Fluorine bubbles were observed in 5×1015/cm2BF+2‐implanted (001) and (111) Si annealed at 1000–1100 °C. Bubbles were found to form in samples annealed at 1100 °C for a time as short as 10 s. The bubbles were distributed mostly near the original amorphous/crystalline interface and silicon surface. The growth of bubbles was seen to be intimately related to the presence of residual defects. Possible ramifications of bubble formation in device applications are discussed.