A point defect injection study was performed to investigate the effect of F on B diffusion when interstitials were injected from the surface. 185keV, 2.3 x 1015/cm2 F+ was implanted into Si with a B marker layer located at about Rp/2 of the F implant. This was followed by rapid thermal annealing at 1000C for 15 to 120s in an O ambient. The wafers were covered with different layers prior to anneal to introduce different point defect injection effects. When interstitials were injected from the surface, F strongly suppresses B diffusion for anneal times of 15 and 30s. For longer anneal times, F became progressively less effective and the B diffusion coefficient approaches the value obtained in samples without fluorine. This effect of F on B diffusion suppression correlates with the presence of a shallow secondary-ion mass spectroscopy F peak at about Rp/2. These results supported earlier work showing that vacancy–fluorine clusters at about Rp/2 were responsible for the suppression of B diffusion and that these clusters anneal out during long anneal times. A problem with B cross-contamination during F implantation was also identified.

Effect of Fluorine on Boron Diffusion under Interstitial Injection from the Surface. M.N.Kham, H.A.W.El Mubarek, J.M.Bonar, D.Chivers, P.Ashburn: Nuclear Instruments and Methods in Physics Research B, 2006, 253[1-2], 100-4