Etching characteristics and mechanism of Ge2 Sb2 Te5 thin films in inductively coupled Cl2 Ar plasma

This work reports the investigations of both etch characteristics and mechanisms for the Ge2 Sb2 Te5 (GST) thin films in the Cl2 Ar inductively coupled plasma. The GST etch rates and etch selectivities over Si O2 were measured as functions of the Cl2 Ar mixing ratio (43%-86% Ar), gas pressure (4-10 mTorr), and source power (400-700 W). Langmuir probe diagnostics and zero-dimensional (global) plasma modeling provided the information on plasma parameters and behaviors of plasma active species. From the model-based analysis of surface kinetics, it was found that with variations of the Cl2 Ar mixing ratio and gas pressure, the GST etch rate follows the changes of Cl atom density and flux but contradicts with those for positive ions. The GST etch mechanism in the Cl2 -containing plasmas represents a combination of spontaneous and ion-assisted chemical reactions with no limitation by ion-surface interaction kinetics such as physical sputtering of the main material or the ion-stimulated desorption of low volatile reaction products.