Time-resolved measurement of radical populations in extreme-ultraviolet-light-induced hydrogen plasma

Liu, Chang; Tanaka, Nozomi; Zhu, Bingli; Nishihara, Katsunobu; Fujioka, Shinsuke; Kang, K.; Suh, Youngduk; Kim, Jeong-Gil; Ozawa, Ken; Kubo, Minoru

doi:10.35848/1882-0786/ac4faa

Cited by 4 publications

(1 citation statement)

References 25 publications

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“…Horst et al measured the spatial integrated values of electron density (n e ) by microwave cavity resonance spectroscopy, 21) Beckers et al measured hydrogen-ion energies using the electrostatic quadrupole plasma analyzer, 26) and C. Liu et al evaluated n , e T , e and hydrogen radical density by optical emission spectroscopy. 27) In these attempts, either the T e is not measured or the measurements are performed at a few Pa pressure conditions, which is lower than the pressure that would be used in an actual EUV light source.…”

Section: Introductionmentioning

confidence: 99%

Feasibility study on reactive ion etching occurrence in EUV-induced photoionized hydrogen plasmas based on electron temperature and electron density measurements

Kouge

Tomita

Hotta

et al. 2022

Jpn. J. Appl. Phys.

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Temporal evolutions of electron temperature (T e) and electron density (n e) of photoionized hydrogen plasmas, which were induced by radiation from laser-produced Sn-plasma EUV sources, were measured using the Laser Thomson Scattering (LTS) technique. Measured T e and n e ranged from 0.5–2.5 eV and 1016–1018 m-3, respectively, for hydrogen pressures of 50–400 Pa. The T e of this EUV-induced hydrogen plasma decayed with the thermal relaxation time between electrons and gases. The maximum value of T e in the time variation depended on hydrogen pressure. The lower the pressure, the higher the maximum T e, and it reached approximately 2 eV at 50 Pa. The sheath potential between the EUV-induced hydrogen plasma and the unbiased wall might be exceeded 6 eV at 50 Pa, which is sufficient to enhance the removal of Sn-debris from a Mo/Si multilayer mirror via reactive ion etching processes.

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Section: Introductionmentioning

confidence: 99%

Feasibility study on reactive ion etching occurrence in EUV-induced photoionized hydrogen plasmas based on electron temperature and electron density measurements

Kouge

Tomita

Hotta

et al. 2022

Jpn. J. Appl. Phys.

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Efficient photo-dissociation-induced production of hydrogen radicals using vacuum ultraviolet light from a laser-produced plasma

Hernandez,

Tanaka,

Yamada

et al. 2024

Applied Physics Letters

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One of the critical issues in lithography using extreme ultraviolet (EUV) light is tin contamination of the EUV collector mirrors in the tin-based LPP-EUV light source. The contamination can be removed by the reaction of tin atoms with hydrogen radicals producing stannane (SnH4), which is gaseous at the normal temperature. Hydrogen radicals can be produced from hydrogen molecules through photo-dissociation and photo-ionization induced by broadband radiation emitted from the EUV light source. In this work, an efficient production of hydrogen radical using vacuum ultraviolet (VUV) light emitted from laser-produced high-Z plasma is experimentally demonstrated. A two-dimensional radiation hydrodynamic simulation, coupled with photoionization and photo-dissociation cross sections, also shows the efficient hydrogen radical production by increased VUV light emission, as observed in the experiment.

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Absolute density measurement of hydrogen radicals in XUV induced plasma for tin contamination cleaning via laser-induced fluorescence

Tanaka,

Zhu,

Liu

et al. 2024

Applied Physics Letters

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Effective cleaning of tin contamination on the collecting mirrors in extreme ultraviolet source is one of the key techniques to improve throughput and cost performance of extreme ultraviolet lithography. Hydrogen radicals produced in hydrogen plasma that is induced by wideband extreme ultraviolet radiation are expected to be utilized for in situ tin contamination cleaning in extreme ultraviolet sources. In this Letter, we clarified absolute density and cleaning ability of the hydrogen radicals produced by intense extreme ultraviolet pulse through ground state population density measurement by laser-induced fluorescence technique. The experimentally obtained radical parameters coincided well with simulation results and collisional radiative model. It was found that the extreme ultraviolet induced plasma was in quasi-steady state with abundant amount of hydrogen radicals in ground state. Further, it was found that the in situ tin contamination cleaning in extreme ultraviolet lithography source would become more practical with increase in operational parameters, such as extreme ultraviolet emission intensity, gas pressure, and radical production cross section.

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Time-resolved measurement of radical populations in extreme-ultraviolet-light-induced hydrogen plasma

Cited by 4 publications

References 25 publications

Feasibility study on reactive ion etching occurrence in EUV-induced photoionized hydrogen plasmas based on electron temperature and electron density measurements

Feasibility study on reactive ion etching occurrence in EUV-induced photoionized hydrogen plasmas based on electron temperature and electron density measurements

Efficient photo-dissociation-induced production of hydrogen radicals using vacuum ultraviolet light from a laser-produced plasma

Absolute density measurement of hydrogen radicals in XUV induced plasma for tin contamination cleaning via laser-induced fluorescence

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