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阳极层离子源可输出高密度离子束流, 广泛用于等离子体清洗和辅助沉积, 但大束流下内部易发生放电击穿, 且大量离子轰击内外阴极导致明显刻蚀, 易造成样品污染. 本文提出阳极环绕磁屏蔽罩和内外阴极溅射屏蔽板的设计方案, 并仿真研究了其对离子源电磁场和等离子体放电输运的影响. 发现阳极环绕磁屏蔽罩可切断离子源内部阴阳极间的磁场回路, 消除打火条件. 内外阴极溅射屏蔽板选择溅射产额低且绝缘性能好的氧化铝, 既可阻挡离子溅射, 又能屏蔽阴极外表面电场, 使等离子体放电向阳极压缩, 在抑制阴极刻蚀行为的同时提升离子输出效率. 当距离阴极外表面9 mm时, 溅射屏蔽板的作用效果最优, 不仅能获得稳定放电和高效输出, 还可大幅削弱阴极刻蚀行为并减少污染. 实验结果显示: 改进离子源无内部打火, 输出高效且清洁, 相同电流下离子输出效率较原离子源实际提高36%; 玻璃基片在经过1 h清洗后, 表面成分几乎不变, 来自阴极溅射的Fe元素含量仅为0.03%, 比原离子源低2个数量级, 含量约为原离子源的0.6%, 实验结果验证了理论分析.High beam-anode layer ion source can produce high-density ions, and has been widely used in plasma cleaning and assisted deposition. However, when increasing the ion-beams, arcing always occurs inside the ion source and serious etching will take place on the cathode, which results in sample pollution especially in long-time cleaning. In this work, two structures are designed, which are magnetic shielding around the anode and sputtering shielding on the top of the inner cathode and outer cathode, respectively. Based on the particle-in-cell/Monte Carlo collision method and test particle Monte Carlo method, the influence of designed structure on the electromagnetic field and the plasma properties of the ion source are studied through self-established simulation technique. The results show that the magnetic shielding around the anode cuts off the magnetic induction line between the cathode and anode, eliminating the arcing condition in the ion source. The sputtering shielding for the cathode uses alumina ceramic because of its extremely low sputtering yield and high insulation performance. Therefore, the sputtering shields can not only resist the ion sputtering, but also shield the electric field on the outer surface of the cathode. As a result, the plasma discharge region is compressed towards the anode and away from the cathode simultaneously, which provides a stronger electric field force directing to the output region for Ar +ions, and also results in a suppressed cathode etching behavior but an improved Ar +ion output efficiency. The optimized calculation shows that the best distance from the sputtering shield to the cathode surface is 9 mm. The discharge experiments reveal that the modified ion source can eliminate the inside arcing and provide a clean and strong ion beam with a high efficiency. At the same discharge current, the output efficiency of the modified ion source is 36% higher than that of the original ion source. When used in the plasma cleaning, the glass substrate remains transparent and keeps the original element composition ratio unchanged. The detected Fe content, coming from the cathode sputtering, is only 0.03% after the one-hour plasma cleaning, which is 2 orders of magnitude smaller than that cleaned by the original ion source. The Fe content of the modified ion source is about 0.6% of the original ion source, which is in good agreement with the result of simulation optimization.
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Keywords:
- large beam-anode layer ion source/
- cathode etching/
- electromagnetic shielding/
- output properties
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号反应方程式 反应速率系数kr/(m3⋅s–1) 反应能量
阈值/eV反应类型 1 e + Ar → Ar + e $ 2.336 \times {10^{ - 14}}{T_{\text{e}}}^{1.609} \exp [ {0.0618{{( {\ln {T_{\text{e}}}} )}^2} - 0.1171{{ ( {\ln {T_{\text{e}}}} )}^3}} ] $ — 弹性碰撞 2 e + Ar → Ar++ 2e $ 2.34 \times {10^{ - 14}}{T_{\text{e}}}^{0.59} \exp \left( { - 17.44/{T_{\text{e}}}} \right) $ 15.76 电离碰撞 3 e + Ar → Arm+ e $ 2.5 \times {10^{ - 15}}{T_{\text{e}}}^{0.74} \exp \left( { - 11.56/{T_{\text{e}}}} \right) $ 11.56 激发碰撞 4 e + Arm→ Ar++ 2e $ 6.8 \times {10^{ - 15}}{T_{\text{e}}}^{0.67} \exp \left( { - 4.2/{T_{\text{e}}}} \right) $ 4.2 激发态电离 5 e + Arm→ Ar + e $ 4.3 \times {10^{ - 16}}{T_{\text{e}}}^{0.74} $ –11.56 退激发碰撞 6 Ar++ Ar → Ar++ Ar 硬球碰撞 — 弹性碰撞 7 Ar++ Ar → Ar + Ar+ 硬球碰撞 — 电荷交换 
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d/mm 峰值密度/m–3 峰值位置
坐标/mm放电面
积/mm2无溅射屏蔽板 1.68×1016 (31.5, 52.5) 170.25 7 6.79×1014 (31.0, 50.5) 10.25 9 2.89×1015 (32.0, 51.0) 66.00 11 8.27×1015 (32.0, 52.0) 115.00 13 1.42×1016 (31.5, 52.5) 153.75 下载:
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d/mm 输出的Fe
原子比例/%溅射屏蔽板阻挡
Fe原子比例/%返回阴极的Fe
原子比例/%无溅射
屏蔽板19.4 — 80.6 7 0.3 21.1 78.6 9 0.3 24.5 75.2 11 0.3 25.8 73.9 13 0.8 27.3 71.9 下载:
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原子百
分比/%空白玻璃
基片原离子源清洗的
玻璃基片改进离子源清洗的
玻璃基片C 12.61 12.83 10.93 O 55.27 57.33 56.73 Na 7.23 4.57 7.23 Mg 1.91 1.41 1.97 Si 20.51 16.69 20.90 Ca 2.46 2.10 2.22 Fe 0 5.08 0.03 下载:
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