An ion source microwave window with composite functional film and surface texture and its preparation method

Abstract

The present invention relates to the technical field of ion source microwave windows, and specifically to an ion source microwave window with a composite functional film and surface texture and a preparation method thereof. The ion source microwave window comprises a microwave window substrate layer, a composite functional film layer and a surface texture layer; the ion source microwave window is particularly suitable for electron cyclotron resonance (ECR) ion sources and related applications, and can effectively suppress surface sparking, reduce ablation, improve microwave coupling efficiency, extend the service life of the microwave window, and has excellent thermal conductivity and breakdown resistance, especially under high-power microwave excitation and high-density plasma environments.

Description

Technical Field

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

[0002] Electron cyclotron resonance (ECR) is a core technology in plasma physics, materials science, and nuclear fusion. Its efficient, contactless energy coupling mechanism is irreplaceable in both industry and scientific research. Microwave windows are key components in ECR plasma sources, isolating the vacuum plasma chamber from the ambient microwave transmission system while efficiently transmitting microwave energy. Ion source microwave windows, as key components for microwave energy transmission, are also widely used in various accelerator systems. Currently, common ion source microwave windows are made of materials such as AlN and Si3N4, which offer excellent microwave transmission and high mechanical strength. However, in practical applications, long-term exposure to intense plasma environments can lead to surface damage such as discharge initiation, arcing, surface ablation, and cracking. Furthermore, under the influence of high-power microwaves and high-energy ion beams, the microwave window surface is highly susceptible to damage such as sparking, ablation, and electron bombardment, which can affect the stability and continuous operation of the ion source system. These issues limit the long-term reliability of microwave windows.

[0003] In order to improve the performance of microwave windows, existing technologies have attempted to enhance the durability of microwave windows 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. Figure 1 Therefore, there is an urgent need for a new design that can effectively extend the service life of the microwave window while ensuring microwave transmittance and anti-penetration properties.

[0004] In response to the above technical problems, the present invention provides an ion source microwave window with a composite functional film and surface texture, which is particularly suitable for electron cyclotron resonance (ECR) ion sources and related applications. Especially under high-power microwave excitation and high-density plasma environments, it can effectively suppress surface sparking, 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 film and surface texture, which can effectively suppress surface sparking, reduce ablation, improve microwave coupling efficiency and extend the service life of the microwave window.

[0006] The primary purpose of the present invention is to provide an ion source microwave window with a composite functional film and surface texture. 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.

[0007] Preferably, the microwave window substrate layer is disc-shaped, made of AlN ceramics, has a thickness of 1 to 3 mm, and has excellent microwave transmittance and high thermal conductivity.

[0008] Preferably, the composite functional film layer is prepared from a DLC film or a Si-doped DLC film, has good thermal conductivity and breakdown resistance, and can effectively reduce electron bombardment and plasma erosion.

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

[0010] Preferably, the surface texture layer has one or more of a honeycomb, columnar or conical structure, which can significantly reduce the concentration of electric field intensity, inhibit discharge initiation, and prevent surface impurities from being adsorbed.

[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] A second object of the present invention is to provide a method for preparing an ion source microwave window, comprising the following steps:

[0013] (1) Prepare the microwave window substrate layer from conventional ceramics by hot pressing or CVD;

[0014] (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;

[0015] (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.

[0016] The beneficial effects of the present invention are: improving microwave coupling efficiency: the combination of the composite functional film and the surface texture can optimize the electric field distribution of the microwave coupling system, and compared with the traditional single BN layer, the microwave energy transmission is more uniform;

[0017] Suppressing sparking: The composite film layer's breakdown resistance and surface micro-nano texture design effectively suppress sparking and discharge phenomena on the microwave window surface.

[0018] Prevent ablation: The combination of surface texture design and DLC film effectively slows down the surface ablation caused by plasma bombardment and extends the service life of the microwave window.

