silicon carbide powder.

[0048] 61 - upper circular surface of the heat conducting tower, 62 - middle circular surface of the heat conducting tower, 63 - lower circular surface of the heat conducting tower.

[0049] 71-inner ring of the heat-conducting ring, 72-spokes of the heat-conducting ring, 73-outer ring of the heat-conducting ring. DETAILED DESCRIPTION

[0050] The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0051] It should be noted that the following detailed descriptions are all illustrative and intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used herein have the same meanings as those commonly understood by those skilled in the art to which the present invention belongs.

[0052] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit exemplary embodiments according to the present invention. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprising" and / or "including" are used in this specification, it indicates the presence of features, steps, operations, devices, components and / or combinations thereof.

[0053] In the absence of conflict, the embodiments in this application and the features in the embodiments may be combined with each other.

[0054] In order to make the technical solution of the present invention more clearly understood by those skilled in the art, the following glossary is first provided:

[0055] Radial temperature gradient inside the powder: In the present invention, it refers to the temperature difference between the center of the silicon carbide powder surface and the edge of the silicon carbide powder surface per unit length. In a general crucible structure, the greater the radial temperature gradient inside the material, the easier it is for the sublimated powder at the edge to agglomerate toward the center to form recrystallization, affecting the transmission of components to the growth chamber and being detrimental to crystal growth.

[0056] Axial temperature gradient inside the powder: In the present invention, it refers to the temperature difference between the surface of the silicon carbide powder and the corresponding bottom of the silicon carbide powder per unit length. In a general crucible structure, the larger the axial temperature gradient inside the material, the easier it is for the components released by the sublimation of the material to crystallize on the surface of the material, affecting the transmission of the components to the growth chamber, which is not conducive to crystal growth.

[0057] Low temperature zone position: in the present invention, it refers to the position of the region in the powder material where the temperature inside the powder material is lower during the growth process.

[0058] High temperature zone position: in the present invention, it refers to the position of the area with higher temperature inside the powder during the growth process.

[0059] Crystal growth rate: In the present invention, it refers to the change in weight of silicon carbide single crystal per unit time. The faster the crystal growth rate, the higher the crystal growth efficiency.

[0060] Powder utilization rate: in the present invention, it refers to the ratio of the mass of silicon carbide powder converted into the mass of silicon carbide single crystal during the growth process of silicon carbide single crystal. From the perspective of SiC single crystal preparation cost, the higher the powder utilization rate, the higher the crystal growth efficiency.

[0061] Example 1

[0062] Silicon carbide crystal growth device, such as Figure 1 As shown in (a) and (b), it includes a heating barrel, a crucible and a heat-conducting component. The heating barrel includes a heating barrel cover 1 and a heating barrel body 2. This embodiment is suitable for a graphite crucible with a silicon carbide seed crystal on the top and silicon carbide powder inside. A cylindrical heat-conducting rod 8 extending upward to the inside of the crucible is installed at the center of the bottom of the barrel body; the crucible includes a crucible cover 3 and a crucible body 5, the silicon carbide seed crystal 4 is fixed at the crucible cover position above the crucible, the surface from the silicon carbide seed crystal 4 to the silicon carbide powder 10 is a growth cavity 9, and the bottom of the growth cavity 9 is a loading area. The center of the bottom of the crucible body 5 has a hole, which allows the heat-conducting rod 8 at the bottom of the heating barrel to extend into the loading area; the heat-conducting component includes a heat-conducting tower 6 and a heat-conducting ring 7, both of which are located in the crucible loading area, and the heat-conducting tower 6 can be assembled and sealed with the center hole at the bottom of the crucible through a bottom thread, and the inside of the heat-conducting tower 6 is a hollow structure, such as Figure 2 and Figure 3 As shown, the heat-conducting rod 8 at the bottom of the heating barrel can be embedded in the heat-conducting tower 6, and the heat-conducting ring 7 is divided into a heat-conducting ring inner ring 71 and a heat-conducting ring outer ring 73. The heat-conducting ring inner ring 71 and the heat-conducting ring outer ring 73 are connected by a plurality of heat-conducting ring spokes 72, and the heat-conducting ring inner ring 71 can be inserted into the heat-conducting tower 6.

