Effect of Gas Mixing Ratio on Etch Behavior of Y₂O₃ Thin Films in Cl₂/Ar and BCl₃/Ar Inductively Coupled Plasmas

This paper reports the results of a model-based analysis of the etch mechanism for the Y₂O₃ thin films in the Cl₂/Ar and BCl₃/Ar inductively coupled plasma. It was found that the BCl₃/Ar plasma provides higher etch rate (except the case of pure BCl₃ and Cl₂ gases) as well as shows the non-monotonic dependence of the etch rate on the Ar mixing ratio. Plasma diagnostics by Langmuir probes indicated the noticeable influence of Ar mixing ratio on electron temperature and total density of positive ions. Using the model-based analysis of plasma chemistry and etch kinetics, it was demonstrated that the behavior of the Y₂O₃ etch rate in both gas mixtures generally corresponds to the neutral-flux-limited etch regime of the ion-assisted chemical reaction while the obtained differences cannot be explained assuming the Cl atoms to be the main chemically active species. Probably, in the BCl₃-bases plasmas, the etch kinetics is significantly influenced by the BCl_x radicals.