Modification of He implantation induced defects using fluorine co-implantation

During device manufacture, metal contamination has a large effect on silicon-based device performance. Of the available gettering techniques, helium implantation is widely used but the high fluence required is a major drawback. In this paper, the impact of F co-implantation on He implantation-induced defects has been carefully studied. Firstly, our results show that both interstitial and vacancy defects are present in the defect band for all implantation conditions. We show that F implantation may lead to cavity formation at high temperature as expected. The TEM observations also show that, at high temperature, the shape and size of the He-induced defects are significantly affected by the fluorine co-implantation. In particular, cavities are drastically modified by the addition of F, which promotes cavity growth. These results enable us to understand the defect interactions better and constitute a good background to gettering techniques for future device processing.