Lift-off with solvent for negative resist using low energy electron beam exposure

Abstract

Lift-off and direct etch are the two most popular pattern transfer methods for electron beam lithography. For some applications negative resist would offer significantly less exposure time than positive one. Unfortunately, lift-off using negative resist is very challenging because the resist profile is typically positively tapered due to electron forward scattering, and upon exposure, negative resist is cross-linked and thus insoluble in solvents. Here, the authors will show that low energy exposure can circumvent both issues simultaneously, and the authors achieved liftoff of Cr with polystyrene resist using a solvent xylene. Moreover, low energy exposure offers proportionally higher resist sensitivity. Lastly, since low energy electrons are mostly stopped inside the resist layer, radiation damage to the sublayer is greatly reduced. Thus, the current method may be employed to fabricate metal nanostructures on top of an organic conducting layer.