Reliable micro-electro-mechanical (MEM) switch design for ultra-low-power logic

Fundamental energy-efficiency limits for transistor-based digital logic circuits have led to renewed interest in micro-electro-mechanical (MEM) switches [1-12] because they have the ideal characteristics of zero off-state leakage and abrupt switching behavior. Reliable operation with high endurance is a key requirement for digital logic applications, and historically has been a challenge for mechanical computing devices. This paper discusses various failure modes for MEM switches, with particular focus on contact stiction due to welding. Experimental results show that device endurance (number of on/off switching cycles before welding-induced failure) improves exponentially with decreasing contact temperature, and that it depends on the contact material, contact voltage (V_C), on-state resistance (R_ON) and load capacitance. A contact reliability model calibrated to the experimental data projects that endurance will exceed 10¹⁵ cycles at 1V operating voltage. Implications for switch contact design, logic applications and dimension scaling are discussed.