A method for reducing wafer surface fogging by optimizing cleaning processes

Abstract

The present application relates to wafer cleaning technical field, especially to a method for reducing wafer surface atomization by optimizing cleaning process, which comprises three steps of pretreatment cleaning, zoned deep cleaning and post-treatment cleaning. The pretreatment cleaning removes organic residues by using ultrasonic wave and specific formula of pretreatment liquid; the zoned deep cleaning improves cleaning efficiency by combining high-pressure zone and low-pressure zone design, porous flow guide plate and airflow guide device; the post-treatment cleaning removes residual pollutants by using high-purity deionized water and rotary cleaning. The method significantly reduces wafer surface roughness to below 0.1 nm, reduces atomization phenomenon and has no corrosion scratch, which is suitable for optical device cleaning and has wide applicability.

Description

Technical Field

[0001] This invention belongs to the field of semiconductor manufacturing and cleaning process technology, specifically a method for reducing wafer surface fogging by optimizing the cleaning process. Background Technology

[0002] In semiconductor manufacturing, wafer surface haze is a significant factor affecting product quality. Haze is primarily caused by a variety of factors, including micro-damage to the wafer surface, uneven chemical etching, polishing slurry residue, particulate contamination, and optical interference effects. These defects not only increase wafer surface roughness but also affect its optical and electrical properties, thereby reducing the overall performance of semiconductor devices. Therefore, optimizing cleaning processes to reduce wafer surface haze has become a key research focus.

[0003] A search revealed a patent, CN110148555B, for a hydrofluoric acid mist cleaning process before a potential barrier, published on July 9, 2021. This patent provides a method for removing residual water stains and oxide layers from wafer surfaces by controlling the amount of hydrofluoric acid mist. Specifically, by modifying an FSI cleaning machine to add hydrofluoric acid mist, surface residues can be effectively removed, while the etching rate can be stabilized by controlling the chamber temperature and cold spin time. However, this technical solution has the following shortcomings: First, the amount of hydrofluoric acid mist needs to be precisely controlled; too little may lead to incomplete cleaning, while too much may cause wafer surface defects. Second, this method is highly dependent on chamber temperature and process parameters. Finally, the hydrofluoric acid mist exhibits a certain selectivity in etching silicon surfaces, which may lead to uneven etching in localized areas, thereby affecting the wafer surface quality.

[0004] A search revealed a patent, CN105513999B, which discloses a two-phase flow atomizing jet cleaning device and method with gas protection, published on April 5, 2019. This patent utilizes a liquid distribution pipeline with a preset angle and a gas outlet mesh plate with a vertical gas guide outlet to form ultra-fine atomized droplets with uniform and controllable particle size, combined with a protective gas outlet for cleaning. This method effectively reduces the size of the atomized particles, avoiding damage to the wafer surface pattern structure, while controlling the oxygen content in the cleaning chamber to reduce watermark defects. However, this technical solution also has some problems: First, the device involves the design of multiple liquid distribution pipelines and gas guide outlets; second, although this method can reduce watermark defects, its effect on removing organic residues and metal ion contamination is limited; finally, the use of protective gas requires an additional gas supply system, further increasing operating costs and energy consumption.

[0005] The aforementioned problems indicate that existing cleaning processes still have room for improvement in removing wafer surface residues, controlling etching uniformity, and reducing particulate contamination. Therefore, this invention provides a method for reducing wafer surface haze by optimizing the cleaning process, aiming to comprehensively consider cleaning efficiency, surface quality, process complexity, and cost-effectiveness, thereby meeting the demands of modern semiconductor manufacturing for high-precision, high-quality wafers. Summary of the Invention

[0006] The purpose of this invention is to provide a method for reducing wafer surface fogging by optimizing the cleaning process, so as to solve the problems mentioned in the background art.

[0007] To achieve the above objectives, the present invention provides the following technical solution: A method for reducing wafer surface haze by optimizing the cleaning process includes the following steps: Step 1: Pre-treatment cleaning The wafer to be cleaned is placed in a cleaning tank, which is then filled with a pretreatment solution. The wafer is immersed in the pretreatment solution for 8-12 minutes. Subsequently, the ultrasonic generator is activated to perform ultrasonic cleaning in the cleaning tank. The temperature in the cleaning tank is maintained at 50-55℃, the ultrasonic frequency is set to 80-90kHz, and the ultrasonic cleaning time is 10-15 minutes. After cleaning, the wafer is removed and placed in a vacuum drying chamber for drying. The vacuum degree in the drying chamber is maintained at 0.02-0.03MPa, and the drying time is 5-8 minutes.

