Mechanical characterization of micromachined capacitive switches: Design consideration and experimental verification

The mechanical modeling and experimental study of radio frequency (RF) micromachined capacitive switches is presented in this paper. The micromachined capacitive switch, fabricated using bulk and surface micromachining techniques, consists of a thin metal membrane suspended over a center conductor, and fixed at both ends to the ground conductors of a coplanar waveguide (CPW) line. A static mechanical model considering complicated geometry and the residual stress effect of the bridge is established to demonstrate the pull-in instability phenomenon of the micromachined capacitive switch, and to predict the effective stiffness constant and critical collapse voltage of the bridge for several typical bridge geometries. An optoelectronic laser interferometric system, based on a modified Michelson interferometer incorporated with optoelectronic devices is developed to evaluate the membrane deformation characteristics of the micromachined capacitive switch with different applied dc bias voltages. It is illustrated that the analytical solution is well agreed with the numerical simulation and experiment.