Apparatus and method for efficient deposition of silicon carbide single crystals

Abstract

The application provides a device for efficiently depositing silicon carbide single crystals, which comprises an atmosphere furnace, heat insulation devices arranged from outside to inside, a heating device, a container, a carbon source fixed in the container, a seed holder arranged above the container, and a seed fixed at the bottom of the seed holder. The heat insulation devices are arranged in the atmosphere furnace. The upper part of the container is open and used for containing silicon molten liquid. The bottom of the container is provided with a rotating shaft used for driving the container to rotate. The rotating shaft is connected with a rotating motor in sequence through the heat insulation devices and the atmosphere furnace. The heating device is arranged outside the container and used for heating the silicon molten liquid in the container. The upper end of the seed holder is connected with a first driving mechanism used for controlling the seed holder to move up and down. The device provided by the application can quickly deposit silicon carbide crystals, has high purity, and can easily obtain and process raw materials, thereby reducing cost and improving efficiency.

Description

Technical Field

[0001] This invention relates to an apparatus and method for efficiently depositing silicon carbide single crystals, belonging to the field of silicon carbide single crystal deposition production technology. Background Technology

[0002] Silicon carbide (SiC) crystal materials possess excellent properties such as a wide bandgap, high breakdown electric field, high thermal conductivity, high electron mobility, high mechanical properties, and radiation resistance. Therefore, SiC substrates have become the most promising third-generation semiconductor materials and a crucial foundational material for the country's "leapfrog development" in the semiconductor industry. They are widely used in power devices such as MOSFETs, IGBTs, DC-DC converter modules, and high-power chip heat sinks such as lasers, 5G amplifier chips, and power chip packaging. Due to the superior properties of SiC crystal materials, they have groundbreaking application prospects in chip manufacturing, replacing silicon-based materials, and in chip packaging, replacing ceramic-based and metal-based materials.

[0003] Because silicon carbide requires harsh liquid phase conditions—specifically, an atmosphere above 1010 Pa and 2800°C—to form a liquid phase, these conditions are difficult to meet, making the liquid phase pulling technique used for single-crystal silicon unsuitable for silicon carbide single-crystal materials. However, due to the low vaporization pressure of silicon carbide single crystals, existing technologies primarily employ the "physical vapor transport (PVT)" method for silicon carbide single-crystal deposition.

[0004] The main drawbacks of this method are as follows: 1. Low deposition efficiency: The evaporation efficiency of silicon carbide vapor is not very high to begin with, and its saturated vapor pressure is very low. If silicon carbide is prepared by carbon + silicon reaction, its deposition efficiency will be further reduced. The deposition efficiency of this method is about 3-5 μm / h.

[0005] 2. High energy consumption: The energy required for silicon carbide vaporization is enormous. During PVT deposition, maintaining the gradient temperature in the gaseous SiC transport channels is challenging and energy consumption is substantial. Furthermore, the low deposition efficiency results in high energy consumption per unit area.

[0006] 3. Difficulty in raw material preparation: Direct gasification of high-purity silicon carbide powder is currently the most common method used in PVT. Due to the high hardness of silicon carbide, the powder is difficult to process, and the purification of silicon carbide is also one of the factors contributing to its high raw material cost.

[0007] 4. Deposit purity: Due to the decomposition reaction that occurs during the high-temperature vaporization deposition of silicon carbide, "impurities" from the decomposition reaction will be mixed in during the seed deposition process. This is one of the important reasons for crystallization defects.

[0008] 5. Huge waste of raw materials: During the transfer process in the vaporization temperature zone of the PVT method, some vapors will condense in the transfer space, causing crystallization defects; at the same time, some vapors will condense outside the seed target, resulting in waste of raw materials.

[0009] Essentially, the principle of PVT (Polyhydrodynamic Transformation) for depositing SiC single crystals is based on the low vaporization pressure of SiC material. During the operation of vapor-phase PVT, it is crucial to control the temperature and atmosphere along the deposition path to create conditions conducive to the transport of gaseous SiC towards the seed crystal. This can lead to target delamination and crystallization defects, which is one of the main reasons for the low efficiency, extremely high cost, and numerous crystal defects in single-crystal SiC deposition and growth.

[0010] Therefore, finding a device and method for depositing silicon carbide single crystals that can efficiently deposit different crystal phases according to needs, and that is easy to operate and low in cost, is a technical problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0011] To address the shortcomings of the prior art, the present invention aims to provide a device for rapidly depositing silicon carbide single crystals. This device enables the silicon carbide to be transported in a liquid environment after generation and gradually deposited and grown on the seed crystal surface. The gaseous silicon carbide moves rapidly in the solution, thereby greatly accelerating the reaction rate and deposition rate. Moreover, the device allows for the rapid deposition of silicon carbide crystals with high purity, and the raw materials are readily available and easy to process, which can reduce costs and improve efficiency.

[0012] According to an embodiment of the present invention, a first embodiment is provided as follows: an apparatus for efficiently depositing silicon carbide single crystals, comprising an atmosphere furnace; a heat insulation device, a heating device, and a container arranged from the outside to the inside; a carbon source fixed inside the container; a seed holder disposed above the container; and a seed crystal fixed at the bottom of the seed holder; wherein the heat insulation device is disposed inside the atmosphere furnace; the container has an opening at the top for holding molten silicon, and a rotating shaft is provided at the bottom of the container for driving the container to rotate, the rotating shaft passing through the heat insulation device and the atmosphere furnace in sequence and connected to a rotating motor; the heating device is disposed outside the container for heating the molten silicon inside the container; and the upper end of the seed holder is connected to a first driving mechanism for controlling the up and down movement of the seed holder.

[0013] Furthermore, in a more preferred embodiment of the present invention, the device further includes: a catalyst disposed above the container, a second driving mechanism connected above the catalyst for controlling the up-and-down movement of the catalyst, and a heater connected to the catalyst for controlling the temperature of the catalyst. The heater on the catalyst is a heating wire or a medium-frequency or high-frequency heating device; using a wire for heating facilitates the up-and-down movement.

