JP5733350B2 - Silica glass containing TiO2 and method for producing the same - Google Patents
Silica glass containing TiO2 and method for producing the same Download PDFInfo
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- JP5733350B2 JP5733350B2 JP2013151586A JP2013151586A JP5733350B2 JP 5733350 B2 JP5733350 B2 JP 5733350B2 JP 2013151586 A JP2013151586 A JP 2013151586A JP 2013151586 A JP2013151586 A JP 2013151586A JP 5733350 B2 JP5733350 B2 JP 5733350B2
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- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 title claims description 14
- 238000004519 manufacturing process Methods 0.000 title description 7
- GWEVSGVZZGPLCZ-UHFFFAOYSA-N Titan oxide Chemical compound O=[Ti]=O GWEVSGVZZGPLCZ-UHFFFAOYSA-N 0.000 title description 6
- 125000002887 hydroxy group Chemical group [H]O* 0.000 claims description 28
- 239000011521 glass Substances 0.000 description 97
- 229910010413 TiO 2 Inorganic materials 0.000 description 90
- 229910004298 SiO 2 Inorganic materials 0.000 description 80
- 238000000034 method Methods 0.000 description 27
- 239000000463 material Substances 0.000 description 25
- 230000003287 optical effect Effects 0.000 description 16
- 238000001900 extreme ultraviolet lithography Methods 0.000 description 13
- 239000002243 precursor Substances 0.000 description 10
- -1 SiCl 4 Chemical class 0.000 description 8
- 238000001816 cooling Methods 0.000 description 8
- 239000000203 mixture Substances 0.000 description 8
- 238000009826 distribution Methods 0.000 description 7
- 239000004071 soot Substances 0.000 description 6
- 239000010936 titanium Substances 0.000 description 6
- 238000005259 measurement Methods 0.000 description 5
- 239000002994 raw material Substances 0.000 description 5
- 238000007496 glass forming Methods 0.000 description 4
- 239000001307 helium Substances 0.000 description 4
- 229910052734 helium Inorganic materials 0.000 description 4
- SWQJXJOGLNCZEY-UHFFFAOYSA-N helium atom Chemical compound [He] SWQJXJOGLNCZEY-UHFFFAOYSA-N 0.000 description 4
- 230000007062 hydrolysis Effects 0.000 description 4
- 238000006460 hydrolysis reaction Methods 0.000 description 4
- 239000011261 inert gas Substances 0.000 description 4
- 239000000758 substrate Substances 0.000 description 4
- 238000000862 absorption spectrum Methods 0.000 description 3
- 239000000460 chlorine Substances 0.000 description 3
- 239000010419 fine particle Substances 0.000 description 3
- 238000004017 vitrification Methods 0.000 description 3
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 description 2
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 2
- 229910003902 SiCl 4 Inorganic materials 0.000 description 2
- 229910002808 Si–O–Si Inorganic materials 0.000 description 2
- 238000010521 absorption reaction Methods 0.000 description 2
- 238000011088 calibration curve Methods 0.000 description 2
- 125000004432 carbon atom Chemical group C* 0.000 description 2
- 230000000052 comparative effect Effects 0.000 description 2
- 230000003247 decreasing effect Effects 0.000 description 2
- 239000002245 particle Substances 0.000 description 2
- 238000000206 photolithography Methods 0.000 description 2
- 238000010583 slow cooling Methods 0.000 description 2
- 238000001228 spectrum Methods 0.000 description 2
- 229910052719 titanium Inorganic materials 0.000 description 2
- ZAMOUSCENKQFHK-UHFFFAOYSA-N Chlorine atom Chemical compound [Cl] ZAMOUSCENKQFHK-UHFFFAOYSA-N 0.000 description 1
- PXGOKWXKJXAPGV-UHFFFAOYSA-N Fluorine Chemical compound FF PXGOKWXKJXAPGV-UHFFFAOYSA-N 0.000 description 1
- 229910003691 SiBr Inorganic materials 0.000 description 1
- UGACIEPFGXRWCH-UHFFFAOYSA-N [Si].[Ti] Chemical compound [Si].[Ti] UGACIEPFGXRWCH-UHFFFAOYSA-N 0.000 description 1
- 239000006096 absorbing agent Substances 0.000 description 1
- 150000004703 alkoxides Chemical class 0.000 description 1
- 125000000217 alkyl group Chemical group 0.000 description 1
- 238000000137 annealing Methods 0.000 description 1
- 229910052786 argon Inorganic materials 0.000 description 1
- 150000001649 bromium compounds Chemical class 0.000 description 1
- 239000000919 ceramic Substances 0.000 description 1
- 229910052801 chlorine Inorganic materials 0.000 description 1
- 150000001805 chlorine compounds Chemical class 0.000 description 1
- SLLGVCUQYRMELA-UHFFFAOYSA-N chlorosilicon Chemical compound Cl[Si] SLLGVCUQYRMELA-UHFFFAOYSA-N 0.000 description 1
- 150000001875 compounds Chemical class 0.000 description 1
- 238000007796 conventional method Methods 0.000 description 1
- 229910052906 cristobalite Inorganic materials 0.000 description 1
- 238000005520 cutting process Methods 0.000 description 1
- 230000008021 deposition Effects 0.000 description 1
- 238000001514 detection method Methods 0.000 description 1
- 238000004031 devitrification Methods 0.000 description 1
- 238000011156 evaluation Methods 0.000 description 1
- 239000011737 fluorine Substances 0.000 description 1
- 229910052731 fluorine Inorganic materials 0.000 description 1
- 150000002222 fluorine compounds Chemical class 0.000 description 1
- 239000007789 gas Substances 0.000 description 1
- 229910052736 halogen Inorganic materials 0.000 description 1
- 150000002367 halogens Chemical class 0.000 description 1
- CPBQJMYROZQQJC-UHFFFAOYSA-N helium neon Chemical compound [He].[Ne] CPBQJMYROZQQJC-UHFFFAOYSA-N 0.000 description 1
- XMBWDFGMSWQBCA-UHFFFAOYSA-N hydrogen iodide Chemical compound I XMBWDFGMSWQBCA-UHFFFAOYSA-N 0.000 description 1
- 238000001459 lithography Methods 0.000 description 1
- 238000000465 moulding Methods 0.000 description 1
- 229910052757 nitrogen Inorganic materials 0.000 description 1
- 239000005373 porous glass Substances 0.000 description 1
- 239000004065 semiconductor Substances 0.000 description 1
- 229910052710 silicon Inorganic materials 0.000 description 1
- 150000003377 silicon compounds Chemical class 0.000 description 1
- 239000000377 silicon dioxide Substances 0.000 description 1
- 238000000859 sublimation Methods 0.000 description 1
- 230000008022 sublimation Effects 0.000 description 1
- 238000005979 thermal decomposition reaction Methods 0.000 description 1
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
-
- 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
Description
本発明は、ＴｉＯ２を含有するシリカガラス（以下、本明細書では、ＴｉＯ２−ＳｉＯ２ガラスと記す）およびその製造方法に関し、特にＥＵＶリソグラフィに使用される露光装置光学材として用いられるＴｉＯ２−ＳｉＯ２ガラスおよびその製造方法に関する。なお、本発明でいうＥＵＶ（Ｅｘｔｒｅｍｅ Ｕｌｔｒａ Ｖｉｏｌｅｔ）光とは、軟Ｘ線領域または真空紫外域の波長帯の光を指し、具体的には波長が０．２〜１００ｎｍ程度の光のことである。 The present invention is a silica glass containing TiO 2 (hereinafter, in this specification, referred to as TiO 2 -SiO 2 glass) and relates to a manufacturing method thereof, TiO 2, particularly used as an exposure apparatus optical material for use in EUV lithography It relates to —SiO 2 glass and a method for producing the same. The EUV (Extreme Ultra Violet) light referred to in the present invention refers to light in the wavelength band of the soft X-ray region or the vacuum ultraviolet region, specifically, light having a wavelength of about 0.2 to 100 nm. .
