Diffusion of boron near projected ranges of B and BF₂ ions implanted in silicon

In this study, we examined the diffusion of boron near the projected ranges of high-dose ¹¹B and BF₂ ions implanted in silicon. A buried layer of ¹⁰B was formed and the redistribution of ¹⁰B was used to monitor the diffusion behavior. Boron precipitation at 850°C produces the pileup of ¹⁰B in the peak region of ¹¹B. The formation of a band of boron clusters was indicated by the accumulation of ¹⁰B between the projected range and the diffusion tail of the ¹¹B profiles during annealing at 750°C, following ¹¹B⁺ implantation. The ¹⁰B redistribution at 750°C also demonstrated the retardation of transient enhanced diffusion (TED) in the peak region. Under BF₂⁺ implantation, TED retardation near the projected range of ¹¹B is suppressed by the decrease in implantation energy, because the surface proximity effect reduces the density of end-of-range (EOR) defects at low implantation energies. Boron clustering is suppressed in front of the diffusion tail of ¹¹B because only a peak of ¹⁰B at the EOR dislocations exists at 750°C following BF₂⁺ implantation.