Table-top reflectometer in the extreme ultraviolet for surface sensitive analysis

Abstract

We suggest a reflectometer for thin film analysis based on a plasma-discharge source utilizing extreme ultraviolet (XUV) radiation in a wavelength region of 4–40 nm. In contrast to other laboratory based reflectometers, which are designed for the near normal incidence case to characterize XUV multilayer optics and maskblanks, in our approach we move to a selectable fixed grazing incidence angle that enables surface sensitive analysis of almost arbitrary ultrathin film systems providing high elemental contrast due to the characteristic absorption of XUV by matter. Most materials (e.g., Si, Al, Gd, and Ag) exhibit characteristic absorption edges allowing not only to determine layer thicknesses, surface or interlayer roughnesses in a stack, but also elemental composition and even analyzing the absorption fine structures. Together with our simulations we show that our polychromatic approach makes it possible to provide all these parameters in one measurement.