Silicon carbide crystal growth device

Abstract

This invention discloses a silicon carbide crystal growth apparatus, comprising: a crucible, a seed crystal holder, silicon carbide powder, a filter plate, and a crucible lid. The crucible has a mouth; the seed crystal holder is disposed inside the crucible, with a seed crystal disposed on the side of the seed crystal holder facing away from the mouth; the silicon carbide powder is disposed inside the crucible and located below the seed crystal, with a powder evaporation zone formed on the side of the silicon carbide powder facing the seed crystal, the diameter ratio of the powder evaporation zone to the seed crystal being D, wherein 1.4 ≤ D ≤ 1.6; the filter plate is disposed inside the crucible and located between the silicon carbide powder and the seed crystal; and the crucible lid is disposed on the mouth of the crucible. This silicon carbide crystal growth apparatus can improve the growth rate of large-size silicon carbide single crystals and control defects such as dislocation density and stacking faults to a low level, thereby meeting the demand for large-size and high-quality silicon carbide single crystals in high-end applications.

Description

Technical Field

[0001] This invention relates to the field of silicon carbide crystal growth technology, and in particular to a silicon carbide crystal growth apparatus. Background Technology

[0002] Silicon carbide (SiC), as a core material for third-generation semiconductors, possesses advantages such as high temperature resistance, high breakdown voltage, and high thermal conductivity, making it indispensable in fields such as new energy vehicles, power electronics, and VR glasses. Currently, physical vapor transport (PVT) is the mainstream technology for preparing large-size SiC single crystals. This is because micro-convex growth allows the Si / C vapor phase components to be transported uniformly along a gentle curved surface, while maintaining the radial temperature gradient within a suitable range to reduce thermal stress concentration and thus suppress impurity aggregation and defect formation. The micro-convex morphology has been proven to be the ideal morphology for high-quality crystals. However, excessively convex growth leads to a sharp increase in the radial temperature gradient, significantly increasing thermal stress and dislocations. Conversely, if the crystal is grown concavely, the transport momentum of the Si / C vapor phase components is insufficient, and airflow stagnation zones are easily formed, causing carbon to accumulate in the center, resulting in severely excessive stacking fault density and phase transition defects.

[0003] The PVT method for growing silicon carbide single crystals currently faces more prominent problems: on the one hand, the growth of large-size silicon carbide, which balances gas phase transport and axial temperature field uniformity, results in a low growth rate; on the other hand, the concave growth trend of large-size silicon carbide crystals is obvious, which leads to problems such as excessive stacking faults, increased phase transformation rate, high dislocation density and concentrated carbon-encapsulated defects, thus limiting the growth quality of large-size single crystals. Summary of the Invention

[0004] The present invention aims to at least solve one of the technical problems existing in the prior art. To this end, one object of the present invention is to provide a silicon carbide crystal growth device that can improve the growth rate of large-size silicon carbide single crystals and control defects such as dislocation density and stacking faults at a low level, so as to meet the demand of high-end applications for large-size and high-quality silicon carbide single crystals.

[0005] A silicon carbide crystal growth apparatus according to an embodiment of the present invention includes: a crucible having a crucible opening; a seed crystal holder disposed inside the crucible, with a seed crystal disposed on the side of the seed crystal holder facing away from the crucible opening; silicon carbide powder disposed inside the crucible and below the seed crystal, with a powder evaporation zone formed on the side of the silicon carbide powder facing the seed crystal, the diameter ratio of the powder evaporation zone to the seed crystal being D, wherein 1.4 ≤ D ≤ 1.6; a filter plate disposed inside the crucible and between the silicon carbide powder and the seed crystal; and a crucible lid covering the crucible opening.

[0006] According to the silicon carbide crystal growth apparatus of the present invention, by controlling the ratio of the diameter of the powder evaporation zone to that of the seed crystal within the range of 1.4 to 1.6, the axial and radial temperature gradients of the seed crystal reach a balanced value, which is beneficial to providing sufficient power for gas phase transport. This satisfies the power requirements of gas phase transport, improves the growth rate of silicon carbide single crystals, and avoids excessive convexity, which would cause the crystal to have a micro-convex state. This is beneficial to controlling defects such as dislocation density and stacking faults at a low level, so as to meet the demand of high-end applications for large-size, high-quality silicon carbide single crystals, and further improve the reliability of the silicon carbide crystal growth apparatus.

[0007] In some embodiments of the present invention, the silicon carbide crystal growth apparatus includes a graphite ring placed on the surface of the silicon carbide powder to shield the edge portion of the silicon carbide powder. The outer ring surface of the graphite ring is in contact with the inner wall surface of the crucible, and the portion of the silicon carbide powder located within the inner ring surface region of the graphite ring forms the powder evaporation zone.

[0008] In some embodiments of the present invention, in the radial direction of the crucible, the graphite ring covers the silicon carbide powder for a length of L, and the radius of the silicon carbide powder is R, wherein 1 / 6 ≤ L / R ≤ 1 / 4.

[0009] In some embodiments of the present invention, the filter plate includes a central portion, an inner ring portion, and an outer ring portion. The inner ring portion is arranged around the central portion, and the outer ring portion is arranged around the inner ring portion. The outer ring portion is fixed to the crucible. The diameter of the central portion is equal to the diameter of the powder evaporation zone. The width of the inner ring portion is equal to the width of the graphite ring. The porosity of the central portion is greater than that of the inner ring portion.

[0010] In some embodiments of the present invention, the porosity of the central portion is 35% to 40%, and the porosity of the inner ring portion is 20% to 25%.

[0011] In some embodiments of the present invention, the central portion is provided with a plurality of first filter holes, and the inner ring portion is provided with a plurality of second filter holes, wherein the orifice area of ​​the first filter holes is larger than the orifice area of ​​the second filter holes.

[0012] In some embodiments of the present invention, the pore widths of the first filter pore and the second filter pore gradually increase in the direction from the seed crystal to the silicon carbide powder.