[0014] Furthermore, as a more preferred embodiment of the present invention, the second drive mechanism is preferably an electro-hydraulic push rod, more preferably a CNC electro-hydraulic push rod, and the heater is preferably a heating wire, more preferably a tungsten wire, more preferably a nickel-chromium alloy heating wire, and more preferably a ceramic heating wire.

[0015] Furthermore, in a more preferred embodiment of the present invention, the catalyst is a platinum group metal, a transition metal, an alloy containing a platinum group metal, or an alloy containing a transition metal. Preferably, it is a platinum group metal; more preferably, platinum; more preferably, a platinum alloy with a platinum weight content of 10-40%; more preferably, a platinum alloy with a platinum weight content of 20-30%; more preferably, a platinum alloy with a platinum weight content of 20%; more preferably, palladium; more preferably, osmium; more preferably, iridium; more preferably, ruthenium; more preferably, rhodium. Preferably, it is a transition metal; more preferably, silver; more preferably, chromium; more preferably, nickel.

[0016] Furthermore, in a more preferred embodiment of the present invention, the catalyst is cylindrical with openings at both ends, and the sidewalls of the catalyst are located between the seed crystal holder and the inner sidewall of the container, wherein the sidewalls of the catalyst are mesh-like. The catalyst is preferably annular, and the sidewalls of the catalyst are preferably fence-like, more preferably perforated.

[0017] Furthermore, in a more preferred embodiment of the present invention, the container is a graphite crucible, serving as one of the carbon source providers.

[0018] Furthermore, as a more preferred embodiment of the present invention, the container is made of a high-temperature resistant material, preferably a high-temperature resistant ceramic, preferably tungsten, preferably tantalum, and preferably a tungsten alloy.

[0019] Furthermore, in a more preferred embodiment of the present invention, the heating device is an electric heating wire, preferably a tungsten wire.

[0020] According to an embodiment of the present invention, a second embodiment is provided by depositing silicon carbide single crystals using the apparatus in the first embodiment of the present invention: A method for efficiently depositing silicon carbide single crystals includes the following steps: The carbon source is fixed at the bottom of the container, and high-purity silicon is placed inside the container. Silicon carbide seeds are fixed on the bottom surface of the seed holder. The container and the seed holder are placed in the atmosphere furnace, with the seed holder above the container. The atmosphere furnace is then sealed and a vacuum is drawn. When the vacuum degree reaches 10 -4 When the temperature is below Pa, the container is heated by a heating device to melt the high-purity silicon into a molten state called silicon melt. The seed crystal holder is moved down to form capillary contact between the silicon carbide seed crystal and the silicon melt. At this time, the C and Si reaction is already proceeding slowly. Some of the generated SiC exists in the silicon melt as a gas phase and diffuses throughout the entire atmosphere furnace, and gradually condenses and crystallizes in various places. The container continues to be heated to the growth temperature of the desired crystal phase, and the container is rotated while inert gas is introduced into the atmosphere furnace to increase the pressure inside the atmosphere furnace, so that the gas pressure inside the atmosphere furnace reaches the saturation gas pressure of the silicon melt of SiC crystal at this temperature, and the temperature is kept constant so that silicon carbide single crystals gradually precipitate on the silicon carbide crystal. As the level of the molten silicon decreases, the seed crystal holder also gradually decreases, maintaining capillary contact between the silicon carbide seed crystal and the molten silicon, thus ensuring the continued precipitation of silicon carbide single crystals.

[0021] Furthermore, as a more preferred embodiment of the present invention, the method further includes the following steps: placing a catalyst above the molten silicon; after the container rotates, moving the catalyst down to 2-10 mm below the surface of the molten silicon to catalyze the formation of silicon carbide; moving the catalyst back up from the molten silicon every 2-5 minutes; and connecting the catalyst to a heater for heating, maintaining the catalyst temperature 50-100°C higher than the molten silicon temperature. Preferably, the catalyst is moved down to 3-8 mm below the surface of the molten silicon, more preferably 4-7 mm, and even more preferably 5-6 mm, which is beneficial to improving the SiC formation efficiency. Then, based on the SiC formation and deposition efficiency, the frequency and time of the catalyst moving up and down from and into the molten silicon are adjusted to keep the SiC formation and deposition efficiency basically consistent. Preferably, the catalyst is moved back up from the molten silicon every 2-5 minutes, more preferably every 3-4 minutes, and even more preferably every 3 minutes.

[0022] Furthermore, as a more preferred embodiment of the present invention, the method further includes the following steps: the seed holder is rotatable, the seed holder and the container rotate in opposite directions, and the rotation speed of the seed holder and the container is 30-50 r / min, preferably 35-45 r / min, more preferably 35-40 r / min, and even more preferably 40 r / min.

[0023] Furthermore, in a more preferred embodiment of the present invention, the vacuum degree after evacuation in the sealed atmosphere furnace is 10. -4 Pa, the distance from which the seed holder moves down to form capillary contact between the silicon carbide seed and the molten silicon is 0.3-1.5 mm. Preferably 0.5-1.2 mm, more preferably 0.5-1.2 mm, even more preferably 0.6-1 mm, and even more preferably 0.8-1 mm.

