Method for preparing yttrium fluoride composite ceramic coating through atmospheric plasma spraying and application

Abstract

The invention relates to the technical field of surface engineering, discloses a method and a system for preparing a yttrium fluoride composite ceramic coating through atmospheric plasma spraying, and aims to solve the problems that the yttrium fluoride coating generates a brittle aluminum fluoride layer on the surface of an aluminum substrate due to fluorine ion diffusion, so that the bonding strength is low, and the yttrium fluoride coating is easy to peel off and lose efficacy. The method comprises the following steps: sequentially carrying out mechanical polishing, ultrasonic cleaning and sand blasting roughening on an aluminum base material; preparing composite powder formed by mixing yttrium fluoride, yttrium oxide and nanometer aluminum oxide according to the mass ratio of 75: 20: 5; sequentially depositing a yttrium oxide transition layer, a composite barrier layer and a yttrium fluoride functional layer by adopting atmospheric plasma spraying; and finally carrying out vacuum post-heat treatment. According to the system, through the synergistic effect of the three layers of gradient structures, the transition layer forms an yttrium aluminate metallurgical bonding interface, the barrier layer inhibits fluorine ion diffusion through the dual mechanisms of nanometer aluminum oxide physical barrier and yttrium oxide chemical adsorption, and the functional layer guarantees the plasma erosion resistance. According to the method, the bonding strength of the coating is remarkably improved to 50 MPa or above, the porosity is lower than 3%, stripping is avoided under 500-hour high-energy plasma bombardment, the process cost is reduced by 40%, and the method is suitable for cavity protection of semiconductor etching equipment.

Description

Technical Field

[0001] This invention belongs to the field of surface engineering technology, specifically relating to a method and application for preparing yttrium fluoride composite ceramic coatings by atmospheric plasma spraying. Background Technology

[0002] As semiconductor manufacturing processes continue to evolve towards 7nm and below nodes, the long-term stability of etching equipment in high-density plasma environments has become a core bottleneck restricting yield and production capacity. The etching chamber, as a key reaction vessel for process gas ionization and selective material removal, requires its inner wall coating to maintain structural integrity and chemical inertness under extreme physicochemical conditions. Yttrium fluoride, due to its excellent resistance to fluorine plasma erosion, high dielectric strength, and low metal impurity release characteristics, is widely regarded as an ideal candidate material to replace traditional yttrium oxide coatings. However, when yttrium fluoride coatings are directly deposited on aluminum alloy substrates using atmospheric plasma spraying technology, the active fluoride ions released during the spraying process easily penetrate the coating / substrate interface, undergoing an irreversible reaction with aluminum to form a brittle aluminum fluoride phase. This leads to a sharp drop in interfacial bonding strength, and the coating is prone to lamellar peeling under thermal cycling or mechanical stress, severely weakening the chamber's protective lifespan.

[0003] In the prior art, the patent solution with publication number CN107287545B, while improving the corrosion resistance of the coating to some extent by controlling the oxygen content and deposition thickness of the yttrium fluoride spraying material, failed to effectively block the diffusion path of fluoride ions to the aluminum substrate. The interfacial reaction layer remained, and the bonding strength was not fundamentally improved. Another solution with publication number CN112063950B attempted to introduce oxy-yttrium fluoride components to optimize the chemical stability of the coating, but similarly neglected the physicochemical mechanism of interfacial fluoride migration. Furthermore, the stringent limitations on the particle size and packing density of the sprayed powder significantly increased the material preparation cost and the difficulty of controlling the process window. None of the above solutions have constructed a systematic solution from substrate surface state control and interfacial reaction suppression to the densification of the functional layer, resulting in the coating still facing the risk of early failure in high-end etching equipment.

[0004] Therefore, there is an urgent need for an atmospheric plasma spraying method that can synergistically optimize the parameters of substrate pretreatment, interface transition layer construction, and functional layer deposition. This method should suppress fluoride ion penetration through a dual mechanism of physical barrier and process synergy, fundamentally solving the problem of interface bonding failure between yttrium fluoride coating and aluminum substrate. At the same time, it should take into account the feasibility of the process and the controllability of costs, so as to meet the urgent needs of advanced semiconductor manufacturing for high reliability and long service life of cavity protective coatings. Summary of the Invention

[0005] This invention provides a method and application for preparing yttrium fluoride composite ceramic coatings using atmospheric plasma spraying. It aims to address the technical shortcomings of existing yttrium fluoride coatings on aluminum substrates, where the diffusion of fluoride ions leads to the formation of a brittle aluminum fluoride layer at the interface, resulting in insufficient coating bonding strength and easy peeling failure. Simultaneously, it overcomes the engineering bottlenecks of stringent control of spraying material composition, complex processes, high costs, and difficulty in large-scale application. This invention constructs a multi-layer gradient composite structure coating system, introduces a synergistic mechanism between the interface transition layer and the functional barrier layer, and optimizes the powder material ratio and thermal spraying process parameters. Without altering the substrate's intrinsic properties, it significantly improves the metallurgical bonding strength between the coating and the aluminum substrate, effectively inhibiting the penetration and diffusion of fluoride ions to the substrate interface, and ensuring the structural integrity and service stability of the coating under long-term high-energy plasma bombardment.

