Electron beam lithography with a bilayer resist

A method for processing a material stack, the method comprising:

• depositing a hydrogen silsesquioxane layer on the material stack;
• depositing a diffusion barrier layer on the hydrogen silsesquioxane layer to form a bilayer, wherein the diffusion barrier layer is comprised of 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 to obtain a desired width for a selected feature geometry;
• directing the electron beam through a surface of the bilayer to form an exposed portion of the bilayer, wherein the electron beam applies the dose in the exposed portion of the bilayer 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, wherein an energy spread of the electron beam is controlled by adjusting an η corrected energy point spread function according to an onset exposure dose Dl described by:
• Dl(ρ,η)=A1+η/1+2ρη
• where η is an energy ratio of backscattered and forward scattered electrons, ρ is a local pattern density %, and A sets a baseline dose at half filling where ρ=50%;
• and
• developing the hydrogen silsesquioxane layer, wherein the exposed portion of the hydrogen silsesquioxane layer exposed to the electron beam remains on the material stack.

A method for processing a material stack, the method comprising:

• depositing a hydrogen silsesquioxane layer on the material stack;
• depositing an aluminum layer on the hydrogen silsesquioxane layer to form a bilayer;
• directing an electron beam through a surface of the bilayer to form an exposed portion of the bilayer, wherein an energy spread of the electron beam is controlled by adjusting an η corrected energy point spread function according to an onset exposure dose Dl described by:
• D
• ⁢
• 1
• ⁢
• (
• ρ
• ,
• η
• )
• =
• A
• ⁢
• 1
• +
• η
• 1
• +
• 2
• ⁢
• ρη
• where η is an energy ratio of backscattered and forward scattered electrons, ρ is a local pattern density %, and A sets a baseline dose at half filling where ρ=50%;
• and
• developing the bilayer with tetramethylammonium hydroxide, wherein the tetramethylammonium hydroxide removes the aluminum layer and an unexposed portion of the hydrogen silsesquioxane layer, leaving the exposed portion of the hydrogen silsesquioxane layer on the material stack,
• wherein processing of the material stack forms a quantum dot qubit.