A method for controlling metal content in an epitaxial furnace cavity

Abstract

The present invention relates to a method for controlling the metal content of an epitaxial furnace cavity. The method comprises the following stages: a cleaning stage to remove residual material within the cavity; first, gas is introduced into the cavity to remove dust and impurities; then, a heating element is used to remove organic matter and moisture from the substrate surface; after completing these steps, the temperature and pressure within the cavity are maintained stable; and finally, an etching stage is performed to remove residual material from the substrate surface; a coating stage to grow a silicon layer of controllable thickness on the substrate surface; first, gas is introduced into the cavity to remove residual material; after completing these steps, the temperature and pressure within the cavity are maintained stable; and finally, a coating stage to form a silicon layer of controllable thickness on the substrate surface; and a cooling stage to ensure that the cavity temperature is maintained at 25°C; first, gas is introduced into the cavity to remove residual material; then, the substrate temperature is lowered to 25°C. By optimizing the etching and coating steps, the problem of excessive metal content in epitaxial wafers is improved, thereby enhancing the quality of epitaxial wafers.

Description

Technical Field

[0001] The present invention relates to the technical field of semiconductor manufacturing, and in particular to a method for controlling the metal content of an epitaxial furnace cavity. Background Art

[0002] Epitaxial furnaces utilize a reduction reaction between trichlorosilane or silicon chloride and hydrogen to grow single crystal epitaxial growth on single-crystal silicon substrates. As the number of epitaxial wafers produced increases, the reactor chamber of the epitaxial furnace must be shut down for cleaning and maintenance. During component replacement, metal contaminants are introduced from outside, increasing the level of metal contaminants within the reactor chamber. Even low concentrations can reduce the quality of the epitaxial wafers and ultimately lead to reduced device performance. Existing methods for cleaning the reactor chamber primarily involve introducing hydrogen chloride gas into the chamber to etch away any remaining silicon oxide, which is then removed through exhaust treatment to improve the chamber environment.

[0003] Traditional cleaning methods have poor effects on improving metal content and cannot remove metal impurities remaining on the substrate surface, causing metal impurities to penetrate into the epitaxial wafer, resulting in excessive metal content in the epitaxial wafer, thereby reducing the quality of the epitaxial wafer and adversely affecting the performance of components. Summary of the Invention

[0004] The present invention aims to solve the problems existing in the above-mentioned prior art and provides a method for controlling the metal content of an epitaxial furnace cavity. By optimizing the etching process and coating process in the scheme, the problem of excessive metal content in epitaxial wafers is improved, thereby improving the quality of epitaxial wafers.

[0005] The present invention solves the technical problem by adopting a technical method: a method for controlling the metal content of an epitaxial furnace cavity, comprising the following stages:

[0006] S100, the first stage of cleaning, removing residual substances in the cavity; first, gas is introduced into the cavity to remove dust and impurities, and then the heating element is gradually raised to a certain temperature to remove organic matter and moisture on the surface of the substrate. After the organic matter and moisture on the surface of the substrate are completely evaporated, etching gas is used to remove residual substances on the surface of the substrate;

[0007] S200, the second stage of coating, growing a silicon layer of controllable thickness on the surface of the base; first, gas is introduced into the cavity to remove residual substances on the surface, then the temperature and pressure are monitored using temperature and pressure detection devices to ensure the stability of the temperature and pressure in the cavity, and then the reaction gas is used for coating to form a silicon layer of controllable thickness on the surface of the base;

[0008] S300, the third stage of cooling, ensures that the cavity temperature is 25°C; first, gas is introduced into the cavity to remove residual substances on the surface, and then the substrate temperature is reduced to 25°C.

[0009] In this scheme, the first stage of cleaning is used to effectively remove residual substances on the surface of the substrate; then the second stage of coating is used to form a silicon layer with controllable thickness on the surface of the base. The silicon layer has a stable structure and good adhesion to the metal material, which reduces the outward diffusion of metal contaminants attached to the surface of the substrate.

