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WO2009116690A1 - Verre de silice contenant du tio<sb>2</sb> - Google Patents

Verre de silice contenant du tio<sb>2</sb> Download PDF

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Publication number
WO2009116690A1
WO2009116690A1 PCT/JP2009/056205 JP2009056205W WO2009116690A1 WO 2009116690 A1 WO2009116690 A1 WO 2009116690A1 JP 2009056205 W JP2009056205 W JP 2009056205W WO 2009116690 A1 WO2009116690 A1 WO 2009116690A1
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WO
WIPO (PCT)
Prior art keywords
tio
sio
glass
temperature
thermal expansion
Prior art date
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Ceased
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PCT/JP2009/056205
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English (en)
Inventor
Akio Koike
Yasutomi Iwahashi
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AGC Inc
Original Assignee
Asahi Glass Co Ltd
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Filing date
Publication date
Application filed by Asahi Glass Co Ltd filed Critical Asahi Glass Co Ltd
Publication of WO2009116690A1 publication Critical patent/WO2009116690A1/fr
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

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Classifications

    • C—CHEMISTRY; METALLURGY
    • C03—GLASS; MINERAL OR SLAG WOOL
    • C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
    • C03B19/00—Other methods of shaping glass
    • C03B19/14—Other methods of shaping glass by gas- or vapour- phase reaction processes
    • C03B19/1453—Thermal after-treatment of the shaped article, e.g. dehydrating, consolidating, sintering
    • C03B19/1461—Thermal after-treatment of the shaped article, e.g. dehydrating, consolidating, sintering for doping the shaped article with flourine
    • C—CHEMISTRY; METALLURGY
    • C03—GLASS; MINERAL OR SLAG WOOL
    • 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
    • C03C3/00—Glass compositions
    • C03C3/04—Glass compositions containing silica
    • C03C3/06—Glass compositions containing silica with more than 90% silica by weight, e.g. quartz
    • C—CHEMISTRY; METALLURGY
    • C03—GLASS; MINERAL OR SLAG WOOL
    • 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
    • C03C4/00—Compositions for glass with special properties
    • C03C4/0085—Compositions for glass with special properties for UV-transmitting glass
    • C—CHEMISTRY; METALLURGY
    • C03—GLASS; MINERAL OR SLAG WOOL
    • C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
    • C03B2201/00—Type of glass produced
    • C03B2201/06—Doped silica-based glasses
    • C03B2201/08—Doped silica-based glasses doped with boron or fluorine or other refractive index decreasing dopant
    • C03B2201/12—Doped silica-based glasses doped with boron or fluorine or other refractive index decreasing dopant doped with fluorine
    • C—CHEMISTRY; METALLURGY
    • C03—GLASS; MINERAL OR SLAG WOOL
    • C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
    • C03B2201/00—Type of glass produced
    • C03B2201/06—Doped silica-based glasses
    • C03B2201/20—Doped silica-based glasses doped with non-metals other than boron or fluorine
    • C03B2201/23—Doped silica-based glasses doped with non-metals other than boron or fluorine doped with hydroxyl groups
    • C—CHEMISTRY; METALLURGY
    • C03—GLASS; MINERAL OR SLAG WOOL
    • C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
    • C03B2201/00—Type of glass produced
    • C03B2201/06—Doped silica-based glasses
    • C03B2201/30—Doped silica-based glasses doped with metals, e.g. Ga, Sn, Sb, Pb or Bi
    • C03B2201/40—Doped silica-based glasses doped with metals, e.g. Ga, Sn, Sb, Pb or Bi doped with transition metals other than rare earth metals, e.g. Zr, Nb, Ta or Zn
    • C03B2201/42—Doped silica-based glasses doped with metals, e.g. Ga, Sn, Sb, Pb or Bi doped with transition metals other than rare earth metals, e.g. Zr, Nb, Ta or Zn doped with titanium
    • C—CHEMISTRY; METALLURGY
    • C03—GLASS; MINERAL OR SLAG WOOL
    • 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
    • C03C2201/00—Glass compositions
    • C03C2201/06—Doped silica-based glasses
    • C03C2201/08—Doped silica-based glasses containing boron or halide
    • C03C2201/12—Doped silica-based glasses containing boron or halide containing fluorine
    • C—CHEMISTRY; METALLURGY
    • C03—GLASS; MINERAL OR SLAG WOOL
    • 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
    • C03C2201/00—Glass compositions
    • C03C2201/06—Doped silica-based glasses
    • C03C2201/20—Doped silica-based glasses containing non-metals other than boron or halide
    • C03C2201/23—Doped silica-based glasses containing non-metals other than boron or halide containing hydroxyl groups
    • C—CHEMISTRY; METALLURGY
    • C03—GLASS; MINERAL OR SLAG WOOL
    • 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
    • C03C2201/00—Glass compositions
    • C03C2201/06—Doped silica-based glasses
    • C03C2201/30—Doped silica-based glasses containing metals
    • C03C2201/40—Doped silica-based glasses containing metals containing transition metals other than rare earth metals, e.g. Zr, Nb, Ta or Zn
    • C03C2201/42—Doped silica-based glasses containing metals containing transition metals other than rare earth metals, e.g. Zr, Nb, Ta or Zn containing titanium
    • C—CHEMISTRY; METALLURGY
    • C03—GLASS; MINERAL OR SLAG WOOL
    • 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
    • C03C2203/00—Production processes
    • C03C2203/40—Gas-phase processes
    • C—CHEMISTRY; METALLURGY
    • C03—GLASS; MINERAL OR SLAG WOOL
    • 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
    • C03C2203/00—Production processes
    • C03C2203/50—After-treatment
    • C03C2203/52—Heat-treatment
    • C03C2203/54—Heat-treatment in a dopant containing atmosphere
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P40/00—Technologies relating to the processing of minerals
    • Y02P40/50—Glass production, e.g. reusing waste heat during processing or shaping
    • Y02P40/57—Improving the yield, e-g- reduction of reject rates

Definitions

  • the present invention relates to a TiO 2 -containing silica glass (hereinafter referred to as "TiO 2 -SiO 2 glass" in this specification), and in particular, to a TiO 2 -SiO 2 glass to be used as an optical member of an exposure tool for EUVL lithography.
  • the EUV (extreme ultraviolet) light as referred to in the invention refers to light having a wavelength in a soft X-ray region or a vacuum ultraviolet region, specifically light having a wavelength of from about 0.2 to 100 nm.
  • an exposure tool for manufacturing an integrated circuit by transferring a fine circuit pattern onto a wafer has hitherto been widely utilized.
  • the exposure tool is hence required to form a circuit pattern image with high resolution on a wafer surface at a long focal depth, and shortening of the wavelength of an exposure light source is being advanced.
  • the exposure light source is further advancing from conventional g-line (wavelength: 436 nm), i-line (wavelength: 365 nm) and a KrF excimer laser (wavelength: 248 nm), and an ArF excimer layer (wavelength: 193 nm) is coming to be employed.
