Articles

Contamination transport in immersion lithography

[+] Author Affiliations
Gregory F. Nellis

University of Wisconsin, Computational Mechanics Center, Department of Mechanical Engineering, Room 280, Mechanical Engineering Building, 1513 University Avenue, Madison, Wisconsin 53706

Mohamed S. El-Morsi

University of Wisconsin, Computational Mechanics Center, Department of Mechanical Engineering, Room 280, Mechanical Engineering Building, 1513 University Avenue, Madison, Wisconsin 53706

Chris Van Peski

SEMATECH, 2706 Montopolis Drive, Austin, Texas 78741

Andrew Grenville

SEMATECH, 244 Wood Street, M/S C-161, Lexington, Massachusetts 02420-9108

J. Micro/Nanolith. MEMS MOEMS. 5(1), 013007 (February 02, 2006). doi:10.1117/1.2167947
History: Received April 02, 2005; Revised August 09, 2005; Accepted August 10, 2005; Published February 02, 2006
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In immersion lithography at 193nm, water is inserted between a resist-coated wafer and the final lens element to improve resolution and depth of focus. Experiments have shown that some chemicals in the resist, particularly the photoacid generators, are soluble and therefore will leach out of the resist layer when exposed to water. Diffusion of this contamination across the lens-wafer gap may, over time, build up on the lens and therefore degrade the performance of the tool. We present models that describe the transport of contaminants in the under-lens region of an immersion tool. The mass flux of contaminants onto the lens is quantified for a reasonable range of parameters under various 2-D steady-state and transient flow conditions. A critical mass flux is estimated to provide a context for interpreting these results; the critical mass flux is defined as the level of mass flux that might, over a period of one year, result in a layer of contamination that is sufficiently thick so as to affect the optical transmission of the system.

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© 2006 Society of Photo-Optical Instrumentation Engineers

Citation

Gregory F. Nellis ; Mohamed S. El-Morsi ; Chris Van Peski and Andrew Grenville
"Contamination transport in immersion lithography", J. Micro/Nanolith. MEMS MOEMS. 5(1), 013007 (February 02, 2006). ; http://dx.doi.org/10.1117/1.2167947


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