[0006] As one embodiment of the present invention, the method for preparing yttrium fluoride composite ceramic coating by atmospheric plasma spraying includes the following steps:

[0007] The first step involves pre-treating the surface of the aluminum substrate. This pre-treatment includes sequential mechanical grinding, ultrasonic cleaning, and sandblasting roughening. Mechanical grinding uses 240-mesh silicon carbide sandpaper to grind the surface repeatedly in a single direction until no visible oxide film remains. Ultrasonic cleaning uses a cleaning solution of deionized water and anhydrous ethanol at a 1:1 volume ratio, and is performed for 10 minutes at a frequency of 40 kHz and a power of 300 W. Sandblasting roughening uses brown corundum abrasive with a particle size range of 0.3 mm to 0.5 mm, a spray pressure of 0.4 MPa, a spray angle of 80°, and a spray distance of 150 mm. After treatment, the surface roughness of the substrate reaches 3.5 μm to 5 μm.

[0008] The second step involves preparing a composite spraying powder material. This composite spraying powder material is composed of a uniformly mixed yttrium fluoride main phase powder, yttrium oxide transition phase powder, and nano-alumina dispersed phase powder in a mass percentage ratio of 75:20:5. The yttrium fluoride main phase powder has a purity of not less than 99.9% and an average particle size of 30 μm to 50 μm, exhibiting a spherical or near-spherical shape. The yttrium oxide transition phase powder has a purity of not less than 99.5% and an average particle size of 20 μm to 40 μm, exhibiting an irregular polygonal shape. The nano-alumina dispersed phase powder has a purity of not less than 99.9% and an average particle size of 50 nm to 100 nm, exhibiting a spherical shape.

[0009] The third step involves sequentially depositing a transition layer, a barrier layer, and a functional layer on the pretreated aluminum substrate surface using an atmospheric plasma spraying system. The transition layer is deposited using pure yttrium oxide powder at a spraying power of 40kW, a primary gas flow rate of 40L / min (argon), a secondary gas flow rate of 8L / min (hydrogen), a powder feed rate of 30g / min, and a spraying distance of 100mm, with a thickness controlled to be 20µm to 30µm. The barrier layer is deposited using the aforementioned composite spraying powder material at a spraying power of 45kW and a primary gas flow rate of argon. The deposition process is carried out with a flow rate of 45 L / min, a secondary gas flow rate of 10 L / min, a powder feeding rate of 25 g / min, and a spraying distance of 120 mm, with the thickness controlled to be 50 μm to 80 μm. The functional layer is deposited using pure yttrium fluoride powder under the following process parameters: a spraying power of 50 kW, a primary gas flow rate of 50 L / min, a secondary gas flow rate of 12 L / min, a powder feeding rate of 20 g / min, and a spraying distance of 150 mm, with the thickness controlled to be 100 μm to 200 μm.

[0010] The fourth step is to perform a post-heat treatment on the entire coating after all coating deposition is completed. The post-heat treatment is carried out in a vacuum furnace with a vacuum degree of not less than -103 Pa, a heating rate of 5℃ / min, a holding temperature of 400℃, and a holding time of two hours. Then, the coating is cooled to room temperature in the furnace.

[0011] In one embodiment of the present invention, the transition layer is used to generate a yttrium aluminate metallurgical bonding layer with a thickness of less than 5 μm by a controllable in-situ reaction between yttrium oxide and the surface of the aluminum substrate during high-temperature spraying. This bonding layer has a thermal expansion coefficient similar to that of the aluminum substrate, which can effectively alleviate the thermal stress concentration between the coating and the substrate. At the same time, yttrium oxide itself has strong chemical inertness and can block the migration of fluoride ions towards the substrate.

[0012] In one embodiment of the present invention, the nano-alumina dispersed phase in the barrier layer is uniformly distributed at the grain boundaries of yttrium fluoride and yttrium oxide during the spraying process, forming a physical diffusion barrier network. Its high melting point and chemical stability can effectively pin the migration path of fluoride ions. The yttrium oxide phase, as a fluoride ion adsorption carrier, captures free fluoride ions through lattice vacancies, reducing their active concentration. The yttrium fluoride phase, as the main structure, provides resistance to plasma corrosion. The synergistic effect of the three phases achieves a reduction of more than 80% in the diffusion flux of fluoride ions.

[0013] In one embodiment of the present invention, the functional layer is deposited with high-purity yttrium fluoride powder to ensure that the coating surface has optimal resistance to fluorine plasma erosion and dielectric properties. Its dense structure can prevent process gases from penetrating into the underlying structure and maintain the long-term effectiveness of the barrier layer.

[0014] As one embodiment of the present invention, the post-heat treatment process promotes the healing of microcracks inside the coating and the release of residual stress. At the same time, it promotes the grain growth and interface densification of the yttrium aluminate phase between the transition layer and the substrate, thereby increasing the overall bonding strength of the coating to no less than 50 MPa and reducing the porosity to below 3%.

[0015] As one embodiment of the present invention, the method for preparing a yttrium fluoride composite ceramic coating by atmospheric plasma spraying is applied to the protection of the inner wall of a semiconductor etching equipment cavity. The cavity is made of 6061 aluminum alloy or 7075 aluminum alloy, and the working environment is a fluorine-containing plasma atmosphere with a plasma energy density of not less than 10 W / cm². 2 The operating temperature range is 50℃ to 200℃, and the continuous working time is not less than 500 hours.

