193 nm光学薄膜是100 nm步进扫描光刻机系统中主要用到的光学薄膜。分析了膜料光学常数的不确定性、高折射率膜材料消光系数、水吸收以及膜层表面粗糙度对薄膜光学性能的影响。结果表明,要镀制出反射率大于98.5%的高反膜,必须将高折射率材料的消光系数k控制在0.0034以内,同时膜层表面的粗糙度σ控制在1 nm以内。膜层性能同时还受其使用环境中水气含量及其水气中杂质含量的影响,要减少膜层水吸收的影响,就必须提高薄膜的致密度,采用离子成膜技术,或者改变膜层的使用环境。在考虑相关因素的前提下,设计了在光刻机曝光系统中主要用到的增透膜、高反膜,并分析了其实际性能与设计结果存在差别的原因。

193 nm optical thin films are one of the key components in the 100 nm step and scan microlithography systems.The paper analysized the influence of the optical constants of substrates and thin films, the extinction coefficient of high refractive materials and the surface roughness on the reflectance of HR mirrors. It showed that to obtain a mirror with reflectance of more than 98.5%, the extinction coefficient of the high-refractive material must be below 0.0034 and at the same time, with a surface roughness σ≤1 nm. The influence of the water absorption on the optical performance of the coatings was also analysized and the possible reasons resulted in the difference between the practical and theoretical performance were discussed.