Silicon carbide crystal growth apparatus and growth method

Abstract

The application provides a silicon carbide crystal growth device and a growth method, and belongs to the technical field of silicon carbide crystal growth. The application solves the problem that the amount of the crystal growth atmosphere in the prior art is difficult to control. The application comprises a crucible, a diameter expansion ring, a partition assembly and a heating assembly. The diameter expansion ring is arranged on the outer circumferential side of a seed crystal fixing area. The diameter expansion ring has an inclined surface. The partition assembly comprises a partition ring and a cover. The partition ring is arranged on the bottom of the crucible and is arranged opposite to the seed crystal fixing area. The outer circumferential side of the partition ring is opposite to the inclined surface. The outer circumferential side of the partition ring is used for arranging a first raw material. The cover is connected to the partition ring and is a separable connection. The cover is made of graphite or polycrystalline silicon carbide. The thickness of the cover is less than or equal to 0.5 mm. The cover and the partition ring form an accommodation cavity. The accommodation cavity is used for arranging a second raw material. The application can stabilize the diameter expansion, ensure the crystal quality, reduce the temperature gradient of the crystal growth interface and improve the resistivity uniformity of the crystal after the diameter expansion.

Description

Technical Field

[0001] This application belongs to the field of silicon carbide crystal growth technology, and more specifically, relates to a silicon carbide crystal growth apparatus and growth method. Background Technology

[0002] Silicon carbide (SiC) crystal, as a third-generation semiconductor material, has broad application prospects in high-temperature, high-frequency, and high-voltage electronic devices due to its high breakdown field strength, high thermal conductivity, and excellent chemical stability. However, there are significant problems in the diameter expansion growth of silicon carbide crystals in existing technologies.

[0003] In the existing silicon carbide crystal diameter expansion process, a heater needs to be added to the top of the crucible. The growth atmosphere (such as Si / C gas phase) is deposited towards the outer edge of the crystal through the top thermal field to achieve diameter expansion growth. However, this method is prone to causing a large radial temperature gradient, which leads to a decrease in the resistivity uniformity of various parts of the crystal. In addition, excessive saturated growth atmosphere tends to accumulate at the angle between the crystal edge and the inner wall of the diameter expansion ring, resulting in the precipitation of polycrystalline silicon carbide, which hinders the single crystal diameter expansion growth and reduces the crystal quality. However, if the raw materials for crystal growth are reduced, it is difficult to provide a sufficient amount of growth atmosphere to meet the diameter expansion growth requirements.

[0004] Based on the above, the technical problem with this application is that the amount of crystal diameter expansion growth atmosphere is difficult to control. Summary of the Invention

[0005] The purpose of this application is to address the aforementioned problems in the prior art by proposing a silicon carbide crystal growth apparatus and method, which solves the problem of difficulty in controlling the amount of growth atmosphere during crystal diameter expansion in the prior art and improves the quality of the expanded crystal.

[0006] The objective of this application can be achieved through the following technical solution: A silicon carbide crystal growth apparatus, comprising: a crucible, wherein a seed crystal fixing area is provided at the top of the crucible for fixing a seed crystal; an expanding ring, wherein the expanding ring is disposed on the outer periphery of the seed crystal fixing area, the expanding ring having an inclined surface extending in a direction away from the seed crystal fixing area; and a partition assembly, wherein the partition assembly comprises: a partition ring, wherein the partition ring is disposed at the bottom of the crucible and directly opposite the seed crystal fixing area, the outer periphery of the partition ring being opposite to the inclined surface, the partition ring... The outer periphery is used to hold the first raw material; a cover body, which is connected to the partition ring and is detachable, is made of graphite or polycrystalline silicon carbide, and its thickness is ≤0.5mm. The cover body and the partition ring enclose a receiving cavity, which is used to hold the second raw material; and a heating assembly, which includes: a first heater, which is located below the crucible and acts on the outer periphery of the partition ring; and a second heater, which is located on the inner periphery of the first heater and acts on the receiving cavity. For example, a seed crystal fixing plate is generally provided on the top of the crucible, and the bottom surface of the seed crystal fixing plate serves as the seed crystal fixing area, where the seed crystal can be fixed. The diameter expansion ring is used to guide the transmission of the growth atmosphere and serves as a guide for crystal diameter expansion growth. The two heaters of the partition assembly and heating assembly work together to first enclose the second raw material within the accommodating cavity using a partition ring and a cover. The first heater is controlled to cause the first raw material on the outer periphery of the partition ring to sublimate. The sublimation atmosphere of the first raw material is deposited in the seed crystal fixing region by the thermal field and the expansion ring. As crystal growth progresses, the second heater is controlled to heat the cover until it melts through or is corroded by the sublimation atmosphere of the second raw material. This allows the sublimation atmosphere of the second raw material to be added to the crystal growth interface, achieving a two-stage supply of the crystal growth atmosphere. The growth atmosphere is neither excessive nor insufficient, ensuring stable diameter expansion while preventing the precipitation of polycrystalline silicon carbide, thus improving the quality of the expanded crystal. Simultaneously, it reduces the temperature gradient at the crystal growth interface, thereby improving the resistivity uniformity of the expanded crystal. Preferably, the particle size of the first and second raw materials can be controlled and adjusted. For example, the particle size of the first raw material can be configured to be larger than that of the second raw material. Since smaller particle sizes are easier to sublimate, when the cover needs to be decomposed to separate from the partition ring, the second raw material can quickly sublimate to supply the growth atmosphere. Regarding the cover, when graphite is used, the Si gas phase in the growth atmosphere can react with it, decomposing the cover with a thickness ≤0.5mm. When polycrystalline silicon carbide is used, the cover with a thickness ≤0.5mm will sublimate and decompose under continuous thermal action. However, when the cover thickness exceeds 0.5mm, effective decomposition becomes difficult, thus interfering with crystal growth in the height direction. Neither graphite nor polycrystalline silicon carbide will contaminate the crystal growth.Regarding the heating components, the first heater is preferably annular, and as a preferred embodiment, a third heater is also provided, which is disposed on the outer periphery of the crucible. The third heater and the first heater together heat the outer periphery of the separating ring. The second heater is preferably disposed at the bottom of the crucible and located within the inner ring of the first heater. It should be noted that the thickness of the cover is preferably configured to be ≥0.3mm. When the thickness of the cover is <0.3mm, it is difficult to maintain a stable support shape, and the installation difficulty of the cover will also increase significantly.

