High-efficiency silicon carbide single crystal growth method

Abstract

The invention relates to the field of silicon carbide crystal growth, in particular to a high-efficiency silicon carbide single crystal growth method which comprises the following steps: (S.1) providing a reverse thermal field environment of which the temperature is sequentially reduced from top to bottom in the vertical direction; (S.2) heating the silicon carbide powder so as to generate silicon carbide sublimation gas; (S.3) the silicon carbide sublimation gas is introduced into the thermal field environment along with the carrier gas, so that the silicon carbide sublimation gas is layered under screening of the carrier gas, and a silicon-rich atmosphere located at the top of the thermal field environment and a supersaturated atmosphere located at the bottom of the thermal field environment are obtained; and (S.4) contacting the supersaturated atmosphere with a seed crystal arranged at the bottom of the thermal field environment so as to grow the silicon carbide single crystal on the surface of the seed crystal. Through the reverse thermal field design, carrier gas screening layering and carbon powder dynamic compensation mechanism, the problems that in traditional silicon carbide single crystal growth, silicon gas phase enrichment inhibits the crystallization rate, and defects are caused by unbalance of the stoichiometric ratio are systematically solved.

Description

Technical Field

[0001] The invention relates to the field of silicon carbide crystal growth, and in particular to a high-efficiency silicon carbide single crystal growth method. Background Art

[0002] As a typical representative of the third-generation wide bandgap semiconductor materials, silicon carbide (SiC) has 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).

[0003] At present, physical vapor transport (PVT) is the mainstream technology for preparing silicon carbide single crystals. It sublimates silicon carbide powder source at high temperature (temperature range 2000-2500℃) to make the sublimation products (including Si, C, SiC x The gas phase components (such as carbon atoms) are transported to the low-temperature seed crystal region (about 2000-2200°C) driven by the temperature gradient and epitaxially crystallized. However, this process faces significant technical bottlenecks in industrial applications.

[0004] First, the silicon carbide powder source exhibits non-stoichiometric decomposition characteristics during high-temperature sublimation. The initial volatile atmosphere is mainly silicon-rich gas phase (such as Si, Si2C), which causes the powder to gradually become carbon-rich. At the same time, near the crystal growth interface, due to the temperature gradient and the kinetic characteristics of gas phase transmission, silicon-based gas phase components (such as Si) are prone to local enrichment. According to the chemical reaction equilibrium equation of silicon carbide crystallization (Si(g) + C(s) SiC(s)), the increase in silicon partial pressure at the growth interface will significantly inhibit the forward reaction rate of silicon carbide deposition. As the crystal growth time increases (typical growth cycle 5-10 days / furnace), the silicon enrichment effect continues to intensify, causing the growth rate to gradually decrease 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 single crystal thickness (the current 8-inch ingot thickness 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 silicon partial pressure and aggravate the growth rate attenuation.

[0005] Existing improvement schemes mostly focus on thermal field optimization (for example, a crucible for growing large-sized silicon carbide single crystals with publication number CN213172678U) or powder ratio adjustment, such as by adjusting the axial temperature gradient of the crucible or doping compensating agents to adjust the gas phase components. However, these methods are difficult to fundamentally solve the physical and chemical mechanism problem of the dynamic accumulation of silicon partial pressure at the growth interface. Especially in the process of large-sized crystal growth, the silicon self-compensation ability of the traditional PVT process is limited, resulting in a significant reduction in efficiency in the later stage of crystal growth, which significantly increases the unit thickness manufacturing cost. Therefore, it is urgent to develop a new method that can actively regulate the atmosphere components of the growth interface and suppress the silicon enrichment effect, so as 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 dynamic accumulation of silicon partial pressure at the growth interface in the prior art method for depositing silicon carbide crystals, which leads to a significant reduction in efficiency in the later stage of crystal growth. Therefore, a high-efficiency silicon carbide single crystal growth method is provided to overcome the above-mentioned shortcomings.

[0007] To achieve the above-mentioned purpose, the present invention is implemented by the following technical solutions: First, the present invention provides a high-efficiency silicon carbide single crystal growth method, comprising the following steps: (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.

