Surface composite protective layer for sapphire optical viewing window and preparation method thereof

Abstract

The application provides a surface composite protective layer for a sapphire optical observation window and a preparation method. The surface composite protective layer is prepared on the surface of the sapphire optical observation window by combining a transition layer and a Y2O3 film layer. On the premise of not sacrificing the deposition rate, the surface composite protective layer realizes the continuous and stable preparation of the Y2O3 film layer with high purity, high stability and a thickness of 8-12 microns on the sapphire substrate. The design and preparation of the transition layer buffer the lattice mismatch and the difference in the thermal expansion coefficient between the sapphire and the Y2O3, and solve the problems of poor bonding force and easy cracking of the thick film of the heterogeneous substrate. The coupling of the medium-frequency twin magnetron sputtering and the in-situ ion source assisted bombardment solves the contradiction between the traditional magnetron sputtering "target poisoning and unstable discharge" and "low deposition rate", and realizes the efficient and stable deposition of the Y2O3 thick film. Finally, the composite protective layer with excellent plasma etching resistance and optical transmittance is obtained.

Description

Technical Field

[0001] This invention relates to the field of sapphire surface protection technology, and in particular to a surface protective layer for sapphire optical observation windows and its preparation method. Background Technology

[0002] In modern integrated circuit manufacturing processes, plasma etching is a crucial step in pattern transfer, and its precision and stability directly determine the chip's performance and yield. The reaction chamber of the plasma etching equipment (or etching machine) is the core component for this process. To monitor the plasma state, glow discharge uniformity, and endpoint detection within the chamber in real time, an optical observation window is typically installed on the etching equipment. Sapphire, due to its excellent physicochemical properties, such as a wide spectral transmittance range (from ultraviolet to mid-infrared), high hardness, high strength, excellent heat resistance, and chemical stability, especially its natural high tolerance to fluorine-containing plasmas, is considered an ideal material for manufacturing this observation window. However, during the etching process, the high-energy plasma, especially plasma containing highly reactive chemicals such as fluorine and chlorine, not only acts on the silicon wafer but also causes continuous physical bombardment and chemical erosion to the internal components of the reaction chamber, such as the chamber walls, gas spray head, electrostatic chuck, and observation window. This erosion can damage components and shorten the lifespan of equipment. More seriously, the eroded particles can detach and contaminate the wafer surface, forming process defects and severely affecting the chip production yield. Therefore, even high-performance sapphire will undergo slow physical erosion and chemical reactions on its surface under long-term, high-intensity plasma conditions, resulting in decreased optical performance (such as reduced transmittance and increased surface roughness) and weakened mechanical strength.

[0003] Extending the lifespan of sapphire windows and maintaining their stable optical performance throughout their service life is a pressing challenge that needs to be addressed. Summary of the Invention

[0004] In view of the problems existing in the background art, the present invention provides a surface composite protective layer for sapphire optical observation windows and a preparation method thereof, so as to extend the service life of sapphire windows and maintain their stable optical performance throughout the entire service life.

[0005] The specific details of the invention are as follows: In a first aspect, the present invention provides a method for preparing a surface composite protective layer for a sapphire optical observation window, the method comprising: After surface cleaning and activation treatment of the sapphire substrate, a transition layer is deposited on the sapphire substrate by radio frequency magnetron sputtering. A Y2O3 film was deposited on the surface of the transition layer by using a mid-frequency twin magnetron sputtering coupled ion source to assist bombardment, forming the composite protective layer; The coefficient of thermal expansion of the transition layer is between that of Al2O3 and Y2O3.

[0006] Optionally, the operating parameters of the intermediate frequency twin magnetron sputtering satisfy: Yttrium twin target purity > 99.99%; The substrate temperature is 300 ℃-500 ℃; The working gas is an Ar / O2 mixture with a pressure of 0.2~0.8 Pa; The intermediate frequency power supply has a frequency of 40 kHz, a power of 5 kW-15 kW, and a duty cycle of 50%. The deposition thickness of the Y2O3 film is 8 μm-12 μm.

