CHARACTERIZATION OF METALLIC MULTILAYERS FOR X-RAY OPTICS

X-ray reflectivity is a sensitive tool for characterizing interfaces i n multilayers. Using an appropriate model, the low-angle theta-2theta spectra can be fit to yield the thickness and roughness of each layer. For Si/Mo, a model that includes an interlayer at the Mo on Si interf ace gives much better results than a simple bilayer model. Non-specula r X-ray scattering measurements are particularly sensitive to roughnes s that is correlated from layer to layer because correlated roughness gives rise to resonant scattering in particular non-specular direction s. The non-specular behavior can be understood in terms of current the ories of X-ray scattering from multilayers. Structural parameters, suc h as spatial frequencies of the correlated roughness and a coherence l ength for the correlations can be determined from these data. For the Si/Mo multilayers studied, spatial frequencies below 1/200 angstrom-1 are correlated throughout the multilayer.