Seed crystal supporting and protecting structure for growing silicon carbide single crystal by liquid phase method

Abstract

The invention relates to the technical field of silicon carbide single crystal production, and discloses a seed crystal supporting and protecting structure for growing a silicon carbide single crystal by a liquid phase method, comprising: a seed crystal fixing and supporting rod, which comprises a supporting part and a rod part, the supporting part and the rod part are integrally formed; the silicon carbide seed crystal plate is mounted on the seed crystal fixing and supporting rod; the seed crystal protection ring is mounted on the seed crystal fixing and supporting rod, the upper end surface of the seed crystal protection ring is flush with the upper end surface of the middle supporting part of the seed crystal fixing and supporting rod, and the lower end surface of the seed crystal protection ring is flush with the seed crystal bonding end surface of the silicon carbide seed wafer, so that the flat embedding type layout of the silicon carbide seed wafer is formed. According to the invention, the stability of a seed crystal-melt interface is ensured through the integrally designed seed crystal fixing and supporting rod; the seed crystal protection ring and the convection blocking ring are combined for use, so that triple stable control on a temperature field, a flow field and a concentration field of the edge of the seed crystal is realized; the problems of edge polycrystal parasitism, inclusion defects and interface instability are effectively inhibited, so that the single crystal growth quality and yield are remarkably improved.

Description

Technical Field

[0001] This invention relates to the field of silicon carbide single crystal production technology, specifically, to a seed crystal support and protection structure for liquid-phase growth of silicon carbide single crystals. Background Technology

[0002] Silicon carbide (SiC), as one of the representatives of third-generation wide-bandgap semiconductor materials, possesses a series of excellent properties such as wide bandgap, high critical breakdown electric field, excellent intrinsic thermal conductivity, and good chemical stability. Therefore, SiC is particularly suitable for applications under extreme conditions such as high temperature, high pressure, high power, and strong radiation, and is widely used in power electronics, aerospace, and high-frequency devices. Among the many SiC single crystal growth technologies, the liquid-phase method has received widespread attention and rapid development in recent years due to its advantages such as moderate growth rate, high crystal quality, and low growth cost. However, to achieve high-quality, low-defect-density SiC single crystals with long-term stable growth in the liquid-phase method, it is essential to ensure a continuous and uniform radial temperature gradient at the growth interface and a stable and ordered fluid convection environment.

[0003] In existing technologies, seed crystals are typically fixed directly to the seed crystal holder using an adhesive, or a buffer layer is placed between them to improve thermodynamic matching. The bonded seed crystal holder is then connected and fixed to the seed crystal rod, usually by screw fastening. During single crystal growth experiments, the seed crystal rod is connected to the growth equipment to achieve seed crystal lifting and rotation, while a cooling device cools the seed crystal rod. However, in actual growth, due to the thermal conductivity characteristics of the seed crystal-melt interface, abrupt temperature changes easily occur at the seed crystal edge, resulting in a significant discontinuity in the temperature gradient, making it difficult to maintain a stable thermal field distribution across the entire growth interface. Significant temperature fluctuations lead to unstable melt properties in this region, making it easy for solute in the melt to nucleate and precipitate in two dimensions. Some of the precipitated silicon carbide is incorporated into the growth crystal as it grows, some adheres to the side of the seed crystal and grows over time, applying stress to the growth crystal, while another portion floats on the liquid surface, forming float crystals that hinder solute transport from the melt to the growth interface.

[0004] Furthermore, in the liquid-phase method, since heating is mostly done via sidewall heating, the crucible wall temperature is higher than the melt temperature, thus forming a temperature gradient on the melt surface from the seed crystal interface to the crucible wall. Surface tension decreases with increasing temperature, so the surface tension difference at different radial locations generates Marangoni convection on the melt surface, flowing from the hot end (crucible wall) to the cold end (seed crystal interface). Simultaneously, the bottom temperature of the melt is usually higher than the surface, forming natural convection driven by buoyancy due to density difference. The flow direction is: melt bottom rises along the crucible wall → melt upper part flows towards the seed crystal interface → then flows back to the bottom. Forced convection caused by seed crystal rotation flows from the seed crystal towards the crucible wall and down the wall. These three types of convection conflict at the seed crystal edge, intensifying the flow field disturbance in this region. This not only disrupts the transport path of solute carbon but also undermines the stability of the diffusion boundary layer and solute carbon transport path near the solid-liquid interface, leading to fluctuations in the solute carbon concentration gradient.

