A functionally graded rps intracavity multilayer composite corrosion resistant coating and a method of making the same

Abstract

The application relates to the field of semiconductors, and particularly relates to a functional gradient-based RPS cavity inner multilayer composite corrosion-resistant coating and a preparation method thereof. The preparation method of the functional gradient-based RPS cavity inner multilayer composite corrosion-resistant coating comprises the following steps: cleaning and surface activation of an RPS aluminum cavity; micro-arc oxidation treatment, in-situ growth of an aluminum oxide transition layer; deposition of a ta-C gradient intermediate layer on the aluminum oxide transition layer; coating of SiO2 sol on the ta-C gradient intermediate layer through a self-adaptive spin coating process to form a dense SiO2 barrier layer; preparation of a Y2O3 sol of Ce 4+ , UV curing through a step-by-step gradient deposition spin coating mode to construct a gradient Y2O3 corrosion-resistant functional layer; and obtaining the functional gradient-based RPS cavity inner multilayer composite corrosion-resistant coating after curing. The application provides an RPS cavity integrated gradient protective coating with high bonding strength, excellent stress buffering, extreme anti-permeability and super-strong corrosion resistance.

Description

Technical Field

[0001] This application relates to the semiconductor field, and mainly to a functionally graded RPS intracavity multilayer composite corrosion-resistant coating and its preparation method. Background Technology

[0002] As a core component in semiconductor dry etching and chemical vapor deposition (CVD) chamber cleaning, the remote plasma source (RPS) is subjected to long-term chemical erosion, ion bombardment, and frequent thermal cycling loads by high-density fluorine / chlorine-based plasma on its aluminum inner wall. Under these extreme conditions, a single protective coating material is insufficient to meet the requirements for long-term service.

[0003] Currently, the industry generally believes that an ideal protection system requires the construction of a composite structure with the synergistic effect of multiple materials. Among them, yttrium oxide (Y2O3) with its excellent resistance to fluorine-based plasma corrosion, diamond-like carbon (ta-C) with its high hardness and enhanced interfacial bonding ability, and silicon dioxide (SiO2) with its dense barrier effect due to its low porosity, together constitute the core material combination for RPS cavity protection. The bottom layer relies on the alumina ceramic layer grown in situ using micro-arc oxidation technology to achieve metallurgical bonding with the aluminum substrate, fundamentally solving the basic problem of adhesion.

[0004] Although the superior properties of the aforementioned materials are widely recognized, and the corresponding unit preparation technologies (such as micro-arc oxidation, FCVA, and sol-gel method) are maturing, the existing technology system reveals the following systemic challenges in the synergistic adaptation of "materials-structure-process-performance" when systematically integrating four materials with vastly different physicochemical properties—alumina, ta-C, SiO2, and Y2O3—to construct long-lasting and stable gradient functional coatings for the complex three-dimensional structure of RPS cavities: (1) Problems of abrupt changes in interlayer performance and weakened interface bonding Existing technical solutions mostly employ simple "double-layer stacking" structures (such as "micro-arc oxidation layer / Y2O3 layer" or "ta-C layer / Y2O3 layer"), lacking precise interlayer functional gradient design. This structure ignores the drastic differences in physical properties such as thermal expansion coefficient and Young's modulus between different materials.

[0005] For example, directly depositing a high-modulus ta-C layer on a relatively porous micro-arc oxidation layer with a lower modulus, or directly preparing a Y2O3 sol-gel layer on a ta-C layer, will generate huge residual stress and thermal mismatch stress at the interface. During the frequent thermal cycling of the RPS cavity, these stress concentration points are prone to inducing the nucleation and propagation of microcracks, ultimately leading to macroscopic cracking of the coating or peeling off from the substrate, causing the protective system to completely fail. While existing technologies employ multilayer sealing techniques to improve the surface condition of the micro-arc oxidation layer, they do not address the gradient bonding design with high-performance PVD coatings such as ta-C.

[0006] (2) Challenges of uniform coverage and gradient structure integrity in complex three-dimensional cavities The complex geometry of RPS cavities, including air passages, deep grooves, and hidden surfaces, presents significant challenges to achieving uniform coverage of multilayer coatings and precise implementation of pre-defined gradient structures. The inherent "line-of-sight deposition" characteristic of PVD technologies like FCVA results in weak or missing ta-C coatings in the back-facing areas and deep recesses of the cavity, compromising its functional integrity as a continuous barrier layer. Furthermore, traditional sol-gel coating processes are prone to uneven coating due to hydrodynamic effects on complex three-dimensional surfaces, leading to significant thickness discrepancies between the SiO2 and Y2O3 layers at corners, creating localized weaknesses in protection. Current technologies lack an integrated solution that can synergistically ensure uniform and complete coverage of various coating types, such as metals, ceramics, and polymer solutions, on complex inner walls. For example, while existing technologies demonstrate the feasibility of preparing Y2O3 coatings on fiber surfaces using the sol-gel method, their processes suffer from significant limitations in controlling the uniformity of the complex three-dimensional cavity.

[0007] (3) The contradiction between insufficient compatibility of the entire process chain and performance synergy optimization Constructing the four-layer structure of "micro-arc oxidation / ta-C / SiO2 / Y2O3" involves a complex multi-step process chain, and there are coupling effects between the preceding and following process steps. Existing technologies have not been able to resolve these contradictions well.

[0008] For example, to obtain high SP 3The high content of ta-C layer requires optimized ion bombardment energy, which may potentially damage the surface microstructure of the underlying micro-arc oxidation layer. Furthermore, the reactive species generated during subsequent UV curing of SiO2 and Y2O3 gels may oxidize the deposited ta-C layer surface, degrading its performance. A more significant challenge lies in simultaneously achieving high hardness in the ta-C layer, low porosity densification in the SiO2 layer, and full cross-linking and crystallization of the Y2O3 sol-gel layer, all while maintaining temperatures consistently below the aluminum substrate's tolerance. This is a problem that existing technologies have not fully solved. While the low-temperature curing concept mentioned in existing technologies has some reference value, integrating it with various high-tech processes such as FCVA and sol-gel still faces significant challenges in achieving full-process compatibility.

