P-type silicon carbide powder as well as preparation method and application thereof

Abstract

The invention relates to the technical field of silicon carbide materials, in particular to P-type silicon carbide powder and a preparation method and application thereof.The preparation method includes the steps that S1, dopant particles are subjected to plasma cleaning treatment, screening treatment and drying treatment; and S2, heating the reaction chamber, constructing a gradient temperature zone, conveying dopant particles into the reaction chamber from the top of the reaction chamber, conveying the preheated mixed gas into the reaction chamber from the bottom of the reaction chamber, regulating the pressure in the reaction chamber, and forming the P-type silicon carbide polycrystalline powder with a gradient structure, discharging from the bottom of the reaction chamber; and S3, collecting the P-type silicon carbide polycrystalline powder, placing the collected P-type silicon carbide polycrystalline powder in a graphite crucible, raising the temperature in the graphite crucible, carrying out heat preservation, and cooling to obtain the P-type silicon carbide powder. When the doping agent is used for crystal growth, the diffusion process of doping agent particles in a powder system can be limited, and the effect of sufficiently and stably supplying Al in the crystal growth process is achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of silicon carbide materials, and in particular to a P-type silicon carbide powder and a preparation method and application thereof. Background Art

[0002] P-type conductive silicon carbide (P-SiC) single crystals are a key material in device manufacturing, primarily used in high-performance, high-voltage, and high-temperature bipolar devices requiring hole injection or specific polarity structures. Although P-type SiC typically has higher resistivity than N-type substrates (lower doping efficiency) and is more expensive, it plays an irreplaceable role in key applications such as high-voltage bipolar power devices and SiC BJTs (bipolar junction transistors). Currently, the primary method for growing P-SiC single crystals is the physical vapor transport (PVT) method, which achieves the P-type property by introducing aluminum (Al) during crystal growth. However, doping uniformity and concentration control remain technical challenges in this field. Because the PVT method typically requires high-temperature growth (>2000°C), precisely controlling the dopant volatilization rate and transport process under these high temperatures makes it extremely difficult to accurately control the dopant. This results in uneven doping concentration distribution in the axial and radial directions of the crystal, with concentration deviations exceeding 30%. This uneven doping distribution will seriously affect the consistency of the electrical properties of P-SiC single crystal materials, bringing many uncertainties to subsequent device manufacturing and applications.

[0003] Although the prior art has disclosed solutions such as optimizing the dopant introduction method and improving the preparation process, these solutions still cannot systematically solve the difficult problem of balancing doping uniformity, crystal quality, and process difficulty and cost. Specifically, patent number CN202310026577.9 discloses a connecting rod design that is introduced by dividing the crucible into two independent parts. By limiting the size and material of the connecting rod and using a single coil heating system for heating, two independent temperature fields are achieved for silicon carbide (SiC) powder and doping source, reducing the degree of coupling between the two temperature fields. While ensuring the normal sublimation and decomposition of SiC powder, the doping source is kept at a low temperature, which is conducive to obtaining uniformly doped crystals. However, the single heating field and double crucible structure adopted by this method are significantly different from the current mainstream thermal field structure that can stably prepare SiC single crystals. This difference leads to a significant increase in the difficulty of the process. In actual operation, it is difficult to ensure the consistency of product quality when repeatedly implemented, and large-scale batch production is impossible. The patent number is CN202210221527.1, which specifically discloses that SiC grains or SiC polycrystalline blocks containing doping elements are first prepared, and then the SiC grains or polycrystalline blocks that seal the doping elements are used as the growth source to grow P-type crystals. The doping elements are locked by the SiC grains or polycrystalline blocks to achieve uniform and continuous release of the doping elements, which can greatly improve the uniformity of the doping elements in the axial and radial directions of the crystal ingot and improve the crystal quality. However, there is an upper limit on the doping concentration of aluminum (Al) in silicon carbide single crystals, which limits the flexibility of the doping concentration in SiC single crystals. Moreover, in the growth environment of silicon carbide single crystals, the stability of the Al-C chemical bond is far less than that of the Si-C bond, which will cause the Al doping concentration to be difficult to maintain stability during the long growth process and fluctuate. At the same time, when it is necessary to prepare P-SiC single crystals with low resistivity (high aluminum doping), the process difficulty will increase significantly.

[0004] The present invention provides a P-type silicon carbide powder and a preparation method and application thereof, in order to solve the problems existing in the prior art such as the inability of the preparation method to prepare P-SiC single crystals efficiently and on a large scale, the difficulty of the preparation process, and the uneven doping of the P-SiC single crystals. Summary of the Invention

[0005] The purpose of the present invention is to provide a P-type silicon carbide powder and its preparation method and application, so as to solve the problems existing in the prior art that the existing preparation methods cannot prepare P-SiC single crystals efficiently and on a large scale, the preparation process is difficult, and the P-SiC single crystal doping is uneven.

