Method for increasing content of semiconductor silicon carbide coarse particles

Abstract

The invention relates to a method for increasing the content of semiconductor silicon carbide coarse particles, which comprises the following steps: weighing high-purity Si powder and high-purity C powder according to a certain stoichiometric ratio, uniformly mixing, and filling into a graphite crucible; putting the graphite crucible filled with the mixture of the high-purity Si powder and the high-purity C powder into a vacuum synthesis furnace, closing a furnace cover, vacuumizing, and filling inert gas to the required pressure intensity; uniformly dividing the crucible into four areas from top to bottom, heating according to a certain heating rate, controlling the temperature of each area, and simultaneously carrying out heat preservation operation so as to carry out high-temperature synthesis; and after a period of time, the required silicon carbide powder can be obtained. The method is reasonable, feasible, ingenious in design, low in operation difficulty and suitable for large-scale commercial application of the high-purity silicon carbide powder, the production cost is reduced, and the method has good market prospects and development space for the prior art.

Description

Technical Field

[0001] The invention relates to the technical field of silicon carbide semiconductor powder processing, and in particular to a method for increasing the content of semiconductor silicon carbide coarse particles. Background Art

[0002] As a third-generation semiconductor material, high-purity silicon carbide has high bandgap width, high conductivity, Excellent properties such as high thermal conductivity make it suitable for making high-temperature, high-frequency, radiation-resistant and high-power electronic devices, and it has important application value in the fields of optoelectronics and microelectronics. It has great application potential in the fields of 5G base stations, new energy vehicles, photovoltaics, wind power, high-speed rail, fast charging, etc. The industrial preparation of high-purity silicon carbide powder often adopts the self-propagating high-temperature synthesis process, using solid silicon source and carbon source as raw materials to continuously react at high temperature, and finally obtain high-purity silicon carbide powder. At present, the growth of SiC single crystals mostly adopts the physical vapor transport method (PVT). The equipment used for the physical vapor transport method to grow SiC single crystals is simple, and the process is easy to control. More importantly, this method can grow high-quality and large-sized SiC single crystals. The principle of crystal growth is to sublimate and recrystallize the raw silicon carbide powder under high temperature conditions, and grow on the silicon carbide seed crystal to form a single crystal or polycrystal of silicon carbide. The particle size of silicon carbide powder for crystal growth is generally required to be above 0.4mm. The reason is that the existing technology believes that the density of finer powder particles piled together will become higher, making it difficult for silicon carbide powder below the surface to sublimate, which will reduce the speed and efficiency of sublimation. Under current technical conditions, the proportion of 0.4mm coarse silicon carbide powder synthesized by self-propagating high-temperature synthesis process is about 50%. In order to promote the large-scale popularization and rapid reduction of costs of domestic silicon carbide powder, a method is needed to increase the content of coarse semiconductor silicon carbide particles, thereby reducing the production cost of silicon carbide powder.

[0003] In the existing technology, the proportion of silicon carbide powders synthesized by the self-propagating high-temperature synthesis process is about 50% or more. This has led to the semiconductor silicon carbide powders being mainly imported from abroad, and the price remains high, with an average selling price of 1,000-1,200 yuan / kg, which has seriously restricted the development of the silicon carbide semiconductor industry.

[0004] How to design a method that is reasonable and feasible, ingenious in design, precise in temperature control, good in process stability, low in operating difficulty, to increase the content of coarse particles in semiconductor silicon carbide, adapt to large-scale commercial applications of high-purity silicon carbide powder, and greatly reduce production costs is a problem that needs to be solved at present. Summary of the invention

[0005] In order to solve the technical problems that the silicon carbide powder synthesized by the self-propagating high-temperature synthesis process in the prior art has a low content of coarse silicon carbide particles, the price of imported silicon carbide powder remains high, and it cannot be widely popularized and applied, which seriously restricts the development of the silicon carbide semiconductor industry, the present invention provides a method for increasing the content of coarse silicon carbide particles in semiconductor silicon carbide, so as to achieve the purpose of making the method reasonable and feasible, ingeniously designed, low in difficulty in operation, suitable for large-scale commercial application of high-purity silicon carbide powder, and reducing production costs.

[0006] The technical solution adopted by the present invention to solve the above technical problems is: a method for increasing the content of coarse particles of semiconductor silicon carbide, comprising the following steps: Step 1, weighing high-purity Si powder and high-purity C powder according to a certain stoichiometric ratio, mixing them evenly, and then loading them into a graphite crucible; Step 2: Place the graphite crucible containing the mixture of high-purity Si powder and high-purity C powder into a vacuum synthesis furnace, close the furnace cover, and after evacuation, fill it with inert gas to the required pressure; Step 3, the crucible is evenly divided into four regions from top to bottom, the temperature is increased at a certain heating rate, and the temperature of each region is controlled, and a heat preservation operation is performed at the same time, so as to perform high temperature synthesis; Step 4: Cool down and stop the furnace. After a period of time, the desired silicon carbide powder can be obtained.

