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Proceedings Paper

RELAX: resolution enhancement by laser-spectrum adjusted exposure
Author(s): Ivan Lalovic; Nigel Farrar; Kazuhiro Takahashi; Eric Kent; Daniel Colon; German Rylov; Alden Acheta; Koji Toyoda; Harry Levinson
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Paper Abstract

In this work, we demonstrate a resolution enhancement technique for DUV lithography in which the light source spectrum is modified in order to improve the imaging performance of given device patterns. With this technique, termed RELAX, the imaging depth of focus (DOF) can be improved significantly for contact holes, and potentially line-space patterns. The improvement in the DOF comes at the expense of modest deterioration of other process performance metrics, such as exposure latitude and exposure bias, due to reduced image contrast at best focus. Compared to the FLEX-based techniques, RELAX allows a continuum of tunable spectral conditions without the drawback of multiple exposure passes, which is especially critical for step-and-scan lithography. Spectrum modification is accomplished by replacing the line narrowing and wavemeter modules of the excimer laser light source with RELAX-enabled modules. Direct wavefront modification of the laser output has been demonstrated to provide the optimum method for producing a double peak spectrum, which simulation has shown to produce the maximum DOF benefit. Results from imaging experiments of attenuated-PSM contact structures exposed using 248nm dipole illumination showed DOF improvements of up to 70% with a double peak separation of about 2pm. Lateral chromatic effects at this separation were negligible. These results agreed well with previous double exposure experiments1 and simulations of some of the design structures. The process improvements were obtained without a need for re-biasing of the mask structures, although a dose adjustment was required.

Paper Details

Date Published: 12 May 2005
PDF: 9 pages
Proc. SPIE 5754, Optical Microlithography XVIII, (12 May 2005); doi: 10.1117/12.601002
Show Author Affiliations
Ivan Lalovic, Advanced Micro Devices, Inc. (United States)
Nigel Farrar, Cymer, Inc. (United States)
Kazuhiro Takahashi, Canon Inc. (Japan)
Eric Kent, Advanced Micro Devices, Inc. (United States)
Daniel Colon, Cymer, Inc. (United States)
German Rylov, Cymer, Inc. (United States)
Alden Acheta, Advanced Micro Devices, Inc. (United States)
Koji Toyoda, Canon USA Inc. (United States)
Harry Levinson, Advanced Micro Devices, Inc. (United States)

Published in SPIE Proceedings Vol. 5754:
Optical Microlithography XVIII
Bruce W. Smith, Editor(s)

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