Method for producing 3C-SiC single crystals

Abstract

The present invention provides a method for producing 3C-SiC single crystals, comprising the steps of: (1) fixing a SiC seed to a graphite seed holder and fixing the graphite seed holder to a graphite pulling rod; (2) adding a flux containing Si and Al to a graphite crucible; (3) subsequently loading the graphite crucible and the graphite pulling rod into a growth furnace; (4) evacuating the growth furnace and then flowing gas to control the atmospheric pressure and the crystal type of 3C-SiC in the growth furnace; (5) heating the graphite crucible until the flux is completely melted to form a melt and reach the growth temperature of SiC; and (6) pushing down the graphite pulling rod to contact the SiC seed with the melt, thereby growing a 3C-SiC single crystal. The flux further contains a 3d group transition metal whose melting point is lower than the growth temperature of SiC. The method of the present invention is capable of growing high quality, large size (eg, 2-6 inches), low defect, single crystal type, uniformly doped n-type, p-type and semi-insulating 3C-SiC single crystals.

Description

[Technical Field]

[0001] The present invention relates to the field of semiconductor material technology. Specifically, the present invention relates to a method for producing 3C-SiC single crystals. [Background technology]

[0002] Silicon carbide (SiC) is a wide-bandgap compound semiconductor with excellent performance. Its breakdown field strength and saturated electron drift velocity are 10 times and twice those of Si, respectively, and its thermal conductivity is 10 times and three times that of GaAs, respectively. These excellent properties give SiC unique application advantages in high-temperature, high-voltage, high-frequency, and high-temperature devices. These SiC devices have enormous application potential in fields such as electric vehicles, rail transit, high-voltage power transmission and transformation, solar power generation, and 5G communications.

[0003] Currently, the most widely applied type is 4H-SiC, which is the crystal form consistently used in currently commercialized junction barrier Schottky diodes (JBS) and metal oxide semiconductor field effect transistor (MOSFET) devices.

[0004] The Si-C double atomic layer has a small difference in the bond energy of SiC crystals formed by different stacking methods, which allows the formation of different crystal types in SiC. Currently, there are more than 200 crystal types discovered for SiC, with the most common being cubic, hexagonal, and rhombohedral structures. Compared to 4H-SiC, cubic 3C-SiC has a smaller band gap (2.40 eV) and a higher isotropic electron mobility (1000 cm). 2 V -1 S -1 ), which has a lower defect state density at the SiO2 / 3C-SiC interface, is a potentially ideal substrate for fabricating high frequency, high temperature, high power, high voltage devices and other thin film materials. For example, 3C-SiC can be used as a substrate material for growing GaN epitaxial layers to fabricate SiC-based GaN microwave radio frequency devices.

[0005] 3C-SiC is unstable and transforms into hexagonal SiC at temperatures above 1900°C. This phase transition temperature is lower than the optimal temperature (2000-2300°C) for SiC growth by physical vapor transport (PVT). Therefore, growing large-size, high-quality 3C-SiC single crystal substrates using the currently most mature PVT method is extremely difficult, resulting in the scarcity of high-quality, large-size 3C-SiC single crystal substrates currently on the market. While Si and 3C-SiC typically have a nearly 20% lattice mismatch and a large difference in thermal expansion coefficient, the resulting 3C-SiC single crystals contain high-density defects, such as reversed-phase grain boundaries and stacking faults. Furthermore, the thickness of 3C-SiC grown by CVD is typically only a few hundred microns. These factors significantly hinder progress in 3C-SiC device research. Therefore, there is a strong demand for the development of a growth technique that can grow high-quality, large-sized 3C-SiC single crystals.

[0006] The liquid phase method, especially the top seed solution growth method (TSSG), has advantages over the PVT method, such as a lower growth temperature (1700-1900°C) and the ability to grow SiC single crystals in a state close to thermodynamic equilibrium, and is expected to enable the growth of large-sized, high-quality 3C-SiC single crystal substrates. The literature (Journal of Crystal Growth 318 (2011) 389-393; Journal of Crystal Growth 310 (2008) 1438-1442) reports that the TSSG method was used to grow 18 x 18 mm 3C-SiC single crystal substrates using Si as a flux. 2 However, this method can only produce 3C-SiC single crystals using a 6H-SiC seed with a 0-degree misorientation angle, and the resulting crystals are polycrystalline 6H-SiC particles, so single crystal ingots and wafers cannot be obtained. Therefore, there is currently a need for a method that can grow high-quality, large-sized 3C-SiC single crystals. Summary of the Invention [Problem to be solved by the invention]

[0007] An object of the present invention is to provide a method for producing 3C-SiC single crystals that is capable of growing high quality, large size (e.g., 2-6 inches) 3C-SiC single crystals, and that is capable of growing semi-insulating 3C-SiC single crystals, n-type conductivity 3C-SiC single crystals, or p-type conductivity 3C-SiC single crystals. [Means for solving the problem]

[0008] The above object of the present invention is achieved by the following technical solutions.

[0009] The method for producing a 3C-SiC single crystal provided by the present invention comprises: (1) fixing a SiC seed to a graphite seed holder and fixing the graphite seed holder to a graphite lifting rod; (2) placing a flux containing Si and Al into a graphite crucible; Next, step (3) of placing the graphite crucible and the graphite pulling rod in a growth furnace; (4) evacuating the growth furnace and then flowing gas to control the pressure in the growth furnace and the crystal type of 3C—SiC; (5) heating the graphite crucible until the flux is completely melted to form a melt and reach a growth temperature of SiC; and (6) pressing down the graphite pulling rod to bring the SiC seed into contact with the melt and further grow a 3C-SiC single crystal; The flux further contains a 3d group transition metal whose melting point is lower than the growth temperature of SiC, and is used to adjust the properties of the flux, such as the solubility of C and the surface tension.

