Titania-doped quartz glass and making method, EUV lithographic member and photomask substrate
AssigneeShin-Etsu Chemical Co., Ltd.
InventorsShigeru Maida, Motoyuki Yamada
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Abstract
A titania-doped quartz glass containing 3-12 wt % of titania at a titania concentration gradient less than or equal to 0.01 wt %/μm and having an apparent transmittance to 440 nm wavelength light of at least 30% at a thickness of 6.35 mm is of such homogeneity that it provides a high surface accuracy as required for EUV lithographic members, typically EUV lithographic photomask substrates.
Claims15
A titania-doped quartz glass containing 3 to 12% by weight of titania at a titania concentration gradient less than or equal to 0.01 wt %/μm and having an apparent transmittance to 440 nm wavelength light of at least 30% at a thickness of 6.35 mm.
A method for preparing a titania-doped quartz glass, comprising the steps of subjecting a silicon source gas and a titanium source gas to flame hydrolysis with the aid of a combustible gas and a combustion-supporting gas in a furnace, to thereby form synthetic silica fine particles, depositing the silica fine particles on a rotating target, and concurrently melting and vitrifying the deposited silica into titania-doped quartz glass, wherein
- the target is rotated at a speed of at least 5 rpm,
- the flow rates of the silicon source gas, the titanium source gas, the combustible gas and the combustion-supporting gas are controlled to a variation within ±1%/hr, and
- the temperatures of the gases fed into or taken out of the furnace and the ambient atmosphere surrounding the furnace are controlled to a variation within ±2.5° C.
Dependencies are inferred from the claim text.