Ion bombardment and titanium film growth on polyimide

The effects of Ar ion bombardment on the polyimide (PI) surface chemistry, Ti film growth, and the Ti/polyimide interface have been studied using x-ray photoelectron spectroscopy (XPS). The Ti films were grown in an ultrahigh vacuum chamber onto spin coated polyimide substrates and then analyzed in situ by XPS. The substrates were, prior to Ti film deposition, exposed to ion doses of 3.8 x and 30 x 10/sup 14/ ions/cm2 using 2-keV Ar ions. By monitoring the chemical shifts in the C 1s level arising from the polyimide molecular structure, a preferential bond breaking of imide carbonyl groups and formation of graphitelike carbons were observed as a consequence of the ion bombardment. As Ti was deposited a C 1s peak corresponding to Ti--C formation was observed for both as-prepared and ion bombarded samples. The initial Ti film growth was studied by measuring the decrease in the C 1s level as a function of the amount of deposit. As expected for polymers the film growth is three dimensional in its character where islands of depositing atoms are formed in the initial stages. However, on ion bombarded PI substrates the number of nucleation sites is so large that the Ti film growth is comparable with a calculated layer-by-layer growth