[0016] As one embodiment of the present invention, during service, the coating structure has a transition layer that maintains the metallurgical bonding stability of the interface, a barrier layer that continuously inhibits the penetration of fluoride ions into the substrate, and a functional layer that resists plasma physical sputtering and chemical erosion. The synergistic effect of the three layers ensures that the coating does not peel off, blister, or have penetrating cracks after 500 hours of plasma bombardment, with a surface roughness change rate of less than 10% and a mass loss rate of less than 0.5%.

[0017] In one embodiment of the present invention, the composite spraying powder material is mixed using a three-dimensional mixer for two hours at a rotation speed of 30 r / min. After mixing, the powder's flowability index is not less than 254 s / 50g, and its loose density is not less than 1.8 g / m³. 3 It meets the requirements for continuous and stable powder feeding in atmospheric plasma spraying.

[0018] In one embodiment of the present invention, the substrate surface is immediately coated after the sandblasting roughening treatment, with an interval of no more than two hours, in order to prevent surface re-oxidation or adsorption of pollutants from affecting the coating adhesion performance.

[0019] In one embodiment of the present invention, during the atmospheric plasma spraying process, a circulating water cooling system is provided on the back of the substrate to control the surface temperature of the substrate to not exceed 250°C, thereby preventing the aluminum alloy substrate from overheating and softening or undergoing a phase change.

[0020] In one embodiment of the present invention, the total thickness of the coating is controlled within the range of 170 μm to 310 μm, wherein the thickness ratio of the transition layer, the barrier layer, and the functional layer is 1:2.5:5. This ratio is determined by thermal stress simulation and fluoride ion diffusion kinetics calculation, which can take into account the bonding strength, barrier performance, and process feasibility.

[0021] In one embodiment of the present invention, the nano-alumina dispersed phase forms a three-dimensional network distribution structure in the barrier layer, with a volume fraction of 5% and an average spacing of less than 500 nm. This scale can effectively hinder the diffusion path of fluoride ions along the grain boundary, while not affecting the overall density and mechanical strength of the coating.

[0022] In one embodiment of the present invention, the yttrium oxide transition phase powder accounts for 20% of the barrier layer. Its polygonal morphology can increase the mechanical interlocking area with the yttrium fluoride main phase and improve the bonding strength within the layer. At the same time, its surface hydroxyl groups can react with fluoride ions at high temperature to generate yttrium fluoride oxide, thereby achieving chemical adsorption and fixation.

[0023] As one embodiment of the present invention, before the functional layer is deposited, the surface of the barrier layer is lightly cleaned with argon plasma to remove surface adsorbed impurities and loose particles. The cleaning power is 20kW, the argon flow rate is 10L / min, and the processing time is 30s, so as to improve the interlayer bonding quality.

[0024] As one embodiment of the present invention, the microstructure of the coating cross section shows that there is a continuous yttrium aluminate reaction layer at the interface between the transition layer and the substrate, with uniform thickness; the barrier layer presents a composite structure in which yttrium fluoride grains are wrapped by yttrium oxide and nano-alumina; the functional layer is a dense columnar crystal growth morphology, and there are no obvious pores or cracks at the interlayer interface.

[0025] In one embodiment of the present invention, the coating undergoes a scratch test, with a critical load of not less than 80N; it undergoes a thermal shock cycle test, showing no cracking or peeling after 100 cycles between 200°C and room temperature; and it undergoes an electrochemical impedance spectroscopy test, maintaining an impedance modulus of 10 in a fluorine-containing electrolyte. 7 (Ω·cm 2 The above demonstrates its excellent corrosion resistance and impermeability.

[0026] As one embodiment of the present invention, the coating prepared by the method can extend the maintenance cycle of the semiconductor etching cavity by more than three times, reduce the particle contamination rate by 90%, and increase the overall equipment yield by 5% in practical applications of semiconductor etching cavities.

[0027] Compared with the prior art, the advantages and positive effects of the present invention are as follows:

[0028] This invention fundamentally solves the technical problem of insufficient bonding strength between the yttrium fluoride coating and the aluminum substrate due to the formation of brittle aluminum fluoride caused by fluoride ion diffusion at the interface by constructing a three-layer gradient structure system consisting of a yttrium oxide transition layer, a yttrium fluoride-yttrium oxide-nano alumina composite barrier layer, and a yttrium fluoride functional layer. The transition layer forms a yttrium aluminate metallurgical bonding interface through in-situ reaction, significantly improving the bonding strength between the coating and the substrate. The barrier layer utilizes the dual mechanisms of the physical barrier of nano alumina and the chemical adsorption of yttrium oxide to effectively inhibit the penetration of fluoride ions into the substrate, achieving a diffusion inhibition efficiency of over 80%. The functional layer ensures the surface layer's resistance to plasma erosion. The synergistic effect of the three layers increases the coating bonding strength to over 50 MPa, with a porosity of less than 3%, and prevents peeling failure under 500 hours of high-energy plasma bombardment. Meanwhile, this invention uses conventional atmospheric plasma spraying equipment and standardized powder materials, eliminating the need for special atmosphere protection or complex precursor treatment. The process parameters are clear and controllable, reducing production costs by 40%, making it suitable for large-scale industrial applications and meeting the comprehensive requirements of advanced semiconductor equipment with seven-nanometer and below processes for high reliability, long life, and low cost of cavity protective coatings. Attached Figure Description

[0029] Figure 1 This is a schematic diagram of the overall technical solution architecture of the method and application of preparing yttrium fluoride composite ceramic coating by atmospheric plasma spraying proposed in this invention.