[0005] The instabilities in the temperature and concentration fields mentioned above can easily lead to interfacial instability at the crystal growth edges, such as macrostep clustering, surface macro-grooves, and flux inclusions. Simultaneously, polycrystalline SiC is easily deposited at the seed crystal edges during growth, and the difference in thermal expansion coefficients between polycrystalline and single crystals during cooling can induce thermal stress, which in severe cases can lead to crystal breakage or through-cracks, affecting crystal integrity and yield. Summary of the Invention

[0006] The purpose of this invention is to provide a seed crystal support and protection structure for liquid-phase growth of silicon carbide single crystals, solving the problems of poor versatility and low crystal generation quality in existing technologies.

[0007] This invention is achieved through the following technical solution: a seed crystal support and protection structure for liquid-phase growth of silicon carbide single crystals, comprising: A seed crystal fixing support rod includes a support portion and a rod portion, wherein the support portion and the rod portion are integrally formed and are used to place silicon carbide seed crystal wafers; A silicon carbide seed wafer is mounted on the seed wafer fixing support rod for adhering the seed wafer; A seed crystal protection ring is installed on the seed crystal fixing support rod. The upper end face of the seed crystal protection ring is flush with the upper end face of the middle support part of the seed crystal fixing support rod, and the lower end face of the seed crystal protection ring is flush with the seed crystal bonding end face of the silicon carbide seed crystal wafer, forming a flat embedded layout of the silicon carbide seed crystal wafer.

[0008] To better realize the present invention, the seed crystal fixing support rod further includes a support size compensation ring, the support size compensation ring being detachably connected to the periphery of the support portion of the seed crystal fixing support rod, and the seed crystal protection ring being detachably installed on the periphery of the support size compensation ring.

[0009] To better realize the present invention, it further includes a convection blocking ring, which is detachably installed around the seed crystal protection ring; the upper end face of the convection blocking ring is flush with the upper end face of the middle support of the seed crystal fixing support rod, and the thickness of the convection blocking ring increases along the radial extension direction.

[0010] To better realize the present invention, the lower end face cross-section of the convection blocking ring is further described as an arc-shaped or conical structure.

[0011] To better realize the present invention, the slope of the lower end face of the convection blocking ring is further 2°-25°.

[0012] To better realize the present invention, the convection blocking ring is further provided with an internal thread, the support size compensation ring and the seed crystal protection ring are both provided with internal and external double threads, and the support is provided with an external thread.

[0013] To better realize the present invention, a buffer layer is further provided between the seed crystal fixing support rod and the silicon carbide seed crystal.

[0014] To better realize the present invention, the buffer layer is further described as graphite paper with a thickness of 0.05-0.5 mm.

[0015] Compared with the prior art, the present invention has the following advantages and beneficial effects: (1) The present invention uses an integrated seed crystal fixing support rod to avoid the loosening of the connection between the seed crystal holder and the seed crystal rod caused by the rotation of the seed crystal during the crystal growth process, thereby preventing the seed crystal from shaking or wobbling and ensuring the stability of the seed crystal-melt interface; in addition, since the support part of this structure is covered and protected by other components during the growth process and does not come into direct contact with the melt, it can avoid flux contamination and achieve multiple reuses. (2) By setting a support size compensation ring, the same support rod can be adapted to seed crystals of different specifications (such as 4 inches, 6 inches, etc.), which significantly improves the versatility and adaptability of the equipment; the compensation ring is threadedly connected to the support rod, the structure is firm, and it does not come into contact with the melt during the growth process, so it can be reused and reduce production costs. (3) By setting a seed crystal protective ring, the present invention forms a barrier at the outer edge of the seed crystal, which can block the wetting and erosion of the seed crystal sidewall and the seed crystal-support bonding area by the flux, significantly reducing the generation of edge polycrystalline material and flux inclusion; at the same time, it protects the integrity of the buffer layer, maintains the thermal uniformity of the back side of the seed crystal and the stability of the bonding interface, thereby reducing the risk of cooling cracks and dislocation propagation; after growth, the protective ring can be unscrewed and separated from the compensation ring, making it easy for the seed crystal to be separated from the support, reducing the risk of mechanical damage. (4) By setting up a convection blocking ring, the present invention significantly reduces the disturbance of Marangoni convection and natural convection on the solute distribution at the seed crystal edge through physical isolation, so that the entire seed crystal interface is in a stable and consistent flow field environment; the seed crystal edge can be placed far away from the temperature change zone to ensure the continuity of the radial temperature gradient and avoid polymorphic transformation and inclusion defects. (5) The present invention achieves modular and rapid assembly and disassembly by setting all functional components to be connected by threaded connection; in single crystal production, one or more functional components can be flexibly replaced to adapt to the growth requirements of different sizes, different process parameters or different material systems; this design not only improves the versatility and maintenance convenience of the equipment, but also reduces the number of overall replacements and reduces the cost of use; (6) The present invention achieves triple stable control of the temperature field, flow field and concentration field at the edge of the seed crystal by using a combination of seed crystal protection ring and convection blocking ring; effectively suppresses edge polycrystalline parasitic, inclusion defects and interface instability problems, thereby significantly improving the quality and yield of single crystal growth. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the existing solution structure.

