Mechanical, and electrical effects generated by the galvanic corrosion of polysilicon immersed in various hydrofluoric acid (HF)-based solutions are described. Micromachined test structures consisting of phosphorus-doped polysilicon in contact with a gold metallization layer are utilized. A suite of otherwise identical test (metal added) and reference (no metal) structures were used to investigate changes in key performance parameters. Corroded test structures demonstrate an increase in through-thickness strain gradient, a decrease in the characteristic frequency of mechanical resonance, no change in in-plane strain, greatly increased electrical resistance, a decrease in hardness, and a decrease in elastic modulus. Noteworthy results were observed for aqueous-hydrochloric acid, ethanol, water, ammonium fluoride (found in buffered oxide etchant), Triton-X-100, as well as vapor-HF based chemistries. This first systematic study validates preliminary experiments and demonstrates the impact of corrosion on miniaturized structures, indicating a potential influence upon the material properties, design, performance, fatigue, tribology (friction/ wear), manufacture, and packaging of micro-and nano-scale devices.

Volume Subject Area:
Microelectromechanical Systems
Topics:
Electrolytic corrosion, Mechanical properties, Polysilicon, Thin films, Metals, Corrosion, Design, Elastic moduli, Electrical resistance, Ethanol, Fatigue, Friction, Materials properties, Micromachining, Nanoscale devices, Packaging, Resonance, Strain gradient, Tribology, Vapors, Water, Wear
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