Silicon carbide crystal growth crucible suitable for resistance method

Abstract

The invention relates to a silicon carbide crystal growth crucible suitable for a resistance method, and belongs to the technical field of semiconductor material preparation. The crucible comprises a side wall, a bottom, an upper cover and an inner cavity defined by the side wall and the bottom. The side walls comprise the upper side wall and the lower side wall, and the inner cavity is correspondingly divided into an upper cavity and a lower cavity. The upper cavity is an equal-diameter cylinder, and the lower cavity is in a frustum shape which is gradually expanded from top to bottom. The structure can obviously optimize the thermal field distribution of a raw material area, increase the axial temperature gradient to strengthen the conveying power, reduce the radial temperature gradient, effectively inhibit parasitic crystallization on the surface of powder, and improve the raw material utilization rate and the gas-phase conveying stability. Through active geometric design, a thermal field, a flow field and a material field are cooperatively regulated and controlled, key equipment support is provided for growth of high-quality and large-size silicon carbide single crystals, and the method has important engineering value for promoting industrial development of wide bandgap semiconductors.

Description

Technical Field

[0001] This invention relates to the design of a crucible device in the silicon carbide single crystal growth process, and more particularly to a silicon carbide crystal growth crucible suitable for the resistance method, belonging to the field of semiconductor material preparation technology. Background Technology

[0002] Traditional semiconductors are based on silicon, and their performance is closely related to the bonding characteristics at the atomic level. Silicon belongs to Group 4 of the periodic table, with four electrons in its outermost shell. It tends to form a tetrahedral structure through covalent bonds. Furthermore, silicon is located in the third period, with one more electron shell than carbon in the second period. This weakens the attraction of the silicon nucleus to the outer valence electrons due to increased distance and shielding by the inner electrons, resulting in a larger atomic radius and ultimately longer Si-Si bond lengths and lower bond energies. This weaker bonding makes silicon crystals susceptible to instability at higher temperatures due to increased atomic vibrations and even bond breakage. Moreover, its band gap of only about 1.12 eV and narrow potential barrier make devices prone to thermally excited carriers under high temperatures or strong electric fields, leading to a surge in leakage current and making it unsuitable for high-temperature, high-voltage, and high-power applications.

[0003] In comparison, although carbon and silicon both belong to Group IV, carbon has a smaller atomic radius and stronger nuclear-electron binding force, resulting in a C-C bond energy as high as 347 kJ / mol. In silicon carbide, carbon and silicon form C-Si covalent bonds through sp³ hybridization. This retains the strong binding properties of carbon while the small atomic radius and strong electronegativity of carbon shorten the bond length, increasing the C-Si bond energy to approximately 318 kJ / mol (significantly higher than the ~220 kJ / mol of Si-Si bonds, but lower than the ~347 kJ / mol of C-C bonds). This stronger covalent bonding endows SiC with higher lattice bonding strength (Debye temperature of approximately 1200 K, far exceeding silicon's 645 K) and lower lattice vibration amplitude. At the atomic level, breaking its lattice or exciting charge carriers requires higher energy. Therefore, the band gap of SiC is significantly widened to 2.3–3.3 eV (e.g., approximately 3.26 eV for 4H-SiC). This characteristic directly translates into practical advantages: the wide bandgap raises the electron transition barrier, making the critical breakdown electric field of SiC 10 times that of silicon; strong bonding promotes efficient phonon heat transfer, resulting in a thermal conductivity (approximately 490 W / (m·K)) far exceeding that of silicon (approximately 150 W / (m·K)); under certain crystal forms, the effective electron mass is small, scattering is weak, and drift velocity is higher; the lattice is more stable and can withstand high temperatures of several hundred degrees Celsius. These advantages make SiC naturally suitable for high-temperature, high-frequency, and high-power requirements, becoming a new choice to break through the performance limits of silicon-based materials. Currently, the mainstream method for growing single crystals is the physical vapor transport (PVT) method, among which the resistance heating method, due to its higher and more uniform temperature and significant diameter expansion advantages, is driving the development of SiC towards larger sizes, further releasing the potential endowed by atomic properties.

