Atomic layer etching of 3D structures in silicon: Self-limiting and nonideal reactions
Atomic layer etching of 3D structures in silicon: Self-limiting and nonideal reactions
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DOI：
10.1116/1.4979661
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发表时间：
2017-05-01
影响因子：
2.9
通讯作者：
Kushner, Mark J.
中科院分区：
文献类型：
--
作者：
Huard, Chad M.;Zhang, Yiting;Kushner, Mark J.
当前（和未来）微电子制造要求对等离子蚀刻的保真度提出了前所未有的要求。随着器件特征缩小到原子尺寸，用于定义这些器件的等离子体蚀刻工艺必须解决这些尺度。通过将蚀刻过程分离为多个自限制步骤的周期，传统等离子体蚀刻中紧密耦合的不同物理过程可以在很大程度上解耦并单独优化。这种原子层蚀刻（ALE）技术可以在每个循环中理想地去除厚度一致的均匀材料层。ALE有望改善均匀性，减少损伤，增加选择性，并最大限度地减少宽高比依赖蚀刻（ARDE）率。ALE的实际实现取决于系统能在多接近理想的情况下运行，以及对非理想条件的容忍度。本文讨论了利用Ar/Cl-2等离子体对二维沟槽和三维特征在硅的ALE中非理想性后果的计算研究结果。作者发现，理想的ALE在ALE循环的所有步骤中都需要自我限制的过程。包括连续（非自限）蚀刻反应的步骤降低了ALE解耦工艺参数的能力。除了取决于每周期脉冲长度的蚀刻深度外，非自限工艺可以重新引入ARDE并产生表面粗糙度。通过控制子周期脉冲时间，这些有害影响可以最小化，并且可以恢复ALE的许多好处。即使是非理想的ALE工艺，经过适当优化，仍然比具有相似化学和离子能量分布的连续蚀刻具有优势。利用传统的电感耦合等离子体反应器产生的磁通，一个示例ALE工艺能够清除三维翅片型场效应晶体管中的角，并且比连续工艺明显减少过蚀刻。(C) 2017年美国真空学会。
Current (and future) microelectronics fabrication requirements place unprecedented demands on the fidelity of plasma etching. As device features shrink to atomic dimensions, the plasma etching processes used to define these devices must resolve these scales. By separating etching processes into cycles of multiple, self-limited steps, different physics processes which are closely coupled in traditional plasma etching can be largely decoupled and separately optimized. This technique, atomic layer etching (ALE), can ideally remove uniform layers of material with consistent thickness in each cycle. ALE holds the promise of improving uniformity, reducing damage, increasing selectivity, and minimizing aspect ratio dependent etching (ARDE) rates. The practical implementation of ALE depends on how close to ideal the system can be operated and the tolerance to nonideal conditions. In this paper, results are discussed from a computational investigation of the consequences of nonidealities in the ALE of silicon using Ar/Cl-2 plasmas for both two dimensional trenches and three dimensional features. The authors found that ideal ALE requires self-limited processes during all steps of the ALE cycle. Steps that include continuous (non-self-limited) etching reactions reduce the ability of ALE to decouple process parameters. In addition to an etch depth that depends on pulse length per cycle, non-self-limited processes can reintroduce ARDE and produce surface roughening. By controlling subcycle pulse times, these deleterious effects can be minimized, and many of the benefits of ALE can be restored. Even nonideal ALE processes, when properly optimized, still provide benefits over continuous etching with similar chemistries and ion energy distributions. Using fluxes generated by a conventional inductively coupled plasma reactor, an example ALE process is able to clear the corners in a three-dimensional fin based field effect transistor case study with significantly less over-etch than the continuous process. (C) 2017 American Vacuum Society.