Synthetic silica glass molded body, method of molding the same, and method of inspecting synthetic silica glass molded body

Abstract

A method of molding a synthetic silica glass molded body by accommodating a synthetic silica glass block in a mold provided with a pressing portion, and by pressing the block while heating, the method comprising: a step of washing the synthetic silica glass block so that a concentration of copper which is present on the surface of the synthetic silica glass block is 2 ng/cm 2 or less, and so that a concentration of aluminium thereon is 10 ng/cm 2 or less, before accommodating the synthetic silica glass block in the mold; a step of heating high purity carbon powders in which a content of copper is 40 wt.ppb or less and a content of aluminium is 100 wt.ppb or less at a temperature condition of 1200° C. to 1900° C.; a step of heating the mold at a temperature condition of 1700° C. to 1900° C.; a step of applying the high purity carbon powders after the heating step on the inner surface of the mold after the heating step, before accommodating the synthetic silica glass block in the mold; and a step of molding the synthetic silica glass block in a predetermined form by pressing the block by means of the pressing portion while heating so as to the temperature of the block can be within a hold temperature range of 1500° C. to 1700° C., after accommodating the washed synthetic silica glass block in the mold.

1 . A method of molding a synthetic silica glass molded body by accommodating a synthetic silica glass block in a mold provided with a pressing portion, and by pressing the block while heating, the method comprising:
 a step of washing the synthetic silica glass block so that a concentration of copper which is present on the surface of the synthetic silica glass block is 2 ng/cm 2  or less, and so that a concentration of aluminium thereon is 10 ng/cm 2  or less, before accommodating the synthetic silica glass block in the mold;   a step of heating high purity carbon powders in which a content of copper is 40 wt.ppb or less and a content of aluminium is 100 wt.ppb or less at a temperature condition of 1200° C. to 1900° C.;   a step of heating the mold at a temperature condition of 1700° C. to 1900° C.;   a step of applying the high purity carbon powders after the heating step on the inner surface of the mold after the heating step, before accommodating the synthetic silica glass block in the mold; and   a step of molding the synthetic silica glass block in a predetermined form by pressing the block by means of the pressing portion while heating so as to the temperature of the block can be within a hold temperature range of 1500° C. to 1700° C., after accommodating the washed synthetic silica glass block in the mold.   
     
     
         2 . The method of molding a synthetic silica glass molded body according to  claim 1 , wherein the heating temperature in the step of heating the high purity carbon powders is in a condition of 1200° C. to 1600° C. 
     
     
         3 . The method of molding a synthetic silica glass molded body according to  claim 1 , wherein the step of heating the high purity carbon powders and the step of heating the mold are simultaneously performed. 
     
     
         4 . The method of molding a synthetic silica glass molded body according to  claim 1 , wherein a content of copper in the mold after the heating step is 80 wt.ppb or less. 
     
     
         5 . The method of molding a synthetic silica glass molded body according to  claim 1 , wherein the applied amount of the high purity carbon powders in the step of applying the high purity carbon powders is 7 mg/cm 2  to 200 mg/cm 2 . 
     
     
         6 . The method of molding a synthetic silica glass molded body according to  claim 1 , wherein a concentration of OH group in the synthetic silica glass block is 900 ppm to 1300 ppm by mass. 
     
     
         7 . The method of molding a synthetic silica glass molded body according to  claim 1 , wherein, in the step of molding the synthetic silica glass block, the silica glass block is pressed in the predetermined form by means of the pressing portion so that a maximum pressure can be 0.2 kg/cm 2  to 1.0 kg/cm 2 . 
     
     
         8 . A synthetic silica glass molded body molded by accommodating a synthetic silica glass block in a mold provided with a pressing portion, and by pressing the block while heating, wherein, in at least 60% by volume or more of a region of the synthetic silica glass molded body, conditions that:
 a concentration of copper is 0.2 wt.ppb or less and a concentration of aluminium is 10 wt.ppb or less; and   the concentrations of copper and aluminium are represented by the following equation (1):
   [Cu]+0.03×[Al]<0.4 wt.ppb  (1)
 
   
       (where [Cu] shows the concentration (wt. ppb) of copper, and [Al] shows the concentration (wt. ppb) of aluminium.) are satisfied. 
     
     
         9 . The synthetic silica glass molded body according to  claim 8 , wherein the region satisfies a condition that a ratio of a bright line intensity of a spectrum line having a wavelength of 254 nm and a fluorescent light intensity from a green to a yellow fluorescent light having a center wavelength of 500 nm to 600 nm (fluorescent light intensity/bright line intensity) is 0.005 or less in visible-ultraviolet spectra which are obtained by measuring in a direction perpendicular to an irradiation direction of a spectrum line, when the region is irradiated with the spectrum line of an Hg lamp having a wavelength of 254 nm, at an irradiance condition of 10 mW/cm 2  or more, which has been transmitted through a filter for blocking the visible light or reducing an intensity thereof. 
     
     
         10 . The synthetic silica glass molded body according to  claim 8 , wherein the region satisfies a condition that a ratio of a minimum value and a maximum value of a fluorescent light intensity (minimum/maximum) is 0.2 to 1.0 when measuring the fluorescent light intensity of yellowish green fluorescent light having a center wavelength of 550 nm which is generated by irradiating a KrF excimer laser light over the entire surface area of the region perpendicular to an irradiation direction of the KrF excimer laser light after the region is irradiated with 3×10 4  pulses of the KrF excimer laser light having a wavelength of 248 nm at a repetition frequency of 100 Hz and in an energy density of 100 mJ/(cm 2 ·pulse). 
     
     
         11 . A method of inspecting a synthetic silica glass molded body, comprising:
 a step of irradiating the synthetic silica glass molded body with a spectrum line of an Hg lamp having a wavelength of 254 nm, at an irradiance condition of 10 mW/cm 2  or more, which has been transmitted through a filter for any one of blocking a visible light and reducing an intensity thereof;   a step of measuring, in a direction perpendicular to the irradiation direction of the spectrum line, an intensity of a bright line having a wavelength of 254 nm emitted by the synthetic silica glass molded body, and a fluorescent light intensity from a green to a yellow fluorescent light having a center wavelength of 500 nm to 600 nm emitted by the synthetic silica glass molded body; and   a step of screening a portion which satisfies a condition that a ratio of the bright line intensity and the fluorescent light intensity (fluorescent light intensity/bright line intensity) is 0.005 or less.   
     
     
         12 . The method of inspecting a synthetic silica glass molded body according to  claim 11 , wherein a measurement surface of the synthetic silica glass molded body is previously polished. 
     
     
         13 . A method of inspecting a synthetic silica glass member, comprising:
 a step of irradiating a synthetic silica glass member with 3×10 4  pulses of a KrF excimer laser light having a wavelength of 248 nm at a repetition frequency of 100 Hz and in an energy density of 100 mJ/(cm 2 ·pulse);   a step of measuring a fluorescent light intensity of yellowish green fluorescent light having a center wavelength of 550 nm emitted by the synthetic silica glass member over the entire surface area of the synthetic silica glass member perpendicular to the irradiation direction of the KrF excimer laser light; and   a step of determining whether a condition that a ratio of a minimum value and a maximum value of the fluorescent light intensity of the yellowish green fluorescent light (minimum/maximum) is 0.2 to 1.0 is satisfied or not.   
     
     
         14 . The method of inspecting a synthetic silica glass member according to  claim 13 , wherein the step of irradiating the KrF excimer laser light is performed in an aluminium-made chamber purged with a nitrogen gas.