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Proceedings Paper

EUV absorption in a laser-produced plasma source
Author(s): Michael P. Kanouff; Harry Shields; Luis J. Bernardez; Glenn D. Kubiak
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Paper Abstract

Laser produced plasmas (LPP) provide a stable source of EUV making them well suited for use in next-generation lithography tools. The plasma is generated by directing a laser at a target composed of a partially condensed gas after it undergoes a supersonic expansion through a nozzle and enters a vacuum chamber. The expansion process results in very cold temperatures such that the gas partially condenses forming a mixture of gas and small clusters. The clusters absorb the laser energy leading to the formation of the plasma, but the excess gas absorbs some of the emitted EUV reducing the net output of the LPP. Calculations were carried out to determine the amount of EUV absorbed by the gaseous xenon that surrounds the plasma. The Navier-Stokes equations were solved to obtain the gas density field. Observations from experiments were used for the shape of the plasma, which showed it to be approximately that of a prolate spheroid. The relative EUV signal strength was obtained as a function of the direction angle by calculating the absorption of EUV in the gas surrounding the plasma and integrating over the plasma surface. Calculated results for the normalized EUV energy distribution compare well with measurements of the EUV angular distribution obtained in experiments.

Paper Details

Date Published: 20 August 2001
PDF: 8 pages
Proc. SPIE 4343, Emerging Lithographic Technologies V, (20 August 2001); doi: 10.1117/12.436682
Show Author Affiliations
Michael P. Kanouff, Sandia National Labs. (United States)
Harry Shields, TRW Space & Electronics Group (United States)
Luis J. Bernardez, Sandia National Labs. (United States)
Glenn D. Kubiak, Sandia National Labs. (United States)

Published in SPIE Proceedings Vol. 4343:
Emerging Lithographic Technologies V
Elizabeth A. Dobisz, Editor(s)

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