Effect of ultrathin Mo and MoSix layer on Ti silicide reaction

Abstract

The presence of a small amount of Mo was shown to have a significant effect on the C49–TiSi2 to C54–TiSi2 phase transformation in the Ti–Si reaction. The formation of the C54–TiSi2 phase was facilitated when an ultrathin layer of either Mo or α-MoSix was inserted at or close to the Ti/Si interface. Mo deposited on the surface of Ti had no beneficial effect on the Ti–silicide reaction; neither did Mo implanted into preexisting C49–TiSi2 films. The optimum thickness of interfacial Mo and α-MoSix layers was found to be less than 0.3 nm. Transmission electron microscopy and diffraction investigations demonstrated that Mo did not alter the sequence of the Ti–Si reaction, as proposed in recent studies. Rather, the most obvious effect of molybdenum was a reduction of the grain size of the C49–TiSi2 phase, which could lead to an increase in the nucleation density of the desired C54–TiSi2 phase and account for the observed reduction in formation temperature.