Metastable phase formation in titanium-silicon thin films

Abstract

The formation of TiSi₂ thin films on silicon substrates has been investigated with several transmission electron microscope techniques. For films formed either by reacting titanium with a silicon substrate or by sintering a codeposited (Ti+Si) mixture, electron diffraction patterns show that a metastable phase—TiSi₂ (C49 or ZrSi₂ structure)—forms prior to the equilibrium phase—TiSi₂ (C54 structure). High‐resolution images indicate that the metastable TiSi₂‐silicon interface is atomically sharp, with no ‘‘glassy membrane’’ layer present. The annealing temperature required to transform the metastable TiSi₂ to the low resistivity, equilibrium TiSi₂ increases as the thin‐film impurity content increases. Previous studies of TiSi₂ formation are discussed in light of these results.