Effects of a thin Au Interlayer on the formation of low-resistivity CoSi₂ on (001)Si substrate

In this study we investigate the effects of a thin Au interlayer on the formation of cobalt silicide thin films on (001)Si substrate. The presence of a thin Au interlayer in the Co/Au/Co/(001)Si samples was found to decrease the temperature needed for the formation of the CoSi₂ phase by about 100-190 °C compared to that needed for Co/(001)Si samples. The effect on the formation of CoSi₂ became more pronounced as the thickness of the Au interlayer increased. These results are explained in the context of classical nucleation theory. Cross-sectional transmission electron microscopy (TEM) observations show that both the CoSi₂ surface and CoSi₂/Si interface in Co/Au/Co/(001)Si samples are much smoother than those in Co/Au/Si samples. In addition, the TEM, energy dispersion spectrometry, and secondary ion mass spectroscopy analyses of the Co/Au/Co/(001)Si samples reveal that after annealing a large amount of Au atoms have diffused from the original interface position to be dispersed in the CoSi₂ layers and at the grain boundaries.