Mo/Si多层膜表面保护层设计

为提高Mo/Si多层膜的稳定性与使用寿命，通过分析多层膜驻波电场的分布，对表面保护层及多层膜最上层材料的厚度进行优化设计，使优化后的反射率最高.计算表明，一定厚度的表面保护层总对应一个最优的最上层材料厚度.在13.36 nm波长，膜对数为50的Mo/Si多层膜10度入射的理论反射率为74.47%；当添加厚度为2.3 nm的Ru作为表面保护层，对应多层膜最上层Si的优化厚度为3.93 nm，其理论反射率为75.20％.设计结果表明，通过优化设计表面保护层，可以提高多层膜稳定性，改善多层膜性能.

Design of Capping Layers on Mo/Si Multilayer

In order to improve the stability and lifetime of Mo/Si multilayers,the design of capping layers on Mo/Si multilayer was investigated.By analyzing the electrical field distribution of multilayer standing wave,both the thicknesses of capping layer and uppermost material layer can be optimized to enable the highest reflectivity.Theoretical calculation shows that a certain thickness of the capping layer always corresponds to an optimized uppermost material thickness.A theoretical reflectivity of 74.47% can be achieved at 13.36 nm for a typical Mo/Si multilayer consisting of 50 bi-layers at incident angle of 10°.When a 2.3nm Ru layer is added as capping layer onto the multilayer surface,meanwhile with the thickness of uppermost Si layer optimized to 3.93nm,the theoretical reflectivity will be improved to 75.20%.The research results indicate that the stability and performance of the multilayer can be improved by the optimized design of capping layers.