Thermal field device for growing crystal and control method

Abstract

The invention discloses a thermal field device for growing crystals and a control method. The thermal field device for growing crystals comprises a furnace body; the accommodating device is arranged in the furnace body and comprises a shell and a bracket, a first accommodating cavity and a second accommodating cavity are defined in the shell, the bracket is arranged in the shell and is used for placing a seed crystal, the seed crystal is suitable for dividing the second accommodating cavity into a first part and a second part, the first accommodating cavity is used for accommodating a crystal raw material and is communicated with the first part, and the second accommodating cavity is communicated with the second part; a coating raw material is arranged in the second part; the first heating piece is arranged in the furnace body and is used for heating a crystal raw material, so that a crystal grows on one side of the seed crystal; and the second heating piece is arranged in the furnace body, and the second heating piece is used for heating the coating raw material, so that the other side of the seed crystal is coated. According to the thermal field device provided by the embodiment of the invention, the seed crystal can be subjected to crystal growth operation and film coating operation at the same time, and the quality of the grown crystal can be improved.

Description

Technical Field

[0001] The present invention relates to the technical field of crystal growth, and more specifically, to a thermal field device and a control method for growing crystals. Background Art

[0002] Silicon carbide (SiC) crystals have been widely studied and applied because of their excellent physical, chemical, and electrical properties, which can meet the stringent requirements of modern high-tech fields for materials. Currently, the main methods for growing SiC crystals include physical vapor transport method (PVT method), chemical vapor deposition method (CVD method), high-temperature chemical vapor deposition method (HTCVD method), etc. Among them, the SiC crystal growth system realized by the PVT method can control the thermal field structure, monitored temperature, pressure range, etc. within a suitable range by adjusting the thermal field structure, monitoring the temperature, pressure range, etc., so as to obtain high-quality SiC crystals.

[0003] The controllable variables in the PVT method for producing SiC crystal growth systems usually include: graphite material, thermal field temperature, thermal field pressure, felt material and size, relative position of the thermal field and the coil, purity and flow rate of the doping gas, fixing method of the seed crystal, back treatment of the seed crystal, etc. The necessary conditions for producing high-crystallinity SiC crystals by the PVT method are: high-quality seed crystals with low defect density, appropriate growth temperature and growth pressure, appropriate axial and radial temperature gradients, and continuous supply of gaseous materials.

[0004] In the related art, during the process of growing SiC crystals, defects such as corrosion are likely to occur on the back surface of the seed crystal, which affects the SiC crystals grown on the front surface of the seed crystal, resulting in damage to the quality of the obtained SiC crystals. Summary of the Invention

[0005] The present invention aims to at least solve one of the technical problems existing in the prior art. For this reason, an object of the present invention is to provide a thermal field device for growing crystals, which can prevent defects such as corrosion from easily occurring on the back surface of the seed crystal during the process of growing SiC crystals, and is not likely to affect the SiC crystals grown on the front surface of the seed crystal, and the quality of the obtained SiC crystals is good.

[0006] Another object of the present invention is to provide a control method for the thermal field device for growing crystals.

[0007] A thermal field device according to an embodiment of the present invention includes: a furnace body; a containing device, the containing device is arranged inside the furnace body and includes a housing and a bracket, the housing defines a first containing cavity and a second containing cavity, the bracket is arranged inside the housing for placing a seed crystal, the seed crystal is adapted to divide the second containing cavity into a first part and a second part, the first containing cavity is used for containing crystal raw materials and is communicated with the first part, and a coating raw material is arranged in the second part; a first heating element, the first heating element is arranged inside the furnace body, and the first heating element is used for heating the crystal raw materials to grow a crystal on one side of the seed crystal; a second heating element, the second heating element is arranged inside the furnace body, and the second heating element is used for heating the coating raw material to coat the other side of the seed crystal.

[0008] The thermal field device according to an embodiment of the present invention can simultaneously perform crystal growth operation and coating operation on the seed crystal, making the protective film not easily fall off from the seed crystal, having a good protective effect on crystal growth, resulting in high-quality crystals grown, with fewer process steps and good process coherence, which is beneficial to improving the efficiency of crystal growth.

[0009] In addition, the thermal field device according to the above embodiment of the present invention may further have the following additional technical features:

[0010] According to some embodiments of the present invention, the first containing cavity, the first part of the second containing cavity, and the second part of the second containing cavity are arranged in sequence from top to bottom. The upper surface of the seed crystal is used for crystal growth, the lower surface of the seed crystal is coated, and the bracket contacts the edge of the seed crystal.

[0011] According to some embodiments of the present invention, a porous plate is arranged inside the housing. The porous plate divides the inside of the housing into the first containing cavity and the second containing cavity. The porous plate is provided with a plurality of first communication holes communicating the first containing cavity and the second containing cavity. A part of the porous plate is recessed to form a containing groove communicating with the first communication holes, and the containing groove is used for containing a filtering member.

[0012] According to some embodiments of the present invention, an installation component is arranged in the second part, the coating raw material is arranged on the installation component, the second heating element is arranged in the second part and is adjacent to the installation component, and the second heating element is a resistance heating element.

[0013] According to some embodiments of the present invention, the second part of the second containing cavity includes a communicating coating cavity and a bearing cavity. The bearing cavity is located on the side of the coating cavity away from the first containing cavity. The coating raw material is arranged in the bearing cavity, the second heating element is located outside the containing device, and the second heating element is used for heating the wall of the bearing cavity to heat the coating raw material inside the bearing cavity.

[0014] According to some embodiments of the present invention, a cooling flow channel is defined within the furnace wall of the furnace body for circulating a cooling fluid, and the wall portion of the carrying cavity abuts and cooperates with the furnace wall of the furnace body.

[0015] According to some embodiments of the present invention, the second part of the second accommodating cavity includes a coating cavity and a carrying cavity that are communicated. The carrying cavity is located on a side of the coating cavity away from the first accommodating cavity. The coating raw material is disposed in the carrying cavity. A second communication hole is provided in the wall portion of the carrying cavity. The second heating member is located outside the accommodating device, and the second heating member is adapted to heat the coating raw material through the second communication hole.

[0016] According to some embodiments of the present invention, the second heating member includes an electron gun and a deflection electric field generator.

[0017] A control method for a thermal field device for growing crystals according to an embodiment of the present invention includes: controlling a first heating member to heat a crystal raw material and controlling a second heating member to heat a coating raw material.

[0018] According to some embodiments of the present invention, the control method further includes: when a preset time is reached, controlling the second heating member to stop heating and controlling the first heating member to continuously heat the crystal raw material.

[0019] Additional aspects and advantages of the present invention will be given in part in the following description, become apparent in part from the following description, or be learned through the practice of the present invention. Description of the Drawings

[0020] The above and / or additional aspects and advantages of the present invention will become apparent and be readily understood from the description of the embodiments in conjunction with the following drawings, in which:

[0021] Figure 1 is a cross-sectional view of a thermal field device according to a first embodiment of the present invention;

[0022] Figure 2 is a cross-sectional view of a thermal field device according to a second embodiment of the present invention;

[0023] Figure 3 is a cross-sectional view of a thermal field device according to a third embodiment of the present invention;

[0024] Figure 4 is Figure 3 a partial enlarged view of the circled area A in ;

[0025] Figure 5 is a schematic diagram of a control method according to an embodiment of the present invention;

[0026] Figure 6Schematic diagram of a control method according to a specific embodiment of the present invention.