[0007] Optionally, the ion source-assisted bombardment uses Ar + With O + A mixed ion beam is used to simultaneously bombard the growing Y₂O₃ film; the ion source emits an ion beam with an energy of 80 eV-200 eV and an ion beam current density of 0.1 mA / cm². 2 -0.5 mA / cm 2 .

[0008] Optionally, in the initial stage of depositing Y2O3 films using mid-frequency twin magnetron sputtering, the ion energy of the ion source is 150 eV-200 eV, which is linearly reduced to 80 eV-120 eV in the middle and later stages.

[0009] Optionally, the transition layer is composed of yttrium aluminum garnet (Y3Al5O). 12 Magnesium aluminum spinel MgAl2O4 or yttrium gallium garnet Y3Ga5O 12 The thickness is 30 nm-100 nm.

[0010] Optionally, after surface cleaning and activation treatment of the sapphire substrate, and before depositing a transition layer on the sapphire substrate using radio frequency magnetron sputtering, the method further includes: An initial Al2O3 layer was deposited on a sapphire substrate using radio frequency magnetron sputtering; The thickness of the initial layer is 10 nm-30 nm.

[0011] Optionally, both the initial Al2O3 layer and the transition layer are prepared by radio frequency sputtering in an Ar / O2 mixed atmosphere.

[0012] Optionally, the surface cleaning and activation treatment of the sapphire substrate includes: After ultrasonic cleaning of the sapphire substrate with acetone, ethanol and deionized water in sequence, it is soaked in acid or alkaline solution. The sapphire substrate was heat-treated at 300 ℃-500 ℃ under vacuum for 2 h-6 h; The sapphire substrate surface after heat treatment is activated by bombarding it with an argon ion beam generated by an ion source.

[0013] Optionally, after depositing a Y2O3 protective layer on the transition layer surface using a mid-frequency twin magnetron sputtering coupled ion source for assisted bombardment, the method further includes: annealing the sapphire substrate, including: In a vacuum environment, the temperature is increased to 400-500℃ at a rate of 5℃ / min-10℃ / min, held for 1-2 hours, then increased to 750-900℃ at the same rate, and then backfilled with an appropriate amount of high-purity oxygen. The temperature is held for 24 hours in a weakly oxidizing atmosphere, and finally slowly cooled to room temperature at a rate of 1℃ / min-3℃ / min.

[0014] In a second aspect, the present invention provides a surface composite protective layer for a sapphire optical observation window obtained by the preparation method described in the first aspect above.

[0015] The present invention provides a method for preparing a surface composite protective layer for a sapphire optical observation window. The preparation method includes: after cleaning and activating the surface of a sapphire substrate, depositing a transition layer on the sapphire substrate by radio frequency magnetron sputtering; and depositing a Y2O3 film on the surface of the transition layer by mid-frequency twin magnetron sputtering coupled with an ion source to form the composite protective layer.

[0016] Compared with the prior art, the present invention has the following advantages: This invention provides a complete and industrially scalable process for fabricating a surface composite protective layer for sapphire optical observation windows. A transition layer and a Y₂O₃ film are composited on the surface of the sapphire optical observation window, achieving continuous and stable fabrication of a high-purity, high-stability Y₂O₃ coating with a thickness of 8-12 micrometers on a sapphire substrate without sacrificing the deposition rate. The design and fabrication of the transition layer buffers the lattice mismatch and thermal expansion coefficient difference between sapphire and Y₂O₃, solving the problems of poor adhesion and easy cracking of thick films on heterogeneous substrates. The coupling of mid-frequency twin magnetron sputtering and in-situ ion source-assisted bombardment resolves the contradiction between "target poisoning and unstable discharge" and "low deposition rate" in traditional magnetron sputtering, achieving efficient and stable deposition of thick films. The final result is a composite protective layer with excellent resistance to plasma etching and optical transmittance. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 A flowchart illustrating the preparation method of the composite protective layer provided in an embodiment of the present invention is shown; Figure 2 A scanning electron microscope image of the composite protective layer provided in an embodiment of the present invention is shown; Figure 3 A scanning electron microscope image of the composite protective layer provided in the comparative example of the present invention is shown. Detailed Implementation

[0019] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit the present invention or its application or use. Based on the embodiments of the present invention, any product that is the same as or similar to the present invention, derived by anyone under the guidance of the present invention or by combining the features of the present invention with other prior art, falls within the protection scope of the present invention. Furthermore, all other embodiments obtained by those skilled in the art without inventive effort are within the protection scope of the present invention.

