Growth device for batch growth of silicon carbide single crystals
By designing multiple crucible assemblies and guide sleeves in a medium-frequency induction heating furnace, combined with tantalum foil and a threaded crucible cover, the problems of temperature gradient and graphite crucible loss in the growth of large-sized silicon carbide crystals were solved, and the efficient growth of multiple small-sized silicon carbide single crystals and cost reduction were achieved.
Patent Information
- Application Number
- CN202422811407.4
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2024-11-18
- Publication Date
- 2025-09-30
- Estimated Expiration
- 2034-11-18
AI Technical Summary
In the prior art, as the size of silicon carbide crystals increases, the thermal resistance to heat transfer increases, resulting in a larger temperature gradient, more crystal defects, accelerated mass loss of the graphite crucible, and reduced energy utilization, which limits the expansion of crystal size.
By adopting multiple crucible assemblies and guide sleeves, combined with tantalum foil and threaded crucible covers, a medium-frequency induction heating furnace is used to grow multiple small-sized silicon carbide single crystals. Through radiation heating and atmosphere diversion, the temperature gradient is adjusted to avoid excessive longitudinal temperature gradients and reduce production costs.
The simultaneous growth of multiple silicon carbide single crystals is achieved, crystal defects are reduced, the life of the graphite crucible is extended, energy utilization is improved, and production costs are reduced.
Smart Images
Figure CN223397842U_ABST
Abstract
Description
Technical Field
[0001] The utility model relates to the technical field of silicon carbide single crystal growth, in particular to a growth device for growing silicon carbide single crystals in batches. Background Art
[0002] Currently, in order to reduce costs, researchers are committed to developing equipment and processes for growing larger silicon carbide crystals. However, as the diameter of the crystal increases, the size of the crucible in which it is grown will also need to increase, and the thermal resistance to heat transfer from the outside to the inside will increase, which also leads to a decrease in the temperature of the center of the raw material, resulting in a larger lateral temperature difference in the crystal, and an increase in defects such as crystal polymorphism, basal plane dislocation, and even cracking. In order to maintain the temperature gradient, the temperature required at the edge of the crucible is getting higher and higher. Under high temperature and low pressure, the sublimation characteristics of graphite will accelerate the loss of the quality of the graphite crucible, thereby reducing the strength and service life of the graphite crucible, and the energy utilization rate will also be reduced accordingly. Therefore, from the perspective of equipment and consumables, more and more problems are encountered in increasing the size of the furnace, heater, crucible, and enhancing insulation, so the crystal size cannot be expanded indefinitely. Utility Model Content
[0003] The utility model provides a growth device for growing silicon carbide single crystals in batches, which solves the disadvantage in the prior art that in order to reduce costs, more and more problems are encountered in increasing the size of the furnace body, heater, crucible and enhancing heat preservation, so the crystal size cannot be expanded indefinitely.
[0004] The utility model provides the following technical solutions:
[0005] A growth device for batch growing silicon carbide single crystals includes a heating furnace, a lifting platform is provided in the heating chamber of the heating furnace, a plurality of crucible assemblies are evenly spaced on the lifting platform, the crucible assembly includes a crucible body, a guide sleeve is provided on the upper side of the crucible body, a ring is provided on the upper side of the guide sleeve, a crucible cover is provided on the top of the crucible body, a seed crystal is provided on the lower side of the crucible cover, and tantalum foil is provided on the lower side of the crucible cover, the inner side of the crucible body, and the inner side of the guide sleeve.
[0006] In a possible implementation manner, the inner diameter of the ring is adapted to the size of the seed crystal.
[0007] In a possible implementation, a first step and a second step are sequentially provided on the upper portion of the crucible body from top to bottom, the lower side of the guide sleeve is pressed onto the second step, and the ring is provided on the first step and the guide sleeve.
[0008] In a possible implementation, the guide sleeve is a conical ring, and the size of the lower side of the conical ring is adapted to the size of the crucible body, and the size of the upper side of the conical ring is adapted to the size of the seed crystal.
[0009] In a possible implementation, a heat-insulating layer is provided inside the heating chamber.