[0008] Step 2: Zoned Deep Cleaning A partition plate is installed inside the cleaning chamber, dividing the chamber into a high-pressure zone and a low-pressure zone. A perforated guide plate is installed on the partition plate, with a perforation diameter of 0.5~1.0 mm and a spacing of 2~3 mm. A spray device is installed in the high-pressure zone, with nozzles having a diameter of 0.8~1.2 mm and an angle of 45°~60° with the horizontal plane. An airflow guiding device is installed in the low-pressure zone, consisting of multiple arc-shaped guide vanes with a radius of curvature of 5~8 cm and a spacing of 1~2 cm between adjacent vanes. The wafer is cleaned sequentially through the high-pressure zone and the low-pressure zone. The cleaning fluid flow rate in the high-pressure zone is 1.5~2.0 m / s, and the airflow velocity in the low-pressure zone is 0.8~1.2 m / s. The residence time of the wafer in the high-pressure zone is 3~5 minutes, and in the low-pressure zone it is 2~3 minutes.

[0009] Step 3: Post-treatment cleaning The wafers that have undergone zoned deep cleaning are transferred to a post-processing tank, which is filled with deionized water with a resistivity of not less than 18 MΩ·cm. After the wafers are immersed in the deionized water for 5 to 8 minutes, the rotary cleaning device is started at a speed of 300 to 400 rpm for 3 to 5 minutes. After cleaning, the wafers are removed and placed in a constant temperature drying oven at a temperature of 60 to 70°C for 10 to 15 minutes.

[0010] In a further optimization of the above technical solution, the pretreatment solution is an ethylene glycol monomethyl ether solution with a mass fraction of 2.0~2.5%, and sodium citrate with a mass fraction of 0.5~1.0% is added to the ethylene glycol monomethyl ether solution.

[0011] In a further optimization of the above technical solution, the pretreatment solution is a 2.3% (w / w) ethylene glycol monomethyl ether solution, and the ethylene glycol monomethyl ether solution contains 0.8% (w / w) sodium citrate.

[0012] In a further optimization of the above technical solution, the nozzle of the spraying device is made of ceramic material, and the inner wall of the nozzle is coated with a polytetrafluoroethylene coating with a thickness of 0.1~0.2mm.

[0013] In a further optimization of the above technical solution, the arc-shaped guide vane of the airflow guiding device is made of aluminum alloy, and the surface of the arc-shaped guide vane is anodized, with the thickness of the anodized layer being 10~15μm.

[0014] In a further optimization of the above technical solution, the cleaning solution is a nitric acid solution with a mass fraction of 1.5~2.0%, and hydrogen peroxide with a mass fraction of 0.1~0.3% is added to the nitric acid solution.

[0015] In a further optimization of the above technical solution, the deionized water contains 0.01-0.02% by mass of a nonionic surfactant, which is a polyoxyethylene ether compound.

[0016] Further optimization of the above technical solution involves using corrosion-resistant stainless steel for the partition plate, with a thickness of 2 to 3 millimeters.

[0017] In a further optimization of the above technical solution, the drive motor of the rotary cleaning device is connected to the rotary support via a transmission shaft, and a bearing is installed at the bottom of the rotary support to achieve stable rotation. Compared with existing technologies, the advantages of this invention are as follows: This invention performs preliminary cleaning of the wafer surface through a pretreatment cleaning stage, utilizing ultrasound and a pretreatment solution with a specific formula to remove organic residues and microparticles. Subsequently, the zoned deep cleaning stage, through the design of high-pressure and low-pressure zones, combined with the diversion effect of a porous guide plate and the optimized design of the airflow guiding device, significantly improves cleaning efficiency while avoiding damage to the wafer surface during cleaning. The post-treatment cleaning stage, through the combination of high-purity deionized water and a rotary cleaning device, further removes residual contaminants and ensures that there are no watermarks left on the wafer surface. Experimental data show that the surface roughness of the wafer cleaned using the method of this invention is reduced to below 0.1 nm, haze is significantly reduced, and the cleaning process causes no corrosion or scratches to the wafer surface. Furthermore, the method of this invention can also be applied to the cleaning of optical devices, demonstrating broad applicability. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the process flow for the pretreatment and cleaning stage in the method of the present invention; Figure 2 This is a schematic diagram of the cleaning chamber structure in the partitioned deep cleaning stage of the method of the present invention; Figure 3 This is a schematic diagram of the operation of the rotary cleaning device in the post-processing cleaning stage of the method of the present invention. Figure 4 This is a flowchart illustrating the overall process flow of the method of the present invention.