[0024] Furthermore, as a more preferred embodiment of the present invention, the growth conditions of the crystal phases are as follows: the growth temperature of the 3C crystal phase is 1400-1800℃, preferably 1500-1700℃, more preferably 1500-1600℃; the growth temperature of the 4H silicon carbide crystal phase is 1800-2000℃, preferably 1800-1900℃, more preferably 1850-1900℃; and the growth temperature of the 6H silicon carbide crystal phase is 2200-2400℃, preferably 2200-2300℃, more preferably 2300℃. The saturated vapor pressure of the 3C crystal phase in the molten silicon is 1*10⁻⁶. 5 Pa-5*10 5 Pa, preferably 2*10 5 Pa-4*10 5 Pa, more preferably 3*10 5 Pa, more preferably 2.5*10 5 Pa, more preferably 1.5*10 5 Pa, more preferably 1.8*10 5 Pa; the saturated vapor pressure of the 4H crystalline phase in molten silicon is 1*10 Pa. 5 Pa-5*10 5 Pa, preferably 2*10 5 Pa-4*10 5 Pa, more preferably 3*10 5 Pa, more preferably 3.5*10 5 Pa, more preferably 2.6*10 5 Pa, more preferably 3.2*10 5 Pa; the saturated vapor pressure of the 6H crystalline phase in molten silicon is 1*10 Pa. 5 Pa-5*10 5 Pa, preferably 2*10 5 Pa-4*10 5 Pa, more preferably 3*10 5 Pa, more preferably 4*10 5 Pa, more preferably 4.5*10 5 Pa, more preferably 4.8*10 5 Pa, more preferably 5*10 5 Pa.

[0025] Furthermore, in a more preferred embodiment of the present invention, the carbon source is a high-purity, porous, and loosely structured carbon structure or an inlet providing a carbon source. The carbon source is preferably charcoal, more preferably graphene, more preferably a carbon-doped metal, and even more preferably an inlet providing a carbon source. This inlet is a one-way opening, and the carbon source is brought into the atmosphere furnace through the inlet by external power, such as pressurized inert gas, and enters the container from the bottom to react with the molten silicon. There may be one or more carbon sources, all located within the container.

[0026] The carbon-silicon reaction in this invention is essentially a redox reaction: C + Si → SiC. Under suitable atmospheric conditions, the addition of a catalyst catalyzes the rapid reaction of carbon and silicon, which can greatly improve the SiC formation efficiency. Since SiC exists in the gas phase in the silicon melt of this application, it is utilized to "transport" SiC in the silicon melt in a gas-liquid phase manner, and under suitable atmospheric conditions, the desired SiC single crystal ingot is grown on the seed surface.

[0027] Compared with existing technologies, the technical solution provided in this application mainly utilizes the reaction of carbon and silicon at high temperatures to generate silicon carbide. Silicon carbide is "dissolved" in the high-temperature molten silicon in an aerosol form and transported along with the molten silicon. Under suitable atmospheric conditions, it gradually deposits and grows on the seed crystal surface. Simultaneously, a catalyst can be added to accelerate the C+Si reaction to generate SiC. Different crystal phases are generated through a crystallization atmosphere, and the deposition rate of silicon carbide can be adjusted by regulating the atmosphere within different seed crystal growth temperature ranges. This application can control the reaction rate of C+Si by controlling the intervention of the catalyst and adjusting the atmosphere to maintain a basic consistency and balance between the rate of SiC generation and its aerosol phase transport and deposition growth. This significantly improves the transport efficiency of SiC single crystals, thereby increasing deposition efficiency and reducing unit production costs. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of the apparatus for efficiently depositing silicon carbide single crystals according to the present invention; Figure label: Atmosphere furnace 1, heat insulation device 2, heating device 3, container 4, rotating shaft 41, carbon source 5, seed holder 6, seed crystal 7, rotating motor 8, first drive mechanism 91, second drive mechanism 92, catalyst 10, heater 101. Detailed Implementation

[0029] To enable those skilled in the art to better understand the technical solutions in this application, the technical solutions in the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of the embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0030] It should be noted that when a component is referred to as being "fixed to" or "set on" another component, it can be directly on or indirectly set on the other component; when a component is referred to as being "connected to" another component, it can be directly connected to or indirectly connected to the other component.

[0031] It should be understood that the terms "length", "width", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", and "outer" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or component referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application.

[0032] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this application, "multiple" or "several" means two or more, unless otherwise explicitly specified.

[0033] It should be noted that the structures, proportions, sizes, etc., shown in the accompanying drawings of this specification are only for the purpose of assisting those skilled in the art in understanding and reading the content disclosed in the specification, and are not intended to limit the conditions under which this application can be implemented. Therefore, they have no substantial technical significance. Any modifications to the structure, changes in the proportions, or adjustments to the size should still fall within the scope of the technical content disclosed in this application, provided that they do not affect the effects and purposes that this application can produce.

[0034] According to an embodiment of the present invention, a first embodiment is provided as follows: an apparatus for efficiently depositing silicon carbide single crystals, comprising an atmosphere furnace 1; a heat insulation device 2, a heating device 3, and a container 4 arranged from the outside to the inside; a carbon source 5 fixed inside the container 4; a seed holder 6 disposed above the container 4; and a seed crystal 7 fixed at the bottom of the seed holder 6; wherein the heat insulation device 2 is disposed inside the atmosphere furnace 1; the container 4 has an opening at the top for holding molten silicon, and a rotating shaft 41 is provided at the bottom of the container 4 for driving the container 4 to rotate, the rotating shaft 4 passing through the heat insulation device 2 and the atmosphere furnace 1 in sequence and connected to a rotating motor 8; the heating device 2 is disposed outside the container 4 for heating the molten silicon inside the container 4; and the upper end of the seed holder 6 is connected to a first driving mechanism 91 for controlling the up and down movement of the seed holder.

