Crucible for growing high-purity semi-insulating silicon carbide crystals

Abstract

The invention relates to the technical field of preparation of silicon carbide crystals, and discloses a crucible for growing high-purity semi-insulating silicon carbide crystals, which comprises an inner container layer, a transition layer and an outer support layer which are sequentially compounded from inside to outside, the inner container layer of the crucible is of a composite structure of a high-purity tantalum carbide matrix and rare earth oxide, rare earth elements form a continuous segregation layer through a grain boundary diffusion behavior in a high-temperature crystal growth environment, grain boundary active sites are passivated, oxygen impurities are prevented from permeating inwards, meanwhile, gradual matching of thermal expansion coefficients is achieved through the gradient material design of the transition layer, and the thermal expansion coefficient is increased. The interface stress in the thermal cycle process is fully absorbed, the interlayer stripping risk is avoided, so that high stability and long service life of the semi-insulating characteristic of the silicon carbide crystal are guaranteed, the microgroove array structure arranged on the outer surface of the inner container layer is subjected to pyrolytic carbon coating treatment, a regular gaseous substance transmission path is constructed, the polymorphic phase change tendency of a crystal growth interface is reduced, and the service life of the silicon carbide crystal is prolonged. Therefore, a silicon carbide single crystal structure with uniform height and no inclusion is obtained.

Description

Technical Field

[0001] This invention relates to the field of silicon carbide crystal preparation technology, specifically to a crucible for growing high-purity semi-insulating silicon carbide crystals. Background Technology

[0002] Silicon carbide crystal is a covalent compound composed of carbon and silicon. Its crystal structure consists of over 250 polymorphs formed by different stacking methods of Si-C tetrahedra. Common 3C-SiC cubic, 4H-SiC, and 6H-SiC hexagonal polymorphs are widely used in semiconductor devices and optoelectronics due to their differences in electrical and optical properties. This material possesses excellent physicochemical properties such as a wide bandgap, high breakdown field strength, and high thermal conductivity, making it suitable for high-temperature and high-frequency environments. Silicon carbide is a preferred substrate material for manufacturing high-performance power electronic devices, solid-state microwave devices, solid-state sensors, and high-temperature integrated circuits.

[0003] Currently, due to the high-temperature extreme environment during the growth of high-purity semi-insulating silicon carbide crystals, the inner liner of the crucible cannot block the diffusion of oxygen elements at the grain boundaries in real time during crystal growth. When oxygen impurity penetration defects occur in the grain boundary region, the oxygen vacancy concentration of the silicon carbide crystal will exceed the standard, causing the crystal resistivity to deteriorate sharply from the semi-insulating level to the conductive level, and the stability of the semi-insulating performance of the crystal cannot be guaranteed.

[0004] Therefore, a crucible for growing high-purity semi-insulating silicon carbide crystals is proposed to solve the above problems. Summary of the Invention

[0005] (0) Technical problems to be solved To address the shortcomings of existing technologies, this invention provides a crucible for growing high-purity semi-insulating silicon carbide crystals, thus solving the problems mentioned in the background section.

[0006] (II) Technical Solution To achieve the above objectives, the present invention provides the following technical solution: a crucible for growing high-purity semi-insulating silicon carbide crystals, comprising an inner liner layer, a transition layer, and an outer support layer sequentially laminated from the inside out: The inner liner is made of high-purity tantalum carbide material with a purity ≥99.9995wt%, a grain size of 5-20μm, and a porosity ≤0.03vol%. The transition layer is a gradient composite structure, which includes, from the inside out, a tantalum carbide-silicon carbide mixed phase layer, a silicon carbide-titanium carbide composite layer, and a titanium carbide layer. In the tantalum carbide-silicon carbide mixed phase layer, the volume fraction of tantalum carbide decreases from 100% to 40%, and the volume fraction of silicon carbide increases from 0% to 60%. The outer support layer is made of carbon fiber reinforced silicon carbide matrix composite, with the carbon fiber volume fraction being 45 - 60% and the fiber weaving angle being 30° - 45°; The crucible as a whole has a frustum-shaped structure, with the sidewall cone angle being 30° - 45°, the inner liner layer wall thickness being 3 - 8 mm, the transition layer thickness being 2 - 5 mm, and the outer support layer thickness being 8 - 15 mm; The inner surface roughness Ra of the crucible is ≤ 0.1 μm, and the range of the radial gradient change of the thermal expansion coefficient is 4.8× / K to 6.3× / K.

