Ion source microwave window with composite functional film and surface texture and preparation method thereof

Abstract

The invention relates to the technical field of ion source microwave windows, in particular to an ion source microwave window with a composite functional film and a surface texture and a preparation method thereof, and the ion source microwave window is composed of a microwave window matrix layer, a composite functional film layer and a surface texture layer; the composite material is especially suitable for an electron cyclotron resonance (ECR) ion source and related applications thereof, can effectively inhibit the surface sparking phenomenon, reduce ablation, improve the microwave coupling efficiency and prolong the service life of a microwave window especially in high-power microwave excitation and high-density plasma environments, and has excellent heat-conducting property and breakdown resistance.

Description

Technical Field

[0001] The present invention relates to the technical field of ion source microwave windows, and particularly relates to an ion source microwave window with a composite functional thin film and surface texture and a preparation method thereof. Background Art

[0002] Electron Cyclotron Resonance (ECR) is a core technology in the fields of plasma physics, materials science, and nuclear fusion. Its efficient and non-contact energy coupling mechanism is irreplaceable in industry and scientific research. The microwave window is a key component in the ECR plasma source, used to isolate the microwave transmission system in the vacuum plasma chamber and the atmospheric environment, and at the same time efficiently transmit microwave energy. At the same time, as a key component for microwave energy transmission, the ion source microwave window is widely used in various accelerator systems. Currently, common ion source microwave windows mostly use materials such as AlN, Si 3 N 4 etc. Their advantages lie in good microwave transmission performance and relatively high mechanical strength. However, in practical applications, since the microwave window is exposed to a strong plasma environment for a long time, phenomena such as discharge initiation, arc discharge, surface ablation, and cracks are likely to occur on the surface. And under the action of high-power microwaves and high-energy ion beams, the surface of the microwave window is extremely vulnerable to damage such as arcing, ablation, and electron bombardment, thus affecting the stability and continuous operation of the ion source system. These problems limit the long-term stability of the microwave window.

[0003] In order to improve the performance of the microwave window, existing technologies have tried to enhance the durability of the microwave window by increasing the thickness of the ceramic layer, using metal or ceramic protective layers, etc. However, these methods usually increase the complexity and cost of the system and fail to effectively solve problems such as discharge and ablation, as Figure 1 shown. Therefore, there is an urgent need for a new design that can effectively extend the service life of the microwave window while ensuring microwave transmissivity and breakdown resistance.

[0004] Aiming at the above technical problems, the present invention provides an ion source microwave window with a composite functional thin film and surface texture, which is particularly suitable for Electron Cyclotron Resonance (ECR) ion sources and their related applications. Especially in a high-power microwave excitation and high-density plasma environment, it can effectively suppress surface arcing phenomena, reduce ablation, improve microwave coupling efficiency, and extend the service life of the microwave window. Summary of the Invention

[0005] The purpose of the present invention is to provide an ion source microwave window with a composite functional thin film and surface texture, which can effectively suppress surface arcing phenomena, reduce ablation, improve microwave coupling efficiency, and extend the service life of the microwave window.

[0006] The primary objective of the present invention is to provide an ion source microwave window with a composite functional thin film and surface texture. The ion source microwave window is composed of a microwave window substrate layer, a composite functional thin film layer, and a surface texture layer. The composite functional thin film layer is deposited on the vacuum-side surface of the microwave window substrate layer, and the surface texture layer covers the upper surface of the composite functional thin film.

[0007] Preferably, the microwave window substrate layer is disc-shaped, prepared from AlN ceramic, with a thickness of 1 - 3 mm, having excellent microwave permeability and high thermal conductivity.

[0008] Preferably, the composite functional thin film layer is prepared from DLC thin film or Si-doped DLC thin film, having good thermal conductivity, breakdown resistance, and being able to effectively reduce electron bombardment and plasma erosion.

[0009] Preferably, the thickness of the composite functional thin film layer is 2 - 5 μm.

[0010] Preferably, the surface texture layer is one or several of honeycomb, columnar, or conical structures, which can significantly reduce the concentration of electric field strength, inhibit the initiation of discharge, and prevent the adsorption of surface impurities.

