24 March 2016 Root cause analysis of overlay metrology excursions with scatterometry overlay technology (SCOL)
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We demonstrate a novel method to establish a root cause for an overlay excursion using optical Scatterometry metrology. Scatterometry overlay metrology consists of four cells (two per directions) of grating on grating structures that are illuminated with a laser and diffracted orders measured in the pupil plane within a certain range of aperture. State of art algorithms permit, with symmetric considerations over the targets, to extract the overlay between the two gratings. We exploit the optical properties of the target to extract further information from the measured pupil images, particularly information that maybe related to any change in the process that may lead to an overlay excursion. Root Cause Analysis or RCA is being developed to identify different kinds of process variations (either within the wafer, or between different wafers) that may indicate overlay excursions. In this manuscript, we demonstrate a collaboration between Globalfoundries and KLA-Tencor to identify a symmetric process variation using scatterometry overlay metrology and RCA technique.
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Karsten Gutjahr, Karsten Gutjahr, Dongsuk Park, Dongsuk Park, Yue Zhou, Yue Zhou, Winston Cho, Winston Cho, Ki Cheol Ahn, Ki Cheol Ahn, Patrick Snow, Patrick Snow, Richard McGowan, Richard McGowan, Tal Marciano, Tal Marciano, Vidya Ramanathan, Vidya Ramanathan, Pedro Herrera, Pedro Herrera, Tal Itzkovich, Tal Itzkovich, Janay Camp, Janay Camp, Michael Adel, Michael Adel, "Root cause analysis of overlay metrology excursions with scatterometry overlay technology (SCOL)", Proc. SPIE 9778, Metrology, Inspection, and Process Control for Microlithography XXX, 97781M (24 March 2016); doi: 10.1117/12.2219668; https://doi.org/10.1117/12.2219668

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