[0007] Preferably, the inner liner layer further contains uniformly dispersed rare earth oxide nanoparticles. The rare earth oxide is at least one of lanthanum oxide, yttrium oxide or gadolinium oxide, with a particle size of 50 - 200 nm, a doping amount of 0.01 - 0.5 wt%, and a continuous grain boundary segregation layer is formed on the surface of the inner liner layer, with the segregation layer thickness being 10 - 100 nm.

[0008] Preferably, the grain boundary segregation layer of the rare earth oxide nanoparticles satisfies the following conditions: The atomic concentration of rare earth elements in the segregation layer ≥ 5 at%; The orientation relationship between the segregation layer and the tantalum carbide matrix is (111)_TaC / / (110)_ ; The area ratio of the segregation layer covering the grain boundaries on the surface of the inner liner layer ≥ 95%.

[0009] Preferably, the transition layer of the gradient composite structure satisfies the following component gradient function defined in segments: Let r be the radial distance from the inner surface of the crucible, then: When 0 ≤ r ≤ 2 mm: Volume fraction of tantalum carbide ; Volume fraction of silicon carbide ; Volume fraction of titanium carbide ; When 2 mm < r ≤ 4 mm: Volume fraction of tantalum carbide ; Volume fraction of silicon carbide ; Volume fraction of titanium carbide .

[0010] Preferably, the carbon fiber in the outer support layer is a high-modulus pitch-based carbon fiber with a single filament tensile modulus ≥800GPa. The fiber bundle adopts a three-dimensional needle-punched braided structure with a braiding density of 8-12 layers / cm. A nano-boron carbide dispersed phase is introduced into the silicon carbide matrix. The nano-boron carbide has a particle size of 50-300nm and is added in an amount of 3-8% of the matrix volume.

[0011] Preferably, the distribution of the boron carbide nano-dispersed phase in the silicon carbide matrix satisfies: Along the radial direction from the inside to the outside, the concentration gradient of boron carbide nanoparticles increases, and the rate of change of the concentration gradient is 1.5 vol% / mm; The bonding strength between nano-boron carbide and carbon fiber interface is ≥200MPa.

[0012] Preferably, the outer surface of the inner liner of the crucible is provided with a microgroove array structure, wherein the depth of the microgroove is 0.1-0.5 mm, the width is 0.05-0.2 mm, the spacing between the grooves is 0.3-1 mm, and the angle between the direction of the microgroove and the axis of the crucible is 10°-30°; the microgroove is filled with a pyrolytic carbon coating, the coating thickness is 20-50 μm, and the density is ≥2.0 g / cm³.

[0013] Preferably, the microgroove array structure includes a main groove and branch grooves. The main grooves are distributed along a spiral line with a pitch of 5-10 mm. The angle between the branch grooves and the main grooves is 45°-60°, and the length of the branch grooves is 3-5 times the width of the main grooves.

[0014] Preferably, the top opening edge of the crucible is provided with an annular flange, the flange width is 15-25mm and the thickness is 3-8mm; the flange is embedded with a molybdenum metal wire mesh, the molybdenum wire diameter is 0.1-0.3mm, the mesh density is 80-120 mesh, and the volume of the molybdenum wire mesh accounts for 15-25% of the flange volume.

[0015] Preferably, the outer surface of the crucible is covered with an antioxidant coating, and the coating consists of the following components from the inside out: Hafnium carbide binder layer, with a thickness of 5-15 μm; Iridium reflective layer, with a thickness of 2-8 μm and a grain size ≤1 μm; Yttrium oxide stabilized zirconia thermal insulation layer, with a thickness of 20-50 μm and a porosity of ≤5 vol%.

