# US 8,541,326 B2 · Optical member for deep ultraviolet and process for producing same

> Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt

- Number: US 8,541,326 B2
- Document ID: US8541326B2
- Status: Granted
- Kind: B2
- Application number: 13/459,624
- Filed: 2012-04-30
- Published: 2012-08-23
- Granted: 2013-09-24
- Earliest claimed: 2009-10-30
- Assignees: Asahi Glass Company, Limited
- Applicants: Ryusuke Morita; Takuya Nakagawa; Kei Iwata; Masaaki Takata
- Inventors: Ryusuke Morita; Takuya Nakagawa; Kei Iwata; Masaaki Takata
- Web page: https://patentgrep.com/patent/US8541326B2

## CPC

- C03C 3/06: with more than 90% silica by weight, e.g. quartz {(C03C3/045 takes precedence)}
- C03B 19/1453: {Thermal after-treatment of the shaped article, e.g. dehydrating, consolidating, sintering}
- C03C 4/0085: {for UV-transmitting glass}
- G03F 1/50: Mask blanks not covered by G03F1/20 - G03F1/34; Preparation thereof
- G03F 7/70958: {Optical materials or coatings, e.g. with particular transmittance, reflectance or anti-reflection properties}
- C03B 2201/03: Impurity concentration specified
- C03B 2201/04: Hydroxyl ion (OH)
- C03C 2201/21: containing molecular hydrogen
- C03C 2201/23: containing hydroxyl groups
- Y02P 40/57: Improving the yield, e-g- reduction of reject rates
- C03C: CHEMICAL COMPOSITION OF GLASSES, GLAZES OR VITREOUS ENAMELS; SURFACE TREATMENT OF GLASS; SURFACE TREATMENT OF FIBRES OR FILAMENTS MADE FROM GLASS, MINERALS OR SLAGS; JOINING GLASS TO GLASS OR OTHER MATERIALS
- C03B: MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
- G03F: PHOTOMECHANICAL PRODUCTION OF TEXTURED OR PATTERNED SURFACES, e.g. FOR PRINTING, FOR PROCESSING OF SEMICONDUCTOR DEVICES; MATERIALS THEREFOR; ORIGINALS THEREFOR; APPARATUS SPECIALLY ADAPTED THEREFOR; (phototypographic composing devices B41B; photosensitive materials or processes for photographic purposes G03C; electrophotography, sensitive layers or processes therefor G03G)
- Y02P: CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS

## Abstract

The present invention relates to an optical member for deep ultraviolet having a wavelength of 250 nm or shorter, containing a synthetic silica glass which does not substantially contain a halogen element, has a maximum OH group content of less than 10 ppm by weight, has contents of ODC (oxygen deficient centers) and E-prime center of each less than 1×1014 cm−3, does not substantially contain SiH and peroxy linkage, and has a fictive temperature of 1,050° C. or lower.

## Claims

### Claim 1

An optical member comprising:
a synthetic silica glass which does not substantially contain a halogen element, has a maximum OH group content of less than 10 ppm by weight, has contents of an oxygen deficient center and an E-prime center of each less than 1×1014 cm−3, does not substantially contain SiH and peroxy linkage, and has a fictive temperature of 1,050° C. or lower,
wherein the synthetic silica glass is transparent to a deep ultraviolet light having a wavelength of 250 nm or shorter.

### Claim 2 (depends on 1)

The optical member according to claim 1, wherein variation in the fictive temperature in the synthetic silica glass is 5° C. or less.

### Claim 3 (depends on 1)

A process for producing the optical member according to claim 1,
wherein the process comprises:
synthesizing a porous synthetic silica glass body having a volume average bulk density of 0.33 g·cm−3 or more, the synthesizing comprising growing glass fine particles by a flame hydrolysis reaction of a raw material comprising a silicon compound;
pre-sintering the porous synthetic silica glass body after the synthesizing;
subjecting the porous synthetic silica glass body to a heat treatment at a temperature in a range of from 1,050 to 1,250° C. for more than 90 hours in vacuum at a pressure of 1×10−2 Pa or less; and
performing a transparent vitrification of the porous synthetic silica glass body to obtain the synthetic silica glass.

