Mallavarapu Akhila, Ajay Paras, Sreenivasan S V
NASCENT Engineering Research Center, The University of Texas at Austin, Austin, Texas 78758, United States.
Nano Lett. 2020 Nov 11;20(11):7896-7905. doi: 10.1021/acs.nanolett.0c02539. Epub 2020 Nov 2.
Top-down patterning along with metal-assisted chemical etching (MACE) can enable the fabrication of highly controlled wafer-scale silicon nanowires (Si-NWs). Maximizing the NW aspect ratio, while avoiding collapse, can enable many important applications. A precise experimental technique has been developed here to study the onset of Si-NW collapse. This experimental approach has resulted in unexpectedly tall Si-NWs for oversized wires separated by sub-50-nm gaps. As compared to known theory, a factor of 4.5 increase in maximum aspect ratio was achieved for uncollapsed nanowires with 200-nm pitch and 25-nm spacing. This discrepancy between known theory and experimental results was eliminated when the gold-resist caps (which are a feature of our MACE process) on top of these nanowires were removed. This led us to incorporate electrostatic repulsion into known theoretical formulations, which matched the experimental results. In summary, this work provides new experimental and theoretical insights into nanowire collapse behavior.
自上而下的图案化技术与金属辅助化学蚀刻（MACE）相结合，可以实现高度可控的晶圆级硅纳米线（Si-NW）的制造。在避免纳米线塌陷的同时最大化其纵横比，能够实现许多重要应用。本文开发了一种精确的实验技术来研究Si-NW塌陷的起始点。这种实验方法已经制造出了间隔小于50nm的超大尺寸纳米线中意外高的Si-NW。与已知理论相比，对于间距为200nm、间隔为25nm的未塌陷纳米线，其最大纵横比提高了4.5倍。当去除这些纳米线上的金抗蚀剂帽（这是我们MACE工艺的一个特点）时，已知理论与实验结果之间的这种差异就消除了。这使我们将静电排斥纳入已知的理论公式中，该公式与实验结果相匹配。总之，这项工作为纳米线塌陷行为提供了新的实验和理论见解。
