Diffraction based overlay metrology: accuracy and performance on front end stack

Philippe Leray; Shaunee Cheng; Daniel Kandel; Michael Adel; Anat Marchelli; Irina Vakshtein; Mauro Vasconi; Bartlomiej Salski

doi:10.1117/12.772516

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22 March 2008 Diffraction based overlay metrology: accuracy and performance on front end stack

Philippe Leray, Shaunee Cheng, Daniel Kandel, Michael Adel, Anat Marchelli, Irina Vakshtein, Mauro Vasconi, Bartlomiej Salski

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Proceedings Volume 6922, Metrology, Inspection, and Process Control for Microlithography XXII; 69220O (2008) https://doi.org/10.1117/12.772516
Event: SPIE Advanced Lithography, 2008, San Jose, California, United States

Abstract

The overlay metrology budget is typically 1/10 of the overlay control budget resulting in overlay metrology total measurement uncertainty requirements of 0.57 nm for the most challenging use cases of the 32nm technology generation. Theoretical considerations show that overlay technology based on differential signal scatterometry (SCOL^TM) has inherent advantages, which will allow it to achieve the 32nm technology generation requirements and go beyond it. In this work we present results of an experimental and theoretical study of SCOL. We present experimental results, comparing this technology with the standard imaging overlay metrology. In particular, we present performance results, such as precision and tool induced shift, for different target designs. The response to a large range of induced misalignment is also shown. SCOL performance on these targets for a real stack is reported. We also show results of simulations of the expected accuracy and performance associated with a variety of scatterometry overlay target designs. The simulations were carried out on several stacks including FEOL and BEOL materials. The inherent limitations and possible improvements of the SCOL technology are discussed. We show that with the appropriate target design and algorithms, scatterometry overlay achieves the accuracy required for future technology generations.

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Philippe Leray, Shaunee Cheng, Daniel Kandel, Michael Adel, Anat Marchelli, Irina Vakshtein, Mauro Vasconi, and Bartlomiej Salski "Diffraction based overlay metrology: accuracy and performance on front end stack", Proc. SPIE 6922, Metrology, Inspection, and Process Control for Microlithography XXII, 69220O (22 March 2008); https://doi.org/10.1117/12.772516

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