The chemistry of the Al polyimide interface is examined by x‐ray photoelectron spectroscopy sputter profiling. Al deposited on polyimide films without an in situ Ar backsputter shows a clearly defined 50‐Å Al2O3 layer just prior to the polyimide. This layer is identified by the O/Al atom ratio at 1.5, and the binding energy of the Al 2p transition. There is a clear separation of the Al/Al2O3/polyimide layers in the sputter profiles. Deposition of Al on polyimide surfaces after Argon backsputtering produces a diffuse Al/polyimide interface with no Al2O3 present. There is evidence in the Al 2p spectra for Al–C or Al–O–C type bonds, while the C 1s spectrum clearly has a metal carbide component. Increased adhesion of Al to polyimide surfaces with Ar backsputtering may be due to the differences in chemistry observed in these two instances