WO2000015570A1 - Optical component made of silica glass and method for the production thereof - Google Patents

Optical component made of silica glass and method for the production thereof Download PDF

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Publication number
WO2000015570A1
WO2000015570A1 PCT/EP1999/003342 EP9903342W WO0015570A1 WO 2000015570 A1 WO2000015570 A1 WO 2000015570A1 EP 9903342 W EP9903342 W EP 9903342W WO 0015570 A1 WO0015570 A1 WO 0015570A1
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WIPO (PCT)
Prior art keywords
quartz glass
hydrogen
optical component
molecules
content
Prior art date
Application number
PCT/EP1999/003342
Other languages
German (de)
French (fr)
Inventor
Bruno Uebbing
Bodo KÜHN
Original Assignee
Heraeus Quarzglas Gmbh & Co. Kg
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Filing date
Publication date
Application filed by Heraeus Quarzglas Gmbh & Co. Kg filed Critical Heraeus Quarzglas Gmbh & Co. Kg
Priority to EP99969079A priority Critical patent/EP1049654A1/en
Priority to KR1020007005233A priority patent/KR20010032101A/en
Priority to JP2000570115A priority patent/JP2002524382A/en
Publication of WO2000015570A1 publication Critical patent/WO2000015570A1/en

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Classifications

    • 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
    • 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
    • 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
    • C03B2201/20—Doped silica-based glasses doped with non-metals other than boron or fluorine
    • C03B2201/21—Doped silica-based glasses doped with non-metals other than boron or fluorine doped with molecular hydrogen
    • 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
    • C03B2207/00—Glass deposition burners
    • C03B2207/30—For glass precursor of non-standard type, e.g. solid SiH3F
    • C03B2207/32—Non-halide
    • 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
    • C03C2201/21—Doped silica-based glasses containing non-metals other than boron or halide containing molecular hydrogen
    • 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
    • C03C2203/00—Production processes
    • C03C2203/40—Gas-phase processes

