A method to extract the lateral and normal components of motion from the capacitance change of a moving MEMS comb drive

Abstract

MEMS comb drives made in surface micromachining can suffer from a parasitic out-of-plane motion (levitation) in addition to the intended lateral motion. We have developed a model that accurately describes the capacitance changes of an actuated comb drive that suffers from levitation. We show that the model can be used to very accurately extract the lateral motion as a function of actuation voltage. This enables us to use the comb drive as a position sensor with very high accuracy, which does not suffer from levitation-induced nonlinearities. © 2007 IOP Publishing Ltd.