[0011] Preferably, the surface texture layer is honeycomb-shaped, with a pore diameter of 50 - 200 μm and a pore depth of 2 - 3 μm.

[0012] The second objective of the present invention is to provide a method for preparing the ion source microwave window, including the following steps: (1) Take a conventional ceramic and prepare the microwave window substrate layer by hot pressing sintering or CVD method; (2) Prepare a composite functional thin film on the vacuum-side surface of the microwave window substrate layer prepared in step (1) by using magnetron sputtering, ion beam assisted deposition, or hot filament CVD process; (3) Prepare a surface texture layer on the basis of the composite functional thin film prepared in step (2) by using laser direct writing, laser pulse etching, or mask plasma etching technology.

[0013] The beneficial effects of the present invention are as follows: improving microwave coupling efficiency: the combination of the composite functional thin film and surface texture can optimize the electric field distribution of the microwave coupling system. Compared with the traditional single BN layer, the microwave energy transmission is more uniform; Suppressing the arcing phenomenon: the breakdown resistance of the composite thin film layer and the design of the surface micro-nano texture effectively suppress the arcing and discharge phenomena on the surface of the microwave window.

[0014] Preventing ablation: the combination of the surface texture design and DLC thin film effectively slows down the surface ablation caused by plasma bombardment and extends the service life of the microwave window.

[0015] Good thermal management: The DLC film has excellent thermal conductivity and can effectively conduct the heat in the high-temperature area to the substrate layer, avoiding structural damage caused by overheating.

[0016] Long service life and high stability: This microwave window can operate stably in the environment of long-term high-power microwaves and high-density plasmas, and its service life is significantly improved. Brief Description of the Drawings

[0017] Figure 1 The ion source microwave window after high temperature and frequent ablation by firing; Figure 2 Schematic diagram of the ion source microwave window with composite functional film and surface texture; Figure 3 Schematic diagram of the surface texture pattern; Figure 4 Schematic diagram of the coupling between the ion source microwave and the cavity; Note: 1. Discharge cavity; 2. Microwave window; 3. BJ-32 waveguide; 4. Transition waveguide; 5. BJ-26 waveguide Figure 5 Electric field simulation results of the common ion source microwave window; Figure 6 Electric field results of the ion source microwave window with the new surface texture; Figure 7 Comparison results of the power deposition of the two ion source microwave windows. Detailed Description of the Invention

[0018] The exemplary embodiments of the present invention will be described in more detail below with reference to the accompanying drawings. Although the exemplary embodiments of the present invention are shown in the drawings, it should be understood that the present invention can be implemented in various forms and should not be limited by the embodiments set forth herein. On the contrary, these embodiments are provided so that the present invention can be more thoroughly understood and the scope of the present invention can be fully conveyed to those skilled in the art.

[0019] In the present invention, the AlN ceramic is aluminum nitride ceramic, which is a hexagonal ceramic material mainly composed of covalent bonds and has characteristics such as high thermal conductivity, low thermal expansion coefficient, excellent electrical insulation, high temperature resistance, and chemical corrosion resistance. It is widely used in fields such as electronic packaging, aerospace, semiconductors, and military industry.

[0020] In the present invention, the DLC film refers to a diamond-like carbon film, which is a metastable material formed by the combination of sp3 and sp2 bonds in recent years. It combines the excellent properties of diamond and graphite and has high hardness, high resistivity, good optical properties, and excellent tribological properties.

[0021] In the present invention, the CVD mentioned refers to chemical vapor deposition, which is a chemical engineering technology. This technology mainly uses one or several gaseous compounds or elements containing thin film elements to carry out chemical reactions on the substrate surface to form a thin film. Chemical vapor deposition is a new technology for preparing inorganic materials developed in recent decades. The chemical vapor deposition method has been widely used for purifying substances, developing new crystals, depositing various single crystals, polycrystals or glassy inorganic thin film materials. These materials can be oxides, sulfides, nitrides, carbides, or binary or multi-element intermetallic compounds in groups III-V, II-IV, IV-VI, and their physical functions can be precisely controlled through the deposition process of gas phase doping. Chemical vapor deposition has become a new field in inorganic synthetic chemistry.

