The application of a helicon plasma source in reactive sputter deposition of tungsten nitride thin films

A reactive helicon wave plasma (HWP) sputtering method is used for the deposition of tungsten nitride (WNx) thin films N-2 is introduced downstream in the diffusion chamber. The impacts of N-2 on the Ar-HWP parameters, such as ion energy distribution functions (IEDFs), electron energy probability functions (EEPFs), electron temperature (T-e) and density (n(e)), are investigated. With the addition of N-2, a decrease in electron density is observed due to the dissociative recombination of electrons with N-2(+). The similar IEDF curves of Ar+ and N-2(+) indicate that the majority of N-2(+) stems from the charge transfer in the collision between Ar+ and N-2. Moreover, due to the collisions between electrons and N-2 ions, EEPFs show a relatively lower T-e with a depletion in the high-energy tail. With increasing negative bias from 50 to 200 V, a phase transition from hexagonal WN to fcc-WN0.5 is observed, together with an increase in the deposition rate and roughness.