Fluorine effects in BF/sub 2//sup +/ implants at various energies

The effects of fluorine co-implanted with boron in BF/sub 2//sup +/ implants at conventional energies (50-80 keV) are well-known. These effects include the pile-up of fluorine in regions of residual damage near the boron peak, the amorphous/crystalline interface, and the end of range, and the formation of fluorine bubbles after annealing. However, ultra-low energy BF/sub 2//sup +/ implants (below 5 keV) and plasma-doped samples do not show any of these effects. In order to identify the transition where the fluorine effects disappear, a series of BF/sub 2//sup +/ implants at energies ranging from 2 to 50 keV and doses of 5/spl times/10/sup 14/ to 5/spl times/10/sup 15/ cm/sup -2/ were performed. The implants were rapidly annealed at temperatures of 900-1000/spl deg/C for 30 s and then analyzed using SIMS and TEM. The results suggest a dependency of these undesirable fluorine effects on ion energy, implant dose, and anneal temperature.