Study of the electrical contact resistance of multi-contact MEMS relays fabricated using the MetalMUMPs process

The reliability of electrostatically actuated ohmic contact type MEMS relays has been investigated. Multi-contact MEMS relays laterally actuated using electrostatic comb-drive actuators were used in this study. The MEMS relays were fabricated using the MetalMUMPs process, which uses a 20 mu m thick electroplated nickel as the structural layer. A 3 mu m thick gold layer was electroplated on the electrical contact surfaces. An example MEMS relay with planar contacts of area 80 mu m x 20 mu m and spacing of 10 mu m between the movable and fixed contacting surfaces is discussed. The overall size of the relay is approximately 3 mm x 3 mm. 'Resistance versus applied voltage' characteristics have been studied. At an applied dc bias voltage of 120 V, the movable fingers make initial contact with the fixed fingers. The 'resistance versus applied voltage' characteristics have been measured for an applied bias voltage in the range of 172 - 220 V. Reliability testing of the MEMS relay up to one million actuations has been carried out and the resistance degradation with actuation cycles is discussed.