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Proceedings Paper

CD-bias reduction in CD-SEM line-width measurement for the 32-nm node and beyond using the model-based library method
Author(s): Chie Shishido; Maki Tanaka; Mayuka Osaki
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Paper Abstract

The measurement accuracy of critical-dimension scanning electron microscopy (CD-SEM) at feature sizes of 10 nm and below is investigated and methods for improving accuracy and reducing CD bias (the difference between true and measured CD values) are proposed. Simulations indicate that CD bias varies with feature size (CD) when the electron scatter range exceeds the CD. As the change in the CD-SEM waveform with decreasing CD is non-uniform, the CD bias in the results is strongly dependent on the algorithm employed to process the CD-SEM data. Use of the threshold method with a threshold level equal to 50% (Th = 50%) is shown to be effective for suppressing the dependence of CD bias on CD. Through comparison of experimental CD-SEM measurements of silicon line patterns (7-40 nm) with atomic force microscopy (AFM) measurements, it is confirmed that the threshold method (Th = 50%) is a effective as predicted, affording a largely invariant CD bias. The model-based library (MBL) method, which is theoretically capable of eliminating CD bias, is demonstrated to reduce the CD bias to near-zero levels. These experiments demonstrate the feasibility of next-generation CD-SEM for the measurement of feature sizes of the order of 10 nm and smaller.

Paper Details

Date Published: 23 March 2009
PDF: 10 pages
Proc. SPIE 7272, Metrology, Inspection, and Process Control for Microlithography XXIII, 72722C (23 March 2009); doi: 10.1117/12.813948
Show Author Affiliations
Chie Shishido, Hitachi, Ltd. (Japan)
Maki Tanaka, Hitachi High-Technologies Corp. (Japan)
Mayuka Osaki, Hitachi, Ltd. (Japan)

Published in SPIE Proceedings Vol. 7272:
Metrology, Inspection, and Process Control for Microlithography XXIII
John A. Allgair; Christopher J. Raymond, Editor(s)

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