Dr. Akihisa Nagano Profile

Dr. Akihisa Nagano

at USHIO INC.

SPIE Involvement:

Author

Publications (10)

Proceedings Article | 21 November 2023 Paper

High-brightness LDP source

Masataka Mamizuka, Teruaki Kawajiri, Koji Suzuki, Yusuke Teramoto, Takahiro Shirai, Shunichi Morimoto, Hidenori Watanabe, Akihisa Nagano, Daisuke Yajima, Noritaka Ashizawa, Kazuya Aoki, Yoshihiko Sato

Proceedings Volume 12750, 1275012 (2023) https://doi.org/10.1117/12.2687785

KEYWORDS: Plasma, Extreme ultraviolet, Extreme ultraviolet lithography, Tin, Reliability, Light sources, Electrodes

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Proceedings Article | 29 September 2023 Paper

High-brightness LDP source

Kazuya Aoki, Yoshihiko Sato, Yusuke Teramoto, Takahiro Shirai, Shunichi Morimoto, Hidenori Watanabe, Akihisa Nagano, Daisuke Yajima, Noritaka Ashizawa

Proceedings Volume 12915, 1291509 (2023) https://doi.org/10.1117/12.2688117

KEYWORDS: Extreme ultraviolet, Plasma, Tin, Extreme ultraviolet lithography, Inspection, Reliability, Plasma generation, Semiconductors, Light sources, Ions

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Proceedings Article | 26 May 2023 Presentation + Paper

Improvement of LDP EUV source performance for actinic patterned mask inspection

Safak Sayan, Kishore Chakravorty, Yusuke Teramoto, Bárbara Santos, Akihisa Nagano, Noritaka Ashizawa, Takahiro Shirai, Shunichi Morimoto, Hidenori Watanabe, Kazuya Aoki, Yoshihiko Sato

Proceedings Volume PC12494, PC124940E (2023) https://doi.org/10.1117/12.2671128

KEYWORDS: Extreme ultraviolet, Plasma, Tin, Inspection, Electrodes, Laser irradiation, Vacuum chambers, Reliability, Ions, Pulsed laser operation

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Proceedings Article | 1 December 2022 Presentation + Paper

High-brightness LDP source for EUVL mask inspection

Ryuta Furuya, Kazuya Aoki, Yusuke Teramoto, Takahiro Shirai, Shunichi Morimoto, Hirdenori Watanabe, Akihisa Nagano, Daisuke Yajima, Noritaka Ashizawa, Yoshihiko Sato

Proceedings Volume 12292, 122920G (2022) https://doi.org/10.1117/12.2641777

KEYWORDS: Plasma, Extreme ultraviolet, Electrodes, Inspection, Photomasks, Light sources, Extreme ultraviolet lithography, Ions, Cameras, Laser irradiation

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Proceedings Article | 16 September 2022 Paper

High-brightness LDP source for EUVL mask inspection

Kazuya Aoki, Yoshihiko Sato, Yusuke Teramoto, Takahiro Shirai, Shunichi Morimoto, Hidenori Watanabe, Akihisa Nagano, Daisuke Yajima, Noritaka Ashizawa

Proceedings Volume 12325, 123250I (2022) https://doi.org/10.1117/12.2642210

KEYWORDS: Extreme ultraviolet, Plasma, Inspection, Extreme ultraviolet lithography, Photomasks, Ions, Tin, Reliability, Plasma generation, Light sources

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Proceedings Article | 30 September 2021 Presentation

High-brightness LDP EUV source for EUV mask inspection

Noritaka Ashizawa, Yoshihiko Sato, Hidenori Watanabe, Yusuke Teramoto, Takahiro Shirai, Shunichi Morimoto, Hironobu Yabuya, Kazuya Aoki, Daisuke Yajima, Akihisa Nagano

Proceedings Volume 11854, 118540L (2021) https://doi.org/10.1117/12.2600974

KEYWORDS: Extreme ultraviolet, Inspection, Plasma, Reliability, Tin, Light sources, Laser development, Extreme ultraviolet lithography, Electrodes

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Proceedings Article | 5 May 2017 Presentation

High-radiance LDP source for mask inspection and beam line applications (Conference Presentation)