  • g-line wavelength: 436 nm
  • i-line wavelength: 365 nm
  • KrF excimer laser wavelength: 248 nm
  • an ArF excimer layer wavelength: 193 nm
  • an immersion lithography technique and a double exposure technique, each using an ArF excimer laser are regarded as being leading.
  • EUVL extreme ultraviolet light
  • the optical member of an exposure tool for EUVL includes a photomask and a mirror and is basically configured with (1) a substrate, (2) a reflective multilayer formed on the substrate and (3) an absorber layer formed on the reflective multilayer.
  • the multilayer the formation of layers by alternately laminating Mo/Si is investigated; and for the absorber layer, Ta and Cr are investigated.
  • the substrate a material having a low coefficient of thermal expansion is required so as not to generate a strain even under irradiation with EUV light, and a glass having a low coefficient of thermal expansion or the like is investigated.
  • the TiO 2 -SiO 2 glass is known as an extremely low thermal expansion material having a coefficient of thermal expansion (CTE) lower than that of a silica glass. Also, since the coefficient of thermal expansion can be controlled by the TiO 2 content in glass, a zero-expansion glass whose coefficient of thermal expansion is close to 0 can be obtained. Accordingly, the TiO 2 -SiO 2 glass involves a possibility as a material to be used in an optical member of an exposure tool for EUVL.
  • CTE coefficient of thermal expansion
  • Patent Document 1 discloses a method in which a TiO 2 -SiO 2 porous glass body is formed and converted it into a glass body, and a mask substrate is then obtained.
  • the optical member of an exposure tool for EUVL reaches a temperature of about 100 °C during the film formation of a reflective film or the like at the time of its manufacture. Also, since EUV light with high energy is irradiated at the time of use in the exposure tool for EUVL, there is a concern that the temperature of the member locally rises.
  • the optical member of an exposure tool for EUVL has a wide temperature region where the coefficient of thermal expansion is substantially zero.
  • the conventional TiO 2 -SiO 2 glasses have a narrow temperature region where the coefficient of thermal expansion is substantially zero, and hence, were insufficient for the use as an optical member of an exposure tool for EUVL.
  • Patent Document 2 a TiO 2 -SiO 2 glass having a fictive temperature of 1,200 °C or lower, an F concentration of 100 ppm or more and a coefficient of thermal expansion in the range of from O to 100 0 C of O ⁇ 200 ppb/°C, and a method for manufacturing this TiO 2 -SiO 2 glass.
  • the TiO 2 -SiO 2 glass undergoes little change in the coefficient of thermal expansion relative to a temperature change, namely wide in the temperature range where the coefficient of thermal expansion is substantially zero, is excellent in homogeneity of the coefficient of thermal expansion and the mechanical properties in glass, and is extremely suitable as a raw material of the member which constitutes an optical system to be used for EUVL.
  • Patent Document 1 US- A-2002/ 157421
  • Patent Document 2 JP-A-2005- 104820
  • the TiO 2 -SiO 2 glass disclosed in Patent Document 2 has a wide temperature range where the coefficient of thermal expansion is substantially zero, if at least one of the F concentration and the fictive temperature varies, the temperature dependence of a coefficient of thermal expansion varies, and the temperature region where the coefficient of thermal expansion is substantially zero varies.
  • the temperature in an exposure tool for EUVL is strictly controlled.
  • the coefficient of thermal expansion is substantially zero under this strictly controlled temperature.
  • the TiO 2 -SiO 2 glass disclosed in Patent Document 2 there may be the case where the coefficient of thermal expansion is not substantially zero at the temperature in the exposure tool, and hence, the TiO 2 -SiO 2 glass disclosed in Patent Document 2 was not necessarily sufficient as the optical member of an exposure tool for EUVL.
  • Example 1 With respect to the TiO 2 -SiO 2 glass disclosed in Patent Document 2, it is shown in Example 1 that the widest temperature range in which the coefficient of thermal expansion is substantially zero is 7.6 °C. However, with respect to the TiO 2 - SiO 2 glass disclosed in Patent Document 2, this temperature range was not necessarily sufficient, taking into account the facts that when at least one of the F concentration and the fictive temperature varies, the temperature region in which the coefficient of thermal expansion is substantially zero varies and that there is a concern that the temperature of the optical member locally rises upon irradiation with EUV light.
  • an object of the invention is to provide a TiO 2 -SiO 2 glass having suitable thermal expansion properties as an optical member of an exposure tool for EUVL. More specifically, an object of the invention is to provide a TiO 2 -SiO 2 glass whose coefficient of thermal expansion upon irradiation with EUV light is substantially zero when used as an optical member of an exposure tool for EUVL.
  • the invention provides a TiO 2 - containing silica glass (hereinafter referred to as "TiO 2 -SiO 2 glass of the invention") having a TiO 2 content of from 3 to 9 % by mass; a temperature, at which a coefficient of thermal expansion is O ppb/°C, falling within the range of from 15 to 35 0 C; a fictive temperature of 850 0 C or lower; and a temperature width, in which a coefficient of thermal expansion is 0 ⁇ 5 ppb/°C, of 7.8 °C or greater.
  • TiO 2 -SiO 2 glass of the invention having a TiO 2 content of from 3 to 9 % by mass; a temperature, at which a coefficient of thermal expansion is O ppb/°C, falling within the range of from 15 to 35 0 C; a fictive temperature of 850 0 C or lower; and a temperature width, in which a coefficient of thermal expansion is 0 ⁇ 5 ppb/°C, of 7.8
  • the TiO 2 -SiO 2 glass of the invention has an F concentration of 1 ,000 ppm or more.
  • the TiO 2 -SiO 2 glass of the invention has a fictive temperature of 800 °C or lower and an OH concentration of 600 ppm or more.
  • the TiO 2 -SiO 2 glass of the invention a temperature range where a coefficient of thermal expansion is substantially zero is wide, and the temperature region where a coefficient of thermal expansion is substantially zero includes the temperatures of an optical member upon irradiation with EUV light. Therefore, the TiO 2 -SiO 2 glass of the invention is extremely suitable as an optical member of an exposure tool for EUVL.
  • Fig. 1 is a graph plotting the relationship between CTE and the temperature.
  • Fig. 2 is a graph plotting the relationship between CTE and the temperature, with respect to Examples 1 to 6.
  • the TiO 2 -SiO 2 glass of the invention has a temperature, at which a coefficient of thermal expansion (CTE) is 0 ppb/°C (cross-over temperature; COT), falling within the range of from 15 to 35 °C and a temperature width ⁇ T, in which a coefficient of thermal expansion (CTE) is 0 ⁇ 5 ⁇ pb/°C, of 7.8 °C or greater.
  • CTE coefficient of thermal expansion
  • the COT and ⁇ T of the TiO 2 -SiO 2 glass can be determined by measuring a coefficient of thermal expansion (CTE) of the TiO 2 -SiO 2 glass by a known method, for example, by measuring thermal expansion of a sample by continuous temperature rise in the range of from -50 to +100 °C or in a wider range than this or by stepwise temperature rise in the range of from 15 to 35 °C using a thermodilatometer capable of detecting elongation of the sample by a laser interferometric dilatometer, and plotting the relationship between CTE and the temperature as shown in Fig. 1.