[0027] Reference numerals:

[0028] Thermal field device 100; seed crystal 200; crystal raw material 300; coating raw material 400; filter element 500;

[0029] Furnace body 10; furnace wall 11; cooling channel 111;

[0030] Containing device 20; housing 21; first containing cavity 211; second containing cavity 212; first part 2121; second part 2122; coating cavity 2123; bearing cavity 2124; second communication hole 2125; bracket 22;

[0031] First heating element 30; first resistance heating element 311; first electrode 312;

[0032] Second heating element 40; second resistance heating element 411; second electrode 412; electron gun 421; deflection electric field generator 422;

[0033] Perforated plate 50; containing groove 52;

[0034] Mounting component 60; isolation component 70; support column 80; heat insulation component 90. Detailed description of specific embodiments

[0035] The embodiments of the present invention will be described in detail below. Examples of the embodiments are shown in the drawings, where the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the drawings are exemplary only for explaining the present invention and should not be construed as limiting the present invention.

[0036] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc. indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are 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, and thus should not be construed as limiting the present invention.

[0037] In the description of the present invention, the "first feature" and the "second feature" may include one or more of such features. The meaning of "a plurality" is two or more. The first feature being "above" or "below" the second feature may include the first and second features being in direct contact, or may include the first and second features not being in direct contact but being in contact through additional features therebetween. The first feature being "above", "over" and "on" the second feature includes the first feature being directly above and obliquely above the second feature, or merely indicating that the first feature has a higher horizontal height than the second feature.

[0038] The thermal field device 100 for growing crystals according to an embodiment of the present invention will be described below with reference to the accompanying drawings. Here, the crystal may be a silicon carbide crystal. For ease of understanding, the crystal grown by the thermal field device 100 is taken as a silicon carbide crystal as an example for explanation below. Embodiments in which the crystal grown by the thermal field device 100 is other crystals can also be obtained.

[0039] Refer to Figures 1-4 As shown, the thermal field device 100 according to an embodiment of the present invention may include: a furnace body 10, a receiving device 20, a first heating element 30, and a second heating element 40.

[0040] Specifically, the receiving device 20 is provided inside the furnace body 10. For example, the furnace body 10 may define a sealed cavity, and the receiving device 20 can be arranged in the sealed cavity, facilitating evacuation of the sealed cavity to provide a vacuum environment for the receiving device 20.

[0041] The receiving device 20 includes a housing 21 and a bracket 22. The housing 21 may define another sealed cavity, and the sealed cavity includes a first receiving cavity 211 and a second receiving cavity 212. The bracket 22 is arranged inside the housing 21 for placing a seed crystal 200. The seed crystal 200 can divide the second receiving cavity 212 into a first part 2121 and a second part 2122. The seed crystal 200 may be a silicon carbide plate about 5 mm. The first receiving cavity 211 is used for receiving crystal raw materials 300 and is in communication with the first part 2121. The crystal raw materials 300 may be silicon carbide powder. The second part 2122 is provided with coating raw materials 400, and the coating raw materials 400 may be silicon carbide powder.

[0042] The first heating element 30 is provided inside the furnace body 10. The first heating element 30 is used for heating the crystal raw materials 300 so that a crystal (4H-SiC single crystal, 4H is a crystal form) grows on one side (i.e., the carbon surface, such as Figures 1-3 the upper surface of the seed crystal 200 in the figure) of the seed crystal 200. The first receiving cavity 211 and the first part 2121 are the crystal growth thermal fields. The first heating element 30 may be one or more. The first heating element 30 may be arranged close to the crystal growth thermal field to heat the crystal growth thermal field to generate a high-temperature environment and construct the temperature required for sublimation of the crystal raw materials 300 and the temperature gradient for crystal growth.

[0043] The first heating element 30 may include a first electrode 312 and a first resistive heating element 311 made of graphite. The first electrode 312 is used to connect to the power supply system outside the thermal field device 100. For example, by connecting the power supply system through the first electrode 312, the power of the first resistive heating element 311 is controlled to be 25 kw. In the axial direction (i.e., Figures 1-3 the up and down direction in the figure), in the distribution from the crystal raw material 300 to the seed crystal 200, the temperature gradually decreases, forming a temperature difference of 120°C - 150°C. For example, the temperature inside the crystal raw material 300 is 2250°C, and the temperature of the carbon surface of the seed crystal 200 is 2100°C - 2130°C.

[0044] The crystal raw material 300 can be silicon carbide powder. The silicon carbide powder sublimes in a high-temperature environment to produce gaseous substances. The gaseous substances are transported from the high-temperature region to the low-temperature region under the action of the temperature gradient in the crystal growth thermal field, so as to be transported from the first accommodation cavity 211 to the first part 2121, and the gaseous substances are deposited and crystallized on the carbon surface of the seed crystal 200 to generate the required silicon carbide crystal.

[0045] The second heating element 40 is arranged in the furnace body 10. The second heating element 40 is used to heat the coating raw material 400 so that the other side of the seed crystal 200 (i.e., the silicon surface, such as Figures 1-3 the lower surface of the seed crystal 200 in the figure) is coated. The second part 2122 is the coating thermal field. The second heating element 40 can be one or more. The second heating element 40 can be arranged in the coating thermal field to heat the coating thermal field to generate a high-temperature environment.

[0046] The second heating element 40 can be a resistive heating element or other forms of heating elements. For example, the second heating element 40 includes a second electrode 412 and a second resistive heating element 411 made of graphite. The second electrode 412 is used to connect to the power supply system outside the thermal field device 100. For example, by connecting the power supply system through the second electrode 412, the power of the second resistive heating element 411 is controlled to be 15 kw, so that the second heating element 40 generates a temperature such as 2250°C that can decompose and sublime the coating raw material 400. At this time, the heating temperature of the second heating element 40 can be controlled by adjusting the power of the second resistive heating element 411 to control the decomposition efficiency of the coating raw material 400.

[0047] The coating raw material 400 can be silicon carbide, Ta (tantalum), Zr (zirconium), TiN (titanium nitride), ZrO (zirconium oxide), TaC (tantalum carbide), etc. For example, when the coating raw material 400 is silicon carbide powder, the silicon carbide powder will decompose in a high-temperature environment. The decomposed silicon carbide powder converges towards the back surface of the seed crystal 200, i.e., the silicon surface. Eventually, a protective film is formed by coating on the silicon surface of the seed crystal 200, which is beneficial to maintaining the carbon-silicon balance of the seed crystal 200, inhibiting the evaporation of the back surface of the seed crystal 200, reducing the possibility of backside corrosion of the seed crystal 200, improving the back surface quality of the seed crystal 200, and further protecting the crystal grown on the carbon surface of the seed crystal 200.

[0048] Different from the crystal growth on the carbon surface of the seed crystal 200, the coating deposition thickness on the silicon surface of the seed crystal 200 needs to be controlled to achieve the technical effect of forming a protective film. For example, the film thickness of the protective film on the silicon surface of the seed crystal 200 is controlled to be 1 mm - 3 mm. If the protective film is too thin, the protection effect on the crystal grown on the carbon surface of the seed crystal 200 is poor; if the protective film is too thick, it will affect the film formation uniformity, adhesion, and stable protection effect, and the protection effect on the crystal grown on the carbon surface of the seed crystal 200 is poor. Therefore, making the thickness of the protective film 1 mm - 3 mm is beneficial to taking into account both the material cost and the protection effect on the crystal grown on the carbon surface of the seed crystal 200.

