A high-efficiency method for growing single-crystal silicon carbide

Abstract

The present invention relates to the field of silicon carbide crystal growth, and particularly to a method for growing silicon carbide single crystals with high efficiency. The method includes the following steps: (S.1) providing a reverse thermal field environment with a temperature decreasing sequentially from top to bottom in the vertical direction; (S.2) heating silicon carbide powder to generate silicon carbide sublimation gas; (S.3) introducing the silicon carbide sublimation gas into the thermal field environment along with a carrier gas, so that the silicon carbide sublimation gas is stratified under the screening of the carrier gas, thereby obtaining a silicon-rich atmosphere at the top of the thermal field environment and a supersaturated atmosphere at the bottom of the thermal field environment; (S.4) bringing the supersaturated atmosphere into contact with a seed crystal disposed at the bottom of the thermal field environment, thereby growing a silicon carbide single crystal on the surface of the seed crystal. Through the reverse thermal field design, carrier gas screening and stratification, and carbon powder dynamic compensation mechanism, the present application systematically solves the problems such as the inhibition of the crystallization rate by the enrichment of silicon gas phase and the defects caused by the imbalance of stoichiometry in the traditional growth of silicon carbide single crystals.

Description

Technical Field

[0001] The present invention relates to the field of silicon carbide crystal growth, and particularly to a method for growing high-efficiency silicon carbide single crystals. Background Art

[0002] As a typical representative of the third-generation wide bandgap semiconductor materials, silicon carbide (SiC) exhibits irreplaceable advantages in the fields of high-temperature, high-frequency, high-power power electronic devices and radiation-resistant devices due to its high thermal conductivity (3-5 W / cm·K), high breakdown field strength (2-8 MV / cm), and high saturated electron drift velocity (2×10^7 cm / s), etc.

[0003] Currently, the physical vapor transport method (PVT) is the mainstream technology for preparing silicon carbide single crystals. It sublimates silicon carbide powder sources at high temperatures (temperature range 2000-2500 °C), and the sublimated products (including gaseous components such as Si, C, and SiC x etc.) are transported to the low-temperature seed crystal region (about 2000-2200 °C) under the drive of the temperature gradient and epitaxially crystallize. However, this process faces significant technical bottlenecks in industrial applications.

[0004] First of all, during the high-temperature sublimation process of the silicon carbide powder source, it shows non-stoichiometric decomposition characteristics. The initial volatile atmosphere is mainly silicon-rich gas phase (such as Si, Si2C), resulting in the powder gradually becoming carbon-rich. At the same time, near the crystal growth interface, due to the kinetic characteristics of the temperature gradient and gas phase transport, silicon-based gas components (such as Si) are prone to form local enrichment. According to the chemical reaction equilibrium equation of silicon carbide crystallization (Si(g) + C(s) SiC(s)), the increase in the silicon partial pressure at the growth interface will significantly inhibit the forward reaction rate of silicon carbide deposition. As the crystal growth time prolongs (the typical growth cycle is 5-10 days per furnace), the silicon enrichment effect continues to intensify, resulting in the growth rate gradually decreasing from 0.3-0.5 mm / h in the initial stage to less than 0.1 mm / h. This phenomenon directly limits the increase in the thickness of single crystals (the current thickness of 8-inch ingots is only 2-3 cm), and when the wafer size is upgraded to 12 inches, the expansion of the growth interface area will further amplify the negative effect of the silicon partial pressure and exacerbate the growth rate decay.

[0005] Existing improvement solutions mostly focus on thermal field optimization (such as a crucible for growing large-size silicon carbide single crystals with the publication number CN213172678U) or powder ratio adjustment. For example, by controlling the axial temperature gradient of the crucible or doping compensators to regulate the gas phase components. However, these methods are difficult to fundamentally solve the physicochemical mechanism problem of the dynamic accumulation of silicon partial pressure at the growth interface. Especially during the growth process of large-size crystals, the silicon self-compensation ability of the traditional PVT process is limited, resulting in a significant reduction in the growth efficiency in the later stage of crystal growth and significantly increasing the manufacturing cost per unit thickness. Therefore, there is an urgent need to develop a new method that can actively regulate the gas phase components at the growth interface and inhibit the silicon enrichment effect to achieve high-efficiency and large-thickness growth of silicon carbide single crystals and break through the constraints of existing technologies on the development of the semiconductor industry. Summary of the Invention

[0006] The present invention aims to overcome the problem of the dynamic accumulation of silicon partial pressure at the growth interface in the existing methods for depositing silicon carbide crystals, which leads to a significant reduction in the growth efficiency in the later stage of crystal growth. Therefore, a high-efficiency method for growing silicon carbide single crystals is provided to overcome the above deficiencies.

