SURFACE-ROUGHNESS CHARACTERIZATION OF SOFT-X-RAY MULTILAYER FILMS ON THE NANOMETER-SCALE

The soft x-ray reflectivity of multilayer films is affected by the sur face roughness on the transverse nanometer scale. Scanning tunneling m icroscopy (STM) is an ideal instrument for providing high-lateral-reso lution roughness measurements for soft x-ray multilayer films that can not be obtained with other types of instruments on the transverse nano meter scale. The surface roughnesses of Mo/Si, Mo/C, and W/Si soft x-r ay multilayer films prepared by an ion-beam-sputtering technique were measured with a STM on the vertical and transverse attributes. The fil m roughnesses and average spatial wavelengths added to the substrates depend on the multilayer film fabrication conditions, i.e., material c ombinations, number of layers, and individual layer thickness. These w ere estimated to lead to a loss of specular reflectivity and variation s of the soft x-ray scattering angle distribution. This method points the way to further studies of soft x-ray multilayer film functional pr operties and can be used as basic guidance for selecting the best coat ing conditions in the fabrications of soft x-ray multilayer films. (C) 1996 American Vacuum Society.