Dust-free cleaning process for AL meltallizing coating

Abstract

The invention relates to the technical field of surface treatment, discloses a dust-free cleaning process for an AL meltallizing coating, and aims to overcome the defects of an existing cleaning process for the AL meltallizing coating in the aspects of removing particles in micro-pores and passivating tips prone to falling off. The process comprises the steps of ultrapure water pre-cleaning, supercritical fluid deep cleaning, plasma surface modification, high-purity inert gas microjet purging and high-temperature vacuum degassing and surface stabilization. By the adoption of the technical scheme, the cleanliness of the AL meltallizing coating can be remarkably improved, particles and organic pollutants in micro-pores can be thoroughly removed, tips prone to falling off are passivated, secondary pollution is avoided, the cleaning period is shortened, and the production yield of semiconductors and liquid crystal panel products and the equipment utilization rate are increased.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of surface treatment, and particularly relates to a dust-free cleaning process for AL melting spraying coating. BACKGROUND

[0002] With the rapid development of the semiconductor and liquid crystal display panel industries, the cleanliness requirements for vacuum equipment parts in the production environment are increasingly stringent. As a key surface treatment technology, AL melting spraying coating is widely used in the protection and regeneration of core components such as vacuum equipment cavities, clamps, and transmission systems due to its excellent wear resistance, corrosion resistance, and thermal protection performance. The surface state directly affects the production yield and equipment operation stability.

[0003] Among them, the AL melting spraying coating is long-term served in extreme working conditions such as high vacuum and plasma, and its surface will inevitably adsorb micro-particles, form easily detached tips, and deposit organic matter. If these contaminants are not effectively removed, they will seriously threaten the product quality during semiconductor manufacturing and liquid crystal panel display processes. Therefore, the cleaning process for AL melting spraying coating has become a key link to ensure the stable operation of high-performance equipment.

[0004] However, the existing AL melting spraying coating cleaning technology still has many shortcomings. Traditional cleaning methods, such as high-pressure water washing or simple ultrasonic cleaning, are not effective in removing particles inside the micro-pores of the melting spraying coating and easily detached tip structures, resulting in high particle levels in the cavity after the parts are put into use, which seriously affects product yield and significantly increases unnecessary Dummy run time costs. Some technologies that focus on optimizing coating materials or improving oxidation resistance have complex and high-energy consumption preparation processes, and do not provide targeted and efficient solutions in the cleaning process, but may introduce new pollution or increase cleaning difficulty. These problems show that the existing AL melting spraying coating cleaning technology has obvious shortcomings in micro-pore particle removal, easily detached tip processing, cleaning efficiency, process simplification, and final cleanliness guarantee. There is an urgent need for a dust-free cleaning process that can provide higher cleanliness, stability, and efficiency. SUMMARY

[0005] To solve the deficiencies of the existing AL melting spraying coating cleaning process in removing particles in micro-pores and processing easily detached tips, the present application provides a dust-free cleaning process for AL melting spraying coating, which aims to effectively remove fine contaminants on the coating surface through systematic multi-stage processing, improve coating cleanliness, and reduce the risk of particle contamination during subsequent use, thereby meeting the stringent requirements of the semiconductor and liquid crystal display panel industries for high-cleanliness parts.

[0006] According to one aspect of the present application, a dust-free cleaning process for AL melting spraying coating is provided, which includes the following steps:

[0007] First, an ultrapure water pre-cleaning stage is performed to remove macro contaminants and loose particles on the surface of the AL spray coating;

[0008] Next, a supercritical fluid deep cleaning stage is performed to remove fine particles and organic contaminants from the microscopic pores of the coating.

[0009] Next, a plasma surface modification stage is carried out to passivate the easily detached tip structures on the coating surface and activate the subsurface areas;

[0010] Subsequently, a high-purity inert gas microjet purge stage is carried out to efficiently remove loose particles and reaction products after plasma treatment;

[0011] Finally, a high-temperature vacuum degassing and surface stabilization stage is carried out to completely remove the residual gas and moisture inside the coating and stabilize the surface structure.

[0012] As an embodiment of the present invention, the ultrapure water pre-cleaning stage includes:

[0013] The Al spray coating to be cleaned is immersed in ultrapure water with a resistivity greater than 18 megohm-cm. The immersion process is carried out in a cleaning tank with automatic stirring. The cleaning tank is made of high-purity stainless steel and equipped with a constant-temperature heating device. The ultrapure water temperature is maintained at 20 to 30 degrees Celsius. The immersion time is set to 10 to 20 minutes. An ultrasonic transducer array with a frequency of 40 to 80 kHz is installed at the bottom of the cleaning tank to assist the ultrapure water in cleaning the coating surface. The ultrasonic power density is controlled between 1 watt and 5 watts per liter of solution. The ultrasonic cleaning duration is set to 5 to 10 minutes. The ultrasonic cavitation effect and the scouring action of the ultrapure water remove dust, floating dust, and some weakly bound large particles from the coating surface. After cleaning, the coating is removed from the cleaning tank and sprayed with high-pressure ultrapure water at a pressure of 0.5 MPa to 1 MPa to thoroughly rinse away loose particles and residual cleaning medium adhering to the surface.

[0014] As an embodiment of the present invention, the supercritical fluid deep cleaning stage includes:

[0015] The AL spray coating pre-cleaned by ultrapure water is placed in a special high-pressure reaction kettle with corrosion-resistant inner wall and sealing structure. High-purity carbon dioxide gas is injected into the reaction kettle, and heated and pressurized to a supercritical state. The temperature of the supercritical state is set between 35 degrees Celsius and 60 degrees Celsius, and the pressure is set between 8 megapascals and 20 megapascals. Under this supercritical condition, carbon dioxide exhibits similar low viscosity and high diffusivity as a gas, and similar solubility as a liquid. The supercritical carbon dioxide can penetrate into the micron-level or even nanometer-level pores of the AL spray coating, dissolve and carry away the organic contaminants adsorbed on the pore wall. The duration of the cleaning process is set to 30 minutes to 120 minutes. Further, the supercritical carbon dioxide contains 3 to 7 percent by volume of a co-solvent, isopropyl alcohol, to enhance the solubility of certain polar organic compounds. After cleaning, the supercritical carbon dioxide is gradually gasified and discharged through a precisely controlled pressure relief process. The pressure relief rate is controlled at 0.5 megapascals to 1 megapascal per minute to take advantage of the expansion effect of carbon dioxide gasification to physically strip inorganic particles attached to the deep pores and carry them out with the gas stream, thereby achieving volatile removal of the cleaning medium without residue, avoiding the secondary pollution and drying problems caused by liquid residue after traditional wet cleaning. The high-pressure reaction kettle is integrated with a fluid circulation system and a particle capture filter to ensure the cleanliness of the fluid during the cleaning process and effectively collect the detached particles.

[0016] As an embodiment of the present application, the plasma surface modification stage comprises:

[0017] The AL spray coating pre-cleaned by supercritical fluid deep cleaning is placed in a high-vacuum plasma treatment chamber. The chamber is evacuated to a base pressure below 10 negative fourth power pascals. Then, high-purity inert gas, argon, is introduced at a flow rate of 50 standard cubic centimeters per minute to 200 standard cubic centimeters per minute. A low-temperature plasma is excited inside the chamber by a radio frequency power source with a frequency of 13.56 megahertz and a power setting of 50 watts to 500 watts. High-energy ions in the plasma bombard the surface of the AL spray coating, removing surface molecular layer contaminants and performing microscopic sputter etching and passivation on easily detached tip structures. The passivation process slightly removes the tip material to make it more rounded or smooth in shape, thereby significantly reducing the risk of detachment in subsequent use. The plasma treatment time is set to 5 minutes to 30 minutes. The plasma treatment effectively improves the microscopic morphology of the coating surface, increases the surface flatness and bonding strength, and reduces potential particle sources. The chamber is equipped with a temperature control system to ensure that the coating surface temperature does not exceed 100 degrees Celsius during the treatment process, preventing thermal damage to the AL spray coating structure.

