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Reflective deep-ultraviolet Fourier ptychographic microscopy for nanoscale imaging



Kwanseob Park, Yoon Sung Bae, Sang-Soo Choi, Martin Sohn


Fourier ptychographic microscopy (FPM) that has high space-bandwidth-product and phase imaging capability requires significant resolution enhancement in reflection mode for imaging of nanoscale semiconductor devices. A direct way to nanoscale resolution is by scaling the wavelength of the light source. Here, we present a reflective FPM using a deep-ultraviolet (DUV) light source, as an alternative way to FPM using an extreme-ultraviolet (EUV) light source that successfully achieved sub-100 nm imaging. The DUV reflective FPM used a 193 nm excimer laser and a catadioptric objective with a high numerical aperture (NA 0.75) for imaging sub-100 nm targets. An aperture scanning illumination optics enables angle-varied illumination for obtaining spatial frequency-shifted images and energy fluence optimization to avoid damage to optical components and provide enough fluence for imaging. The performance of the DUV FPM is evaluated by comparing it to conventional DUV microscopy for a series of molybdenum silicide (MoSi) multiline with a minimum linewidth of 80 nm, showing that contrast enhancement ratio increases as the target linewidth decreases. In addition, it is found that the choice of image sequence for FP reconstruction significantly impacts the quality of the recovered image in the imaging application of the smaller target. We believe that these results verified effective imaging of sub-100 nm targets and compared to EUV, catadioptric optics of DUV FPM allows combining super-resolution techniques into the FPM system for further improvement of spatial resolution down to deep subwavelength range (<30 nm) with a wide field of view.
Proceedings Title
Reflective deep-ultraviolet Fourier ptychographic microscopy for nanoscale imaging
Conference Dates
February 25-March 2, 2023
Conference Location
San Jose, CA, US
Conference Title
SPIE Advanced Lithography + Patterning


deep ultraviolet, Fourier ptychography, semiconductor


Park, K. , Bae, Y. , Choi, S. and Sohn, M. (2023), Reflective deep-ultraviolet Fourier ptychographic microscopy for nanoscale imaging, Reflective deep-ultraviolet Fourier ptychographic microscopy for nanoscale imaging , San Jose, CA, US, [online], (Accessed April 23, 2024)
Created April 29, 2023, Updated May 15, 2023