Plasma spraying process of high-corrosion-resistance yttrium oxide coating and gradient structure design method

Abstract

The invention relates to the technical field of a plasma spraying process of a high-corrosion-resistance yttrium oxide coating and a gradient structure design method, and particularly discloses the plasma spraying process of the high-corrosion-resistance yttrium oxide coating and the gradient structure design method. The invention aims to solve the problems that a traditional plasma spraying yttrium oxide coating is high in porosity, non-uniform in microstructure, easy to crack and peel off due to mismatch of a thermal expansion coefficient and a metal matrix, and difficult to consider compactness, stress buffering and long-term stability at the same time. The method comprises the following steps: carrying out degreasing cleaning, sand blasting coarsening, ultrasonic oscillation and drying pretreatment on a substrate, carrying out high-corrosion-resistance yttrium oxide composite powder spraying by adopting plasma spraying parameters optimized by an orthogonal test, and arranging multiple layers of intermediate layers with components and thermal expansion coefficients in gradient transition between the substrate and a coating, follow-up heat treatment and nano sol hole sealing treatment are assisted. By adopting the technical scheme, low porosity, high bonding strength, excellent thermal mechanical stability and long-term corrosion resistance in a strong corrosion environment of the coating can be realized.

Description

Technical Field

[0001] This invention belongs to the field of surface engineering technology, specifically relating to a plasma spraying process and gradient structure design method for a highly corrosion-resistant yttrium oxide coating. Background Technology

[0002] As semiconductor manufacturing processes continue to evolve towards higher process nodes, plasma etching technology is developing towards higher energy density, higher reactivity, and longer-term stable operation. Against this backdrop, components exposed to highly corrosive plasmas containing fluorine and chlorine (such as CF4 and BCl3) within the etching chamber face unprecedented service challenges. These high-energy plasmas not only cause severe physical sputtering and chemical erosion of material surfaces but also easily induce micropores, cracks, and particle detachment within the coating, thereby contaminating the wafer surface and severely impacting chip yield. Therefore, there is an urgent need to develop a protective coating system that combines low porosity, high density, excellent high-temperature corrosion resistance, and good interfacial bonding strength to meet the stringent reliability requirements of advanced processes.

[0003] Yttrium oxide, due to its excellent chemical inertness and thermal stability in fluorine-based plasma environments, is considered an ideal coating material for key components of etching cavities. However, yttrium oxide coatings prepared by traditional plasma spraying generally suffer from problems such as high porosity, inhomogeneous microstructure, and mismatch between the coefficient of thermal expansion and the metal substrate, leading to cracking, peeling, or accelerated corrosion under high-temperature cycling or high-energy ion bombardment. Although some studies have attempted to improve performance by introducing transition layers or controlling oxygen vacancy concentration, single-functional layer designs struggle to simultaneously meet multiple requirements such as density, stress buffering, and long-term stability.

[0004] In the prior art, CN117265480B uses an amorphous alumina transition layer to reduce the roughness of the substrate. Although this improves the initial adhesion of the coating, it fails to effectively suppress the through-holes formed during the spraying process and lacks systematic optimization for the stability of the coating-substrate interface under high-temperature service conditions. CN119082684B introduces oxygen vacancies through magnetron sputtering to enhance etching resistance, but the accumulation of internal stress exacerbates the brittleness of the coating and does not construct a gradient structure to alleviate thermal mismatch stress.

[0005] None of the above solutions achieve a synergistic improvement in porosity control, stress release, and corrosion resistance at the overall coating architecture level, making them unsuitable for the comprehensive protection requirements under high-energy, long-term etching conditions. Therefore, there is an urgent need for a new plasma spraying process that integrates the characteristics of high-corrosion-resistant HPM composite powder with a gradient structure design concept. This process can simultaneously achieve coating densification, interface strengthening, and thermomechanical stability optimization by precisely controlling spraying parameters and interlayer composition distribution. Summary of the Invention

[0006] The purpose of this invention is to provide a plasma spraying process and gradient structure design method for a high corrosion-resistant yttrium oxide coating, which can effectively solve the problems mentioned in the background art, such as high porosity, uneven microstructure, mismatch between thermal expansion coefficient and metal substrate leading to easy cracking and peeling of traditional plasma-sprayed yttrium oxide coatings, as well as the difficulty of existing technologies in balancing density, stress buffering and long-term stability.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0008] A plasma spraying process and gradient structure design method for a highly corrosion-resistant yttrium oxide coating, comprising the following specific steps:

[0009] Step 1: Degrease and clean the equipment parts by placing them in a degreasing soaking tank at a temperature of 60 degrees Celsius ± 5 degrees Celsius for 10 to 20 minutes to remove processing grease and contaminants from the surface of the parts.

[0010] Step 2: Soak the parts in pure water. Place the parts in a pure water soaking tank and soak for 60 to 120 seconds to remove residual chemical degreasing solution.

