Analysis of on-chip spiral inductors using the distributed capacitance model

Abstract

A distributed capacitance model (DCM) for monolithic spiral inductors is developed to predict the equivalent coupling capacitances C <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">p</sub> between the two terminals and the equivalent capacitance between the metal track and the substrate C/sub sub/. Therefore, the characteristics of inductors such as the S parameter, the quality factor Q, and the self-resonant frequency f/sub SR/ can be predicted by its series inductance, equivalent capacitances, and series resistance. A large number of inductors have been implemented in 0.25- and 0.35-μm CMOS processes to demonstrate the prediction accuracy. For planar and multilayer inductors, DCM can provide a quick and accurate assessment to the design of monolithic spiral inductors.