[0049] The coating raw material 400 is preferably the same material as the seed crystal 200 and the crystal grown on the carbon surface of the seed crystal 200. For example, if the seed crystal 200 is silicon carbide and the crystal grown on the carbon surface of the seed crystal 200 is silicon carbide, then the coating raw material 400 is preferably silicon carbide. Of course, the coating raw material 400 can also be selected as high-melting-point materials such as Ta, Zr, TiN, ZrO, or TaC, or their mixtures. However, as the melting point of the coating raw material 400 increases, the temperature of the coating thermal field must be increased, which easily interferes with the temperature distribution and gradient of the crystal growth thermal field. And the thermal expansion coefficients of the same material are the same, making the protective film formed by coating not easy to detach. Therefore, the coating raw material 400 is preferably silicon carbide with a relatively low melting point, which can not only have a certain protection effect on the growing crystal but also is not easy to generate a high temperature near the crystal growth thermal field to damage the thermal field.

[0050] For easy understanding, the following takes the crystal raw material 300 as silicon carbide powder and the coating raw material 400 as silicon carbide powder as an example for explanation. Embodiments where the coating raw material 400 is other substances can also be obtained.

[0051] The fixation of the seed crystal 200 is crucial for crystal growth. In some related technologies, the back surface of the seed crystal is usually bonded to the graphite cover in the thermal field device using carbon-like glue. During the crystal growth process, in the heating-up and constant-temperature stages, due to the different thermal expansion coefficients of the seed crystal and graphite itself, it is easily affected by mechanical stress, resulting in crack formation or even separation, which may cause dislocations and macroscopic defects. In addition, regarding the bonding firmness between the seed crystal and the graphite cover, pores or gaps will cause evaporation on the back surface of the seed crystal, resulting in serious through defects, such as TSD (screw dislocation), microtube defects, etc. For another example, more serious back corrosion will lead to serious problems such as hexagonal cavities, polycrystalline penetration, ablation, etc. Therefore, the bonding of the seed crystal can be said to be the most crucial first step in crystal growth by the PVT method. Currently, it is very difficult to standardize and unify the control standards or operation methods for seed crystal bonding before crystal growth.

[0052] In the present application, the coating raw material 400 is heated by the second heating element 40 to form a protective film on the back surface of the seed crystal 200, so as to replace the seed crystal 200 bonding process, which is beneficial to solving the serious through-type defects caused by the bonding of the seed crystal 200 and solving the back corrosion situation during the crystal growth process.

[0053] In some related technologies, the seed crystal with a coated back surface is placed in the thermal field device for crystal growth operation. Although a protective film can be formed on the back surface of the seed crystal, it is necessary to first perform a coating operation on the seed crystal and then perform a crystal growth operation on the coated seed crystal, which is equivalent to separating the coating process from the crystal growth process, resulting in discontinuous processes, high process complexity, and wasting a lot of time and financial resources. Moreover, during the multiple heating-up and cooling-down processes in the crystal growth process, the protective film formed by the pre-coating is likely to fall off, peel off, and become ineffective.

[0054] In the present application, the thermal field device 100 is provided with a first accommodation cavity 211 for placing the crystal raw material 300, a first heating element 30 for heating the crystal raw material 300, a second part 2122 for placing the coating raw material 400, and a second heating element 40 for heating the coating raw material 400. It can perform crystal growth operation and coating operation simultaneously after placing the seed crystal 200 in the thermal field device 100, combining the coating process and the crystal growth process into one, reducing the process steps, having good process continuity, low process complexity, reducing the waste of time and financial resources, and having higher crystal growth efficiency.

[0055] And during the crystal growth process, a coating operation is carried out for a period of time simultaneously, which can play a protective role in the growing crystal during the crystal growth process, such as in the initial stage of crystal growth, reducing the heating and cooling processes experienced by the protective film, and facilitating the reduction of the risks of the protective film falling off, peeling off, and failing. In particular, in the initial stage of crystal growth, by continuously carrying out the coating operation to continuously protect the growing crystal, the quality of the crystal grown in the initial stage is good, and thus the crystal grown in the later stage has a good foundation, and the grown crystal is less likely to have defects.

[0056] According to the thermal field device 100 of the embodiment of the present invention, the operations of growing crystals and coating can be carried out on the seed crystal 200 simultaneously, so that the protective film is not easily peeled off from the seed crystal 200, the protective effect on the growing crystal is good, the quality of the grown crystal is high, and the process steps are few, the process coherence is good, which is conducive to improving the efficiency of growing crystals.

[0057] In some embodiments, as Figures 1-3 shown, the housing 21 of the accommodating device 20 includes a split bottom plate, a housing body, and a cover plate, and the housing body may also include a plurality of split components. This makes the accommodating device 20 easy to disassemble and assemble, facilitating the placement of the coating raw material 400, the crystal raw material 300, the bracket 22, etc. into or out of the housing 21, and the operation is convenient. The materials of the housing 21 and the bracket 22 may be graphite, and the graphite material has a good heat insulation effect, which is conducive to maintaining the stability of the temperature gradient of the thermal field (such as the crystal growth thermal field and the coating thermal field) inside the housing 21.

[0058] In some embodiments, as Figures 1-3 shown, the furnace body 10 is provided with a water cooling system. Specifically, the furnace wall 11 of the furnace body 10 is a hollow structure, so that a cooling flow channel 111 is defined inside the furnace wall 11, and the cooling flow channel 111 is used for circulating cooling water. The heat conducted outward from the inside of the furnace body 10 is taken away through the circulation of the water cooling system, enabling the thermal field device 100 to work continuously and stably, reducing the temperature of the furnace body 10, and reducing the possibility of damage to the furnace body 10 due to excessive temperature.

[0059] In some embodiments, as Figures 1-3 shown, an isolation component 70 is further provided inside the furnace body 10. The isolation component 70 defines another sealed cavity, the accommodating device 20 is arranged inside the isolation component 70, and the first heating element 30 is arranged outside the isolation component 70, making the sealing of the internal thermal field of the accommodating device 20 better. The isolation component 70 may be a cylinder made of graphite to achieve the isolation between the internal thermal field of the accommodating device 20 and the first heating element 30, and reduce the corrosion of the first heating element 30 by the components escaping from the internal thermal field of the accommodating device 20.

[0060] In some embodiments, as Figures 1-3As shown, a heat-insulating component 90 is further provided inside the furnace body 10, and the heat-insulating component 90 is arranged outside the isolating component 70. The heat-insulating component 90 is used to make the temperature of the internal thermal field of the accommodating device 20 more stable and reduce the possibility of the temperature of the internal thermal field of the accommodating device 20 being transmitted outward. The heat-insulating component 90 can be a hard felt made of graphite material.

