Shallow Junction Ion Implantation in Ge and Associated Defect Control

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Abstract
We have studied implant-induced damage, defect annealing, and recrystallization of B, Ga, P, As, and Sb introduced in Ge by ion implantation at high doses, such that dopant chemical concentrations are above the corresponding solubility in Ge, with energies that target about 100-nm junction depths. It is shown that the amount of damage induced in the Ge lattice increases with the mass of the implanted ion, as expected. Implanted B produces local amorphous regions, although crystalline Ge zones are present in the implanted layer. P is a self-amorphizing ion, creating a continuous amorphous layer during implantation. However, a low thermal budget is sufficient to fully regrow the amorphous layer, without evidence of residual extended defects, as evaluated by cross-sectional transmission electron microscopy. Conversely, high concentrations of As cause a significant decrease of the regrowth rate of the damaged layer during rapid thermal annealing in the 400–600°C range studied. Finally, high-dose implantation of heavy ions such as Sb induces dramatic morphologic changes in Ge that are not recovered by post-implant rapid thermal annealing.