従来から、光リソグラフィ技術においては、ウェハ上に微細な回路パターンを転写して集積回路を製造するための露光装置が広く利用されている。集積回路の高集積化および高機能化に伴い、集積回路の微細化が進み、露光装置には深い焦点深度で高解像度の回路パターンをウェハ面上に結像させることが求められ、露光光源の短波長化が進められている。露光光源は、従来のｇ線（波長４３６ｎｍ）、ｉ線（波長３６５ｎｍ）やＫｒＦエキシマレーザ（波長２４８ｎｍ）から進んでＡｒＦエキシマレーザ（波長１９３ｎｍ）が用いられようとしている。また、さらに回路パターンの線幅が１００ｎｍ以下となる次世代の集積回路に対応するため、露光光源としてＦ２レーザ（波長１５７ｎｍ）を用いることが有力視されているが、これも線幅が７０ｎｍ世代までしかカバーできないと見られている。 Conventionally, in an optical lithography technique, an exposure apparatus for manufacturing an integrated circuit by transferring a fine circuit pattern onto a wafer has been widely used. As integrated circuits become highly integrated and highly functional, miniaturization of integrated circuits advances, and the exposure apparatus is required to form a high-resolution circuit pattern on the wafer surface with a deep focal depth. Short wavelength is being promoted. As an exposure light source, an ArF excimer laser (wavelength 193 nm) is going to be used, proceeding from conventional g-line (wavelength 436 nm), i-line (wavelength 365 nm) or KrF excimer laser (wavelength 248 nm). Further, in order to cope with a next-generation integrated circuit in which the line width of the circuit pattern is 100 nm or less, it is considered promising to use an F 2 laser (wavelength 157 nm) as an exposure light source, which also has a line width of 70 nm. It is considered that only generations can be covered.
このような流れにあって、露光光源としてＥＵＶ光（極端紫外光）のうち代表的には波長１３ｎｍの光を用いたリソグラフィ技術が、５０ｎｍ以降の複数世代にわたって適用可能と見られ注目されている。ＥＵＶリソグラフィ（以下、「ＥＵＶＬ」と略する）の像形成原理は、投影光学系を用いてマスクパターンを転写する点では、従来のフォトリソグラフィーと同じである。しかし、ＥＵＶ光のエネルギー領域では光を透過する材料が無いために、屈折光学系は用いることができず、光学系はすべて反射光学系となる。 In such a flow, a lithography technique that typically uses light having a wavelength of 13 nm among EUV light (extreme ultraviolet light) as an exposure light source is considered to be applicable over a plurality of generations after 50 nm, and is attracting attention. . The image forming principle of EUV lithography (hereinafter abbreviated as “EUVL”) is the same as that of conventional photolithography in that a mask pattern is transferred using a projection optical system. However, since there is no material that transmits light in the EUV light energy region, the refractive optical system cannot be used, and all the optical systems are reflective optical systems.
ＥＵＶＬに用いられる露光装置光学材はフォトマスクやミラーなどであるが、（１）基材、（２）基材上に形成された反射多層膜、（３）反射多層膜上に形成された吸収体層、から基本的に構成される。多層膜は、Ｍｏ／Ｓｉが交互に層を形成することが検討され、吸収体層には、成膜材料として、ＴａやＣｒが検討されている。基材としては、ＥＵＶ光照射の下においても歪みが生じないよう低熱膨張係数を有する材料が必要とされ、低熱膨張係数を有するガラス等が検討されている。 The exposure apparatus optical material used for EUVL is a photomask or mirror, but (1) a base material, (2) a reflective multilayer film formed on the base material, and (3) an absorption formed on the reflective multilayer film. It is basically composed of body layers. As for the multilayer film, it is considered that Mo / Si alternately forms layers, and Ta and Cr are studied as film forming materials for the absorber layer. As the base material, a material having a low thermal expansion coefficient is required so that distortion does not occur even under EUV light irradiation, and glass having a low thermal expansion coefficient is being studied.
ＴｉＯ２−ＳｉＯ２ガラスは、石英ガラスよりも小さい熱膨張係数（Ｃｏｅｆｆｉｃｉｅｎｔ ｏｆ Ｔｈｅｒｍａｌ Ｅｘｐａｎｓｉｏｎ；ＣＴＥ）を有する超低熱膨張材料として知られ、またガラス中のＴｉＯ２含有量によって熱膨張係数を制御できるために、熱膨張係数が０に近いゼロ膨張ガラスが得られる。したがって、ＴｉＯ２−ＳｉＯ２ガラスはＥＵＶＬ用露光装置光学材に用いる材料としての可能性がある。 TiO 2 —SiO 2 glass is known as an ultra-low thermal expansion material having a smaller coefficient of thermal expansion (CTE) than quartz glass, and the coefficient of thermal expansion can be controlled by the TiO 2 content in the glass. In addition, a zero expansion glass having a thermal expansion coefficient close to 0 is obtained. Therefore, TiO 2 —SiO 2 glass has a possibility as a material used for the exposure apparatus optical material for EUVL.
従来のＴｉＯ２−ＳｉＯ２ガラスの作製方法は、まず、シリカ前駆体とチタニア前駆体をそれぞれ蒸気形態に転化させてこれらを混合する。この蒸気形態となった混合物は、バーナーに導入され熱分解することでＴｉＯ２−ＳｉＯ２ガラス粒子となる。このＴｉＯ２−ＳｉＯ２ガラス粒子は耐火性容器中に堆積され、堆積と同時にそこで溶融されてＴｉＯ２−ＳｉＯ２ガラスとなる。しかし、この方法で作製されるＴｉＯ２−ＳｉＯ２ガラスは、熱膨張係数がほぼゼロとなる温度領域が室温付近のみに限られていた。
また、米国特許出願には、ＴｉＯ２−ＳｉＯ２多孔質ガラス体を形成し、ガラス体にした後、マスク基板を得る方法が開示されている（例えば、特許文献１参照。）。
In the conventional method for producing TiO 2 —SiO 2 glass, first, a silica precursor and a titania precursor are each converted into a vapor form and mixed. The mixture in the vapor form is introduced into a burner and thermally decomposed to become TiO 2 —SiO 2 glass particles. The TiO 2 —SiO 2 glass particles are deposited in a refractory container and melted there at the same time as the deposition to become TiO 2 —SiO 2 glass. However, in the TiO 2 —SiO 2 glass produced by this method, the temperature range in which the thermal expansion coefficient is almost zero is limited to only around room temperature.
