Absence of Electrical Contact Resistance Degradation in MEMS Relays Subject to Hot Switching

We conduct preliminary hot switching experiments in ultra-high purity nitrogen atmosphere on MEMS relays over two orders of magnitude supply voltage, <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$V_{s}$</tex>, from 0.1 V to 10 V. In the relay design presented, a contact bar contacts two fixed traces, each platinum-coated, to achieve electrical continuity. For <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\boldsymbol{V}_{s}\geq 0.5 \mathrm{V}$</tex>, negligible change in electrical contact resistance is observed over twenty million cycles. There is, however, progressive morphological counterface damage evolution, which increases with <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$V_{s}$</tex>. For mechanical cycling alone, wear can be observed over a small portion of the counterfaces. For <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$0.1 \leq V_{s}\leq 0.5 \mathrm{V}$</tex>, counterface areal damage is approximately the same, but qualitatively different from that due to mechanical cycling. At <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$V_{s} = 10 V$</tex>, damage manifests in the form of mounds and pits in one of the contacts pairs, suggestive of field evaporation. The other contact pair exhibits material transfer, indicative of electromigration. We attribute these observations to a small time difference in when the contact bar contacts each trace. These findings contribute to the fundamental understanding of reliability of electrical contacts and are important for nanoelectromechanical relays, which will operate below 1 V and in which hot switching is preferred in logic circuitry.