Transient enhanced diffusion of arsenic in silicon

The transient enhanced diffusion (TED) of As in silicon samples implanted at 35 keV with dose 5x10(15) cm(-2) has been investigated in the temperature range between 750 and 1030 degreesC by comparing experimental and simulated profiles. For temperatures higher than 900 degreesC the phenomenon is of modest entity and vanishes after a few seconds, whereas at lower temperatures diffusivity enhancements of some order of magnitude have been observed. The anomalous shift of the junction depth, evaluated at 2x10(18) cm(-3), is about 12 nm at 900 degreesC and increases up to 45 nm at 750 degreesC. It has been verified that the two are the contributions, that generate the interstitial excess responsible for the TED: (i) the implantation damage and (ii) the aggregation in clusters of the As atoms. From an experiment that allows us to separate the two contributions, we estimate that about one third of the TED observed in the first 20 min of annealing at 800 degreesC is due to the defects produced by clustering. The influence of clustering on the shape of the As profiles after diffusion at different temperatures is also discussed.