Reconstruction of sub-wavelength features and nano-positioning of gratings using coherent Fourier scatterometry
Nitish Kumar (TU Delft - ImPhys/Optics)
Peter Petrik (TU Delft - ImPhys/Optics, Hungarian Academy of Sciences)
Gopika K.P. Ramanandan (External organisation)
Omar El Gawhary (VSL Dutch Metrology Institute, TU Delft - ImPhys/Optics)
Sarathi Roy (TU Delft - ImPhys/Optics)
Silvania F. Pereira (TU Delft - ImPhys/Pereira group)
Wim M.J. Coene (ASML)
H. Paul Urbach (TU Delft - ImPhys/Urbach group)
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Abstract
Optical scatterometry is the state of art optical inspection technique for quality control in lithographic process. As such, any boost in its performance carries very relevant potential in semiconductor industry. Recently we have shown that coherent Fourier scatterometry (CFS) can lead to a notably improved sensitivity in the reconstruction of the geometry of printed gratings. In this work, we report on implementation of a CFS instrument, which confirms the predicted performances. The system, although currently operating at a relatively low numerical aperture (NA = 0.4) and long wavelength (633 nm) allows already the reconstruction of the grating parameters with nanometer accuracy, which is comparable to that of AFM and SEM measurements on the same sample, used as reference measurements. Additionally, 1 nm accuracy in lateral positioning has been demonstrated, corresponding to 0.08% of the pitch of the grating used in the actual experiment.