[0009] In summary, although the technologies of each unit constituting this multi-layer system are mature, the existing technology lacks a systematic approach that can collaboratively innovate from three dimensions: material gradient design, three-dimensional uniform film formation process, and full-process compatibility control. As a result, it is impossible to prepare an integrated gradient protective coating for RPS cavities that combines high bonding strength, excellent stress buffering, extreme impermeability, and super corrosion resistance.

[0010] Therefore, there is an urgent need in this field for a novel, integrated preparation method and structural design to systematically solve the aforementioned integration bottleneck problem. Summary of the Invention

[0011] In view of the shortcomings of the prior art, the purpose of this application is to provide a multi-layer composite corrosion-resistant coating for RPS cavity based on functional gradient and its preparation method, aiming to prepare an integrated gradient protective coating for RPS cavity with high bonding strength, excellent stress buffering, extreme impermeability and ultra-strong corrosion resistance.

[0012] The technical solution of this application is as follows: A method for preparing a functionally graded RPS intracavity multilayer composite corrosion-resistant coating includes the following steps: The RPS aluminum cavity is cleaned and its surface activated; The RPS aluminum cavity is subjected to micro-arc oxidation treatment to grow an alumina transition layer with a gradient pore structure in situ. Sp is deposited on the surface of the alumina transition layer 3 A ta-C gradient intermediate layer with gradually varying bond content; SiO2 sol was coated on the surface of the ta-C gradient intermediate layer by an adaptive spin coating process, and after drying and densification, a dense SiO2 barrier layer was formed. Formulating Ce 4+A controllable proportion of Y₂O₃ sol was spin-coated using a stepwise gradient deposition method, followed by UV curing, to construct Ce on the surface of the dense SiO₂ barrier layer. 4+ Gradient-deposited Y2O3 corrosion-resistant functional layer; After curing, the functionally graded RPS cavity multilayer composite corrosion-resistant coating is obtained.

[0013] Furthermore, when employing the filtered cathode vacuum arc technology, the substrate bias voltage in the FCVA control system is continuously adjusted according to the time function V(t) = 400 + 10t (t ∈ [0, 30] min), so that sp 3 The content increased smoothly from 45% to 65%.

[0014] Furthermore, the adaptive spin coating process includes: For flat areas, a standard spin coating curve is used, with the low-speed stage at 400-600 rpm / 5-15s and the high-speed stage at 2000-3000 rpm / 20-30s. The rotation speed in the deep groove area is 700-900 rpm, and the time is 30-60 seconds; A combination of intermittent spot coating and spin coating is used around the air passage holes.

[0015] Furthermore, the formulation of Ce 4+ The Y₂O₃ sol with controllable proportions is prepared by using yttrium and cerium sources as raw materials, and controlling the Ce content by adjusting the amount of complexing solvent. 4+ The proportion is 20%-90%.

[0016] Furthermore, the spin-coating method for the stepwise gradient deposition is as follows: First coating with low Ce 4+ A Y₂O₃ sol of a certain proportion forms a 200-300nm substrate; the low Ce content... 4+ Ce in Y2O3 sol of a certain proportion 4+ The proportion is 20-30%; Ce in the second coating 4+ A Y₂O₃ sol in a specific ratio forms a 100-200 nm intermediate layer; the Ce in the intermediate layer... 4+ Ce in Y2O3 sol of a certain proportion 4+ The proportion is 50-60%. Third coating with high Ce 4+ A Y₂O₃ sol of a certain proportion forms a 0-100 nm surface layer; the high Ce content... 4+ Ce in Y2O3 sol of a certain proportion 4+ The proportion is 80-90%.

[0017] Furthermore, the ultraviolet curing process involves: after a single coating of Y₂O₃ sol, curing with 172nm ultraviolet light at 50-60mW / cm². 2 Curing time is 5-10 minutes.

[0018] Ce 4+ It can improve the crystallinity of Y2O3 and its resistance to fluorine plasma corrosion, but excessive content will increase brittleness. Therefore, a surface high Ce content is used. 4+ To enhance corrosion resistance, the bottom layer has low Ce content. 4+ This enhances toughness and adhesion to the dense SiO2 barrier layer. Each layer is immediately cured with 172nm UV light after coating, effectively suppressing component interdiffusion, ensuring a clear and stable gradient structure, and achieving synergistic optimization of corrosion resistance and interface reliability.

[0019] Furthermore, the micro-arc oxidation treatment employs a bipolar pulse power supply with control parameters of: initial 8-12 A / dm. 2 400-500Hz, 18-23% duty cycle, duration 5-15 minutes, followed by 12-15 A / dm. 2 23-30% duty cycle, time 40-60 minutes.

[0020] Furthermore, the cleaning process includes ultrasonic cleaning with acetone, anhydrous ethanol, and water; The surface activation includes soaking in 5-10% dilute nitric acid for 5-8 minutes and then drying.

[0021] Although unit technologies such as micro-arc oxidation, FCVA, sol-gel and UV curing have been disclosed, the existing technologies have neither applied the "alumina / ta-C / SiO2 / Y2O3" four-layer system to the RPS aluminum cavity, nor solved the three major coupling problems of interlayer performance abrupt change, uneven three-dimensional coverage and low temperature process compatibility.