[0019] The attached figures are labeled as follows: 1. Cleaning tank; 2. Ultrasonic generator; 3. Heating device; 4. Divider plate; 5. High-pressure zone; 6. Low-pressure zone; 7. Spraying device; 8. Airflow guiding device; 9. Rotary cleaning device; 10. Post-treatment tank. Detailed Implementation

[0020] This invention provides a method for reducing wafer surface fogging by optimizing the cleaning process, as detailed below. Figure 1 To be continued Figure 4 The technical solution of the present invention will be described in detail below with specific embodiments. In this embodiment, the wafer cleaning process is divided into three stages: pre-processing cleaning, zoned deep cleaning, and post-processing cleaning. Each stage involves specific equipment structures, operating parameters, and the connection and cooperation relationships between components. Example

[0021] First, the specific implementation method of the pretreatment and cleaning stage is described. For example... Figure 1As shown, the core equipment for the pretreatment cleaning stage includes a cleaning tank 1, an ultrasonic generator 2, and a heating device 3. The cleaning tank 1 is a sealed rectangular cavity with a support for holding the wafers. The bottom of the support has a porous support plate to ensure the cleaning solution evenly covers the wafer surface. The ultrasonic generator 2 is installed at the bottom of the cleaning tank 1, with its vibration panel directly connected to the inner wall of the tank to ensure efficient transfer of ultrasonic energy to the cleaning solution. The heating device 3 is located on the outer wall of the cleaning tank 1 and communicates with the inner cavity via a heat-conducting medium to maintain the cleaning solution temperature between 50 and 55°C. In actual operation, the wafers to be cleaned are placed on the support in the cleaning tank 1, and then a pretreatment solution is injected. The pretreatment solution consists of a 2.3% (w / w) ethylene glycol monomethyl ether solution and a 0.8% (w / w) sodium citrate solution. After the wafers are immersed in the pretreatment solution for 8 to 12 minutes, the ultrasonic generator 2 is activated, with the ultrasonic frequency set to 80 to 90 kHz, and the cleaning time is 10 to 15 minutes. During this process, the high-frequency vibrations generated by the ultrasonic generator 2 propagate through the bottom of the cleaning tank 1 into the cleaning fluid, creating a cavitation effect of tiny bubbles, thereby effectively removing organic residues and microparticles from the wafer surface. After cleaning, the wafer is removed and placed in a vacuum drying chamber for drying. The vacuum level in the drying chamber is maintained at 0.02 to 0.03 MPa, and the drying time is 5 to 8 minutes. In this stage, the synergistic effect between the cleaning tank 1, the ultrasonic generator 2, and the heating device 3 ensures the stability of the cleaning fluid temperature and the ultrasonic energy, thus achieving preliminary cleaning of the wafer surface.

[0022] The following is a detailed implementation of the zoned deep cleaning stage. For example... Figure 2As shown, the core equipment in this stage includes a partition plate 4, a high-pressure zone 5, a low-pressure zone 6, a spray device 7, and an airflow guiding device 8. The partition plate 4 is a rectangular plate vertically installed inside the cleaning chamber, made of corrosion-resistant stainless steel. It divides the cleaning chamber into two areas: high-pressure zone 5 and low-pressure zone 6. A perforated guide plate is installed on the partition plate 4, with orifices ranging from 0.5 to 1.0 mm in diameter and a spacing of 2 to 3 mm, guiding the cleaning fluid from high-pressure zone 5 to low-pressure zone 6. The high-pressure zone 5 contains the spray device 7, which consists of multiple nozzles with a diameter of 0.8 to 1.2 mm. These nozzles are made of ceramic and coated with a 0.1 to 0.2 mm thick polytetrafluoroethylene (PTFE) layer to enhance their corrosion resistance. The nozzles are at an angle of 45° to 60° to the horizontal plane and are connected to an external cleaning fluid supply system via pipes. The cleaning fluid flow rate is 1.5 to 2.0 m / s. The low-pressure zone 6 is equipped with an airflow guiding device 8, which consists of multiple arc-shaped guide vanes made of aluminum alloy with an anodized surface. The thickness of the anodized layer is 10 to 15 μm to improve its corrosion resistance. The radius of curvature of the arc-shaped guide vanes is 5 to 8 cm, and the spacing between adjacent guide vanes is 1 to 2 cm. This guide vanes direct airflow from one side of the low-pressure zone 6 to the other, with an airflow velocity of 0.8 to 1.2 m / s. In actual operation, the wafer is sequentially cleaned through the high-pressure zone 5 and the low-pressure zone 6. In the high-pressure zone 5, a spray device 7 uses high-speed jets of cleaning fluid to impact the wafer surface. The cleaning fluid contains 1.5 to 2.0% nitric acid solution and 0.1 to 0.3% hydrogen peroxide by mass to further remove contaminants from the wafer surface. The wafer resides in high-pressure zone 5 for 3 to 5 minutes, then enters low-pressure zone 6. In low-pressure zone 6, the airflow guiding device 8 optimizes the airflow direction through the design of arc-shaped guide vanes, preventing airflow from damaging the wafer surface. The wafer resides in low-pressure zone 6 for 2 to 3 minutes. During this stage, the positional relationship and functional coordination between the separator 4, the spray device 7, and the airflow guiding device 8 ensure the rational distribution of cleaning fluid and airflow, thereby significantly improving cleaning efficiency.

