Method for removing coating on inner wall of MPCVD equipment

Abstract

The invention discloses a method for removing a coating on the inner wall of MPCVD equipment, which specifically comprises the following steps: mixing an alcoholic solution and an aqueous solution, and putting the mixture into a bubbling device; closing a door of the cavity of the MPCVD equipment, and vacuumizing the cavity; opening a hydrogen valve on the bubbling device, enabling hydrogen to enter the bubbling device, enabling the hydrogen to carry the volatilized alcohol-water mixed solution to enter a reaction chamber of the MPCVD equipment, placing a molybdenum sheet on a sample table, starting microwaves, and activating plasmas; the temperature of the molybdenum sheet, the microwave power and the pressure are increased; the microwave and hydrogen valves are closed; the temperature of the molybdenum sheet is reduced; the cavity door of the equipment is opened; according to the method, hydrogen is utilized for bubbling, the aqueous solution with certain volatility is brought into the reaction cavity, the bonding strength of the coating and the inner wall of the equipment is remarkably reduced under the high-temperature condition, and the coating on the inner wall of the equipment can be efficiently removed after simple purging of an air gun.

Description

Technical Field

[0001] This invention belongs to the field of coating treatment technology, specifically relating to a method for removing the coating from the inner wall of an MPCVD equipment. Background Technology

[0002] Diamond is a special material that combines many excellent properties. It not only has extremely high hardness, high thermal conductivity, and high carrier mobility, but also has a large band gap, low dielectric constant, high breakdown electric field, and excellent physical properties such as acid resistance, heat resistance, and radiation resistance. It has a wide range of applications in many industrial fields and is known as the ultimate semiconductor.

[0003] To fabricate high-quality, large-size diamond single crystal wafers, microwave plasma chemical vapor deposition (MPCVD) is typically employed. The main influencing factors in the MPCVD process are the substrate quality, temperature, gas ratio and flow rate, microwave power, and reaction pressure. As the MPCVD equipment operates for longer periods, a coating of increasing thickness deposits in regions below the diamond crystal synthesis temperature, primarily distributed on the stainless steel cavity inner wall and quartz window. These coatings have complex structures and compositions, easily affecting the quality of the diamond single crystal. Furthermore, when the coating thickness reaches a certain level, it is prone to detachment, potentially falling onto the growing diamond single crystal surface and disrupting the growth process.

[0004] To ensure the cleanliness of the inner walls of the equipment and avoid interference from coating residues on the equipment's operational accuracy or media conduction, coating removal has become a core part of routine equipment maintenance. Currently, manual wiping is the mainstream method, but this method has several limitations and cannot meet the needs of efficient and precise maintenance. In terms of efficiency, it requires manual operation section by section, which is time-consuming, labor-intensive, and costly, and can easily extend the maintenance cycle when maintaining multiple pieces of equipment. In terms of cleaning effectiveness, it can only remove loose and detached coatings, and stubborn coatings are difficult to remove. Moreover, the narrow space of the cylindrical cavity has hidden dead corners, and wiping tools cannot cover all areas, making it difficult to achieve thorough cleaning. To compensate for these shortcomings, the cavity needs to be disassembled for maintenance periodically, but disassembly and assembly can wear down the sealing surfaces and reduce the precision of components, which shortens the equipment's lifespan and increases the risk of failure and maintenance costs. Summary of the Invention

[0005] The purpose of this invention is to provide a method for removing the coating on the inner wall of an MPCVD equipment, which can efficiently remove the coating on the inner wall of the equipment without dismantling the cavity.

[0006] The technical solution adopted in this invention is a method for removing the coating on the inner wall of an MPCVD device, specifically implemented according to the following steps: Step 1: Mix the alcohol solution with the aqueous solution to obtain an alcohol-water solution, and place it into a bubbling device, ensuring that the upper surface height of the alcohol-water solution does not exceed the gas outlet of the bubbling device; Step 2: Close the MPCVD equipment chamber door and evacuate the chamber. Step 3: Open the hydrogen valve on the bubbling device, and hydrogen enters the bubbling device, allowing the hydrogen to carry the volatile alcohol-water mixture into the reaction chamber of the MPCVD equipment. Place a molybdenum sheet on the sample stage, turn on the microwave, and activate the plasma. Step 4: Increase the temperature, microwave power, and pressure of the molybdenum sheet to 800℃-1000℃, the microwave power to 2000W-5000W, the cavity pressure to 60Torr-150Torr, and the duration to 1h-5h. Step 5: Turn off the microwave and hydrogen valves, lower the temperature of the molybdenum sheet, open the equipment cavity door, and use an air gun to blow and clean the inner wall of the equipment to remove the peeling coating, thus completing the cleaning of the coating on the inner wall of the equipment.

