The etch characteristics of Al2O3 films was investigated by using BCl3/Cl-2/Ar inductively coupled plasma. The Al2O3 thin films were grown by atomic layer deposition method. The behavior of etch rate of Al2O3 thin films was investigated as a function of BCl3 ratio to Cl-2/Ar plasma, r.f. power, d.c. bias and pressure. In order to understand the changes of radicals, volume density of Cl, B radical and BCl molecule were investigated with optical emission spectroscopy (OES). The volume density of B radical increased in all the conditions. The chemical states of Al2O3 thin films were studied with X-ray photoelectron spectroscopy. The etch mechanism of ALD deposited Al2O3 can be explained with the competition between chemical etching by formation volatile AlCl3, Al2Cl6 or BOCl3 and physical sputtering by energetic ions. (C) 2003 Elsevier B.V. All rights reserved.