
Proceedings Paper
Accuracy of overlay measurements: tool and mark asymmetry effectsFormat | Member Price | Non-Member Price |
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Paper Abstract
Results of recent Investigations uncovering significant
errors in overlay (O/L) measurements are reported. The two major
contributors are related to the failures of symmetry of the
overlay measurement tool and of the mark. These may result In
measurement errors on the order of 100 nm. Methodology based on
the conscientious verification of assumptions of symmetry is
shown to be effective in identifying the extent and sources of
such errors. This methodology can be used to arrive at an
estimate of the relative accuracy of the O/L measurements, even
in absence of certified O/L reference materials. Routes to
improve the accuracy of O/L measurements are outlined and some
examples of improvements are given.
Errors in O/L measurements associated with the asymmetry of
the metrology tool can be observed by comparing the O/L
measurements taken at 0 and 180 degree orientations of the sample
in reference to the tool. Half the difference of these
measurements serves as an estimate of such tool related bias in
estimating O/L. This is called tool induced shift (TIS). Errors
of this kind can be traced to asymmetries of tool components, e.
g., camera, illumination misalignment, residual asymmetric
aberrations etc. Tool asymmetry leads to biased O/L estimates
even on symmetric O/L measurement marks. Its impact on TIS
depends on the optical properties of the structure being
measured, the measurement procedure and on the combination of
tool and sample asymmetries. It is also a function of design and
manufacture of the O/L metrology tool. In the absence of
certified O/L samples, measurement accuracy and repeatability may
be improved by demanding that TIS be small for all tools on all
structures.
Paper Details
Date Published: 1 June 1990
PDF: 23 pages
Proc. SPIE 1261, Integrated Circuit Metrology, Inspection, and Process Control IV, (1 June 1990); doi: 10.1117/12.20042
Published in SPIE Proceedings Vol. 1261:
Integrated Circuit Metrology, Inspection, and Process Control IV
William H. Arnold, Editor(s)
PDF: 23 pages
Proc. SPIE 1261, Integrated Circuit Metrology, Inspection, and Process Control IV, (1 June 1990); doi: 10.1117/12.20042
Show Author Affiliations
Daniel J. Coleman, IBM/East Fishkill Facility (United States)
Patricia J. Larson, IBM/East Fishkill Facility (United States)
Alexander D. Lopata, IBM/East Fishkill Facility (United States)
Patricia J. Larson, IBM/East Fishkill Facility (United States)
Alexander D. Lopata, IBM/East Fishkill Facility (United States)
William A. Muth, IBM/East Fishkill Facility (United States)
Alexander Starikov, IBM/East Fishkill Facility (United States)
Alexander Starikov, IBM/East Fishkill Facility (United States)
Published in SPIE Proceedings Vol. 1261:
Integrated Circuit Metrology, Inspection, and Process Control IV
William H. Arnold, Editor(s)
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