[0007] In the aforementioned silicon carbide crystal growth apparatus, the cover includes: a first part connected to the partition ring, the first part having a thickness of H1, and an average distance D1 from the first part to the inclined surface; and a second part disposed on and connected to the first part, the second part having a thickness of H2, and a shortest distance D2 from the second part to the inclined surface; wherein H2 < H1, and D2 < D1. For example, the first part is barrel-shaped or ring-shaped, and the second part is cap-shaped. It is understood that because D2 < D1, meaning the first part is closer to the heated area than the second part, and the second part is closer to the seed crystal fixing area and the inclined surface of the expansion ring, and the first part receives heat in both atmosphere supply stages for a longer period, H2 is configured to be less than H1 to prevent the first part from decomposing and being destroyed during the first heater heating process, thus losing its isolation function.

[0008] In the aforementioned silicon carbide crystal growth apparatus, the cover further includes a third part, which is disposed between the first part and the partition ring. The thickness of the third part is H3, where H3 < H1. A detachment structure is formed between the partition ring and the third part, allowing the second part to have a vertically downward degree of freedom after the third part decomposes. It is understood that by introducing the third part and the detachment structure, and controlling H3 < H1, the cover is allowed to automatically detach downwards after decomposition at a predetermined temperature, ensuring that the crystal is not interfered with by the top of the cover during vertical growth.

[0009] In the aforementioned silicon carbide crystal growth apparatus, the cover has a first state and a second state; in the first state, the third part is solid to support the first part and the second part, and a guide channel is formed between the first part, the second part, and the inclined surface, the guide channel extending to the seed crystal fixing area; in the second state, the third part decomposes and vaporizes, and the first part and the second part have vertically downward degrees of freedom to avoid the crystal growing in the seed crystal fixing area. Understandably, during the initial crystal growth, the growth atmosphere needs to be concentrated on the seed crystal, i.e., the location of the seed crystal fixing area. Therefore, the second part of the cover is positioned closer to the seed crystal fixing area, thus forming a guide channel between the first part, the second part, and the inclined surface of the expansion ring, guiding the growth atmosphere to quickly gather at the seed crystal for crystal growth. However, when the seed crystal grows to a certain thickness, the initial height position of the second part can easily interfere with the continued growth of the crystal, and the crystal also needs to expand its diameter along the inclined surface of the expansion ring. Therefore, by configuring the third part to decompose before the first and second parts, the first and second parts are ensured to fall without the support of the third part. The height position of the second part changes to avoid the growing crystal, and at this time, it is no longer necessary to rely on the guide channel to guide the growth atmosphere.

[0010] In the aforementioned silicon carbide crystal growth apparatus, the detachment structure includes: a detachment cavity, which is formed within the partition ring and is annular; a support portion, which is part of the partition ring and is circumferentially disposed below and connected to the detachment cavity; and a connecting portion, which is part of the partition ring and is disposed above the detachment cavity, and is connected to the third part. It can be understood that by setting an annular detachment cavity, it can be ensured that after the third part decomposes, the first part can effectively fall into the detachment cavity, and the distance between the second part and the seed crystal fixing area will also increase. The support portion can be used to support the second part that has not yet decomposed in time. The distance between the support portion and the seed crystal fixing area is a preset distance, configured to be sufficient for the seed crystal to grow in the height direction. The connecting portion is used to temporarily connect the third part to the partition ring, and is disconnected from the connecting portion when the third part decomposes subsequently.

