Classifications

• • C—CHEMISTRY; METALLURGY
  • C03—GLASS; MINERAL OR SLAG WOOL
  • C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
  • C03B19/00—Other methods of shaping glass
  • C03B19/14—Other methods of shaping glass by gas- or vapour- phase reaction processes
  • C03B19/1453—Thermal after-treatment of the shaped article, e.g. dehydrating, consolidating, sintering
  • C03B19/1461—Thermal after-treatment of the shaped article, e.g. dehydrating, consolidating, sintering for doping the shaped article with flourine
• • C—CHEMISTRY; METALLURGY
  • C03—GLASS; MINERAL OR SLAG WOOL
  • C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
  • C03B19/00—Other methods of shaping glass
  • C03B19/06—Other methods of shaping glass by sintering, e.g. by cold isostatic pressing of powders and subsequent sintering, by hot pressing of powders, by sintering slurries or dispersions not undergoing a liquid phase reaction
  • C03B19/066—Other methods of shaping glass by sintering, e.g. by cold isostatic pressing of powders and subsequent sintering, by hot pressing of powders, by sintering slurries or dispersions not undergoing a liquid phase reaction for the production of quartz or fused silica articles
• • C—CHEMISTRY; METALLURGY
  • C03—GLASS; MINERAL OR SLAG WOOL
  • C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
  • C03B19/00—Other methods of shaping glass
  • C03B19/10—Forming beads
  • C03B19/1005—Forming solid beads
  • C03B19/106—Forming solid beads by chemical vapour deposition; by liquid phase reaction
• • C—CHEMISTRY; METALLURGY
  • C03—GLASS; MINERAL OR SLAG WOOL
  • C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
  • C03B19/00—Other methods of shaping glass
  • C03B19/10—Forming beads
  • C03B19/1095—Thermal after-treatment of beads, e.g. tempering, crystallisation, annealing
• • 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
• • C—CHEMISTRY; METALLURGY
  • C03—GLASS; MINERAL OR SLAG WOOL
  • C03C—CHEMICAL COMPOSITION OF GLASSES, GLAZES OR VITREOUS ENAMELS; SURFACE TREATMENT OF GLASS; SURFACE TREATMENT OF FIBRES OR FILAMENTS MADE FROM GLASS, MINERALS OR SLAGS; JOINING GLASS TO GLASS OR OTHER MATERIALS
  • C03C3/00—Glass compositions
  • C03C3/04—Glass compositions containing silica
  • C03C3/06—Glass compositions containing silica with more than 90% silica by weight, e.g. quartz
• • C—CHEMISTRY; METALLURGY
  • C03—GLASS; MINERAL OR SLAG WOOL
  • C03C—CHEMICAL COMPOSITION OF GLASSES, GLAZES OR VITREOUS ENAMELS; SURFACE TREATMENT OF GLASS; SURFACE TREATMENT OF FIBRES OR FILAMENTS MADE FROM GLASS, MINERALS OR SLAGS; JOINING GLASS TO GLASS OR OTHER MATERIALS
  • C03C4/00—Compositions for glass with special properties
  • C03C4/0085—Compositions for glass with special properties for UV-transmitting glass
• • G—PHYSICS
  • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
  • G03F—PHOTOMECHANICAL PRODUCTION OF TEXTURED OR PATTERNED SURFACES, e.g. FOR PRINTING, FOR PROCESSING OF SEMICONDUCTOR DEVICES; MATERIALS THEREFOR; ORIGINALS THEREFOR; APPARATUS SPECIALLY ADAPTED THEREFOR
  • G03F1/00—Originals for photomechanical production of textured or patterned surfaces, e.g., masks, photo-masks, reticles; Mask blanks or pellicles therefor; Containers specially adapted therefor; Preparation thereof
  • G03F1/22—Masks or mask blanks for imaging by radiation of 100nm or shorter wavelength, e.g. X-ray masks, extreme ultraviolet [EUV] masks; Preparation thereof
  • G03F1/24—Reflection masks; Preparation thereof
• • C—CHEMISTRY; METALLURGY
  • C03—GLASS; MINERAL OR SLAG WOOL
