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

Abstract

The etching properties of ZnO thin lms in an inductively coupled Cl2/BCl3/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 % Cl2 gas addition to BCl3(80 %)/ Ar(20 %) plasma. The X-ray photoelectron spectroscopy (XPS) analyses of the ZnO surfaces etched at various Cl2/(Cl2+BCl3+Ar) mixing ratios revealed the formation of ZnClx and ClOx reaction by-products as a result of the increased etch rate with increasing Cl2 addition, compared with 20 % Ar/80 % BCl3 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 ionassisted chemical reaction.