Abstract: A method, apparatus, and system for processing a material stack. A hydrogen silsesquioxane layer is deposited on the material stack. A diffusion barrier layer is deposited on the hydrogen silsesquioxane layer to form a bilayer. The diffusion barrier layer comprises a material having a thickness that increases an amount of time before the hydrogen silsesquioxane layer ages to change a dose in an electron beam needed to expose the hydrogen silsesquioxane layer for a selected feature geometry with a desired width. The electron beam is directed through a surface of the bilayer to form an exposed portion of the bilayer. The electron beam applies the dose that is selected based on a pattern density of features for the material stack to have a desired level of exposure of the hydrogen silsesquioxane layer for the selected feature geometry. The hydrogen silsesquioxane layer is developed. The exposed portion remains on material stack.