[0004] The basic principle of resistance heating is as follows: silicon carbide powder raw material is placed in the high-temperature zone of a graphite crucible. The outside of the graphite crucible is a conductor with resistance (heater). Current passes through the heater and converts electrical energy into heat energy, thereby causing the raw material to sublimate at high temperature, producing a gaseous component containing silicon vapor (Si, Si2, Si3), silicon carbide molecules (SiC, Si2C, SiC2), and carbon vapor (C, C2, C3). Under the action of the temperature gradient, these gaseous components diffuse to the relatively low-temperature seed crystal region and condense and crystallize on the surface of the seed crystal to grow silicon carbide single crystals.

[0005] During silicon carbide crystal growth, the thermal field structure determines the distribution of the entire temperature field, affecting the radial and axial temperature gradients, thereby influencing the sublimation and crystallization of the gas phase components. This plays a crucial role in the quality, rate, and stability of crystal growth.

[0006] The traditional crucible thermal field used for crystal growth is a simple cylindrical container. The lower part is filled with silicon carbide powder (high temperature zone), the upper part is equipped with a seed crystal (low temperature zone), the middle is a cavity, and the outside is a heater. When current passes through the heater, the resistance is converted into heat energy. At high temperature, the silicon carbide powder sublimates, and the various gas phase components are transported to the seed crystal under the action of the axial temperature gradient and crystallize upon cooling, thereby growing silicon carbide single crystals.

[0007] For example, the invention patent with authorization announcement number CN 112609238 B discloses a crucible, apparatus, and application for N-type silicon carbide single crystal growth. The crucible includes sidewalls, a bottom, and an inner cavity enclosed by the sidewalls and bottom. The crucible also includes a top cover for sealing the inner cavity. At least a portion of the sidewalls is made of a permeable graphite material used to permeate nitrogen gas into the silicon carbide single crystal. Although it improves upon traditional crucibles by using the graphite walls of the crucible sidewalls to permeate nitrogen gas during PVT crystal growth to balance the uneven nitrogen doping and resistivity distribution caused by the radial and axial temperature gradients in PVT silicon carbide crystal growth, the crucible body is essentially still a simple cylindrical container.

[0008] This type of crucible thermal field has certain shortcomings. First, in silicon carbide PVT crystal growth, the axial temperature gradient (ΔTz) and radial temperature gradient (ΔTr) are the two most crucial and fundamental thermal parameters controlling the entire growth process. ΔTz is the temperature difference along the growth axis (from powder to seed crystal), and it is the fundamental driving force for the physical vapor transport (PVT) process. Without the axial temperature gradient, gaseous matter cannot be transported, and crystal growth will stop. ΔTr is the temperature distribution difference perpendicular to the growth axis within the plane of the growth interface (seed crystal surface), which determines the shape of the crystal growth interface (concave, convex, flat). In the powder region of a traditional crucible, because the heater is on the outside of the crucible, there is a natural radial temperature difference (hot at the edges, cold in the middle); due to the different heat outputs in different areas of the heater, there is also an axial temperature difference in the powder region (hot at the bottom, cold at the top). Under such circumstances, a local "low-temperature zone" will form in the central area of ​​the upper surface of the powder, causing the temperature there to reach the condensation point of the SiC gaseous components, thus making crystallization easy to occur in this area.

[0009] This phenomenon means that the gaseous material that should be transported to the seed crystal region for crystallization crystallizes directly on the surface of the powder, greatly reducing the utilization rate of raw materials. Furthermore, because the gaseous components are "intercepted" midway, less gaseous material is transported to the seed crystal region, significantly slowing down the crystal growth rate and thus prolonging the growth cycle, leading to increased costs. More seriously, crystallization on the powder surface alters the geometry and thermal radiation characteristics of the cavity's inner surface, disrupting the established temperature and convection fields; affecting the internal temperature distribution and sublimation rate of the powder, causing fluctuations in the sublimation process, thereby disrupting stable growth conditions, increasing the probability of heterogeneous nucleation during crystallization, increasing defect generation, and affecting product quality and yield. Summary of the Invention

[0010] To address the above problems, the present invention provides a silicon carbide crystal growth crucible suitable for the resistance method.