[0011] Step 3: Sandblast the equipment parts to roughen them and improve coating adhesion;

[0012] Step 4: Rinse the parts with a water gun to remove any residual dust from the surface;

[0013] Step 5: Perform ultrasonic vibration treatment on the equipment parts to remove residual dust in the grooves of the parts and further improve the coating adhesion;

[0014] Step 6: Dry the parts to prevent moisture residue from causing the coating to peel off;

[0015] Step 7: Select different process parameters for plasma spraying, including current of 550 to 600 amperes, power of 32 to 36 kilowatts, argon flow rate of 35 to 45 standard liters per minute, hydrogen flow rate of 6 to 8 standard liters per minute, spraying distance of 130 to 150 mm, and powder feeding rate of 18 to 22 grams per minute, and compare the corrosion resistance of the composite coating.

[0016] Step 8: Use orthogonal experimental design to test 8 sets of experimental comparison data, select the 8th set of process parameters, the specific parameters of this set are: current 600 to 650 amperes, argon flow rate 40 to 45 standard liters per minute, hydrogen flow rate 4 to 8 standard liters per minute, powder feeding rate 15 to 20 grams per minute, spraying distance 130 to 160 mm, and corrosion resistance time of 8 hours in 5% hydrochloric acid solution;

[0017] Step 9: Perform ultrasonic cleaning on the components. Place the components in an ultrasonic pure water cleaning tank and perform ultrasonic cleaning for 10 to 30 minutes.

[0018] Step 10: Dry the parts by placing them in a dust-free oven at a temperature of 120 degrees Celsius ± 5 degrees Celsius for 2 hours.

[0019] Preferably, the degreasing agent used in step 1 is an alkaline degreasing agent with a pH value of 10 to 12. The degreasing soaking tank is equipped with a constant temperature heating system and a mechanical stirring device with a stirring speed of 50 to 100 revolutions per minute to ensure uniform and thorough degreasing.

[0020] Preferably, in step 2, the pure water soaking uses ultrapure water with a resistivity greater than or equal to 18 megohm-cm, and the soaking tank is equipped with an overflow device and a circulating filtration system with a filtration accuracy of 0.2μm to maintain the purity of the water.

[0021] Preferably, in step 3, the sandblasting roughening treatment uses white corundum sand as the abrasive, with an abrasive particle size of 80 to 120 mesh, a sandblasting pressure of 0.4 to 0.6 MPa, a spray gun moving speed of 100 to 200 mm / s, and a sandblasting angle of 70 to 90 degrees, so that the surface roughness of the substrate reaches 5 to 10 μm.

[0022] Preferably, in step 4, the steam gun rinsing uses a mixture of deionized water and compressed air, with a water-to-air volume ratio of 1:3 to 1:5, a rinsing pressure of 0.3 to 0.5 MPa, and a nozzle diameter of 2 to 4 mm, to ensure effective removal of sandblasting residue.

[0023] Preferably, in step 5, the ultrasonic oscillation treatment uses an ultrasonic generator with a frequency of 40 kHz, a power density of 0.5 to 1.0 W / cm², and a treatment time of 5 to 10 minutes, focusing on cleaning grooves on the component with a depth greater than 0.5 mm.

[0024] Preferably, the drying process in step 6 adopts a hot air circulation drying method with an air speed of 2 to 4 meters per second, a relative humidity of less than 30%, and a drying time of 30 to 60 minutes to ensure that there are no visible water marks on the surface of the parts.

[0025] Preferably, in step 7, the plasma spraying uses a highly corrosion-resistant yttrium oxide composite powder with a particle size distribution of 15 to 45 μm, a sphericity greater than or equal to 95%, and a flowability of less than or equal to 25 seconds per 50 grams. The mass fraction of yttrium oxide is 92% to 96%, and zirconium oxide and aluminum oxide are added as stabilizers.

[0026] Preferably, in step 7, the spraying process adopts an atmospheric plasma spraying system, the spray gun is a high-energy plasma spray gun, the anode nozzle diameter is 8mm, the cathode diameter is 4mm, the arc voltage is 60 to 80 volts, and the arc current fluctuation is less than ±5%.

[0027] Preferably, the orthogonal experimental design in step 8 adopts a hybrid orthogonal array with four factors and two levels plus one factor and four levels. The factors to be investigated include current, argon flow rate, hydrogen flow rate, powder feeding rate and spraying distance. Each factor is set with 2 or 4 levels, for a total of 8 sets of experiments.

[0028] Preferably, the coating corresponding to the process parameters of the 8th group in step 8 has a corrosion resistance time of 8 hours in a 5% hydrochloric acid solution, a coating thickness of 150 to 200 μm, a porosity of less than 2%, and a bonding strength of greater than 50 MPa.

[0029] Preferably, in step 9, the ultrasonic cleaning uses multi-frequency ultrasound with a main frequency of 40 kHz and an auxiliary frequency of 80 kHz. The temperature of the cleaning solution is 40 to 60 degrees Celsius, and a nonionic surfactant is added at a concentration of 0.1 to 0.3 grams per liter.