[0006] The technical solution of the present invention is: a method for preparing P-type silicon carbide powder, the preparation method comprising the following steps: S1, performing plasma cleaning on the dopant particles, and then performing screening and drying on the dopant particles in sequence; the dopant particles are compounds containing aluminum; S2. The reaction chamber is heated and a gradient temperature zone is constructed inside the reaction chamber. Thereafter, dopant particles are transported from the top of the reaction chamber into the reaction chamber, and simultaneously, the preheated mixed gas is transported from the bottom of the reaction chamber into the reaction chamber. The pressure inside the reaction chamber is regulated so that the mixed gas contacts the dopant particles inside the reaction chamber and reacts on the dopant particles, sequentially depositing silicon carbide polycrystalline and amorphous silicon carbide layers on the surfaces of the dopant particles to form a gradient structured P-type silicon carbide polycrystalline powder, which is then discharged from the bottom of the reaction chamber. The mixed gas includes a silicon carbide source gas and a carrier gas. S3. Collect the formed P-type silicon carbide polycrystalline powder and place it in a graphite crucible. Under an inert atmosphere, increase the temperature in the graphite crucible and keep it warm. Then, cool it to room temperature to obtain P-type silicon carbide powder with a gradient structure.

[0007] Preferably, in step S1, the plasma cleaning process is performed to clean the dopant particles at a power of 50-300W under mixed atmosphere conditions; The mixed atmosphere includes argon and hydrogen, and the volume ratio of argon to hydrogen in the mixed atmosphere is (10-20):1; The screening process is to use a screening device to screen out dopant particles with a D50 particle size of 0.05-1 mm; The drying process is carried out under vacuum conditions at 100-200°C.

[0008] Preferably, the dopant particles are aluminum carbide particles or aluminum nitride particles.

[0009] Preferably, in step S2, the gradient temperature zone includes a low temperature zone, a medium temperature zone, and a high temperature zone arranged in sequence from the bottom to the top of the reaction chamber; The temperature of the high temperature zone is 1100-1200°C; The temperature of the medium temperature zone is 1000-1100°C; The temperature of the low temperature zone is 800-1000°C.

[0010] Preferably, in step S2, the feeding rate of the dopant particles is controlled at 1×10 2 ~1×10 4 In the range of mol / h·m²; The preheating process is to heat the mixed gas to 200-500°C.

[0011] Preferably, in step S2, the particle size of the P-type silicon carbide polycrystalline powder is 0.1-10 mm, and the ratio of the total thickness d1 of the silicon carbide polycrystalline and the amorphous silicon carbide layer to the particle size of the dopant particles is (0.1-5):1.

[0012] Preferably, in step S3, the temperature in the graphite crucible is increased to 1000-1200° C., and the heating rate is 5-10° C. / min.

[0013] The present invention also provides a P-type silicon carbide powder, which is prepared by the above-mentioned preparation method.

[0014] The present invention also provides an application of the P-type silicon carbide powder, including using the powder as a raw material to grow a P-type silicon carbide single crystal.

[0015] Compared with the prior art, the advantages of the present invention are: (1) The present invention provides a P-type silicon carbide powder and its preparation method and application. The preparation method is to make the mixed gas and the mixed gas and the dopant particles fully contact and react inside the reaction chamber by constructing a gradient temperature zone and relying on the gravity of the dopant particles themselves and the buoyancy of the upward airflow they receive in the fluidized bed, and then quickly deposit silicon carbide polycrystalline and amorphous silicon carbide layers on the surface of the dopant particles in turn, and then obtain P-type silicon carbide powder with a gradient structure through high-temperature treatment; the preparation method can prepare P-type silicon carbide powder in large quantities and continuously; at the same time, when the P-type silicon carbide powder is used as a raw material for crystal growth, it can rely on the dopant element to The invention can limit the kinetics of the diffusion of dopants in SiC and the diffusion process of dopant particles in the powder system, thereby achieving the effect of sufficient and stable supply of Al in the crystal growth process, helping to grow P-SiC single crystals with flexible doping amounts and excellent doping uniformity, effectively improving the growth quality of single crystals, and systematically solving the balance problem between doping uniformity, crystal quality and process cost; it can also prepare P-SiC single crystals efficiently and on a large scale; and solves the problems existing in the prior art such as the inability of existing preparation methods to prepare P-SiC single crystals efficiently and on a large scale, the difficulty of the preparation process, and the uneven doping of P-SiC single crystals. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The present invention will be further described below with reference to the accompanying drawings and embodiments: Figure 1 This is a process flow chart of the method for preparing P-type silicon carbide powder according to the present invention; Figure 2 Schematic diagram of the structure of the reaction chamber of the present invention; Figure 3 Schematic diagram of the structure of the P-type silicon carbide polycrystalline powder of the present invention; Figure 4This is a schematic structural diagram of the P-type silicon carbide powder with a gradient structure according to the present invention; Among them: 1. fluidized bed; 2. feed port; 3. air inlet; 4. discharge port; 5. dopant particles; 6. polycrystalline silicon carbide; 7. amorphous silicon carbide layer; 8. polycrystalline silicon carbide layer. DETAILED DESCRIPTION

