The electrical dopant activation of high-dose 49BF2 ion implanted layers was investigated as a function of annealing time and temperature using rapid thermal annealing (RTA) and furnace annealing (FA). Fast recrystallization using RTA produces low sheet resistance, and prolonged annealing at low temperatures causes electrical dopant deactivation. The deactivation was controlled by a diffusion limited process with an activation energy (E(a)) value of 3.46 eV, which is equal to the E(a) value of boron diffusion in the amorphous region that regrows to a single crystal. RTA yields low sheet resistances compared with FA, because RTA minimizes not only the redistribution of fluorine atoms in the amorphous region during the recrystallization, but also the electrical dopant deactivation during the time the wafer is cooling.