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极紫外光刻系统中的碳污染会降低多层膜反射率,在保证光学元件性能的前提下,如何选择碳清洗工艺是一项重要课题。通过对不同清洗工艺的原理分析,揭示了不同工艺对多层膜反射率的影响主要体现在膜层氧化、刻蚀及表面粗糙度劣化等方面。基于时域有限差分方法及总积分散射理论,研究了不同影响因素与多层膜反射率的关系。结果表明,膜层氧化及表面粗糙度劣化是导致多层膜反射率下降的主要因素,而刻蚀的影响相对较小。基于以上分析结果,射频氢等离子体及原子氢清洗技术,在去除光学元件表面沉积碳的同时,不会显著降低光学元件性能,可优先考虑采用。
Carbon contamination in EUV lithography system will reduce the reflectivity of multi-layer film. How to choose carbon cleaning process is an important issue on the premise of ensuring the performance of optical components. By analyzing the principle of different cleaning processes, it is revealed that the influence of different processes on the reflectivity of multilayer films is mainly reflected in the aspects of film oxidation, etching and surface roughness degradation. Based on the finite-difference time-domain method and the theory of total-integral scattering, the relationship between the different influencing factors and the reflectivity of multilayer films was studied. The results show that the film oxidation and the degradation of the surface roughness are the main factors leading to the decrease of the reflectivity of the multilayer films, but the influence of etching is relatively small. Based on the above analysis results, RF hydrogen plasma and atomic hydrogen cleaning technology, in the removal of optical elements deposited on the surface of carbon at the same time, does not significantly reduce the performance of optical components, may be preferred to use.