[0019] Good thermal management: DLC film has excellent thermal conductivity and can effectively transfer heat from high-temperature areas to the substrate layer, avoiding structural damage caused by overheating.

[0020] Long life and high stability: The microwave window can operate stably in long-term high-power microwave and high-density plasma environments, and its service life is significantly improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 Ion source microwave window after high temperature and frequent ignition ablation;

[0022] Figure 2 Schematic diagram of the ion source microwave window with composite functional film and surface texture;

[0023] Figure 3 Schematic diagram of surface texture patterns;

[0024] Figure 4 Schematic diagram of the coupling between the ion source microwave and the cavity;

[0025] Note: 1. Discharge cavity; 2. Microwave window; 3. BJ-32 waveguide; 4. Transition waveguide; 5. BJ-26 waveguide

[0026] Figure 5 Electric field simulation results of commonly used ion source microwave windows;

[0027] Figure 6 Electric field results of ion source microwave window for new surface texture;

[0028] Figure 7 Comparison of microwave window power deposition results for two ion sources. DETAILED DESCRIPTION

[0029] Exemplary embodiments of the present invention will be described in more detail below with reference to the accompanying drawings. Although exemplary embodiments of the present invention are shown in the accompanying drawings, it should be understood that the present invention can be implemented in various forms and should not be limited by the embodiments described herein. Rather, these embodiments are provided to enable a more thorough understanding of the present invention and to fully convey the scope of the present invention to those skilled in the art.

[0030] In the present invention, the AlN ceramic is aluminum nitride ceramic (Aluminum Nitride), which is a hexagonal ceramic material based on covalent bonds. It has high thermal conductivity, low thermal expansion coefficient, excellent electrical insulation, high temperature resistance and chemical corrosion resistance, and is widely used in electronic packaging, aerospace, semiconductors, military industry and other fields.

[0031] In the present invention, the DLC film refers to a diamond-like carbon film, which is a recently emerging metastable material generated by the combination of sp3 and sp2 bonds. It has the excellent properties of both diamond and graphite, and has high hardness, high resistivity, good optical properties and excellent tribological properties.

[0032] In the present invention, the CVD refers to chemical vapor deposition, which is a chemical technology that mainly utilizes one or more gaseous compounds or simple substances containing thin film elements to react chemically on the surface of a substrate to form a thin film. Chemical vapor deposition is a new technology for preparing inorganic materials developed in recent decades. Chemical vapor deposition has been widely used to purify substances, develop new crystals, and deposit various single crystal, polycrystalline or glassy inorganic thin film materials. These materials can be oxides, sulfides, nitrides, carbides, or binary or multi-element compounds in groups III-V, II-IV, and 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.

[0033] In the present invention, the hot wire CVD process is called hot wire chemical vapor deposition, which is a process for preparing diamond films. Its main principle is to pass a mixture of carbon-containing gas and hydrogen into a reaction furnace chamber through low-pressure vapor deposition at high temperature, and decompose it into carbon-containing active groups and excited hydrogen atoms through a hot wire (tungsten wire or molybdenum wire) at high temperature, which are then deposited on the substrate to form a carbon film.

[0034] The following examples only disclose some parameters of the present invention. The texture parameters are optimized according to the operating frequency, microwave wavelength and surface electric field distribution.

[0035] Example 1

[0036] like Figure 2-3, an ion source microwave window with a composite functional film and a surface texture, the ion source microwave window includes 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. The microwave window substrate layer is disc-shaped, made of AlN ceramic, with a thickness of 1 mm, and has excellent microwave transmittance and high thermal conductivity. The composite functional film layer is made of DLC film, has good thermal conductivity and breakdown resistance, and can effectively reduce electron bombardment and plasma erosion. The composite functional film layer is 2 μm thick. The surface texture layer is honeycomb-shaped, with a pore diameter of 50 μm and a pore depth of 2 μm, which can significantly reduce the concentration of electric field intensity, inhibit discharge initiation, and prevent surface impurity adsorption.

