Nanoscale grating characterization through EUV spectroscopy aided by machine learning techniques
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.