[0017] The present invention will be described in further detail below with reference to specific embodiments: The present invention provides a method for preparing P-type silicon carbide powder, such as Figure 1 As shown, the specific steps include: S1. Plasma cleaning the dopant particles at a power of 50 to 300 W for 0.1 to 60 minutes in a mixed atmosphere of argon and hydrogen to remove surface oxides. Screening the dopant particles to select dopant particles with a D50 particle size of 0.05 to 1 mm is then performed. The selected dopant particles are then dried in a vacuum drying oven under vacuum at 100 to 200° C. for 1 to 10 hours. The dopant particles are compounds containing aluminum and have a purity of 3N to 7N. The dopant particles are preferably aluminum carbide particles or aluminum nitride particles. Plasma cleaning of the dopant particles can, on the one hand, remove oxides from the particle surface and clean the surface; on the other hand, the long-term plasma impact can effectively increase the surface roughness and surface activity of the dopant particles, which is beneficial to the early deposition of silicon carbide on the particles; in some embodiments, the dopant particles may not be dried; in addition, if the D50 particle size of the dopant particles is in the range of 0.05 to 1 mm and has a high degree of dryness, etc., they may not be cleaned, screened, or dried and can be directly transported to the reaction chamber.

[0018] S2, such as Figure 2 As shown, a fluidized bed 1 is used as a reaction chamber, and the reaction chamber is heated. In addition, a low-temperature zone, a medium-temperature zone, and a high-temperature zone are sequentially arranged in the reaction chamber from the bottom to the top of the reaction chamber, that is, a gradient temperature zone is constructed inside the reaction chamber; wherein the temperature of the high-temperature zone is 1100-1200°C, and the high temperature is conducive to the activation of the dopant particles; the temperature of the medium-temperature zone is 1000-1100°C, which is conducive to the rapid deposition of silicon carbide polycrystalline on the surface of the dopant particles; the temperature of the low-temperature zone is 800-1000°C, which is conducive to making the silicon carbide deposited on the outermost layer of the particles dense amorphous silicon carbide, and serving as the final shell to complete the encapsulation of the dopant particles; then, the dopant particles are placed at a temperature of 1×10 2 ~1×10 4A feed rate of mol / h·m² is delivered to the reaction chamber from a feed port 2 at the top of the reaction chamber. At the same time, a mixed gas is delivered to the reaction chamber from an air inlet 3 at the bottom of the reaction chamber. The pressure inside the reaction chamber is regulated so that the pressure inside the reaction chamber is always maintained in the range of 0.1 to 10 bar. This allows the mixed gas and the mixed gas to fully contact the dopant particles 5 inside the reaction chamber and react on the dopant particles. Non-dense silicon carbide polycrystalline 6 is deposited on the surface of the dopant particles 5 to form dopant particles coated with silicon carbide polycrystalline. As deposition continues, the dopant particles coated with silicon carbide polycrystalline are affected by the buoyancy of the upward airflow and their own gravity in the reaction chamber. When the particle size is large enough, the particles fall to a low temperature zone. Under the action of the low temperature, a dense amorphous silicon carbide layer 7 is deposited on the outermost layer of the particles, forming a P-type silicon carbide polycrystalline powder with a gradient structure, which is finally discharged from a discharge port 4 at the bottom of the reaction chamber. The total particle size of the obtained P-type silicon carbide polycrystalline powder is within the range of 0.1 to 10 mm; and Figure 3 As shown, in the P-type silicon carbide polycrystalline powder, the ratio of the total thickness d1 of the silicon carbide polycrystalline and the amorphous silicon carbide layer to the particle size of the dopant particles is (0.1-5):1. The mixed gas includes a silicon carbide source gas and a carrier gas, and the carbon-silicon ratio in the mixed gas is 1:1. The silicon carbide source gas is one or more of methyltrichlorosilane, chlorosilane, silane, hydrocarbon gas, etc., and the carrier gas is hydrogen and / or argon. Specifically, when the silicon carbide source gas is methyltrichlorosilane, the carrier gas needs to include hydrogen. When chlorosilane and / or silane is used as the silicon source, the silicon carbide source gas also needs to include hydrocarbon gas, and the carrier gas also needs to include hydrogen. The silicon carbide source gas can also include chlorosilane, methyltrichlorosilane, silane, and hydrocarbon gas. The hydrocarbon gas can be ethylene, propylene, propane, etc. The purity of the silicon carbide source gas, hydrocarbon gas, and hydrogen is 5N to 7N. Before the mixed gas is transported into the reaction chamber, it is necessary to preheat the mixed gas to 200-500°C to avoid directly transporting the cold mixed gas into the reaction chamber, which may cause large temperature fluctuations in the reaction chamber. This improves the stability of the temperature fields in the reaction chamber and helps to increase the generation rate of P-type silicon carbide polycrystalline powder.

