Preparation device and method based on growth of large-size silicon carbide single crystals

Abstract

The invention discloses a preparation device and method for growing a large-size silicon carbide single crystal. A raw material gas phase in a high-temperature area is transmitted to the surface of a seed crystal in a low-temperature area for crystal growth by using a physical gas phase transmission method; the device comprises a furnace chamber, a movable sectional type heating system, a thermal insulation material, a graphite crucible, porous graphite, a seed crystal unit, a crystal growth induction forming device and an electric field device. The method comprises the following steps: installing a seed crystal unit in a crucible filled with silicon carbide powder, placing the crucible in a heater, and carrying out a crystal growth stage to prepare the silicon carbide single crystal. The whole growth process of the crystal is in a constant temperature state, thermal stress caused by the temperature difference between the growth end and the seed crystal end and the temperature difference between the crystal edge and the crystal center in the top end seed crystal method crystal growth process is avoided, the dislocation defect of the crystal is reduced, and finally the high-quality silicon carbide single crystal is obtained. And the production cost is reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of crystal growth, and in particular to a device and method for preparing a large-size silicon carbide single crystal by substrate growth. Background Art

[0002] Silicon carbide crystal (SiC) is a third-generation wide-bandgap semiconductor material with properties such as wide bandgap, high thermal conductivity, high electron saturation mobility, and high breakdown electric field. Therefore, it is considered to be an ideal semiconductor material for manufacturing optoelectronic devices, high-frequency and high-power devices, and high-temperature electronic devices. These excellent properties make it have broad application prospects in high-voltage power grids, new energy vehicles, high-power charging piles, 5G communications and other fields.

[0003] At present, the main methods for growing silicon carbide include vapor transport (PVT), liquid phase epitaxy (LPE), chemical vapor deposition (CVD), etc. The mainstream commercialized method for preparing silicon carbide single crystals is physical vapor transport (PVT). The growth furnace for growing silicon carbide single crystals in this method generally heats the raw materials in the growth chamber to decompose the raw materials, and then crystallizes and grows at the seed crystal with a lower temperature, thereby achieving crystal growth. This method has the advantages of high crystal quality, low cost and relatively mature process, but due to the limitations of equipment and growth structure, the preparation of high-quality and high-thickness silicon carbide crystals is limited, especially because silicon carbide has a large number of polymorphs, and the growth conditions of 4H, 6H, 15R and 3C are relatively close. The slight change of the C / Si ratio on the seed crystal surface during the growth process and the imbalance of the proportion of the growth components can easily lead to the phenomenon of crystal inclusion during the growth process.

[0004] During the crystal growth process of the PVT method, silicon carbide has no melting point. The ordinary inductive heating method heats the crucible through high-frequency alternating current electromagnetic induction. The temperature of the part near the crucible wall is high. Due to the poor thermal conductivity of the powder, the temperature of the central part of the raw material area is low. Especially for large-sized ingots, the crucible size is large, and this problem is more prominent. The part close to the heating source will decompose first. The middle area of ​​the raw material area will cause raw material recrystallization due to the temperature gradient, thereby blocking the transport of the growing components. As the silicon carbide crystal continues to grow, the raw material transport state in the middle part of the raw material is different from the transport state when the crystal just starts to grow, resulting in changes in the chemical component ratio of the seed crystal growth surface, causing defects and reducing the quality of the silicon carbide single crystal. High-purity argon is expensive, and a single use as a protective carrier gas causes huge waste, resulting in an increase in the manufacturing cost of silicon carbide. Summary of the invention

[0005] The object of the present invention is to provide a device and method for preparing large-size silicon carbide single crystals based on growth, so as to solve the problems raised in the above-mentioned background technology.

