Electrical Contact Resistance and Device Lifetime Measurements of Au-RuO2-Based RF MEMS Exposed to Hydrocarbons in Vacuum and Nitrogen Environments

Abstract

Electrical Contact Resistance (ECR) measurements are reported for RF micro-electromechanical switches with Au-RuO 2 contacts, situated within an ultrahigh vacuum system equipped with in situ oxygen plasma cleaning capabilities. Two studies are reported, each involving a comparison of the ECR in vacuum and nitrogen environments for measurements performed immediately after cleaning. The first study reports measurements of initial resistance (resistance measured upon first time closure) versus pressure as dodecane gas is admitted to the chamber. A significant increase is observed at pressures in vacuum as low as 10 -5 torr, (P/P sat \ 10 -4 ) consistent with earlier reports involving repetitive cycling of macroscopic switches in partial pressures of hydrocarbons in nitrogen. Somewhat unexpectedly, however, the resistance only doubles, even for pressures sufficiently high as to result in full monolayer condensation. In a second study, switch lifetimes in vacuum (10 -8 -10 -9 torr) and nitrogen gas environments are compared, for switches operated immediately afterward, or alternatively left open for a number of days before operation. Although it was expected that vacuum would reduce and/or prevent contamination of the electrical contact surfaces, no enhancement or extension of lifetime was observed: Continuous operation of a switch in a nitrogen environment immediately after plasma cleaning was in fact the only procedure observed to indefinitely prolong device lifetime. The results suggest that (1) Hydrocarbon reaction products, but not mobile physisorbed hydrocarbons themselves, are responsible for increasing ECR by orders of magnitude and (2) Repetitive cycling motion of a clean switch in nitrogen inhibits formation of physisorbed hydrocarbon contaminants on the contacts, while vacuum levels far superior to 10 -9 torr are required to prevent contamination.

Review: Electrostatically actuated nanobeam-based nanoelectromechanical switches – materials solutions and operational conditions

“…Electrically conductive stable oxides could also be considered as prospective NEM switch contact materials, as they have shown reliable performance for microscale contacts. For example, switches based on ruthenium oxide RuO 2 –Au contacts [ 149 , 151 – 152 ] reached more than 10 10 switching cycles without failure, surpassing such materials combinations as Pt–Au and Ir–Au [ 149 ]. As RuO 2 has lower surface reactivity than, for example, Pt, the RuO 2 –Au contact material combination prevents cycling-induced tribopolymer accumulation [ 149 ].…”

Effect of Substrate Support on Dynamic Graphene/Metal Electrical Contacts

“…To address these challenges, solutions have been proposed to improve permanent contacts between graphene and electrode materials by e-beam nano-welding [ 21 ], or incorporating adhesion layers or changing the contact geometries [ 22 ]. However, in the case of dynamic or periodically actuated electrical contacts, which are essential for devices such as microelectromechanical systems (MEMS), controlling electrical current flow in the contact zone is not a straightforward procedure, even for well-studied noble metal interfaces [ 23 , 24 , 25 ].…”

Microstructure and Electrical Contact Performance of Wires in Corrosion Air

“…It is found that corrosion product due to the surrounding environment, such as atmospheric corrosion, temperature, humidity, dust contamination [7][8][9][10], has long been known as one of the major degradation mechanisms for electrical contacts, which will cause high contact resistance and even poor reliability of electric system. Contact failure caused by corrosion shows that the corrosion behavior of connectors should be taken under consideration, especially for the devices used in field environments [11][12][13][14].…”