[0063] In this embodiment, the heating barrel and the heat conducting rod 8 are made of graphite, and the heat conducting tower 6 and the heat conducting ring 7 are made of at least one of graphite, metal carbide or metal. The graphite material includes at least one of isostatic graphite and extruded graphite, the metal carbide material includes at least one of tantalum carbide and niobium carbide, and the metal material includes at least one of tantalum and niobium.

[0064] In some preferred embodiments, the wall thickness of the heating barrel is consistent with the wall thickness of the crucible, the inner diameter of the heating barrel is consistent with the outer diameter of the crucible, and the height of the heating barrel is 120% to 200% of the height of the crucible.

[0065] In other embodiments, the diameter and height of the crucible can be adjusted according to the actual required size of the grown crystal.

[0066] In some preferred embodiments, the height of the charging area is 30% to 60% of the height of the crucible, and the height of the growth chamber is 40% to 70% of the height of the crucible.

[0067] In some preferred embodiments, the height of the heat conducting rod 8 is slightly lower than the height of the charging area, and the diameter of the heat conducting rod is 5% to 15% of the diameter of the crucible and slightly smaller than the diameter of the hollow cylinder inside the heat conducting tower.

[0068] In some preferred embodiments, the total height of the heat conducting tower 6 is consistent with the height of the loading area and slightly higher than the height of the heat conducting rod. The diameter of the internal cylindrical hollow structure of the heat conducting tower 6 is 10% to 20% of the diameter of the crucible, which is slightly larger than the diameter of the heat conducting rod 8.

[0069] In some preferred embodiments, the side of the heat-conducting tower 6 that contacts the silicon carbide powder 10 in the crucible is truncated, and the number of truncated cones of the heat-conducting tower can be adjusted according to actual requirements. The top diameter of the heat-conducting tower 6 is 10% to 20% of the diameter of the crucible, and the bottom diameter of the heat-conducting tower 6 is 15% to 30% of the diameter of the crucible, which is consistent with the size of the central hole at the bottom of the crucible. The inner diameter of the heat-conducting ring 7 is adjusted according to the number of truncated cones of the heat-conducting tower 6, and the outer diameter of the heat-conducting ring 7 is 80% to 90% of the diameter of the charging area.

[0070] In other preferred embodiments, the silicon carbide single crystal growth device includes the graphite crucible, a heating barrel and a heating system arranged on the periphery of the heating barrel, and the space between the heating barrel and the heating system is filled with insulation material.

[0071] Example 2

[0072] This embodiment provides a silicon carbide single crystal growth device, the operation of which specifically includes the following steps:

[0073] (1) Select a double-layer truncated cone structure heat-conducting tower 6, the height of which is 56% of the height of the crucible 5, the height of the two truncated cones is 28% of the height of the crucible 5, the diameters of the truncated cone surfaces 61 and 62 are 15% and 25% of the diameter of the crucible, respectively, and the diameters of the lower surfaces of the two truncated cones are 20% and 30% of the diameter of the crucible 5, respectively. The heat-conducting tower 6 is connected to the hole at the bottom of the crucible 5, and then the crucible 5 is placed in the heating barrel 2, the height of the heating barrel 2 is 130% of the height of the crucible 5. The heat-conducting rod 8 is embedded in the cylindrical cavity inside the heat-conducting tower 6, the inner diameter of the heat-conducting tower 6 is 12% of the diameter of the crucible 5, and the diameter of the heat-conducting rod 8 is 10% of the diameter of the crucible 5;

[0074] (2) Spread the silicon carbide powder evenly in the charging area 10 at the bottom of the crucible 5. After the height of the powder is level with the height of the heat-conducting tower circular surface 62 of the heat-conducting tower 6, insert the heat-conducting ring with the same inner diameter 71 as the lower circular surface 63 of the heat-conducting tower into the circular surface 62 of the heat-conducting tower and place it on the material plane. Then continue to add silicon carbide powder until the height of the powder is finally level with the circular surface 61 of the heat-conducting tower. Place the heat-conducting ring with the same inner diameter 71 as the circular surface 62 of the heat-conducting tower on the surface of the powder, and insert the inner ring 71 of the heat-conducting ring into the circular surface 61 of the heat-conducting tower. The outer diameters 73 of the two heat-conducting rings are both 90% of the diameter of the charging area 10. Finally, the height of the charging area 10 is 60% of the height of the crucible 5, and the total charge is 5000g.