[0007] The invention is further characterized in that, In step 1, the alcohol solution is anhydrous ethanol or isopropanol with a purity greater than 99.9%; the volume ratio of alcohol solution in the alcohol-water solution is 0.1-0.5:1.

[0008] In step 2, the vacuum level inside the cavity should not exceed 5 × 10⁻⁶. -2 Torr.

[0009] Preferably, the vacuum level inside the cavity is no higher than 2×10⁻⁶. -2 Torr.

[0010] In step 3, the hydrogen flow rate is set to 100 sccm-1000 sccm.

[0011] Preferably, the hydrogen flow rate is set to 500 sccm-800 sccm.

[0012] In step 4, preferably, the temperature of the molybdenum sheet reaches 900℃-1000℃, the microwave power is 3000W-5000W, the cavity pressure range is 80Torr-150Torr, and the duration is 3h-4h.

[0013] In step 5, the molybdenum sheet cooling time is 10-30 minutes, and the purging time is 3-10 minutes.

[0014] The beneficial effects of this invention are as follows: The method for removing the coating on the inner wall of MPCVD equipment utilizes hydrogen bubbling to introduce a volatile aqueous solution into the reaction chamber. Under high-temperature conditions, the bonding strength between the coating and the inner wall of the equipment is significantly reduced. After a simple purging with an air gun, the coating on the inner wall of the equipment can be removed efficiently. Compared with manual wiping, this method can achieve highly efficient removal of the coating on the inner wall of the equipment, especially in corner areas that are difficult to clean manually. This method also results in a more stable distribution of the MPCVD microwave plasma, further improving the growth stability of diamond single crystals, allowing for better observation of abnormal growth, and increasing overall production efficiency. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of hydrogen gas introducing an aqueous solution into the reaction chamber in Example 1. Detailed Implementation

[0016] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0017] The method for removing the coating from the inner wall of an MPCVD device according to the present invention is implemented according to the following steps: Step 1: Mix the alcohol solution with the aqueous solution to obtain an alcohol-water solution, and then put it into the bubbling device, ensuring that the upper surface height of the alcohol-water solution does not exceed the gas outlet of the bubbling device; The alcohol solution is anhydrous ethanol or isopropanol with a purity greater than 99.9%; The volume ratio of alcohol to aqueous alcohol solution is 0.1-0.5:1; Preferably, the volume ratio of alcohol to aqueous alcohol solution is 0.2-0.3:1; Step 2: Close the MPCVD equipment chamber door and evacuate the chamber to a vacuum level not exceeding 5 × 10⁻⁶. -2 Torr; Preferably, the cavity vacuum level is no higher than 2×10⁻⁶. -2 Torr; Step 3: Open the hydrogen valve at the front end of the bubbling device to allow hydrogen to enter the bubbling device. Set the hydrogen flow rate to 100 sccm-1000 sccm so that the hydrogen carries the volatile alcohol-water mixture into the reaction chamber of the MPCVD equipment. Place a 2-inch molybdenum sheet on the sample stage and turn on the microwave to activate the plasma. The preferred hydrogen flow rate is 500 sccm-800 sccm; Step 4: Increase the temperature, microwave power, and pressure of the molybdenum sheet to 800℃-1000℃, the microwave power to 2000W-5000W, the cavity pressure to 60Torr-150Torr, and the duration to 1h-5h. Preferably, the temperature of the molybdenum sheet reaches 900℃-1000℃, the microwave power is 3000W-5000W, the cavity pressure range is 80Torr-150Torr, and the duration is 3h-4h. Step 5: Close the microwave and hydrogen valves to lower the temperature of the molybdenum sheet. The molybdenum sheet should be cooled for 10-30 minutes. Then, open the equipment cavity door and use an air gun to blow clean the inner wall of the equipment for 3-10 minutes. After blowing, use a vacuum cleaner to clean the detached inner wall coating to complete the cleaning of the inner wall coating of the equipment.

