Vote-taking for EUV lithography: a radical approach to mitigate mask defects

Vote-taking lithography sums up N mask images, each at 1/N dose, to mitigate the mask defects on each individual mask. The fundamental assumption is that the mask defects do not correlate in position from mask to mask, and so each individual defect will be blended with good images from the other N-1 masks. This paper will explore vote-taking for EUV lithography with both simulation and experimental results. PROLITH simulations will show the size of defects that can be healed for different N, the number of masks. SEM images of NXE 3300 exposures will be shown that are similar to those predicted from simulation. The implementation of vote-taking lithography for High Volume Manufacturing has huge practical and economic barriers. Some expose tool capabilities that could enable vote-taking lithography will be discussed. Besides defect mitigation, we briefly speculate on other possible imaging benefits opened up by voting with several exposure passes.