Reactive Deposition Epitaxy of CoSi2 Films on Clean and Oxygen-Adsorbed Si(001) Surfaces

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We have studied the surfactant effects of adsorbed oxygen layers of 1-2 monolayer thicknesses on the film evolution of CoSi2(001) in reactive deposition epitaxy at 470°C on Si(001). The O atoms segregating to the growth front play essential roles in suppressing the Si outward diffusion from the substrate and Co lateral migration, which promote two-dimensional layer growth of CoSi2(001) films and make the surfaces smooth. A kinetic mechanism is suggested in which Co atoms easily diffuse without interaction through the O layers toward the substrate and react with Si atoms. Nevertheless, {111}-twinned CoSi2 is formed at the very initial growth stage on O-adsorbed Si, similarly to that on clean Si. We have also investigated the morphology and crystallinity of ${\sim}20$-nm-thick CoSi2(001) films. The O atoms remaining on the surface effectively restrain film surface roughening even at this thickness; however, they cannot lower the interface roughness owing to the formation of {111} facets and {111}-twinned boundaries. The twin boundaries formed in the initial stage grow into the substrate during the epitaxy.
Published by the Japan Society of Applied Physics through the Institute of Pure and Applied Physicsの論文
2003-12-15