Showing papers on "Constraint graph (layout) published in 1996"

Multilayer routing method and structure for semiconductor integrated circuit

Abstract: A constraint graph is generated by representing plural nets by using vertices and correlation in the horizontal and vertical directions among the nets by using edges. Then, clustering is conducted so that each of the vertices of the constraint graph is assigned to any one of plural layers in view of a channel height and so as to minimize the number of stacked vias. Next, routing topology is obtained on the basis of obtained clusters of the respective layers and the constraint graph, and routing patterns satisfying a design rule are obtained on the basis of the routing topology. In the clustering, the number of the stacked vias is minimized while retaining the minimum channel height in view of the final routing patterns. Accordingly, the routing patterns satisfying a desired design rule can realize a high density, resulting in a compact semiconductor integrated circuit.

Method for optimizing track assignment in a grid-based channel router

Abstract: A method for optimal track assignment in a grid-based channel router Initially, interconnection information is extracted from a global routing result Multiple pin nets derived from the interconnection information are decomposed into simpler mapped segments A channel grid map is then built and marked with existing objects Next, a vertical constraint graph specifying the relative positions of the mapped segments is constructed A first track is computed A track assignment loop is repeated until all requisite connections are realized The track assignment loop includes the steps of breaking cycles and long paths and collecting a set of feasible links One or more weighting functions are assigned to each such feasible link A dynamic programming approach is used to select an optimal set of feasible links according to the weighting functions In addition, an optimal set of feasible links corresponding to unpreferred layers is collected by applying dynamic programming Finally, the chosen feasible links are physically realized on the current track