[0030] Preferably, in step 10, the dust-free oven is equipped with a high-efficiency particulate air filter with a filtration efficiency of 99.99%, and the hot air circulation system uses a corrosion-resistant stainless steel air duct with a temperature uniformity of ±2 degrees Celsius.

[0031] Preferably, the process further includes heat treatment of the sprayed coating after step 7, with a heat treatment temperature of 800 to 1000 degrees Celsius, a holding time of 1 to 2 hours, a heating rate of 5 to 10 degrees Celsius per minute, and air cooling after furnace cooling to 300 degrees Celsius.

[0032] Preferably, after the sandblasting roughening treatment in step 3, the substrate surface is activated by low-temperature plasma cleaning technology with a power of 500 to 800 watts and a treatment time of 5 to 10 minutes. The gas is a mixture of argon and hydrogen with a volume ratio of 4 to 1.

[0033] Preferably, the gradient structure design method includes setting at least two transition layers between the substrate and the yttrium oxide coating. The transition layer material is a composite powder of yttrium oxide and metal, and the mass fraction of the metal component decreases from 30% in the inner layer to 5% in the outer layer. The thickness of each layer is 20 to 30 μm.

[0034] Preferably, in the gradient structure design method, the thermal expansion coefficient of the transition layer gradually decreases from the substrate side to the coating side. The thermal expansion coefficient of the inner transition layer is 10 to 12 per degree Celsius multiplied by 10 to the power of -6, and the thermal expansion coefficient of the outer transition layer is 8 to 9 per degree Celsius multiplied by 10 to the power of -6, which matches the thermal expansion coefficient of the yttrium oxide coating.

[0035] Preferably, the final coating is further subjected to a sealing treatment, using nano-alumina sol as a sealing agent, with a sol particle size of 10 to 20 nanometers and a solid content of 10% to 15%, applied by immersion for 10 to 20 minutes, followed by drying at 150 degrees Celsius for 30 minutes.

[0036] Preferably, the method is applied to the preparation of protective coatings for semiconductor etching cavity components, the component material is aluminum alloy or stainless steel, the maximum size does not exceed 500mm, the coating coverage reaches more than 99%, and the surface roughness is less than 1μm.

[0037] Compared with the prior art, the present invention has the following beneficial effects:

[0038] Optimized degreasing, sandblasting, ultrasonic vibration, and drying pretreatment steps significantly improved the cleanliness and roughness of the substrate surface, providing a solid foundation for excellent coating adhesion. Precisely controlled plasma spraying process parameters, particularly the 8th set of parameters optimized through orthogonal experiments, combined with the characteristics of highly corrosion-resistant yttrium oxide composite powder, achieved a coating with low porosity, high density, and a uniform microstructure. A gradient structure design method was introduced, effectively mitigating the thermal expansion coefficient mismatch between the coating and the substrate through multiple transition layers, reducing internal stress, and enhancing interfacial bonding strength and thermomechanical stability. Subsequent heat treatment and sealing processes further improved the crystallinity and sealing properties of the coating, thereby comprehensively enhancing its corrosion resistance, chemical stability, and long-term service life in highly corrosive plasma environments. Attached Figure Description

[0039] Figure 1 This is a schematic diagram of the overall technical solution architecture of the plasma spraying process and gradient structure design method for the high corrosion-resistant yttrium oxide coating proposed in this invention.

[0040] Figure 2 This is a schematic diagram of the core principle framework of the gradient structure design method in this invention;

[0041] Figure 3 This is a logical flow diagram of the substrate surface pretreatment and cleaning process in this invention;

[0042] Figure 4 This is a logical flowchart of the optimization of plasma spraying process parameters and orthogonal experimental design in this invention;

[0043] Figure 5 This is a logical flow diagram of the coating post-treatment process (including heat treatment and sealing) in this invention;

[0044] Figure 6This is a schematic diagram illustrating the multi-level thermal expansion coefficient matching and stress buffering relationship between the substrate, gradient transition layer, and yttrium oxide coating in this invention. Detailed Implementation

[0045] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments.

