Characterization of Gold-Gold Microcontact Behavior Using a Nanoindenter Based Setup

Gold-gold microcontact behavior of MEMS switches under cycling and hot-switching conditions was characterized experimentally. A nanoindenter based experimental setup was developed where a cantilever beam with contact bump was cycled in and out of physical contact with a flat plate to simulate the action of a MEMS ohmic contact switch. This arrangement offered a simple method to simulate MEMS switches with minimum fabrication effort. Cantilever beam and flat plate were fabricated from silicon, and then sputter coated with 300 nm of gold as the contact material. All contacts failed in adhesion with lifetimes ranging from 10 000 to more than one million cycles. Three failure mechanisms of the contacting surfaces were observed: ductile separation, delamination and brittle separation with short (less than 70 000 cycles), mid (190 000-500 000 cycles) and long (more than one million cycles) life, respectively. Resistance, contact adhesion, threshold force and distance, strain hardening, and plastic deformation were monitored during cycling. Initial contamination of the contact was burnt out quickly during cycling which resulted in a constant threshold force. Contact resistance was practically constant during the cycling in all tests. Time-dependent and plastic deformations of the contact were observed, and these were initially large which then decreased to a constant value with cycling. Thus, elastic-viscoplastic material model(s) with strain hardening capability are needed for the analysis of gold-gold microcontact. (C) Koninklijke Brill NV, Leiden, 2010