An Extremely Low Contact-Resistance MEMS Relay Using Meshed Drain Structure and Soft Insulating Layer

This paper presents an electrostatically actuated microelectromechanical systems (MEMS) relay with a stacked-electrode structure having meshed drain electrode and a soft dielectric layer under the contact material to achieve high contact force and low hardness simultaneously, with the aim of providing ultralow contact resistance. In particular, a novel method for laying benzocyclobutene polymer under the contact layer to enlarge the contact area by reducing the effective hardness is proposed and theoretically analyzed. This could reduce the contact resistance by more than half in the case of an Au-Au contact. The fabricated devices have pull-in voltage of 32-43 V, switching time of 25 μs, and current driving capability of 350 mA in a hot-switching condition. Furthermore, the achieved minimum contact resistance is as low as 4 mΩ, which, to our knowledge, is the lowest value reported to date. In addition, negligible variation of contact resistance was observed during 1.4 × 10⁶ hot-switching cycles in a 100-mA current level. The fabricated MEMS relay in the relatively low current of 1 mA was able to operate for more than 100 million cycles without failure before the test was stopped.