Overlay accuracy calibration

Eran Amit; Dana Klein; Guy Cohen; Nuriel Amir; Michael Har-Zvi; Cindy Kato; Hiroyuki Kurita

doi:10.1117/12.2011416

18 April 2013 Overlay accuracy calibration

Eran Amit, Dana Klein, Guy Cohen, Nuriel Amir, Michael Har-Zvi, Cindy Kato, Hiroyuki Kurita

Proceedings Volume 8681, Metrology, Inspection, and Process Control for Microlithography XXVII; 86811G (2013) https://doi.org/10.1117/12.2011416
Event: SPIE Advanced Lithography, 2013, San Jose, California, United States

Abstract

In order to fulfill the ever tightening requirements of advanced node overlay budgets, overlay metrology is becoming more and more sensitive to even the smallest imperfections in the metrology target. Under certain circumstances, inaccuracy due to such target imperfections can become the dominant contribution to the metrology uncertainty and cannot be quantified by the standard TMU contributors. In this paper we describe a calibration method that makes the overlay measurement robust to target imperfections without diminishing its sensitivity to the target overlay. The basic assumption of the method is that overlay measurement result can be approximated as the sum of two terms: the accurate overlay and the measurement inaccuracy (independently of the conventional contributors). While the first term (the “real overlay”) is robust it is known that the overlay target inaccuracy depends on the measurement conditions. This dependence on measurement conditions is used to estimate quantitative inaccuracy by means of the overlay quality merit which was described in previous publications. This paper includes the theoretical basis of the method as well as experimental validation.

Citation Download Citation

Eran Amit, Dana Klein, Guy Cohen, Nuriel Amir, Michael Har-Zvi, Cindy Kato, and Hiroyuki Kurita "Overlay accuracy calibration", Proc. SPIE 8681, Metrology, Inspection, and Process Control for Microlithography XXVII, 86811G (18 April 2013); https://doi.org/10.1117/12.2011416

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