[0018] Preferably, the cooling time for the molybdenum sheet is 10-15 minutes; Use an air gun to blow clean the inner wall of the equipment, preferably for 8-10 minutes; The method for removing coatings from the inner wall of MPCVD equipment according to the present invention controls the amount of water introduced into the reaction chamber by adjusting the hydrogen flow rate and the volatility of the alcohol-water solution in the bubbling device. This enables efficient removal of coatings of varying thicknesses, allowing the coating to detach automatically and be quickly removed after simple purging, thus improving equipment maintenance efficiency and the growth quality of diamond single crystals. Using the method of the present invention, the coating removal rate is greater than 90%, and the quartz window coating removal rate is greater than 95%. After coating removal, multiple growth cycles can be performed without coating detachment, and the coating removal process does not damage the inner wall of the equipment.

[0019] In a specific embodiment of the present invention, the device used is an MPCVD device with a cylindrical cavity and operating parameters of 6 kW to 2.45 GHz.

[0020] Example 1 The method for removing the coating from the inner wall of an MPCVD device according to the present invention specifically includes the following steps: Step 1: Mix anhydrous ethanol and aqueous solution in a certain proportion, with the volume ratio of anhydrous ethanol being 10%, and place the mixture into a bubbling device, ensuring that the height of the liquid surface does not exceed the outlet of the bubbling device. Step 2: Close the MPCVD equipment chamber door and evacuate the chamber to a vacuum level of 5×10⁻⁶. -2 Torr; Step 3: Open the hydrogen valve at the front end of the bubbling device to allow hydrogen to enter. Set the hydrogen flow rate to 100 sccm to allow the hydrogen to carry the volatile alcohol-water solution into the reaction chamber. Place a 2-inch molybdenum sheet on the sample stage, turn on the microwave, and activate the plasma. Step 4: Start heating to bring the molybdenum sheet to 800°C, with a microwave power of 2000W, a cavity pressure range of 60 Torr, and a duration of 1 hour.

[0021] Step 5: Close the microwave and hydrogen valves to lower the temperature of the molybdenum sheet. The molybdenum sheet should be cooled for 30 minutes. After that, open the equipment cavity door and use an air gun to blow clean the inner wall of the equipment for 3 minutes. After blowing clean, use a vacuum cleaner to clean the detached inner wall coating to complete the cleaning of the inner wall coating of the equipment.

[0022] After completion, by observing the inner wall and quartz window of MPCVD, the coating removal rate reached 90%.

[0023] Example 2 The method for removing the coating from the inner wall of an MPCVD device according to the present invention specifically includes the following steps: Step 1: Mix anhydrous ethanol and pure water in a certain proportion, with the volume ratio of anhydrous ethanol being 30%, and place the mixture into a bubbling device, ensuring that the height of the liquid surface does not exceed the outlet of the bubbling device. Step 2: Close the MPCVD equipment chamber door and evacuate the chamber to a vacuum level of 2×10⁻⁶. -2 Torr; Step 3: Open the hydrogen valve at the front end of the bubbling device, allowing hydrogen to enter the bubbling device. Set the hydrogen flow rate to 1000 sccm, so that the hydrogen carries the volatile alcohol-water solution into the reaction chamber. Figure 1 As shown, a 2-inch molybdenum sheet is placed on the sample stage to activate the plasma; Step 4: Start heating up to 1000℃ for the molybdenum sheet, with a microwave power of 5000W, a cavity pressure range of 150 Torr, and a duration of 5 hours.

[0024] Step 5: Close the microwave and hydrogen valves to lower the temperature of the molybdenum sheet. The molybdenum sheet should be cooled for 10 minutes. After that, open the equipment cavity door and use an air gun to blow the inner wall of the equipment for 10 minutes. After blowing, use a vacuum cleaner to clean the detached inner wall coating to complete the cleaning of the inner wall coating of the equipment.

[0025] After completion, by observing the inner wall of MPCVD and the quartz window, the coating removal rate reached 95%.

