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 interestin g and often non-equilibrium interactions with defects and metals during sub sequent implantation and annealing. This paper gives an overview of such in teractions, concentrating on cavities produced by H-implantation. The evolu tion of cavities during annealing is briefly treated, followed by illustrat ions of the very efficient gettering ability of cavities for fast diffusing metals. For low metal concentrations introduced into the nearsurface by im plantation, the metal atoms decorate the cavity walls during annealing but can be displaced by oxygen under certain conditions. At high metal concentr ations, precipitation and second phase (silicide) formation can occur at ca vities but silicide formation and dissolution are found to be controlled by the availability or removal of silicon interstitials, leading to non-equil ibrium behaviour. When silicon that contains cavities is irradiated with si licon ions, irradiation-induced defects interact with cavities, leading to preferential amorphisation at certain temperatures. Continued irradiation l eads to cavity shrinkage during bombardment, which is most efficient when t he region around the cavities is amorphised. (C) 2001 Elsevier Science B.V. All rights reserved.