帽层对极紫外多层膜反射特性影响分析

介绍了在极紫外波段，利用帽层材料来减少多层膜反射镜因外部环境干扰而造成的反射率降低，使多层膜光学元件能够长时间稳定工作.计算了在139nm波长处Mo/Si极紫外多层膜反射镜在表面镀制不同帽层材料时的理论最大反射率，利用单纯形调优法，对帽层和多层膜的周期厚度进行优化，同时把分层理论用于多层膜帽层优化,可使多层膜的反射率得到进一步提高.分析了在加入帽层前后多层膜外层电场强度的分布变化情况. 关键词： 多层膜 反射率 帽层 极紫外

Analysis of the reflective performance of EUV multilayer under the influence of capping layer

In this paper we present a solution that addresses the reflectance loss due to oxidation. The solution is a capping layer (CL) that acts as an effective oxidation barrier when the multilayer (ML) is exposed to the extreme ultraviolet (EUV) light in the presence of water vapor, so that the optical element of multilayer can be used as long as possible. The theoretical reflectivity of ML Mo/Si EUV mirrors is calculated at 13.9nm under the different CL materials. The thicknesses of the CL and standard ML are optimized by the simplex method, meanwhile the reflectivity of ML can be further enhanced when the layer-by-layer theory is used. Finally the electric-field intensity distribution in the top layers of the ML is analyzed when the CL is added.