V-GR: 3D Global Routing with via Minimization and Multi-Strategy Rip-Up and Rerouting

In VLSI, a large number of vias may reduce manufacturability, degrade circuit performance, and increase layout area required for interconnection. In this paper, we propose a 3D global router V-GR, which considers minimizing the number of vias. V-GR uses a modified via-aware routing cost that considers the impact of wire density on the via. This cost function is more sensitive to the number of vias. Meanwhile, a novel multi-strategy rip-up & rerouting framework is developed for V-GR to solve the overflowed net, effectively optimizing wire length, overflow, and minimizing the number of vias. The proposed framework first leverages two proprietary routing techniques, namely the 3D monotonic routing and 3D 3-via-stack routing, to control the number of vias and reduce overflow. Additionally, the framework incorporates an RSMT-aware expanded source 3D maze routing algorithm to build routing paths with shorter wire length. Experimental results on the ICCAD'19 contest benchmarks show that, V-GR achieves high-quality results, reducing vias by 8% and overflow by 7.5% in the global routing phase. Moreover, to achieve a fair comparison, TritonRoute is used to conduct detailed routing, and Innovus is used to evaluate the final solution. Comparison shows that V-GR achieves 4.7% reduction in vias and 8.7% reduction in DRV, while maintaining almost the same wire length.