[0006] To achieve the above object, the present invention provides the following technical solution: a device and method for preparing large-size silicon carbide single crystals based on growth, comprising the following steps: S1, bonding and fixing the large-sized silicon carbide seed crystal on both sides of the seed crystal holder; S2, a combination of a crystal growth induction molding device and a seed crystal unit; S3, placing the growth device assembled in S2 in the middle of the porous graphite, filling the silicon carbide powder between the crucible and the porous graphite, and sealing the graphite crucible; S4, wrap the graphite crucible with insulation material to provide suitable temperature conditions; S5, placing the assembled growth component inside the coil heater, ensuring that the graphite crucible and the heater are in concentric positions, and the heater adopts segmented heating; S6, applying an adjustable electric field to the seed crystal holder and the bottom of the crucible to adjust the movement direction of the carbon-silicon groups of the growth components and arrange them regularly on the crystal interface; S7, the furnace chamber is evacuated and filled with high-purity argon gas, the temperature of the crystal growth furnace is heated to reach the crystal growth temperature, the temperature and pressure are kept constant for a period of time to complete the growth of silicon carbide crystals, the power is reduced and cooled to room temperature, argon gas is filled to atmospheric pressure, the furnace chamber is opened, and the crystal is taken out.

[0007] Preferably, the device includes a furnace body, an insulation layer and a crucible, an argon circulation device is provided at the bottom of the furnace body, a crucible is provided in the furnace body, an insulation layer is provided on the outer wall of the crucible, an electric field device is provided in the middle position of a group of outer walls opposite to each other of the crucible, porous graphite is provided inside the two sides of the crucible without the electric field device, silicon carbide powder is filled between the porous graphite and the inner wall, and a crystal growth induction molding device is provided in the middle position relative to the porous graphite.

[0008] Preferably, in step S1, the bonding surface of the seed crystal holder is polished to a thickness within 10 mm and a diameter within 50 mm larger than the diameter of the seed crystal. The seed crystal is bonded to both sides of the seed crystal holder, and the seed crystal is bonded to the graphite holder adhesive. The adhesive is carbonized at high temperature, and the carbonization temperature is not higher than 800°C.

[0009] Preferably, in step S2, the inner diameter of the crystal growth induction molding device is the same as the diameter of the seed crystal and is expanded to be 10-20 mm larger than the diameter of the seed crystal.

[0010] Preferably, in step S3, the thickness of the porous graphite is 3-10 mm, and the seed crystal is placed in the middle of the porous graphite.

[0011] Preferably, the crucible in step S3 is made of graphite, tungsten, molybdenum, tantalum, tungsten alloy, molybdenum alloy, tantalum alloy, etc. The inner surface of the graphite crucible is coated with tantalum and has a cylindrical shape. The crucible has a height of 200-600 mm, an outer diameter of 300-600 mm, a wall thickness of 5-20 mm, a bottom thickness of 5-20 mm, and can be disassembled and assembled at both ends. The radial thickness of the silicon carbide powder is 100-200 mm.

[0012] Preferably, the thermal insulation material in step S4 is composed of soft graphite felt, hard glue or a combination of the two, with a thickness of 5-100 mm.

[0013] Preferably, the inner diameter of the heater in step S5 is 400-700 mm, there is a gap between the heater and the outer surface of the insulation material, the body height is 300-900 mm, the concentricity deviation between the crucible and the heater is not more than 5 mm, and the movable segmented heating technology is adopted. By setting multiple movable heating areas in the growth device, the temperature and growth rate of each area are different. The growth interface growth rate is adjusted according to the growth thickness of the crystal to ensure the crystal quality.

[0014] Preferably, in step S6, the electric field strength at the seed crystal end and the material region is adjusted during the growth process, so that the charged growth groups move under the action of the electric field and are regularly arranged at the growth interface.

[0015] Preferably, in step S7, the growth temperature is 2100-2350° C., the argon pressure in the growth chamber is 200-3000 Pa, the growth time is 50-24 hours, and the cooling time is 10-80 hours. The argon released after the growth is completed is recycled and reused through a purification system to reduce the consumption of argon.

[0016] Compared with the prior art, the present invention has the following beneficial effects: 1. The method of the present invention can grow large-size single crystals with a thickness of 20-50 mm and a thickness of 6-12 inches, and the grown crystals have no obvious defects such as polymorphism.