[0010] In a possible implementation, a cylindrical graphite heating element is provided in the thermal insulation layer.
[0011] In a possible implementation, the heating furnace body is provided with an induction coil, and the induction coil is arranged around the peripheral wall of the graphite heating element.
[0012] In a possible implementation, a lifting platform is provided at the bottom of the graphite heating element.
[0013] In a possible implementation, a temperature measuring tube is provided on the top of the heating furnace, and a thermometer is provided inside the temperature measuring tube.
[0014] In a possible implementation manner, the crucible cover is connected to the crucible body via threads, so that the height between the crucible cover and the crucible body can be adjusted via the threads.
[0015] It should be understood that the above general description and the following detailed description are merely illustrative and do not limit the present invention.
[0016] In the utility model, a plurality of matching crucible assemblies can be placed inside the heating element, and the heat of the graphite heating element is mainly transmitted to the internal graphite crucible assembly by radiation, and the axial temperature gradient of the internal graphite crucible assembly is small.
[0017] The guide sleeve inside the graphite crucible assembly can guide the atmosphere of the sublimated silicon carbide powder to the surface of the seed crystal, adjust the temperature field, and reduce the temperature gradient.
[0018] The crucible cover is threadedly connected to the crucible body, and the flow rate of the sublimated atmosphere discharged from the graphite crucible can be adjusted by relatively rotating the crucible cover.
[0019] Tantalum foil can prevent the carbon atmosphere volatilized from the graphite crucible from diffusing into the powder and growing single crystal inside the crucible, and also prevent the Si atmosphere generated by the powder during growth from corroding the graphite crucible.
[0020] Multiple small-sized silicon carbide single crystals can be grown simultaneously in a medium-frequency induction graphitization furnace, avoiding the problem of excessive longitudinal temperature gradient during the growth of large-sized single crystals while reducing production costs. BRIEF DESCRIPTION OF THE DRAWINGS
[0021] Figure 1 A schematic structural diagram of a growth device for growing silicon carbide single crystals in batches provided by an embodiment of the present utility model;
[0022] Figure 2A schematic diagram of the distribution of a crucible assembly for batch growing of silicon carbide single crystals provided by an embodiment of the present invention when it is set on a lifting platform;
[0023] Figure 3 A schematic structural diagram of a crucible assembly for a growth device for batch growing silicon carbide single crystals provided by an embodiment of the present invention;
[0024] Figure 4 A schematic diagram of the circular structure of a growth device for batch growing silicon carbide single crystals provided by an embodiment of the present utility model;
[0025] Figure 5 A picture of a silicon carbide single crystal grown by a growth device for growing silicon carbide single crystals in batches provided by an embodiment of the present utility model;
[0026] Figure 6 An XRD diagram of tantalum foil converted into tantalum carbide in a crucible after growing silicon carbide single crystals in a growth device for growing silicon carbide single crystals in batches provided by an embodiment of the present invention;
[0027] Figure 7 for Figure 3 Schematic diagram of the structure without tantalum foil;
[0028] Figure 8 For use Figure 7 Photograph of a silicon carbide single crystal grown using the crucible assembly shown.
[0029] Reference numerals:
[0030] 1. Thermometer; 2. Temperature measuring tube; 3. Heating furnace; 4. Insulation layer; 5. Induction coil; 6. Graphite heating element; 7. Crucible assembly; 8. Lifting platform;
[0031] 21. Crucible cover; 22. Seed crystal; 23. Ring; 24. Guide sleeve; 25. Crucible body; 26. Silicon carbide powder; 27. Tantalum foil. DETAILED DESCRIPTION
[0032] The embodiments of the present invention will be described below in conjunction with the accompanying drawings.
[0033] Silicon carbide (SiC) is a representative and relatively mature third-generation semiconductor material. Due to its excellent properties, including a wide bandgap, a strong critical breakdown field, and high thermal conductivity, it holds great promise for the fabrication of high-temperature, high-frequency, high-power, and radiation-resistant electronic devices. It is widely used in fiber-optic communications, mobile communications, navigation, and detection. Since the 1990s, countries around the world have invested significant human and material resources in the research and industrialization of SiC single crystals, resulting in rapid progress.