Definitions

  • the present invention relates to an optical component for transmitting ultraviolet radiation of a wavelength of 250 nm and shorter, made of synthetic quartz glass, which is obtained by forming fine-grained SiO 2 by flame hydrolysis of a chlorine-free silicon compound, deposited on a substrate and directly glazed.
  • the invention further relates to a method for producing an optical component made of synthetic quartz glass for the transmission of ultraviolet radiation of a wavelength of 250 nm and shorter, comprising the production of synthetic, hydrogen-containing quartz glass, by synthesis of fine-grained SiO 2 by means of flame hydrolysis of a chlorine-free silicon compound, and deposition and direct vitrification of the fine-grained SiO 2 on a substrate to form the hydrogen-containing quartz glass.
  • Such optical components made of synthetic quartz glass are used in particular for the transmission of high-energy, ultraviolet laser radiation, for example in the form of optical fibers or in the form of exposure optics in microlithography devices for the production of highly integrated circuits in semiconductor chips.
  • the exposure systems of modern microlithography devices are equipped with excimer lasers that emit high-energy, pulsed UV radiation with a wavelength of 248 nm (KrF laser) or 193 nm (ArF laser). It is known that such short-wave UV radiation can induce defects in the optical components and the associated absorptions which are characteristic of the type and quality of the respective quartz glass.
  • SAT effect damage behavior is observed in which the induced absorption rises linearly with continuous UV radiation, or in which it leads to saturation after an initial increase, or in which the induced defects accumulate in such a way that they become sudden and strong Express increase in absorption.
  • the sharp increase in absorption with the damage behavior described last is referred to in the literature as the SAT effect.
  • the radiation resistance of a quartz glass can depend on its structural properties, such as density, refractive index and homogeneity, or on its chemical composition. The influence of the chemical composition of the quartz glass on the damage behavior when irradiated with high-energy UV light is described, for example, in EP-A1 401 845.
  • a high radiation resistance was accordingly found in a high-purity quartz glass, which has a relatively high OH content in the range from 100 to approx. 1000 ppm by weight and at the same time a relatively high hydrogen concentration of at least 5 ⁇ 10 16 molecules per cm 3 (based on the volume of the Quartz glass).
  • the favorable influence of hydrogen on radiation resistance can be explained by the fact that it can contribute to the healing of defects and thus to a slower increase in radiation-induced absorption. Due to this effect of hydrogen, EP-A1 401 845 recommends loading optical components with high requirements with regard to radiation resistance with hydrogen.
  • the damage behavior of optical components can be different if the quartz glass has been obtained by different manufacturing processes, or that chemical or structural differences may exist, but these are not clear
  • the reason for the observed differences in damage behavior are.
  • the optical component according to the present invention is best characterized by its manufacturing process.
  • the production processes of synthetic quartz glass by flame hydrolysis of silicon-containing compounds can be differentiated on the basis of the starting substances and on the way in which the deposited SiO 2 particles are glazed.
  • SiCI 4 is a frequently used starting material in the production of synthetic quartz glass by flame hydrolysis.
  • other, for example chlorine-free, silicon-containing organic compounds are also used, such as silanes or siloxanes.
  • the production of quartz glass using alkoxysilanes is described in EP-A1 525 984; the production of quartz glass using siloxanes in EP-A1 463 045. Based on these starting substances, practically chlorine-free quartz glass can be produced.
  • the SiO 2 particles can be vitrified directly during the deposition on the substrate, which is referred to below as "direct vitrification”.
  • direct vitrification in the so-called “soot process”, the temperature during the deposition of the SiO 2 particles is kept so low that a porous soot body is formed, but none or only slight glazing of the SiO 2 particles occurs. Glazing with the formation of quartz glass requires a subsequent sintering of the soot body. Both manufacturing processes lead to a dense, transparent, high-purity quartz glass.
  • a generic optical component for the transmission of UV radiation of a wavelength of less than 300 nm and a method for its production are known from EP-A1 780 345.
  • the component described therein is obtained by depositing synthetic quartz glass on a substrate by flame hydrolysis of a chlorine-free polymethylsiloxane compound in the form of SiO 2 particles and vitrifying it directly.
  • the optical component produced in this way shows a damage behavior which, in comparison to a standard component, is characterized by the absence of the so-called SAT effect.
  • the standard component also consists of synthetic quartz glass, but a chlorine-containing starting material - namely SiCI 4 - was used in its manufacture. The observed effect in the known optical component may therefore be due to its low chlorine content, which is given as less than 3 ppm.
  • the present invention is therefore based on the object of providing an optical component which has a high long-term stability for the transmission of ultraviolet radiation of a wavelength of 250 nm and shorter, and which in particular shows a damage behavior in which the induced absorption into a saturation at a low level flows into. Furthermore, the invention is based on the object of specifying a method for producing such an optical component.
  • the quartz glass has a hydrogen content of less than 5 ⁇ 10 16 molecules / cm 3 .
  • the optical component according to the invention is characterized by a combination of features which can be summarized as follows: the component consists of synthetically produced quartz glass, the quartz glass is synthesized by flame hydrolysis of chlorine-free starting materials, the quartz glass is glazed directly during the deposition, and the hydrogen content of the quartz glass is set to a maximum of 5x10 16 molecules / cm 3 (based on the volume of the quartz glass).
  • the characteristic damage behavior of the optical component produced in this way in relation to high-energy UV radiation can be seen in the fact that the induced absorption initially rises rapidly, but then quickly leads to saturation at a low level.
  • This characteristic damage behavior is clearly dependent on the manufacturing conditions specified above. It changes as soon as one of the parameters in the manufacture of the component is changed, for example by using a soot process for the synthesis of the quartz glass instead of the direct glazing.
  • the hydrogen content of the quartz glass must be less than 5 ⁇ 10 16 molecules / cm 3 in order to achieve the desired radiation resistance. An explanation for this would be that the hydrogen not only contributes to the healing of radiation-induced defects, but also generates defects that are particularly noticeable in long-term radiation. It has been shown that the low hydrogen content of less than 5 ⁇ 10 16 molecules / cm 3 not only saturates the radiation-induced absorption, but also that the saturation level is comparatively low in comparison with a quartz glass with a higher hydrogen content.
  • the quartz glass contains hydrogen after vitrification, in a concentration that can be above the above-mentioned maximum limit of 5x10 16 molecules / cm 3 . It may be necessary to expel the hydrogen from the component.
  • the hydrogen content here and below means a hydrogen content averaged over the volume of the optical component (arithmetic mean of at least three measuring points evenly distributed over the component), it being assumed that the entire component is used for the transmission of UV radiation . In the case of optical components in which this requirement is not met, it is sufficient if the average hydrogen content is below the maximum value mentioned above, at least in the optically stressed volume range.
  • the hydrogen content is determined on the basis of a Raman measurement, which was carried out by Khotimchenko et al., "Determining the Content of Hydrogen Dissolved in Quartz Glass Using the Methods of Raman Scattering and Mass Spectrometry" in "Zhurnal Prikladnoi Spectoskopii", Vol 46, No.
  • the product gives the hydrogen concentration of the quartz glass in a volume of 1 cm 3 .
  • the detection limit for hydrogen with this measuring method is currently around 5x10 15 molecules / cm 3 .
  • An optical component in which the quartz glass has a hydrogen content of less than 2 ⁇ 10 16 molecules / cm 3 , in particular less than 5 ⁇ 10 15 molecules / cm 3 has proven to be particularly advantageous, that is to say the hydrogen content is below the current detection limit.
  • a component of this type is distinguished by particularly good long-term stability in relation to high-energy UV radiation and a particularly low saturation level of the absorption induced by the UV radiation.
  • an especially favorable damage behavior is shown by an optical component in which the quartz glass has an OH content of at least 400 ppm by weight.
  • the OH content refers to a value averaged over the quartz glass volume. It is determined spectroscopically.
  • the quartz glass has a chlorine content of at most 1 ppm by weight.
  • the indication of this chlorine content also relates to a value averaged over the quartz glass volume and is determined by wet chemistry. Chlorine or chlorine-containing compounds are often used to remove hydroxyl ions or contaminants from quartz glass. A chlorine content above 1 ppm by weight can, however, have an adverse effect on the damage behavior of the optical component.
  • the technical problem specified above is achieved, based on the process mentioned at the outset, in that the hydrogen-containing quartz glass is subjected to a hydrogen reduction treatment in which its hydrogen content is adjusted to a value below 5 ⁇ 10 16 molecules / cm 3 .
  • the hydrogen content of the quartz glass is adjusted to a value below 5 ⁇ 10 16 molecules / cm 3 by means of a hydrogen reduction treatment.
  • the hydrogen content can be set from a first, high concentration in a defined manner and therefore reproducibly to a second concentration below 5x10 16 molecules / cm 3 .
  • the optical components produced in this way therefore show reproducible damage behavior.
  • the hydrogen content of the quartz glass in the hydrogen reduction treatment is brought below 2x10 16 molecules / cm 3 , even better to a value below 5x10 15 molecules / cm 3 , i.e. to a concentration below the current detection limit of Raman Method lies.
  • a component manufactured in this way is characterized by particularly good long-term stability against high-energy UV radiation and a particularly low saturation level of the radiation-induced absorption.
  • the hydrogen reduction treatment advantageously comprises a thermal treatment of the quartz glass, a treatment under vacuum, and / or a treatment in a chemically reactive atmosphere.
  • the treatment variants mentioned can be used alternatively or cumulatively.
  • thermal treatment hereinafter referred to as tempering
  • a hydrogen-free atmosphere for example under inert gas or in a vacuum
  • tempering has proven to be particularly effective in order to adjust the hydrogen content of the quartz glass.
  • Annealing causes hydrogen to diffuse out of the quartz glass blank, the areas near the surface first becoming poor in hydrogen and only later the central areas of the blank.
  • the temperature, the tempering time and the tempering atmosphere taking into account the wall thickness or thickness of the quartz glass blank to be tempered, must be set so that the hydrogen is removed to a sufficient extent.
  • the tempering of quartz glass for optical components is a frequently used process step, which is usually used to reduce mechanical stress affect the optical properties of the glass.
  • the tempering proposed here for removing hydrogen differs from the known tempering methods in that, according to the invention, a quartz glass with an average hydrogen content of less than 5x10 16 molecules / cm 3 , preferably less than 2x10 16 molecules / cm 3 , and is particularly advantageously set to a value below 5x10 15 molecules / cm 3 .
  • the method is particularly effective when the hydrogen-containing quartz glass is formed into an intermediate product, the smallest lateral dimension of which does not exceed 100 mm, preferably 80 mm, the hydrogen reduction treatment being carried out partially or completely on the intermediate product.
  • the hydrogen reduction treatment is based on diffusion processes in quartz glass, for example the diffusion of hydrogen during tempering. The required diffusion times depend crucially on the relevant layer thickness.
  • optical components can be in very large layer thicknesses.
  • lenses for microlithography devices can have diameters of around 250 mm and thicknesses of around 100 mm.
  • the quartz glass blanks required for this have diameters of around 300 mm and thicknesses of over 100 mm.
  • Adequate hydrogen reduction treatment would require extremely long treatment times for such components, which would no longer be economically justifiable.
  • an intermediate product is formed from the hydrogen-containing quartz glass, the geometric dimensions of which are chosen so that the hydrogen can be easily driven off.
  • the smallest lateral dimension is understood to mean, for example, the outer diameter in the case of a rod-shaped intermediate product, the wall thickness in the case of a tubular one, or the thickness in the case of a plate-shaped intermediate product.
  • Such an intermediate product allows the hydrogen reduction treatment to be carried out in economically justifiable periods of time. It may be sufficient to only reduce the hydrogen content in the intermediate product without falling below the above-mentioned maximum values if the further treatment of the quartz glass allows complete hydrogen reduction in the sense of the present invention.
  • the component is formed from the intermediate product in a subsequent molding step.
  • FIG. 1 shows a diagram with two absorption curves, one of which represents the damage behavior of an optical component according to the invention and the other the damage behavior of an optical component according to the prior art.
  • a number of laser pulses is plotted on the x-axis of the diagram according to FIG. 1, and the absorption coefficient in the unit 1 / cm to the base e is plotted on the y-axis.
  • a disk-shaped substrate is arranged so that it faces vertically downward with one of its flat sides.
  • a deposition burner is arranged below the substrate and has a center nozzle which is coaxially surrounded by four ring nozzles. The deposition burner is aimed at the substrate, which rotates about its central axis.
  • the center nozzle of the deposition burner is supplied with methyltrimethoxysilane using a carrier gas (nitrogen), the other nozzles (in order from the inside out) a separation gas (nitrogen), oxygen and completely hydrogen.
  • Oxygen and hydrogen react with one another to form an oxyhydrogen gas flame, in which the methyltrimethoxysilane flowing out of the central nozzle hydrolyses and is deposited on the substrate in the form of finely divided SiO 2 .
  • the SiO 2 deposited on the substrate is vitrified directly by the heat of the oxyhydrogen gas to form a rod-shaped quartz glass blank. Due to the starting substances used, the quartz glass blank is practically chlorine-free (the chlorine content is
  • the quartz glass blank is then clamped in a quartz glass lathe, zone by zone heated to a temperature of approx. 2000 ° C and twisted.
  • a suitable homogenization process is described in EP-A1 673 888.
  • After repeated twisting there is a quartz glass body in the form of a round rod with a diameter of 80 mm and a length of approx. 800 mm, which is streak-free in three directions and which, averaged over its volume, has a hydrogen concentration of approx. 5x10 17 molecules / cm 3 and one OH content of about 900 ppm by weight.
  • the round rod is then subjected to a hydrogen reduction treatment by being under vacuum is annealed at 1100 ° C for a period of 200 h. Thereafter, the average hydrogen concentration of the round rod is approx. 3x10 16 molecules / cm 3 .
  • a circular quartz glass block with an outer diameter of 240 mm and a length of 90 mm is formed from this by hot deformation at a temperature of 1700 ° C. and using a nitrogen-flushed melting mold.
  • the quartz glass block After a further tempering process, in which the quartz glass block is heated to 1100 ° C under air and atmospheric pressure and then cooled at a cooling rate of 1 ° C / h, only a stress birefringence of maximum 2 nm / cm is measured, and the refractive index distribution is so homogeneous that the difference between the maximum value and the minimum value is less than 1x10 ⁇ .
  • the hydrogen content of the quartz glass block can no longer be detected using the Raman method and is therefore below 5x10 15 molecules / cm 3 ; its average OH content remains unchanged at approx. 900 ppm by weight.
  • the quartz glass block produced in this way is directly suitable as a blank for the production of an optical lens for a microlithography device.
  • the measurement samples were produced using a process variant.
  • the round rod present after the twisting was formed directly into the quartz glass block by annealing without prior hydrogen reduction treatment.
  • Two cylindrical measurement samples A and B with the dimensions 10 mm ⁇ 10 mm ⁇ 40 mm were cut from the quartz glass block, and the four long sides of each were polished.
  • test sample B was then subjected to a conventional tempering program, which comprises heating at a temperature of 800 ° C. for 5 hours in air.
  • the mean hydrogen content of sample B after this temper treatment was 1x10 17 molecules / cm 3 ; and the average OH content at 900 ppm by weight.
  • Measurement sample A was subjected to a hydrogen reduction treatment which, similar to the tempering program for measurement sample B, comprises heating in air at a temperature of 800 ° C., but for a period of 15 hours.
  • the mean hydrogen content of sample A after this tempering and hydrogen reduction treatment was in the range of the detection limit at about 5x10 15 molecules / cm 3 ; and the average OH content at 900 ppm by weight.
  • the absorption curve labeled "A" in FIG. 1 was obtained for measurement sample A and the absorption curve labeled "B" for measurement sample B.
  • the absorption curve "A" for the optical component produced according to the invention in accordance with measurement sample A initially shows a rapid increase, which indicates a rapid onset of damage to the quartz glass, but which, after a pulse number of approximately 1,000,000, saturates to an absolute value of the absorption coefficient of approx. 0.12 cm “1 flows out, which means a surprisingly low saturation level under these conditions.
  • the absorption curve "B" for an optical component according to the prior art shows a significantly slower increase with an approximately constant slope.
  • sample B no saturation of the induced absorption can be seen up to a pulse number of 15,000,000.
  • the absorption curves "A", "B” intersect. This means that the transmission of the optical component according to the invention is better at higher pulse numbers than that of the other optical component. This shows that the optical component according to the invention has more favorable damage behavior with regard to long-term stability.

Abstract

An optical component for transmitting ultraviolet radiation having a wavelength of 250 nm and less and made of synthetic silica glass, which is produced by subjecting a chlorine-free silicon compound to flame hydrolysis, which is shaped in the form of fine-grained SiO2, deposited on a substrate and directly vitrified is already known in prior art. Based on the above-mentioned optical component, the invention aims at providing an optical component exhibiting high long-time stability for the transmission of ultraviolet radiation with a wavelength of 250 nm and less and particularly a behavior in case of deterioration in which induced absorption leads to low level saturation. To this end, the silica glass has a hydrogen content of less than 5x1016 molecules/cm3. A method for the production of the optical component includes the production of a synthetic hydrogen-containing silica glass by synthesis of fine-grained SiO¿2? by means of flame-hydrolysis of a chlorine-free silicon compound and depositing and vitrifying the fine-grained SiO2 on a substrate to form the hydrogen-containing silica glass, wherein the hydrogen-containing silica glass is subjected to a hydrogen reduction treatment, wherein its hydrogen content is set to a value under 5x10?16¿ molecules/cm3.

