Characterization of PdAu thin films on oxidized silicon wafers: interdiffusion and reaction

Abstract

Plasma-deposited thin films prepared at room temperature, ranging from 46 to 250Å of PdAu on ∼45–50Å Si-oxide and Si-oxynitride films grown on Si wafers were studied. Grazing incidence X-ray diffraction, X-ray reflectivity, and XPS depth profile techniques were used to characterize the thin films. A reactive interface involving Pd- and Au-silicides is formed, linking the thin film to the Si-oxide and Si-oxynitride films: a small fraction of Pd and Au atoms from PdAu migrate into the Si substrate, first penetrating the oxide layer, and the small fraction of Si atoms from the oxide layer migrate into the PdAu film and form a silicide interlayer consisting of a reactive interface made up of mixtures of Au- and Pd-silicides interspersed within the matrix of PdAu and substrate. The concentration profiles of these silicides have a maximum at the interface with decay on both sides. The density and the face-centered cubic (fcc) lattice parameter of the film are determined to be ∼13±1g/cm3 and ∼4.004±0.014Å, respectively. The ideal film density is expected to be ∼15.5g/cm3, which suggests substantial defect density and light material mixture, causing more than 13% reduction in the mass density of the film.