Plasma immersion ion cleaning of oxidized steel surfaces using hexafluoroethane and argon plasmas

For many years it has been known that cleaning of substrates using plasma t echniques prior to physical vapor deposition processes can significantly im prove coating adhesion. This article investigates the use of hexafluoroetha ne and argon plasmas in a pulsed glow discharge cleaning process. Applied v oltages varied from - 2 to - 8 kV with a constant chamber pressure of 10 mT orr and etching times ranged from 15 to 120 min. Results indicate that in m ost cases, the hexafluoroethane plasmas removed 25% more oxygen atoms than the argon plasmas at similar applied voltages. Most of the oxygen removal w as observed within the first 15 min with diminishing removal with increased cleaning time beyond 30 min. Plasma analysis revealed that the principal p lasma specie was CF3 and reaction products for oxygen removal were carbon d ioxide and carbon monoxide. The hexafluoroethane plasmas were determined to clean through a chemically enhanced sputtering while argon plasmas cleaned by physical sputtering only. (C) 2001 American Vacuum Society.