[0035] In this technical solution, it should be noted that the atmosphere furnace is a crystal growth furnace or other furnace body capable of withstanding high temperatures and adjustable pressure. The entire device is set inside the furnace body for easy adjustment of the overall atmosphere. The container is heated by a heating device, and the heat insulation device is made of fireproof and heat-insulating materials to maintain the high temperature inside the crystal growth furnace and reduce energy consumption. The carbon source is fixed at the bottom of the container 4, which allows the silicon molten liquid to maintain the maximum contact area with the carbon source during the continuous reaction and descent process, maximizing the immersion of the carbon source for reaction. A rotating shaft 41 is set at the bottom of the container to seal the motor that drives the crystal growth furnace, causing the container to rotate and thus playing a stirring role. The motor can be infinitely speed-regulated and the speed is adjustable. The rotating shaft is connected to the crystal growth furnace by a dynamic seal, and the upper end of the seed holder is also connected to the crystal growth furnace by a dynamic seal. The specific connection method is existing technology. The seed holder is connected to the first drive mechanism 91, which can also drive the rotation of the seed holder. When it rotates in the opposite direction to the container, it can effectively increase the stirring rate of the silicon molten liquid. The overheating device heats the molten silicon in the container, which then reacts with the carbon source located in the container at a high temperature. The atmosphere furnace can be evacuated or inert gas can be introduced to regulate the pressure inside the atmosphere furnace. When silicon carbide dissolves in the molten silicon in a gaseous state, lowering the gas pressure is beneficial for silicon carbide precipitation. This principle is used to regulate the pressure inside the entire atmosphere furnace, so that the reaction can proceed while precipitation occurs. Silicon carbide crystals precipitate on the seed crystals, making them easy to remove. The upper end of the seed crystal holder is connected to the first driving mechanism 91 to control the up and down movement of the seed crystal holder. When the liquid level of the molten silicon drops due to the reaction, the seed crystal holder needs to be lowered by a certain displacement to maintain contact between the seed crystals and the liquid level, so as to ensure the continuous precipitation of silicon carbide crystals.

[0036] The first drive mechanism 91 is an electro-hydraulic actuator or an electric actuator, etc., capable of controlling reciprocating motion. The first drive mechanism 91 is connected to the upper end of the seed holder, which passes through the atmosphere furnace and is sealed to it. The seed holder is made of high-purity graphite. The holder head has different shapes and sizes depending on the shape of the seed crystal, facilitating disassembly and clamping. After deposition is completed, the seed holder, along with the ingot, is sliced ​​by a cutting machine, retaining a portion of the seed crystal as seed crystals for the second deposition. This seed holder can also be made of other high-temperature resistant materials, such as tungsten, tantalum, and other metal alloys, or other ceramic materials, with high-purity graphite being preferred.

[0037] The seed crystal is a silicon carbide seed crystal. Different SiC crystals with different lattice forms can be selected according to the requirements. It is connected to the seed crystal holder by high temperature isostatic pressing welding method, which can ensure that it will not loosen under high temperature conditions.

[0038] The carbon source is pure carbon, preferably high-purity porous graphite, which is fixed to the bottom of the graphite crucible using high-temperature isostatic pressing welding. This serves as the carbon provider in the silicon carbide reaction. Using high-purity porous graphite facilitates increasing the contact area between the molten silicon and the carbon. The heating device is a high-frequency, medium-frequency, or tungsten wire heating device. One or more sets of high-frequency, medium-frequency, or tungsten wire heating devices are used to heat the material in the crystal growth furnace. Under the joint control of temperature monitoring, a constant, stepped temperature zone can be formed to ensure the deposition and growth of SiC crystals.

[0039] Specifically, in this embodiment of the invention, the device further includes: a catalyst 10 disposed above the container 4, a second driving mechanism 92 connected above the catalyst 10 for controlling the up and down movement of the catalyst, and a heater 101 connected to the catalyst 10 for controlling the temperature of the catalyst 10.

[0040] It should be noted that by setting a second driving mechanism 92 above the catalyst to control its up-and-down movement, the catalyst is easily immersed in the molten silicon, catalyzing the reaction between silicon and carbon. The second driving mechanism 92 has the same structure as the first driving mechanism 91, suspending the catalyst below via a rigid rod or frame, controlling its entry and exit from the surface of the molten silicon, thereby controlling the generation and deposition rates of silicon carbide. The rigid rod or frame is connected to the atmosphere furnace via a dynamic seal. A heater is connected to the catalyst 10 to independently control its temperature, ensuring it is higher than the temperature of the molten silicon. This prevents silicon carbide crystals, elemental silicon, and elemental carbon from condensing on the catalyst to form a film layer, which would affect the catalytic reaction. The temperature of the catalyst is controlled to be 50-100°C higher than the temperature of the molten silicon. The heater can be a tungsten filament or other heat-conducting structure. A temperature probe is installed on the catalyst, and the catalyst is immediately heated when its temperature drops below the temperature of the molten silicon.

[0041] Specifically, in this embodiment of the invention, the catalyst 10 is a platinum group metal, a transition metal, an alloy containing a platinum group metal, or an alloy containing a transition metal.

[0042] It should be noted that platinum group metals have excellent catalytic redox reaction properties. By utilizing the redox catalytic effects of platinum group metals and transition metals, the reaction between carbon and silicon can be greatly accelerated, thereby increasing the deposition efficiency.

[0043] Specifically, in this embodiment of the invention, the catalyst 10 is a cylindrical shape with openings at both ends, and the sidewall of the catalyst 10 is located between the seed crystal holder 6 and the inner sidewall of the container 4, and the sidewall of the catalyst is in the form of a mesh.

[0044] It should be noted that the catalyst is set in a cylindrical shape so that it can surround the seed crystal to catalyze the formation of silicon carbide, thereby accelerating the efficiency. The mesh shape is set to increase the contact area between the catalyst and carbon and silicon, thereby increasing the catalytic efficiency and accelerating the formation and deposition of silicon carbide.

[0045] Specifically, in this embodiment of the invention, the container 4 is a graphite crucible, or made of other high-temperature resistant materials.

[0046] It should be noted that in the structure of the crystal growth furnace, the graphite crucible not only serves as a container for the molten silicon but also, together with the high-purity porous graphite carbon source, constitutes the C source provider within the furnace. To reduce the crucible's corrosion efficiency, its volume should be large rather than small, and high-purity porous graphite is placed at its bottom as another C source provider. Provided the carbon source supply is sufficient, this crucible can be made of other high-temperature resistant materials, such as tungsten, tantalum, and other metal alloys, or other ceramic materials; high-purity graphite crucibles are preferred.