In addition, US Patent Application discloses a method of obtaining a mask substrate after forming a TiO 2 —SiO 2 porous glass body and forming the glass body (see, for example, Patent Document 1).
ＥＵＶＬ用露光装置光学材は、反射膜などの成膜の際には１００℃程度の温度になる。また、露光時に、高エネルギー線が照射されるので、部材の温度が局所的には上昇するおそれがある。 The EUVL exposure apparatus optical material has a temperature of about 100 ° C. when a reflective film or the like is formed. Moreover, since a high energy ray is irradiated at the time of exposure, there exists a possibility that the temperature of a member may rise locally.
このため、ＥＵＶＬ用露光装置光学材は、熱膨張係数がほぼゼロとなる温度領域が広いことが好ましいが、従来のＴｉＯ２−ＳｉＯ２ガラスでは、熱膨張係数がほぼゼロとなる温度領域が狭く、ＥＵＶＬ用露光装置光学材に用いるには不充分であった。 For this reason, it is preferable that the exposure apparatus optical material for EUVL has a wide temperature range in which the thermal expansion coefficient is almost zero, but the conventional TiO 2 —SiO 2 glass has a narrow temperature range in which the thermal expansion coefficient is almost zero. , It was insufficient for use in an EUVL exposure apparatus optical material.
本発明の態様１は、仮想温度が１０００℃以下であり、ＯＨ基濃度が６００ｐｐｍ以下であり、かつ−５０〜１５０℃での熱膨張係数が０±２００ｐｐｂ／℃であり、仮想温度のばらつきが７０℃以内である、ＴｉＯ２を含有することを特徴とするシリカガラスを提供する。 In aspect 1 of the present invention, the fictive temperature is 1000 ° C. or lower, the OH group concentration is 600 ppm or lower, and the thermal expansion coefficient at −50 to 150 ° C. is 0 ± 200 ppb / ° C. A silica glass characterized by containing TiO 2 which is within 70 ° C. is provided.
態様２は、ＴｉＯ２を１〜１２質量％含有する、態様１のシリカガラスを提供する。 Aspect 2 provides the silica glass of Aspect 1 containing 1 to 12% by mass of TiO 2 .
態様３は、ＯＨ基濃度が７０ｐｐｍ以上６００ｐｐｍ以下である態様１または２のシリカガラスを提供する。 Aspect 3 provides the silica glass of Aspect 1 or 2, wherein the OH group concentration is 70 ppm or more and 600 ppm or less.
本発明によれば、熱膨張係数の温度変化が小さい、つまり熱膨張係数がほぼゼロとなる温度範囲が広く、またガラス中の熱膨張係数および機械的特性の均質性に優れたＴｉＯ２−ＳｉＯ２ガラスを得ることができる。したがって、ＥＵＶＬに使用される光学系を構成する部材の素材としてきわめて好適である。 According to the present invention, the temperature change of the coefficient of thermal expansion is small, that is, the temperature range in which the coefficient of thermal expansion is almost zero is wide, and TiO 2 —SiO excellent in homogeneity of the coefficient of thermal expansion and mechanical properties in the glass. Two glasses can be obtained. Therefore, it is extremely suitable as a material for members constituting an optical system used in EUVL.
ＴｉＯ２−ＳｉＯ２ガラスは、含有するＴｉＯ２濃度により、熱膨張係数が変化することが知られており、室温付近ではＴｉＯ２を約７質量％含むＴｉＯ２−ＳｉＯ２ガラスの熱膨張係数がほぼゼロとなる。 TiO 2 —SiO 2 glass is known to have a coefficient of thermal expansion that varies depending on the concentration of TiO 2 contained, and the thermal expansion coefficient of TiO 2 —SiO 2 glass containing about 7% by mass of TiO 2 is near room temperature. Nearly zero.
本発明のＴｉＯ２−ＳｉＯ２ガラスとはＴｉＯ２を１〜１２質量％含有するシリカガラスのことが好ましい。ＴｉＯ２の含有量が１質量％未満であるとゼロ膨張にならないおそれがあり、１２質量％を超えると熱膨張係数が負となる可能性があるからである。ＴｉＯ２の含有量は、より好ましくは５〜９質量％である。 The TiO 2 —SiO 2 glass of the present invention is preferably a silica glass containing 1 to 12% by mass of TiO 2 . This is because if the content of TiO 2 is less than 1% by mass, zero expansion may not occur, and if it exceeds 12% by mass, the thermal expansion coefficient may be negative. The content of TiO 2 is more preferably 5 to 9% by mass.
本発明において仮想温度は１０００℃以下が好ましい。 In the present invention, the fictive temperature is preferably 1000 ° C. or lower.
発明者は、仮想温度とゼロ膨張の温度範囲の広さに関連があることを見出した。その結果に基づくと、仮想温度が１０００℃を超えるとゼロ膨張の温度範囲が狭く、ＥＵＶＬ用露光装置光学材に用いる材料には不充分になるおそれがある。なお、本明細書中では、ガラスの熱膨張係数がほぼゼロとなる温度範囲をゼロ膨張の温度範囲とも称する。ゼロ膨張の温度範囲を広げるには、仮想温度は９５０℃以下が好ましく、９００℃以下がより好ましく、８５０℃以下であることが特に好ましい。 The inventor has found that there is a relationship between the fictive temperature and the breadth of the zero expansion temperature range. Based on the result, when the fictive temperature exceeds 1000 ° C., the temperature range of zero expansion is narrow, and there is a fear that the material used for the EUVL exposure apparatus optical material may be insufficient. In the present specification, a temperature range in which the thermal expansion coefficient of glass is almost zero is also referred to as a zero expansion temperature range. In order to widen the temperature range of zero expansion, the fictive temperature is preferably 950 ° C. or lower, more preferably 900 ° C. or lower, and particularly preferably 850 ° C. or lower.
本発明における仮想温度を得るには、例えば、５００℃を超える温度、特に６００〜１２００℃の温度にて５時間以上保持した後、１０℃／ｈｒ以下の平均降温速度で５００℃まで降温する方法が効果的である。上記に従い、ＴｉＯ２−ＳｉＯ２ガラス体を９００℃で１００時間保持した後、１０℃／ｈｒの速度で５００℃まで降温し大気放冷したところ、ＴｉＯ２−ＳｉＯ２ガラス体の仮想温度は８６０℃となった。
保持温度が高温であるほど保持温度は短くともよく、保持温度が低い場合は、構造緩和に時間がかかるため、適当な仮想温度を得るために保持時間を長くする必要がある。
In order to obtain the fictive temperature in the present invention, for example, a method of holding at a temperature exceeding 500 ° C., particularly at a temperature of 600 to 1200 ° C. for 5 hours or more and then decreasing the temperature to 500 ° C. at an average temperature decreasing rate of 10 ° C./hr or less. Is effective. Accordance with the above, after holding for 100 hours at 900 ° C. The TiO 2 -SiO 2 glass body was cooled to cool the atmosphere to 500 ° C. at a rate of 10 ° C. / hr, the fictive temperature of the TiO 2 -SiO 2 glass body 860 It became ℃.