[0010] The present inventors have unexpectedly discovered that when the flux of the present invention simultaneously contains Si, Al, and a 3d group transition metal whose melting point is lower than the growth temperature of SiC, and when nitrogen gas or oxygen gas is contained in the mixed gas, it is possible to produce various 3C-SiC single crystals, such as semi-insulating 3C-SiC single crystals, n-type conductivity 3C-SiC single crystals, and p-type conductivity 3C-SiC single crystals.

[0011] Without wishing to be bound by theory, in the present invention, the 3d group transition metal may play a role in adjusting the performance of the flux, such as the solubility of C, the surface tension, etc.

[0012] Preferably, in the method of the present invention, the 3d group transition metal is one or more selected from Fe, Co, Ni and Ti.

[0013] Preferably, in the method of the present invention, the atomic molar ratio of Si to Al to the 3d group transition metal in the flux is (30-70):(0.01-20):(30-70).

[0014] In the present invention, the atomic molar ratio of Si to Al to the 3d-group transition metal in the flux is preferably within the above-mentioned preferred range. If the Al content is too high, the SiC single crystal will be doped with a large amount of Al, which will cause problems of Al volatilization and SiC crystal cracking. If the Al content is too low, the viscosity of the flux will increase. Similarly, if the 3d-group transition metal content is too high, the Si content will decrease, and if the 3d-group transition metal content is too low, the C solubility in the flux will be too low, which is disadvantageous for improving the growth rate of the SiC single crystal.

[0015] Preferably, in the method of the present invention, the flux further comprises a rare earth metal having a melting point lower than the growth temperature of SiC. Without wishing to be bound by theory, in the present invention, the rare earth metal may play a role in adjusting the performance of the flux, such as the solubility of C, surface tension, etc.

[0016] Preferably, in the method of the present invention, the rare earth metal is one or more selected from La, Pr and Ce.

[0017] Preferably, in the method of the present invention, the atomic molar ratio of Si, Al, 3d group transition metal and rare earth metal in the flux is (30-70):(0.01-20):(30-70):(0.1-20).

[0018] In the present invention, the molar ratio of Si, Al, 3d group transition metal, and rare earth metal in the flux is preferably within the above-mentioned suitable range, because if the content of the rare earth metal is too high or too low, the solid-liquid interfacial energy between the flux, graphite, and SiC seed changes, affecting the growth of SiC single crystals.

[0019] Preferably, in the method of the present invention, the flux further comprises a Group IIIA metal other than Al and / or a Group IVA metal having a melting point lower than the growth temperature of SiC. Without wishing to be bound by theory, in the present invention, the Group IIIA metal other than Al may play a role in adjusting flux properties such as viscosity, surface tension, C solubility, etc.

[0020] Preferably, in the method of the present invention, the Group IIIA metal and / or Group IVA metal other than Al is one or more selected from Ga, In, Ge, and Sn.

[0021] Preferably, in the method of the present invention, the atomic molar ratio of Si to Al to the 3d group transition metal to the rare earth metal to the IIIA group metal other than Al in the flux is (30-70):(0.01-20):(30-70):(0.1-20):(0.1-20).

[0022] In the present invention, the molar ratio of Si, Al, 3d group transition metal, rare earth metal, and IIIA group metal other than Al in the flux is preferably within the above-mentioned preferred range, because if the content of IIIA group metal other than Al is too high, the flux will volatilize violently, and if the content of IIIA group metal other than Al is too low, the viscosity of the flux will increase.

[0023] Preferably, in the method of the present invention, the step (4) of evacuating the growth furnace is performed by evacuating the growth furnace for 10 -2 The purpose is to draw a vacuum to less than Pa.

[0024] Preferably, in the method of the present invention, the gas is a mixture of nitrogen gas and one or more gases selected from helium (He), argon (Ar), and hydrogen (H), or a mixture of oxygen gas and one or more gases selected from helium (He) and argon (Ar).

[0025] Preferably, in the method of the present invention, the volume of nitrogen gas or oxygen gas in the gas occupies 0.1% to 50%.

[0026] Preferably, in the method of the present invention, the pressure inside the growth furnace in step (4) is controlled to be 0.2 to 2.0 atm.

[0027] Preferably, in the method of the present invention, the SiC seed is a 2 to 6 inch SiC wafer with a deflection angle of either 0°, 4° or 8°.

[0028] Preferably, in the method of the present invention, the SiC seed is a semi-insulating SiC single crystal substrate, an n-type conductivity SiC single crystal substrate, or a p-type conductivity SiC single crystal substrate.

[0029] Preferably, in the method of the present invention, the inner diameter of the graphite crucible is 5 mm or more larger than the diameter of the SiC seed, the thickness of the graphite crucible is 10 mm or more, and the inner wall of the graphite crucible is dense, porous, honeycomb, or multi-grooved.

[0030] Preferably, in the method of the present invention, the growth of the 3C-SiC single crystal in step (6) is carried out by a method including the following steps: (i) controlling the temperature during the growth of the 3C-SiC single crystal, so that the temperature of the SiC seed during the growth of the single crystal is 1700°C to 1900°C, and the temperature of the melt is gradually increased from the surface closest to the SiC seed to the bottom of the graphite crucible, with a temperature gradient of 3°C to 30°C / cm; (ii) Periodically rotating the SiC seed and the graphite crucible at accelerated and decelerated speeds while slowly pulling up the SiC seed.

[0031] Preferably, in the method of the present invention, the periodic accelerated and decelerated rotation is performed under the following conditions: the graphite crucible and the SiC seed are rotated in opposite directions, the rotation speed is ±0 to 200 r / min, and the rotation acceleration is ±0 to 30 r / min. 2 is.

[0032] Preferably, in the method of the present invention, the SiC seed is pulled up at a speed of 1 to 3000 μm / h.

