Application of a Two-Step Growth to the Formation of Epitaxial CoSi2 Films on Si(001) Surfaces: Comparative Study using Reactive Deposition Epitaxy

Epitaxial growth of 20-nm-thick CoSi2 films on Si(001) surfaces has been investigated for a two-step growth and reactive deposition epitaxy (RDE) at growth temperatures of 320–680°C using in-situ reflection high-energy electron diffraction and scanning tunneling microscopy, and ex-situ X-ray diffraction and atomic force microscopy. For the RDE, three-dimensional CoSi2 islands with a {115}-faceted structure grow along the <110 > directions and pinholes or channels with depths over ∼20 nm are formed. However, for the two-step growth, no {115}-faceted islands exist and the depth of pinholes or channels decreases greatly. In the two-step growth, cobalt is solely deposited at an elevated substrate temperature on an epitaxial CoSi2(001) film formed by solid-phase epitaxy of 0.23-nm-thick Co as the first step. The first-step CoSi2 film has effects on restraining the Si diffusion from the substrate at the pinhole sites and promoting the layer-by-layer growth at the second step. The original two-step growth technique will be highly suitable for the realization of high-quality epitaxial CoSi2 contacts in the future ULSI technology.