Split-it!: from litho etch litho etch to self-aligned double patterning decomposition

Abstract

Double Patterning (DP) is still the most viable lithography option for sub-22nm nodes. The two main types of DP are Litho Etch Litho Etch (LELE) and Self-Aligned Double Patterning (SADP). Of those two, SADP has the advantage of lower sensitivity to overlay error. However SADP imposes a lot of restrictions on the layout. One of the ways to do SADP decomposition is to use an LELE decomposer while prohibiting stitches, and to generate mandrel and trim masks from LELE masks using some Boolean characterization equations. In this paper, we propose an SADP decomposer based on an LELE decomposer that is used to decide which target polygons are mandrel and which are non-mandrel. However the core of the LELE decomposer has been made SADP-aware, such that it gives less priority to pairs of polygons separated by spacing values that are prohibited by SADP. Then, a mandrel and trim masks generator uses the LELE decomposer output and produces the final mandrel and trim masks. Experimental results show that adding SADPawareness to the core of the decomposer has decreased the average number of coloring conflicts by 38%. The proposed decomposer is faster than the previous SADP decomposition approaches that use Integer Linear Programming (ILP) and Satisfiability (SAT).