  Extreme ultraviolet (EUV) lithography is the leading lithography technique in
CMOS mass production, moving towards the sub-10 nm half-pitch (HP) regime with
the ongoing development of the next generation high-numerical aperture
(high-NA) EUV scanners. Hitherto, EUV interference lithography (EUV-IL)
utilizing transmission gratings has been a powerful patterning tool for the
early development of EUV resists and related processes, playing a key role in
exploring and pushing the boundaries of photon-based lithography. However,
achieving pattering with HPs well below 10 nm using this method presents
significant challenges. In response, our study introduces a novel EUV-IL setup
that employs mirror-based technology and circumvents the limitations of
diffraction efficiency towards the diffraction limit that is inherent in
conventional grating-based approaches. We present line/space patterning of HSQ
resist down to HP 5 nm using the standard EUV wavelength 13.5 nm, and the
compatibility of the tool with shorter wavelengths beyond EUV. The mirror-based
interference lithography tool paves the way towards the ultimate photon-based
resolution at EUV wavelengths and beyond. This advancement is vital for
scientific and industrial research, addressing the increasingly challenging
needs of nanoscience and technology and future technology nodes of CMOS
manufacturing in the few-nanometer HP regime.