[0033] In a specific embodiment of the present invention, the flux may be in the form of metal particles or metal blocks, and the metals in the flux do not form compounds with melting points higher than the growth temperature of the SiC single crystal.

[0034] In a specific embodiment of the present invention, the inner diameter of the graphite crucible is 5 mm or more larger than the diameter of the SiC seed, the thickness of the graphite crucible is 10 mm or more, and the inner wall of the graphite crucible is dense, porous, honeycomb, or multi-grooved, thereby increasing the contact area between the melt and the graphite crucible, improving the dissolution rate and concentration of C in the flux melt, and improving the growth rate and quality of SiC.

[0035] In a specific embodiment of the present invention, the mixed gas is a mixture of nitrogen gas and argon or nitrogen gas and helium, with a volume ratio of nitrogen gas of 0.1% to 50%. The mixed gas is filled into the high-temperature growth furnace until the pressure reaches 0.2-2.0 KPa. During growth, the mixed gas may be a flowing or non-flowing atmosphere.

[0036] In a specific embodiment of the present invention, the graphite crucible and the graphite pulling rod are rotated in opposite directions with periodic acceleration and deceleration, the rotation speed is ±0 to 200 r / min, and the rotation acceleration is ±0 to 30 r / min. 2 When the graphite pulling rod rotates forward or backward, the rotation speed of the graphite pulling rod may be ±0 to 200 r / min, and the forward or reverse rotation time may be 5 to 180 min. For example, when the graphite pulling rod rotates forward, the rotation speed is 5 to 200 r / min, the forward rotation time is 5 to 180 min, the forward rotation speed of the seed rod is then slowly decelerated to 0 rpm and then accelerated in the reverse direction to 5 to 200 r / min, the total acceleration and deceleration time is 1 to 60 min, and the reverse rotation time of the graphite pulling rod is also 5 to 180 min, and the graphite pulling rod rotates cyclically until growth is completed. [Effects of the Invention]

[0037] The present invention has the following beneficial effects:

[0038] The growth temperature of the present invention is 1700-1900°C, which is lower than the phase transition temperature of 3C-SiC. The method of the present invention can grow high-quality, large-sized (e.g., 2-6 inches), low-defect, single-crystal, uniformly doped 3C-SiC single crystals, and can achieve the growth of n-type, p-type, and semi-insulating 3C-SiC single crystals. Furthermore, the method of the present invention has other advantages, such as low growth temperature, easy diameter expansion, low growth cost, and suitability for large-scale industrial production. [Brief explanation of the drawings]

[0039] Hereinafter, the implementation of the present invention will be described in detail with reference to the drawings. [Figure 1] 1A and 1B are photographs of a 2-inch 3C-SiC single crystal and a 1 mm thick wafer grown in Example 1. FIG. 1C shows that the wafer appears green in strong light. [Figure 2] 1 shows the results of a hole test on a 2-inch 3C—SiC single crystal grown in Example 1. [Figure 3] FIG. 1 is a powder X-ray diffraction pattern of the 3C—SiC single crystal grown in Example 1 tested after being crushed into powder. [Figure 4] 1 is a Raman spectrum of the 3C—SiC single crystal grown in Example 3. [Figure 5] 1A and 1B are (a) HRTEM and (b) SAED diagrams of the 3C—SiC single crystal grown in Example 4. [Figure 6] 1A and 1B are an AFM image and a step height distribution diagram, respectively, of a 3C—SiC single crystal grown in Example 6. [Figure 7] 1 is a photograph of a 4-inch 3C—SiC single crystal grown in Example 7. [Figure 8] 10 is a photograph of defects in a 4-inch 3C—SiC single crystal grown in Example 7. [Figure 9] 1 is a photograph of a SiC single crystal grown in Comparative Example 1. DETAILED DESCRIPTION OF THE INVENTION

[0040] The present invention will now be described in more detail in connection with specific embodiments, and the examples provided are for the purpose of illustrating the present invention and are not intended to limit the scope of the present invention. [Example]

[0041] A 2-inch semi-insulating SiC single crystal seed substrate with a 0° misorientation angle was fixed to a 20 mm thick graphite seed holder, and the graphite seed holder was fixed to a graphite pulling rod. The C-plane was the growth surface. Si:Ti:Al single particles with a molar ratio of 60:39.99:0.01 were uniformly mixed and then placed in a graphite crucible for compaction. The graphite crucible had an inner diameter of 55 mm, a height of 100 mm, and a wall thickness of 10 mm. The graphite crucible used had a porous inner wall and a flat bottom. The graphite crucible and graphite pulling rod were placed in a high-temperature growth furnace, the furnace chamber of the high-temperature growth furnace was closed, and the furnace chamber was heated to 1000 K by using a mechanical pump and a molecular pump. -3 The furnace was evacuated to a pressure of 0.2 atm or less, and argon gas and nitrogen gas in a volume ratio of 70:30 were introduced until the pressure inside the high-temperature growth furnace reached 0.2 atm. The gas valve was then closed to stop the gas filling. The graphite crucible was heated to control the temperature during the 3C-SiC single crystal growth process, and the temperature of the SiC seed during the single crystal growth process was raised to 1800°C. The graphite pulling rod was pushed down to bring it into contact with the molten flux, initiating the growth of the 3C-SiC single crystal. During growth, the temperature gradient of the melt was 10°C / cm. The graphite pulling rod to which the SiC seed was fixed rotated forward and backward at a speed of 100 r / min, with a rotational acceleration of ±30 r / min. 2 The graphite lifting rod was started and rotated in both directions for 5 minutes, then slowly decelerated to 0 rpm, and then accelerated to 100 rpm in the opposite direction for a total of 10 minutes. This was repeated until the growth was complete. The graphite crucible rotated in both directions at a speed of 20 rpm, with a rotational acceleration of ±30 rpm. 2The graphite crucible was started and rotated in both directions for 5 minutes. It was then slowly decelerated to 0 rpm and then accelerated to 20 rpm in the opposite direction for a total of 10 minutes. This process was repeated until growth was complete. The graphite pulling rod was pulled upward at a speed of 60 μm / h. After 60 hours of growth, the graphite pulling rod was pulled upward at a speed of 10 mm / h to completely separate the grown crystal from the molten flux surface, and heating was stopped. The grown crystal and graphite crucible were then slowly cooled to room temperature, and the chamber of the high-temperature growth furnace was opened, and the grown crystal was removed.

