Global routing considerations in a cell synthesis system

Cell synthesis is the process of turning a netlist into an efficient IC layout without being restricted to a library of predesigned cells or a fixed floorplan. Normally, this job is broken into at least three parts: placement, routing, and detailed cell generation. Each of these tasks is often divided further into a global and a detailed phase. A cell synthesis system, called sea of devices (SOD), is presented with emphasis on its routing phase. In particular, SOD uses a new model for the global routing problem. This model is based on traditional Steiner trees, but includes detailed geometric information specific to the cell synthesis problem. The system models diffusion strips, congestion, and existing feedthroughs as a cost function associated with regions on the routing plane. A sequence of algorithms based on spanning trees. Steiner trees, maze routing, and channel routing techniques is used to find solutions that make use of this detailed knowledge. The presentation includes some discussion of the algorithms that tie the routing phases together and illustrates the underlying support structures, which are needed for efficient access.<>