[0047] When using graphite crucibles, as SiC is formed, the inner wall of the graphite crucible is gradually eroded by the molten silicon, becoming thinner and eventually losing its function, requiring replacement. At high temperatures, the saturated solubility of carbon (C) in molten silicon is approximately 19%, and the inner wall of the crucible is smooth and dense. As the efficiency of the SiC reaction gradually increases, relying solely on graphite crucibles as the C source is insufficient to keep pace with the increased efficiency. Therefore, the use of high-purity porous graphite is necessary to maintain the silicon-carbon reaction at a relatively high efficiency level.

[0048] According to an embodiment of the present invention, a second embodiment is provided: a method for efficiently depositing silicon carbide single crystals, comprising the following steps: The carbon source is fixed at the bottom of the container, and high-purity silicon is placed inside the container. Silicon carbide seeds are fixed on the bottom surface of the seed holder. The container and the seed holder are placed in the atmosphere furnace, with the seed holder above the container. The atmosphere furnace is then sealed and a vacuum is drawn. When the vacuum degree reaches below 10⁻⁴ Pa, the container is heated by a heating device to melt the high-purity silicon into a molten state called silicon melt. The seed crystal holder is moved down to form capillary contact between the silicon carbide seed crystal and the silicon melt. At this time, the C and Si reaction is already proceeding slowly. Some of the generated SiC exists in the silicon melt as a gas and diffuses throughout the entire atmosphere furnace, gradually condensing and crystallizing in various places. The container continues to be heated to the growth temperature of the desired crystal phase, and the container is rotated while inert gas is introduced into the atmosphere furnace to increase the pressure inside the atmosphere furnace, so that the gas pressure inside the atmosphere furnace reaches the saturation gas pressure of the silicon melt of SiC crystal at this temperature, and the temperature is kept constant so that silicon carbide single crystals gradually precipitate on the silicon carbide crystal. As the level of the molten silicon decreases, the seed crystal holder also gradually decreases, maintaining capillary contact between the silicon carbide seed crystal and the molten silicon, thus ensuring the continued precipitation of silicon carbide single crystals.

[0049] This solution provides a method for efficiently depositing silicon carbide single crystals. It should be noted that this solution uses an apparatus for efficiently depositing silicon carbide single crystals from the first solution of this invention. The carbon source is fixed to the bottom of the container using a high-temperature isostatic pressing welding method. High-purity silicon is placed in the container and, after it melts at high temperature, it is immersed in the carbon source to fully contact and react with the carbon source. The seed crystal is fixed on the seed holder using a high-temperature isostatic pressing welding method to prevent the seed crystal from falling off at high temperature. After sealing the furnace, a vacuum is drawn to prevent C and silicon from being oxidized by oxygen in the air at high temperature, which would affect the deposition efficiency and purity.

[0050] After the container is heated to 1400℃, the high-purity silicon gradually melts into a liquid, immersing the carbon source. The carbon source dissolves in part of the silicon melt. Silicon and C gradually begin to react under high temperature. At the same time, the seed crystal holder is moved down until the seed crystal and the silicon melt form capillary contact. Because the temperature of the seed crystal is relatively low, when silicon carbide exists in the silicon melt in a gaseous phase, it is easy to move towards the seed crystal and precipitate.

[0051] The temperature of the molten silicon is raised to the required crystal phase formation temperature according to the needs. The container is rotated to act as a stirrer, and an inert gas is introduced into the atmosphere furnace to regulate the pressure. The temperature is maintained at the required crystal phase formation temperature. The internal pressure is regulated by the inert gas. When the pressure is high, the dissolved silicon carbide is more likely to exist in the molten silicon. However, when the pressure is released, the solubility of the gaseous silicon carbide decreases and it is easier to precipitate. The precipitation rate of silicon carbide is increased by releasing the pressure intermittently, thereby accelerating the deposition efficiency.

[0052] As the reaction proceeds, silicon gradually decreases, and the level of the molten silicon gradually drops. To ensure the continuous precipitation of silicon carbide crystals on the seed crystal, capillary contact between the seed crystal and the molten silicon surface must be maintained. Therefore, the seed crystal holder needs to be gradually lowered according to the reaction rate until the required reaction amount is reached or the molten silicon surface drops below the surface of the carbon source, preventing the seed crystal from descending further and making contact with the molten silicon. The tensional capillary contact between the seed crystal and the molten silicon surface is mainly achieved by controlling the appropriate height of the SiC seed crystal above the molten silicon. Relying on the surface tension and capillary action of the molten silicon, the SiC seed crystal makes contact with the molten silicon surface, promoting the rapid and efficient deposition and growth of the reaction product SiC (gas-liquid dissolved state) on the seed crystal surface.

[0053] Specifically, in this embodiment of the invention, the method further includes the following steps: placing a catalyst above the molten silicon, and after the container is rotated, moving the catalyst down to 2-10 mm below the surface of the molten silicon to catalyze the formation of silicon carbide. Every 2-5 minutes, the catalyst is moved up away from the molten silicon, and the catalyst is connected to a heater for heating to keep the temperature of the catalyst higher than the temperature of the molten silicon.

[0054] It should be noted that the catalyst placed above the molten silicon is a catalyst for the reaction of carbon and silicon. After the catalyst is immersed in the molten silicon, the C and silicon dissolved in the molten silicon come into contact with the catalyst surface and accelerate the reaction to form silicon carbide. The catalyst is located 2-10 mm below the surface of the molten silicon, close to the seed crystal, which facilitates the precipitation of silicon carbide on the seed crystal. Moreover, the catalyst is lifted up every 2-10 minutes. This can control the rate of the catalytic reaction and prevent silicon carbide from depositing on the catalyst surface and forming a surface film that affects the catalytic reaction. In addition, a heater is connected to the catalyst to keep its temperature 50-100°C higher than the temperature of the molten silicon. This is also to prevent silicon carbide from depositing on the catalyst surface and instead allow silicon carbide to deposit on the seed crystal at a lower temperature.

[0055] Specifically, in this embodiment of the invention, the method further includes the following steps: the seed holder is rotatable, the seed holder and the container rotate in opposite directions, and the rotation speed of the seed holder and the container is 30-50 r / min.

