A novel PMMA/NEB bilayer process for sub-20 nm gold nanoslits by a selective electron beam lithography and dry etch

A novel electron beam lithography process using PMMA/NEB bilayer was successfully developed for the generation of ultrafine slits as well as broad trenches in a thick gold film. Slit-widths from micrometers down to sub-20 nm as the minimum feature size have been achieved. Electron beam lithography on the bilayer of PMMA/NEB with opposite tones between the top and the bottom layer was carefully studied by the contrast curve method. The processing parameters in both electron beam lithography and dry-etch were optimized for achieving ultrafine PMMA/NEB lines as the templates for forming nanoslits in Au films by the subsequent metallization and lift-off. The developed process is not only capable of replicating nano-trenches in Au film, but also applicable for manufacturing concave nanostructures in metals as a whole.