Extreme ultraviolet (EUV) lithography takes the forefront as a key nanopatterning technique in the current mass production of CMOS chips. EUV interference lithography (EUV-IL) is pivotal for photoresist development and scientific projects involving nanopatterning. These systems typically employ two or more transmission diffraction gratings on thin silicon nitride membranes. Coherent EUV light diffracts through the gratings, creating an interference pattern in the photoresist. However, challenges as reduced diffraction efficiency and complex nanofabrication for sub-10 nm patterning hinder the pursuit of the ultimate resolution. To this end, we report the latest results of our mirror interference lithography (MIL) setup that uses reflected light to overcome transmission-grating challenges. Two mirrors with a central stop create an interference pattern with grazing angle dependent pitch. We achieved resolutions down to 5 nm HP at EUV wavelength, marking a new resolution record in nanolithography. This method is valuable for testing photoresists and pattern transfer techniques for high- and hyper-NA EUV lithography, or fabricating high-resolution nanostructures for scientific purposes.
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