[0013] In some embodiments of the present invention, the first filter hole and the second filter hole are tapered holes, the bottom edge of the first filter hole is 1.2mm~1.3mm, the top edge of the first filter hole is 0.8mm~0.9mm, and the height of the first filter hole is 0.9mm~1.1mm; the bottom edge of the second filter hole is 1.0mm~1.1mm, the top edge of the second filter hole is 0.6mm~0.7mm, and the height of the second filter hole is 0.9mm~1.1mm.

[0014] In some embodiments of the present invention, the crucible is provided with a first step portion and a second step portion, the first step portion is provided above the second step portion, the edge of the seed crystal holder is provided on the first step portion, and the outer ring portion is provided on the second step portion.

[0015] In some embodiments of the present invention, the silicon carbide crystal growth apparatus includes a graphite cylinder that passes through the central region of the silicon carbide powder, and the edge of the seed crystal holder is provided with a plurality of through holes that are arranged around the seed crystal holder.

[0016] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0017] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, in which:

[0018] Figure 1 A cross-sectional view of a silicon carbide crystal growth apparatus provided in some embodiments of the present invention; Figure 2 A diagram of dislocation data for comparative crystal B provided in related technologies; Figure 3 A diagram of dislocation data for a comparative crystal C provided in related technologies; Figure 4 Dislocation data diagrams of crystal A provided in some embodiments of the present invention; Figure 5 This is a schematic diagram of the structure of a filter plate provided in some embodiments of the present invention; Figure 6 A partial cross-sectional view of a filter plate provided in some embodiments of the present invention; Figure 7 This is a schematic diagram of crystal A provided for some embodiments of the present invention.

[0019] Figure label: 100. Silicon carbide crystal growth apparatus; 10. Crucible; 10a. Crucible opening; 11. First step; 12. Second step; 20. Seed crystal holder; 21. Seed crystal; 30. Silicon carbide powder; 31. Powder evaporation zone; 40. Filter plate; 41. Central part; 41a. First filter hole; 42. Inner ring part; 42a. Second filter hole; 43. Outer ring part; 50. Crucible lid; 60. Graphite ring; 70. Graphite cylinder. Detailed Implementation

[0020] Embodiments of the present invention are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein 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 accompanying drawings are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0021] In the description of this invention, 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," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this invention 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. Therefore, they should not be construed as limitations on this invention.

[0022] Furthermore, features specified as "first" or "second" may explicitly or implicitly include one or more of the same feature, used to distinguish and describe features, without any order or distinction of importance.

[0023] In the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0024] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; 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; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0025] The following is for reference. Figures 1-5 The following describes a silicon carbide crystal growth apparatus 100 according to an embodiment of the present invention.

[0026] like Figure 1 As shown, the silicon carbide crystal growth apparatus 100 of this embodiment includes: a crucible 10, a seed crystal holder 20, silicon carbide powder 30, a filter plate 40, and a crucible lid 50. The crucible 10 has a crucible opening 10a. The seed crystal holder 20 is disposed inside the crucible 10, and a seed crystal 21 is disposed on the side of the seed crystal holder 20 facing away from the crucible opening 10a. The silicon carbide powder 30 is disposed inside the crucible 10 and located below the seed crystal 21. A powder evaporation zone 31 is formed on the side of the silicon carbide powder 30 facing the seed crystal 21, and the diameter ratio of the powder evaporation zone 31 to the seed crystal 21 is D, where 1.4 ≤ D ≤ 1.6. The filter plate 40 is disposed inside the crucible 10 and located between the silicon carbide powder 30 and the seed crystal 21. The crucible lid 50 covers the crucible opening 10a.

[0027] The crucible 10 may refer to a component used for supporting and mounting the structure. The crucible 10 is provided with a crucible opening 10a to facilitate the installation of other components.

[0028] The seed crystal holder 20 can refer to the component that mounts and supports the seed crystal 21, with the seed crystal 21 located on the side of the seed crystal holder 20 facing away from the crucible opening 10a. Optionally, the seed crystal holder 20 and the seed crystal 21 can be connected by adhesive bonding.

[0029] Silicon carbide powder 30 can refer to the raw material of silicon carbide crystals. Silicon carbide powder 30 is placed inside crucible 10 and located below seed crystal 21. A powder evaporation zone 31 is formed on the side of silicon carbide powder 30 facing seed crystal 21. The diameter ratio of powder evaporation zone 31 to seed crystal 21 is D, which can be, but is not limited to, 1.4, 1.5, 1.6, etc.

[0030] The filter plate 40 can refer to a component used to filter gaseous impurities in silicon carbide. The filter plate 40 is disposed inside the crucible 10 and located between the silicon carbide powder 30 and the seed crystal 21. The shape of the filter plate 40 can be, but is not limited to, a circular plate, a square plate, an irregular plate, etc. For example, the filter plate 40 can be a circular plate.

[0031] The crucible lid 50 can refer to the component that covers the opening 10a of the crucible.

[0032] The crucible 10, seed crystal holder 20, filter plate 40, and crucible lid 50 can all be made of graphite. Graphite has excellent high-temperature resistance and chemical stability, enabling it to withstand the high-temperature environment during silicon carbide crystal growth. Furthermore, it is not prone to chemical reactions with silicon carbide gas or other components, thus ensuring the stable operation of the silicon carbide crystal growth device 100 and the quality of the grown silicon carbide crystals. Additionally, although the crucible 10 itself is made of graphite, it has density, allowing gas to diffuse out.

[0033] Additionally, it should be noted that other components and operations of the silicon carbide crystal growth apparatus 100 are known to those skilled in the art and will not be described in detail here. For example, the silicon carbide crystal growth apparatus 100 may also include a heating system, a water cooling system, a gas supply system, and a vacuum system. The heating system mainly consists of induction coils and a medium-frequency power supply, using medium-frequency induction heating to raise the temperature of the thermal field. The water cooling system mainly consists of cooling circulating water, various cooling branches, flow meters, and valves, providing a cooling source for the furnace platform and various branches requiring cooling. The gas supply system mainly consists of various gas supply branches, including a process gas argon system, a nitrogen system, and a compressed air system. The vacuum system mainly consists of a quartz tube, a vacuum pump, and a proportional valve, providing a vacuum environment and pressure control.