Description

Optisches Bauteil aus Quarzglas und Verfahren für seine Herstellung Optical component made of quartz glass and process for its production
Die vorliegende Erfindung betrifft ein optisches Bauteil für die Übertragung ultravioletter Strahlung einer Wellenlänge von 250 nm und kürzer, aus synthetischem Quarzglas, das erhalten wird, indem feinkörniges SiO2 durch Flammenhydrolyse einer chlorfreien Siliciumverbindung gebildet, auf einem Substrat abgeschieden und direkt verglast wird.The present invention relates to an optical component for transmitting ultraviolet radiation of a wavelength of 250 nm and shorter, made of synthetic quartz glass, which is obtained by forming fine-grained SiO 2 by flame hydrolysis of a chlorine-free silicon compound, deposited on a substrate and directly glazed.
Weiterhin betrifft die Erfindung ein Verfahren zur Herstellung eines optischen Bauteils aus synthetischem Quarzglas für die Übertragung ultravioletter Strahlung einer Wellenlänge von 250 nm und kürzer, umfassend die Herstellung von synthetischem, wasserstoffhaltigem Quarzglas, durch Synthese von feinkörnigem SiO2 mittels Flammenhydrolyse einer chlorfreien Siliciumverbindung, sowie Abscheiden und direktes Verglasen des feinkörnigen SiO2 auf einem Substrat unter Bildung des wasserstoffhaltigen Quarzglases.The invention further relates to a method for producing an optical component made of synthetic quartz glass for the transmission of ultraviolet radiation of a wavelength of 250 nm and shorter, comprising the production of synthetic, hydrogen-containing quartz glass, by synthesis of fine-grained SiO 2 by means of flame hydrolysis of a chlorine-free silicon compound, and deposition and direct vitrification of the fine-grained SiO 2 on a substrate to form the hydrogen-containing quartz glass.
Derartige optische Bauteile aus synthetischem Quarzglas werden insbesondere für die Übertragung energiereicher, ultravioletter Laserstrahlung eingesetzt, beispielsweise in Form von optischen Fasern oder in Form von Belichtungsoptiken in Mikrolithographiegeräten für die Herstellung hochintegrierter Schaltungen in Halbleiterchips. Die Belichtungssysteme moderner Mi- krolithographiegeräte sind mit Excimerlasern bestückt, die energiereiche, gepulste UV-Strahlung einer Wellenlänge von 248 nm (KrF-Laser) oder von 193 nm (ArF-Laser) abgeben. Es ist bekannt, daß derartige kurzwellige UV-Strahlung in den optischen Bauteilen Defekte und damit einhergehend Absorptionen induzieren kann, die für Art und Qualität des jeweiligen Quarzglases charakteristisch sind. So werden beispielsweise Schädigungsverhalten beobachtet, bei denen bei andauernder UV-Bestrahlung die induzierte Absorption linear ansteigt, oder bei der sie nach einem anfänglichen Anstieg in eine Sättigung mündet, oder bei der sich die induzierten Defekte derart akkumulieren, daß sie sich in einer plötzlichen und starken Zunahme der Absorption äußern. Der starke Anstieg der Absorption bei dem zuletzt beschriebenen Schädigungsverhalten wird in der Literatur als SAT-Effekt bezeichnet. Die Strahlenbeständigkeit eines Quarzglases kann von seinen strukturellen Eigenschaften, wie Dichte, Brechzahlverlauf und Homogenität, oder von seiner chemischen Zusammensetzung abhängen. Der Einfluß der chemischen Zusammensetzung des Quarzglases auf das Schädigungsverhalten bei der Bestrahlung mit energiereichem UV-Licht ist beispielsweise in der EP-A1 401 845 beschrieben. Eine hohe Strahlenbeständigkeit wurde demnach bei einem- hochreinen Quarzglas gefunden, das einen relativ hohen OH-Gehalt im Bereich von 100 bis ca. 1000 Gew.ppm und gleichzeitig eine relativ hohe Wasserstoffkonzentration von mindestens 5x1016 Molekülen pro cm3 (bezogen auf das Volumen des Quarzglases) aufweist. Der günstige Einfluß des Wasserstoffes auf die Strahlenbeständigkeit läßt sich dadurch erklären, daß dieser zu einem Ausheilen von Defekten, und damit zu einem langsameren Anstieg der strahleninduzierten Absorption beitragen kann. Aufgrund dieser Wirkung des Wasserstoffes wird in der EP-A1 401 845 empfohlen, optische Bauteile, an die hohe Anforderungen hinsichtlich der Strahlenbeständigkeit gestellt werden, mit Wasserstoff zu beladen.Such optical components made of synthetic quartz glass are used in particular for the transmission of high-energy, ultraviolet laser radiation, for example in the form of optical fibers or in the form of exposure optics in microlithography devices for the production of highly integrated circuits in semiconductor chips. The exposure systems of modern microlithography devices are equipped with excimer lasers that emit high-energy, pulsed UV radiation with a wavelength of 248 nm (KrF laser) or 193 nm (ArF laser). It is known that such short-wave UV radiation can induce defects in the optical components and the associated absorptions which are characteristic of the type and quality of the respective quartz glass. For example, damage behavior is observed in which the induced absorption rises linearly with continuous UV radiation, or in which it leads to saturation after an initial increase, or in which the induced defects accumulate in such a way that they become sudden and strong Express increase in absorption. The sharp increase in absorption with the damage behavior described last is referred to in the literature as the SAT effect. The radiation resistance of a quartz glass can depend on its structural properties, such as density, refractive index and homogeneity, or on its chemical composition. The influence of the chemical composition of the quartz glass on the damage behavior when irradiated with high-energy UV light is described, for example, in EP-A1 401 845. A high radiation resistance was accordingly found in a high-purity quartz glass, which has a relatively high OH content in the range from 100 to approx. 1000 ppm by weight and at the same time a relatively high hydrogen concentration of at least 5 × 10 16 molecules per cm 3 (based on the volume of the Quartz glass). The favorable influence of hydrogen on radiation resistance can be explained by the fact that it can contribute to the healing of defects and thus to a slower increase in radiation-induced absorption. Due to this effect of hydrogen, EP-A1 401 845 recommends loading optical components with high requirements with regard to radiation resistance with hydrogen.
Es hat sich aber gezeigt, daß trotz ähnlicher chemischer oder struktureller Eigenschaften des Quarzglases das Schädigungsverhalten von optischen Bauteilen verschieden sein kann, wenn das Quarzglas nach unterschiedlichen Herstellungsverfahren erhalten worden ist, oder, daß zwar chemische oder strukturelle Unterschiede vorhanden sein mögen, diese aber nicht eindeutig Ursache für die beobachteten Unterschiede im Schädigungsverhalten sind. Aus diesen Gründen läßt sich das optische Bauteil gemäß der vorliegenden Erfindung am besten durch sein Herstellungsverfahren kennzeichnen.However, it has been shown that, despite similar chemical or structural properties of the quartz glass, the damage behavior of optical components can be different if the quartz glass has been obtained by different manufacturing processes, or that chemical or structural differences may exist, but these are not clear The reason for the observed differences in damage behavior are. For these reasons, the optical component according to the present invention is best characterized by its manufacturing process.
Die Herstellungsverfahren von synthetischem Quarzglas durch Flammenhydrolyse siliciumhal- tiger Verbindungen kann man anhand der Ausgangssubstanzen sowie anhand der Art und Weise der Verglasung der abgeschiedenen SiO2-Partikel unterscheiden. Eine häufig eingesetzte Ausgangssubstanz bei der Herstellung von synthetischem Quarzglas durch Flammenhydrolyse ist SiCI4. Es werden aber auch andere, beispielsweise chlorfreie siliciumhaltige organische Verbindungen verwendet, wie Silane oder Siloxane. Die Herstellung von Quarzglas unter Verwendung von Alkoxysilanen ist in der EP-A1 525 984 beschrieben; die Herstellung von Quarzglas unter Verwendung von Siloxanen in der EP-A1 463 045. Aufgrund dieser Ausgangssubstanzen kann praktisch chlorfreies Quarzglas erzeugt werden.The production processes of synthetic quartz glass by flame hydrolysis of silicon-containing compounds can be differentiated on the basis of the starting substances and on the way in which the deposited SiO 2 particles are glazed. SiCI 4 is a frequently used starting material in the production of synthetic quartz glass by flame hydrolysis. However, other, for example chlorine-free, silicon-containing organic compounds are also used, such as silanes or siloxanes. The production of quartz glass using alkoxysilanes is described in EP-A1 525 984; the production of quartz glass using siloxanes in EP-A1 463 045. Based on these starting substances, practically chlorine-free quartz glass can be produced.
Das Verglasen der SiO2-Partikel kann direkt, während der Abscheidung auf dem Substrat erfolgen, was im folgenden als "direkte Verglasung" bezeichnet wird. Im Unterschied dazu wird bei dem sogenannten "Soot-Verfahren" die Temperatur während der Abscheidung der SiO2-Partikel so niedrig gehalten, daß ein poröser Sootkörper gebildet wird, aber keine oder nur eine geringe Verglasung der SiO2-Partikel eintritt. Das Verglasen unter Bildung von Quarzglas erfordert ein nachträgliches Sintern des Sootkörpers. Beide Herstellungsverfahren führen zu einem dichten, transparenten, hochreinen Quarzglas.The SiO 2 particles can be vitrified directly during the deposition on the substrate, which is referred to below as "direct vitrification". In contrast to this, in the so-called “soot process”, the temperature during the deposition of the SiO 2 particles is kept so low that a porous soot body is formed, but none or only slight glazing of the SiO 2 particles occurs. Glazing with the formation of quartz glass requires a subsequent sintering of the soot body. Both manufacturing processes lead to a dense, transparent, high-purity quartz glass.
