EUV mask surface cleaning effects on lithography process performance Page: 1 of 16
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EUV mask surface cleaning effects on lithography
process performance
Running title: EUV mask surface cleaning effects on lithography process performance
Running Authors: George, Naulleau, Chen, and Liang
Simi A. Georgea), Lorie Mae Baclea-an and Patrick P. Naulleau
Center for X-ray Optics, Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, CA, 94720
Robert J. Chen and Ted Liang
Intel Corporation, Santa Clara, CA 95052
a)Electronic Mail: sapeorpeIlbl.pov
Material Names: Carbon, Ruthenium, Hexamethyldisilazane
The reflective, multilayer based, mask architectures for extreme ultraviolet (EUV) lithography
are highly susceptible to surface oxidation and contamination. As a result, EUV masks are
expected to undergo cleaning processes in order to maintain the lifetimes necessary for high
volume manufacturing. For this study, the impact of repetitive cleaning of EUV masks on
imaging performance was evaluated. Two, high quality industry standard, EUV masks are used
for this study with one of the masks undergoing repeated cleaning and the other one kept as a
reference. Lithographic performance, in terms of process window analysis and line edge
roughness, was monitored after every two cleans and compared to the reference mask
performance. After 8x clean, minimal degradation is observed. The cleaning cycles will be
continued until significant loss imaging fidelity is found.
1. Introduction
Extreme ultraviolet lithography (EUVL) 1-4 mask lifetime is one of the critical challenges
to be resolved as the technology is being prepared for high volume manufacturing (HVM). The
reflective, multilayer based, mask architectures requisite for EUVL are highly susceptible to
surface oxidation and contamination. Contamination of the EUV reticle due to various surface
deposition processes leads to the loss of image contrast and exposure latitude in patterning' 7. As
a result, achieving workable mask lifetimes necessitate the cleaning of contaminated masks. For
this purpose, several mask cleaning methods are being investigated"'9.
For a mask cleaning process to be practical, negligible negative impact on mask
performance after repeated cleaning is a requirement. Mask surface damage and the increased
LER that may result from repetitive cleaning still remains a concern. We recently reported
lithographic performance comparison of a contaminated mask that was cleaned to a new
uncontaminated mask10. Our findings indicated that the performance was not significantly
affected by the cleaning process while the cleaning process effectively removed significant
amount of deposits from the mask pattern sidewalls. Another completed study involved a mask
with an outdated architecture, which was imaged before and after cleaning. Lithographic
performance analysis showed that the observed resist LER increased significantly after
undergoing an intentionally aggressive multiple cleans test.
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George, Simi; Baclea-an, Lorie Mae; Naulleau, Patrick; Chen, Robert J. & Liang, Ted. EUV mask surface cleaning effects on lithography process performance, article, June 18, 2010; Berkeley, California. (https://digital.library.unt.edu/ark:/67531/metadc1013997/m1/1/: accessed April 25, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.