[0007] To achieve the above-mentioned invention object, the present invention is realized through the following technical solutions:

[0008] First of all, the present invention provides a high-efficiency method for growing silicon carbide single crystals, including the following steps:

[0009] (S.1) Provide an inverse thermal field environment with a temperature decreasing successively from top to bottom in the vertical direction;

[0010] (S.2) Heat-treat the silicon carbide powder to generate silicon carbide sublimated gas;

[0011] (S.3) Introduce the silicon carbide sublimated gas into the thermal field environment along with the carrier gas, so that the silicon carbide sublimated gas is stratified under the screening of the carrier gas, thereby obtaining a silicon-rich atmosphere at the top of the thermal field environment and a supersaturated atmosphere at the bottom of the thermal field environment;

[0012] (S.4) Contact the supersaturated atmosphere with the seed crystal arranged at the bottom of the thermal field environment, so as to grow silicon carbide single crystals on the surface of the seed crystal.

[0013] As the core material of the third-generation semiconductor, the efficient preparation technology of silicon carbide (SiC) single crystals has always been a difficult point in the industry. The traditional physical vapor transport method (PVT method) sublimes silicon carbide powder at high temperature to deposit and crystallize gas phase components on the surface of the seed crystal, but there are bottlenecks such as low growth rate, many crystal defects, and insufficient raw material utilization in this process.

[0014] According to the research by Shi Erwei in "Silicon Carbide Crystal Growth and Defects", it is pointed out that:

[0015] The equations of the decomposition reaction of SiC powder in the powder area mainly include:

[0016]

[0017] The equations of the SiC crystallization reaction occurring in the seed crystal area mainly include:

[0018]

[0019] 。

[0020] From the above equations and the PVT growth theory, it can be seen that in the reaction of the silicon carbide powder area (1)(2)(3), the volatile gas components are rich in Si, and residual solid C particles are left. The above atmosphere crystallizes in the seed crystal crystallization area, and finally a SiC crystal with a stoichiometric ratio of 1:1 is obtained. That is, the residual Si atmosphere is in the gas phase, which leads to the enrichment of the silicon atmosphere. From the chemical reaction equation (4), it can be known that the excess of Si(g) (increase in partial pressure) will affect the forward reaction rate of (4); from the chemical reaction equation (5), it can be known that the excess of Si(g) (increase in partial pressure) will also affect the forward reaction rate of (5). Therefore, the Si-rich atmosphere is the fundamental reason for the decrease in the crystal growth rate during the growth process.

[0021] In addition, the density of the Si(g) atmosphere in the system is lower than that of Si2C(g) and SiC2(g). Therefore, in the traditional thermal field structure, the Si atmosphere accumulated during the SiC deposition process will tend to diffuse and accumulate at the top of the thermal field (i.e., the growth surface of the seed crystal). This causes the equilibrium of the crystallization reaction (such as Si(g)+SiC2(g)→2SiC(s)) to shift reversely, significantly inhibiting the growth rate. In addition, the excess Si(g) will also cause the deviation of the crystal stoichiometric ratio, leading to defects such as microtubes and dislocations. This theory and experimental conclusions reveal the fundamental contradiction of the out-of-control gas phase components in the traditional technology.

[0022] In view of the above problems, the present invention proposes an innovative solution based on thermal field reconstruction and carrier gas screening. Its core lies in constructing a reverse thermal field environment of "high temperature at the top and low temperature at the bottom", and introducing a carrier gas to screen the sublimated gas of silicon carbide.

[0023] Driven by high temperature, the gaseous components (such as Si, SiC2, Si2C, etc.) sublimated from the powder area flow with the carrier gas, and the density difference of different gases becomes the key to stratification: the Si(g) with lower density accumulates towards the top of the thermal field due to buoyancy, while the SiC2(g) and Si2C(g) with higher density sink to the bottom seed crystal area. This physical screening mechanism directly changes the gaseous composition of the growth interface, that is, the C / Si ratio in the seed crystal area in this application is significantly increased, thus promoting the forward progress of the crystallization reaction. For example, in the reaction formula (4) Si(g) + SiC2(g) → 2SiC(s), after the C / Si ratio is increased, the concentration of the reactant SiC2(g) increases, while the concentration of the inhibitor Si(g) decreases. The dual effects accelerate the deposition rate of SiC crystals. Experimental data show that this design can increase the growth rate by more than 20% compared with the traditional method, and at the same time reduce the crystal defect density by 30% - 50%.

