The pursuit of sculpting materials at increasingly smaller and deeper scales remains a persistent subject in the field of micro- and nanofabrication. Anisotropic deep-reactive ion etching of silicon at cryogenic temperatures (cryo-DRIE) was investigated for fabricating arrays of vertically aligned Si nanowires (NWs) of a large range of dimensions from micrometers down to 30 nm in diameter, combined with commonly used wafer-scale lithography techniques based on optical, electron-beam, nanoimprint, and nanosphere/colloidal masking. Large selectivity of ∼100 to 120 and almost 700 was found with resists and chromium hard masks, respectively. This remarkable selectivity enables the successful transfer of patterned geometries while preserving spatial resolution to a significant extent. Depending on the requirements by applications, various shapes, profiles, and aspect ratios were achieved by varying process parameters synchronously or asynchronously. High aspect ratios of up to 100 comparable to the best result by metal-assisted wet-chemical etching and sub-μm trenches by DRIE were obtained with NW diameter of 200 nm, at an etch rate of ∼4 μm/min without being collapsed. At the same time, low surface roughness values were maintained on the NW top, sidewall, and bottom surface of ∼0.3, ∼13, and ∼2 nm, respectively, as well as high pattern fidelity and integrity, which were measured using angle-resolved Fourier microscopy, combined atomic force, and scanning electron microscopy on selected NWs. This work establishes the foundation in the controllable development of Si nanoarchitectures, especially at sub-100 nm structures, for energy-harvesting and storage, damage-free optoelectronics, quantum, photovoltaics, and biomedical devices.

中文翻译：

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低温下硅纳米线阵列的深反应离子蚀刻

对越来越小和更深尺度的雕刻材料的追求仍然是微纳米制造领域的一个持久课题。研究了在低温下对硅进行各向异性深反应离子蚀刻 (cryo-DRIE)，以制造垂直排列的硅纳米线 (NW) 阵列，其尺寸范围从微米到直径 30 nm，并与常用的晶圆相结合。基于光学、电子束、纳米压印和纳米球/胶体掩模的大规模光刻技术。使用抗蚀剂和铬硬掩模分别发现约 100 至 120 和近 700 的大选择性。这种卓越的选择性能够成功转移图案几何形状，同时在很大程度上保留空间分辨率。根据应用的要求，通过同步或异步改变工艺参数来实现各种形状、轮廓和纵横比。高达 100 的高深宽比可与金属辅助湿化学蚀刻和 DRIE 亚微米沟槽的最佳结果相媲美，NW 直径为 200 nm，蚀刻速率为 ∼4 μm/min，且不会塌陷。同时，NW 顶部、侧壁和底部表面分别保持约 0.3、约 13 和约 2 nm 的低表面粗糙度值，以及高图案保真度和完整性，这是使用角度测量来测量的。对选定的纳米线进行了傅立叶显微镜、组合原子力和扫描电子显微镜的解析。这项工作为硅纳米结构的可控开发奠定了基础，特别是亚100纳米结构，用于能量收集和存储、无损伤光电子学、量子、光伏和生物医学设备。