[0011] The technical solution of the present invention to solve the above problems is as follows:

[0012] A silicon carbide crystal growth crucible suitable for resistance method includes sidewalls, a bottom, and an inner cavity enclosed by the sidewalls and the bottom, and also includes a top cover for sealing the inner cavity; the sidewalls include an upper sidewall and a lower sidewall, such that the inner cavity is divided into an upper cavity corresponding to the upper sidewall and a lower cavity corresponding to the lower sidewall; the diameter of the upper cavity is constant with height; the diameter of the lower cavity varies with height, specifically gradually decreasing from bottom to top until it is equal to the diameter of the upper cavity.

[0013] This invention provides an innovative crucible structure specifically for silicon carbide (SiC) crystal growth using the resistance heating method. This solution is not a simple improvement on traditional crucibles, but rather a proactive, structured solution for controlling the thermal and material fields based on a deep understanding of the atomic-level bonding characteristics of SiC, the physical mechanism of PVT growth, and the core challenges of current processes. Its fundamental goal is to resolve the irreconcilable process contradictions inherent in the "simple container" structure of traditional cylindrical crucibles when pursuing large-size, high-quality SiC single crystal growth, thereby simultaneously optimizing crystal quality, growth rate, and raw material utilization.

[0014] Background technology has clearly pointed out that the excellent properties (wide bandgap, high breakdown field strength, and high thermal conductivity) of SiC materials due to their strong C-Si covalent bonds (~318 kJ / mol) are key to breaking through the limits of silicon-based semiconductors. However, the physical basis for transforming these "atomic-level" excellent properties into "wafer-level" perfect single crystals is the resistance heating PVT method. The essence of this process is to drive the sublimation, transport, and controlled crystallization of gaseous components within a sealed high-temperature chamber through a precisely controlled thermal field (axial temperature gradient ΔTz and radial temperature gradient ΔTr). The fundamental defect of traditional cylindrical crucibles revealed by background technology is that their geometry is passive and homogeneous. When placed in a thermal environment with natural inhomogeneity generated by an external heater, the temperature field and mass transport field formed inside are the result of "forced adaptation" rather than the product of "active design." This directly leads to two core contradictions: 1) The contradiction of "self-crystallization" in the powder region: Under non-uniform external heating, the bottom and sidewalls of the uniform cylindrical lower cavity are heated strongly, while the central region is heated weakly. This makes it very easy for a "cold trap" below the vapor condensation temperature to form at the center of the powder's upper surface, causing the raw material vapor to sublimate and crystallize on the powder surface before reaching the seed crystal. This not only wastes raw materials and reduces the growth rate, but more seriously, the spontaneously formed parasitic crystals will disrupt the stability of the entire thermal field and vapor flow, destroy the uniformity of crystal growth, and introduce defects. 2) The contradiction between growth stability and rate: In order to ensure crystal quality (such as reducing defect density), it is necessary to reduce the radial temperature gradient (ΔTr) at the growth interface to maintain a flat or slightly convex growth interface. However, this often means that the axial temperature gradient (ΔTz) needs to be reduced, which will weaken the driving force of vapor transport and reduce the growth rate. The simple structure of traditional crucibles makes it difficult to decouple or independently optimize these two factors.

[0015] The "upper straight, lower conical" chamber design of this invention is a direct response to the aforementioned contradictions. It is no longer a "simple container," but a "precision reactor" with clearly defined functional zones and active thermal field control capabilities.

[0016] Firstly, the upper crystallization cavity is a cylindrical shape with a uniform diameter, designed to provide a geometrically stable and thermally symmetrical crystallization environment for the seed crystal growth interface. This helps reduce the radial temperature gradient (ΔTr) and promotes the flattening and stress release of the growth interface. Secondly, the lower raw material cavity is a frustum-shaped cone (or described as a linearly narrowing structure) that gradually expands from top to bottom. Its core function is to reshape the thermal field distribution of the powder area. The physical mechanism is that the cone-shaped structure changes the relative position and thermal coupling relationship between the powder and the heating wall. Under external resistance heating conditions, the inverted cone design causes the raw material area, especially its central region, to be closer to the high-temperature sidewall, thereby effectively increasing the temperature in this area and eliminating the "low-temperature cold trap" that is easily formed in the central region of the powder surface in traditional cylindrical crucibles due to insufficient heat flow. This "cold trap" is the main reason why the gas phase components undergo undesirable sublimation and crystallization (i.e., "parasitic crystallization") on the powder surface during transport. Eliminating the "cold trap" is a prerequisite for eradicating parasitic crystallization and ensuring effective sublimation and transport of the raw material.

