Timing-Aware Layer Assignment for Advanced Process Technologies Considering via Pillars

Interconnect delay is a key factor that affects the chip performance in layer assignment. Particularly in the advanced process technologies of 5 nm and beyond, interconnect delay has grown significantly due to the increase of circuit scale. Moreover, coupling effect existed in wires reduces the accuracy of delay evaluation. On the other hand, the size of vias is often ignored in layer assignment, which enlarges the mismatch between global routing and detailed routing. To solve these problems, we propose
VPT
, a timing-aware layer assignment algorithm considering via pillars, which includes the following five key techniques: 1) via pillar structure combined with nondefault-rule (NDR) wires is adopted to form a net delay optimization system for advanced process technologies; 2) a synthetical model that can adapt to varying types and sizes of both vias and wires is designed to evaluate overflow effectively; 3) a sorting strategy is devised to reduce uncertainty of layer assignment flow and improve stability of the proposed algorithm; 4) an awareness strategy based on multiaspect congestion assessment is designed to reduce overflow significantly; and 5) a net scalpel algorithm is devised to minimize the maximum delay of nets, so that the timing behaviors can be improved systematically. The experimental results on multiple benchmarks confirm that the proposed algorithm leads to lower delay and less overflow, while achieving the best solution quality among the existing algorithms with the shortest runtime.