The higher the holding temperature, the shorter the holding temperature. When the holding temperature is low, it takes time to relax the structure. Therefore, it is necessary to lengthen the holding time in order to obtain an appropriate fictive temperature.
仮想温度は以下のように測定する。鏡面研磨されたＴｉＯ２−ＳｉＯ２ガラスについて、吸収スペクトルを赤外分光計（Ｎｉｋｏｌｅｔ社製Ｍａｇｎａ７６０）を用いて取得する。この際、データ間隔は約０．５ｃｍ−１にし、吸収スペクトルは、６４回スキャンさせた平均値を用いる。このようにして得られた赤外吸収スペクトルにおいて、約２２６０ｃｍ−１付近に観察されるピークがＴｉＯ２−ＳｉＯ２ガラスのＳｉ−Ｏ−Ｓｉ結合による伸縮振動の倍音に起因する。このピーク位置を用いて、仮想温度が既知で同組成のガラスにより検量線を作成し、仮想温度を求める。あるいは、表面の反射スペクトルを同様の赤外分光計を用いて、同様に測定する。このようにして得られた赤外反射スペクトルにおいて、約１１２０ｃｍ−１に観察される最も大きなピークがＴｉＯ２−ＳｉＯ２ガラスのＳｉ−Ｏ−Ｓｉ結合による伸縮振動に起因する。このピーク位置を用いて、仮想温度が既知で同組成のガラスにより検量線を作成し、仮想温度を求める。 The fictive temperature is measured as follows. For the mirror-polished TiO 2 —SiO 2 glass, an absorption spectrum is obtained using an infrared spectrometer (Magna 760 manufactured by Nikolet). At this time, the data interval is set to about 0.5 cm −1 , and the average value obtained by scanning 64 times is used as the absorption spectrum. In the infrared absorption spectrum thus obtained, the peak observed in the vicinity of about 2260 cm −1 is due to the overtone of stretching vibration due to the Si—O—Si bond of the TiO 2 —SiO 2 glass. Using this peak position, a calibration curve is created with glass having the same fictive temperature and the same composition, and the fictive temperature is obtained. Alternatively, the reflection spectrum of the surface is similarly measured using a similar infrared spectrometer. In the infrared reflection spectrum thus obtained, the largest peak observed at about 1120 cm −1 is due to stretching vibration due to the Si—O—Si bond of the TiO 2 —SiO 2 glass. Using this peak position, a calibration curve is created with glass having the same fictive temperature and the same composition, and the fictive temperature is obtained.
本発明においてＯＨ基濃度は６００ｐｐｍ以下であることが好ましく、より好ましくは４００ｐｐｍ以下、特に好ましくは２００ｐｐｍ以下である。 In the present invention, the OH group concentration is preferably 600 ppm or less, more preferably 400 ppm or less, and particularly preferably 200 ppm or less.
ＯＨ基濃度が高いと、構造緩和が早いため、温度分布のつきやすい径の大きなガラス体を製造する場合に、仮想温度分布がつきやすくなると考えられる。 When the OH group concentration is high, structural relaxation is quick, and thus it is considered that a virtual temperature distribution is likely to be obtained when manufacturing a glass body having a large diameter that is easy to have a temperature distribution.
ＯＨ基濃度がガラスの構造緩和に影響を及ぼすことは石英ガラスについては以前から知られている（ＡＩＰ・Ｃｏｎｆ．・Ｐｒｏｃ．・４６９，５０７・(１９９９)）。これはＯＨ基が、ガラスの網目構造においてネットワークを切断する終端基となるためであり、終端基が多いほどガラスの構造緩和は容易になると考えられるからである。つまり、ＯＨ基が多いほど構造緩和の時間は短くなるので、仮想温度は、冷却時に生じるガラス体内の温度分布の影響を受け易くなる。 It has been known about quartz glass that the OH group concentration affects the structural relaxation of glass (AIP, Conf., Proc., 469, 507, (1999)). This is because the OH group serves as a terminal group for cutting the network in the glass network structure, and it is considered that the structural relaxation of the glass becomes easier as the number of terminal groups increases. That is, as the number of OH groups increases, the time for structural relaxation becomes shorter. Therefore, the fictive temperature is easily affected by the temperature distribution in the glass body that occurs during cooling.
比較的低いＯＨ基濃度のＴｉＯ２−ＳｉＯ２ガラスを得るための製造方法としては、これには限定されないが、スート法が使用できる。スート法とは、ガラス形成原料となるＳｉ前駆体とＴｉ前駆体を火炎加水分解もしくは熱分解させて得られるＴｉＯ２−ＳｉＯ２ガラス微粒子（スート）を堆積させ、その後透明ガラス化温度まで加熱して透明ＴｉＯ２−ＳｉＯ２ガラス体を得る製造方法である。またスート法はその作り方により、ＭＣＶＤ法、ＯＶＤ法、およびＶＡＤ法などがある。 The production method for obtaining TiO 2 —SiO 2 glass having a relatively low OH group concentration is not limited to this, but a soot method can be used. In the soot method, TiO 2 —SiO 2 glass fine particles (soot) obtained by flame hydrolysis or thermal decomposition of a Si precursor and a Ti precursor as glass forming raw materials are deposited, and then heated to a transparent vitrification temperature. And a transparent TiO 2 —SiO 2 glass body. The soot method includes an MCVD method, an OVD method, and a VAD method depending on how to make the soot method.
ＯＨ基濃度は以下のように測定する。赤外分光光度計による測定を行い、２．７μｍ波長での吸収ピークからＯＨ基濃度を求める（Ｊ．Ｐ．Ｗｉｉｌｉａｍｓ ｅｔ．ａｌ．，Ａｍｅｒｉｃａｎ Ｃｅｒａｍｉｃ Ｓｏｃｉｅｔｙ Ｂｕｌｌｅｔｉｎ，５５（５），５２４，１９７６）。本法による検出限界は０．１ｐｐｍである。 The OH group concentration is measured as follows. Measurement is performed with an infrared spectrophotometer, and the OH group concentration is determined from the absorption peak at a wavelength of 2.7 μm (JP Wiilliams et. Al., American Ceramic Society Bulletin, 55 (5), 524, 1976). The detection limit by this method is 0.1 ppm.
本発明によれば、０〜１００℃の広い温度域においてＴｉＯ２−ＳｉＯ２ガラスを熱膨張係数が０±２００ｐｐｂ／℃の範囲内であるゼロ膨張ガラスとなし得る。またＴｉＯ２−ＳｉＯ２ガラスの仮想温度が１０００℃以下の場合は、熱膨張係数がほぼゼロを示す温度域がより広くなり、−５０〜１５０℃の範囲において、熱膨張係数を０±２００ｐｐｂ／℃の範囲内となし得る。 According to the present invention, TiO 2 —SiO 2 glass can be made into zero expansion glass having a thermal expansion coefficient in the range of 0 ± 200 ppb / ° C. in a wide temperature range of 0 to 100 ° C. Further, when the fictive temperature of TiO 2 —SiO 2 glass is 1000 ° C. or lower, the temperature range where the thermal expansion coefficient is almost zero becomes wider, and in the range of −50 to 150 ° C., the thermal expansion coefficient is 0 ± 200 ppb / Within the range of ° C.
