Influence of fluorine implant on boron diffusion: Determination of process modeling parameters

Abstract

The effects of low-dose ion implants with Si+, Ne+, and F+ on the transient enhanced diffusion of B in silicon after annealing at 900 °C for 30 min have been investigated. Processing conditions such as implant dose (3.5×1013 cm−2) and energy (30–60 keV) were chosen to simulate the lightly doped drain implant in a 0.35 μm complementary metal-oxide-semiconductor technology. An epitaxially grown B-doping superlattice is used to extract directly depth profiles of average Si self-interstitial concentration after processing. For Si+ the transient enhanced diffusion of B increases with the energy of the implanted ion. Ne+ implanted with the same energy as Si+ causes more transient enhanced diffusion, while Ne+ implanted with the same range as Si+ causes slightly less. Implantation of F+ enhances the B diffusivity considerably less than Si or Ne implantation. These effects were modeled using simulations of defect diffusion in the presence of traps. A trap concentration of (2.4±0.5)×1016 cm−3 gave good agreement in all situations except F+ implantation, where (6.6±0.6)×1016 cm−3 traps were necessary. It is proposed that this is caused by additional traps for Si interstitials that are related to F+.