Influence of oxygen on the sputtering of aluminum oxide for the surface passivation of crystalline silicon

While sputtering has been shown to be capable of depositing aluminum oxide suitable for surface passivation, the mechanisms for this are yet to be firmly established and its potential realized. In this paper, we investigate the relationships between the oxygen in the sputtering process to the resulting composition of the deposited film and the surface passivation obtained. We find that surface passivation is not strongly dependent on the bulk composition of the film. Instead the results indicate that the interfacial silicon oxide layer that forms after annealing between the aluminum oxide film and the silicon is a much more important factor; it is this combined structure of aluminum oxide, silicon oxide and silicon that is crucial for obtaining negative charges and excellent surface passivation.