Dimensional Metrology with Small Angle X-ray Scattering
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Introduction
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Sidewall angle is one of five major inspection
metrology challenges in the “International Technology Roadmap
for Semiconductors” (ITRS).
Need for fast, nondestructive measurement method.
Cross-sectional SEM and AFM cannot meet projected need.
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Experimental Approach
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Measurement of a test sample at multiple angles of incidence
Construct Fourier space map of the pattern cross section.
Left: Theoretical result of this protocol for a model
trapezoid The intensity streaks provide the sidewall angle.
The intensity map also provides a check for a particular model
cross-sectional profile; a limitation in current metrologies
such as light scatterometry.
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Results
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Left: The intensity of one Bragg diffraction
peak recorded as a function of sample rotation angle. This data
is compared with the theoretical model.
The distance between the maxima determines the average sidewall
angle of the features.
For a trapezoidal cross section, the sidewall angle precision
is approximately +/- 0.2 degrees.
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Additional Benefits
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| Method applicable to dense, high aspect ratio patterns, even
sub-10 nm.
Methodology applicable to arbitrary cross section, requiring
only the solution of a new model for analysis.
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Publication
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“Sidewall and Pattern Cross Section Metrology using Small
Angle X-ray Scattering”
Journal of Applied Physics to appear in 2004.
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NIST Contributors
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Wen-li Wu*
Ronald L. Jones*
Tengjiao Hu
Christopher Soles
Bryan Vogt
Eric Lin
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Collaborators:
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Diego Casa (Argonne)
Qinghuang Lin (IBM) |
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