On wiring overlap layouts

Abstract

A layout model called vertical-two-overlap is introduced. The following results are established for an arbitrary vertical-two-overlap layout W with area A. 1. A linear time algorithm for obtaining a two-layer wiring of W, if one exists, is devised. Also, by increasing the area to at most 2A a two-layer wirable layout is obtained. 2. To decide three-layer wirability of an arbitrary vertical-two-overlap layout is NP-complete. However, W can be converted into a three-layer wirable layout with area at most 3/2 A. 3. W is always four-layer wirable and a four-layer wiring thereof can be constructed in O(A) time.<>