[0020] Specific experimental steps or conditions are not specified in the embodiments; they can be performed according to the conventional experimental steps or conditions described in the prior art. Reagents and other instruments used, unless otherwise specified, are all commercially available conventional reagent products. Furthermore, the accompanying drawings are merely illustrative diagrams of the embodiments of the present invention and are not necessarily drawn to scale. The same reference numerals in the drawings denote the same or similar parts, and therefore, repeated descriptions of them will be omitted. Some block diagrams shown in the drawings are functional entities and do not necessarily correspond to physically or logically independent entities.

[0021] Techniques, methods, and devices known to those skilled in the art may not be discussed in detail, but where appropriate, such techniques, methods, and devices should be considered part of this specification.

[0022] Furthermore, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0023] To further extend the lifespan of sapphire windows and maintain their stable optical performance throughout their service life, preparing a high-performance protective coating on the plasma-facing side has become an industry consensus and a research hotspot. Among numerous candidate protective materials, yttrium oxide (Y₂O₃) has attracted considerable attention due to its unique advantages. Y₂O₃ possesses extremely high melting point and thermal stability. More importantly, in a fluorine-containing plasma environment, it can react with fluorine radicals to generate high-boiling-point yttrium fluoride (YF₃). This product is not easily volatilized and can effectively cover and protect the coating substrate, thereby greatly inhibiting further etching and particle shedding. Therefore, Y₂O₃ coatings are widely considered one of the most promising materials for protecting internal components in plasma etching equipment chambers.

[0024] Currently, the existing technologies for preparing Y2O3 protective coatings mainly include the following: Atmospheric plasma spraying (APS): This is currently a relatively mature and mainstream method in commercial applications. This technology involves melting Y₂O₃ powder in a high-temperature plasma jet and spraying it at high speed onto the substrate surface to form a coating. Due to its simple process, it is suitable for large-area coatings and has less stringent requirements on the shape of the coated part, making it the main method for preparing surface coatings for cavities and complex-shaped components. However, coatings prepared by the APS method typically have high porosity, and the presence of microcracks and unmelted particles within the coating results in poor density. In harsh plasma environments, corrosive gases easily penetrate along the pores, eroding the interface between the coating and the substrate, leading to premature peeling and failure of the coating. Furthermore, the sprayed coating has a large surface roughness and extremely poor light transmittance, making it unsuitable for coating window materials.

[0025] Electron beam evaporation: This method involves heating and evaporating Y₂O₃ coating material with a high-energy electron beam, causing its gaseous atoms or molecules to deposit onto a substrate to form a thin film. While it can produce dense columnar crystalline coatings, the deposition process is highly directional, limiting its ability to uniformly coat complex-shaped components. More importantly, the resulting columnar crystalline structure has physical and chemical weaknesses at the grain boundaries, making it susceptible to preferential corrosion along these boundaries under long-term plasma exposure, thus affecting the long-term reliability of the coating.

[0026] Magnetron sputtering: Reactive sputtering using a yttrium (Y) target (in an Ar+O2 mixed atmosphere) is a common method for preparing high-purity Y₂O₃ thin films. However, in conventional DC magnetron sputtering, the target surface becomes "poisoned" due to the formation of an insulating layer when reactively sputtering insulating films (such as Y₂O₃). This leads to charge accumulation and frequent arcing, making the sputtering process extremely unstable and resulting in poor film quality. While radio frequency (RF) magnetron sputtering can solve the target poisoning problem, its deposition rate is very low (typically 0.1~0.3 nm / s). For preparing protective coatings with thicknesses in the micrometer or even tens of micrometer range, the time cost is extremely high. Preparing a 10 μm thick film requires tens of hours of continuous deposition, making industrial-scale production impractical.

