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Proceedings Paper

Thermal management of EUV lithography masks using low-expansion glass substrates
Author(s): Steven E. Gianoulakis; Avijit K. Ray-Chaudhuri; Scott Daniel Hector
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Paper Abstract

Lithographic masks must maintain dimensional stability during exposure in a wafer stepper. In extreme UV lithography, multilayer coatings are deposited on a flat mask, substrate to make the mask surface reflective at EUV wavelengths. About 40 percent of the incident EUV radiation is absorbed by the multilayer coatings causing a temperature rise. The choice of mask substrate material affects dimensional stability due to thermal expansion and/or deformation. Finite element modeling has ben used to investigate the proper choice of mask substrate material and to explore the efficacy of various thermal management strategies. This modeling indicates that significant machine design and engineering challenges are necessary in order to employ Si as a mask substrate. Even if these challenges can be met, the thermal expansion of Si is likely to be too large to meet overlay error budgets for lithography at ground rules beyond the 100 nm technology node. ULE - a single phase, fused silica glass doped with titania - has near zero thermal expansion at the temperatures where EUV lithography is performed. Due to its small coefficient of thermal expansion, ULE does not undergo appreciable instantaneous or transient thermal expansion that results in image placement error.

Paper Details

Date Published: 25 June 1999
PDF: 8 pages
Proc. SPIE 3676, Emerging Lithographic Technologies III, (25 June 1999); doi: 10.1117/12.351133
Show Author Affiliations
Steven E. Gianoulakis, Sandia National Labs. (United States)
Avijit K. Ray-Chaudhuri, Sandia National Labs. (United States)
Scott Daniel Hector, Motorola (United States)

Published in SPIE Proceedings Vol. 3676:
Emerging Lithographic Technologies III
Yuli Vladimirsky, Editor(s)

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