[0034] The usage process of the silicon carbide crystal growth device 100 is as follows: After the silicon carbide crystal growth device 100 is assembled, it is transferred to the hot zone and then transferred to the crystal growth furnace for crystal growth. During the silicon carbide crystal growth process, silicon carbide powder 30 sublimates to form silicon carbide gas. The silicon carbide gas is transported upward from the powder evaporation zone 31 and filtered through the filter plate 40 to remove larger particles of impurities in the silicon carbide gas. After the silicon carbide gas is filtered, it continues to be transported upward to the seed crystal 21, where it cools and crystallizes. Excess gas diffuses out from the crucible 10.

[0035] Understandably, the growth rate of small-sized silicon carbide single crystals is higher than that of large-sized single crystals. This is not a problem common to both sizes; the core issue is that large-sized growth, in order to balance temperature field uniformity and crystal integrity, is forced to sacrifice growth rate. For small-sized silicon carbide single crystals, thermal field uniformity is easily achieved, allowing for the use of high axial temperature gradients and high sublimation temperatures to increase growth rate without significantly exacerbating defects, thus balancing rate and quality. For large-sized silicon carbide single crystals, using the same high growth rate as small-sized crystals would directly amplify radial temperature gradients and uneven gas phase transport, leading to a surge in defects such as increased concavity, dislocation multiplication, and carbon encapsulation, resulting in a significant decrease in yield. Therefore, in actual production, it is necessary to reduce the axial temperature gradient and slow down the sublimation and deposition rates to maintain the growth morphology and crystal quality of large-sized single crystals, ultimately resulting in a lower growth rate, which is an inherent technical bottleneck for large-sized growth.

[0036] Furthermore, the growth of large-sized silicon carbide crystals is prone to exacerbated radial temperature gradient imbalance and thermal stress-induced growth anisotropy, leading to a pronounced concave growth trend. This results in problems such as excessive stacking faults, increased phase transformation rate, high dislocation density, and concentrated carbon-encapsulated defects, limiting the growth quality of large-sized single crystals. Specifically, the radial temperature gradient imbalance is exacerbated: the thermal conduction path of the large-sized crucible is longer, the edges near the crucible wall dissipate heat quickly and have a lower temperature, while the center has a higher temperature accumulation, creating a radial temperature difference amplification effect of "high at the center and low at the edge"; the gas phase is easily transported and deposited rapidly to the lower-temperature edges, and the growth rate at the edge of the seed crystal is faster than at the center, ultimately forming a concave surface. In small-sized crystals, the thermal conduction path is shorter, the radial temperature difference is easier to control, and the concave trend is weaker. Thermal stress-induced growth anisotropy: the thermal stress distribution of large-sized single crystals is more uneven, the thermal stress is released quickly at the edges, and the anisotropy of crystal growth is more significant. The concentration of thermal stress at the center inhibits the growth rate, further widening the growth difference of "fast at the edge and slow at the center," forming a concave surface. Large-sized silicon carbide crystals can refer to silicon carbide crystals ranging from 8 inches to 12 inches.

[0037] Furthermore, if D < 1.4, the area of ​​the powder evaporation zone 31 is small, and the axial temperature gradient of the crucible 10 sidewall is significant, resulting in a decrease in the overall axial temperature gradient, a slow growth rate, and a higher likelihood of defects. The core reason for the significant axial temperature gradient of the crucible 10 sidewall is that the powder evaporation zone 31 is too small, amplifying the axial temperature gradient suppression effect of the crucible 10 sidewall. The size of the powder evaporation zone 31 is much smaller than the seed crystal 21, and the powder evaporation zone 31 is completely within the range of thermal radiation / thermal conduction influence of the crucible 10 sidewall. The low-temperature cold source effect of the crucible 10 sidewall (the crucible 10 for silicon carbide single crystal growth is heated by an external induction coil. Although the crucible wall is directly heated to a high temperature by induction, it is also the only radial heat dissipation boundary of the thermal field, possessing the dual attributes of "heating + cold source," which is the root of the cold source effect. Among them, the heating attribute: heat is transferred only to the edge of the attached powder through thermal conduction, belonging to "local contact heating," with an extremely narrow heat transfer range; the cold source attribute: the outer side of the crucible wall is directly exposed to the low temperature of the thermal field) In the contact zone between the high-temperature layer and the vacuum chamber, the high-temperature crucible wall continuously dissipates heat to the outer low-temperature region through thermal radiation and conduction, which is a type of "global radiative heat dissipation," and the heat dissipation rate is much greater than the heat transfer rate to the powder. This heat will directly penetrate into the axial thermal field of the powder-seed crystal 21: the axial temperature gradient of PVT growth relies on the temperature difference between the powder region (high temperature) and the seed crystal 21 region (low temperature) to provide the gas phase transport force. However, the sidewall of crucible 10 is a low-heat-capacity cold region, which will quickly carry away the heat from the powder region, causing the actual temperature of the powder region to decrease, the axial temperature difference between the powder and the seed crystal 21 to narrow significantly, the axial temperature gradient to decrease directly, and the driving force for gas phase sublimation and transport to be insufficient.

[0038] At this point, the radial temperature change of the edge and middle region of seed crystal 21 is as follows: the overall temperature of the center and edge of seed crystal 21 is relatively high, and the radial temperature difference is small (almost no gradient). Due to the low axial temperature gradient and slow gas phase transport rate, the crystallization heat released by the gas phase deposition on the surface of seed crystal 21 cannot be quickly conducted away by the thermal field. In addition, the small powder area causes the gas phase to only uniformly cover the surface of seed crystal 21, with no obvious center-edge gas phase transport difference. Finally, the temperature of the center and edge of seed crystal 21 tends to be consistent, and the radial temperature gradient decreases.