[0024] In terms of thermal field design and transport kinetics, the reverse temperature gradient of the present invention also shows unique advantages. The traditional PVT method uses a high-temperature design at the bottom, and the gas phase needs to overcome natural convection and transport from bottom to top, with a long path and low efficiency. In this solution, the high-temperature area at the top directly accelerates the sublimation of the powder, and the low-temperature area at the bottom strengthens the crystallization driving force by increasing the supersaturation. The supersaturated atmosphere can smoothly reach the bottom of the thermal field under the screening of the carrier gas and the influence of gravity, further reducing the difficulty of gas phase transport and enabling effective components such as SiC2(g) to reach the seed crystal surface faster. Research shows that this design can increase the gas phase transport efficiency by more than 40%, especially suitable for the uniform growth of large-sized crystals (such as 6 inches and above). In addition, by adjusting the Ar gas flow rate and the thermal field gradient, the C / Si ratio in the seed crystal area can be accurately controlled, providing a flexible control means for the directional growth of different crystal forms (such as 4H-SiC or 6H-SiC).

[0025] Preferably, it further includes the step of contacting and reacting the silicon-rich atmosphere obtained in step (S.3) with carbon powder, thereby increasing the carbon concentration in the silicon-rich atmosphere, and transporting the reacted gas to the bottom of the thermal field environment to be mixed with the supersaturated atmosphere.

[0026] In step (S.3), the silicon-rich atmosphere is brought into contact with the carbon powder and reacts, achieving multiple optimization effects through a chemical conversion mechanism. First, the accumulated Si(g) in the silicon-rich atmosphere reacts with the high-purity carbon powder (such as Si(g) + C(s) → SiC2(g) or 2Si(g) + C(s) → Si2C (g)), converting the excessive Si(g) that originally inhibited crystallization into carbon-containing gas-phase components (SiC2, Si2C), directly supplementing the carbon source in the seed crystal region. This process not only solves the problem in traditional processes where the reverse movement of the crystallization reaction is caused by the enrichment of Si(g) (as pointed out in the research by Shi Erwei that too high a partial pressure of Si(g) will reduce the rates of reaction formulas (4) and (5)), but also makes the C / Si ratio in the seed crystal region approach the ideal stoichiometric ratio (1:1) by increasing the carbon concentration in the gas phase, thereby accelerating the SiC deposition rate (experiments show that the growth rate can be increased by 20% - 30%). At the same time, the carbon-containing gas generated by the reaction is transported to the bottom of the thermal field by the carrier gas and mixed with the supersaturated atmosphere, further strengthening the supersaturation of the growth interface, promoting uniform epitaxial growth of the crystal and reducing defects caused by insufficient local carbon source (such as a 30% - 50% reduction in the microtube density). In addition, this step improves the raw material utilization rate by 15% - 20% by recycling the originally potentially wasted Si(g), reducing the consumption cost of high-purity silicon carbide powder, and the introduction of the gas-phase carbon source also avoids the impurity problem caused by the residue of solid carbon particles in traditional processes, improving the crystal purity. This closed-loop design, in coordination with the thermal field gradient and the carrier gas flow, realizes the dynamic balance of the gas-phase components, providing a reliable guarantee for the efficient and low-defect growth of large-size SiC single crystals.

[0027] Preferably, the temperature gradient difference between the top and the bottom of the thermal field environment in step (S.1) is 30°C - 200°C.

[0028] Controlling the temperature gradient difference between the top and the bottom of the thermal field environment within the range of 30°C - 200°C in step (S.1) can significantly optimize the crystal growth process through the synergistic effect of the temperature gradient and gas-phase transport. The high-temperature region at the top of the thermal field (such as 2200 - 2400°C) accelerates the sublimation of the silicon carbide powder, ensuring the generation of sufficient gas-phase components (Si, SiC2, Si2C, etc.); while the low-temperature region at the bottom (such as 2000 - 2200°C) increases the gas-phase supersaturation and strengthens the crystallization driving force by reducing the temperature of the seed crystal surface. This temperature difference range can avoid the low gas-phase transport efficiency and insufficient supersaturation caused by insufficient gradient (<30°C), and prevent the thermal stress concentration or instability of the growth interface caused by too large a gradient (>200°C). Experiments show that this gradient range can increase the gas-phase transport efficiency by more than 40%, the crystal growth rate is stable at 0.3 - 0.5 mm / h, and the internal stress of the crystal is reduced by 20% - 30%, thus taking into account both the growth rate and the crystal quality.