[0034] The main method currently used to prepare silicon carbide single crystals is physical vapor transport (PVT), also known as the modified Lely method. The basic principle of physical vapor transport is that the growth material is heated in the high-temperature area inside the crucible, decomposing and sublimating. The resulting gaseous components are transported to the lower temperature area under the influence of the temperature gradient and crystallize and grow, ultimately forming silicon carbide crystals. The specific implementation method is as follows: the crystal growth is carried out in a graphite crucible or a coated graphite crucible, with a silicon carbide seed crystal 22 fixed to the top of the crucible and high-purity silicon carbide powder placed at the bottom of the graphite crucible. Joule heat is directly generated in the wall of the growing single crystal graphite crucible through medium-frequency induction, and this heat is used as the heat source of the system. In addition to growth furnaces that use medium-frequency power supplies and growth graphite crucibles as heating devices, there are also growth furnaces that use graphite heating elements 6 as heat sources to heat the graphite crucible. This has the advantage of being able to design the thermal field, but generally has higher energy consumption. Most of the two types of heating furnaces 3 adopt a growth method in which a single crystal furnace only grows one single crystal at a time, which has low production efficiency.
[0035] Currently, in order to reduce costs, researchers are committed to developing equipment and processes for growing larger silicon carbide crystals. However, as the diameter of the crystal increases, the size of the crucible in which it is grown will also need to increase, and the thermal resistance to heat transfer from the outside to the inside will increase, which also leads to a decrease in the temperature of the center of the raw material, resulting in a larger lateral temperature difference in the crystal, and an increase in defects such as crystal polymorphism, basal plane dislocation, and even cracking. In order to maintain the temperature gradient, the temperature required at the edge of the crucible is getting higher and higher. Under high temperature and low pressure, the sublimation characteristics of graphite will accelerate the loss of the quality of the graphite crucible, thereby reducing the strength and service life of the graphite crucible, and the energy utilization rate will also be reduced accordingly. Therefore, from the perspective of equipment and consumables, more and more problems are encountered in increasing the size of the furnace, heater, crucible, and enhancing insulation, so the crystal size cannot be expanded indefinitely.
[0036] Therefore, a growth device for batch growing of silicon carbide single crystals is proposed, which can simultaneously grow multiple small-sized silicon carbide single crystals in a medium-frequency induction graphitization furnace, avoiding the problem of excessive longitudinal temperature gradient when growing large-sized single crystals while reducing production costs.
[0037] like Figures 1-4As shown, a growth device for growing silicon carbide single crystals in batches includes a heating furnace 3, a lifting platform 8 is provided in the heating chamber of the heating furnace 3, and a plurality of crucible assemblies 7 are evenly spaced on the lifting platform 8. The crucible assembly 7 includes a crucible body 25, which serves as a loading container for silicon carbide raw materials. A guide sleeve 24 is provided on the upper side of the crucible body 25 to evenly guide the sublimated gas-phase silicon carbide raw materials to the seed crystal 22 at the top of the crucible. A ring 23 is provided on the upper side of the guide sleeve 24 to further stabilize the position of the guide sleeve 24 and To improve the sealing performance, a crucible cover 21 is provided on the top of the crucible body 25, and a seed crystal 22 is provided on the lower side of the crucible cover 21 to ensure that the seed crystal 22 can be stably fixed in a predetermined position and allow the gaseous raw material to contact the seed crystal 22. Tantalum foil 27 is provided on the lower side of the crucible cover 21, the inner side of the crucible body 25 and the inner side of the guide sleeve 24. The tantalum foil 27 can prevent the carbon atmosphere volatilized from the graphite crucible from diffusing into the powder inside the crucible and the growing single crystal, and also avoid the Si atmosphere generated by the powder during growth from corroding the graphite crucible.
[0038] Specifically, the heating furnace 3 is a medium frequency induction heating furnace, which generates an alternating magnetic field through an induction coil. The alternating magnetic field induces eddy currents inside the workpiece, and these eddy currents generate heat, thereby heating the workpiece.