[0039] At this point, the changes in growth rate, defects, and convexity are as follows: 1) Growth rate: The decrease in axial temperature gradient directly leads to a double decrease in the powder sublimation rate and gas phase transport rate, resulting in a significant slowdown in growth rate, far below the requirements for high-speed growth of large-size single crystals; 2) Causes of defects: Under low-speed growth, the crystallization heat on the surface of seed crystal 21 is prone to accumulate, and the migration time of gas phase atoms on the surface of seed crystal 21 is too long, which easily leads to disordered lattice arrangement. At the same time, insufficient axial temperature gradient will lead to uneven transport of gas phase components (Si / C), which easily induces stacking faults, polymorphic inclusions, and microtube defects; in addition, the cold source effect of the sidewall of crucible 10 will cause slight undercooling at the edge of seed crystal 21, which easily leads to dislocation multiplication; 3) Crystal convexity: Since there is no significant difference in temperature and gas phase deposition rate between the center and edge of seed crystal 21, the crystal surface is flat without obvious bumps or depressions. However, the flat surface is prone to local overgrowth due to the accumulation of crystallization heat, inducing defects. At the same time, the comparison crystal B obtained when D < 1.4 can be sliced ​​for inspection to obtain a reference. Figure 2 .

[0040] If D > 1.6, the powder evaporation zone 31 is too large, and the radial temperature gradient at the seed crystal 21 increases with the increase of D value, resulting in increased crystal surface convexity, significantly increased thermal stress, and a corresponding increase in dislocations and defects in the crystal. The core reason for the increase in the radial temperature gradient at the seed crystal 21 with the increase of D value is that the powder evaporation zone 31 is too large, and the radial temperature gradient at the seed crystal 21 increases linearly with the increase of D value. The gas phase in the high-temperature zone at the center of the powder is rapidly transported to the center of the seed crystal 21, where it is deposited and releases a large amount of crystallization heat, causing the temperature at the center of the seed crystal 21 to continue to rise. When the gas phase in the low-temperature zone at the edge of the powder is transported to the edge of the seed crystal 21, due to the long path and large heat loss, the crystallization heat released by the gas phase deposition is less, and the edge of the seed crystal 21 directly faces the cold source radiation of the side wall of the crucible 10, resulting in rapid heat dissipation. Ultimately, the radial temperature difference between the center and the edge of the seed crystal 21 increases with the increase of D value.

[0041] At this point, the changes in growth rate, defects, and convexity are as follows: 1) Growth rate: The powder evaporation zone 31 is large, with sufficient overall sublimation and a high axial temperature gradient. The growth rate at the center of seed crystal 21 is extremely fast, but the growth rate at the edge is significantly lower due to insufficient gas phase transport, exhibiting a non-uniform growth pattern of "fast at the center and slow at the edge"; 2) Defect formation: The excessive radial temperature gradient on the surface of seed crystal 21 generates a significant thermal stress difference, with thermal stress concentration at the center and cold contraction at the edge, inducing dislocations to extend and multiply from the edge to the center; simultaneously, the gas phase atomic arrangement is prone to disorder under high-speed growth at the center, easily forming carbon encapsulation and vacancy defects, while low-speed growth at the edge easily leads to undergrowth and lattice distortion; 3) Crystal convexity: Because the deposition rate at the center of seed crystal 21 is much faster than at the edge, the crystal surface will continuously convex towards the center of seed crystal 21 over time, and the convexity increases sharply with the increase of D value. Excessive convexity will lead to further accumulation of thermal stress at the center of seed crystal 21, and may even cause crystal cracking. At the same time, the comparison crystal C obtained when D>1.6 can be sliced ​​for inspection to obtain a reference. Figure 3 .

[0042] Therefore, considering the above factors, with 1.4 ≤ D ≤ 1.6, a basic temperature field of "central heat accumulation and edge gradient heat dissipation" is constructed. This satisfies the axial temperature gradient required for growth while mitigating the radial temperature gradient, providing a suitable thermal field foundation for subsequent convexity and defect control. For example, the ratio (D) of the diameter of the powder evaporation zone 31 to the diameter of the seed crystal 21 is set to 1.5. The bottom heat radiation received by the powder center is superimposed with the reverse heat radiation from the crystallization of the seed crystal 21, while reducing the heat loss from the center to the side wall of the crucible 10. This achieves high-temperature heat accumulation at the center of the powder, ensuring high-temperature and high-sublimation heat input. The outer edge of the powder (close to the crucible wall) is in contact with the crucible wall and has a slightly higher temperature, but only a small amount of gradient heat radiation occurs to the cold area of ​​the side wall of the crucible 10. The heat dissipation rate forms a gradient heat dissipation characteristic with the heat dissipation rate gradually increasing from the inside to the outside, avoiding excessive sublimation at the edge caused by sudden heating of the crucible wall. This basic temperature field not only establishes a suitable axial temperature gradient between the powder region and the seed crystal 21 region, providing sufficient thermal power for vapor sublimation, transport, and deposition to meet the rate requirements of single crystal growth, but also regulates the radial thermal gradient of the powder region to a moderate range, simultaneously mitigating the radial temperature gradient in the seed crystal 21 region. This fundamentally avoids the problem of excessive growth rate differences caused by steep radial temperature gradients, laying a suitable and stable thermal field foundation for subsequent precise control of crystal convexity and defect suppression. Simultaneously, crystal A with 1.4 ≤ D ≤ 1.6 was sliced ​​for inspection, obtaining reference values. Figure 4 .

[0043] In the above technical solutions, refer to Figures 2 to 4 The screw dislocation density (TSD) of crystal A relative to comparative crystals B and C is 0ea / The basal dislocation density (BPD) is 71ea / The ductile dislocation density (TED) is 627ea / The total dislocation density (SUM) is 699ea / The data is superior and the effect is obvious. According to the silicon carbide crystal growth apparatus 100 of this embodiment, by controlling the diameter ratio of the powder evaporation zone 31 and the seed crystal 21 within the range of 1.4 to 1.6, the axial and radial temperature gradients of the seed crystal 21 reach a balanced value. This facilitates providing sufficient power for gas phase transport, satisfying the power requirements of gas phase transport and increasing the growth rate of silicon carbide single crystals. It also avoids excessive convexity, which would cause the crystal to exhibit a micro-convex state. This helps to control defects such as dislocation density and stacking faults at a low level, meeting the demand for large-size, high-quality silicon carbide single crystals in high-end applications, and further improving the reliability of the silicon carbide crystal growth apparatus 100.

