The evolution and disappearance of the dislocation loops associated with pre-amorphisation

Abstract

The control of implanted depth distributions by pre-amorphising silicon results in the production of defects which can impair the performance of devices fabricated in this fashion. The most stable-and therefore the most troublesomdefects are the dislocation loops which form at the amorphous/ crystalline interface on annealing. A simple model for the evolution of these loops with annealing is presented. By using this model the temperature and time of the anneal required to remove these loops can be predicted. It also explains the anneal's dependence on the mass of the amorphising ion, the implantation temperature and the amorphous layer thickness. The model is shown to be supported by the currently available data.

A model of diffusion-controlled annealing of dislocation loops in pre-amorphized silicon

“…It is intended that the present theory should at least provide a framework for the understanding of experimental observations of pre-amorphization-induced loops. One might expect intuitively that the mean spacing of the loops, which is of order would be an important parameter in determining whether loop coarsening would occur (Thornton and Hill 1989), but this quantity docs not appear explicitly in the equations derived in the present work.…”

“…The loops are of interstitial type (Brotherton et al 1986) and arise from the clustering of excess self-interstitials, remaining after interstitialvacancy recombination, in the region which was damaged but not amorphized (Thornton, Webb, Wilson and Paus 1988). Annealing out of the loops is generally found to be easier when the amorphous layer is made thinner (Ajmera and Rozgonyi 1986) and it has been suggested that this effect is due to the reduced distance over which interstitials have to diffuse to the surface (Thornton and Hill 1989).…”