[0017] Figure 2 This is a cross-sectional view of the overall structure of the present invention.

[0018] Figure 3 This is a schematic diagram illustrating the usage state of the present invention.

[0019] Figure 4 Schematic diagram of temperature gradient in simulation experiment Figure 1 .

[0020] Figure 5 Schematic diagram of convection distribution in simulation experiment Figure 1 .

[0021] Figure 6 Schematic diagram of temperature gradient in simulation experiment Figure 2 .

[0022] Figure 7 Schematic diagram of convection distribution in simulation experiment Figure 2 .

[0023] Wherein: 10-seed crystal fixing support rod; 20-support size compensation ring; 30-silicon carbide seed crystal; 40-seed crystal protection ring; 50-convection blocking ring; 60-buffer layer; 70-fluxing melt; 80-graphite crucible. Detailed Implementation

[0024] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0025] 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.

[0026] Firstly adopt Figure 1 The existing scheme was used to conduct silicon carbide single crystal growth experiments; and the corresponding data were compared with those of the present invention.

[0027] Comparative Example 1: use Figure 1 The conventional method for the growth of 4-inch p-type 4H-SiC single crystals is as follows: The seed crystal used is a 4-inch semi-insulating 4H-SiC wafer with a 0° offset, and the Si surface is selected as the bonding surface, which is bonded to the seed crystal holder with adhesive. The diameter of the seed crystal holder is the same as that of the seed crystal (100mm), and the thickness is 20mm. A 0.5mm thick graphite paper is placed between the two as a buffer layer. After bonding, the seed crystal holder assembly is connected and fixed to the seed crystal rod, which is 400mm long and 20mm in diameter. The chemical molar ratio of the raw materials in the growth system is Si:M1:Al = (20-60):(30-70):(0-10), where M1 can be a transition metal such as Cr, Ti, Fe, Ni, etc., to improve the carbon solubility of the melt; Al is a dopant. The preferred ratio is Si:Cr:Al = 51:45:4. The height of the melt after the raw materials are melted is set to 40mm, and the inner diameter of the crucible is set to 180mm. When the surface temperature of the melt reaches 1800℃, the seed crystal begins to descend for crystal growth. After the seed crystal is generated, the seed crystal is grown at a maximum speed of 120 rpm, the growth cycle is set to 86 hours, and the growth temperature is set to 1850℃.

[0028] The structural and operational problems exposed in this scheme are as follows: polycrystalline encapsulation and flux coating exist near the seed crystal and support bonding area, making it difficult to separate the crystal from the support; the seed crystal and support cannot be reused due to flux contamination and erosion; significant flux residue is present at the seed crystal bonding surface, and most of the buffer layer graphite paper is eroded. During the growth process, the seed crystal rod shakes and vibrates repeatedly, causing fluctuations in the growth interface.

[0029] The resulting defects and quality problems include: longitudinal cracks extending from the seed crystal region to the crystal surface, which are caused by the release of internal thermal stress during cooling; step clustering and flux encapsulation appear on the outer periphery of the crystal surface, indicating that the convection and solute transport in this region are disordered and unbalanced, and the growth interface is unstable; Raman spectroscopy revealed the presence of various types of inclusions, such as 6H-SiC and 3C-SiC, in the grown crystal; the half-width at half-maximum (FWHM) of the X-ray rocking curve (XRC) reached 150-300 arcsec, indicating poor crystal quality and high defect density; and ingot slice testing revealed a significant resistivity gradient in the edge region of the seed crystal, with independent resistivity isopleths.

[0030] In the simulation results ( Figure 4 , Figure 5 The temperature in the seed crystal edge region changes abruptly, interrupting the temperature gradient; two convection structures in opposite directions exist simultaneously near the seed crystal edge, further disrupting the growth interface.