[0022] The core of this application lies in the three-in-one gradient design: (1) the "dense inner and porous outer" structure of the alumina transition layer provides an anchoring foundation for ta-C; (2) by program-controlled FCVA bias, the intermediate layer sp of the ta-C gradient is achieved. 3 The content transitions from 45% to 65%, effectively alleviating thermal stress in the upper and lower layers; (3) SiO2, as a dense ion barrier layer, interacts with Ce. 4+ The gradient-distributed Y2O3 corrosion-resistant functional layers form complementary functions. The entire process is completed at ≤150°C, achieving a balance between high adhesion, high uniformity, and strong corrosion resistance.

[0023] This application also provides a functionally graded RPS intracavity multilayer composite corrosion-resistant coating.

[0024] Furthermore, the functionally graded RPS cavity multilayer composite corrosion-resistant coating includes an alumina transition layer, a ta-C gradient intermediate layer, a SiO2 dense barrier layer, and a Y2O3 corrosion-resistant functional layer. The thickness of the alumina transition layer is 50±5μm, the thickness of the ta-C gradient intermediate layer is 80±10nm, the thickness of the SiO2 dense barrier layer is 150±20nm, and the thickness of the Y2O3 corrosion-resistant functional layer is 300-600nm.

[0025] Compared with the prior art, this application has the following beneficial effects: 1. High interfacial bonding strength and excellent thermal shock resistance: The metallurgical bonding with the aluminum substrate is achieved through in-situ growth of the alumina transition layer by micro-arc oxidation. The innovative multi-layer composite sealing and ta-C gradient intermediate layer gradient transition design effectively alleviate the problem of abrupt changes in interlayer thermal expansion coefficient and Young's modulus, improves the interfacial bonding strength, and ensures that the multi-layer composite corrosion-resistant coating in the RPS cavity based on functional gradient remains intact under the frequent thermal cycling conditions of the RPS cavity, significantly extending the service life of the protection system.

[0026] 2. Uniform 3D Coverage and Complete Gradient Structure: For the complex 3D structure of the RPS cavity, by optimizing the FCVA deposition tooling and adaptive spin coating process, uniform coverage of the ta-C gradient intermediate layer, SiO2 dense barrier layer, and Y2O3 corrosion-resistant functional layer in complex areas such as gas passage holes and deep grooves was achieved. The thickness deviation was controlled within ±15%, ensuring the integrity of the gradient structure and the consistency of protective performance, and eliminating local protection weaknesses.

[0027] 3. Low-temperature compatibility throughout the entire process and synergistic performance optimization: The core process steps are strictly controlled below the aluminum substrate's tolerance temperature (≤400℃). In particular, through the synergistic process of UV curing and low-temperature heat treatment, the low porosity of the SiO2 dense barrier layer and the full curing of the Y2O3 corrosion-resistant functional layer are simultaneously achieved while ensuring the safety of the substrate. This solves the inherent contradiction between high-temperature densification and the thermal compatibility of the substrate, and achieves synergistic optimization of the performance of each layer.

[0028] 4. Synergistic effect of corrosion resistance and penetration resistance, providing excellent comprehensive protection: The surface Y2O3 corrosion-resistant functional layer provides excellent resistance to fluorine-based plasma corrosion, the middle ta-C gradient intermediate layer effectively blocks the penetration of corrosive media due to its high hardness and density, and the bottom alumina transition layer ensures the system adheres firmly. The multi-layered synergistic "corrosion resistance-barrier-toughness" integrated protection system exhibits a significant synergistic enhancement effect. Its resistance to CF4 / O2 plasma corrosion is greatly improved compared to a single Y2O3 coating, providing more durable and reliable protection for the RPS cavity. Attached Figure Description

[0029] Figure 1 This is a flowchart illustrating the preparation method of the functionally graded RPS intracavity multilayer composite corrosion-resistant coating of this application.

[0030] Figure 2 This is an electronic image of the energy dispersive spectroscopy (EDS) analysis of the functionally graded RPS intracavity multilayer composite corrosion-resistant coating of Embodiment 1 of this application.

[0031] Figure 3 This is an energy dispersive spectroscopy (EDS) analysis of specific elements in the functionally graded RPS intracavity multilayer composite corrosion-resistant coating of Embodiment 1 of this application.

[0032] Figure 4 This is the elemental distribution energy spectrum of the functionally graded RPS cavity multilayer composite corrosion-resistant coating of Embodiment 1 of this application.

[0033] Figure 5 This is a SEM image of the surface of the functionally graded RPS intracavity multilayer composite corrosion-resistant coating in Embodiment 1 of this application.

[0034] Figure 6 This is a SEM image of another surface of the functionally graded RPS intracavity multilayer composite corrosion-resistant coating of Embodiment 1 of this application.

[0035] Figure 7 This is a SEM image of the surface of the functionally graded RPS intracavity multilayer composite coating, which is shown in Comparative Example 1 of this application. Detailed Implementation

[0036] This application provides a functionally graded RPS intracavity multilayer composite corrosion-resistant coating and its preparation method. To make the objectives, technical solutions, and effects of this application clearer and more explicit, the following provides a more detailed description. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0037] This application provides a method for preparing a functionally graded RPS intracavity multilayer composite corrosion-resistant coating, comprising the following steps: A method for preparing a functionally graded RPS intracavity multilayer composite corrosion-resistant coating, comprising the following steps: Step 1: RPS aluminum cavity pretreatment: The RPS aluminum cavity is subjected to multi-step ultrasonic cleaning and surface activation to remove surface contaminants and construct a hydroxylated surface, providing a clean and highly active substrate for subsequent coating preparation.

[0038] Specifically, the core components of the cavity are ultrasonically cleaned with acetone (100W, 40kHz, 5min), anhydrous ethanol (100W, 40kHz, 3min), and deionized water (100W, 40kHz, 5min, repeated twice) without disassembling. After cleaning, the surface is hydroxylated by soaking in 5-10% dilute nitric acid for 5-8min and then dried at 70℃ for 30min to provide an active substrate for the uniform growth of the micro-arc oxide layer.

