Epitaxial growth of CoSi2 on Si wafer using Co/Ta bilayer

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Abstract
A CoSi2 epitaxial layer was grown by thermal annealing of Co/Ta bilayer on a Si(100) wafer in the NH3 ambient. During thermal annealing an intermediate Ta layer between a Co layer and a Si wafer played two important roles for epitaxial growth of CoSi2. One was a reduction of a native oxide on a Si substrate, which resulted in an atomically clean Si surface. The other was a limitation of a flux of Co atoms to the Si surface, which made CoSi2 the most stable phase among several cobalt silicide ones. Both roles of the Ta layer made it possible to produce an epitaxial layer of CoSi2 with a coherent interface with a Si substrate, even at the early stage of thermal annealing.