21 April 2014 Innovative techniques for improving overlay accuracy by using DCM (device correlated metrology) targets as reference
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Overlay metrology performance as Total Measurement Uncertainty (TMU), design rule compatibility, device correlation and measurement accuracy are been challenged at 2x nm node and below. Process impact on overlay metrology becoming critical, and techniques to improve measurement accuracy becomes increasingly important. In this paper, we present an innovative methodology for improving overlay accuracy. A propriety quality metric, Qmerit, is used to identify overlay metrology measurement settings with least process impacts and reliable accuracies. Using the quality metric, an innovative calibration method, ASC (Archer Self Calibration) is then used to remove the inaccuracies. Accuracy validation can be achieved by correlation to reference overlay data from another independent metrology source such as CDSEM data collected on DCM (Device Correlated Metrology) hybrid target or electrical testing. Additionally, reference metrology can also be used to verify which measurement conditions are the most accurate. In this paper we bring an example of such use case.
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Wei-Jhe Tzai, Wei-Jhe Tzai, Simon C. C. Hsu, Simon C. C. Hsu, Howard Chen, Howard Chen, Charlie Chen, Charlie Chen, Yuan Chi Pai, Yuan Chi Pai, Chun-Chi Yu, Chun-Chi Yu, Chia Ching Lin, Chia Ching Lin, Tal Itzkovich, Tal Itzkovich, Lipkong Yap, Lipkong Yap, Eran Amit, Eran Amit, David Tien, David Tien, Eros Huang, Eros Huang, Kelly T. L. Kuo, Kelly T. L. Kuo, Nuriel Amir, Nuriel Amir, "Innovative techniques for improving overlay accuracy by using DCM (device correlated metrology) targets as reference", Proc. SPIE 9050, Metrology, Inspection, and Process Control for Microlithography XXVIII, 90501R (21 April 2014); doi: 10.1117/12.2046671; https://doi.org/10.1117/12.2046671

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