Adhesion effects on contact opening dynamics in micromachined switches

We propose a technique to measure the opening time for micromachined switches and present substantial experimental data for switches with gold–gold contacts. The data demonstrate that contact opening time increases dramatically as apparent contact area increases or as pull-apart force or contact resistance decreases. A model of opening time is also presented with model parameters that fit the experimental data. Moreover, we show that transient mechanical vibrations can play an important role in reducing switch opening time.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/87500/2/103535_1.pd

Low-force contact heating and softening using micromechanical switches in diffusive-ballistic electron-transport transition

We demonstrate softening of the gold-to-gold contact in surface micromachined microelectromechanical switches under electrostatic force near 30 μN30μN, which results from the heating of contact asperities sustaining electron transport. A bias potential that causes the switch contacts to soften is measured for initial contact resistance varying between 0.5 and 300 Ω300Ω. The asperity sizes in this range are comparable to the electron mean-free path at room temperature. We show that contact spots smaller than the mean-free path require larger bias for softening. Our results can be explained using a model accounting for ballistic electron transport in the contact.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/87858/2/023507_1.pd

Asperity heating for repair of metal contact RF-MEMS switches

We have experimentally observed the failure of metal contact RF MEMS switches due to a rapid rise in contact resistance during switching. We were able to repair the failed switches through heating the contact asperities by applying sufficient contact voltage. The data suggest the hypothesis that increasing contact resistance is caused by strain hardening of the contact surface. With this understanding, appropriate corrective measures can be taken to overcome failure, and suggestions for doing so are given in the paper.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/87250/4/Saitou87.pd

Effect of Nanoscale Heating on Electrical Transport in RF MEMS Switch Contacts

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.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/87261/4/Saitou21.pd