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Journal of Micro/Nanolithography, MEMS, and MOEMS

Image placement error: closing the gap between overlay and imaging
Author(s): Eric Hendrickx; Alberto Colina; Alex van der Hoff; Jo M. Finders; Geert Vandenberghe
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Paper Abstract

We perform experimental and theoretical studies of image placement error induced by aberrations of the projection lens. The goal is to experimentally determine the magnitude of the image placement errors, to compare experiments and simulations, and to screen possible correction strategies. The calculations and experiments are done for ArF lithography. Theoretically, we simulate image placement error using the projection lens aberration data and simulators such as Prolith or Solid-C. Features with low and high sensitivities to lens aberrations are identified, together with a reference feature that has low sensitivity for image placement error. Dedicated reticles are fabricated to print various features at different illumination conditions on the same substrate. The resulting patterns could be analyzed using top-down scanning electron microscopy (SEM), but also optically with the standard optical overlay tool KLA5200. For both techniques, the experimentally found image placement errors are in excellent agreement with simulations. In simulations, we calculate the dependency of the image placement error on pattern density, pattern orientation, and illumination conditions. These tendencies are experimentally reproduced. We conclude with a case study that demonstrates a possible correction strategy for image placement error.

Paper Details

Date Published: 1 July 2005
PDF: 15 pages
J. Micro/Nanolith. 4(3) 033006 doi: 10.1117/1.2008229
Published in: Journal of Micro/Nanolithography, MEMS, and MOEMS Volume 4, Issue 3
Show Author Affiliations
Eric Hendrickx, IMEC (Belgium)
Alberto Colina, ASML Netherlands B.V. (Netherlands)
Alex van der Hoff, ASML Netherlands B.V. (Netherlands)
Jo M. Finders, ASML Netherlands B.V. (Netherlands)
Geert Vandenberghe, IMEC (Belgium)


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