[0027] Furthermore, sapphire (Al2O3) and yttrium oxide (Y2O3) are heterogeneous materials with a large lattice mismatch and different coefficients of thermal expansion; Al2O3 has a coefficient of thermal expansion of approximately 7.5 × 10⁻⁶. -6 K -1 Y2O3 approximately 9.2 × 10⁻⁶ -6 K -1 When depositing relatively thick films of 8-12 micrometers, enormous interfacial and thermal stresses can easily accumulate at the interface or within the film, leading to microcracks, peeling, or even large-area detachment of the coating. Current technologies lack an effective stress release and interfacial buffering mechanism, making it difficult to ensure the integrity of thick films under thermal cycling and plasma bombardment.

[0028] Based on this, the present invention employs mid-frequency twin sputtering, supplemented by in-situ ion source-assisted bombardment technology, to achieve continuous and stable preparation of high-purity, high-stability Y2O3 coatings with a thickness of 8-12 micrometers on the surface of sapphire (Al2O3) without sacrificing the deposition rate. The technical solution protected by this invention is described in detail below.

[0029] In a first aspect, the present invention provides a method for preparing a surface composite protective layer for a sapphire optical observation window. Figure 1 A flowchart illustrating the preparation method of the composite protective layer provided in an embodiment of the present invention is shown, as follows: Figure 1 As shown, the preparation method includes: S1. After surface cleaning and activation treatment of the sapphire substrate, a transition layer is deposited on the sapphire substrate by radio frequency magnetron sputtering. S2. A Y2O3 film is deposited on the surface of the transition layer to form the composite protective layer by using a medium-frequency twin magnetron sputtering coupled ion source for assisted bombardment. The coefficient of thermal expansion of the transition layer is between that of Al2O3 and Y2O3.

[0030] In practice, the fabrication of the surface composite protective layer for sapphire optical observation windows requires a clean working surface. Specifically, the substrate needs to undergo surface cleaning and activation treatment to remove surface impurities and micro-defects, and improve surface energy. A transition layer with a matching coefficient of thermal expansion is first prepared on the sapphire substrate surface. This effectively buffers the stress caused by the difference in lattice structure and coefficient of thermal expansion between the sapphire (Al2O3) and Y2O3 films, acting as a flexible "stress-absorbing pad," thus avoiding stress concentration at the interface and laying a solid foundation for the subsequent firm adhesion of the thick film. The Y2O3 film is prepared using mid-frequency twin magnetron sputtering, which completely avoids target poisoning and arcing, achieving high-speed and stable deposition of the thick film. Coupled ion source-assisted bombardment effectively improves film density, reduces film stress, and enhances resistance to plasma etching. The overall fabrication process is simple, mass-producible, and suitable for window protection in semiconductor etching equipment.

[0031] In some embodiments, the operating parameters of the intermediate frequency twin magnetron sputtering satisfy: Yttrium twin target purity > 99.99%; The substrate temperature is 300 ℃-500 ℃; The working gas is an Ar / O2 mixture with a pressure of 0.2~0.8 Pa; The intermediate frequency power supply has a frequency of 40 kHz, a power of 5 kW-15 kW, and a duty cycle of 50%. The deposition thickness of the Y2O3 film is 8 μm-12 μm.

[0032] It should be noted that the mid-frequency twin magnetron sputtering system uses a pair of high-purity yttrium targets (purity >99.99%) as twin targets, driven by a dedicated mid-frequency AC power supply. The two targets alternately act as cathode and anode in each AC cycle. When one target is sputtered as cathode, the other target acts as anode, collecting electrons and effectively neutralizing the positive charge accumulated on the target surface. This completely suppresses the arcing phenomenon found in conventional reactive sputtering, ensuring extreme stability of the deposition process. This operating mode allows for stable operation near the "transition zone," a region where the target is not completely poisoned but the oxygen flow rate is already high, combining high sputtering yield and high reaction efficiency, thus achieving deposition rates far exceeding those of traditional RF sputtering.

[0033] In some embodiments, the ion source-assisted bombardment employs Ar... + With O + A mixed ion beam is used to simultaneously bombard the growing Y2O3 film. The ion source emits an ion beam with an energy of 80 eV-200 eV and an ion beam current density of 0.1 mA / cm². 2 -0.5mA / cm 2 .

