Spatial profiles of electron density, electron temperature, average ionic charge, and EUV emission of laser-produced Sn plasmas for EUV lithography

Yuta Sato, Kentaro Tomita, Syoichi Tsukiyama, Toshiaki Eguchi, Kiichiro Uchino, Kouichiro Kouge, Hiroaki Tomuro, Tatsuya Yanagida, Yasunori Wada, Masahito Kunishima, Takeshi Kodama, Hakaru Mizoguchi

Research output: Contribution to journalArticlepeer-review

4 Citations (Scopus)

Abstract

Spatial profiles of the electron density (ne), electron temperature (Te), and average ionic charge (Z) of laser-produced Sn plasmas for EUV lithography, whose conversion efficiency (CE) is sufficiently high for practical use, were measured using a collective Thomson scattering (TS) technique. For plasma production, Sn droplets of 26μm diameter were used as a fuel. First, a picosecond-pulsed laser was used to expand a Sn target. Next, a CO2 laser was used to generate plasmas. By changing the injection timing of the picosecond and CO2 lasers, three different types of plasmas were generated. The CEs of the three types of plasmas differed, and ranged from 2.8 to 4.0%. Regarding the different plasma conditions, the spatial profiles of ne, Te, and Z clearly differed. However, under all plasma conditions, intense EUV was only observed at a sufficiently high Te (> 25 eV) and in an adequate ne range [1024-(2 × 1025)m-3]. These plasma parameters lie in the efficient-EUV light source range, as predicted by simulations.

Original languageEnglish
Article number036201
JournalJapanese journal of applied physics
Volume56
Issue number3
DOIs
Publication statusPublished - Mar 2017

All Science Journal Classification (ASJC) codes

  • Engineering(all)
  • Physics and Astronomy(all)

Fingerprint Dive into the research topics of 'Spatial profiles of electron density, electron temperature, average ionic charge, and EUV emission of laser-produced Sn plasmas for EUV lithography'. Together they form a unique fingerprint.

Cite this