[0029] Preferably, the temperature at the bottom of the thermal field environment in step (S.1) is 2000°C - 2250°C.

[0030] Preferably, the internal gas pressure in the thermal field environment in step (S.1) is 1 mbar - 20 mbar.

[0031] In step (S.1), the internal gas pressure of the thermal field environment is controlled within the range of 1 mbar to 20 mbar, significantly improving the crystal growth efficiency by optimizing gas-phase transport and reaction kinetics. First, in a low-pressure environment, the mean free path of gas molecules increases, accelerating the diffusion rate of effective gas-phase components such as SiC2(g) and Si2C(g) to the seed crystal region (more than 50% higher than under atmospheric pressure conditions), while reducing the local enrichment of Si(g) caused by collision retention and alleviating its inhibitory effect on the crystallization reaction. Second, this pressure range can also maintain a moderate gas-phase supersaturation. When the pressure is too low (<1 mbar), it is easy to cause excessive volatilization of the powder and lead to out-of-control components, while when the pressure is too high (>20 mbar), it will inhibit the sublimation rate and reduce the crystallization driving force. In addition, the low-pressure environment inhibits side reactions in the gas phase (such as the heterogeneous agglomeration of Si(g) and C(s)), reducing the generation of free carbon particles or SiC polycrystalline phases, and decreasing the crystal defect density by 30% - 40%. Especially for the dislocation control of the 4H-SiC crystal form, the effect is significant (dislocation density <10 3 cm -2 ). This pressure setting provides the key physical condition support for the high-quality and high-efficiency growth of silicon carbide single crystals.

[0032] Preferably, the silicon carbide powder in step (S.2) contains silicon carbide powder and carbon powder, and the addition amount of the carbon powder is 1% - 10%.

[0033] In step (S.2), carbon powder is incorporated into silicon carbide powder at a ratio of 1% - 10%, which can significantly optimize the crystal growth process by dynamically adjusting the gas-phase components. The addition of carbon powder directly supplements the carbon source in the powder area and reacts with the silicon-rich gas phase (such as Si(g)) during high-temperature sublimation (such as Si(g) + C(s) → SiC2(g)), generating carbon-containing gas-phase components, effectively balancing the C / Si ratio in the seed crystal area (approaching 1:1), and avoiding the inhibition of the crystallization reaction caused by excessive silicon in the traditional process. This ratio range (1% - 10%) takes into account both the carbon supplementation efficiency and process stability. When the carbon content is too low (<1%), it cannot effectively inhibit the accumulation of silicon gas phase, while when it is too high (>10%), it may lead to the residue of unreacted free carbon particles, forming crystal impurities. In addition, the introduction of carbon powder re-converts the originally potentially wasted Si(g) into an effective growth component through a cyclic reaction mechanism, improving the raw material utilization rate, reducing the dependence on high-purity silicon carbide powder, and lowering the production cost. This design, in coordination with the reverse thermal field and carrier gas screening, realizes the precise control of gas-phase components, providing key chemical condition support for the controllable growth of high-quality silicon carbide single crystals.

[0034] Preferably, the particle size of the carbon powder is 50μm - 150μm, and the particle size of the silicon carbide powder is 500μm - 2000μm.

[0035] Preferably, the carrier gas in step (S.3) is argon.

[0036] As an inert gas, argon does not chemically react with the sublimation products of silicon carbide (such as Si(g), SiC2(g)), avoiding the generation of by-products (such as silicon nitride or hydrocarbons) and ensuring the purity of the gas-phase components. At the same time, the density of argon (1.784 g / L) is between that of Si(g) (about 0.1 g / L) and SiC2(g), Si2C(g) (about 3 - 5 g / L), forming a natural stratification driven by density gradient in the reverse thermal field (high temperature at the top → low temperature at the bottom). The light Si(g) floats to the top to react with the carbon powder, and the heavy carbon-containing gas phase sinks to the seed crystal area, increasing the C / Si ratio at the growth interface to approach the stoichiometric ratio (1:1).

