An investigation of the Ba2Ti9O20 (BTO) thin-film etch characteristics and mechanism in the Cl-2/Ar inductively coupled plasma was carried out. The BTO etch rate as well as the BTO/Pt etch selectivity were measured as functions of Cl-2/Ar mixing ratio (0-100% Ar), gas pressure (4-10 mTorr), input power (400-700 W), and bias power (50-300 W). A combination of plasma diagnostics by Langmuir probes and zero-dimensional plasma modeling provided the information on plasma parameters, gas-phase compositions, and fluxes of active species on the etched surface. It was found that the behavior of the BTO etch rate corresponds to the reaction-rate-limited etch regime, when the etch rate is limited neither by physical sputtering of the main material nor by the ion-stimulated desorption of low volatile reaction products. (c) 2008 The Electrochemical Society.