熱膨張係数は、レーザー干渉式熱膨張計（ＵＬＶＡＣ社製レーザー膨張計ＬＩＸ−１）を用いて−１５０〜＋２００℃の範囲で測定する。 The thermal expansion coefficient is measured in a range of −150 to + 200 ° C. using a laser interference thermal dilatometer (Laser dilatometer LIX-1 manufactured by ULVAC).
本明細書では、「仮想温度のばらつき」を少なくとも１つの面内における３０ｍｍ×３０ｍｍ内での仮想温度の最大値と最小値の差と定義する。仮想温度のばらつきは１００℃以内であることが好ましく、特に好ましくは７０℃以内である。仮想温度のばらつきが上記範囲を超えると、場所により、熱膨張係数に差を生じるおそれがある。 In this specification, “variation of virtual temperature” is defined as the difference between the maximum value and the minimum value of virtual temperature within 30 mm × 30 mm in at least one plane. The variation in fictive temperature is preferably within 100 ° C., particularly preferably within 70 ° C. If the variation in the fictive temperature exceeds the above range, there may be a difference in the coefficient of thermal expansion depending on the location.
仮想温度のばらつきは以下のように測定できる。所定のサイズに成形した透明ＴｉＯ２−ＳｉＯ２ガラス体をスライスし、５０ｍｍ×５０ｍｍ×１０ｍｍのＴｉＯ２−ＳｉＯ２ガラスブロックとする。このＴｉＯ２−ＳｉＯ２ガラスブロックの５０ｍｍ×５０ｍｍ面について、１０ｍｍピッチの間隔で前述の方法に従い仮想温度の測定を行うことで、成形ＴｉＯ２−ＳｉＯ２ガラス体の仮想温度のばらつきを求める。 The variation in fictive temperature can be measured as follows. A transparent TiO 2 —SiO 2 glass body molded into a predetermined size is sliced to obtain a 50 mm × 50 mm × 10 mm TiO 2 —SiO 2 glass block. The virtual temperature of the formed TiO 2 —SiO 2 glass body is determined by measuring the virtual temperature according to the method described above at intervals of 10 mm on the 50 mm × 50 mm surface of the TiO 2 —SiO 2 glass block.
本明細書では、「ＯＨ基濃度のばらつき」は、少なくとも１つの面内における３０ｍｍ×３０ｍｍ内でのＯＨ基濃度の最大値と最小値の差と定義する。ＯＨ基濃度のばらつきは、５０ｐｐｍ以内が好ましく、より好ましくは３０ｐｐｍ以内、特に好ましくは１０ｐｐｍ以内である。ＯＨ基濃度のばらつきが上記範囲を超えると、場所により構造緩和時間の差が大きくなり、仮想温度に差が生じるおそれがある。 In this specification, “variation in OH group concentration” is defined as the difference between the maximum value and the minimum value of the OH group concentration within 30 mm × 30 mm in at least one plane. The variation of the OH group concentration is preferably within 50 ppm, more preferably within 30 ppm, and particularly preferably within 10 ppm. If the variation in the OH group concentration exceeds the above range, the difference in structure relaxation time increases depending on the location, which may cause a difference in fictive temperature.
ＯＨ基濃度のばらつきは、以下のように測定できる。所定のサイズに成形した透明ＴｉＯ２−ＳｉＯ２ガラス体をスライスし、５０ｍｍ×５０ｍｍ×１０ｍｍのＴｉＯ２−ＳｉＯ２ガラスブロックとする。このＴｉＯ２−ＳｉＯ２ガラスブロックの５０ｍｍ×５０ｍｍ面について、１０ｍｍピッチの間隔で前述の方法に従いＯＨ基濃度の測定を行うことで、成形ＴｉＯ２−ＳｉＯ２ガラス体のＯＨ基濃度のばらつきを求める。 Variation in OH group concentration can be measured as follows. A transparent TiO 2 —SiO 2 glass body molded into a predetermined size is sliced to obtain a 50 mm × 50 mm × 10 mm TiO 2 —SiO 2 glass block. By measuring the OH group concentration according to the method described above at intervals of 10 mm for the 50 mm × 50 mm surface of the TiO 2 —SiO 2 glass block, the variation in the OH group concentration of the molded TiO 2 —SiO 2 glass body is obtained. .
ＴｉＯ２−ＳｉＯ２ガラスをＥＵＶＬ用露光装置光学材として使用するときに、ガラス中におけるＴｉＯ２／ＳｉＯ２組成比を均一にすることは、基板内での熱膨張係数の分布を小さくするという点で極めて重要である。このＴｉＯ２／ＳｉＯ２組成比の変動は、ガラスの屈折率に影響を及ぼすので、ＴｉＯ２−ＳｉＯ２組成均一性の指標として、屈折率の変動幅Δｎを用いることができる。本発明においてΔｎは少なくとも１つの面内における３０ｍｍ×３０ｍｍ内での屈折率の最大値と最小値の差と定義する。Δｎは２×１０−４以内が好ましく、特に好ましくは１．５×１０−４以内である。Δｎが上記範囲を超えると、熱膨張係数のばらつきが大きくなるおそれがある。このようなΔｎを得るためには、スート法を用いることが効果的である。 When TiO 2 —SiO 2 glass is used as an EUVL exposure apparatus optical material, making the TiO 2 / SiO 2 composition ratio uniform in the glass reduces the distribution of thermal expansion coefficient in the substrate. It is extremely important. Since the fluctuation of the TiO 2 / SiO 2 composition ratio affects the refractive index of the glass, the refractive index fluctuation width Δn can be used as an index of TiO 2 —SiO 2 composition uniformity. In the present invention, Δn is defined as the difference between the maximum value and the minimum value of the refractive index within 30 mm × 30 mm in at least one plane. Δn is preferably within 2 × 10 −4 , particularly preferably within 1.5 × 10 −4 . If Δn exceeds the above range, the variation in the thermal expansion coefficient may be increased. In order to obtain such Δn, it is effective to use the soot method.
Δｎは以下のように測定する。４０ｍｍ×４０ｍｍ×４０ｍｍの立方体に成形した透明ＴｉＯ２−ＳｉＯ２ガラス体から、立方体の各面より厚さ１ｍｍでスライスし、３８ｍｍ×３８ｍｍ×１ｍｍの板状ＴｉＯ２−ＳｉＯ２ガラスブロックを得る。フィゾー干渉計にて、オイルオンプレート法で、本ガラスブロックの３８ｍｍ×３８ｍｍの面にヘリウムネオンレーザ光を垂直にあて、３８ｍｍ×３８ｍｍ面内での屈折率の変動幅を測定する。 Δn is measured as follows. A transparent TiO 2 —SiO 2 glass body formed into a 40 mm × 40 mm × 40 mm cube is sliced at a thickness of 1 mm from each side of the cube to obtain a plate-like TiO 2 —SiO 2 glass block of 38 mm × 38 mm × 1 mm. With a Fizeau interferometer, helium neon laser light is vertically applied to the 38 mm × 38 mm surface of the present glass block by the oil-on-plate method, and the fluctuation range of the refractive index in the 38 mm × 38 mm surface is measured.