  • CTE coefficient of thermal expansion
  • the temperature in the exposure tool for EUVL is strictly controlled so as to fall within 22 ⁇ 3 °C.
  • the temperature of the optical member to be placed in the exposure tool for EUVL becomes 22 ⁇ 3 °C.
  • the temperature of the optical member locally rises because EUV light with high energy is irradiated.
  • the coefficient of thermal expansion of the optical member is substantially zero under the temperature condition of the optical member upon irradiation with EUV light.
  • the phrase "the coefficient of thermal expansion being substantially zero" means that the coefficient of thermal expansion is 0 ⁇ 5 ppb/°C.
  • the COT is preferably from 17 to 31 °C, and the COT is more preferably from 19 to 27 °C.
  • the ⁇ T is preferably 8.5 °C or greater, and more preferably 9 °C or greater.
  • the TiO 2 -SiO 2 glass of the invention satisfying the foregoing COT and ⁇ T requirements can be obtained by regulating either or both of the glass composition and the fictive temperature.
  • TiO 2 -SiO 2 glass (I) An embodiment of the TiO 2 -SiO 2 glass of the invention satisfying the foregoing COT and ⁇ T requirements (hereinafter referred to as "TiO 2 -SiO 2 glass (I)") satisfies the following requirements.
  • TiO 2 content 3 to 9 % by mass Fictive temperature: 850 °C or lower F concentration: 1,000 ppm or more Accordingly, the TiO 2 -SiO 2 glass (1) contains F in addition to TiO 2 and SiO 2 .
  • TiO 2 -SiO 2 glass (1) though the remainder exclusive of TiO 2 and F is SiO 2 , other components than TiO 2 , SiO 2 and F may be contained. It is known that the coefficient of thermal expansion of the TiO 2 -SiO 2 glass varies with the concentration OfTiO 2 to be contained (see, for example, P. C. Schultz and H T. Smyth, in: R W. Douglas and B. Ellis, Amorphous Materials, Willey, New York, p.453 (1972)). Accordingly, it is possible to control the COT of the TiO 2 -SiO 2 glass by controlling the TiO 2 content.
  • the TiO 2 -SiO 2 glass (1) has a TiO 2 content of from 3 to 9 % by mass.
  • the TiO 2 content is less than 3 % by mass or exceeds 9 % by mass, there is a concern that the COT does not exist in the temperature region of from 15 to 35 0 C.
  • the TiO 2 content is less than 3 % by mass, the COT is lower than 15 °C.
  • the TiO 2 content is preferably 5 % by mass or more, and more preferably 6 % by mass or more.
  • the TiO 2 content exceeds 9 % by mass the COT exceeds 35 °C.
  • the TiO 2 content is preferably 8 % by mass or less.
  • the present inventors have found that the fictive temperature is correlated with the width of the temperature range of zero expansion, namely, the fictive temperature is correlated with the ⁇ T, and more specifically, when the fictive temperature is high, the ⁇ T is small, whereas when the fictive temperature is low, the ⁇ T is great.
  • the TiO 2 -SiO 2 glass (1) Owing to the fictive temperature of 850 °C or lower, the TiO 2 -SiO 2 glass (1) has ⁇ T of 7.8 0 C or greater.
  • the ⁇ T is smaller than 7.8 °C; and there is a concern, though it depends on the COT of the glass, that when the TiO 2 -SiO 2 glass (1) is used as an optical member of an exposure tool for EUVL, the coefficient of thermal expansion of the optical member upon irradiation with EUV light may be not substantially zero.
  • the fictive temperature is preferably 830 °C or lower, and more preferably 800 °C or lower. In order to make the ⁇ T greater, the fictive temperature is especially preferably 780 0 C or lower.
  • the TiO 2 -SiO 2 glass (1) having a fictive temperature of 850 °C or lower
  • a method of keeping a TiO 2 -SiO 2 glass molded article formed in a prescribed shape at a temperature of from 700 to 1,200 °C for 2 hours or more, and then decreasing the temperature to any temperature between 300 and 700 °C at an average cooling rate of 5 °C/hr or lower is preferred.
  • the obtained TiO 2 -SiO 2 glass had a fictive temperature of 750 °C.
  • the temperature decrease is carrier out preferably at an average cooling rate of 3 °C/hr or lower, and more preferably at an average cooling rate of 1 °C/hr or less.
  • the fictive temperature when the temperature decrease is carried out at a rate of 1 °C/hr or lower, the fictive temperature can be 700 °C or lower. In that case, however, when the glass is cooled at a low cooling rate, for example, at a rate of 1 °C/hr or lower, only in the temperature range of from 900 to 600 °C and at a cooling rate of 5 °C/hr or higher in other temperature region, the time can be shortened.
  • the fictive temperature of the TiO 2 -SiO 2 glass can be measured by known procedures. In the Examples as described below, the fictive temperature of the TiO 2 - SiO 2 glass was measured by the following procedures.
  • an absorption spectrum is obtained by an infrared spectrometer (Magna 760, manufactured by Nikolet Company was used in the Examples as described below).
  • a data-taking interval is set up at about 0.5 cm "1 , and an average value obtained by scanning 64 times is employed for the absorption spectrum.
  • a peak observed in the vicinity of 2,260 cm "1 is attributed to an overtone of stretching vibration by an Si-O-Si bond of the TiO 2 -SiO 2 glass.
  • a calibration curve is prepared from a glass of the same composition having a known fictive temperature by using this peak position, thereby determining the fictive temperature.
  • a reflection spectrum of the surface is measured in the same manner by using the same infrared spectrometer.
  • a peak observed in the vicinity of 1,120 cm "1 is attributed to stretching vibration by an Si-O-Si bond of the TiO 2 -SiO 2 glass.
  • a calibration curve is prepared from a glass of the same composition having a known fictive temperature by using this peak position, thereby determining the fictive temperature.
  • the TiO 2 -SiO 2 glass (1) of the invention is used as an optical member of an exposure tool for EUVL, it is important to make the TiO 2 /SiO 2 composition ratio in the glass uniform from the standpoint of reducing a variation of the coefficient of thermal expansion in the glass.
  • the variation of the fictive temperature is preferably within 50 °C, and more preferably within 30 °C.
  • the variation of the fictive temperature can be controlled within 50 °C by regulating a variation of the F concentration to 1,000 ppm or less, keeping a TiO 2 -SiO 2 glass molded article at a temperature of from 700 to 1,200 °C for 2 hours or more, and then decreasing the temperature to 700 °C or lower at an average cooling rate of 5 °C/hr or lower.
  • the "variation of the fictive temperature” is defined as a difference between the maximum value and the minimum value of the fictive temperature within an area of 30 mm x 30 mm in at least one plane.
  • the variation of the fictive temperature can be measured as follows.