[0017] This structure actively modulates the temperature gradient by altering the axial and radial heat flux density distributions. The conical cavity enhances bottom-up axial heat conduction, thereby establishing and maintaining a more significant and stable axial temperature gradient (ΔTz) in the powder region. This is the core driving force for the directional transport of vapor phase components to the seed crystal face. Simultaneously, due to the improved thermal state in the central region, the radial temperature uniformity of the powder surface and even the entire raw material region is significantly optimized, reducing the radial temperature gradient (ΔTr). A uniform raw material volatilization surface is fundamental to generating a stable and uniform vapor flow, thereby achieving a flat growth interface and uniform doping.

[0018] As a preferred embodiment of the above technical solution, the lower cavity is a silicon carbide powder placement area.

[0019] As a preferred embodiment of the above technical solution, the diameter of the lower cavity gradually decreases from bottom to top, specifically in a linear manner.

[0020] As a preferred embodiment of the above technical solution, the angle between the generatrix of the lower side wall of the longitudinal section of the crucible and the central axis is 10~15°.

[0021] As a preferred embodiment of the above technical solution, the volume of the upper cavity is 1.5 to 2.5 times the volume of the lower cavity.

[0022] As a preferred embodiment of the above technical solution, the bottom inner surface of the lower cavity is provided with a plurality of uniformly distributed protrusions or grooves to increase the contact area between the silicon carbide powder and the bottom of the crucible and improve heating uniformity.

[0023] On the bottom inner surface of the conical lower cavity, regularly arranged protrusions or grooves are introduced. This design aims to increase the effective contact area and heat exchange efficiency between the raw material powder and the bottom of the high-temperature crucible at the microscale, promoting the uniform penetration of heat into the deep layers of the powder bed, thereby further improving the uniformity and rate stability of powder sublimation. It is a powerful complement to the macroscopic thermal field optimization effect of the conical structure.

[0024] As a preferred embodiment of the above technical solution, a temperature sensing element is embedded inside the side wall and / or bottom, which is insulated from the crucible body material, and the signal lead of the temperature sensing element is led out from the side wall or bottom of the crucible.

[0025] Temperature sensors (such as tungsten-rhenium thermocouples) that are insulated from the graphite matrix are integrated into the sidewalls and / or bottom of the crucible. This enables in-situ, real-time, and precise monitoring of the temperature in key areas inside the crucible (such as the high-temperature powder zone and the near-growth interface zone). This technology elevates process control from indirect inference based on external parameters to direct feedback based on the actual internal thermal state, providing crucial data support for verifying thermal field design, optimizing heating power strategies, and achieving closed-loop precise control of the growth process.

[0026] As a preferred embodiment of the above technical solution, the top edge of the upper sidewall is provided with an outwardly horizontally extending annular flange, and the upper cover is sealed to the upper sidewall through the annular flange.

[0027] As a preferred embodiment of the above technical solution, the top cover and the side wall are positioned and assembled using mutually matching stepped surfaces.

[0028] An annular flange is provided at the top of the upper chamber, and a precision stepped surface is used to position and seal the upper cover. In extreme environments exceeding 2300°C, this structure ensures the airtightness of the reaction chamber, prevents impurities from entering, and guarantees the precise repeatability of the relative position between the upper cover (seed crystal support surface) and the crucible body. This is a prerequisite for obtaining a stable growth interface shape and crystal orientation, and also ensures the multiple recycling of the crucible.

[0029] As a further preferred embodiment of the above technical solution, the upper and lower sidewalls are made of isostatically pressed graphite, and the thickness of the lower sidewall is greater than that of the upper sidewall to match the thermal expansion requirements of the high-temperature zone in the lower cavity. At the same time, the radial heat flux density is adjusted by the thickness difference to promote uniform sublimation of the powder in the lower cavity.

[0030] Based on the isotropic properties of isostatically pressed graphite, the lower sidewall, which bears a higher heat load, is designed to be thicker than the upper sidewall. The thicker lower sidewall not only enhances the mechanical strength of the high-temperature zone to resist thermal deformation, but its higher radial thermal resistance also helps guide more heat flow axially (from bottom to top). This synergizes with the intention of the tapered structure to guide axial heat flow, further optimizing the heat flow path and strengthening the axial temperature gradient.

