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Proceedings Paper

EUV spectroscopy of xenon ions created using an electron beam ion trap
Author(s): K. Fahy; E. Sokell; G. O'Sullivan; A. Cummings; A. Aguilar; J. D. Gillaspy; J. M. Pomeroy; J. N. Tan
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Paper Abstract

Laser-produced plasma source development for Extreme Ultra Violet (EUV) lithography has concentrated on xenon, since XeXI emits at 13.5 nm, the wavelength at which the reflectivity of MoSi mirrors is centred. However it is not obvious that the required conversion efficiencies can be achieved using xenon, and tin has been identified as a strong emitter at this wavelength. The transitions responsible in tin are 4p6 4dn-4p5 4dn+1 + 4p6 4dn-14f occurring in a number of adjacent ion stages that merge to form an unresolved transition array (UTA). This UTA is similar to a feature that appears between 10 nm to 11 nm in xenon, which thus provides information directly relevant to tin. The present experimental studies on xenon were performed at the NIST Electron Beam Ion Trap (EBIT). EBITs were developed to perform spectroscopic studies of highly charged ions. The experiments involved changing EBIT parameters, such as the electron beam energy, so that the distribution of ion stages within the plasma changed systematically. Analysis of the corresponding EUV spectra yields information about the contribution of various ion stages to the evolution of the UTA between 10 nm - 11 nm. Previously reported data for the ion stages XeVII through to XeXI are used to identify features occurring in the EBIT spectrum. When the EBIT relative intensities are compared to those from vacuum spark sources they are found to give better agreement with the calculated gA values (statistically weighted Einstein A-coefficients).

Paper Details

Date Published: 3 June 2005
PDF: 12 pages
Proc. SPIE 5826, Opto-Ireland 2005: Optical Sensing and Spectroscopy, (3 June 2005); doi: 10.1117/12.605209
Show Author Affiliations
K. Fahy, Univ. College Dublin (Ireland)
E. Sokell, Univ. College Dublin (Ireland)
G. O'Sullivan, Univ. College Dublin (Ireland)
A. Cummings, Univ. College Dublin (Ireland)
A. Aguilar, National Institute of Standards and Technology (United States)
J. D. Gillaspy, National Institute of Standards and Technology (United States)
J. M. Pomeroy, National Institute of Standards and Technology (United States)
J. N. Tan, National Institute of Standards and Technology (United States)

Published in SPIE Proceedings Vol. 5826:
Opto-Ireland 2005: Optical Sensing and Spectroscopy
Gerard D. O'Sullivan; Brian D. MacCraith; Hugh James Byrne; Enda McGlynn; Alan G. Ryder, Editor(s)

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