[0042] FIG. 1 is a photograph of a 2-inch n-type 3C—SiC single crystal grown in this example.

[0043] Figure 2 shows the results of a Hall test on the n-type 3C-SiC single crystal grown in this example. The Hall coefficient of the grown n-type 3C-SiC single crystal was -0.000898m 3 / C, and the carrier type of the grown SiC single crystal was proven to be n-type, and the carrier concentration was 8.684 × 10 18 cm -3 and the resistivity of the crystal is 0.004761 Ω·cm.

[0044] FIG. 3 shows the powder X-ray diffraction pattern of 2 inches of n-type 3C—SiC grown in this example, which was tested after being crushed into powder, demonstrating that the grown material was a 3C—SiC single crystal. [Example]

[0045] A 4-inch n-type 4H-SiC seed single crystal substrate with a 4° misorientation was fixed to a 40 mm thick graphite seed holder, and the graphite seed holder was fixed to a graphite pull rod. The C-plane was the growth surface. Si:Fe:Al single particles with a molar ratio of 70:10:20 were uniformly mixed and then placed in a graphite crucible for compaction. The graphite crucible had an inner diameter of 150 mm, a height of 150 mm, and a wall thickness of 20 mm. The graphite crucible used had a multi-grooved trench-shaped inner wall and a groove-shaped bottom with a concave middle and protruding sides. The graphite crucible and graphite pull rod were placed in a high-temperature growth furnace, and the furnace chamber of the high-temperature growth furnace was closed. The furnace chamber was heated to 1000 K by using a mechanical pump and a molecular pump. -4 The furnace was evacuated to 100 Pa, and flowing helium gas and nitrogen gas was introduced at a gas volume ratio of 80:20. The pressure inside the high-temperature growth furnace was constantly controlled to 0.4 atm. The graphite crucible was heated to control the temperature during the 3C-SiC single crystal growth process, and the temperature of the SiC seed during the single crystal growth process was raised to 1700°C. The graphite pulling rod was pushed down to bring it into contact with the molten flux, initiating the growth of the 3C-SiC single crystal. During growth, the temperature gradient of the melt was 30°C / cm. The graphite pulling rod to which the SiC seed was fixed rotated forward and backward at a speed of 150 r / min, with a rotational acceleration of ±30 r / min. 2 The graphite lifting rod was started and rotated in the forward and reverse directions for 5 minutes, then slowly decelerated to 0 rpm, and then accelerated in the reverse direction to 150 rpm for a total of 10 minutes. This was repeated until the growth was completed. The graphite crucible rotated in the forward and reverse directions at a speed of 0 rpm, and the rotational acceleration was ±0 rpm. 2The graphite pulling rod was pulled upward at a rate of 100 μm / h. After 80 hours of growth, the graphite pulling rod with the attached seed was pulled up at a rate of 10 mm / h to completely separate the grown crystal from the liquid surface of the flux, and heating was stopped. The grown crystal and graphite crucible were then slowly cooled to room temperature, after which the chamber of the high-temperature growth furnace was opened and the grown crystal was removed. Since the SiC single crystal of this example contained Al and N doping, the 4-inch semi-insulating 3C-SiC single crystal of the present invention was obtained. [Example]

[0046] A 6-inch n-type 4H-SiC seed single crystal substrate with an 8° misorientation angle was fixed to a 10 mm thick graphite seed holder, and the graphite seed holder was fixed to a graphite pulling rod. The Si surface was used as the growth surface. Si:Co:Y:Al single particles with a molar ratio of 30:60:5:5 were uniformly mixed and then placed in a graphite crucible for compaction. The graphite crucible had an inner diameter of 200 mm, a height of 150 mm, and a wall thickness of 20 mm. The graphite crucible used had a dense, flat inner wall and a dense, flat bottom. The graphite crucible and graphite pulling rod were placed in a high-temperature growth furnace, the furnace chamber of the high-temperature growth furnace was closed, and the furnace chamber was heated to 1000 K by using a mechanical pump and a molecular pump. -5 The furnace was evacuated to a pressure of 0.2 Pa or less, and helium gas and nitrogen gas in a volume ratio of 95:5 were introduced until the pressure inside the high-temperature growth furnace reached 0.2 atm. The gas valve was then closed to stop the gas filling. The graphite crucible was heated to control the temperature during the 3C-SiC single crystal growth process, and the temperature of the SiC seed during the single crystal growth process was raised to 1900°C. The graphite pulling rod was pushed down to bring it into contact with the molten flux, initiating the growth of the 3C-SiC single crystal. During growth, the temperature gradient of the melt was 10°C / cm. The graphite pulling rod to which the SiC seed was fixed rotated forward and backward at a speed of 20 r / min, with a rotational acceleration of ±5 r / min. 2The graphite lifting rod was started and rotated in both directions for 5 minutes, then slowly decelerated to 0 rpm, and then accelerated to 20 rpm in the opposite direction for a total of 1 minute. This was repeated until the growth was complete. The graphite crucible rotated in both directions at a speed of 5 rpm, with a rotational acceleration of ±5 rpm. 2 The graphite crucible was started and rotated in both directions for 5 minutes. It was then slowly decelerated to 0 rpm and then accelerated to 5 rpm in the opposite direction for a total of 1 minute. This process was repeated until growth was complete. The graphite pulling rod was pulled upward at a speed of 100 μm / h. After 120 hours of growth, the graphite pulling rod was pulled upward at a speed of 30 mm / h to completely separate the grown crystal from the flux melt surface, and heating was stopped. The grown crystal and graphite crucible were then slowly cooled to room temperature, and the chamber of the high-temperature growth furnace was opened, and the grown crystal was removed.

