Determination of the layered structure in Mo/Si multilayers by grazing incidence X-ray reflectometry

The formation of intermediate layers was investigated in Mo/Si multilayers produced by e-beam evaporation and ion-beam smoothening. A model of a four-layer step profile structure of the multilayer period was applied successfully to account for grazing incidence X-ray reflectivity of the structures. We have used a special method to determine the multilayer period composition, namely the use of a laterally graded multilayer of which only the thickness of the spacer layer was varied. The well-known modulation of the Bragg peak intensities of 0.154 nm X-rays was then used to determine the thickness and the composition of the silicides formed at the boundaries. The impact of the polishing conditions on the thickness and composition of the intermediate layers was investigated. The study allowed optimization of the composition of Mo/Si multilayer for use at near-normal incidence in the 12.5-15 nm wavelength area for Extreme UV Lithography.