  • a transparent TiO 2 -SiO 2 glass body formed in a prescribed size is sliced to form a TiO 2 - SiO 2 glass block of 50 mm x 50 mm x 6.35 mm.
  • the variation of the fictive temperature of the formed TiO 2 -SiO 2 glass body is determined.
  • the TiO 2 -SiO 2 glass (1) has an F concentration of 1,000 ppm or more.
  • F the addition of F affects the structural relaxation of the glass ⁇ Journal of Applied Physics, 91(8), 4886 (2002)). According to this, by the addition of F, the structural relaxation time is accelerated so that it becomes easy to realize a glass structure having a low fictive temperature (first effect). Therefore, for the purpose of lowering the fictive temperature of the TiO 2 -SiO 2 glass, it is an effective measure to add F.
  • the F concentration is regulated preferably to 3,000 ppm or more, and more preferably to 5,000 ppm or more.
  • the F concentration is preferably 30,000 ppm or less, and more preferably 20,000 ppm or less.
  • the F concentration can be measured by using a known method and, for example, can be measured according to the following procedures. That is, a TiO 2 -SiO 2 glass is melted by heating with anhydrous sodium carbonate, and distilled water and hydrochloric acid are added to the obtained melt in a volume ratio to the melt of 1, respectively, thereby preparing a sample liquid. An electromotive force of the sample liquid is measured by a radio meter using No. 945-220 and No.
  • a manufacturing method in which a TiO 2 -SiO 2 glass fine particle (soot) obtained by flame hydrolysis or thermal decomposition of an Si precursor and a Ti precursor serving as glass-forming raw materials is deposited and grown by a soot process, thereby obtaining a porous TiO 2 - SiO 2 glass body; and after treating the obtained porous TiO 2 -SiO 2 glass body in an F- containing atmosphere, it is heated to a transparent vitrification temperature or higher, thereby obtaining an F-containing TiO 2 -SiO 2 glass.
  • the F-containing atmosphere is preferably an inert gas atmosphere containing from 0.1 to 100 % by volume of an F- containing gas (for example, SiF 4 , SFe, CHF 3 , CF 4 , C 2 F 6 , C 3 F 8 , F 2 , etc.). It is preferred that the treatment in such an atmosphere at a pressure of from 10,000 to 200,000 Pa for from several ten minutes to several hours is carried out at a high temperature of the densification temperature or lower as described below. Also, when it is intended to lower the treatment temperature for obtaining the same doping amount of F, this can be attained by prolonging the treatment time, specifically, keeping the porous TiO 2 -SiO 2 glass body for from 5 to several ten hours. In order to increase the transmittance of the obtained glass, it is preferred to mix an oxygen gas in the heat treatment atmosphere. Examples of the soot process include an MCVD process, an OVD process and a VAD process depending upon the preparation manner.
  • an F- containing gas for example, Si
  • the densification temperature as referred to in this specification means a temperature at which the porous glass body can be densified to such an extent that a void cannot be confirmed by an optical microscope.
  • the transparent vitrification temperature as referred to herein means a temperature at which a crystal cannot be confirmed by an optical microscope, and a transparent glass is obtained.
  • F- containing materials are used as an Si precursor and a Ti precursor serving as glass- forming raw materials, or an Si precursor and a Ti precursor are subjected to flame hydrolysis or thermal decomposition in an F-containing atmosphere to obtain an F- containing porous TiO 2 -SiO 2 glass body, thereby obtaining an F-containing TiO 2 -SiO 2 glass body.
  • the TiO 2 -SiO 2 glass (1) so far as the variation of the fictive temperature falls within 50 °C, and the variation of the F concentration falls within 1,000 ppm, it enables the distribution of the coefficient of thermal expansion to fall within 30 ppb/°C within an area of 30 mm x 30 mm in at least one plane, and hence is suitable as an optical member of an exposure tool for EUVL.
  • the distribution of the coefficient of thermal expansion of the TiO 2 -SiO 2 glass can be measured by using a known method. For example, a transparent TiO 2 -SiO 2 glass body formed in a prescribed size is cut and divided into TiO 2 -SiO 2 glass small pieces of 15 mm x 15 mm x 1 mm, and the respective small pieces are measured for a coefficient of thermal expansion according to the foregoing method, thereby determining the variation of the coefficient of thermal expansion of a formed TiO 2 -SiO 2 glass block.
  • a manufacturing method including the following steps (a) to (e) can be adopted. Step (a):
  • TiO 2 -SiO 2 glass fine particles obtained through flame hydrolysis of an Si precursor and a Ti precursor serving as glass-forming raw materials are deposited and grown on a substrate, thereby forming a porous TiO 2 -SiO 2 glass body.
  • the glass- forming raw material is not particularly limited so far as it is a raw material capable of being gasified.
  • Si precursor examples include silicon halides such as chlorides, for example, SiCl 4 , SiHCl 3 , SiH 2 Cl 2 , SiH 3 Cl, etc., fluorides, for example, SiF 4 , SiHF 3 , SiH 2 F 2 , etc., bromides, for example, SiBr 4 , SiHBr 3 , etc., and iodides, for example, SiI 4 , etc.; and alkoxysilanes represented by R n Si(OR) 4- U (wherein R represents an alkyl group having from 1 to 4 carbon atoms; n represents an integer of from 0 to 3; and the plural R may be the same or different).
  • silicon halides such as chlorides, for example, SiCl 4 , SiHCl 3 , SiH 2 Cl 2 , SiH 3 Cl, etc.
  • fluorides for example, SiF 4 , SiHF 3 , SiH 2 F 2 , etc.
  • bromides for example, SiBr 4 , Si
  • examples of the Ti precursor include titanium halides, for example, TiCl 4 , TiBr 4 , etc.; and alkoxy titaniums represented by R n Ti(OR) 4 . ⁇ (wherein R represents an alkyl group having from 1 to 4 carbon atoms; n represents an integer of from 0 to 3; and the plural R may be the same or different).
  • R represents an alkyl group having from 1 to 4 carbon atoms
  • n represents an integer of from 0 to 3; and the plural R may be the same or different.
  • a compound of Si and Ti such as a silicon titanium double alkoxide can be used.
  • a seed rod made by silica glass (for example, the seed rod described in JP-B- 63-24973) can be used as the substrate.
  • the shape of the substrate to be used is not limited to a rod form but also may be in a tabular form : Step (b):
  • the porous TiO 2 -SiO 2 glass body obtained in the step (a) is kept in an F- containing atmosphere, thereby obtaining an F-containing porous TiO 2 -SiO 2 glass body.
  • This F-containing atmosphere is preferably an inert gas atmosphere containing from 0.1 to 100 % by volume of an F-containing gas (for example, SiF 4 , SF 6 , CHF 3 , CF 4 , C 2 F O , C 3 F 8 , F 2 , etc.). It is preferred that the treatment in such an atmosphere at a pressure of from
  • the use of a temperature which is higher than the transparent vitrification temperature is not preferred because the densification of the porous TiO 2 -SiO 2 glass body proceeds so that it becomes hard to incorporate F into the interior of the porous TiO 2 -SiO 2 glass body.
