Chromium and its oxides have been playing a vital role in the fabrication of micro- and nano-scale structures in numerous applications for several decades. Controllable, robust and anisotropically dry-etched hard masks and their optimal etch recipes are required in state-of-the-art device fabrication techniques. In terms of manufacturability and repeatability, a mechanistic understanding of the plasma-etching process of chromium oxide (Cr2O3) is necessary for its adoption as a hard mask. We present a systematic investigation of plasma etching of chromium oxide films via an inductively coupled plasma-reactive ion etching (ICP-RIE) system in nanoscale. The effects of plasma composition, ICP source power and HF platen power on the etch rate, sidewall profile, surface morphology, and dc-bias have been methodically investigated. We paid particular attention to studying how oxygen content can be used to control the etch profile of nano trenches using chlorine/oxygen gas mixtures, including extremes of very low and very high oxygen content. It was found that chromium oxide etch mechanisms are dependent strongly on the oxygen level. We achieved desirable vertical sidewalls with reasonable etch rates when the oxygen content is in the range 10–40% in the plasma. Oxygen content below 10% resulted in positively tapered etch profiles with low etch rates. On the other hand, bowl-like etch profiles with undercut formation was observed at high oxygen content above 40%, caused by re-emission of the reactive species at this regime. As a hard mask material, patterning Cr2O3 films compared to Cr metal is advantageous in terms of etch uniformity and reproducibility. Contrary to Cr, Cr2O3 is not as sensitive to chamber wall conditions.

中文翻译：

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氧对亚微米制造氧化铬硬掩模蚀刻各向异性的作用

几十年来，铬及其氧化物在众多应用中的微米和纳米级结构的制造中发挥着至关重要的作用。最先进的器件制造技术需要可控、坚固且各向异性的干蚀刻硬掩模及其最佳蚀刻配方。在可制造性和可重复性方面，对氧化铬 (Cr2O3) 的等离子体蚀刻工艺的机械理解对于将其用作硬掩模是必要的。我们通过纳米级电感耦合等离子体反应离子蚀刻 (ICP-RIE) 系统对氧化铬膜的等离子体蚀刻进行了系统研究。已经有条不紊地研究了等离子体成分、ICP 源功率和 HF 压板功率对蚀刻速率、侧壁轮廓、表面形态和直流偏置的影响。我们特别注意研究如何使用氧含量来控制使用氯/氧气混合物的纳米沟槽的蚀刻轮廓，包括极低和极高的氧含量。发现氧化铬蚀刻机制强烈依赖于氧含量。当等离子体中的氧含量在 10-40% 范围内时，我们以合理的蚀刻速率获得了理想的垂直侧壁。低于 10% 的氧含量导致具有低蚀刻速率的正锥形蚀刻轮廓。另一方面，在高于 40% 的高氧含量下观察到具有底切形成的碗状蚀刻轮廓，这是由于在该状态下反应性物质的重新发射造成的。作为硬掩模材料，与 Cr 金属相比，对 Cr2O3 膜进行图案化在蚀刻均匀性和再现性方面具有优势。与 Cr 相反，