Ein gattungsgemäßes optisches Bauteil für die Übertragung von UV-Strahlung einer Wellenlänge von weniger als 300 nm, und ein Verfahren für seine Herstellung sind aus der EP-A1 780 345 bekannt. Das darin beschriebene Bauteil wird erhalten, indem synthetisches Quarzglas durch Flammenhydrolyse einer chlorfreien Polymethylsiloxan-Verbindung in Form von SiO2-Partikeln auf einem Substrat abgeschieden und direkt verglast wird.A generic optical component for the transmission of UV radiation of a wavelength of less than 300 nm and a method for its production are known from EP-A1 780 345. The component described therein is obtained by depositing synthetic quartz glass on a substrate by flame hydrolysis of a chlorine-free polymethylsiloxane compound in the form of SiO 2 particles and vitrifying it directly.
Das so hergestellte optische Bauteil zeigt bei Bestrahlung mit gepulstem Excimerlaser (Wellenlänge: 248 nm; Intensität 360 mJ/cm2) ein Schädigungsverhalten, das im Vergleich zu einem Standardbauteil durch ein Ausbleiben des sogenannten SAT-Effektes gekennzeichnet ist. Das Standardbauteil besteht ebenfalls aus synthetischem Quarzglas, bei dessen Herstellung aber ein chlorhaltiges Ausgangsmaterial - nämlich SiCI4 - eingesetzt wurde. Der beobachtete Effekt ist bei dem bekannten optischen Bauteil daher möglicherweise auf dessen niedrigen Chlor-Gehalt zurückzuführen, der mit kleiner 3 ppm angegeben wird.When irradiated with a pulsed excimer laser (wavelength: 248 nm; intensity 360 mJ / cm 2 ), the optical component produced in this way shows a damage behavior which, in comparison to a standard component, is characterized by the absence of the so-called SAT effect. The standard component also consists of synthetic quartz glass, but a chlorine-containing starting material - namely SiCI 4 - was used in its manufacture. The observed effect in the known optical component may therefore be due to its low chlorine content, which is given as less than 3 ppm.
Die strahlungsinduzierte Absorption bei dem nach dem oben beschriebenen Verfahren hergestellten, bekannten optischen Bauteil zeigt zwar keinen SAT-Effekt, sondern einen relativ flachen Anstieg. Es ist aber nicht ersichtlich, daß der Anstieg in eine Sättigung münden könnte und welches Sättigungsniveau sich gegebenenfalls einstellen würde. Für Anwendungen optischer Bauteile, bei denen die Langzeitstabilität im Vordergrund steht, ist häufig aber nicht der anfängliche Anstieg der Absorption entscheidend, sondern das Erreichen eines Sättigungswertes und dessen absolutes Niveau.The radiation-induced absorption in the known optical component produced by the method described above does not show a SAT effect, but rather a relatively flat increase. However, it is not evident that the increase could lead to saturation and which saturation level would possibly arise. For applications in optical components where long-term stability is paramount, it is often not the initial increase in absorption that is decisive, but rather the achievement of a saturation value and its absolute level.
Der vorliegenden Erfindung liegt daher die Aufgabe zugrunde, ein optisches Bauteil bereitzustellen, das für die Übertragung ultravioletter Strahlung einer Wellenlänge von 250 nm und kürzer eine hohe Langzeitstabilität aufweist, und das insbesondere ein Schädigungsverhalten zeigt, bei dem die induzierte Absorption in eine Sättigung auf niedrigem Niveau einmündet. Weiterhin liegt der Erfindung die Aufgabe zugrunde, ein Verfahren zur Herstellung eines derartigen optischen Bauteils anzugeben.The present invention is therefore based on the object of providing an optical component which has a high long-term stability for the transmission of ultraviolet radiation of a wavelength of 250 nm and shorter, and which in particular shows a damage behavior in which the induced absorption into a saturation at a low level flows into. Furthermore, the invention is based on the object of specifying a method for producing such an optical component.
Hinsichtlich des optischen Bauteils wird diese Aufgabe ausgehend von dem eingangs angegebenen optischen Bauteil erfindungsgemäß dadurch gelöst, daß das Quarzglas einen Wasserstoffgehalt von weniger als 5x1016 Molekülen/cm3 aufweist. Das optische Bauteil gemäß der Erfindung zeichnet sich durch eine Kombination von Merkmalen aus, die sich wie folgt zusammenfassen lassen: Das Bauteil besteht aus synthetisch hergestelltem Quarzglas, das Quarzglas wird durch Flammenhydrolyse von chlorfreien Ausgangsstoffen synthetisiert, das Quarzglas wird bei der Abscheidung direkt verglast, und der Wasserstoffgehalt des Quarzglases wird auf maximal 5x1016 Moleküle/cm3 (bezogen auf das Volumen des Quarzglases) eingestellt.With regard to the optical component, this object is achieved, based on the optical component specified at the outset, in that the quartz glass has a hydrogen content of less than 5 × 10 16 molecules / cm 3 . The optical component according to the invention is characterized by a combination of features which can be summarized as follows: the component consists of synthetically produced quartz glass, the quartz glass is synthesized by flame hydrolysis of chlorine-free starting materials, the quartz glass is glazed directly during the deposition, and the hydrogen content of the quartz glass is set to a maximum of 5x10 16 molecules / cm 3 (based on the volume of the quartz glass).
Das charakteristische Schädigungsverhalten des so hergestellten optischen Bauteils gegenüber energiereicher UV-Strahlung zeigt sich darin, daß die induzierte Absorption zwar zunächst rasch ansteigt, jedoch anschließend schnell in eine Sättigung auf niedrigem Niveau einmündet. Dieses charakteristisches Schädigungsverhalten ist deutlich abhängig von den oben angegebenen Herstellungsbedingungen. Es verändert sich, sobald einer der Parameter bei der Herstellung des Bauteils geändert wird, indem beispielsweise für die Synthese des Quarzglases anstelle der direkten Verglasung ein Sootprozeß eingesetzt wird. Besonders überraschend ist, daß der Wasserstoffgehalt des Quarzglases weniger als 5x1016 Moleküle/cm3 betragen muß, damit sich die gewünschte Strahlenbeständigkeit ergibt. Eine Erklärung dafür wäre, daß der Wasserstoff nicht nur zur Ausheilung strahleninduzierter Defekte beiträgt, sondern auch selbst Defekte erzeugt, die sich insbesondere bei Langzeit-Bestrahlungen bemerkbar machen. Es hat sich gezeigt, daß durch den niedrigen Wasserstoffgehalt von weniger als 5x1016 Molekülen/cm3 nicht nur eine Sättigung der strahlungsinduzierten Absorption erzielt wird, sondern auch, daß das Sättigungsniveau im Vergleich mit einem Quarzglas mit höherem Wasserstoffgehalt vergleichsweise niedrig ist.The characteristic damage behavior of the optical component produced in this way in relation to high-energy UV radiation can be seen in the fact that the induced absorption initially rises rapidly, but then quickly leads to saturation at a low level. This characteristic damage behavior is clearly dependent on the manufacturing conditions specified above. It changes as soon as one of the parameters in the manufacture of the component is changed, for example by using a soot process for the synthesis of the quartz glass instead of the direct glazing. It is particularly surprising that the hydrogen content of the quartz glass must be less than 5 × 10 16 molecules / cm 3 in order to achieve the desired radiation resistance. An explanation for this would be that the hydrogen not only contributes to the healing of radiation-induced defects, but also generates defects that are particularly noticeable in long-term radiation. It has been shown that the low hydrogen content of less than 5 × 10 16 molecules / cm 3 not only saturates the radiation-induced absorption, but also that the saturation level is comparatively low in comparison with a quartz glass with a higher hydrogen content.
Dabei ist zu beachten, daß bedingt durch die Gegenwart von Wasserstoff beim Herstellungsverfahren des optischen Bauteils, das Quarzglas nach dem Verglasen Wasserstoff enthält, und zwar in einer Konzentration, die oberhalb der oben genannten Maximalgrenze von 5x1016 Molekülen/cm3 liegen kann. Gegebenenfalls ist es erforderlich, den Wasserstoff aus dem Bauteil auszutreiben.It should be noted that due to the presence of hydrogen in the manufacturing process of the optical component, the quartz glass contains hydrogen after vitrification, in a concentration that can be above the above-mentioned maximum limit of 5x10 16 molecules / cm 3 . It may be necessary to expel the hydrogen from the component.
