Proceedings of the
9th International Conference of Asian Society for Precision Engineering and Nanotechnology (ASPEN2022)
15 – 18 November 2022, Singapore

Exploration of optimate surface roughness of plasma-based atom-selective etching process of single-crystal silicon

Bing Wu1 and Hui Deng1,a

1Department of Mechanical and Energy Engineering, Southern University of Science and Technology, No. 1088, Xueyuan Road, Shenzhen, Guangdong, 518055, China


Single crystal silicon (Si) is the most widely used material in the electronic industry. The atomic-scale smooth surface of Si is important for advancing quantum electronics and X-ray optics. In our previous study, to realize the damage-free, highly efficient, and atomic-level polishing of single-crystal Si, plasma-based atom-selective etching (PASE) was proposed. According to the mechanism of PASE, an atomic-scale ultrasmooth Si surface with well-arranged two dangling bonds could be obtained theoretically. In this work, optimization of plasma etching parameters was conducted to further explore the optimate surface roughness of Si. Plasma diagnostics were conducted to investigate the plasma temperature and composition of radicals. The effects of RF power, the flow rate of reactive gases, work distance, and irradiation time on the optimate surface roughness of PASE for Si were investigated. A ground Si (100) surface was smoothed to the roughness below 0.15 nm over 10 µm2 by PASE within 2 min. This optimate surface roughness is better than that of conventional CMP, in which a Sa roughness of 0.3 nm can be obtained. However, it was found that the thin oxide layer on the Si surface affected the surface roughness, hindering further reduction of roughness. Overall, this study has shown the potential of PASE for achieving atomic-scale ultrasmooth surface of Si. Also, better surface roughness is assumed to be achievable if appropriate vacuum systems without post-PASE oxidation or contamination are adopted.

Keywords: Single-crystal silicon, atomic-scale polishing, plasma etching, roughness, oxide

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