Fluorine incorporation in preamorphized silicon

We studied the effect of implanted fluorine on B-doped silicon formed by Si preamorphization, solid phase epitaxy (SPE) regrowth and post-SPE thermal treatments. We showed that the fluorine is an efficient diffusion inhibitor for boron, revealing the crucial importance of F implementation in the future generation devices. In samples doped with B we observed an anomalous F accumulation at the dopant implantation peak. Since the physical mechanisms driving these phenomena are not yet well understood, we investigated the effect of the presence of B and/or As on the F incorporation during the SPE process at 580 degrees C. By using As coimplantation (thus modifying the SPE rate) we demonstrated that the above mentioned increased F incorporation is due to a kinetic effect, related to the SPE rate modification by doping, while a F-B chemical bonding is refused. These data shade new light upon the mechanism responsible for B diffusion reduction by F.