Mr-EBL: Ultra-high sensitivity negative-tone electron beam resist for highly selective silicon etching and large-scale direct patterning of permanent structures

Abstract

Electron beam lithography (EBL) is the state-of-the-art technique for rapid prototyping of nanometer-scale devices. Even so, processing speeds remain limited for the highest resolution patterning. Here, we establish Mr-EBL as the highest throughput negative tone electron-beam-sensitive resist. The 10 μC cm-2 dose requirement enables fabricating a 100 mm2 photonic diffraction grating in a ten minute EBL process. Optimized processing conditions achieve a critical resolution of 75 nm with 3× faster write speeds than SU-8 and 1-2 orders of magnitude faster write speeds than maN-2400 and hydrogen silsesquioxane. Notably, these conditions significantly differ from the manufacturers' recommendations for the recently commercialized Mr-EBL resist. We demonstrate Mr-EBL to be a robust negative etch mask by etching silicon trenches with aspect ratios of 10 and near-vertical sidewalls. Furthermore, our optimized processing conditions are suitable to direct patterning on integrated circuits or delicate nanofabrication stacks, in contrast to other negative tone EBL resists. In conclusion, Mr-EBL is a highly attractive EBL resist for rapid prototyping in nanophotonics, MEMS, and fluidics.