[0030] Figure 2 This is a schematic diagram of the core principle framework of the multi-layer gradient composite structure coating system in this invention;

[0031] Figure 3 This is a flowchart illustrating the logical process of aluminum substrate pretreatment and composite powder material preparation in this invention.

[0032] Figure 4 This is a logical flow diagram of the three-stage spraying deposition and post-heat treatment of the transition layer, barrier layer and functional layer in this invention;

[0033] Figure 5 This is a schematic diagram of the multi-level interaction between the coating structure and the aluminum substrate and the fluoride ion diffusion inhibition mechanism in this invention;

[0034] Figure 6 SEM image of the cross-sectional morphology of the composite coating magnified 150 times for an embodiment of the present invention;

[0035] Figure 7 This is a SEM image of the cross-sectional morphology of the functional layer in the composite coating, magnified 500 times, according to an embodiment of the present invention. Detailed Implementation

[0036] Figure 1-5As shown in the figure, the method for preparing yttrium fluoride composite ceramic coating by atmospheric plasma spraying, as one embodiment of the present invention, encompasses four core stages: aluminum substrate surface pretreatment, composite spraying powder material preparation, multi-layer gradient structure coating deposition, and post-heat treatment. The entire process aims to suppress the diffusion of fluoride ions to the aluminum substrate interface, improve coating bonding strength, and ensure the long-term service stability of the coating in a high-energy plasma environment. This is achieved through a three-pronged approach: material composition design, structural gradient construction, and synergistic optimization of process parameters.

[0037] In the first step, the aluminum substrate surface undergoes pretreatment, which includes mechanical grinding, ultrasonic cleaning, and sandblasting roughening. Mechanical grinding uses 240-mesh silicon carbide sandpaper to grind in a single direction until no visible oxide film remains. This operation aims to thoroughly remove the naturally formed alumina passivation film on the aluminum substrate surface, exposing a fresh metal surface and providing a clean base for subsequent sandblasting roughening and coating deposition. During grinding, constant pressure and a unidirectional trajectory must be maintained to avoid cross-grinding, which could disrupt the direction of surface scratches and affect the uniformity of subsequent sandblasting. Ultrasonic cleaning uses a cleaning solution of deionized water and anhydrous ethanol at a 1:1 volume ratio, cleaned for 10 minutes at a frequency of 40 kHz and a power of 300 W. This step dissolves and removes micron-sized particles and organic contaminants remaining from grinding, ensuring the substrate surface is free of grease, dust, and chemical residues. After cleaning, the substrate must be immediately transferred to a dry, clean environment to prevent secondary contamination from moisture and dust in the air. The sandblasting roughening treatment uses brown corundum abrasive with a particle size ranging from 0.3 mm to 0.5 mm, a blasting pressure of 0.4 MPa, a blasting angle of 80°, and a blasting distance of 150 mm. After treatment, the surface roughness of the substrate reaches 3.5 μm to 5 μm. During sandblasting, the abrasive impacts the aluminum substrate surface at high speed, forming a uniformly distributed micron-sized pit and protrusion structure, significantly increasing the mechanical bonding area between the coating and the substrate. The 80° blasting angle ensures that the abrasive impacts the surface in a near-vertical direction, avoiding localized stress concentration or surface tearing caused by oblique impact. The 150 mm blasting distance ensures that the abrasive's kinetic energy is sufficiently attenuated before impact, preventing excessive erosion of the substrate surface and structural damage. After sandblasting, the substrate surface is immediately coated, with an interval not exceeding two hours, to prevent surface re-oxidation or adsorption of contaminants that could affect the coating's adhesion. If coating needs to be delayed due to equipment scheduling or process arrangements, the substrate must be temporarily stored in an inert gas protection chamber with nitrogen purity not less than 99.9% and relative humidity controlled below 5%.

[0038] In the second step, a composite spraying powder material is prepared. This composite spraying powder material is composed of a uniformly mixed yttrium fluoride main phase powder, yttrium oxide transition phase powder, and nano-alumina dispersed phase powder in a mass percentage ratio of 75:20:5. The yttrium fluoride main phase powder has a purity of not less than 99.9%, an average particle size of 30 μm to 50 μm, and is spherical or near-spherical. This morphology ensures excellent flowability and melt uniformity of the powder during atmospheric plasma spraying, reduces the proportion of unmelted particles, and improves the coating density. The yttrium oxide transition phase powder has a purity of not less than 99.5%, an average particle size of 20 μm to 40 μm, and is irregularly polygonal. This morphology design aims to enhance its mechanical interlocking ability with the yttrium fluoride main phase in the barrier layer. Simultaneously, the polygonal edges are more likely to react with fluoride ions during high-temperature melting to generate a yttrium fluoride oxide phase, achieving chemical adsorption and fixation. The nano-alumina dispersed phase powder has a purity of no less than 99.9%, an average particle size of 50nm to 100nm, and is spherical. This size and morphology ensure that it can be uniformly dispersed at the grain boundaries of yttrium fluoride and yttrium oxide during spraying, forming a physical diffusion barrier network. Its high melting point and chemical stability can effectively pin the migration path of fluoride ions. The mixing process uses a three-dimensional mixer with a mixing time of two hours and a rotation speed of 30r / min. After mixing, the powder flowability index is no less than 254s / 50g, and the loose density is no less than 1.8g / m³. 3 This system meets the requirements for continuous and stable powder feeding in atmospheric plasma spraying. During the mixing process, the three-dimensional mixer uses the compound rotational motion of the container in three-dimensional space to cause powder components of different particle sizes and densities to repeatedly tumble, shear, and diffuse under the action of gravity and inertial forces, ultimately achieving a uniform distribution at the microscale. After mixing, the powder needs to be sieved through an 80-mesh sieve to remove agglomerated particles and impurities, ensuring that the powder feeding system is free from clogging risks. After sieving, the powder is placed in a dry, sealed container filled with dry nitrogen to prevent the powder from absorbing moisture and clumping, which would affect the stability of the spraying.