[0023] Finally, the specific implementation method of the post-treatment cleaning stage is discussed. For example... Figure 3As shown, the core equipment in this stage includes a post-processing tank 10 and a rotary cleaning device 9. The post-processing tank 10 is a rectangular tank with a rotating support inside for fixing the wafers. The rotating support is connected to the bottom of the post-processing tank 10 via bearings to achieve stable rotation. The rotary cleaning device 9 is installed on top of the post-processing tank 10, and its drive motor is connected to the rotating support via a transmission shaft to drive the wafers to rotate and clean in deionized water. High-purity deionized water with a resistivity of not less than 18 MΩ·cm is injected into the post-processing tank 10, and a nonionic surfactant (polyoxyethylene ether compound) with a mass fraction of 0.01 to 0.02% is added to reduce the surface tension of the water, thereby improving the cleaning effect. In actual operation, the wafers after zoned deep cleaning are transferred to the post-processing tank 10. After soaking in the deionized water for 5 to 8 minutes, the rotary cleaning device 9 is started. The rotation speed of the rotary cleaning device 9 is 300 to 400 rpm, and the cleaning time is 3 to 5 minutes. During this process, the rotary cleaning device 9 uses high-speed rotation to evenly cover the wafer surface with deionized water, while centrifugal force is used to remove residual contaminants from the wafer surface. After cleaning, the wafer is removed and placed in a constant-temperature drying oven, with the temperature set at 60 to 70°C and the drying time at 10 to 15 minutes. In this stage, the mechanical connection and motion coordination between the post-processing tank 10 and the rotary cleaning device 9 ensure thorough cleaning of the wafer surface while avoiding watermarks.

[0024] The complete implementation process of the method of the present invention has been described above, in conjunction with the appendix. Figure 4 The overall process flow diagram clearly shows the operational sequence and key parameters of the three stages: pretreatment cleaning, zoned deep cleaning, and post-treatment cleaning. In practical applications, the equipment structure, operating parameters, and connections and coordination between components in each stage constitute a complete cleaning process system. This system effectively reduces haze on the wafer surface while ensuring that the cleaning process does not cause any corrosion or scratches to the wafer surface.

[0025] To enable those skilled in the art to fully understand and implement this invention, the specific implementation principle of this invention will be further explained below in conjunction with a specific application scenario. Example

[0026] In semiconductor manufacturing, haze on the wafer surface is a significant factor affecting product quality. This invention optimizes the cleaning process by employing specific equipment structures and operating parameters in the pre-treatment cleaning, zoned deep cleaning, and post-treatment cleaning stages to reduce wafer surface haze. The following is in conjunction with the appendix... Figures 1 to 4 It elaborates in detail on the specific operating principles of each stage and the technical effects they achieve.

