High-Definition Nanoimprint Stamp Fabrication by Atomic Layer Etching

ABSTRACT: Nanoimprint lithography (NIL) has the potential for low-cost and
high-throughput nanoscale fabrication. However, the NIL quality and resolution are
usually limited by the shape and size of the nanoimprint stamp features. Atomic
layer etching (ALE) can provide a damage-free pattern transfer with ultimate etch
control for features of all length scales, down to the atomic scale, and for all feature
geometries, which is required for good quality and high-resolution nanoimprint
stamp fabrication. Here, we present an ALE process for nanoscale pattern transfer
and high-resolution nanoimprint stamp preparation. This ALE process is based on
chemical adsorption of a monoatomic layer of dichloride (Cl2) on the silicon
surface, followed by the removal of a monolayer of Cl2-modified silicon by argon
bombardment. The nanopatterns of different geometries, loadings, and pitches
were fabricated by electron beam lithography on a silicon wafer, and ALE was
subsequently performed for pattern transfer using a resist as an etch mask. The
post-ALE patterns allowed us to study the different effects and limitations of the
process, such as trenching and sidewall tapering. The ALE-processed silicon wafers were used as hard nanoimprint stamps in a thermal nanoimprint process. Features as small as 30 nm were successfully transferred into a poly(methyl methacrylate) layer, which demonstrated the great potential of ALE in fabricating nanoimprint stamps with ultrahigh resolution.