This article reports a study carried out on a model-based analysis of the etch mechanism for ZrO2 thin films in a BCl3/He inductively coupled plasma. It was found that an increase in the He mixing ratio at a fixed gas pressure and input power results in an increase in the ZrO2 etch rate, which changes from 36 to 57 nm/min for 0-83% He. Langmuir probe diagnostics and zero-dimensional plasma modeling indicated that both plasma parameters and active species kinetics were noticeably influenced by the initial composition of the BCl3/He mixture, resulting in the nonmonotonic or nonlinear behaviors of species densities. Using the model-based analysis of etch kinetics, it was demonstrated that the behavior of the ZrO2 etch rate corresponds to the ion-flux-limited etch regime of the ion-assisted chemical reaction. (c) 2008 American Vacuum Society.