Avoiding end-of-range dislocations in ion implanted silicon

End-of-range dislocations, which occur from amorphizing implants, are formed if a critical amount of damage is present in the amorphous-crystalline transition region. Here, we investigate the role of the substrate temperature and of the implant energy in residual damage formation. 100 keV Ge implants at room and liquid-nitrogen temperature and ultra-shallow implants of 20 keV Ge and As and 5 keV B at room temperature were performed at different doses above the amorphization threshold. Samples were subsequently annealed at 200, 400, 600 and 900 °C. From the study of the low temperature annealing behaviour of the implanted samples by Rutherford backscattering channelling, we determine the number of displaced atoms located inside amorphous zones in the amorphous crystalline transition region. We conclude that this number should be maximized to avoid dislocation formation. Plan-view transmission electron microscopy is used to analyse implanted samples after the last annealing at 900 °C for 15 min. All the ultrashallow implanted samples are found to be dislocation free.