Transient Phase Formation During the Growth of Epitaxial CoSi2 by Annealing of Co/Ti Bi-Layers on (100) Si

Abstract

AbstractPhase evolution during the annealing of Co/Ti bi-layers on (100) Si has been studied by x-ray diffraction and analytical electron microscopy. X-ray diffraction performed in situ during annealing revealed a reaction pathway involving the formation of a transient phase when epitaxial CoSi2 films were grown. Analytical electron microscopy was used to identify this phase as a spinel-related phase, isostructural with Co2TiO4. This phase grows as a result of the presence of the Ti interlayer and a small amount of oxygen from the annealing ambient. Annealing in vacuum or other purified inert gases yielded polycrystalline CoSi2 films which form via a different reaction pathway that does not involve a spinel phase. This spinel phase may serve both to reduce the native oxide from the underlying Si substrate and to control interdiffusion between Si and Co during the reaction, thereby promoting epitaxial growth.