[0039] Step 2: Micro-arc oxidation to prepare an alumina transition layer: The pretreated aluminum cavity is placed in the electrolyte as the anode and micro-arc oxidation is performed by a bipolar pulse power supply to grow an alumina transition layer with a gradient pore structure in situ.

[0040] Specifically, the electrolyte is a silicate-phosphate composite system (Na2SiO3 70-90g / L, Na3PO4 15-25g / L, NaOH 5-10g / L, pH 11.5±0.5, water balance).

[0041] Micro-arc oxidation uses a bipolar pulse power supply, with "step-up" control parameters: initial 8-12 A / dm. 2 400-500Hz, 18-23% duty cycle (5-15min), followed by 12-15A / dm 2 23-30% duty cycle (40-60 min), electrolyte temperature controlled at 25±5℃.

[0042] The final alumina transition layer has a gradient structure of "dense inner layer - porous outer layer" with a thickness of 50±5μm, which balances support and anchoring effect.

[0043] Step 3: FCVA preparation of the ta-C gradient intermediate layer: Sp was deposited on the surface of the alumina transition layer using filtered cathode vacuum arc (FCVA) technology. 3 A ta-C gradient intermediate layer with gradually varying bond content achieves a smooth performance transition with the upper and lower layers.

[0044] Vacuum was applied to ≤5×10 before FCVA deposition. -3 Pa, argon ion bombardment activates the surface; ta-C gradient intermediate layer sp is achieved by adjusting the substrate bias voltage. 3 Bond content gradient: initial -400V (sp 3 45%-50%, 10 minutes), gradually decrease to -100V (sp 3 60%-65%, 20 min).

[0045] The final thickness of the ta-C gradient intermediate layer is 80±10nm, which eliminates interlayer thermal mismatch stress.

[0046] This application targets aluminum-based RPS cavities, employing FCVA technology to deposit an amorphous carbon (ta-C) interlayer. The bias gradient design is not intended to enhance adhesion, but rather to regulate sp... 3 Bond content to achieve functional gradient: By setting the matrix bias voltage in the FCVA control system to be continuously adjusted according to the time function V(t) = 400 + 10t (t∈[0,30] min) (unit: V), the sp 3 The content smoothly increases from 45% to 65%, forming a transition layer with a high Young's modulus. This design effectively buffers the mismatch between the modulus and thermal expansion coefficient between the bottom layer of micro-arc alumina (high modulus, porous) and the top layer of SiO2 (lower modulus, dense), significantly suppressing interfacial stress concentration and cracking during thermal cycling. It is an innovative functional gradient structure for extreme working conditions.

[0047] Step 4: Preparation of a dense SiO2 barrier layer using the sol-gel method: A highly stable SiO2 sol was prepared and coated onto the surface of a ta-C gradient intermediate layer using an adaptive spin coating process. After densification by low-temperature drying, a continuous corrosion ion barrier was constructed.

[0048] SiO2 sol was prepared according to the following formula: TEOS: ethanol: water: catalyst (preferably nitric acid) = 1: (3.8-4.2): (0.8-1.2): (0.005-0.015) (molar ratio). After stirring at 35-45℃ for 55-65 min, it was aged for 24-48 h and then filtered through a 0.22 μm filter membrane.

[0049] After drying at 120℃ for 30 minutes, the thickness of the SiO2 dense barrier layer is 150±20nm, which improves the efficiency of corrosion ion penetration barrier.

[0050] "Adaptive spin coating" is a coating process proposed in this application for complex three-dimensional structures of RPS cavities (such as deep grooves and air passages). The rotation speed and angle are adjusted in real time through a multi-axis linkage system: (1) For flat areas, a standard spin coating curve is used (first at a low speed of 400-600 rpm for 5-15 s, then at a high speed of 2000-3000 rpm for 20-30 s); (2) For deep groove areas (grooves with a depth greater than 2 mm), the rotation speed is reduced to 700-900 rpm and extended to 30-60 s to improve the sol filling performance; (3) A composite method of intermittent spot coating combined with spin coating is used around the air passages to ensure full coverage. This strategy significantly improves the uniformity and integrity of the coating on complex geometric surfaces.

[0051] Regarding the composite method of intermittent spot coating combined with spin coating: 1. Amount of adhesive applied: Each application volume is 0.5–2.0 μL, preferably 1.0 μL, and is controlled by a high-precision piezoelectric dispensing valve to ensure that the SiO2 sol is accurately deposited in the periphery of the pores without overflowing into the pores.

[0052] Dotting location and number of times: Evenly distribute 4–8 points around the edge of the air passage (depending on the size of the hole; 4 points for holes <1 mm, 6–8 points for holes ≥1 mm); apply 1–2 coats to each point, with an interval of 2–3 seconds to facilitate initial wetting and spreading.

[0053] 3. Coordination of dotting and spinning techniques: First, perform spot coating → let stand for 5–10 seconds to allow the sol to initially wet the hole edges → then start low-speed spin coating (700-900 rpm, 10–20 s) to promote uniform spreading; Alternatively, a cycle of "dot coating - short spin coating - re-dot coating" can be used 1-2 times to achieve multiple layers of touch-up coating.

[0054] This parameter combination has been experimentally verified to effectively avoid "dry spots" or "shrinkage" around the holes, while also preventing blockage of the air passage.

[0055] Step 5: UV curing to prepare the Y2O3 corrosion-resistant functional layer: Precise formulation of Ce 4+ By using a stepwise spin-coating-172nm UV curing process, a graded component Y2O3 corrosion-resistant functional layer is constructed on the surface of a dense SiO2 barrier layer using a controllable proportion of Y2O3 sol, thus completing the preparation of a multi-layer composite corrosion-resistant coating for RPS cavity based on functional gradient.