[0018] As an embodiment of the present application, the high-purity inert gas micro-jet blowing stage comprises:

[0019] The AL spray coating after plasma surface modification is transferred to a high-cleanliness blowing area. The blowing area is maintained in a clean environment with an ISO level of Class 4. The coating surface is micro-jet blown by high-purity inert gas. The inert gas is high-purity nitrogen or high-purity argon with a purity higher than 99.9999%, and is finally filtered through an end filter with a pore size less than 10 nanometers. The gas is sprayed to the AL spray coating surface through a plurality of microporous nozzle arrays at a specific angle and speed. The nozzle aperture is controlled at 0.1 millimeter to 0.5 millimeter, and the gas spraying pressure is controlled at 0.2 megapascal to 0.5 megapascal. The distance between the nozzle and the coating surface is set at 5 millimeters to 15 millimeters. The spraying angle is inclined to the coating surface, with an angle range of 30 degrees to 60 degrees, to maximize the shear force effect and efficiently remove the loose particles and possible reaction products attached after plasma treatment. The blowing process ensures uniform coverage of all surface areas of the coating by precisely controlling the nozzle moving path and speed. The blowing time is set at 10 minutes to 30 minutes. A vacuum suction system and high-efficiency particle capture device are provided below the blowing area to immediately capture and remove the particles blown off, preventing secondary pollution.

[0020] As an embodiment of the present application, the high-temperature vacuum degassing and surface stabilization stage comprises:

[0021] The AL spray coating after high-purity inert gas micro-jet blowing is placed in a high-vacuum baking oven. The baking oven has a high-temperature-resistant, ultra-clean cavity environment inside. First, the baking oven cavity is evacuated by a high-vacuum pump group, with a vacuum degree lower than 10 negative fifth power pascal. Then, the cavity is heated. The baking temperature is set at 150 degrees Celsius to 300 degrees Celsius, and the temperature rising rate is controlled at 2 degrees Celsius to 5 degrees Celsius per minute. The baking time is set at 60 minutes to 240 minutes. The high-temperature vacuum degassing treatment is used to completely remove residual water molecules, oxygen and other volatile gases adsorbed in the internal pores and surface of the AL spray coating, thereby preventing the release of these gases during subsequent vacuum equipment operation, causing cavity pollution. At the same time, the high-temperature treatment can also further stabilize the coating microstructure through appropriate annealing effect, relieve internal stress, make the coating surface more dense and stable, and fundamentally reduce the risk of particle regeneration or falling off. After baking, it is slowly cooled to room temperature in a vacuum state, and then high-purity inert gas is introduced for vacuum breaking treatment to avoid re-pollution of the clean coating by ambient air. The high-purity inert gas is nitrogen with a purity higher than 99.9999%.

[0022] As an embodiment of the present application, the cleaning process further comprises an online particle monitoring and cleanliness evaluation step:

[0023] After the high-temperature vacuum degassing and surface stabilization stage, the AL spray coating is subjected to a final cleanliness test in a cleanroom environment of ISO Grade 2 or higher. The test includes scanning the coating surface using a high-sensitivity laser particle counter to quantify the number and size distribution of residual particles on the surface. The laser particle counter can detect particles larger than 0.1 microns in size. At the same time, high-resolution scanning electron microscopy or atomic force microscopy is used to examine the microstructure of key areas of the coating to evaluate the treatment effect of the easily detached tip structure and the cleanliness of the pores. The test data are transmitted in real time to the central control system for analysis and recording, and compared with the preset cleanliness standard. The test results serve as the final basis for determining whether the AL spray coating meets the on-machine requirements, ensuring that each cleaned coating component meets the ultra-high cleanliness standards for semiconductor and liquid crystal panel manufacturing.

[0024] Compared with the prior art, the present application has the advantages and positive effects that:

[0025] The present application provides a dust-free cleaning process for AL spray coating, which significantly improves the cleanliness of AL spray coating through a multi-stage, multi-mechanism cleaning and surface treatment strategy.

[0026] The present application uses the low surface tension, high permeability and adjustable solubility of supercritical carbon dioxide to effectively solve the problem of removing small particles and organic contaminants from the micro-pores, which is difficult to achieve in the prior art, and achieves complete removal of deep-layer contaminants inside the coating.

[0027] The present application uses high-energy ions to micro-etch and passivate the easily detached tip structure on the coating surface during the plasma surface modification stage, which fundamentally eliminates the main source of particle pollution in the coating during vacuum equipment operation, and avoids the damage to the coating or the generation of new particles that may be caused by traditional physical cleaning.

[0028] The present application combines high-purity inert gas micro-jet blowing and high-temperature vacuum degassing treatment to ensure the removal of residual volatile cleaning medium and the complete removal of gas and moisture inside the coating, and further stabilizes the microstructure of the coating, significantly reduces the level of particles in the coating cavity after on-machine, and avoids the secondary pollution caused by liquid residue and incomplete drying in the traditional cleaning process.

[0029] The cleaning process of the present application is simple and efficient, the stages are closely linked, and the entire process is carried out in a strictly controlled clean environment, effectively shortening the cleaning period and reducing the time cost of trial production operation.

[0030] The whole scheme of the present application has high originality and non-obviousness, which combines various advanced cleaning and surface treatment technologies organically to form a complete system with synergistic effect, effectively solves the significant deficiencies of the existing AL spraying coating cleaning technology in micro-pore particle removal, easy-to-fall tip treatment, cleaning efficiency and process simplification, etc., thereby improving the production yield and equipment utilization rate of semiconductor and liquid crystal panel products BRIEF DESCRIPTION OF DRAWINGS

[0031] Figure 1 is a schematic diagram of the overall technical scheme of the AL spraying coating dust-free cleaning process proposed by the present application;

[0032] Figure 2 is a schematic diagram of the core principle of the supercritical fluid deep cleaning in the present application;

[0033] Figure 3 is a logic flow framework diagram of the AL spraying coating dust-free cleaning in the present application;

[0034] Figure 4 is a schematic diagram of the core principle of the plasma surface modification in the present application;

[0035] Figure 5 is a logic flow framework diagram of the high-temperature vacuum degassing and surface stabilization stage in the present application;

[0036] Figure 6 is a logic flow framework diagram of the online particle monitoring and cleanliness evaluation in the present application;

[0037] Figure 7 is a schematic diagram of the core principle of the AL spraying coating easy-to-fall tip structure passivation modification by plasma in the present application. DETAILED DESCRIPTION

[0038] In the following description, specific terminology and configurations are used to set forth the embodiments of the present application for the purpose of understanding. However, these descriptions are not intended to limit the present application, and those skilled in the art can understand that various modifications and substitutions can be made without departing from the spirit and scope of the present application. The accompanying drawings are only used to illustrate the exemplary embodiments of the present application, are not drawn to scale, and should not be interpreted as limiting the present application.

[0039] The embodiment provides a dust-free cleaning process of an AL melting spraying coating. The process aims to solve the problems of the existing AL melting spraying coating cleaning technology in removing particles in micro pores and easy-to-fall-off tips, improve the cleanliness of the coating, thereby reducing the risk of particle pollution in the production process of semiconductors and liquid crystal panels, improving the yield and reducing the pre-operation time cost. The application combines supercritical fluid deep cleaning, plasma surface modification, high-temperature vacuum degassing and surface stabilization, and online particle monitoring and cleanliness evaluation through multi-stage cooperative processing, forming an efficient, thorough and controllable dust-free cleaning process. The whole process embodies the layer-by-layer progression and closed-loop control from macroscopic pollution removal to microscopic structure optimization and finally to the verification of the final cleanliness.

[0040] Specifically, the dust-free cleaning process of the AL melting spraying coating comprises the following steps:

[0041] S1. Pre-cleaning the AL melting spraying coating with ultrapure water;

[0042] S2. Deep cleaning the AL melting spraying coating after pre-cleaning with a supercritical fluid;

[0043] S3. Plasma surface modification of the AL melting spraying coating after deep cleaning;

[0044] S4. Micro-jet blowing of the AL melting spraying coating after surface modification with high-purity inert gas;

[0045] S5. High-temperature vacuum degassing and surface stabilization treatment of the AL melting spraying coating after micro-jet blowing;

[0046] S6. Online particle monitoring and cleanliness evaluation of the AL melting spraying coating after treatment.

