Influence of thin film thickness variations on pattern fidelity of x-ray masks

In x-ray mask fabrication with absorber structuring on unthinned wafers it is important that all layers which cover the mask membrane, are homogeneous in thickness and composition. It is demonstrated in this paper that Si sub 3 N sub 4 layers (90 nm) with high stress (1x10 over the 9 power N/square meter) used as antireflective coatings create pattern distortions greater than 0.1 micrometer if thickness variations exceed plusminus 5% over an area of 25x25 square millimeters.