  • C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
  • C03B2201/00—Type of glass produced
  • C03B2201/06—Doped silica-based glasses
  • C03B2201/08—Doped silica-based glasses doped with boron or fluorine or other refractive index decreasing dopant
  • C03B2201/12—Doped silica-based glasses doped with boron or fluorine or other refractive index decreasing dopant doped with fluorine
• • C—CHEMISTRY; METALLURGY
  • C03—GLASS; MINERAL OR SLAG WOOL
  • C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
  • C03B2201/00—Type of glass produced
  • C03B2201/06—Doped silica-based glasses
  • C03B2201/30—Doped silica-based glasses doped with metals, e.g. Ga, Sn, Sb, Pb or Bi
  • C03B2201/40—Doped silica-based glasses doped with metals, e.g. Ga, Sn, Sb, Pb or Bi doped with transition metals other than rare earth metals, e.g. Zr, Nb, Ta or Zn
  • C03B2201/42—Doped silica-based glasses doped with metals, e.g. Ga, Sn, Sb, Pb or Bi doped with transition metals other than rare earth metals, e.g. Zr, Nb, Ta or Zn doped with titanium
• • C—CHEMISTRY; METALLURGY
  • C03—GLASS; MINERAL OR SLAG WOOL
  • C03C—CHEMICAL COMPOSITION OF GLASSES, GLAZES OR VITREOUS ENAMELS; SURFACE TREATMENT OF GLASS; SURFACE TREATMENT OF FIBRES OR FILAMENTS MADE FROM GLASS, MINERALS OR SLAGS; JOINING GLASS TO GLASS OR OTHER MATERIALS
  • C03C2201/00—Glass compositions
  • C03C2201/06—Doped silica-based glasses
  • C03C2201/08—Doped silica-based glasses containing boron or halide
  • C03C2201/12—Doped silica-based glasses containing boron or halide containing fluorine
• • C—CHEMISTRY; METALLURGY
  • C03—GLASS; MINERAL OR SLAG WOOL
  • C03C—CHEMICAL COMPOSITION OF GLASSES, GLAZES OR VITREOUS ENAMELS; SURFACE TREATMENT OF GLASS; SURFACE TREATMENT OF FIBRES OR FILAMENTS MADE FROM GLASS, MINERALS OR SLAGS; JOINING GLASS TO GLASS OR OTHER MATERIALS
  • C03C2201/00—Glass compositions
  • C03C2201/06—Doped silica-based glasses
  • C03C2201/30—Doped silica-based glasses containing metals
  • C03C2201/40—Doped silica-based glasses containing metals containing transition metals other than rare earth metals, e.g. Zr, Nb, Ta or Zn
  • C03C2201/42—Doped silica-based glasses containing metals containing transition metals other than rare earth metals, e.g. Zr, Nb, Ta or Zn containing titanium
• • C—CHEMISTRY; METALLURGY
  • C03—GLASS; MINERAL OR SLAG WOOL
  • C03C—CHEMICAL COMPOSITION OF GLASSES, GLAZES OR VITREOUS ENAMELS; SURFACE TREATMENT OF GLASS; SURFACE TREATMENT OF FIBRES OR FILAMENTS MADE FROM GLASS, MINERALS OR SLAGS; JOINING GLASS TO GLASS OR OTHER MATERIALS
  • C03C2203/00—Production processes
  • C03C2203/40—Gas-phase processes
• • C—CHEMISTRY; METALLURGY
  • C03—GLASS; MINERAL OR SLAG WOOL
  • C03C—CHEMICAL COMPOSITION OF GLASSES, GLAZES OR VITREOUS ENAMELS; SURFACE TREATMENT OF GLASS; SURFACE TREATMENT OF FIBRES OR FILAMENTS MADE FROM GLASS, MINERALS OR SLAGS; JOINING GLASS TO GLASS OR OTHER MATERIALS
  • C03C2203/00—Production processes
  • C03C2203/50—After-treatment
  • C03C2203/52—Heat-treatment
  • C03C2203/54—Heat-treatment in a dopant containing atmosphere
• • 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
  • C03C2204/00—Glasses, glazes or enamels with special properties

Definitions

• the present invention relates to a method for producing a blank of titanium-doped, high-siliceous glass with a predetermined
• Fluorine content for use in EUV lithography comprising a
• Synthesis process in which fluorine-doped TiO 2 -SiO 2 soot particles are produced and further processed by consolidation and vitrification to the blank.
