Thermal oxidation, of Czochralski and float-zone samples with damaged and undamaged surfaces, was carried out in a Cu-contaminated ambient in order to determine the role that was played by the O supersaturation of the starting material and the effect of the formation of oxidation-induced stacking faults. The microstructure was studied by using transmission electron microscopy and secondary ion mass spectrometry, and the minority carrier diffusion length was analyzed by using the electron beam-induced current technique. It was shown that the thermal oxidation of Czochralski material led to the precipitation of large Cu colonies that were associated with oxidation stacking faults, decorated with O, at the Si/SiO2 interface. In the case of float-zone material, the oxidation stacking faults were the nucleation sites of Cu precipitates. When there was no oxidation stacking fault formation (undamaged initial surface), Cu precipitation could occur on dislocation nets. The extended defects were highly recombinant when they were associated with Cu precipitates. The diffusion length decreased in regions that were free of Cu colonies. This indicated the growth of point-like defects during the thermal treatment process, and the diffusion length was restored by hydrogenation.

A.Correia, D.Ballutaud, J.L.Maurice: Journal of the Electrochemical Society, 1995, 142[3], 898-902