[0019] S3. Collect the P-type silicon carbide polycrystalline powder formed above and place it in a graphite crucible. In an inert atmosphere, increase the temperature in the graphite crucible at a heating rate of 5 to 10°C / min. The temperature in the graphite crucible needs to be increased to 1000 to 1200°C and kept warm for several hours. At this time, a dense amorphous silicon carbide layer 7 is deposited on the outermost layer of the particles and will be converted into a dense polycrystalline silicon carbide layer 8. After that, it is naturally cooled to room temperature and then taken out. Figure 4As shown, a P-type silicon carbide powder with a gradient structure is obtained, namely a P-SiC powder with a gradient structure consisting of dopant particles as the core and coated with a dense polycrystalline silicon carbide layer. Due to the significant difference in saturated vapor pressure between silicon carbide and dopant particles, the P-type silicon carbide powder also exhibits an effective control function on the diffusion behavior of the aluminum source. That is, under a large saturated vapor pressure difference, the diffusion process of the dopant particles in the powder system is constrained, thereby enabling the P-type silicon carbide powder to accurately adjust the distribution and diffusion rate of the aluminum source. At the same time, during the crystal growth process using this P-type silicon carbide powder as the raw material, the P-type silicon carbide powder is always in the high temperature zone. As the silicon carbide coated on the dopant particles sublimates in large quantities, the dopant particles also begin to enter a sublimation state. This sublimation mechanism also ensures that the supply of dopant is always higher than the actual demand, thereby compensating for some of the losses caused by premature volatilization of Al or overflow of Al into the cavity, helping to maintain the dynamic balance of dopant content during the crystal growth process.

[0020] The present invention provides a P-type silicon carbide powder, which is prepared by the above-mentioned preparation method.

[0021] The present invention provides an application of the P-type silicon carbide powder, including using the P-type silicon carbide powder as a raw material to grow a P-type silicon carbide single crystal (P-SiC single crystal). Specifically, the P-type silicon carbide powder is placed in a crucible and grown using physical vapor deposition (PVT). During the growth process, the temperature inside the growth chamber is 2100-2300°C and the pressure is 0.001-0.01 bar. The growth time is 50-300 hours, and after the growth is completed, a P-SiC single crystal ingot is obtained. Example 1

[0022] S1. Plasma cleaning of 6N purity dopant particles at a power of 300 W for 20 minutes in a mixed atmosphere of argon and hydrogen in a volume ratio of 20:1 was performed to remove oxides attached to the surface of the dopant particles. A screening device was then used to screen out dopant particles with a D50 particle size of 0.05 mm. The dopant particles were then dried. The dopant particles were aluminum carbide particles. S2, heat the reaction chamber, and construct a low temperature zone, a medium temperature zone, and a high temperature zone in the reaction chamber from the bottom to the top of the reaction chamber, so that the temperature of the high temperature zone is 1100°C, the temperature of the medium temperature zone is 1000°C, and the temperature of the low temperature zone is 800°C; then, the temperature of the reaction chamber is 1×10 3The dopant particles are fed into the reaction chamber from a feed port at a feed rate of 1 mol / h·m². Simultaneously, a mixed gas is fed into the reaction chamber from a gas inlet. The pressure in the reaction chamber is adjusted to approximately 1 bar, allowing the mixed gas, the mixed gas, and the dopant particles to fully contact and react within the reaction chamber to form a P-type silicon carbide polycrystalline powder with a gradient structure, which is then discharged from a discharge port at the bottom of the reaction chamber. The flow ratio of methyltrichlorosilane to hydrogen in the mixed gas is 1:5, and the purity of both methyltrichlorosilane and hydrogen is 6N. The resulting P-type silicon carbide polycrystalline powder has a D50 particle size of 0.5 mm. S3. Collect the formed P-type silicon carbide polycrystalline powder and place it in a graphite crucible. Under argon atmosphere, increase the temperature in the graphite crucible to 1200°C at a heating rate of 10°C / min and keep it warm for 10 hours. After that, naturally cool it to room temperature and take it out to obtain P-type silicon carbide powder with a gradient structure.

