Efficient over-cell routing method for transparent standard cells

In this paper a new routing method for transparent standard cells is presented. The method enlarges the original netlist to allow for the optimal application of bipartite graphs matching. This routing approach aims to reduce the number of tracks used in the routing channels and thus delivers better results as previously published methods. This is achieved by maximization of strictly vertical routing segments, which are used for interconnections between terminals of a multi-terminal net conduced in different cell rows. The problem of finding the strictly vertical routing segments is formulated as a matching problem in a bipartite graph. During the routing phase the netlist is enlarged by supplementary terminals to increase the maximum matching cardinality. The here described method can be applied to over-cell routing independently of the used design style.