[0011] In the aforementioned silicon carbide crystal growth apparatus, the first part has multiple micropores with a pore diameter ≤ 10 μm and a porosity ranging from 5% to 10%. It is understood that the micropores can serve as auxiliary exhaust channels, releasing a small amount of growth atmosphere. The rise of this small amount of growth atmosphere can accelerate crystal growth without causing excessive accumulation of growth atmosphere at the growth interface, thus preventing polycrystalline formation. Furthermore, by pre-setting the porosity of the first part, the decomposition rate of the first part can be increased, avoiding incomplete decomposition. Preferably, the pore diameter of the micropores should be greater than 0.5 μm; otherwise, blockage may occur.

[0012] In the aforementioned silicon carbide crystal growth apparatus, the main material component of the cover accounts for ≥99.995% of the total material. It can be understood that by controlling the proportion of the main material component of the cover to above 99.995%, the introduction of impurities is reduced, the dislocation density of the crystal can be significantly reduced, and the electrical performance of the silicon carbide substrate processed subsequently can be improved.

[0013] Another objective of this application is to provide a silicon carbide crystal growth method, applied to the aforementioned silicon carbide crystal growth apparatus, comprising the following steps: preparing a first raw material, a second raw material, and a cover; starting a first heater and controlling its temperature at T1, causing the first raw material to sublimate and be transported along the expansion ramp to the seed crystal surface for deposition and growth; starting a second heater and controlling its temperature at T2, where T2-T1≥80℃, causing the cover to decompose and triggering the sublimation of the second raw material. For example, the heating rate of the first heater is controlled at 5℃ / min~10℃ / min. Through staged heating, the cover decomposes in the later stages of crystal growth, replenishing sufficient growth atmosphere, and achieving an expansion success rate of over 90%.

[0014] The aforementioned silicon carbide crystal growth method further includes the following steps: controlling the first heater to start first, followed by the second heater, and controlling the ratio of the heating time of the first heater to the heating time of the second heater to be (3-5):1. It can be understood that by prioritizing the start of the first heater to ensure early-stage growth stability and shortening the heating time of the second heater, energy consumption can be reduced by 15%.

[0015] In the aforementioned silicon carbide crystal growth method, the "preparation of the first raw material, the second raw material, and the cover" includes: installing the cover, and controlling the minimum distance D between the installation position of the cover and the seed crystal fixing area to be ≥55mm. It can be understood that by controlling the minimum distance D between the installation position of the cover and the seed crystal fixing area to be ≥55mm, interference with crystal growth is avoided, and sufficient time is given for the cover to disassemble to avoid the crystal growth interface.

[0016] In the aforementioned silicon carbide crystal growth method, the "preparation of the first raw material, the second raw material, and the cover" includes: filling the micropores of the cover with B4C, controlling the filling amount of B4C M ≤ 0.1ϕVρ, where ϕ is the porosity of the micropores, V is the volume of the cover, and ρ is the density of B4C. It is important to note that B4C sublimates at temperatures above 2200℃, generating boron vapor. This vapor diffuses through the micropores to the surface of the cover, accelerating its decomposition, similar to chemical etching. Furthermore, boron atoms act as surfactants at the silicon carbide crystal growth interface, reducing the edge polycrystalline nucleation rate. The sublimation temperature of B4C, 2200℃, highly coincides with the silicon carbide crystal growth temperature of 2100℃ to 2300℃, ensuring its release as needed during growth. In addition, boron is a commonly used dopant in silicon carbide crystal growth; trace amounts of residual boron can be incorporated into the crystal lattice without generating independent impurity phases.

[0017] Compared with the prior art, this application has the following beneficial effects:

[0018] This application utilizes a separator ring and a housing to first enclose the second raw material within a cavity. The first heater is controlled to cause the first raw material on the outer periphery of the separator ring to sublimate. The atmosphere of the first raw material sublimation is deposited in the seed crystal fixing region by the thermal field and the expansion ring. As crystal growth proceeds, the second heater is controlled to heat the housing so that it melts through or is corroded by the atmosphere of the second raw material sublimation, allowing the sublimation atmosphere of the second raw material to be added to the crystal growth interface. This achieves the supply of the crystal growth atmosphere in two stages, ensuring that the growth atmosphere does not precipitate excessive polycrystalline silicon carbide or is insufficient for normal diameter expansion growth. While stabilizing the diameter expansion, the crystal quality is guaranteed. At the same time, by reducing the temperature gradient at the crystal growth interface, the resistivity uniformity of each part after crystal diameter expansion can be improved. Attached Figure Description

[0019] Figure 1 This is a simplified structural diagram of the crystal growth apparatus of this application;

[0020] Figure 2 This is a simplified structural diagram of the crystal growth apparatus of this application after the addition of a third heater;

[0021] Figure 3 yes Figure 1 Enlarged structural diagram of region A in the middle;

[0022] Figure 4 This is a simplified structural diagram of the cover body of this application;

[0023] Figure 5 This is a simplified structural diagram of the third part of the crystal growth apparatus of this application when it is not decomposed;

[0024] Figure 6This is a simplified structural diagram of the third part of the crystal growth apparatus of this application after disassembly.

