Fabrication and Characterization of Nanostructured Ta-Si-N Films

In this paper, the morphology and properties of nanostructured Ta-Si-N thin films fabricated by reactively cosputtering have been studied. The Ta-Si-N film is a mixed composite consisting of the Ta-Si, Ta-N and Si-N compounds. The TaN phase is polycrystalline while SiNx is amorphous. As Si is added to the Ta-N compound to form Ta-Si-N, the micro structure becomes nanocrystalline grains embedded in an amorphous matrix i.e. amorphous-like micro structure, which is also affected by the nitrogen flow ratio i.e. FN2%= FN2/( FN2+FAr) times 100% during sputtering. Amorphous-like Ta-Si-N films obtained at small FN2% of 2-10% had smaller roughness, lower resistivity and larger nanohardness compared to polycrystalline films at high FN2% of 20- 30%. The variation of Ta-Si-N micro structure leads to the different electrical and mechanical properties of films. The electric resistivity of Ta-Si-N increases with increasing FN2% while the nanohardness first increases to a maximum of 15.19 GPa from FN2% of 2% to 3%, then decreases with increasing FN2%. The higher hardness in amorphous-like Ta-Si-N exhibits a larger stiffness and resilience than polycrystalline one.