The thermal stability of Al thin films on titanium carbide (Ti xC, where x defines the atomic ratio Ti/C) films reactively sputter deposited on Si substrate has been studied using Auger electron spectroscopy and x-ray diffraction. The stability of the deposited structure increases with increasing carbon content in the TixC films. However, an enhanced stability is obtained for a Ti3.1C film that is preannealed at 750°C for 30 min to induce a phase separation to a titanium silicide inner layer and a TixC outer layer prior to Al deposition. Such a film with an Al top layer maintains its structure even following 550°C-30 min heat treatment. The lower temperature (500°C) failure observed in other cases results from severe intermixing of layers and the formation of the ternary compound Ti7Al5Si12, whereas failures observed at 600°C result from similar intermixing and formation of the compound Al4C3, indicating the decomposition of TiC.