Secondary defects in 1-10 keV As- and BF2-implanted Si

The damage formation and the generation, evolution and dissolution of the secondary defects in very low-energy (1, 5 and 10 keV) As- and BF ₂-implanted (100) Si with a dose of 5×10¹⁴/cm² have been investigated by transmission electron microscopy. The continuous amorphous layer formation from the surface is observed in all the as-implanted layers except the 1 keV BF₂ implantation. After annealing at 550°C, {311} self-interstitial defects remain in the region between the amorphous/crystalline interface and ~2Rp (projected range) depth, independent of implantation conditions, although in samples implanted with 1 keV BF₂, no secondary defects of any type are observed. However, the annealing behavior of defects formed at temperatures higher than 700°C shows a strong dependence on implantation conditions. That is, with the decrease of an implant energy, the defects are dissolved at a lower annealing temperature due to the surface proximity effect of defects. On the other hand, the density and size of defects are larger in BF₂-implanted layers than those in As implantation for implantation energies above 5 keV. This difference is explained by trapping of B and F atoms on the defects during annealing