[0025] Figure 7 This is a simplified structural diagram of the first and second parts of the crystal growth apparatus of this application after disassembly.

[0026] Figure 8 This is a flowchart illustrating the third crack control strategy of this application;

[0027] Figure 9 This is a schematic diagram of resistivity testing of silicon carbide crystals after conventional diameter expansion using existing technology.

[0028] Figure 10 This is a schematic diagram of resistivity testing of silicon carbide crystal after diameter expansion using the crystal growth apparatus of this application.

[0029] In the figure, 100 is the crucible; Q is the seed crystal fixing area; 200 is the diameter expansion ring; 210 is the inclined surface; 300 is the partition assembly; 310 is the partition ring; 320 is the cover; 321 is the first part; 3211 is the micropore; 322 is the second part; 323 is the third part; 330 is the accommodating cavity; 340 is the detachment structure; 341 is the detachment cavity; 342 is the support part; 343 is the connecting part; 400 is the heating assembly; 410 is the first heater; 420 is the second heater; 430 is the third heater; Y1 is the first raw material; Y2 is the second raw material; S is the guide channel; and T is the crystal. Detailed Implementation

[0030] To make the above-mentioned objectives, features, and advantages of this application more apparent and understandable, specific embodiments of this application are described in detail below with reference to the accompanying drawings. Many specific details are set forth in the following description to provide a thorough understanding of this application. However, this application can be implemented in many other ways different from those described herein, and those skilled in the art can make similar modifications without departing from the spirit of this application. Therefore, this application is not limited to the specific embodiments disclosed below.

[0031] In the description of this application, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc., indicating the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application.

[0032] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this application, "multiple" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0033] In this application, unless otherwise expressly specified and limited, the terms "installation," "connection," "joining," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components, unless otherwise expressly limited. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0034] In this application, unless otherwise expressly specified and limited, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature is in indirect contact with the second feature through an intermediate medium. Furthermore, "above," "on top of," and "over" the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0035] It should be noted that when an element is referred to as being "fixed to" or "set on" another element, it can be directly on the other element or there may be an intervening element. When an element is considered to be "connected to" another element, it can be directly connected to the other element or there may be an intervening element. The terms "vertical," "horizontal," "upper," "lower," "left," "right," and similar expressions used herein are for illustrative purposes only and do not represent the only embodiments.

