
Proceedings Paper
Progress toward traceable nanoscale optical critical dimension metrology for semiconductorsFormat | Member Price | Non-Member Price |
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Paper Abstract
Non-imaging optical critical dimension (OCD) techniques have rapidly become a preferred method for
measuring nanoscale features in semiconductors. OCD relies upon the measurement of an optical reflectance
signature from a grating target as a function of angle, wavelength and/or polarization. By comparing the signature
with theoretical simulations, parameters of the grating lines such as critical dimension (CD) linewidth,
sidewall angle, and line height can be obtained. Although the method is sensitive and highly repeatable, there
are many issues to be addressed before OCD can be considered a traceable metrology. We report on progress
towards accurate, traceable measurement, modeling, and analysis of OCD signatures collected on the NIST
goniometric optical scatter instrument (GOSI), focusing on recent results from grating targets fabricated using
the single-crystal critical dimension reference materials (SCCDRM) process. While we demonstrate good correlation
between linewidth extracted from OCD and that measured by scanning electron microscopy (SEM),
we also find systematic deviations between the experimentally obtained optical signatures and best fit theoretical
signatures that limit our ability to determine uncertainty in OCD linewidth. We then use the SCCDRM line
profile model and a χ2 goodness-of-fit analysis on simulated signatures to demonstrate the theoretical confidence
limits for the grating line parameters in the case of normally distributed noise. This analysis shows that
for the current SCCDRM implementation, line height and oxide layer undercut are highly correlated parameters,
and that the 3-σ confidence limits in extracted linewidth depend on the target pitch. Prospects for traceable
OCD metrology will be discussed.
Paper Details
Date Published: 10 September 2007
PDF: 9 pages
Proc. SPIE 6672, Advanced Characterization Techniques for Optics, Semiconductors, and Nanotechnologies III, 66720L (10 September 2007); doi: 10.1117/12.734080
Published in SPIE Proceedings Vol. 6672:
Advanced Characterization Techniques for Optics, Semiconductors, and Nanotechnologies III
Angela Duparré; Bhanwar Singh; Zu-Han Gu, Editor(s)
PDF: 9 pages
Proc. SPIE 6672, Advanced Characterization Techniques for Optics, Semiconductors, and Nanotechnologies III, 66720L (10 September 2007); doi: 10.1117/12.734080
Show Author Affiliations
Heather J. Patrick, KT Consulting, Inc. (United States)
National Institute of Standards and Technology (United States)
National Institute of Standards and Technology (United States)
Thomas A. Germer, National Institute of Standards and Technology (United States)
Published in SPIE Proceedings Vol. 6672:
Advanced Characterization Techniques for Optics, Semiconductors, and Nanotechnologies III
Angela Duparré; Bhanwar Singh; Zu-Han Gu, Editor(s)
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