[0027] First, in the pretreatment cleaning stage, such as Figure 1 As shown, the wafer to be cleaned is placed in cleaning tank 1. The bottom of the support in cleaning tank 1 is designed with a porous support plate to ensure that the cleaning solution can evenly cover the wafer surface. A pretreatment solution is then injected, which consists of a 2.3% (w / w) ethylene glycol monomethyl ether solution and a 0.8% (w / w) sodium citrate solution. After the wafer is immersed in the pretreatment solution for 8 to 12 minutes, the ultrasonic generator 2 is activated. Its vibration panel is directly connected to the inner wall of cleaning tank 1, efficiently transferring ultrasonic energy into the cleaning solution. The ultrasonic frequency is set to 80 to 90 kHz, and the cleaning time is 10 to 15 minutes. During this process, the high-frequency vibration generated by the ultrasonic waves induces a cavitation effect of tiny bubbles in the cleaning solution. This cavitation effect, through localized high pressure and high temperature, effectively removes organic residues and tiny particles from the wafer surface. The heating device 3 maintains the cleaning solution temperature between 50 and 55°C through a heat-conducting medium. This temperature range ensures the activity of the cleaning solution while avoiding damage to the wafer surface due to excessive temperature. After cleaning, the wafers are transferred to a vacuum drying chamber for drying. The vacuum level in the drying chamber is maintained between 0.02 and 0.03 MPa, and the drying time is 5 to 8 minutes. During this stage, the synergistic effect between the cleaning tank 1, the ultrasonic generator 2, and the heating device 3 ensures the stability of the cleaning solution temperature and the ultrasonic energy, thereby achieving preliminary cleaning of the wafer surface.

[0028] Next, in the zoned deep cleaning stage, such as Figure 2As shown, the wafer is cleaned sequentially through a high-pressure zone 5 and a low-pressure zone 6. A partition plate 4 divides the cleaning chamber into two areas, and a perforated guide plate is installed on it. The perforation diameter of the guide plate is 0.5 to 1.0 mm, and the spacing between the perforations is 2 to 3 mm, which guides the cleaning fluid from the high-pressure zone 5 to the low-pressure zone 6. A spray device 7 is installed in the high-pressure zone 5. The nozzle diameter of the spray device 7 is 0.8 to 1.2 mm, and the inner wall of the nozzle is coated with a polytetrafluoroethylene coating with a thickness of 0.1 to 0.2 mm to enhance its corrosion resistance. The nozzle is at an angle of 45° to 60° with the horizontal plane and is connected to an external cleaning fluid supply system through a pipe. The cleaning fluid flow rate is 1.5 to 2.0 m / s. In the high-pressure zone 5, the high-speed jet of cleaning fluid impacts the wafer surface. The cleaning fluid contains 1.5 to 2.0% nitric acid solution and 0.1 to 0.3% hydrogen peroxide by mass. These chemical components further remove contaminants from the wafer surface through a redox reaction. The wafer remains in high-pressure zone 5 for 3 to 5 minutes before entering low-pressure zone 6. Low-pressure zone 6 is equipped with an airflow guiding device 8, which consists of multiple arc-shaped guide vanes made of aluminum alloy with an anodized layer thickness of 10 to 15 μm to improve corrosion resistance. The radius of curvature of the arc-shaped guide vanes is 5 to 8 cm, and the spacing between adjacent vanes is 1 to 2 cm. This guides the airflow from one side of low-pressure zone 6 to the other, with an airflow velocity of 0.8 to 1.2 m / s. During this stage, the positional relationship and functional coordination between the separator 4, the spray device 7, and the airflow guiding device 8 ensure the rational distribution of cleaning fluid and airflow, significantly improving cleaning efficiency while avoiding damage to the wafer surface during the cleaning process.

[0029] Finally, in the post-treatment cleaning stage, such as Figure 3 As shown, the wafers, after being subjected to zoned deep cleaning, are transferred to the post-processing tank 10. High-purity deionized water with a resistivity of not less than 18 MΩ·cm is injected into the post-processing tank 10, and a nonionic surfactant (polyoxyethylene ether compound) with a mass fraction of 0.01 to 0.02% is added. After the wafers are immersed in the deionized water for 5 to 8 minutes, the rotary cleaning device 9 is activated at a speed of 300 to 400 rpm for 3 to 5 minutes. During this process, the rotary cleaning device 9 uses high-speed rotation to evenly cover the wafer surface with deionized water, while simultaneously using centrifugal force to remove residual contaminants from the wafer surface. After cleaning, the wafers are removed and placed in a constant-temperature drying oven at a temperature of 60 to 70°C for 10 to 15 minutes. In this stage, the mechanical connection and motion coordination between the post-processing tank 10 and the rotary cleaning device 9 ensure thorough cleaning of the wafer surface while preventing watermarks.

[0030] As can be seen from the specific application scenarios described above, the method of this invention effectively removes organic residues and microparticles from the wafer surface through the ultrasonic cavitation effect and a pretreatment solution with a specific formulation in the pretreatment cleaning stage. The high-pressure and low-pressure zone design in the partitioned deep cleaning stage, combined with the diversion effect of the porous guide plate and the optimized design of the airflow guiding device, significantly improves cleaning efficiency and avoids damage to the wafer surface. The high-purity deionized water and rotary cleaning device in the post-treatment cleaning stage further remove residual contaminants and ensure no watermarks remain on the wafer surface. Experimental data shows that the surface roughness of the wafer cleaned using this method is reduced to below 0.1 nm, a significant reduction in fogging is observed, and the cleaning process causes no corrosion or scratches to the wafer surface.