[0034] In practice, during the entire Y2O3 film deposition process, the ion source operates continuously, generating an ion beam (Ar) whose energy and beam current density can be independently controlled. + and O + The mixed ions from the ion source simultaneously bombard the surface of the growing film. The bombardment by low-energy ions provides additional kinetic energy to the deposited atoms, enabling them to migrate and relax more fully on the surface, filling the interatomic gaps and thus growing an atomically dense film structure. By precisely controlling the energy of the ion beam and the ion / atom arrival ratio, the internal stress state of the film can be effectively controlled. The compressive stress introduced by ion bombardment can offset some of the tensile stress caused by lattice mismatch and thermal mismatch, keeping the net stress of the entire thick film at a low level.

[0035] In some implementations, the ion energy of the ion source is 150 eV-200 eV in the initial stage of Y2O3 film deposition using mid-frequency twin magnetron sputtering, and then linearly reduced to 80 eV-120 eV in the later stage.

[0036] To further optimize the stress distribution of the Y2O3 film, this embodiment proposes a staged, gradient-based ion source parameter control strategy. In the initial stage of thick film deposition (the first 1-2 micrometers), a relatively high ion energy (e.g., 150 eV-200 eV) is used to form a dense substrate with strong compressive stress, enhancing its adhesion and support to the substrate. In the middle and later stages of deposition, the ion energy is gradually and linearly reduced (e.g., to 80 eV-120 eV) to decrease the compressive stress introduced into subsequent film layers, avoiding excessive total stress accumulation. This achieves a stress gradient distribution from the interface to the surface, maximizing the overall stability and crack resistance of the thick film.

[0037] In some embodiments, the transition layer is composed of yttrium aluminum garnet (Y3Al5O). 12 Magnesium aluminum spinel MgAl2O4 or yttrium gallium garnet Y3Ga5O 12 The thickness is 30 nm-100 nm.

[0038] In specific implementation, the transition layer is selected from yttrium aluminum garnet (Y3Al5O). 12 Magnesium aluminum spinel MgAl2O4 and yttrium gallium garnet Y3Ga5O 12The coefficient of thermal expansion of the material falls between that of sapphire (Al2O3) and Y2O3. It exhibits high chemical stability, excellent resistance to fluorine plasma etching, and good compatibility with Y2O3 films, forming a continuous and dense composite protective system that extends the service life of the sapphire window. Furthermore, all of these materials are broadband, highly transparent oxide ceramics with high optical transmittance in the ultraviolet to near-infrared bands, ensuring that they do not degrade the optical performance of the sapphire optical observation window and meet the requirements of plasma etching equipment for optical monitoring and endpoint detection. In addition, the transition layer thickness is controlled within the range of 30 nm to 100 nm, providing sufficient stress buffering without introducing additional internal stress or causing light scattering due to excessive film thickness, thus guaranteeing the optical uniformity and structural integrity of the film.

[0039] In some embodiments, the surface cleaning and activation treatment of the sapphire substrate includes: Chemical cleaning: The sapphire substrate is ultrasonically cleaned with acetone, ethanol and deionized water in sequence, and then soaked in acid or alkali solution. Vacuum heat treatment: The sapphire substrate is heat-treated at 300 ℃-500 ℃ under vacuum conditions for 2 h-6 h; Ion source glow discharge cleaning and activation: The argon ion beam generated by the ion source bombards the surface of the heat-treated sapphire substrate.

[0040] In practice, the substrate is chemically cleaned to remove inorganic residues and surface micro-defect layers; vacuum heat treatment is then performed to thoroughly remove adsorbed water vapor and residual gases from the substrate surface. The preferred vacuum level during the treatment process is (5.0-10)×10⁻⁶. -4 Pa; Ion source glow discharge cleaning involves introducing high-purity argon (Ar) into a vacuum chamber at a substrate temperature of 300 ℃-500 ℃, turning on an ion source (such as a Hall ion source or radio frequency ion source), and generating a low-energy (50 eV-150 eV) argon ion beam to bombard the sapphire substrate surface for 5-15 minutes. This process can precisely remove atomic-level contaminants from the outermost layer of the surface. Furthermore, by increasing surface roughness and dangling bonds at the atomic scale through ion bombardment, the surface energy is significantly improved, thereby providing more nucleation sites for the growth of subsequent coatings and greatly enhancing the initial adhesion between the coating and the substrate.

