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Proceedings Paper

New low-voltage SEM technology for imaging and metrology of submicrometer contact holes and other high-aspect-ratio structures
Author(s): Kevin M. Monahan; Guillermo L. Toro-Lira; Mark P. Davidson
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Paper Abstract

In this work we present the results of a radically different approach to imaging of high-aspect ratio structures such as contact holes. Our approach utilizes two backscattered electron detection subsystems, one optimized for imaging at the top, like most SEM detectors, and another optimized for imaging at the base of submicrometer structures. These detection systems produce signals that can be combined in real-time to produce an image which resembles the 'extended focus' images obtained with confocal optical microscopes. Unlike confocal images, however, backscattered electron images have the inherent linearity and resolution characteristic of electron-beam technology. Backscattered electron imaging has been used to solve a number of vexing problems in monitoring semiconductor process. For example, contact hole measurement with secondary electrons has typically been done with a minimum or zero signal at the base of the structure, so that the measurement value obtained either has poor precision or is the result of extrapolation. In the case of backscattered electrons, the signal can have its maximum at the base of the structure, allowing high- precision measurement with no need for extrapolation. These results are supported by extensive Monte Carlo simulations.

Paper Details

Date Published: 4 August 1993
PDF: 11 pages
Proc. SPIE 1926, Integrated Circuit Metrology, Inspection, and Process Control VII, (4 August 1993); doi: 10.1117/12.148952
Show Author Affiliations
Kevin M. Monahan, Metrologix, Inc. (United States)
Guillermo L. Toro-Lira, Metrologix, Inc. (United States)
Mark P. Davidson, Metrologix, Inc. (United States)

Published in SPIE Proceedings Vol. 1926:
Integrated Circuit Metrology, Inspection, and Process Control VII
Michael T. Postek, Editor(s)

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