Modeling and Measurement of the Dynamic Performance of an OHMIC Contact-Type RF MEMS Switch

A dynamic model has been developed to investigate the transient mechanical response of an ohmic contact-type RF MEMS switch. The model combines the built-in characteristics of a commercial finite element package and a finite difference method. The model includes a realistic geometry, the electrostatic actuation, two-dimensional squeeze-film damping, slip-flow terms due to molecular effects, the nonlinear elastic contact, and the JKR adhesive force. The time-dependent characteristics of the microswitch, which include switching speed, electrostatic force, squeeze-film damping force, slip-flow, impact force, and contact tip bounce have been simulated using this model. Contact tip bounce is observed for a single-step actuation voltage whereas a properly tailored dual-actuation pulse can be used to eliminate bounce while maintaining a fast closing time. The slip-flow of the gas film between the two sides of the electrostatic actuator results in a larger correction at low actuation voltages than at high actuation voltages. The simulated results are in good agreement with experimental measurements of the microswitch.