Study of Dynamics in Metallic MEMS Cantilevers - Pull-In Voltage and Actuation Speed

For different metals and varying geometries, this paper presents simulations of electrostatically actuated MEMS cantilevers regarding their influence on pull-in voltage and actuation speed. Three-dimensional electromechanical modeling including many non-linearities has been performed to study some static but mainly dynamic features. The results show that the involved parameters have different influences on the actuation speed and pull-in voltage: lower length, higher thickness as well as lower density and higher Young’s modulus of material diminish the actuation time, while longer length, smaller thickness, and smaller Young’s modulus reduce the actuation voltages. Shorter actuation times and smaller actuation voltages cannot be obtained and optimized simultaneously. Different metals such as Au, Ag, Cu, Ti, Ni, Al, W, Cr, Ta, and Mo as well as artificial metals are studied and compared. In this study, Al is found to be the best material for achieving shorter actuation times and smaller actuation voltages. The design rules of MEMS cantilevers are derived considering the large variety of studied parameters. Many involved non-linearities are discussed in detail influencing the MEMS dynamics. Finally, the actuation times are related to the existing experimental actuation times of optical MEMS shutters and MEMS cantilevers.