Low-cost single-layer clock trees with exact zero Elmore delay skew

Abstract

We give the first single-layer clock tree construction with exact zero skew according to the Elmore delay model. The previous Linear-Planar-DME method guarantees a planar solution under the linear delay model. In this paper, we use a Linear-Planar-DME variant connection topology to construct a low-cost zero skew tree (ZST) according to the Elmore delay model. While a linear-delay ZST is trivially converted to an Elmore-delay ZST by “detouring” wires, the key idea is to defer this detouring as much as possible to reduce tree cost. Costs of our planar ZST solutions are comparable to those of the best previous non-planar ZST solutions, and substantially improve over previous planar clock routing methods.