本発明により得られるＴｉＯ２−ＳｉＯ２ガラスにおいて、仮想温度のばらつきが１００℃以内，ＯＨ基濃度のばらつきが５０ｐｐｍ以内、Δｎが２×１０−４以内の場合、熱膨張係数分布を少なくとも１つの面内における３０ｍｍ×３０ｍｍ内で３０ｐｐｂ／℃以内となし得、ＥＵＶＬ用露光装置光学材として最適である。 In the TiO 2 —SiO 2 glass obtained by the present invention, when the fictive temperature variation is within 100 ° C., the OH group concentration variation is within 50 ppm, and Δn is within 2 × 10 −4 , the thermal expansion coefficient distribution is at least one It can be made within 30 ppb / ° C. within 30 mm × 30 mm in the plane, and is optimal as an exposure apparatus optical material for EUVL.
熱膨張係数分布は以下のように測定する。所定のサイズに成形した透明ＴｉＯ２−ＳｉＯ２ガラス体を切断し、１０ｍｍ×１０ｍｍ×１０ｍｍのＴｉＯ２−ＳｉＯ２ガラス小片となるよう分割する。この各小片について前述の方法に従い、熱膨張係数の測定を行うことで、成形ＴｉＯ２−ＳｉＯ２ガラスブロックの熱膨張係数のばらつきを求める。 The thermal expansion coefficient distribution is measured as follows. A transparent TiO 2 —SiO 2 glass body molded into a predetermined size is cut and divided into 10 mm × 10 mm × 10 mm TiO 2 —SiO 2 glass pieces. The variation of the thermal expansion coefficient of the formed TiO 2 —SiO 2 glass block is determined by measuring the thermal expansion coefficient of each piece according to the method described above.
本発明のＴｉＯ２−ＳｉＯ２ガラスを製造するためには、以下の製法が採用できる。
（ａ）工程
ガラス形成原料であるＳｉ前駆体およびＴｉ前駆体を火炎加水分解させて得られるＴｉＯ２−ＳｉＯ２ガラス微粒子を基材に堆積、成長させて多孔質ＴｉＯ２−ＳｉＯ２ガラス体を形成させる。ガラス形成原料としては、ガス化可能な原料であれば特に限定されないが、Ｓｉ前駆体としては、ＳｉＣｌ４、ＳｉＨＣｌ３、ＳｉＨ２Ｃｌ２、ＳｉＨ３Ｃｌなどの塩化物、ＳｉＦ４、ＳｉＨＦ３、ＳｉＨ２Ｆ２などのフッ化物、ＳｉＢｒ４、ＳｉＨＢｒ３などの臭化物、ＳｉＩ４などのヨウ化物といったハロゲン化ケイ素化合物、またＲｎＳｉ（ＯＲ）４−ｎ（ここにＲは炭素数１〜４のアルキル基、ｎは０〜３の整数）で示されるアルコキシシランが挙げられ、またＴｉ前駆体としては、ＴｉＣｌ４、ＴｉＢｒ４などのハロゲン化チタン化合物、またＲｎＴｉ（ＯＲ）４−ｎ（ここにＲは炭素数１〜４のアルキル基、ｎは０〜３の整数）で示されるアルコキシチタンが挙げられる。また、Ｓｉ前駆体およびＴｉ前駆体として、シリコンチタンダブルアルコキシドなどのＳｉとＴｉの化合物を使用することもできる。
In order to produce the TiO 2 —SiO 2 glass of the present invention, the following production method can be employed.
(A) Step TiO 2 —SiO 2 glass fine particles obtained by flame hydrolysis of Si precursor and Ti precursor, which are glass forming raw materials, are deposited and grown on a substrate to form a porous TiO 2 —SiO 2 glass body. Let it form. The glass forming raw material is not particularly limited as long as it is a gasifiable raw material. Examples of the Si precursor include chlorides such as SiCl 4 , SiHCl 3 , SiH 2 Cl 2 , and SiH 3 Cl, SiF 4 , SiHF 3 , fluorides such as SiH 2 F 2, SiBr 4, bromides such as SiHBr 3, halogenated silicon compounds such as iodide such as SiI 4, R n Si (OR) 4- n ( wherein R is 1 to 4 carbon atoms In addition, the Ti precursor includes titanium halide compounds such as TiCl 4 and TiBr 4, and RnTi (OR) 4-n (here R is an alkyl group having 1 to 4 carbon atoms, and n is an integer of 0 to 3). In addition, Si and Ti compounds such as silicon titanium double alkoxide can be used as the Si precursor and the Ti precursor.
前記基材としては石英ガラス製の種棒（例えば特公昭６３−２４９７３号公報記載の種棒）を使用できる。また棒状に限らず板状の基材を使用してもよい。 As the base material, a seed rod made of quartz glass (for example, a seed rod described in Japanese Patent Publication No. 63-24973) can be used. Moreover, you may use not only rod shape but a plate-shaped base material.
（ｂ）工程
（ａ）工程で得られた多孔質ＴｉＯ２−ＳｉＯ２ガラス体を透明ガラス化温度まで昇温して透明ガラス化し、透明ＴｉＯ２−ＳｉＯ２ガラス体を得る。透明ガラス化温度は、通常は１４００〜１７００℃であり、特に１４５０〜１６５０℃であることが好ましい。
(B) Step The porous TiO 2 —SiO 2 glass body obtained in the step (a) is heated to a transparent vitrification temperature to form a transparent glass to obtain a transparent TiO 2 —SiO 2 glass body. The transparent vitrification temperature is usually 1400 to 1700 ° C, and particularly preferably 1450 to 1650 ° C.
雰囲気としては、ヘリウムなどの不活性ガス１００％の雰囲気、またはヘリウムなどの不活性ガスを主成分とする雰囲気であることが好ましい。圧力については、減圧または常圧であればよい。特に常圧の場合はヘリウムガスを用いることができる。また、減圧の場合は１３０００Ｐａ以下が好ましい。なお、本明細書における「Ｐａ」は、ゲージ圧ではなく絶対圧の意である。 The atmosphere is preferably an atmosphere of 100% inert gas such as helium or an atmosphere mainly composed of an inert gas such as helium. The pressure may be reduced pressure or normal pressure. In particular, helium gas can be used at normal pressure. Moreover, in the case of pressure reduction, 13000 Pa or less is preferable. In the present specification, “Pa” means not a gauge pressure but an absolute pressure.
また工程（ａ）と（ｂ）の間に、以下のような工程（ａ）−１の処理を施すことにより、工程（ｂ）により得られる透明ＴｉＯ２−ＳｉＯ２ガラスに含有されるＯＨ基濃度を容易に制御することが可能である。 Moreover, the OH group contained in the transparent TiO 2 —SiO 2 glass obtained by the step (b) by performing the following process (a) -1 between the steps (a) and (b). It is possible to easily control the concentration.
工程（ａ）−１：多孔質ＴｉＯ２−ＳｉＯ２ガラス体を塩素やフッ素などのハロゲンを含有する雰囲気下にて保持することにより、多孔質ＴｉＯ２−ＳｉＯ２ガラス体中のＯＨ基濃度を減少させることができる。 Step (a) -1: by the porous TiO 2 -SiO 2 glass body is held in an atmosphere containing a halogen such as chlorine or fluorine, an OH group concentration of the porous TiO 2 -SiO 2 glass body in Can be reduced.