[0007] The above is a basic implementation of the present invention, and further improvements, perfections and limitations can be made on the above basis: For example, in step 1, the molar ratio of high-purity Si powder to high-purity C powder is 1:1.05-1:1.10; the total weight of the Si powder and C powder is 30.75-31.5 kg; The above is a basic implementation of the present invention, and further improvements, perfections and limitations can be made on the above basis: for example, the insulation layer arranged in the vacuum synthesis furnace in step 2 is graphite carbon felt, and an aperture is opened at the bottom of the graphite carbon felt, and the aperture size is 15-20 cm.

[0008] The above is a basic implementation of the present invention, and further improvements, perfections and limitations can be made on the above basis: for example, the vacuum pressure in step 2 is 0.5 Pa, and the inert gas is argon.

[0009] The above is a basic implementation of the present invention, and further improvements, perfections and limitations can be made on the above basis: as described in step 3, the first area occupies one quarter of the volume of the crucible, the temperature is controlled at 1950-2100 ° C, and the insulation time is 18-25H; the second area occupies one quarter of the volume of the crucible, the temperature is controlled at 2100-2200 ° C, and the insulation time is 18-25H; the third area occupies one quarter of the volume of the crucible, the temperature is controlled at 2150-2200 ° C, and the insulation time is 18-25H; the fourth area occupies one quarter of the volume of the crucible, the temperature is controlled at 1950-2100 ° C, and the insulation time is 18-25H; The above is a basic implementation manner of the present invention, and further improvements, perfections and limitations can be made on the above basis: for example, the cooling and furnace stopping time in step 4 is 20-30 hours, the silicon carbide powder has a particle size of 0.4 mm and a coarse content of ≥75%, and the purity of the silicon carbide powder is above 99.99995%.

[0010] Compared with the prior art, the present invention has the following beneficial effects: First, the present invention changes the temperature field distribution inside the graphite crucible by opening holes at the bottom of the graphite carbon felt, and changes the traditional annular temperature field distribution into a layered temperature field distribution. The annular temperature field distribution has a high temperature at the bottom and a low temperature at the top, which causes the powder temperature at the bottom to fail to meet the set requirements during the powder synthesis process, and thus cannot continue to sublimate and synthesize large-particle powders.

[0011] Second, the present invention controls the temperature distribution of each layer accurately and timely, and the layered temperature field distribution is conducive to the formation of large-particle powder in each layer, thereby increasing the content of large-particle powder as a whole.

[0012] Third, the present invention also adopts a large-sized powder synthesis furnace for synthesis, which solves the shortcoming of low output of small-sized powder synthesis furnaces, and realizes the stability of the synthesis process by controlling the temperature in layers, thereby greatly improving the powder synthesis amount in a single furnace.

[0013] Fourth, the present invention changes the temperature field distribution in the crucible through the carbon felt protective layer structure, increases the synthesis amount of large-particle silicon carbide in each layer, and increases the coarse content of the single-furnace particle size of 0.4 mm by more than 25%.

[0014] Fifth, the scheme for changing the structure of the carbon felt protective layer in the technical solution of the present invention is simple, the implementation effect is obvious, and the precise temperature control realizes the stability of the process.

[0015] Sixth, the present invention effectively reduces the production cost of high-purity silicon carbide semiconductor powder by increasing the content of large-sized synthesis furnaces and large-particle powders, providing technical support for the large-scale popularization and application of domestic silicon carbide powders and the rapid reduction of costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 This is a schematic diagram of the thermal field of the synthetic crucible; In the figure, 1. graphite crucible, 2. crucible tray, 3. lower insulation hole, 4. carbon insulation layer, 5. silicon powder and carbon powder mixture. DETAILED DESCRIPTION

[0017] The specific implementation modes of the present invention are further described in detail below in conjunction with the accompanying drawings.

[0018] Example 1 like Figure 1 As shown, Figure 1 This is a schematic diagram of the thermal field of the synthetic crucible; A method for increasing the content of coarse particles of semiconductor silicon carbide comprises the following steps: Step 1, weighing high-purity Si powder and high-purity C powder according to a certain stoichiometric ratio, mixing them evenly, and then loading them into a graphite crucible; Step 2: Place the graphite crucible containing the mixture of high-purity Si powder and high-purity C powder into a vacuum synthesis furnace, close the furnace cover, and after evacuation, fill it with inert gas to the required pressure; Step 3, the crucible is evenly divided into four regions from top to bottom, the temperature is increased at a certain heating rate, and the temperature of each region is controlled, and a heat preservation operation is performed at the same time, so as to perform high temperature synthesis; Step 4: Cool down and stop the furnace. After a period of time, the desired silicon carbide powder can be obtained.

