Apparatus for producing synthetic quartz glass

  • US 6,920,766 B2
  • Filed: 05/30/2002
  • Issued: 07/26/2005
  • Est. Priority Date: 03/07/1997
  • Status: Expired due to Fees
First Claim
Patent Images

1. An apparatus for producing a synthetic quartz glass preform by flame hydrolysis which is adapted for application of high-energy DUV-radiation in the wavelength range under 250 nm, has a leading plateau surface followed by a parabolic surface which is followed by a cylindrical surface, a core with an OH-content of ≧

  • 1150 ppm, a strain birefringence of ≦

    5 nm/cm, a H2-content of ≧



    1018 molecules/cm3, a CI-content of ≦

    20 ppm, an amount of contaminating trace elements Cr, Co, Fe, Ni, Cu, V, Zn, Al, Li, K, Na up to 500 ppb and which is substantially free of stratifications, and has a stability of which towards high-energy DUV-radiation is given by a transmissions reduction of Δ

    T ≦

    0.1%/cm thickness, when the synthetic quartz glass is subjected to the following radiation, wavelength λ

    1=248 nm, laser shot frequency ≧

    300 Hz, laser shot rate ≧

    109, and energy density ≦

    10 mJ/cm2, as well as wavelength λ

    2=193 nm, laser shot frequency ≧

    300 Hz, laser shot rate ≧

    109, and energy density ≦

    5 mJ/cm2, the apparatus comprising;

    a burner having nozzles providing a silicon compound, hydrogen and oxygen and forming melted particles of a silicon composition at a temperature of at least 2,000°

    C.;

    a preform supporting arrangement for rotatably supporting the preform to rotate about a horizontal rotation axis;

    a horizontally arranged muffle, the muffle comprising an internal chamber extending horizontally, a larger opening and a smaller opening communicating with the chamber on opposite horizontal sides of the muffle;

    the larger opening being adapted for removing the preform and being open for exhausting gases;

    the smaller one for receiving the burner and being open around the burner for intaking air from the surrounding environment;

    the chamber substantially gradually narrowing from the larger opening to the smaller opening, the chamber having a parabolic portion adapted to envelope the parabolic surface of said preform at a distance “

    a”

    in the range of 5 mm to 100 mm, at least said parabolic portion being at least approximately rotation-symmetrical to the axis of rotation of said preform; and

    the burner being disposed opposite the plateau surface at a position having a central burner axis offset from and substantially parallel to the horizontal rotation axis so as to deposit the melted particles at a temperature of at least 2,000°

    C. on the plateau surface.

View all claims
    ×
    ×

    Thank you for your feedback

    ×
    ×