Dry etching characteristics of zinc oxide thin films in Cl2-based plasma

Abstract

We investigated the etching characteristics of zinc oxide (ZnO) and the effect of additive gases in a Cl2-based inductively coupled plasma. The inert gases were argon, nitrogen, and helium. The maximum etch rates were 44.3, 39.9, and 37.9 nm/min for Cl2(75%)/Ar(25%), Cl2(50%)/N2(50%), and Cl2(75%)/He(25%) gas mixtures, 600 W radiofrequency power, 150 W bias power, and 2 Pa process pressure. We obtained the maximum etch rate by a combination of chemical reaction and physical bombardment. A volatile compound of Zn-Cl. achieved the chemical reaction on the surface of the ZnO thin films. The physical etching was performed by inert gas ion bombardment that broke the Zn-O bonds. The highly oriented (002) peak was determined on samples, and the (013) peak of Zn2SiO4 was observed in the ZnO thin film sample based on x-ray diffraction spectroscopy patterns. In addition, the sample of Cl2/ He chemistry showed a high full-width at half-maximum value. The root-mean-square roughness of ZnO thin films decreased to 1.33 nm from 5.88 nm at Cl2(50%)/N2(50%) plasma chemistry. © 2011 KIEEME.