Mask 3D effect reduction and defect printability of etched multilayer EUV mask

We report on the reduction of the mask 3D effect in an etched 40-pair multilayer extreme ultraviolet (EUV) lithography mask by measuring the printed ΔCD (horizontal–vertical) on exposure with a high-NA small field exposure tool (HSFET). We compared these patterns with those of a conventional Ta-based absorber EUV lithography mask. Next, we examined the programmed pattern defect printability of the etched 40-pair multilayer EUV lithography mask and showed that defect printability of the etched multilayer mask was hardly influenced by the direction of EUV illumination. We conclude that the mask 3D effect reduction contributes to simple specifications of the mask pattern defect printability in EUV lithography.