[0056] It should be noted that the seed crystal holder is connected to a rotating motor, which is infinitely variable in speed and its rotation speed is adjustable. The rotation of the seed crystal holder and the container creates a stirring effect on the molten silicon, accelerating the movement of aerosolized silicon carbide within the molten silicon, thus speeding up the reaction rate and deposition rate. Furthermore, the opposite direction of rotation between the seed crystal holder and the container greatly enhances the stirring effect; the stirring rate is equivalent to the sum of the rotation speeds of the seed crystal holder and the container.

[0057] Specifically, in this embodiment of the invention, the vacuum level of the sealed atmosphere furnace after evacuation is 10. -4 The distance between the seed holder and the silicon carbide seed crystal forming capillary contact with the molten silicon is 0.3-1.5 mm.

[0058] It should be noted that evacuating the sealed atmosphere furnace is necessary to prevent oxygen in the air from oxidizing carbon and silicon, generating impurities, and affecting reaction efficiency. If the distance between the seed holder and the surface of the molten silicon is too large, the silicon carbide crystal cannot make contact with the surface of the molten silicon, and the crystal cannot be deposited on the seed. If the distance between the seed holder and the surface of the molten silicon is too small, or even if the seed holder is immersed in the molten silicon, the seed cannot maintain a temperature lower than that of the molten silicon, which is not conducive to the precipitation of the seed. Therefore, it is necessary to control the distance between the silicon carbide seed and the molten silicon to form capillary contact at 0.3-1.5 mm, so that the crystal can precipitate on the seed while keeping its temperature slightly lower than that of the molten silicon.

[0059] Specifically, in this embodiment of the invention, the growth conditions of the crystal phase are as follows: the growth temperature of the 3C crystal phase is 1400-1800℃, and the saturated vapor pressure of the 3C crystal phase in the molten silicon is 1*10. 5Pa-5*10 5 Pa; the growth temperature of the 4H silicon carbide crystal phase is 1800-2000℃, and the saturated vapor pressure of the 4H crystal phase in molten silicon is 1*10 Pa. 5 Pa-5*10 5 The growth temperature of the 6H silicon carbide crystal phase is 2200-2400℃, and the saturated vapor pressure of the 6H crystal phase in molten silicon is 1*10 Pa. 5 Pa-5*10 5 Pa.

[0060] It should be noted that for different crystal forms, under their corresponding stable temperature conditions, the deposition atmosphere of the atmosphere furnace can be gradually adjusted to saturate the solubility of silicon carbide in the molten silicon at this temperature and pressure, making it easier to precipitate. Based on the different characteristics of various SiC crystal phases, such as 3C (1400-1800℃), 4H (1800-2000℃), and 6H (2200-2400℃), and not limited to these listed crystal forms, any scheme that can produce the corresponding crystal form within a defined temperature range should be included in the scope of this application. The deposition temperature of other crystal phases can be determined by adjusting the atmosphere pressure after the reaction at that temperature and characterizing the obtained crystals.

[0061] In this application's scheme, in addition to temperature conditions, other atmospheric conditions are also included. A preset program is established, and after the preset conditions are met, the platinum catalyst is lowered below the surface of the molten silicon. Simultaneously, it moves up and down according to a preset motion pattern, catalyzing the SiC formation efficiency. The generated SiC (gaseous, transported in a gas-liquid solution within the molten silicon) gradually deposits and grows on the seed crystal. As deposition and growth proceed, the surface of the molten silicon gradually decreases, and the position or movement range of the catalyst is adjusted progressively according to the program settings to maintain a stable deposition rate, thus coordinating with the deposition and growth of the SiC ingot. Example 1

[0062] An apparatus for efficiently depositing silicon carbide single crystals includes an atmosphere furnace 1; a heat insulation device 2, a heating device 3, and a container 4 arranged from the outside to the inside; a carbon source 5 fixed inside the container 4; a seed holder 6 disposed above the container 4; and a seed crystal 7 fixed at the bottom of the seed holder 6. The heat insulation device 2 is disposed inside the atmosphere furnace 1. The container 4 has an opening at the top for holding molten silicon, and a rotating shaft 41 at the bottom of the container 4 for rotating the container 4. The rotating shaft 4 passes through the heat insulation device 2 and the atmosphere furnace 1 and is connected to a rotating motor 8. The heating device 2 is disposed outside the container 4 for heating the molten silicon inside the container 4. The upper end of the seed holder 6 is connected to a first drive mechanism 91 for controlling the up-and-down movement of the seed holder. Example 2

[0063] Repeat Example 1, except that the device further includes: a catalyst 10 disposed above the container 4, a second drive mechanism 92 connected above the catalyst 10 for controlling the up and down movement of the catalyst, and a heater 101 connected to the catalyst 10 for controlling the temperature of the catalyst 10. Example 3

[0064] Example 1 is repeated, except that the catalyst 10 is a platinum group metal, specifically platinum. Example 4

[0065] Repeat Example 1, except that the catalyst 10 is a cylindrical shape with openings at both ends, the sidewall of the catalyst 10 is located between the seed holder 6 and the inner sidewall of the container 4, and the sidewall of the catalyst is in the form of a mesh. Example 5

[0066] Repeat Example 1, except that container 4 is a graphite crucible. Example 6