[0047] The overall technical solution architecture can be referred to the accompanying Figure 1 The core principle framework of the supercritical fluid deep cleaning can be referred to the accompanying Figure 2 The logic flow framework of the AL melting spraying coating dust-free cleaning can be referred to the accompanying Figure 3 The core principle framework of the plasma surface modification can be referred to the accompanying Figure 4 The logic flow framework of the high-temperature vacuum degassing and surface stabilization stage can be referred to the accompanying Figure 5 The logic flow framework of the online particle monitoring and cleanliness evaluation can be referred to the accompanying Figure 6 The core principle of the plasma passivation modification of the AL melting spraying coating easy-to-fall-off tip structure can be referred to the accompanying Figure 7 .

[0048] S1. Deep cleaning the AL melting spraying coating with a supercritical fluid

[0049] This step aims to utilize the unique physicochemical properties of supercritical fluids to achieve deep removal of stubborn particulate contaminants inside the micro-pores and on the surface of AL sprayed coatings. Supercritical fluids possess high diffusivity and low viscosity of gases, while having high solubility capacity like liquids, enabling them to effectively penetrate into tiny pores and crevices that are inaccessible to traditional solvents, dissolve and carry contaminants away from the coating surface.

[0050] The specific operation process of this step can be further refined into the following sub-steps:

[0051] S11. Pre-treat the AL sprayed coating to be cleaned;

[0052] S12. Load the pre-treated AL sprayed coating into the supercritical fluid cleaning equipment;

[0053] S13. Establish a supercritical cleaning environment in the equipment and inject cleaning media;

[0054] S14. Maintain the supercritical cleaning environment and perform dynamic circulation cleaning;

[0055] S15. Perform pressure reduction separation and cleaning media recovery.

[0056] S11. Pre-treat the AL sprayed coating to be cleaned

[0057] Before introducing the AL sprayed coating component into the supercritical fluid cleaning equipment, preliminary pretreatment is required to remove macro-contaminants of larger size on the coating surface that are easily peeled off, so as to avoid blocking the pipeline or affecting the cleaning efficiency in the subsequent supercritical cleaning process. This pretreatment stage usually includes mechanical preliminary cleaning and ultrasonic assisted pre-washing.

[0058] Specifically, mechanical preliminary cleaning includes carefully wiping the coating surface with clean dust-free cloth or soft-bristled brush to remove visible dust, loose particles and larger attachments. The tools used in this process must be strictly certified dust-free level consumables, and the operator must wear clean gloves in accordance with semiconductor production standards to prevent the introduction of new sources of contamination. Wiping action should be gentle and consistent in direction to avoid scratching the coating surface or pushing surface particles into deeper pores.

[0059] Subsequently, ultrasonic-assisted pre-cleaning is performed. The coated part is immersed in an ultrapure water solution containing a mild alkaline or neutral cleaning agent. The ultrasonic cleaning equipment generates high-frequency sound waves, which form countless micro-bubbles in the liquid. These bubbles rapidly form and collapse under pressure (cavitation effect), generating local high-speed micro-jets and shock waves, which strip the contaminants attached to the coating surface and shallow pores. The cleaning agent must be compatible with the AL spray coating material and must not cause corrosion or other adverse chemical reactions. For example, an ultrapure water-based cleaning agent with a pH range of 6.5 to 7.5 can be used. The cleaning temperature is usually controlled at 25-35°C, and the cleaning time is set at 5-10 minutes to avoid excessive cleaning damage to the coating. During cleaning, the ultrapure water solution is continuously filtered through a precision filter to ensure the cleanliness of the cleaning solution itself, usually with a filtration accuracy of 0.2 microns. After pre-treatment, the coated part needs to be repeatedly rinsed with a large amount of ultrapure water until there is no residual cleaning agent on the surface, and dried by blowing nitrogen or in clean air to remove surface moisture. The dried part is immediately transferred to a clean container, ready for the next supercritical fluid cleaning. All operating environments must be completed in a Class 100 or Class 1000 clean room to ensure dust-free throughout the pre-treatment process.

[0060] S12. Loading the pre-treated AL spray coating into the supercritical fluid cleaning equipment

[0061] The AL spray coating part after pre-treatment and drying is carefully transferred by an automated mechanical arm or manually into the cleaning cavity of the supercritical fluid cleaning equipment. This loading process must be carried out in a highly clean environment, such as an ISO Class 4 or Class 5 clean room, to prevent the part from being contaminated again by particles or organic matter during the transfer process. The cleaning cavity is usually made of high-strength stainless steel or special alloy, which can withstand high pressure and wide temperature range. Before loading, the cleaning cavity itself will be subjected to strict cleanliness tests, including surface particle counting and residual organic matter analysis, to ensure that its initial state meets the process requirements. The placement of the part inside the cavity needs to be optimally designed to ensure that the cleaning medium can flow evenly and without dead angles through all the surfaces to be cleaned, especially those with complex geometry and deep pores. For example, a specially designed support frame or basket can be used to suspend the part inside the cavity, avoiding direct contact with the cavity wall and ensuring maximum cleaning contact area. After loading, the cleaning cavity is sealed and the air tightness of the cavity is ensured by an automatic valve system, providing the necessary conditions for subsequent establishment of a supercritical environment. Leak detection is performed during the sealing process, such as by a helium mass spectrometer leak detector to detect the sealing interface, ensuring that the leakage rate is below a certain threshold, such as one times ten to the minus seventh power pascal per cubic centimeter per second.

[0062] S13. Establishing a supercritical cleaning environment in the equipment and injecting cleaning medium

[0063] The core of this step is to adjust the internal environment of the cleaning cavity of the loaded component to a supercritical state, and introduce a high-purity cleaning medium. The widely used supercritical cleaning medium is carbon dioxide, which is non-toxic, non-flammable, chemically inert, and has a low critical temperature (31.1°C) and a relatively low critical pressure (7.38 MPa), making it easy to implement and operate.

[0064] First, the cleaning cavity is deeply evacuated by a vacuum pump set. The vacuum pump set usually includes a combination of vane pumps, Roots pumps, and turbo molecular pumps, which can evacuate the cavity pressure to less than 10-3 Pa, to completely remove air, moisture, and other volatile contaminants inside the cavity, avoiding their mixing with the cleaning medium or affecting the cleaning effect in the supercritical state. The vacuum degree is monitored in real time by a high-precision vacuum gauge.

[0065] Subsequently, high-purity liquid carbon dioxide is injected into the cleaning cavity through a dedicated delivery pipeline. The purity of the injected carbon dioxide usually reaches >99.999%, and is subjected to precise filtration to remove trace amounts of particles and moisture that may be present. At the same time of injection, the heating system is started to accurately control the temperature of the cavity, causing the internal temperature of the cavity to gradually increase and stabilize above the critical temperature of carbon dioxide, for example, 40 to 80°C. At the same time, the high-pressure pump continuously pressurizes the injected carbon dioxide, causing its pressure to exceed the critical pressure, for example, between 10 and 30 MPa. After the temperature and pressure both exceed the critical point of carbon dioxide, the carbon dioxide is converted into a supercritical fluid state.

[0066] At this stage, the physical parameters of supercritical carbon dioxide, such as density, viscosity, and diffusion coefficient, are collected in real time by sensors and compared with the pre-set process parameters to ensure that it is in the optimal cleaning window. For example, the density may be between 0.5 and 0.9 g / cm3, and the viscosity may be on the order of 10-5 Pa s. The pressure sensor and temperature sensor must have an accuracy of 0.0001% to ensure accurate control of the parameters.

[0067] To enhance the cleaning effect, a small amount of auxiliary solvent, called a co-solvent, such as ethanol or acetone, can be added to the supercritical carbon dioxide. The amount of co-solvent added is usually 5% to 10% of the total mass of supercritical carbon dioxide, and its role is to improve the solubility of supercritical carbon dioxide for certain specific organic contaminants, such as oil stains or resin residues. The co-solvent is accurately injected by a metering pump and thoroughly mixed with the supercritical carbon dioxide in a mixer to ensure uniformity.