### Claim 4 (depends on 3)

The process according to claim 3, wherein the porous synthetic silica glass body synthesized has a variation in the bulk density of 0.1 g·cm−3 or less.

### Claim 5 (depends on 2)

A process for producing the optical member according to claim 2,
wherein the process comprises:
synthesizing a porous synthetic silica glass body having a volume average bulk density of 0.33 g·cm−3 or more, the synthesizing comprising growing glass fine particles by a flame hydrolysis reaction of a raw material comprising a silicon compound;
pre-sintering the porous synthetic silica glass body after the synthesizing;
subjecting the porous synthetic silica glass body to a heat treatment at a temperature in a range of from 1,050 to 1,250° C. for more than 90 hours in vacuum at a pressure of 1×10−2 Pa or less; and
performing a transparent vitrification of the porous synthetic silica glass body to obtain the synthetic silica glass.

### Claim 6 (depends on 5)

The process according to claim 5, wherein the porous synthetic silica glass body synthesized has a variation in the bulk density of 0.1 g·cm−3 or less.

### Claim 7 (depends on 3)

The process according to claim 3, wherein the porous synthetic silica glass body having the volume average bulk density of the 0.37 g·cm−3 or more is synthesized before the pre-sintering.

### Claim 8 (depends on 7)

The process according to claim 7, wherein the pressure in the heat treatment is 3×10−3 Pa or less.

### Claim 9 (depends on 8)

The process according to claim 8, wherein the pressure in the heat treatment is 1×10−3 Pa or less.

### Claim 10 (depends on 9)

The process according to claim 9, wherein the temperature in the heat treatment is in a range of from 1,100 to 1,200° C.

### Claim 11

A process for producing an optical member, comprising:
synthesizing a porous synthetic silica glass body having a volume average bulk density of 0.33 g·cm−3 or more, the synthesizing comprising growing glass fine particles by a flame hydrolysis reaction of a raw material comprising a silicon compound;
pre-sintering the porous synthetic silica glass body after the synthesizing;
subjecting the porous synthetic silica glass body to a heat treatment at a temperature in a range of from 1,050 to 1,250° C. for more than 90 hours in vacuum at a pressure of 1×10−2 Pa or less; and
performing a transparent vitrification of the porous synthetic silica glass body to obtain a synthetic silica glass.

### Claim 12 (depends on 11)

The process according to claim 11, wherein the porous synthetic silica glass body having the volume average bulk density of the 0.37 g·cm−3 or more is synthesized before the pre-sintering.

### Claim 13 (depends on 12)

The process according to claim 12, wherein the pressure in the heat treatment is 1×10−3 Pa or less.

### Claim 14 (depends on 13)

The process according to claim 13, wherein the temperature in the heat treatment is in a range of from 1,100 to 1,200° C.

### Claim 15 (depends on 11)

An optical member produced by the process according to claim 11, wherein the synthetic silica glass does not substantially contain a halogen element, has a maximum OH group content of less than 10 ppm by weight, has contents of an oxygen deficient center and an E-prime center of each less than 1×1013 cm−3, does not substantially contain SiH and peroxy linkage, and has a fictive temperature of 1,050° C. or lower.

### Claim 16 (depends on 15)

The optical member according to claim 15, wherein variation in the fictive temperature in the synthetic silica glass is 1° C. or less.

### Claim 17 (depends on 1)

The optical member according to claim 1, wherein the synthetic silica glass has the maximum OH group content of 5 ppm by mass or less and 1 ppm by mass or more.

### Claim 18 (depends on 17)

The optical member according to claim 17, wherein the fictive temperature is 1,020° C. or lower.

### Claim 19 (depends on 17)

The optical member according to claim 17, wherein variation in the fictive temperature in the synthetic silica glass is 1° C. or less.

### Claim 20 (depends on 17)

The optical member according to claim 17, wherein the contents of the oxygen deficient center and the E-prime center in the synthetic silica glass are each less than 1×1013 cm−3.