[0016] (III) Beneficial Effects Compared with the prior art, the present invention provides a crucible for growing high-purity semi-insulating silicon carbide crystals, which has the following beneficial effects: 1. In this invention, the inner liner of the crucible adopts a composite structure of high-purity tantalum carbide matrix and rare earth oxide. Under the high-temperature crystal growth environment, rare earth elements form a continuous segregation layer through grain boundary diffusion behavior, passivating the active sites of grain boundaries and preventing oxygen impurities from penetrating inward. At the same time, the gradient material design of the transition layer realizes the gradual matching of the coefficient of thermal expansion, fully absorbs the interfacial stress during the thermal cycling process, avoids the risk of interlayer peeling, and thus ensures the high stability and long service life of the semi-insulating properties of silicon carbide crystal.

[0017] 2. In this invention, the microgroove array structure on the outer surface of the inner liner is coated with pyrolytic carbon to construct a regular gaseous material transport path, regulate the flow pattern and distribution uniformity of the reaction gas on the inner wall of the crucible, and, together with the multiphase composite barrier effect of the transition layer, enhance the mass transfer efficiency of the gas-solid interface at high temperature, eliminate the concentration fluctuations caused by local turbulence, and reduce the tendency of polymorphic phase transition at the crystal growth interface, thereby obtaining a highly uniform silicon carbide single crystal structure without inclusions.

[0018] 3. In this invention, the outer support layer adopts a composite system of carbon fiber reinforced matrix and nano-ceramic phase. The three-dimensional woven structure and gradient dispersed nanoparticles form a multi-level toughening mechanism, which improves the crack resistance of the material under extreme thermal shock conditions. At the same time, the synergistic protective effect of the multi-layer anti-oxidation coating on the outer surface of the crucible forms a dense heat-oxygen double barrier, avoiding structural deterioration caused by high-temperature oxidation, thereby ensuring that the crucible maintains complete sealing and mechanical stability during repeated high-temperature-cooling cycles. Detailed Implementation

[0019] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all 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.

[0020] Example 1: A crucible for growing high-purity semi-insulating silicon carbide crystals, comprising an inner liner layer, a transition layer, and an outer support layer sequentially laminated from the inside out: The inner liner is made of high-purity tantalum carbide material with a purity ≥99.9995wt%, a grain size of 5μm, and a porosity ≤0.03vol%. The transition layer is a gradient composite structure, which consists of a tantalum carbide-silicon carbide mixed phase layer, a silicon carbide-titanium carbide composite layer and a titanium carbide layer from the inside to the outside. In the tantalum carbide-silicon carbide mixed phase layer, the volume fraction of tantalum carbide decreases from 100% to 40%, and the volume fraction of silicon carbide increases from 0% to 60%. The outer support layer is composed of carbon fiber reinforced silicon carbide matrix composite material, with a carbon fiber volume fraction of 45% and a fiber weaving angle of 30°. The crucible as a whole has a frustum-shaped structure, the side wall taper angle is 30°, the wall thickness of the inner liner layer is 3 mm, the thickness of the transition layer is 2 mm, and the thickness of the outer support layer is 8 mm; The surface roughness Ra of the inner surface of the crucible is ≤0.1 μm, and the radial gradient of the thermal expansion coefficient is 4.8× / K.

[0021] The inner liner layer further contains uniformly dispersed rare earth oxide nanoparticles. The rare earth oxide is at least one of lanthanum oxide, yttrium oxide or gadolinium oxide, with a particle size of 50 nm, a doping amount of 0.01 wt%, and a continuously distributed grain boundary segregation layer is formed on the surface of the inner liner layer, and the thickness of the segregation layer is 10 nm.

[0022] The grain boundary segregation layer of the rare earth oxide nanoparticles satisfies the following conditions: The atomic concentration of rare earth elements in the segregation layer ≥ 5 at%; The orientation relationship between the segregation layer and the tantalum carbide matrix is (111)_TaC / / (110)_ ; The area ratio of the segregation layer covering the grain boundaries on the surface of the inner liner layer ≥ 95%.

[0023] The transition layer of the gradient composite structure satisfies the following component gradient function defined in segments: Let r be the radial distance from the inner surface of the crucible, then: When 0 ≤ r ≤ 2 mm: Volume fraction of tantalum carbide ; Volume fraction of silicon carbide ; Volume fraction of titanium carbide ; When 2 mm < r ≤ 4 mm: Volume fraction of tantalum carbide ; Volume fraction of silicon carbide ; Volume fraction of titanium carbide .

