Direct observations of the nucleation and growth of NiSi2 on Si (001)

The formation of epitaxial nickel disilicide (NiSi₂) 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. NiSi₂ is a promising candidate, offering a lower temperature of formation and lower silicon consumption. The chapter explores the nucleation of epitaxial NiSi₂ at the boundary between the nickel monosilicide and the silicon substrate at the free surface of the film. It discusses the observations in terms of the relief of lattice strain in response to the volume contraction associated with this reaction. The chapter outlines direct observations of the nucleation of NiSi₂ and discusses the observations in terms of strain relief at the free surface of the film. Selected area diffraction patterns confirmed that the film was comprised entirely of NiSi within one hour of attaining this temperature.