The authors present a novel approach for the structural characterization of periodic nanostructures using spectrally resolved broadband scatterometry in the extreme ultraviolet (EUV) wavelength range. The implemented metrology method combines 0th and ±1st diffraction order spectrum measurements of a nanograting under broadband illumination from 8 nm to 17 nm for model-based reconstruction of geometrical parameters. For the experimental investigations, a compact stand-alone scatterometer setup is designed and realized. The setup enables measurements of spectrally resolved 0th and ±1st diffraction orders of a grating that is illuminated at various grazing incidence angles. The acquired data serves as a basis for the reconstruction of the grating’s geometry using rigorous optical finite element method (FEM). The method is applied to arrays of lines and spaces with sub-100 nm feature size.
In this contribution nanoscale gratings are characterized by means of broadband EUV spectroscopy with wavelengths from 10 nm to 15 nm. The study focuses on the specifics of this spectral range that can be beneficial for metrology applications in lithography. Experimental investigations are carried out on fused silica nanoscale line gratings in a stand-alone laboratory-based setup. A corresponding sensitivity study is carried out analyzing the influence of grating parameter variations on EUV reflectance curves. Subsequently, experimental uncertainties are propagated to accuracies of grating parameter extraction. Using rigorous simulations in combination with machine learning, limitations of the technique are discussed regarding industrially relevant gratings. Extending the method through analysis of higher diffraction orders is evaluated.
The authors present studies on laboratory-based spectroscopy in the extreme ultraviolet (EUV) performed on a variety of thin film materials. This work focuses on spectroscopic measurements of EUV reflectivity and transmittance at wavelengths between 10 nm and 15 nm. The presented applications of the technique include the reconstruction of optical constants for novel materials such as EUV photoresists and absorbers, the characterization of EUV pellicles and ultrathin layer systems as well as the characterization of nanostructured surfaces.
The authors report on critical dimension metrology on nanoscale gratings by means of laboratory-based spectroscopic reflectometry in the extreme ultraviolet (EUV). EUV reflectivity spectra of nanoscale gratings under grazing incidence illumination and their dependency on the geometrical grating parameters are discussed. A laboratory-based setup to measure such spectra is introduced and its main features are presented. A nanoscale grating with a grating period below 100 nm, consisting of multiple nanometer-size layers of materials, is experimentally investigated in the setup. The experimental results are consequently compared to a rigorous model fit of the reflectivity and thus the ability to model the grating’s interaction with EUV radiation is shown.
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