[0017] 2. The present invention can effectively make the material uniformly decompose during the entire silicon carbide crystal growth process, and the material zone is always close to the high-temperature zone at the edge of the crucible, so as to keep the atmospheric composition of the growth interface stable during the entire growth process, thereby effectively ensuring that the grown crystal is a low-defect single crystal.

[0018] 3. Two crystals are grown in one furnace. During the growth process, both ends of the crystal are always in a constant temperature range, with a small temperature gradient, small thermal stress, and low crystal dislocation density.

[0019] 4. Argon gas is recovered and reused. During the crystal growth process, the protective carrier gas argon is collected, purified and reused again to reduce the cost of the entire growth process. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1It is a schematic diagram of the structure of the present invention.

[0021] In the figure: 1 crystal growth induction molding device, 2 seed crystal holder, 3 seed crystal, 4 furnace body, 6 insulation layer, 7 crucible, 8 porous graphite, 9 silicon carbide powder, 10 argon gas recycling module, 11 electric field device. DETAILED DESCRIPTION

[0022] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0023] A device and method for growing large-size silicon carbide single crystals, characterized in that it includes the following steps: S1, bonding and fixing the large-sized silicon carbide seed crystal on both sides of the seed crystal holder; S2, a combination of a crystal growth induction molding device and a seed crystal unit; S3, placing the growth device assembled in S2 in the middle of the porous graphite, filling the silicon carbide powder between the crucible and the porous graphite, and sealing the graphite crucible; S4, wrap the graphite crucible with insulation material to provide suitable temperature conditions; S5, placing the assembled growth component inside the coil heater, ensuring that the graphite crucible and the heater are in concentric positions, and the heater adopts segmented heating; S6, applying an adjustable electric field to the seed crystal holder and the bottom of the crucible to adjust the movement direction of the carbon-silicon groups of the growth components and arrange them regularly on the crystal interface; S7, the furnace chamber is evacuated and filled with high-purity argon gas, the temperature of the crystal growth furnace is heated to reach the crystal growth temperature, the temperature and pressure are kept constant for a period of time to complete the growth of silicon carbide crystals, the power is reduced and cooled to room temperature, argon gas is filled to atmospheric pressure, the furnace chamber is opened, and the crystal is taken out.

[0024] Preferably, the device includes a furnace body, an insulation layer and a crucible, an argon circulation device is provided at the bottom of the furnace body, a crucible is provided in the furnace body, an insulation layer is provided on the outer wall of the crucible, an electric field device is provided in the middle position of a group of outer walls opposite to each other of the crucible, porous graphite is provided inside the two sides of the crucible without the electric field device, silicon carbide powder is filled between the porous graphite and the inner wall, and a crystal growth induction molding device is provided in the middle position relative to the porous graphite.

[0025] Preferably, in step S1, the bonding surface of the seed crystal holder is polished to a thickness within 10 mm and a diameter within 50 mm larger than the diameter of the seed crystal. The seed crystal is bonded to both sides of the seed crystal holder, and the seed crystal is bonded to the graphite holder adhesive. The adhesive is carbonized at high temperature, and the carbonization temperature is not higher than 800°C.

[0026] Preferably, in step S2, the inner diameter of the crystal growth induction molding device is the same as the diameter of the seed crystal and is expanded to be 10-20 mm larger than the diameter of the seed crystal.

[0027] Preferably, in step S3, the thickness of the porous graphite is 3-10 mm, and the seed crystal is placed in the middle of the porous graphite.

[0028] Preferably, the crucible in step S3 is made of graphite, tungsten, molybdenum, tantalum, tungsten alloy, molybdenum alloy, tantalum alloy, etc. The inner surface of the graphite crucible is coated with tantalum and has a cylindrical shape. The crucible has a height of 200-600 mm, an outer diameter of 300-600 mm, a wall thickness of 5-20 mm, a bottom thickness of 5-20 mm, and can be disassembled and assembled at both ends. The radial thickness of the silicon carbide powder is 100-200 mm.

[0029] Preferably, the thermal insulation material in step S4 is composed of soft graphite felt, hard glue or a combination of the two, with a thickness of 5-100 mm.