[0023] The prepared P-type silicon carbide powder with a gradient structure was used as raw material, evenly mixed and placed in a crucible, and single crystals were grown using physical vapor deposition. During the crystal growth process, the temperature in the growth chamber was controlled at 2250°C and the pressure was 0.003 bar. After 150 hours of growth, a P-SiC single crystal ingot A2 with a thickness of 15 mm was obtained. Example 2

[0024] S1. Plasma cleaning of 6N purity dopant particles at a power of 300 W for 30 minutes in a mixed atmosphere of argon and hydrogen in a volume ratio of 10:1 was performed to remove oxides attached to the surface of the dopant particles. A screening device was then used to screen out dopant particles with a D50 particle size of 0.5 mm. The dopant particles were then dried. The dopant particles were aluminum carbide particles. S2, heat the reaction chamber, and construct a low temperature zone, a medium temperature zone, and a high temperature zone in the reaction chamber from the bottom to the top of the reaction chamber, so that the temperature of the high temperature zone is 1150°C, the temperature of the medium temperature zone is 1050°C, and the temperature of the low temperature zone is 900°C; then, the temperature of the reaction chamber is 1×10 3 The dopant particles are fed into the reaction chamber from a feed port at a feed rate of 10 mol / h·m². Simultaneously, a mixed gas is fed into the reaction chamber from a gas inlet. The pressure in the reaction chamber is adjusted to approximately 5 bar, allowing the mixed gas, the mixed gas, and the dopant particles to fully contact and react within the reaction chamber to form a P-type silicon carbide polycrystalline powder with a gradient structure, which is then discharged from a discharge port at the bottom of the reaction chamber. The flow ratio of methyltrichlorosilane to hydrogen in the mixed gas is 1:5, and the purity of both methyltrichlorosilane and hydrogen is 6N. The resulting P-type silicon carbide polycrystalline powder has a D50 particle size of 2 mm. S3. Collect the formed P-type silicon carbide polycrystalline powder and place it in a graphite crucible. Under argon atmosphere, increase the temperature in the graphite crucible to 1200°C at a heating rate of 8°C / min and keep it warm for 10 hours. After that, naturally cool it to room temperature and take it out to obtain P-type silicon carbide powder with a gradient structure.

[0025] The P-type silicon carbide powder with a gradient structure was used as raw material, uniformly mixed and placed in a crucible, and single crystals were grown using physical vapor deposition. During the crystal growth process, the temperature in the growth chamber was controlled at 2250°C and the pressure was 0.003 bar. After 150 hours of growth, a P-SiC single crystal ingot A2 with a thickness of 15 mm was obtained. Example 3

[0026] S1. Plasma cleaning of 6N purity dopant particles at a power of 300 W for 60 minutes in a mixed atmosphere of argon and hydrogen in a volume ratio of 20:1 was performed to remove oxides attached to the surface of the dopant particles. A screening device was then used to screen out dopant particles having a D50 particle size of 0.5 mm. The dopant particles were then dried. The dopant particles were aluminum nitride particles. S2, heat the reaction chamber, and construct a low temperature zone, a medium temperature zone, and a high temperature zone in the reaction chamber from the bottom to the top of the reaction chamber, so that the temperature of the high temperature zone is 1150°C, the temperature of the medium temperature zone is 1050°C, and the temperature of the low temperature zone is 900°C; then, the temperature of the reaction chamber is 1×10 3 The dopant particles are fed into the reaction chamber at a feed rate of mol / h·m². Simultaneously, a mixed gas is fed into the reaction chamber from the gas inlet. The pressure in the reaction chamber is adjusted to approximately 5 bar, allowing the mixed gas, the mixed gas, and the dopant particles to fully contact and react within the reaction chamber to form a P-type silicon carbide polycrystalline powder with a gradient structure, which is then discharged from the discharge port at the bottom of the reaction chamber. The flow ratio of methyltrichlorosilane to hydrogen in the mixed gas is 1:10, and the purity of both methyltrichlorosilane and hydrogen is 6N. The resulting P-type silicon carbide polycrystalline powder is nitrogen-aluminum co-doped and has a D50 particle size of 2.5 mm. S3. Collect the formed P-type silicon carbide polycrystalline powder and place it in a graphite crucible. Under argon atmosphere, increase the temperature in the graphite crucible to 1200°C at a heating rate of 5°C / min and keep it warm for 5 hours. After that, naturally cool it to room temperature and take it out to obtain P-type silicon carbide powder with a gradient structure and co-doped with nitrogen and aluminum.

