Superposition Model for Dielectric Charging of RF MEMS Capacitive Switches Under Bipolar Control-Voltage Waveforms

Abstract—Bipolar control-voltage waveforms, under which the control voltage alternates between positive and negative after each cycle, have been proposed to mitigate dielectric charging in elec-trostatically actuated RF microelectromechanical system capaci-tive switches. In this study, dielectric charging under bipolar wave-forms is modeled and characterized quantitatively. In general, the experimental results agree with predictions based on the superpo-sition of unipolar charging models that are extracted under posi-tive and negative voltages, respectively. The basic assumptions for such a superposition model are examined in detail and validated experimentally. The current analysis indicates that, while bipolar waveforms can reduce charging, it is difficult to fine tune the wave-forms to completely eliminate charging. Index Terms—Charge injection, dielectric films, dielectric mate-rials, microelectromechanical devices, switches. I