[0031] In summary, the present invention has the following beneficial effects:

[0032] 1. Growth kinetics optimization: A stable axial high temperature difference (ΔTz) drives a higher effective transport and growth rate; a uniformly reduced radial temperature difference (ΔTr) promotes the formation of a flat growth interface; the combination of the two improves the growth rate while creating ideal thermodynamic conditions for high-quality crystal growth.

[0033] 2. Improved raw material utilization and process stability: Completely eliminates parasitic crystallization on the powder surface, enabling almost all gas phase components to be effectively transported to the growth interface, significantly improving raw material utilization and single-yield efficiency; at the same time, the constant sublimation interface characteristics ensure the stability of the temperature field, vapor flow field and concentration field throughout the entire crystal growth cycle, greatly enhancing the repeatability of the process and the consistency of crystal performance.

[0034] 3. Crystal defect suppression: The elimination of parasitic crystal layers fundamentally eliminates solid particle contamination and heterogeneous nucleation caused by crystal layer peeling, significantly reducing the density of bulk defects such as inclusions and polycrystalline material; the improvement of radial thermal uniformity at the growth interface effectively reduces thermoelastic stress, inhibits the proliferation and extension of dislocations, and helps to obtain single crystals with low dislocation density.

[0035] 4. Enhanced system reliability and economy: A stable and non-volatile thermal environment reduces thermal shock to the graphite heater, insulation layer and crucible itself, extends the service life of key consumables and components, reduces the overall operating cost of a single growth cycle, and helps maintain the process stability of the production equipment in the long term.

[0036] 5. In summary, the silicon carbide crystal growth crucible of this invention, starting from the intrinsic laws of physical vapor transport processes, achieves synergistic optimization of the thermal field, flow field, and material field within the crystal growth system through proactive geometric and structural design. This design transcends the function of a traditional crucible as a simple container, evolving into a "reactor" capable of precisely controlling the growth environment. It not only provides an effective solution to overcome long-standing process challenges such as parasitic crystallization in the powder region and radial inhomogeneity, but also lays a crucial equipment foundation for achieving higher growth rates, better crystal quality, and more stable and repeatable SiC single crystal preparation processes. It has clear engineering application value for promoting cost reduction, efficiency improvement, and high-quality development in the wide-bandgap semiconductor industry. Attached Figure Description

[0037] Figure 1 This is a schematic diagram of the structure of the present invention;

[0038] Figure 2 This is a stress defect diagram of a silicon carbide single crystal prepared using a conventional crucible;

[0039] Figure 3 This is a stress defect diagram of a silicon carbide single crystal prepared using the crucible of this invention;

[0040] In the diagram, the component names represented by each number are as follows:

[0041] 1-Sidewall,

[0042] 2-Bottom

[0043] 3-Inner cavity,

[0044] 4-Top cover,

[0045] 5-seed crystal,

[0046] 6-Silicon carbide powder,

[0047] 7-Heater,

[0048] 11-Upper sidewall,

[0049] 12-Lower sidewall,

[0050] 31-Upper cavity,

[0051] 32-Inferior cavity. Detailed Implementation

[0052] The present invention will be further explained and described below with reference to the accompanying drawings.

[0053] This specific embodiment is merely an explanation of the present invention and is not intended to limit the invention. Any changes made by those skilled in the art after reading this specification, as long as they fall within the scope of the claims, will be protected by patent law.

[0054] This embodiment provides a crucible suitable for growing silicon carbide single crystals using resistance heating. The crucible is integrally machined from high-purity, isotropic isostatic graphite with an ash content of less than 5 ppm to meet the purity requirements for semiconductor-grade crystal growth.

[0055] like Figure 1 As shown, the crucible is a rotating body with an axisymmetric structure, comprising a sidewall 1, a bottom 2, and a top cover 4. The sidewall 1 and bottom 2 together form an inner cavity 3 with an open top, and the top cover 4 is used to seal the opening of this inner cavity. The sidewall 1 is further structurally divided into an upper sidewall 11 and a lower sidewall 12. The upper sidewall 11 is a standard cylindrical shape, with its inner wall surface being a vertical cylindrical surface. The lower sidewall 12 is an inverted frustum shape, with its inner wall surface being a conical surface that gradually expands from top to bottom. Thus, the inner cavity is clearly divided into two functional regions: an upper cavity 31 (crystal growth region) corresponding to the upper sidewall 11, and a lower cavity 32 (raw material sublimation region) corresponding to the lower sidewall 12.

