Magnesium oxide thin film has been widely used as a buffer layer and substrate for growing various thin film materials because of very low Gibbs free energy, low dielectric constant and low refractive index. The investigations of the MgO etching characteristics in BCl3/Ar plasma were carried out using the inductively coupled plasma system. It was found that the increasing BCl3 in the mixing ratio of BCl3/Ar plasma causes monotonic MgO etch rate. The results showed in the BCl3-rich plasma that the etching process is dominantly supplied by the chemical pathway through the ion-assisted chemical reaction. (c) 2006 Elsevier B.V. All tights reserved.