  • the treatment temperature and treatment time as follows can be set in accordance with the amount of F to be incorporated through doping into the porous TiO 2 -SiO 2 glass body.
  • the porous TiO 2 -SiO 2 glass body in an inert gas atmosphere containing from 5 to several tens % by volume of an F-containing gas at 1,000 °C or higher for from 2 to several ten hours.
  • an oxygen gas in the heat treatment atmosphere it is preferred to mix an oxygen gas in the heat treatment atmosphere.
  • the glass body is kept in an oxygen-containing atmosphere at from 300 to 1,300 0 C for from 5 to several ten hours to such an extent that it is not densified. This is made for the purpose of preventing coloration of the glass in the sequent heat treatment.
  • the concentration of oxygen in the atmosphere is preferably from 1 to 100 %, and for the purpose of preventing coloration of the glass more surely, it is more preferably from 20 to 100 %.
  • Pa as referred to in this specification means an absolute pressure, not a gauge pressure.
  • a reduced pressure preferably 13,000 Pa or lower, and especially 1,300 Pa or lower
  • the F-containing porous TiO 2 -SiO 2 glass body obtained in the step (b) is subjected to a temperature rise to the transparent vitrification temperature, thereby obtaining an F-containing transparent TiO 2 -SiO 2 glass body.
  • the transparent vitrification temperature is usually from 1,250 to 1,750 0 C, and especially preferably from 1,300 to 1,700 °C.
  • the temperature is preferably from 1,250 to 1,650 0 C, and especially preferably from 1,300 to 1,600 °C.
  • an atmosphere of 100 % of an inert gas such as helium or argon, or an atmosphere containing, as a major component, an inert gas such as helium is preferred.
  • reduced pressure or normal pressure is applicable. In particular, in the case of normal pressure, helium or argon can be used. Also, in the case of a reduced pressure, the pressure is preferably 13,000 Pa or lower.
  • the F-containing transparent TiO 2 -SiO 2 glass body obtained in the step (c) is heated at a temperature of the softening point or higher and formed in a desired shape, thereby obtaining an F-containing formed TiO 2 -SiO 2 glass body.
  • the forming temperature is preferably from 1,500 to 1,800 0 C. When the forming temperature is lower than 1,500 °C, since the viscosity of the F-containing transparent TiO 2 -SiO 2 glass is high, deformation due to own weight does not substantially proceed.
  • step (c) and the step (d) can be carried out continuously or simultaneously.
  • the TiO 2 -SiO 2 glass body obtained in the step (c) or the step (d) is kept at a temperature of from 700 to 1,200 °C for 2 hours or more and then subjected to an annealing treatment for decreasing the temperature to 700 °C or lower at an average cooling rate of 5 °C/hr or lower, thereby controlling the fictive temperature of the TiO 2 - SiO 2 glass.
  • the TiO 2 -SiO 2 glass body obtained in the step (c) or the step (d) is subjected to an annealing treatment for decreasing the temperature to 700 °C or lower at an average cooling rate of 5 °C/hr or lower, thereby controlling the fictive temperature of the TiO 2 -SiO 2 glass.
  • the atmosphere is preferably an atmosphere of 100 % of an inert gas such as helium, argon, or nitrogen, an atmosphere containing, as a major component, such an inert gas, or an air atmosphere; and the pressure is preferably reduced pressure or normal pressure.
  • an inert gas such as helium, argon, or nitrogen
  • the pressure is preferably reduced pressure or normal pressure.
  • the slowest cooling rate in the temperature decrease profile of the step (e) is preferably 1 °C/hr or lower, more preferably 0.5 °C/hr or lower, and especially preferably 0.3 °C/hr or lower.
  • TiO 2 -SiO 2 glass (2) Another embodiment of the TiO 2 -SiO 2 glass of the invention satisfying the foregoing COT and ⁇ T requirements (hereinafter referred to as "TiO 2 -SiO 2 glass (2)") satisfies the following requirements.
  • TiO 2 content 3 to 9 % by mass .
  • Fictive temperature 800 0 C or lower
  • the TiO 2 -SiO 2 glass (2) contains OH in addition to TiO 2 and SiO 2 .
  • the TiO 2 -SiO 2 glass (2) has a TiO 2 content of from 3 to 9 % by mass.
  • the COT does not exist in the temperature range of from 15 to 35 °C. Specifically, when the TiO 2 content is less than 3 % by mass, the COT exceeds 35 °C, and when the TiO 2 content exceeds 9 % by mass, the COT is lower than 15 0 C.
  • the TiO 2 content is preferably from 5 to 9 % by mass, and more preferably from 6 to 8 % by mass.
  • the TiO 2 -SiO 2 glass (2) Owing to the fictive temperature of 800 °C or lower and the OH concentration of 600 ppm or more, the TiO 2 -SiO 2 glass (2) has ⁇ T of 7.8 °C or greater. When the fictive temperature exceeds 800 °C, the ⁇ T is smaller than 7.8 0 C; and there is a concern, though it depends on the COT of the glass, that when the TiO 2 -SiO 2 glass (2) is used as an optical member of an exposure tool for EUVL, the coefficient of thermal expansion of the optical member upon irradiation with EUV light may be not substantially zero. Taking into account the fact that the lower the fictive temperature, the greater the ⁇ T, the fictive temperature is preferably 780 °C or lower, and more preferably 750 0 C or lower.
  • a method of decreasing the temperature to 700 °C or lower at an average cooling rate of 1 °C/hr or lower is more preferred; and a method of decreasing the temperature to 700 °C or lower at an average cooling rate of 0.5 °C/hr or lower is especially preferred.
  • the TiO 2 -SiO 2 glass (2) is used as an optical member of an exposure tool for EUVL, it is important to make the TiO 2 /SiO 2 composition ratio in the glass uniform from the standpoint of reducing a variation of the coefficient of thermal expansion in the glass.
  • a variation of the fictive temperature is preferably within 50 °C, and especially preferably within 30 °C.
  • the variation of the fictive temperature can be controlled to 50 °C or lower by regulating the variation of the OH concentration to 200 ppm or less, keeping the TiO 2 -SiO 2 glass molded article at a temperature of from 700 to 1,200 °C for 2 hours or more, and then decreasing the temperature to 700 °C or lower at an average cooling rate of 3 °C/hr or lower.
  • the TiO 2 -SiO 2 glass (2) has an OH concentration of 600 ppm or more.
  • the structural relaxation of the glass is accelerated so that it becomes easy to realize a glass structure having a low fictive temperature. Therefore, for the purpose of lowering the fictive temperature of the TiO 2 -SiO 2 glass, it is an effective measure to incorporate OH.
  • the TiO 2 - SiO 2 glass (2) having a fictive temperature of 800 °C or lower can be obtained.
  • the OH concentration is less than 600 ppm, a TiO 2 -SiO 2 glass having a fictive temperature of 800 0 C ot lower cannot be obtained, even if the procedures (A) are carried out.
  • the OH concentration is regulated preferably to 1,000 ppm or more, and more preferably to 1,300 ppm or more.
