Direct observations of the nucleation and growth of NiSi 2 on Si (001)

Abstract

The formation of epitaxial nickel disilicide from agglomerated films of nickel monosilicide has been studied using a modified ultrahigh vacuum transmission electron microscope. Nickel films 12nm in thickness were deposited by in-situ electron beam evaporation and annealed at temperatures of up to 850°C. We observe the nucleation of epitaxial nickel disilicide at the boundary between the nickel monosilicide and the silicon substrate at the free surface of the film. The mono/disilicide interface is then observed to propagate through the monosilicide island. We discuss our observations in terms of the relief of lattice strain in response to the volume contraction associated with this reaction.