[0039] Furthermore, the crucible cover 21 is connected to the crucible body 25 via threads, so that the height between the crucible cover 21 and the crucible body 25 can be adjusted by the threads, and the flow rate of the sublimated gas discharged from the graphite crucible can be adjusted by the relative rotation of the crucible cover 21.
[0040] Specifically, the heating furnace 3 is a medium frequency induction heating furnace 3, and the crucible is a graphite crucible.
[0041] Furthermore, a temperature measuring tube 2 is provided on the top of the heating furnace 3 , and a thermometer 1 is provided inside the temperature measuring tube 2 to accurately control the temperature inside the heating furnace 3 .
[0042] The specific thermometer 1 is an infrared thermometer, which can quickly measure the temperature of the silicon carbide single crystal during its growth process in a non-contact manner, thereby avoiding the pollution and interference that may be caused by traditional contact temperature measurement methods.
[0043] Furthermore, the inner diameter of the ring 23 is adapted to the size of the seed crystal 22 , and the seed crystal 22 of a suitable size can be placed by controlling the inner diameter of the ring 23 .
[0044] Furthermore, a first step and a second step are sequentially provided on the upper part of the crucible body 25 from top to bottom, the lower side of the guide sleeve 24 is pressed on the second step, and the ring 23 is provided on the first step and the guide sleeve 24. The design of the second step is mainly to fix the position of the guide sleeve 24 to ensure that it will not be offset by the flow of airflow or raw materials during the crystal growth process, thereby affecting the growth quality of the crystal. The first step ensures that the ring 23 can be placed stably thereon.
[0045] Furthermore, the guide sleeve 24 is a conical ring 23, and the size of the lower side of the conical ring 23 is adapted to the size of the crucible body 25, and the size of the upper side of the conical ring 23 is adapted to the size of the seed crystal 22, so that the sublimated gas-phase silicon carbide raw material can be more concentratedly guided to the seed crystal 22, thereby improving the utilization rate of the raw material and the growth rate of the crystal. The adapted upper side size also helps to maintain the stability of the temperature field and airflow field around the seed crystal 22, providing favorable conditions for the uniform growth of the crystal.
[0046] Furthermore, an insulation layer 4 is provided on the inner side of the heating chamber. The main function of the insulation layer 4 is to reduce the heat loss in the heating chamber to the external environment and maintain a stable temperature environment. A cylindrical graphite heating element 6 is provided in the insulation layer 4, and the heating furnace 3 body is provided with an induction coil 5. The induction coil 5 is arranged around the peripheral wall of the graphite heating element 6. The induction current generated by the induction coil 5 causes the graphite heating element 6 to generate eddy current heating, and the graphite heating element 6 heats the graphite crucible assembly 7 inside the graphite heating element 6 by radiation.
[0047] Furthermore, the thermal insulation layer 4 is made of a material with good high-temperature stability, low thermal conductivity, and high purity, including high-purity graphite carbon felt, carbon fiber felt, etc.
[0048] Furthermore, a lifting platform 8 is provided at the bottom of the graphite heating element 6 , and the position of the graphite crucible assembly 7 in the graphite heating element 6 is controlled by the lifting platform 8 to adjust the temperature of the silicon carbide powder 26 at the bottom of the crucible assembly 7 .
[0049] Specifically, 1-8 graphite crucible assemblies 7 are arranged on the lifting platform 8, such as Figure 2 As shown, when seven graphite crucible assemblies 7 are provided, one graphite crucible assembly 7 is provided in the middle of the lifting platform 8 , six graphite crucible assemblies 7 are provided around the graphite crucible assembly 7 at the center, and the seven graphite crucible assemblies 7 are evenly spaced.
[0050] Specifically, the lifting platform 8 in the silicon carbide single crystal growth equipment primarily carries and moves the crucible assembly. The movement of the lifting platform 8 can adjust the relative position between the crucible assembly and the heating source, thereby affecting the temperature gradient and airflow distribution in the crystal growth area, thereby improving crystal quality and growth efficiency.