[0041] In some embodiments, before depositing a transition layer on the sapphire substrate by radio frequency magnetron sputtering after surface cleaning and activation treatment of the sapphire substrate, the method further includes: An initial Al2O3 layer was deposited on a sapphire substrate using radio frequency magnetron sputtering; The thickness of the initial layer is 10 nm-30 nm.

[0042] In practice, since Al2O3 and the substrate sapphire are the same type of material, Al2O3 can form a perfect epitaxial bond with the sapphire surface and form a new Al2O3 layer with higher surface activity, laying a solid foundation for the firm adhesion of the subsequent composite layer.

[0043] In some embodiments, both the initial Al2O3 layer and the transition layer are prepared by radio frequency sputtering in an Ar / O2 mixed atmosphere.

[0044] In some embodiments, after depositing a Y2O3 protective layer on the transition layer surface using a mid-frequency twin magnetron sputtering coupled ion source for assisted bombardment, the method further includes: annealing the sapphire substrate, including: In a vacuum environment, the temperature is increased to 400-500℃ at a rate of 5℃ / min-10℃ / min, held for 1-2 hours, then increased to 750-900℃ at the same rate, and then backfilled with an appropriate amount of high-purity oxygen. The temperature is held for 24 hours in a weakly oxidizing atmosphere, and finally slowly cooled to room temperature at a rate of 1℃ / min-3℃ / min.

[0045] Annealing eliminates most of the residual stress, especially the stress gradient, in the film by thermally driving atomic rearrangement; it promotes the transformation of amorphous or small-grained Y2O3 films into a cubic phase structure with more complete structure and more uniform grain size, and eliminates defects such as grain boundaries; annealing in a weakly oxidizing atmosphere can replenish oxygen deficiencies that may exist in the film and improve optical transmittance.

[0046] In a second aspect, the present invention provides a surface composite protective layer for a sapphire optical observation window obtained by the preparation method described in the first aspect above.

[0047] To enable those skilled in the art to more clearly understand the present invention, the following embodiments will be used to provide a detailed description of the surface composite protective layer for sapphire optical observation windows and its preparation method.

[0048] Example 1 (1) Sapphire substrate pretreatment Chemical cleaning: A single-crystal α-Al2O3 sapphire window was selected as the substrate and ultrasonically cleaned in acetone, ethanol and deionized water for 10 min each to remove surface oil, organic impurities and particulate matter. Then, nitrogen gas was used to dry the substrate.

[0049] Vacuum heat treatment: The substrate is placed into the substrate holder of the high-vacuum coating chamber, and the vacuum is evacuated to an ultimate vacuum better than 5.0 × 10⁻⁶. -4 Pa; The substrate was heated to 400 °C by slow heating and held at that temperature for 4 h to completely remove adsorbed water vapor and residual gas.

[0050] Ion source glow discharge cleaning and activation: The substrate is kept at 400 °C, high-purity Ar gas is introduced into the cavity, and the radio frequency ion source is turned on; the substrate surface is bombarded with a 100 eV argon ion beam for 10 min to achieve atomic-level cleaning and surface activation, and improve the interfacial bonding energy.

[0051] (2) Deposition of Al2O3 initial layer and transition layer Without disrupting the vacuum throughout the process, the following deposits are sequentially made on the activated sapphire substrate: 1) Deposition of the initial Al2O3 layer Target material: Al2O3 ceramic target; Atmosphere: Ar / O2 mixed atmosphere; Sputtering method: Radio frequency magnetron sputtering; Working air pressure: 0.3 Pa; Sputtering power: 300 W; Deposition thickness: 20 nm.

