LOW-STRESS AND OPTICALLY TRANSPARENT CHROMIUM-OXIDE LAYER FOR X-RAY MASK MAKING

This article describes the properties of dc-sputtered chromium oxide l ayers such as internal stress, density, growth rate, and microstructur e. Besides these mechanical properties, the composition of the layers and the optical properties such as transmissivity and refractive index were also investigated. Transparent, low-stress, and smooth chromium oxide layers were obtained by optimizing the sputtering conditions: ga s pressure, O2 content in the working gas, dc-power density, and annea ling temperature. The most critical parameter is the O2 content in the working gas. Using these optimized chromium oxide layers in the mask fabrication process as a masking, as well as an etch stop layer for th e W etching, the etching behavior during absorber patterning in a subt ractive x-ray mask production process was improved.