[0024] The carbon fiber in the outer support layer is a high-modulus pitch-based carbon fiber, the single-filament tensile modulus ≥ 800 GPa, the fiber bundle adopts a three-dimensional needle-punched knitting structure, the knitting density is 8 layers / cm, and nano-boron carbide dispersed phase is introduced into the silicon carbide matrix. The particle size of the nano-boron carbide is 50 nm, and the addition amount is 3% of the matrix volume.

[0025] The distribution of the nano-boron carbide dispersed phase in the silicon carbide matrix satisfies: Along the radial direction from the inside to the outside, the concentration gradient of nano-boron carbide increases, and the rate of change of the concentration gradient is 1.5 vol% / mm; The bonding strength between nano-boron carbide and carbon fiber interface is ≥200MPa.

[0026] The outer surface of the inner liner of the crucible is provided with a microgroove array structure. The microgroove depth is 0.1 mm, the width is 0.05 mm, the spacing between the grooves is 0.3 mm, and the angle between the direction of the microgroove and the axis of the crucible is 10°. The microgroove is filled with a pyrolytic carbon coating with a thickness of 20 μm and a density ≥2.0 g / cm³.

[0027] The microgroove array structure includes a main groove and branch grooves. The main grooves are distributed along a spiral with a pitch of 5 mm. The branch grooves are at an angle of 45° to the main grooves, and the length of the branch grooves is 3 times the width of the main grooves.

[0028] The top opening edge of the crucible is provided with an annular flange, which is 15mm wide and 3mm thick. The flange is inlaid with a molybdenum metal wire mesh with a diameter of 0.1mm and a mesh density of 80 mesh. The volume of the molybdenum wire mesh accounts for 15% of the volume of the flange.

[0029] The outer surface of the crucible is covered with an antioxidant coating, which consists of the following layers from the inside out: Hafnium carbide binder layer, 5 μm thick; Iridium reflective layer, 2μm thick, grain size ≤1μm; Yttrium oxide stabilized zirconia insulation layer, 20 μm thick, porosity ≤5 vol.

[0030] Example 2: A crucible for growing high-purity semi-insulating silicon carbide crystals, comprising an inner liner layer, a transition layer, and an outer support layer sequentially laminated from the inside out: The inner liner is made of high-purity tantalum carbide material with a purity ≥99.9995wt%, a grain size of 10μm, and a porosity ≤0.03vol%. The transition layer is a gradient composite structure, which consists of a tantalum carbide-silicon carbide mixed phase layer, a silicon carbide-titanium carbide composite layer and a titanium carbide layer from the inside to the outside. In the tantalum carbide-silicon carbide mixed phase layer, the volume fraction of tantalum carbide decreases from 100% to 40%, and the volume fraction of silicon carbide increases from 0% to 60%. The outer support layer is composed of carbon fiber reinforced silicon carbide matrix composite material, with a carbon fiber volume fraction of 50% and a fiber weaving angle of 35°. The crucible has a frustum-shaped structure with a 40° cone angle on the side wall, a 5mm thick inner liner, a 3mm thick transition layer, and a 10mm thick outer support layer. The inner surface roughness Ra of the crucible is ≤0.1μm, and the coefficient of thermal expansion has a radial gradient of 5.5× / K.

[0031] The inner liner layer further contains uniformly dispersed rare earth oxide nanoparticles. The rare earth oxide is at least one of lanthanum oxide, yttrium oxide or gadolinium oxide, with a particle size of 100 nm, a doping amount of 0.03 wt%, and a continuously distributed grain boundary segregation layer is formed on the surface of the inner liner layer, and the thickness of the segregation layer is 50 nm.

[0032] The grain boundary segregation layer of the rare earth oxide nanoparticles satisfies the following conditions: The atomic concentration of rare earth elements in the segregation layer ≥ 5 at%; The orientation relationship between the segregation layer and the tantalum carbide matrix is (111)_TaC / / (110)_ ; The area ratio of the segregation layer covering the grain boundaries on the surface of the inner liner layer ≥ 95%.

[0033] The transition layer of the gradient composite structure satisfies the following component gradient function defined in segments: Let r be the radial distance from the inner surface of the crucible, then: When 0 ≤ r ≤ 2 mm: Volume fraction of tantalum carbide ; Volume fraction of silicon carbide ; Volume fraction of titanium carbide ; When 2 mm < r ≤ 4 mm: Volume fraction of tantalum carbide ; Volume fraction of silicon carbide ; Volume fraction of titanium carbide .

