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Proceedings Paper

Linewidth Edge Detection Algorithm for Coherent Image Profiles
Author(s): Diana Nyyssonen; Bob Monteverde
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Paper Abstract

Accurate CD linewidth and overlay measurement are dependent upon the ability to correctly find edges of line objects. Software algorithms used to find edges often have difficulty distinguishing the edges of features to be measured from surrounding noise and coherent edge ringing. The problem becomes even more difficult when an optical scanning microscope operates in a highly coherent mode and enhanced edge ringing and interference effects are present. Simple edge detection algorithms such as thresholding and steepest slope become confused and may select erroneous artifacts. As a result, optical measurement systems have leaned toward high NA illumination systems and broad spectral bandwidth, both of which reduce coherent edge ringing but are accompanied by a loss in accuracy. Alternative techniques such as correlation and adaptive signal processing also have difficulties finding true edges due to the variation in image profiles resulting from changes in materials, layer thickness, edge slope, etc. This paper describes an alternative approach based on a combination of mean-square integration (MSI) and adaptive techniques with function parameters determined from the digitized waveform. This approach has been successfully utilized on experimental data and appears to work for a wide variety of signal waveforms. Theoretical and experimental results are given.

Paper Details

Date Published: 19 July 1989
PDF: 7 pages
Proc. SPIE 1087, Integrated Circuit Metrology, Inspection, and Process Control III, (19 July 1989); doi: 10.1117/12.953088
Show Author Affiliations
Diana Nyyssonen, CD Metrology, Inc. (United States)
Bob Monteverde, VLSI Standards Incorporated (United States)

Published in SPIE Proceedings Vol. 1087:
Integrated Circuit Metrology, Inspection, and Process Control III
Kevin M. Monahan, Editor(s)

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