CHARACTERIZATION OF SPUTTER DEPOSITED TUNGSTEN FILMS FOR X-RAY MULTILAYERS

The microstructural and optical properties of tungsten thin films prepared by dc magnetron sputtering were investigated as a function of the argon pressure. The films were characterized by x-ray photoelectron spectroscopy (XPS), scanning tunneling microscopy (STM), x-ray diffraction (XRD), grazing x-ray reflectometry (GXR), and spectroscopic ellipsometry (SE). From the analysis of the XPS data, the films were found to consist of a base tungsten layer, a graded oxide transition layer, and a surface oxide layer. Also, the thickness of the oxide layers were determined. XRD indicated that the films were either amorphous or composed of crystallites with grain size < 100 angstrom. STM and GXR have revealed that the films grown at low pressures were the smoothest. Finally, SE measurements allowed the determination of the dielectric function of a compact tungsten layer. Further SE analysis of the films indicated that with increasing argon pressure, the films developed into a more voided columnar structure.