[0047] Figure 4 shows the Raman diagram of the p-type 3C-SiC single crystal grown in this example, demonstrating that all the grown wafers were 3C-SiC single crystals, with no other crystal types present. [Example]

[0048] A 2-inch n-type 3C-SiC single crystal seed substrate with a 0° misorientation angle was fixed to a 20 mm thick graphite seed holder, and the graphite seed holder was fixed to a graphite pull rod. The Si surface was the growth surface. Si:Ni:Ce:Ga:Al single particles with a molar ratio of 40:30:15:14.9:0.1 were uniformly mixed and then placed in a graphite crucible and compacted. The graphite crucible had an inner diameter of 100 mm, a height of 150 mm, and a wall thickness of 20 mm. The graphite crucible used had a honeycomb-shaped inner wall and a flat bottom. The graphite crucible and graphite pull rod were placed in a high-temperature growth furnace, the furnace chamber was closed, and the furnace chamber was heated to 1000 K by using a mechanical pump and a molecular pump. -3The furnace was evacuated to a pressure of 0.2 atm or less, and argon gas and nitrogen gas in a volume ratio of 85:15 were introduced until the pressure inside the high-temperature growth furnace reached 0.2 atm. The gas valve was then closed to stop the gas filling. The graphite crucible was heated to control the temperature during the 3C-SiC single crystal growth process, and the temperature of the SiC seed during the single crystal growth process was raised to 1900°C. The graphite pulling rod was pushed down to bring it into contact with the molten flux, initiating the growth of the 3C-SiC single crystal. During growth, the temperature gradient of the melt was 10°C / cm. The graphite pulling rod to which the SiC seed was fixed rotated forward and backward at a speed of 200 r / min, with a rotational acceleration of ±30 r / min. 2 The graphite lifting rod was started and rotated in both directions for 20 minutes, then slowly decelerated to 0 rpm, and then accelerated to 200 rpm in the opposite direction for a total of 20 minutes. This was repeated until the growth was completed. The graphite crucible rotated in both directions at a speed of 20 rpm, with a rotational acceleration of ±30 rpm. 2 The graphite crucible was started and rotated in both directions for 5 minutes. It was then slowly decelerated to 0 rpm and then accelerated to 20 rpm in the opposite direction for a total of 10 minutes. This process was repeated until growth was complete. The graphite pulling rod was pulled upward at a speed of 60 μm / h. After 60 hours of growth, the graphite pulling rod was pulled upward at a speed of 10 mm / h to completely separate the grown crystal from the molten flux surface, and heating was stopped. The grown crystal and graphite crucible were then slowly cooled to room temperature, and the chamber of the high-temperature growth furnace was opened, and the grown crystal was removed.

[0049] Figure 5 shows HRTEM and SAED patterns of the n-type 3C-SiC single crystal grown in this example, further confirming that the grown SiC single crystal is a 3C-SiC single crystal. [Example]

[0050] A 2-inch p-type 3C SiC single crystal wafer with a 0° misorientation angle was fixed to a 30 mm-thick graphite seed holder, and the graphite seed holder was fixed to a graphite pull rod. The Si surface was the growth surface. Si:Ni:Ce:Ga:Al single particles with a molar ratio of 40:40:10:2:8 were uniformly mixed and then placed in a graphite crucible and compacted. The graphite crucible had an inner diameter of 100 mm, a height of 150 mm, and a wall thickness of 10 mm. The graphite crucible used had a sawtooth inner wall. The graphite crucible and graphite pull rod were placed in a high-temperature growth furnace, the furnace chamber of the high-temperature growth furnace was closed, and the furnace chamber was heated to 100°C using a mechanical pump and a molecular pump. -3 The furnace was evacuated to a pressure of 1 Pa or less, and argon gas and nitrogen gas in a volume ratio of 95:5 were introduced until the pressure inside the high-temperature growth furnace reached 1 atm. The gas valve was then closed and gas filling was stopped. The graphite crucible was heated to control the temperature during the 3C-SiC single crystal growth process, and the temperature of the SiC seed during the single crystal growth process was raised to 1900°C. The graphite pulling rod was pushed down to bring it into contact with the molten flux, initiating the growth of the 3C-SiC single crystal. During growth, the temperature gradient of the melt was 10°C / cm. The graphite pulling rod to which the SiC seed was fixed rotated forward and backward at a speed of 150 r / min, with a rotational acceleration of ±30 r / min. 2 The graphite lifting rod was started and rotated in both directions for 60 min, then slowly decelerated to 0 rpm, and then accelerated to 150 rpm in the opposite direction for a total of 30 min. This was repeated until the growth was complete. The graphite crucible rotated in both directions at a speed of 50 rpm, with a rotational acceleration of ±30 rpm. 2The graphite crucible was started and rotated in both directions for 60 min. It was then slowly decelerated to 0 rpm and then accelerated in the opposite direction to 50 rpm for a total of 30 min. This process was repeated until growth was complete. The graphite pulling rod was pulled upward at a speed of 60 μm / h. After 60 h of growth, the graphite pulling rod was pulled upward at a speed of 10 mm / h to completely separate the grown crystal from the flux melt surface, and heating was stopped. The grown crystal and graphite crucible were then slowly cooled to room temperature. The chamber of the high-temperature growth furnace was then opened, and the grown crystal was removed. A 2-inch p-type 3C-SiC single crystal was obtained by the growth method of the present invention. [Example]

