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Proceedings Paper

Reflection control in hyper-NA immersion lithography
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Paper Abstract

The impact of bottom reflection on critical dimension (CD) processing window is intensively investigated with a simulation using a full diffraction model (FDM) in which the effective reflectivity is calculated from standing wave amplitude. Most importantly, the optical phase shift of the reflection is used as a design criterion and was found to be the primary factor that affects the UV distribution, and, hence, has a strong impact on exposure latitude and depth of focus. Foot exposure (FE) is introduced as a new metric to characterize the phase shift. Some single-layer and dual-layer bottom anti-reflective coating (BARC) designs were implemented with an Exitech MS-193i immersion micro-stepper (NA=1.3) for 45-nm dense lines at the Resist Test Center (RTC) at International SEMATECH, Albany, New York. The experimental results show that FE is closely related to the CD processing window. In contrast to conventional BARC usage, a small amount of substrate reflection with a controlled optical phase shift dramatically improves CD processing window.

Paper Details

Date Published: 1 April 2008
PDF: 7 pages
Proc. SPIE 6924, Optical Microlithography XXI, 69244A (1 April 2008); doi: 10.1117/12.772899
Show Author Affiliations
Zhimin Zhu, Brewer Science, Inc. (United States)
Emil Piscani, International SEMATECH (United States)
Kevin Edwards, Brewer Science, Inc. (United States)
Brian Smith, Brewer Science, Inc. (United States)

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

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