New method for chemical characterization of polymer materials in industrial devices : AFM-IR with FIB sample preparation

We have applied AFM-IR to characterize the chemical structure of polyimide film near the interface with a copper substrate as a model system of an industrial device. AFM-IR requires sample preparation of slicing a sample to be a thin film before its measurement. We have adopted FIB processing as the sample preparation method because a microtome is difficult to slice the cupper substrate. From the comparison between the spectra obtained by traditional FT-IR-ATR, AFM-IR with microtome preparation and FIB processing, we conclude that the damage on polyimide due to ion beam irradiation is so negligible as to characterize the chemical structure of polyimide. We have found the production of carboxylate near the interface by AFM-IR spectral measurement. Furthermore, we have succeeded in visualizing the distribution of carboxylate with a spatial resolution of a few hundreds nanometers which has been difficult to be achieved by a traditional microscopic IR spectroscopy. AFM-IR in conjunction with FIB processing is a useful and promising tool for nanometer scale characterization of chemical structure of polymer materials in organic/inorganic composites such as micro-structured semiconductor devices.