Contact resistance evaluation of micro-contacts with upper hemisphere and lower planar or engineered surfaces

This paper presents a comparison of the resistance performance of Au-Au micro-contacts fabricated with planar and engineered lower contacts. Gray-scale lithography was used to construct 3D structures into photoresist. The structures were then etched into a silicon wafer using a Trion reactive ion etch (RIE) system. The engineered lower contact surfaces consisted of 2D pyramids and 3D pyramid patterns paired with a hemispherical upper contact. A microelectromechanical systems (MEMS) micro-contact support structure, consisting of a fixed-fixed beam, was micro machined as the upper contact. The micro-contact support structure was used as the platform for a hemisphere shaped upper contact. The micro-contacts were actuated using an external, calibrated load. To observe micro-contact performance, the contact resistance and force required to close the contact, were monitored throughout testing. Next the micro-contacts underwent contact resistance testing to evaluate how the engineered lower contacts affected performance. Results show that the 3D pyramid design closely matched the hemisphere/planar contact data with a contact resistance of 0.7Ω after 10⁷ cycles. The 2D pyramid pattern resulted in a higher contact resistance during initial testing and then ended with a contact resistance of 1.083Ω after 10⁷ cycles.