Electrical signatures and thermal stability of interstitial clusters in ion implanted Si

Deep level transient spectroscopy (DLTS) investigations have been used to c haracterize the electrical properties of interstitial clusters in ion-impla nted Si. Both n- and p-type samples were implanted with 145 keV-1.2 MeV Si ions to doses of 1 x 10(10)-5 x 10(13) cm(-2) and annealed at 450-750 degre es C, On samples annealed at temperatures above 550 degrees C, the residual damage is dominated by two hole traps (B lines) in p-type and five electro n traps (K lines) in n-type samples. Analyses of the spectra and defect dep th profiles reveal that these signatures are related to Si self-interstitia l clusters, and experiments confirm that these clusters do not embody large numbers of impurities such as C, O, B, or P. Four deep level signatures ex hibit similar annealing behavior, suggesting that they arise from the same defect structure. On the other hand, the remaining signatures exhibit diffe rent annealing behaviors and are tentatively associated with different clus ter configurations. We have found that the thermal stability of the cluster s is enhanced by either increasing the Si dose or by reducing the impurity content of the substrate. The explanation of these effects proposes that bi gger and more stable clusters are formed when the concentration of free int erstitials available for clustering is increased and the competing intersti tial trapping at impurities is inhibited. Finally, in samples implanted at doses of greater than or equal to 1x10(13) cm(-2), most of the DLTS signals exhibit a complex and nonmonotonic annealing behavior providing evidence t hat the clusters can transform between electronic configurations. (C) 1998 American Institute of Physics. [S0021-8979(98)01121-9].