Formation of Polyimide/Substrate Interfaces: Investigation of Interfacial Chemistry of Polyamic Acid with Surfaces of Silicon, Copper, and Chromium

Abstract

We report the results of a spectroscopic study of the initial interface formation between polyimide and a variety of surfaces. Soft X-ray photoemission spectroscopy and near-edge X-ray absorption fine-structure measurements were performed on thin layers of in situ deposited polyamic acid on clean surfaces of Si, Cu, and Cr. The results show a range of reactivity at the interface. Polyamic acid on Cr exhibited the greatest reactivity, which was further enhanced by heating, resulting in molecular fragmentation. The Si 2p core-level spectrum from a polyamic acid/Si(111) interface suggested a complex structure containing three oxidation states of Si with +1 and +2 being dominant, while the carbonyl feature in the C 1s spectrum was totally absent. Copper exhibited the least reactivity of the three substrates investigated; there is spectroscopic evidence for a carboxylate complex being formed at the interface. Similar to previous results for metals deposited onto polyimide surfaces, the main reactive moiety in these systems is initially the carbonyl group. The results for polyamic acid on Cr show striking similarity to previous results for Cr deposited on polyimide surfaces. The terminal step in the polymer/Cr reaction pathway results in molecular dissociation and compound formation at the interface. © 1989, American Chemical Society. All rights reserved.