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Proceedings Paper

The flash memory battle: How low can we go?
Author(s): Eelco van Setten; Onno Wismans; Kees Grim; Jo Finders; Mircea Dusa; Robert Birkner; Rigo Richter; Thomas Scherübl
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Paper Abstract

With the introduction of the TWINSCAN XT:1900Gi the limit of the water based hyper-NA immersion lithography has been reached in terms of resolution. With a numerical aperture of 1.35 a single expose resolution of 36.5nm half pitch has been demonstrated. However the practical resolution limit in production will be closer to 40nm half pitch, without having to go to double patterning alike strategies. In the relentless Flash memory market the performance of the exposure tool is stretched to the limit for a competitive advantage and cost-effective product. In this paper we will present the results of an experimental study of the resolution limit of the NAND-Flash Memory Gate layer for a production-worthy process on the TWINSCAN XT:1900Gi. The entire gate layer will be qualified in terms of full wafer CD uniformity, aberration sensitivities for the different wordlines and feature-center placement errors for 38, 39, 40 and 43nm half pitch design rule. In this study we will also compare the performance of a binary intensity mask to a 6% attenuated phase shift mask and look at strategies to maximize Depth of Focus, and to desensitize the gate layer for lens aberrations and placement errors. The mask is one of the dominant contributors to the CD uniformity budget of the flash gate layer. Therefore the wafer measurements are compared to aerial image measurements of the mask using AIMSTM 45-193i to separate the mask contribution from the scanner contribution to the final imaging performance.

Paper Details

Date Published: 11 April 2008
PDF: 14 pages
Proc. SPIE 6924, Optical Microlithography XXI, 69244I (11 April 2008); doi: 10.1117/12.773266
Show Author Affiliations
Eelco van Setten, ASML Netherlands B.V. (Netherlands)
Onno Wismans, ASML Netherlands B.V. (Netherlands)
Kees Grim, ASML Netherlands B.V. (Netherlands)
Jo Finders, ASML Netherlands B.V. (Netherlands)
Mircea Dusa, ASML TDC (United States)
Robert Birkner, Carl Zeiss SMS GmbH (Germany)
Rigo Richter, Carl Zeiss SMS GmbH (Germany)
Thomas Scherübl, Carl Zeiss SMS GmbH (Germany)

Published in SPIE Proceedings Vol. 6924:
Optical Microlithography XXI
Harry J. Levinson; Mircea V. Dusa, Editor(s)

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