[0022] In the present invention, the hot filament CVD process is fully called hot filament chemical vapor deposition, which is a process method for preparing diamond films. Its main principle is through low-pressure chemical vapor deposition at high temperature. A mixed gas of carbon-containing gas and hydrogen is introduced into the reaction furnace cavity, and at high temperature, it is decomposed by a hot filament (tungsten filament or molybdenum filament) into carbon-containing active groups and excited hydrogen atoms, so as to deposit on the substrate to form a carbon film.

[0023] The following examples only disclose some parameters of the present invention, and the texture parameters are optimized and designed according to the working frequency, microwave wavelength and surface electric field distribution.

[0024] Example 1

[0025] Such as Figure 2-3 , an ion source microwave window with a composite functional thin film and surface texture, the ion source microwave window includes a microwave window substrate layer, a composite functional thin film layer and a surface texture layer. The composite functional thin film layer is deposited on the vacuum side surface of the microwave window substrate layer, and the surface texture layer covers the upper surface of the composite functional thin film. The microwave window substrate layer is in a disc shape, made of AlN ceramic, with a thickness of 1 mm, having excellent microwave permeability and high thermal conductivity. The composite functional thin film layer is made of DLC thin film, having good thermal conductivity, breakdown resistance, and can effectively reduce electron bombardment and plasma erosion. The thickness of the composite functional thin film layer is 2 μm. The surface texture layer is in a honeycomb shape, with a pore diameter of 50 μm and a pore depth of 2 μm, which can significantly reduce the concentration of electric field strength, inhibit the initiation of discharge, and prevent surface impurity adsorption.

[0026] Example 2

[0027] Such as Figure 2-3, an ion source microwave window with a composite functional thin film and surface texture, the ion source microwave window comprising a microwave window substrate layer, a composite functional thin film layer, and a surface texture layer. The composite functional thin film layer is deposited on the vacuum-side surface of the microwave window substrate layer, and the surface texture layer covers the upper surface of the composite functional thin film. The microwave window substrate layer is disc-shaped, made of AlN ceramic, with a thickness of 3 mm, having excellent microwave permeability and high thermal conductivity. The composite functional thin film layer is made of DLC thin film, having good thermal conductivity, breakdown resistance, and being able to effectively reduce electron bombardment and plasma erosion. The thickness of the composite functional thin film layer is 5 μm. The surface texture layer is honeycomb-shaped, with a pore diameter of 200 μm and a pore depth of 3 μm, which can significantly reduce the concentration of electric field strength, inhibit the initiation of discharge, and prevent surface impurity adsorption.

[0028] Example 3,

[0029] Such as Figure 2-3 , an ion source microwave window with a composite functional thin film and surface texture, the ion source microwave window comprising a microwave window substrate layer, a composite functional thin film layer, and a surface texture layer. The composite functional thin film layer is deposited on the vacuum-side surface of the microwave window substrate layer, and the surface texture layer covers the upper surface of the composite functional thin film. The microwave window substrate layer is disc-shaped, made of AlN ceramic, with a thickness of 2 mm, having excellent microwave permeability and high thermal conductivity. The composite functional thin film layer is made of DLC thin film, having good thermal conductivity, breakdown resistance, and being able to effectively reduce electron bombardment and plasma erosion. The thickness of the composite functional thin film layer is 5 μm. The surface texture layer is honeycomb-shaped, with a pore diameter of 50 μm and a pore depth of 3 μm, which can significantly reduce the concentration of electric field strength, inhibit the initiation of discharge, and prevent surface impurity adsorption.

