Toward Optimal Filler Cell Insertion with Complex Implant Layer Constraints

Modern circuits often contain standard cells of different threshold voltages (multi-VTs) to achieve a better trade-off between timing and power consumption. Due to the heterogeneous cell structures, the multi-VTs cells impose various implant layer constraints, further complicating the already time-consuming filler cell insertion process. In this paper, we present a fast and near-optimal algorithm to solve the filler insertion problem with complex implant layer rules and minimum filler width constraints. We first propose an inference-driven detecting algorithm to identify each design rule violation accurately. Then, a dynamic-programming-based insertion method is developed to reduce the implant layer violations. Finally, we design a contour-driven violation refinement strategy to further improve manufacturability. Experimental results show that our algorithm can reduce the number of violations significantly compared with state-of-the-art works. Besides, with our identifier in the legalization stage, we can avoid conflicts in advance and solve almost all violations after filler insertion in industrial cases.