Fluorine –Vacancy Engineering: A Viable Solution for Dopant Diffusion Suppression in SOI Substrates

This paper reviews progress in vacancy engineering using a silicon implant into SOI substrates and considers the prospects for vacancy engineering using fluorine implantation. Vacancy engineering using a silicon implant comprises a high energy silicon implant into an SOI substrate, to separate the excess vacancies in the SOI layer and the excess interstitials below the buried oxide. Results on vacancy-engineering show that a properly optimized high energy silicon implant is able to suppress boron transient enhanced diffusion. Results are also presented on the behaviour of fluorine in bulk silicon and it is shown that a high energy fluorine implant not only completely suppresses boron transient enhanced diffusion but also significantly reduces boron thermal diffusion. The suppression of boron thermal diffusion is due to the formation of vacancyfluorine clusters that form at approximately half the range of the fluorine implant. Finally, fluorine implantation is applied to SOI wafers, with the aim of separating the vacancy-fluorine clusters in the active layer from interstitial dislocation loops below the buried oxide layer. These results show a high energy fluorine implant into SOI substrates is also effective in suppressing boron diffusion.