[0037] Example 2

[0038] like Figure 2-3 , an ion source microwave window with a composite functional film and a surface texture, the ion source microwave window includes 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. The microwave window substrate layer is disc-shaped, made of AlN ceramic, with a thickness of 3mm, and has excellent microwave transmittance and high thermal conductivity. The composite functional film layer is made of DLC film, has good thermal conductivity and breakdown resistance, and can effectively reduce electron bombardment and plasma erosion. The composite functional film layer is 5μm thick. The surface texture layer is honeycomb-shaped, with a pore diameter of 200μm and a pore depth of 3μm, which can significantly reduce the concentration of electric field intensity, inhibit discharge initiation, and prevent surface impurity adsorption.

[0039] Example 3

[0040] like Figure 2-3 , an ion source microwave window with a composite functional film and a surface texture, the ion source microwave window includes 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. The microwave window substrate layer is disc-shaped, made of AlN ceramic, with a thickness of 2mm, and has excellent microwave transmittance and high thermal conductivity. The composite functional film layer is made of DLC film, has good thermal conductivity and breakdown resistance, and can effectively reduce electron bombardment and plasma erosion. The composite functional film layer is 5μm thick. The surface texture layer is honeycomb-shaped, with a pore diameter of 50μm and a pore depth of 3μm, which can significantly reduce the concentration of electric field intensity, inhibit discharge initiation, and prevent surface impurity adsorption.

[0041] Example 4

[0042] like Figure 2-3 , an ion source microwave window with a composite functional film and a surface texture, the ion source microwave window includes 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. The microwave window substrate layer is disc-shaped, made of AlN ceramic, with a thickness of 2mm, and has excellent microwave transmittance and high thermal conductivity. The composite functional film layer is made of Si-doped DLC film, has good thermal conductivity and breakdown resistance, and can effectively reduce electron bombardment and plasma erosion. The composite functional film layer is 5μm thick. The surface texture layer is columnar, with a pore diameter of 50μm and a pore depth of 3μm, which can significantly reduce the concentration of electric field intensity, inhibit discharge initiation, and prevent surface impurity adsorption.

[0043] Example 5

[0044] like Figure 2-3 , an ion source microwave window with a composite functional film and a surface texture, the ion source microwave window includes 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. The microwave window substrate layer is disc-shaped, made of AlN ceramic, with a thickness of 5mm, and has excellent microwave transmittance and high thermal conductivity. The composite functional film layer is made of Si-doped DLC film, has good thermal conductivity and breakdown resistance, and can effectively reduce electron bombardment and plasma erosion. The composite functional film layer is 4μm thick. The surface texture layer is conical, with a pore diameter of 100μm and a pore depth of 3μm, which can significantly reduce the concentration of electric field intensity, inhibit discharge initiation, and prevent surface impurity adsorption.

[0045] Example 6

[0046] preparation:

[0047] (1) Prepare a microwave window substrate layer of conventional ceramic by hot pressing and sintering, with a thickness of 2 mm;

[0048] (2) using a magnetron sputtering process to prepare a composite functional film on the vacuum side surface of the microwave window substrate layer prepared in step (1), with a thickness of 5 μm;

[0049] (3) A surface texture layer is prepared on the basis of the composite functional film prepared in step (2) by using a laser direct writing plasma etching technique. The surface texture layer is honeycomb-shaped, with a pore diameter of 50 μm and a pore depth of 3 μm.

[0050] Example 7: Coupling of ion source microwave window and cavity

[0051] like Figure 4 As shown, the ion source microwave window is coupled to the cavity according to a conventional method, which is the discharge cavity 1, microwave window 2, BJ-32 waveguide 3, transition waveguide 4 and BJ-26 waveguide 5 in sequence.

