Cut Mask Optimization for Multi-Patterning Directed Self-Assembly Lithography

Line-end cut process has been used to create very fine metal wires in sub-14nm technology. Cut patterns split regular line patterns into a number of wire segments with some segments being used as actual routing wires. In sub-7nm technology, cuts are smaller than optical resolution limit, and a directed self-assembly lithography with multiple patterning (MP-DSAL) is considered as a patterning solution. We address cut mask optimization problem for MP-DSAL, in which cut locations are determined in such a way that cuts are grouped into manufacturable clusters and assigned to one of masks without MP coloring conflicts; minimizing wire extensions is also pursued in the process. Only a restricted version of this problem has been addressed before while we do not assume any such restrictions. The problem is formulated as ILP first, and a fast heuristic algorithm is also proposed for application to larger circuits. Experimental results indicate that the ILP can remove all coloring conflicts, and reduce total wire extensions by 93% on average compared to those obtained by the restricted approach. Heuristic achieves a similar result with less than 1% of coloring conflicts and 91% reduction in total wire extensions.