Mechanical design and optimization of capacitive micromachined switch

Design and optimization of a shunt capacitive micromachined switch is prese nted. The micromachined switch consists of a thin metal membrane called the "bridge" suspended over a center conductor, and fixed at both ends to the ground conductors of a coplanar waveguide (CPW) line. A static electromecha nical model considering the residual stress effects is developed to predict the effective stiffness constant and the critical collapse voltage of the bridge for several typical bridge geometries. The deformation of the bridge and its contact behavior with the dielectric layer are analyzed using the finite element method (FEM) in order to explore a good contact field with d ifferent bridge geometries. Furthermore, a nonlinear dynamic model that cap tures the effects of electrostatic forces, elastic deformation, residual st ress, inertia, and squeeze film damping is developed, and is used for predi cting the switching speed (including the switching-down and the switching-u p time) and the Q-factor. The effects of variation of important parameters on the mechanical performance have been studied in detail, and the results are expected to be useful in the design of optimum shunt capacitive microma chined switch. The results may also be useful in the design of actuators wi th membranes or bridges. (C) 2001 Elsevier Science B.V. All rights reserved .