[0010] Preferably, the first stage of cleaning specifically includes the following steps:

[0011] S110, purging, using inert gas as the cleaning gas, moving the nozzle to clean, ensuring that there is no visible dust and impurities remaining in the cavity, and then using an optical microscope to inspect the inner surface of the cavity to confirm that there are no residual particles;

[0012] S120, heating, gradually raising the temperature from room temperature to 1000°C by means of heating elements, ensuring uniform temperature distribution throughout the entire process;

[0013] S130, baking, gradually increasing the temperature to 1000° C., and then maintaining a constant temperature for baking, until organic matter and moisture on the substrate surface are completely evaporated and the surface appears dry, using a detection device to detect the substrate surface to confirm that no organic matter and moisture remain;

[0014] S140, stabilization: After the baking is completed, the temperature and pressure in the epitaxial cavity are kept stable, and the temperature and pressure are monitored using a temperature and pressure monitoring device to ensure the stability of the environmental conditions in the cavity;

[0015] S150, etching, use etching gas to etch, and use a microscope to check the substrate surface to confirm

[0016] No residual substances.

[0017] During this stage, dust and impurities on the surface are removed by purging the epitaxial furnace cavity; organic matter and moisture on the substrate surface are removed through high-temperature baking treatment; residual substances can be effectively removed by etching gas; and after the baking treatment, the temperature and pressure in the cavity are stabilized to provide suitable environmental conditions for the implementation of the etching step.

[0018] Preferably, the etching step lasts for 36 seconds to 53 seconds. Prolonging the etching time can completely remove the residual substances on the surface of the base.

[0019] Preferably, the gas used in the etching step is hydrogen chloride, and the etching rate is 0.25 μm / s, which can effectively remove residual substances on the surface of the base.

[0020] Preferably, the second stage coating specifically includes the following steps:

[0021] S210, purging, using inert gas as the cleaning gas, moving the nozzle to clean, ensuring that there is no visible dust and impurities remaining in the cavity, and then using an optical microscope to inspect the inner surface of the cavity to confirm that there are no residual particles;

[0022] S220, stabilizing, maintaining the temperature and pressure in the epitaxial cavity stable, monitoring the temperature and pressure using a temperature and pressure monitoring device to ensure the stability of the environmental conditions in the cavity;

[0023] S230, coating, using reactive gas for coating to grow a silicon layer with controllable thickness on the surface of the base, and using a thickness measuring device to measure the thickness of the silicon layer to ensure its uniformity and thickness control.

[0024] During this stage, the inside of the epitaxial furnace chamber is purged to remove surface residues; the temperature and pressure inside the chamber are stabilized to create good environmental conditions for the subsequent coating steps; in addition, the thickness-controlled silicon layer grown on the surface of the base during the coating step acts as a protective film, effectively blocking the diffusion of metal contaminants into the epitaxial wafer.

[0025] Preferably, the thickness of the silicon layer in the coating step is 1-2 μm. Increasing the thickness of the silicon layer can reduce the impact of metal contaminants on the epitaxial wafer, but too thick a silicon layer can cause adhesion between the base and the pins supporting the external base. After considering the advantages and disadvantages of both, the thickness of the silicon layer is controlled between 1-2 μm.

[0026] Preferably, the reaction gases used in the coating step are trichlorosilane and hydrogen, which are used to grow a silicon layer with controllable thickness on the surface of the base, and the silicon layer acts as a protective film.

[0027] Preferably, the coating step lasts for 45s to 125s. Prolonging the coating step can increase the thickness of the silicon layer on the surface of the base, thereby effectively preventing metal contaminants on the substrate surface from diffusing into the epitaxial layer.

[0028] Preferably, argon gas is introduced as a carrier in the coating step, and the argon gas accounts for 10% to 30% of the total gas flow, so that the coating step is further optimized and the uniformity and thickness control of the protective film are ensured.

