Electrical performance of degraded MEMS metallic switches (ohmic contacts) is studied analytically in this paper. The degradation mechanism is based on gradual growth of an insulating film at the contact interface and the characteristics of the insulating film are assumed to be known without considering details regarding the physical and chemical origins of the growth mechanisms. The present study relies on recently developed theories for electrical contact resistance (ECR) of clean and fully-contaminated (i.e., the entire contact area is coated with an insulating film) rough surfaces thus, bridging the gap between these two extreme cases. A relationship is obtained between the degraded ECR and the metallic conductance area. The effect of tunneling currents on the performance of partially-contaminated surfaces is found to be negligible due to the considerable current flow across the metallic asperity contacts.

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