Routability-Aware Pin Access Optimization for Monolithic 3D Designs

With the increasing design complexity (especially, the increasing number of design rules), pin access for detailed routing has attracted much attention. Monolithic 3D design (M3D for short) has emerged as a promising technology to alleviate this pin access challenge by providing redundant pins and free routing tracks. This paper addresses the problem of pin access optimization for M3D designs to improve routability during detailed routing. Unlike existing work that uses integer linear programming (ILP) to maximize the total number of pre-routed nets on free routing tracks without considering the influence of a net on pin access congestion, we present new pin access congestion estimation based on the probability of pin access conflicts and a novel weighted ILP formulation. A dynamic programming algorithm is proposed to refine detailed placement to obtain a better initial solution. Experimental results show that our algorithm achieves significant routability improvements.