Introduction: In Very Large Scale Integration (VLSI), routing is the process of making
connections among objects reasonable in the specific area and some cost metrics (i.e., routability) are
optimized. It is a crucial step in VLSI physical design as the performance of a chip depends on the
routing results heavily.
Methods: In this paper, by congestion-based routing modeling, a multilevel based routing optimization
method is developed to solve the VLSI routing problem. In the routing optimization method, the global
and the detailed routing phases run alternately. At each level of the multilevel framework, global and
detailed routing paths for each local net are identified.
Moreover, some strategies are used to improve the routing results.
Results: After detailed routing, a resource estimation is designed to obtain more accurate routing
resources for the next level, and an ultimate congestion strategy is used to improve the pass rate of the
nets. Experimental results on standard tested benchmarks demonstrate that the proposed method is
effective and efficient to improve the routability of a chip.