Extraction methods for approximation of IC capacitance in circuit simulation

Prediction of circuit performance has always required accurate models of both active devices and capacitive loading. Until recently, a single, approximated capacitance value per conductor sufficed for interconnect performance modeling. However, as feature sizes shrink and device counts grow, simple approximations become inadequate. Full analytical solutions for the problem exist, but high resource use makes them impractical for real designs. Instead, capacitance extraction tools rely on increasingly complex approximations. We discuss the factors requiring greater precision in approximation, common approximation techniques and tools, and some of our experiences using them