[0056] Y₂O₃ sol uses yttrium and cerium sources as raw materials, and the Ce content is controlled by adjusting the amount of complexing solvent. 4+ The proportion is 20%-90%.

[0057] Spin coating employs a "stepwise gradient deposition" method, with the first coating being a low-Ce layer. 4+ Proportional sol, exposed to 172nm ultraviolet light (50-60mW / cm) 2 Curing time is 5-10 minutes, followed by two applications with gradually increasing Ce. 4+ The final thickness of the Y2O3 corrosion-resistant functional layer is 300nm-600nm, and the chamber temperature during the curing process is ≤150℃, achieving resistance to CF4 plasma corrosion.

[0058] "Stepwise gradient deposition" refers to the process of constructing Ce using three spin-coating-UV curing cycles. 4+ Y2O3 corrosion-resistant functional layer with concentration decreasing from the surface to the interior: initial coating with low Ce 4+ A Y₂O₃ sol (20-30%) is used to form a 200-300 nm underlayer; Ce is then applied in the second coating. 4+A Y₂O₃ sol (50-60%) is used to form a 100-200 nm intermediate layer; a third coating with high Ce content is then applied. 4+ A Y2O3 sol (80-90%) is used to form a surface layer of 0-100 nm, preferably 50-100 nm. The total thickness is the sum of the thicknesses of the three coating layers, approximately 300-600 nm.

[0059] This application employs a metal alkoxide hydrolysis-complexation sol-gel method to prepare Ce-containing... 4+ The doped Y2O3 sol is as follows: 1. Raw materials: Yttrium source: Yttrium nitrate Y(NO3)3·6H2O or yttrium isopropoxide Y(OC3H7)3; Cerium source: cerium(III) nitrate hexahydrate Ce(NO3)3·6H2O or cerium ammonium nitrate (NH4)2Ce(NO3)6 (providing Ce) 4 + ); Complexing solvent: acetylacetone (acac, C5H8O2); Cosolvent (optional): anhydrous ethanol or isopropanol; Catalyst (optional): Small amount of nitric acid (pH≈2–3).

[0060] Acetylacetone is the preferred complexing solvent because it can effectively chelate Y. 3+ / Ce 4+ This inhibits excessively rapid hydrolysis and improves sol stability. However, the technical solution of this application is not limited to acetylacetone; other β-diketone or polyol complexing solvents with similar functions can also be used.

[0061] 2. Preparation process (taking 100mL sol as an example): The calculated amounts of yttrium salt and cerium salt are adjusted according to the target Ce. 4+ Dissolve in 30 mL of anhydrous ethanol in a molar ratio (e.g., 85%, 55%, 25%). Slowly add 40–60 mL of acetylacetone and stir for 30 min to form a transparent complex solution; Add deionized water (H2O / Y) 3+ (Molar ratio ≈ 4–6) and continue stirring for 2 hours to complete partial hydrolysis and polycondensation; After aging for 12–24 hours, the solution was filtered through a 0.22 μm filter membrane to obtain a stable, low-viscosity (8–12 cP) Y2O3 sol.

[0062] If a catalyst is present, it is added after the yttrium and cerium sources are dissolved in anhydrous ethanol and before the addition of acetylacetone to adjust the pH of the system. Its function is to inhibit the growth of Y-. 3+ / Ce 4+It prevents excessively rapid hydrolysis, avoids precipitation, and promotes the formation of stable complexes with acetylacetone, thereby improving the uniformity and stability of the sol.

[0063] Alternatively, the amounts of yttrium and cerium salts can be fixed, and the target Ce can be achieved by adjusting the amount of acetylacetone. 4+ The effect of molar ratio.

[0064] Concentration information: High Ce 4+ The proportion of Y2O3 sol (85%), etc., refers to Ce 4+ The proportion of total rare earth metal ions (Y) 3+ +Ce 4+ The molar percentage of ).

[0065] For example: Coating sol: Ce 4+ :(Y 3+ +Ce 4+ The total rare earth metal concentration was 85 mol / L, and the total rare earth metal concentration was controlled at 0.3–0.6 mol / L to ensure that the film thickness was within the range of 0–100 nm.

[0066] This design is based on the following principle: Ce 4+ It can improve the crystallinity of Y2O3 and its resistance to fluorine plasma corrosion, but excessive content will increase brittleness. Therefore, a surface high Ce content is used. 4+ To enhance corrosion resistance, the bottom layer has low Ce content. 4+ This enhances toughness and adhesion to the dense SiO2 barrier layer. Each layer is immediately cured with 172nm UV light after coating, effectively suppressing component interdiffusion, ensuring a clear and stable gradient structure, and achieving synergistic optimization of corrosion resistance and interface reliability.

[0067] This application effectively alleviates the problem of abrupt changes in interlayer thermal expansion coefficient and Young's modulus by using a multi-layer composite sealing and ta-C gradient intermediate layer design, improves the interfacial bonding strength, and enables the multi-layer composite corrosion-resistant coating in the RPS cavity based on functional gradient to remain intact under the frequent thermal cycling conditions of the RPS cavity, thus significantly extending the service life of the protection system.

[0068] Multi-layer composite sealing embodies a three-level collaborative mechanism: (1) The micro-arc oxidation layer itself has a gradient structure of "dense inside and porous outside", which provides an anchoring foundation; (2) The ta-C gradient intermediate layer is deposited by FCVA to physically fill the micropores on the oxide layer surface with a nanoscale dense structure; (3) The SiO2 sol further penetrates the residual pores at the molecular level and forms a dense chemical barrier layer after UV curing.

[0069] This multi-level system of "micro-arc oxidation (self-generated pores) → ta-C (physical sealing) → SiO2 (chemical sealing)" seals the pore channels step by step, significantly reducing the overall porosity and effectively improving the coating's resistance to corrosive media.

