The thermal stability of the interface between Ti and Se-passivated n-type Si(001) is investigated. As-deposited Ti contacts show ohmic characteristics. After annealing at temperatures from 200°C to 480°C in air, the Se-passivated samples are much more resistant to Schottky transition as compared to the bare samples. The bare samples turn to Schottky at 300°C, whereas the passivated samples are ohmic all the way to 400°C. A difference of over 100°C is observed between the two types of samples. Schottky barrier heights are determined using capacitance-voltage and activation-energy methods. The bare samples reach a maximum barrier height of 0.39eV as determined by activation-energy measurements, while the passivated samples saturate at 0.19eV. We deduce that a monolayer of Se suppresses silicidation between Ti and Si by eliminating dangling bonds on Si(001).