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Proceedings Paper

Wafer-shape based in-plane distortion predictions using superfast 4G metrology
Author(s): Leon van Dijk; Jeffrey Mileham; Ilja Malakhovsky; David Laidler; Harold Dekkers; Sven Van Elshocht; Doug Anberg; David M. Owen; Richard van Haren
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Paper Abstract

With the latest immersion scanners performing at the sub-2 nm overlay level, the non-lithography contributors to the OnProduct-Overlay budget become more and more dominant. Examples of these contributors are etching, thin film deposition, Chemical-Mechanical Planarization and thermal anneal. These processes can introduce stress or stress changes in the thin films on top of the silicon wafers, resulting in significant wafer grid distortions. High-order wafer alignment (HOWA) is the current ASML solution for correcting wafers with a high order grid distortion introduced by non-lithographic processes, especially when these distortions vary from wafer-to-wafer. These models are currently successfully applied in high volume production at several semiconductor device manufacturers. An important precondition is that the wafer distortions remain global as the polynomial-based HOWA models become less effective for very local distortions. Wafer-shape based feed forward overlay corrections can be a possible solution to overcome this challenge. Thin film stress typically has an impact on the unclamped, free-form shape of the wafers. When an accurate relationship between the wafer shape and in-plane distortion (IPD) after clamping is established then feedforward overlay control can be enabled. In this work we assess the capability of wafer-shape based IPD predictions via a controlled experiment. The processinduced IPDs are accurately measured on the ASML TWINSCANTM system using its SMASH alignment system and the wafer shapes are measured on the Superfast 4G inspection system. In order to relate the wafer shape to the IPD we have developed a prediction model beyond the standard Stoney approximation. The match between the predicted and measured IPD is excellent (~1-nm), indicating the feasibility of using wafer shape for feed-forward overlay control.

Paper Details

Date Published: 28 March 2017
PDF: 13 pages
Proc. SPIE 10145, Metrology, Inspection, and Process Control for Microlithography XXXI, 101452L (28 March 2017); doi: 10.1117/12.2257475
Show Author Affiliations
Leon van Dijk, ASML Netherlands B.V. (Netherlands)
Jeffrey Mileham, Ultratech, Inc. (United States)
Ilja Malakhovsky, ASML Netherlands B.V. (Netherlands)
David Laidler, IMEC (Belgium)
Harold Dekkers, IMEC (Belgium)
Sven Van Elshocht, IMEC (Belgium)
Doug Anberg, Ultratech, Inc. (United States)
David M. Owen, Ultratech, Inc. (United States)
Richard van Haren, ASML Netherlands B.V. (Netherlands)

Published in SPIE Proceedings Vol. 10145:
Metrology, Inspection, and Process Control for Microlithography XXXI
Martha I. Sanchez, Editor(s)

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