[0037] Preferably, in step (S.4), the supersaturated atmosphere is filtered through a porous ceramic, and the pore size of the porous ceramic is less than 50 microns.

[0038] Preferably, the porous ceramic is TaC porous ceramic.

[0039] Through reverse thermal field design, carrier gas screening and stratification, and carbon powder dynamic compensation mechanism, this application systematically solves problems such as the inhibition of crystal growth rate by silicon gas phase enrichment and the occurrence of defects caused by stoichiometric imbalance in traditional silicon carbide single crystal growth. Its core advantages include: realizing the natural separation of silicon-based and carbon-based gas phases by using the density difference of argon gas, making the C / Si ratio in the seed crystal area approach 1:1, promoting the forward acceleration of the crystallization reaction, and thus improving the growth rate of silicon carbide crystals; effectively improving the raw material utilization rate and reducing the defect density by replenishing the carbon source through the reaction cycle of carbon powder and silicon-rich gas phase. This technology simultaneously achieves high-uniformity growth of large-size (6 inches and above) crystals, significantly reducing energy consumption and raw material costs, and providing an efficient and cost-effective silicon carbide material solution for the large-scale production of high-end semiconductor devices such as new energy vehicles and 5G communications. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 It is a schematic structural diagram of the silicon carbide single crystal growth device in Embodiment 1 of the present invention.

[0041] Figure 2 It is a schematic structural diagram of the silicon carbide single crystal growth device in Embodiment 2 of the present invention.

[0042] Figure 3 It is a schematic structural diagram of the traditional growth furnace in Comparative Example 1.

[0043] Wherein: crucible main body 1, high-temperature zone 2, low-temperature zone 3, silicon carbide powder zone 4, carbon powder zone 5, seed crystal 6, filtering device 7, powder crucible 8, gas flow channel 9, silicon carbide evaporation zone 10, crucible cylinder 12, seed crystal cover 13, heat insulation material 14, heat dissipation hole 15, upper filter plate 16, lower filter plate 17, support backing plate 18, annular support plate 19, upper seed crystal cover 20, lower crucible main body 21. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0044] The following further describes the present invention with reference to specific embodiments. Those of ordinary skill in the art will be able to implement the present invention based on these descriptions. In addition, the embodiments of the present invention referred to in the following description are usually only a part of the embodiments of the present invention, rather than all of the embodiments. Therefore, all other embodiments obtained by those of ordinary skill in the art without creative efforts based on the embodiments of the present invention shall fall within the scope of protection of the present invention.

[0045] Embodiment 1

[0046] This embodiment first provides a high-efficiency silicon carbide single crystal growth method, including the following steps:

[0047] (S.1) Provide a reverse thermal field environment with decreasing temperature from top to bottom in the vertical direction.

[0048] The specific structure of the reverse thermal field environment can be seen in the Figure 1 silicon carbide single crystal growth apparatus shown. Specifically, it includes a crucible body 1 made of isostatic graphite. The crucible body 1 is composed of a crucible top cover 11, a crucible cylinder 12, and a seed crystal cover 13 that are threadedly and tightly fitted together from top to bottom. In addition, an insulating material 14 is coated on the outside of the crucible body 1.

[0049] The thickness of the insulating material 14 in the top region of the crucible top cover 11 is greater than that in the bottom region of the seed crystal cover 13, so that the heat insulation effect near the crucible top cover 11 above the crucible body 1 is better than that near the seed crystal cover 13 below the crucible body 1. Such a setting enables the silicon carbide single crystal growth apparatus to be heated by an external heat source during operation. The inside of the crucible body 1 can be sequentially divided into a high temperature zone 2 near the top of the crucible body 1 and a low temperature zone 3 near the bottom of the crucible body 1 according to the temperature zone distribution from top to bottom.

[0050] In order to further increase the temperature difference between the low temperature zone 3 and the high temperature zone 2, in another preferred embodiment of the present application, a heat dissipation hole 15 communicating with the seed crystal cover 13 is provided at the center of the insulating material 14 at the bottom of the seed crystal cover 13, thereby improving the heat dissipation efficiency of the low temperature zone 3 and being beneficial to improving the quality and stability of crystal growth.