[0034] The carbon fiber in the outer support layer is high-modulus pitch-based carbon fiber, the single-filament tensile modulus ≥ 800 GPa, the fiber bundle adopts a three-dimensional needle-punched knitting structure, the knitting density is 10 layers / cm, and nano-boron carbide dispersed phase is introduced into the silicon carbide matrix. The particle size of the nano-boron carbide is 150 nm, and the addition amount is 5% of the matrix volume.

[0035] The distribution of the nano-boron carbide dispersed phase in the silicon carbide matrix satisfies: Along the radial direction from the inside to the outside, the concentration gradient of nano-boron carbide increases, and the rate of change of the concentration gradient is 1.5 vol% / mm; The bonding strength between the nano-boron carbide and the carbon fiber interface ≥ 200 MPa.

[0036] A micro-groove array structure is provided on the outer surface of the crucible inner liner layer. The depth of the micro-groove is 0.3 mm, the width is 0.1 mm, the groove pitch is 0.8 mm, and the angle between the micro-groove direction and the crucible axis is 20°; the micro-groove is filled with a pyrolytic carbon coating, the coating thickness is 35 μm, and the density ≥ 2.0 g / cm³.

[0037] The microgroove array structure includes a main groove and branch grooves. The main grooves are distributed along a spiral with a pitch of 8 mm. The branch grooves are at an angle of 50° to the main grooves, and the length of the branch grooves is 4 times the width of the main grooves.

[0038] The top opening edge of the crucible is provided with an annular flange, which is 20 mm wide and 5 mm thick. The flange is inlaid with a molybdenum metal wire mesh with a diameter of 0.2 mm and a mesh density of 100 mesh. The volume of the molybdenum wire mesh accounts for 20% of the volume of the flange.

[0039] The outer surface of the crucible is covered with an antioxidant coating, which consists of the following layers from the inside out: Hafnium carbide binder layer, with a thickness of 5-15 μm; Iridium reflective layer, 5μm thick, with grain size ≤1μm; Yttrium oxide stabilized zirconia thermal insulation layer, 30 μm thick, porosity ≤5 vol.

[0040] Example 3: A crucible for growing high-purity semi-insulating silicon carbide crystals, comprising an inner liner layer, a transition layer, and an outer support layer sequentially laminated from the inside out: The inner liner is made of high-purity tantalum carbide material with a purity ≥99.9995wt%, a grain size of 20μm, and a porosity ≤0.03vol%. The transition layer is a gradient composite structure, which consists of a tantalum carbide-silicon carbide mixed phase layer, a silicon carbide-titanium carbide composite layer and a titanium carbide layer from the inside to the outside. In the tantalum carbide-silicon carbide mixed phase layer, the volume fraction of tantalum carbide decreases from 100% to 40%, and the volume fraction of silicon carbide increases from 0% to 60%. The outer support layer is composed of carbon fiber reinforced silicon carbide matrix composite material, with a carbon fiber volume fraction of 60% and a fiber weaving angle of 45°. The crucible has a frustum-shaped structure with a 45° cone angle on the side wall, an inner liner wall thickness of 8 mm, a transition layer thickness of 5 mm, and an outer support layer thickness of 15 mm. The inner surface roughness Ra of the crucible is ≤0.1μm, and the coefficient of thermal expansion has a radial gradient of 6.3× / K.

[0041] The inner liner further comprises uniformly dispersed rare earth oxide nanoparticles, wherein the rare earth oxide is at least one of lanthanum oxide, yttrium oxide or gadolinium oxide, the particle size is 200 nm, the doping amount is 0.5 wt%, and a continuously distributed grain boundary segregation layer is formed on the surface of the inner liner, the segregation layer having a thickness of 100 nm.

[0042] The grain boundary segregation layer of rare earth oxide nanoparticles satisfies the following conditions: Rare earth element atomic concentration in the segregation layer ≥ 5 at%; The orientation relationship between the segregation layer and the tantalum carbide matrix is (111)_TaC / / (110)_ ; The area ratio of the segregation layer covering the grain boundaries on the surface of the inner liner layer is ≥95%.

