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Scalable Isotropic Atomic Layer Etching of SiO2via Thermo-Radical Activation
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- Authors
- Min Kyun Sohn, Jieun Kim, Seong Hyun Lee, Sun Kyu Jung, Jin-Ha Kim, Subin Heo, Sang-Hoon Kim, Jeong Woo Park, Dongwoo Suh
- Issue Date
- 2026-01
- Citation
- Langmuir, v.42, no.3, pp.2680-2687
- ISSN
- 0743-7463
- Publisher
- American Chemical Society
- Language
- English
- Type
- Journal Article
- Abstract
- Wafer scale atomic layer etching (ALE), one of the key fabrication processes of both cutting-edge gate-all-around (GAA) and complementary field-effect transistors, is essential for the implementation of a 3D gate stack where a few nanometer-thick gate oxide should be etched out in an isotropic manner. In the present study, we successfully resolved the limit of conventional thermal ALE, which has been using excessively reactive and corrosive HF, by adopting plasma-assisted thermal ALE with SF6 for the source of fluorine radicals. As a result, we successfully established self-limiting etching conditions and, in turn, an optimized ALE in a 6 in. wafer scale with a uniformity of more than 99% at 5 Torr. We suggested a step-by-step ALE mechanism of surface oxide layers consisting of conversion by trimethylaluminum, fluorination by F*, and removal, which was supported by the combination of an alternative fluorination reaction and X-ray photoelectron spectroscopy analysis. After the fabrication of silicon GAA multichannel nanostructure, deposition of SiO2 by ALD, and applying the optimized ALE, we confirmed that the oxide layers are conformally etched out from cross-sectional transmission electron microscopy.
- KSP Keywords
- Cutting-edge, Electron Microscopy(TEM and SEM), Etching conditions, Field Effect Transistor(FET), Gate stack(GS), Gate-all-around, Plasma-assisted, Self-limiting, Spectroscopy analysis, Step-by-step, Transmission Electron Microscopy(TEM)