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ULE ® Glass with Improved Thermal Properties for EUVL Masks and Projection Optics Substrates
Author(s) -
Hrdina Kenneth E.,
Duran Carlos A.
Publication year - 2014
Publication title -
international journal of applied glass science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.383
H-Index - 34
eISSN - 2041-1294
pISSN - 2041-1286
DOI - 10.1111/ijag.12041
Subject(s) - extreme ultraviolet lithography , materials science , substrate (aquarium) , thermal expansion , projection (relational algebra) , thermal , optics , range (aeronautics) , atmospheric temperature range , composite material , optoelectronics , thermodynamics , physics , computer science , algorithm , oceanography , geology
Ultra‐ L ow E xpansion ULE ® Glass is the material of choice for substrates for masks and projection optics mirrors in EUV lithography. A key parameter is the temperature of zero crossover ( T zc ), which is the temperature at which the coefficient of thermal expansion (expansivity, α( T )) is equal to zero. As the temperature of the glass departs from T zc , the absolute value of α( T ) increases proportionally to the slope of the expansivity curve. As EUVL matures, substrates will experience wider temperature changes, while higher resolution demands tighter constrains in substrate deformation. We present data showing that through modification of the fictive temperature of the glass, T f , the expansivity slope can be lowered. This is combined with better control of T zc , which can be tuned to a narrower range to better match the requirements of each substrate. Depending on the application, performance improvements can exceed 30% with respect to traditional ULE ® Glass.