Investigation of the interfacial reaction between metal and fluorine-contained polyimides

In this work, thin metal films (⁠Cr and Ta⁠) were deposited on fluorine-contained polyimides, 6FDA–BisAAF, and 6FDA–PPD. The chemical states of the metal∕polyimide samples were characterized by using x-ray photoelectron spectroscopy (XPS). XPS analysis reveals that metal–C⁠, C–O⁠, and metal–O bondings are present in metallized 6FDA–BisAAF and 6FDA–PPD. C–F bonds are observed in bare 6FDA–BisAAF and 6FDA–PPD; however, they are not seen in the metallized samples. Disappearance of the C–F bonding is attributed to the disruption of CF3 side groups from the main chains of 6FDA–BisAAF and 6FDA–PPD when the chains are exposed to the plasma during the metal deposition. Nevertheless, the disruption of CF3 side groups also creates sites for the formation of metal–C or C–O bondings, which provide a positive adhesion strength at the metal∕polyimide interface, as revealed by the tape test.