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Proceedings Paper

Debris mitigation for EUV sources using directional gas flows
Author(s): Wouter Soer; Dion Klunder; Maarten van Herpen; Leon Bakker; Vadim Banine
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Paper Abstract

Practical EUV sources not only generate the desired EUV radiation at a wavelength of 13.5 nm but also produce debris that severely limits the lifetime of the collecting optics in the lithographic system. In this paper, we address the possibility of reducing the exposure of the collecting optics to debris by using directional gas flows, focusing particularly on mitigation of ballistic microparticles. The purpose of the gas flow is to change the direction of the particles such that they can subsequently be captured by a foil trap. Two types of gas flows are considered: (i) longitudinal gas flows, i.e. with a flow direction essentially parallel to the velocity of the microparticles, and (ii) transversal gas flows, having a flow direction essentially perpendicular to that of the microparticles. We have conducted contamination experiments using both types of flows in Xe- and Sn-based experimental EUV sources with Ar gas. The experiments show that directional gas flows suppress microparticles in the same way a buffer gas does unless the flow velocity becomes of the same order as the thermal velocity of the gas (~ 102 m/s). A high-speed longitudinal gas flow is expected to be more efficient in thermalizing the microparticles than a stationary buffer gas; this could however not be confirmed due to experimental constraints. Our experiments with a high-speed transversal gas flow show that submicron debris particles can successfully be suppressed by one order of magnitude. A transversal gas flow combined with a suitable foil trap structure may thus present an effective method for mitigation of microparticles.

Paper Details

Date Published: 24 March 2006
PDF: 6 pages
Proc. SPIE 6151, Emerging Lithographic Technologies X, 61514B (24 March 2006); doi: 10.1117/12.682357
Show Author Affiliations
Wouter Soer, Philips Research (Netherlands)
Dion Klunder, Philips Research (Netherlands)
Maarten van Herpen, Philips Research (Netherlands)
Leon Bakker, Philips Research (Netherlands)
Vadim Banine, ASML Netherlands (Netherlands)

Published in SPIE Proceedings Vol. 6151:
Emerging Lithographic Technologies X
Michael J. Lercel, Editor(s)

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