Pre-layout parasitic estimation in interconnects

Interconnect lengths have become a dominant factor in the design of integrated circuits. The parasitics associated with the interconnects account for a significant part of signal delay. The estimation of interconnect lengths prior to placement helps in determining the delay early in the design phase. In this paper, a methodology to estimate the interconnect lengths prior to layout, is presented. The approach is heuristics based. Various layouts have been studied to observe typical placement and routing patterns. The methodology uses the gate level netlist and properties of the cells obtained from the standard cell libraries for the estimation. The results have been compared with the detailed routing wire lengths obtained after synthesis of the gate level netlist. Cadence Buildgates was used for syntheises and Cadence Encounter used for placement and routing of the circuits. The methodology presented is independent of the technology being used. However the wire lengths will vary with the use of different placement and routing tools