Complex Photonic Systems (COPS), MESA+ Institute for Nanotechnology, University of Twente, PO Box 217, 7500 AE Enschede, The Netherlands.
MESA+ Nanolab, MESA+ Institute for Nanotechnology, University of Twente, PO Box 217, 7500 AE Enschede, The Netherlands.
Nanotechnology. 2023 Mar 16;34(22). doi: 10.1088/1361-6528/acc034.
Periodic arrays of deep nanopores etched in silicon by deep reactive ion etching are desirable structures for photonic crystals and other nanostructures for silicon nanophotonics. Previous studies focused on realizing as deep as possible nanopores with as high as possible aspect ratios. The resulting nanopores suffered from structural imperfections of the nanopores, such as mask undercut, uneven and large scallops, depth dependent pore radii and tapering. Therefore, our present focus is to realize nanopores that have as cylindrical as possible shapes, in order to obtain a better comparison of nanophotonic observations with theory and simulations. To this end in our 2-step Bosch process we have improved the mask undercut, the uneven scallops, pore widening and positive tapering by optimizing a plethora of parameters such as the etch step time, capacitively coupled plasma (ion energy) and pressure. To add further degrees of control, we implemented a 3-step DREM (deposit, remove, etch, multistep) process. Optimization of the etching process results in cylindrical nanopores with a diameter in the range between 280 and 500 nm and a depth around 7m, corresponding to high depth-to-diameter aspect ratios between 14 and 25, that are very well suited for the realization of silicon nanophotonic structures.
通过深反应离子刻蚀（DRIE）在硅中刻蚀的周期性深纳米孔阵列是光子晶体和其他硅纳米光子学纳米结构的理想结构。以前的研究集中在实现尽可能深的纳米孔和尽可能高的纵横比。由此产生的纳米孔存在纳米孔的结构缺陷，例如掩模下切、不均匀和大的扇贝形、深度相关的孔径和渐缩。因此，我们目前的重点是实现尽可能圆柱形的纳米孔，以便更好地将纳米光子学观察结果与理论和模拟进行比较。为此，在我们的两步 Bosch 工艺中，我们通过优化大量参数，例如刻蚀步骤时间、电容耦合等离子体（离子能量）和压力，改善了掩模下切、不均匀的扇贝形、孔径变宽和正渐缩。为了增加进一步的控制程度，我们实现了三步 DREM（沉积、去除、刻蚀、多步）工艺。优化的刻蚀工艺得到了直径在 280nm 到 500nm 之间、深度约为 7μm 的圆柱形纳米孔，其深径比高达 14 到 25，非常适合实现硅纳米光子学结构。