[0036] Please refer to the attached diagram in the instruction manual. Figure 1The silicon carbide crystal growth apparatus of this application includes: a crucible 100, an expanding ring 200, a partition assembly 300, and a heating assembly 400. The top of the crucible 100 is provided with a seed crystal fixing area Q, which is used to fix a seed crystal. The expanding ring 200 is disposed on the outer periphery of the seed crystal fixing area Q and has an inclined surface 210 extending in a direction away from the seed crystal fixing area Q. The partition assembly 300 includes: a partition ring 310, which is disposed at the bottom of the crucible 100 and directly opposite the seed crystal fixing area Q. The outer periphery of the partition ring 310 is opposite to the inclined surface 210, and the outer periphery of the partition ring 310 is used for... A first raw material Y1 is placed in the crucible 100. A cover 320 is attached to a separator ring 310 and is detachably connected. The cover 320 is made of graphite or polycrystalline silicon carbide, and its thickness is ≤0.5mm. The cover 320 and separator ring 310 enclose a cavity 330, which is used to place a second raw material Y2. The heating assembly 400 includes a first heater 410 and a second heater 420. The first heater 410 is located below the crucible 100 and acts on the outer periphery of the separator ring 310. The second heater 420 is located on the inner periphery of the first heater 410 and acts on the cavity 330. For example, a seed crystal fixing plate (not shown) is generally provided on the top of the crucible 100. The bottom surface of the seed crystal fixing plate serves as the seed crystal fixing area Q, where the seed crystal can be fixed. The expansion ring 200 is used to guide the transmission of the growth atmosphere and serves as a guide for crystal expansion growth. The two heaters of the partition assembly 300 and the heating assembly 400 cooperate to first enclose the second raw material Y2 in the accommodating cavity 330 using the partition ring 310 and the cover 320. The first heater 410 is controlled to cause the first raw material Y1 on the outer periphery of the partition ring 310 to sublimate. The sublimation atmosphere of the first raw material Y1 is deposited in the seed crystal fixing region Q by the thermal field and the expansion ring 200. As crystal growth progresses, the second heater 420 is controlled to heat the cover 320 until it melts through or is corroded by the sublimation atmosphere of the second raw material Y2. This allows the sublimation atmosphere of the second raw material Y2 to be added to the crystal growth interface, thus supplying the crystal growth atmosphere in two stages. This ensures that the growth atmosphere does not excessively precipitate polycrystalline silicon carbide nor is insufficient for normal diameter expansion growth, stabilizing diameter expansion while maintaining crystal quality. Furthermore, by reducing the temperature gradient at the crystal growth interface, the resistivity uniformity of different parts of the crystal after diameter expansion can be improved. (See reference...) Figure 9 and Figure 10 , Figure 9 This is a schematic diagram of resistivity testing of silicon carbide crystals after conventional diameter expansion using existing technology. Figure 10This is a schematic diagram of resistivity detection of a silicon carbide crystal after diameter expansion using the crystal growth apparatus of this application. It is evident that the uniformity of resistivity of the crystal grown by diameter expansion is significantly improved after this application. Preferably, the particle size of the first raw material Y1 and the second raw material Y2 can be controlled and adjusted. For example, if the particle size of the first raw material Y1 is configured to be larger than that of the second raw material Y2, since smaller particle sizes are easier to sublimate, when the cover 320 needs to be decomposed to achieve separation from the separator ring 310, the second raw material Y2 can quickly sublimate to supply the growth atmosphere. Regarding the cover 320, when the cover 320 is made of graphite, the Si gas phase in the growth atmosphere can react with it, decomposing the cover 320 with a thickness ≤0.5mm. When the cover 320 is made of polycrystalline silicon carbide, the cover 320 with a thickness ≤0.5mm is subjected to continuous thermal action and sublimates and decomposes. However, when the thickness of the cover 320 exceeds 0.5mm, effective decomposition is difficult, thus interfering with crystal growth in the height direction. Regarding the material used for the cover 320, neither graphite nor polycrystalline silicon carbide will cause contamination to crystal growth. When graphite is used, it can react and decompose with the Si gas phase when the temperature inside the crucible 100 exceeds 2200°C. Regarding the heating assembly 400, the first heater 410 is preferably annular, and is disposed at the bottom of the crucible 100. In some embodiments, such as... Figure 2 As shown, a third heater 430 is also provided, which is disposed on the outer periphery of the crucible 100. The third heater 430 and the first heater 410 together heat the outer periphery of the separator ring 310. The second heater 420 is preferably disposed at the bottom of the crucible 100 and located within the inner ring of the first heater 410. It should be noted that the thickness of the cover 320 is preferably configured to be ≥0.3mm. When the thickness of the cover 320 is <0.3mm, it is difficult to maintain a stable support shape, and the installation difficulty of the cover 320 will also be greatly increased. Regarding the tilt angle of the inclined surface 210, it is preferably 30° to 60°, and this angle range has a better guiding effect on the flow of the growth atmosphere.

[0037] In some embodiments, the cover 320 includes a first portion 321 and a second portion 322. The first portion 321 is connected to the partition ring 310. The thickness of the first portion 321 is H1, and the average distance from the first portion 321 to the inclined surface 210 is D1. The second portion 322 is disposed on and connected to the first portion 321. The thickness of the second portion 322 is H2, and the shortest distance from the second portion 322 to the inclined surface 210 is D2; wherein H2 < H1, and D2 < D1. Exemplarily, the first portion 321 is barrel-shaped or ring-shaped, and the second portion 322 is cap-shaped. It is understandable that since D2 < D1, that is, the first part 321 is closer to the heated area than the second part 322, the second part 322 is closer to the seed crystal fixing area Q and the inclined surface 210 of the expansion ring 200, and the first part 321 is subjected to heat in both atmosphere supply stages and the heating time is longer, so H2 is configured to be less than H1, so as to avoid the first part 321 being decomposed and destroyed when the first heater 410 is heated, thus losing its isolation function.

[0038] See Figure 3 and Figure 4 In some embodiments, the cover 320 further includes a third portion 323 disposed between the first portion 321 and the partition ring 310. The thickness of the third portion 323 is H3, where H3 < H1. A detachment structure 340 is formed between the partition ring 310 and the third portion 323. The detachment structure 340 allows the second portion 322 to have a vertically downward degree of freedom after the third portion 323 decomposes. It is understood that by introducing the third portion 323 and the detachment structure 340, and controlling H3 < H1, the cover 320 is allowed to automatically detach downward after decomposition at a predetermined temperature, ensuring that the crystal is not interfered with by the top of the cover 320 during vertical growth.

