Photoelectric, optical and microstructural characterization of thin palladium silicide (Pd2Si) layers fabricated by magnetron sputtering from a stoichiometric target

Abstract

The properties of thin Pd2Si layers fabricated by means of magnetron sputtering deposition from a stoichiometric target was examined. Optical parameters were determined using spectroscopic ellipsometry. The refraction indexes (n) and extinction coefficients (k) of a Pd2Si layer as a function of light wavelength were obtained. The microstructural properties of the Pd2Si layer were investigated using Transmission Electron Microscopy (TEM), Energy-Dispersive X-ray Spectroscopy (EDS), X-ray Diffraction (XRD), X-ray reflectivity (XRR) and Secondary Ion Mass Spectrometry (SIMS). The work function of the silicide layer was measured on the fabricated metal(Pd2Si)-insulator-semiconductor (MIS) structures using Internal Photoemission Spectroscopy (IPS). The IPS technique was used to determine the barrier energy heights at the gate/dielectric (EBG) and dielectric/substrate (EBS) interfaces of the investigated Pd2Si/SiO2/Si system. The appropriate model allowing calculations of fractions of light absorbed by the gate and transmitted to the substrate was developed. The barrier energy from the Fermi level of the silicide gate and from the substrate valence band to the dielectric conduction band are estimated to be EBG = 4.11 ± 0.05 eV and EBS = 4.34 ± 0.05 eV, respectively. Taking the measured barrier height values and reported values of Si electron affinity (χSi = 4.05 eV) and Si band gap (EG = 1.12 eV), the electron affinity of the thermally grown oxide (SiO2) was determined to be χSiO2 = 0.83 ± 0.05 eV and the Pd2Si work function equal to ϕM = 4.94 ± 0.1 eV. It is shown that the application of a single, stoichiometric sputtering target allows to obtain thin Pd2Si layers with work function value resembling that for the bulk material.