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Proceedings Paper

Lens heating challenges for negative tone develop layers with freeform illumination: a comparative study of experimental vs. simulated results
Author(s): Scott Halle; Michael Crouse; Aiqin Jiang; Youri van Dommelen; Tim Brunner; Blandine Minghetti; Matt Colburn; Youping Zhang
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Paper Abstract

Negative tone development (NTD) processes have been widely explored as a way to enhance the printability of dark field features such as contact holes and trenches. A key consequence of implementing NTD processes and subsequent tone reversal of dark field reticles is the significantly higher transmission of bright field masks and thus higher light intensity in the projection optics. This large increase in mask transmission coupled with the higher throughput requirements of multiple patterning and the use of freeform illumination created by source mask optimization creates a significant amount of lens heating induced aberrations that must be characterized and mitigated. In this paper, we examine the lens heating induced aberrations for high transmission reticles common to NTD using both simulations and experiments on a 193 immersion lithography tool. We observe a substantial amount of aberrations as described by even and odd order Zernike drifts during the course of a wafer exposure lot. These Zernike drifts per lot are demonstrated to have the following lithographic effects: critical dimension shifts, pitch dependent best focus shifts and image placement errors between coarse and fine patterned features. Lastly, mitigation strategies are demonstrated using various controllers and lens manipulators, including FlexWave with full Zernike control up to Z64, to substantially reduce the lens heating effects observed on-wafer.

Paper Details

Date Published: 21 February 2012
PDF: 19 pages
Proc. SPIE 8326, Optical Microlithography XXV, 832607 (21 February 2012); doi: 10.1117/12.916312
Show Author Affiliations
Scott Halle, IBM Research (United States)
Michael Crouse, ASML (United States)
Aiqin Jiang, ASML (United States)
Youri van Dommelen, ASML (United States)
Tim Brunner, IBM Research (United States)
Blandine Minghetti, ASML (United States)
Matt Colburn, IBM Research (United States)
Youping Zhang, Brion Technologies, Inc. (United States)

Published in SPIE Proceedings Vol. 8326:
Optical Microlithography XXV
Will Conley, Editor(s)

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