[0075] (3) The silicon carbide seed crystal 4 is fixed on the crucible cover 3, and then the crucible cover 3 is placed on the crucible 5 to form a closed structure of the crucible. Then the heating barrel cover 1 is placed on the heating barrel 2 to form a closed structure.

[0076] (4) placing the heating barrel 2 together with the graphite crucible 5 into the growth device, sealing the growth device, and evacuating the interior thereof;

[0077] (5) The inside of the growth device after vacuum treatment is heated, and a carrier gas is filled into the inside of the growth device, and the heating barrel is heated to 2150° C. for crystal growth, and the temperature is kept for 200 hours. The power of the heating power supply during the growth process is 18570W. After the growth is completed, the system is cooled to obtain a silicon carbide single crystal.

[0078] The graphite crucible 5 was taken out from the growth furnace to obtain a silicon carbide single crystal, and it was found that the silicon carbide powder was all loose graphitized residues, without any crystals inside or on the surface of the powder, and there was no silicon carbide powder crystal on the heat tower 6 and the two heat conducting rings 7, and the two heat conducting rings 7 had a large displacement toward the bottom of the crucible 5 relative to the initial position. This shows that the powder has moved from the low temperature zone to the high temperature zone during the growth process.

[0079] The mass of the silicon carbide single crystal weighed on a balance is 4563g, the mass of the leaked component is 102g, and the mass of the remaining silicon carbide powder is 335g. Through calculation, it can be known that the crystal growth rate is 22.8g / H and the powder conversion rate is 91.26%. This shows that the utilization rate of silicon carbide powder in this method is high, and the increase in the mass of the single crystal per unit time is large. Numerical simulation of this embodiment is carried out to obtain the temperature field diagram of the powder in the graphite crucible 5 as shown in the figure below: Figure 4 As shown, the distribution of isotherms in the graphite crucible 5 is sparse, indicating that the radial temperature gradient of the powder is small, the powder is heated evenly as a whole, and the crystallization of the edge powder in the center is suppressed, which is beneficial to improving the utilization rate of the powder. At the same time, the temperature field diagram shows that the top position of the charging area 10 near the growth chamber 9 is a low temperature zone, and the charging area 10 near the bottom of the crucible 5 and the heat transfer tower 6 is a high temperature zone. During the growth process, the powder moves from the low temperature zone to the high temperature zone with the movement of the heat transfer ring 7 to the bottom of the crucible 5, which reduces the axial temperature gradient of the powder. Under the condition of ensuring a high single crystal growth rate, the small axis ladder near equilibrium growth of the charging area is achieved.

[0080] The insulation structure was weighed using a balance, and it was found that the insulation structure had increased in weight by 8g. At the same time, the heating barrel 2 structure was weighed using a balance, and it was found that the heating barrel 2 had increased in weight by 89g, indicating that the heating barrel 2 structure has good sealing properties and can effectively prevent component leakage.

[0081] Example 3

[0082] The difference from Example 1 is:

[0083] This embodiment provides a method for growing silicon carbide crystals, which specifically includes the following steps:

[0084] (1) Select a heat-conducting tower 6 with only a single-layer truncated cone structure, that is, the heat-conducting tower 6 only includes an upper circular surface 61 and a lower circular surface 62. The height of the heat-conducting tower 6 is 56% of the height of the crucible, the diameter of the upper circular surface 61 is 15% of the diameter of the crucible, the diameter of the lower circular surface 62 is 30% of the diameter of the crucible, and the height of the heat-conducting tower 6 is 56% of the height of the crucible. The heat-conducting tower 6 is connected to the hole at the bottom of the crucible 5, and then the crucible 5 is placed in the heating barrel 2. The height of the heating barrel 2 is 130% of the height of the crucible 5. The heat-conducting rod 8 is embedded in the cylindrical cavity inside the heat-conducting tower 6. The diameter of the cavity inside the heat-conducting tower 6 is 12% of the diameter of the crucible, and the diameter of the heat-conducting rod 8 is 10% of the diameter of the crucible;

[0085] (2) The silicon carbide powder is evenly spread in the charging area 10 at the bottom of the crucible 5. The height of the powder is finally slightly higher than the upper circular surface 61 of the heat conducting tower. A heat conducting ring with an inner diameter 71 that is the same as the lower circular surface 63 of the heat conducting tower is placed on the surface of the powder. The inner ring 71 of the heat conducting ring is inserted into the upper circular surface 61 of the heat conducting tower. The outer diameter 73 of the heat conducting ring is 90% of the diameter of the charging area. The height of the charging area 10 is finally 60% of the height of the crucible 5. The total charge is 5320g.