[0029] Preferably, the third stage cooling specifically includes the following steps:

[0030] S310, purge, use inert gas as the cleaning gas, move the nozzle to clean, ensure that there is no visible dust and impurities remaining in the cavity, and then use an optical microscope to check the inner surface of the cavity to confirm that there are no residual particles;

[0031] S320, cooling, first lowering the substrate temperature to room temperature, and using a temperature monitoring device to monitor the temperature to ensure that the temperature is stable at 25°C.

[0032] After completing the first stage of cleaning and the second stage of coating, the epitaxial furnace chamber is still in a high temperature state, so the main purpose of this stage is to cool it down.

[0033] The present invention has the following beneficial effects:

[0034] 1. Through multi-stage cleaning, coating and cooling steps, the metal content of the epitaxial wafer is effectively reduced, and the purity and quality of the epitaxial wafer are improved. This not only extends the service life of the epitaxial wafer, but also improves the performance and reliability of the epitaxial wafer, making it suitable for the manufacture of high-performance semiconductor devices.

[0035] 2. Through the cleaning steps, including purging, heating, baking, stabilization and etching, the dust, impurities, organic matter and moisture in the cavity, as well as the residual substances on the surface of the substrate are completely removed, ensuring the cleanliness of the cavity and providing a pure environment for subsequent epitaxial growth, reducing the risk of contamination of the epitaxial wafer.

[0036] 3. In the etching step, hydrogen chloride gas is used for etching, and the etching time is extended to the preset time to ensure that the residual substances on the substrate surface are completely removed and confirm that there are no residual substances on the substrate surface, thereby improving the cleanliness of the substrate surface and providing a high-quality substrate for subsequent epitaxial growth.

[0037] 4. In the coating step, a silicon layer with a thickness of 1-2 μm is generated on the surface of the base through purging, stabilization and coating. Trichlorosilane and hydrogen are used as reaction gases, and the coating time is extended to the preset time to ensure the uniform growth and thickness control of the silicon layer. In addition, the introduction of argon as a carrier further improves the transmission efficiency of the reaction gas, ensures the uniformity and thickness control of the silicon layer, and effectively blocks the diffusion of metal contaminants on the surface of the substrate to the epitaxial layer. Through the cooling step, the substrate temperature is reduced to the preset temperature, ensuring the stability of the cavity temperature, providing a reliable environment for subsequent processes, and improving the quality and reliability of the epitaxial wafer. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 It is a flow chart of the solution of the present invention;

[0039] Figure 2 This is the metal test result after the preventive maintenance of the cavity in the present invention;

[0040] Figure 3 This is the metal test result inside the cavity after 60s of coating in the present invention. DETAILED DESCRIPTION

[0041] The following is combined with Figures 1 to 3The present invention will be further described:

[0042] Combine Figure 1 As shown, the present invention provides a method for controlling the metal content of an epitaxial furnace cavity. The design method is generally divided into three stages: cleaning, coating, and cooling.

[0043] S100, the first stage of cleaning, removes residual substances in the cavity. First, an inert gas is introduced into the cavity to remove dust and impurities. After completion, an optical microscope is used to inspect the inner surface of the cavity to confirm that there are no residual particles. Then, the heating element is gradually raised to a certain temperature to remove organic matter and moisture on the surface of the substrate. After the organic matter and moisture on the surface of the substrate are completely evaporated, the substrate surface is inspected using a detection device to confirm that no organic matter and moisture remain. Then, a temperature and pressure detection device is used to monitor the temperature and pressure to ensure the stability of the temperature and pressure in the cavity. Finally, an etching gas is used to remove residual substances on the surface of the base, and the base surface is inspected using a microscope to ensure that there are no residual substances.

[0044] In this embodiment, the heating element can be configured as a resistance wire or an infrared lamp to achieve temperature control during the cleaning process, thereby achieving precise heating or baking.

[0045] This stage cleans the chamber of residual material, ensuring a clean interior of the epitaxial furnace, providing a good foundation for subsequent epitaxial growth. Furthermore, the etching in this stage effectively removes residual material from the susceptor surface, ensuring a clean surface and reducing the impact of residual material on subsequent processes.