[0008] As the core material of the third-generation semiconductor, the efficient preparation technology of silicon carbide (SiC) single crystal has always been a difficult problem in the industry. The traditional physical vapor transport method (PVT method) sublimates silicon carbide powder at high temperature to deposit and crystallize the gas phase components on the surface of the seed crystal, but this process has bottlenecks such as low growth rate, many crystal defects, and insufficient raw material utilization.

[0009] According to Shi Erwei's research in "Silicon Carbide Crystal Growth and Defects": The equations for the decomposition reaction of SiC powder in the powder zone mainly include: The equations for SiC crystallization reaction in the seed crystal area mainly include: .

[0010] From the above equations and PVT growth theory, it can be seen that the silicon carbide powder area reacts (1)(2)(3), resulting in the volatile gas phase component being rich in Si and residual solid C particles. The above atmosphere crystallizes in the seed crystallization area, and finally obtains SiC crystals with a stoichiometric ratio of 1:1, that is, the residual Si atmosphere is in the gas phase, which leads to the enrichment of silicon atmosphere. From the chemical reaction equation (4), it can be seen that excess Si (g) (increased partial pressure) will affect the forward reaction rate of (4); from the chemical reaction equation (5), it can be seen that excess Si (g) (increased partial pressure) will also affect the forward reaction rate of (5). Therefore, the Si-rich atmosphere is the root cause of the reduced crystal growth rate during the growth process.

[0011] In addition, the density of 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 move in the opposite direction, significantly inhibiting the growth rate. In addition, excessive Si(g) will also cause the crystal stoichiometric ratio to deviate, causing defects such as micropipes and dislocations. This theoretical and experimental conclusion reveals the fundamental contradiction of the loss of control of the gas phase components in traditional technologies.

[0012] In view of the above problems, the present invention proposes an innovative solution based on thermal field reconstruction and carrier gas screening. The core of the solution is to construct a reverse thermal field environment of "high temperature at the top and low temperature at the bottom" and introduce carrier gas to screen the silicon carbide sublimation gas.

[0013] Driven by high temperature, the gas phase components (Si, SiC2, Si2C, etc.) generated by the sublimation of the powder area flow with the carrier gas, and the density difference of different gases becomes the key to stratification: Si(g) with lower density is enriched at the top of the thermal field due to buoyancy, while SiC2(g) and Si2C (g) with higher density sink to the bottom seed crystal area. This physical screening mechanism directly changes the gas phase composition of the growth interface, that is, the C / Si ratio of the seed crystal area is significantly improved in this application, thereby promoting the forward 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 effect accelerates 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, while reducing the crystal defect density by 30%-50%.

[0014] In terms of thermal field design and transport dynamics, the reverse temperature gradient of the present invention also shows unique advantages. The traditional PVT method adopts a bottom high temperature design, and the gas phase needs to overcome natural convection to transmit from bottom to top, with a long path and low efficiency. In this scheme, the top high temperature zone directly accelerates the sublimation of the powder, and the bottom low temperature zone 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 transmission, so that effective components such as SiC2 (g) can reach the surface of the seed crystal faster. Studies have shown that this design can increase the gas phase transport efficiency by more than 40%, and is particularly suitable for the uniform growth of large-size 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 of the seed crystal area can be accurately controlled, providing flexible control means for the directional growth of different crystal forms (such as 4H-SiC or 6H-SiC).

[0015] Preferably, the method further 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.

[0016] In step (S.3), the silicon-rich atmosphere is contacted with carbon powder and reacts, achieving multiple optimization effects through a chemical conversion mechanism. First, the Si(g) accumulated in the silicon-rich atmosphere reacts with high-purity carbon powder (such as Si(g) + C(s) →SiC2(g) or 2Si(g) + C(s) →Si2C (g)), converting the excess Si(g) that originally inhibits crystallization into carbon-containing gas phase components (SiC2, Si2C), directly replenishing the carbon source in the seed crystal area. This process not only solves the problem of reverse movement of the crystallization reaction caused by Si(g) enrichment in the traditional process (such as the excessive Si(g) partial pressure pointed out in Shi Erwei's research that reduces the rate of reaction equations (4) and (5)), but also increases the carbon concentration in the gas phase to make the C / Si ratio in the seed crystal area approach the ideal stoichiometric ratio (1:1), 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, which further strengthens the supersaturation of the growth interface, promotes uniform epitaxy of the crystal and reduces defects caused by insufficient local carbon sources (such as a 30%-50% reduction in microtube density). In addition, this step increases the raw material utilization rate by 15%-20% by recycling Si(g) that might have been discarded, reducing the consumption cost of high-purity silicon carbide powder, and the introduction of gas-phase carbon source also avoids the impurity problem caused by residual solid carbon particles in traditional processes, thereby improving the purity of the crystal. This closed-loop design achieves a dynamic balance of gas-phase components under the coordination of thermal field gradient and carrier gas flow, providing a reliable guarantee for the efficient and low-defect growth of large-size SiC single crystals.

