Dr. Kunihiko Kasama Profile

Dr. Kunihiko Kasama

Technical Advisor at Ushio Inc

SPIE Involvement:

Conference Program Committee | Author

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

Read Abstract +

Proceedings Article | 18 March 2016 Paper

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

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

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

Read Abstract +

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

Read Abstract +

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

Read Abstract +

Conference Committee Involvement (5)

International Conference on Extreme Ultraviolet Lithography 2025

21 September 2025 | Monterey, California, United States

International Conference on Extreme Ultraviolet Lithography 2024

30 September 2024 | Monterey, California, United States

International Conference on Extreme Ultraviolet Lithography 2023

2 October 2023 | Monterey, California, United States

International Conference on Extreme Ultraviolet Lithography 2022

26 September 2022 | Monterey, California, United States

International Conference on Extreme Ultraviolet Lithography 2021

27 September 2021 | Online Only, United States

Keywords/Phrases

Search In:

Publication Years