[0051] A 6-inch n-SiC single crystal wafer with a 4° misalignment angle was fixed to a 40 mm thick graphite seed holder, and the graphite seed holder was fixed to a graphite pulling rod. The Si surface was the growth surface. Si:Ni:Ce:Al single particles with a molar ratio of 40:40:10:10 were uniformly mixed and then placed in a graphite crucible and compacted. The graphite crucible had an inner diameter of 200 mm, a height of 200 mm, and a wall thickness of 30 mm. The graphite crucible used had a sawtooth-machined sidewall and a porous bottom. The graphite crucible and graphite pulling rod were placed in a high-temperature growth furnace, the furnace chamber was closed, and the furnace chamber was heated to 1000 K by using a mechanical pump and a molecular pump. -3 The furnace was evacuated to a pressure of 0.8 atm or less, and argon gas and nitrogen gas in a volume ratio of 70:30 were introduced until the pressure inside the high-temperature growth furnace reached 0.8 atm. The gas valve was then closed and gas filling was stopped. The graphite crucible was heated to control the temperature during the 3C-SiC single crystal growth process, and the temperature of the SiC seed during the single crystal growth process was raised to 1900°C. The graphite pulling rod was pushed down to contact the molten flux, initiating the growth of the 3C-SiC single crystal. During growth, the temperature gradient of the melt was 10°C / cm, and the graphite pulling rod to which the SiC seed was fixed rotated forward and backward at a speed of 200 r / min, with a rotational acceleration of ±12 r / min. 2The graphite lifting rod was started and rotated in both directions for 180 min, then slowly decelerated to 0 rpm, and then accelerated to 200 rpm in the opposite direction for a total of 60 min. This was repeated until the growth was complete. The graphite crucible rotated in both directions at a speed of 100 rpm, with a rotational acceleration of ±12 rpm. 2 The graphite crucible was started and rotated in both directions for 180 min. It was then slowly decelerated to 0 rpm and then accelerated in the opposite direction to 200 rpm for a total of 60 min. This process was repeated until growth was complete. The graphite pulling rod was pulled upward at a speed of 60 μm / h. After 80 h of growth, the graphite pulling rod was pulled upward at a speed of 10 mm / h to completely separate the grown crystal from the flux melt surface, and heating was stopped. The grown crystal and graphite crucible were then slowly cooled to room temperature, and the chamber of the high-temperature growth furnace was opened, and the grown crystal was removed.

[0052] Figure 6 shows (a) an AFM image and (b) a step height distribution diagram of the n-type 3C-SiC single crystal grown in this example. Figure 6 shows that the 3C-SiC single crystal grew by the step flow method, with the step flow height ranging from 15 to 35 nm. [Example]

[0053] A 4-inch n-type 3C-SiC single crystal wafer with a 0° misalignment was fixed to a 10 mm thick graphite seed holder, and the graphite seed holder was fixed to a graphite pull rod. The C-plane was the growth surface. Si:Ti:Ce:Al single particles with a molar ratio of 50:40:9.99:0.01 were uniformly mixed and then placed in a graphite crucible and compacted. The graphite crucible had an inner diameter of 150 mm, a height of 200 mm, and a wall thickness of 10 mm. The graphite crucible used had sawtoothed side walls and a porous bottom. The graphite crucible and graphite pull rod were placed in a high-temperature growth furnace, the furnace chamber was closed, and the furnace chamber was heated to 1000 K by using a mechanical pump and a molecular pump. -3The furnace was evacuated to a pressure of 0.8 Pa or less, and argon gas and nitrogen gas in a volume ratio of 80:20 were introduced until the pressure inside the high-temperature growth furnace reached 0.8 atm. The gas valve was then closed and gas filling was stopped. The graphite crucible was heated to control the temperature during the 3C-SiC single crystal growth process, and the temperature of the SiC seed during the single crystal growth process was raised to 1900°C. The graphite pulling rod was pushed down to bring it into contact with the molten flux, initiating the growth of the 3C-SiC single crystal. During growth, the temperature gradient of the melt was 10°C / cm. The graphite pulling rod to which the SiC seed was fixed rotated forward and backward at a speed of 5 r / min, with a rotational acceleration of ±5 r / min. 2 The graphite lifting rod was started and rotated in the forward and reverse directions for 5 minutes, then slowly decelerated to 0 rpm, and then accelerated to 5 r / min in the reverse direction for a total of 1 minute. This was repeated until the growth was completed. The graphite crucible rotated in the forward and reverse directions at a speed of 5 r / min, with a rotational acceleration of ±5 r / min. 2 The graphite crucible was started and rotated in both directions for 5 min. It was then slowly decelerated to 0 rpm and then accelerated to 5 rpm in the opposite direction for a total of 1 min. This process was repeated until growth was complete. The graphite pulling rod was pulled upward at a speed of 150 μm / h. After 120 h of growth, the graphite pulling rod was pulled upward at a speed of 20 mm / h to completely separate the grown crystal from the flux melt surface. Heating was then stopped. The grown crystal and graphite crucible were then slowly cooled to room temperature. The chamber of the high-temperature growth furnace was then opened, and the grown crystal was removed, yielding a 4-inch n-type 3C-SiC single crystal described in this example. Figure 7 shows a photograph of the 3C-SiC single crystal ingot grown in this example. Figure 8 shows a photograph of defects in the 3C-SiC single crystal grown in this example. The 3C-SiC grown by the present invention was found to be free of antiphase grain boundary defects and to have a stacking fault density of only 150 / cm. [Example]

