Titania-doped quartz glass and making method

Abstract

A titania-doped quartz glass which experiences a reduction in OH group concentration of less than or equal to 100 ppm upon heat treatment at 900° C. for 100 hours is suitable as the EUV lithography member.

1 . A titania-doped quartz glass which experiences a reduction in OH group concentration of less than or equal to 100 ppm upon heat treatment at 900° C. for 100 hours. 
     
     
         2 . The titania-doped quartz glass of  claim 1  wherein the difference between maximum and minimum reductions of OH group concentration upon the 900° C./100-hr heat treatment is less than or equal to 50 ppm. 
     
     
         3 . The titania-doped quartz glass of  claim 1 , having an OH group concentration of 300 ppm to 950 ppm after the 900° C./100-hr heat treatment. 
     
     
         4 . The titania-doped quartz glass of  claim 1 , having an OH group concentration gradient of less than or equal to 100 ppm/cm after the 900° C./100-hr heat treatment. 
     
     
         5 . The titania-doped quartz glass of  claim 1 , having a hydrogen molecule concentration of less than or equal to 5×10 17  molecules/cm 3 . 
     
     
         6 . The titania-doped quartz glass of  claim 1 , containing 3 to 10% by weight of titania. 
     
     
         7 . An EUV lithographic member comprising the titania-doped quartz glass of  claim 1 . 
     
     
         8 . The member of  claim 7 , which is a EUV lithographic photomask substrate. 
     
     
         9 . The member of  claim 7 , which is a mirror in a reflecting optical system of a EUV lithography apparatus. 
     
     
         10 . A method for preparing a titania-doped quartz glass, comprising the steps of subjecting a silicon-providing reactant gas and a titanium-providing reactant gas to oxidation or flame hydrolysis with the aid of a combustible gas and a combustion-supporting gas, to thereby form synthetic silica-titania fine particles, depositing the silica-titania fine particles on a rotating target, and concurrently melting and vitrifying the deposited particles into titania-doped quartz glass,
 the method further comprising the step of feeding oxygen gas as the combustion-supporting gas through a central tube of a burner in admixture with the silicon-providing reactant gas and the titanium-providing reactant gas in a molar ratio of oxygen gas to the sum of the silicon-providing reactant gas and the titanium-providing reactant gas of at least 5.   
     
     
         11 . A method for preparing a titania-doped quartz glass, comprising the steps of subjecting a silicon-providing reactant gas and a titanium-providing reactant gas to oxidation or flame hydrolysis with the aid of a combustible gas and a combustion-supporting gas, to thereby form synthetic silica-titania fine particles, depositing the silica-titania fine particles on a rotating target, and concurrently melting and vitrifying the deposited particles into titania-doped quartz glass,
 the method further comprising the step of injecting hydrogen gas as the combustible gas through one or more hydrogen gas feed tubes of a burner at a linear velocity of less than or equal to 100 m/sec.   
     
     
         12 . The method of  claim 10  wherein
 the flow rates of the combustible gas, the combustion-supporting gas, the silicon-providing reactant gas and the titanium-providing reactant gas are controlled so that respective variations of the flow rates may fall within ±1%, 
 the temperatures of cooling air introducing from the outside of a quartz glass manufacturing furnace thereinto, exhaust gas from the furnace, and ambient air surrounding the furnace are controlled so that respective variations of the temperatures may fall within ±2.5° C., and 
 the target is rotated at a rotational speed of at least 5 rpm when the silica-titania fine particles are deposited on the rotating target.