In this study, a cyclic isotropic plasma atomic layer etching (ALE) process was developed for aluminum oxide that involves fluorination with NF3 plasma and ligand exchange with trimethylaluminum (TMA). The isotropic plasma ALE consists of two steps: fluorination and removal. During the fluorination step, the Al2O3 surface was fluorinated to AlOFx with NF3 plasma at 100 °C. The formation of the AlOFx layer was confirmed by x-ray photoelectron spectroscopy analysis, and the atomic fraction of fluorine on the surface was saturated at 25% after 50 s of plasma fluorination. The depths of the fluorinated layers were in the range of 0.79–1.14 nm at different plasma powers. In the removal step, the fluorinated layer was removed by a ligand exchange reaction with TMA at an elevated temperature range of 250–480 °C. The etch per cycle (EPC) was 0.20–0.30 nm/cycle and saturated after 30 s in the temperature range of 290–330 °C. No etching was observed below 250 °C, and the EPC increased in the temperature range of 250–300 °C during the removal step with the ligand exchange reaction and reached the maximum at 300 °C. Then, the EPC was significantly reduced at high temperatures, possibly due to TMA decomposition. The fluorine atomic fraction on the surface was reduced to 14% after the removal. In conclusion, Al2O3 was successfully etched at the atomic scale by the cyclic plasma ALE process. The average surface roughness of Al2O3 was reduced from 8.6 to 5.3 Å after 20 cycles of etching.
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Research Article|
April 22 2022
Atomic layer etching of Al2O3 with NF3 plasma fluorination and trimethylaluminum ligand exchange
Special Collection:
Atomic Layer Etching (ALE)
Jihyun Kim;
Jihyun Kim
1
School of Chemical Engineering, Sungkyunkwan University (SKKU)
, Suwon 16419, Republic of Korea
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Dahee Shim;
Dahee Shim
1
School of Chemical Engineering, Sungkyunkwan University (SKKU)
, Suwon 16419, Republic of Korea
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Yongjae Kim;
Yongjae Kim
2
SKKU Advanced Institute of Nanotechnology (SAINT), Sungkyunkwan University (SKKU)
, Suwon 16419, Republic of Korea
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Heeyeop Chae
Heeyeop Chae
a)
1
School of Chemical Engineering, Sungkyunkwan University (SKKU)
, Suwon 16419, Republic of Korea
2
SKKU Advanced Institute of Nanotechnology (SAINT), Sungkyunkwan University (SKKU)
, Suwon 16419, Republic of Korea
a)Author to whom correspondence should be addressed: hchae@skku.edu
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a)Author to whom correspondence should be addressed: hchae@skku.edu
Note: This paper is part of the 2023 Special Topic Collection on Atomic Layer Etching (ALE).
J. Vac. Sci. Technol. A 40, 032603 (2022)
Article history
Received:
November 11 2021
Accepted:
April 04 2022
Citation
Jihyun Kim, Dahee Shim, Yongjae Kim, Heeyeop Chae; Atomic layer etching of Al2O3 with NF3 plasma fluorination and trimethylaluminum ligand exchange. J. Vac. Sci. Technol. A 1 May 2022; 40 (3): 032603. https://doi.org/10.1116/6.0001616
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