Capacitively coupled wafer-bearing cathodes are widely used in etching and deposition processes. Uniform electric field and plasma density across the wafer surface are necessary for process control all the way to the edge of the wafer. Terminating structures at the wafer edge such as focus rings are used to improve uniformity and minimize costly edge exclusion. The focus ring can be viewed as an arbitrary impedance element at the wafer edge that balances the sheath voltage above it and the region above the wafer, minimizing field variation at the wafer edge. To validate this assumption, a one-dimension circuit model with focus rings was developed. The simulations were compared to experimental results measured using hairpin probe, VI probe, and a retarding field energy analyzer (Impedans RFEA). It was found that the focus ring coupling acts as a voltage divider only in high voltage cases, and the sheath voltage drop over the focus ring will increase in low voltage cases and does not rigorously follow the voltage divider model typically used.
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July 2021
Research Article|
June 11 2021
Focus ring geometry influence on wafer edge voltage distribution for plasma processes
Yuhua Xiao
;
Yuhua Xiao
1
North Carolina State University Department of Nuclear Engineering
, Raleigh North Carolina 27695-7909
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Yao Du
;
Yao Du
1
North Carolina State University Department of Nuclear Engineering
, Raleigh North Carolina 27695-7909
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Carl Smith
;
Carl Smith
1
North Carolina State University Department of Nuclear Engineering
, Raleigh North Carolina 27695-7909
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Sang Ki Nam;
Sang Ki Nam
2
Samsung Electronics Co., Ltd., Mechatronics Research Division
, Suwon 443-742, South Korea
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Hoki Lee;
Hoki Lee
2
Samsung Electronics Co., Ltd., Mechatronics Research Division
, Suwon 443-742, South Korea
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Jang-Yeob Lee;
Jang-Yeob Lee
2
Samsung Electronics Co., Ltd., Mechatronics Research Division
, Suwon 443-742, South Korea
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Steven Shannon
Steven Shannon
a)
1
North Carolina State University Department of Nuclear Engineering
, Raleigh North Carolina 27695-7909a)Author to whom correspondence should be addressed: scshanno@ncsu.edu
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a)Author to whom correspondence should be addressed: scshanno@ncsu.edu
J. Vac. Sci. Technol. A 39, 043006 (2021)
Article history
Received:
February 12 2021
Accepted:
May 24 2021
Citation
Yuhua Xiao, Yao Du, Carl Smith, Sang Ki Nam, Hoki Lee, Jang-Yeob Lee, Steven Shannon; Focus ring geometry influence on wafer edge voltage distribution for plasma processes. J. Vac. Sci. Technol. A 1 July 2021; 39 (4): 043006. https://doi.org/10.1116/6.0000981
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