Timing optimization of interconnect by simultaneous net-ordering, wire sizing and spacing

This paper addresses the problem of ordering and sizing parallel wires in a single metal layer within an interconnect channel of a given width, such that cross-capacitances are optimally shared for circuit timing optimization. Using an Elmore delay model including cross capacitances for a bundle of wires, we show that an optimal wire ordering is uniquely determined, such that best timing can be obtained by proper allocation of wire widths and inter-wire spaces. The optimal order, called BMI (Balanced Monotonic Interleaved) depends only on the size of drivers for a wide range of cases. Heuristics are presented for simultaneous ordering, sizing and spacing of wires. Examples for 90-nanometer technology are analyzed and discussed.