Automatic Variable-Width Routing for VLSI

Some of the essentials for layout of complex VLSI circuits are hierarchical design based on macrocells of arbitrary size and shape, power nets with local varying width, signal nets with individual width and very compacted layouts which still have to guarantee all geometrical design rules. This paper is devoted to the problem of automatic routing with real geometries. VWROUT, a Variable Width Routing System is presented. This includes planar power net routing with variable width on a single layer, loose and final routing of signal nets with variable width on two layers (H-V routing), and layout compaction with design-rule verification. Though automatic routing systems have been developed successfully, the intention of this paper is to demonstrate that layout programs of today have not yet become perfect. A lot of effort in software development is necessary in order that automatic layouts can compared with manual designs.