[0061] In some embodiments, as Figures 1-3 shown, support columns 80 are further provided inside the furnace body 10. The support columns 80 connect the isolating component 70 and the furnace body 10, and connect the heat-insulating component 90 and the furnace body 10 to support the isolating component 70 and the heat-insulating component 90, reduce the contact area between the isolating component 70 and the furnace body 10, and reduce the contact area between the heat-insulating component 90 and the furnace body 10, so as to reduce the possibility of the temperature of the internal thermal field of the accommodating device 20 being transmitted outward, which is beneficial to maintaining the stability of the internal thermal field temperature of the accommodating device 20, and is also beneficial to reducing the temperature transmitted to the furnace body 10 to reduce the possibility of the furnace body 10 being damaged due to excessive temperature.

[0062] In some embodiments of the present invention, as Figures 1-3 shown, the first accommodating cavity 211, the first part 2121 of the second accommodating cavity 212, and the second part 2122 of the second accommodating cavity 212 are arranged in sequence from top to bottom, so that the upper surface of the seed crystal 200 faces the first accommodating cavity 211 and the first part 2121, and the upper surface of the seed crystal 200 is used for crystal growth. The lower surface of the seed crystal 200 faces the second part 2122, and the lower surface of the seed crystal 200 is coated. The bracket 22 contacts the edge of the seed crystal 200. As Figures 1-3 shown, the bracket 22 can overlap with a part of the lower surface of the seed crystal 200 to support the seed crystal 200 on the bracket 22, realizing the loading and fixing of the seed crystal 200, and the installation of the seed crystal 200 is more stable. The seed crystal 200 can also be clamped with the bracket 22 to be installed on the bracket 22, and the installation method of the seed crystal 200 is not limited.

[0063] By arranging the first accommodating cavity 211, the first part 2121, and the second part 2122 in sequence from top to bottom, the upper surface of the seed crystal 200 does not need to contact other components such as the bracket 22, which can ensure that the entire upper surface of the seed crystal 200 is used for crystal growth, increase the crystal growth range, and is not easy to affect the crystal growth at the carbon surface edge of the seed crystal 200, so that the quality of the crystal grown on the upper surface of the seed crystal 200 is better.

[0064] In some embodiments, as Figures 1-3 shown, a part of the lower surface of the seed crystal 200 overlaps with the bracket 22, and the part of the bracket 22 extending into the housing 21 to support the lower surface of the seed crystal 200 has a dimension of 1 mm - 1.5 mm extending into the interior of the housing 21. For example Figures 1-3As shown, the housing 21 and the bracket 22 are cylindrical. In the radial direction of the housing 21, the size of the bracket 22 extending into the interior of the housing 21 is 1 mm - 1.5 mm.

[0065] If the above size is too large, the portion of the lower surface of the seed crystal 200 for coating will be too small, affecting the protective effect of the protective film on the crystal grown on the upper surface of the seed crystal 200; if the above size is too small, the seed crystal 200 will be unstable during installation, easily causing the seed crystal 200 to shake or even fall off the bracket 22. Therefore, making the size of the portion of the bracket 22 extending into the interior of the housing 21 be 1 mm - 1.5 mm can balance the protective effect on the crystal grown on the upper surface of the seed crystal 200 and the installation firmness of the seed crystal 200. For example, the size of the portion of the bracket 22 extending into the interior of the housing 21 is 1 mm, 1.2 mm, 1.5 mm.

[0066] In some embodiments of the present invention, as Figures 1-3 shown, a porous plate 50 is provided in the housing 21. The porous plate 50 divides the interior of the housing 21 into a first accommodation cavity 211 and a second accommodation cavity 212. The porous plate 50 is provided with a plurality of first communication holes communicating the first accommodation cavity 211 and the second accommodation cavity 212, so that the gaseous substance sublimated in the first accommodation cavity 211 can enter the second accommodation cavity 212 through the first communication holes. The porous plate 50 can be partially provided with the first communication holes or integrally provided with the first communication holes.

[0067] A part of the porous plate 50 is recessed to form an accommodation groove 52 communicating with the first communication holes. The accommodation groove 52 is used to accommodate the filter element 500. The part of the porous plate 50 opposite to the accommodation groove 52 can be provided with a plurality of first communication holes, and the part of the porous plate 50 not opposite to the accommodation groove 52 is not provided with the first communication holes, so that the gaseous substance in the first accommodation cavity 211 can enter the second accommodation cavity 212 only after being filtered by the filter element 500.

[0068] The filter element 500 is used to block impurities (such as metal particles, oxides, etc.) in the crystal raw material 300 from being transmitted to the first part 2121, reduce the impurity content in the grown crystal, and improve the crystal purity. And the filter element 500 can make the gaseous substance more evenly distributed, promote the uniform precipitation of the gaseous substance on the front surface (i.e., the carbon surface) of the seed crystal 200, and reduce the defects in crystal growth. The filter element 500 can be high-purity graphite or porous ceramics, etc.

[0069] In some embodiments, as Figures 1-3As shown, the diameter of the first communication hole is 0.5 mm - 1 mm. If the diameter of the first communication hole is too small, it is prone to blockage. If the diameter of the first communication hole is too large, impurities in the crystal raw material 300 will be transmitted to the first part 2121, affecting the purity of the grown crystal. Therefore, making the diameter of the first communication hole 0.5 mm - 1 mm is beneficial to ensuring the communication effect of the first communication hole and improving the purity of the grown crystal. For example, the diameter of the first communication hole is 0.5 mm, 0.8 mm, 1 mm, etc.

[0070] In some embodiments, as Figures 1-3 shown, the shell body of the housing 21 includes a plurality of separate components. For example, the shell body includes a first wall portion located on the upper side and a second wall portion located on the lower side. The first wall portion and the second wall portion are snap-connected, and the porous plate 50 can be fixed between the first wall portion and the second wall portion, making the installation of the porous plate 50 more firm and the sealing performance inside the accommodating device 20 better.

[0071] In the first embodiment of the present invention, as Figure 1 shown, an installation component 60 is provided in the second part 2122. The coating raw material 400 is provided on the installation component 60. The second heating element 40 is provided in the second part 2122 and is adjacent to the installation component 60. For example, the installation component 60 is an installation rack. The installation rack is provided with a groove for accommodating the coating raw material 400. The second heating element 40 is provided in the installation rack and is located below the groove to heat the coating raw material 400 in the groove. The installation component 60 can be a crucible made of graphite, which has good heat preservation and heat insulation effects.

[0072] Providing the installation component 60 and the second heating element 40 in the second part 2122 does not require major changes to the accommodating device 20 to install the second heating element 40 and the installation component 60, which is convenient for installation.

[0073] As Figure 1 shown, the second heating element 40 is a resistance heating element. For example, the second heating element 40 includes a second electrode 412 and a second resistive heating body 411 made of graphite. The second electrode 412 is used to connect to the power supply system outside the thermal field device 100. Heating the coating raw material 400 through the resistance heating element is essentially through heat conduction, making the resistance heating element generate heat and heating the area carrying the coating raw material 400 to reach the temperature point at which the coating raw material 400 begins to decompose and sublimate.

[0074] The resistance heating element has a simple structure, is easy to install, and has a low cost. Therefore, heating the coating raw material 400 through the resistance heating element can simplify the structure of the thermal field device 100, reduce the manufacturing cost of the thermal field device 100, and is beneficial to popularization and use.

