Anomalous migration of fluorine and electrical activation of boron in BF+2-implanted silicon

Fluorine distribution profiles for silicon implanted with 150-keV 1×1015-cm−2 BF+2 at room temperature or at −110 °C have been measured by SIMS as a function of anneal temperature. Anomalous migration of fluorine during annealing is observed, and is explained in terms of recrystallization and impurity-gettering effects. Electrical carrier distribution profiles of room-temperature BF+2-implanted silicon, measured by differential Hall effect methods, demonstrate that boron is electrically activated by epitaxial recrystallization during 550 °C annealing. However, a damaged region near the crystalline-amorphous interface remains after recrystallization. This damaged layer is apparently responsible for the fluorine gettering.