• EUV lithography highly integrated structures with a line width of less than 50 nm are produced by means of microlithographic projection devices.
• radiation from the EUV range extreme ultraviolet light, also called soft X-ray radiation
• the projection devices are equipped with mirror elements consisting of high-siliceous and titania-doped glass (also referred to below as “T1O2-SiO2 glass” or as “Ti-doped silica glass”), which are provided with a reflective layer system is characterized by an extremely low coefficient of thermal expansion (CTE), which is adjustable by the concentration of titanium.
• CTE coefficient of thermal expansion
• volume of the mirror substrate to an inhomogeneous temperature distribution with temperature differences which may be up to 50 ° C according to the literature.
• the glass of the mirror substrate blank had a CTE which would be zero over the entire temperature range of the operating temperatures occurring in use.
• the temperature range with a CTE around zero may be very narrow.
• the temperature at which the coefficient of thermal expansion of the glass is equal to zero is also referred to below as the zero-crossing temperature or as Tzc (Temperature of Zero Crossing).
• Tzc Temporal of Zero Crossing
• the titanium concentration is usually adjusted to give a CTE of zero in the temperature range between 20 ° C and 45 ° C.
• Volume ranges of the mirror substrate having a temperature higher or lower than the preset T Z c expand or contract so that, despite the overall low CTE of the TiO 2 -SiO 2 glass, the image quality of the mirror suffers.
• Temperature is a glass property that governs the state of order
• a higher fictitious temperature of the TiO 2 -SiO 2 glass is accompanied by a lower order state of the glass structure and a greater deviation from the most favorable structural arrangement.
• the fictitious temperature is characterized by the thermal history of the glass, especially the last cooling process.
• the last cooling process inevitably results in different conditions for near-surface areas of a glass block than for central areas, so that different volume areas of the mirror substrate blank already have different fictitious temperatures due to their different thermal history
• the fictive temperature is also influenced by the proportion of fluorine, since fluorine affects the structure relaxation.
• Fluorine doping allows the setting of a lower fictitious temperature - - and consequently a lower slope of CTE over temperature.
• WO 201 1/078414 A2 discloses, in the case of a blank for a mirror substrate or for a masking plate of SiO 2 -TiO 2 glass, the concentration of titanium oxide over the thickness of the blank stepwise or continuously to the temperature distribution established during operation adapt, that at each point the condition for the zero-crossing temperature T Z c are met, so the thermal expansion coefficient for the locally adjusting temperature is substantially equal to zero.
• a CTE is defined as substantially equal to zero if the remaining linear expansion in operation at each point is 0 ⁇ 50ppb / ° C. This is to be achieved in that at the
• the concentration of titanium or silicon-containing starting substances is varied so that sets a predetermined concentration profile in the blank.
• the fluorine is already added during the deposition of TiO 2 -SiO 2 -Sootpumble as fluorine-containing starting material of the flame hydrolysis, so that a SiO 2 -Sootpulver with a fluorine-titanium Codot mich accumulates, the
• the S1O2 soot particles are flowed through in a powder bed by an inert gas stream and supplied from this to a burner, which vitrifies the soot particles in a fuel gas flame and simultaneously doped with fluorine by feeding a fluorine reagent.
• the burner is arranged on a heated deposition space into which the fluorine doped and vitrified S1O2 particles are deposited and form a massive quartz glass blank there.
• the invention is therefore based on the object to provide a method for producing a blank from a fluorine-doped TiO 2 -SiO 2 glass, in which a particularly homogeneous distribution of the titanium and the fluorine is achieved in the glass.