[0075] In the second embodiment of the present invention, as Figure 2As shown, the second part 2122 of the second accommodation chamber 212 includes a connected coating chamber 2123 and a carrying chamber 2124. The carrying chamber 2124 is located on the side of the coating chamber 2123 away from the first accommodation chamber 211. The coating raw material 400 is provided in the carrying chamber 2124. The second heating element 40 is located outside the accommodation device 20. The second heating element 40 is used to heat the wall of the carrying chamber 2124 to heat the coating raw material 400 inside the carrying chamber 2124. The coating chamber 2123 and the carrying chamber 2124 are connected, so that the gaseous substance generated after the coating raw material 400 in the carrying chamber 2124 is heated can be transmitted to the coating chamber 2123, and then transmitted to the back of the seed crystal 200 for coating.

[0076] The high-temperature environment of the thermal field for crystal growth on the front of the seed crystal 200 is generated by the first heating element 30, and the high-temperature environment of the thermal field for coating on the back of the seed crystal 200 is generated by the second heating element 40. If the high-temperature environment on the back of the seed crystal 200 is too high, it is likely to affect the temperature gradient of the high-temperature environment on the front of the seed crystal 200, resulting in the quality of the crystal grown on the front of the seed crystal 200. In this application, the second part 2122 is divided into a connected coating chamber 2123 and a carrying chamber 2124, which can increase the distance between the coating raw material 400 and the seed crystal 200 within a suitable range, so as to concentrate the energy generated by the second heating element 40 in a small area far from the crystal growth thermal field, that is, concentrated in the carrying chamber 2124 far from the seed crystal 200, which can reduce the influence of the high-temperature environment on the back of the seed crystal 200 on the crystal grown on the front of the seed crystal 200, and is conducive to improving the quality of the crystal grown on the front of the seed crystal 200.

[0077] Since the second heating element 40 indirectly heats the coating raw material 400 inside the carrying chamber 2124 by heating the wall of the carrying chamber 2124, and it is necessary to make the coating raw material 400 sublimate, the heating energy generated by the second heating element 40 on the wall of the carrying chamber 2124 needs to be higher than the energy required for the sublimation of the coating raw material 400, so that the wall temperature of the carrying chamber 2124 is higher than the temperature required for the sublimation of the coating raw material 400. If the wall temperature of the carrying chamber 2124 is too high, it is easy to perforate or even melt.

[0078] In some embodiments of this application, such as Figure 2As shown, a cooling channel 111 is defined within the furnace wall 11 of the furnace body 10 for circulating a cooling fluid. The wall of the bearing cavity 2124 abuts and mates with the furnace wall 11 of the furnace body 10, and can cool the wall of the bearing cavity 2124 through the cooling fluid, reducing the temperature of the wall of the bearing cavity 2124, so that the temperature of the wall of the bearing cavity 2124 will not be too high to cause damage such as perforation and melting of itself, which is beneficial to protecting the bearing cavity 2124. It is not necessary for the whole wall of the bearing cavity 2124 to abut and mate with the furnace wall 11. Only a part of the wall of the bearing cavity 2124 needs to abut and mate with the furnace wall 11 to control the overall temperature of the wall of the bearing cavity 2124, so that the internal coating raw material 400 can sublimate and the wall itself will not be damaged due to excessive temperature, such as perforation, improving the working reliability of the thermal field device 100.

[0079] In some embodiments, as Figures 2-4 shown, an opening is made at the bottom of the isolation component 70 to define a bearing cavity 2124 by sinking a part of the bottom plate of the accommodating device 20. The bottom plate is made of graphite, and has a good heat preservation and heat insulation effect.

[0080] In some embodiments, as Figures 2-4 shown, the second heating element 40 includes an electron gun 421 and a deflection electric field generator 422, so that the high-energy electron beam emitted by the electron gun 421 forms a heating source with high energy after passing through the deflection electric field generator 422. The high-energy beam changes its direction after passing through the deflection electric field, such as rotating by 90° along a path, so as to heat the wall of the bearing cavity 2124 and concentrate the energy on a local area. This heating source directly heats the surface of the wall of the bearing cavity 2124. The electron gun 421 can be composed of a tungsten filament, a hot cathode and an anode for accelerating electrons. After the tungsten filament is heated by current, the cathode electrons have enough energy to heat the coating raw material 400 in the bearing cavity 2124 after being accelerated and focused, so that the coating raw material 400 is decomposed by heat.

[0081] The electron gun 421 can directly heat the wall of the bearing cavity 2124 to achieve local heating, and will not directly heat the inside of the second accommodating cavity 212. The heat radiation range is smaller, the affected area of the heating range is smaller, the influence on the thermal field of crystal growth is smaller, and it is not easy to destroy the temperature gradient of the crystal growth thermal field, which is beneficial to improving the quality of the grown crystal. By using the electron gun 421 to heat the coating raw material 400, local heating can be realized to reduce the influence on the thermal field of crystal growth, and there is no need to overly lengthen the distance between the wall of the bearing cavity 2124 and the seed crystal 200 to reduce the influence of the heating area of the electron gun 421 on the thermal field of crystal growth, making the distance between the wall of the bearing cavity 2124 and the seed crystal 200 appropriate, and the effect of the coating raw material 400 deposited on the silicon surface of the seed crystal 200 after decomposition is better.

[0082] It is particularly important to maintain the temperature stability of the crystal growth thermal field. Crystal growth requires an axial temperature gradient. Usually, the temperature at the seed crystal 200 is relatively low, and the temperature at the crystal raw material 300 is relatively high, with a difference of about 80 - 120 °C. During the crystal growth process, it is very necessary to maintain the temperature and its stability. If the temperature or gradient changes drastically, it will cause defects such as phase transformation, microtubes, and polycrystals in the crystal.

[0083] In some embodiments, the material of the wall of the carrier cavity 2124 is graphite. The graphite surface accumulates the high energy generated by the electron gun 421, which can achieve local rapid heating to heat the coating raw material 400 inside. The wall of the carrier cavity 2124 made of graphite abuts and cooperates with the furnace wall 11, and can cool the wall of the carrier cavity 2124 through the cooling fluid in the furnace wall 11, reducing the temperature of the wall of the carrier cavity 2124, so that the temperature of the wall of the carrier cavity 2124 will not be too high to cause damage such as perforation and melting to itself, playing a certain protective role for the wall of the carrier cavity 2124.

[0084] The energy beam generated by the electron gun 421 is directly converged on the surface of the wall of the carrier cavity 2124, and then transferred to the coating raw material 400 through the heat conduction of the wall of the carrier cavity 2124. Therefore, the energy transfer efficiency is reduced. Although it is possible to achieve sublimation with a small temperature change of the coating raw material 400, for high-melting-point coating raw materials 400, such as high-melting-point materials or their mixtures such as Ta, Zr, TiN, ZrO, or TaC, the heating efficiency will be impaired, and it is necessary to increase the voltage and current of the electron gun 421. Therefore, the coating raw material 400 is preferably silicon carbide. The melting point of silicon carbide is lower than that of high-melting-point materials or their mixtures such as Ta, Zr, TiN, ZrO, or TaC. There is no need to increase the voltage and current of the electron gun 421 too much, reducing the degree of heating efficiency impairment and being easy to implement.