Yusuke Teramoto, Bárbara Santos, Guido Mertens, Ralf Kops, Margarete Kops, Alexander von Wezyk, Klaus Bergmann, Hironobu Yabuta, Akihisa Nagano, Noritaka Ashizawa, Yuta Taniguchi, Daiki Yamatani, Takahiro Shirai, Kunihiko Kasama

Proceedings Volume 10143, 101431L (2017) https://doi.org/10.1117/12.2258139

KEYWORDS: Inspection, Mirrors, Extreme ultraviolet, Laser development, Plasma, Reliability, Photomasks, Extreme ultraviolet lithography, Ruthenium, Sputter deposition

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Proceedings Article | 18 March 2016 Paper

High-radiance LDP source: clean, reliable, and stable EUV source for mask inspection

Proceedings Volume 9776, 97760L (2016) https://doi.org/10.1117/12.2219219

KEYWORDS: Extreme ultraviolet, Ruthenium, Tin, Plasma, Inspection, Extreme ultraviolet lithography, Reliability, Photomasks, Ions, Mirrors

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High-throughput and -resolution actinic mask inspection tools are needed as EUVL begins to enter into volume production phase. To realize such inspection tools, a high-radiance EUV source is necessary. Ushio’s laser-assisted discharge-produced plasma (LDP) source is able to meet industry’s requirements in radiance, cleanliness, stability and reliability. Ushio’s LDP source has shown the peak radiance at plasma of 180 W/mm²/sr and the area-averaged radiance in a 200-μm-diameter circle behind the debris mitigation system of 120 W/mm²/sr. A new version of the debris mitigation system is in testing phase. Its optical transmission was confirmed to be 73 %, which is 4 % lower than that of the previous version and therefore will be improved. Cleanliness of the system is evaluated by exposing Ru mirrors placed behind the debris mitigation system. Ru sputter rate was proven to be sufficiently low as 3~5 nm/Gpulse at 7 kHz, whereas frequency-dependent sputter rate was 1~3 nm/Gpulse at 5~9 kHz as previously reported. Sn deposition remained very low (< 0.05 nm) and did not grow over time. A new technique to suppress debris was tested and preliminary results were promising. Time-of-flight signal of fast ions was completely suppressed and Ru sputter rate of exposed mirrors at 3 kHz was approximately 1.3 nm/Gpulse, whereas the conventional mitigation system (new version) resulted in Ru sputter rate of 0.7 nm/Gpulse. This new technique also allows increasing the radiance efficiency by 30 %. Stability tests were done at several different discharge frequencies. Pulse energy stability was approximately 10 %. Dose energy stability dropped from approximately 2 % to 0.1 % when feedback control was activated. EUV emission position stability was studied at 3 kHz. Deviation of the plasma center of gravity was 6 μm, which is 3 % of plasma diameter and therefore considered to be negligible. Reliability tests were performed on both R and D and prototype machines and up to 200 hours of non-interrupted operation was demonstrated.

Proceedings Article | 19 March 2015 Paper

High-radiance LDP source for mask-inspection application

Yusuke Teramoto, Bárbara Santos, Guido Mertens, Ralf Kops, Margarete Kops, Alexander von Wezyk, Hironobu Yabuta, Akihisa Nagano, Takahiro Shirai, Noritaka Ashizawa, Kiyotada Nakamura, Kunihiko Kasama

Proceedings Volume 9422, 94220F (2015) https://doi.org/10.1117/12.2086606

KEYWORDS: Extreme ultraviolet, Inspection, Photomasks, Plasma, Tin, Reliability, Lithography, Feedback control, Ruthenium, Extreme ultraviolet lithography

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Proceedings Article | 17 April 2014 Paper

High-radiance LDP source for mask inspection application

Yusuke Teramoto, Bárbara Santos, Guido Mertens, Ralf Kops, Margarete Kops, Felix Küpper, Gota Niimi, Hironobu Yabuta, Akihisa Nagano, Takuma Yokoyama, Masaki Yoshioka, Takahiro Shirai, Noritaka Ashizawa, Hiroto Sato, Kiyotada Nakamura, Kunihiko Kasama

Proceedings Volume 9048, 904813 (2014) https://doi.org/10.1117/12.2046423

KEYWORDS: Extreme ultraviolet, Inspection, Photomasks, Plasma, Tin, Laser stabilization, Reliability, Extreme ultraviolet lithography, Electrodes, Lithography

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Showing 5 of 10 publications

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