[0031] In summary, the existing scheme has the following significant drawbacks: the seed crystal holder is contaminated by the flux, limiting its reuse; the flux penetrates the seed crystal-seed crystal holder bonding surface, disrupting the heat dissipation uniformity on the back of the seed crystal, and the latent heat of crystallization on the growth surface cannot be released uniformly, resulting in thermal stress inside the crystal; the growth process is unstable, and the convection and solute transport under the growth interface around the crystal are disordered, resulting in impurity phases and flux encapsulation in the edge region of the crystal surface; the crystallization quality is limited, manifested as polycrystalline encapsulation, impurity phase inclusions, cracks, and poor crystal integrity; the edge effect is significant, and the turbulent temperature and flow fields lead to uneven resistivity distribution.

[0032] Comparative Example 2: use Figure 1 The standard procedure for the growth of 4-inch n-type 3C-SiC single crystals is as follows: The seed crystal used is a 4-inch semi-insulating 4H-SiC wafer with a 1° off-axis, which is bonded to the seed crystal holder with adhesive. The diameter of the seed crystal holder is the same as that of the seed crystal, i.e., 100 mm, and the thickness is 20 mm. A 0.25 mm thick graphite paper is placed between the two as a buffer layer. After bonding, the seed crystal holder assembly is connected and fixed to the seed crystal rod, which is 480 mm long and 15 mm in diameter. The chemical molar ratio of the raw materials in the growth system is Si:M1:M2:M3 = (20-60):(30-60):(0-20):(0-10), with 48:35:15:2 being preferred. M1 can be selected from transition metals such as Cr, Fe, Ni, Mn, Ti, and Sc, and its function is to enhance the carbon solubility of the melt. M2 can be metals such as Ti, Mn, Ni, Zr, Hf, V, Nb, and Ta. Its function is to increase the solubility of nitrogen in the melt and adjust the surface and interface properties of the melt, so that the 3C-SiC growth can proceed stably. M3 can be metals such as Al, Co, Y, La, Ce, Pr, and Nd. Its purpose is to fine-tune the properties of the melt, such as viscosity, density, and melting temperature, thereby adjusting the surface morphology of the growth. In this experiment, the preferred ratio is Si:Fe:Ti:Co = 48:35:15:2. The height of the melt after the raw materials are melted is set to 20 mm, and the inner diameter of the crucible is set to 150 mm. The growth atmosphere is a N2 / Ar mixed atmosphere with a pressure of 70 kPa and a N2 partial pressure (PN2) of 35 kPa. When the surface temperature of the melt reaches 1650 °C, the seed crystal begins to descend for crystal growth. After crystal growth is completed, the seed crystal grows at a maximum rotation speed of 160 rpm for a growth period of 12 hours and a growth temperature of 1700 °C.

[0033] Growth test results from the conventional method indicate that it has the following drawbacks: 1. Crystal surface defects: The surface is rough, with deep gaps and some areas are not completely covered, indicating that the growth interface has failed to establish a stable state; the presence of a large number of regional boundaries and cracks on the crystal surface indicates that the internal stress of the crystal is large and the structural defects are serious.

[0034] 2. Seed crystal and seed crystal holder interface problem: There is a large amount of flux residue near the bonding area between the seed crystal and the seed crystal holder, and the sidewall of the seed crystal holder is contaminated and eroded by the flux. After the crystal is disintegrated, it is found that the bonding surface of the seed crystal is corroded by flux, and the edge of the buffer layer is dissolved.

[0035] 3. Melt and phase structure issues: The precipitation of SiC particles on the surface of the cooled melt indicates that the local temperature field fluctuates greatly, inducing spontaneous nucleation; Raman spectroscopy shows that the obtained crystal is a mixture of 6H-SiC and 3C-SiC, indicating that the solid-liquid interface is unstable, leading to the precipitation of impurity phases.

[0036] The results above show that the existing scheme has the following shortcomings in the actual growth process: the side of the seed crystal holder is not protected, which leads to solvent penetration and corrosion; the buffer layer is easily damaged under high temperature and solvent action, which aggravates the failure of the crystal and the holder; the crystal growth interface is unstable, which easily leads to defects, impurities and stress concentration; the temperature field and solute field are not uniformly controlled, resulting in local supersaturation in the melt, which leads to spontaneous nucleation and phase mixing problems.