[0085] In the third embodiment of the present invention, as Figures 3-4 shown, the second part 2122 of the second accommodation cavity 212 includes a communicating coating cavity 2123 and a carrier cavity 2124. The carrier cavity 2124 is located on the side of the coating cavity 2123 away from the first accommodation cavity 211. The coating raw material 400 is provided in the carrier cavity 2124. The wall of the carrier cavity 2124 is provided with a second communication hole 2125. The second heating element 40 is located outside the accommodation device 20, and the second heating element 40 can heat the coating raw material 400 through the second communication hole 2125. The coating cavity 2123 and the carrier cavity 2124 are communicated, so that the gaseous substances generated after the coating raw material 400 in the carrier cavity 2124 is heated can be transmitted to the coating cavity 2123, and then transmitted to the back of the seed crystal 200 for coating.

[0086] By dividing the second part 2122 into a connected coating cavity 2123 and a supporting cavity 2124, the distance between the coating raw material 400 and the seed crystal 200 can be increased within an appropriate range, thereby reducing the impact of the high temperature environment on the back of the seed crystal 200 on the crystal growing on the front of the seed crystal 200, thereby improving the quality of the crystal growing on the front of the seed crystal 200.

[0087] The second heating element 40 can directly heat the coating raw material 400 in the carrying cavity 2124 through the second connecting hole 2125 instead of indirectly heating it. Therefore, the heating efficiency of the coating raw material 400 can be improved, and the temperature of the wall of the carrying cavity 2124 will not be too high to affect the thermal field of crystal growth, thereby reducing the impact on the thermal field of crystal growth.

[0088] In some embodiments, at least part of the wall of the bearing cavity 2124 is a hollow structure for circulating cooling fluid, so that the temperature of the wall is not too high and melted. For example, the wall can be a hollow structure made of copper, which has good heat transfer performance and fast cooling speed, so that the temperature of the cooling fluid inside the wall of the bearing cavity 2124 can be kept at a low temperature to continuously cool the wall, so that the wall is not easily melted due to excessive temperature, thereby improving the protection effect of the wall.

[0089] In some embodiments, Figures 2-4 As shown, the second heating element 40 includes an electron gun 421 and a deflection electric field generator 422. The electron gun 421 can concentrate energy in a small range to achieve precise heating, and the deflection electric field generator 422 can change the heating direction of the electron gun 421, for example. Figure 2 and Figure 4 FIG. 4 shows that the emission direction of the accelerated electrons in the electron gun 421 is changed by the deflection electric field generator 422 .

[0090] Therefore, through the electron gun 421 and the deflection electric field generator 422, the energy emitted by the electron gun 421 can be accurately transmitted through the second connecting hole 2125 to directly heat the coating raw material 400 in the bearing cavity 2124, the heating direction is controllable, and the energy generated by the electron gun 421 is more absorbed by the coating raw material 400, which facilitates the control of the heating efficiency of the coating raw material 400. Moreover, the coating raw material 400 is directly heated by the electron gun 421, and the interior of the second accommodating cavity 212 is not directly heated, and the wall of the bearing cavity 2124 is not easy to radiate heat to the coating cavity 2123 of the second accommodating cavity 212, the heat radiation range is smaller, and it is less likely to affect the growing crystal thermal field, and it is not easy to destroy the temperature gradient of the crystal growth thermal field, which is conducive to improving the quality of the growing crystal.

[0091] In some embodiments, the material of the wall of the bearing cavity 2124 is copper, and the wall of the bearing cavity 2124 is a hollow structure to allow the circulation of a cooling fluid, so that the wall of the bearing cavity 2124 is not easily melted due to excessive temperature, which plays a certain protective role for the wall of the bearing cavity 2124.

[0092] For example, in some embodiments, as Figures 2-4 shown, an opening is made at the bottom of the isolation member 70 to define a bearing cavity 2124 by sinking a part of the bottom plate of the accommodating device 20. The bottom plate is made of graphite. The sunken part of the bottom plate is an opening, and a copper crucible made of copper is connected to the lower side of the sunken part of the bottom plate. The wall of the copper crucible is a hollow structure and a cooling fluid passes through the wall, which can protect the copper crucible from being melted.

[0093] The top of the copper crucible is connected to the sunken part of the bottom plate made of graphite, and the sunken part of the bottom plate and the copper crucible together define the bearing cavity 2124. A second communication hole 2125 is opened on the side of the sunken part of the bottom plate facing the incident side of the electron gun 421 to allow the electron beam to pass through. The deflection direction of the high-energy beam of the electron gun 421 is changed by the deflection electric field generator 422. After passing through the deflection electric field, the high-energy beam changes along a 180° semi-circular arc path and enters the bearing cavity 2124 through the second communication hole 2125, directly heating the coating raw material 400 to reduce the interference with the crystal growth thermal field and efficiently heating and melting the coating raw material 400. On the one hand, the stability of the crystal growth thermal field can be maintained, and on the other hand, the coating efficiency of the coating raw material 400 and the quality of the protective film can be improved. In particular, for the coating raw material 400 with a high melting point, directly heating the coating raw material 400 can improve the coating efficiency.

[0094] As Figure 5 shown, the control method of the thermal field device 100 for growing crystals according to an embodiment of the present invention includes:

[0095] S1: Control the first heating member 30 to heat the crystal raw material 300 and control the second heating member 40 to heat the coating raw material 400.

[0096] At the same time, turn on the first heating member 30 and the second heating member 40, so that the first heating member 30 heats the crystal growth thermal field to a high-temperature environment, so that the crystal raw material 300 in the first accommodation cavity 211 sublimes to generate gaseous substances. The gaseous substances are transmitted to the first part 2121 and deposited and crystallized on the front surface of the seed crystal 200, so that crystals grow on the front surface of the seed crystal 200.

[0097] At the same time, the second heating member 40 heats the coating thermal field to a high-temperature environment, so that the coating raw material 400 in the second part 2122 sublimes to generate gaseous substances, and the gaseous substances are transmitted to the back surface of the seed crystal 200 for deposition to form a protective film.

[0098] The heating effect of the first heating element 30 can be controlled. For example, in an embodiment where the first heating element 30 is a resistive heating element, the power of the first heating element 30 is controlled to control the high-temperature environment of the crystal growth thermal field and obtain the temperature gradient required for growing the crystal. The heating effect of the second heating element 40 can be controlled. For example, in an embodiment where the second heating element 40 is a resistive heating element, the power of the second heating element 40 is controlled. In an embodiment where the second heating element 40 includes an electron gun 421 and a deflection electric field generator 422, the current and voltage of the electron gun 421 are controlled to control the high-temperature environment of the coating thermal field and obtain a protective film with a desired thickness.

[0099] If the coating is started on the back surface of the seed crystal 200 and then the crystal growth is started on the front surface of the seed crystal 200, it is easy to cause the protective film formed by the coating to undergo more temperature change processes and thus easily fall off, resulting in a poor protection effect on the crystal growth on the front surface of the seed crystal 200. If the coating is started on the back surface of the seed crystal 200 after the crystal growth on the front surface of the seed crystal 200, it will cause the back surface of the seed crystal 200 to be unprotected during the initial stage of crystal growth, resulting in poor quality of the crystal grown in the initial stage, and further resulting in poor quality of the crystal grown continuously on the basis of the initial crystal in the later stage.

[0100] Therefore, in the present application, the coating is started on the back surface of the seed crystal 200 while the crystal growth is started on the front surface of the seed crystal 200, which can synchronously protect the growing crystal through the protective film during the initial stage of crystal growth on the front surface of the seed crystal 200, and is beneficial to improving the quality of the crystal grown on the front surface of the seed crystal 200.