[0027] The prepared P-type silicon carbide powder was used as raw material, evenly mixed and placed in a crucible, and single crystals were grown using physical vapor deposition. During the crystal growth process, the temperature in the growth chamber was controlled at 2250°C and the pressure was 0.003 bar. After 150 hours of growth, a nitrogen-aluminum co-doped P-SiC single crystal ingot A3 with a thickness of 15 mm was obtained. Example 4

[0028] S1, heat the reaction chamber, and construct a low temperature zone, a medium temperature zone, and a high temperature zone in the reaction chamber from the bottom to the top of the reaction chamber, so that the temperature of the high temperature zone is 1150°C, the temperature of the medium temperature zone is 1050°C, and the temperature of the low temperature zone is 900°C; then, the temperature of the reaction chamber is 1×10 3 The dopant particles are delivered into the reaction chamber at a feed rate of mol / h·m². Simultaneously, a mixed gas is delivered into the reaction chamber from the gas inlet. The pressure in the reaction chamber is adjusted to approximately 5 bar, allowing the mixed gas, the mixed gas, and the dopant particles to fully contact and react within the reaction chamber to form a P-type silicon carbide polycrystalline powder having a gradient structure, which is then discharged from the discharge port at the bottom of the reaction chamber. The dopant particles are aluminum nitride particles with a purity of 6N. The flow ratio of methyltrichlorosilane to hydrogen in the mixed gas is 1:10, and the purity of both methyltrichlorosilane and hydrogen is 6N. This forms a nitrogen-aluminum co-doped P-type silicon carbide polycrystalline powder with a D50 particle size of 2.3 mm. S3. Collect the formed P-type silicon carbide polycrystalline powder and place it in a graphite crucible. Under argon atmosphere, increase the temperature in the graphite crucible to 1200°C at a heating rate of 5°C / min and keep it warm for 5 hours. After that, naturally cool it to room temperature and take it out to obtain P-type silicon carbide powder with a gradient structure and co-doped with nitrogen and aluminum.

[0029] The prepared P-type silicon carbide powder was used as raw material, uniformly mixed, and placed in a crucible for single crystal growth using physical vapor deposition. During the crystal growth process, the temperature in the growth chamber was controlled at 2250°C and the pressure was 0.003 bar. After 150 hours of growth, a nitrogen-aluminum co-doped P-SiC single crystal ingot with a thickness of 15mm, A4, was obtained. Example 5

[0030] S1. Plasma cleaning of 6N purity dopant particles at a power of 300 W for 20 minutes in a mixed atmosphere of argon and hydrogen in a volume ratio of 20:1 was performed to remove oxides attached to the surface of the dopant particles. A screening device was then used to screen out dopant particles with a D50 particle size of 0.05 mm. The dopant particles were then dried. The dopant particles were aluminum carbide particles. S2, heat the reaction chamber, and construct a low temperature zone, a medium temperature zone, and a high temperature zone in the reaction chamber from the bottom to the top of the reaction chamber, so that the temperature of the high temperature zone is 1100°C, the temperature of the medium temperature zone is 1000°C, and the temperature of the low temperature zone is 800°C; then, the temperature of the reaction chamber is 1×10 3 The dopant particles are fed into the reaction chamber from a feed port at a feed rate of mol / h·m². Simultaneously, a mixed gas is fed into the reaction chamber from a gas inlet. The pressure in the reaction chamber is adjusted to approximately 1 bar, allowing the mixed gas, the mixed gas, and the dopant particles to fully contact and react within the reaction chamber to form a P-type silicon carbide polycrystalline powder with a gradient structure, which is then discharged from a discharge port at the bottom of the reaction chamber. The mixed gas includes chlorosilane, ethylene, and hydrogen, and the molar ratio of chlorosilane to ethylene in the mixed gas is 1:1. The purity of the chlorosilane, ethylene, and hydrogen is 6N. The resulting P-type silicon carbide polycrystalline powder has a D50 particle size of 0.5 mm. S3. Collect the formed P-type silicon carbide polycrystalline powder and place it in a graphite crucible. Under argon atmosphere, increase the temperature in the graphite crucible to 1200°C at a heating rate of 10°C / min and keep it warm for 10 hours. After that, naturally cool it to room temperature and take it out to obtain P-type silicon carbide powder with a gradient structure.

[0031] The prepared P-type silicon carbide powder with a gradient structure was used as raw material, evenly mixed and placed in a crucible, and single crystals were grown using physical vapor deposition. During the crystal growth process, the temperature in the growth chamber was controlled at 2250°C and the pressure was 0.003 bar. After 150 hours of growth, a P-SiC single crystal ingot with a thickness of 15 mm, A5, was obtained.

