(A) new strategy for combining placement and routing for marcrocell layout

Abstract

In this thesis, a new strategy for combining placement and global routing for microcell layout is studied and analytical strategies for detailed routing on channels and switch boxes are proposed for a complete layout. The first strategy solves a layout problem by interlocking placement and global routing in stepwise motion. This approach can avoid the shortcomings resulting from the conventional approaches which partition IC layout problems into smaller steps and then solve each step sequentially step by step in order to reduce the complexity of overall layout problem, while their solutions may be distant from the global optimum solution. The strategy uses an FDR (Force Directed Relaxation)[10][11] result as an initial placement because the result is a nearly global optimum solution without consideration of inter-module overlaps. The proposed strategy consists of module orientation, global routing, block size enlargement according to the global routing result and diffusion[28][29], which is defined as the process of relieving the inter-module overlaps by spreading the modules from overcrowded regions to less-crowdes regions. Experimental results run on several benchmark[30] examples and show the potential adventages of the proposed strategy over the conventional approaches. For detailed routing for channels, an analytic procedure which is not only to two-layer but also to three-layer channel routing problems, is presented. The channel routing problem is formulated as a quadratic 0-1 integer programming where the quadratic function represents the amount of inter-net overlaps. The 0-1 variables in the formulation indicate the movement of each net segment generated by net partitioning. The proposed procedure analytically decides on the parallel moves of all the net segments from one track to the neighboring track, followed by a postprocessing heuristic procedure to improve the result. Experiments on the benchmark examples produced good results. The proposed proced...