Anomalous behavior in the dependence of carrier activation on implant dose for extremely shallow source/drain extensions activated by flash lamp annealing

We investigated the influence of extremely high doping concentrations on the sheet resistance of ion implants annealed by FLA. As the implant depth was ultra-shallow and the amount of dopant atoms high, the concentration of dopant near the surface was exceedingly high, above the solid solubility limit, resulting in high Rs. The cause of this is mainly due to the formation of clusters, which was confirmed by calculation and experimental data. The clustering was occurred during the preheating process before the Xe-lamp flash irradiation.