[0046] Currently, as semiconductor manufacturing processes continue to evolve towards higher process nodes, plasma etching technology is developing towards higher energy density, higher reactivity, and longer-term stable operation. Against this backdrop, components exposed to highly corrosive plasmas containing fluorine and chlorine within the etching chamber face unprecedented service challenges. These high-energy plasmas not only cause severe physical sputtering and chemical erosion of material surfaces but also easily induce micropores, cracks, and particle detachment within the coating, thereby contaminating the wafer surface and severely impacting chip yield. Therefore, there is an urgent need to develop a protective coating system that combines low porosity, high density, excellent high-temperature corrosion resistance, and good interfacial bonding strength to meet the stringent reliability requirements of advanced processes. To address the aforementioned technical problems, this invention proposes an optimized pretreatment process involving degreasing and cleaning, sandblasting and roughening, ultrasonic vibration, and drying. This significantly improves the cleanliness and roughness of the substrate surface, providing a foundation for excellent coating adhesion. By employing precisely controlled plasma spraying process parameters, particularly the 8th set of parameters optimized through orthogonal experiments, combined with the characteristics of highly corrosion-resistant yttrium oxide composite powder, a low-porosity, high-density, and uniform microstructure is achieved in the coating. A gradient structure design method is introduced, effectively mitigating the thermal expansion coefficient mismatch between the coating and the substrate through multiple transition layers, reducing internal stress, and enhancing interfacial bonding strength and thermomechanical stability. Subsequent heat treatment and sealing treatment further improve the crystallinity and sealing properties of the coating, thereby comprehensively enhancing the coating's corrosion resistance, chemical stability, and long-term service life in highly corrosive plasma environments. This invention is applied to the plasma spraying process and gradient structure design method for highly corrosion-resistant yttrium oxide coatings.

[0047] refer to Figure 3The logical flow diagram of the substrate surface pretreatment and cleaning process in this invention clearly illustrates the complete processing link from the original component to the clean substrate before spraying. In the above-mentioned plasma spraying process and gradient structure design method for high corrosion-resistant yttrium oxide coating, step 1 involves degreasing and cleaning the equipment components by placing them in a degreasing soaking tank at a temperature of 60 degrees Celsius ± 5 degrees Celsius for 10 to 20 minutes to remove processing grease and contaminants from the component surface. Specifically, the degreasing agent used in step 1 is an alkaline degreasing agent with a pH value of 10 to 12. The degreasing soaking tank is equipped with a constant temperature heating system and a mechanical stirring device, with a stirring speed of 50 to 100 revolutions per minute to ensure uniform and thorough degreasing. The alkaline environment of the degreaser effectively saponifies and emulsifies residual mineral oil, cutting fluid, and fingerprint contaminants on the metal surface. A constant temperature control system maintains the solution temperature fluctuation within ±2 degrees Celsius. A mechanical stirring device uses rotating blades to create forced convection, ensuring the degreaser fully contacts all surface areas of the component. This is especially beneficial for etched cavity components with complex geometries or deep cavities, preventing dead zones in the cleaning process. The degreasing time is dynamically adjusted based on the component's surface area to volume ratio, with a lower limit of 10 minutes for small components and an upper limit of 20 minutes for large components, ensuring complete dissolution and removal of grease without damaging the base metal.

[0048] In the aforementioned plasma spraying process and gradient structure design method for high corrosion-resistant yttrium oxide coatings, step 2 involves immersing the component in pure water. The component is placed in a pure water immersion tank and immersed for 60 to 120 seconds to remove residual chemical degreasing solution. Specifically, the pure water immersion in step 2 uses ultrapure water with a resistivity greater than or equal to 18 megohm-cm. The immersion tank is equipped with an overflow device and a circulating filtration system with a filtration accuracy of 0.2 μm to maintain water purity. The high resistivity of ultrapure water ensures extremely low ion content, avoiding secondary pollution. The overflow device continuously introduces fresh ultrapure water and discharges bottom sediments. The circulating filtration system uses a polyethersulfone membrane filter to intercept suspended particles in real time, ensuring that the water conductivity remains below 0.055 microsiemens per centimeter during the immersion process. The immersion time is set to 60 to 120 seconds, which is sufficient to replace residual alkaline degreasing solution on the surface and in the crevices of the component, while preventing slight corrosion of the aluminum alloy substrate due to prolonged immersion.

[0049] In the aforementioned plasma spraying process and gradient structure design method for high corrosion-resistant yttrium oxide coatings, step 3 involves sandblasting the equipment components to roughen them and improve coating adhesion. Specifically, in step 3, white corundum abrasive is used as the abrasive, with a particle size of 80 to 120 mesh. The sandblasting pressure is 0.4 to 0.6 MPa, the spray gun moving speed is 100 to 200 mm / s, and the sandblasting angle is 70 to 90 degrees, resulting in a substrate surface roughness of 5 to 10 μm. White corundum abrasive has high hardness and sharp edges, effectively impacting the metal surface to form uniformly distributed anchoring pits. The sandblasting pressure is controlled within the range of 0.4 to 0.6 MPa; too low a pressure will not form a sufficiently deep rough structure, while too high a pressure will easily cause plastic deformation of the substrate or embedding of abrasive particles. The spray gun moves uniformly along a preset trajectory at a speed of 100 to 200 mm / s to ensure uniform processing, and the sandblasting angle is 70 to 90 degrees, impacting the surface perpendicularly or nearly perpendicularly to maximize the roughness generation efficiency. After processing, a profilometer was used to measure multiple points to ensure that the arithmetic mean roughness Ra value was stable in the range of 5 to 10 μm, providing an ideal mechanical interlocking interface for subsequent coatings.

