Interfacial reactions of titanium thin films on BF+2 -implanted (001)Si

Abstract

Interfacial reactions of titanium thin films on BF+2 -implanted (001)Si have been studied by both cross-sectional and planview transmission electron microscopy as well as by sheet resistivity measurement. Amorphous Ti-Si interlayers were observed in Ti films on blank and implanted samples following 400 °C annealing. The presence of the doping impurities was found to promote the early growth of the C54-TiSi2 phase. 100% surface coverage of TiSi2 on silicon was found in implantation amorphous samples annealed at 1000 °C for 1 h. The C54-TiSi2/Si interface energy and/or the silicide surface energy are thought to be lowered by the presence of the doping impurities to improve the surface morphology at high temperatures. The distribution of fluorine bubbles in doped samples with Ti overlayers annealed at 500–1000 °C indicated that (1) the solubilities of F in Ti silicides are very low, (2) the diffusivities of F in both C49- and C54-TiSi2 are rather high, and (3) most of fluorine atoms in TiSi2 layer escaped into ambient during 900–1000 °C annealing. The end-of-range defects were found to be not significantly affected by the TiSi2 formation. In samples annealed at 700–800 °C, the sheet resistance values were found to be the same in spite of the difference in distribution of doping impurities and defect structure.

X-ray photoemission spectroscopy study of silicidation of Ti on BF2+-implanted polysilicon

“…However, several groups reported small F containing bubbles forming in BF 2 ϩ -implanted polySi after annealing, but they were visible only under high-resolution cross-sectional TEM ͑XTEM͒. 26,34,49 Furthermore, their density decreases while their size increases with annealing temperature. 12,49 Immediately after the deposition of Ti, the Ti/Si interface does not react.…”

“…26,34,49 Furthermore, their density decreases while their size increases with annealing temperature. 12,49 Immediately after the deposition of Ti, the Ti/Si interface does not react. 3 Butz, Rubloff, and Ho and Hsu et al reported that Ti thin films on Si can be transformed to Ti 5 Si 3 , TiSi, and TiSi 2 after steady-state annealing between 500 and 600°C, and only TiSi 2 can be observed after annealing above 650°C.…”

<title>Microstructure-property studies for semiconductor interfaces using high-resolution electron microscopy</title>

“…The growth of the amorphous phase at Ti-Si interfaces during low-temperature annealing (below 450°C) is now well-documented (e.g. 17,21,22 ) and results in non-ohmic contacts to p+ silicon in 0.3 micron via holes23. Holloway et al 24 have carefully considered the thermodynamic and kinetic conditions for the amorphous phase reaction, showing that it is energetically favored over the physical Ti-Si interface and can be produced so long as crystallization is avoided by fast diffusion of one species (i.e.…”

Formation of TiSi2 on nitrogen ion implanted (001)Si

“…N 1 implantation was introduced in an attempt to suppress both channeling and TED. 9 In addition, the morphological stability of C54-TiSi 2 during high temperature annealing is crucial to the development of ULSI technology. Low-resistivity TiSi 2 is perhaps the most attractive candidate for the self-aligned technology of ULSI circuits because it possesses the lowest resistivity among all silicides, low contact resistance, and good thermal properties as well as compatibility with the self-aligned silicidation process.…”