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Proceedings Paper

Reaching for the true overlay in advanced nodes
Author(s): Chiew-seng Koay; Bassem Hamieh; Nelson Felix; John Gaudiello
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Paper Abstract

Traditionally, the total measurement uncertainty (TMU) of overlay metrology focuses on dynamic precision, toolinduced-shift, and matching, while rarely examining inaccuracy. However, some researchers have recently shown that measurement inaccuracy can still be large despite optimized small TMU. Moreover, this inaccuracy can consume a significant portion of the overlay budget in the advanced nodes. In addition to qualifying the overlay error of inline wafers, overlay metrology is also used for improving on-product overlay as it provides corrective feedback to the lithography scanner. The accuracy of the correction terms as a result depends directly upon the measurement accuracy. As such, enhanced overlay accuracy will improve the overlay performance of reworked wafers, or subsequently exposed wafers. We have previously shown that a segmented Blossom target is more prone to asymmetry-induced inaccuracy than a nonsegmented target is [1]. Since target segmentation is inevitable for SADP and SAQP patterning processes, their resulting overlay performance leaves a lot to be desired. In our quest to reach for the true overlay, this paper reports our investigations on accuracy enhancement techniques for image-based targets, such as redundancy and self-calibration, and on the use of simulation-optimized scatterometry-based targets.

Paper Details

Date Published: 28 March 2017
PDF: 10 pages
Proc. SPIE 10145, Metrology, Inspection, and Process Control for Microlithography XXXI, 101450B (28 March 2017); doi: 10.1117/12.2260007
Show Author Affiliations
Chiew-seng Koay, IBM Corp. (United States)
Bassem Hamieh, IBM Corp. (United States)
Nelson Felix, IBM Corp. (United States)
John Gaudiello, IBM Corp. (United States)


Published in SPIE Proceedings Vol. 10145:
Metrology, Inspection, and Process Control for Microlithography XXXI
Martha I. Sanchez, Editor(s)

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