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Proceedings Paper

Image simulation and surface reconstruction of undercut features in atomic force microscopy
Author(s): Xiaoping Qian; John Villarrubia; Fenglei Tian; Ronald Dixson
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Paper Abstract

CD-AFMs (critical dimension atomic force microscopes) are instruments with servo-control of the tip in more than one direction. With appropriately "boot-shaped" or flared tips, such instruments can image vertical or even undercut features. As with any AFM, the image is a dilation of the sample shape with the tip shape. Accurate extraction of the CD requires a correction for the tip effect. Analytical methods to correct images for the tip shape have been available for some time for the traditional (vertical feedback only) AFMs, but were until recently unavailable for instruments with multi-dimensional feedback. Dahlen et al. [J. Vac. Sci. Technol. B23, pp. 2297-2303, (2005)] recently introduced a swept-volume approach, implemented for 2-dimensional (2D) feedback. It permits image simulation and sample reconstruction, techniques previously developed for the traditional instruments, to be extended for the newer tools. We have introduced [X. Qian and J. S. Villarrubia, Ultramicroscopy, in press] an alternative dexel-based method, that does the same in either 2D or 3D. This paper describes the application of this method to sample shapes of interest in semiconductor manufacturing. When the tip shape is known (e.g., by prior measurement using a tip characterizer) a 3D sample surface may be reconstructed from its 3D image. Basing the CD measurement upon such a reconstruction is shown here to remove some measurement artifacts that are not removed (or are incompletely removed) by the existing measurement procedures.

Paper Details

Date Published: 5 April 2007
PDF: 12 pages
Proc. SPIE 6518, Metrology, Inspection, and Process Control for Microlithography XXI, 651811 (5 April 2007); doi: 10.1117/12.712399
Show Author Affiliations
Xiaoping Qian, Illinois Institute of Technology (United States)
John Villarrubia, National Institute of Standards and Technology (United States)
Fenglei Tian, Illinois Institute of Technology (United States)
Ronald Dixson, National Institute of Standards and Technology (United States)

Published in SPIE Proceedings Vol. 6518:
Metrology, Inspection, and Process Control for Microlithography XXI
Chas N. Archie, Editor(s)

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