[0039] In the third step, an atmospheric plasma spraying system is used to sequentially deposit a transition layer, a barrier layer, and a functional layer on the pretreated aluminum substrate surface. The transition layer is deposited using pure yttrium oxide powder under the following process parameters: spraying power of 40kW, argon as the primary gas with a flow rate of 40L / min, hydrogen as the secondary gas with a flow rate of 8L / min, powder feed rate of 30g / min, and spraying distance of 100mm. The thickness is controlled to be 20µm to 30µm. This combination of process parameters ensures that the yttrium oxide powder is fully melted in the plasma flame without excessive vaporization, and the molten droplets impact the substrate surface at an appropriate velocity, forming a dense transition layer structure with a certain porosity. The function of the transition layer is to generate a yttrium aluminate metallurgical bonding layer with a thickness of less than 5µm through a controlled in-situ reaction between yttrium oxide and the aluminum substrate surface during high-temperature spraying. This bonding layer has a thermal expansion coefficient similar to that of the aluminum substrate, effectively alleviating thermal stress concentration between the coating and the substrate. Simultaneously, yttrium oxide itself has strong chemical inertness, which can prevent fluoride ions from migrating towards the substrate. During the spraying process, a circulating water cooling system is installed on the back of the substrate to control the surface temperature of the substrate to not exceed 250℃, preventing the aluminum alloy substrate from overheating, softening, or undergoing a phase transformation. The circulating water cooling system uses deionized water as the cooling medium, with a flow rate of not less than 5L / min and an inlet water temperature controlled between 20℃ and 25℃ to ensure that the substrate temperature remains stable within the process window. After the transition layer is deposited, the surface must be visually inspected and its roughness measured to ensure that there is no local accumulation, no cracks, and no peeling, and that the surface roughness is maintained within the range of 4µm to 6µm, providing a uniform substrate for the deposition of the barrier layer.

[0040] The barrier layer is deposited using the aforementioned composite sprayed powder material under the following process parameters: spraying power of 45kW, argon as the main gas with a flow rate of 45L / min, hydrogen as the secondary gas with a flow rate of 10L / min, powder feeding rate of 25g / min, and spraying distance of 120mm. The thickness is controlled to be 50µm to 80µm. This combination of process parameters ensures that the yttrium fluoride main phase in the composite powder is fully melted to form a continuous matrix, the yttrium oxide transition phase is partially melted to retain some of its original morphology to enhance mechanical interlocking, and the nano-alumina dispersed phase remains uniformly distributed in a solid state at the grain boundaries. In the barrier layer, the nano-alumina dispersed phase is uniformly distributed at the grain boundaries of yttrium fluoride and yttrium oxide during spraying, forming a physical diffusion barrier network. Its high melting point and chemical stability effectively pin the migration path of fluoride ions. The yttrium oxide phase, as a fluoride ion adsorption carrier, captures free fluoride ions through lattice vacancies, reducing their active concentration. The yttrium fluoride phase, as the main structure, provides resistance to plasma corrosion. The synergistic effect of these three phases reduces the fluoride ion diffusion flux by more than 80%. During spraying, a powder feed rate of 25 g / min and a spraying distance of 120 mm ensure that the molten droplets are fully cooled during flight, avoiding excessive spreading that could lead to agglomeration or sedimentation of the nano-phase. The optimized ratio of argon flow rate (45 L / min) and hydrogen flow rate (10 L / min) optimizes the flame temperature and velocity, allowing the composite powder to deposit within the optimal melting window. During the barrier layer deposition process, the coating thickness and surface temperature must be monitored in real time. An infrared thermometer is used to record the substrate surface temperature every 30 seconds to ensure it does not exceed 250°C. After deposition, the barrier layer surface undergoes a light argon plasma cleaning process to remove adsorbed impurities and loose particles. The cleaning power is 20kW, the argon flow rate is 10L / min, and the treatment time is 30s to improve the interlayer bonding quality. The cleaned surface must immediately proceed to the functional layer coating process, avoiding exposure to air for more than five minutes.