[0019] The molar ratio of the high-purity Si powder and the high-purity C powder in step 1 is 1:1.05; the total weight of the Si powder and the C powder is 30.75 kg.

[0020] The insulation layer provided in the vacuum synthesis furnace in step 2 is graphite carbon felt, and an aperture is provided at the bottom of the graphite carbon felt, and the aperture size is 15 cm.

[0021] The vacuum pressure in step 2 is 0.5 Pa, and the inert gas is argon.

[0022] In the step 3, the first area occupies one quarter of the volume of the crucible, the temperature is controlled at 1950°C, and the insulation time is 18 hours; the second area occupies one quarter of the volume of the crucible, the temperature is controlled at 2100°C, and the insulation time is 18 hours; the third area occupies one quarter of the volume of the crucible, the temperature is controlled at 2150°C, and the insulation time is 18 hours; the fourth area occupies one quarter of the volume of the crucible, the temperature is controlled at 1950°C, and the insulation time is 18 hours; The cooling and furnace stopping time in step 4 is 20 hours, the particle size of the silicon carbide powder is 0.4 mm and the coarse content is ≥ 75%, and the purity of the silicon carbide powder is above 99.99995%.

[0023] Example 2 A method for increasing the content of coarse particles of semiconductor silicon carbide comprises the following steps: Step 1, weighing high-purity Si powder and high-purity C powder according to a certain stoichiometric ratio, mixing them evenly, and then loading them into a graphite crucible; Step 2: Place the graphite crucible containing the mixture of high-purity Si powder and high-purity C powder into a vacuum synthesis furnace, close the furnace cover, and after evacuation, fill it with inert gas to the required pressure; Step 3, the crucible is evenly divided into four regions from top to bottom, the temperature is increased at a certain heating rate, and the temperature of each region is controlled, and a heat preservation operation is performed at the same time, so as to perform high temperature synthesis; Step 4: Cool down and stop the furnace. After a period of time, the desired silicon carbide powder can be obtained.

[0024] The molar ratio of the high-purity Si powder and the high-purity C powder in step 1 is 1:1.08; the total weight of the Si powder and the C powder is 31.25 kg.

[0025] The thermal insulation layer provided in the vacuum synthesis furnace in step 2 is graphite carbon felt, and an aperture is provided at the bottom of the graphite carbon felt, and the aperture size is 18 cm.

[0026] The vacuum pressure in step 2 is 0.5 Pa, and the inert gas is argon.

[0027] In the step 3, the first area occupies one quarter of the volume of the crucible, the temperature is controlled at 2050°C, and the insulation time is 21 hours; the second area occupies one quarter of the volume of the crucible, the temperature is controlled at 2150°C, and the insulation time is 21 hours; the third area occupies one quarter of the volume of the crucible, the temperature is controlled at 2180°C, and the insulation time is 21 hours; the fourth area occupies one quarter of the volume of the crucible, the temperature is controlled at 2050°C, and the insulation time is 21 hours; The cooling and furnace stopping time in step 4 is 25 hours, the particle size of the silicon carbide powder is 0.4 mm and the coarse content is ≥ 75%, and the purity of the silicon carbide powder is above 99.99995%.

[0028] Example 3 A method for increasing the content of coarse particles of semiconductor silicon carbide comprises the following steps: Step 1, weighing high-purity Si powder and high-purity C powder according to a certain stoichiometric ratio, mixing them evenly, and then loading them into a graphite crucible; Step 2: Place the graphite crucible containing the mixture of high-purity Si powder and high-purity C powder into a vacuum synthesis furnace, close the furnace cover, and after evacuation, fill it with inert gas to the required pressure; Step 3, the crucible is evenly divided into four regions from top to bottom, the temperature is increased at a certain heating rate, and the temperature of each region is controlled, and a heat preservation operation is performed at the same time, so as to perform high temperature synthesis; Step 4: Cool down and stop the furnace. After a period of time, the desired silicon carbide powder can be obtained.

[0029] The molar ratio of the high-purity Si powder and the high-purity C powder in step 1 is 1:1.10; the total weight of the Si powder and the C powder is 31.5 kg.

[0030] The thermal insulation layer provided in the vacuum synthesis furnace in step 2 is graphite carbon felt, and an aperture is provided at the bottom of the graphite carbon felt, and the aperture size is 20 cm.

[0031] The vacuum pressure in step 2 is 0.5 Pa, and the inert gas is argon.