[0017] Preferably, 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.

[0018] In step (S.1), the temperature gradient difference between the top and bottom of the thermal field environment is controlled within the range of 30℃-200℃, which can significantly optimize the crystal growth process through the synergistic effect of temperature gradient and gas phase transport. The high temperature zone at the top of the thermal field (such as 2200-2400℃) accelerates the sublimation of silicon carbide powder to ensure the generation of sufficient gas phase components (Si, SiC2, Si2C, etc.); while the low temperature zone at the bottom (such as 2000-2200℃) reduces the surface temperature of the seed crystal, increases the gas phase supersaturation, and strengthens the crystallization driving force. This temperature difference range can not only avoid the low gas phase transport efficiency and insufficient supersaturation caused by insufficient gradient (<30℃), but also prevent thermal stress concentration or growth interface instability caused by excessive gradient (>200℃). Experiments show that this gradient range can increase the gas phase transport efficiency by more than 40%, stabilize the crystal growth rate at 0.3-0.5mm / h, and reduce the internal stress of the crystal by 20%-30%, thereby taking into account both the growth rate and crystal quality.

[0019] Preferably, in the step (S.1), the temperature at the bottom of the thermal field environment is 2000°C-2250°C.

[0020] Preferably, in the step (S.1), the internal air pressure of the thermal field environment is 1 mbar-20 mbar.

[0021] In step (S.1), the internal gas pressure of the thermal field environment is controlled within the range of 1 mbar to 20 mbar, and the crystal growth efficiency is significantly improved by optimizing the gas phase transport and reaction kinetics. First, under low pressure conditions, the mean free path of gas molecules increases, which accelerates the diffusion rate of effective gas phase components such as SiC2(g) and Si2C(g) to the seed crystal area (more than 50% higher than that under normal pressure conditions), while reducing the local enrichment of Si(g) due to collision retention, alleviating its inhibitory effect on the crystallization reaction. Secondly, 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 cause the components to lose control, while when the pressure is too high (>20 mbar), it will inhibit the sublimation rate and reduce the driving force for crystallization. In addition, the low pressure environment inhibits side reactions in the gas phase (such as heterogeneous agglomeration of Si(g) and C(s)), reduces the generation of free carbon particles or SiC polycrystalline phase, and reduces the crystal defect density by 30%-40%, especially the dislocation control effect on 4H-SiC crystal type (dislocation density <10 3 cm -2 ). This gas pressure setting provides key physical conditions for the high-quality and high-efficiency growth of silicon carbide single crystals.

[0022] Preferably, the silicon carbide powder in the step (S.2) contains silicon carbide powder and carbon powder, wherein the amount of the carbon powder added is 1%-10%.

[0023] In step (S.2), carbon powder is added to the silicon carbide powder at a ratio of 1%-10%, so that the crystal growth process can be significantly optimized 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)) to generate carbon-containing gas phase components, effectively balancing the C / Si ratio in the seed crystal area (approaching 1:1), and avoiding the inhibition of crystallization reaction caused by excessive silicon in traditional processes. This ratio range (1%-10%) takes into account both carbon supplementation efficiency and process stability. When the carbon content is too low (<1%), it cannot effectively inhibit silicon gas phase accumulation, while too high (>10%) may cause unreacted free carbon particles to remain and form crystal impurities. In addition, the introduction of carbon powder converts Si(g) that may have been discarded into effective growth components through a cyclic reaction mechanism, thereby improving the utilization rate of raw materials, reducing dependence on high-purity silicon carbide powder, and reducing production costs. This design, through the collaboration of reverse thermal field and carrier gas screening, achieves precise control of gas phase components, providing key chemical conditions to support the controllable growth of high-quality silicon carbide single crystals.

