Correlation between the gas composition and the stoichiometry of SnOx films prepared by DC magnetron reactive sputtering

The properties of tin oxide thin films deposited by d.c. magnetron sputteri ng of a Sn target are strongly dependent on the sputtering conditions. The aim of the present work is to investigate the discharge parameters such as discharge voltage, deposition rate and ion composition of the discharge as a function of the oxygen partial pressure and to compare them with the stoi chiometry of the deposited films. Working in the constant current discharge mode, we observe, with increasing oxygen partial pressure, a decrease of t he discharge voltage followed by a slight increase and a drop of the deposi tion rate. For each experimental condition, we measure the gas composition by glow discharge mass spectrometry (Sn+, SnO+, SnO2+, O+, O-2(+)) and the stoichiometry of the deposited films by X-ray photoemission spectroscopy. T he results are fitted by means of a model, taking into account the plasma-s urface interactions. All the data are fitted by the same equation, with onl y four fitting parameters, namely the sticking-reaction coefficients of O a nd O-2 on Sn and SnO surfaces. (C) 2001 Elsevier Science B.V. All rights re served.