[0067] A method for efficiently depositing silicon carbide single crystals includes the following steps: High-purity porous graphite was fixed to the bottom of a graphite crucible, and high-purity silicon was placed inside the graphite crucible. Silicon carbide seeds were fixed to the bottom surface of a seed holder. Both the graphite crucible and the seed holder were placed in an atmosphere furnace, with the seed holder positioned above the graphite crucible. The vacuum level of the sealed atmosphere furnace after evacuation was 10. -4 Pa; After the graphite crucible is heated to 1400℃, high-purity silicon is dissolved into a molten silicon liquid. The seed crystal holder is then moved down to a distance of 1mm between the silicon carbide seed crystal and the molten silicon liquid, so that the silicon carbide seed crystal and the molten silicon liquid form capillary contact. The seed crystal is a 3C phase seed crystal. The container is heated further to the growth temperature of the 3C crystal phase, 1650℃, and rotated while inert gas is introduced into the atmosphere furnace to increase the pressure inside the furnace, bringing the pressure inside the furnace to the saturation pressure of SiC crystal at 1650℃, which is 1.8*10⁻⁶. 5 At Pa, maintain a constant temperature to allow silicon carbide single crystals to gradually precipitate on the silicon carbide crystal. As the level of the molten silicon decreases, the seed crystal holder is also gradually lowered to maintain capillary contact between the silicon carbide seed crystal and the molten silicon, allowing the silicon carbide single crystal to continue to precipitate until the level of the molten silicon is below the top of the high-purity porous graphite. Example 7

[0068] Repeat Example 6, except that the method further includes the following steps: placing a platinum block above the molten silicon, and after the container rotates, moving the platinum block down to 2-10 mm below the surface of the molten silicon to catalyze the formation of silicon carbide. Every 3 minutes, the platinum block is moved up away from the molten silicon, and the platinum block is connected to a heater for heating to keep the temperature of the platinum block higher than the temperature of the molten silicon. Example 8

[0069] Repeat Example 7, except that the method further includes the following steps: the seed holder is rotatable, the seed holder and the container rotate in opposite directions, and the rotation speed of the seed holder and the container is 30-50 r / min. Example 9

[0070] Example 7 was repeated, except that the graphite crucible was further heated to the growth temperature of the 4H crystal phase, 1900°C, with a saturated vapor pressure of 3.2 × 10⁻⁶. 5 Pa. Example 10

[0071] Repeat Example 7, except that the platinum block is lifted once every 2 minutes. Example 11

[0072] Repeat Example 7, except that the platinum block is lifted every 5 minutes. Comparative Example 1 High-purity SiC powder is placed inside a graphite crucible, with the seed crystal positioned above it. A vacuum is evacuated from the furnace and maintained. The graphite crucible is heated to 1400°C, while a stepped temperature is maintained within the transfer channel to keep the seed crystal temperature lower than that of the graphite crucible. At this point, SiC begins to vaporize and gradually grow on the seed crystal.

[0073] Comparative Example 2 High-purity SiC powder is placed inside a graphite crucible, with the seed crystal positioned above it. A vacuum is evacuated from the furnace and maintained. The graphite crucible is heated to 1800°C, while a stepped temperature is maintained within the transfer channel to keep the seed crystal temperature lower than that of the graphite crucible. At this point, SiC begins to vaporize and gradually grow on the seed crystal.

[0074] Silicon carbide single crystals were deposited using the methods of Examples 6-9 and Comparative Examples 1-2, and the deposition efficiency and consumption were compared and contrasted as shown in Table 1.

[0075] Table 1. Efficiency Comparison of Examples 6-9 and Comparative Examples 1-2

[0076] Example 6 is an embodiment of the preparation of 3C crystalline phase without catalyst and without stirring in this application. Example 7 is an embodiment of the preparation of 3C crystalline phase with catalyst but without stirring in this application. Example 8 is an embodiment of the preparation of 3C crystalline phase with catalyst and stirring in this application. Example 9 is an embodiment of the preparation of 4H crystalline phase without catalyst and without stirring in this application. Example 10 is an embodiment of the preparation of 3C crystalline phase by adding catalyst to accelerate the frequency of catalyst removal and immersion from molten silicon. Example 11 is an embodiment of the preparation of 3C crystalline phase by adding catalyst to slow down the frequency of catalyst removal and immersion from molten silicon. Example 12 is an embodiment of the preparation of 3C crystalline phase by adding catalyst, where the gas pressure during crystalline phase deposition does not reach the saturated vapor pressure. Comparative Examples 1 and 2 use the physical vapor transport (PVT) method, where Comparative Example 1 prepares 3C crystalline phase and Comparative Example 2 prepares 4H crystalline phase.

[0077] As can be seen from the comparison of different embodiments, when using the apparatus of the present invention to deposit silicon carbide crystals, compared with the traditional physical vapor transport (PVT) method for depositing silicon carbide crystals, the deposition rate is faster and the crystallization defects are lower. When using the apparatus of the present invention to deposit silicon carbide crystals, the use of a catalyst can greatly accelerate the crystal deposition efficiency. Furthermore, the addition of rotation to form a stirring operation can further increase the deposition rate. However, as in Example 10, by increasing the frequency of the catalyst being removed from and immersed in the silicon melt, the catalytic reaction is slowed down, and the silicon carbide formation rate is slowed down. However, since the temperature and pressure of this application remain constant, the precipitation rate of silicon carbide remains unchanged, so the deposition efficiency is the same as in Example 7. However, when the 3C crystal phase is prepared as in Example 11 and a catalyst is added to slow down the frequency of the catalyst being removed from and immersed in the silicon melt, the silicon carbide formation efficiency is improved, and the silicon carbide quickly reaches saturation in the silicon melt, resulting in a significant increase in deposition efficiency.

[0078] As can be seen from the table, the deposition efficiency of the physical vapor-liquid phase transport (PVQT) method of this invention is significantly better than that of the physical vapor transport (PVT) method. Moreover, in terms of the deposition atmosphere, this application uses constant temperature control, which makes operation easier and the reaction more stable. In terms of energy consumption, the energy consumption per unit of PVQT is much less than that of PVT. In terms of raw material consumption, PVT consumes more raw materials due to the off-target effect of vapor transport, while PVQT consumes very little raw materials because by controlling a suitable crystallization atmosphere, raw material waste can be almost zero. In terms of corrosion of production equipment, PVT, due to the propagation effect of the vapor phase, will cause the entire crystallization chamber space to gradually narrow. The two methods result in almost identical erosion of the crucible. In terms of raw material costs, the PVT method requires high-purity SiC powder as the raw material for its gasification crystallization, while the PVQT method only requires high-purity silicon material. The raw material costs of the two methods differ greatly. In terms of crystallization defects, since the gas phase carries a high amount of energy, decomposition reactions will occur during the gas phase transport process, generating new C and Si compounds, such as Si2C and SiC2, which will affect the crystallization effect and produce crystallization defects. The solid phase releases more heat and is prone to stress.

