Effects of X-ray mask structures and processes on X-ray mask distortion

We measured the distortion of 0.8 μm thick Ta absorbers patterned on 2 μm thick SiC membranes. The maximum membrane diameter was 60 mm, and the largest field-window was 40 × 40 mm. This paper describes the relationship between the distortion and the shape of the blocker pattern. We got a distortion less than 0.10 μm using a parallel-cross blocker and filling the area outside the blocker pattern with dummy patterns with the same pattern density as the cell region.