大口径大陡度曲面基底深紫外薄膜均匀性和稳定性控制技术研究

With the development of high-precision deep ultraviolet (DUV) lithography technology, higher technical requirements are put on the total loss, uniformity and stability of DUV optical coatings deposited on strongly curved substrate, so the researches about generation mechanism of optical loss and control technologies of uniformity and stability for thin films fabricated on strongly curved substrate have very important scientific significance and application value. The project intends to study the physical mechanism of DUV film growth and its performance, the influence mechanism of environmental factors on the performance degradation of thin film, and the control technology for DUV optical coatings formed on strongly curved substrate. The study will focus on the fluoride films (MgF2, AlF3, LaF3 and GdF3) deposited by thermal evaporation. Firstly, the mechanism of DUV film loss will be obtained based on theoretical calculations and experimental studies. Secondly, the mechanism of environmental factors leading to the performance degradation of DUV film was determined from experimental analysis. Last but not least, through co-evaporation technology, shadowing mask to control deposition angle and thickness of thin film deposited on strongly curved substrate and post-processing technology, high-performance of DUV optical coatings will be prepared, which can perfect for the development of high-precision DUV lithography system.

随着深紫外光刻技术的发展，对大口径大陡度曲面基底深紫外薄膜的总损耗、均匀性和稳定性提出了越来越高的技术要求，研究深紫外薄膜损耗产生机制以及曲面基底均匀性和稳定性控制技术具有非常重要的科学意义和应用价值。本项目拟开展深紫外薄膜生长及其性能的物理机制、环境因素对深紫外薄膜性能衰退的影响机制和大口径大陡度曲面基底深紫外薄膜性能控制技术等方面的研究。针对热蒸发氟化物薄膜（MgF2、AlF3、LaF3和GdF3），依据理论计算和实验分析，研究深紫外薄膜损耗的产生机制；基于实验研究确定环境因素致使深紫外薄膜性能老化的机理，结合双源共蒸发技术、修正挡板控制膜料沉积角和厚度分布技术以及后处理技术等方面的研究，实现低损耗、均匀性和稳定性均理想的大口径大陡度曲面基底深紫外薄膜制备，为高精密深紫外光刻技术发展提供基础技术支撑。

研究基于蒙特卡罗动力学理论的热蒸发金属氟化物薄膜生长仿真，兼顾沉积粒子表面扩散和高温退火因素，理论研究沉积温度、沉积速率和沉积角等关键工艺参数对热蒸发金属氟化物薄膜生长结构的影响；结合热蒸发制备工艺实验研究，确立金属氟化物薄膜在深紫外波段的光学性能与制备工艺参数的关联性。通过对热蒸发工艺制备的金属氟化物薄膜在存储过程中的深紫外波段光学损耗和红外特征谱线的定量表征，研究氟化物薄膜在存放过程中光学损耗和吸附水含量的变化规律；并验证了紫外辐照后处理技术对存储后性能衰退的金属氟化物薄膜性能恢复的可靠性。结合x射线光电子能谱仪分别对存放性能退化和紫外辐照处理的金属氟化物薄膜特征能谱进行表征，通过对O1s能级峰位的解析，确定存放性能退化和紫外辐照处理的金属氟化物薄膜中影响薄膜性能的关键成份：水、氧化镁和氢氧化镁；进而确立这三种组分对存储过程中金属氟化物薄膜性能老化的作用机理。实验研究大口径大陡度曲面基底上热蒸发工艺制备金属氟化物薄膜的性能分布规律，确定影响大口径大陡度曲面基底上成膜一致性和环境稳定性的两个关键因素：膜层厚度均匀性和膜料沉积角分布差异。研究了修正挡板技术实现大口径大陡度曲面基底上膜厚均匀性和沉积角分布差异调控。实验验证了使用修正挡板技术控制大口径大陡度曲面基底成膜均匀性的可靠性，对大口径大陡度凸椭球形曲面基底，未使用修正挡板前厚度均匀性为74%，使用修正挡板控制后曲面上成膜均匀性优于99.2%。开展宽入射角范围上深紫外增透膜消偏振分离膜系设计和制备研究，实现高透过率、偏振分离小、环境稳定性好的深紫外增透膜膜系制备，实测膜系在193nm波长的弱吸收损耗0.11%，总积分散射损耗517ppm，总光学损耗约为0.16%。本项目的顺利开展，为高精密深紫外薄膜制备奠定技术基础。