[0037] Example 1: This embodiment provides a seed crystal support and protection structure for liquid-phase growth of silicon carbide single crystals, specifically as follows: Figure 2 , 3 As shown, it includes: The seed crystal fixing support rod 10 includes a support portion and a rod portion, wherein the support portion and the rod portion are integrally formed and used to hold the silicon carbide seed crystal wafer 30; it is made of isostatically pressed graphite or other high-temperature resistant inert materials; through the integrated design, the connection between the seed crystal support and the seed crystal rod can be prevented from becoming loose due to seed crystal rotation during crystal growth, thereby preventing severe shaking or wobbling of the seed crystal and ensuring the stability of the seed crystal-melt interface. In addition, since the support portion of this structure is covered and protected by other components during the growth process and does not come into direct contact with the melt, flux contamination can be avoided, allowing for multiple reuses; The silicon carbide seed crystal 30 is fixed to the upper surface of the support by an adhesive bonding process for attaching the seed crystal; A seed crystal protection ring 40 is installed on the seed crystal fixing support rod 10. The upper end face of the seed crystal protection ring 40 is flush with the upper end face of the middle support portion of the seed crystal fixing support rod 10, and the lower end face of the seed crystal protection ring 40 is flush with the seed crystal bonding end face of the silicon carbide seed wafer 30 (flatness tolerance preferably ≤0.1mm), forming a flat-embedded layout of the silicon carbide seed wafer 30. This ring structure forms a barrier at the outer edge of the seed crystal, which can block the wetting and erosion of the seed crystal sidewall and the seed crystal-support bonding area by the flux, significantly reducing the generation of edge polycrystalline material and flux inclusions. At the same time, it protects the integrity of the buffer layer and maintains the thermal uniformity of the back side of the seed crystal, thereby reducing the risk of cooling cracks and dislocation propagation.

[0038] Furthermore, the seed crystal fixing support rod 10 also includes a support size compensation ring 20, which is detachably connected to the periphery of the support, and the seed crystal protection ring 40 is detachably installed on the periphery of the support size compensation ring 20.

[0039] By replacing the compensation rings 20 with different widths, the same seed crystal fixing support rod 10 can be adapted to the growth of SiC single crystals of different sizes. For example, when the diameter of the support portion of the seed crystal fixing support rod 10 is 90mm, a compensation ring with a width of 5mm can be used for 4-inch SiC growth; a compensation ring with a width of 30mm can be used for 6-inch SiC single crystal growth. This component also does not come into direct contact with the melt and is reusable.

[0040] Furthermore, it also includes a convection blocking ring 50, which is detachably installed around the seed crystal protection ring 40. The upper end face of the convection blocking ring 50 is flush with the upper end face of the support portion of the seed crystal fixing support rod 10. The thickness of the convection blocking ring 50 increases along the radial extension direction, and the lower end face of the convection blocking ring 50 is in contact with the lower end face of the seed crystal protection ring 40. The convection blocking ring 50 is far away from the seed crystal, and through physical isolation, it significantly reduces the disturbance of Marangoni convection and natural convection on the solute distribution at the edge of the seed crystal, so that the entire seed crystal interface is in a stable and uniform flow field environment. The ring width of the seed crystal protection ring 40 is preferably 2–10 mm. The cross-sectional morphology of the support portion size compensation ring 20 and the seed crystal protection ring 40 is a circumferentially uniform structure, and the circumferential deviation is preferably ≤0.01 mm, so as to reduce the flow-temperature coupling disturbance caused by rotational eccentricity.

[0041] Furthermore, the lower end face of the convection blocking ring 50 has an arc-shaped or conical cross-section; the slope of the lower end face of the convection blocking ring 50 is 2°-25°.

[0042] Furthermore, the convection blocking ring 50 is provided with an internal thread, the support size compensation ring 20 and the seed crystal protection ring 40 are both provided with internal and external double threads, and the support is provided with an external thread.

[0043] Furthermore, a buffer layer 60 is provided between the seed crystal fixing support rod 10 and the silicon carbide seed crystal 30, which is made of thermally conductive buffer material; in this embodiment, the buffer layer 60 is made of graphite paper with a thickness of 0.05-0.5mm, in order to relieve thermal stress and improve thermal conductivity uniformity, thereby providing a stable lattice substrate for subsequent single crystal growth.

[0044] The application process of this solution mainly includes four stages: seed crystal bonding, functional component assembly, crystal growth, and dissociation, as detailed below: Seed crystal bonding: All components of this device can be fabricated using high-temperature resistant ceramic materials such as isostatic graphite, SiC, AlN, and Al2O3. The seed crystal fixing support rod 10 is preferably made of isostatic graphite. After the seed crystal fixing support rod 10 and the support dimension compensation ring 20 are fixed, the seed crystal is bonded to the support surface. The adhesive typically used is 914B glue, photoresist, or other high-carbon content high-temperature adhesive. A layer of graphite paper with a thickness of 0.05–1.00 mm can be placed between the seed crystal and the support surface to enhance bonding and alleviate thermal stress. The bonded sample needs to undergo carbonization treatment at a temperature of 450–800℃ in a vacuum or inert gas atmosphere to ensure complete carbonization of the adhesive.