[0031] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for reducing wafer surface haze by optimizing the cleaning process, characterized in that... Includes the following steps: Step 1: Pre-treatment cleaning The wafer to be cleaned is placed in a cleaning tank, which is filled with a pretreatment solution. The wafer is immersed in the pretreatment solution for 8 to 12 minutes. Then, the ultrasonic generator is activated to perform ultrasonic cleaning in the cleaning tank. The temperature in the cleaning tank is maintained at 50 to 55 degrees Celsius, the ultrasonic frequency is set to 80 to 90 kHz, and the ultrasonic cleaning time is 10 to 15 minutes. After cleaning, the wafer is removed and placed in a vacuum drying chamber for drying. The vacuum degree in the drying chamber is maintained at 0.02 to 0.03 MPa, and the drying time is 5 to 8 minutes. Step 2: Zoned Deep Cleaning A partition plate is installed inside the cleaning chamber, dividing the chamber into a high-pressure zone and a low-pressure zone. A perforated guide plate is installed on the partition plate, with orifice diameters of 0.5 to 1.0 mm and orifice spacing of 2 to 3 mm. A spray device is installed in the high-pressure zone, with nozzle diameters of 0.8 to 1.2 mm and an angle of 45 to 60 degrees between the nozzle and the horizontal plane. An airflow guiding device is installed in the low-pressure zone, consisting of multiple arc-shaped guide vanes with a radius of curvature of 5 to 8 cm and a spacing of 1 to 2 cm between adjacent vanes. The wafer is sequentially cleaned through the high-pressure zone and the low-pressure zone. The cleaning fluid flow rate in the high-pressure zone is 1.5 to 2.0 m / s, and the airflow velocity in the low-pressure zone is 0.8 to 1.2 m / s. The residence time of the wafer in the high-pressure zone is 3 to 5 minutes, and in the low-pressure zone, it is 2 to 3 minutes. Step 3: Post-treatment cleaning The wafers, after being deep-cleaned in sections, are transferred to a post-processing tank filled with deionized water with a resistivity of not less than 18 megohm-cm. After the wafers are immersed in the deionized water for 5 to 8 minutes, a rotary cleaning device is started at a speed of 300 to 400 revolutions per minute for 3 to 5 minutes. After cleaning, the wafers are removed and placed in a constant-temperature drying oven at a temperature of 60 to 70 degrees Celsius for 10 to 15 minutes.

2. The method according to claim 1, characterized in that... The pretreatment solution is an ethylene glycol monomethyl ether solution with a mass fraction of 2.0 to 2.5%, and sodium citrate with a mass fraction of 0.5 to 1.0% is added to the ethylene glycol monomethyl ether solution.

3. The method according to claim 2, characterized in that... The pretreatment solution is a 2.3% (w / w) ethylene glycol monomethyl ether solution, with 0.8% (w / w) sodium citrate added to the ethylene glycol monomethyl ether solution.

4. The method according to claim 1, characterized in that... The nozzles of the spray device are made of ceramic material, and the inner wall of the nozzles is coated with a polytetrafluoroethylene coating with a thickness of 0.1 to 0.2 mm.

5. The method according to claim 1, characterized in that... The arc-shaped guide vane of the airflow guiding device is made of aluminum alloy, and the surface of the arc-shaped guide vane is anodized, with the thickness of the anodized layer being 10 to 15 micrometers.

6. The method according to claim 1, characterized in that... The cleaning solution is a nitric acid solution with a mass fraction of 1.5 to 2.0%, and hydrogen peroxide with a mass fraction of 0.1 to 0.3% is added to the nitric acid solution.

7. The method according to claim 1, characterized in that... The deionized water contains 0.01 to 0.02% by mass of a nonionic surfactant, which is a polyoxyethylene ether compound.

8. The method according to claim 1, characterized in that... The partition is made of corrosion-resistant stainless steel and has a thickness of 2 to 3 millimeters.

9. The method according to claim 1, characterized in that... The drive motor of the rotary cleaning device is connected to the rotary support via a transmission shaft, and a bearing is installed at the bottom of the rotary support to achieve smooth rotation.

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