Improved multi-lot overlay performance via phase-based ADI overlay measurements

Doogyu Lee; Jungmin Lee; Eunji Lee; Jeongjin Lee; Seung Yoon Lee; Chan Hwang; Pieter Kapel; Seung-Bin Yang; Mi-Yeon Baek; Jeroen Wefers Bettink; Se-Ra Jeon; Thomas Kim; Aileen Soco; Olger Zwier; Koen van Witteveen

doi:10.1117/12.2627719

26 May 2022 Improved multi-lot overlay performance via phase-based ADI overlay measurements

Doogyu Lee, Jungmin Lee, Eunji Lee, Jeongjin Lee, Seung Yoon Lee, Chan Hwang, Pieter Kapel, Seung-Bin Yang, Mi-Yeon Baek, Jeroen Wefers Bettink, Se-Ra Jeon, Thomas Kim, Aileen Soco, Olger Zwier, Koen van Witteveen

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Proceedings Volume 12053, Metrology, Inspection, and Process Control XXXVI; 1205316 (2022) https://doi.org/10.1117/12.2627719
Event: SPIE Advanced Lithography + Patterning, 2022, San Jose, California, United States

Abstract

State of the art after-develop (ADI) overlay is measured with multi-wavelength micro diffraction-based overlay techniques. A micro diffraction-based overlay target consists of two pairs of gratings, with the same pitch in the top and bottom layer. The gratings in the top layer have a bias offset with respect to the bottom layer in the positive or negative direction. When illuminated, +1st and -1st order light is diffracted. The asymmetry in the intensity of these signals contains the overlay information. In this paper, ADI overlay is measured with a new dark-field target design for ADI overlay. Like a micro diffraction-based overlay target, it consists of pairs of gratings in the top and bottom layer. Instead of a bias offset between top and bottom gratings, different pitches are used resulting in a continuous-bias throughout the grating pair. When illuminated the diffracted light contains moiré fringes, in which the overlay is stored in the phases. This technique has improved accuracy and robustness by design, because it is immune to symmetrical process changes like stack height variations and grating imbalance. Additionally, it shows more stable behavior through wavelength, both in signal strength and overlay. These characteristics make it possible, with a single wavelength, to achieve similar or better performance than micro diffraction-based overlay using a multi-wavelength solution, resulting in higher throughput. This is demonstrated on Samsung’s latest memory node where on average an 21% reduction is achieved in the 3sigma of the mis reading correction with a single-wavelength phase-based overlay measurements, compared to multi-wavelength micro diffraction-based overlay measurements.

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Doogyu Lee, Jungmin Lee, Eunji Lee, Jeongjin Lee, Seung Yoon Lee, Chan Hwang, Pieter Kapel, Seung-Bin Yang, Mi-Yeon Baek, Jeroen Wefers Bettink, Se-Ra Jeon, Thomas Kim, Aileen Soco, Olger Zwier, and Koen van Witteveen "Improved multi-lot overlay performance via phase-based ADI overlay measurements", Proc. SPIE 12053, Metrology, Inspection, and Process Control XXXVI, 1205316 (26 May 2022); https://doi.org/10.1117/12.2627719

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