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

Abstract

Abstract A reactive helicon wave plasma (HWP) sputtering method is used for the deposition of tungsten nitride (WN x ) thin films. N2 is introduced downstream in the diffusion chamber. The impacts of N2 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 N2, a decrease in electron density is observed due to the dissociative recombination of electrons with N 2 + . The similar IEDF curves of Ar+ and N2 + indicate that the majority of N 2 + stems from the charge transfer in the collision between Ar+ and N2. Moreover, due to the collisions between electrons and N2 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.