• the synthesis process comprises a method step in which TiO 2-SiO 2 soot particles are formed by flame hydrolysis of silicon and titanium-containing starting materials and a subsequent process step in which the TiO 2 -SiO 2 -Soot particle in - Are exposed to a moving powder bed a fluorine-containing reagent and reacted to the fluorine-doped TiO 2 -SiO 2 soot particles.
• TiO.sub.2-SiO.sub.2 soot particles are produced which, at a correspondingly high temperature in the separation chamber, assemble to form a porous TiO.sub.2-SiO.sub.2 soot body of low density on a substrate surface. Due to the flow conditions, individual soot particles can not reach the substrate surface or be torn away from there and form the so-called pulverulent "soot waste" which is collected in corresponding filter systems.
• the problem is the lack of purity of Sootabfalls, as on the way to the filter system and in the filter system itself numerous
• Impurities can come into contact with the soot particles.
• the substrate surface in the process chamber for depositing the soot particles is arranged at a greater distance from the burner, or if the substrate surface is cooled in a targeted manner, the TiO.sub.2-SiO.sub.2 soot particles essentially remain separated from one another and fall as powder on the substrate surface or in to a collecting vessel.
• Soot particles are open structured agglomerates of smaller aggregates of
• BET Brunauer-Emmett-Teller
• the invention it is proposed to collect TiO 2 -SiO 2 soot particles in a moving powder bed and to treat them there with a fluorine-containing reagent.
• the movement of the powder bed either by external action or by blowing the fluorine reagent or another gas stream, causes a slight turbulence of the finely divided soot particles, so that the fluorine reagent can react optimally with the TiO 2 -SiO 2 soot particles.
• the fluorine can react with the individual soot particles in the moving powder bed within a very short time. In this way, the doping of the T1O2-SiO2 soot particles with fluorine takes place.
• the distribution of the fluorine according to the invention The method according to the invention is compared to doping a TiO 2 -SiO 2 soot body by the action of a gaseous or else liquid
• Fluorine reagent according to the prior art substantially homogeneous. Due to the open structure of the agglomerated soot particles, the fluorine-containing reagent receives maximum surface contact with the TiO 2 -SiO 2 soot particles, resulting in the particularly homogeneous incorporation of fluorine in the TiO 2 -SiO 2 structure. Even with the fluorine doping directly during the deposition of the ⁇ 2 - SiO 2 soot particles, no homogeneous distribution of the fluorine is achieved, since the reaction time is very short and even the smallest temperature variances during the deposition influence the distribution of the fluorine and also of the titanium in soot particles.
• the homogeneous distribution of fluorine and titanium in the fluorinated TiO 2 -SiO 2 soot particles is a prerequisite for the fact that the desired blank of titanium-doped, high-silica glass with a given fluorine content for use in EUV lithography also a particularly homogeneous Having distribution of the two doping elements, so that an optimized course of the CTE is achieved with a low slope over the operating temperature range.
• OMCTS octamethylcyclotetrasiloxane
• SiO2-TiO2 particles proven.
• silicon tetrachloride SiCl 4
• SiCl 4 silicon tetrachloride
• Titanium tetrachloride (TiCl 4 ) are used.
• the OMCTS and titanium isopropoxide are preferably used as chlorine-free feedstocks;
• the combination of SiCI 4 with TiCl 4 in the context of the invention is considered equivalent.
• the TiO 2 -SiO 2 soot particles have an average particle size in the range of 20 nm to 500 nm and a BET specific surface area in the range of 50 m 2 / g to 300 m 2 / g.
• the soot particles contain nanoparticles as primary particles with particle sizes in the range of a few nanometers to 100 nm. Such nanoparticles typically have a BET specific surface area of from 40 to 800 m 2 / g.
• an average particle size in the range of 20 nm to 500 nm and a BET specific surface area in the range of 50 m 2 / g to 300 m 2 / g are achieved.
• This characteristic of the TiO 2 -SiO 2 soot particles has a pronounced reactivity and also a favorable effect on the further processability when consolidating the fluorine-doped TiO 2 -SiO 2 soot particles by granulating or / and compressing.
• a dopant content in these ranges is important in view of a small spread of the CTE and its course over the operating temperature.
