Etching characteristics and mechanism of Ga-doped ZnO thin films in inductively-coupled HBr/X (X = Ar, He, N-2, O-2) plasmas

Abstract

We investigated the etch characteristics and mechanisms of Ga-doped ZnO (Ga-ZnO) thin films in HBr/X (X = Ar, He, N-2, O-2) inductively-coupled plasmas. The etch rates of Ga-ZnO thin films were measured as a function of the additive gas fraction in the range of 0-100% for Ar, He, N-2, and O-2 at a fixed gas pressure (6 mTorr), input power (700 W), bias power (200 W), and total gas flow rate (40 sccm). The plasma chemistry was analyzed using a combination of the global (zero-dimensional) plasma model and Langmuir probe diagnostics. By comparing the behavior of the etch rate and fluxes of plasma active species, we found that the Ga-ZnO etch process was not limited by ion-surface interaction kinetics and appeared in the reaction rate-limited etch regime. In the HBr/O-2 plasma, the etch kinetics were probably influenced by oxidation of the etched surface. (C) 2011 Elsevier Ltd. All rights reserved.