[0068] S14. Maintain the supercritical cleaning environment and perform dynamic circulating cleaning

[0069] After establishing a stable supercritical cleaning environment and injecting the cleaning medium, this step will ensure that the supercritical fluid continuously and effectively acts on the AL spray coating surface and internal pores through dynamic circulation and precise parameter control.

[0070] Firstly, the cleaning medium continuously flows inside the cavity through the circulation pump. The circulation pump extracts supercritical fluid from one outlet of the cleaning cavity, passes through the heater (maintaining the set temperature), booster pump (maintaining the set pressure), filter (removing dissolved and carried contaminants), and then re-injects it into the cleaning cavity from another inlet, forming a closed-loop circulation system. This dynamic circulation flow can continuously update the cleaning medium, continuously remove dissolved contaminants from the coating surface, and separate them from the system, thereby maintaining the high activity and cleanliness of the cleaning medium. The circulation flow is usually controlled within the range of five to twenty effective volumes of the reactor per hour (unit: liters), where the effective volume of the reactor refers to the internal net space of the cleaning cavity, such as calculated by the cavity geometry, to ensure sufficient medium exchange rate.

[0071] During the cleaning process, the temperature and pressure inside the cavity are precisely adjusted and real-time feedback through the PID control system. For example, by adjusting the heater power and high-pressure pump speed, the temperature fluctuation is controlled within plus or minus zero point five degrees Celsius, and the pressure fluctuation is controlled within plus or minus zero point one megapascal. This precise control is crucial for maintaining the stability of the supercritical state, as even slight changes in temperature or pressure can cause significant changes in the properties of supercritical fluid, affecting the cleaning effect.

[0072] The cleaning duration is one of the key parameters of this step, and its value range is usually determined according to the degree of AL spray coating contamination, component geometry, and required cleanliness level, such as forty minutes to one hundred and twenty minutes. Long cleaning time helps supercritical fluid penetrate and dissolve deep contaminants more fully, but excessive cleaning time may lead to increased energy consumption and reduced efficiency. Therefore, it is necessary to optimize the cleaning duration through experimental verification and online monitoring data.

[0073] To further enhance the cleaning effect, acoustic assistance or mechanical stirring can be introduced. For example, by setting a high-frequency piezoelectric transducer outside the cleaning cavity, low-intensity ultrasonic waves are generated, which interact with the supercritical fluid, further improving the stripping efficiency of contaminants. Alternatively, by designing the flow channel structure inside the cavity, turbulent or vortex flow is generated, increasing the shear force of supercritical fluid on the coating surface.

[0074] Throughout the dynamic circulation cleaning process, the filter continuously filters the supercritical fluid flowing out of the cavity to capture and remove the dissolved and peeled off contaminant particles. The filter adopts a multi-stage filtration system, including a coarse filter and a fine filter, and the fine filter has a filtration accuracy of zero point zero two microns, ensuring the cleanliness of the circulating medium. The captured contaminants are stored in a separate collection container for subsequent processing.

[0075] The cleaning effect of this step directly depends on the solubility and mass transfer efficiency of the supercritical fluid to the contaminants. The solubility is determined by the density, temperature of the supercritical fluid and the intermolecular force between the contaminants; the mass transfer efficiency is affected by the diffusion coefficient and fluid velocity. For particulate contaminants, the supercritical fluid can penetrate the interface between the particles and the coating, weaken the adhesion, and be carried away by the fluid shear force. For organic contaminants, the supercritical fluid can dissolve these substances. The successful execution of this step significantly reduces the particle and organic residue on the surface of the AL sprayed coating, providing a clean substrate for subsequent plasma surface modification.

[0076] The solubilization and mass transfer process of supercritical fluid to solid surface contaminants can be described by the following simplified formula:

[0077] ; wherein C represents the concentration of contaminants in the supercritical fluid, t represents time, k m represents the mass transfer coefficient, A represents the effective area of the cleaning medium in contact with the coating surface, C s represents the saturation solubility of the contaminants in the supercritical fluid. This formula characterizes the rate of contaminants entering the supercritical fluid from the surface of the AL sprayed coating, and this process optimizes k m (e.g. by adjusting the flow rate and turbulence intensity) and maximizes A (through optimized placement of components and flow channel design), and maintains high C s (by precisely controlling temperature, pressure and cosolvent addition), to achieve efficient contaminant removal.

[0078] S15. Perform pressure reduction separation and cleaning medium recovery

[0079] When the set cleaning time reaches or the online monitoring system confirms that the cleanliness meets the standard, this step will enter the pressure reduction separation stage, converting the supercritical fluid into a gaseous state, so that the contaminants dissolved therein are precipitated and separated from the cleaning medium, and finally the cleaning medium is recovered.

[0080] First, stop the operation of the supercritical fluid circulating pump, and slowly reduce the pressure and temperature inside the cleaning cavity. The pressure reduction process needs to be precisely controlled, for example, gradually reducing the pressure at a rate of zero point five to one megapascal per minute, while reducing the temperature at a rate of five to ten degrees Celsius per minute. Slow pressure reduction rate can prevent mechanical impact on the coating surface caused by rapid pressure drop due to sudden expansion of gas, avoiding secondary pollution or structural damage.

[0081] When the pressure and temperature drop below the critical point of carbon dioxide, the supercritical carbon dioxide will be converted into gaseous carbon dioxide. At this time, due to the sharp decline in the solubility of gaseous carbon dioxide for pollutants, the pollutants originally dissolved in it will precipitate from the solution in solid or liquid form. These precipitated pollutants are usually high molecular organic matter, particles, etc.

[0082] Subsequently, gaseous carbon dioxide is introduced into the recovery system through the pressure reducing valve and the separator. The separator usually uses cyclone separation or multi-stage sedimentation separation technology to completely separate the precipitated solid or liquid pollutants from the gaseous carbon dioxide. The separated pollutants are collected in a special waste collection tank, waiting for subsequent environmental treatment.

[0083] Pure gaseous carbon dioxide is then sent to the liquefaction system. The liquefaction system converts gaseous carbon dioxide back into liquid carbon dioxide by cooling and compression, and stores it in a high-pressure storage tank for next cleaning cycle. The recovery rate is usually more than 95%, greatly reducing the consumption and operating cost of the cleaning medium. The recovered carbon dioxide is purified again by a precision filter and adsorbent before being reused, to remove possible trace impurities and moisture, ensuring the cleanliness of its recycling.

[0084] This step ensures the effective separation of pollutants and cleaning medium and the efficient recycling of cleaning medium through fine pressure reduction and separation control, which not only improves the economy of the process, but also meets the green and environmentally friendly production concept. Through supercritical fluid cleaning, the particles and organic pollutants on the surface and in the deep pores of the AL sprayed coating are significantly removed, providing a clean substrate for subsequent fine modification and stabilization treatment.

[0085] S2. Plasma surface modification of the cleaned AL sprayed coating

[0086] This step aims to use plasma technology to modify the AL sprayed coating surface that has been cleaned by supercritical fluid, especially to passivate the inherent easy-to-shed sharp structure of the sprayed coating, while activating the surface to improve its cleanliness, stability and anti-particle adsorption capacity. The plasma modification process can change the surface morphology and chemical properties of the material at the molecular level without affecting its bulk properties.

[0087] The specific operation process of this step can be further refined into the following sub-steps:

[0088] S21. Load the cleaned AL LSP coating into the plasma modification device;

[0089] S22. Establish a vacuum environment in the modification chamber and introduce plasma working gas;

[0090] S23. Start the plasma source for surface modification and tip passivation;

[0091] S24. Stop the plasma source and perform residual gas removal.

[0092] S21. Load the cleaned AL LSP coating into the plasma modification device

[0093] After supercritical fluid cleaning and drying, the AL LSP coating parts need to be quickly transferred to the vacuum chamber of the plasma modification device in a strict clean environment, such as an ISO Class 3 or 4 clean room, through an automated handling system or a dust-free operator. During the transfer process, the parts should avoid contact with any surface that may introduce contamination. The plasma modification chamber is usually made of high-purity stainless steel, and the internal surface is treated by electrolytic polishing to reduce surface roughness, reduce particle adsorption and outgassing. Before loading, the inside of the chamber will be detected by a residual gas analyzer to ensure that there is no residual high molecular organic matter or particles.