[0044] In some embodiments of the present invention, reference is made to Figure 1 The silicon carbide crystal growth apparatus 100 includes a graphite ring 60, which is placed on the surface of silicon carbide powder 30 to shield the edge portion of silicon carbide powder 30. The outer ring surface of the graphite ring 60 is in contact with the inner wall surface of the crucible 10. The portion of silicon carbide powder 30 located in the inner ring surface area of ​​the graphite ring 60 forms a powder evaporation zone 31.

[0045] In the above technical solution, the graphite ring 60 can suppress excessive sublimation in the edge region of the powder. The inner diameter of the graphite ring 60 is consistent with the diameter of the powder evaporation zone 31. This matching of the inner diameter of the graphite ring 60 and the diameter of the powder evaporation zone 31 allows for precise fit to the outer contour of the powder evaporation zone 31, achieving a heat control effect of "full exposure at the center and circumferential coverage at the edges." This ensures unobstructed heat radiation in the central region of the powder, laying the foundation for uniform sublimation. Conversely, if the inner diameter of the graphite ring 60 is too small or too large, it will lead to obstruction of the central hot zone of the powder or failure of edge heat control, exacerbating uneven gas phase distribution.

[0046] Furthermore, the graphite ring 60 has the following effect on the temperature of the central region of the seed crystal 21: It does not significantly decrease or increase the temperature, maintaining a stable temperature. It only acts on the edge of the powder evaporation zone 31 and does not change the thermal accumulation state of the powder center. Therefore, it has no direct temperature control effect on the central region of the seed crystal 21. The graphite ring 60 has the following effect on the temperature of the edge region of the seed crystal 21: It significantly increases the edge temperature, providing thermal insulation and reducing heat loss from the powder edge. Simultaneously, the graphite ring 60 covers the edge of the powder evaporation zone 31, and its high thermal conductivity and low radiation loss characteristics reduce heat conduction / radiation from the powder edge to the sidewall of the crucible 10, increasing the actual temperature of the powder edge and raising the gas phase temperature transported to the edge of the seed crystal 21 from the source.

[0047] In the above technical solution, the graphite ring 60 is used to shield the edge of the silicon carbide powder 30. No powder sublimation occurs at the covered area, and graphite has a thermal conductivity, which increases the temperature of the powder near the crucible wall. On the one hand, it maintains the driving force for axial transport of the gas phase and increases the growth rate of silicon carbide crystals. On the other hand, it avoids thermal stress concentration caused by excessive radial temperature gradient at the seed crystal 21, improves the growth quality of silicon carbide crystals, and further improves the reliability of the silicon carbide crystal growth device 100.

[0048] In some embodiments of the present invention, reference is made to Figure 1 In the radial direction of the crucible 10, the graphite ring 60 covers the silicon carbide powder 30 for a length of L, and the radius of the silicon carbide powder 30 is R, where 1 / 6≤L / R≤1 / 4.

[0049] L / R can be, but is not limited to, 1 / 6, 1 / 5, 1 / 4, etc.

[0050] Understandably, when L / R < 1 / 6, the amount of powder sublimation at the edge of the powder evaporation zone 31 increases, leading to a higher deposition rate at the edge of the seed crystal 21, approaching the deposition rate at the center of the seed crystal 21. This results in a decrease in crystal convexity and may even form a concave surface. Conversely, when L / R > 1 / 4, the amount of powder sublimation at the edge of the powder evaporation zone 31 decreases significantly, resulting in a higher vapor deposition rate at the center of the seed crystal 21 than at the edge. This leads to an increase in crystal convexity, as well as an increase in the number of stacking faults and the dislocation density.

[0051] In the above technical solution, by setting L / R in the range of 1 / 6 to 1 / 4, the heat conduction and powder sublimation inhibition effect of the graphite ring 60 can be used to reduce the heat loss of the edge powder and reduce the radial temperature gradient. This allows the amount of powder sublimation at the edge of the powder evaporation zone 31 to be at an appropriate value, making the vapor deposition rate at the center of the seed crystal 21 slightly greater than that at the edge of the seed crystal 21. This results in the silicon carbide crystal growing in a micro-convex state, reducing the number of stacking faults and dislocation density, improving the growth quality of the silicon carbide crystal, and further enhancing the reliability of the silicon carbide crystal growth device 100.

[0052] In some embodiments of the present invention, reference is made to Figure 1 and Figure 5 The filter plate 40 includes a central portion 41, an inner ring portion 42, and an outer ring portion 43. The inner ring portion 42 is arranged around the central portion 41, and the outer ring portion 43 is arranged around the inner ring portion 42. The outer ring portion 43 is fixed to the crucible 10. The diameter of the central portion 41 is equal to the diameter of the powder evaporation zone 31. The width of the inner ring portion 42 is equal to the width of the graphite ring 60. The porosity of the central portion 41 is greater than that of the inner ring portion 42.

[0053] In the above technical solution, the diameter of the central portion 41 is equal to the diameter of the powder evaporation zone 31, and the width of the inner ring portion 42 is equal to the width of the graphite ring 60. Furthermore, the porosity of the central portion 41 is greater than that of the inner ring portion 42. This allows control over the gas phase flow rate of the central portion 41 and the inner ring portion 42, ensuring that the gas phase deposition rate at the center of the seed crystal 21 is greater than that at the edge of the seed crystal 21. This prevents the crystal from exhibiting reduced convexity or a concave surface, thus improving the growth quality of the silicon carbide crystal. The equal width of the inner ring portion 42 and the graphite ring 60 also allows for matching of the gas phase flow between the graphite ring 60 and the filter plate 40, which is beneficial for ensuring controllable crystal morphology.