[0032] Comparative Example 1 Aluminum carbide powder (D50 particle size: 20 μm), carbon powder (D50 particle size: 20 μm), and silicon powder (D50 particle size: 2000 μm) were mixed in a mass ratio of 1:1:3 and then loaded into a furnace for sintering. This resulted in nitrogen-aluminum co-doped silicon carbide powder. The furnace pressure was 900 mbar, the sintering temperature was 1800°C, and the sintering time was 4 hours.

[0033] The nitrogen-aluminum co-doped silicon carbide powder obtained above was used as raw material to grow single crystals by physical vapor deposition. During the crystal growth process, the temperature in the growth chamber was controlled at 2250°C and the pressure was 0.003 bar. After 150 hours of growth, a P-SiC single crystal ingot B1 with a thickness of 15 mm was obtained.

[0034] Comparative Example 2 Aluminum carbide powder with a particle size of 20 μm, carbon powder with a particle size of 20 μm, and silicon powder with a particle size of 2000 μm were mixed in a mass ratio of 1:1:3, and then loaded into a furnace for hydrogen purge treatment. After that, the powder was sintered to obtain aluminum-doped silicon carbide powder. The purge treatment process includes: first vacuuming to 1×10 -5 mbar, and maintain the pressure for 1 hour, then introduce hydrogen to 100mbar; repeat 3-5 times; the pressure in the furnace is 900mbar, the sintering temperature is 1800℃, and the sintering time is 4h.

[0035] The sintered silicon carbide powder was used to grow a silicon carbide single crystal. The growth time was 150 h, the growth temperature was 2250 ° C, and the pressure was 0.003 bar. After the growth was completed, a 15 mm thick P-SiC single crystal ingot, B2, was obtained.

[0036] The P-SiC single crystal ingots A1-A4 prepared in Examples 1-4 and the P-SiC single crystal ingots B1-B2 prepared in Comparative Examples 1-2 were sliced, each slice having a thickness of 800 μm. The resistivity of all wafers formed by cutting each P-SiC single crystal ingot was then detected by a capacitance method, and the average and range of the data were calculated. The range refers to the difference in resistivity between the wafer with the highest resistivity and the wafer with the lowest resistivity among all wafers formed by cutting a P-SiC single crystal ingot. The specific test data is shown in Table 1.

[0037] Table 1. Average resistivity and range of all wafers cut from each P-SiC single crystal ingot

[0038] Comparing Example 1, Example 2, and Example 5 with Comparative Example 2, it can be seen that when the P-type silicon carbide powder with a gradient structure prepared in Example 1, Example 2, and Example 5 is used as a raw material for crystal growth, the final obtained wafer has a lower average resistivity and a smaller range. This further illustrates that by using the P-type silicon carbide powder provided by the present invention as a raw material and adopting the traditional physical vapor deposition method for crystal growth, a P-SiC single crystal with an adjustable doping amount and excellent doping uniformity can be grown. Moreover, since the preparation method of the P-type silicon carbide powder provided by the present invention can prepare P-type silicon carbide powder in large quantities, it can solve the problems existing in the prior art that the existing preparation methods cannot prepare P-SiC single crystals efficiently and on a large scale and the preparation process is difficult. The silicon carbide powder sintered in Comparative Example 2 was used as a raw material for crystal growth, and the resulting wafers had an average resistivity of 2 Ω·cm, which is relatively high. This may be because the aluminum doping amount and doping uniformity were limited by the process, failing to reach the ideal doping level, resulting in the low resistivity of the wafers. In addition, although a gas purge operation was performed during the preparation of the silicon carbide powder, it was difficult to completely remove the nitrogen in the chamber, which resulted in a small amount of nitrogen being incorporated into the silicon carbide powder. Nitrogen doping interferes with the resistance characteristics of the wafer, making it difficult for the final wafer to achieve the goals of low resistivity and high resistivity uniformity.

[0039] Comparing Example 3 and Example 4 with Example 1, it can be seen that although the P-type silicon carbide powder with a gradient structure and nitrogen-aluminum co-doped prepared in Examples 3 and 4 is used as raw material for crystal growth, and the grown ingots are cut to make chips, the average resistivity of these chips is comparable to the average resistivity of the chips finally made by growing and cutting the nitrogen-aluminum co-doped silicon carbide powder raw material sintered in Comparative Example 1; however, the range of the chips finally made by growing and cutting the P-type silicon carbide powder with a gradient structure and nitrogen-aluminum co-doped prepared in Examples 3 and 4 is significantly smaller; further indicating that the P-SiC single crystal ingot obtained by growing the P-type silicon carbide powder with a gradient structure and nitrogen-aluminum co-doped prepared in Examples 3 and 4 as raw material has a higher doping uniformity; thus, it can be seen that by growing the P-type silicon carbide powder with a gradient structure provided by the present invention as raw material, a P-SiC single crystal with better doping uniformity can be obtained. In addition, by comparing the nitrogen-aluminum co-doped P-type silicon carbide polycrystalline powder prepared in Example 3 with the nitrogen-aluminum co-doped P-type silicon carbide polycrystalline powder prepared in Example 4, it can be seen that plasma cleaning of the dopant particles can increase the roughness of the dopant particle surface, which helps silicon carbide polycrystalline to deposit on the dopant particles.