[0046] S200, the second stage of coating, grows a silicon layer of controllable thickness on the surface of the substrate. First, an inert gas is introduced into the chamber to remove dust and impurities. After completion, the inner surface of the chamber is inspected using an optical microscope to confirm the absence of residual particles. Temperature and pressure detection devices are then used to monitor the temperature and pressure to ensure stability within the chamber. Reactive gases are then used for coating, forming a silicon layer of controllable thickness on the surface of the substrate. A thickness measurement device is used to measure the thickness of the silicon layer to ensure uniformity and controllability.

[0047] In this stage, a silicon layer with controllable thickness is grown on the surface of the base. The silicon acts as a protective film, which can prevent metal contaminants from diffusing into the epitaxial wafer.

[0048] S300, the third stage of cooling, ensures the chamber temperature is at 25°C. First, an inert gas is introduced into the chamber to remove dust and impurities. After completion, the inner surface of the chamber is inspected using an optical microscope to confirm that there are no residual particles. The substrate temperature is then lowered to room temperature and monitored using a temperature monitoring device to ensure that the temperature has dropped to 25°C.

[0049] After removing the metal residue in the cavity, the temperature in the cavity is still high. Therefore, the main function of this stage is to cool it down.

[0050] In order to further illustrate the effect achieved by the first stage cleaning, the first stage cleaning is further explained. The specific steps to achieve the first stage cleaning include:

[0051] S110, purge, use high-purity nitrogen as the cleaning gas, and move the nozzle in a large-angle circular swing to clean, ensuring that there is no visible dust and impurities remaining in the cavity. At this time, the swing angle of the nozzle is 120°, the swing frequency is 1Hz, the nozzle is 10cm away from the epitaxial cavity wall, the gas flow rate is 500-1000sccm, and the purge should make the air flow speed in the epitaxial cavity reach 1-2m / s. The entire purge process takes 5s. After purging, use an optical microscope to check the inner surface of the cavity to confirm that there are no residual particles. In this step, the dust and impurities on the surface of the cavity can be effectively removed by purging the epitaxial furnace cavity.

[0052] S120, heating, through infrared lamp heating, the temperature in the cavity is heated at a rate of 10℃ / s, so that the temperature in the cavity gradually rises from room temperature (about 25℃) to 1000℃. The entire heating process lasts for 30s. During this process, it is necessary to ensure that the temperature distribution is uniform to avoid local overheating. In order to ensure that the temperature deviation does not exceed ±5℃, a thermocouple is used to monitor the temperature in the cavity. In this step, the main purpose of heating is to make the temperature in the epitaxial furnace cavity meet the requirements of the subsequent process environment.

[0053] S130: Bake. When the temperature reaches 1000°C, stop heating and maintain the temperature at 1000°C. To remove organic matter and moisture from the substrate surface, bake the chamber at a constant temperature for 45 seconds. Once the organic matter and moisture on the substrate surface have completely evaporated and the surface appears dry, use an infrared spectrometer to inspect the substrate surface to confirm that no organic matter or moisture remains.

[0054] S140, Stabilization. After baking, the temperature and pressure in the chamber need to be kept stable for 10 seconds to ensure that the environmental conditions in the chamber are suitable for the subsequent etching steps. To ensure that the temperature and pressure fluctuate within the set value range within ±1%, thermocouples and pressure sensors are used to monitor the temperature and pressure in the chamber.

[0055] S150, etching, using hydrogen chloride gas for etching. The entire etching process takes 43 seconds, with a gas flow rate of 1000 sccm, an etching rate of 0.25 μm / s, and an etching temperature of 1000°C. During this process, residual substances (such as oxides and metal particles) on the surface of the base will be completely removed. To confirm the absence of residual substances, the base surface is inspected using a scanning electron microscope.

[0056] In this step, hydrogen chloride gas is used as the etching gas, and the etching rate is controlled at 0.25μm / s, which can effectively remove residual materials on the substrate surface. By optimizing the etching time and controlling it to 43s, the residual materials on the substrate surface can be completely removed while preventing corrosion of the substrate surface due to excessive etching time, which could damage the equipment and products. This optimization of the etching step effectively removes residual materials on the substrate surface, reduces metal contamination, and improves the quality and purity of the epitaxial wafer.

