An investigation of the thermal stability and Schottky behavior of Ti-W thin film contacts to n-Si in the presence of an Al overlayer is reported. Rutherford backscattering spectroscopy, glancing-incidence x-ray diffraction, and current-voltage measurements were used to characterize the multilayer contact structures. The low Schottky barrier height, 0.51 eV, of the Al/Ti 80W20/n-Si structure was repeatedly measured after 30-min anneals up to 500°C. This stability was improved to 600°C when a diffusion barrier layer of Ti30W 70 alloy was included. The detection and significance of Al penetration in low Schottky barrier height contacts to Si have been discussed.