Impact of stringently controlled vacuum environments with in situ surface cleaning on contact resistance of gold and ruthenium based radio frequency microelectromechanical switches.

摘要

Radio frequency microelectromechanical system (RF MEMS) switches have many promising advantages over solid state switches, particularly with respect to signal stability, cutoff frequency, insertion loss and power consumption characteristics. While gold has traditionally been employed for RF MEMS contacts on account of its chemical inertness and low resistivity, its softness has proven problematic in terms of reliability for commercial applications. The use of materials other than gold appears to be necessary, and a better understanding of the mechanisms causing premature failure has become increasingly necessary. Prior studies of RF MEMS contacts have been performed in air, nitrogen and vacuum environments that ranged in pressure from 10-3 to 10 -7 torr. Since these studies were performed in conditions where condensation of contaminants can easily occur, their reproducibility is uncertain. The studies performed for this dissertation involved operation of switches in a stringently controlled vacuum environment, with in situ oxygen plasma surface cleaning and controlled hydrocarbon gas exposure. Three primary topics were studied, and are reported on herein: (1) The impact of in situ oxygen plasma cleaning on the resistance of Ru and Au-Ru based RF MEMS contacts in vacuum, (2) documentation of pentane and dodecane exposure levels that result in an increase in contact resistance for Ru and Au-Ru based contacts, and (3) switch lifetime measurements as a function of surrounding gas environment.