[0054] In some embodiments of the present invention, reference is made to Figure 1 and Figure 5 The porosity of the central part 41 is 35%~40%, and the porosity of the inner ring part 42 is 20%~25%.

[0055] The porosity of the central portion 41 can be, but is not limited to, 35%, 36%, 37%, 38%, 39%, 40%, etc.

[0056] The porosity of the inner ring portion 42 can be, but is not limited to, 20%, 21%, 22%, 23%, 24%, 25%, etc.

[0057] In the above technical solution, the porosity of the central portion 41 is 35%~40%, and the porosity of the inner ring portion 42 is 20%~25%. This allows the porosity of the central portion 41 and the inner ring portion 42 to be within an appropriate range, precisely controlling the gas phase flow rate of the central portion 41 and the inner ring portion 42. This ensures sufficient gas phase flow in the central region of the seed crystal 21 to maintain a high growth rate. At the same time, the lower porosity of the inner ring portion 42 appropriately limits the gas phase flow in the edge region, preventing the edge growth rate from being too fast and causing the formation of concave surfaces. This further optimizes the radial growth uniformity of the crystal, keeps the silicon carbide crystal surface in a stable micro-convex state, effectively reduces thermal stress and defects caused by excessive differences in growth rates, and improves the growth quality of large-size silicon carbide single crystals.

[0058] In some embodiments of the present invention, reference is made to Figure 5 and Figure 6 The central part 41 is provided with a plurality of first filter holes 41a, and the inner ring part 42 is provided with a plurality of second filter holes 42a. The orifice area of ​​the first filter holes 41a is larger than the orifice area of ​​the second filter holes 42a.

[0059] The number of first filter holes 41a can be, but is not limited to, two, three, four, five, etc.

[0060] The number of second filter holes 42a can be, but is not limited to, two, three, four, five, etc.

[0061] The diameter of the central portion 41 is equal to that of the powder evaporation zone 31, and the width of the inner ring portion 42 is equal to that of the graphite ring 60. The core function of the large-pore area in the central portion 41 is to match the high-concentration gas phase transport in the center of the powder. Its diameter is consistent with the previous two, enabling precise correspondence between the filtration control area and the powder sublimation heat zone and the heat control boundary of the graphite ring 60. This allows the large-pore area to completely cover the high sublimation area of ​​the powder, maximizing the reduction of gas phase transport resistance. The small-pore area in the inner ring portion 42 precisely connects to the powder edge area covered by the graphite ring 60, specifically controlling the low-concentration gas phase. This avoids airflow deviation and stagnation caused by misalignment between the filtration area and the gas phase distribution area, increasing the probability of intercepting low-concentration carbon particles. Simultaneously, through structural synergy, it guides uniform gas phase transport, ensuring a gas phase throughput of ≥95%, significantly reducing the density of carbon encapsulation defects. Furthermore, in conjunction with the previous two, it further balances the deposition rate, guiding the crystal to form a micro-convex ideal surface, reducing the number of dislocations to below 2000, and significantly improving the crystallization quality of 8-inch single crystals. For example, refer to... Figure 7 The 8-inch crystals grown using this process exhibit a slightly convex shape, and refer to... Figure 4 The dislocation density is less than 2000 and the crystal has an encapsulation area of ​​less than 1% of the area. The stacking fault and other data meet the high standards required for epitaxy.

[0062] In the above technical solution, the orifice area of ​​the first filter hole 41a is larger than that of the second filter hole 42a. On the one hand, the powder sublimates quickly in the central region, and the larger first filter hole 41a can accommodate the high-concentration gas phase, reducing transport resistance and avoiding excessive radial temperature gradient caused by thermal accumulation, which can lead to defects such as stacking faults and dislocations, thereby improving the growth rate and quality of silicon carbide crystals. On the other hand, the central region has a large number of carbon particles, and the large pores can reduce the agglomeration and deposition of carbon particles in the channels, improving the reliability of the filter plate 40. Moreover, the powder at the edge of the powder evaporation zone 31 is restricted by the graphite ring 60, resulting in a low gas phase concentration. The small edge pores are just right to accommodate the low-concentration gas phase, which can moderately increase the airflow resistance at the edge and guide the edge gas phase to uniformly cover the edge of the seed crystal 21, reducing the radial temperature gradient. In addition, the secondary edge has fewer carbon particles, and the small pores can fully contact the carbon particles without affecting the gas phase transport, achieving a highly efficient interception effect.

[0063] Specifically, the large central pores are adapted to the high flow rate characteristics of the high-concentration gas phase at the center of the powder, allowing carbon particles to "flow smoothly with the gas phase without stagnation," fundamentally preventing carbon particle agglomeration. Simultaneously, the adsorption layer on the pore wall achieves precise interception, completely avoiding the encapsulation problem caused by free carbon. Furthermore, the upper surface of the filter plate 40 is coated with tantalum carbide to intercept carbon particles. Even when the powder sublimates slowly, the carbon particles will have more sufficient contact with the tantalum carbide, and the large pores will not clog them, thus not affecting subsequent airflow transport.

[0064] Furthermore, the radial temperature difference (temperature gradient) in the seed crystal 21 region is primarily determined by the distribution of crystallization heat release from vapor deposition. The temperature of the large-size seed crystal 21 region is not solely determined by thermal radiation; the crystallization heat released from vapor deposition is the main source of temperature in the seed crystal 21 region. At the center of the seed crystal 21, due to the rapid deposition of a high-concentration vapor phase, crystallization heat is concentrated and released in large quantities, resulting in a continuously rising temperature. At the edges of the seed crystal 21, due to poor transport of a low-concentration vapor phase, deposition is discontinuous, crystallization heat release is less and more dispersed, and the temperature is lower. This is the core internal factor contributing to the formation of the radial temperature gradient in the seed crystal 21. The design of the small holes at the edge of the filter plate 40 optimizes the vapor phase deposition state at the edge, making the release of crystallization heat at the edge more stable and sufficient, thus reducing the temperature difference with the center from an internal perspective and achieving a lower temperature gradient. The small holes at the edge increase airflow resistance, changing the low-concentration vapor phase from "rapid flow" to "uniform spreading," avoiding edge deposition gaps and insufficient crystallization heat release. After the graphite ring 60 is restricted, the gas phase concentration of the edge powder is already low. If there is no resistance at the edge of the filter plate 40 (large holes), the low-concentration gas phase will flow directly to the center of the seed crystal 21 due to the strong suction effect of the high-concentration gas phase in the center. This will further reduce the gas phase supply at the edge of the seed crystal 21, resulting in very little heat release during crystallization, a continuous drop in temperature, and a further widening of the temperature difference with the center.

