UV-Nanoimprint and Deep Reactive Ion Etching of High Efficiency Silicon Metalenses: High Throughput at Low Cost with Excellent Resolution and Repeatability

Abstract

As metasurfaces begin to find industrial applications there is a need to develop scalable and cost-effective fabrication techniques which offer sub-100nm resolution while providing high throughput and large area patterning. Here we demonstrate the use of UV-Nanoimprint Lithography and Deep Reactive Ion Etching (Bosch and Cryogenic) towards this goal. Robust processes are described for the fabrication of silicon rectangular pillars of high pattern fidelity. To demonstrate the quality of the structures, metasurface lenses, which demonstrate diffraction limited focusing and close to theoretical efficiency for NIR wavelengths λ ∈ (1.3 μm, 1.6 μm), are fabricated. We demonstrate a process which removes the characteristic sidewall surface roughness of the Bosch process, allowing for smooth 90-degree vertical sidewalls. We also demonstrate that the optical performance of the metasurface lenses is not affected adversely in the case of Bosch sidewall surface roughness with 45 nm indentations (or scallops). Next steps of development are defined for achieving full wafer coverage.

Combining nano-scale imprint lithography and reactive ion etching to fabricate high-quality surface relief gratings

“…The feasibility of using a continuous directional sputter-etch process using a low-pressure Ar plasma for the removal of the residual layers has also been demonstrated by Dirdal et al in the structuring of silicon via NIL. 10 However, in contrast to our study, they do not address the resist modification and do not report on structural modifications of the resist caused by the Ar breakthrough.…”

“…Although some scientific papers have demonstrated the potential of NIL for optical applications very well, [8][9][10] our literature research indicates that the application of nanoimprint lithography for the fabrication of SRGs using TiO 2 has been relatively underrepresented. For this reason, we investigated the fabrication process of SRGs using TiO 2 .…”

UV-assisted nanoimprint lithography: the impact of the loading effect in silicon on nanoscale patterns of metalens

“…This approach has been instrumental in developing nanostructures and surfaces with exceptional hydrophobic properties through refined etching techniques. 37 Additionally, it has played a crucial role in producing silicon nanostructures and trenches with high aspect ratios and controlled profiles. When it comes to making optical devices, Bosch DRIE might be the go-to choice for scenarios where swift production and cost efficiency are key, such as in silicon metalens manufacturing.…”

Novel multi-layer nanoimprint lithography material system enabling nano-patterning of functional optical layers

“…This said, it is known, that these kinds of materials tend to have a high intrinsic etch resistance making the pattern transfer difficult and challenging. Accordingly, standard UV-NIL resists, that are already proven to be suitable for pattern transfer like the mr-NIL210 [4], mr-NIL212FC [5]) of less demanding substrates need to be employed not a as single resist but in the frame of multi-layer systems in order to comply with the requirements of these applications…”