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Lamellar gratings are widely used diffractive optical elements and are prototypes of structural elements in integrated
electronic circuits. EUV scatterometry is very sensitive to structure details and imperfections, which makes it suitable for
the characterization of nanostructured surfaces. As compared to X-ray methods, EUV scattering allows for steeper angles
of incidence, which is highly preferable for the investigation of small measurement fields on semiconductor wafers. For
the control of the lithographic manufacturing process, a rapid in-line characterization of nanostructures is indispensable.
Numerous studies on the determination of regular geometry parameters of lamellar gratings from optical and Extreme
Ultraviolet (EUV) scattering also investigated the impact of roughness on the respective results. The challenge is to
appropriately model the influence of structure roughness on the diffraction intensities used for the reconstruction of the
surface profile. The impact of roughness was already studied analytically but for gratings with a periodic pseudoroughness,
because of practical restrictions of the computational domain. Our investigation aims at a better
understanding of the scattering caused by line roughness. We designed a set of nine lamellar Si-gratings to be studied by
EUV scatterometry. It includes one reference grating with no artificial roughness added, four gratings with a periodic
roughness distribution, two with a prevailing line edge roughness (LER) and another two with line width roughness
(LWR), and four gratings with a stochastic roughness distribution (two with LER and two with LWR). We show that the
type of line roughness has a strong impact on the diffuse scatter angular distribution. Our experimental results are not
described well by the present modelling approach based on small, periodically repeated domains.
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