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Comparison of Electron Imaging Modes for Dimensional Measurements in the Scanning Electron Microscope†

Published online by Cambridge University Press:  25 July 2016

Michael T. Postek ,
András E. Vladár ,
John S. Villarrubia  and
Atsushi Muto
Michael T. Postek*
Affiliation:
Engineering Physics Division, National Institute of Standards and Technology, 100 Bureau Drive, MS 8120, Gaithersburg, MD 20899, USA
András E. Vladár
Affiliation:
Engineering Physics Division, National Institute of Standards and Technology, 100 Bureau Drive, MS 8120, Gaithersburg, MD 20899, USA
John S. Villarrubia
Affiliation:
Engineering Physics Division, National Institute of Standards and Technology, 100 Bureau Drive, MS 8120, Gaithersburg, MD 20899, USA
Atsushi Muto
Affiliation:
Hitachi High Technologies America, Inc., 22610 Gateway Center Drive, Suite 100, Clarksburg, MD 20871, USA
*
*Corresponding author. postek@nist.gov
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Abstract

Dimensional measurements from secondary electron (SE) images were compared with those from backscattered electron (BSE) and low-loss electron (LLE) images. With the commonly used 50% threshold criterion, the lines consistently appeared larger in the SE images. As the images were acquired simultaneously by an instrument with the capability to operate detectors for both signals at the same time, the differences cannot be explained by the assumption that contamination or drift between images affected the SE, BSE, or LLE images differently. Simulations with JMONSEL, an electron microscope simulator, indicate that the nanometer-scale differences observed on this sample can be explained by the different convolution effects of a beam with finite size on signals with different symmetry (the SE signal’s characteristic peak versus the BSE or LLE signal’s characteristic step). This effect is too small to explain the >100 nm discrepancies that were observed in earlier work on different samples. Additional modeling indicates that those discrepancies can be explained by the much larger sidewall angles of the earlier samples, coupled with the different response of SE versus BSE/LLE profiles to such wall angles.

Keywords

metrologybackscattered electronslow loss electronssecondary electronsJMONSELelectron beam modeling
Type
Technique and Instrumentation Development
Information
Microscopy and Microanalysis , Volume 22 , Issue 4 , August 2016 , pp. 768 - 777
Copyright
© Microscopy Society of America 2016 

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Footnotes

†

Contribution of the National Institute of Standards and Technology; not subject to copyright.

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