Redundant Via insertion in SADP process with cut merging and optimization

Line-end cuts in self-aligned double patterning (SADP) process are employed for printing lD-gridded patterns. Redundant via (RV) requires another cut, named RV cut, to be introduced, which may cause coloring conflicts or design rule violations with adjacent line-end cuts. RV insertion should be coordinated together with cut optimization so that maximum number of RVs are inserted while incurring no coloring conflicts among cuts. A technique named cut merging is addressed to remove cut conflicts and thereby increase the number of RV candidates. Cut redistribution and color assignment (for both line-end and RV cuts) are also taken into account to further increase RV candidates.