Low energy electron beam top surface image processing using chemically amplified AXT resist

High resolution processes are demonstrated with a positive-mode chemically amplified AXT top surface imaging resist system exposed with a low energy electron beam. Top surface imaging is an ideal match to low energy electron beam lithography because it allows thick resist layers to be patterned despite the limited penetration depth of the electron beam. The three key steps of the process are exposure, silylation, and etch development. All three steps influence the final process sensitivity, contrast, and resolution. The AXT has a poly(hydroxy styrene) base resin, and has been formulated both with and without a dye used to enhance optical absorption. We have achieved sub 100 nm resolution both with and without a postexposure bake. Critical area doses below 1 μC/m² are demonstrated. The edge roughness and density of etch residue from silylation defects have been compared for a variety of oxygen plasma etch systems.