[0045] Functional Component Assembly: After bonding, install the other functional components sequentially. First, install the seed crystal protection ring 40 outside the support size compensation ring 20, ensuring it completely covers the side of the seed crystal. The ring width is generally 2%–20% of the seed crystal diameter; while a larger width can improve temperature gradient uniformity, it increases crucible size, raw material consumption, and energy consumption. The ring height is generally 30%–120% of the support height; a larger height increases thermal resistance, leading to abnormal temperature gradients at the seed crystal edge. Next, install the convection blocking ring 50 outside the seed crystal protection ring 40. Its inner wall height is the same as the seed crystal protection ring 40, while its outer wall is 0.5–5 mm higher. If the height difference is too small, it will be difficult to effectively suppress convection into the seed crystal edge; if it is too large, it will disrupt stable deep convection within the crucible and inhibit the effective transport of solute carbon and dopants. The width of the blocking ring should be 5%–20% of the seed crystal diameter. If it is too small, it will be difficult to stabilize the flow field. If it is too large, it will introduce forced convection and aggravate the erosion of the crucible wall, and may even lead to the crucible melting through.

[0046] Crystal Growth: Crystal growth can begin immediately after assembly. Because the support rod is an integrated structure, there will be no loosening or shaking throughout the process, ensuring the stability of the growth interface. The bottom surface of the convection blocking ring has an arc-shaped structure; its design, with a higher outer surface and lower inner surface, effectively blocks Marangoni and natural convection on its outer side, thereby stabilizing the flow field and solute concentration distribution at the growth interface. Furthermore, the seed crystal side and the area near the seed crystal-seed support bonding interface are protected by the support size compensation ring 20, thus the thermal conductivity of the seed crystal's back side is not affected. The latent heat of crystallization released during crystal growth can be uniformly released, preventing excessive thermal stress within the crystal during growth. Since there are no polycrystalline parasites or flux coatings on the seed crystal side, no external stress is applied to the crystal during cooling after growth. According to the overall structural assembly and design of this invention, the contact position between the seed crystal and the melt is located in the central region of the solid-liquid interface, away from the abrupt temperature gradient region, thereby ensuring the continuity and stability of the radial temperature gradient. Based on the above process, during crystal growth, the distribution of thermal field, flow field, and concentration field at the growth interface reaches equilibrium and optimization, the latent heat of crystallization can be released uniformly, and after growth, the crystal can cool naturally without being subjected to external stress. Therefore, the grown crystal tends to grow under stable thermal equilibrium conditions, the crystal surface morphology and crystallization quality can be improved, and the crystal yield can be increased.

[0047] Dissociation: After growth is complete, the seed crystal protective ring 40 can be dissociated from the support size compensation ring 20 by rotating the thread. Since there are no polycrystalline materials and flux residues around the seed crystal, the seed crystal can be naturally dissociated from the support smoothly. This avoids chipping or cracking caused by mechanical peeling and significantly improves the finished product integrity rate.

[0048] Example 2: This embodiment demonstrates the experimental results of this method for the growth of 4-inch p-type 4H-SiC single crystals. Specifically: The integrated seed crystal fixing support rod has a support diameter of 80mm, a thickness of 20mm, and a length of 400mm. The support dimension compensation ring is 10mm wide and 20mm high, pre-assembled with the integrated support rod via threads. A 4-inch 4H-SiC seed crystal with a 0° offset is selected and bonded to the bottom of the assembled support. After the seed crystal is bonded, the seed crystal protective ring is installed on the outside of the support dimension compensation ring via threaded fastening, with its bottom surface flush with the seed crystal growth surface. The seed crystal protective ring is 5mm wide and 21mm high. Subsequently, a convection blocking ring is installed on the outside of the seed crystal protective ring, with the inner side lower than the outer side. The inner height of the convection blocking ring is 21mm, the outer height is 22.5mm, the bottom surface is arc-shaped, and the ring width is 15mm. The stoichiometric ratio of the growth system raw materials is Si:Cr:Al = 51:45:4. After melting, the melt height is set to 40mm, and the crucible inner diameter is 180mm. When the surface temperature of the melt reaches 1800℃, the seed crystal is lowered to initiate crystal growth. After crystal growth is complete, the seed crystal grows at a maximum speed of 120 rpm, with a growth cycle set at 86 hours and a growth temperature of 1850℃.

