Chemical Reaction on the Surface of As-Doped ZnO Thin Films during the Dry Etching Process

Abstract

The etching properties of ZnO thin films in an inductively coupled Cl(2)/BCl(3)/Ar plasma (ICP) were studied in terms of the etch rate and the selectivity as functions of the gas mixing ratio, the ICP coil power and the dc bias voltage. A maximum etch rate of 425 nm/min was obtained for a mixture Of 10% Cl(2) gas addition to BCl(3)(80%)/Ar(20%) plasma. The X-ray photoelectron spectroscopy (XPS) analyses of the ZnO surfaces etched at various Cl(2)/(Cl(2)+BCl(3)+Ar) mixing ratios revealed the formation of ZnCl(x). and ClO(x), reaction by-products as a result of the increased etch rate with increasing Cl(2) addition, compared with 20% Ar/80% BCl(3) plasma etching. From the analysis of these data, we propose that the maximum etch rate may be explained by the concurrence of chemical and physical pathways in the ion-assisted chemical reaction.