Mr. Afu Chiu Profile

Afu Chiu

at Qoniac Taiwan Ltd

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Author

Publications (3)

Proceedings Article | 10 April 2024 Poster + Paper

Overlay control improvements through dynamic sampling

Onur Demirer, Robin Maximilian Zech, Chao-Jen Tsou, W. Wang, C. Huang, Elvis Yang, Afu Chiu, Alexander Muehle, Holger Bald, Clemens Utzny, Scott Eitapence, Boris Habets, Norman Birnstein

Proceedings Volume 12955, 1295527 (2024) https://doi.org/10.1117/12.3009830

KEYWORDS: Semiconducting wafers, Overlay metrology, Control systems, Simulations, Scanners, Metrology, Lithography, Advanced process control, High volume manufacturing

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Proceedings Article | 28 April 2023 Poster + Paper

Development of novel focus spot detection methods for high-volume manufacturing

Syed Naime Mohammad, Chao-Jen Tsou, Afu Chiu, Norman Birnstein, Erick deGouw, Clemens Utzny, Philip Groeger, Stefan Buhl, W. Wang, C. Huang, Elvis Yang, T. Yang, K. Chen

Proceedings Volume 12494, 1249415 (2023) https://doi.org/10.1117/12.2657965

KEYWORDS: Semiconducting wafers, Scanners, Contamination, High volume manufacturing, Particles, Neodymium, Tunable filters, Defense systems, Sensors, Image enhancement

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Proceedings Article | 26 March 2019 Paper

Overlay run-to-run control based on device structure measured overlay in DRAM HVM

Hsiao Lun Chu, Foster Huang, Steven Tottewitz, Boris Habets, Patrick Lomtscher, Hsiao-Lin Hsu, Afu Chiu, Rex Liu

Proceedings Volume 10959, 109592P (2019) https://doi.org/10.1117/12.2515203

KEYWORDS: Overlay metrology, Etching, Device simulation, Feedback control, Lithography, Measurement devices, Semiconducting wafers, Control systems, High volume manufacturing, Inspection

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In leading edge lithography, overlay is usually controlled by feedback based on measurements on overlay targets, which are located between the dies. These measurements are done directly after developing the wafer. However, it is well-known that the measurement on the overlay marks does not always represent the actual device overlay correctly. This can be due to different factors, including mask writing errors, target-to-device differences and non-litho processing effects, for instance by the etch process.¹

In order to verify these differences, overlay measurements are regularly done after the final etch process. These post-etch overlay measurements can be performed by using the same overlay targets used in post-litho overlay measurement or other targets. Alternatively, they can be in-device measurements using electron beam measurement tools (for instance CD-SEM). The difference is calculated between the standard post-litho measurement and the post-etch measurement. The calculation result is known as litho-etch overlay bias.

This study focuses on the feasibility of post-etch overlay measurement run-to-run (R2R) feedback instead of post-lithography R2R feedback correction. It is known that the post-litho processes have strong non-linear influences on the in-device overlay signature and, hence, on the final overlay budget. A post-etch based R2R correction is able to mitigate such influences.²

This paper addresses several questions and challenges related to post-etch overlay measurement with respect to R2R feedback control. The behavior of the overlay targets in the scribe-line is compared to the overlay behavior of device structures. The influence of different measurement methodologies (optical image-based overlay vs. electron microscope overlay measurement) was evaluated. Scribe-line standard overlay targets will be measured with electron microscope measurement. In addition, the influence of the intra-field location of the targets on device-to-target shifts was evaluated.

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