Roughness Correlations in Si/Mo Multilayers

Abstract

Low-angle x-ray diffraction with hard x-rays is a standard technique for characterization of interface quality in multilayers. Although the specular reflectivity, measured by a θ-2θ scan, is very sensitive to interface roughness, it reveals little about the nature of the roughness. Fortunately, more information can be obtained from an analysis of the non-specular scattering of the x-rays. The theory of non-specular scattering of x-rays from multilayers only recently has been developed to a level which allows for comparison with experiment.1,2,3,4,5 A key feature of non-specular scattering from multilayers, explained clearly in reference 3, is that correlated roughness should give rise to resonant scattering in particular non-specular directions. Such a resonant intensity has been observed experimentally.2,6,7,8 It is clear from the theories referenced above that correlated roughness can account for the non-specular features we and others have observed. Having an appropriate theory now gives us the possibility to use non-specular measurements to compliment the standard specular characterization techniques.