[0054] A 6-inch semi-insulated 3C-SiC single crystal wafer with a 0° misalignment was fixed to a 30 mm thick graphite seed holder, and the graphite seed holder was fixed to a graphite pull rod. The Si surface was the growth surface. Si:Ti:Ce:Al single particles with a molar ratio of 50:40:9.9:0.1 were uniformly mixed and then placed in a graphite crucible and compacted. The graphite crucible had an inner diameter of 200 mm, a height of 300 mm, and a wall thickness of 10 mm. The graphite crucible used had a sawtoothed sidewall and a porous bottom. The graphite crucible and graphite pull rod were placed in a high-temperature growth furnace, the furnace chamber was closed, and the furnace chamber was heated to 1000 K by using a mechanical pump and a molecular pump. -3 The furnace was evacuated to a pressure of 0.2 atm or less, and argon gas and nitrogen gas were introduced in a volume ratio of 99.9:0.1 until the pressure inside the high-temperature growth furnace reached 0.2 atm. The gas valve was then closed and gas filling was stopped. The graphite crucible was heated to control the temperature during the 3C-SiC single crystal growth process, and the temperature of the SiC seed during the single crystal growth process was raised to 1800°C. The graphite pulling rod was pushed down to bring it into contact with the molten flux, initiating the growth of the 3C-SiC single crystal. During growth, the temperature gradient of the melt was 5°C / cm. The graphite pulling rod to which the SiC seed was attached rotated forward and backward at a speed of 150 r / min, with a rotational acceleration of ±5 r / min. 2 The graphite lifting rod was started and rotated in both directions for 5 minutes, then slowly decelerated to 0 rpm, and then accelerated to 5 r / min in the opposite direction for a total of 1 minute. This was repeated until the growth was complete. The graphite crucible rotated in both directions at a speed of 30 r / min, with a rotational acceleration of ±5 r / min. 2The graphite crucible was started and rotated in both directions for 5 minutes. It was then slowly decelerated to 0 rpm and then accelerated to 5 rpm in the opposite direction for a total of 10 minutes. This process was repeated until growth was complete. The graphite pulling rod was pulled upward at a speed of 150 μm / h. After 84 hours of growth, the graphite pulling rod was pulled upward at a speed of 20 mm / h to completely separate the grown crystal from the flux melt surface, and heating was stopped. The grown crystal and graphite crucible were then slowly cooled to room temperature. The chamber of the high-temperature growth furnace was opened, and the grown crystal was removed, yielding a 6-inch semi-insulating 3C-SiC single crystal described in this example. Comparative Example 1

[0055] A 4-inch n-SiC single crystal wafer with a 4° misalignment was fixed to a 10 mm thick graphite seed holder, and the graphite seed holder was fixed to a graphite pulling rod. The C-plane was the growth surface. Si:Ti:Ce single particles with a molar ratio of 50:40:10 were uniformly mixed and then placed in a graphite crucible and compacted. The graphite crucible had an inner diameter of 150 mm, a height of 200 mm, and a wall thickness of 10 mm. The graphite crucible used had a sawtooth-machined sidewall and a porous bottom. The graphite crucible and graphite pulling rod were placed in a high-temperature growth furnace, the furnace chamber was closed, and the furnace chamber was heated to 1000 K by using a mechanical pump and a molecular pump. -3 The furnace was evacuated to a pressure of 0.8 Pa or less, and argon gas and nitrogen gas in a volume ratio of 80:20 were introduced until the pressure inside the high-temperature growth furnace reached 0.8 atm. The gas valve was then closed and gas filling was stopped. The graphite crucible was heated to control the temperature during the 3C-SiC single crystal growth process, and the temperature of the SiC seed during the single crystal growth process was raised to 1900°C. The graphite pulling rod was pushed down to bring it into contact with the molten flux, initiating the growth of the 3C-SiC single crystal. During growth, the temperature gradient of the melt was 10°C / cm. The graphite pulling rod to which the SiC seed was fixed rotated forward and backward at a speed of 5 r / min, with a rotational acceleration of ±5 r / min. 2The graphite lifting rod was started and rotated in the forward and reverse directions for 5 minutes, then slowly decelerated to 0 rpm, and then accelerated to 5 r / min in the reverse direction for a total of 1 minute. This was repeated until the growth was completed. The graphite crucible rotated in the forward and reverse directions at a speed of 5 r / min, with a rotational acceleration of ±5 r / min. 2 The graphite crucible was started and rotated in both directions for 5 minutes. It was then slowly decelerated to 0 rpm and then accelerated in the opposite direction to 5 rpm for a total of 1 minute. This process was repeated until growth was complete. The graphite pulling rod was pulled upward at a speed of 150 μm / h. After 120 hours of growth, the graphite pulling rod was pulled upward at a speed of 20 mm / h to completely separate the grown crystal from the molten flux surface. Heating was then stopped. The grown crystal and graphite crucible were then slowly cooled to room temperature. The chamber of the high-temperature growth furnace was opened, and the grown crystal was removed. As shown in Figure 9, in this comparative example, the viscosity of the flux was high because no Al was added, resulting in many trenches at the crystal boundaries. Comparative Example 2

