The reaction kinetics of Al with Ti22W78alloys has been investigated under vacuum annealing conditions. In particular, the effects of Cu in Al and venting during deposition of TiW were studied. It was observed that Cu did not play any significant role in the kinetics of the interdiffusion of Al and TiW. During the reaction process at temperatures around 500 °C, Ti accumulated on the surface of the samples with or without Cu in Al. The Ti accumulation is diffusion limited with an activation energy of 2.4 eV. Interface oxides are believed to be primarily responsible for the stability of Al/TiW metallization.