[0079] This invention is essentially a "Physical Vapor-to-Liquid Phase Transport (PVQT) method." Its principle is that under high temperature and a suitable atmosphere, and with the aid of a catalyst, SiC generated from the C+Si reaction is "dissolved" in the high-temperature molten silicon in a vapor-solid manner. It is transported along with the molten silicon and, under suitable atmospheric conditions, gradually deposits and grows on the seed crystal surface. By controlling the intervention of the platinum catalyst to control the C+Si reaction rate and adjusting the appropriate atmosphere to maintain a basic consistency and balance between the rate of SiC generation, its vapor-solid phase transport, and its deposition growth, the deposition and growth efficiency of SiC single crystals can be significantly improved.

[0080] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. An apparatus for high rate deposition of silicon carbide single crystals, comprising: It includes an atmosphere furnace (1) configured to withstand high temperatures and have adjustable pressure; a heat insulation device (2), a heating device (3), and a container (4) arranged from the outside to the inside; a carbon source (5) fixed inside the container (4); a seed holder (6) arranged above the container (4); and a seed crystal (7) fixed to the seed holder (6). The heat insulation device (2) is installed inside the atmosphere furnace (1); The container (4) has an opening at the top for holding molten silicon. The bottom of the container (4) is provided with a rotating shaft (41) for driving the container (4) to rotate. The rotating shaft (41) passes through the heat insulation device (2) and the atmosphere furnace (1) in sequence and is connected to the rotating motor (8). The heating device (3) is disposed on the outside of the container (4) and is used to heat the molten silicon inside the container (4); The upper end of the seed holder (6) is connected to the first drive mechanism (91) for controlling the up and down movement of the seed holder; The device further includes a catalyst (10) disposed above the container (4), and a second drive mechanism (92) is connected above the catalyst (10) for controlling the up and down movement of the catalyst.

2. The apparatus for efficient deposition of silicon carbide single crystals according to claim 1, wherein The catalyst (10) is connected to a heater (101) for controlling the temperature of the catalyst (10).

3. The apparatus for high rate deposition of silicon carbide single crystals of claim 2, wherein The catalyst (10) is one of the following: platinum group metals, transition metals, alloys containing platinum group metals, and alloys containing transition metals.

4. The apparatus for efficient deposition of silicon carbide single crystals of claim 1, wherein, The catalyst (10) is a cylindrical shape with openings at both ends. The sidewall of the catalyst (10) is located between the seed crystal holder (6) and the inner sidewall of the container (4). The sidewall of the catalyst is mesh-like.

5. The apparatus for efficient deposition of silicon carbide single crystals as claimed in claim 1, wherein, The container (4) is a graphite crucible or made of other high-temperature resistant materials.

6. A method for efficiently depositing a silicon carbide single crystal, the method comprising: Includes the following steps: The carbon source is fixed at the bottom of the container, and high-purity silicon is placed inside the container. Silicon carbide seeds are fixed on the bottom surface of the seed holder. The container and the seed holder are placed in the atmosphere furnace, with the seed holder above the container. The atmosphere furnace is then sealed and a vacuum is drawn. The container is heated to melt the high-purity silicon into a molten silicon liquid. The seed crystal holder is then moved down to allow the silicon carbide seed crystal to form capillary contact with the molten silicon liquid. The container continues to be heated to the growth temperature of the desired crystal phase, and the container is rotated while inert gas is introduced into the atmosphere furnace to increase the pressure inside the atmosphere furnace, so that the gas pressure inside the atmosphere furnace reaches the saturation gas pressure of the silicon melt of SiC crystal at this temperature, and the temperature is kept constant so that silicon carbide single crystals gradually precipitate on the silicon carbide seed crystal. As the level of the molten silicon decreases, the seed crystal holder also gradually decreases, maintaining capillary contact between the silicon carbide seed crystal and the molten silicon, thus ensuring the continued precipitation of silicon carbide single crystals. The method further includes the following steps: placing a catalyst above the molten silicon, and after the container is rotated, moving the catalyst down to 2-10 mm below the surface of the molten silicon to catalyze the formation of silicon carbide, and moving the catalyst up away from the molten silicon every 2-5 minutes. The growth conditions for the crystalline phase are as follows: the growth temperature of the 3C crystalline phase is 1400-1800℃, and the saturated vapor pressure of the 3C crystalline phase in the molten silicon is 1*10. 5 Pa-5*10 5 Pa; the growth temperature of the 4H silicon carbide crystal phase is 1800-2000℃, and the saturated vapor pressure of the 4H crystal phase in molten silicon is 1*10 Pa. 5 Pa-5*10 5 The growth temperature of the 6H silicon carbide crystal phase is 2200-2400℃, and the saturated vapor pressure of the 6H crystal phase in molten silicon is 1*10 Pa. 5 Pa-5*10 5 Pa.

7. The method of claim 6, wherein the silicon carbide single crystal is grown at a rate of at least 1 mm / hour. The catalyst is connected to a heater for heating, and the temperature of the catalyst is maintained 50-100°C higher than the temperature of the molten silicon.

8. The method of claim 6, wherein the silicon carbide single crystal is grown at a rate of at least 1 mm / hour. The method further comprises the following steps: the seed crystal holder is rotatable, the seed crystal holder and the container rotate in opposite directions, and the rotation speeds of the seed crystal holder and the container are both 30-50 r / min.

9. The method of claim 6, wherein the silicon carbide single crystal is grown at a rate of at least 1 mm / hour. The vacuum degree after the closed atmosphere furnace is vacuumed is 10 -4 Pa, and the seed holder is moved downward to a distance of 0.3-1.5mm to form capillary contact between the silicon carbide seed and the silicon molten liquid.

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