[0065] In some embodiments of the present invention, reference is made to Figure 6 In the direction from the seed crystal 21 to the silicon carbide powder 30, the pore width of the first filter hole 41a and the second filter hole 42a gradually increases.

[0066] In the above technical solution, the widths of the first filter hole 41a and the second filter hole 42a gradually increase, with the larger hole near the powder evaporation zone 31. This allows for the full acceptance of high-concentration gaseous components of the powder, reducing the impact force on the pores and improving the reliability of the filter plate 40. Utilizing the high inertia of carbon particles enhances the interception effect. Compared to cylindrical pores, this avoids pore blockage. Furthermore, the narrow upper portion of the hole effectively constrains the gas phase, preventing amorphous deposition of components at the seed crystal 21. Simultaneously, the narrow upper and wide lower design optimizes airflow uniformity, to some extent assisting in the growth of micro-convex crystals, reducing stacking faults and dislocation density, and improving the growth quality of silicon carbide single crystals.

[0067] In some embodiments of the present invention, reference is made to Figure 6 The first filter hole 41a and the second filter hole 42a are tapered holes. The bottom edge of the first filter hole 41a is 1.2mm~1.3mm, the top edge of the first filter hole 41a is 0.8mm~0.9mm, and the height of the first filter hole 41a is 0.9mm~1.1mm. The bottom edge of the second filter hole 42a is 1.0mm~1.1mm, the top edge of the second filter hole 42a is 0.6mm~0.7mm, and the height of the second filter hole 42a is 0.9mm~1.1mm.

[0068] In the above technical solution, the first filter hole 41a and the second filter hole 42a are tapered holes, which have a simple structure and are easy to process and manufacture. Moreover, the range of their dimensions can be designed to adapt to different D values, fully accept the high concentration of gas phase components of the powder, reduce the impact force on the pores, and improve the reliability of the filter plate 40.

[0069] In some embodiments of the present invention, reference is made to Figure 1 The crucible 10 is provided with a first step portion 11 and a second step portion 12. The first step portion 11 is located above the second step portion 12. The edge of the seed crystal holder 20 is located on the first step portion 11, and the outer ring portion 43 is located on the second step portion 12.

[0070] In the above technical solution, the edge of the seed crystal holder 20 is located on the first step 11, and the outer ring portion 43 is located on the second step 12. This provides a stable support platform for the seed crystal holder 20, ensuring that the seed crystal 21 is in the preset growth position. Furthermore, the second step 12 precisely limits the outer ring portion 43 of the filter plate 40, ensuring that the positional correspondence between the center portion 41 and the inner ring portion 42 of the filter plate 40 and the powder evaporation zone 31 and graphite ring 60 remains consistent. This stabilizes the gas phase transport path and throughput, ensuring the stability and consistency of crystal growth parameters, and further improving the reliability of the silicon carbide crystal growth device 100. Simultaneously, the structure is simple and easy to install.

[0071] In some embodiments of the present invention, reference is made to Figure 1 The silicon carbide crystal growth device 100 includes a graphite cylinder 70, which is inserted into the central region of the silicon carbide powder 30. The edge of the seed crystal holder 20 is provided with multiple through holes, which are arranged around the seed crystal holder 20.

[0072] The number of through holes can be, but is not limited to, two, four, six, eight, ten, twelve, etc. For example, the number of through holes is twelve, and the diameter of the through holes is 3mm.

[0073] Understandably, the hollow channel inside the graphite cylinder 70 enhances bottom thermal radiation, eliminating the thermal barrier of the solid graphite pillar. This allows the thermal radiation from the graphite heating element at the bottom of the crucible 10 to directly reach the center of the powder through the hollow channel, raising the center temperature of the powder to a stable sublimation range of 2200-2250℃, thus thermodynamically preventing gas phase condensation and crystallization. Simultaneously, the graphite cylinder 70 and graphite ring 60 provide gas phase confinement: the hollow graphite pillar enhances central sublimation, while the graphite ring 60, with its larger surface area at the powder edge, suppresses excessive diffusion of the gas phase at the edge. This allows the gas phase to be uniformly transported along the "center → edge" path to the seed crystal 21, reducing condensation losses in the cold zone of the hot zone and increasing the effective deposition ratio of the gas phase.

[0074] In the above technical solution, the edge of the seed crystal holder 20 is provided with multiple through holes to balance the concentration of the gas phase at the seed crystal 21. The graphite cylinder 70 is inserted into the central area of ​​the silicon carbide powder 30, which can improve the powder utilization rate and alleviate the crystallization phenomenon caused by the low temperature at the center of the powder.

[0075] The following is combined with Figure 1 , Figure 5 and Figure 6 This describes a specific embodiment of the silicon carbide crystal growth apparatus 100 of the present invention.

[0076] The silicon carbide crystal growth apparatus 100 includes: a crucible 10, a seed crystal holder 20, silicon carbide powder 30, a filter plate 40, a crucible cover 50, a graphite ring 60, and a graphite cylinder 70.

[0077] The crucible 10 has a crucible opening 10a, a first step 11 and a second step 12. The first step 11 is located above the second step 12. The edge of the seed crystal holder 20 is located on the first step 11, and the outer ring portion 43 is located on the second step 12.