Unter dem Wasserstoffgehalt wird hier und im folgenden ein über das Volumen des optischen Bauteils gemittelter Wasserstoffgehalt verstanden (arithmetisches Mittel von mindestens drei über das Bauteil gleichmäßig verteilten Meßstellen), wobei davon ausgegangen wird, daß das gesamte Bauteil für die Übertragung der UV-Strahlung beansprucht wird. Bei optischen Bauteilen, bei denen diese Voraussetzung nicht erfüllt ist, genügt es, wenn mindestens im optisch beanspruchten Volumenbereich der mittlere Wasserstoffgehalt unterhalb des oben genannten Maximalwertes liegt. Der Wasserstoffgehalt wird aufgrund einer Raman-Messung ermittelt, die von Khotimchenko et al., "Determining the Content of Hydrogen Dissolved in Quartz Glass Using the Methods of Raman Scattering and Mass Spectrometry" in "Zhurnal Prikladnoi Spektroskopii", Vol 46, No. 6, (1987), Seiten 987 bis 991 beschrieben worden ist. Hierzu wird das Verhältnis der Flächenintensitäten der Raman-Absorptionsbande bei einer Wellenzahl von 4135 cm"1 - die Wasserstoffmolekülen in Quarzglas zugeschrieben wird - und der Raman-Absorptionsbande bei einer Wellenzahl von 800 cm"1 - die SiO2 zugeschrieben wird - ermittelt und mit einer Konstante k (k = 1 ,22x1021) multipliziert. Das Produkt ergibt die Wasserstoffkonzentration des Quarzglases in einem Volumen von 1 cm3.The hydrogen content here and below means a hydrogen content averaged over the volume of the optical component (arithmetic mean of at least three measuring points evenly distributed over the component), it being assumed that the entire component is used for the transmission of UV radiation . In the case of optical components in which this requirement is not met, it is sufficient if the average hydrogen content is below the maximum value mentioned above, at least in the optically stressed volume range. The hydrogen content is determined on the basis of a Raman measurement, which was carried out by Khotimchenko et al., "Determining the Content of Hydrogen Dissolved in Quartz Glass Using the Methods of Raman Scattering and Mass Spectrometry" in "Zhurnal Prikladnoi Spectoskopii", Vol 46, No. 6, (1987), pages 987 to 991. For this purpose, the ratio of the area intensities of the Raman absorption band at a wave number of 4135 cm "1 - which is attributed to hydrogen molecules in quartz glass - and the Raman absorption band at a wave number of 800 cm " 1 - which is attributed to SiO 2 - is determined and with one Constant k (k = 1, 22x10 21 ) multiplied. The product gives the hydrogen concentration of the quartz glass in a volume of 1 cm 3 .
Die Nachweisgrenze für Wasserstoff liegt bei dieser Meßmethode derzeit bei ca. 5x1015 Molekülen/cm3. Als besonders vorteilhaft hat sich ein optisches Bauteil erwiesen, bei dem das Quarzglas einen Wasserstoffgehalt von weniger als 2x1016 Molekülen/cm3 , insbesondere von weniger als 5x1015 Molekülen/cm3 , aufweist, der Wasserstoffgehalt also unterhalb der derzeitigen Nachweisgrenze liegt. Ein derartiges Bauteil zeichnet sich durch eine besonders gute Langzeitstabilität gegenüber energiereicher UV-Strahlung und ein besonders niedriges Sättigunsniveau der durch die UV-Strahlung induzierten Absorption aus.The detection limit for hydrogen with this measuring method is currently around 5x10 15 molecules / cm 3 . An optical component in which the quartz glass has a hydrogen content of less than 2 × 10 16 molecules / cm 3 , in particular less than 5 × 10 15 molecules / cm 3 , has proven to be particularly advantageous, that is to say the hydrogen content is below the current detection limit. A component of this type is distinguished by particularly good long-term stability in relation to high-energy UV radiation and a particularly low saturation level of the absorption induced by the UV radiation.
Ein besonders günstiges Schädigungsverhalten zeigt ein optisches Bauteil, bei dem das Quarzglas einen OH-Gehalt von mindestens 400 Gew.-ppm aufweist. Der OH-Gehalt bezieht sich, entsprechend dem Wasserstoff-Gehalt, auf einen über das Quarzglas-Volumen gemittel- ten Wert. Er wird spektroskopisch ermittelt.An especially favorable damage behavior is shown by an optical component in which the quartz glass has an OH content of at least 400 ppm by weight. According to the hydrogen content, the OH content refers to a value averaged over the quartz glass volume. It is determined spectroscopically.
Als vorteilhaft hat es sich auch erwiesen, daß das Quarzglas einen Chlorgehalt von höchstens 1 Gew.-ppm aufweist. Die Angabe dieses Chlor-Gehaltes bezieht sich ebenfalls auf einen über das Quarzglas-Volumen gemittelten Wert und wird naßchemisch ermittelt. Chlor oder chlorhaltige Verbindungen werden häufig zum Entfernen von Hydroxyl-Ionen oder von Verunreinigungen aus Quarzglas eingesetzt. Ein Chlorgehalt oberhalb von 1 Gew.-ppm kann sich jedoch auf das Schädigungsverhalten des optischen Bauteils ungünstig auswirken.It has also proven to be advantageous that the quartz glass has a chlorine content of at most 1 ppm by weight. The indication of this chlorine content also relates to a value averaged over the quartz glass volume and is determined by wet chemistry. Chlorine or chlorine-containing compounds are often used to remove hydroxyl ions or contaminants from quartz glass. A chlorine content above 1 ppm by weight can, however, have an adverse effect on the damage behavior of the optical component.
Hinsichtlich des Verfahrens wird die oben angegebene technische Aufgabe ausgehend von dem eingangs genannten Verfahren erfindungsgemäß dadurch gelöst, daß das wasserstoffhaltige Quarzglas einer Wasserstoff-Reduktionsbehandlung unterzogen wird, in der sein Wasserstoffgehalt auf einen Wert unterhalb von 5x1016 Molekülen/cm3 eingestellt wird.With regard to the process, the technical problem specified above is achieved, based on the process mentioned at the outset, in that the hydrogen-containing quartz glass is subjected to a hydrogen reduction treatment in which its hydrogen content is adjusted to a value below 5 × 10 16 molecules / cm 3 .
Bezüglich der Charakteristika des Schädigungsverhaltens beim erfindungsgemäß herzustellenden optischen Bauteil sowie hinsichtlich der Bedeutung des Ausdruckes "Wasserstoffgehalt" wird auf die obigen Erläuterungen verwiesen. Beim Verfahren zur Herstellung des optischen Bauteils ist es wesentlich, daß der Wasserstoffgehalt des Quarzglases mittels einer Wasserstoff-Reduktionsbehandlung auf einen Wert unterhalb von 5x1016 Molekülen/cm3 eingestellt wird. Mittels der Wasserstoff-Reduktionsbehandlung läßt sich der Wasserstoff-Gehalt ausgehend von einer ersten, hohen Konzentration, in definierter Art und Weise und daher reproduzierbar auf eine zweite Konzentration unterhalb von 5x1016 Molekülen/cm3 einstellen. Die so hergestellten optischen Bauteile zeigen daher ein reproduzierbares Schädigungsverhalten.With regard to the characteristics of the damage behavior in the optical component to be produced according to the invention and with regard to the meaning of the expression "Hydrogen content" is referred to the above explanations. In the process for producing the optical component, it is essential that the hydrogen content of the quartz glass is adjusted to a value below 5 × 10 16 molecules / cm 3 by means of a hydrogen reduction treatment. By means of the hydrogen reduction treatment, the hydrogen content can be set from a first, high concentration in a defined manner and therefore reproducibly to a second concentration below 5x10 16 molecules / cm 3 . The optical components produced in this way therefore show reproducible damage behavior.
Gemäß einer bevorzugten Verfahrensvariante wird der Wasserstoffgehalt des Quarzglases in der Wasserstoff-Reduktionsbehandlung unterhalb von 2x1016 Molekülen/cm3 , noch besser auf einen Wert unterhalb von 5x1015 Molekülen/cm3 gebracht, also auf eine Konzentration, die unterhalb der derzeitigen Nachweisgrenze der Raman-Methode liegt. Ein so hergestelltes Bauteil zeichnet sich durch eine besonders gute Langzeitstabilität gegenüber energiereicher UV- Strahlung und ein besonders niedriges Sättigunsniveau der strahlungsinduzierten Absorption aus.According to a preferred process variant, the hydrogen content of the quartz glass in the hydrogen reduction treatment is brought below 2x10 16 molecules / cm 3 , even better to a value below 5x10 15 molecules / cm 3 , i.e. to a concentration below the current detection limit of Raman Method lies. A component manufactured in this way is characterized by particularly good long-term stability against high-energy UV radiation and a particularly low saturation level of the radiation-induced absorption.
Die Wasserstoff-Reduktionsbehandlung umfaßt vorteilhafterweise eine thermische Behandlung des Quarzglases, eine Behandlung unter Vakuum, und/oder eine Behandlung in einer chemisch reaktiven Atmosphäre. Die genannten Behandlungsvarianten können alternativ oder kumulativ angewandt werden. Als besonders wirksam erweist sich jedoch eine thermische Behandlung (im folgenden als Tempern bezeichnet) in einer wasserstoff-freien Atmosphäre, zum Beispiel unter Inertgas oder im Vakuum, um den Wasserstoffgehalt des Quarzglases einzustellen. Dies gilt für Quarzglas, das nach dem Verglasen und gegebenenfalls erforderlichen Nachbehandlungsschritten, wie beispielsweise einem Heißverformungs- oder einem Homogenisierungs-Schritt, einen zu hohen Wasserstoffgehalt aufweist. Durch das Tempern diffundiert Wasserstoff aus dem Quarzglas-Rohling heraus, wobei die oberflächennahen Bereiche zuerst an Wasserstoff verarmen und erst später die zentralen Bereiche des Rohlings. Es ist deshalb darauf zu achten, daß der Wasserstoffgehalt insbesondere in demjenigen Bereich ausreichend entfernt wird, der beim bestimmungsgemäßen Einsatz des daraus hergestellten Bauteils am stärksten optisch belastet wird; das sind im allgemeinen gerade die zentralen Bereiche des Rohlings. Beim Austreiben des Wasserstoffes durch Tempern sind die Temperatur, die Temperzeit und die Temper-Atmosphäre unter Berücksichtigung der Wandstärke oder Dicke des zu tempernden Quarzglas-Rohlings so einzustellen, daß der Wasserstoff in ausreichendem Maße entfernt wird. Das Tempern von Quarzglas für optische Bauteile ist ein häufig angewandter Verfahrensschritt, der üblicherweise zum Abbau mechanischer Spannungen dient, die die optischen Eigenschaften des Glases beeinträchtigen. In der Zielsetzung und im Ergebnis unterscheidet sich das hier zum Entfernen von Wasserstoff vorgeschlagene Tempern von den bekannten Temperverfahren darin, daß erfindungsgemäß ein Quarzglas mit einem mittleren Wasserstoffgehalt von weniger als 5x1016 Molekülen/cm3, vorzugsweise von weniger 2x1016 Molekülen/cm3, und besonders vorteilhaft auf einen Wert unterhalb von 5x1015 Molekülen/cm3 eingestellt wird.The hydrogen reduction treatment advantageously comprises a thermal treatment of the quartz glass, a treatment under vacuum, and / or a treatment in a chemically reactive