[0041] The functional layer is deposited using pure yttrium fluoride powder under the following process parameters: spraying power of 50kW, argon as the main gas with a flow rate of 50L / min, hydrogen as the secondary gas with a flow rate of 12L / min, powder feed rate of 20g / min, and spraying distance of 150mm. The thickness is controlled to be between 100µm and 200µm. This combination of process parameters ensures that the yttrium fluoride powder is completely melted in the high-temperature flame and impacts the substrate surface at high speed, forming a dense columnar crystal growth morphology with an intralayer porosity of less than 3% and a surface roughness of less than 5µm. The use of high-purity yttrium fluoride powder in the functional layer ensures that the coating surface has optimal resistance to fluorine plasma erosion and dielectric properties. Its dense structure prevents process gases from penetrating into the underlying structure, maintaining the long-term effectiveness of the barrier layer. During the spraying process, the combination of a powder feed rate of 20g / min and a spraying distance of 150mm ensures that the molten droplets have adequate cooling time before impact, avoiding excessive melting and resulting in excessive coating stress. A primary argon flow rate of 50 L / min and a secondary hydrogen flow rate of 12 L / min provide a sufficiently high-temperature flame to ensure complete melting and good spreading of yttrium fluoride. During the functional layer deposition process, a laser rangefinder is used to monitor the coating thickness in real time, ensuring the total thickness is controlled within the range of 170 μm to 310 μm. The thickness ratio of the transition layer, barrier layer, and functional layer is 1:2.5:5, which was optimized through thermal stress simulation and fluoride ion diffusion kinetics calculations to balance bonding strength, barrier effectiveness, and process feasibility. After deposition, a macroscopic inspection of the coating surface is performed to ensure no cracks, bubbles, or localized peeling, and that the surface has a uniform gloss and no significant color difference.

[0042] In the fourth step, after all coating deposition is completed, the entire coating undergoes a post-heat treatment. This post-heat treatment is performed in a vacuum furnace with a vacuum level not lower than -103 Pa, a heating rate of 5°C / min, a holding temperature of 400°C, and a holding time of two hours, followed by furnace cooling to room temperature. This post-heat treatment process promotes the healing of microcracks within the coating, releases residual stress, and simultaneously promotes grain growth and interface densification of the yttrium aluminate phase between the transition layer and the substrate. This increases the overall bonding strength of the coating to not less than 50 MPa and reduces the porosity to below 3%. The vacuum environment ensures that the coating does not react with oxygen or moisture at high temperatures, preventing yttrium fluoride oxidation or moisture absorption that could lead to performance degradation. The heating rate of 5°C / min ensures a slow release of the thermal expansion difference between the coating and the substrate, preventing interface cracking due to thermal shock. The combination of a holding temperature of 400°C and a holding time of two hours ensures sufficient growth and densification of the yttrium aluminate phase, while also promoting stress relaxation within the coating. The furnace cooling process ensures that the coating cools down slowly, avoiding rapid cooling that could cause thermal stress to re-accumulate. After the post-heat treatment, the coating must be cooled to below 50°C in a vacuum environment before being removed to prevent high-temperature exposure to air from causing surface oxidation or moisture absorption.

[0043] During service, the coating structure exhibits a three-layer structure: the transition layer maintains the metallurgical bonding stability at the interface, the barrier layer continuously inhibits the penetration of fluoride ions into the substrate, and the functional layer resists plasma physical sputtering and chemical erosion. This synergistic effect ensures that the coating exhibits no peeling, blistering, or penetrating cracks after 500 hours of plasma bombardment, with a surface roughness change rate of less than 10% and a mass loss rate of less than 0.5%. Microscopic analysis of the coating cross-section reveals a continuous yttrium aluminate reaction layer with uniform thickness at the interface between the transition layer and the substrate; the barrier layer presents a composite structure where yttrium fluoride grains are encapsulated by yttrium oxide and nano-alumina; and the functional layer exhibits a dense columnar crystal growth morphology with no obvious pores or cracks at the interlayer interfaces. The coating passes scratch tests with a critical load of no less than 80 N; after 100 cycles between 200°C and room temperature in a thermal shock cycle test, it shows no cracking or peeling; and electrochemical impedance spectroscopy tests show that the impedance modulus remains at 10 in a fluorinated electrolyte. 7 (Ω·cm 2 The above demonstrates its excellent corrosion and penetration resistance. In practical applications of semiconductor etching cavities, the coating prepared by this method can extend the cavity maintenance cycle by more than three times, reduce particle contamination rate by 90%, and improve the overall equipment yield by 5%.

[0044] This invention fundamentally solves the technical problem of insufficient bonding strength between the yttrium fluoride coating and the aluminum substrate due to the formation of brittle aluminum fluoride caused by fluoride ion diffusion at the interface by constructing a three-layer gradient structure system consisting of a yttrium oxide transition layer, a yttrium fluoride-yttrium oxide-nano alumina composite barrier layer, and a yttrium fluoride functional layer. The transition layer forms a yttrium aluminate metallurgical bonding interface through in-situ reaction, significantly improving the bonding strength between the coating and the substrate. The barrier layer utilizes the dual mechanisms of the physical barrier of nano alumina and the chemical adsorption of yttrium oxide to effectively inhibit the penetration of fluoride ions into the substrate, achieving a diffusion inhibition efficiency of over 80%. The functional layer ensures the surface layer's resistance to plasma erosion. The synergistic effect of the three layers increases the coating bonding strength to over 50 MPa, with a porosity of less than 3%, and prevents peeling failure under 500 hours of high-energy plasma bombardment. Meanwhile, this invention uses conventional atmospheric plasma spraying equipment and standardized powder materials, eliminating the need for special atmosphere protection or complex precursor treatment. The process parameters are clear and controllable, reducing production costs by 40%, making it suitable for large-scale industrial applications and meeting the comprehensive requirements of advanced semiconductor equipment with seven-nanometer and below processes for high reliability, long life, and low cost of cavity protective coatings.

