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Published online by Cambridge University Press: 15 February 2011
We investigated the redistribution of oxygen after a thermally induced reaction of an evaporated chromium film deposited on an Si<100> substrate. To monitor the redistribution, 18O was implanted in the metal film or in the silicon substrate. Depth profiles were determined by the isotope-specific reaction 18O (p,α) 15N before and after thermal annealing. Silicide formation was monitored by 2 MeV 4He+ backscattering spectrometry.
It was found that oxygen in the chromium film remains stationary with respect to the chromium during silicide formation, but oxygen in the silicon substrate accumulates at the silicon-silicide interface. The phase formed is CrSi2, as for the unimplanted reference samples. The effect of oxygen on the rate of silicide formation is much more pronounced when the oxygen is in the silicon substrate rather than in the chromium film. This asymmetry is attributed to the fact that silicon is the dominant diffusing species during CrSi2 formation. These results are contrasted with those for nickel and platinum, where the metal moves in the silicide formed by these metals.