Etching characteristics and mechanism of ZnO thin films in inductively coupled HBr/Ar plasma

The etching characteristics and mechanisms of ZnO thin films in an HBr/Ar inductively coupled plasma were investigated. The etch rate of ZnO was measured as a function of the HBr/Ar mixing ratio in the range of 0-100% Ar at a fixed gas pressure (6 mTorr), input power (900 W) and bias power (200 W). The plasma diagnostics were performed by double Langmuir probe measurements and quadrupole mass spectrometry. A global (0-dimensional) plasma model was used to obtain the data on the densities and fluxes of the active species. It was found that the etch rate of ZnO is proportional to the flux of Br atoms, but inversely proportional to those of the H atoms and positive ions. This suggests that the ZnO etch process is not limited by the ion-surface interaction kinetics and that the Br atoms are the main chemically-active species.