ALUMINUM DEPOSITION ON SF6 PLASMA-TREATED POLYCARBONATE - AN AFM, XPSAND MASS-SPECTROSCOPY STUDY

A systematic investigation was made of the chemical and morphological influences of SF6 plasma on polycarbonate and the influence of plasma treatment on Al metallization. Mass and ion spectroscopy were used for characterization of the plasma and the etching process, X-ray photoel ectron spectroscopy (XPS) measurements were applied for the chemical c haracterization, while atomic force microscopy (AFM) (static and dynam ic mode) served to inspect the surface morphology, All analytical tech niques were performed in an ultrahigh vacuum system, in order to preve nt the polycarbonate sample from bring exposed to ambient air after th e plasma treatment. During the etching process rye used mass differenc e spectra to demonstrate the removal of masses 19, 28 and 32 correspon ding to HF, CO (N-2) and CF. Additionally, the inclusion of fluorine H as also observed by this technique. The XPS spectra of polycarbonate s urfaces show a significant inclusion of fluorine (C-F, C-F-2) and a re duction of the oxygen content after the plasma treatment. Aluminium me tallization leads to the formation of an Al-F interlayer; metallic gro wth of iii is only observed when the metallic layers become thicker th an a few nanometres. The AFM investigations have shown that even a sho rt plasma treatment causes changes in morphology (structures with an e xtension of 20-40 nm), After extended plasma exposure the surface beco mes very rough, resulting in poor Al adhesion. On untreated polycarbon ate, Al grows in the form of weakly bound clusters, which can only be imaged in the dynamic AFM mode. After plasma treatment, Al grows in th e form of well-adhering Bat layers without clustering. (C) 1998 John W iley & Sons, Ltd.