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Proceedings Paper

In-die photomask registration and overlay metrology with PROVE using 2D correlation methods
Author(s): D. Seidel; M. Arnz; D. Beyer
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Paper Abstract

According to the ITRS roadmap, semiconductor industry drives the 193nm lithography to its limits, using techniques like double exposure, double patterning, mask-source optimization and inverse lithography. For photomask metrology this translates to full in-die measurement capability for registration and critical dimension together with challenging specifications for repeatability and accuracy. Especially, overlay becomes more and more critical and must be ensured on every die. For this, Carl Zeiss SMS has developed the next generation photomask registration and overlay metrology tool PROVE® which serves the 32nm node and below and which is already well established in the market. PROVE® features highly stable hardware components for the stage and environmental control. To ensure in-die measurement capability, sophisticated image analysis methods based on 2D correlations have been developed. In this paper we demonstrate the in-die capability of PROVE® and present corresponding measurement results for shortterm and long-term measurements as well as the attainable accuracy for feature sizes down to 85nm using different illumination modes and mask types. Standard measurement methods based on threshold criteria are compared with the new 2D correlation methods to demonstrate the performance gain of the latter. In addition, mask-to-mask overlay results of typical box-in-frame structures down to 200nm feature size are presented. It is shown, that from overlay measurements a reproducibility budget can be derived that takes into account stage, image analysis and global effects like mask loading and environmental control. The parts of the budget are quantified from measurement results to identify critical error contributions and to focus on the corresponding improvement strategies.

Paper Details

Date Published: 13 October 2011
PDF: 13 pages
Proc. SPIE 8166, Photomask Technology 2011, 81661E (13 October 2011); doi: 10.1117/12.896592
Show Author Affiliations
D. Seidel, Carl Zeiss SMS GmbH (Germany)
M. Arnz, Carl Zeiss SMT GmbH (Germany)
D. Beyer, Carl Zeiss SMS GmbH (Germany)

Published in SPIE Proceedings Vol. 8166:
Photomask Technology 2011
Wilhelm Maurer; Frank E. Abboud, Editor(s)

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