X-ray photoemission spectroscopy has been used to investigate the chemical bonding and reactivity of the Al-polyimide interface. At 300 °C substrate temperature, initial deposition of A1 reacts with polyimide up to about 3.5 ml. The reaction occurs mainly with the carbonyl group, resulting in the formation of an intermixed layer. The basic reaction continues with reduced rate up to about 11.5 ml, then unreacted A1 appeared on the surface. Further deposition of A1 caused formation of unreacted A1 islands, as confirmed by cross-sectional TEM observations. © 1985, American Vacuum Society. All rights reserved.