[0101] Since the thermal field device 100 according to the embodiment of the present invention has the above-mentioned beneficial technical effects, therefore, according to the control method of the embodiment of the present invention, the operations of growing the crystal and coating the film can be simultaneously performed on the seed crystal 200, so that the protective film is not easily detached from the seed crystal 200, the protection effect on the growing crystal is good, the quality of the grown crystal is high, and the number of process steps is small, and the process coherence is good, which is beneficial to improving the efficiency of growing the crystal.

[0102] In some embodiments, as Figure 5 shown, the control method further includes:

[0103] S2: When the preset time is reached, control the second heating element 40 to stop heating and control the first heating element 30 to continuously heat the crystal raw material 300.

[0104] After the first heating element 30 and the second heating element 40 are turned on simultaneously, when the heating duration of the first heating element 30 and the second heating element 40 reaches the preset time, a crystal with a certain thickness and good quality has grown on the front surface of the seed crystal 200, and the thickness of the protective film formed on the back surface of the seed crystal 200 also meets the requirements. At this time, the second heating element 40 can be turned off to stop coating the back surface of the seed crystal 200, while the first heating element 30 continues to work to continue growing the crystal on the front surface of the seed crystal 200. Since a crystal with better quality has grown on the front surface of the seed crystal 200 and there is also a certain thickness of the protective film on the back surface of the seed crystal 200, the crystal that continues to grow on the basis of the crystal with better quality in the initial stage is not likely to produce defects, so that the quality of the crystal grown after the preset time is still very good. Continuing to heat the second heating element 40 will cause the thickness of the protective film to be too thick, affecting the film-forming uniformity, adhesion and stable protection effect, and having a poor protection effect on the crystal grown on the carbon surface of the seed crystal 200.

[0105] Here, the preset time can be determined according to the actual situation. For example, the time from when the second heating element 40 is turned on until the thickness of the protective film on the back surface of the seed crystal 200 meets the requirements is recorded as the preset time. Generally, when the thickness of the protective film reaches 1 mm - 3 mm, it meets the protection requirements.

[0106] In some embodiments, the preset time is 25.67 h - 40.67 h (h represents hours). If the preset time is too short, the thickness of the protective film cannot meet the requirements, and it is difficult to achieve the effect of protecting the crystal grown on the front surface of the seed crystal 200. If the preset time is too long, the protective film will be too thick, exceeding the required thickness of the protective film, which not only causes waste of the coating raw material 400, but also affects the film-forming uniformity, adhesion and stable protection effect, and has a poor protection effect on the crystal grown on the carbon surface of the seed crystal 200. Therefore, setting the preset time to 25.67 h - 40.67 h is beneficial to taking into account the protection effect of the crystal growth on the front surface of the seed crystal 200 and the installation stability of the seed crystal 200. For example, the preset time is 25.67 h, 20 h or 40.67 h, etc.

[0107] Meanwhile, the crystal raw material 300 is heated by the first heating element 30 to grow a crystal on the carbon surface of the seed crystal 200, and the coating raw material 400 is heated by the second heating element 40 to coat the silicon surface of the seed crystal 200, so as to continuously coat during the initial stage of crystal growth. Specifically, for example, the diameter of the seed crystal 200 is 6 inches, the preset time is 25.67 h - 40.67 h, the growth rate of the crystal in the initial stage is controlled by the first heating element 30 to be 6.2 g / h - 6.5 g / h, or 100.1 μm / h - 104.98 μm / h. After the preset time, the corresponding growth weight of the crystal in the initial stage is 159.15 g - 264.36 g, or the growth thickness of the crystal in the initial stage is 2.57 mm - 4.27 mm. The coating operation is also continuously carried out within the preset time. For example, when the preset time is 25.67 h, the growth rate of the crystal is controlled by the first heating element 30 to be 6.2 g / h or 100.1 μm / h, and the growth weight of the crystal in the initial stage is 159.15 g.

[0108] The growth thickness or weight of the crystal in the initial stage can be obtained through experiments. For example, the first method is to stop the growth after the preset time of crystal growth, take it out and directly measure to see if the growth parameters of the crystal are appropriate. The second method is to set the preset time to 30 h, pass more nitrogen before 25 h of crystal growth, stop passing nitrogen after 25 h, the crystal grown at 30 h will consume all the nitrogen, and then continue to complete the remaining crystal growth time. The growth thickness of the crystal can be calculated through the color difference of the crystal grown in the nitrogen-passing and non-nitrogen-passing stages.

[0109] In a specific embodiment, as Figure 6 shown, after preparing the raw materials (seed crystal 200, crystal raw material 300, coating raw material 400 and filter element 500), assembling the hot field device 100 and putting the raw materials into the hot field device 100, the control method, that is, the crystal growth process, further includes vacuum acquisition, leak rate detection, and gradually raising the first heating element 30 to the target power. Specifically, the control method further includes 12 steps:

[0110] T1: Evacuate the inside of the furnace body 10 for 1 h.

[0111] T2: Conduct process leak detection for 30 min (min stands for minute).

[0112] During the crystal growth process, detect and eliminate problems such as gas leakage in the hot field device 100.

[0113] T3: Increase the pressure to 80000 Pa in 30 min (Ar flow rate 1000 sccm (standard cubic centimeters per minute)), turn off the first heating element 30, and turn off the second heating element 40.

[0114] The first heating element 30 is in the off state, and the second heating element 40 is in the off state, that is, the crystal raw material 300 and the coating raw material 400 are not heated.

[0115] T4: Maintain the pressure at 80000 Pa for 10 min (Ar flow rate reduced to 50 sccm), the first heating element 30 is off, and the second heating element 40 is off.

[0116] The first heating element 30 is in the off state, and the second heating element 40 is in the off state, that is, the crystal raw material 300 and the coating raw material 400 are not heated.

[0117] T5: Reduce the pressure to 10000 Pa in 30 min (Ar flow rate reduced to 50 sccm), the first heating element 30 is turned on with a power of 5 kw, and the second heating element 40 is turned on and in the heating state.

[0118] Turn on the first heating element 30 and the second heating element 40 simultaneously to heat the crystal raw material 300 and the coating raw material 400 at the same time, which is equivalent to step S1.

[0119] In the embodiment where the second heating element 40 is a resistance heating element, as Figure 1 shown, control the heating power of the second heating element 40 to be 15 kw - 25 kw. When the coating raw material 400 is silicon carbide powder, the power of the second heating element 40 is 15 kw. When the coating raw material 400 is a powder of high melting point materials such as Ta, Zr, TiN, ZrO or TaC or a mixture thereof, the power of the second heating element 40 is greater than 15 kw.

[0120] In the embodiment where the second heating element 40 includes an electron gun 421 and a deflection electric field generator 422 and indirectly heats the coating raw material 400 through the sunken part of the bottom plate, as Figure 2 shown, control the current of the second heating element 40 to be 110 A - 150 A. In the embodiment where the second heating element 40 includes an electron gun 421 and a deflection electric field generator 422 and directly heats the coating raw material 400 through the second communication hole 2125, as Figures 3-4 shown, control the current of the second heating element 40 to be 80 A - 100 A.

