Ion bombardment of polyimide films

Abstract

Surface modification techniques such as wet chemical etching, oxidizing flames, and plasma treatments (inert ion sputtering and reactive ion etching) have been used to change the surface chemistry of polymers and improve adhesion. With an increase in the use of polyimides for microelectronic applications, the technique of ion sputtering to enhance polymer-to-metal adhesion is receiving increased attention. For this study, the argon-ion bombardment surfaces of pyromellitic dianhydride and oxydianiline (PMDA–ODA) and biphenyl tetracarboxylic dianhydride and phenylene diamine (BPDA–PDA) polyimide films were characterized with x-ray photoelectron spectroscopy (XPS) as a function of ion dose. Graphite and high-density polyethylene were also examined by XPS for comparison of C 1s peak width and binding-energy assignments. Results indicate that at low ion doses the surface of the polyimide does not change chemically, although adsorbed species are eliminated. At higher doses the chemical composition is altered and is dramatically reflected in the C 1s spectra where graphiticlike structures become evident and the prominent carbonyl peak is reduced significantly. Both polyimides demonstrate similar chemical changes after heavy ion bombardment. Atomic composition of PMDA–ODA and BPDA–PDA polymers are almost identical after heavy ion bombardment.