[0070] The process provided in this application begins with a multi-step pretreatment of the aluminum cavity: ultrasonic cleaning is performed sequentially using acetone, anhydrous ethanol, and deionized water, followed by activation with dilute nitric acid to construct a hydroxylated surface, providing a clean and highly active substrate for subsequent coating growth; then, an alumina transition layer with a gradient structure of "dense inner layer - porous outer layer" is grown in situ in a silicate-phosphate composite electrolyte using a bipolar pulsed micro-arc oxidation process; subsequently, a filtered cathode vacuum arc technology is employed, and the substrate bias voltage is controlled by a program to achieve sp 3 A ta-C gradient intermediate layer was deposited, with a gradual transition in bond content from 45% to 65%. Subsequently, a highly stable SiO2 sol was prepared using the sol-gel method, and an adaptive spin-coating process was employed to construct a continuous, dense, ion-corroding SiO2 barrier layer on the surface of the ta-C gradient intermediate layer. Finally, Ce was constructed under strictly controlled temperature (≤150℃) conditions using stepwise spin-coating and 172nm UV curing. 4+ A precisely proportioned and controllable Y2O3 corrosion-resistant functional layer was developed to complete the preparation of a multi-layer composite corrosion-resistant coating for RPS cavity based on functional gradient.

[0071] To address systemic challenges in existing technologies, such as abrupt changes in interlayer performance, uneven coverage of complex three-dimensional structures, and insufficient compatibility across the entire process chain, this method achieves synergistic protection through a four-layer gradient structure design of "micro-arc oxidation / ta-C / SiO2 / Y2O3". By growing a micro-arc oxidation layer in situ on the aluminum substrate surface, an alumina transition layer metallurgically bonded to the substrate is formed, fundamentally solving the adhesion problem of subsequent coating systems. The ta-C gradient intermediate layer prepared by FCVA is further enhanced by sp... 3 Gradual content variation effectively alleviates interlayer thermal mismatch stress; adaptive spin coating process ensures uniform coverage of the sol-gel layer on the complex three-dimensional surface of the cavity; and ultraviolet curing technology achieves full cross-linking and crystallization of the functional layer while ensuring substrate safety. This integrated protection system of "tough substrate - gradient transition - dense barrier - corrosion-resistant surface" systematically solves the long-term protection requirements of RPS aluminum cavities under extreme plasma conditions, providing a reliable technical solution for semiconductor dry etching and cavity cleaning equipment.

[0072] The present application will be further described below through specific embodiments.

[0073] Example 1 To address the long-term protection requirements of aluminum cavities in semiconductor remote plasma sources (RPS) within CF4 / O2 plasma environments, this embodiment discloses a method for preparing a multilayer composite corrosion-resistant coating within the RPS cavity based on functional gradients. The specific steps are as follows: Step 1: Pre-treatment of RPS aluminum cavity, including the following steps: A Φ300mm×500mm RPS aluminum cavity (made of 6061 aluminum alloy) was selected, and a three-step ultrasonic cleaning process was adopted: (1) Removal of organic pollutants: Place the cavity in a 2000ml glass container, pour in 50ml of acetone until the cavity surface is completely submerged, turn on the ultrasonic cleaner with a power of 100W and a frequency of 40kHz, and clean continuously for 5 minutes. The dissolving properties of acetone are used to effectively remove organic pollutants such as grease from the cavity surface.

[0074] (2) Residual impurity cleaning: Transfer the cavity to a clean 2000ml glass container, pour in 50ml of anhydrous ethanol, and clean for 3 minutes while maintaining the same ultrasonic parameters (100W, 40kHz) to further clean residual acetone and tiny particulate impurities.

[0075] (3) Water washing and activation: Place the cavity into a new 2000ml glass container, pour in 100ml of deionized water, and ultrasonically clean (100W, 40kHz) for 5 minutes. Repeat this water washing step once.

[0076] The surface was then soaked in 8% dilute nitric acid solution for 6 minutes to build a hydroxylated surface, and finally dried in a 70°C forced-air drying oven for 30 minutes.

[0077] Step 2: Micro-arc oxidation to prepare an alumina transition layer, including the following steps: (1) Electrolyte preparation: In a 20L plastic electrolytic cell, prepare a silicate-phosphate composite electrolyte with the following components: Na2SiO3 80g / L, Na3PO4 20g / L, and NaOH 8g / L. Make up the volume with deionized water, stir evenly, and then adjust the pH to 11.5 with a pH meter.

[0078] (2) Micro-arc oxidation treatment: The pretreated cavity is used as the anode and a 316L stainless steel plate is used as the cathode, and it is placed in the electrolyte.

[0079] A bipolar pulse power supply is used, with control parameters in "stepped boost" mode: initial stage current density 10A / dm². 2 500Hz frequency, 20% duty cycle, processing time 10 minutes; subsequent stages increase current density to 13A / dm³. 2 The duty cycle is 25%, and the treatment time is 50 minutes. During the treatment, the electrolyte temperature is controlled at 25±5℃ through a circulating water cooling system.

[0080] (3) Post-treatment: After the micro-arc oxidation is completed, the cavity is removed, the residual electrolyte on the surface is rinsed with high-pressure deionized water, and then placed in a 70℃ drying oven for 30 minutes.

[0081] The thickness of the alumina transition layer is 50 μm.

[0082] Step 3: Prepare the ta-C gradient intermediate layer using FCVA, including the following steps: (1) Equipment preparation: Transfer the cavity to the vacuum chamber of the FCVA equipment and evacuate it to 3×10. -3 Pa.

[0083] (2) Surface activation: Argon ion bombardment was performed for 10 minutes with a bias voltage of -600V to activate the surface of the alumina layer.