[0030] Preferably, the inner diameter of the heater in step S5 is 400-700 mm, there is a gap between the heater and the outer surface of the insulation material, the body height is 300-900 mm, the concentricity deviation between the crucible and the heater is not more than 5 mm, and the movable segmented heating technology is adopted. By setting multiple movable heating areas in the growth device, the temperature and growth rate of each area are different. The growth interface growth rate is adjusted according to the growth thickness of the crystal to ensure the crystal quality.

[0031] Preferably, in step S6, the electric field strength at the seed crystal end and the material region is adjusted during the growth process, so that the charged growth groups move under the action of the electric field and are regularly arranged at the growth interface.

[0032] Preferably, in step S7, the growth temperature is 2100-2350° C., the argon pressure in the growth chamber is 200-3000 Pa, the growth time is 50-24 hours, and the cooling time is 10-80 hours. The argon released after the growth is completed is recycled and reused through a purification system to reduce the consumption of argon. Example

[0033] See also Figure 1The present invention provides a technical solution: a device and method for preparing large-size silicon carbide single crystals based on growing the same, the device comprising a furnace body 4, a heat-insulating layer 6 and a crucible 7, an argon circulation device 10 is provided at the bottom of the furnace body 4, a crucible 7 is provided in the furnace body 4, a heat-insulating layer 6 is provided on the outer wall of the crucible 7, an electric field device 11 is provided at the middle position of a group of outer walls opposite to the crucible 7, porous graphite 8 is provided inside the two sides of the crucible 7 without the electric field device, silicon carbide powder 9 is filled between the porous graphite 8 and the inner wall, and a crystal growth induction molding device 1 is provided at the middle position of the porous graphite 8. Example

[0034] (1) A silicon carbide seed crystal 3 with a thickness of 500 μm is attached to a graphite holder by means of a graphite adhesive, and a pressing block is used to make the seed crystal 3 fit tightly with the seed crystal holder 2. After a high temperature treatment at 800°C, the seed crystal 3 is fixed on the seed crystal holder 2.

[0035] (2) Loading raw materials: Mix part of the silicon carbide powder and the active ingredient evenly, load the raw materials between the crucible and the porous graphite, and place the active ingredient near the porous graphite.

[0036] (3) Place the seed crystal holder with the seed crystal bonded to it in the middle of the porous graphite cylinder, cover the crucible with the lid, and provide a good insulation layer.

[0037] (4) Place the assembled growth assembly into the crystal growth furnace, with the growth assembly and the heater in a concentric circle, ensuring that the crucible and the heater are not in direct contact, seal the furnace chamber, and evacuate the chamber to a pressure of less than 10 -5 pa.

[0038] (5) Fill the growth furnace with high-purity argon at a flow rate of 100 sscm and a protective gas high-purity argon pressure of 400 mbar. Control the heating rate at 10°C / min, heat the crucible to a temperature of 2200-2500°C, gradually reduce the crystal growth pressure to 3-10 mbar, and maintain constant temperature and pressure for 100 hours. During the growth process, adjust the power and position of the heater through a precise control system to ensure that the crystal growth interface is at a constant temperature, adjust the electric field strength between the crucible end and the seed crystal holder, control the arrangement of the charged groups on the growth interface, complete the crystal growth, cool down to room temperature at a rate of 10°C / min, fill the furnace chamber pressure to atmospheric pressure, take out the crystal, and obtain a high-quality silicon carbide crystal.

[0039] (6) During the entire growth process, an argon purification device is installed at the furnace chamber outlet. Through filtering, dust removal, purification and other steps, a closed argon circulation system is established to purify and recycle the argon and reduce the external supplement of argon.