[0050] In addition, after the sandblasting roughening treatment in step 3, the substrate surface undergoes an activation treatment using low-temperature plasma cleaning technology. The power is 500 to 800 watts, the treatment time is 5 to 10 minutes, and the gas is a mixture of argon and hydrogen in a volume ratio of 4:1. This activation treatment is carried out in a vacuum chamber, with the working pressure maintained at 50 to 100 Pa. The high-energy particles generated by the plasma discharge bombard the surface, further removing nanoscale organic contaminants and increasing the surface energy, reducing the water contact angle to below 10 degrees, and significantly improving the wettability and spreading ability of the subsequent powder coating.

[0051] In the aforementioned plasma spraying process and gradient structure design method for high corrosion-resistant yttrium oxide coatings, step 4 involves rinsing the components with a water-air gun to remove residual dust from the surface. Specifically, step 4 uses a mixture of deionized water and compressed air as the rinsing medium, with a water-to-air volume ratio of 1:3 to 1:5, a rinsing pressure of 0.3 to 0.5 MPa, and a nozzle diameter of 2 to 4 mm to ensure effective removal of sandblasting residue. The water-air mixture utilizes the Venturi effect to form a high-speed atomized jet, which can wash away loosely attached white corundum particles while avoiding water stains caused by pure water rinsing. The rinsing pressure of 0.3 to 0.5 MPa balances cleaning power with protection of the rough surface structure of the substrate, and the nozzle diameter of 2 to 4 mm adapts to the rinsing needs of components of different sizes. The operator holds the spray gun and moves it in a single direction to prevent cross-contamination.

[0052] In the aforementioned plasma spraying process and gradient structure design method for high corrosion-resistant yttrium oxide coatings, step 5 involves ultrasonically vibrating the equipment components to remove residual dust from the grooves and further improve coating adhesion. Specifically, step 5 uses a 40 kHz ultrasonic generator with a power density of 0.5 to 1.0 W / cm², and a processing time of 5 to 10 minutes, focusing on cleaning grooves deeper than 0.5 mm. Ultrasonic waves generate cavitation in the liquid, causing tiny bubbles to rapidly grow and violently collapse under sound pressure, releasing localized high-temperature and high-pressure shock waves that effectively remove stubborn dust from hidden areas such as grooves and threaded holes. A power density of 0.5 to 1.0 W / cm² ensures sufficient cavitation intensity for cleaning without damaging the substrate. The processing time is adjusted according to the depth and number of grooves, with a maximum of 10 minutes for complex structures.

[0053] In the aforementioned plasma spraying process and gradient structure design method for the high corrosion-resistant yttrium oxide coating, step 6 involves drying the components to prevent residual moisture from causing coating peeling. Specifically, step 6 employs a hot air circulation drying method with an air velocity of 2 to 4 meters per second, a relative humidity of less than 30%, and a drying time of 30 to 60 minutes, ensuring no visible water marks on the component surface. A multi-directional air supply system is installed in the hot air drying chamber, with an air velocity of 2 to 4 meters per second to promote moisture evaporation. The relative humidity is strictly controlled below 30% using silica gel desiccant or a refrigerated dehumidifier. The 30 to 60-minute drying time is sufficient to remove surface-adsorbed water and microporous capillary water. Immediately after drying, the component proceeds to the spraying process to prevent the re-adsorption of moisture from the air.

[0054] refer to Figure 1The schematic diagram of the overall technical solution architecture of the plasma spraying process and gradient structure design method for high corrosion-resistant yttrium oxide coating proposed in this invention illustrates the integrated process from pretreatment, gradient spraying to post-treatment. In the aforementioned plasma spraying process and gradient structure design method for high corrosion-resistant yttrium oxide coating, step 7 involves selecting different process parameters for plasma spraying. The parameter ranges include a current of 550 to 600 amperes, a power of 32 to 36 kilowatts, an argon flow rate of 35 to 45 standard liters per minute, a hydrogen flow rate of 6 to 8 standard liters per minute, a spraying distance of 130 to 150 mm, and a powder feeding rate of 18 to 22 grams per minute, comparing the corrosion resistance of the composite coating. Specifically, in step 7, the plasma spraying uses high corrosion-resistant yttrium oxide composite powder with a particle size distribution of 15 to 45 μm, a sphericity greater than or equal to 95%, and a flowability less than or equal to 25 seconds per 50 grams. The yttrium oxide mass fraction is 92% to 96%, and zirconium oxide and alumina are added as stabilizers. This composite powder is prepared using a plasma spheroidization process to ensure high sphericity, facilitating pneumatic transport and melting. The introduction of zirconium oxide and alumina suppresses the phase transformation of yttrium oxide at high temperatures and reduces oxygen vacancy concentration, thereby improving chemical stability. The spraying process employs an atmospheric plasma spraying system with a high-energy plasma spray gun. The anode nozzle diameter is 8 mm, the cathode diameter is 4 mm, the arc voltage is 60 to 80 volts, and the arc current fluctuation is less than ±5%. Stable arc parameters ensure that the plasma flame temperature reaches 12,000 to 15,000 Kelvin, allowing the powder particles to fully melt and impact the substrate surface at high speed, forming a dense layered structure.

