Method for producing titanium-doped synthetic quartz glass

• US 9,796,617 B2
• Filed: 02/07/2014
• Issued: 10/24/2017
• Est. Priority Date: 02/12/2013
• Status: Active Grant

• Current Assignee: Heraeus Quarzglas GmbH & Co. KG (Heraeus Holding GMBH)
• Original Assignee: Heraeus Quarzglas GmbH & Co. KG (Heraeus Holding GMBH)
• Inventors: Fabian, Heinz, Thomas, Stephan
• Primary Examiner(s): Franklin, Jodi C
• Application Number:
  US14/767,466
• Publication Number:
  US 20150376047A1
• Time in Patent Office: 1,355 Days
• CPC Class Codes: C03B 19/14 by gas- or vapour- phase reaction processes
• CPC Class Codes: C03B 19/1415 Reactant delivery systems
• CPC Class Codes: C03B 2201/12 doped with fluorine C03B2201/14 takes precedence
• CPC Class Codes: C03B 2201/42 doped with titanium
• CPC Class Codes: C03B 2207/32 Non-halide
• CPC Class Codes: C03B 2207/34 Liquid, e.g. mist or aerosol
• CPC Class Codes: C03C 2201/42 containing titanium
• 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

Abstract

A method for producing titanium-doped synthetic quartz glass includes:

• • (A) providing a liquid SiO₂ feedstock material that comprises more than 60% by weight of the polyalkylsiloxane D4;
  • (B) evaporating the liquid SiO₂ feedstock material to produce a gaseous SiO₂ feedstock vapor;
  • (C) evaporating a liquid TiO2 feedstock material to produce a gaseous TiO2 feedstock vapor;
  • (D) converting the SiO₂ feedstock vapor and the TiO2 feedstock vapor into SiO2 particles and TiO2 particles, respectively;
  • (E) depositing the SiO2 particles and the TiO2 particles on a deposition surface while forming a titanium-doped SiO₂ soot body;
  • (F) vitrifying the titanium-doped SiO₂ soot body while forming the synthetic quartz glass, whereby the TiO2 concentration of the synthetic quartz glass is between 5% by weight and 11% by weight.

The liquid SiO₂ feedstock material comprises at least one additional component made of the polyalkylsiloxane D3 having a weight fraction of mD3 and one additional component made of the polyalkylsiloxane D5 having a weight fraction of mD5 at a weight ratio of mD3/mD5 in a range of 0.01 to 1, and the liquid SiO₂ feedstock material provided is evaporated while maintaining the weight ratio of mD3/mD5 and at least 99% by weight thereof are evaporated to form the gaseous SiO₂ feedstock vapor.

Claims

1. A method for producing titanium-doped synthetic quartz glass comprising:

(A) providing a liquid SiO₂ feedstock material comprising more than 60% by weight of the polyalkylsiloxane D4;

(B) evaporating the liquid SiO₂ feedstock material to produce a gaseous SiO₂ feedstock vapor;

(C) evaporating a liquid TiO2 feedstock material to produce a gaseous TiO2 feedstock vapor;

(D) converting the SiO₂ feedstock vapor and the TiO2 feedstock vapor into SiO2 particles and TiO2 particles, respectively;

(E) depositing the SiO2 particles and the TiO2 particles on a deposition surface while forming a titanium-doped SiO₂ soot body;

(F) vitrifying the titanium-doped SiO₂ soot body while forming the synthetic quartz glass, whereby the TiO2 concentration of the synthetic quartz glass is between 5% by weight and 11% by weight;

wherein the liquid SiO₂ feedstock material comprises at least one additional component made of the polyalkylsiloxane D3 having a weight fraction of mD3 and one additional component made of the polyalkylsiloxane D5 having a weight fraction of mD5 at a weight ratio of mD3/mD5 in a range of 0.01 to 1, and the liquid SiO₂ feedstock material provided is evaporated while maintaining the weight ratio of mD3/mD5 and at least 99% by weight thereof are evaporated to form the gaseous SiO₂ feedstock vapor.

2. The method according to claim 1, wherein the evaporation comprises:

heating the TiO2 feedstock material; and

introducing the heated TiO2 feedstock material into an expansion chamber such that at least a first portion of the TiO2 feedstock material evaporates as a result of a drop in pressure.

3. The method according to claim 1, wherein the evaporation comprises:

heating the TiO2 feedstock material;

introducing the heated TiO2 feedstock material into an expansion chamber; and

mixing the TiO2 feedstock material with a heated diluting agent such that at least a second portion of the TiO2 feedstock material evaporates as a result of a lowering of the dew point.

4. The method according to claim 2, wherein at least 99.95% by weight of the TiO2 feedstock material is transitioned into the TiO₂ feedstock vapor as a result of the drop in pressure and/or lowering of the partial pressure.

5. The method according to claim 1, wherein the TiO2 concentration of the synthetic quartz glass is between 7% by weight and 10% by weight.

6. The method according to claim 5, wherein the TiO2 concentration of the synthetic quartz glass is between 7.8% by weight and 8.9% by weight.

7. The method according to claim 1, wherein the Ti3+ concentration of the synthetic quartz glass is between 1 ppm and 200 ppm.

8. The method according to claim 7, wherein the Ti3+ concentration of the synthetic quartz glass is between 1 ppm and 20 ppm.

9. The method according to claim 1, wherein a variation □

Ti3+/Ti3+ of the Ti3+ concentration of the synthetic quartz glass at a surface used for optical purposes is 0.8 or less.

10. The method according to claim 9, wherein a variation □

Ti3+/Ti3+ of the Ti3+ concentration of the synthetic quartz glass at a surface used for optical purposes is between 0.0002 and 0.5.

11. The method according to claim 1, wherein the internal transmission at a path length of 1 mm in a wavelength range from 400 nm to 700 nm is at least 80%.

12. The method according to claim 11, wherein the internal transmission at a path length of 1 mm in a wavelength range from 400 nm to 700 nm is at least 90%.

13. The method according to claim 1, wherein a fictive temperature of the synthetic quartz glass is maximally 1,050°

C.

14. The method according to claim 13, wherein a fictive temperature of the synthetic quartz glass is maximally 950°

C.

15. The method according to claim 1, wherein the thermal expansion coefficient in a temperature window from 0°

C. to 100°

C. is maximally 0±

150 ppb/°

C.

16. The method according to claim 1, wherein the titanium-doped SiO₂ soot body is doped with fluorine.

17. The method according to claim 16, wherein the fluorine concentration of the synthetic quartz glass is at least 100 ppm by weight.

18. The method according to claim 1, wherein the polyalkylsiloxane D3, which has a weight fraction of mD3, and the liquid TiO2 feedstock material, which has a weight fraction of mTiO2, are evaporated at a weight ratio of mTiO2/mD3 in a range of 0.1 to 10.

19. The method according to claim 1, wherein the liquid TiO2 feedstock material comprises at least 80% by weight titanium isopropoxide (Ti{OCH(CH3)2}4).

20. A method comprising:

producing a synthetic quartz glass according to claim 1; and

producing EUV mirror substrates from the synthetic quartz glass.