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Proceedings Paper

Stable tin droplets for LPP EUV sources
Author(s): Bob Rollinger; Oran Morris; Reza S. Abhari
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Paper Abstract

A key component of EUV LPP sources is the droplet generator. Small tin droplets, when combined with a igh power laser, deliver a regenerative target with high CE. This is mandatory for long-term operation in an EUV source. The overall source stability directly correlates with the stability of the fuel delivery system. In this work, droplets are imaged directly at the irradiation site. The droplet diameter and position are extracted from recorded droplet train images. Tin droplets are successfully generated at diameters of 35-58um, with droplet velocities ranging from 8 to 12m/s. The obtained droplet sizes limit the amount of neutral atoms and residual tin at the plasma formation site. The droplet velocities lead to droplet spacings of up to 8 droplet diameters. The resulting spacing helps to minimize the plasma-droplet train interaction. The droplet generator frequency range fulfills the requirements for low power metrology tools and high power HVM sources. Stability of the droplet generator is studied at 20kHz. The droplet diameter stability presents no significant fluctuations. The lateral droplet stability is in the range of 1.8% (3σ) of the droplet diameter, so no influence on source stability is expected. The variations in drop-to-drop distance, which go up to 7.3% (3σ) can influence source stability for the case of constant laser triggering.

Paper Details

Date Published: 8 April 2011
PDF: 7 pages
Proc. SPIE 7969, Extreme Ultraviolet (EUV) Lithography II, 79692W (8 April 2011); doi: 10.1117/12.879538
Show Author Affiliations
Bob Rollinger, ETH Zürich (Switzerland)
Oran Morris, ETH Zürich (Switzerland)
Reza S. Abhari, ETH Zürich (Switzerland)

Published in SPIE Proceedings Vol. 7969:
Extreme Ultraviolet (EUV) Lithography II
Bruno M. La Fontaine; Patrick P. Naulleau, Editor(s)

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