（ｃ）工程
（ｂ）工程で得られた透明ＴｉＯ２−ＳｉＯ２ガラス体を軟化点以上の温度に加熱して所望の形状に成形し、成形ＴｉＯ２−ＳｉＯ２ガラス体を得る。成形加工の温度としては、１５００〜１８００℃が好ましい。１５００℃以下では、ＴｉＯ２−ＳｉＯ２ガラスの粘度が高いため、実質的に自重変形が行われず、またＳｉＯ２の結晶相であるクリストバライトの成長またはＴｉＯ２の結晶相であるルチルもしくはアナターゼの成長が起こり、いわゆる失透が生じる。１８００℃以上では、ＳｉＯ２の昇華が無視できなくなる。
(C) Step The transparent TiO 2 —SiO 2 glass body obtained in the step (b) is heated to a temperature equal to or higher than the softening point and formed into a desired shape to obtain a molded TiO 2 —SiO 2 glass body. The molding process temperature is preferably 1500 to 1800 ° C. Below 1500 ° C., the viscosity of the TiO 2 —SiO 2 glass is high, so that substantially no self-weight deformation occurs, and the growth of cristobalite, which is the crystalline phase of SiO 2 , or the growth of rutile or anatase, which is the crystalline phase of TiO 2. Occurs, so-called devitrification occurs. Above 1800 ° C., SiO 2 sublimation cannot be ignored.
（ｄ）工程
（ｃ）工程で得られた成形ＴｉＯ２−ＳｉＯ２ガラス体を、５００℃を超える温度、例えば６００〜１２００℃の温度、にて５時間以上保持した後、１０℃／ｈｒ以下の平均降温速度で５００℃以下まで降温するアニール処理を行い、ＴｉＯ２−ＳｉＯ２ガラスの仮想温度を制御する。５００℃以下まで降温した後は放冷できる。この場合の雰囲気は、ヘリウム、アルゴン、窒素などの不活性ガス１００％の雰囲気下、これらの不活性ガスを主成分とする雰囲気下、または空気雰囲気下で、圧力は減圧または常圧が好ましい。
(D) the step (c) obtained in the step formed TiO 2 -SiO 2 glass body, temperatures in excess of 500 ° C., for example 600 to 1200 ° C. in temperature and, after holding for more than 5 hours, 10 ° C. / hr or less The virtual temperature of the TiO 2 —SiO 2 glass is controlled by performing an annealing process for lowering the temperature to 500 ° C. or less at an average temperature drop rate of 5 ° C. After cooling down to 500 ° C. or lower, it can be allowed to cool. The atmosphere in this case is preferably an atmosphere of 100% inert gas such as helium, argon or nitrogen, an atmosphere containing such an inert gas as a main component, or an air atmosphere, and the pressure is preferably reduced or normal pressure.
本発明により得られるＴｉＯ２−ＳｉＯ２ガラスは、ＥＵＶＬに使用されるマスク基板、ミラー基材やステージなどの半導体露光装置光学材として最適である。 The TiO 2 —SiO 2 glass obtained by the present invention is optimal as an optical material for a semiconductor exposure apparatus such as a mask substrate, a mirror base material, or a stage used for EUVL.
以下、実施例により本発明をさらに詳細に説明するが、本発明はこれらに限定されない。なお、以下の実施例のガラス組成は全てＴｉＯ２＝７．４質量％、ＳｉＯ２＝９２．６質量％である。 EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited to these. Note that all the glass compositions of the following examples TiO 2 = 7.4 mass%, SiO 2 = 92.6 wt%.
［例１]
ＴｉＯ２−ＳｉＯ２ガラスのガラス形成原料であるＴｉＣｌ４とＳｉＣｌ４を、それぞれガス化させた後に混合させ、酸水素炎中で加熱加水分解（火炎加水分解）させることで得られるＴｉＯ２−ＳｉＯ２ガラス微粒子を基材に堆積・成長させて、直径８ｃｍ、長さ１２ｃｍの多孔質ＴｉＯ２−ＳｉＯ２ガラス体を形成した（（ａ）工程）。
[Example 1]
TiCl 4 and SiCl 4 as glass-forming raw material for TiO 2 -SiO 2 glass, was mixed after each is gasified, TiO 2 -SiO to subjecting the mixture to heat hydrolysis in an oxyhydrogen flame (flame hydrolysis) Two glass fine particles were deposited and grown on a base material to form a porous TiO 2 —SiO 2 glass body having a diameter of 8 cm and a length of 12 cm (step (a)).
得られた多孔質ＴｉＯ２−ＳｉＯ２ガラス体をＨｅ１００％雰囲気下で１５５０℃まで昇温し、この温度で１０時間保持し透明ガラス化し、透明ＴｉＯ２−ＳｉＯ２ガラス体を得た（（ｂ）工程）。 The obtained porous TiO 2 —SiO 2 glass body was heated to 1550 ° C. in a He 100% atmosphere and kept at this temperature for 10 hours to form a transparent glass to obtain a transparent TiO 2 —SiO 2 glass body ((b ) Process).
得られた透明ＴｉＯ２−ＳｉＯ２ガラス体を、軟化点以上の１６００℃に加熱して自重変形を行わせ、所定のサイズのブロック形状に成形し、成形ＴｉＯ２−ＳｉＯ２ガラス体を得た。（（ｃ）工程）
得られた成形ＴｉＯ２−ＳｉＯ２ガラス体を電気炉内に設置し、９５０℃にて１００時間保持した後、５００℃まで５℃／ｈｒで降温し、その後室温まで放冷し（（ｄ）工程）、ＴｉＯ２−ＳｉＯ２ガラスを得た。
The obtained transparent TiO 2 —SiO 2 glass body was heated to 1600 ° C. above the softening point to cause its own weight deformation and molded into a block shape of a predetermined size to obtain a molded TiO 2 —SiO 2 glass body. . (Step (c))
The obtained molded TiO 2 —SiO 2 glass body was placed in an electric furnace, held at 950 ° C. for 100 hours, cooled to 500 ° C. at 5 ° C./hr, and then allowed to cool to room temperature ((d) Step), TiO 2 —SiO 2 glass was obtained.
［例３］
例１における工程（ｄ）において、スライスした後の冷却条件を変え、成形ＴｉＯ２−ＳｉＯ２ガラス体を電気炉内に設置し、１３００℃にて２時間保持した後、５００℃まで５℃／ｈｒで降温し、その後室温まで放冷した。これ以外は例１と全く同様の方法により、ＴｉＯ２−ＳｉＯ２ガラスを得た。
[Example 3]
In the step (d) in Example 1, the cooling conditions after slicing were changed, the molded TiO 2 —SiO 2 glass body was placed in an electric furnace, held at 1300 ° C. for 2 hours, and then up to 500 ° C. at 5 ° C. / The temperature was lowered with hr and then allowed to cool to room temperature. A TiO 2 —SiO 2 glass was obtained in the same manner as in Example 1 except for this.
