Dynamic identification of electrostatically actuated MEMS in the frequency domain

Micro-electro-mechanical systems (MEMS) are commonly constituted by suspended structures such as beams and spring-supported plates and are applied in a wide range of fields such as sensing, optics, radio frequency communications, fluidics, biology, etc. The components that form the basis of MEMS devices are often actuated using electrostatic capacitive strategy, and performances are improved by the micro-scale dielectric gap between the electrodes. The dynamic dimensioning and characterization are made more complicated by the nonlinearity of the electrostatic actuation and by the electro-mechanical coupling, which involves the capacitive force and the elastic reaction of the structure. The dynamic characterization is affected by specific problems related to electro-mechanical coupling, which need a dedicated approach. Some of the effects that take place during the dynamic tests on electrostatically actuated MEMS are studied in this work and are described using compact analytic models; using the proposed approaches, results of experiments in the presence of electro-mechanical coupled domains can be predicted and interpreted correctly. Structural properties such as residual stress or strain dependent on the fabrication process may influence the measurements in both, the static and dynamic fields. The goal of this study is to describe the most common experimental problems related to the dynamic characterization of electrostatically actuated microsystems; theoretical approaches that are able to describe the effects involved are proposed to predict and interpret experimental results.