Patent · US Active

Blank made of titanium-doped silica glass and method for the production thereof

US9540271B2 · kind B2 · utility

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1References

20Claims

0Family size

Assignee

HERAEUS QUARZGLAS GMBH & CO. KG · DE

Inventors

Klaus Becker · Hanau, DE
Stefan Ochs · Bad Camberg, DE
Stephan Thomas · Großkrotzenburg, DE

Key dates

Filing date	Jun 24, 2015
Grant date	Jan 10, 2017
Priority date	—
Expiry date	Jun 24, 2035

Classification

Technology area (CPC C)Chemistry; Metallurgy
CPC primaryC03C2203/50
WIPO fieldOther special machines
WIPO sectorMechanical engineering

Abstract

A blank made of titanium-doped silica glass for a mirror substrate for use in EUV lithography is provided. The blank includes a surface portion to be provided with a reflective film and having an optically used area (CA) over which a coefficient of thermal expansion (CTE) has a two-dimensional inhomogeneity (dCTE) distribution profile averaged over a thickness of the blank. A maximum inhomogeneity (dCTEmax) of less than 5 ppb/K is defined as a difference between a CTE maximum value and a CTE minimum value. The dCTEmax is at least 0.5 ppb/K. The CA forms a non-circular area having a centroid. The dCTE distribution profile is not rotation-symmetrical and is defined over the CA, such that straight profile sections normalized to a unit length and extending through the centroid of the area yield a dCTE family of curves forming a curve band with a bandwidth of less than 0.5×dCTEmax.

Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.