[0040] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A device and method for growing large-size silicon carbide single crystals, characterized in that: The following steps are involved: S1, bonding and fixing the large-sized silicon carbide seed crystal on both sides of the seed crystal holder; S2, a combination of a crystal growth induction molding device and a seed crystal unit; S3, placing the growth device assembled in S2 in the middle of the porous graphite, filling the silicon carbide powder between the crucible and the porous graphite, and sealing the graphite crucible; S4, wrap the graphite crucible with insulation material to provide suitable temperature conditions; S5, placing the assembled growth component inside the coil heater, ensuring that the graphite crucible and the heater are in concentric positions, and the heater adopts segmented heating; S6, applying an adjustable electric field to the seed crystal holder and the bottom of the crucible to adjust the movement direction of the carbon-silicon groups of the growth components and arrange them regularly on the crystal interface; S7, the furnace chamber is evacuated and filled with high-purity argon gas, the temperature of the crystal growth furnace is heated to reach the crystal growth temperature, the temperature and pressure are kept constant for a period of time to complete the growth of silicon carbide crystals, the power is reduced and cooled to room temperature, argon gas is filled to atmospheric pressure, the furnace chamber is opened, and the crystal is taken out.

2. The device and method for growing large-size silicon carbide single crystals according to claim 1 are characterized in that: The device includes a furnace body, a thermal insulation layer and a crucible. An argon circulation device is provided at the bottom of the furnace body, a crucible is provided in the furnace body, an thermal insulation layer is provided on the outer wall of the crucible, an electric field device is provided in the middle position of a group of outer walls opposite to each other of the crucible, porous graphite is provided inside the two sides of the crucible without the electric field device, silicon carbide powder is filled between the porous graphite and the inner wall, and a crystal growth induction molding device is provided in the middle position relative to the porous graphite.

3. The device and method for growing large-size silicon carbide single crystals according to claim 1, characterized in that In step S1, the bonding surface of the seed crystal holder is polished to a thickness within 10 mm and a diameter within 50 mm larger than the diameter of the seed crystal. The seed crystal is bonded to both sides of the seed crystal holder. The seed crystal is bonded to the graphite holder adhesive. The adhesive is carbonized at high temperature, and the carbonization temperature is not higher than 800°C.

4. The device and method for growing large-size silicon carbide single crystals according to claim 1, characterized in that In step S2, the inner diameter of the crystal growth induction molding device is the same as the diameter of the seed crystal and is expanded to be 10-20 mm larger than the diameter of the seed crystal.

5. The device and method for growing large-size silicon carbide single crystals according to claim 1, characterized in that: In step S3, the thickness of the porous graphite is 3-10 mm, and the seed crystal is placed in the middle of the porous graphite.

6. The device and method for growing large-size silicon carbide single crystals according to claim 1, characterized in that: The crucible in step S3 is made of graphite, tungsten, molybdenum, tantalum, tungsten alloy, molybdenum alloy, tantalum alloy, etc. The inner surface of the graphite crucible is coated with tantalum. The shape is cylindrical. The crucible height is 200-600 mm, the outer diameter is 300-600 mm, the wall thickness is 5-20 mm, the bottom thickness is 5-20 mm, the two ends can be disassembled and assembled, and the radial thickness of the silicon carbide powder is 100-200 mm.

7. The device and method for growing large-size silicon carbide single crystals according to claim 1, characterized in that In step S4, the thermal insulation material is composed of soft graphite felt, hard glue or a combination of the two, with a thickness of 5-100 mm.

8. The device and method for growing large-size silicon carbide single crystals according to claim 1, characterized in that Step S5: The inner diameter of the heater is 400-700 mm, and there is a gap between the heater and the outer surface of the insulation material. The body height is 300-900 mm. The concentricity deviation between the crucible and the heater is not more than 5 mm. The movable segmented heating technology is adopted. By setting multiple movable heating areas in the growth device, the temperature and growth rate of each area are different. The growth interface growth rate is adjusted according to the growth thickness of the crystal to ensure the quality of the crystal.

9. The device and method for growing large-size silicon carbide single crystals according to claim 1, characterized in that In step S6, the electric field strength at the seed crystal end and the material region is adjusted during the growth process so that the charged growth groups move under the action of the electric field and are arranged regularly at the growth interface.

10. The device and method for growing large-size silicon carbide single crystals according to claim 1, characterized in that In step S7, the growth temperature is 2100-2350° C., the argon pressure in the growth chamber is 200-3000 Pa, the growth time is 50-24 hours, and the cooling time is 10-80 hours. The argon released after the growth is completed is recycled and reused through a purification system to reduce the consumption of argon.

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