GROWTH OF COBALT AND COBALT DISILICIDE ON SI(100)

The growth of Co on Si(100) and the initial stages of the formation of cobalt silicides have been studied by means of a multitechnique approach. Adsorption of Co on Si(100) at room temperature does not result in reaction and formation of a few ML-thick CoSi2 overlayer, contrary to adsorption on (111) surfaces. Rather, a layer-by-layer growth of metallic Co with some Si interdiffused is observed. The formation of CoSi2 requires annealing to 350-degrees-C, a temperature much lower than in the (111) surface. Annealing to 600-degrees-C results in additional Si-enrichment at the surface produced by disruption of the CoSi2 overlayer. The thin CoSi2 "template" layer, which is crucial to achieve epitaxial growth, contains Si at the outer surface, as demonstrated by chemical titration.