New placement prediction and mitigation techniques for local routing congestion

Local routing congestion is becoming increasingly important as complex design rules make local pin access the bottleneck for modern designs and routers. Since congestion analysis based on global routing does not model these effects, routability-driven placement and physical synthesis fail to alleviate local congestion. This work models routing congestion at the placement level in order to apply local congestion mitigation. We propose a local congestion metric that computes a “routing-difficulty” score for every cell in the design library. To disperse local congestion, we apply a suite of detailed placement techniques called MILOR (Movement, cell Inflation and Legalization, and Optimization within a Row). Experimental results show that our techniques can significantly improve routing quality on real industry designs from 65, 45, and 32 nanometer technologies.