  • the OH concentration of the TiO 2 -SiO 2 glass can be measured by using a known method.
  • the OH concentration can be determined from an absorption peak at a wavelength of 2.7 ⁇ m through the measurement by an infrared spectrometer (see J.P. Williams, et al., American Ceramic Society Bulletin, 55(5), 524, 1976).
  • the detection limit by this method is 0.1 ppm.
  • the OH-containing TiO 2 -SiO 2 glass can be manufactured by adopting a soot process or a direct method the same as in the foregoing F-containing TiO 2 -SiO 2 glass.
  • a TiO 2 -SiO 2 glass fine particle (soot) obtained by flame hydrolysis or thermal decomposition of an Si precursor and a Ti precursor serving as glass-forming raw materials is deposited and grown by a soot process, thereby obtaining a porous TiO 2 -SiO 2 glass body; and after treating the obtained porous TiO 2 -SiO 2 glass body in a water vapor-containing atmosphere, it is heated to a densification temperature or higher in a water vapor-containing atmosphere and further heated to a transparent vitrification temperature or higher, thereby obtaining an OH-containing TiO 2 -SiO 2 glass.
  • the glass-forming raw material is not particularly limited so far as it is a raw material capable of being gasified.
  • Si precursor examples include silicon halides such as chlorides (for example, SiCU, SiHCh, SiH 2 Cl 2 , SiH 3 Cl, etc.), fluorides (for example, SiF 4 , SiHF 3 , SiH 2 F 2 , etc.), bromides (for example, SiBr 4 , SiHBr 3 , etc.) and iodides (for example, SiI 4 , etc.); and alkoxysilanes represented by R n Si(OR) 4 ., (wherein R represents an alkyl group having from 1 to 4 carbon atoms; and n represents an integer of from 0 to 3).
  • silicon halides such as chlorides (for example, SiCU, SiHCh, SiH 2 Cl 2 , SiH 3 Cl, etc.), fluorides (for example, SiF 4 , SiHF 3 , SiH 2 F 2 , etc.), bromides (for example, SiBr 4 , SiHBr 3 , etc.) and iodides (for example,
  • examples of the Ti precursor include titanium halides (for example, TiCl 4 , TiBr 4 , etc.); and alkoxy titaniums represented by R n Ti(OR) 4- D (wherein R represents an alkyl group having from 1 to 4 carbon atoms; and n represents an integer of from 0 to 3).
  • a compound of Si and Ti such as a silicon titanium double alkoxide can be used.
  • a seed rod made by silica glass (for example, the seed rod described in JP-B- 63-24973) can be used as the substrate. Also, the shape of the substrate to be used is not limited to a rod form but also may be in a tabular form. Step (b):
  • the porous TiO 2 -SiO 2 glass body obtained in the step (a) is subjected to a temperature rise to a densification temperature in a water vapor-containing atmosphere, thereby obtaining an OH-containing TiO 2 -SiO 2 dense body.
  • the densification temperature is in general from 1,250 to 1,550 °C, and especially preferably from 1,300 to 1,500 0 C.
  • the temperature is preferably from 1,250 to 1,450 °C, and especially preferably from 1,300 to 1,400 °C.
  • an inert gas atmosphere where water vapor partial pressure (P H2O ) is from 50,000 to 100,000 Pa is preferred.
  • Helium is preferred as the inert gas. It is preferred that the treatment is carried out at a pressure of from about 50,000 to 100,000 Pa under such an atmosphere.
  • step (b) it is preferred for attaining improved homogeneity of the TiO 2 -SiO 2 dense body that after placing the porous TiO 2 -SiO 2 glass body under a reduced pressure (preferably 13,000 Pa or lower, and especially 1,300 Pa or lower), an inert gas and an inert gas containing water vapor or water vapor is introduced until a prescribed water vapor partial pressure is attained, so that that atmosphere contains water vapor.
  • a reduced pressure preferably 13,000 Pa or lower, and especially 1,300 Pa or lower
  • the OH-containing TiO 2 -SiO 2 dense body obtained in the step (b) is subjected to a temperature rise to the transparent vitrification temperature, thereby obtaining an OH-containing transparent TiO 2 -SiO 2 glass body.
  • the transparent vitrification temperature is usually from 1,350 to 1,800 °C, and especially preferably from 1,400 to 1,750 °C.
  • the temperature is preferably from 1,350 to 1,750 °C, and especially preferably from 1,400 to 1,700 °C.
  • an atmosphere of 100 % of an inert gas such as helium or argon, or an atmosphere containing, as a major component, an inert gas such as helium and/or argon, is preferred.
  • a reduced pressure or normal pressure is applicable. In the case of a reduced pressure, the pressure is preferably 13,000 Pa or lower.
  • the OH-containing transparent TiO 2 -SiO 2 glass body obtained in the step (c) is heated at a temperature of the softening point or higher and formed in a desired shape, thereby obtaining an OH-containing formed TiO 2 -SiO 2 glass body.
  • the forming temperature is preferably from 1,500 to 1,800 °C. When the forming temperature is lower than 1,500 °C, since the viscosity of the OH-containing transparent TiO 2 -SiO 2 glass body is high, deformation due to own weight does not substantially proceed.
  • Step (c) and the step (d) can be carried out continuously or simultaneously. Also, in the case where the shape of the glass body obtained in the step (c) is accepted, the step (d) may be omitted.
  • the TiO 2 -SiO 2 glass body obtained in the step (c) or the step (d) is subjected to an annealing treatment for decreasing the temperature to 700 °C or lower at an average cooling rate of 3 °C/hr or lower, thereby controlling the fictive temperature of the TiO 2 -SiO 2 glass.
  • the TiO 2 -SiO 2 glass can natural cooling can be adaptable.
  • the atmosphere is preferably an atmosphere of 100 % of an inert gas such as helium, argon or nitrogen, an atmosphere containing, as a major component, such an inert gas, or an air atmosphere; and the pressure is preferably a reduced pressure or normal pressure.
  • the slowest cooling rate in the temperature decrease profile of the step (e) is preferably 1 °C/hr or lower, more preferably 0.5 °C/hr or lower, and especially preferably 0.3 °C/hr or lower.
  • an absolute value of an average coefficient of thermal expansion in the range of from 15 to 35 °C is preferably 30 ppb/°C or lower. According to this, even when the temperature of the optical member changes, changes in dimension and shape can be minimized.
  • the absolute value of an average coefficient of linear thermal expansion in the range of from 15 to 35 °C is more preferably 15 ppb/°C or lower, further preferably 10 ppb/°C or lower, and especially preferably 5 ppb/°C or lower.
  • TiO 2 -SiO 2 glass fine particles obtainable by gasifying each of TiCl 4 and SiCl 4 which were glass-forming raw materials of a TiO 2 -SiO 2 glass and then mixing and subjecting the mixture to heat hydrolysis (flame hydrolysis) in an oxyhydrogen flame was deposited and grown on a substrate, thereby forming a porous TiO 2 -SiO 2 glass body (step (a)).
