Effect of nanoscale heating on electrical transport in RF MEMS switch contacts

Abstract

Abstract-This paper explores contact heating in microelectromechanical systems (MEMS) switches with contact spot sizes less than 100 nm in diameter. Experiments are conducted to demonstrate that contact heating causes a drop in contact resistance. However, existing theory is shown to over-predict heating for MEMS switch contacts because it does not consider ballistic transport of electrons in the contact. Therefore, we extend the theory and develop a predictive model that shows excellent agreement with the experimental results. It is also observed that mechanical cycling causes an increase in contact resistance. We identify this effect as related to the build-up of an insulating film and demonstrate operational conditions to prevent an increase in contact resistance. The improved understanding of contact behavior gained through our modeling and experiments allows switch performance to be improved.[1424]

Cryogenic Performance of RF MEMS Switch Contacts

“…• C to 100 • C [2], [3]. The authors who reported the lower temperature did not rule out thermal breakdown of bonds between the gold and an adsorbed film layer as the mechanism producing decreased resistance at 65…”

“…• C [2]. An accurate representation of the surface roughness is needed to generate meaningful predictions for contact area and resistance.…”

“…No prior work on contact resistance at cryogenic temperatures for metal contacting RF MEMS switches has been published, but an observation of decreased contact resistance with increasing temperature ranging from room temperature to 373 K [2] has been reported in the literature. In the latter case, the experimental results were unable to discern the individual contributions from surface morphology changes and adsorbed film effects on the overall contact resistance value.…”

An Asperity-Based Finite Element Model for Electrical Contact of Microswitches

“…The current is constricted when passing through small asperities, heating in contact is extremely localized on the asperity proximity [16]. Another concern in the work is to investigate the thermoelectrical behavior of electrical contacts.…”

“…An analytical expression for voltage-temperature (V-T) relation was given by Holm [8], in which the maximum temperature depended only on the total voltage of a long constriction; while for the small spots, size on the order of mean free path, the expression of Holm was invalid [4]. Jensen et al then considered the ballistic effect, and introduced an improved model for small spots [16].…”