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Proceedings Paper

Enhancing the applications space of diffraction based overlay metrology by increasing throughput and target pitch flexibility
Author(s): Simon Mathijssen; Herman Heijmerikx; Farzad Farhadzadeh; Marc Noot; Lineke van der Sneppen; Longfei Shen; Fei Jia; Jolly Xu; Huajun Qin; Arie den Boef; Elliott Mc Namara; Kaustuve Bhattacharyya; Chao Fang; Yaobin Feng
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Paper Abstract

Metrology requirements at advanced nodes are not only tightening on specifications but also broadening in terms of flexibility needed to cover variety of product stacks. Metrology targets need to be process compatible and at the same time these targets should also be readable by the metrology system. In some cases, process conditions require a target pitch that is large compared to the wavelength used by the metrology system. Examples of these situations include for instance topography transfer or stacks with thick resist (for e.g. 3D-NAND). Traditionally overlay is extracted from the asymmetry in the positive and negative first diffraction order generated from μDBO targets. However, when the pitch is large, the targets generate multiple higher diffraction orders. Current state-of-the-art diffraction based overlay systems do not take into account the effect of these higher diffraction orders and typically only select the first diffraction order. This is done by reducing the pitch of the target, tuning the wavelength or by changing the angle of incidence of the illumination light. To address wavelength over pitch flexibility an advanced algorithm was introduced on a new metrology system in the fab, providing full flexibility in the selection of measurement wavelength and pitch. To obey the specifications on accuracy and throughput, we will present a new metrology system that is, compared to its predecessor, about 2x faster and able to measure more accurately because of the ability to measure multiple wavelengths within the same time frame.

Paper Details

Date Published: 20 March 2020
PDF: 7 pages
Proc. SPIE 11325, Metrology, Inspection, and Process Control for Microlithography XXXIV, 113252L (20 March 2020); doi: 10.1117/12.2551899
Show Author Affiliations
Simon Mathijssen, ASML (Netherlands)
Herman Heijmerikx, ASML (Netherlands)
Farzad Farhadzadeh, ASML (Netherlands)
Marc Noot, ASML (Netherlands)
Lineke van der Sneppen, ASML (Netherlands)
Longfei Shen, ASML (Netherlands)
Fei Jia, ASML (Netherlands)
Jolly Xu, ASML (Netherlands)
Huajun Qin, ASML (Netherlands)
Arie den Boef, ASML (Netherlands)
Elliott Mc Namara, ASML (Netherlands)
Kaustuve Bhattacharyya, ASML (Netherlands)
Chao Fang, YMTC (China)
Yaobin Feng, YMTC (China)

Published in SPIE Proceedings Vol. 11325:
Metrology, Inspection, and Process Control for Microlithography XXXIV
Ofer Adan; John C. Robinson, Editor(s)

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