On Optimum Cell Models for Over-the-Cell Routing

Abst r act Over-theCell routing has led to significant improvement in the layout area in standard cell designs, and several over-the-cell routers have been developed. The effectiveness of utilization of the over-the-cell metal layers is determined by the cell model. As a result, research is focused on development of new cell models. Based o n the locations of terminals there are two classes of models in use, a class of Boundary Terminal Models ( B T M ) and a class of Center Terminal Models (CTM) . The first class performs well for the channels with large set of independent nets, on the other hand, C T M performs well for channels with large vertical constraint chains. In this paper, we present two results. First, we introduce a new class of cell model called Middle Terminal Model M T M ) that combines the advantages of