[0055] The gradient structure design method includes setting at least two transition layers between the substrate and the yttrium oxide coating. The transition layer material is a composite powder of yttrium oxide and a nickel-based alloy (such as Inconel 600), with the metal content decreasing by mass fraction from 30% in the inner layer to 5% in the outer layer. Each layer has a thickness of 20 to 30 μm. (Reference) Figure 2 The schematic diagram of the core principle framework of the gradient structure design method in this invention illustrates the continuous transition between composition and performance. The inner transition layer is rich in metals (such as nickel or cobalt), and its coefficient of thermal expansion is close to that of the stainless steel or aluminum alloy substrate. The outer transition layer has a lower metal content, and its coefficient of thermal expansion gradually approaches that of pure yttrium oxide. Specifically, in the gradient structure design method, the coefficient of thermal expansion of the transition layer gradually decreases from the substrate side to the coating side. The coefficient of thermal expansion of the inner transition layer is 10 to 12 per degree Celsius multiplied by 10 to the power of -6, and the coefficient of thermal expansion of the outer transition layer is 8 to 9 per degree Celsius multiplied by 10 to the power of -6, which matches the coefficient of thermal expansion of the yttrium oxide coating. (Reference) Figure 6The schematic diagram of the multi-level thermal expansion coefficient matching and stress buffering relationship between the substrate, gradient transition layer and yttrium oxide coating in this invention intuitively presents the gradient release mechanism of thermal stress. By adjusting the powder ratio of the powder feeding system layer by layer, different composite powders are switched in real time during the spraying process to achieve continuous transition of composition and performance, effectively suppressing interfacial peeling caused by thermal expansion mismatch during thermal cycling.

[0056] In the aforementioned plasma spraying process and gradient structure design method for the high corrosion-resistant yttrium oxide coating, step 8 involves using orthogonal experimental design to test eight sets of comparative experimental data and selecting the eighth set of process parameters. Specifically, these parameters are: current 600-650 amperes, argon flow rate 40-45 standard liters per minute, hydrogen flow rate 4-8 standard liters per minute, powder feed rate 15-20 grams per minute, and spraying distance 130-160 mm, achieving a corrosion resistance time of 8 hours in a 5% hydrochloric acid solution. Specifically, the orthogonal experimental design in step 8 employs a mixed orthogonal array with four factors at two levels plus one factor at four levels. The factors examined include current, argon flow rate, hydrogen flow rate, powder feed rate, and spraying distance. Each factor has two or four levels, resulting in a total of eight sets of experiments. Through range analysis and variance analysis, the influence weights of each factor on coating porosity, bonding strength and corrosion resistance were determined, and the 8th parameter combination was finally selected. The specific levels of each factor in the orthogonal experiment were as follows: current level: 550A, 600A, 650A; argon flow rate level: 35SLPM, 40SLPM, 45SLPM; hydrogen flow rate level: 4SLPM, 6SLPM, 8SLPM; powder feeding rate level: 15g / min, 18g / min, 20g / min, 22g / min; spraying distance level: 130mm, 140mm, 150mm, 160mm. The experimental results are shown in Table 1. Range analysis (R value) determined that the current was the most important influencing factor (R=12.5). Analysis of variance (F value=15.2, p<0.05) confirmed that the comprehensive score of the 8th group of parameters (current 650A, argon 45SLPM, hydrogen 8SLPM, powder feeding 20g / min, distance 160mm) was the highest (corrosion resistance time 8 hours, porosity 1.8%, bonding strength 52MPa). Based on this, the parameters of this group were selected.

[0057] Under these parameters, a high current (600 to 650 amperes) provides sufficient heat to ensure complete powder melting, while a moderately reduced hydrogen flow rate (4 to 8 standard liters per minute) minimizes the adverse effects of the reducing atmosphere on yttrium oxide. Optimizing the powder feed rate (15 to 20 grams per minute) and spraying distance (130 to 160 mm) ensures droplet deposition under optimal flight conditions. The coating corresponding to the process parameters in step 8 exhibits a corrosion resistance time of 8 hours in a 5% hydrochloric acid solution, a coating thickness of 150 to 200 μm, a porosity of less than 2%, and a bonding strength greater than 50 MPa. Coating thickness is monitored online using an eddy current thickness gauge, porosity is determined using cross-sectional SEM images via image analysis, and bonding strength is tested using tensile testing according to ASTM C633 standards.

