EUV extendibility research at Berkeley Lab

Extreme ultraviolet (EUV) Lithography remains the preferred technology to replace DUV immersion lithography in high volume production at the 7-nm node and beyond. With numerous 0.33 numerical aperture (NA) tools in the field, EUV has proven itself as technically extremely capable, yet availability remains a gating item for the insertion of EUV into high volume production. With 0.33-NA so close to production, the research and development activity in EUV has now in large part shifted over to high NA (≥ 0.5). High NA EUV significantly stresses several current challenges and gives rise to fundamentally new challenges. The most significant new challenge arises from angular bandwidth limitations of the mask multilayer requiring the use of anamorphic optics [1] or new multilayer material systems. The most significant extended challenge revolves around stochastics in photoresist materials and exposure processes. To address these challenges, a new suite of tools has and is being developed at Berkeley Lab including a variable NA mask imaging microscope [2] and a 0.5-NA microfield exposure tool [3–5]. These tools build on to existing facilities at Berkeley including a 0.3-NA microfield exposure tool [6] and an EUV reflectometer/scatterometer [7].