Aqueous base development and acid diffusion length optimization in negative epoxy resist for electron beam lithography

A new aqueous base developable, chemically amplified negative resist based on epoxy chemistry is evaluated for high-resolution, high-speed e-beam lithography. This resist is formulated using partially hydrogenated poly(hydroxy styrene) and epoxy novolac polymers. Degree of hydrogenation controls the aqueous base solubility and microphase separation phenomena. Reduction of edge roughness compared to the pure epoxy systems is observed whereas the absence of swelling phenomena allows lithography up to 100 nm regime and a sensitivity of 4–8 $\mu {\mathrm{C/cm}}^{\mathrm{2}}$ at 50 keV. The diffusion coefficient has been evaluated both from high-resolution line and dot exposures and it is found to be ${\text{5×10}}^{\text{−14}}\hspace{0.5em}{\mathrm{cm}}^{\mathrm{2}}\mathrm{/s}$ for the optimal thermal processing conditions selected.