Vibration-Based Monitoring and Diagnosis of Dielectric Charging in RF-MEMS Switches

Dielectric charging due to metal-dielectric contact is one of the major modes of failure in capacitive radio frequency microelectromechanical systems (MEMS) switches, and it leads to actuation voltage fluctuations and, eventually, to device failure. Failure prognostics for such devices require novel methods to monitor the extent and location of trapped parasitic charges on or in the dielectric layer. Motivated by the success of resonant electrostatic force microscopy for mapping local trapped charges, we present in this paper a technique that monitors the resonance frequencies of multiple eigenmodes of the bridge conductor of the switch as a means to detect parasitic charges and nonuniformities in electric fields in the switch that could arise from nonuniform parasitic charge distribution. Both theory and experiments are presented to demonstrate the technique. Moreover, its potential advantages and limitations as a new diagnostic tool for MEMS health monitoring are discussed.