[0058] Following step 7, the sprayed coating undergoes heat treatment at 800 to 1000 degrees Celsius for 1 to 2 hours at a heating rate of 5 to 10 degrees Celsius per minute. After furnace cooling to 300 degrees Celsius, it is then air-cooled. The heat treatment is performed in an air-atmosphere muffle furnace, with slow heating to avoid thermal shock. The holding process promotes the crystallization of the amorphous phase and eliminates residual stress. Furnace cooling to 300 degrees Celsius followed by air cooling prevents rapid cooling from introducing new stress. After heat treatment, the crystallinity of the coating is significantly improved, and XRD patterns show that the main phase is cubic yttrium oxide, with no impurity phases formed.

[0059] refer to Figure 5 The logical flow diagram of the post-coating treatment process (including heat treatment and sealing) in this invention illustrates the synergistic effect of heat treatment and sealing. It also includes sealing the final coating using nano-alumina sol as the sealing agent. The sol particle size is 10 to 20 nanometers, and the solid content of the sealing agent is 10% to 15%. The sol is applied by immersion for 10 to 20 minutes, followed by drying at 150 degrees Celsius for 30 minutes. The nano-alumina sol has high permeability, penetrating deep into the micropores of the coating surface. After drying, it forms a dense alumina network, effectively blocking the penetration path of corrosive media. After sealing, the corrosion resistance time of the coating in a 5% hydrochloric acid solution can be further extended to more than 12 hours.

[0060] In the aforementioned plasma spraying process and gradient structure design method for high corrosion-resistant yttrium oxide coatings, step 9 involves ultrasonically cleaning the component by placing it in an ultrasonic pure water cleaning tank for 10 to 30 minutes. Specifically, step 9 uses multi-frequency ultrasound with a main frequency of 40 kHz and an auxiliary frequency of 80 kHz. The cleaning solution temperature is 40 to 60 degrees Celsius, and a nonionic surfactant is added at a concentration of 0.1 to 0.3 g / L. The multi-frequency ultrasound covers cavitation bubbles of different sizes, efficiently removing unmelted particles or dust that may adhere during the spraying process. The nonionic surfactant reduces surface tension and enhances the wetting ability of the cleaning solution on micropores.

[0061] In the aforementioned plasma spraying process and gradient structure design method for the high corrosion-resistant yttrium oxide coating, step 10 involves drying the component by placing it in a cleanroom oven at a temperature of 120 degrees Celsius ± 5 degrees Celsius for 2 hours. Specifically, the cleanroom oven in step 10 is equipped with a high-efficiency particulate air filter with a filtration efficiency of 99.99%, and the hot air circulation system uses corrosion-resistant stainless steel ducts with a temperature uniformity of ± 2 degrees Celsius. The high-efficiency filter ensures that the drying environment achieves ISO Class 5 cleanliness, preventing particulate contamination of the finished coating surface, and the temperature uniformity ensures the overall performance consistency of the coating.

[0062] The method is applied to the preparation of protective coatings for semiconductor etching cavity components. The components are made of aluminum alloy or stainless steel, with a maximum size not exceeding 500 mm. The coating coverage reaches over 99%, and the surface roughness is less than 1 μm. For a typical etching cavity cover plate (400 mm x 300 mm), a robot equipped with a plasma spray gun is used to scan along a pre-programmed path to ensure full coverage of complex curved surfaces. After slight polishing, the surface roughness Ra value of the coating is controlled at 0.8 μm, meeting the stringent particle control requirements of semiconductor processes.

[0063] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of the present invention is defined by the appended claims and their equivalents.

Claims

1. A plasma spraying method for preparing a highly corrosion-resistant yttrium oxide coating, characterized in that: The specific steps include the following: Step 1: Degrease and clean the equipment parts by placing them in a degreasing soaking tank at a temperature of 60℃±5℃ for 10 to 20 minutes. Step 2: Immerse the component in pure water. Place the component in a pure water immersion tank and immerse for 60 to 120 seconds. Step 3: Roughen the equipment parts with sandblasting; Step 4: Rinse the parts with a steam gun; Step 5: Perform ultrasonic vibration treatment on the equipment components; Step 6: Dry the components; Step 7: Deposit at least two transition layers on the component surface using the first set of plasma spraying process parameters. The first set of spraying parameters includes a current of 550 to 600 amperes, a power of 32 to 36 kilowatts, an argon flow rate of 35 to 45 standard liters per minute, a hydrogen flow rate of 6 to 8 standard liters per minute, a spraying distance of 130 to 150 mm, and a powder feed rate of 18 to 22 grams per minute. Step 8: Perform the final spraying of the yttrium oxide coating using the second set of optimized process parameters. The second set of optimized parameters includes a current of 600 to 650 amperes, an argon flow rate of 40 to 45 standard liters per minute, a hydrogen flow rate of 4 to 8 standard liters per minute, a powder feed rate of 15 to 20 grams per minute, and a spraying distance of 130 to 160 mm. Step 9: Perform ultrasonic cleaning on the coated parts; Step 10: Dry the parts.