[0043] The transition layer of the gradient composite structure satisfies the following composition gradient function defined in segments: Let r be the radial distance from the inner surface of the crucible, then: When 0 ≤ r ≤ 2 mm: Volume fraction of tantalum carbide ; Volume fraction of silicon carbide ; Volume fraction of titanium carbide ; When 2 mm < r ≤ 4 mm: Volume fraction of tantalum carbide ; Volume fraction of silicon carbide ; Volume fraction of titanium carbide .

[0044] The carbon fibers in the outer support layer are high-modulus pitch-based carbon fibers, the single-filament tensile modulus is ≥800 GPa, the fiber bundle adopts a three-dimensional needle-punched knitting structure, the knitting density is 12 layers / cm, and a nano-boron carbide dispersion phase is introduced into the silicon carbide matrix. The particle size of the nano-boron carbide is 300 nm, and the addition amount is 8% of the matrix volume.

[0045] The distribution of the nano-boron carbide dispersion phase in the silicon carbide matrix satisfies: Along the radial direction from the inside to the outside, the concentration gradient of nano-boron carbide increases, and the concentration gradient change rate is 1.5 vol% / mm; The bonding strength between the nano-boron carbide and the carbon fiber interface is ≥200 MPa.

[0046] A micro-groove array structure is provided on the outer surface of the inner liner layer of the crucible. The depth of the micro-groove is 0.5 mm, the width is 0.2 mm, the groove pitch is 1 mm, and the angle between the micro-groove direction and the crucible axis is 30°; the micro-groove is filled with a pyrolytic carbon coating, the coating thickness is 50 μm, and the density is ≥2.0 g / cm³.

[0047] The micro-groove array structure includes main grooves and branch grooves. The main grooves are distributed along a helix with a pitch of 10 mm, the angle between the branch grooves and the main grooves is 60°, and the length of the branch grooves is 5 times the width of the main grooves.

[0048] A ring flange is provided at the opening edge of the top of the crucible. The width of the flange is 25 mm and the thickness is 8 mm; a molybdenum metal wire mesh is embedded inside the flange. The diameter of the molybdenum wire is 0.3 mm, the mesh density is 120 meshes, and the volume of the molybdenum wire mesh accounts for 25% of the volume of the flange.

[0049] The outer surface of the crucible is covered with an antioxidant coating, which consists of the following layers from the inside out: Hafnium carbide binder layer, 15 μm thick; Iridium reflective layer, 8μm thick, with grain size ≤1μm; Yttrium oxide stabilized zirconia thermal insulation layer, 50 μm thick, porosity ≤5 vol%.

[0050] Comparative Example 1: The difference between this comparative example and Example 1 is that rare earth oxide nanoparticles were not added to the inner liner of this comparative example.

[0051] Comparative Example 2 differs from Example 1 in that the transition layer in this comparative example does not have a composition gradient function for tantalum carbide / silicon carbide / titanium carbide.

[0052] Comparative Example 3 differs from Example 1 in that the outer surface of the inner liner layer in this comparative example does not have a microgroove array structure and a pyrolytic carbon coating.

[0053] Comparative Example 4 differs from Example 1 in that the outer support layer in this comparative example does not introduce a nano-boron carbide dispersion phase.

[0054] The performance of the silicon carbide crystal growth crucibles prepared in Examples 1-3 and Comparative Examples 1-4 was tested. The test items and methods are as follows: High-temperature sealing test: Under argon protection, the crucible is heated to 2200℃ and maintained for 50 hours. The gas leakage rate per unit time is detected by helium mass spectrometer leak detector. Impurity blocking performance was tested by analyzing the oxygen and iron content in the grown silicon carbide crystal using inductively coupled plasma mass spectrometry (ICP-MS) in a crystal growth simulation environment, and calculating the impurity blocking efficiency. Thermal shock stability test: 100 cycles of high temperature 2200℃-room temperature 25℃ were performed using a laser thermal shock test system. The number and length of microcracks on the inner wall of the crucible were observed using an industrial endoscope. For the gas phase mass transfer uniformity test, a silicon film was deposited on the inner wall of the crucible using a vapor deposition simulation device. The film thickness distribution difference was measured by a laser interferometer, and the gas phase transport uniformity coefficient was calculated.