Claims

1. A method for preparing yttrium fluoride composite ceramic coatings by atmospheric plasma spraying, characterized in that, include: The aluminum substrate surface was subjected to mechanical grinding, ultrasonic cleaning, and sandblasting roughening pretreatment in sequence. The mechanical grinding used 240-mesh silicon carbide sandpaper to grind back and forth in one direction until no visible oxide film was visible on the surface. The ultrasonic cleaning used a cleaning solution of deionized water and anhydrous ethanol at a volume ratio of 1:1 at a frequency of 40 kHz and a power of 300 W for 10 minutes. The sandblasting roughening used brown corundum abrasive with a particle size of 0.3 mm to 0.5 mm, a spray pressure of 0.4 MPa, a spray angle of 80°, and a spray distance of 150 mm. After treatment, the surface roughness of the substrate was 3.5 μm to 5 μm. A composite spraying powder material is prepared by uniformly mixing yttrium fluoride main phase powder, yttrium oxide transition phase powder, and nano-alumina dispersed phase powder in a mass percentage ratio of 75:20:

5. The yttrium fluoride main phase powder has a purity of not less than 99.9%, an average particle size of 30 μm to 50 μm, and is spherical or near-spherical. The yttrium oxide transition phase powder has a purity of not less than 99.5%, an average particle size of 20 μm to 40 μm, and is irregularly polygonal. The nano-alumina dispersed phase powder has a purity of not less than 99.9%, an average particle size of 50 nm to 100 nm, and is spherical. An atmospheric plasma spraying system was used to sequentially deposit a transition layer, a barrier layer, and a functional layer on the surface of a pretreated aluminum substrate. The transition layer was deposited using pure yttrium oxide powder at a spraying power of 40 kW, a main argon flow rate of 40 L / min, a secondary hydrogen flow rate of 8 L / min, a powder feed rate of 30 g / min, and a spraying distance of 100 mm, with a thickness of 20 μm to 30 μm. The barrier layer was deposited using the composite spraying powder material at a spraying power of 45 kW, a main argon flow rate of 45 L / min, a secondary hydrogen flow rate of 10 L / min, a powder feed rate of 25 g / min, and a spraying distance of 120 mm, with a thickness of 50 μm to 80 μm. The functional layer was deposited using pure yttrium fluoride powder at a spraying power of 50 kW, a main argon flow rate of 50 L / min, a secondary hydrogen flow rate of 12 L / min, a powder feed rate of 20 g / min, and a spraying distance of 150 mm, with a thickness of 100 μm to 200 μm. After all coating deposition is completed, the entire coating is subjected to post-heat treatment, which is performed at a vacuum degree of not less than -10. 3 The process was carried out in a vacuum furnace at a heating rate of 5°C / min, a holding temperature of 400°C, and a holding time of two hours, followed by cooling to room temperature in the furnace. The nano-alumina dispersed phase forms a three-dimensional network distribution structure in the barrier layer, with a volume fraction of 5% and an average spacing of less than 500 nm. This scale can effectively hinder the diffusion path of fluoride ions along the grain boundaries without affecting the overall density and mechanical strength of the coating. The yttrium oxide transition phase powder accounts for 20% of the barrier layer. Its polygonal morphology can increase the mechanical interlocking area with the yttrium fluoride main phase and improve the bonding strength within the layer. At the same time, its surface hydroxyl groups can react with fluoride ions at high temperature to generate yttrium fluoride oxide, thereby achieving chemical adsorption and fixation.

2. The method for preparing yttrium fluoride composite ceramic coating by atmospheric plasma spraying according to claim 1, characterized in that, The transition layer serves to generate a yttrium aluminate metallurgical bonding layer with a thickness of less than 5 μm through an in-situ reaction between yttrium oxide and the surface of the aluminum substrate during high-temperature spraying. The thermal expansion coefficient of this bonding layer is similar to that of the aluminum substrate to alleviate thermal stress concentration, while the chemical inertness of yttrium oxide prevents fluoride ions from migrating to the substrate.

3. The method for preparing yttrium fluoride composite ceramic coating by atmospheric plasma spraying according to claim 2, characterized in that, The nano-alumina dispersed phase in the barrier layer is uniformly distributed at the grain boundaries of yttrium fluoride and yttrium oxide to form a physical diffusion barrier network. The yttrium oxide phase captures free fluoride ions through lattice vacancies to reduce their active concentration, and the yttrium fluoride phase, as the main structure, provides resistance to plasma corrosion. The three work together to reduce the fluoride ion diffusion flux by more than 80%.

4. The method for preparing yttrium fluoride composite ceramic coating by atmospheric plasma spraying according to claim 3, characterized in that, The dense columnar crystalline structure of the functional layer prevents process gases from penetrating into the underlying structure, thus maintaining the long-term effectiveness of the barrier layer and ensuring that the coating surface has optimal resistance to fluorine plasma erosion and dielectric properties.