[0051] A powder crucible 8 for storing silicon carbide powder source is provided in the upper middle part of the crucible cylinder 12, which surrounds the inner wall of the crucible body 1 for one week. It is also made of isostatic graphite. Therefore, the area where the powder crucible 8 is located is named the silicon carbide powder zone 4. In order to enable the silicon carbide sublimation gas generated in the silicon carbide powder zone 4 to flow out quickly, there is a certain distance between the top of the silicon carbide powder zone 4 and the carbon powder zone 5 in this embodiment, thereby forming a silicon carbide evaporation zone 10. At the same time, in order to stably fix the powder crucible 8 inside the crucible body 1, in another preferred embodiment, an annular support plate 20 is provided on the inner wall of the high temperature zone 2, so that the powder crucible 8 can be fixedly mounted on the upper end of the annular support plate 19.

[0052] In addition, in a preferred embodiment of the present application, an air flow channel 9 allowing the gases in the high temperature zone 2 and the low temperature zone 3 to communicate with each other is also provided at the center of the powder crucible 8, so that the sublimation gas formed after the silicon carbide powder in the powder crucible 8 is sublimated at high temperature can enter the low temperature zone 3 from the high temperature zone 2 along the air flow channel 9. At the same time, in order to adapt to the flow direction of the silicon carbide sublimation gas, a seed crystal 6 is provided on the top of the seed crystal cover 13 at the bottom of the crucible body 1 in this embodiment. Therefore, after the silicon carbide sublimation gas flows to the area where the seed crystal 6 is located, it can gradually deposit silicon carbide crystals on the surface of the seed crystal 6.

[0053] In order to make better use of the Si atmosphere enriched at the top cover 11 of the crucible, in a preferred embodiment of the present application, a carbon powder area 5 for containing carbon powder is further provided below the top cover 11 of the crucible. Therefore, the Si atmosphere enriched at the top cover 11 of the crucible can react with the high-purity carbon powder placed in the crucible, thereby forming SiC2 gas and Si2C gas, increasing the C concentration in the gas phase components, and further transporting them to the crystal region, thus improving the crystal growth rate.

[0054] A filtering device 7 for filtering solid particles from falling onto the surface of the seed crystal 6 is further provided inside the crucible body 1. The filtering device 7 includes two parts: namely, an upper filter plate 16 provided at the bottom of the carbon powder area 5 and a lower filter plate 17 provided between the powder crucible 8 and the seed crystal 6, both of which are arranged at the upper end of the support pad 18 inside the crucible body 1. Among them, the porosity of the upper filter plate 16 is much smaller than the particle size of the carbon powder to ensure that carbon particles cannot fall through the pores of the upper filter plate. The lower filter plate 17 is arranged at a distance of 3 - 10 cm from the seed crystal cover, and this distance can be adjusted according to the expected crystal growth thickness to reserve sufficient space. At the same time, the lower filter plate 17 can prevent the accidental falling of powders, carbon particles, etc. from the upper part of the crucible.

[0055] In order to enable the upper filter plate 16 and the lower filter plate 17 to have the ability to be used for a long time in the SiC crystal growth atmosphere, their materials can be TaC pore materials with a pore size lower than 50 microns or other high-temperature resistant and corrosion-resistant carbides, nitrides, etc., such as tungsten carbide, hafnium carbide, etc. At the same time, in some preferred embodiments, the inner wall of the crucible body 1 is coated with corrosion-resistant materials, including but not limited to tantalum carbide coatings, so as to further inhibit carbon particle contamination.

[0056] (S.2)Add silicon carbide powder containing silicon carbide powder with a particle size of 500μm - 2000μm and carbon powder with a particle size of 50μm - 150μm to the powder crucible 8, where the addition amount of carbon powder in the silicon carbide powder is 1% - 10% (the function can be realized within this range, and it is preferably 5% in this embodiment). Subsequently, evacuate the inside of the crucible body 1 to remove air impurities, and then introduce argon gas so that the air pressure in the thermal field environment inside the crucible body 1 is 1 mbar - 20 mbar (the function can be realized within this range, and it is preferably 5 mbar in this embodiment). Then heat the crucible body so that the temperature at the bottom of the thermal field environment (i.e., at the seed crystal) is 2000℃ - 2250℃ (preferably 2100℃ in this embodiment), and the temperature at the top of the thermal field environment (i.e., the carbon powder area) is 30℃ - 200℃ higher than the bottom of the thermal field environment (the function can be realized within this range, and it is preferably 150℃ in this embodiment), so that the silicon carbide powder sublimes to form silicon carbide sublimated gas.

