Oxidation of NiSi and Ni(Pt)Si: Molecular vs. Atomic Oxygen

Abstract

ABSTRACTX-ray photoelectron spectroscopy (XPS) has been used to characterize the reactivities of clean, stoichiometric NiSi and Ni(Pt)Si films on n-doped Si(100) substrates in O2, and in O+O2 environments. In the presence of O+O2, NiSi and Ni(Pt)Si form Ni silicate and Pt silicate overlayers, respectively, with oxide/silicate overlayer thicknesses of 41(4) Å (NiSi) and 28(3) Å (Ni(Pt)Si) after 4.5x104 L exposure. Exposure to O2 yields, for each material, a ∼7(1) Å thick SiO2 overlayer without transition metal oxidation. O+O2 induces rapid Si oxidation, formation of metal-rich silicides, and then the kinetically-driven oxidation of Ni or Pt to form a silicate. This may pose significant processing problems in silicate removal and unwanted Ni diffusion into other areas of the device.