[0094] The placement of the parts inside the chamber is crucial and needs to ensure that the plasma can uniformly cover all the surfaces to be modified. For example, a rotating clamp or multi-axis robot can be used to expose the parts to the plasma at multiple angles during the modification process. For parts with complex geometries, the placement position and attitude need to be optimized through simulation to avoid creating plasma shadow zones. After loading is complete, the chamber door is automatically closed and sealed, and an initial leak test is performed to ensure the air tightness of the chamber, providing a guarantee for the subsequent establishment of a high vacuum environment.

[0095] S22. Establish a vacuum environment in the modification chamber and introduce plasma working gas

[0096] After the components are loaded and the chamber is sealed, the modification chamber is first deeply evacuated by a high vacuum pump set (usually consisting of a mechanical pump, a Roots pump, a turbo-molecular pump, or a cryogenic pump). The target pressure of the evacuation is usually lower than 10-4 Pa, to thoroughly remove air, water vapor, trace organic matter, and a small amount of volatile substances that may remain in the pores after supercritical cleaning. The high vacuum environment is the basis for stable and uniform plasma generation, and also avoids the activation of these residual gases in the plasma, forming undesirable byproducts that affect the modification effect or introduce secondary pollution. The degree of vacuum is monitored in real time by a full-range vacuum gauge, such as a wide-range composite vacuum gauge.

[0097] After reaching the preset vacuum degree, the plasma working gas is introduced into the chamber through a high-precision mass flow controller. The choice of working gas depends on the desired modification effect. For example, inert gases such as argon are commonly used for physical sputter etching and surface activation, removing trace oxide layers on the surface and exposing fresh surfaces; hydrogen can be used in a reducing atmosphere to remove oxides and passivate the surface; oxygen or nitrogen can be used to form new chemical bonds on the surface, improving hydrophilicity or corrosion resistance; fluorine-containing gases such as carbon tetrafluoride can be used for etching or forming a hydrophobic layer. In this invention, considering the passivation of the AL melt-sprayed coating and the improvement of surface cleanliness, the commonly used working gas combination includes a mixture of high-purity argon and a small amount of hydrogen. Argon is mainly used for physical bombardment to remove surface-adsorbed atomic groups and passivate the tip, while hydrogen can provide a reducing atmosphere to reduce the aluminum oxide layer and further remove trace hydrocarbons. The purity of the gas is extremely high, usually > 99.9999%, to avoid the introduction of impurities. The gas flow is precisely adjusted by a mass flow controller, for example, the argon flow can be set to fifty to one hundred standard cubic centimeters per minute, and the hydrogen flow can be set to five to ten standard cubic centimeters per minute. The introduction of working gas stabilizes the chamber pressure between ten and one hundred pascals, which is the ideal pressure range for stable plasma generation. A pressure sensor monitors the pressure in the chamber in real time, and adjusts the gas flow through a feedback control system to maintain stable pressure.

[0098] S23. Start the plasma source for surface modification and tip passivation

[0099] After a stable vacuum and working gas environment is established, the plasma source is started to excite the working gas to form a plasma in the modification chamber, which modifies the surface of the AL melt-sprayed coating and passivates the easily detached tip. The plasma source usually uses a radio frequency power source or a microwave power source to ionize the working gas through a high-frequency electromagnetic field, producing a high-energy mixture containing electrons, ions, radicals, and neutral particles.

[0100] The plasma modification process can be further divided into two mechanisms: physical bombardment and chemical reaction, or a combination of both. For AL thermal spray coatings, the surface is rough and has a large number of microscopic pores and irregular tips, which are prone to shedding particles under mechanical or thermal stress. The key to plasma modification is to passivate these tips.

[0101] Physical bombardment mechanism:

[0102] When high-energy ions (such as argon ions) are accelerated to bombard the coating surface under the action of an electric field, a physical sputtering effect occurs. This bombardment can effectively remove residual small particles attached to the coating surface and inside the pores, and perform microscopic-level "grinding" or "finishing" on sharp corners and protrusions. By controlling the ion energy and bombardment angle, the rounding of the tips, i.e., passivation, can be achieved, making them less likely to shed. Ion energy is usually controlled by adjusting the bias voltage of the radio frequency power supply, for example, fifty to three hundred volts. Too high an energy can cause damage to the coating, and too low an energy will not achieve good passivation.

[0103] Chemical reaction mechanism:

[0104] Active radicals (such as hydrogen radicals, oxygen radicals) generated in the plasma can chemically react with residual organic matter or oxides on the coating surface. Hydrogen radicals can react with hydrocarbons to generate volatile substances such as methane and water, thereby achieving deeper organic matter removal. Oxygen radicals can react with surface metal atoms to form a dense oxide layer, enhancing the oxidation resistance and stability of the coating. For AL thermal spray coatings, by selecting the appropriate reactive gas, for example, adding a small amount of hydrogen to argon, both the physical bombardment of the tips and the reduction cleaning and activation of the surface can be achieved, preparing for subsequent stabilization treatment.

[0105] Precise control of plasma parameters is crucial. The power of the radio frequency power supply is usually between three hundred and fifteen hundred watts, and the frequency is thirteen point five six megahertz to generate high-density plasma. The plasma excitation duration is usually set to ten to thirty minutes, depending on the coating thickness, surface condition, and desired modification depth. During this process, the intensity and uniformity of the plasma are monitored in real time by a photoelectric sensor inside the chamber. In addition, an optical emission spectrometer can be used to analyze the active species in the plasma in real time, ensuring that the desired active particle concentration reaches the expected level.

[0106] The core principle of plasma passivation modification of easily shed tip structures can be referred to the attached Figure 7 As shown in the figure. Under the action of the plasma, the free energy of the coating surface changes. Plasma bombardment rearranges surface atoms or removes unstable sharp structures, thereby reducing the local surface energy, making it

[0107] wherein, represents the change in surface free energy, and respectively represent the surface tension or surface energy density after and before modification, A new and A old respectively represent the surface area after and before modification. By plasma passivation, the atomic structure of the tip is rearranged, resulting in an increase in the local radius of curvature, thereby reducing the surface free energy of the region and reducing the tendency of particle shedding. For example, atoms in high-curvature regions have higher unsaturated bonds and are more easily removed or restructured into more stable configurations by physical bombardment. The passivated tip becomes smooth, effectively reducing the risk of it as a particle source.

[0108] S24. Stop the plasma source and perform residual gas purge

[0109] After the completion of plasma modification, first, turn off the radio frequency power source or other plasma source, stop the plasma excitation. Then, turn off the working gas supply, and re-evacuate the cavity by the high vacuum pump set until the cavity pressure returns to the initial high vacuum state, usually lower than ten to the negative fifth power of pascal. The purpose of this step is to completely remove the residual working gas, reaction byproducts and any volatile substances that may be produced in the plasma process inside the cavity, to prevent these substances from being adsorbed again on the coating surface in the subsequent processing stage, affecting cleanliness.

[0110] The residual gas purge time is usually five to fifteen minutes, depending on the cavity volume and pumping capacity. During this process, the residual gas analyzer can monitor the gas composition in the cavity in real time to ensure that the concentration of all harmful or undesirable gas components is reduced to below the detection limit. When the cavity cleanliness meets the requirements, the cavity is slowly backfilled to atmospheric pressure by inert gas (such as high-purity nitrogen or argon), and then the cavity door is opened to take out the modified AL spray coating component, ready for the next high-temperature vacuum degassing and surface stabilization stage. The purity of the backfilled inert gas also needs to reach >99.9999%, and it is filtered by particles to avoid introducing contamination in this final step.

