Disclosed is a process for passivating a metal surface in a metal/polyimide structure, such as a polyimide layer on a semiconductor substrate containing a pattern of metallization. The process involves the formation of an intermediate layer of a silsesquioxane polymer between the polyimide layer and the substrate. The silsesquioxane layer passivates the metal, to inhibit interaction between the metal surface and the polyimide precursor material used in forming the polyimide, to provide a moisture-resistant and oxidation-resistant interface.