The 1-2-3 Routing Algorithm or the Single Channel 2-Step Router on 3 Interconnection Layers

In this paper an algorithm is presented for the single channel routing on 3 interconnection layers. First some general characteristics of routing on 3 interconnection layers are presented. Then the specifications are introduced of the routing problem on 3 interconnection layers that will be considered. Pins will be allowed to come out on both the diffusion/poly layer and the second metal layer with the routing done on both the first and second metal layer. If only the first metal layer was to be used horizontally then the routing problem could be solved by a simple left-edge channel algorithm. However the 1-2-3 algorithm presented here will solve identical problems with a smaller number of tracks and via's since it makes use of some specific characteristics of routing on 3 interconnection layers.