A multi-layer router utilizing over-cell areas

A new methodology is presented for the solution of a multi-layer routing problem that has the potential to outperform channel-based multi-layer routing algorithms by expanding the routing regions to include areas over the cells. It is assumed that four routing layers are available. Routing is completed in two steps. A selected group of nets is routed in the between-cell areas using existing channel-routing algorithms and the first two routing layers. Then the remaining nets are routed over the entire layout area, between-cell and over-cell areas, using a new two-dimensional router and the next two routing layers. The router used for over-cell routing recognizes arbitrarily sized obstacles, for example, due to power and ground routing or sensitive circuits in the underlying cells. The proposed router was tested on a number of macro-cell layout examples