Sub-Nanometer Line Edge Roughness in Helium-ion Lithography

Abstract In semiconductor manufacturing, precise control of line edge roughness (LER) below 0.5 nm is essential, yet challenged by extreme ultraviolet (EUV) lithography limitations. Accurately characterizing EUV resist is pivotal for reaching the upper limits of manufacturing precision. However, a strategy for achieving sub-nanometer accuracy in characterizing EUV resist remains elusive, impeding the iterative development of EUV resist. This study introduces a strategy for extracting the line edge of patterned EUV resist with near-atomic resolution. By using a scanning transmission electron microscope (STEM) to characterize patterned resist on a suspended thin film, we significantly reduce charge accumulation during the characterization process. This technique allows for the extraction of resist line edges with markedly reduced background noise and enhances the traceability of the exposure process. Utilizing this characterization method, we identified a process window for fabricating nanostructures with sub-nanometer roughness and achieved the smoothest nanostructure with an LER value of 0.2 nm.