极紫外（EUV）反射镜在使用过程中的氧化及表面碳污染沉积，严重影响了极紫外光刻（EUVL）技术的工业应用。为了延长EUV 反射镜的稳定性与使用寿命，一般采取在Mo/Si多层膜表面添加保护层。采用直流反应磁控溅射技术，建立氧气流量与溅射电压之间的“迟滞回线”关系，进而准确掌握不同氧化物保护层所需氧气量，以此减少过多的活性氧对下层Mo/Si多层膜的影响，提高镜面的反射率。选用RuO2与TiO2两种保护层材料进行比较，根据充氧量的不同，分析不同反应阶段的薄膜特性。针对催化性和物理稳定性更好的TiO2 薄膜，在晶相、表面粗糙度、截面均匀性和化学组分等方面给予评价。研制出膜质致密均匀的非晶态TiO2薄膜，其表面粗糙度优于100 pm；TiO2纯度(质量分数)达97.2%；保护层厚度为2 nm 的Mo/Si多层膜的反射率损失小于5%，满足EUV 外多层膜的基本要求。

The development of industrial applications of extreme ultraviolet lithography (EUVL) severely based on surface oxidation and carbon contamination on using extreme ultraviolet (EUV) reflective mirrors. The capping layer coating on the Mo/Si multilayer is a promising method to improve the stability and service life of the reflective mirrors. The capping layer is prepared by direct current reactive magnetron sputtering. The "hysteresis loop”of oxygen flow and sputtering voltage is established, the required oxygen flow for different oxides is accurately grasped. Choosing the RuO2 and TiO2 as the capping layer materials; the different film characteristics in each state is analyzed. For TiO2 films, crystal phase, surface roughness, cross section uniformity and chemical composition are evaluated. 97.2% TiO2 content (mass fraction) of Ti-oxide is obtained; reflectivity of Mo/Si multilayer with 2 nm TiO2 as capping layer is controlled in 5%; surface roughness less than 100 pm, dense and uniform amorphous TiO2 films is fabricated to make this capping layer achieve the basic requirements of EUV.