Ultraviolet-light irradiation of a radio-frequency plasma applied to fluoropolymer sputtering deposition

Abstract

The excited states of molecular species in plasma play an important role in the organic film deposition process. The film structure and its characteristics are very dependent on this film preparation process. Although plasma species are in an excited transition state to spontaneously decompose and react easily with relatively stable molecules, they are not excited to the electronic transition state sufficiently to dissociate into multivalenced carbon species and polymerized into a polyolefinic film. In this research, ultraviolet-light irradiation is used during radio-frequency fluoropolymer sputtering as an excitation source to enhance the dissociation of molecular species in plasma. The film obtained has an olefin and cross-linking rich structure. The effects of this process on the film structure and its lubricating characteristics are examined. The plasma-emission analysis and mass spectroscopy showed that the bond dissociation of the sputtered segments has been stimulated by this photoassisted process. Consequently, the number of C■C bonds in the film obtained from photoassisted sputtering has increased in comparison with a film obtained from conventional sputtering, as observed by IR and XPS analyses. The resistance of the film to Ar ion bombardment was enhanced by the photoassisted sputtering. The film obtained from polychlorotrifluoroethylene (PCTFE) sputtered in CF4 had an extremely long lubrication life due to an increase in the rigid olefinic structure.