[0086] (3) The silicon carbide seed crystal 4 is fixed on the crucible cover 3, and then the crucible cover 3 is placed on the crucible 5 to form a closed structure of the crucible 5. Then, the heating barrel cover 1 is placed on the heating barrel 2 to form a closed structure.

[0087] (4) placing the heating barrel together with the graphite crucible 5 into the growth device, sealing the growth device, and evacuating the interior thereof;

[0088] (5) The inside of the growth device after vacuum treatment is heated, and a carrier gas is filled into the inside of the growth device, and the heating barrel 2 is heated to 2150° C. for crystal growth, and the temperature is kept for 200 hours. The power of the heating power supply during the growth process is 18300 W. After the growth is completed, the system is cooled to obtain a silicon carbide single crystal.

[0089] The graphite crucible 5 was taken out from the growth furnace to obtain a silicon carbide single crystal. It was found that part of the silicon carbide powder was loose graphitized residue, with very few silicon carbide crystal particles inside the powder. There was no silicon carbide powder crystal on the heat-conducting tower 6 and the heat-conducting ring 7, and the heat-conducting ring 7 was partially moved downward relative to the initial position. The description shows that the powder has achieved the movement from the low-temperature zone to the high-temperature zone during the growth process, but only one layer of the heat-conducting ring 7 structure is insufficient to heat the temperature field in the crucible 5. The mass of the silicon carbide single crystal was weighed on a balance and was 4183g, the mass of the leaked component was 98g, and the mass of the remaining silicon carbide powder was 1039g. By calculation, it can be known that the crystal growth rate is 20.9g / H, and the powder conversion rate is 78.6%. It shows that the utilization rate of silicon carbide powder in this method is still relatively high.

[0090] The insulation structure was weighed using a balance, and it was found that the insulation structure had increased in weight by 9g. At the same time, the heating barrel 2 structure was weighed using a balance, and it was found that the heating barrel 2 had increased in weight by 81g, indicating that the heating barrel 2 structure has good sealing properties and can effectively prevent components from leaking out.

[0091] Example 4

[0092] The difference from Example 1 is:

[0093] This embodiment provides a method for growing silicon carbide crystals, which specifically includes the following steps:

[0094] (1) A heat-conducting tower 6 with a three-layer truncated cone structure is selected. The heat-conducting tower 6 is connected to the hole at the bottom of the crucible 5. The height of the heat-conducting tower 6 is 56% of the height of the crucible. The upper surface diameters of the three-layer truncated cones are 12%, 17% and 25% of the diameter of the crucible 5 respectively. The lower surface diameters of the three-layer truncated cones are 15%, 20% and 30% of the diameter of the crucible respectively. The heights of the three-layer truncated cones are 18%, 18% and 20% of the height of the crucible respectively. Then, the crucible 5 is placed in the heating barrel 2. The height of the heating barrel 2 is 140% of the height of the crucible 5. The heat-conducting rod 8 is embedded in the cylindrical cavity inside the heat-conducting tower 6. The inner diameter of the heat-conducting tower 6 is 11% of the diameter of the crucible 5. The diameter of the heat-conducting rod 8 is 10% of the diameter of the crucible;

[0095] (2) The silicon carbide powder is evenly spread in the charging area 10 at the bottom of the crucible 5, and the height of the powder is finally slightly higher than the upper circular surface 61 of the heat conduction tower. Two heat conduction rings with inner diameters from large to small are successively buried in the silicon carbide powder. The position of the heat conduction ring 7 is consistent with the height of the circular surface of the heat conduction tower corresponding to the inner diameter. The heat conduction ring 7 with the smallest inner diameter is inserted into the heat conduction tower. The outer diameters of the three heat conduction rings are all 90% of the diameter of the charging area 10. The height of the final charging area 10 is 60% of the height of the crucible 5. The total loading is 4570g. Due to the large number of components, the loading amount is relatively small.

