6 May 2005 Properties of EUV and particle generations from laser-irradiated solid- and low-density tin targets
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Properties of laser-produced tin (Sn) plasmas were experimentally investigated for application to the Extreme Ultra-Violet (EUV) lithography. Optical thickness of the Sn plasmas affects strongly to EUV energy, efficiency, and spectrum. Opacity structure of uniform Sn plasma was measured with a temporally resolved EUV spectrograph coupled with EUV backlighting technique. Dependence of the EUV conversion efficiency and spectra on Sn target thickness were studied, and the experimental results indicate that control of optical thickness of the Sn plasma is essential to obtain high EUV conversion efficiency and narrow spectrum. The optical thickness is able to be controlled by changing initial density of targets: EUV emission from low-density targets has narrow spectrum peaked at 13.5 nm. The narrowing is attributed to reduction of satellite emission and opacity broadening in the plasma. Furthermore, ion debris emitted from the Sn plasma were measured using a charge collector and a Thomson parabola ion analyzer. Measured ablation thickness of the Sn target is between 30 and 50 nm for the laser intensity of 1.0 x 1011 W/cm2 (1.064 μm of wavelength and 10 ns of pulse duration), and the required minimum thickness for sufficient EUV emission is found to be about 30 nm under the same condition. Thus almost all debris emitted from the 30 nm-thick mass-limited Sn targets are ions, which can be screened out by an electro-magnetic shield. It is found that not only the EUV generation but also ion debris are affected by the Sn target thickness.
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Shinsuke Fujioka, Shinsuke Fujioka, Hiroaki Nishimura, Hiroaki Nishimura, Tomoharu Okuno, Tomoharu Okuno, Yezheng Tao, Yezheng Tao, Nobuyoshi Ueda, Nobuyoshi Ueda, Tsuyoshi Ando, Tsuyoshi Ando, Hiroto Kurayama, Hiroto Kurayama, Yuzuri Yasuda, Yuzuri Yasuda, Shigeaki Uchida, Shigeaki Uchida, Yoshinori Shimada, Yoshinori Shimada, Michiteru Yamaura, Michiteru Yamaura, Qincui Gu, Qincui Gu, Keiji Nagai, Keiji Nagai, Takayoshi Norimatsu, Takayoshi Norimatsu, Hiroyuki Furukawa, Hiroyuki Furukawa, Atsushi Sunahara, Atsushi Sunahara, Young-G. Kang, Young-G. Kang, Masakatsu Murakami, Masakatsu Murakami, Katsunobu Nishihara, Katsunobu Nishihara, Noriaki Miyanaga, Noriaki Miyanaga, Yasukazu Izawa, Yasukazu Izawa, "Properties of EUV and particle generations from laser-irradiated solid- and low-density tin targets", Proc. SPIE 5751, Emerging Lithographic Technologies IX, (6 May 2005); doi: 10.1117/12.598692; https://doi.org/10.1117/12.598692

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