Interaction of defects and metals with nanocavities in silicon

Ion implantation of H or He into silicon, followed by annealing can create a band of nanocavities. Such nanocavities can exhibit a range of interesting and often non-equilibrium interactions with defects and metals during subsequent implantation and annealing. This paper gives an overview of such interactions, concentrating on cavities produced by H-implantation. The evolution of cavities during annealing is briefly treated, followed by illustrations of the very efficient gettering ability of cavities for fast diffusing metals. For low metal concentrations introduced into the near-surface by implantation, the metal atoms decorate the cavity walls during annealing but can be displaced by oxygen under certain conditions. At high metal concentrations, precipitation and second phase (silicide) formation can occur at cavities but silicide formation and dissolution are found to be controlled by the availability or removal of silicon interstitials, leading to non-equilibrium behaviour. When silicon that contains cavities is irradiated with silicon ions, irradiation-induced defects interact with cavities, leading to preferential amorphisation at certain temperatures. Continued irradiation leads to cavity shrinkage during bombardment, which is most efficient when the region around the cavities is amorphised.