[0040] The above embodiments are only for illustrating the technical concept and features of the present invention, and their purpose is to enable people familiar with this technology to understand the content of the present invention and implement it accordingly, and they are not intended to limit the scope of protection of the present invention. For those skilled in the art, it is obvious that the present invention is not limited to the details of the above exemplary embodiments, and the present invention can be implemented in other specific forms without departing from the spirit or basic characteristics of the present invention. Therefore, no matter from which point of view, the embodiments should be regarded as exemplary and non-restrictive. The scope of the present invention is defined by the appended claims rather than the above description, and it is intended that all changes that fall within the meaning and scope of the equivalent elements of the claims are included in the present invention.

Claims

1. A method for preparing P-type silicon carbide powder, characterized in that: The following steps are involved: S1, performing plasma cleaning on the dopant particles, and then performing screening and drying on the dopant particles in sequence; the dopant particles are compounds containing aluminum; S2. The reaction chamber is heated and a gradient temperature zone is established inside the reaction chamber. Thereafter, dopant particles are transported from the top of the reaction chamber into the reaction chamber, and simultaneously, the preheated mixed gas is transported from the bottom of the reaction chamber into the reaction chamber. The pressure inside the reaction chamber is regulated so that the mixed gas contacts the dopant particles inside the reaction chamber and reacts on the dopant particles, sequentially depositing silicon carbide polycrystalline and amorphous silicon carbide layers on the surfaces of the dopant particles to form a gradient structured P-type silicon carbide polycrystalline powder, which is then discharged from the bottom of the reaction chamber. The mixed gas includes a silicon carbide source gas and a carrier gas. S3. Collect the formed P-type silicon carbide polycrystalline powder and place it in a graphite crucible. Under an inert atmosphere, increase the temperature in the graphite crucible and keep it warm. Then, cool it to room temperature to obtain P-type silicon carbide powder with a gradient structure.

2. The method for preparing P-type silicon carbide powder according to claim 1, wherein: In step S1, the plasma cleaning process is performed to clean the dopant particles at a power of 50-300W under mixed atmosphere conditions; The mixed atmosphere includes argon and hydrogen, and the volume ratio of argon to hydrogen in the mixed atmosphere is (10-20):1; The screening process is to use a screening device to screen out dopant particles with a D50 particle size of 0.05-1 mm; The drying process is carried out under vacuum conditions at 100-200°C.

3. The method for preparing P-type silicon carbide powder according to claim 1, wherein: The dopant particles are aluminum carbide particles or aluminum nitride particles.

4. The method for preparing P-type silicon carbide powder according to claim 1, wherein: In step S2, the gradient temperature zone includes a low temperature zone, a medium temperature zone, and a high temperature zone arranged in sequence from the bottom to the top of the reaction chamber; The temperature of the high temperature zone is 1100-1200°C; The temperature of the medium temperature zone is 1000-1100°C; The temperature of the low temperature zone is 800-1000°C.

5. The method for preparing P-type silicon carbide powder according to claim 4, characterized in that: In step S2, the feeding rate of the dopant particles is controlled at 1×10 2 ~1×10 4 In the range of mol / h·m²; The preheating process is to heat the mixed gas to 200-500°C.

6. The method for preparing P-type silicon carbide powder according to claim 1, characterized in that: In step S2, the particle size of the P-type silicon carbide polycrystalline powder is 0.1-10 mm, and the ratio of the total thickness d1 of the silicon carbide polycrystalline and the amorphous silicon carbide layer to the particle size of the dopant particles is (0.1-5):

1.

7. The method for preparing P-type silicon carbide powder according to claim 1, characterized in that: In step S3, the temperature in the graphite crucible is increased to 1000-1200°C, and the heating rate is 5-10°C / min.

8. A P-type silicon carbide powder, characterized in that: The product is prepared by the preparation method according to any one of claims 1 to 7.

9. The use of the P-type silicon carbide powder according to claim 8, characterized in that: Including using it as a raw material to grow P-type silicon carbide single crystal.

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