Dense high aspect ratio hydrogen silsesquioxane nanostructures by 100keV electron beam lithography

We investigated the fabrication of dense, high aspect ratio hydrogen silsesquioxane (HSQ) nanostructures by 100keV electron beam lithography. The samples were developed using a high contrast developer and supercritically dried in carbon dioxide. Dense gratings with line widths down to 25nm were patterned in 500nm-thick resist layers and semi-dense gratings with line widths down to 10nm (40nm pitch) were patterned in 250nm-thick resist layers. The dense HSQ nanostructures were used as molds for gold electrodeposition, and the semi-dense HSQ gratings were iridium-coated by atomic layer deposition. We used these methods to produce Fresnel zone plates with extreme aspect ratio for scanning transmission x-ray microscopy that showed excellent performance at 1.0keV photon energy.