Micro-contact Resistance of Au-Au on Engineered Contact Surfaces using Gray-scale Lithography

This paper presents a comparison of Au-Au microcontacts fabricated with planar and engineered lower contacts. It compares the effects of engineered lower contact surfaces to planar lower contact surface on micro-contact resistance performance. 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 hemispheres, 2D pyramids and 3D pyramid patterns. A microelectromechanical systems (MEMS) micro-contact support structure, consisting of a fixed-fixed beam, was micromachined 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 0.7 Omega after 10(exp 7) cycles. The 2D pyramid pattern resulted in a higher contact resistance during initial testing and then ended with a contact resistance of 1.083 Omega after 10(exp 7) cycles