[0057] In order to further illustrate the effect achieved by the second stage coating, the second stage coating is further explained. The specific steps for achieving the second stage coating include:

[0058] S210, purge, use high-purity nitrogen as the cleaning gas, and move the nozzle in a large-angle circular swing to clean, ensuring that there is no visible dust and impurities remaining in the cavity. At this time, the swing angle of the nozzle is 120°, the swing frequency is 1Hz, the nozzle is 10cm away from the epitaxial cavity wall, the gas flow rate is 500-1000sccm, and the purge should make the air flow rate in the epitaxial cavity reach 1-2m / s. The entire purge process takes 30s. After purging, use an optical microscope to check the inner surface of the cavity to confirm that there are no residual particles. In this step, the residues on the surface of the cavity can be effectively removed by purging the epitaxial furnace cavity.

[0059] S220, Stabilization: After baking, the temperature and pressure inside the chamber need to be kept stable for 15 seconds to ensure that the environmental conditions inside the chamber are suitable for the subsequent coating steps. To ensure that the temperature and pressure fluctuate within the set range within ±1%, thermocouples and pressure sensors are used to monitor the temperature and pressure inside the chamber.

[0060] S230, coating, using trichlorosilane and hydrogen for coating, so that a silicon layer with controllable thickness grows on the surface of the base. The silicon layer acts as a protective film, which can effectively prevent the diffusion of metal contaminants to the epitaxial wafer. The entire coating process takes 60 seconds, the flow rate of trichlorosilane is 100-500sccm, the flow rate of hydrogen is 1000-5000sccm, and the coating temperature is 1000℃. During the coating process, precise control of gas flow and reaction time should be ensured to generate a uniform and thickness-controlled silicon layer. The thickness range of the silicon layer should be controlled within 1-2μm. During this process, an ellipsometer is needed to measure the thickness of the silicon layer to ensure its uniformity and thickness control.

[0061] In this step, silicon trichloride gas and hydrogen react to form silicon. Trichlorosilane and hydrogen undergo a chemical vapor deposition reaction at high temperatures, forming a uniform silicon layer with controllable thickness on the substrate surface. Trichlorosilane is a commonly used silicon source gas with high reactivity. At high temperatures, trichlorosilane decomposes and releases silicon atoms, which react with hydrogen to form a silicon layer. Hydrogen, as a reducing agent, can promote the decomposition of trichlorosilane, increasing the growth rate and quality of the silicon layer. At the same time, hydrogen can also remove oxides from the substrate surface, ensuring the purity and uniformity of the silicon layer.

[0062] In addition, the introduction of an appropriate amount of argon as a carrier in the coating step improves the uniformity and controllability of the coating process and ensures the consistent thickness of the protective film. The total proportion of argon in the total gas flow should be between 10% and 30%.

[0063] Table 1

[0064]

[0065] Combined with attachment Figure 2 , Attachment Figure 3 As shown in the figure, the bulk metal test value after preventive maintenance of the cavity is 2.68e12. The bulk metal content in the cavity is required to be less than 5e10, so the bulk metal content is seriously exceeded. Comparing the bulk metal content in the cavity at different coating times in Table 1, it can be concluded that the longer the coating time, the lower the bulk metal content in the cavity. However, if the coating time is too long, the base and the pins of the external support base will stick together, affecting the service life of the cavity. Therefore, the coating time needs to be controlled within a reasonable range. After testing, it was decided to optimize the time of the coating step, and finally the coating stage time was controlled to 60s. On the one hand, this optimization scheme effectively prevents the diffusion of metal contaminants into the epitaxial wafer, and on the other hand, it prevents the base from sticking to the pins of the external support base, thereby improving the reliability and stability of the process.