[0039] See Figure 3In some embodiments, the detachment structure 340 includes a detachment cavity 341, a support portion 342, and a connecting portion 343. The detachment cavity 341 is formed within the partition ring 310 and is annular. The support portion 342 is part of the partition ring 310 and is circumferentially disposed below and connected to the detachment cavity 341. The connecting portion 343 is part of the partition ring 310 and is disposed above the detachment cavity 341, and is connected to the third part 323. It can be understood that by providing an annular detachment cavity 341, it can be ensured that after the third part 323 decomposes, the first part 321 can effectively fall into the detachment cavity 341, and the distance between the second part 322 and the seed crystal fixing region Q will also increase. The support part 342 can be used to support the second part 322 that has not yet been decomposed. The distance between the support part 342 and the seed crystal fixing area Q is a preset distance. The preset distance is configured to be sufficient for the seed crystal to grow in the height direction. The connecting part 343 is used to temporarily connect the third part 323 to the separating ring 310. When the third part 323 is decomposed, it will be disconnected from the connecting part 343.

[0040] See Figure 4 In some embodiments, the first portion 321 has multiple micropores 3211, the pore size of which is ≤10μm, and the porosity of the first portion 321 ranges from 5% to 10%. It is understood that the micropores 3211 can serve as auxiliary venting channels to release a small amount of growth atmosphere. The rise of this small amount of growth atmosphere can accelerate crystal growth without causing excessive accumulation of growth atmosphere at the growth interface, thus preventing polycrystalline formation. Furthermore, by presetting the porosity of the first portion 321, the decomposition rate of the first portion 321 can be increased, avoiding incomplete decomposition. Preferably, the pore size of the micropores 3211 should be greater than 0.5μm; otherwise, blockage may occur.

[0041] In some embodiments, the main material component of the cover 320 accounts for ≥99.995% of the total material. It is understood that by controlling the proportion of the main material component of the cover 320 to above 99.995%, the introduction of impurities is reduced, the crystal dislocation density can be significantly reduced, and the electrical performance of the silicon carbide substrate in subsequent processing can be improved.

[0042] It should be noted that the cover 320 has a first state and a second state; in the first state, such as Figure 5 As shown, the third part 323 is solid to support the first part 321 and the second part 322. A guide channel S is formed between the first part 321, the second part 322, and the inclined surface 210, and the guide channel S extends to the seed crystal fixing region Q. In the second state, the third part 323 decomposes into a vapor phase, as shown... Figure 6As shown, the second part 322 and the first part 321 have a vertically downward degree of freedom to avoid the crystal T growing in the seed crystal fixing region Q; the cover 320 also has a third state, such as Figure 7 As shown, the first part 321 and the second part 322 are decomposed, leaving sufficient space above the separating ring 310 for crystal T to grow. It is understandable that during the initial growth of crystal T, the growth atmosphere needs to be concentrated on the seed crystal, i.e., at the location of the seed crystal fixing region Q. Therefore, the first part 321 of the cover 320 is positioned closer to the seed crystal fixing region Q, thus forming a guiding channel S between the first part 321, the second part 322, and the inclined surface 210 of the expansion ring 200. This guides the growth atmosphere converted from the first raw material Y1 to quickly gather at the seed crystal for crystal growth. However, once the seed crystal grows to a certain thickness, the initial height of the first part 321 can easily interfere with the continued growth of crystal T. Furthermore, the crystal T also needs to grow along the inclined surface 210 of the expansion ring 200. Therefore, by configuring the third part 323 to decompose preferentially over the first part 321 and the second part 322, the first part 321 and the second part 322 are ensured to fall without the support of the third part 323. The height position of the first part 321 changes to avoid the growing crystal T, and at this time, it is not necessary to rely on the guide channel S to guide the growth atmosphere. When the cover 320 enters the third state, that is, after complete decomposition, the second raw material Y2 can be completely sublimated to provide for the growth of crystal T.

[0043] See Figure 8 The silicon carbide crystal growth method of this application, applied to the silicon carbide crystal growth apparatus of this application, includes the following steps:

[0044] S100, Prepare the first raw material Y1, the second raw material Y2, and the cover 320;

[0045] S200, Start the first heater 410, control the temperature of the first heater 410 to T1, so that the first raw material Y1 sublimates and is transported along the expansion slope to the surface of the seed crystal for deposition and growth.

[0046] S300: Start the second heater 420 and control its temperature to T2, where T2-T1 ≥ 80℃, causing the cover 320 to decompose and triggering the sublimation of the second raw material Y2. For example, the heating rate of the first heater 410 is controlled to be 5℃ / min to 10℃ / min. Through staged heating, the cover 320 is ensured to decompose in the later stages of crystal growth, providing sufficient growth atmosphere and achieving a diameter expansion success rate of over 90%.