[0056] A 4-inch semi-insulating SiC single crystal wafer with a 0° misalignment was fixed to a 10 mm thick graphite seed holder, and the graphite seed holder was fixed to a graphite pull rod. The C-plane was the growth surface. In this example, Al-free Si and Ce were used as fluxes, with a molar ratio of Si to Ce of 90:10. Si and Ce single particles were uniformly mixed and then placed in a graphite crucible for compaction. The graphite crucible had an inner diameter of 150 mm, a height of 200 mm, and a wall thickness of 10 mm. The graphite crucible used had sawtooth-machined side walls and a porous inner bottom. The graphite crucible and graphite pull rod were placed in a high-temperature growth furnace, the furnace chamber was closed, and the furnace chamber was heated to 1000 K by using a mechanical pump and a molecular pump. -3The furnace was evacuated to a pressure of 0.8 Pa or less, and argon gas and nitrogen gas in a volume ratio of 80:20 were introduced until the pressure inside the high-temperature growth furnace reached 0.8 atm. The gas valve was then closed and gas filling was stopped. The graphite crucible was heated to control the temperature during the 3C-SiC single crystal growth process, and the temperature of the SiC seed during the single crystal growth process was raised to 1900°C. The graphite pulling rod was pushed down to contact the molten flux, initiating the growth of the 3C-SiC single crystal. During growth, the temperature gradient of the melt was 10°C / cm, and the graphite pulling rod to which the SiC seed was fixed rotated forward and backward at a speed of 5 r / min, with a rotational acceleration of ±5 r / min. 2 The graphite lifting rod was started and rotated in the forward and reverse directions for 5 minutes, then slowly decelerated to 0 rpm, and then accelerated to 5 r / min in the reverse direction for a total of 1 minute. This was repeated until the growth was completed. The graphite crucible rotated in the forward and reverse directions at a speed of 5 r / min, with a rotational acceleration of ±5 r / min. 2 The graphite crucible was started and rotated in both directions for 5 min. It was then slowly decelerated to 0 rpm and then accelerated to 5 rpm in the opposite direction for a total of 1 min. This process was repeated until growth was complete. The graphite pulling rod was pulled upward at a speed of 150 μm / h. After 120 h of growth, the graphite pulling rod was pulled upward at a speed of 20 mm / h to completely separate the grown crystal from the molten flux. Heating was then stopped. The grown crystal and graphite crucible were then slowly cooled to room temperature. The chamber of the high-temperature growth furnace was opened, and the grown crystal was removed. In this comparative example, the solubility of C in Si was low, and almost no grown crystal was observed on the SiC seed.

[0057] It should be noted that the above examples are merely for illustrating the technical solutions of the present invention, and are not intended to be limiting. Specific process parameters may be optimized and adjusted, but the gist of the present invention remains clear. Those skilled in the art will appreciate that any modifications or equivalent replacements to the technical solutions of the present invention do not depart from the spirit and scope of the technical solutions of the present invention, and all of them should be included in the scope of the claims of the present invention.

Claims

1. (1) fixing a SiC seed to a graphite seed holder and fixing the graphite seed holder to a graphite lifting rod; Step (2) of placing a flux containing Si and Al into a graphite crucible; Next, step (3) of placing the graphite crucible and the graphite pulling rod in a growth furnace; (4) evacuating the growth furnace and then flowing gas to control the atmospheric pressure in the growth furnace and the crystal type of 3C—SiC; (5) forming a melt by heating the graphite crucible until the flux is completely melted and reaches a growth temperature of SiC; and (6) pushing down the graphite pull rod to bring the SiC seed into contact with the melt and further growing a 3C—SiC single crystal; The flux further contains a 3d group transition metal whose melting point is lower than the growth temperature of SiC. A method for producing 3C-SiC single crystals.

2. 2. The method of claim 1, wherein the Group 3d transition metal is one or more selected from Fe, Co, Ni, and Ti.

3. 2. The method of claim 1, wherein the atomic molar ratio of Si to Al to the 3d group transition metal in the flux is (30-70):(0.01-20):(30-70).

4. The method of claim 1 , wherein the flux further comprises a rare earth metal having a melting point below the growth temperature of SiC.

5. the rare earth metal is one or more selected from La, Pr, and Ce, The method according to claim 4, wherein the atomic molar ratio of Si, Al, the 3d group transition metal and the rare earth metal in the flux is preferably (30-70):(0.01-20):(30-70):(0.1-20).

6. The method of claim 1 , wherein the flux further comprises a Group IIIA metal and / or a Group IVA metal other than Al whose melting point is lower than the growth temperature of SiC.

7. the Group IIIA metal and / or Group IVA metal other than Al is one or more selected from Ga, In, Ge, and Sn; The method according to claim 6, wherein the atomic molar ratio of Si to Al to the 3d group transition metal to the rare earth metal to the IIIA group metal and / or IVA group metal other than Al in the flux is preferably (30-70):(0.01-20):(30-70):(0.1-20):(0.1-20).

8. The step (4) of evacuating the growth furnace is carried out by evacuating the growth furnace for 10 minutes. -2 and drawing a vacuum to less than Pa. Preferably, the gas is a mixture of nitrogen gas and one or more gases selected from helium, argon, and hydrogen, or a mixture of oxygen gas and one or more gases selected from helium and argon, and preferably, the volume of nitrogen gas or oxygen gas in the gas accounts for 0.1% to 50%; Preferably, the control of the pressure in the growth furnace in the step (4) is performed by controlling the pressure in the growth furnace to 0.2-2.0 atm; Preferably, the SiC seed is a 2-6 inch SiC wafer with a deflection angle of either 0°, 4° or 8°; Preferably, the SiC seed is any one of a semi-insulating SiC single crystal substrate, an n-type conductivity type SiC single crystal substrate, and a p-type conductivity type SiC single crystal substrate; 2. The method according to claim 1, wherein the inner diameter of the graphite crucible is 5 mm or more larger than the diameter of the SiC seed, the thickness of the graphite crucible is 10 mm or more, and the inner wall of the graphite crucible is dense, porous, honeycomb, or multi-grooved.

9. 2. The method of claim 1, wherein the growth of the 3C-SiC single crystal in step (6) is carried out by a method comprising the steps of: (i) controlling the temperature during the growth of the 3C-SiC single crystal, so that the temperature of the SiC seed during the growth of the single crystal is 1700°C to 1900°C, and the temperature of the melt is gradually increased from the surface closest to the SiC seed to the bottom of the graphite crucible, with a temperature gradient of 3°C to 30°C / cm; (ii) Periodically rotating the SiC seed and the graphite crucible at accelerated and decelerated speeds while slowly pulling up the SiC seed.

10. The periodic accelerated and decelerated rotation is performed under the following conditions: the graphite crucible and the SiC seed are rotated in opposite directions, the rotation speed is ±0 to 200 r / min, and the rotation acceleration is ±0 to 30 r / min. 2 and The method according to claim 9, wherein the pulling is preferably carried out at a speed of 1 to 3000 μm / h.

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