It was noted that conducting and charge-trapping defects in the buried oxide of SIMOX structures depended upon the processing conditions. Samples which were implanted with O ions in a channelling direction of a Si wafer contained more defects of both types than did those prepared using a non-channelling direction. Thus, a correlation could exist between excess Si in oxide-forming Si clusters (amphoteric photo-sensitive defects) and the density of conducting defects. It was suggested that interstitial Si atoms, which were generated during implantation and annealing, formed filaments in structural channels in the buried oxide. However, the density of conducting defects could also be affected by factors such as contamination and/or the extent of lateral inhomogeneity of the trapping defects. The defects in the buried oxide were distributed in a laterally inhomogeneous manner. This could result in a varying density of conducting defects for a given integrated density of amphoteric defects. The observation of defects in the upper Si layer, and their correlation with conducting defects in the buried oxide, indicated the possible involvement of a contaminant in the formation of conducting channels in the buried oxide.

V.V.Afanasev, G.A.Brown, H.L.Hughes, S.T.Liu, A.G.Revesz: Journal of the Electrochemical Society, 1996, 143[1], 347-52