  • the obtained porous TiO 2 -SiO 2 glass body was kept in air at 1,200 °C for 4 hours together with substrate and then separated from the substrate.
  • porous TiO 2 -SiO 2 glass body was placed in an atmosphere- controllable electric furnace, and the pressure was reduced to about 1,000 Pa at room temperature. Thereafter, the resulting porous TiO 2 -SiO 2 glass body was kept in this atmosphere at 1,100 °C under normal pressure for 4 hours while introducing a mixed gas of He and SiF 4 in a ratio 90/10 (by volume), thereby effecting doping with F.
  • step (b) Thereafter, the system was kept in an atmosphere of 100 % O 2 at 1,050 °C under normal pressure for 4 hours; and thereafter, after raising the temperature to 1,450 °C in an atmosphere of 100 % He, the system was kept at this temperature for 4 hours, thereby obtaining an F-containing TiO 2 -SiO 2 dense body (step (b)).
  • the obtained F-containing TiO 2 -SiO 2 dense body was heated to 1,650 °C in an argon atmosphere using a carbon furnace, thereby obtaining an F-containing transparent TiO 2 -SiO 2 glass body (step (c)).
  • the obtained glass was kept at 1,000 °C for 10 hours and then subjected to temperature decrease to 300 °C at a rate of 5 °C/hr, followed by allowing it to stand for natural cooling (step (e)).
  • TiO 2 -SiO 2 glass fine particles obtainable by gasifying each of TiCl 4 and SiCl 4 which were glass-forming raw materials of a TiO 2 -SiO 2 glass and then mixing and subjecting the mixture to heat hydrolysis (flame hydrolysis) in an oxyhydrogen flame was deposited and grown on a substrate, thereby forming a porous TiO 2 -SiO 2 glass body (step (a)).
  • the obtained porous TiO 2 -SiO 2 glass body was kept in air at 1,200 °C for 6 hours together with the substrate and then separated from the substrate.
  • porous TiO 2 -SiO 2 glass body was placed in an atmosphere- controllable electric furnace, and the pressure was reduced to about 1,000 Pa at room temperature. Thereafter, water was charged in a glass-made bubbler; bubbling with an He gas was carried out at 100 °C at atmospheric pressure; and the resulting porous TiO 2 -SiO 2 glass body was kept in this atmosphere at 1,000 0 C under normal pressure for 4 hours while introducing water vapor together with an He gas into the furnace, thereby effecting doping with OH.
  • step (b) Thereafter, after raising the temperature to 1,450 °C in the same atmosphere, the system was kept at this temperature for 4 hours, thereby obtaining an OH-containing TiO 2 -SiO 2 dense body (step (b)).
  • the obtained OH-containing TiO 2 -SiO 2 dense body was heated to 1,700 °C in an argon atmosphere using a carbon furnace, thereby obtaining an OH-containing transparent TiO 2 -SiO 2 glass body (step (c)).
  • the obtained glass was kept at 1,100 °C for 10 hours and then subjected to temperature decrease to 900 °C at a rate of 10 °C/hr; then subjected to temperature decrease at 700 °C at a rate of 1 °C/hr; and further subjected to temperature decrease to 500 °C at a rate of 10 °C/hr, followed by allowing it to stand for natural cooling (step
  • TiO 2 -SiO 2 glass fine particles obtainable by gasifying each OfTiCl 4 and SiCl 4 which were glass-forming raw materials of a TiO 2 -SiO 2 glass and then mixing and subjecting the mixture to heat hydrolysis (flame hydrolysis) in an oxyhydrogen flame was deposited and grown on a substrate, thereby forming a porous TiO 2 -SiO 2 glass body (step (a)).
  • the obtained porous TiO 2 -SiO 2 glass body was kept in air at 1,200 °C for 4 hours together with the substrate and then separated from the substrate. Thereafter, the porous TiO 2 -SiO 2 glass body was placed in an atmosphere- controllable electric furnace, and the pressure was reduced to about 1,000 Pa at room temperature. Thereafter, the resulting porous TiO 2 -SiO 2 glass body was kept in this atmosphere at 900 °C under normal pressure for 1 hour while introducing a mixed gas of He and SiF 4 in a ratio of 90/10 (by volume), thereby effecting doping with F.
  • step (b) Thereafter, the system was kept in an atmosphere of 100 % O 2 at 1,050 °C under normal pressure for 4 hours, and the temperature was then raised to 1,450 °C in an atmosphere of 100 % He, followed by keeping at this temperature for 4 hours, thereby obtaining an F-containing TiO 2 -SiO 2 dense body (step (b)).
  • the obtained F-containing TiO 2 -SiO 2 dense body was heated at 1,700 0 C in an argon atmosphere using a carbon furnace, thereby obtaining an F-containing transparent TiO 2 -SiO 2 glass body (step (c)).
  • the obtained transparent TiO 2 -SiO 2 glass body was allowed to stand for cooling from 1,700 °C within the furnace.
  • the average cooling rate to 700 °C exceeded 5 °C/hr (step (e)).
  • TiO 2 -SiO 2 glass fine particles obtainable by gasifying each of TiCU and SiCU which were glass-forming raw materials of a TiO 2 -SiO 2 glass and then mixing and subjecting the mixture to heat hydrolysis (flame hydrolysis) in an oxyhydrogen flame was deposited and grown on a substrate, thereby forming a porous TiO 2 -SiO 2 glass body (step (a)).
  • the obtained porous TiO 2 -SiO 2 glass body was kept in air at 1,200 0 C for 4 hours together with the substrate and then separated from the substrate. Thereafter, the porous TiO 2 -SiO 2 glass body was placed in an atmosphere- controllable electric furnace, and the pressure was reduced to about 1,000 Pa at room temperature. Thereafter, the temperature was raised to 1,450 0 C in an atmosphere of 100 % He, followed by keeping at this temperature for 4 hours, thereby obtaining a TiO 2 -SiO 2 dense body (step (b)).
  • the obtained TiO 2 -SiO 2 dense body was heated at 1,750 °C in an argon atmosphere using a carbon furnace, thereby obtaining a transparent TiO 2 -SiO 2 glass body (step (c)). Subsequently, in the carbon furnace, the obtained transparent TiO 2 -SiO 2 glass body was allowed to stand for cooling from 1,750 °C within the furnace. The average cooling rate to 700 °C exceeded 5 °C/hr (step (e)).
  • Example 6 TiO 2 -SiO 2 glass fine particles obtainable by gasifying each OfTiCl 4 and SiCl 4 which are glass-forming raw materials of a TiO 2 -SiO 2 glass and then mixing, and subjecting the mixture to heat hydrolysis (flame hydrolysis) in an oxyhydrogen flame is deposited and grown on a substrate, thereby forming a porous TiO 2 -SiO 2 glass body (step (a)). Since it is hard to handle the obtained porous TiO 2 -SiO 2 glass body without any treatment, the obtained porous TiO 2 -SiO 2 glass body is kept in air at 1,200 °C for 4 hours together with the substrate and then separated from the substrate.
