Etching Behavior and Mechanism of In- and Ga-Doped ZnO Thin Films in Inductively Coupled BCl₃/Cl₂/Ar Plasmas

The etching characteristics and mechanism of In- and Ga-doped ZnO (IGZO) thin films in BCl₃/Cl₂/Ar inductively coupled plasma at a fixed gas pressure (6 mTorr) were investigated. It was found that the substitution of Cl₂ for BCl₃ in the BCl₃/Cl₂/Ar gas mixture results in the maximum IGZO etching rate in 40% BCl₃ + 40% Cl₂ + 20% Ar. In both Cl₂-rich (20% BCl₃ + 60% Cl₂ + 20% Ar) and BCl₃-rich (60% BCl₃ + 20% Cl₂ + 20% Ar) plasmas, increases in input power (500–800 W) and bias power (100–250 W) cause the monotonic acceleration of the IGZO etching process. Plasma diagnostics using Langmuir probes and zero-dimensional plasma modeling provided the data on plasma parameters and fluxes of active species. It was concluded that the IGZO etching process is not limited by the ion–surface interaction kinetics as well as involves BCl_x radicals.