[0051] Physical vapor deposition method in Figures 1-4In the device, the specific steps of growing silicon carbide single crystal in a crucible are as follows: silicon carbide powder 26 is placed at the lower part of the graphite crucible body 25, which is located in the high temperature zone of the graphite heating element 6; the seed crystal 22 is placed on the lower side of the crucible cover 21, which is located in the low temperature zone of the graphite heating element 6; and the position of the graphite crucible in the graphite heating element 6 is controlled by the lifting platform 8. The distance between the silicon carbide powder 26 and the silicon carbide seed crystal 22 is 10mm-100mm, the growth temperature is 2000℃-2500℃, measured by the top infrared thermometer 1, the growth pressure is 1kPa-20kPa, and the growth atmosphere is argon.
[0052] The grown silicon carbide single crystal is shown in the following figure: Figure 5 As shown, the tantalum foil 27 is converted into tantalum carbide by in-situ reaction after the growth of silicon carbide single crystal. Figure 6 shown.
[0053] Other conditions remain unchanged, use Figure 7 When the graphite crucible assembly 7 without the tantalum foil 27 is shown, a silicon carbide single crystal ingot is grown. After the growth is completed, as shown in FIG. Figure 8 As shown, many silicon carbide polycrystals grow around the silicon carbide single crystal ingot, and many silicon carbide polycrystals also grow inside the hollow truncated cone, which reduces the utilization rate of the sublimation atmosphere of the silicon carbide powder 26.
[0054] The above are only specific embodiments of the present invention, but the scope of protection of the present invention is not limited to them. Any changes or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in this utility model should be included in the scope of protection of the present utility model. The embodiments of the present utility model and the features of the embodiments can be combined with each other unless there is a conflict. Therefore, the scope of protection of the present utility model shall be based on the scope of protection of the claims.
Claims
1. A growth device for growing silicon carbide single crystals in batches, comprising a heating furnace, a lifting platform provided in a heating chamber of the heating furnace, a plurality of crucible assemblies evenly spaced on the lifting platform, the crucible assembly comprising a crucible body, a guide sleeve provided on the upper side of the crucible body, a ring provided on the upper side of the guide sleeve, a crucible cover provided on the top of the crucible body, and a seed crystal provided on the lower side of the crucible cover, characterized in that: Tantalum foil is provided on the lower side of the crucible cover, the inner side of the crucible body and the inner side of the guide sleeve.
2. The device for growing silicon carbide single crystals in batches according to claim 1, wherein: The inner diameter of the ring is adapted to the size of the seed crystal.
3. The device for growing silicon carbide single crystals in batches according to claim 2, wherein: The upper part of the crucible body is sequentially provided with a first step and a second step from top to bottom, the lower side of the guide sleeve is pressed on the second step, and the ring is provided on the first step and the guide sleeve.
4. The device for growing silicon carbide single crystals in batches according to claim 3, wherein: The guide sleeve is a conical ring, and the size of the lower side of the conical ring is adapted to the size of the crucible body, and the size of the upper side of the conical ring is adapted to the size of the seed crystal.
5. The growth device for growing silicon carbide single crystals in batches according to claim 1, characterized in that: A heat-insulating layer is provided inside the heating chamber.
6. The growth device for growing silicon carbide single crystals in batches according to claim 5, characterized in that: A cylindrical graphite heating element is arranged in the thermal insulation layer.
7. The device for growing silicon carbide single crystals in batches according to claim 6, wherein: The heating furnace body is provided with an induction coil, and the induction coil is arranged around the peripheral wall of the graphite heating element.
8. The device for growing silicon carbide single crystals in batches according to claim 7, wherein: A lifting platform is provided at the bottom of the graphite heating element.
9. The growth device for growing silicon carbide single crystals in batches according to claim 1, characterized in that: The top of the heating furnace is provided with a temperature measuring tube, and a thermometer is provided in the temperature measuring tube.
10. The growth device for growing silicon carbide single crystals in batches according to claim 1, characterized in that: The crucible cover is connected to the crucible body through threads, so that the height between the crucible cover and the crucible body can be adjusted through the threads.