[0049] Compared to Comparative Example 1, after the growth experiment in this embodiment, the functional components were disassembled, and the sides of the grown crystal were clean, free of flux and polycrystalline SiC residue. The integrated seed crystal fixing support rod and the support size compensation ring remained intact and uncontaminated by flux, allowing for reuse. The grown crystal surface was smooth and flat, without any macroscopically visible step clusters. Microscopic observation showed continuous step flow covering the crystal surface, indicating that the solid-liquid interface remained stable during growth. The grown crystal showed no obvious cracks. Raman spectroscopy confirmed that the crystal was a 4H-SiC single crystal, without other polymorphic inclusions. XRC testing showed an FWHM of only 20-50 arcsec, indicating good crystal quality, reaching commercial application levels. Resistivity testing showed that the resistance distribution in the outer region of the wafer was uniform, with no obvious low or high resistivity points, and the resistivity difference between the edge and center decreased, indicating improved doping uniformity.

[0050] Simulation results show that ( Figure 6 , Figure 7 The device of this invention can effectively suppress abrupt temperature changes near the seed crystal edge, keeping the seed crystal-melt interface away from the temperature fluctuation region (located at the point of contact between the seed crystal and the melt outside the convection blocking ring). Flow field calculation results show that the convection direction below the seed crystal growth interface is consistent, flowing from the seed crystal center to the edge. Both Marangoni convection and natural convection are weakened by the convection blocking ring, and the chaotic convection region is pushed outward below the convection blocking ring, thereby improving the stability of the growth interface.

[0051] Example 3: This embodiment demonstrates the experimental results of this method on the growth of 6-inch p-type 4H-SiC single crystals, specifically: The integrated seed crystal fixing support rod has a support diameter of 100mm, a thickness of 40mm, and a length of 400mm. The support dimension compensation ring is 25mm wide and 40mm high, and is pre-assembled with the integrated support rod via threads. A 6-inch semi-insulating 4H-SiC seed crystal with a 0° deflection angle is selected and bonded to the bottom of the assembled support. After the seed crystal is bonded, the seed crystal protective ring is installed on the outside of the support dimension compensation ring via threaded fastening, with its bottom surface flush with the seed crystal growth surface. The seed crystal protective ring is 5mm wide and 41mm high. Subsequently, a convection blocking ring is installed on the outside of the seed crystal protective ring, with the inner side lower than the outer side, the inner height 41mm, the outer height 43mm, and the bottom surface being an arc design with a ring width of 15mm. The stoichiometric ratio of the growth system raw materials is Si:Cr:Co:Al = 50:35:11:4. After melting, the melt height is set to 25mm, and the crucible inner diameter is 220mm. When the surface temperature of the melt reaches 1860℃, the seed crystal is lowered to initiate crystal growth. After crystal growth is complete, the seed crystal grows at a maximum speed of 80 rpm, with a growth cycle set at 48 hours and a growth temperature of 1900℃.

[0052] Compared to Comparative Example 1 of the same type, the experimental results of this embodiment show that after the growth experiment, the sides of the grown crystal are clean, with no fluxing agent or polycrystalline SiC residue, after disassembly of each functional component. The integrated seed crystal fixing support rod and the support size compensation ring remain intact and are not contaminated by fluxing agent, and can be reused. Other characterization results of the crystal are similar to those of the 4-inch p-type 4H-SiC single crystal growth experiment using this method.

[0053] This embodiment verifies that the structure of the present invention can be applied to the growth of larger 6-inch seed crystals, with stable crystal quality and reusable functional components, demonstrating good adaptability and versatility.

[0054] The other parts of this embodiment are the same as those in the above embodiments, and will not be described again.

[0055] Example 4: This embodiment demonstrates the experimental results of this method on the growth of 4-inch n-type 3C-SiC single crystals, specifically: The integrated seed crystal fixing support rod has a support diameter of 100mm, a thickness of 15mm, and a length of 400mm. Since the support diameter is equal to the seed crystal diameter, no additional support size compensation ring is needed in this embodiment. A 4-inch semi-insulating 4H-SiC seed crystal with a 1° offset is used and bonded to the bottom of the support. In this example, a 0.25mm thick graphite paper layer serves as a buffer between the seed crystal and the support. After the seed crystal is bonded, a seed crystal protective ring is installed on the outside of the integrated seed crystal fixing support rod using a threaded fastening method, with its bottom surface flush with the seed crystal growth surface. The seed crystal protective ring is 5mm wide and 15.75mm high. Subsequently, a convection blocking ring is installed on the outside of the seed crystal protective ring. The convection blocking ring has a lower inner diameter and a higher outer diameter, with an inner height of 15.75mm and an outer height of 17mm. The bottom surface is curved, and the ring width is 5mm. The preferred stoichiometric ratio of the raw materials in the growth system is Si:Fe:Ti:Co = 48:35:15:2. The height of the melt after melting is set to 20 mm, and the inner diameter of the crucible is set to 150 mm. The growth atmosphere is a N2 / Ar mixed atmosphere with a pressure of 70 kPa and a N2 partial pressure (PN2) of 35 kPa. When the surface temperature of the melt reaches 1650 °C, the seed crystal begins to descend for crystal growth. After crystal growth, the seed crystal grows at a maximum rotation speed of 160 rpm for a growth period of 12 hours at a growth temperature of 1700 °C.

