Characterization of laterally nanopatterned W/Si multilayers

We present a structural study of two amorphous periodic W/Si multilayer gratings obtained by etching the planar multilayer up to the multilayer substrate based on scanning-electron and atomic force microscopy observations and X-ray reflectivity measurements of coherent grating truncation rods. Two different exposure modes to prepare resist mask were examined to optimize the resulting grating structure. The real structural parameters of a more perfect grating were extracted from fitting the measured grating truncation rods. The simulations are based on the matrix modal eigenvalue approach of the dynamical theory of reflectivity by gratings which generalizes the Fresnel transmission and reflection coefficients for lateral diffraction. The interface imperfections are taken into account by the coherent amplitude approach which averages the propagation matrices of the wave field over random interface displacements.