Reduction of boron thermal diffusion in silicon by high energy fluorine implantation

Abstract

This letter investigates the effect of a deep F+ implant on the diffusion of boron in silicon. The effects on boron thermal diffusion and transient enhanced diffusion are separately studied by characterizing the diffusion of a buried boron marker layer in wafers with and without a 185 keV, 2.3 ×1015 cm−2 F+ implant, and with and without a 288 keV, 6 ×1013 cm−2 P+ implant. In samples given both P+ and F+ implants, the fluorine completely eliminates the transient, enhanced boron diffusion caused by the P+ implant, and in samples implanted with F+ only, the fluorine suppresses the boron thermal diffusion by 65%. These results are explained by the effect of the fluorine on the vacancy concentration in the vicinity of the boron profile.