Aerial-image simulations of soft and phase defects in 193-nm lithography for 100-nm node

We report results from fast aerial-image simulations of defects with variable transmission and residual phase (which we call soft or phase defects in this work) in 193-nm lithography for the 100-nm node. These results include a qualitative benchmarking of mask-types and their sensitivity to defects with variable transmission and residual phase. We treat the cases of soft (phase) defects on 1) binary masks, 2) binary masks with assist-bars, 3) bright-field attenuated phase-shift masks, 4) bright-field attenuated phase-shift masks with assist-bars, and 5) alternating phase-shift masks. The focus of this paper is to study deviations of critical features close to such defects, thereby limiting the discussion to isolated lines. The various optical enhancement techniques show striking differences in their sensitivity to defects, which may lead to differences in repair criteria for mask making. Furthermore, we show that the distance between critical feature and defect is a critical parameter and that differences in aspect ratio of the defects studied here have a negligible effect on the critical feature.