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Proceedings Paper

Reduced pellicle impact on overlay using high order intrafield grid corrections
Author(s): Robert de Kruif; Tasja van Rhee; Eddy van der Heijden
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Paper Abstract

Placement of a pellicle on a reticle will result in mechanical distortion of the reticle. Due to the mechanical distortion, exposure of the reticle with the pellicle will show additional image distortion, resulting in a reduced overlay performance on the wafer. Furthermore, a pellicle is a consumable and might be replaced during the lifetime of a reticle, introducing a different image distortion. Based on experimental reticle measurements before and after pellicle placement and modeling of the resulting data it has been suggested by Cotte [1] that the impact of the pellicle can be reduced by 50% using linear corrections. These corrections are common available on most exposure tools. Cotte reported that by correcting for the third order term in x-direction was said to reduce the impact of the pellicle by another 25%. We studied the impact of pellicle induced mechanical distortion on the overlay performance of the reticle. We experimentally tested pellicle induced distortion using a standard 193-nm pellicle and a standard ASML overlay reticle. The experiments included mask registration measurements before and after pellicle placement, as well as wafer data from exposures of the reticle before and after pellicle placement on an ASML TWINSCANTM XT:1400. We showed that, by using an intrafield grid correction model consisting of 15 coefficients of a third order polynomial regression model, we can execute grid corrections on the exposure tool enabling a reduction of the pellicle induced additional overlay to a level comparable to the situation without a pellicle.

Paper Details

Date Published: 27 May 2009
PDF: 11 pages
Proc. SPIE 7470, 25th European Mask and Lithography Conference, 74700O (27 May 2009); doi: 10.1117/12.835186
Show Author Affiliations
Robert de Kruif, ASML Netherlands B.V. (Netherlands)
Tasja van Rhee, ASML Netherlands B.V. (Netherlands)
Eddy van der Heijden, ASML Netherlands B.V. (Netherlands)

Published in SPIE Proceedings Vol. 7470:
25th European Mask and Lithography Conference
Uwe F. W. Behringer, Editor(s)

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