Effect of Galvanic Corrosion-Induced Roughness on Sidewall Adhesion in Polycrystalline Silicon Microelectromechanical Systems

A custom microdevice was used to study the effect of hydrofluoric acid processing on the force of adhesion at a silicon sidewall contact interface. Devices exposed to acidic etchant solution for a longer period of time were found to have a significantly higher surface roughness and a lower adhesion force. These results are attributed to an accelerated formation of porous silicon caused by a release etch-induced galvanic couple between the structural silicon and the gold electrical contact pads. Experiments are interpreted in light of galvanic corrosion mechanisms and the effect on the principal components in nanoscale adhesion.