［例４］
例１における工程（ｄ）において、スライスした後の冷却条件を変え、成形ＴｉＯ２−ＳｉＯ２ガラス体を電気炉内に設置し、８００℃にて１５０時間保持した後、５００℃まで５℃／ｈｒで降温し、その後室温まで放冷した。これ以外は例１と全く同様の方法により、ＴｉＯ２−ＳｉＯ２ガラスを得た。
[Example 4]
In the step (d) in Example 1, the cooling conditions after slicing were changed, the molded TiO 2 —SiO 2 glass body was placed in an electric furnace, held at 800 ° C. for 150 hours, and then increased to 500 ° C. at 5 ° C. / The temperature was lowered with hr and then allowed to cool to room temperature. A TiO 2 —SiO 2 glass was obtained in the same manner as in Example 1 except for this.
これら例１〜例４の測定結果を表１に仮想温度の測定結果を図１にまとめる。なお、ＯＨ基濃度、熱膨張係数、仮想温度の評価方法については、それぞれ前述の測定法にしたがって行った。屈折率の変動幅Δｎについては、３０ｍｍ×３０ｍｍ×５ｍｍのサンプルで評価を行った。ここで例１および４は参考例、例３は比較例である。 The measurement results of Examples 1 to 4 are summarized in Table 1, and the measurement results of the virtual temperature are summarized in FIG. In addition, about the evaluation method of OH group density | concentration, a thermal expansion coefficient, and fictive temperature, it performed according to the above-mentioned measuring method, respectively. The fluctuation range Δn of the refractive index was evaluated using a sample of 30 mm × 30 mm × 5 mm. Here, Examples 1 and 4 are reference examples, and Example 3 is a comparative example.
例１は仮想温度が１０００℃よりも低いので、熱膨張係数は０〜１００℃および−５０〜１５０℃の２種の温度域において、ともに０±２００ｐｐｂ／℃の範囲内となった。例３は、仮想温度が１０００℃よりも高いので、熱膨張係数は０〜１００℃および−５０〜１５０℃の２種の温度域において、ともに０±２００ｐｐｂ／℃の範囲内とはならなかった。例４は仮想温度が特に低く（８５０℃以下）、熱膨張係数は０〜１００℃および−５０〜１５０℃の２種の温度域において、ともに０±１５０ｐｐｂ／℃の範囲内となった。 Since the fictive temperature of Example 1 was lower than 1000 ° C., the thermal expansion coefficient was in the range of 0 ± 200 ppb / ° C. in two temperature ranges of 0 to 100 ° C. and −50 to 150 ° C. In Example 3, since the fictive temperature was higher than 1000 ° C., the thermal expansion coefficient did not fall within the range of 0 ± 200 ppb / ° C. in two temperature ranges of 0 to 100 ° C. and −50 to 150 ° C. . In Example 4, the fictive temperature was particularly low (850 ° C. or lower), and the thermal expansion coefficient was within the range of 0 ± 150 ppb / ° C. in two temperature ranges of 0 to 100 ° C. and −50 to 150 ° C.
［例５］
例１において、成形ＴｉＯ２−ＳｉＯ２ガラス体を３０ｍｍ×３０ｍｍ×１０ｍｍのＴｉＯ２−ＳｉＯ２ガラス小片に切断した。得られたＴｉＯ２−ＳｉＯ２ガラス小片を電気炉内に設置し、９００℃にて１００時間保持した後、５００℃まで５℃／ｈｒで降温し、その後室温まで放冷した（例５−徐冷）。また、９００℃にて１００時間保持した後、大気放冷した（例５−急冷）。これ以外は例１と全く同様の方法により、ＴｉＯ２−ＳｉＯ２ガラスを得た。
[Example 5]
In Example 1, a molded TiO 2 —SiO 2 glass body was cut into 30 mm × 30 mm × 10 mm TiO 2 —SiO 2 glass pieces. The obtained TiO 2 —SiO 2 glass piece was placed in an electric furnace, held at 900 ° C. for 100 hours, then cooled to 500 ° C. at 5 ° C./hr, and then allowed to cool to room temperature (Example 5—Slow cold). Moreover, after hold | maintaining at 900 degreeC for 100 hours, it cooled to air | atmosphere (Example 5-rapid cooling). A TiO 2 —SiO 2 glass was obtained in the same manner as in Example 1 except for this.
［例６］
ゼロ膨張ＴｉＯ２−ＳｉＯ２ガラスとして知られるコーニング社製ＵＬＥ（製品名）ガラスの２００ｍｍ×２００ｍｍ×１０ｍｍのブロックをさらに３０ｍｍ×３０ｍｍ×１０ｍｍのＴｉＯ２−ＳｉＯ２ガラス小片に切断した。得られたＴｉＯ２−ＳｉＯ２ガラス小片を電気炉内に設置し、９００℃にて１００時間保持した後、５００℃まで５℃／ｈｒで降温し、その後室温まで放冷した（例６−徐冷）。また、９００℃にて１００時間保持した後、大気放冷した（例６−急冷）。
[Example 6]
A 200 mm × 200 mm × 10 mm block of ULE (product name) glass from Corning, known as zero expansion TiO 2 —SiO 2 glass, was further cut into 30 mm × 30 mm × 10 mm TiO 2 —SiO 2 glass pieces. The obtained TiO 2 —SiO 2 glass piece was placed in an electric furnace, held at 900 ° C. for 100 hours, then cooled to 500 ° C. at 5 ° C./hr, and then allowed to cool to room temperature (Example 6-slow cold). Moreover, after hold | maintaining at 900 degreeC for 100 hours, it air-cooled (Example 6-rapid cooling).
これら例５および例６の測定結果を表２にまとめる。なお、ここで例５は実施例、例６は比較例である。 The measurement results of Examples 5 and 6 are summarized in Table 2. Here, Example 5 is an example and Example 6 is a comparative example.
例５は、ＯＨ基濃度が低いために、徐冷処理と急冷処理による仮想温度差が１００℃以内になっている。例６はＯＨ基濃度が高いために、徐冷処理と急冷処理による仮想温度差が１００℃以内にはなっていない。 In Example 5, since the OH group concentration is low, the fictive temperature difference between the slow cooling process and the rapid cooling process is within 100 ° C. In Example 6, since the OH group concentration is high, the virtual temperature difference between the slow cooling process and the rapid cooling process is not within 100 ° C.
この結果は、径の大きいＴｉＯ２−ＳｉＯ２ガラス体に徐冷処理をしたときのガラス体の仮想温度分布が、ＯＨ基濃度が低いときは１００℃以内になるが、ＯＨ基濃度が高いときは１００℃以上になるおそれがあることを示唆している。すなわち、ＯＨ基濃度が低いと仮想温度のバラツキは小さくなり、熱膨張係数の均質性が向上し、ＥＵＶ用露光装置光学材として好適となることを示している。 This result shows that the virtual temperature distribution of the glass body when the TiO 2 —SiO 2 glass body having a large diameter is annealed is within 100 ° C. when the OH group concentration is low, but when the OH group concentration is high. Suggests that there is a risk of 100 ° C. or higher. That is, when the OH group concentration is low, the variation in the fictive temperature becomes small, the homogeneity of the thermal expansion coefficient is improved, and it is indicated that it is suitable as an optical material for an EUV exposure apparatus.
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