Influence of design and fabrication on RF performance of capacitive RF MEMS switches

Shunt capacitive radio-frequency microelectromechanical system (RF MEMS) switches were fabricated on silicon substrate and characterized in the RF domain. Various switch typologies were obtained by three different approaches, which are: (1) the change of the bridge geometric parameters, (2) the covering of the actuator with a floating metal, and (3) the deposition of the bridge directly on the actuator. The S parameters of the fabricated switches were measured in the up and down states, observing the impact on the RF performance of the variation of the geometric parameters and the fabrication process. The electromagnetic modelling of the fabricated switches was used to interpret the measured RF behaviour, allowing to elucidate the drawbacks of the non-perfect conforming of the bridge on the actuator. Finally, the reliability of the fabricated RF MEMS switches under a bipolar voltage excitation was evaluated by cycling tests. Hence, the study presented here provides guidelines to solve some issues of the tight correlation between design, fabrication, performance, and reliability of RF MEMS switches, in view of a large-scale development of these devices.