Implantation with As ions having ultra-low energies was studied by using structural, chemical and electrical techniques. Near-surface damage annealing, and its effect upon the electrical activation of ultra-shallow As in Si, was investigated as a function of the annealing ambient. Double-alignment medium-energy ion scattering, high-resolution transmission electron microscopy and low-energy secondary ion mass spectrometry were used to assess the dopant behavior and crystal recovery in the near-surface regions. The electrical activation of As was measured using spreading resistance profiling, 4-point probes and van der Pauw methods. It was found that a marked redistribution of the dopant into the SiO2/Si interface region occurred during re-growth of the damaged Si layer. An inactive metastable As solid solution was formed in the near-surface region after amorphous layer re-growth. Electrical activation of the dopant occurred upon dissociation of the As solid solution, when the dopant concentration fell to the steady-state level. The As diffusion which was observed was shown to be enhanced by short (10s) annealing times at 1100C. When annealing at high temperatures in an oxidizing ambient, the dopant was retained at high concentrations in the solid and a higher level of electrical activation was observed. Significant out-diffusion of the dopant was observed during high temperature annealing under non-oxidizing conditions which reduced the level of activation.

Electrical Activation of Ultralow Energy As Implants in Si. S.Whelan, V.Privitera, G.Mannino, M.Italia, C.Bongiorno, A.La Magna, E.Napolitani: Journal of Applied Physics, 2001, 90[8], 3873-8

Table 1

Diffusivity of As in Si