The solid state chemistry of Co-Si and Ni-Si binary thin film systems

The kinetics and mechanism of Co- and Ni-silicide formation on single crystal (Si) and amorphous (Si(a)) silicon substrates was studied. Rutherford backscattering, Auger electron spectroscopy, secondary ion mass spectometry and scanning electron microscopy characterized the silicide formation. Ni-silicides showed a sequential single phase growth, while the first and second phases of Co-silicide grew simultaneously in the presence of the metal. The effect of O on Co- and Ni-silicide formation was investigated for different O concentrations in the metal and Si layers. Co2Si and Ni2Si growth ceased at an O content in Co and Ni of 8 at.% and 18 at.%. When O resided in a Si(a) layer, Co2Si and Ni2Si formation stopped at an O concentration of 28 at.%. NiSi formation in the presence of Ni2Si and unreacted Ni-metal was found at an O concentration ≥10 at.% for the Ni and Si(a) layers. For O in Si(a), NiSi formation was faster than on undoped Si(a). As Au enhances the availability of Si, its effect on Co- and Ni-silicide formation was studied. Co-silicide formation in the presence of Au differed in phase sequence and growth rate. All three Co-silicide phases grew from first reaction. CoSi2 grew with a lower activation energy than without Au. No change in phase sequence occurred for Ni-silicide formation in the presence of Au. The difference in the effect of Au on Co- and Ni-silicide formation was due to the slower diffusivity of Co during formation than that of Ni during Ni-silicide formation. Co-silicide formation in the presence of Au was slower on Si(a) than on Si. O doping of Si(a) led to the growth, in the presence of Au, of Co2Si. Higher O doping of Si led to the formation of thinner Co2Si layers. 257 refs., 103 figs., 10 tabs