22 March 2010 The effect of line roughness on the reconstruction of line profiles for EUV masks from EUV scatterometry
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The development of EUV lithography is critically based on the availability of suitable metrology equipment. The Physikalisch-Technische Bundesanstalt (PTB) operates an EUV reflectometry facility at the electron storage ring BESSY II, particularly to support the development of Extreme Ultraviolet Lithography. It has been shown that EUV scatterometry is a versatile metrology for characterizing periodic structures regarding critical dimension (CD) and other profile properties. The short wavelength of EUV is particularly advantageous, since it increases the sensitivity to structure roughness. On the other hand, structure roughness also modifies the diffraction intensities used for structure reconstruction based on rigorous calculations of EUV diffraction. We present here first investigations of the influence of roughness-induced modifications of diffraction intensities on the subsequent reconstruction of line profiles. A method is developed to numerically estimate changes in measured diffraction intensities induced by line edge and line width roughness. Finally, the reconstructed profiles for undisturbed and disturbed diffraction intensities are compared. For absorber lines of trapezoidal cross section, the height and mean CD at 50% height appear to be rather insensitive even for unrealistically large roughness amplitudes of up to 14 nm 1σ. The sidewall angle, however, decreases significantly with increasing roughness, with a particular sensitivity to line edge roughness as compared to line width roughness.
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Akiko Kato, Akiko Kato, Frank Scholze, Frank Scholze, } "The effect of line roughness on the reconstruction of line profiles for EUV masks from EUV scatterometry", Proc. SPIE 7636, Extreme Ultraviolet (EUV) Lithography, 76362I (22 March 2010); doi: 10.1117/12.845596; https://doi.org/10.1117/12.845596

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