[0052] The ion source microwave window is coupled to the cavity using conventional methods. The coupling system consists of the following parts:

[0053] (1) Discharge chamber: This is the core part of the ion source, where high-density plasma is generated. In this part, microwave energy is transmitted to the plasma through the microwave window, thereby exciting electron cyclotron resonance (ECR). The discharge chamber design should be able to support the interaction between high-power microwaves and plasma, while also having good structural strength and breakdown resistance.

[0054] (2) Microwave Window: Microwave windows are used to isolate the vacuum environment from the external atmosphere while effectively transmitting microwave energy. They must have excellent microwave transmittance, high temperature resistance, and anti-penetration properties. They are usually made of AlN ceramic or similar materials. To extend the service life of microwave windows, composite functional films and surface texture designs are used to effectively reduce surface ablation and sparking.

[0055] (3) BJ-32 waveguide: The waveguide is a key component of microwave energy transmission. Its function is to conduct microwave signals from the microwave source to the microwave window. The BJ-32 waveguide can effectively reduce microwave losses during transmission through its optimized structural design.

[0056] (4) Transition waveguide: Transition waveguide is used to connect different types of waveguides. Its design ensures a smooth transition of microwave signals between different waveguides, reduces signal reflection and attenuation, and thus improves microwave coupling efficiency.

[0057] (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 structurally connected to the previous waveguide and achieves the final transfer of energy through efficient transmission.

[0058] Example 8, application case

[0059] like Figure 5 As shown in the figure, when using a conventional microwave window, the electric field intensity inside the cavity fluctuates significantly. Simulation results show that the maximum electric field is not concentrated inside the cavity, but rather occurs in the BJ-26 waveguide section. This uneven electric field distribution reduces the efficiency of microwave energy transmission, preventing the plasma from being fully and effectively excited, and thus affecting the efficiency of the ion source.

[0060] The existence of electric field fluctuations not only reduces the energy utilization rate, but may also have an adverse effect 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 conventional microwave windows. Excessive microwave reflection will lead to energy loss during transmission, which in turn affects the stability and power output of the ion source. Especially under high power input conditions, excessive reflection loss will significantly reduce the overall efficiency of the system, making it impossible for the ion source to achieve ideal performance during operation. After applying a microwave window with a new surface texture design, such as Figure 6 As shown in the figure, 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 to the conventional microwave window. This result shows that the new microwave window can significantly improve the focusing effect of microwave energy, reduce electric field fluctuations, and effectively improve energy utilization 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 excitation effect of the plasma, thereby improving the performance and stability of the ion source. At the same time, the optimized microwave window also reduces reflection loss, ensuring efficient energy transmission, especially under high power input conditions, which can better guarantee the stable operation and high power output of the system.

[0061] Example 9, application case

[0062] like Figure 7 The results show that the power deposition of AlN microwave window and DLC surface textured microwave window in plasma environment is significantly higher, close to 8.0×10 8 W / m³. This indicates that, under the use of conventional microwave windows, the microwave energy deposition is relatively concentrated, which can effectively transmit energy. However, it may easily cause surface ablation and sparking under long-term high-power excitation, affecting the durability of the microwave window. In contrast, the power deposition of the DLC surface textured microwave window is significantly lower, only about 2.6×10 8 W / m³. This indicates that the surface texture design effectively mitigates the concentration of microwave energy, thereby reducing the degree of plasma erosion on the microwave window surface and reducing the occurrence of ablation and sparking. Through the optimized surface structure, the DLC microwave window can more evenly distribute microwave power, extending 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 consists 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. The surface texture layer is honeycomb-shaped, with a pore diameter of 50-200μm and a pore depth of 2-3μm.

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

3. The ion source microwave window according to claim 1, wherein: 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, wherein: The thickness of the composite functional film layer is 2-5 μm.

5. The method for preparing an ion source microwave window according to any one of claims 1 to 4, characterized in that: The steps include: (1) Prepare the microwave window substrate layer from conventional ceramics by hot pressing 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) A surface texture layer is prepared on the basis of the composite functional film prepared in step (2) by laser direct writing, laser pulse etching or mask plasma etching technology.

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