5. The method for preparing yttrium fluoride composite ceramic coating by atmospheric plasma spraying according to claim 4, characterized in that, The post-heat treatment promotes the healing of microcracks inside the coating, releases residual stress, and promotes the growth of yttrium aluminate phase grains and interface densification between the transition layer and the substrate, thereby increasing the overall bonding strength of the coating to no less than 50 MPa and reducing the porosity to below 3%.

6. The method for preparing yttrium fluoride composite ceramic coating by atmospheric plasma spraying according to claim 5, characterized in that, The composite spraying powder material is mixed using a three-dimensional mixer for two hours at a speed of 30 r / min. After mixing, the powder's flowability index is not less than 254 s / 50g, and its loose density is not less than 1.8 g / m³. 3 .

7. The method for preparing yttrium fluoride composite ceramic coating by atmospheric plasma spraying according to claim 6, characterized in that, The substrate surface is immediately coated after sandblasting roughening treatment, with an interval of no more than two hours. If coating is delayed, the substrate is temporarily stored in an inert gas protection box with nitrogen purity of not less than 99.9% and relative humidity of less than 5%.

8. The method for preparing yttrium fluoride composite ceramic coating by atmospheric plasma spraying according to claim 7, characterized in that, During the atmospheric plasma spraying process, a circulating water cooling system is installed on the back of the substrate to control the surface temperature of the substrate to not exceed 250°C. The circulating water cooling system uses deionized water with a flow rate of not less than 5L / min and an inlet water temperature of 20°C to 25°C.

9. A system for preparing yttrium fluoride composite ceramic coatings by atmospheric plasma spraying, characterized in that, include: The aluminum substrate surface pretreatment module is used to sequentially perform mechanical grinding, ultrasonic cleaning, and sandblasting roughening pretreatment on the aluminum substrate surface. The mechanical grinding uses 240-mesh silicon carbide sandpaper to grind back and forth in one direction until no visible oxide film is visible on the surface. The ultrasonic cleaning uses a cleaning solution of deionized water and anhydrous ethanol mixed at a volume ratio of 1:1 at a frequency of 40 kHz and a power of 300 W for 10 minutes. The sandblasting roughening uses brown corundum abrasive with a particle size of 0.3 mm to 0.5 mm, a spray pressure of 0.4 MPa, a spray angle of 80°, and a spray distance of 150 mm. After treatment, the surface roughness of the substrate is 3.5 μm to 5 μm. The composite spraying powder material preparation module is used to prepare a composite spraying powder material composed of yttrium fluoride main phase powder, yttrium oxide transition phase powder, and nano-alumina dispersed phase powder in a mass percentage ratio of 75:20:

5. The yttrium fluoride main phase powder has a purity of not less than 99.9%, an average particle size of 30 μm to 50 μm, and is spherical or near-spherical. The yttrium oxide transition phase powder has a purity of not less than 99.5%, an average particle size of 20 μm to 40 μm, and is irregularly polygonal. The nano-alumina dispersed phase powder has a purity of not less than 99.9%, an average particle size of 50 nm to 100 nm, and is spherical. A multi-layer gradient coating deposition module is used to sequentially deposit a transition layer, a barrier layer, and a functional layer on the surface of a pretreated aluminum substrate using an atmospheric plasma spraying device. The transition layer is deposited using pure yttrium oxide powder at a spraying power of 40kW, a main gas argon flow rate of 40L / min, a secondary gas hydrogen flow rate of 8L / min, a powder feeding rate of 30g / min, and a spraying distance of 100mm, with a thickness of 20µm to 30µm. The barrier layer is deposited using the composite spraying powder material at a spraying power of 45kW, a main gas argon flow rate of 45L / min, a secondary gas hydrogen flow rate of 10L / min, a powder feeding rate of 25g / min, and a spraying distance of 120mm, with a thickness of 50µm to 80µm. The functional layer is deposited using pure yttrium fluoride powder at a spraying power of 50kW, a main gas argon flow rate of 50L / min, a secondary gas hydrogen flow rate of 12L / min, a powder feeding rate of 20g / min, and a spraying distance of 150mm, with a thickness of 100µm to 200µm. The post-coating heat treatment module is used to perform post-heat treatment on the entire coating after all coating deposition is completed. The post-heat treatment is performed under a vacuum degree not lower than -10. 3 The process was carried out in a vacuum furnace at a heating rate of 5°C / min, a holding temperature of 400°C, and a holding time of two hours, after which the furnace was cooled to room temperature.

10. The system for preparing yttrium fluoride composite ceramic coatings by atmospheric plasma spraying according to claim 9, characterized in that, In the multilayer gradient coating deposition module, the transition layer generates a yttrium aluminate metallurgical bonding layer with a thickness of less than 5 μm through in-situ reaction of yttrium oxide with the aluminum substrate surface to alleviate thermal stress and block fluoride ion migration; in the barrier layer, the nano-alumina dispersed phase is distributed at the grain boundaries to form a physical barrier, the yttrium oxide phase captures fluoride ions, and the yttrium fluoride phase provides corrosion resistance, synergistically reducing the fluoride ion diffusion flux by more than 80%; the functional layer has a dense columnar crystal structure to prevent gas penetration and maintain the effectiveness of the barrier layer; the post-heat treatment module promotes microcrack healing, stress release, and interface densification, so that the bonding strength is not less than 50 MPa and the porosity is less than 3%.

Images