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⁺.