[0111] S3. High-temperature vacuum degassing and surface stabilization treatment of the AL spray coating after plasma surface modification

[0112] This step is a key link in the dust-free cleaning process of AL spray coating, which aims to further remove volatile organic compounds, adsorbed water and gas molecules that may be left in the deep pores and grain boundaries of the coating, and through the high-temperature activation process, to promote the coating surface to a more stable physical and chemical state, thereby minimizing the risk of particle shedding due to outgassing or surface instability in future use.

[0113] The specific operation process of this step can be further refined into the following sub-steps:

[0114] S31. Load the AL spray coating after plasma modification into a high-temperature vacuum degassing device;

[0115] S32. Establish a high-vacuum environment in the degassing cavity;

[0116] S33. Perform high-temperature degassing treatment on the coating;

[0117] S34. Implement inert atmosphere cooling and surface stabilization.

[0118] S31. Load the AL spray coating after plasma modification into a high-temperature vacuum degassing device

[0119] The AL spray coating component after plasma surface modification is quickly and carefully transferred to the interior of the vacuum furnace body of the high-temperature vacuum degassing device by an automated mechanical arm or a dust-free operator in a strict clean room environment (e.g., ISO Class 3). The vacuum furnace body is usually made of special stainless steel materials with high temperature resistance and low outgassing rate, and is equipped with an advanced heating system and a high vacuum pump interface. Before the component is loaded, the interior of the vacuum furnace body is subjected to strict cleanliness verification, including surface particle counting and residual gas analysis, to ensure that its initial state meets the ultra-high vacuum (UHV) level requirements and avoid introducing new pollution.

[0120] The placement of the component in the furnace body needs to ensure uniform heat transfer and avoid local overheating or uneven heating. A support made of high-purity graphite or ceramic material is usually used to place the component in the center area of the furnace body, ensuring that there is enough gap between the component and the furnace wall for heat radiation and gas diffusion. For example, the support is designed as a multi-layer structure, each layer carrying the component and being exposed to the high-temperature and vacuum environment in three hundred and sixty degrees. After loading is completed, the furnace body door is automatically closed and sealed, and strict leakage detection is performed to ensure the airtightness of the furnace body under high vacuum and high temperature conditions.

[0121] S32. Establish a high-vacuum environment in the degassing cavity

[0122] After the AL spray coating component is loaded and sealed in the furnace body, the furnace body is first subjected to deep vacuum by a set of high-efficiency vacuum pumps. The vacuum pump set is usually composed of a pre-pump (such as a dry scroll pump or a Roots pump), a high-vacuum pump (such as a turbo molecular pump), and an ultra-high vacuum pump (such as a cryogenic pump or an ion pump) in multiple stages in series to achieve wide-range and high-efficiency vacuum pumping capability. The target pressure of vacuum pumping is usually set in the range of ten to the minus sixth power pascal to ten to the minus eighth power pascal, i.e., the ultra-high vacuum (UHV) level. Such low pressure can ensure that the moisture, organic matter and other gas molecules adsorbed inside and on the surface of the coating can be effectively desorbed and pumped out of the furnace body.

[0123] The vacuuming process is a step-by-step procedure. First, a rough pump is used to quickly remove most of the air and coarse volatiles, then switch to a high vacuum pump and ultra-high vacuum pump for fine evacuation. During this process, the vacuum level inside the furnace is monitored in real-time by different range vacuum gauges, such as Pirani gauge, ionization gauge, etc., to ensure accurate control of the vacuuming process and achieve the target vacuum level. The vacuum evacuation time is usually several hours or even longer to ensure that all pumpable substances in the cavity are completely removed. At the same time, the residual gas analyzer (RGA) continuously monitors the gas composition in the furnace, providing real-time gas partial pressure data for evaluating the degassing effect and identifying potential contamination sources, such as water vapor, nitrogen, oxygen, and various organic molecules. When the RGA shows that the partial pressure of all target contaminants is below a certain threshold, it is considered that the vacuum environment is successfully established.

[0124] S33. High-temperature degassing treatment of the coating

[0125] After successfully establishing a high vacuum environment, the furnace begins to be heated accurately. The heating system usually adopts resistance heating or infrared radiation heating method to ensure the uniformity and stability of the temperature inside the furnace. The temperature control system (such as PID controller) will heat the AL spray coating parts according to the preset temperature rising curve. The temperature rising rate is usually controlled at five to ten degrees Celsius per minute to avoid potential micro-cracks or peeling caused by sudden temperature changes due to internal stress of the coating.

[0126] The target degassing temperature for AL spray coating is usually set between two hundred and four hundred degrees Celsius, and a certain holding time is maintained, such as thirty minutes to one hundred and twenty minutes. At this high temperature, the molecules physically or chemically adsorbed on the surface and internal pores of the coating obtain sufficient thermal energy, overcome the adsorption energy barrier, desorb from the coating material and enter the vacuum environment. For example, water molecules adsorbed on the surface of aluminum begin to desorb in large quantities above 150°C, while some high-boiling-point organic substances require higher temperatures to completely volatilize. High-temperature degassing can effectively remove deep-seated contaminants that are difficult to remove at normal temperature and pressure, such as water molecules in the grain boundaries of aluminum oxide, hydrocarbon residues, and trace amounts of unstable products that may be formed during plasma modification.

[0127] During the high-temperature degassing process, the residual gas analyzer continuously monitors the composition and concentration of the desorbed gases. It is usually observed that the partial pressure of water vapor (mass number eighteen), carbon dioxide (mass number forty-four), and various hydrocarbon fragments (such as mass numbers twenty-eight, forty-three, fifty-seven, etc.) increases. When the partial pressure of these gas components gradually decreases over time and stabilizes at a baseline level, it indicates that the degassing process has been basically completed. The temperature uniformity inside the furnace is monitored in real-time by multiple thermocouples to ensure that the components at different positions are heated consistently, with a temperature gradient controlled within plus or minus five degrees Celsius.

[0128] S34. Implementing inert atmosphere cooling and surface stabilization

[0129] After the high-temperature degassing is completed, the AL spray coating parts are not immediately removed, but enter the inert atmosphere cooling and surface stabilization phase. First, the heating system is turned off, and the furnace is allowed to cool naturally under vacuum conditions for a period of time until the temperature drops to about 150-200 degrees Celsius. This slow cooling process helps to relieve the thermal stress inside the coating and avoid structural damage caused by rapid cooling.

[0130] When the temperature drops to the preset range, the furnace is slowly backfilled to a lower positive pressure state, such as 0.1 MPa, by high-purity inert gas (such as high-purity nitrogen or high-purity argon, with a purity of >99.9999% and passing through a precision particle filter). Then, the furnace continues to cool under the protection of an inert atmosphere until the temperature of the parts drops to room temperature. The introduction of an inert atmosphere is to prevent re-oxidation or re-adsorption of moisture and organic matter in the air when the high-temperature parts come into contact with the air, thereby ensuring the effects of degassing and plasma modification. The inert atmosphere can effectively isolate the external environment and maintain the cleanliness and stability of the coating surface.

[0131] In the inert atmosphere, a thin and dense oxide layer will gradually form on the surface of the AL spray coating, but unlike oxidation in air, this oxide layer is formed in a controlled clean atmosphere, with a more regular structure and fewer defects, thereby improving the surface passivation effect and stability of the coating. This stabilized surface is not easy to re-adsorb particles or react with active substances in the environment. The cooling rate is precisely controlled by the PID temperature control system within the range of 5-15 degrees Celsius per minute, with a temperature sensor (such as a K-type thermocouple) monitoring the coating surface temperature in real time, and the heater power and inert gas flow are adjusted through feedback to ensure that the internal stress of the coating is fully released. When the temperature of the parts completely drops to room temperature, the furnace door can be opened, and the processed AL spray coating parts are removed in a clean environment, ready for the final online particle monitoring and cleanliness evaluation. The entire high-temperature vacuum degassing and surface stabilization process significantly improves the bulk cleanliness and surface stability of the AL spray coating, reducing its potential as a source of outgassing and particles in a vacuum environment.

