线性渐变透过率薄膜元件是光刻系统中光可变衰减器的关键元件。采用电子束蒸发实现了近线性248 nm渐变透过率光学薄膜的设计与制备。通过对敏感度进行计算和优化,基于减反膜基础膜系实现了低敏感非规整膜系的设计。采用紫外光控-晶控组合的高精度膜厚监控措施,可使膜厚的控制精度达到0.3%,误差容忍度达到0.5%。在248 nm S偏振光照射下,采用JGS1熔融石英基片以及Al2O3和SiO2膜料制备的透射膜,在入射角为21°~35°的范围内实现了透过率从10%到97.8%的线性调控,满足光可变衰减器的性能需求。

Linearly graded transmittance films are a key component of variable attenuators in lithography systems. In this work, the design and fabrication of a 248-nm near-linearly graded optical transmittance film were realized using electron beam evaporation technology. Through sensitivity calculation and optimization, a low-sensitivity nonregular film design was obtained using an anti-reflection film. High-precision film thickness monitoring method with UV light control-crystal control combination realized a film thickness control accuracy of 0.3% and an error tolerance of 0.5%. The transmittance film, which was deposited on a JGS1 fused silica substrate using Al2O3 and SiO2 as film materials, realized linear transmittance control from 10% to 97.8% in an incidence angle range of 21°--35° under 248-nm S-polarized light, which meets the performance requirements of optical variable attenuators.