Design technology co-optimization of back end of line design rules for a 7 nm predictive process design kit

Abstract

This paper discusses the back-end-of-line (BEOL) layers for a 7 nm predictive process design kit (PDK). The rationale behind choosing a particular lithographic process—EUV lithography, self-aligned double patterning (SADP), and litho-etch litho-etch (LELE)—for different layers, in addition to some design rule values, is described. The rules are based on the literature and on design technology co-optimization (DTCO) evaluation of standard cell based designs and automated place-and-route experiments. Decomposition criteria and design rules to ensure conflict-free coloring of SADP metal topologies and manufacturable SADP photolithography masks are discussed in detail. Their efficacy is demonstrated through successful coloring and photolithography mask derivation for target metal shape layouts, which represent corner cases, by using the Mentor Graphics Calibre and multi-patterning tools. Edge placement errors, misalignment, and critical dimension uniformity are included in the analysis.