[0096] (3) The silicon carbide seed crystal 4 is fixed on the crucible cover 3, and then the crucible cover 3 is placed on the crucible 5 to form a closed structure of the crucible. Then the heating barrel cover 1 is placed on the heating barrel 2 to form a closed structure.

[0097] (4) placing the heating barrel 2 together with the graphite crucible 5 into the growth device, sealing the growth device, and evacuating the interior thereof;

[0098] (5) The inside of the growth device after vacuum treatment is heated, and a carrier gas is filled into the inside of the growth device, and the heating barrel 2 is heated to 2150° C. for crystal growth, and the temperature is kept for 200 hours. The power of the heating power supply during the growth process is 19010W. After the growth is completed, the system is cooled to obtain a silicon carbide single crystal.

[0099] (6) The graphite crucible 5 is taken out from the growth furnace to obtain a silicon carbide single crystal. It is found that the silicon carbide powder is partly loose graphitized residues. There is no silicon carbide powder crystallization on the heat conducting tower and the heat conducting ring. The three heat conducting rings 7 are all moved downward relative to the initial position, indicating that the powder has moved from the low temperature zone to the high temperature zone during the growth process. The mass of the silicon carbide single crystal is 3946g, the mass of the leaked component is 107g, and the mass of the remaining silicon carbide powder is 417g. By calculation, it can be known that the crystal growth rate is 19.73g / H and the powder conversion rate is 86.3%. It is shown that the utilization rate of silicon carbide powder in this method is high, but the increase in crystal mass per unit time is small. This is because the amount of loading is reduced, and there is more graphitized residue in the later stage of growth, which is not conducive to the heat transfer of the crucible 5. The remaining powder is difficult to sublimate, which reduces the crystal growth rate.

[0100] The insulation structure was weighed using a balance, and it was found that the insulation structure had increased in weight by 7g. At the same time, the heating barrel structure was weighed using a balance, and it was found that the heating barrel had increased in weight by 69g, indicating that the heating barrel structure has good sealing properties and can effectively prevent components from leaking out.

[0101] Comparative Example 1

[0102] In this comparative example, the silicon carbide powder as the raw material is directly placed at the bottom of the graphite crucible 5, and no heating barrel 2 components are added outside the crucible 5. At the same time, no heat-conducting components are placed in the crucible 5 to grow the silicon carbide single crystal. The other growth conditions are exactly the same as those in Example 1. After the growth is completed, the graphite crucible 5 is taken out of the growth furnace to obtain the silicon carbide single crystal. It is found that the silicon carbide powder has a relatively serious crystallization situation inside and on the surface, indicating that the axial and radial temperature gradients inside the powder are large, and the powder utilization rate is low. The mass of the silicon carbide single crystal weighed by a balance is 2842g, the mass of the leaked silicon component is 113g, the mass of the remaining silicon carbide powder is 2045g, the crystal growth rate is 14.21g / H, and the powder utilization rate is only 56.8%. It shows that the temperature field distribution inside the powder in this embodiment is uneven, and the utilization rate of the silicon carbide powder is low.

[0103] The temperature field diagram of the graphite crucible powder is obtained by numerical simulation of this comparative example. Figure 5 As shown in the figure, due to the reduction of the height of the heating barrel, the corresponding crucible position will move down and the corresponding high temperature zone will move up. Figure 5 This is reflected in the temperature field distribution diagram. Figure 4 The medium temperature field distribution diagram is different. The isotherm distribution in the loading area shows a morphology with more isotherms on the edge of the crucible and less in the center of the powder. This shows that the temperature field of the powder shows large radial and axial gradients. This also explains that in the actual growth process, the center of the powder is severely crystallized, which greatly hinders the transmission of components, is not conducive to the sublimation of the powder, and causes waste of powder.

[0104] The insulation structure was weighed using a balance, and it was found that the insulation structure had gained 101 g in weight, indicating that most of the components seeping out of the crucible condensed on the insulation structure, and the rest condensed in the single crystal furnace.

[0105] Comparative Example 2

[0106] In this comparative example, the heat-conducting tower shape 7 is changed to a hollow cylindrical graphite barrel, and the heating barrel 2 component is no longer added outside the crucible 5, and silicon carbide single crystal growth is carried out. The other growth conditions are exactly the same as those in Example 1. After the growth is completed, the graphite crucible 5 is taken out of the growth furnace to obtain a silicon carbide single crystal. It is found that crystallization occurs inside and on the surface of the silicon carbide powder, and a large amount of recrystallized silicon carbide polycrystals exist on the side of the hollow cylindrical graphite that contacts the powder. This indicates that the axial and radial temperature gradients inside the powder are large, resulting in a large amount of crystallization of the components on the hollow cylindrical graphite barrel, which seriously hinders the upward transmission of the components and leads to low powder utilization.

