Polyimide - Substrate Bonding Studies Using -APS Coupling Agent

Application of polyimides in microelectronics fabrication for interlevel dielectric, passivation, or device isolation requires that the polymer films maintain interface integrity with a variety of surfaces at high temperature and during solvent processing. y-aminopropyltriethoxy-silane (y-APS) in aqueous solution is the most commonly employed adhesion promoter for the bonding of polyimides to inorganic substrates including silicon oxide, silicon nitride, and ceramic. The adhesion of pyromellitic-dianhydride-oxydianiline (PMDA-ODA) derived polyimide films on y-APS-treated silicon oxide and silicon nitride surfaces under high-temperature processing is considered. Using the standard 90° peel test for adhesion measurements, it is shown that polymer-substrate interface stability is completely maintained even after multiple thermal cycles with 25° 375° 25°C excursions in nitrogen and in forming gas ambients. X-ray photoelectron spectroscopy (XPS) of the polyimide side and the substrate surface exposed in the peel adhesion measurement was used to ascertain the elemental composition and detailed chemistry at the locus of failure. These data show that the peel occurs within the polyimide film near the polymer/substrate interface.