Automatic beam focusing in the 2nd generation PBW line at sub-10 nm line resolution

Abstract Proton beam writing (PBW) has the ability to fabricate high aspect ratio 3D micro/nano-structures with precise edges, smooth and straight side-walls. The newly developed 2 nd generation PBW line has a high lens demagnification and is equipped with a superior quality resolution standard, which results in a spatial beam resolution down to 19 nm × 30 nm (van Kan et al., 2012). Fine lithographic hydrogen silsesquioxane (HSQ) patterns featuring 19 nm line width and 60 nm spacing have been fabricated using the 2 nd generation PBW line (Yao et al., 2014). In those experiments, beam focusing was done by manually adjusting the currents of the magnetic quadrupole lens power supplies to achieve a small beam spot size. Here we present an automatic focusing program which can focus a 2 MeV proton beam down to 9.3 nm × 32 nm in less than 10 min.