Self-implantation (MeV) was investigated as a means of producing buried defect layers for gettering metallic impurities in Czochralski or float-zone Si. The properties of implanted and annealed wafers were studied by using a wide range of techniques. It was found that metallic contaminants such as Fe and Cu were effectively gettered to buried extended defect layers that were produced by implantation using fluences of up to 1015/cm2. The concentration of Fe in regions near to the buried defects could be reduced to below 1010/cm3 in samples which were annealed at 900C. The region above the damage layer appeared to be free of electrically active defects having very high generation lifetimes. The structure and width of the buried defect band was sensitive to the implanted ion fluence and to the O content of the wafer. Thus defect layers formed by high ion fluences (1015/cm2) were wider in float-zone wafers than in Czochralski wafers. For fluences of about 1014/cm2, dislocations extended from the buried damage band, in both directions, during annealing and were observed at depths of up to 10μ. These dislocations intersected the wafer surface in both Czochralski and float-zone wafers, thus making fluences of less than 5 x 1014/cm2 unsuitable for device fabrication.

R.A.Brown, O.Kononchuk, I.Bondarenko, A.Romanowski, Z.Radzimski, G.A.Rozgonyi, F.Gonzalez: Journal of the Electrochemical Society, 1997, 144[8], 2872-81