IMPLANT DAMAGE AND TRANSIENT ENHANCED DIFFUSION IN SI

Transmission electron microscopy is used to address two key questions for ion-implant technology in Si. First, how does ion damage influence the diffusion of implanted dopants: and, second, when and how does da mage evolve into extended dislocations seen after prolonged anneals. T he answer to both questions turns out to involve ''{311} defects'', th e interstitial agglomerates also known as ''rod-like defects''. At low doses, {311} defects evaporate during annealing, and emit interstitia ls. The characteristic time for the decay of {311}s, and its activatio n energy of 3.6 +/- 0.1 eV, relate precisely with the observed duratio n of the burst of interstitials seen in accurate diffusion measurement s. We also use {311} counting to assess the accuracy of the ''plus one '' approximation for the excess interstitials seen after implantation. At higher doses, the {311} defects can also undergo a series of unfau lting reactions. In contrast to earlier reports on {311}s formed durin g electron irradiation, we observe that {311}s initially ''unfault'' t o yield Frank loops, followed by unfaulting of Frank loops to give a/2 [110]s. We relate our observations for a ''phase diagram'' for {311} b ehaviour to earlier studies of dislocation loop formation.