[0056] The upper cavity 31 is a cylindrical cavity with a constant diameter. Its diameter D1 is determined according to the target crystal size, such as 150 mm, 200 mm, etc., to accommodate the growth of 4-inch, 6-inch, or 8-inch ingots. The height H1 of the upper cavity 4 is designed to be the sum of the maximum crystal growth height and the necessary seed crystal mounting and gas phase diffusion space, typically accounting for about 60% to 70% of the total crucible height. The constant diameter structure of the upper cavity 31 provides a geometric space with stable boundary conditions and extremely high symmetry, aiming to form a uniform axial temperature gradient and a very small radial temperature gradient, providing a stable and consistent growth environment for the crystal. The thickness T1 of the upper sidewall 11 is uniform, for example, 30 mm.

[0057] The lower cavity 32 is an inverted frustum-shaped cavity, which is the area for containing silicon carbide raw material powder. Its top opening diameter is equal to the diameter D1 of the upper cavity 31, achieving a smooth transition. Its bottom diameter D2 is smaller than D1, forming a tapered space that gradually expands from top to bottom. The angle α between the generatrix of the sidewall (inner surface contour line) of the lower cavity 5 and the central axis of the crucible is designed to be between 10° and 15°, preferably 12°. This tapered design is one of the core technical features. The ratio of the volume V2 of the lower cavity 32 to the volume V1 of the upper cavity 31 is controlled between 1:1.5 and 1:2.5, for example, V1:V2=2:1, to ensure sufficient raw material supply and a reasonable crystal growth space ratio. The thickness T2 of the lower sidewall 12 is greater than the thickness T1 of the upper sidewall 11. For example, T2 can be designed to be 40~50 mm. This differentiated wall thickness design is intended to match the higher operating temperature of the lower cavity, enhance its structural strength, and guide more heat to be transferred axially from the bottom upwards by increasing radial thermal resistance.

[0058] On the bottom inner surface of the lower cavity 5, a uniformly distributed array of protrusions (or alternatively, a groove structure) is machined. These protrusions are truncated cones or cylinders, with a height of approximately 3-5 mm, and are arranged in concentric rings or a matrix. Their function is to significantly increase the contact area between the silicon carbide powder and the bottom of the high-temperature crucible, improve the uniformity of heat transfer at the bottom, and prevent differences in sublimation rate caused by uneven local heating of the powder.

[0059] Inside the lower sidewall 12, near the lower cavity 32, there are precision-machined mounting holes into which temperature sensing elements (such as S-type or C-type tungsten-rhenium thermocouples) are embedded. The temperature sensing element is insulated from the graphite body by a high-purity boron nitride or pyrolytic boron nitride sleeve, and its signal lead extends from a specific location on the lower sidewall 12 and is sealed. This structure allows for in-situ real-time monitoring of the temperature in the powder zone.

[0060] The top of the upper sidewall 11 is machined with an outwardly extending horizontal annular flange. A matching groove or flat surface is provided at the corresponding position of the upper cover 4. The upper cover 4 fits tightly against the flat surface of the annular flange under its own weight, forming the main sealing surface. To further ensure assembly accuracy and repeatability, mating stepped surfaces are provided at the lower edge of the upper cover 4 and the entrance of the upper cavity 31 to achieve rapid and accurate radial and circumferential positioning. All sealing contact surfaces are precision ground to ensure airtightness at high temperatures.

[0061] The following example illustrates the application of the crucible of the present invention in the production of silicon carbide.

[0062] Raw material preparation: the above-mentioned crucible, high-purity SiC powder, seed crystal holder, and seed crystal.

[0063] Assembly: Spread high-purity SiC powder evenly on the bottom of the crucible to a thickness of 40mm, and place the seed crystal holder and seed crystal on top.