[0024] Preferably, the carbon powder has a particle size of 50 μm-150 μm, and the silicon carbide powder has a particle size of 500 μm-2000 μm.

[0025] Preferably, the carrier gas in the step (S.3) is argon.

[0026] As an inert gas, argon does not react chemically with silicon carbide sublimation products (such as Si(g) and SiC2(g)), thus avoiding the formation 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 Si(g) (about 0.1 g / L) and SiC2(g) and 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, raising the C / Si ratio of the growth interface to close to the stoichiometric ratio (1:1).

[0027] Preferably, in the 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.

[0028] Preferably, the porous ceramic is TaC porous ceramic.

[0029] This application systematically solves the problems of silicon gas phase enrichment inhibiting the crystallization rate and stoichiometric imbalance causing defects in the traditional silicon carbide single crystal growth through reverse thermal field design, carrier gas screening and stratification, and carbon powder dynamic compensation mechanism. Its core advantages include: using the difference in argon density to achieve natural separation of silicon-based and carbon-based gas phases, making the C / Si ratio in the seed crystal area approach 1:1, promoting the positive acceleration of the crystallization reaction, and thus increasing the growth rate of silicon carbide crystals; replenishing the carbon source through the reaction of carbon powder and silicon-rich gas phase, so that the raw material utilization rate is effectively improved, while the defect density is effectively reduced. This technology simultaneously achieves high uniformity growth of large-size (6 inches and above) crystals, significantly reduces energy consumption and raw material costs, and provides 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

[0030] Figure 1 Schematic diagram of the structure of the silicon carbide single crystal growth device in Example 1 of the present invention.

[0031] Figure 2 Schematic diagram of the structure of the silicon carbide single crystal growth device in Example 2 of the present invention.

[0032] Figure 3 This is a schematic diagram of the structure of the traditional growth furnace in Comparative Example 1.

[0033] Wherein: crucible 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, air flow channel 9, silicon carbide evaporation zone 10, crucible tube 12, seed crystal cover 13, thermal insulation material 14, heat dissipation holes 15, upper filter plate 16, lower filter plate 17, support pad 18, annular support plate 19, upper seed crystal cover 20, lower crucible body 21. DETAILED DESCRIPTION

[0034] The present invention is further described below in conjunction with 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 involved in the following description are generally only embodiments of a part of the present invention, rather than all embodiments. Therefore, based on the embodiments in the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative work should fall within the scope of protection of the present invention.

[0035] Example 1 This embodiment first provides a high-efficiency silicon carbide single crystal growth method, comprising the following steps: (S.1) Provide a reverse thermal field environment in which the temperature decreases from top to bottom in the vertical direction.

[0036] The specific structure of the reverse thermal field environment can be seen as follows Figure 1 The silicon carbide single crystal growth device shown in the figure specifically comprises a crucible body 1 made of isostatic graphite, and the crucible body 1 is composed of a crucible top cover 11, a crucible tube 12 and a seed crystal cover 13 which are connected by threaded tight fit from top to bottom. In addition, the outside of the crucible body 1 is also coated with a layer of heat-insulating material 14.

[0037] The thickness of the heat-insulating material 14 at the top area of ​​the crucible top cover 11 is greater than the thickness at the bottom area of ​​the seed crystal cover 13, so that the heat-insulating effect of the crucible body 1 above the crucible top cover 11 is better than the heat-insulating effect of the crucible body 1 below the crucible near the seed crystal cover 13. Such an arrangement enables the interior of the crucible body 1 to be 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 from top to bottom according to the temperature zone distribution when the silicon carbide single crystal growth device is heated by an external heat source during operation.

[0038] 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 connected to the seed crystal cover 13 is provided at the center of the bottom of the seed crystal cover 13 on the thermal insulation material 14, thereby improving the heat dissipation efficiency of the low temperature zone 3 and facilitating improving the quality and stability of crystal growth.

