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Proceedings Paper

Modeling for sub-50-nm x-ray application with phase masks
Author(s): James W. Taylor; Daniel H. Malueg; Franco Cerrina; Mumit Khan; Don Thielman
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Paper Abstract

The CNTech Advanced Lithography Toolset uses a beam propagation method to calculate the intensity profile as it propagates through the mask and into the photoresist. One can construct the membrane, absorber, gap, and resist, each as a series of n-slices to achieve unusually precise calculations. Here a clear X-ray phase mask is modeled with silicon nitride in a configuration called a Bright Peak Enhanced X-ray Phase Mask (BPEXPM). For the optimized structure of this mask, which relies on both diffraction and phase shifting to produce the reduced wafer image, four factors must be controlled; these are: absorber thickness - material and wavelength dependent, absorber wall slope, gap, and resist threshold. A central composite experimental design showed that a 100 nm mask would print a wafer at 35 nm CD using the 70% maximum intensity threshold when the wall slope was 0.5° from the vertical. Additionally: 1) a 100 nm increase in absorber thickness decreased the CD by 1.0 nm; 2) every 1.0 um increase in gap decreased the CD 0.8 nm; and 3) every 1.0 nm increase in mask CD increased the linewidth only 0.1 nm. Other mask processing materials were examined in addition to the 180° (π) phase-shift absorber thickness. Experimental verifications of the modeling results are in progress to demonstrate device construction for devices with lower wafer coverage than would be required for memory devices.

Paper Details

Date Published: 20 May 2004
PDF: 5 pages
Proc. SPIE 5374, Emerging Lithographic Technologies VIII, (20 May 2004); doi: 10.1117/12.535422
Show Author Affiliations
James W. Taylor, Univ. of Wisconsin/Madison (United States)
Daniel H. Malueg, Univ. of Wisconsin/Madison (United States)
Franco Cerrina, Univ. of Wisconsin/Madison (United States)
Mumit Khan, BRAC Univ. (Bangladesh)
Don Thielman, Univ. of Wisconsin/Madison (United States)

Published in SPIE Proceedings Vol. 5374:
Emerging Lithographic Technologies VIII
R. Scott Mackay, Editor(s)

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