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.
Programmed defect masks (PDMs) of a tantalum-based absorber were fabricated by a conventional and improved process that decreased the mask line width roughness (LWR). The improved mask LWR decreased the minimum size of recognizable defects from 18.6 nm to 10.9 nm. The PDMs were printed on wafers and their defect printabilities were compared. The correlation coefficients of the relationship between the mask defect size and deviation of wafer critical dimension (CD) caused by the defects were calculated. A significance test of the correlation coefficients of the PDMs produced by the conventional and improved process indicated there was no significant difference between them. This means that the mask LWR did not have a significant influence on defect printability.