Extension of the Hot-Switching Reliability of RF-MEMS Switches Using a Series Contact Protection Technique

This paper presents a design methodology to drastically improve the hot-switching reliability of contact-type radio frequency microelectromechanical system (RF-MEMS) switches. In the proposed design, sacrificial contacts are placed in parallel with low-resistance contacts to significantly reduce the electric field across the latter. The lower field strength drastically reduces the contact degradation associated with field-induced material transfer. Theoretical and numerical modeling shows that the proposed protection scheme introduces minimal, if any, impact on the RF performance of the switch. To realize the protection scheme, we introduce a novel mechanical design that allows the correct protection actuation sequence to be realized using a single actuator and bias electrode. As a demonstration, several 0-40-GHz RF-MEMS switches are fabricated using a robust copper sacrificial layer technique. Compared with unprotected switches, the protected switch design exhibits over 100 times improvement in the hot-switching lifetime. In particular, we demonstrate a 100-150 million cycle lifetime at 1-W hot switching and 50 million cycles at 2-W hot switching before catastrophic failure, measured in an open-air lab environment. Further optimization of the structural design and contact materials is likely to further increase the hot-switching lifetime.