电感耦合等离子体高效去除光学薄膜表面碳沉积机理研究

The upgrading of the EUV lithography machine and the synchrotron radiation device has led to more prominent carbon deposition on the surface of the optical film. Carbon deposition seriously affects the life of the optical component, and efficient removal of carbon deposition has become an urgent need. In the previous research, the project applicant found that the inductively coupled plasma can significantly improve the carbon deposition removal efficiency by mixing with inert gas and macroscopic discharge parameters. However, the enhancement mechanism of inert gas removal in mixed plasma is still unclear and process optimization under high efficiency conditions cannot be realized. The project plans to carry out in-depth research on the mechanism of plasma efficient carbon removal. Based on the low-temperature and low-voltage RF inductively coupled plasma technology, the emission spectrum diagnostic technology is used to obtain the microscopic information of the plasma state affected by the discharge parameters, and the relationship between the material structure, properties and plasma are established. The enhancement mechanism from three aspects of matter, energy and interaction will be discussed, the essential characteristics of the removal technology will be revealed, and theoretical support will be provided for the high efficiency removal of carbon deposition. Through the real-time monitoring of the removal process implementation state, multi-parameter collaborative control is realized, combined with mass spectrometry diagnostic technology to detect the process end point. The plasma removal technology mixed with inert gas has intellectual property rights, and the research scheme adopted has not been reported at home and abroad.the plasma parameters affecting the plasma state, and establish the correlation between material structure, performance and plasma properties, from matter and energy. The interaction mechanism discusses the enhancement mechanism, reveals the essential characteristics of the removal technology, and achieves high efficiency removal of carbon deposition. Through the real-time monitoring of the removal process implementation state, multi-parameter collaborative control is realized, combined with mass spectrometry diagnostic technology to detect the process end point. The plasma removal mixed with inert gas already has intellectual property rights, and the research scheme adopted has not been reported at home and abroad.

极紫外光刻机及同步辐射装置的升级换代，导致光学薄膜表面碳沉积问题更为突出，碳沉积严重影响光学元件寿命，碳沉积的高效去除成为迫切需求。项目申请人在前期研究中发现，通过与惰性气体混合及宏观放电参量优化，电感耦合等离子体可显著提高碳沉积去除效率，但惰性气体在混合等离子体中去除的增强机理尚不明确，无法实现高效率条件下的工艺优化。本项目计划深入开展等离子体高效去除碳沉积机理研究，以低温低压射频电感耦合等离子体技术为基础，利用发射光谱诊断技术，获取放电参量影响等离子体状态的微观信息，建立材料结构、性能与等离子体属性之间的关联，从物质、能量及相互作用三个方面讨论增强机制，揭示去除技术的本质特征，为实现碳沉积的高效率去除提供理论支撑。通过对去除工艺实施状态的实时监测，实现多参量协同控制，结合质谱诊断技术，探测工艺终点。与惰性气体混合的等离子体去除技术已具备知识产权，所采取的研究方案国内外未见报道。

项目以极紫外光刻系统及同步辐射装置的实际需求为背景，针对光学薄膜表面碳沉积对光学元件寿命影响问题，开展电感耦合等离子体高效去除光学薄膜表面碳沉积机理研究。建立了电感耦合等离子体光谱诊断实验平台，利用实验平台表征在不同工艺条件下等离子体源的光谱特性。建立了多物理场等离子体计算模型，分析不同工艺条件下，等离子体源中的粒子浓度分布。利用原有实验平台，通过石英晶体微天平测定碳层厚度变化速率，在不同条件下，表征等离子体与碳层的反应速率。实验结果表明，有碳样品与无碳样品条件下，氢谱线强度发生显著变化，碳样品对氢谱线对应粒子有强烈吸收。在功率为165±10 W 、气体压强为5±0.5 Pa条件下，氩氢气体混合比对等离子体源中Balmer 线的光谱强度关系紧密。三条光谱线中，Hα谱线强度远强于另外两条，混合气中氢为35%时，三条件谱线均达到峰值。仿真模型计算结果表明，与光谱诊断相同工艺参数条件下，氢自由基粒子浓度与氢谱线强度变化趋势基本一致。通过将光谱诊断及仿真计算结果与碳去除反应速率比较，当氢气体混合比在35±5 %时，碳去除效率达到最佳，推断惰性气体改变混合气体等离子体中的氢自由基的粒子浓度，在一定气体混合比条件下，氢自由基浓度达到峰值，碳去除主要作用机制是碳原子与氢自由基产生还原反应，生成挥发性碳氢化合物分子。研究所取得的成果在极紫外光刻及同步辐射装置的实际操作中有重要的应用价值，研究中所采用的光谱诊断技术在实际应用中，可实时在线监测工艺实施状态，为实现多参量协同控制提供技术支持。