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Proceedings Paper

New concerns with the design of filters for the protection of lithography optics
Author(s): Andrew J. Dallas; William Ding; Brian Hoang; Jon Joriman; Jonathan G. Parsons; Kevin Seguin
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Paper Abstract

The optimal medium in which DUV resists are exposed is becoming increasingly under investigation by lithography tool manufacturers. These medium requirements have created even more design restrictions for effective filtration methods. Traditional airborne molecular contamination control in tracks and exposure tools has focused on the removal of weak bases that poison the resist. Newer concerns, including; the degradation of optics, changes in resist sensitivity, the index of refraction and the demands of tighter geometries, all contribute to the need for quantification and control of gas-phase contamination within exposure tools. As a result, filter manufacturers are required not only to remove a broader spectrum of contaminants (e.g. organic and acid gases), but to supply removal efficiency data, under a variety of conditions including; variable challenge concentrations, mixed stream contamination, humidity (dew points), flow rates, and temperatures. The paper will address these new concerns focusing on the efficiency effects of relative humidity for various contaminant streams using a variety of filter media. In addition, the removal of hydrophilic compounds such as ammonia and sulfur dioxide when drying an air stream will also be considered. This ongoing study has contributed to the design of a point-of-use air-shower filter used to protect lithography lenses. Preliminary field tests by a major manufacturer indicate that the removal of the specified bases, acids and total organics is below detection limits of <0.1 ppb.

Paper Details

Date Published: 26 June 2003
PDF: 17 pages
Proc. SPIE 5040, Optical Microlithography XVI, (26 June 2003); doi: 10.1117/12.485416
Show Author Affiliations
Andrew J. Dallas, Donaldson Co., Inc. (United States)
William Ding, Donaldson Co., Inc. (United States)
Brian Hoang, Donaldson Co., Inc. (United States)
Jon Joriman, Donaldson Co., Inc. (United States)
Jonathan G. Parsons, Donaldson Co., Inc. (United States)
Kevin Seguin, Donaldson Co., Inc. (United States)

Published in SPIE Proceedings Vol. 5040:
Optical Microlithography XVI
Anthony Yen, Editor(s)

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