Congestion based layer assignment of global routing

Congestion is a basic but important objective of multilayer routing problem. Global routing, layer assignment and detailed routing are general stages of multilayer routing. In layer assignment stage, reasonable congestion of routing layer will help to promote routability of follow-up detail routing process. A new congestion based layer assignment algorithm, with the goal of min layer number and via number, is proposed in this paper. This algorithm first acquires heuristic optimal (or near optimal) initial solution by the dynamic assessment of routing resources, and then optimizes the initial solution further by simulated annealing method, and at last minimizes the number of routing layers while the distribution of global routing segments of nets is uniform on each layer. The proposed algorithm has been implemented and tested with industrial circuits and the experimental results are very promising.