[0064] Crystal growth process: Place the crucible filled with material into the crystal growth furnace, evacuate it, and then fill it with doping gas (nitrogen) and inert protective gas (argon) in a certain proportion. Maintain the pressure at 600 Torr. Increase the temperature and decrease the pressure according to the set temperature rise curve, so that the temperature at the top of the crucible is controlled at 2100~2200℃, the temperature at the bottom is controlled at 2300~2400℃, and the pressure is maintained at 10 Torr. This forms an axial temperature gradient to transport the gas phase components to the surface of the seed crystal. Maintain this temperature and pressure for 200 hours, and the crystal growth is completed.

[0065] Effect observation: After the crystal was opened, its thickness was measured using a height gauge. It was found that the thickness of the SiC crystal grown in this embodiment was increased by 3-5 mm compared with that of a traditional crucible. After slicing, KOH wet etching was performed, and the dislocation density was measured using a dislocation analyzer. It was found that the TED value increased from 1821 cm⁻¹. -2 Reduced to 1435cm -2 The decrease exceeded 20%, with the BPD value dropping from 193 cm. -2 Reduced to 132 cm -2 The decline exceeded 30%.

[0066] After cutting, grinding, and polishing the crystals produced by the two types of crucibles (the crucible of this invention and the conventional crucible), we used a stress detector to test the stress of the two batches of wafers. We found that stress defects were significantly improved: the stress diagram of the conventional crucible growth is shown below. Figure 2 As shown, stress defects appear at the edges of the polished sheet; while the stress diagram grown using this invention is as follows. Figure 3 As shown, its polished wafer is free of stress defects, therefore the present invention also significantly improves the stress defects of wafers.

Claims

1. A silicon carbide crystal growth crucible suitable for resistance method, comprising sidewalls (1), a bottom (2), and an inner cavity (3) enclosed by said sidewalls and bottom, and further comprising a top cover (4) for sealing said inner cavity; characterized in that: The sidewalls include an upper sidewall (11) and a lower sidewall (12), such that the inner cavity is divided into an upper cavity (31) corresponding to the upper sidewall and a lower cavity (32) corresponding to the lower sidewall; the diameter of the upper cavity (31) is constant with height; the diameter of the lower cavity (32) varies with height, specifically gradually decreasing from bottom to top until it is equal to the diameter of the upper cavity.

2. The silicon carbide crystal growth crucible suitable for resistance method according to claim 1, characterized in that: The lower cavity (32) is a silicon carbide powder placement area.

3. The silicon carbide crystal growth crucible suitable for resistance method according to claim 1, characterized in that: The diameter of the lower cavity (32) gradually decreases from bottom to top, specifically in a linear manner.

4. A silicon carbide crystal growth crucible suitable for resistance method according to claim 1, characterized in that: The angle between the generatrix of the lower side wall of the longitudinal section of the crucible and the central axis is 10~15°.

5. A silicon carbide crystal growth crucible suitable for resistance method according to claim 1, characterized in that: The volume of the upper cavity is 1.5 to 2.5 times the volume of the lower cavity.

6. A silicon carbide crystal growth crucible suitable for resistance method according to claim 1, characterized in that: The bottom inner surface of the lower cavity is provided with multiple evenly distributed protrusions or grooves to increase the contact area between the silicon carbide powder and the bottom of the crucible and improve heating uniformity.

7. A silicon carbide crystal growth crucible suitable for resistance method according to claim 1, characterized in that: A temperature sensing element, which is insulated from the crucible body material, is embedded inside the side wall and / or bottom. The signal lead of the temperature sensing element is led out from the side wall or bottom of the crucible.

8. A silicon carbide crystal growth crucible suitable for resistance method according to claim 1, characterized in that: The top edge of the upper sidewall is provided with an outwardly horizontally extending annular flange, and the upper cover is sealed to the upper sidewall through the annular flange.

9. A silicon carbide crystal growth crucible suitable for resistance method according to claim 1, characterized in that: The top cover and the side wall are positioned and assembled using matching stepped surfaces.

10. A silicon carbide crystal growth crucible suitable for resistance method according to claim 1, characterized in that: The upper and lower sidewalls are made of isostatically pressed graphite, and the thickness of the lower sidewall is greater than that of the upper sidewall to match the thermal expansion requirements of the high-temperature zone in the lower cavity.

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