atmosphere. The treatment variants mentioned can be used alternatively or cumulatively. However, thermal treatment (hereinafter referred to as tempering) in a hydrogen-free atmosphere, for example under inert gas or in a vacuum, has proven to be particularly effective in order to adjust the hydrogen content of the quartz glass. This applies to quartz glass which, after vitrification and any post-treatment steps that may be necessary, such as a hot deformation or a homogenization step, has an excessively high hydrogen content. Annealing causes hydrogen to diffuse out of the quartz glass blank, the areas near the surface first becoming poor in hydrogen and only later the central areas of the blank. It is therefore important to ensure that the hydrogen content is sufficiently removed, particularly in the area that is most visually stressed when the component made from it is used as intended; these are generally the central areas of the blank. When the hydrogen is expelled by tempering, the temperature, the tempering time and the tempering atmosphere, taking into account the wall thickness or thickness of the quartz glass blank to be tempered, must be set so that the hydrogen is removed to a sufficient extent. The tempering of quartz glass for optical components is a frequently used process step, which is usually used to reduce mechanical stress affect the optical properties of the glass. In the objective and in the result, the tempering proposed here for removing hydrogen differs from the known tempering methods in that, according to the invention, a quartz glass with an average hydrogen content of less than 5x10 16 molecules / cm 3 , preferably less than 2x10 16 molecules / cm 3 , and is particularly advantageously set to a value below 5x10 15 molecules / cm 3 .
Besonders effektiv gestaltet sich das Verfahren, wenn das wasserstoffhaltige Quarzglas zu einem Zwischenprodukt geformt wird, dessen kleinste laterale Abmessung 100 mm, vorzugsweise 80 mm, nicht übersteigt, wobei die Wasserstoff-Reduktionsbehandlung teilweise oder vollständig an dem Zwischenprodukt vollzogen wird. Die Wasserstoff-Reduktionsbehandlung beruht auf Diffusionsvorgängen in Quarzglas, beispielsweise dem Ausdiffundieren von Wasserstoff beim Tempern. Die erforderlichen Diffussionszeiten hängen entscheidend von der relevanten Schichtdicke ab. Optische Bauteile können jedoch in sehr großen Schichtdicken vorliegen. Beispielsweise können Linsen für Mikrolithographiegeräte Durchmesser um 250 mm und gleichzeitig Dicken um 100 mm aufweisen. Die dafür benötigten Quarzglasrohlinge haben Durchmesser um 300 mm und Dicken über 100 mm. Eine ausreichende Wasserstoff-Reduktionsbehandlung würde bei derartigen Bauteilen extrem lange Behandlungszeiten erfordern, die wirtschaftlich nicht mehr vertretbar wären. Zwar lassen sich Diffusionsvorgänge durch Temperaturerhöhung beschleunigen; allerdings sind einer Temperaturerhöhung ebenfalls Grenzen gesetzt, da diese mit unerwünschter plastischer Verformung oder anderen thermisch bedingten Beschädigungen des Bauteils einhergehen kann. Zur Lösung dieses Problems wird aus dem wasserstoffhaltigen Quarzglas ein Zwischenprodukt geformt, dessen geometrische Abmessungen so gewählt sind, daß sich der Wasserstoff leicht austreiben läßt. Unter der kleinsten lateralen Abmessung wird beispielsweise der Außendurchmesser bei einem stabförmi- gen, die Wandstärke bei einem rohrförmigen, oder die Dicke bei einem plattenförmigen Zwischenprodukt verstanden. Eine derartiges Zwischenprodukt erlaubt die Durchführung der Wasserstoff-Reduktionsbehandlung in wirtschaftlich vertretbaren Zeitspannen. Dabei kann es ausreichen, den Wasserstoffgehalt im Zwischenprodukt nur zu reduzieren, ohne daß die oben genannten Maximalwerte unterschritten werden, wenn die weitere Behandlung des Quarzglases eine vollständige Wasserstoffreduktion im Sinne der vorliegenden Erfindung erlaubt. Aus dem Zwischenprodukt wird in einem nachfolgenden Formschritt das Bauteil gebildet.The method is particularly effective when the hydrogen-containing quartz glass is formed into an intermediate product, the smallest lateral dimension of which does not exceed 100 mm, preferably 80 mm, the hydrogen reduction treatment being carried out partially or completely on the intermediate product. The hydrogen reduction treatment is based on diffusion processes in quartz glass, for example the diffusion of hydrogen during tempering. The required diffusion times depend crucially on the relevant layer thickness. However, optical components can be in very large layer thicknesses. For example, lenses for microlithography devices can have diameters of around 250 mm and thicknesses of around 100 mm. The quartz glass blanks required for this have diameters of around 300 mm and thicknesses of over 100 mm. Adequate hydrogen reduction treatment would require extremely long treatment times for such components, which would no longer be economically justifiable. Diffusion processes can be accelerated by increasing the temperature; however, there are also limits to an increase in temperature, since this can be accompanied by undesired plastic deformation or other thermally induced damage to the component. To solve this problem, an intermediate product is formed from the hydrogen-containing quartz glass, the geometric dimensions of which are chosen so that the hydrogen can be easily driven off. The smallest lateral dimension is understood to mean, for example, the outer diameter in the case of a rod-shaped intermediate product, the wall thickness in the case of a tubular one, or the thickness in the case of a plate-shaped intermediate product. Such an intermediate product allows the hydrogen reduction treatment to be carried out in economically justifiable periods of time. It may be sufficient to only reduce the hydrogen content in the intermediate product without falling below the above-mentioned maximum values if the further treatment of the quartz glass allows complete hydrogen reduction in the sense of the present invention. The component is formed from the intermediate product in a subsequent molding step.
Als günstig hat es sich erwiesen, das Quarzglas unter Bildung des Zwischenproduktes zu homogenisieren. Häufig ist eine Homogenisierungsbehandlung des Quarzglases erforderlich, um vorhandene Schlieren zu entfernen. Für die Homogenisierung wird das Quarzglas plastisch verformt. Es bietet sich an, im Rahmen einer solchen Homogenisierung das Zwischenprodukt zu formen, das dann anschließend der Wasserstoff-Reduktionsbehandlung unterzogen wird.It has proven to be advantageous to homogenize the quartz glass to form the intermediate product. A homogenization treatment of the quartz glass is often required to remove existing streaks. The quartz glass becomes plastic for homogenization deformed. It is advisable to form the intermediate product in the course of such a homogenization, which is then subsequently subjected to the hydrogen reduction treatment.
Nachfolgend werden das optische Bauteil und das Verfahren gemäß der Erfindung anhand eines Ausführungsbeispiels und einer Patentzeichnung näher beschrieben. Die einzige Figur der Patentzeichnung (Fig. 1) zeigt ein Diagramm mit zwei Absorptionskurven, von denen die eine das Schädigungsverhalten eines erfindungsgemäßen optischen Bauteils wiedergibt und die andere das Schädigungsverhalten eines optischen Bauteils nach dem Stand der Technik. Auf der x-Achse des Diagramms nach Figur 1 ist eine Anzahl an Laserpulsen aufgetragen, auf der y-Achse der Absorptionskoeffizient in der Einheit 1/cm zur Basis e.The optical component and the method according to the invention are described in more detail below on the basis of an exemplary embodiment and a patent drawing. The only figure in the patent drawing (FIG. 1) shows a diagram with two absorption curves, one of which represents the damage behavior of an optical component according to the invention and the other the damage behavior of an optical component according to the prior art. A number of laser pulses is plotted on the x-axis of the diagram according to FIG. 1, and the absorption coefficient in the unit 1 / cm to the base e is plotted on the y-axis.
Im folgenden wird die Herstellung eines erfindungsgemäßen optischen Bauteils anhand eines Beispiels beschrieben:The production of an optical component according to the invention is described below using an example:
Ein scheibenförmiges Substrat wird so angeordnet, daß es mit einer seiner Flachseiten senkrecht nach unten weist. Unterhalb des Substrates ist ein Abscheidebrenner angeordnet, der eine Mitteldüse aufweist, die von vier Ringdüsen koaxial umgeben ist. Der Abscheidebrenner ist auf das Substrat gerichtet, das um seine Mittelachse rotiert. Der Mitteldüse des Abscheidebrenners wird mittels einer Trägergases (Stickstoff) Methyltrimethoxysilan zugeführt, den anderen Düsen (in der Reihenfolge von innen nach außen) ein Trenngas (Stickstoff), Sauerstoff und ganz außen Wasserstoff. Sauerstoff und Wasserstoff reagieren unter Bildung einer Knallgasflamme miteinander, in der das aus der Mitteldüse ausströmende Methyltrimethoxysilan hy- drolisiert und in Form von feinteiligem SiO2 auf dem Substrat abgeschieden wird. Das auf dem Substrat abgeschiedene SiO2 wird unmittelbar durch die Hitze der Knallgasflamme unter Bildung eines stabförmigen Quarzglasrohlings verglast. Aufgrund der verwendeten Ausgangssubstanzen ist der Quarzglas-Rohling praktisch chlorfrei (der Chlorgehalt liegt unterhalb von 1 Gew.-ppm).A disk-shaped substrate is arranged so that it faces vertically downward with one of its flat sides. A deposition burner is arranged below the substrate and has a center nozzle which is coaxially surrounded by four ring nozzles. The deposition burner is aimed at the substrate, which rotates about its central axis. The center nozzle of the deposition burner is supplied with methyltrimethoxysilane using a carrier gas (nitrogen), the other nozzles (in order from the inside out) a separation gas (nitrogen), oxygen and completely hydrogen. Oxygen and hydrogen react with one another to form an oxyhydrogen gas flame, in which the methyltrimethoxysilane flowing out of the central nozzle hydrolyses and is deposited on the substrate in the form of finely divided SiO 2 . The SiO 2 deposited on the substrate is vitrified directly by the heat of the oxyhydrogen gas to form a rod-shaped quartz glass blank. Due to the starting substances used, the quartz glass blank is practically chlorine-free (the chlorine content is below 1 ppm by weight).