[0121] T6: Maintain the pressure at 10000 Pa for 3 h (Ar flow rate remains 50 sccm), the power of the first heating element 30 is 25 kw, and the second heating element 40 is in the heating state.

[0122] T7: Reduce the pressure to 5000 Pa in 10 min (Ar flow rate remains 50 sccm, nitrogen flow rate 3 sccm), the power of the first heating element 30 is 25 kw, and the second heating element 40 is in the heating state.

[0123] T8: The pressure drops to 200 Pa in 7 hours (the Ar flow rate remains 50 sccm and the nitrogen flow rate is 3 sccm). The power of the first heating element 30 is 25 kw, and the second heating element 40 is in the heating state.

[0124] T9: The pressure is maintained at 200 Pa in 150 hours (the Ar flow rate remains 50 sccm and the nitrogen flow rate is 3 sccm). The power of the first heating element 30 is 25 kw. Among them, the second heating element 40 is in the heating state within 0 h - 15 h (including 15 h), and the second heating element 40 is turned off within 15 h - 150 h (excluding 15 h).

[0125] From the time when the second heating element 40 is turned on in step T5 to the first 15 h of 150 h in step T9 is the preset time, which is about 25.67 h. Step T9 is equivalent to step S2.

[0126] In step T9, the first heating element 30 is always in the heating state. In step T9, after the second heating element 40 is heated for 15 h, it stops heating. At this time, the thickness of the protective film formed by coating is about 1 mm - 3 mm, and the weight of the crystal grown on the front of the seed crystal 200 is about 93 g, or the thickness is about 1.53 mm.

[0127] T10: The pressure rises by 5000 Pa in 30 minutes (the Ar flow rate is 1000 sccm and the nitrogen flow rate is 0 sccm). The power of the first heating element 30 is 25 kw, and the second heating element 40 is in the off state.

[0128] T11: The pressure rises by 50000 Pa in 1 hour (the Ar flow rate is 1000 sccm and the nitrogen flow rate is 0 sccm). The first heating element 30 is turned off, and the second heating element 40 is in the off state.

[0129] T12: Cooling for 48 hours, then opening the furnace.

[0130] Using the thermal field device 100 of the present application and growing silicon carbide crystals according to the control method of the present application can effectively solve the generation of through - dislocations caused by back - corrosion or temperature changes of the seed crystal 200 during the crystal growth process, effectively improve the yield of the obtained crystals, and at the same time reduce the dislocation density.

[0131] For those of ordinary skill in the art, the other compositions and operations of the thermal field device 100 and the control method for growing crystals according to the embodiments of the present invention are known, and will not be described in detail here.

[0132] In the description of the present invention, it should be noted that, unless otherwise clearly defined and limited, the terms "installed", "connected", and "connected" 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.

[0133] In the description of this specification, the descriptions referring to the terms "embodiment", "specific embodiment", "example", etc. mean that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic expressions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in a suitable manner in any one or more embodiments or examples.

[0134] Although the embodiments of the present invention have been shown and described, those of ordinary skill in the art can understand that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and purposes of the present invention, and the scope of the present invention is defined by the claims and their equivalents.

Claims

1. A thermal field device (100) for growing crystals, characterized in that: include: Furnace body (10); A containing device (20), the containing device (20) being arranged in the furnace body (10) and comprising a shell (21) and a bracket (22), the shell (21) defining a first containing cavity (211) and a second containing cavity (212), the bracket (22) being arranged inside the shell (21) for placing a seed crystal (200), the seed crystal (200) being suitable for separating the second containing cavity (212) into a first part (2121) and a second part (2122), the first containing cavity (211) being used for containing a crystal raw material (300) and being in communication with the first part (2121), and a coating raw material (400) being arranged in the second part (2122); a first heating element (30), the first heating element (30) being arranged in the furnace body (10), and the first heating element (30) being used to heat the crystal raw material (300) so as to grow a crystal on one side of the seed crystal (200); A second heating element (40), the second heating element (40) is arranged in the furnace body (10), and the second heating element (40) is used to heat the coating raw material (400) so as to coat the other side of the seed crystal (200).

2. The thermal field device (100) for growing crystals according to claim 1, characterized in that: The first accommodating cavity (211), the first part (2121) of the second accommodating cavity (212), and the second part (2122) of the second accommodating cavity (212) are arranged in sequence from top to bottom, the upper surface of the seed crystal (200) is used for growing crystals, the lower surface of the seed crystal (200) is coated, and the bracket (22) is in contact with the edge of the seed crystal (200).

3. The thermal field device (100) for growing crystals according to claim 1, characterized in that: A porous plate (50) is provided in the shell (21), and the porous plate (50) separates the shell (21) into the first accommodating chamber (211) and the second accommodating chamber (212). The porous plate (50) is provided with a plurality of first communication holes that communicate with the first accommodating chamber (211) and the second accommodating chamber (212). A portion of the porous plate (50) is recessed to form a accommodating groove (52) that communicates with the first communication holes, and the accommodating groove (52) is used to accommodate a filter element.

4. The thermal field device (100) for growing crystals according to claim 1, characterized in that: A mounting component (60) is provided in the second part (2122), the coating raw material (400) is provided on the mounting component (60), the second heating element (40) is provided in the second part (2122) and is adjacent to the mounting component (60), and the second heating element (40) is a resistance heating element.

5. The thermal field device (100) for growing crystals according to claim 1, characterized in that: The second part (2122) of the second accommodating chamber (212) comprises a coating chamber (2123) and a bearing chamber (2124) which are connected to each other. The bearing chamber (2124) is located on a side of the coating chamber (2123) away from the first accommodating chamber (211). The coating raw material (400) is arranged in the bearing chamber (2124). The second heating element (40) is located outside the containing device (20), and the second heating element (40) is used to heat the wall of the carrying cavity (2124) to heat the coating raw material inside the carrying cavity (2124).

6. The thermal field device (100) for growing crystals according to claim 5, characterized in that: A cooling channel (111) is defined in the furnace wall (11) of the furnace body (10) for circulating a cooling fluid, and the wall portion of the bearing cavity (2124) is in abutment with the furnace wall (11) of the furnace body (10).

7. The thermal field device (100) for growing crystals according to claim 1, characterized in that: The second part (2122) of the second accommodating cavity (212) comprises a coating cavity (2123) and a bearing cavity (2124) which are connected to each other. The bearing cavity (2124) is located on a side of the coating cavity (2123) away from the first accommodating cavity (211). The coating raw material (400) is arranged in the bearing cavity (2124). A second connecting hole (2125) is arranged on the wall of the bearing cavity (2124). The second heating element (40) is located outside the containing device (20), and the second heating element (40) is suitable for heating the coating raw material through the second connecting hole (2125).

8. The thermal field device (100) for growing crystals according to any one of claims 5 to 7, characterized in that: The second heating element (40) comprises an electron gun (421) and a deflection electric field generator (422).

9. A method for controlling a thermal field device (100) for growing crystals according to any one of claims 1 to 8, characterized in that: include: The first heating element (30) is controlled to heat the crystal raw material (300), and the second heating element (40) is controlled to heat the coating raw material (400).

10. The control method of the thermal field device (100) for growing crystals according to claim 9, characterized in that: Also includes: When a preset time is reached, the second heating element (40) is controlled to stop heating and the first heating element (30) is controlled to continue heating the crystal raw material (300).

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