Effect of Enhanced Ion Transfer in Process-Induced Electrochemical Corrosion on Surface Morphology and Tribological Properties

The presence of both gold and polycrystalline silicon in a given microelectromechanical systems (MEMS) device can profoundly impact surface properties through an electrochemical reaction occurring during micro-fabrication processing. Tests show a mechanistically similar increase in surface roughness with an increased ratio of gold (cathode) to silicon (anode) surface area, and with prolonged galvanic reaction time. This is attributed to increased ion transfer due to either increased electrochemical current or increased reaction time. Furthermore, microdevices with greater process-induced surface damage were found to have lower contact adhesion. The increased surface roughness decreases the intermolecular forces that contribute to adhesion due to increased average asperity separations. Results are interpreted in light of the principle galvanic corrosion mechanism and the effect on the primary nanoscale intermolecular forces.