Fluorine in Silicon: Diffusion, Trapping, and Precipitation

The effect of vacancies on the behavior of F in crystalline Si has been elucidated experimentally for the first time. With positron annihilation spectroscopy and secondary ion mass spectroscopy, we find that F retards recombination between vacancies ($V$) and interstitials ($I$) because $V$ and $I$ trap F to form complexes. F diffuses in the $V$-rich region via a vacancy mechanism with an activation energy of $2.12\pm 0.08\mathrm{e}\mathrm{V}$. After a long annealing time at 700 °C, F precipitates have been observed by cross-section transmission electron microscopy which are developed from the $V$-type defects around the implantation range and the $I$-type defects at the end of range.