[0039] The middle and upper part of the crucible tube 12 is provided with a powder crucible 8 for storing silicon carbide powder source around the inner wall of the crucible body 1, which is also made of isostatic graphite, so the area where the powder crucible 8 is located is named as silicon carbide powder area 4. In order to allow the silicon carbide sublimation gas generated in the silicon carbide powder area 4 to flow out quickly, in this embodiment, there is a certain distance between the top of the silicon carbide powder area 4 and the carbon powder area 5, thereby forming a silicon carbide evaporation area 10. At the same time, in order to stably fix the powder crucible 8 inside the crucible body 1, in another preferred embodiment, the inner wall of the high temperature zone 2 is provided with an annular support plate 20, so that the powder crucible 8 can be fixedly mounted on the upper end of the annular support plate 19.

[0040] In addition, in a preferred embodiment of the present application, a gas flow channel 9 is provided at the center of the powder crucible 8 to allow the gas in the high temperature zone 2 and the low temperature zone 3 to communicate with each other, so that the sublimation gas formed by the silicon carbide powder in the powder crucible 8 after high temperature sublimation can enter the low temperature zone 3 from the high temperature zone 2 along the gas 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 located at the bottom of the crucible body 1 in this embodiment, so that 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.

[0041] In order to make better use of the Si atmosphere enriched at the crucible top cover 11, in a preferred embodiment of the present application, a carbon powder area 5 for containing carbon powder is provided below the crucible top cover 11. Therefore, the Si atmosphere enriched at the crucible top cover 11 can react with the high-purity carbon powder placed in the crucible to form SiC2 gas and Si2C gas, thereby increasing the C concentration in the gas phase component, which is further transported to the crystal area and the crystal growth rate is improved.

[0042] A filtering device 7 for filtering solid particles falling onto the surface of the seed crystal 6 is also provided inside the crucible body 1. The filtering device 7 includes two parts: 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 provided at the upper end of the support pad 18 inside the crucible body 1. The porosity of the upper filter plate 16 is much smaller than the particle size of the carbon powder to ensure that the carbon particles cannot fall from the pores of the upper filter plate. The lower filter plate 17 is provided at a distance of 3-10 cm from the seed crystal cover. The 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 powder, carbon particles and other accidental particles from falling from the upper part of the crucible.

[0043] In order to enable the upper filter plate 16 and the lower filter plate 17 to be able to be used for a long time in the SiC crystal growth atmosphere, the material thereof can include but is not limited to TaC porous materials with a pore size of less than 50 microns or other high temperature resistant and corrosion resistant carbides, nitrides and other materials, 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 coating, so as to further inhibit the pollution of carbon particles.

[0044] (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 into the powder crucible 8, wherein the amount of carbon powder added to the silicon carbide powder is 1%-10% (the function can be achieved within this range, and 5% is preferred in this embodiment). Subsequently, the interior of the crucible body 1 is evacuated to remove air impurities therein, and then argon gas is introduced therein so that the air pressure of the thermal field environment inside the crucible body 1 is 1 mbar-20mbar (the function can be achieved within this range, and 5 mbar is preferred in this embodiment). The crucible body is then heated so that the temperature at the bottom of the thermal field environment (i.e., the seed crystal) is 2000°C-2250°C (preferably 2100°C in this embodiment), and the temperature at the top of the thermal field environment (i.e., the carbon powder area) is 30°C-200°C higher than the bottom of the thermal field environment (functions can be achieved within this range, preferably 150°C in this embodiment), thereby sublimating the silicon carbide powder to form silicon carbide sublimation gas.

[0045] (S.3) The silicon carbide sublimation gas is layered under the screening of argon 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. The silicon-rich atmosphere at the top of the thermal field environment is contacted and reacted with the carbon powder located inside the carbon powder area 5, thereby increasing the carbon concentration in the silicon-rich atmosphere, and the reacted gas is mixed with the supersaturated atmosphere at the bottom of the thermal field environment.

[0046] (S.4) The supersaturated atmosphere is brought into contact with the seed crystal, thereby growing a silicon carbide single crystal on the surface of the seed crystal. The growth time is adjusted to 10 hours, and the crystal growth rate is calculated.

[0047] Example 2 This embodiment first provides a high-efficiency silicon carbide single crystal growth method, comprising the following steps: (S.1) Provide a reverse thermal field environment in which the temperature decreases from top to bottom in the vertical direction.

[0048] Different from the first embodiment, the specific structure of the reverse thermal field environment in this embodiment can be as follows: Figure 2 Specifically, the difference between the silicon carbide single crystal growth device and the embodiment 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. Accordingly, after such arrangement, the inner wall of the crucible body 1 is provided with components such as the annular support plate 20, which is omitted.

