Simulation approaches for strongly coupled interconnect systems

We propose a new circuit analysis method, namelySemi-Implicit Linear-Centric Analysis (SILCA), for efficientSPICE-accurate transient simulation of deep-submicron VLSIcircuits with strong parasitic coupling effects introduced byinterconnect lines, common substrate, power/ground networks, etc.SILCA is based on two linear-centric techniques. First, a new semi-implicititerative numerical integration scheme is developed, whichapplies dynamic time step control accounting for stiff systems andmeanwhile keeps constant equivalent conductance forcapacitor/inductor companion models. Its convergence and stabilityproperties are characterized. Second, to achieve constant linearizedconductance for nonlinear devices during nonlinear iterationprocess, a successive variable chord method is introduced as analternative of the Newton-Raphson method and the rank-one updatetechnique is implemented for fast LU factorization. With thesetechniques, SILCA reduces the number and cost of required LUfactorizations dramatically. Experimental results on substrate andpower/ground networks have demonstrated that SILCA yieldsSPICE-like accuracy with an over 80X reduction in LUfactorization cost, and an about 20X overall CPU time speedup overSPICE3 for circuits with tens of thousands elements, and theefficiency increases further with the size of a circuit.