[0084] (3) Gradient deposition: By setting the matrix bias voltage in the FCVA control system and continuously adjusting it according to the time function V(t)=400+10t (t∈[0,30]min) (unit: V), the sp 3 The content was smoothly increased from 45% to 65%, achieving sp. 3 Bond content gradient deposition: Initially, a bias voltage of -400V was applied for deposition for 10 minutes, followed by a gradual reduction of the bias voltage to -100V over 30 minutes to complete the preparation of the ta-C gradient intermediate layer.

[0085] The thickness of the ta-C gradient intermediate layer is 80 nm.

[0086] Step 4: Preparation of a dense SiO2 barrier layer using the sol-gel method, including the following steps: (1) Sol preparation: SiO2 sol was prepared according to the molar ratio of TEOS:ethanol:water:nitric acid = 1:4:1:0.01, and magnetically stirred at 500 rpm for 60 minutes in a constant temperature water bath at 40℃. After aging for 24 hours, it was filtered through a 0.22μm PTFE filter membrane.

[0087] (2) Adaptive spin coating process: For flat areas, the standard spin coating curve (500rpm / 10s→2500rpm / 25s) is used. For groove areas with a depth greater than 2mm, use the low-speed long-time mode (800rpm, 40s). For the area around the air passage holes, a combination of intermittent spot coating and low-speed spin coating (800 rpm / 15 s) is used; that is, spot coating is performed first, and the mixture is allowed to stand for 5-10 seconds to allow the sol to initially wet the edge of the hole, and then low-speed spin coating is started to promote uniform spreading.

[0088] Achieve uniform coating of SiO2 sol on the inner wall of the cavity.

[0089] (3) Drying treatment: After coating, transfer the cavity to a 120℃ oven to dry for 30 minutes.

[0090] The SiO2 dense barrier layer is 150 nm thick.

[0091] Step 5: UV curing to prepare the Y2O3 corrosion-resistant functional layer, including the following steps: (1) Sol preparation: Using Y(NO3)3·6H2O and Ce(NO3)3·6H2O as raw materials, the amount of ACAC added was precisely adjusted to control Ce. 4+ Proportion, preparation containing the corresponding Ce 4+ Molar percentage of Y2O3 sol.

[0092] Specifically, the calculated amounts of Y(NO3)3·6H2O and Ce(NO3)3·6H2O are mixed according to the target Ce... 4+ Dissolve in 30 mL of anhydrous ethanol in a molar ratio (e.g., 85%, 55%, 25%). Slowly add 50 mL of acetylacetone and stir for 30 min to form a transparent complex solution; Add deionized water (H2O / Y) 3+ (Molar ratio = 5) and continue stirring for 2 hours to complete partial hydrolysis and polycondensation; After aging for 18 hours, the solution was filtered through a 0.22 μm filter membrane to obtain a stable, low-viscosity Y2O3 sol.

[0093] (2) Gradient deposition: A three-step gradient deposition process is adopted, with Ce being coated for the first time. 4+ A 25% Y₂O₃ sol was cured under 172nm UV light (55mW / cm²) for 8 minutes; subsequent two coatings gradually increased Ce. 4+ The ratio is up to 85%, and each coating is cured with ultraviolet light.

[0094] (3) Temperature control: The temperature of the cavity is always controlled below 150℃ through real-time monitoring throughout the curing process.

[0095] Bottom layer (first time): 250nm; Middle layer (second time): 150nm; Top layer (third time): 80nm; Total: 480nm.

[0096] The functionally graded RPS cavity multilayer composite corrosion-resistant coating prepared in this embodiment was observed to have no obvious cracks or large-area peeling under visual and optical microscopic examination; continuous coating coverage was visible in areas such as the gas path interface, indicating that the adaptive spin coating strategy helps to improve the coating integrity of complex structural surfaces.

[0097] This embodiment fully demonstrates the advantages of the method of the present invention in solving the problems of interfacial bonding of multilayer coatings, uniform coating of complex structures, and compatibility of the entire process, and provides a reliable technical solution for long-term protection of RPS cavities in semiconductor equipment.

[0098] Table 1 shows the elemental quantitative analysis of the multilayer composite corrosion-resistant coating in the RPS cavity based on functional gradient.

[0099] Table 1

[0100] Comparative Example 1 The difference from Example 1 is that step three, FCVA preparation of the ta-C gradient intermediate layer, is omitted; that is, steps four and five are performed directly after step two is completed.

[0101] After thermal shock testing, such as Figure 7 As shown, severe network cracking and curling peeling occurred on the surface of the multilayer composite coating within the RPS cavity based on functional gradient. Cross-sectional analysis confirmed that the cracks originated at the interface between the dense SiO2 barrier layer and the alumina transition layer, which was caused by the mismatch in thermal expansion coefficients and stress concentration at the interface due to the lack of gradient transition.

[0102] Comparative Example 2 The difference from Example 1 is that the adaptive spin coating in step four is replaced by a conventional constant speed spin coating process, and the steps of slowing down and maintaining the speed in the deep groove area and intermittent spot coating of the air passage holes are eliminated.

[0103] The conventional constant speed spin coating process is: using a single high-speed rotation step, with specific parameters of: rotation speed 2500 rpm and duration 30 s.

[0104] Testing revealed that excessive centrifugal force caused excessive ejection of the sol in the deep trench area, resulting in a significantly thinner film in that region compared to the flat areas, with extremely poor thickness uniformity. This substantial deviation in film thickness rendered the deep trench area inadequately protective, making it a vulnerable point for corrosion during subsequent use.

[0105] Comparative Example 3 The difference from Example 1 is that the gradient deposition in step five is changed to a one-step deposition, Ce 4+ The concentration is fixed at 55%, i.e., Ce is coated. 4+ The Y2O3 sol has a content of 55% and the thickness of the Y2O3 corrosion-resistant functional layer is 480nm.