[0049] (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, wherein the amount of carbon powder added to the silicon carbide powder is 1%-10% (the function can be achieved within this range, and 8% is preferred in this embodiment). Subsequently, the crucible body 1 and the powder crucible 8 are vacuumed to remove air impurities therein, and then argon gas is introduced into the crucible body 1 and the powder crucible 8, so that the air pressure of the thermal field environment inside the crucible body 1 and the powder crucible 8 is 1 mbar-20mbar (the function can be achieved within this range, and 10mbar is preferred in this embodiment). The crucible body 1 and the powder crucible are then heated so that the temperature of the bottom of the crucible body 1 (i.e., the seed crystal) is 2000°C-2250°C (preferably 2050°C in this embodiment), and the temperature of the top of the crucible body 1 (i.e., the carbon powder area) is 30°C-200°C (preferably 200°C in this embodiment) higher than the bottom of the crucible body 1. At the same time, the temperature of the powder crucible 8 is raised to the same temperature as the top of the crucible body 1, so that the silicon carbide powder inside the powder crucible 8 sublimates to form silicon carbide sublimation gas, which enters the interior of the crucible body 1 along the pipeline.

[0050] (S.3) The silicon carbide sublimation gas is layered under the screening of the argon gas inside the crucible body 1, thereby obtaining a silicon-rich atmosphere at the top of the crucible body 1 and a supersaturated atmosphere at the bottom of the crucible body 1. The silicon-rich atmosphere at the top of the crucible body 1 is brought into contact and reacted with the carbon powder inside the carbon powder area 5 at the top of the crucible body 1, thereby increasing the carbon concentration in the silicon-rich atmosphere, and the reacted gas is mixed with the supersaturated atmosphere at the bottom of the thermal field environment.

[0051] (S.4) The supersaturated atmosphere is in contact with the seed crystal, thereby growing a silicon carbide single crystal on the surface of the seed crystal. The growth time is adjusted to 10 hours, and the crystal growth rate is calculated.

[0052] Comparative Example 1 Comparative Example 1: Figure 3 The conventional growth furnace structure shown includes an upper seed crystal cover 20 and a lower crucible body 21 which are spliced ​​to each other. The lower crucible body 21 is filled with silicon carbide powder. A seed crystal 6 is bonded to the lower end surface of the upper seed crystal cover 20 .

[0053] Under this traditional PVT growth furnace structure, the crystal growth method operation steps are as follows: Step 1: Filling silicon carbide powder source particles into the lower crucible body 21; Step 2: Evacuate the inside of the growth furnace, open the vacuum port and the vacuum pump, and close the vacuum pump and the vacuum port valve after the vacuum degree inside the growth furnace reaches the required level; Step 3: Set the heater heating strategy, 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 gas pressure at 15 mbar, and the bottom temperature of the lower crucible body 21 is higher than 2250° C.; Step 4: After the crystal has grown stably for 10 hours, turn off the power of the electromagnetic coil, allow the crystal to cool naturally in the furnace, and calculate the crystal growth rate.

[0054] The crystal growth rates of silicon carbide crystals in Example 1, Example 2 and Comparative Example 1 are shown in Table 1 below.

[0055] Table 1 project Crystal growth rate Crystal defects Crystal limit thickness Example 1 ~0.3mm / h <![CDATA[EPD~2000ea / cm 2 ]]> >4cm Example 2 ~0.3mm / h <![CDATA[EPD~2000ea / cm 2 ]]> >4cm Comparative Example 1 ~0.15mm / h <![CDATA[EPD~3000ea / cm 2 ]]> <3cm (increasing thickness will result in a decrease in crystal quality) It can be seen from the data in Table 1 above that the high-efficiency silicon carbide single crystal growth method and device in the present application can effectively increase the growth rate of silicon carbide crystals and effectively reduce the defect rate of the grown silicon carbide crystals.

[0056] The specific embodiments described herein are merely examples of the spirit of the present invention. A person skilled in the art of the present invention may make various modifications or additions to the specific embodiments described or replace them in a similar manner, but this will not deviate from the spirit of the present invention or exceed the scope defined by the appended claims.

Claims

1. A high-efficiency silicon carbide single crystal growth method, 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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