18 June 2007 Differential signal scatterometry overlay metrology: an accuracy investigation
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Abstract
The overlay control budget for the 32nm technology node will be 5.7nm according to the ITRS. The overlay metrology budget is typically 1/10 of the overlay control budget resulting in overlay metrology total measurement uncertainty (TMU) requirements of 0.57nm for the most challenging use cases of the 32nm node. The current state of the art imaging overlay metrology technology does not meet this strict requirement, and further technology development is required to bring it to this level. In this work we present results of a study of an alternative technology for overlay metrology - Differential signal scatterometry overlay (SCOL). Theoretical considerations show that overlay technology based on differential signal scatterometry has inherent advantages, which will allow it to achieve the 32nm technology node requirements and go beyond it. We present results of simulations of the expected accuracy associated with a variety of scatterometry overlay target designs. We also present our first experimental results of scatterometry overlay measurements, comparing this technology with the standard imaging overlay metrology technology. In particular, we present performance results (precision and tool induced shift) and address the issue of accuracy of scatterometry overlay. We show that with the appropriate target design and algorithms scatterometry overlay achieves the accuracy required for future technology nodes.
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Daniel Kandel, Daniel Kandel, Mike Adel, Mike Adel, Berta Dinu, Berta Dinu, Boris Golovanevsky, Boris Golovanevsky, Pavel Izikson, Pavel Izikson, Vladimir Levinski, Vladimir Levinski, Irina Vakshtein, Irina Vakshtein, Philippe Leray, Philippe Leray, Mauro Vasconi, Mauro Vasconi, Bartlomiej Salski, Bartlomiej Salski, } "Differential signal scatterometry overlay metrology: an accuracy investigation", Proc. SPIE 6616, Optical Measurement Systems for Industrial Inspection V, 66160H (18 June 2007); doi: 10.1117/12.725929; https://doi.org/10.1117/12.725929
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