ECO algorithms for removing overlaps between power rails and signal wires [IC layout]

Design ECO (engineering change orders) commonly happens in industry due to constraints or target changes from manufacturing, marketing, reliability, or performance. At each step, designers usually want to modify the existing solution incrementally and keep the design as close as possible to the existing one. In this paper, we address the PSO (power rail - signal wire overlap) problem which solves overlaps between power rails and signal wires due to the changes in power rail design on the top layer of a multiple layer routing region. PSO problems are frequently caused by changes in power delivery system or package design. The new routing solution satisfies the following constraints: (1) Keep the routing of power rails in the new design unchanged. (2) Only the routing of the top two layers is changed. (3) Horizontal (vertical) signal wire segments on the top layer can only move up/down (left/right). (4) For each signal wire segment, the deviation (i.e., the difference between its new position and the old one) should not exceed the user-defined allowable deviation bound. For a set of industrial test circuits, we were able to remove all overlaps between power rails and signal wires with minimal wire deviation.