The defect structure of grown silicon dioxide films

A structural model is proposed to explain various phenomena which occur in grown SiO
2
films. In this model, oxygen interstitials in ionic form are the predominant diffusing species during the growth. In neutral form they can act as acceptor states. Reduction of the oxide by hydrogen (e.g., growth in steam, heat treatment in H
2
containing gas) or by metal (e.g., interaction with the gate electrode in metal-oxide-semiconductor (MOS) devices) results in trivalent silicon. This defect may form a donor surface state. The migration of metal ions under the influence of an electric field can lead to an asymmetric current-voltage characteristic of a Si-SiO
2
-Me system. Transient and hysteresis effects as well as the asymmetric shift in the surface potential caused by biasing MOS devices at relatively high temperatures are attributed to an inhomogeneous distribution of defects in the oxide (as a result of the oxidation) and/or to the motion of metal ions originating from the gate electrode.