Titanium/titanium nitride anti-reflective coatings (ARC) are widely used in the semiconductor industry during photolithography of aluminum metal interconnect lines. The quality and effectiveness of these coatings, however, depend strongly on the ability to control reaction products formed at film interfaces during processing. In the present study, formation of an Al-N compound at the interface between Ti/TiN ARC/BARC and Al-(0.5 wt. %)Cu interconnect was investigated. The effects of deposition temperatures for individual films and ensuing thermal cycling of the whole metal stack on formation of intermetallics were evaluated. The composition and chemical bonding state of an aluminum nitride interfacial layer was evaluated by x-ray photoelectron spectroscopy (XPS) of blanket wafers. These results were combined with measurements made by energy filtered transmission electron microscopy (EFTEM) of thickness and continuity of the film in specimens prepared by focused ion beam milling (FIB). Formation of AIN depends on the thermal cycling history of the metal stacks