[0055] By comparing and analyzing the data in the table, it can be seen that the crucibles prepared in Examples 1-3 for growing high-purity semi-insulating silicon carbide crystals have significantly improved performance in all aspects compared with the crucibles prepared in Comparative Examples 1-4. This indicates that the inner layer of the crucible adopts a composite structure of high-purity tantalum carbide matrix and rare earth oxides. Under the high-temperature crystal growth environment, rare earth elements form a continuous segregation layer through grain boundary diffusion behavior, passivating the active sites at the grain boundaries and preventing oxygen impurities from penetrating inward. At the same time, the gradient material design of the transition layer achieves a gradual matching of the coefficient of thermal expansion, fully absorbs the interfacial stress during the thermal cycling process, avoids the risk of interlayer peeling, and thus ensures the high stability and long service life of the semi-insulating properties of silicon carbide crystals. The microgroove array structure on the outer surface of the inner liner, coated with pyrolytic carbon, constructs a regular gaseous material transport path, regulates the flow pattern and distribution uniformity of the reactant gas on the inner wall of the crucible, and, in conjunction with the multiphase composite barrier effect of the transition layer, enhances the mass transfer efficiency of the gas-solid interface at high temperatures, eliminates concentration fluctuations caused by local turbulence, and reduces the tendency of polymorphic phase transitions at the crystal growth interface, thereby obtaining a highly uniform, inclusion-free silicon carbide single crystal structure. The outer support layer adopts a composite system of carbon fiber reinforced matrix and nano-ceramic phase. The three-dimensional woven structure and gradient-dispersed nanoparticles form a multi-layer toughening mechanism, improving the material's crack resistance under extreme thermal shock conditions. At the same time, the synergistic protective effect of the multi-layer anti-oxidation coating on the outer surface of the crucible forms a dense thermal-oxygen dual barrier, avoiding structural degradation caused by high-temperature oxidation, thus ensuring that the crucible maintains complete sealing and mechanical stability during repeated high-temperature-cooling cycles.

[0056] By comparing and analyzing the relevant data in the table, it can be seen that the crucible prepared by this invention for growing high-purity semi-insulating silicon carbide crystals not only possesses excellent sealing performance, impurity barrier ability, and thermal stability, but also achieves precise control of gas phase transport. This indicates that the technical solution provided by this invention can solve the three major technical bottlenecks in the growth process of high-purity semi-insulating silicon carbide crystals: impurity contamination, thermal stress cracking, and uneven growth, and has broad prospects for industrial application in the field of third-generation semiconductor material preparation.

[0057] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0058] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art 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 appended claims and their equivalents.

Claims

1. A crucible for growing high-purity semi-insulating silicon carbide crystals, characterized in that, It includes an inner liner layer, a transition layer, and an outer support layer that are successively compounded from the inside out: The inner liner layer is made of high-purity tantalum carbide material, with a purity ≥ 99.9995 wt%, a grain size of 5 - 20 μm, and a porosity ≤ 0.03 vol%; The transition layer is a gradient composite structure, which successively includes a tantalum carbide-silicon carbide mixed phase layer, a silicon carbide-titanium carbide composite layer, and a titanium carbide layer from the inside out. In the tantalum carbide-silicon carbide mixed phase layer, the volume fraction of tantalum carbide gradually decreases from 100% to 40%, and the volume fraction of silicon carbide gradually increases from 0% to 60%; The outer support layer is made of carbon fiber reinforced silicon carbide matrix composite material, with a carbon fiber volume fraction of 45 - 60% and a fiber braiding angle of 30° - 45°; The whole crucible is in a frustum shape structure, with a side wall cone angle of 30° - 45°, an inner liner layer wall thickness of 3 - 8 mm, a transition layer thickness of 2 - 5 mm, and an outer support layer thickness of 8 - 15 mm; The inner surface roughness of the crucible is Ra≤0.1μm, and the coefficient of thermal expansion varies along the radial gradient in the range of 4.8× / K to 6.3× / K.

2. The crucible for growing high-purity semi-insulating silicon carbide crystals according to claim 1, characterized in that: The inner liner layer further includes uniformly dispersed rare earth oxide nanoparticles. The rare earth oxide is at least one of lanthanum oxide, yttrium oxide, or gadolinium oxide, with a particle size of 50 - 200 nm, a doping amount of 0.01 - 0.5 wt%, and a continuous grain boundary segregation layer is formed on the surface of the inner liner layer, with a segregation layer thickness of 10 - 100 nm.