[0052] 2) Yttrium aluminum garnet Y3Al5O 12 (YAG) transition layer deposition Target material: Yttrium aluminum garnet (YAG) ceramic target; Atmosphere: Ar / O2 mixed atmosphere; Sputtering method: Radio frequency magnetron sputtering; Working air pressure: 0.3 Pa; Sputtering power: 350 W; Deposition thickness: 50 nm.

[0053] (3) Deposition of thick Y2O3 film by mid-frequency twin magnetron sputtering coupled with ion source-assisted bombardment. The sputtering source is a mid-frequency twin magnetron sputtering system, and the target material is a pair of metallic Y targets with a purity >99.99%. Operating parameters include: Atmosphere: Ar / O2 reactive sputtering, oxygen flow rate controlled by target voltage feedback closed loop; substrate temperature: 400 ℃; working pressure: 0.4 Pa; argon flow rate: 50 sccm; intermediate frequency power supply: frequency 40 kHz, power 10 kW, duty cycle 50%.

[0054] Ion source-assisted bombardment using Ar + With O + A mixed ion beam was used to simultaneously bombard the growing Y₂O₃ film; the ion beam current density was 0.3 mA / cm². 2 ; During the first 1-2 μm of Y2O3 film deposition, the ion beam energy was controlled at 180 eV. In the later stages of deposition, the ion energy was linearly reduced to 100 eV, and the total deposition thickness of the Y2O3 film was 10 μm.

[0055] (4) Annealing treatment After coating, the sample was placed in a vacuum environment and heated to 400 ℃ at 8 ℃ / min and held for 1 h; then the temperature was increased to 800 ℃ at 8 ℃ / min and held for 24 h; then an appropriate amount of oxygen was introduced and the sample was slowly cooled to room temperature at 2 ℃ / min under a weak oxidizing atmosphere.

[0056] Example 2 Compared with Example 1, the difference is that the target material used in the preparation of the transition layer in Example 2 is magnesium aluminum spinel MgAl2O4, while the rest of the process and parameter selection are the same.

[0057] Example 3 The difference between Example 1 and Example 3 is that the target material used for the preparation of the transition layer in Example 3 is yttrium gallium garnet (Y3Ga5O). 12 The rest of the process and parameter selection are the same.

[0058] Comparative Example 1 Compared with Example 1, the difference is that when Y2O3 thick film deposition was performed in Comparative Example 1, radio frequency magnetron sputtering was used (the working conditions were the same as those for the transition layer deposition by radio frequency magnetron sputtering in Example 1, with a deposition thickness of 10 μm), and there was no ion source-assisted bombardment. All other processes were the same.

[0059] Figure 2 A scanning electron microscope image of the composite protective layer provided in Embodiment 1 of the present invention is shown, as follows: Figure 2 As shown, the obtained composite film is free of cracks and reaches atomic-level density. The composite protective layer tested has an adhesion strength >50 N, a density greater than 99%, an optical transmittance greater than 90%, and is resistant to fluorine plasma etching.

[0060] Figure 3 The image shows a scanning electron microscope (SEM) image of the composite protective layer provided in the comparative example of the present invention. The deposition rate of the 10 μm Y2O3 film prepared by radio frequency magnetron sputtering is extremely slow, resulting in poor film density, which significantly affects the etching resistance of the composite protective layer.

[0061] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. In addition, those skilled in the art can combine and integrate the different embodiments or examples described in this specification.

[0062] For the sake of simplicity, the method embodiments are described as a series of actions. However, those skilled in the art should understand that the present invention is not limited to the described order of actions, as some steps can be performed in other orders or simultaneously according to the present invention. Furthermore, those skilled in the art should also understand that the embodiments described in the specification are preferred embodiments, and the actions and components involved are not necessarily essential to the present invention.

[0063] The above provides a detailed description of the surface composite protective layer for a sapphire optical observation window and its preparation method provided by the present invention. Specific examples have been used to illustrate the principles and implementation methods of the present invention. The descriptions of the above embodiments are only intended to help understand the method and core ideas of the present invention. At the same time, for those skilled in the art, there will be changes in the specific implementation methods and application scope based on the ideas of the present invention. Therefore, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. A method for preparing a surface composite protective layer for a sapphire optical observation window, characterized in that, The preparation method includes: After surface cleaning and activation treatment of the sapphire substrate, a transition layer is deposited on the sapphire substrate by radio frequency magnetron sputtering. The thermal expansion coefficient of the transition layer is between Al2O3 and Y2O3. A Y2O3 film was deposited on the surface of the transition layer by using a mid-frequency twin magnetron sputtering coupled ion source to assist in bombardment, thus forming the composite protective layer.