[0106] In the CF4 / O2 plasma corrosion test, the effective protection time of the Comparative Example 3 sample was 45 hours, while the protection time of the Example 1 sample was over 120 hours. The data shows that the service life of a single-layer coating without a gradient design is shortened by more than 60% because it cannot balance internal stress and surface corrosion resistance.

[0107] It should be understood that the application of this application is not limited to the examples above. Those skilled in the art can make improvements or modifications based on the above description, and all such improvements and modifications should fall within the protection scope of this application.

Claims

1. A method for preparing a multilayer composite corrosion-resistant coating for RPS cavities based on functional gradients, characterized in that, Includes the following steps: The RPS aluminum cavity is cleaned and its surface activated; The RPS aluminum cavity is subjected to micro-arc oxidation treatment to grow an alumina transition layer with a gradient pore structure in situ. Sp is deposited on the surface of the alumina transition layer 3 A ta-C gradient intermediate layer with gradually varying bond content; SiO2 sol was coated on the surface of the ta-C gradient intermediate layer by an adaptive spin coating process, and after drying and densification, a dense SiO2 barrier layer was formed. Formulating Ce 4+ A controllable proportion of Y₂O₃ sol was spin-coated using a stepwise gradient deposition method, followed by UV curing, to construct Ce on the surface of the dense SiO₂ barrier layer. 4+ Gradient-deposited Y2O3 corrosion-resistant functional layer; After curing, the functionally graded RPS cavity multilayer composite corrosion-resistant coating is obtained.

2. The method for preparing a multilayer composite corrosion-resistant coating for RPS cavity based on functional gradient according to claim 1, characterized in that, Sp is deposited on the surface of the alumina transition layer 3 The ta-C gradient intermediate layer with gradually varying bond content employs filtered cathode vacuum arc technology; When using filtered cathode vacuum arc technology, the substrate bias voltage in the FCVA control system is continuously adjusted according to the time function V(t) = 400 + 10t, where t ∈ [0, 30] min, so that sp 3 The content increased smoothly from 45% to 65%; V represents the matrix bias voltage, and t represents time.

3. The method for preparing a multilayer composite corrosion-resistant coating for RPS cavity based on functional gradient according to claim 1, characterized in that, The adaptive spin coating process includes: For flat areas, a standard spin coating curve is used, with the low-speed stage at 400-600 rpm / 5-15s and the high-speed stage at 2000-3000 rpm / 20-30s. The rotation speed in the deep groove area is 700-900 rpm, and the time is 30-60 seconds; A combination of intermittent spot coating and spin coating is used around the air passage holes.

4. The method for preparing a multilayer composite corrosion-resistant coating for RPS cavity based on functional gradient according to claim 1, characterized in that, The formulation of Ce 4+ The Y₂O₃ sol with controllable proportions is prepared by using yttrium and cerium sources as raw materials, and controlling the Ce content by adjusting the amount of complexing solvent. 4+ The molar percentage of total rare earth metal ions is 20%-90%; Total rare earth metal ions include Y 3+ Ce 4+ .

5. The method for preparing a multilayer composite corrosion-resistant coating for RPS cavity based on functional gradient according to claim 4, characterized in that, The spin-coating method for the stepwise gradient deposition is as follows: First coating with low Ce 4+ A Y₂O₃ sol of a certain proportion forms a 200-300nm substrate; the low Ce content... 4+ In a Y2O3 sol of a certain proportion, Ce 4+ The molar percentage of total rare earth metal ions is 20-30%; Ce in the second coating 4+ A Y₂O₃ sol in a specific ratio forms a 100-200 nm intermediate layer; the Ce in the intermediate layer... 4+ In a Y2O3 sol of a certain proportion, Ce 4+ The molar percentage of total rare earth metal ions is 50-60%; Third coating with high Ce 4+ A Y₂O₃ sol of a certain proportion forms a 0-100 nm surface layer; the high Ce content... 4+ In a Y2O3 sol of a certain proportion, Ce 4+ The total molar percentage of rare earth metal ions is 80-90%.

6. The method for preparing a multilayer composite corrosion-resistant coating for RPS cavity based on functional gradient according to claim 1, characterized in that, The ultraviolet curing process involves applying a single layer of Y₂O₃ sol coating followed by exposure to 172nm ultraviolet light at 50-60mW / cm². 2 Curing time is 5-10 minutes.

7. The method for preparing a multilayer composite corrosion-resistant coating for RPS cavities based on functional gradients according to claim 1, characterized in that, The micro-arc oxidation process uses a bipolar pulse power supply with the following control parameters: initial 8-12 A / dm. 2 400-500Hz, 18-23% duty cycle, duration 5-15 minutes, followed by 12-15 A / dm. 2 23-30% duty cycle, time 40-60 minutes.

8. The method for preparing a multilayer composite corrosion-resistant coating for RPS cavity based on functional gradient according to claim 1, characterized in that, The cleaning process includes ultrasonic cleaning with acetone, anhydrous ethanol, and water. The surface activation includes soaking in 5-10% dilute nitric acid for 5-8 minutes and then drying.

9. A functionally graded RPS cavity multilayer composite corrosion-resistant coating prepared by the preparation method of the functionally graded RPS cavity multilayer composite corrosion-resistant coating according to any one of claims 1-8.

10. The functionally graded RPS intracavity multilayer composite corrosion-resistant coating according to claim 9, characterized in that, It includes an alumina transition layer, a ta-C gradient intermediate layer, a SiO2 dense barrier layer, and a Y2O3 corrosion-resistant functional layer; The thickness of the alumina transition layer is 50±5μm, the thickness of the ta-C gradient intermediate layer is 80±10nm, the thickness of the SiO2 dense barrier layer is 150±20nm, and the thickness of the Y2O3 corrosion-resistant functional layer is 300-600nm.

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