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.