Phase control and Young's modulus of tungsten thin film prepared by dual ion beam sputtering deposition

Abstract

In this letter, tungsten films of varying thickness from ∼20 nm to ∼80 nm were prepared at different deposition temperature by Dual ion beam sputtering deposition (DIBSD) method. The influence of thickness and deposition temperature on the films phase, microstructure and Young's modulus was studied briefly. The experiments prove that a double-layer structure, formation takes place i.e. β phase tungsten layer (low crystallinity) forms adjacent to the substrate and α tungsten phase layer (high crystallinity) forms above β phase. The increase in both the thickness and deposition temperature promotes the transformation from β phase to α phase which initiates from the interface between two phases. There is a critical thickness of ∼20 nm below which the film is a pure β phase, and the minimum thickness of forming pure α phase is affected by the deposition temperature, with 74 nm at 450°C, and 58 nm at 600°C. Furthermore, the decrease Young's modulus of the tungsten film is ascribed to the formation of β phase which possesses low crystallinity with low density.