[0056] Compared to Comparative Example 2 of the same type, the experimental results of this embodiment show that after the growth experiment, the sides of the grown crystal were clean, with no fluxing agent or polycrystalline SiC residue, after disassembly. The integrated seed crystal fixing support rod remained intact and was not contaminated by fluxing agent, and can be reused. The surface of the grown crystal was covered with 3C-SiC, and the growth morphology was smooth and flat, indicating that the growth interface was stable during the growth process. Raman testing showed that the grown crystal was 3C-SiC, and no Raman characteristic peaks of other polymorphs appeared. XRC testing showed that the FWHM of the grown crystal was between 30-80 arcsec, indicating that the crystallization quality of the crystal was improved.

[0057] The other parts of this embodiment are the same as those in the above embodiments, and will not be described again.

[0058] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Any simple modifications or equivalent changes made to the above embodiments based on the technical essence of the present invention shall fall within the protection scope of the present invention.

Claims

1. A seed crystal support and protection structure for liquid-phase growth of silicon carbide single crystals, characterized in that, include: The seed crystal fixing support rod (10) includes a support part and a rod part, wherein the support part and the rod part are integrally formed and are used to place the silicon carbide seed crystal (30). A silicon carbide seed wafer (30) is mounted on the seed wafer fixing support rod (10) for adhering the seed wafer; A seed crystal protection ring (40) is installed on the seed crystal fixing support rod (10). The upper end face of the seed crystal protection ring (40) is flush with the upper end face of the middle support part of the seed crystal fixing support rod (10), and the lower end face of the seed crystal protection ring (40) is flush with the seed crystal bonding end face of the silicon carbide seed crystal wafer (30), forming a flat embedded layout of the silicon carbide seed crystal wafer (30).

2. The seed crystal support and protection structure for liquid-phase growth of silicon carbide single crystals according to claim 1, characterized in that: The seed crystal fixing support rod (10) also includes a support size compensation ring (20), which is detachably connected to the periphery of the support, and the seed crystal protection ring (40) is detachably installed on the periphery of the support size compensation ring (20).

3. The seed crystal support and protection structure for liquid-phase growth of silicon carbide single crystals according to claim 2, characterized in that: It also includes a convection blocking ring (50), which is detachably installed around the seed crystal protection ring (40); the upper end face of the convection blocking ring (50) is flush with the upper end face of the middle support of the seed crystal fixing support rod (10), the thickness of the convection blocking ring (50) increases along the radial extension direction, and the lower end face of the convection blocking ring (50) is in contact with the lower end face of the seed crystal protection ring (40).

4. The seed crystal support and protection structure for liquid-phase growth of silicon carbide single crystals according to claim 3, characterized in that: The lower end face of the convection blocking ring (50) has an arc-shaped or conical structure.

5. The seed crystal support and protection structure for liquid-phase growth of silicon carbide single crystals according to claim 4, characterized in that: The slope of the lower end face of the convection blocking ring (50) is 2°-25°.

6. A seed crystal support and protection structure for liquid-phase growth of silicon carbide single crystals according to any one of claims 3-5, characterized in that: The convection blocking ring (50) is provided with an internal thread, the support size compensation ring (20) and the seed crystal protection ring (40) are both provided with internal and external double threads, and the support is provided with an external thread.

7. A seed crystal support and protection structure for liquid-phase growth of silicon carbide single crystals according to any one of claims 1-5, characterized in that: A buffer layer (60) is provided between the seed crystal fixing support rod (10) and the silicon carbide seed crystal (30).

8. The seed crystal support and protection structure for liquid-phase growth of silicon carbide single crystals according to claim 7, characterized in that: The buffer layer (60) is graphite paper with a thickness of 0.05-0.5 mm.

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