Etching Characteristics and Mechanism of ZnO and Ga-Doped ZnO Thin Films in Inductively Coupled HBr/Ar/CHF3 Plasma

Abstract

The etching characteristics and mechanisms of ZnO and Ga-doped ZnO (Ga-ZnO) thin films in a HBr/Ar/CHF3 inductively coupled plasma were investigated. The etching rate of ZnO was measured as a function of the CHF3 mixing ratio in the range of 0–15% in a HBr:Ar = 5:2 plasma at a fixed gas pressure (6 mTorr), input power (700 W), bias power (200 W), and total gas flow rate (50 sccm). The plasma chemistry was analyzed by a combination of the global (zero-dimensional) plasma model, Langmuir probe diagnostics (LP) and quadrupole mass spectrometer (QMS) analysis. It was found that the densities of both HBr and Br are significantly affected by the reactions with the CHF3 dissociation products, while both the ZnO and Ga-ZnO etching rates follow the behavior of the Br atom density and flux. This suggests that the ZnO and Ga-ZnO etching processes are not limited by the ion-surface interaction kinetics and appear in the reaction-rate-limited etching regime.