Zum Homogenisieren wird der Quarzglasrohling anschließend in eine Quarzglas-Drehbank eingespannt, zonenweise auf eine Temperatur von ca. 2000 °C erhitzt und dabei verdrillt. Ein dafür geeignetes Homogenisierungsverfahren ist in der EP-A1 673 888 beschrieben. Nach mehrmaligem Verdrillen liegt ein Quarzglaskörper in Form eines Rundstabes mit einem Durchmesser von 80 mm und einer Länge von ca. 800 mm vor, der in drei Richtungen schlierenfrei und der über sein Volumen gemittelt eine Wasserstoffkonzentration von ca. 5x1017 Molekülen/cm3 und einen OH-Gehalt von ca. 900 Gew.-ppm aufweist. Der Rundstab wird anschließend einer Wasserstoff-Reduktionsbehandlung unterzogen, indem er unter Vakuum bei 1100 °C über eine Dauer von 200 h getempert wird. Danach liegt die mittlere Wasserstoffkonzentration des Rundstabes bei ca. 3x1016 Molekülen/cm3 .For homogenization, the quartz glass blank is then clamped in a quartz glass lathe, zone by zone heated to a temperature of approx. 2000 ° C and twisted. A suitable homogenization process is described in EP-A1 673 888. After repeated twisting, there is a quartz glass body in the form of a round rod with a diameter of 80 mm and a length of approx. 800 mm, which is streak-free in three directions and which, averaged over its volume, has a hydrogen concentration of approx. 5x10 17 molecules / cm 3 and one OH content of about 900 ppm by weight. The round rod is then subjected to a hydrogen reduction treatment by being under vacuum is annealed at 1100 ° C for a period of 200 h. Thereafter, the average hydrogen concentration of the round rod is approx. 3x10 16 molecules / cm 3 .
Durch eine Heißverformung bei einer Temperatur von 1700 °C und unter Verwendung einer stickstoffgespülten Schmelzform wird daraus ein kreisrunder Quarzglas-Block mit einem Außendurchmesser von 240 mm und einer Länge von 90 mm gebildet.A circular quartz glass block with an outer diameter of 240 mm and a length of 90 mm is formed from this by hot deformation at a temperature of 1700 ° C. and using a nitrogen-flushed melting mold.
Nach einem weiteren Tempervorgang, bei der der Quarzglas-Block unter Luft und Atmosphärendruck auf 1100 °C erhitzt und anschließend mit einer Abkühlrate von 1 °C/h abgekühlt wird, wird lediglich noch eine Spannungsdoppelbrechung von maximal 2 nm/cm gemessen, und die Brechzahlverteilung ist derart homogen, daß der Unterscheid zwischen dem Maximalwert und dem Minimalwert unterhalb von 1x10^ liegt. Der Wasserstoffgehalt des Quarzglas-Blocks ist mittels der Raman-Methode nicht mehr nachweisbar und liegt somit unterhalb von 5x1015 Moleküle/cm3; sein mittlerer OH-Gehalt liegt unverändert bei ca. 900 Gew.-ppm. Der so hergestellte Quarzglas-Block ist als Rohling für die Herstellung einer optischen Linse für ein Mikroli- thographiegerät unmittelbar geeignet.After a further tempering process, in which the quartz glass block is heated to 1100 ° C under air and atmospheric pressure and then cooled at a cooling rate of 1 ° C / h, only a stress birefringence of maximum 2 nm / cm is measured, and the refractive index distribution is so homogeneous that the difference between the maximum value and the minimum value is less than 1x10 ^. The hydrogen content of the quartz glass block can no longer be detected using the Raman method and is therefore below 5x10 15 molecules / cm 3 ; its average OH content remains unchanged at approx. 900 ppm by weight. The quartz glass block produced in this way is directly suitable as a blank for the production of an optical lens for a microlithography device.
Anhand einer Verfahrensvariante wurden die Meßproben hergestellt, deren Schädigungsverhalten in Figur 1 dargestellt ist. Bei dieser Verfahrensvariante wurde der nach dem Verdrillen vorliegende Rundstab ohne vorherige Wasserstoff-Reduktionsbehandlung durch Tempern unmittelbar zu dem Quarzglas-Block geformt. Aus dem Quarzglas-Block wurden zwei zylindrische Meßproben A und B mit den Abmessungen 10 mm x 10 mm x 40 mm geschnitten, und deren vier lange Seiten jeweils poliert.The measurement samples, the damage behavior of which is shown in FIG. 1, were produced using a process variant. In this variant of the method, the round rod present after the twisting was formed directly into the quartz glass block by annealing without prior hydrogen reduction treatment. Two cylindrical measurement samples A and B with the dimensions 10 mm × 10 mm × 40 mm were cut from the quartz glass block, and the four long sides of each were polished.
Die Meßprobe B wurde anschließend einem üblichen Temperprogramm unterworfen, das ein Heizen bei einer Temperatur von 800 °C während einer Dauer von 5 Stunden in Luft umfaßt. Der mittlere Wasserstoffgehalt der Meßprobe B lag nach dieser Temper-Behandlung bei 1x1017 Molekülen/cm3; und der mittlere OH-Gehalt bei 900 Gew.-ppm.The test sample B was then subjected to a conventional tempering program, which comprises heating at a temperature of 800 ° C. for 5 hours in air. The mean hydrogen content of sample B after this temper treatment was 1x10 17 molecules / cm 3 ; and the average OH content at 900 ppm by weight.
Die Meßprobe A wurde einer Wasserstoff-Reduktionsbehandlung unterworfen, die ähnlich dem Temperprogramm für Meßprobe B ein Heizen bei einer Temperatur von 800 °C in Luft umfaßt, dies jedoch während einer Dauer von 15 Stunden. Der mittlere Wasserstoffgehalt der Meßprobe A lag nach dieser Temper- und Wasserstoff-Reduktionsbehandlung im Bereich der Nachweisgrenze bei ca. 5x1015 Molekülen/cm3; und der mittlere OH-Gehalt bei 900 Gew.-ppm.Measurement sample A was subjected to a hydrogen reduction treatment which, similar to the tempering program for measurement sample B, comprises heating in air at a temperature of 800 ° C., but for a period of 15 hours. The mean hydrogen content of sample A after this tempering and hydrogen reduction treatment was in the range of the detection limit at about 5x10 15 molecules / cm 3 ; and the average OH content at 900 ppm by weight.
Die Meßproben A und B wurden anschließend mit einem UV-Excimerlaser bestrahlt (Wellenlänge λ = 193 nm, Impulsenergie = 100 mJ/cm2, Pulswiederholungsrate = 200 Hz), wobei gleichzeitig die Transmission bei einer Wellenlänge λ = 193 nm gemessen wurde. Dabei wurde für Meßprobe A die in Figur 1 mit "A" bezeichnete Absorptionskurve, und für Meßprobe B die mit "B" bezeichnete Absorptionskurve erhalten.The measurement samples A and B were then irradiated with a UV excimer laser (wavelength λ = 193 nm, pulse energy = 100 mJ / cm 2 , pulse repetition rate = 200 Hz), the transmission being measured at a wavelength λ = 193 nm. there the absorption curve labeled "A" in FIG. 1 was obtained for measurement sample A and the absorption curve labeled "B" for measurement sample B.
Aus den Absorptionskurven lassen sich folgende Schädigungsverhalten entnehmen:The following damage behavior can be seen from the absorption curves:
Die Absorptionskurve "A" für das erfindungsgemäß hergestellte optische Bauteil entsprechend der Meßprobe A zeigt zunächst einen schnellen Anstieg, was also eine rasch einsetzende Schädigung des Quarzglases anzeigt, der aber nach einer Impulszahl von etwa 1.000.000 in eine Sättigung bei einem Absolutwert des Absorptionskoeffizienten von ca. 0,12 cm"1 einmündet, was unter diesen Bedingungen ein überraschend niedriges Sättigungsniveau bedeutet.The absorption curve "A" for the optical component produced according to the invention in accordance with measurement sample A initially shows a rapid increase, which indicates a rapid onset of damage to the quartz glass, but which, after a pulse number of approximately 1,000,000, saturates to an absolute value of the absorption coefficient of approx. 0.12 cm "1 flows out, which means a surprisingly low saturation level under these conditions.
Die Absorptionskurve "B", für ein optisches Bauteil nach dem Stand der Technik, entsprechend der Meßprobe B zeigt demgegenüber einen deutlich langsameren Anstieg mit etwa konstanter Steigung. Bei der Meßprobe B ist bis zu einer Impulszahl von 15.000.000 noch keine Sättigung der induzierten Absorption erkennbar. Bei einer Impulszahl von ca. 5.000.000 schneiden sich die Absorptionskurven "A", "B". Das bedeutet, daß die Transmission des erfindungsgemäßen optischen Bauteils bei höheren Impulszahlen besser ist, als die des anderen optischen Bauteils. Dies zeigt, daß das erfindungsgemäße optische Bauteil in bezug auf die Langzeitstabilität ein günstigeres Schädigungsverhalten aufweist. In contrast, the absorption curve "B" for an optical component according to the prior art, corresponding to the measurement sample B, shows a significantly slower increase with an approximately constant slope. In sample B, no saturation of the induced absorption can be seen up to a pulse number of 15,000,000. With a pulse number of approx. 5,000,000, the absorption curves "A", "B" intersect. This means that the transmission of the optical component according to the invention is better at higher pulse numbers than that of the other optical component. This shows that the optical component according to the invention has more favorable damage behavior with regard to long-term stability.