[0026] Example 3 The method for removing the coating from the inner wall of an MPCVD device according to the present invention specifically includes the following steps: Step 1: Mix isopropanol and pure water in a certain proportion, with isopropanol accounting for 20% by volume, and put it into the bubbling device. The height of the liquid surface should not exceed the gas outlet of the bubbling device. Step 2: Close the MPCVD equipment chamber door and evacuate the chamber to a vacuum level of 2×10⁻⁶. -2 Torr; Step 3: Open the hydrogen valve at the front end of the bubbling device to allow hydrogen to enter the bubbling device. Set the hydrogen flow rate to 800 sccm so that the hydrogen carries the volatile aqueous solution into the reaction chamber. Place a 2-inch molybdenum sheet on the sample stage and activate the plasma. Step 4: Start heating up to 900℃ for the molybdenum sheet, with a microwave power of 3000W, a cavity pressure range of 80 Torr, and a duration of 3 hours.

[0027] Step 5: Close the microwave and hydrogen valves to reduce the temperature of the molybdenum sheet. The molybdenum sheet should be cooled for 20 minutes. After that, open the equipment cavity door and use an air gun to blow the inner wall of the equipment for 10 minutes. After blowing, use a vacuum cleaner to clean the detached inner wall coating to complete the cleaning of the inner wall coating of the equipment.

[0028] After completion, by observing the inner wall of MPCVD and the quartz window, the coating removal rate reached 93%.

[0029] Example 4 The method for removing the coating from the inner wall of an MPCVD device according to the present invention specifically includes the following steps: Step 1: Mix isopropanol and pure water in a certain proportion, with isopropanol accounting for 30% by volume, and put it into the bubbling device. The height of the liquid surface should not exceed the gas outlet of the bubbling device. Step 2: Close the MPCVD equipment chamber door and evacuate the chamber to a vacuum level of 4×10⁻⁶. -2 Torr; Step 3: Open the hydrogen valve at the front end of the bubbling device to allow hydrogen to enter the bubbling device. Set the hydrogen flow rate to 500 sccm so that the hydrogen carries the volatile aqueous solution into the reaction chamber. Place a 2-inch molybdenum sheet on the sample stage and activate the plasma. Step 4: Start heating up to 800℃ for the molybdenum sheet, with a microwave power of 4000W, a cavity pressure range of 100 Torr, and a duration of 5 hours.

[0030] Step 5: Close the microwave and hydrogen valves, reduce the temperature of the molybdenum sheet (20 minutes), open the equipment cavity door, and use an air gun to blow clean the inner wall of the equipment for 8 minutes. After blowing clean, use a vacuum cleaner to clean the detached inner wall coating, thus completing the cleaning of the inner wall coating of the equipment.

[0031] After completion, by observing the inner wall and quartz window of MPCVD, the coating removal rate reached 94%.

[0032] Example 5 The method for removing the coating from the inner wall of an MPCVD device according to the present invention is implemented according to the following steps: Step 1: Mix the alcohol solution with the aqueous solution to obtain an alcohol-water solution, and then put it into the bubbling device, ensuring that the upper surface height of the alcohol-water solution does not exceed the gas outlet of the bubbling device; The alcohol solution is anhydrous ethanol with a purity greater than 99.9%; The volume ratio of alcohol to aqueous alcohol solution is 0.2:1. Step 2: Close the MPCVD equipment chamber door and evacuate the chamber to a vacuum level of 1×10⁻⁶. -2 Torr; Step 3: Open the hydrogen valve at the front end of the bubbling device to allow hydrogen to enter the bubbling device. Set the hydrogen flow rate to 700 sccm so that the hydrogen carries the volatile alcohol-water mixture into the reaction chamber of the MPCVD equipment. Place a 2-inch molybdenum sheet on the sample stage and turn on the microwave to activate the plasma. Step 4: Increase the temperature, microwave power, and pressure of the molybdenum sheet to reach 1000℃, the microwave power to be 3000W, the cavity pressure range to be 60 Torr, and the duration to be 4h. Step 5: Close the microwave and hydrogen valves to lower the temperature of the molybdenum sheet. The molybdenum sheet should be cooled for 20 minutes. Then, open the equipment cavity door and use an air gun to blow clean the inner wall of the equipment for 10 minutes. After blowing clean, use a vacuum cleaner to clean the detached inner wall coating to complete the cleaning of the inner wall coating of the equipment.

