Toward a Polysilicon-Based Electrostatically Actuated DC MEMS Switch

A cantilever-based electrostatically actuated micro-electro-mechanical systems (MEMS) actuator aimed for a DC switch was investigated in the PolyMUMPs process. Our prior MEMS DC switch employed dimples structured underneath the suspended membrane or as stoppers on the fixed substrate to protect the switch against gate-source shorting. However, these structures suffered from conformal coverage, which prevents them from establishing ohmic contacts with the transmission line. To overcome this challenge, a modified design is proposed that uniquely takes advantage of staking Poly 1 pads onto the substrate while the suspended beam remains in Poly 2. Accordingly, the switch exhibits low deflection (700 mm) with a better contact force as well as closing the switch before pull-in occurs. The experimental pull-in voltage results of the reference design switch are inconsistent with the simulation value of 55 V. Based on the preliminary investigation, MEMS polysilicon DC switches can stem from the results of this work.