One of the challenges of EUVL is to bring EUV mask blank defect levels to zero. With uncertainty on when defect free masks may be routinely available, we explore a possibility for effectively using defective EUV mask blanks in production with a defect avoidance strategy. The key idea is to position the pattern/layout on the blank where the defects do not impact the final wafer image. Assuming that layout designs contain some non-critical areas in which defects can be safely positioned, it may be possible to align these regions with a given, small set of defect positions mapped from an imperfect mask blank.Using a few representative assortment of current-node, full-chip layout patterns we run multiple trials against real blank defect maps with various defect counts successfully. Our goal is to assess the probabilities that defect avoidance will work as a function of mask blank defect count, and by lithography layer.
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