# US 5,702,495 A · Silica glass member for UV-lithography, method for silica glass production, and method for silica glass member production

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- Number: US 5,702,495 A
- Document ID: US5702495A
- Status: Granted
- Kind: A
- Application number: 08/479,130
- Filed: 1995-06-07
- Granted: 1997-12-30
- Earliest claimed: 1993-02-10
- Assignees: Nikon Corporation
- Inventors: Hiroyuki Hiraiwa; Kazuhiro Nakagawa; Hiroki Jinbo; Jun Takano; Seishi Fujiwara
- Web page: https://patentgrep.com/patent/US5702495A

## CPC

- C03B 19/1423: {Reactant deposition burners}
- C03B 19/1453: {Thermal after-treatment of the shaped article, e.g. dehydrating, consolidating, sintering}
- C03C 3/06: with more than 90% silica by weight, e.g. quartz {(C03C3/045 takes precedence)}
- C03C 4/0085: {for UV-transmitting glass}
- G02B 1/00: Optical elements characterised by the material of which they are made; Optical coatings for optical elements
- G02B 13/143: {for use with ultraviolet radiation}
- G03F 7/70241: {Optical aspects of refractive lens systems, i.e. comprising only refractive elements}
- G03F 7/70958: {Optical materials or coatings, e.g. with particular transmittance, reflectance or anti-reflection properties}
- C03B 2201/07: Impurity concentration specified
- C03B 2201/21: doped with molecular hydrogen
- C03B 2201/23: doped with hydroxyl groups
- C03B 2203/22: Radial profile of refractive index, composition or softening point
- C03B 2207/06: Concentric circular ports
- C03B 2207/12: Nozzle or orifice plates
- C03B 2207/20: Specific substances in specified ports, e.g. all gas flows specified
- C03B 2207/36: Fuel or oxidant details, e.g. flow rate, flow rate ratio, fuel additives
- C03C 2201/21: containing molecular hydrogen
- C03C 2203/44: chlorine containing
- C03C 2203/52: Heat-treatment
- Y10S 359/90: Methods
- Y10S 501/905: Ultraviolet transmitting or absorbing
- C03B: MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
- 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
- G02B: OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- 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)
- Y10S: TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS

## Abstract

Recent UV-lithography is required to provide a fine and sharp pattern with a line width of 0.5 .mu.m or less. A silica glass member adapted for use as an optical element for UV-lithography, by giving consideration to the RMS value of wave front aberration and the slant element of refractive index, which have not been considered in the art. Also there is provided a silica glass member excellent in durability to the ultraviolet irradiation, by introduction of hydrogen molecules at the synthesis of the silica glass, instead of using a secondary treatment for hydrogen introduction.

## Claims

### Claim 1

A method of producing a silica glass member, comprising emitting Si compound gas, oxygen gas and hydrogen gas from a burner to deposit silica soot by the direct method on a rotating target in such a manner as to form an ingot of transparent silica glass, cutting out of the ingot a silica glass body of cylindrical form with a center substantially at an axis of rotational symmetry of the ingot, and performing heat treatment of the silica glass body, wherein the heat treatment is carried out by using a furnace having a temperature distribution of central symmetry and by making a central axis of the furnace substantially coincident with a central axis of the silica glass body.

### Claim 2

A method of producing a silica glass member, comprising emitting Si compound gas, oxygen gas and hydrogen gas from a burner to deposit silica soot by the direct method on a rotating target in such a manner as to form an ingot of transparent silica glass, cutting out of the ingot a silica glass body of cylindrical form with a center substantially at an axis of rotational symmetry of the ingot, and performing heat treatment of the silica glass body while rotating the silica glass body on a central axis thereof.

### Claim 3

A method of producing silica glass, comprising emitting Si compound gas, oxygen gas and hydrogen gas from a burner that is provided with a circular raw material tube positioned at a central part and adapted to emit the Si compound gas, a plurality of annular combustion tubes positioned concentrically therearound and adapted to emit oxygen gas and hydrogen gas, and a plurality of circular combustion tubes positioned inside the outermost annular combustion tube and adapted to emit oxygen gas, thereby depositing silica soot by the direct method on a target in such a manner as to form an ingot of transparent silica glass, wherein hydrogen gas is used as a carrier gas in emission of the Si compound gas from the circular raw material tube.

### Claim 4

A method of producing silica glass, comprising emitting Si compound gas, oxygen gas and hydrogen gas from a burner that is provided with a circular raw material tube positioned at a central part and adapted to emit the Si compound gas, a plurality of annular combustion tubes positioned concentrically therearound and adapted to emit oxygen gas and hydrogen gas, and a plurality of circular combustion tubes positioned inside the outermost annular combustion tube and adapted to emit oxygen gas, thereby depositing silica soot by the direct method on a target in such a manner as to form an ingot of transparent silica glass, wherein the proportion of oxygen gas and hydrogen gas emitted from the plurality of annular combustion tubes excluding the outermost one is maintained in a hydrogen excess state in comparison with a stoichiometric ratio and with the proportion of oxygen gas and hydrogen gas emitted from the outermost annular combustion tube and the circular combustion tubes positioned therein.

### Claim 5

A method of producing silica glass, comprising emitting Si compound gas, oxygen gas and hydrogen gas from a burner that is provided with a circular raw material tube positioned at a central part and adapted to emit the Si compound gas, a plurality of annular combustion tubes positioned concentrically therearound and adapted to emit oxygen gas and hydrogen gas, and a plurality of circular combustion tubes positioned inside the outermost annular combustion tube and adapted to emit oxygen gas, thereby depositing silica soot by the direct method on a target in such a manner as to form an ingot of transparent silica glass, wherein the proportion of oxygen gas and hydrogen gas emitted from the plurality of annular combustion tubes excluding the outermost one is maintained in a hydrogen excess state in comparison with a stoichiometric ratio, and the proportion of oxygen gas and hydrogen gas emitted from the outermost annular combustion tube and the circular combustion tubes positioned therein is maintained at the stoichiometric ratio or in an oxygen excess state in comparison therewith.

### Claim 6 (depends on 4)

A method according to claim 4, wherein hydrogen gas is used as a carrier gas in emission of the Si compound gas from the circular raw material tube.

### Claim 7 (depends on 5)

A method according to claim 5, wherein hydrogen gas is used as a carrier gas in emission of the Si compound gas from the circular raw material tube .