[0030] Example 4,

[0031] Such as Figure 2-3 , an ion source microwave window with a composite functional thin film and surface texture, the ion source microwave window comprising a microwave window substrate layer, a composite functional thin film layer, and a surface texture layer. The composite functional thin film layer is deposited on the vacuum-side surface of the microwave window substrate layer, and the surface texture layer covers the upper surface of the composite functional thin film. The microwave window substrate layer is disc-shaped, made of AlN ceramic, with a thickness of 2 mm, having excellent microwave permeability and high thermal conductivity. The composite functional thin film layer is made of Si-doped DLC thin film, having good thermal conductivity, breakdown resistance, and being able to effectively reduce electron bombardment and plasma erosion. The thickness of the composite functional thin film layer is 5 μm. The surface texture layer is columnar, with a pore diameter of 50 μm and a pore depth of 3 μm, which can significantly reduce the concentration of electric field strength, inhibit the initiation of discharge, and prevent surface impurity adsorption.

[0032] Example 5

[0033] As Figure 2-3 , an ion source microwave window with a composite functional thin film and surface texture, the ion source microwave window includes a microwave window substrate layer, a composite functional thin film layer, and a surface texture layer. The composite functional thin film layer is deposited on the vacuum-side surface of the microwave window substrate layer, and the surface texture layer covers the upper surface of the composite functional thin film. The microwave window substrate layer is disk-shaped, made of AlN ceramic, with a thickness of 5 mm, having excellent microwave permeability and high thermal conductivity. The composite functional thin film layer is prepared from a Si-doped DLC thin film, having good thermal conductivity, breakdown resistance, and can effectively reduce electron bombardment and plasma erosion. The thickness of the composite functional thin film layer is 4 μm. The surface texture layer is conical, with a pore diameter of 100 μm and a pore depth of 3 μm, which can significantly reduce the concentration of electric field strength, suppress the initiation of discharge, and prevent the adsorption of surface impurities.

[0034] Example 6

[0035] Preparation: (1) Take a conventional ceramic and prepare the microwave window substrate layer by hot pressing sintering, with a thickness of 2 mm; (2) Use a magnetron sputtering process to prepare a composite functional thin film on the vacuum-side surface of the microwave window substrate layer prepared in step (1), with a thickness of 5 μm; (3) Prepare a surface texture layer on the composite functional thin film prepared in step (2) by laser direct writing plasma etching technology. The surface texture layer is honeycomb-shaped, with a pore diameter of 50 μm and a pore depth of 3 μm.

[0036] Example 7. Coupling of the ion source microwave window with the cavity As Figure 4 shown, couple the ion source microwave window with the cavity according to the conventional method, which are in turn the discharge cavity 1, the microwave window 2, the BJ-32 waveguide 3, the transition waveguide 4, and the BJ-26 waveguide 5.

[0037] Couple the ion source microwave window with the cavity by the conventional method. This coupling system consists of the following parts in turn: (1) Discharge cavity: This is the core part of the ion source, where high-density plasma is generated inside. In this part, microwave energy is transmitted through the microwave window into the plasma, thereby exciting electron cyclotron resonance (ECR). The design of the discharge cavity should support the interaction between high-power microwaves and the plasma, and at the same time have good structural strength and breakdown resistance.

[0038] (2) Microwave window: The microwave window is used to isolate the vacuum environment from the external atmosphere while effectively transmitting microwave energy. It must have excellent microwave permeability, high temperature resistance, and breakdown resistance, and is usually made of AlN ceramic or similar materials. To extend the service life of the microwave window, the composite functional film and surface texture design are adopted, which can effectively reduce surface ablation and arcing phenomena.

[0039] (3) BJ-32 waveguide: The waveguide is a key part of microwave energy transmission, and its function is to conduct the microwave signal from the microwave source to the microwave window. Through optimized structural design, the BJ-32 waveguide can effectively reduce microwave loss during transmission.

[0040] (4) Transition waveguide: The transition waveguide is used to connect different types of waveguides. Its design should ensure a smooth transition of the microwave signal between different waveguides, reduce signal reflection and attenuation, and thus improve the microwave coupling efficiency.

[0041] (5) BJ-26 waveguide: As the final microwave transmission channel, the BJ-26 waveguide further transmits the microwave signal to other parts of the ion source. This waveguide is connected to the previous waveguide in structure and realizes the final transfer of energy through efficient transmission.