[0107] The mass of the silicon carbide single crystal weighed on a balance was 2725g, the mass of the leaked silicon component was 107g, and the mass of the remaining silicon carbide powder was 2168g. Calculation showed that the crystal growth rate was 13.63g / H, and the powder utilization rate was only 54.5%.

[0108] Numerical simulation of this comparative example shows that the isotherms in the powder of graphite crucible 5 are densely distributed, indicating that the radial and axial temperature gradients in the charging area are large, the temperature field distribution is uneven, and the temperature of the hollow cylindrical graphite barrel is relatively low, which is consistent with the actual situation.

[0109] The insulation structure was weighed using a balance, and it was found that the insulation structure had increased in weight by 83 g, indicating that most of the components seeping out of the crucible condensed on the insulation structure, and the rest condensed in the single crystal furnace.

[0110] Comparative Example 3

[0111] In this comparative example, the heat conducting tower 6, the heat conducting ring 7 and the heat conducting rod 8 structures are removed, and a heating barrel assembly is added to the crucible 5 to grow a silicon carbide single crystal. The other growth conditions are exactly the same as those in Example 1. The power of the heating power supply during the growth process is 19510W, which is 5% higher than the energy consumption in Example 1. After the growth is completed, the graphite crucible 5 is taken out of the growth furnace to obtain a silicon carbide single crystal. It is found that a large amount of crystals appear inside and on the surface of the silicon carbide powder. This indicates that the axial and radial temperature gradients inside the powder are large, and the powder utilization rate is low. The mass of the silicon carbide single crystal weighed on a balance is 2417g, the mass of the leaked silicon component is 98g, and the mass of the remaining silicon carbide powder is 2485g. The calculated crystal growth rate is 12.08g / H, and the powder utilization rate is only 48.3%. This indicates that the temperature field distribution inside the powder in this embodiment is uneven, and the utilization rate of the silicon carbide powder is low.

[0112] Numerical simulation of this comparative example shows that the isotherms in the graphite crucible powder are densely distributed, indicating that the temperature gradient in the loading area is large and the temperature field distribution is uneven, resulting in severe crystallization in the center of the powder, hindering the upward transport of components and being unfavorable for the utilization of the powder.

[0113] The insulation structure was weighed using a balance, and it was found that the insulation structure had increased in weight by 10 g. At the same time, the heating barrel structure was weighed using a balance, and it was found that the heating barrel had increased in weight by 79 g, indicating that the heating barrel structure can effectively prevent component leakage.

[0114] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made by those skilled in the art within the spirit and principle of the present invention without creative labor shall be included in the protection scope of the present invention.

Claims

1. A silicon carbide single crystal growth device for improving powder utilization, characterized in that: The invention comprises a heating barrel, a crucible and a heat-conducting component, wherein the heating barrel comprises an upper cover and a barrel body which are matched with each other, the crucible is accommodated inside the barrel body, a through hole is arranged at the bottom of the crucible, and a heat-conducting rod is arranged at the bottom of the barrel body, and the heat-conducting rod extends upward to the inside of the crucible through the through hole; The crucible comprises a matching crucible cover and a crucible body, the lower end of the crucible cover is provided with a silicon carbide seed crystal, the lower part of the crucible body is a loading area, the loading area carries silicon carbide powder, and the area between the silicon carbide seed crystal and the surface of the silicon carbide powder is a growth cavity; A heat-conducting component is arranged in the loading area, and the heat-conducting component includes a heat-conducting tower and a heat-conducting ring. A hollow structure is arranged inside the heat-conducting tower, and the heat-conducting tower is sleeved on the outside of the heat-conducting rod. Several layers of heat-conducting rings are arranged on the heat-conducting tower, and the heat-conducting rings extend outward to act on different areas of the loading area.

