19 March 2015 Qmerit-calibrated overlay to improve overlay accuracy and device performance
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In advanced semiconductor industries, the overlay error budget is getting tighter due to shrinkage in technology. To fulfill the tighter overlay requirements, gaining every nanometer of improved overlay is very important in order to accelerate yield in high-volume manufacturing (HVM) fabs. To meet the stringent overlay requirements and to overcome other unforeseen situations, it is becoming critical to eliminate the smallest imperfections in the metrology targets used for overlay metrology. For standard cases, the overlay metrology recipe is selected based on total measurement uncertainty (TMU). However, under certain circumstances, inaccuracy due to target imperfections can become the dominant contributor to the metrology uncertainty and cannot be detected and quantified by the standard TMU. For optical-based overlay (OBO) metrology targets, mark asymmetry is a common issue which can cause measurement inaccuracy, and it is not captured by standard TMU. In this paper, a new calibration method, Archer Self-Calibration (ASC), has been established successfully in HVM fabs to improve overlay accuracy on image-based overlay (IBO) metrology targets. Additionally, a new color selection methodology has been developed for the overlay metrology recipe as part of this calibration method. In this study, Qmerit-calibrated data has been used for run-to-run control loop at multiple devices. This study shows that color filter can be chosen more precisely with the help of Qmerit data. Overlay stability improved by 10~20% with best color selection, without causing any negative impact to the products. Residual error, as well as overlay mean plus 3-sigma, showed an improvement of up to 20% when Qmerit-calibrated data was used. A 30% improvement was seen in certain electrical data associated with tested process layers.
© (2015) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Md Zakir Ullah, Md Zakir Ullah, Mohamed Fazly Mohamed Jazim, Mohamed Fazly Mohamed Jazim, Stella Sim, Stella Sim, Alan Lim, Alan Lim, Biow Hiem, Biow Hiem, Lieu Chia Chuen, Lieu Chia Chuen, Jesline Ang, Jesline Ang, Ek Chow Lim, Ek Chow Lim, Dana Klein, Dana Klein, Eran Amit, Eran Amit, Roie Volkovitch, Roie Volkovitch, David Tien, David Tien, DongSub Choi, DongSub Choi, "Qmerit-calibrated overlay to improve overlay accuracy and device performance", Proc. SPIE 9424, Metrology, Inspection, and Process Control for Microlithography XXIX, 942425 (19 March 2015); doi: 10.1117/12.2085005; https://doi.org/10.1117/12.2085005

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