A new scalable model for spiral inductors on lossy silicon substrate

A new scalable, predictive model for spiral inductors on lossy silicon substrates for radio-frequency integrated circuits (RFICs) is presented. The model is based on an enhanced Partial Element Equivalent Circuit (PEEC) approach. Eddy-current losses in the substrate are efficiently modeled using a complex image approach combined with available closed-form equations for partial inductance. The model further includes the conductor skin and proximity effects through discretization of the spiral segments. The resulting enhanced PEEC model is used to predict the performance of a typical 3.5 turn, 2.0 nH octagonal spiral inductor fabricated in a heavily-doped BiCMOS process. Comparison with measurements over a 100 MHz to 10 GHz frequency range demonstrates the excellent accuracy of the new modeling approach.