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Proceedings Paper

Nanoparticle contamination control for EUVL-technology: especially for photomasks in carriers and scanners
Author(s): Heinz Fissan; Christof Asbach; Thomas A. J. Kuhlbusch; Jing Wang; David Y. H. Pui; Se-Jin Yook; Jung H. Kim
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Paper Abstract

Extreme Ultraviolet Lithography (EUVL) is a leading lithography technology for the sub-32 nm chip manufacturing technology. Photomasks, in a mask carrier or inside a vacuum scanner, need to be protected from contamination by nanoparticles larger than the minimum feature size expected from this technology. The most critical part with respect to contamination in the EUVL-system is the photomask. The protection is made more difficult because protective pellicles cannot be used, due to the attenuation of the EUV beam by the pellicle. We have defined a set of protection schemes to protect EUVL photomasks from particle contamination and developed models to describe their effectiveness at atmospheric pressure (e.g. in mask carriers) or during scanning operation at low pressure. These schemes include that the mask is maintained facing down to avoid gravitational settling and the establishment of a thermal gradient underneath the mask surface to thermophoretically repel particles. Experimental verification studies of the models were carried out in atmospheric-pressure carriers and in a vacuum system down to about 3.3 Pa. Particles with sizes between 60 (for experiments, isn't it 125 nm?) nm and 250 nm were injected into the vacuum chamber with controlled speed and concentration to validate the analytical and numerical models. It could be shown that a deterministic approach using free molecular expressions can be used to accurately describe particle deposition at these low pressure levels. Thermophoresis was found to be very effective at both atmospheric and low pressure against the diffusional particle deposition, whereas inertial particle deposition of large and/or fast particles can likely not be prevented. A review of the models and their verification will be presented in this paper.

Paper Details

Date Published: 28 May 2009
PDF: 10 pages
Proc. SPIE 7364, Nanotechnology IV, 73640N (28 May 2009); doi: 10.1117/12.821654
Show Author Affiliations
Heinz Fissan, Institute of Energy and Environmental Technology e.V. (Germany)
Christof Asbach, Institute of Energy and Environmental Technology e.V. (Germany)
Thomas A. J. Kuhlbusch, Institute of Energy and Environmental Technology e.V. (Germany)
Jing Wang, Univ. of Minnesota (United States)
David Y. H. Pui, Univ. of Minnesota (United States)
Se-Jin Yook, Hanyang Univ. (Korea, Republic of)
Jung H. Kim, The Univ. of Seoul (Korea, Republic of)

Published in SPIE Proceedings Vol. 7364:
Nanotechnology IV
Achim Wixforth, Editor(s)

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