Evaluation of fluorine-related species during Ti silicidation on BF2+-implanted polycrystalline silicon (polySi) under different temperatures has been studied using x-ray photoemission spectroscopy (XPS). The silicidation was carried out under sequential anneals from 500 to 700 degreesC with an interval of 50 degreesC in an ultrahigh vacuum (UHV) within the XPS chamber. The binding energy and peak intensity for Si 2p Ti 2p, F I s, 0 1 s, B I s, and C I s XPS peaks have been measured in the same XPS chamber immediately after the silicidation anneal without breaking the vacuum. The results show that fluorine from the BF2+ implantation is dissociated to form a mixture of SiFx (1 less than or equal to x less than or equal to 4) and TiFx (x = 3,4) -like gaseous species at/near the TiSi2/polySi interface upon silicidation anneal. This can be characterized by the approximately 1.2 eV per Si-F bond chemical shift of the Si 2p core level, and the peak position for Ti 2p core levels with the resolved peaks at 465.1 eV corresponding to the Ti-F bond. The F Is peaks further confirm the presence of SiFx and TiFx species. As the silicidation proceeds to higher temperatures, the intensity of these reaction species decreases due to their out-diffusion from the thin TiSi2 layer. These findings correlate well with the previously reported results on the void fort-nation in sub-quarter-micron BF2+-implanted 2 Ti-salicided polySi lines [H. N. Chua et al., J. Appl. Phys. 87, 8401 (2000)].