Process-dependent effects of water on the chemistry of aluminum oxide and aromatic polyimide interface in composite materials

Abstract Replacement of Cu wires with Al wires has a significant impact on the overall cable and wire fields. This replacement is particularly important for reducing the weight of hybrid vehicles, significantly improving fuel efficiency, and reducing CO2 emissions. A promising analytical protocol is proposed for investigating the Al and polymer coating interface in samples fabricated by semiconductor-device-manufacturing techniques. The samples were analyzed by time-of-flight secondary ion spectrometry (TOF-SIMS), synchrotron hard-X-ray photoelectron spectroscopy (HAXPES), and electron energy loss spectroscopy with scanning transmission electron microscopy (STEM-EELS). The protocol provides information about the chemistry of interfaces fabricated by (1) Al deposition on a polymer substrate and (2) coating of a polymer precursor on Al. Observation of the Al and pyromellitic-dianhydride-oxydianiline-type polyimide (PMDA-ODA PI) interfaces revealed: For (1), the water adsorbed on the pristine PI surface contributed mainly to formation of the Al hydrate. For (2), at the Al/PI interface, the two events occur in a chain: first, hydrolysis of PAA occurred to form the carboxyl group, followed by acid-base reactions between the carboxyl group and hydroxide/oxide to generate water. Thus, Al-O-C=O bonds form at the interface. The proposed protocol is applicable to the investigation of a wide-ranging combination of metals and polymers.