[0066] The introduction of argon as a carrier improves the uniformity and controllability of the coating process, ensures the consistent thickness of the protective film, and effectively blocks the diffusion of metal contaminants. Through annealing treatment, the structure of the epitaxial wafer is further improved, stress is eliminated, and the crystallization quality and electrical properties of the epitaxial layer are improved. These optimization measures further reduce the metal content of the epitaxial wafer, improve the purity and reliability of the epitaxial wafer, and meet the manufacturing needs of high-performance semiconductor devices.

[0067] As shown in Table 2, S1: Purge, time is 5 seconds, this step removes dust and impurities on the surface by purging the epitaxial furnace cavity, S2: Heating, time is 30 seconds, this step heats the substrate to a certain temperature to prepare for subsequent processes, S3: Baking, time is 45 seconds, through high temperature treatment, removes organic matter and moisture on the surface of the substrate, S4: Stabilization, time is 10 seconds, this step ensures that the substrate temperature is stable and provides stable conditions for subsequent processes, S5: Etching, time is 36 seconds to 53 seconds, removes the substrate surface by chemical gas Residual substances on the surface, S6: Purge, time is 30 seconds, purge the epitaxial furnace cavity again to remove surface residues, S7: Stabilize, time is 15 seconds, ensure the stability of substrate temperature, and provide stable conditions for subsequent processes, S8: Coating, time is 45 seconds to 125 seconds, the function is to grow a protective film on the surface of the substrate to effectively block metal pollution, S9: Purge, time is 15 seconds, this step purges the epitaxial furnace cavity again to remove surface residues, S10: Cooling, time is 5 seconds, cool the substrate to room temperature, prepare for the next process.

[0068] Table 2

[0069]

[0070] As shown in Table 3 below, the coating step time is 60 seconds to balance the metal content control and avoid adhesion between the base and the pins of the external support base. By optimizing the coating time, the thickness of the protective film is ensured to be moderate, which not only effectively blocks metal contamination, but also avoids adhesion between the base and the pins of the external support base, thereby improving the reliability and stability of the process; the etching step time is 43 seconds to ensure the removal of residual substances on the base. By precisely controlling the etching time, it is ensured that the residual substances on the substrate surface are completely removed, thereby improving the purity and quality of the epitaxial wafer.

[0071] Table 3

[0072]

[0073] In order to further illustrate the role of the third stage cooling, the third stage cooling is further explained. The specific steps for achieving the third stage cooling include:

[0074] S310, purge, use high-purity nitrogen as the cleaning gas, and move the nozzle in a large-angle circular swing to clean, ensuring that there is no visible dust and impurities remaining in the cavity. At this time, the swing angle of the nozzle is 120°, the swing frequency is 1Hz, the nozzle is 10cm away from the epitaxial cavity wall, the gas flow rate is 500-1000sccm, and the purge should make the air flow speed in the epitaxial cavity reach 1-2m / s. The entire purge process takes 15s. After purging, use an optical microscope to check the inner surface of the cavity to confirm that there are no residual particles. In this step, the residue on the surface of the cavity can be effectively removed by purging the epitaxial furnace cavity.

[0075] S320: Cooling. Using nitrogen as a protective atmosphere, the chamber temperature is rapidly lowered to room temperature. The entire cooling process takes 5 seconds and the gas flow rate is 1000 sccm. To avoid stress caused by temperature gradients, a thermocouple is used to monitor the temperature.

[0076] In order to further illustrate the technical means and effects adopted by the present invention to achieve the predetermined purpose of the invention, the specific implementation methods, structures, features and effects of the present invention are described in detail below in conjunction with the accompanying drawings and preferred embodiments.

[0077] The above description is merely a preferred embodiment of the present invention and does not constitute any form of limitation to the present invention. Although the present invention has been disclosed as above in terms of a preferred embodiment, it is not intended to limit the present invention. Any person skilled in the art can, without departing from the scope of the technical solution of the present invention, make some changes or modifications to equivalent embodiments using the technical contents disclosed above. However, any brief modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention are still within the scope of the technical solution of the present invention.