Claims

Optisches Bauteil aus Quarzglas und Verfahren für seine HerstellungPatentansprüche Optical component made of quartz glass and process for its manufacture
1. Optisches Bauteil für die Übertragung ultravioletter Strahlung einer Wellenlänge von 250 nm und kürzer, aus synthetischem Quarzglas, das durch Flammenhydrolyse einer chlort reien Siliziumverbindung in Form von feinkörnigem SiO2 gebildet, auf einem Substrat abgeschieden und direkt verglast wird, dadurch gekennzeichnet, daß das Quarzglas einen Wasserstoffgehalt von weniger als 5x1016 Molekülen/cm3 aufweist.1. Optical component for the transmission of ultraviolet radiation of a wavelength of 250 nm and shorter, made of synthetic quartz glass, which is formed by flame hydrolysis of a chlorine-free silicon compound in the form of fine-grained SiO 2 , deposited on a substrate and directly glazed, characterized in that Quartz glass has a hydrogen content of less than 5x10 16 molecules / cm 3 .
2. Optisches Bauteil nach Anspruch 1 , dadurch gekennzeichnet, daß das Quarzglas einen Wasserstoffgehalt von weniger als 2x1016 Molekülen/cm3 aufweist.2. Optical component according to claim 1, characterized in that the quartz glass has a hydrogen content of less than 2x10 16 molecules / cm 3 .
3. Optisches Bauteil nach Anspruch 1 oder 2, dadurch gekennzeichnet, daß das Quarzglas einen Wasserstoffgehalt von weniger als 5x1015 Molekülen/cm3 aufweist.3. Optical component according to claim 1 or 2, characterized in that the quartz glass has a hydrogen content of less than 5x10 15 molecules / cm 3 .
4. Optisches Bauteil nach einem der Ansprüche 1 bis 3, dadurch gekennzeichnet, daß das Quarzglas einen OH-Gehalt von mindestens 400 Gew.-ppm aufweist.4. Optical component according to one of claims 1 to 3, characterized in that the quartz glass has an OH content of at least 400 ppm by weight.
5. Optisches Bauteil nach einem der Ansprüche 1 bis 4, dadurch gekennzeichnet, daß das Quarzglas einen Chlor-Gehalt von maximal 1 Gew.-ppm aufweist.5. Optical component according to one of claims 1 to 4, characterized in that the quartz glass has a chlorine content of at most 1 ppm by weight.
6. Verfahren zur Herstellung eines optischen Bauteils aus synthetischem Quarzglas für die Übertragung ultravioletter Strahlung einer Wellenlänge von 250 nm und kürzer, umfassend die Herstellung von synthetischem, wasserstoffhaltigem Quarzglas, durch Synthese von feinkörnigem SiO2 mittels Flammenhydrolyse einer chlorfreien Siliciumverbindung, sowie Abscheiden und Verglasen des feinkörnigen SiO2 auf einem Substrat unter Bildung des wasserstoffhaltigen Quarzglases, dadurch gekennzeichnet, daß das wasserstoffhaltige Quarzglas einer Wasserstoff-Reduktionsbehandlung unterzogen wird, in der sein Wasserstoffgehalt auf einen Wert unterhalb von 5x1016 Molekülen/cm3 eingestellt wird. 6. A method for producing an optical component made of synthetic quartz glass for the transmission of ultraviolet radiation of a wavelength of 250 nm and shorter, comprising the production of synthetic, hydrogen-containing quartz glass, by synthesis of fine-grained SiO 2 by means of flame hydrolysis of a chlorine-free silicon compound, and deposition and vitrification of the fine-grained SiO 2 on a substrate to form the hydrogen-containing quartz glass, characterized in that the hydrogen-containing quartz glass is subjected to a hydrogen reduction treatment in which its hydrogen content is adjusted to a value below 5x10 16 molecules / cm 3 .
7. Verfahren nach Anspruch 5, dadurch gekennzeichnet, daß der Wasserstoffgehalt des Quarzglases in der Wasserstoff-Reduktionsbehandlung auf einen Wert unterhalb von 2x1016 Molekülen/cm3 , vorzugsweise auf einen Wert unterhalb von 5x1015 Molekülen/cm3, eingestellt wird.7. The method according to claim 5, characterized in that the hydrogen content of the quartz glass in the hydrogen reduction treatment to a value below 2x10 16 molecules / cm 3 , preferably to a value below 5x10 15 molecules / cm 3 , is set.
8. Verfahren nach Anspruch 6 oder 7, dadurch gekennzeichnet, daß die Wasserstoff-Reduktionsbehandlung eine thermische Behandlung des Quarzglases, eine Behandlung unter Vakuum, und/oder eine Behandlung in einer chemisch reaktiven Atmosphäre umfaßt.8. The method according to claim 6 or 7, characterized in that the hydrogen reduction treatment comprises a thermal treatment of the quartz glass, a treatment under vacuum, and / or a treatment in a chemically reactive atmosphere.
9. Verfahren nach einem der vorhergehenden Verfahrensansprüche, dadurch gekennzeichnet, daß das wasserstoffhaltige Quarzglas zu einem Zwischenprodukt geformt wird, dessen kleinste laterale Abmessung 100 mm, vorzugsweise 80 mm, nicht übersteigt, und daß die Wasserstoff-Reduktionsbehandlung teilweise oder vollständig an dem Zwischenprodukt vollzogen wird.9. The method according to any one of the preceding method claims, characterized in that the hydrogen-containing quartz glass is formed into an intermediate product, the smallest lateral dimension of which does not exceed 100 mm, preferably 80 mm, and that the hydrogen reduction treatment is carried out partially or completely on the intermediate product .
10. Verfahren nach Anspruch 9, dadurch gekennzeichnet, daß das Quarzglas unter Bildung des Zwischenproduktes homogenisiert wird.10. The method according to claim 9, characterized in that the quartz glass is homogenized to form the intermediate.
11. Verfahren nach einem der Ansprüche 6 bis 9, dadurch gekennzeichnet, daß das Quarzglas homogenisiert wird, und daß die Wasserstoff-Reduktionsbehandlung teilweise oder vollständig vor der Homogensierung des Quarzglases erfolgt. 11. The method according to any one of claims 6 to 9, characterized in that the quartz glass is homogenized and that the hydrogen reduction treatment is carried out partially or completely before the homogenization of the quartz glass.
PCT/EP1999/003342 1998-09-14 1999-05-14 Optical component made of silica glass and method for the production thereof WO2000015570A1 (en)

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EP99969079A EP1049654A1 (en) 1998-09-14 1999-05-14 Optical component made of silica glass and method for the production thereof
KR1020007005233A KR20010032101A (en) 1998-09-14 1999-05-14 Optical component made of silica glass and method for the production thereof
JP2000570115A JP2002524382A (en) 1998-09-14 1999-05-14 Optical member made of quartz glass and method for producing the same

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DE19841932A DE19841932A1 (en) 1998-09-14 1998-09-14 UV transmitting optical component, e.g. a microlithography component used in chip production, consists of flame hydrolyzed and directly vitrified quartz glass of extremely low hydrogen content
DE19841932.5 1998-09-14

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PCT/EP1999/003342 WO2000015570A1 (en) 1998-09-14 1999-05-14 Optical component made of silica glass and method for the production thereof

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EP (1) EP1049654A1 (en)
JP (1) JP2002524382A (en)
KR (1) KR20010032101A (en)
DE (1) DE19841932A1 (en)
WO (1) WO2000015570A1 (en)

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EP0999190A2 (en) * 1998-11-04 2000-05-10 Heraeus Quarzglas GmbH & Co. KG Core glass for an optical fibre preform, a preform produced using the core glass and processes for producing the core glass and an optical fibre
US7534733B2 (en) 2004-02-23 2009-05-19 Corning Incorporated Synthetic silica glass optical material having high resistance to laser induced damage

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DE10142893B4 (en) * 2001-09-03 2005-07-07 Heraeus Quarzglas Gmbh & Co. Kg Process for annealing a blank for a quartz glass optical component
DE102004015766B4 (en) 2004-03-23 2016-05-12 Asahi Glass Co., Ltd. Use of a SiO 2 -tiO 2 glass as a radiation-resistant substrate
DE102004024808B4 (en) * 2004-05-17 2006-11-09 Heraeus Quarzglas Gmbh & Co. Kg Quartz glass blank for an optical component for transmitting extremely short-wave ultraviolet radiation
WO2006104178A1 (en) * 2005-03-29 2006-10-05 Asahi Glass Company, Limited Quartz-type glass and process for its production
DE102010052685A1 (en) 2010-11-26 2012-05-31 J-Fiber Gmbh Process for the production of radiation-resistant quartz glass material and quartz glass body produced therefrom
JP5935765B2 (en) * 2012-07-10 2016-06-15 信越化学工業株式会社 Synthetic quartz glass for nanoimprint mold, method for producing the same, and mold for nanoimprint
DE102013215292A1 (en) 2013-08-02 2015-02-05 Carl Zeiss Smt Gmbh Method for loading a quartz glass blank with hydrogen, lens element and projection objective

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0999190A2 (en) * 1998-11-04 2000-05-10 Heraeus Quarzglas GmbH & Co. KG Core glass for an optical fibre preform, a preform produced using the core glass and processes for producing the core glass and an optical fibre
EP0999190A3 (en) * 1998-11-04 2001-10-10 Heraeus Quarzglas GmbH & Co. KG Core glass for an optical fibre preform, a preform produced using the core glass and processes for producing the core glass and an optical fibre
US6622527B2 (en) 1998-11-04 2003-09-23 Heraeus Quarzglas Gmbh Adjusting the hydrogen content of a preform for an UV-optical fiber
US7534733B2 (en) 2004-02-23 2009-05-19 Corning Incorporated Synthetic silica glass optical material having high resistance to laser induced damage

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KR20010032101A (en) 2001-04-16
EP1049654A1 (en) 2000-11-08
JP2002524382A (en) 2002-08-06

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