2. The plasma spraying process and gradient structure design method for a high corrosion-resistant yttrium oxide coating according to claim 1, characterized in that: In step 1, the degreasing cleaning uses an alkaline degreasing agent with a pH value of 10 to 12. The degreasing soaking tank is equipped with a constant temperature heating system and a mechanical stirring device with a stirring speed of 50 to 100 revolutions per minute. In step 2, the pure water soaking uses ultrapure water with a resistivity ≥18MΩ·cm. The soaking tank is equipped with an overflow device and a circulating filtration system with a filtration accuracy of 0.2μm.

3. The plasma spraying process and gradient structure design method for a high corrosion-resistant yttrium oxide coating according to claim 1, characterized in that: In step 3, the sandblasting roughening treatment uses white corundum sand as the abrasive with a particle size of 80 to 120 mesh, a sandblasting pressure of 0.4 to 0.6 MPa, a spray gun moving speed of 100 to 200 mm / s, and a sandblasting angle of 70 to 90 degrees, so that the surface roughness of the substrate reaches 5 to 10 μm. In step 4, the steam-water gun rinsing uses a mixture of deionized water and compressed air as the medium, with a water-to-air volume ratio of 1:3 to 1:5, a rinsing pressure of 0.3 to 0.5 MPa, and a nozzle diameter of 2 to 4 mm.

4. The plasma spraying process and gradient structure design method for a high corrosion-resistant yttrium oxide coating according to claim 1, characterized in that: In step 5, the ultrasonic oscillation treatment uses an ultrasonic generator with a frequency of 40 kHz, a power density of 0.5 to 1.0 W / cm², and a treatment time of 5 to 10 minutes; in step 6, the drying treatment uses a hot air circulation drying method with a wind speed of 2 to 4 meters per second, a relative humidity of <30%, and a drying time of 30 to 60 minutes.

5. The plasma spraying process and gradient structure design method for a high corrosion-resistant yttrium oxide coating according to claim 1, characterized in that: In step 7, the plasma spraying uses a high corrosion-resistant yttrium oxide composite powder with a particle size distribution of 15 to 45 μm, sphericity ≥95%, and flowability ≤25 seconds / 50 g. The yttrium oxide mass fraction is 92% to 96%, and zirconium oxide and aluminum oxide are added as stabilizers. The spray gun used in the atmospheric plasma spraying system is a high-energy plasma spray gun with an anode nozzle diameter of 8 mm, a cathode diameter of 4 mm, an arc voltage of 60 to 80 volts, and an arc current fluctuation of < ±5%.

6. The plasma spraying process and gradient structure design method for a high corrosion-resistant yttrium oxide coating according to claim 1, characterized in that: In the gradient structure design method, the thermal expansion coefficient of the transition layer gradually decreases from the substrate side to the coating side, and the thermal expansion coefficient of the inner transition layer is 10 to 12 × 10⁻⁶. -6 / ℃, the coefficient of thermal expansion of the outer transition layer is 8 to 9 × 10⁻⁶. -6 / ℃, which matches the coefficient of thermal expansion of the yttrium oxide coating.

7. The plasma spraying process and gradient structure design method for a high corrosion-resistant yttrium oxide coating according to claim 1, characterized in that: It also includes heat treatment of the sprayed coating after step 7, with a heat treatment temperature of 800 to 1000°C, a holding time of 1 to 2 hours, a heating rate of 5 to 10°C per minute, and air cooling after furnace cooling to 300°C; and activation treatment of the substrate surface after sandblasting roughening treatment in step 3, using low-temperature plasma cleaning technology, with a power of 500 to 800 watts, a treatment time of 5 to 10 minutes, and a mixture of argon and hydrogen in a volume ratio of 4:

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8. The plasma spraying process and gradient structure design method for a high corrosion-resistant yttrium oxide coating according to claim 1, characterized in that: The process also includes sealing the final coating by using nano-alumina sol as a sealing agent. The sol particle size is 10 to 20 nanometers, and the solid content of the sealing agent is 10% to 15%. The sol is applied by immersion for 10 to 20 minutes, followed by drying at 150°C for 30 minutes. In step 9, the ultrasonic cleaning uses multi-frequency ultrasound with a main frequency of 40 kHz and an auxiliary frequency of 80 kHz. The cleaning solution temperature is 40 to 60°C, and a nonionic surfactant is added at a concentration of 0.1 to 0.3 g per liter.

9. The plasma spraying process and gradient structure design method for a high corrosion-resistant yttrium oxide coating according to claim 1, characterized in that: The method is applied to the preparation of protective coatings for semiconductor etching cavity components. The component material is aluminum alloy or stainless steel, the maximum size does not exceed 500 mm, the coating coverage reaches more than 99%, and the surface roughness is <1 μm. The coating prepared using the optimized process parameters in step 8 has a corrosion resistance time of ≥8 hours in 5% hydrochloric acid solution, a coating thickness of 150 to 200 μm, a porosity of <2%, and a bonding strength of >50 MPa.

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