[0047] In some embodiments, the method further includes the following steps: controlling the first heater 410 to start first, followed by the second heater 420, and controlling the ratio of the heating time of the first heater 410 to the heating time of the second heater 420 to be (3-5):1. It is understood that by prioritizing the start of the first heater 410 to ensure early growth stability and shortening the heating time of the second heater 420, energy consumption can be reduced.

[0048] In some embodiments, "preparing the first raw material Y1, the second raw material Y2, and the cover 320" includes: installing the cover 320, and controlling the minimum distance D between the installation position of the cover 320 and the seed crystal fixing region Q to be ≥55mm. It is understood that by controlling the minimum distance D between the installation position of the cover 320 and the seed crystal fixing region Q to be ≥55mm, interference with crystal growth is avoided, and sufficient time is given for the cover 320 to disassemble to avoid the crystal growth interface.

[0049] In some embodiments, "preparing the first raw material Y1, the second raw material Y2, and the cover 320" includes: filling the micropores 3211 of the cover 320 with B4C, controlling the filling amount M of B4C to be ≤0.1ϕVρ, where ϕ is the porosity of the micropores 3211, V is the volume of the cover 320, and ρ is the density of B4C. It should be noted that B4C sublimates at temperatures above 2200°C, producing boron vapor. This vapor diffuses through the micropores 3211 to the surface of the cover 320, accelerating the decomposition of the cover 320, similar to chemical etching. Furthermore, boron atoms act as a surfactant at the silicon carbide crystal growth interface, reducing the edge polycrystalline nucleation rate. The sublimation temperature of B4C, 2200°C, highly coincides with the silicon carbide crystal growth temperature of 2100°C to 2300°C, ensuring that it is released as needed during the growth process. In addition, boron is a commonly used dopant in the growth of silicon carbide crystals. Trace amounts of boron residue can be incorporated into the crystal lattice without generating independent impurity phases.

[0050] Table 1 shows some of the experimental test conditions for the silicon carbide crystal growth process in this application:

[0051] Table 1

[0052]

[0053] Multiple combined tests were conducted on the conditions listed in Table 1, and the results are as follows: At a growth temperature between conditions 2 and 3, i.e., approximately 2250℃, the crystal growth rate reached its peak; when the pressure inside crucible 100 reached 5 mbar, the growth atmosphere saturation reached a relatively balanced state; with a growth time of 150 h, the crystal diameter could reach 6 inches or more with an edge polycrystalline ratio of <5%; the porosity of the enclosure 320 was 7.5%, indicating sufficient atmosphere release efficiency; the heating time ratio, specifically the time ratio of the first heater 410 to the second heater 420, was 4:1, resulting in approximately 18% energy consumption reduction, optimal crystal growth uniformity, and a thickness deviation of ±0.2 mm; with a B4C filling amount of 0.08ϕVρ, the polycrystalline suppression rate was improved by approximately 40% compared to the conventional scheme, while maintaining an electrical conductivity of 3×10⁻⁶. 3 S / cm.

[0054] Beneficial effects:

[0055] This application utilizes a separator ring 310 and a cover 320 to first enclose the first raw material Y1 within the accommodating cavity 330. The first heater 410 is controlled to cause the second raw material Y2 on the outer periphery of the separator ring 310 to sublimate. The sublimation atmosphere of the second raw material Y2 is guided by the thermal field and the expansion ring 200 and deposited in the seed crystal fixing region Q. As crystal growth progresses, the second heater 420 is controlled to heat the cover 320 until it melts through or is corroded by the sublimation atmosphere of the second raw material Y2. This allows the sublimation atmosphere of the second raw material Y2 to be added to the crystal growth interface, achieving a two-stage supply of the crystal growth atmosphere. This ensures that the growth atmosphere neither excessively precipitates polycrystalline silicon carbide nor is insufficient for normal diameter expansion growth, stabilizing diameter expansion while guaranteeing crystal quality. Simultaneously, it reduces the temperature gradient at the crystal growth interface. The degree of expansion can improve the resistivity uniformity of each part after crystal diameter expansion; by introducing the third part 323 and the shedding structure 340, and controlling H3 < H1, the cover 320 is allowed to automatically detach downward after decomposition at a predetermined temperature, ensuring that the crystal is not interfered with by the top of the cover 320 when growing vertically; by opening micropores 3211 on the first part 321, a small amount of growth atmosphere can be released, which can accelerate crystal growth and prevent excessive accumulation of growth atmosphere at the growth interface, resulting in polycrystalline growth; and by presetting the porosity of the first part 321, the decomposition rate of the first part 321 can be increased, avoiding incomplete decomposition; by controlling the amount of B4C filled into the micropores 3211, the decomposition of the cover 320 can be accelerated, and the crystal can be prevented from being contaminated to a large extent.

[0056] The specific embodiments described herein are merely illustrative examples of the spirit of this application. Those skilled in the art to which this application pertains may make various modifications or additions to the described specific embodiments or use similar methods to substitute them, without departing from the spirit of this application or exceeding the scope defined by the appended claims.

