The role which was played by the surface in annihilating point defects was studied in ultra-shallow p+/n junctions. The dopant and defect distributions for low-energy implantation lay within a few hundred Angstrom units of the surface. The proximity of the surface was shown to aid the efficient removal of point defects from shallower junctions. The implantation of 5keV BF2 to a dose of 1015/cm2, and of 30keV BF2 to a dose of 3.3 x 1014/cm2, was used to create comparable damage at various depths. After identical annealing treatments, samples which had been implanted to higher energies contained end-of-range dislocation loops, as revealed by cross-sectional transmission electron microscopy. Samples which had been implanted using low energies, where the point defect distribution was closer to the surface, were found to be defect-free. This was attributed to the role which the surface played as an efficient sink for the removal of point defects.

A.Sultan, S.Banerjee, S.List, M.Rodder: Applied Physics Letters, 1996, 69[15], 2228-30