Manufacturing method for SiO2-TiO2 based glass and manufacturing method for photomask substrate made of SiO2-TiO2 based glass

Patent metadata

Field	Value
Publication number	US-10093572-B2
Application number	US-201514660561-A
Country	US
Kind code	B2
Filing date	Mar 17, 2015
Priority date	Sep 18, 2012
Publication date	Oct 9, 2018
Grant date	Oct 9, 2018

Abstract

A method for manufacturing an SiO2—TiO2 based glass upon a target by a direct method, includes: an ingot growing step of growing an SiO2—TiO2 based glass ingot having a predetermined length on the target by flame hydrolysis by feeding a silicon compound and a titanium compound into an oxyhydrogen flame, wherein the ingot growing step includes: a first step of increasing a ratio of a feed rate of the titanium compound to a feed rate of the silicon compound as the SiO2—TiO2 based glass ingot grows until the ratio reaches a predetermined value; and a second step of gradually growing the SiO2—TiO2 based glass ingot after the ratio has reached the predetermined value in the first stage with keeping the ratio within a predetermined range.

First claim

What is claimed is:

1. A method for manufacturing an SiO 2 -TiO 2 based glass having a desired TiO 2 concentration upon a target by a direct method, comprising:
growing an SiO 2 -TiO 2 based glass ingot on the target by flame hydrolysis by feeding a silicon compound and a titanium compound into an oxyhydrogen flame, wherein the growing includes:
growing an initial portion of the SiO 2 -TiO 2 based glass ingot by feeding the titanium compound and the silicon compound into the oxyhydrogen flame in respective feed rates such that the initial portion has a TiO 2 concentration smaller than the desired TiO 2 concentration,
while further feeding the titanium compound and the silicon compound to grow a first further portion of the SiO 2 -TiO 2 based glass ingot on the initial portion, increasing a ratio of the feed rate of the titanium compound to the feed rate of the silicon compound until the first further portion starts growing at the desired TiO 2 concentration, and
then, growing a second further portion of the SiO 2 -TiO 2 based glass ingot while maintaining the second further portion at the desired TiO 2 concentration,
wherein the ratio is adjusted in stages such that an increment of concentration of TiO 2 per cm of the length of the first further portion of the SiO 2 -TiO 2 based glass ingot is equal to or less than 1 mass %.

2. A method for manufacturing an SiO 2 -TiO 2 based glass having a desired TiO 2 concentration upon a target by a direct method, comprising:
growing an SiO 2 -TiO 2 based glass ingot on the target by flame hydrolysis by feeding a silicon compound and a titanium compound into an oxyhydrogen flame, wherein the growing includes:
growing an initial portion of the SiO 2 -TiO 2 based glass ingot by feeding the titanium compound and the silicon compound into the oxyhydrogen flame in respective feed rates such that the initial portion has a TiO 2 concentration smaller than the desired TiO 2 concentration,
while further feeding the titanium compound and the silicon compound to grow a first further portion of the SiO 2 -TiO 2 based glass ingot on the initial portion, increasing a ratio of the feed rate of the titanium compound to the feed rate of the silicon compound until the first further portion starts growing at the desired TiO 2 concentration, and
then, growing a second further portion of the SiO 2 -TiO 2 based glass ingot while maintaining the second further portion at the desired TiO 2 concentration,

wherein the ratio at a start of feeding the silicon compound and the titanium compound is adjusted such that the concentration of TiO 2 in the initial portion of the SiO 2 -TiO 2 based glass is equal to or less than 4 mass %.

3. The method for manufacturing an SiO 2 -TiO 2 based glass according to claim 2 , wherein:
in the increasing the ratio, the ratio is gradually increased such that the temperature of the growth surface of the first further portion of SiO 2 -TiO 2 based glass ingot is maintained at a temperature equal to or higher than a predetermined lower limit temperature.

4. The method for manufacturing an SiO 2 -TiO 2 based glass according to claim 3 , wherein:
the predetermined lower limit temperature is 1600 ° C.

5. The method for manufacturing an SiO 2 -TiO 2 based glass according to claim 2 , wherein:
in the increasing the ratio, the ratio is increased in stages.

6. The method for manufacturing an SiO 2 -TiO 2 based glass according to claim 2 , wherein:
the silicon compound is silicon tetrachloride.

7. The method for manufacturing an SiO 2 -TiO 2 based glass according to claim 2 , wherein:
the titanium compound comprises titanium tetrachloride, tetraisopropoxytitanium or tetrakisdimethylaminotitanium.

8. The method for manufacturing an SiO 2 -TiO 2 based glass according to claim 2 , further comprising:
a preheating process of preheating the target prior to the ingot growing process.

9. The method for manufacturing an SiO 2 -TiO 2 based glass according to claim 2 , wherein:
in the ingot growing, only the silicon compound is fed into the oxyhydrogen flame to form a growth surface of an SiO 2 glass and subsequently feeding of the titanium compound is started.

10. A method for manufacturing a photomask substrate, the method comprising:
manufacturing an SiO 2 -TiO 2 based glass by the method for manufacturing an SiO 2 -TiO 2 based glass according to claim 2 ;
cutting out the second further portion from the manufactured SiO 2 -TiO 2 based glass; and
forming a plate-shaped member by hot pressure forming the glass portion which was cut out in the cutting.

Assignees

• Nikon Corp

Inventors

• Yoshinari Toshio

Classifications

• C03C2203/44

  chlorine containing · CPC title

• C03B32/005

  Hot-pressing vitrified, non-porous, shaped glass products · CPC title

• C03B2207/70

  Control measures · CPC title

• C03C3/06

  with more than 90% silica by weight, e.g. quartz {(C03C3/045 takes precedence)} · CPC title

• C03B2201/42

  doped with titanium · CPC title