Synthetic quartz glass preform and device for the production thereof

• US 20020148256A1
• Filed: 05/30/2002
• Published: 10/17/2002
• Est. Priority Date: 03/07/1997
• Status: Active Grant

• Current Assignee: J-Fiber GmbH (Leoni AG)
• Original Assignee: Schott ML GmbH
• Inventors: Menzel, Andreas, Voitsch, Andreas, Coriand, Frank
• Granted Patent: US 6,920,766 B2
• Time in Patent Office: Days
• US Class Current: 65/144
• CPC Class Codes: C03B 19/1407 Deposition reactors therefor
• CPC Class Codes: C03B 19/1423 Reactant deposition burners
• CPC Class Codes: C03B 2201/07 Impurity concentration specified
• CPC Class Codes: C03B 2201/21 doped with molecular hydrogen
• CPC Class Codes: C03B 2201/23 doped with hydroxyl groups
• CPC Class Codes: C03B 2207/62 Distance
• CPC Class Codes: C03C 2201/21 containing molecular hydrogen
• CPC Class Codes: C03C 2201/23 containing hydroxyl groups
• CPC Class Codes: C03C 2203/40 Gas-phase processes
• CPC Class Codes: C03C 3/06 with more than 90% silica by weight, e.g. quartz C03C3/045 takes precedence
• CPC Class Codes: C03C 4/0085 for UV-transmitting glass

Abstract

A synthetic quartz glass preform is produced by flame hydrolysis with subsequent cooling and is suitable for the application of high-energy DUV radiation in the wave length range under 250 nm. The preform has a core area which contains ≧1150 ppm OH, a strain double refraction of ≦5 nm/cm and a resistance to high-energy DUV radiation as a result of a transmission reduction of ΔT≦0.1%/cm thickness. The quartz glass has been exposed to the following radiation: wavelength λ₁=248 nm, laser shot frequency≧300 Hz, laser shot value≧10⁹ and lumination≦10 mJ/cm², and wavelength λ₂=193 nm, laser shot frequency≧300 Hz, laser shot value≧10⁹ and lumination<5 mJ/cm². Apparatus for producing the preform comprises a horizontally positioned muffle with two different sized openings facing each other. The larger of the openings is for removing the preform, the smaller opening being for introducing a burner. The internal chamber of the muffle narrows from the larger opening to the smaller opening.

Claims

1. Apparatus for producing a synthetic quartz glass preform by flame hydrolysis while being rotated about an axis of rotation thereof and with subsequent cooling and which is adapted for application of high-energy DUV-radiation in the wavelength range under 250 nm, the preform having a core with an OH-content of ≧

1150 ppm, a strain birefringence of ≦

5 nm/cm, a H₂-content of ≧

1·

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 the 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 horizontally arranged muffle, the muffle comprising an internal chamber, a larger opening and a smaller opening communicating with the chamber on opposite sides of the muffle, the larger opening being adapted for removing the preform and the smaller one for receiving a burner, the chamber substantially gradually narrowing from the larger opening to the smaller opening, the chamber having a portion adapted to envelope said preform, at least said portion being at least approximately rotation-symmetrical to the axis of rotation of said preform.

2. Apparatus as claimed in claim 1, wherein the entire length of the muffle is at least equal to double the diameter of the preform.

3. Apparatus as claimed in claim 1, wherein the chamber has a center adapted to receive a leading face of the preform.

4. Apparatus as claimed in claim 1, wherein the muffle is comprised of three superimposed shells.

5. Apparatus as claimed in claim 1, wherein the chamber is so dimensioned that a distance from a surface of the preform to a nearest surface of the chamber is 5 to 100 mm.

6. Apparatus as claimed in claim 1, further comprising a burner and wherein the distance of the burner to a position in the chamber where the leading face of the preform is received is 135 to 350 mm.

7. Device as claimed in claim 11, wherein the smaller opening has a diameter of 50 to 100 mm.