2. The silicon carbide single crystal growth device for improving powder utilization as claimed in claim 1, characterized in that: The heating barrel and the heat conducting rod are made of graphite, and the heat conducting tower and the heat conducting ring are made of at least one of graphite, metal carbide or metal; Or further, the graphite material includes at least one of isostatic graphite and extruded graphite, the metal carbide material includes at least one of tantalum carbide and niobium carbide, and the metal material includes at least one of tantalum and niobium.

3. The silicon carbide single crystal growth device for improving powder utilization as claimed in claim 1, characterized in that: The wall thickness of the heating barrel is consistent with that of the crucible, the inner diameter of the heating barrel is matched with the outer diameter of the crucible, and the height of the heating barrel is 120% to 200% of the height of the crucible.

4. The silicon carbide single crystal growth device for improving powder utilization as claimed in claim 1, characterized in that: The diameter and height of the crucible are adjusted according to the required size of the growing crystal.

5. The silicon carbide single crystal growth device for improving powder utilization as claimed in claim 1, characterized in that: The height of the charging area is 30% to 60% of the height of the crucible, and the growth chamber is 40% to 70% of the height of the crucible.

6. The silicon carbide single crystal growth device for improving powder utilization as claimed in claim 1, characterized in that: The height of the heat-conducting rod is less than the height of the charging area, the diameter of the heat-conducting rod is 5% to 15% of the diameter of the crucible, and the diameter of the hollow structure inside the heat-conducting tower is 10% to 20% of the diameter of the crucible; the total height of the heat-conducting tower is consistent with the height of the charging area and is higher than the height of the heat-conducting rod.

7. The silicon carbide single crystal growth device for improving powder utilization as claimed in claim 1, characterized in that: The heat conduction tower comprises several layers, and the side of each layer in contact with the silicon carbide material is a variable diameter structure, and the diameter increases from top to bottom; Or further, the variable diameter structure is in the shape of a truncated cone.

8. The silicon carbide single crystal growth device for improving powder utilization as claimed in claim 1, characterized in that: The top diameter of the heat-conducting tower is 10% to 20% of the diameter of the crucible, and the bottom diameter of the heat-conducting tower is 15% to 30% of the diameter of the crucible, which is consistent with the size of the central hole at the bottom of the crucible.

9. The silicon carbide single crystal growth device for improving powder utilization as claimed in claim 1, characterized in that: The heat-conducting ring includes an inner ring, an outer ring and spokes, the diameter of the inner ring is set according to the number of layers of the heat-conducting tower or the diameter of the position where the heat-conducting tower is installed, and the diameter of the outer ring is 80% to 90% of the diameter of the charging area; The inner ring and the outer ring are connected by a plurality of spokes arranged around the circumference; Or further, the inner ring, outer ring and spokes are all made of heat-conducting materials, and the diameters of the inner ring, outer ring and the number of spokes are set according to heat conduction requirements.

10. The silicon carbide single crystal growth device for improving powder utilization as claimed in claim 1, characterized in that: The silicon carbide single crystal growth device also includes a heating system arranged outside the heating barrel, and a heat-insulating material is filled between the heating barrel and the heating system.

11. A method for growing a silicon carbide single crystal, characterized in that: The following steps are involved: The heat-conducting tower and the hole at the bottom of the crucible are sealed by threaded connection, and then the crucible is placed in the heating barrel so that the heat-conducting rod is embedded in the cylindrical hole inside the heat-conducting tower; Spread silicon carbide powder evenly on the bottom of the graphite crucible, with the height of the powder being level with the height of the heat-conducting tower. Place the heat-conducting ring on the surface of the powder or bury it in the powder according to the shape of the heat-conducting tower and the inner diameter of the inner ring of the heat-conducting ring, and insert the inner ring of the heat-conducting ring into the heat-conducting tower. Fix the silicon carbide seed crystal on the upper cover of the crucible. Put the heating barrel together with the graphite crucible into the growth device, seal the growth device, and evacuate the inside of the device; The inside of the growth device after vacuum treatment is heated, and a carrier gas is filled into the inside of the growth device. After the heating reaches the expected temperature, the temperature is maintained constant to allow the silicon carbide powder to sublime, and the sublimated powder is transported to the surface of the silicon carbide seed crystal to achieve crystal growth; When the crystal growth is completed, the temperature inside the growth device is lowered, and a carrier gas is filled into the growth device to allow the crystal to cool naturally to obtain a silicon carbide single crystal.

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