[0042] Example 8, Application Case As Figure 5 shown, when using a conventional microwave window, there are significant fluctuations in the electric field intensity inside the cavity. The simulation results show that the maximum value of the electric field is not concentrated inside the cavity, but appears in the BJ-26 waveguide section. This non-uniform electric field distribution will lead to a decrease in the microwave energy transmission efficiency, unable to fully and effectively excite the plasma, and thus affect the working efficiency of the ion source.

[0043] The existence of electric field fluctuations not only reduces the energy utilization rate, but may also have an adverse impact on the stability of the system, further affecting the working effect of the ion source. In addition, the simulation analysis results also show that there is a certain degree of microwave reflection under the conventional microwave window. Excessive microwave reflection will lead to energy loss during transmission, and thus affect the stability and power output of the ion source. Especially under high-power input conditions, the excessive reflection loss will significantly reduce the overall efficiency of the system, making the ion source unable to achieve ideal performance during operation. After applying the microwave window with a new surface texture design, as Figure 6As shown, the electric field intensity distribution has changed significantly. The optimized electric field is effectively concentrated inside the cavity, and the maximum electric field intensity inside the cavity is increased by about 3 times compared with the conventional microwave window. This result indicates that the novel microwave window can significantly improve the focusing effect of microwave energy, reduce electric field fluctuations, and effectively improve the energy utilization rate through the design of surface texture. This optimization of the electric field distribution not only improves the transmission efficiency of microwave energy but also significantly improves the plasma excitation effect, thus enhancing the performance and stability of the ion source. At the same time, the optimized microwave window also reduces reflection losses, ensuring efficient energy transmission. Especially under high-power input conditions, it can better ensure the stable operation and high-power output of the system.

[0044] Example 9, Application Case As Figure 7 shown, the power deposition conditions of the AlN microwave window and the DLC surface texture microwave window in the plasma environment are presented. The results show that the power deposition of the AlN microwave window in the plasma environment is significantly higher, approaching 8.0×10 8 W / m³. This indicates that under the use of a conventional microwave window, the deposition of microwave energy is relatively concentrated, and it can transfer energy well, but it may be prone to surface ablation and arcing phenomena under long-term high-power excitation, affecting the durability of the microwave window. In contrast, the power deposition of the DLC surface texture microwave window is significantly lower, only about 2.6×10 8 W / m³. This shows that the design of the surface texture effectively slows down the concentration of microwave energy, thereby reducing the erosion of the microwave window surface by the plasma and reducing the occurrence of ablation and arcing phenomena. Through the optimized surface structure, the DLC microwave window can distribute microwave power more evenly and extend the service life of the microwave window.

Claims

1. An ion source microwave window with a composite functional film and surface texture, characterized in that: The ion source microwave window is composed of a microwave window substrate layer, a composite functional film layer and a surface texture layer. The composite functional film layer is deposited on the vacuum side surface of the microwave window substrate layer, and the surface texture layer covers the upper surface of the composite functional film.

2. The ion source microwave window according to claim 1, characterized in that: The microwave window substrate layer is in a disc shape, made of AlN ceramics, and has a thickness of 1-3 mm.

3. The ion source microwave window according to claim 1, characterized in that: The composite functional film layer is prepared from a DLC film or a Si-doped DLC film.

4. The ion source microwave window according to claim 3, characterized in that: The thickness of the composite functional film layer is 2-5 μm.

5. The ion source microwave window according to claim 1, characterized in that: The surface texture layer is in one or more of honeycomb, columnar or conical structures.

6. The ion source microwave window according to claim 5, characterized in that: The surface texture layer is honeycomb-shaped, with a pore size of 50-200 μm and a pore depth of 2-3 μm.

7. The method for preparing an ion source microwave window according to any one of claims 1 to 6, characterized in that: The steps include: (1) Using conventional ceramics, prepare a microwave window substrate layer by hot pressing sintering or CVD; (2) preparing a composite functional film on the vacuum side surface of the microwave window substrate layer prepared in step (1) by using magnetron sputtering, ion beam assisted deposition or hot wire CVD process; (3) Preparing a surface texture layer on the basis of the composite functional film prepared in step (2) by laser direct writing, laser pulse etching or mask plasma etching technology.

Images