In-Route Pin Access-Driven Placement Refinement for Improved Detailed Routing Convergence

Pin access is increasingly important in advanced nodes. Neighboring or cell-boundary pins can have degraded pin accessibility, causing design rule violations (DRCs) during routing, which are runtime-expensive to resolve. Conventional physical design tool flow uses pessimistic and/or inaccurate understanding of pin access during the placement stage and keeps the location of cells fixed during routing. This can leave pin access issues unsolvable and block further routing solution improvement. The timeliness of our present work is confirmed by the recent ICCAD-2020 CAD Contest, Problem B formulation from Synopsys, Inc. HuY20. The organizers give a succinct motivation for what we study – to eliminate preserved margins and misalignment issues from conventional placement models. In this work, we develop an in-route, pin access-driven local placement refinement. Experiments across industry designs in a wide range of advanced technology nodes confirm that our optimization can significantly improve routing convergence (i.e., subsequent detailed routing runtime and initial detailed routing DRCs). Our optimization can reduce congestion and wirelength without timing degradation.