Abstract
Evaluation of fluorine-related species during Ti silicidation on
BF
2
+
-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 °C with an interval of 50 °C in an ultrahigh vacuum (UHV) within the XPS chamber. The binding energy and peak intensity for
Si
2p,
Ti
2p,
F
1s,
O
1s,
B
1s,
and
C
1s
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
BF
2
+
implantation is dissociated to form a mixture of
SiF
x
(1⩽x⩽4)
and
TiF
x
(x=3,4)
-like gaseous species at/near the
TiSi
2
/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
1s
peaks further confirm the presence of
SiF
x
and
TiF
x
species. As the silicidation proceeds to higher temperatures, the intensity of these reaction species decreases due to their out-diffusion from the thin
TiSi
2
layer. These findings correlate well with the previously reported results on the void formation in sub-quarter-micron
BF
2
+
-implanted Ti-salicided polySi lines [H. N. Chua et al., J. Appl. Phys. 87, 8401 (2000)].