[0033] Example 6 The method for removing the coating from the inner wall of an MPCVD device according to the present invention is implemented according to the following steps: Step 1: Mix the alcohol solution with the aqueous solution to obtain an alcohol-water solution, and then put it into the bubbling device, ensuring that the upper surface height of the alcohol-water solution does not exceed the gas outlet of the bubbling device; The alcohol solution is isopropanol with a purity greater than 99.9%; The volume ratio of alcohol to aqueous alcohol solution is 0.3:1; Step 2: Close the MPCVD equipment chamber door and evacuate the chamber to a vacuum level of 2×10⁻⁶. -2 Torr; Step 3: Open the hydrogen valve at the front end of the bubbling device to allow hydrogen to enter the bubbling device. Set the hydrogen flow rate to 800 sccm so that the hydrogen carries the volatile alcohol-water mixture into the reaction chamber of the MPCVD equipment. Place a 2-inch molybdenum sheet on the sample stage and turn on the microwave to activate the plasma. Step 4: Increase the temperature, microwave power, and pressure of the molybdenum sheet to reach 950℃, the microwave power to be 4000W, the cavity pressure range to be 100Torr, and the duration to be 3h. Step 5: Close the microwave and hydrogen valves to reduce the temperature of the molybdenum sheet. The molybdenum sheet should be cooled for 10 minutes. Then, open the equipment cavity door and use an air gun to blow clean the inner wall of the equipment for 8 minutes. After blowing, use a vacuum cleaner to clean the detached inner wall coating to complete the cleaning of the inner wall coating of the equipment.

[0034] The method of this invention adjusts the concentration of the aqueous solution entering the reaction chamber by adjusting the hydrogen flow rate, thereby efficiently removing the coating on the inner wall of the MPCVD. This method can efficiently remove the coating on the inner wall of the MPCVD, significantly improving the maintenance efficiency and operational stability of the equipment, and has high application prospects and economic value.

Claims

1. A method for removing the coating from the inner wall of an MPCVD device, characterized in that, The specific steps are as follows: Step 1: Mix the alcohol solution with the aqueous solution to obtain an alcohol-water solution, and place it into a bubbling device, ensuring that the upper surface height of the alcohol-water solution does not exceed the gas outlet of the bubbling device; Step 2: Close the MPCVD equipment chamber door and evacuate the chamber. Step 3: Open the hydrogen valve on the bubbling device, and hydrogen enters the bubbling device, allowing the hydrogen to carry the volatile alcohol-water mixture into the reaction chamber of the MPCVD equipment. Place a molybdenum sheet on the sample stage, turn on the microwave, and activate the plasma. Step 4: Increase the temperature, microwave power, and pressure of the molybdenum sheet to 800℃-1000℃, the microwave power to 2000W-5000W, the cavity pressure to 60Torr-150Torr, and the duration to 1h-5h. Step 5: Turn off the microwave and hydrogen valves, lower the temperature of the molybdenum sheet, open the equipment cavity door, and use an air gun to blow and clean the inner wall of the equipment to remove the peeling coating, thus completing the cleaning of the coating on the inner wall of the equipment.

2. The method for removing the coating from the inner wall of an MPCVD device as described in claim 1, characterized in that, In step 1, the alcohol solution is anhydrous ethanol or isopropanol with a purity greater than 99.9%; the volume ratio of alcohol solution in the alcohol-water solution is 0.1-0.5:

1.

3. The method for removing the coating from the inner wall of an MPCVD device as described in claim 1, characterized in that, In step 2, the vacuum level inside the cavity does not exceed 5 × 10⁻⁶. -2 Torr.

4. The method for removing the coating from the inner wall of an MPCVD device as described in claim 3, characterized in that, The vacuum level inside the cavity is no higher than 2×10 -2 Torr.

5. The method for removing the coating from the inner wall of an MPCVD device as described in claim 1, characterized in that, In step 3, the hydrogen flow rate is set to 100 sccm-1000 sccm.

6. The method for removing the coating from the inner wall of an MPCVD device as described in claim 5, characterized in that, Set the hydrogen flow rate to 500 sccm-800 sccm.

7. The method for removing the coating from the inner wall of an MPCVD equipment as described in claim 1, characterized in that, In step 4, preferably, the temperature of the molybdenum sheet reaches 900℃-1000℃, the microwave power is 3000W-5000W, the cavity pressure range is 80Torr-150Torr, and the duration is 3h-4h.

8. The method for removing the coating from the inner wall of an MPCVD equipment as described in claim 1, characterized in that, In step 5, the molybdenum sheet cooling time is 10-30 minutes, and the purging time is 3-10 minutes.

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