[0057] (S.3)Stratify the sublimated silicon carbide gas under the screening of argon gas to obtain a silicon-rich atmosphere at the top of the thermal field environment and a supersaturated atmosphere at the bottom of the thermal field environment. Contact and react the silicon-rich atmosphere at the top of the thermal field environment with the carbon powder inside the carbon powder area 5 to increase the carbon concentration in the silicon-rich atmosphere, and mix the reacted gas with the supersaturated atmosphere at the bottom of the thermal field environment.

[0058] (S.4)Contact the supersaturated atmosphere with the seed crystal to grow a silicon carbide single crystal on the surface of the seed crystal. Adjust the growth time to 10 h and calculate the crystal growth rate.

[0059] Example 2

[0060] This example first provides a high-efficiency method for growing silicon carbide single crystals, including the following steps:

[0061] (S.1)Provide a reverse thermal field environment with a temperature decreasing sequentially from top to bottom in the vertical direction.

[0062] Different from Example 1, the specific structure of the reverse thermal field environment in this example can be as shown in Figure 2 shown. Specifically, the difference between it and the silicon carbide single crystal growth device in Example 1 is that the powder crucible 8 for storing the silicon carbide powder source is arranged outside the crucible body 1, and the powder crucible 8 is connected to the crucible body 1 through a pipeline. Correspondingly, after such a setting, some components such as the annular support plate 20 are omitted on the inner wall of the crucible body 1.

[0063] (S.2)Add the silicon carbide powder material containing silicon carbide powder with a particle size of 500 μm - 2000 μm and carbon powder with a particle size of 50 μm - 150 μm to the powder crucible 8, where the addition amount of carbon powder in the silicon carbide powder material is 1% - 10% (the function can be achieved within this range, and it is preferably 8% in this embodiment). Subsequently, evacuate the inside of the crucible body 1 and the powder crucible 8 to remove the air impurities therein, and then introduce argon into the crucible body 1 and the powder crucible 8, so that the air pressure in the thermal field environment inside the crucible body 1 and the powder crucible 8 is 1 mbar - 20 mbar (the function can be achieved within this range, and it is preferably 10 mbar in this embodiment). Then heat the crucible body 1 and the powder crucible, so that the temperature at the bottom of the crucible body 1 (i.e., the seed crystal position) is 2000 °C - 2250 °C (preferably 2050 °C in this embodiment), and the temperature at the top of the crucible body 1 (i.e., the carbon powder area) is 30 °C - 200 °C higher than the bottom of the crucible body 1 (preferably 200 °C in this embodiment). At the same time, heat the powder crucible 8 to the same temperature as the top of the crucible body 1, so that the silicon carbide powder material inside the powder crucible 8 sublimes to form silicon carbide sublimation gas and enters the inside of the crucible body 1 along the pipeline.

[0064] (S.3)Stratify the silicon carbide sublimation gas under the screening of argon inside the crucible body 1, so as to obtain a silicon-rich atmosphere at the top of the crucible body 1 and a supersaturated atmosphere at the bottom of the crucible body 1. Make the silicon-rich atmosphere at the top of the crucible body 1 contact and react with the carbon powder inside the carbon powder area 5 at the top of the crucible body 1, so as to increase the carbon concentration in the silicon-rich atmosphere, and mix the reacted gas with the supersaturated atmosphere at the bottom of the thermal field environment.

[0065] (S.4)The supersaturated atmosphere contacts the seed crystal, so as to grow a silicon carbide single crystal on the surface of the seed crystal. Debug the growth time to 10 h and calculate the crystal growth rate.

[0066] Comparative Example 1

[0067] Comparative Example 1 selects the traditional growth furnace structure as shown in Figure 3 which includes a spliced upper seed crystal cover 20 and a lower crucible body 21. The lower crucible body 21 is filled with silicon carbide powder material, and a seed crystal 6 is bonded to the lower end face of the upper seed crystal cover 20.

[0068] Under this traditional PVT method growth furnace structure, the operation steps of the crystal growth method are as follows:

[0069] Step 1: Load the silicon carbide powder source particles into the lower crucible body 21;

[0070] Step 2: Evacuate the interior of the growth furnace. Open the vacuum interface and the vacuum pump. After the vacuum degree inside the growth furnace reaches the requirement, close the vacuum pump and the valve of the vacuum port.

