Invented in the 1960s for demanding applications in astronomy, ULE^®, or ultra-low expansion glass, is a stable titania-silicate glass that exhibits virtually no dimensional changes over extreme temperature variation, making it the material of choice for reflective telescope optics.

The lithography transition from 193 nm to 13.5 nm required a major design shift in stepper optics from refractive to reflective. Produced primarily by flame hydrolysis, the thermal stability of ULE^® glass now makes it an ideal material for extreme ultraviolet lithography (EUV) in semiconductor chip manufacturing. This stability makes ULE glass ideal for applications where high-precision control is essential, such as photomask substrates, machine reference blocks, stepper optics, metrology, and other processes where any shift in material dimensions can compromise performance and accuracy. Combined with more than 60-years of ULE glass production, Corning continues to reduce inclusion and striae levels in the glass as well as offer improved CTE (Coefficient of Thermal Expansion) metrology capabilities.