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Reversible SiO2/SiNx selectivity enabled by trimethylaluminum-assisted SF6 remote plasma etching
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- Authors
- Jieun Kim, Min Kyun Sohn, Seong Hyun Lee, Sun Kyu Jung, Subin Heo, Jaeseoung Park, Jin-Ha Kim, Sang-Hoon Kim, Jeong Woo Park, Dongwoo Suh
- Issue Date
- 2026-11
- Citation
- Applied Surface Science, v.745, pp.1-7
- ISSN
- 0169-4332
- Publisher
- Elsevier
- Language
- English
- Type
- Journal Article
- Abstract
- As device architectures transition to three-dimensional scaling, selective etching with atomic-scale precision and controlled material removal has become critical. This study demonstrates a fluorine-radical-driven etching scheme that achieves high SiNx-over-SiO2 selectivity through pressure-controlled SF6 remote plasma etching, which can be reversed to SiO2-over-SiNx selectivity by trimethylaluminium (TMA)-assisted surface modification. During TMA modification step, SiO2 exhibits self-limiting saturation with increasing TMA exposure, whereas SiNx undergoes etch suppression due to formation of a fluorination-resistant Al–N termination. These contrasting reaction regimes enable tunable selectivity through chamber pressure and TMA exposure control. Without TMA modification, the pressure-controlled process achieves SiNx over SiO2 selectivity of up to 5.7:1. Conversely, at an optimized pressure of 5 Torr with TMA treatment, the etching selectivity of SiO2 over SiNx exceeds 50:1, demonstrating flexible control of material preference. X-ray photoelectron spectroscopy reveals that fluorine radical diffusion is restricted by the Al–N modification layer on SiNx a result of distinct surface termination chemistries. Both films maintain sub-nanometer surface roughness after etching via a radical-driven process. Cross-sectional transmission electron microscopy confirms conformal and isotropic removal within SiO2/SiNx stack structures. This scalable, isotropic, and surface-chemistry-driven process provides a robust solution for atomic precision and high selectivity in next-generation semiconductor devices.
- Keyword
- Fluorine radical, Remote plasma, Selective etching, SiNx, SiO2, TMA
- KSP Keywords
- Atomic scale, Chamber pressure, Dimensional scaling, Electron Microscopy(TEM and SEM), Etching selectivity, Etching via, Exposure Control, Fluorine radical, High selectivity, Material Removal, Modification layer