[0078] The seed crystal holder 20 is located inside the crucible 10, and the seed crystal 21 is provided on the side of the seed crystal holder 20 facing away from the crucible opening 10a.

[0079] Silicon carbide powder 30 is placed inside crucible 10 and located below seed crystal 21. A powder evaporation zone 31 is formed on the side of silicon carbide powder 30 facing seed crystal 21. The diameter ratio of powder evaporation zone 31 to seed crystal 21 is D, where D=1.5.

[0080] The filter plate 40 includes a central portion 41, an inner ring portion 42, and an outer ring portion 43. The inner ring portion 42 is arranged around the central portion 41, and the outer ring portion 43 is arranged around the inner ring portion 42. The outer ring portion 43 is fixed to the crucible 10. The diameter of the central portion 41 is equal to the diameter of the powder evaporation zone 31, and the width of the inner ring portion 42 is equal to the width of the graphite ring 60. The porosity of the central portion 41 is greater than that of the inner ring portion 42. The porosity of the central portion 41 is 38%, and the porosity of the inner ring portion 42 is 23%. The central portion 41 is provided with a plurality of first filter holes 41a, and the inner ring portion 42 is provided with a plurality of second filter holes 42a. The first filter holes 41a and the second filter holes 42a are tapered holes. The bottom edge of the first filter hole 41a is 1.2mm, the top edge of the first filter hole 41a is 0.8mm, and the height of the first filter hole 41a is 1.0mm. The bottom edge of the second filter hole 42a is 1mm, the top edge of the second filter hole 42a is 0.6mm, and the height of the second filter hole 42a is 1mm.

[0081] The crucible lid 50 is placed on the crucible opening 10a.

[0082] A graphite ring 60 is placed on the surface of the silicon carbide powder 30 to shield the edge portion of the silicon carbide powder 30. The outer ring surface of the graphite ring 60 contacts the inner wall surface of the crucible 10, and the portion of the silicon carbide powder 30 located within the inner ring surface region of the graphite ring 60 forms the powder evaporation zone 31. In the radial direction of the crucible 10, the length of the silicon carbide powder 30 covered by the graphite ring 60 is L, and the radius of the silicon carbide powder 30 is R, where L / R = 1 / 5.

[0083] The graphite cylinder 70 is inserted into the central area of ​​the silicon carbide powder 30, and the edge of the seed crystal holder 20 is provided with multiple through holes, which are arranged around the seed crystal holder 20.

[0084] In the description of this specification, references to terms such as "some embodiments," "optionally," "furthermore," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0085] Although embodiments of the invention have been shown and described, those skilled in the art will understand that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the claims and their equivalents.

Claims

1. A silicon carbide crystal growth apparatus, characterized in that, include: A crucible, wherein the crucible is provided with a rim; A seed crystal holder is disposed inside the crucible, and a seed crystal is provided on the side of the seed crystal holder facing away from the mouth of the crucible; Silicon carbide powder is disposed in the crucible and located below the seed crystal. A powder evaporation zone is formed on the side of the silicon carbide powder facing the seed crystal. The diameter ratio of the powder evaporation zone to the seed crystal is D, where 1.4 ≤ D ≤ 1.

6. A filter plate is disposed inside the crucible and located between the silicon carbide powder and the seed crystal; A crucible lid, which is placed over the opening of the crucible.

2. The silicon carbide crystal growth apparatus according to claim 1, characterized in that, The device includes a graphite ring placed on the surface of the silicon carbide powder to shield the edge portion of the silicon carbide powder. The outer ring surface of the graphite ring is in contact with the inner wall surface of the crucible. The portion of the silicon carbide powder located within the inner ring surface area of ​​the graphite ring forms the powder evaporation zone.

3. The silicon carbide crystal growth apparatus according to claim 2, characterized in that, In the radial direction of the crucible, the graphite ring covers the silicon carbide powder for a length of L, and the radius of the silicon carbide powder is R, where 1 / 6 ≤ L / R ≤ 1 / 4.

4. The silicon carbide crystal growth apparatus according to claim 2, characterized in that, The filter plate includes a central portion, an inner ring portion, and an outer ring portion. The inner ring portion is arranged around the central portion, and the outer ring portion is arranged around the inner ring portion. The outer ring portion is fixed to the crucible. The diameter of the central portion is equal to the diameter of the powder evaporation zone. The width of the inner ring portion is equal to the width of the graphite ring. The porosity of the central portion is greater than that of the inner ring portion.

5. The silicon carbide crystal growth apparatus according to claim 4, characterized in that, The porosity of the central portion is 35% to 40%, and the porosity of the inner ring portion is 20% to 25%.

6. The silicon carbide crystal growth apparatus according to claim 4 or 5, characterized in that, The central portion is provided with a plurality of first filter holes, and the inner ring portion is provided with a plurality of second filter holes, wherein the orifice area of ​​the first filter holes is larger than the orifice area of ​​the second filter holes.

7. The silicon carbide crystal growth apparatus according to claim 6, characterized in that, In the direction from the seed crystal to the silicon carbide powder, the pore widths of the first filter hole and the second filter hole gradually increase.

8. The silicon carbide crystal growth apparatus according to claim 7, characterized in that, The first filter hole and the second filter hole are tapered holes. The bottom edge of the first filter hole is 1.2mm~1.3mm, the top edge of the first filter hole is 0.8mm~0.9mm, and the height of the first filter hole is 0.9mm~1.1mm. The bottom edge of the second filter hole is 1.0mm~1.1mm, the top edge of the second filter hole is 0.6mm~0.7mm, and the height of the second filter hole is 0.9mm~1.1mm.

9. The silicon carbide crystal growth apparatus according to claim 4, characterized in that, The crucible has a first step and a second step, the first step is located above the second step, the edge of the seed crystal holder is located on the first step, and the outer ring is located on the second step.

10. The silicon carbide crystal growth apparatus according to claim 1, characterized in that, It includes a graphite cylinder, which is inserted into the central region of the silicon carbide powder, and the edge of the seed crystal holder is provided with multiple through holes, which are arranged around the seed crystal holder.

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