[0032] In the step 3, the first area occupies one quarter of the volume of the crucible, the temperature is controlled at 2100°C, and the insulation time is 25 hours; the second area occupies one quarter of the volume of the crucible, the temperature is controlled at 2200°C, and the insulation time is 25 hours; the third area occupies one quarter of the volume of the crucible, the temperature is controlled at 2200°C, and the insulation time is 25 hours; the fourth area occupies one quarter of the volume of the crucible, the temperature is controlled at 2100°C, and the insulation time is 25 hours; The cooling and furnace stopping time in step 4 is 30 hours, the particle size of the silicon carbide powder is 0.4 mm and the coarse content is ≥ 75%, and the purity of the silicon carbide powder is above 99.99995%.

[0033] In practical applications, the present invention changes the temperature field distribution inside the graphite crucible by opening holes at the bottom of the graphite carbon felt, thereby changing the traditional annular temperature field distribution to a layered temperature field distribution. The annular temperature field distribution has a high temperature at the top and a low temperature at the bottom, which causes the temperature of the powder at the bottom to fail to meet the set requirements during the powder synthesis process, thereby failing to continue to sublimate and synthesize large-particle powder. The present invention accurately and timely controls the temperature distribution of each layer, and the layered temperature field distribution is conducive to the formation of large-particle powders in each layer, thereby increasing the content of large-particle powders as a whole. The present invention also uses a large-sized powder synthesis furnace for synthesis, which solves the shortcoming of low output of small-sized powder synthesis furnaces, and achieves the stability of the synthesis process by controlling the temperature in layers, thereby greatly improving the amount of powder synthesis in a single furnace.

[0034] The method of the present invention is reasonable and feasible, ingeniously designed, and easy to operate. It is suitable for large-scale commercial application of high-purity silicon carbide powder and reduces production costs. It solves the technical problems that the silicon carbide powder synthesized by the self-propagating high-temperature synthesis process in the prior art has a low content of coarse silicon carbide particles, the price of imported silicon carbide powder remains high, and it cannot be widely popularized and applied, which seriously restricts the development of the silicon carbide semiconductor industry. Compared with the prior art, it has good market prospects and development space.

[0035] The preferred specific implementation modes and embodiments of the present invention are described in detail above in conjunction with the accompanying drawings, but the present invention is not limited to the above implementation modes and embodiments, and various changes can be made within the knowledge scope of those skilled in the art without departing from the concept of the present invention.

Claims

1. A method for increasing the content of coarse particles of semiconductor silicon carbide, characterized in that: The following steps are included: Step 1, weighing high-purity Si powder and high-purity C powder according to a certain stoichiometric ratio, mixing them evenly, and then loading them into a graphite crucible; Step 2: Place the graphite crucible containing the mixture of high-purity Si powder and high-purity C powder into a vacuum synthesis furnace, close the furnace cover, and after evacuation, fill it with inert gas to the required pressure; Step 3, the crucible is evenly divided into four regions from top to bottom, the temperature is increased at a certain heating rate, and the temperature of each region is controlled, and a heat preservation operation is performed at the same time, so as to perform high temperature synthesis; Step 4: Cool down and stop the furnace. After a period of time, the desired silicon carbide powder can be obtained.

2. A method for increasing the content of coarse particles of semiconductor silicon carbide according to claim 1, characterized in that: In the step 1, the molar ratio of the high-purity Si powder to the high-purity C powder is 1:1.05-1:1.10; the total weight of the Si powder and the C powder is 30.75-31.5 kg.

3. A method for increasing the content of coarse particles of semiconductor silicon carbide according to claim 2, characterized in that: In step 2, the insulation layer arranged in the vacuum synthesis furnace is graphite carbon felt, and the bottom of the graphite carbon felt is provided with an aperture, and the aperture size is 15-20 cm.

4. A method for increasing the content of coarse particles of semiconductor silicon carbide according to claim 1, characterized in that: The vacuum pressure in step 2 is 0.5 Pa, and the inert gas is argon.

5. A method for increasing the content of coarse particles of semiconductor silicon carbide according to claim 1, characterized in that: In the step three, the first area occupies one quarter of the volume of the crucible, the temperature is controlled at 1950-2100°C, and the insulation time is 18-25H; the second area occupies one quarter of the volume of the crucible, the temperature is controlled at 2100-2200°C, and the insulation time is 18-25H; the third area occupies one quarter of the volume of the crucible, the temperature is controlled at 2150-2200°C, and the insulation time is 18-25H; the fourth area occupies one quarter of the volume of the crucible, the temperature is controlled at 1950-2100°C, and the insulation time is 18-25H.

6. A method for increasing the content of coarse particles of semiconductor silicon carbide according to claim 1, characterized in that: The cooling and furnace stopping time in step 4 is 20-30 hours, the particle size of the silicon carbide powder is 0.4 mm and the coarse content is ≥ 75%, and the purity of the silicon carbide powder is above 99.99995%.

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