Claims

1. A method for controlling the metal content of an epitaxial furnace cavity, characterized in that: The following stages are included: S100, the first stage of cleaning, removing residual substances in the cavity; first, gas is introduced into the cavity to remove dust and impurities, and then the heating element is gradually raised to a certain temperature to remove organic matter and moisture on the surface of the substrate. After the organic matter and moisture on the surface of the substrate are completely evaporated, etching gas is used to remove residual substances on the surface of the substrate; The first stage of cleaning specifically includes the following steps: S110, purging, using inert gas as the cleaning gas, moving the nozzle to clean, ensuring that there is no visible dust and impurities remaining in the cavity, and then using an optical microscope to inspect the inner surface of the cavity to confirm that there are no residual particles; S120, heating, gradually raising the temperature from room temperature to 1000°C by means of heating elements, ensuring uniform temperature distribution throughout the entire process; S130, baking, gradually increasing the temperature to 1000° C., and then maintaining a constant temperature for baking, until organic matter and moisture on the substrate surface are completely evaporated and the surface appears dry, using a detection device to detect the substrate surface to confirm that no organic matter and moisture remain; S140, stabilization: After the baking is completed, the temperature and pressure in the epitaxial cavity are kept stable, and the temperature and pressure are monitored using a temperature and pressure monitoring device to ensure the stability of the environmental conditions in the cavity; S150, etching, using an etching gas to etch, and using a microscope to inspect the substrate surface to confirm that there is no residual material; The etching is performed using hydrogen chloride gas, and the etching step takes 36 to 53 seconds, wherein the entire etching process takes 43 seconds to remove residual substances on the surface of the base. The gas flow rate during the etching process is 1000 sccm, the etching rate is 0.25 μm / s, and the etching temperature is 1000°C. S200, the second stage of coating, growing a silicon layer of controllable thickness on the surface of the base; first, gas is introduced into the cavity to remove residual substances on the surface, then the temperature and pressure are monitored using temperature and pressure detection devices to ensure the stability of the temperature and pressure in the cavity, and then the reaction gas is used for coating to form a silicon layer of controllable thickness on the surface of the base; The second stage coating specifically includes the following steps: S210, purging, using inert gas as the cleaning gas, moving the nozzle to clean, ensuring that there is no visible dust and impurities remaining in the cavity, and then using an optical microscope to inspect the inner surface of the cavity to confirm that there are no residual particles; S220, stabilizing, maintaining the temperature and pressure in the epitaxial cavity stable, monitoring the temperature and pressure using a temperature and pressure monitoring device to ensure the stability of the environmental conditions in the cavity; S230, coating, using a reaction gas to coat, so that a silicon layer with controllable thickness grows on the surface of the base, and using a thickness measuring device to measure the thickness of the silicon layer to ensure its uniformity and thickness control; The thickness of the silicon layer in the coating step is 1-2 μm; the reaction gases used in the coating step are trichlorosilane and hydrogen, which are used to grow a silicon layer with controllable thickness on the surface of the base; argon gas is introduced as a carrier in the coating step, and the argon gas accounts for 10% to 30% of the total gas flow; the coating step lasts for 45 seconds to 125 seconds, wherein the entire coating process lasts for 60 seconds, which is used to prevent metal contaminants on the surface of the substrate from diffusing into the epitaxial layer; the flow rate of trichlorosilane is 100-500 sccm, the flow rate of hydrogen is 1000-5000 sccm, and the coating temperature is 1000°C; S300, the third stage of cooling, ensures that the cavity temperature is 25°C; first, gas is introduced into the cavity to remove residual substances on the surface, and then the substrate temperature is lowered to 25°C; S310, purge, use inert gas as the cleaning gas, move the nozzle to clean, ensure that there is no visible dust and impurities remaining in the cavity, and then use an optical microscope to check the inner surface of the cavity to confirm that there are no residual particles; S320, cooling, first lowering the substrate temperature to room temperature, and using a temperature monitoring device to monitor the temperature, using nitrogen with a flow rate of 1000 sccm as a protective atmosphere, lowering the substrate temperature from 1000°C within 5 seconds to ensure that the temperature is stable at 25°C.

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