Modeling of low-damping laterally actuated electrostatic MEMS

Most parallel-plate electrostatic MEMS feature an electrode moving vertically against a fixed electrode. Operating these systems in air triggers squeeze film damping and results in a low quality factor. In this paper, we present a new class of low-damping laterally actuated MEMS. Side actuation electrodes drive in-plane motions in order to take advantage of low damping couette flow resulting in a quality factor of 128. The design compensates for the small actuation electrodes area by amplifying the fringing electrostatic fields and reducing in-plane compliance which limits the actuation voltage to 40 V. A simple two mask process is proposed to fabricate the MEMS in the device layer of an SOI wafer. A lumped-mass model is developed as a design tool for this class of MEMS. It is validated by comparison to two finite element models.