QQ客服 官方微博 反馈留言

题名	极紫外多层膜光学元件表面污染研究
作者	鹿国庆
学位类别	博士
答辩日期	2014-07
授予单位	中国科学院大学
导师	卢启鹏
学位专业	光学工程
中文摘要	极紫外光刻技术(Extreme ultraviolet lithography-EUVL)作为22-11nm节点的主流光刻技术，其中极紫外多层膜的表面污染和寿命是制约EUVL在大规模生产领域应用的关键之一。EUVL曝光过程中，在EUV辐照和残留碳氢化合物气体以及水蒸气的作用下，EUV光学表面会发生表面碳沉积和表面氧化污染，导致光学元件反射率的降低和芯片产量的减少，此外还会危害光刻质量。     为了深入理解多层膜光学表面碳沉积和氧化的机理和相关影响因素，对实际光刻机内的污染状况进行合理评估和预测，建立了多层膜光学表面碳沉积和氧化的理论模型，并对多层膜表面保护层进行了优化设计和分析，以减少表面污染。主要研究内容如下：     1．建立了EUV辐照下残留CxHy气体在光学表面引起的碳沉积模型。模型包括CxHy在光学表面的传输、扩散，及在EUV光子和二次电子激发下引起的分解。与实验结果的对比表明模型具有较好的准确性。对碳沉积过程的主要影响因素进行分析，结果表明：引起CxHy分解的主要方式是EUV光子分解；碳层厚度随CxHy气体压强的升高和EUV光强的增加而增长，但会趋于饱和；CxHy分子在光学表面的扩散对碳层分布影响很小；具有较小分子量的CxHy分子(<~100 amu)对碳层的贡献较小；当基底温度适度增加时(~30°C)，能够降低表面CxHy的覆盖率，充分地减少碳污染。     2．建立了EUV辐照下残留水蒸气在光学表面引起的氧化模型。模型包括水分子在Ru表面的吸附、解吸附和扩散、EUV光子和二次电子对水分子的分解、氧原子在Ru层中的扩散和氧化。模型预测结果与电子束曝光实验吻合较好，可用来对实际光刻机中的氧化进行预测和评估。根据模型对表面氧化的主要影响因素进行分析，结果表明：引起水分子分解的主要方式是二次电子分解；随着曝光时长的增加，氧化会持续增加，但速率降低；在较高水蒸气偏压和较大EUV光强条件下，氧化物一般会增加，但是当表面氧原子浓度达到1ML时，氧化会趋于稳定；表面温度的增加(>340K)和较弱的水分子表面结合能(~47KJ/mol)会降低表面水分子覆盖度，有效减少氧化。     3．多层膜表面保护层(帽层)能够提高多层膜的稳定性和寿命，本文从光学性能、表面化学稳定性等方面对现有物质进行了系统设计和选择，结果表明Ru、Rh、TiO2、ZrO2相比于其他材料，更适合作为帽层材料。随后对帽层进行优化设计，并从表层电场分布的角度对其进行分析，以减少表层光电子数量，减轻表面污染。当标准Mo/Si多层膜表面Ru帽层的厚度为1.72nm时，反射率最大，为75.59%；当Ru层厚度为2.0nm时，对应的最优顶层Si膜厚度为4.01nm，反射为75.55%；当顶层Si膜厚度为3.25-5.35nm时，Ru层厚度可在一定范围内变化，且反射率均比标准多层膜高。经过优化的多层膜表层电场分布具有以下两个特点：1)多层膜内最上层驻波的波节位于吸收性的帽层中； 2) 帽层中的总电场强度最低。     本文研究内容为EUV多层膜光学表面污染的相关研究提供了理论依据，可对实际光刻机内的污染状况进行合理预测和评估，对多层膜表面污染的控制提供了指导。
英文摘要	Extreme ultraviolet (EUV) lithography is the most promising candidate for the next generation lithography target at the 22-11nm features. One of the most critical issues delaying the delivery of EUV lithography into high volume manufacturing is exposure-induced EUV optics contamination and optics lifetime. When the optic is exposed to EUV radiation the residual hydrocarbons and water vapor will cause carbon deposition and oxidation on the mirror surface which will reduce the EUV reflectivity and the overall system throughput, and also affect the imaging performances.   In order to understand the relevant mechanisms of each of these processes which would be used to estimate the reflectively loss in any given EUV environment, this paper model the EUV-induced carbon contamination and oxidation on mirror surface, and also design and optimize the capping layers(CL) of the multilayer mirror to minimize the surface contamination.   1. A model of the EUV-induced carbon contamination of optics is presented in the presence of residual hydrocarbons. A description of the relevant physical and chemical processes is developed including vapor-phase adsorption, surface desorption, surface diffusion, and molecular dissociation by direct photoabsorption and by secondary electron processes. The model provides a quantitative account of experimental data and suggests that the predominant cause of hydrocarbon dissociation is bond breaking by direct photon absorption. Detailed predictions for carbon deposition for a variety of conditions of EUV power and hydrocarbon pressure are reported. The model predicts that light hydrocarbons (~100 amu) pose a negligible risk to EUV optics and modest increases in substrate temperature (30 °C) will substantially reduce optic contamination.   2. A model of EUV-induced oxidation of a Ru-coated EUV optic is presented in the presence of water vapor. The model describes the key processes including the adsorption and thermal desorption of water to and from the Ru surface, molecular diffusion across the optic surface, and the dissociation of the water by both direct EUV ionization and secondary electron excitation. The model predicts oxide thickness over time, which may later be used to estimate the reflectively loss attributable to the oxide in any given EUV environment. Model predictions provide a good description observed in available electron-beam experiments. The model is also used to estimate oxygen penetration into the Ru coating under various conditions of water partial pressure, EUV power, and temperature. The model predicts reduced oxidation with higher temperatures and for substrates that bind water less tightly than ruthenium.   3. This paper focuses on properties and surface chemistry of different materials, which as thin films could be used as capping layers to protect and extend the lifetime of multilayer mirror optics. The most promising candidates include ruthenium, rhodium, TiO2 and ZrO2. Then the thickness of the capping layer and standard ML are optimized and analyzed from the view of normalized electric-field intensity distribution within the ML. The reflectivity of the standard  Mo/Si ML is highest (75.59%) with a 1.72-nm Ru CL, while with a given 2.0-nm Ru CL, the reflectivity reach the maximum(75.55%) when the final Si layer’s thickness is optimized to 4.01nm. When the thickness of top Si layer is in the range of 3.25-5.35nm nm, the value of Ru CL’s thickness is not controlled precisely for maintaining a relatively high peak R. For optimized Mo/Si ML, the node of the standing wave is located within the absorptive Ru capping layer with the lowest E-field intensity which will minimize the surface contamination.   The research contents of this paper provide theoretical basis for the relevant study of contamination on EUV multilayer mirror surface, whcih can be used to estimate the reflectively loss in any given EUV environment, and provide valuable insight into possible methods for remediation.
语种	中文
公开日期	2014-08-21
内容类型	学位论文
源URL	[http://ir.ciomp.ac.cn/handle/181722/41447]
专题	长春光学精密机械与物理研究所_中科院长春光机所知识产出
推荐引用方式 GB/T 7714	鹿国庆. 极紫外多层膜光学元件表面污染研究[D]. 中国科学院大学. 2014.

个性服务

查看访问统计

相关权益政策

暂无数据

收藏/分享

除非特别说明，本系统中所有内容都受版权保护，并保留所有权利。