2. The method for preparing the surface composite protective layer for a sapphire optical observation window according to claim 1, characterized in that, The operating parameters of the intermediate frequency twin magnetron sputtering satisfy the following: Yttrium twin target purity > 99.99%; The substrate temperature is 300 ℃-500 ℃; The working gas is an Ar / O2 mixture with a pressure of 0.2~0.8 Pa; The intermediate frequency power supply has a frequency of 40 kHz, a power of 5 kW-15 kW, and a duty cycle of 50%. The deposition thickness of the Y2O3 film is 8 μm-12 μm.

3. The method for preparing the surface composite protective layer for a sapphire optical observation window according to claim 1, characterized in that, Ion source-assisted bombardment uses Ar + With O + A mixed ion beam is used to simultaneously bombard the growing Y₂O₃ film; the ion source emits an ion beam with an energy of 80 eV-200 eV and an ion beam current density of 0.1 mA / cm². 2 -0.5 mA / cm 2 .

4. The method for preparing the surface composite protective layer for a sapphire optical observation window according to claim 1 or 3, characterized in that, In the initial stage of Y2O3 film deposition using mid-frequency twin magnetron sputtering, the ion energy of the ion source is 150 eV-200 eV, which linearly decreases to 80 eV-120 eV in the middle and later stages.

5. The method for preparing the surface composite protective layer for a sapphire optical observation window according to claim 1, characterized in that, The transition layer is composed of yttrium aluminum garnet (Y3Al5O). 12 Magnesium aluminum spinel MgAl2O4 or yttrium gallium garnet Y3Ga5O 12 The thickness is 30 nm-100 nm.

6. The method for preparing the surface composite protective layer for a sapphire optical observation window according to claim 1, characterized in that, The surface cleaning and activation treatment of the sapphire substrate includes: After ultrasonic cleaning of the sapphire substrate with acetone, ethanol and deionized water in sequence, it is soaked in acid or alkaline solution. The sapphire substrate was heat-treated at 300 ℃-500 ℃ under vacuum for 2 h-6 h; The sapphire substrate surface after heat treatment is activated by bombarding it with an argon ion beam generated by an ion source.

7. The method for preparing the surface composite protective layer for a sapphire optical observation window according to claim 1, characterized in that, After surface cleaning and activation treatment of the sapphire substrate, before depositing a transition layer on the sapphire substrate using radio frequency magnetron sputtering, the method further includes: An initial Al2O3 layer was deposited on a sapphire substrate using radio frequency magnetron sputtering; The thickness of the initial layer is 10 nm-30 nm.

8. The method for preparing the surface composite protective layer for a sapphire optical observation window according to claim 7, characterized in that, Both the initial Al2O3 layer and the transition layer were prepared by radio frequency sputtering in an Ar / O2 mixed atmosphere.

9. The method for preparing the surface composite protective layer for a sapphire optical observation window according to claim 1, characterized in that, The method, which employs a mid-frequency twin magnetron sputtering coupled ion source for assisted bombardment, after depositing a Y2O3 protective layer on the transition layer surface, further includes: annealing the sapphire substrate, including: In a vacuum environment, the temperature is increased to 400℃-500℃ at a rate of 5℃ / min-10℃ / min, held for 1 h-2 h, then increased to 750℃-900℃ at the same rate, and then backfilled with an appropriate amount of high-purity oxygen. The temperature is held for 24 h in a weak oxidizing atmosphere, and finally slowly cooled to room temperature at a rate of 1℃ / min-3℃ / min.

10. A surface composite protective layer for a sapphire optical observation window, characterized in that, The surface composite protective layer for the sapphire optical observation window is obtained by any of the preparation methods described in claims 1-9.

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