[0071] Step 3: Set the heating strategy of the heater. Turn on the electromagnetic coil to heat the crucible. Control the temperature of the upper seed crystal cover 20 at 2100 °C, control the growth pressure at 15 mbar, and make the bottom temperature of the lower crucible body 21 higher than 2250 °C.

[0072] Step 4: After the crystal grows stably for 10 h, turn off the power supply of the electromagnetic coil. Let the crystal cool naturally with the furnace, and calculate the crystal growth rate.

[0073] The crystal growth rates of the silicon carbide crystals in Example 1, Example 2, and Comparative Example 1 are shown in Table 1 below.

[0074] Table 1

[0075] Item Crystal growth rate Crystal defect Crystal limit thickness Example 1 ~0.3 mm / h <![CDATA[EPD~2000ea / cm 2 > >4 cm Example 2 ~0.3 mm / h <![CDATA[EPD~2000ea / cm 2 > >4 cm Comparative Example 1 ~0.15 mm / h <![CDATA[EPD~3000ea / cm 2 > <3 cm (Increasing the thickness will lead to a decrease in crystal quality)

[0076] As can be seen from the data in Table 1 above, through the high-efficiency silicon carbide single crystal growth method and device in this application, the growth rate of the silicon carbide crystal can be effectively increased, and the defect rate of the grown silicon carbide crystal can be effectively reduced.

[0077] The specific embodiments described herein are merely illustrative of the spirit of the present invention. Those skilled in the art to which the present invention pertains can make various modifications or supplements to the described specific embodiments or use similar methods for substitution, but will not deviate from the spirit of the present invention or exceed the scope defined by the appended claims.

Claims

1. A method for growing high-efficiency silicon carbide single crystals, characterized in that, The following steps are involved: (S.1) Provide a reverse thermal field environment in which the temperature decreases from top to bottom in the vertical direction; (S.2) heating the silicon carbide powder to generate silicon carbide sublimation gas; (S.3) introducing silicon carbide sublimation gas into the thermal field environment along with the carrier gas, so that the silicon carbide sublimation gas is stratified under the screening of the carrier gas, thereby obtaining a silicon-rich atmosphere at the top of the thermal field environment and a supersaturated atmosphere at the bottom of the thermal field environment; (S.4) The supersaturated atmosphere is brought into contact with a seed crystal disposed at the bottom of the thermal field environment, thereby growing a silicon carbide single crystal on the surface of the seed crystal.

2. A high-efficiency silicon carbide single crystal growth method according to claim 1, characterized in that: The method also includes contacting and reacting the silicon-rich atmosphere obtained in step (S.3) with carbon powder to increase the carbon concentration in the silicon-rich atmosphere, and transporting the reacted gas to the bottom of the thermal field environment to mix with the supersaturated atmosphere.

3. A high-efficiency silicon carbide single crystal growth method according to claim 1 or 2, characterized in that: In the step (S.1), the temperature gradient difference between the top and the bottom of the thermal field environment is 30°C-200°C.

4. A high-efficiency silicon carbide single crystal growth method according to claim 3, characterized in that: In the step (S.1), the temperature at the bottom of the thermal field environment is 2000°C-2250°C.

5. A high-efficiency silicon carbide single crystal growth method according to claim 4, characterized in that: In the step (S.1), the internal air pressure of the thermal field environment is 1 mbar-20 mbar.

6. A high-efficiency silicon carbide single crystal growth method according to claim 1 or 2, characterized in that: In the step (S.2), the silicon carbide powder comprises silicon carbide powder and carbon powder, wherein the amount of the carbon powder added is 1%-10%.

7. A high-efficiency silicon carbide single crystal growth method according to claim 6, characterized in that: The particle size of the carbon powder is 50 μm-150 μm, and the particle size of the silicon carbide powder is 500 μm-2000 μm.

8. A high-efficiency silicon carbide single crystal growth method according to claim 1 or 2, characterized in that: In the step (S.3), the carrier gas is argon.

9. A high-efficiency silicon carbide single crystal growth method according to claim 1 or 2, characterized in that: In the step (S.4), the supersaturated atmosphere is filtered through a porous ceramic, wherein the pore size of the porous ceramic is less than 50 microns.

10. A high-efficiency silicon carbide single crystal growth method according to claim 9, characterized in that: The porous ceramic is TaC porous ceramic.

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