3. The crucible for growing high-purity semi-insulating silicon carbide crystals according to claim 1, characterized in that: The grain boundary segregation layer of the rare earth oxide nanoparticles satisfies the following conditions: The atomic concentration of rare earth elements in the segregation layer ≥ 5 at%; The orientation relationship between the segregation layer and the tantalum carbide matrix is ​​(111)_TaC / / (110)_ ; The area ratio of the grain boundary segregation layer covering the surface of the inner liner layer ≥ 95%.

4. The crucible for growing high-purity semi-insulating silicon carbide crystals according to claim 1, characterized in that: The transition layer of the gradient composite structure satisfies the following component gradient function defined in segments: Let r be the radial distance from the inner surface of the crucible, then: When 0 ≤ r ≤ 2 mm: Tantalum carbide volume fraction ; silicon carbide volume fraction ; Titanium carbide volume fraction ; When 2 mm < r ≤ 4 mm: Tantalum carbide volume fraction ; silicon carbide volume fraction ; Titanium carbide volume fraction .

5. The crucible for growing high-purity semi-insulating silicon carbide crystals according to claim 1, characterized in that: The carbon fiber in the outer support layer is high modulus pitch-based carbon fiber, with a single fiber tensile modulus ≥ 800 GPa. The fiber bundle adopts a three-dimensional needle punching braiding structure, with a braiding density of 8 - 12 layers / cm, and nano boron carbide dispersion phase is introduced into the silicon carbide matrix. The nano boron carbide has a particle size of 50 - 300 nm and an addition amount of 3 - 8% of the matrix volume.

6. The crucible for growing high-purity semi-insulating silicon carbide crystals according to claim 1, characterized in that: The distribution of the nano boron carbide dispersion phase in the silicon carbide matrix satisfies: Along the radial direction from the inside out, the concentration gradient of nano boron carbide increases, and the concentration gradient change rate is 1.5 vol% / mm; The bonding strength between nano boron carbide and the carbon fiber interface ≥ 200 MPa.

7. The crucible for growing high-purity semi-insulating silicon carbide crystals according to claim 1, characterized in that: The outer surface of the crucible inner liner layer is provided with a microgroove array structure. The microgroove depth is 0.1 - 0.5 mm, the width is 0.05 - 0.2 mm, the groove spacing is 0.3 - 1 mm, and the microgroove direction forms an angle of 10° - 30° with the crucible axis; The microgrooves are filled with a pyrolytic carbon coating, with a coating thickness of 20 - 50 μm and a density ≥ 2.0 g / cm³.

8. The crucible for growing high-purity semi-insulating silicon carbide crystals according to claim 1, characterized in that: The microgroove array structure includes main grooves and branch grooves. The main grooves are distributed along a spiral line, with a pitch of 5 - 10 mm. The branch grooves form an angle of 四十五° - 60° with the main grooves, and the length of the branch grooves is 3 - 5 times the width of the main grooves. Note: In the above translation, for the angle value "四十五°" which should be in Chinese characters in the original text, it seems there is an error. It should probably be a specific angle value in degrees like "45°". You can correct it according to the actual situation.

9. The crucible for growing high-purity semi-insulating silicon carbide crystals according to claim 1, characterized in that: The top opening edge of the crucible is provided with an annular flange, the flange width is 15-25mm and the thickness is 3-8mm; the flange is embedded with a molybdenum metal wire mesh, the molybdenum wire diameter is 0.1-0.3mm, the mesh density is 80-120 mesh, and the volume of the molybdenum wire mesh occupies 15-25% of the flange volume.

10. A crucible for growing high-purity semi-insulating silicon carbide crystals according to claim 1, characterized in that: The outer surface of the crucible is covered with an antioxidant coating, which consists of the following layers from the inside out: Hafnium carbide binder layer, with a thickness of 5-15 μm; Iridium reflective layer, with a thickness of 2-8 μm and a grain size ≤1 μm; Yttrium oxide stabilized zirconia thermal insulation layer, with a thickness of 20-50 μm and a porosity of ≤5 vol%.

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