Metallic impurity gettering and secondary defect formation in megaelectron volt self-implanted Czochralski and float-zone silicon

Megaelectron volt (MeV) self-implantation has been investigated as a means of producing buried defect layers for gettering metallic impurities in Czochralski (CZ) and float-zone (FZ) silicon. The properties of implanted and annealed wafers were studied by generation lifetime (Zerbst) analysis of transient capacitance data, capacitance-voltage measurements, deep-level transient spectroscopy, scanning electron-beam-induced current microscopy, transmission electron microscopy, optical microscopy with preferential chemical etching, and secondary ion mass spectroscopy. We found that metallic contaminants such as Fe and Cu were effectively gettered to buried extended defect layers formed by implantation of ion fluences less than or similar to 1 x 10(15) Si cm(-2). For example, the concentration of iron in regions near the buried defects can be reduced to below 10(10) cm(-3) in samples annealed at 900 degrees C. The region above the damage layer appears to be free of electrically active defects, having very high generation lifetime values, and is therefore suitable for device processing. However, the structure and width of the buried defect band is sensitive to the implanted ion fluence and the oxygen content of the wafers. For example, the defect layers formed by high ion fluences (similar to 10(15) cm(-2)) are wider in FZ wafers than in CZ wafers. For fluences approximate to 1 x 10(14) cm(2), dislocations extend from the buried damage band in both directions during annealing and are observed at depths up to 10 mu m. These dislocations intersect the wafer surface in both CZ and FZ wafers, making fluences lower than similar or equal to 5 x 10(14) cm(-2) unsuitable for device fabrication.