Flatabø Ranveig, Agarwal Akshay, Hobbs Richard, Greve Martin M, Holst Bodil, Berggren Karl K
University of Bergen, Department of Physics and Technology, Allégaten 55, NO-5007 Bergen, Norway. Research Laboratory of Electronics, Massachusetts Institute of Technology, MA 02139, United States of America.
Nanotechnology. 2018 Jul 6;29(27):275301. doi: 10.1088/1361-6528/aabe22. Epub 2018 Apr 13.
Helium ion beam lithography (HIL) is an emerging nanofabrication technique. It benefits from a reduced interaction volume compared to that of an electron beam of similar energy, and hence reduced long-range scattering (proximity effect), higher resist sensitivity and potentially higher resolution. Furthermore, the small angular spread of the helium ion beam gives rise to a large depth of field. This should enable patterning on tilted and curved surfaces without the need of any additional adjustments, such as laser-auto focus. So far, most work on HIL has been focused on exploiting the reduced proximity effect to reach single-digit nanometer resolution, and has thus been concentrated on single-pixel exposures over small areas. Here we explore two new areas of application. Firstly, we investigate the proximity effect in large-area exposures and demonstrate HIL's capabilities in fabricating precise high-density gratings on large planar surfaces (100 μm × 100 μm, with pitch down to 35 nm) using an area dose for exposure. Secondly, we exploit the large depth of field by making the first HIL patterns on tilted surfaces (sample stage tilted 45°). We demonstrate a depth of field greater than 100 μm for a resolution of about 20 nm.
氦离子束光刻（HIL）是一种新兴的纳米制造技术。与具有相似能量的电子束相比，它的优势在于相互作用体积减小，因此长程散射（邻近效应）降低、光刻胶灵敏度更高且潜在分辨率更高。此外，氦离子束的小角度发散导致较大的景深。这使得在倾斜和弯曲表面上进行图案化时无需任何额外调整，如激光自动聚焦。到目前为止，大多数关于HIL的工作都集中在利用降低的邻近效应来实现个位数纳米级分辨率，因此主要集中在小面积上的单像素曝光。在此，我们探索两个新的应用领域。首先，我们研究大面积曝光中的邻近效应，并展示了HIL使用面积剂量曝光在大平面表面（100μm×100μm，间距低至35nm）制造精确高密度光栅的能力。其次，我们通过在倾斜表面（样品台倾斜45°）上制作首个HIL图案来利用大景深。对于约20nm的分辨率，我们展示了大于100μm的景深。