[0132] S4. Online particle monitoring and cleanliness evaluation of the processed AL spray coating

[0133] This step is the final verification link of the AL spray coating dust-free cleaning process, aiming to comprehensively monitor the surface particles of the coating after the previous three stages of treatment, and evaluate the cleanliness according to industry standards to ensure that the coating meets the strict requirements of ultra-high cleanliness for semiconductor and liquid crystal panel production. This step uses non-contact, high-sensitivity monitoring technology to achieve real-time, quantitative detection of surface particles.

[0134] The specific operation process of this step can be further refined into the following sub-steps:

[0135] S41. Load the treated AL spray coating into the online particle monitoring system;

[0136] S42. Start laser scanning for surface particle counting;

[0137] S43. Analyze particle data and evaluate coating cleanliness;

[0138] S44. Perform subsequent processing according to the evaluation results.

[0139] S41. Load the treated AL spray coating into the online particle monitoring system

[0140] After high-temperature vacuum degassing and surface stabilization treatment, the AL spray coating parts are precisely placed on the workbench of the online particle monitoring system through an automated transmission system or a dust-free operation mechanical arm, while maintaining a clean room environment (e.g. ISO level three). The monitoring system is usually integrated inside the clean room, and its workbench and surrounding environment are strictly controlled for cleanliness, such as providing ultra-clean air flow through independent HEPA or ULPA filters, to ensure that the monitoring process is not disturbed by external environmental particles.

[0141] The positioning of the parts on the workbench must be accurate and repeatable to ensure consistency of the scanned area each time. Precise positioning jigs or vacuum chucks are usually used to fix the parts, and high-precision sensors (such as optical encoders or laser displacement sensors) are used for position calibration. For example, the parts are placed on a X-Y axis movable stage with Z-axis height adjustment function to adapt to different sizes and shapes of parts. After loading is completed, the system will first perform a background particle scan on the stage and parts to confirm the cleanliness of the initial environment.

[0142] S42. Start laser scanning for surface particle counting

[0143] The online particle monitoring system employs high-precision laser scattering principles for surface particle counting. The core components of the system include a high-power, high-stability laser light source (such as a helium-neon laser or a semiconductor laser), and a set of high-sensitivity photodetectors and signal processing units. The laser beam is incident on the AL thermal spray coating surface at a specific angle (e.g., sixty to eighty degrees). When the laser beam scans across the coating surface, if it encounters attached micro-particles, the light will be scattered. The intensity and angle of the scattered light are related to the size, shape, and material of the particles.

[0144] The photodetectors (such as photomultiplier tubes or avalanche photodiodes) collect these scattered light signals and convert them into electrical signals. The signal processing unit amplifies, filters, and digitizes the electrical signals. By analyzing the intensity and duration of the scattered light signals, the system can accurately calculate the number of particles and classify their sizes. For example, the system can detect particles as small as zero point one microns and classify them into different size ranges such as zero point one to zero point five microns, zero point five to one micron, one to five microns, etc.

[0145] The laser scanning process is automated. The laser head or component stage moves at a pre-set speed (five to fifty millimeters per second) and optimized path (such as S-shaped trajectory algorithm, which adapts to the curvature of the coating surface), and integrates a shadow compensation module (such as a multi-angle detector) to handle dead angle areas, to comprehensively scan the entire surface of the coating. The scanning speed is usually between five to fifty millimeters per second, ensuring sufficient sampling density and detection sensitivity. The scanning path can be a spiral line, an S-shaped path, or multiple parallel lines, depending on the geometry and surface area of the component. To improve the reliability of detection, some systems use a dual-laser beam or multi-angle detector design to capture scattered light in different directions, reducing missed detections.

[0146] S43. Analyze particle data and evaluate coating cleanliness

[0147] After the laser scanning is complete, the system generates a detailed particle distribution report. This report contains the following key data: total particle count, particle count distribution in different size ranges, particle density (number of particles per square centimeter), and possibly the largest particle size. The data is visualized through specialized software, which can display the spatial distribution of particles on the coating surface, helping to identify possible local contamination hotspots.

[0148] Based on these detailed particle data, the system will evaluate the cleanliness of the AL spray coating according to pre-set industry standards and customer requirements. The semiconductor and liquid crystal panel industries often have extremely strict limits on the number and size of particles on the surface. For example, for a certain part, it may be required that the number of particles larger than zero point one microns in size on the surface be less than five per square centimeter, and there can be no particles larger than one micron in size. The evaluation process involves a strict comparison of the measured data with these pre-set cleanliness standards.

[0149] The evaluation result will be given in the form of "pass" or "fail", and a detailed analysis report will be provided, pointing out the specific reasons for not meeting the standard (for example, in which area, in which size range of particles exceeds the standard). The evaluation will also take into account factors such as coating material properties, part application scenarios, and expected service life. For example, parts that need to withstand high voltage or are used in critical photolithography equipment will have more stringent cleanliness requirements. The system will also perform trend analysis on historical cleanliness data to identify long-term stability or potential degradation trends in the cleaning process.

[0150] S44. Subsequent processing according to the evaluation result

[0151] According to the cleanliness evaluation result of S43 step, the corresponding subsequent processing measures will be taken:

[0152] If the cleanliness evaluation of the AL spray coating part is "pass", it means that the part has met the use requirements and can be packaged and enter the next production process. The packaging process must be carried out in the highest level of clean room (such as ISO one to three), using certified dust-free packaging materials (such as vacuum sealed bags) to prevent re-particle contamination during storage and transportation. A final surface static elimination treatment will be carried out before packaging to reduce the adsorption of particles in the air.

[0153] If the evaluation result is "fail", it means that there are still particles or other contaminants on the coating surface that exceed the standard. At this time, the part will be marked as "unqualified" and, according to the specific reasons for failure (for example, slight over-standard of particle number or presence of local large particles) and the nature of the coating, it will be decided whether to rework or scrap. For the case of slight over-standard, it may be sent back to the supercritical fluid cleaning stage or the plasma modification stage for secondary cleaning or modification. For example, if large particles remain, the duration of supercritical fluid cleaning or the shear force of the fluid may need to be increased; if there is a trace of organic matter remaining, the plasma gas ratio or power may need to be adjusted. If the cleanliness requirements cannot be met after multiple reworkings, or the coating has been irreversibly damaged, the part will be scrapped to avoid introducing unqualified products into critical production links and causing greater losses.

[0154] In addition, the occurrence of unqualified products will also trigger the review and optimization of the entire cleaning process. By analyzing the failure mode and historical data of unqualified products, engineers can trace the potential problem source, such as the purity of supercritical fluid medium, the stability of plasma parameters, the performance of vacuum degassing equipment, or the fluctuation of clean room environment. For example, if a certain type or location of particles is found to occur repeatedly, the local flow field design of the cleaning equipment or the plasma uniformity may need to be checked. This closed-loop feedback mechanism ensures continuous improvement and optimization of the cleaning process, ultimately achieving consistency and high reliability of AL sputtering coating cleanliness.

[0155] The dust-free cleaning process of the AL sputtering coating provided by the embodiment thoroughly removes particles and organic matter in micro-pores through supercritical fluid deep cleaning, modifies the easily detached tips with plasma passivation, and further stabilizes the surface through high-temperature vacuum degassing. Finally, online particle monitoring is used to ensure cleanliness, thereby effectively solving the problems of poor cleaning effect and high particle pollution risk of AL sputtering coating in the prior art, and significantly improving the performance and service life of vacuum equipment components in the semiconductor and liquid crystal panel manufacturing process.

Claims

1. A dust-free cleaning process for AL spray coating, characterized in that: include: Pre-cleaning the AL spray coating to remove macro contaminants and loose particles on the coating surface; The pre-cleaned AL spray coating is subjected to supercritical fluid deep cleaning to remove fine particles and organic pollutants in the microscopic pores of the coating; Performing plasma surface modification on the Al spray coating after deep cleaning to passivate the tip structure on the coating surface that is easily detached and activate the subsurface area of ​​the coating; The surface-modified Al spray coating is purged with a high-purity inert gas micro-jet to remove loose particles and reaction products after plasma treatment; The Al spray coating after micro jet blowing is subjected to high temperature vacuum degassing and surface stabilization treatment to completely remove residual gas and moisture in the coating and stabilize the surface structure of the coating; Online particle monitoring and cleanliness evaluation are performed on the treated AL spray coating to ensure that the cleanliness of the coating meets the preset requirements.