Claims

1. A silicon carbide crystal growth apparatus, characterized in that, include: A crucible (100) is provided with a seed crystal fixing area (Q) at the top of the crucible (100), the seed crystal fixing area (Q) being used to fix the seed crystal; An expanding ring (200) is disposed on the outer periphery of the seed crystal fixing region (Q). The expanding ring (200) has an inclined surface (210) that extends in a direction away from the seed crystal fixing region (Q). A partition assembly (300), the partition assembly (300) comprising: A partition ring (310) is disposed at the bottom of the crucible (100) and directly opposite the seed crystal fixing area (Q). The outer periphery of the partition ring (310) is opposite to the inclined surface (210). The outer periphery of the partition ring (310) is used to set the first raw material. A cover (320) is connected to the partition ring (310) and is detachably connected. The cover (320) is made of graphite or polycrystalline silicon carbide, and the thickness of the cover (320) is ≤0.5mm. The cover (320) and the partition ring (310) enclose a receiving cavity (330), and the receiving cavity (330) is used to place a second raw material. A heating assembly (400), the heating assembly (400) comprising: A first heater (410) is disposed below the crucible (100) and acts on the outer periphery of the partition ring (310); A second heater (420) is disposed on the inner periphery of the first heater (410) and acts on the receiving cavity (330).

2. The silicon carbide crystal growth apparatus according to claim 1, characterized in that, The cover (320) includes: The first part (321) is connected to the partition ring (310), the thickness of the first part (321) is H1, and the average distance from the first part (321) to the inclined surface (210) is D1; The second part (322) is disposed on the first part (321) and connected to the first part (321), the thickness of the second part (322) is H2, and the shortest distance from the second part (322) to the inclined surface (210) is D2; Wherein, H2 < H1, and D2 < D1.

3. The silicon carbide crystal growth apparatus according to claim 2, characterized in that, The cover (320) further includes a third part (323), which is disposed between the first part (321) and the partition ring (310). The thickness of the third part (323) is H3, where H3 < H1. A detachment structure (340) is formed between the separating ring (310) and the third part (323), the detachment structure (340) allowing the second part (322) to have a vertically downward degree of freedom after the third part (323) is disassembled.

4. The silicon carbide crystal growth apparatus according to claim 3, characterized in that, The cover (320) has a first state and a second state; In the first state, the third part (323) is solid to support the first part (321) and the second part (322), and a guide channel (S) is formed between the first part (321), the second part (322) and the inclined surface (210), and the guide channel (S) extends to the seed crystal fixing area (Q); In the second state, the third part (323) decomposes into a vapor phase, and the first part (321) and the second part (322) have vertically downward degrees of freedom to avoid the crystal growing in the seed crystal fixed region (Q).

5. The silicon carbide crystal growth apparatus according to claim 2, characterized in that, The first part (321) has a plurality of micropores (3211), the pore diameter of the micropores (3211) is ≤10μm, and the porosity of the first part (321) is in the range of 5% to 10%.

6. The silicon carbide crystal growth apparatus according to claim 1, characterized in that, The main material component used in the cover (320) accounts for ≥99.995% of the total material of the cover (320).

7. A method for growing silicon carbide crystals, applied to the silicon carbide crystal growth apparatus as described in any one of claims 1-6, characterized in that, Includes the following steps: Prepare the first raw material, the second raw material, and the cover (320). Connect the cover (320) to the partition ring (310) to form a receiving cavity (330). Enclose the second raw material in the receiving cavity (330) and place the first raw material on the outer periphery of the partition ring (310). Start the first heater (410) and control the temperature of the first heater (410) to T1, so that the first raw material sublimates and is transported along the expansion slope to the surface of the seed crystal for deposition and growth; Start the second heater (420) and control the temperature of the second heater (420) to T2, T2-T1≥80℃, so that the cover (320) decomposes and triggers the sublimation of the second raw material.

8. The silicon carbide crystal growth method according to claim 7, characterized in that, It also includes the following steps: The first heater (410) is controlled to start first, and the second heater (420) is started later. The heating time of the first heater (410) is controlled to be (3-5):

1.

9. The silicon carbide crystal growth method according to claim 7, characterized in that, The "preparation of the first raw material, the second raw material, and the cover (320)" includes: Install the cover (320) and control the minimum distance D between the installation position of the cover (320) and the seed crystal fixing area (Q) to be ≥55mm.

10. The silicon carbide crystal growth method according to claim 7, characterized in that, The "preparation of the first raw material, the second raw material, and the cover (320)" includes: B4C is filled into the micropores (3211) of the cover (320), and the filling amount of B4C is controlled. ,in, V is the porosity of the micropores, V is the volume of the cover (320), and ρ is the density of B4C.

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