Investigation of the aluminium oxidation in an oxygen plasma excited by microwaves

Abstract

Al-coatings of approximately 50 nm thickness were deposited by thermal evaporation on Si(100)-wafers. The changes of the Al-films during oxygen plasma treatment in a 2.45-GHz microwave discharge at a pressure of 0.1 Pa were investigated. To study the oxidation kinetics the formed aluminium oxide was investigated using grazing incidence X-ray reflectometry (GIXR), XPS and IR and the residual Al layers were studied using grazing incidence X-ray diffractometry (GIXRD). It was observed that oxygen plasma treatment lead to reactions at low temperatures (<300°C) where thermal treatment show no noticeable effect. The developed oxide is X-ray amorphous. To quantify the alumina formation the change of the film thickness and of the Al(111) peak integral intensity of the non-reacted part of aluminium were determined time-controlled. From these results it can be concluded that two processes, an oxidation and a sputtering process, influence the oxide film growth. The crystallization behaviour was investigated by means of in situ GIXRD during post-annealing in dependence on different plasma treatments.