2. The dust-free cleaning process of an AL spray coating according to claim 1, characterized in that: The pre-cleaning of the AL spray coating comprises: Immersing the AL spray coating in ultrapure water, wherein the resistivity of the ultrapure water is higher than 18 megohm-cm; The immersion process is carried out in a cleaning tank with an automatic stirring function, the cleaning tank is made of high-purity stainless steel and is provided with a constant temperature heating device; The temperature of the ultrapure water is maintained at 20 to 30 degrees Celsius, and the immersion time is set to 10 to 20 minutes; The ultrapure water is ultrasonically assisted cleaned by an ultrasonic transducer array installed at the bottom of the cleaning tank, wherein the frequency of the ultrasonic transducer array is 40 kHz to 80 kHz, the ultrasonic power density is controlled at 1 watt to 5 watts per liter of solution, and the ultrasonic cleaning duration is set to 5 minutes to 10 minutes; The AL spray coating is taken out from the cleaning tank and sprayed and rinsed with high-pressure ultrapure water at a spray pressure of 0.5 MPa to 1 MPa.

3. The dust-free cleaning process of an AL spray coating according to claim 2, characterized in that: The step of performing supercritical fluid deep cleaning on the pre-cleaned AL spray coating comprises: Placing the pre-cleaned AL spray coating in a dedicated high-pressure reactor, wherein the high-pressure reactor has a corrosion-resistant inner wall and a sealing structure; Injecting high-purity carbon dioxide gas into the high-pressure reactor, and heating and pressurizing it to a supercritical state; The supercritical state temperature is set between 35 degrees Celsius and 60 degrees Celsius, and the pressure is set between 8 MPa and 20 MPa; The supercritical carbon dioxide contains 3% to 7% by volume of a co-solvent, isopropyl alcohol.

4. The dust-free cleaning process for an AL spray coating according to claim 3, characterized in that: The step of performing supercritical fluid deep cleaning on the pre-cleaned AL spray coating further comprises: The cleaning process of maintaining the supercritical state lasts for 30 minutes to 120 minutes; The supercritical carbon dioxide is gradually gasified and discharged through a precisely controlled pressure relief process, wherein the pressure relief rate is controlled at 0.5 MPa to 1 MPa per minute; A fluid circulation system and a particle capture filter are integrated inside the high-pressure reactor.

5. The dust-free cleaning process for an AL spray coating according to claim 4, characterized in that: The plasma surface modification of the Al spray coating after deep cleaning comprises: Placing the deep-cleaned Al spray coating in a high vacuum plasma treatment chamber, and evacuating the interior of the chamber to a base pressure lower than 10 minus fourth Pascals; A high-purity inert gas is introduced into the cavity, wherein the inert gas is argon, and the flow rate of the argon is controlled at 50 standard cubic centimeters per minute to 200 standard cubic centimeters per minute; Exciting low-temperature plasma in the cavity by a radio frequency power supply, wherein the radio frequency power supply has a frequency of 13.56 MHz and the radio frequency power is set at 50 watts to 500 watts; The plasma treatment is performed on the AL spray coating, and the plasma treatment time is set at 5 minutes to 30 minutes. A temperature control system is provided inside the chamber to ensure that the surface temperature of the AL spray coating does not exceed 100 degrees Celsius during the treatment process.

6. The dust-free cleaning process for an AL spray coating according to claim 5, characterized in that: The step of performing high-purity inert gas micro-jet purging on the surface-modified AL spray coating comprises: Transferring the surface-modified AL spray coating to a clean environment with an ISO grade of Class 4; The surface of the Al spray coating is micro-jet purged by high-purity inert gas, wherein the inert gas is high-purity nitrogen or high-purity argon with a purity higher than 99.9999%, and is finally filtered through a terminal filter with a pore size of less than 10 nanometers; The inert gas is sprayed onto the surface of the AL spray coating through a plurality of micro-hole nozzle arrays, the nozzle aperture is controlled to be 0.1 mm to 0.5 mm, and the gas spray pressure is controlled to be 0.2 MPa to 0.5 MPa; The distance between the nozzle and the surface of the AL spray coating is set at 5 mm to 15 mm, and the spray angle is inclined to the coating surface, and the angle range is between 30 degrees and 60 degrees; The purging time is set at 10 minutes to 30 minutes, and a vacuum suction system and a high-efficiency particle capture device are provided below the purging area.

7. The dust-free cleaning process for an AL spray coating according to claim 6, characterized in that: The high-temperature vacuum degassing and surface stabilization treatment of the Al spray coating after the micro-jet purging comprises: Placing the Al spray coating after the micro-jet purging in a high vacuum baking furnace, and evacuating the baking furnace cavity by a high vacuum pump group, wherein the vacuum degree is less than 10 to the negative fifth power Pascal; The baking oven cavity is heated, the baking temperature is set between 150 degrees Celsius and 300 degrees Celsius, and the heating rate is controlled between 2 degrees Celsius and 5 degrees Celsius per minute; The baking temperature and vacuum environment are maintained, and the baking time is set at 60 minutes to 240 minutes.

8. The dust-free cleaning process for an AL spray coating according to claim 7, characterized in that: The online particle monitoring and cleanliness evaluation of the treated AL spray coating includes: Scanning the surface of the AL spray coating using a high-sensitivity laser particle counter to quantify the number and size distribution of particles remaining on the surface, wherein the laser particle counter is capable of detecting particles larger than 0.1 microns; The microstructure of the key area of ​​the AL spray coating is examined using a high-resolution scanning electron microscope or an atomic force microscope; The detection data is transmitted to the central control system in real time for analysis and recording, and compared with the preset cleanliness standards.

9. A dust-free cleaning system for AL spray coating, characterized in that: include: A pre-cleaning module, comprising a cleaning tank, an ultrasonic transducer array, and a high-pressure ultrapure water spraying device, for pre-cleaning the AL spray coating; A supercritical fluid deep cleaning module, comprising a high-pressure reactor, a fluid circulation system and a particle capture filter, for performing supercritical fluid deep cleaning on the pre-cleaned AL spray coating; A plasma surface modification module, comprising a high vacuum plasma processing chamber, a radio frequency power supply and an inert gas introduction device, for performing plasma surface modification on the Al spray coating after deep cleaning; A high-purity inert gas micro-jet purge module, comprising a clean purge area, a micro-hole nozzle array, an inert gas source, a vacuum suction system, and a high-efficiency particle capture device, for performing high-purity inert gas micro-jet purge on the surface-modified AL spray coating; A high-temperature vacuum degassing and surface stabilization treatment module, comprising a high-vacuum baking furnace, a high-vacuum pump unit, and a heating system, for performing high-temperature vacuum degassing and surface stabilization treatment on the Al spray coating after the micro-jet purging; The online particle monitoring and cleanliness assessment module includes a high-sensitivity laser particle counter and a central control system, and is used for online particle monitoring and cleanliness assessment of the treated AL spray coating.

10. The dust-free cleaning system for AL spray coating according to claim 9, characterized in that: The pre-cleaning module is used to: Immersing the AL spray coating in ultrapure water, wherein the resistivity of the ultrapure water is higher than 18 megohm-cm; The immersion process is carried out in a cleaning tank with an automatic stirring function, the cleaning tank is made of high-purity stainless steel and is provided with a constant temperature heating device; The temperature of the ultrapure water is maintained at 20 to 30 degrees Celsius, and the immersion time is set to 10 to 20 minutes; The ultrapure water is ultrasonically assisted cleaned by an ultrasonic transducer array installed at the bottom of the cleaning tank, wherein the frequency of the ultrasonic transducer array is 40 kHz to 80 kHz, the ultrasonic power density is controlled at 1 watt to 5 watts per liter of solution, and the ultrasonic cleaning duration is set to 5 minutes to 10 minutes; The AL spray coating is taken out from the cleaning tank and sprayed and rinsed with high-pressure ultrapure water at a spray pressure of 0.5 MPa to 1 MPa.

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