Leading-edge photomask, to which optical proximity correction (OPC)
and dummy pattern are applied, almost always has complex patterns. Complex patterns such as "Narrow Space", "Thin Pattern", "Dummy Pattern", "Closely Face-to-Face Heads" of Posi Serifs, "Narrow Waisted Pattern" formed by a Nega Serif, "Jogs", etc. are a factor to complicate photomask manufacturing. Some the problems caused by complex patterns are increase in EB writing time, and decrease in performance of etching and cleaning process caused by Cr peeling and, above all, increase in the inspection time. Patterns whose complexity is beyond the resolution limit of inspection tool are detected as false defects. Therefore, it will greatly take time for the data investigation and re-inspection, etc. for assurance, and this causes congestion of half-finished products. To improve the process efficiency, it is necessary to locate false defects, so that the Do-Not-Inspection-Area(DNIR) or replaced with simpler patterns. In order to locate false defects, it is proposed to apply Mask Rule
Check (MRC) to mask data for EB-writing.