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Proceedings Paper

Study of stress birefringence for 193-nm immersion photomasks
Author(s): Eric Cotte; Michael Selle; Karsten Bubke; Silvio Teuber
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Paper Abstract

The goal of the present study was to investigate and quantify reticle stress birefringence in exposure conditions. Birefringence can arise in fused silica photomask substrates due to their state of stress, and cause optical effects such as phase front distortion, ray bifurcation, and polarization changes. These effects potentially produce image blurring and illumination non-uniformity, leading to lower resolution and CD variations, respectively. The main sources of substrate stress studied were the absorber stack, the mounting of a pellicle, and the impact of initial reticle bow when chucking in an exposure tool. Jones calculus was used to relate birefringence at discrete locations in the reticle, derived from the state of stress, to the net birefringence experienced by light passing through the mask. Experimentally-obtained birefringence data as well as analytical calculations of stress birefringence caused by known states of stress were used to validate the models. These results can then be compared to photomask birefringence specifications or employed in optical simulations to determine the precise impact of this substrate stress birefringence.

Paper Details

Date Published: 28 June 2005
PDF: 10 pages
Proc. SPIE 5853, Photomask and Next-Generation Lithography Mask Technology XII, (28 June 2005); doi: 10.1117/12.617034
Show Author Affiliations
Eric Cotte, Advanced Mask Technology Ctr. (Germany)
Michael Selle, SCHOTT Lithotec AG (Germany)
Karsten Bubke, Advanced Mask Technology Ctr. (Germany)
Silvio Teuber, Advanced Mask Technology Ctr. (Germany)

Published in SPIE Proceedings Vol. 5853:
Photomask and Next-Generation Lithography Mask Technology XII
Masanori Komuro, Editor(s)

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