  • the porous TiO 2 -SiO 2 glass body is placed in an atmosphere- controllable electric furnace, and the pressure is reduced to about 1,000 Pa at room temperature. Thereafter, the resulting porous TiO 2 -SiO 2 glass body is kept in this atmosphere at 1,000 °C under normal pressure for 4 hours while introducing a mixed gas of He, O 2 and SiF 4 in a ratio 88/2/10 (by volume), thereby effecting doping with F.
  • step (b) Thereafter, after raising the temperature to 1,450 °C in an atmosphere of 100 % He, the system is kept at this temperature for 4 hours, thereby obtaining an F-containing TiO 2 -SiO 2 dense body (step (b)).
  • the obtained F-containing TiO 2 -SiO 2 dense body is heated to 1,650 °C in an argon atmosphere using a carbon furnace, thereby obtaining an F-containing transparent TiO 2 -SiO 2 glass body (step (c)).
  • the obtained glass is kept at 1,000 °C for 10 hours and then subjected to temperature decrease to 300 °C at a rate of 5 °C/hr, followed by allowing it to stand for natural cooling (step (e)).
  • FIG. 2 is a graph showing the relationship between the CTE and the temperature with respect to the glasses prepared in the foregoing Examples 1 to 6; and the CTE was determined by measuring elongation of a sample by continuous temperature rise in the range of from -50 to +100 0 C using a laser interferometric dilatometer.
  • the coefficient of thermal expansion is substantially zero (0 + 5 ppb/°C) under a temperature condition (under a temperature condition of optical member upon irradiation with EUV light) in an exposure tool at the time of carrying out EUVL
  • the glasses of Examples 1, 2 and 6 are suitable for an optical member of an exposure tool for EUVL.
  • the TiO 2 -SiO 2 glass of the invention a temperature range where a coefficient of thermal expansion is substantially zero is wide, and the temperature region where a coefficient of thermal expansion is substantially zero includes the temperature of an optical member upon irradiation with EUV light. Therefore, the TiO 2 -SiO 2 glass of the invention is extremely suitable as an optical member of an exposure tool for EUVL.

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Abstract

La présente invention porte sur un verre de TiO2-SiO2 ayant des propriétés de dilatation thermique appropriées, en tant qu'élément optique d'un outil d'exposition pour une lithographie par ultraviolet extrême (EUVL). La présente invention porte sur un verre de silice contenant du TiO2, ayant une teneur en TiO2 de 3 à 9 % en masse ; une température, à laquelle un coefficient de dilatation thermique est de 0 ppb/°C, tombant dans la plage de 15 à 35 °C ; une température fictive de 850 °C ou moins ; et une fenêtre de température, dans laquelle un coefficient de dilatation thermique est 0 + 5 ppb/°C, de 7,8°C ou plus.
PCT/JP2009/056205 2008-03-21 2009-03-19 Verre de silice contenant du tio<sb>2</sb> Ceased WO2009116690A1 (fr)

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US20110207593A1 (en) * 2010-02-25 2011-08-25 Carlos Duran Expansivity in Low Expansion Silica-Titania Glasses
EP2428488A1 (fr) * 2010-02-25 2012-03-14 Corning Incorporated Verre en silice dopé au titane à haute transmission et faible dilatation
US8735308B2 (en) 2009-01-13 2014-05-27 Asahi Glass Company, Limited Optical member comprising TiO2-containing silica glass
EP2757078A1 (fr) * 2013-01-22 2014-07-23 Shin-Etsu Chemical Co., Ltd. Élément de lithographie EUV, son procédé de fabrication et verre de quartz dopé au titane
US8901019B2 (en) 2012-11-30 2014-12-02 Corning Incorporated Very low CTE slope doped silica-titania glass
EP3000791B1 (fr) * 2014-09-24 2017-04-26 Heraeus Quarzglas GmbH & Co. KG Procédé de fabrication d'une ébauche en verre contenant de l'acide silicique à haute densité, du fluor et doté de titane pour l'utilisation dans la lithographie EUV et ébauche ainsi obtenue
EP3222592A1 (fr) * 2013-09-13 2017-09-27 Corning Incorporated Verre à très faible expansion
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US9611169B2 (en) 2014-12-12 2017-04-04 Corning Incorporated Doped ultra-low expansion glass and methods for making the same
JP2018513093A (ja) 2015-03-26 2018-05-24 コーニング インコーポレイテッド 極紫外線リソグラフィーに使用するためのガラス複合体
JP7155098B2 (ja) * 2019-12-11 2022-10-18 クアーズテック株式会社 光学素子用シリカガラスおよびその製造方法
US12209046B2 (en) * 2020-05-13 2025-01-28 AGC Inc. Glass substrate for EUVL, manufacturing method thereof, mask blank for EUVL, and manufacturing method thereof

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US8735308B2 (en) 2009-01-13 2014-05-27 Asahi Glass Company, Limited Optical member comprising TiO2-containing silica glass
US8546283B2 (en) 2009-12-25 2013-10-01 Asahi Glass Company, Limited Substrate for EUVL optical member
WO2011078414A3 (fr) * 2009-12-25 2011-08-18 Asahi Glass Company, Limited. Substrat pour élément optique de lithographie euv
JP2011151386A (ja) * 2009-12-25 2011-08-04 Asahi Glass Co Ltd Ｅｕｖｌ光学部材用基材
EP2428488A1 (fr) * 2010-02-25 2012-03-14 Corning Incorporated Verre en silice dopé au titane à haute transmission et faible dilatation
US8541325B2 (en) 2010-02-25 2013-09-24 Corning Incorporated Low expansivity, high transmission titania doped silica glass
US20110207593A1 (en) * 2010-02-25 2011-08-25 Carlos Duran Expansivity in Low Expansion Silica-Titania Glasses
US8901019B2 (en) 2012-11-30 2014-12-02 Corning Incorporated Very low CTE slope doped silica-titania glass
EP2757078A1 (fr) * 2013-01-22 2014-07-23 Shin-Etsu Chemical Co., Ltd. Élément de lithographie EUV, son procédé de fabrication et verre de quartz dopé au titane
JP2014160237A (ja) * 2013-01-22 2014-09-04 Shin Etsu Chem Co Ltd Ｅｕｖリソグラフィ用部材及びその製造方法並びにチタニアドープ石英ガラス
EP3222592A1 (fr) * 2013-09-13 2017-09-27 Corning Incorporated Verre à très faible expansion
US9890071B2 (en) 2013-09-13 2018-02-13 Corning Incorporated Ultralow expansion glass
EP3000791B1 (fr) * 2014-09-24 2017-04-26 Heraeus Quarzglas GmbH & Co. KG Procédé de fabrication d'une ébauche en verre contenant de l'acide silicique à haute densité, du fluor et doté de titane pour l'utilisation dans la lithographie EUV et ébauche ainsi obtenue
US10017413B2 (en) 2014-11-26 2018-07-10 Corning Incorporated Doped silica-titania glass having low expansivity and methods of making the same

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