Suppression of boron transient enhanced diffusion in silicon and silicon germanium by fluorine implantation

Abstract

In this paper, a study is made of the effect of fluorine implantation on boron transient enhanced diffusion in Si and SiGe by characterising the diffusion of boron marker layers in Si and SiGe in samples with and without a 288 keV, 6x10^13 cm-2 P+ implant and with and without a 185 keV, 2.3x10^15 cm-2 F+ implant. It is shown that fluorine implantation totally eliminates boron transient enhanced diffusion caused by the phosphorus implant as well as significantly reduces boron thermal diffusion in both Si and SiGe. Fluorine SIMS profiles for both Si and SiGe samples show the presence of a shallow peak in the vicinity of the boron marker layer and a deep peak close to the range of the fluorine implant. Cross-sectional transmission electron micrographs show the presence of a band of dislocation loops that correlates with the position of the deep fluorine peak, but no defects are present in the position of the shallow fluorine peak. It is proposed that the shallow fluorine peak is due to vacancy-fluorine clusters that are too small to resolve by TEM. The role of the vacancy-fluorine clusters and the dislocation loops on the suppression of boron diffusion in Si and SiGe is discussed.

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