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Proceedings Paper

Interaction forces on mask surfaces relevant to EUV lithography
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Paper Abstract

Due to the increasing impact of smaller particles, mask cleaning continues to become more and more challenging in EUV lithography. To improve mask cleaning efficiency, advances in the fundamental understanding of the interaction between defect particles and mask surfaces are necessary. For this reason, surface force measurements were performed with an atomic force microscope on various mask surfaces relevant to EUV lithography. Experiments in air were carried out to illustrate particle interaction during mask transport and storage, while measurements in deionized ultrapure water were undertaken to investigate the influence of a basic cleaning chemistry. The effects of particle size were studied using SiNx tips with a nominal radius of 10 nm and spherical SiO2 probes with a radius of 500 nm. Particle interactions with mask surfaces in air were characterized by adhesion. Due to comparable surface roughness and surface chemistry, adhesion forces of a quartz mask substrate and a mask blank were similar. However, for a SiO2 sphere, the absolute values of the measured adhesive forces were greater than for a conventionally fabricated SiNx tip consistent with the probes' relative radii. Using a quartz mask substrate and deionized water as the intervening medium, the probe-substrate interaction observed was no longer characterized by attraction, but dominated by repulsive forces and hence potentially advantageous for cleaning purposes.

Paper Details

Date Published: 20 October 2006
PDF: 7 pages
Proc. SPIE 6349, Photomask Technology 2006, 63493E (20 October 2006); doi: 10.1117/12.687175
Show Author Affiliations
R. Hübner, Univ. at Albany, SUNY (United States)
S. Eichenlaub, SEMATECH, Inc. (United States)
A. Rastegar, SEMATECH, Inc. (United States)
R. Geer, Univ. at Albany, SUNY (United States)

Published in SPIE Proceedings Vol. 6349:
Photomask Technology 2006
Patrick M. Martin; Robert J. Naber, Editor(s)

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