Enhanced thermal stability of NiSi films on Si(1 1 1) substrates by a thin Pt interlayer

Abstract

A thin interlayer of Pt can greatly enhance the thermal stability of NiSi films formed by rapid thermal annealing (RTA) on Si(1 1 1) substrates, as was revealed by X-ray diffraction (XRD) data and sheet resistance measurement. High-resolution transmission electron microscopy (HRTEM) reveals a well-defined interface between the Ni(Pt)Si film and the Si(1 1 1) substrate for the Ni/Pt/Si sample annealed at 640°C. The orientation relationship in this sample determined by selected area electron diffraction (SAED) was NiSi(1 0 0)||Si(1 1 1) and NiSi[0 1 ̄ 0]||Si[0 1 1 ̄ ]. With the increase of temperature, the texture of NiSi films transform from NiSi(1 0 0)||Si(1 1 1) to NiSi(0 0 1)||Si(1 1 1). The reduction in the interfacial energy due to the formation of the (1 0 0) textured NiSi film is proposed as a possible reason for the improved thermal stability of NiSi and the transition in NiSi texture during high-temperature annealing. Detailed study on the XRD data combined with Auger electron spectra (AES) indicates PtSi and NiSi form a solid solution following Vegard's law, which adjusts the lattice constant ratio c/ b to 3 and may account for the texture of NiSi(1 0 0)||Si(1 1 1).