Articles

Impact of finite laser bandwidth on the critical dimension of L/S structures

[+] Author Affiliations
Peter De Bisschop

IMEC, Kapeldreef 75, B-3001 Leuven, Belgium

Ivan Lalovic

Cymer Inc., 17075 Thornmint Ct. San Diego, California 92127

Fedor Trintchouk

Cymer Inc., 17075 Thornmint Ct. San Diego, California 92127

J. Micro/Nanolith. MEMS MOEMS. 7(3), 033001 (August 13, 2008). doi:10.1117/1.2964297
History: Received December 02, 2007; Revised April 01, 2008; Accepted April 14, 2008; Published August 13, 2008
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We investigate the effect of finite laser bandwidth on line-space (L/S) imaging, both through simulations and experiment. We will show that the primary effect of laser bandwidth is a change of the optical-proximity behavior of the scanner, i.e., a modification of the critical dimensional pitch [CD(Pitch)] characteristic, and that depth of focus typically remains unaffected. The simulation part of this study resulted in a simple estimator, expressing bandwidth-induced CD changes in terms of the “quadratic focus-sensitivity” (12d2CDdF2) of the L/S structure, a parameter which we call the “second moment” of the laser spectrum, M2, and the longitudinal chromatic-aberration of the scanner (dFdλ) only. The experimental part of this study, in which we measured CD(pitch) curves at different laser-bandwidth settings of the ASML XT:1700i NA=1.20 immersion scanner at Interuniversitary Micro-Electronic Centre (IMEC), confirms the results of the theoretical part, while relating the bandwidth dependency of the CD effects also to the experimentally available E95 metric. We conclude that even though the laser bandwidth of modern scanners is quite low, bandwidth effects do contribute to their proximity behavior and impact proximity stability as well as scanner-to-scanner proximity differences. We present a critical evaluation of current laser-bandwidth metrics and comment on the trade-off between the average laser bandwidth and laser bandwidth stability in order to achieve a required level of proximity control (e.g., between scanners).

© 2008 Society of Photo-Optical Instrumentation Engineers

Topics

Lasers ; Simulations

Citation

Peter De Bisschop ; Ivan Lalovic and Fedor Trintchouk
"Impact of finite laser bandwidth on the critical dimension of L/S structures", J. Micro/Nanolith. MEMS MOEMS. 7(3), 033001 (August 13, 2008). ; http://dx.doi.org/10.1117/1.2964297


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