28 March 2017 Reaching for the true overlay in advanced nodes
Author Affiliations +
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.
Conference Presentation
© (2017) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Chiew-seng Koay, Chiew-seng Koay, Bassem Hamieh, Bassem Hamieh, Nelson Felix, Nelson Felix, John Gaudiello, John Gaudiello, } "Reaching for the true overlay in advanced nodes", Proc. SPIE 10145, Metrology, Inspection, and Process Control for Microlithography XXXI, 101450B (28 March 2017); doi: 10.1117/12.2260007; https://doi.org/10.1117/12.2260007
PROCEEDINGS
10 PAGES + PRESENTATION

SHARE
Back to Top