High-definition nanoimprint stamp fabrication by atomic layer etching

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.