• fluorine-containing reagent SiF, CHF 3 , CF, C2F6, C3F8, F 2 or SF 6 is advantageously used.
• the selection of one of the abovementioned reagents is mainly based on economic aspects in process control.
• the use of SF 6 results in a simultaneous doping with - -
• a further advantageous embodiment of the method according to the invention is that the moving powder bed is formed as a loose bed of TiO 2 -SiO 2 Sootpumblen that of the fluorine-containing reagent
• the flow resistance for the gaseous fluorine-containing reagent is particularly low.
• the fluorine-containing reagent thus very quickly obtains maximum surface contact with the TiO 2 -SiO 2 soot particles, which results in the particularly homogeneous incorporation of fluorine in the TiO 2 -SiO 2 structure.
• the exposure time of the fluorine-containing reagent to the TiO 2 -SiO 2 soot particles in the moving powder bed can be kept short.
• the fluorine-containing reagent acts on the ⁇ 2SiO2 soot particles for a period of at least five minutes.
• a temperature above 1100.degree. C. is disadvantageous because sintering of the TiO.sub.2-SiO.sub.2 soot particles then begins, which reduces the reactive surface of the soot particles and thus negates the advantage of the particularly effective and homogeneous fluorine doping of the loose soot particles.
• the movement of the powder bed comprises a mechanical action.
• the powder bed is already alone by the passage of the fluorine-containing reagent in
• the mechanical action may include, for example, a vibration or a circulation of the powder bed, wherein the
• the consolidation follows. In this case, it has proven useful if the fluorine-doped TiO 2 -SiO 2 soot particles are consolidated by granulation and / or compression. Granulating improves the properties for the
• Further processing Conventional dry or wet granulation processes are possible, and spray granulation is also included. Further processing of the granules is preferably carried out by pressing into a shaped body from which the desired blank is formed by vitrification for use in EUV lithography. Alternatively, the granules can also be used in a slurry, which ultimately leads, after appropriate shaping processes and vitrification, to the blank of titanium-doped, high-silica glass with a given fluorine content for use in EUV lithography. In principle, the consolidation of the fluorine-doped TiO 2 -SiO 2 soot particles is also possible by direct compression, whether uniaxial or isostatic, without prior granulation of the soot particles.
• Titanium-doped, high-siliceous glass shows a brownish coloration due to a more or less concentrated concentration of Ti 3+ ions in the glass matrix, which has proved to be problematic, because this results in limited or even conventional optical measuring methods that require transparency in the visible spectral range not applicable for such blanks. To avoid this coloration, the concentration of Ti 3+ must be reduced before glazing in favor of Ti 4+ .
• the fluorine-doped TiO 2 -SiO 2 soot particles to a conditioning treatment before the vitrification, which comprises an oxidizing treatment with a nitrogen oxide, with oxygen or with ozone.
• the Ti-doped silica glass to be produced by the process according to the invention contains titanium dioxide in the range from 6% by weight to 12% by weight, which corresponds to a titanium content of from 3.6% by weight to 7.2% by weight.
• soot particles - which have less than 120 ppm by weight, a low proportion of OH groups, they can contribute little to the oxidation of Ti 3+ after Ti 4+ .
• oxygen or ozone are used as oxidative treatment reagent nitrogen oxides. If the conditioning treatment is carried out with nitrogen oxides such as nitrous oxide (N 2 O) or nitrogen dioxide (NO 2 ), it is possible the conditioning treatment at temperatures below 600 ° C in one
• Grafitofen as it is also used for the drying and vitrification of S1O2 soot bodies to perform. Upon further heating of the
• a blank is obtained during vitrification with a mean TiO 2 concentration in the range of 6 wt .-% to 12 wt.% And a
• Such a blank made of fluorine and titanium-doped silica glass produced by the process according to the invention is distinguished by particularly high homogeneity of the dopant distribution. This optimizes the local course of the CTE over the optically used area, also referred to as the "clear aperture" area.
• the local distribution of the CTE over the CA region of the blank varies with a deviation from
• the invention is based on a patent drawing and a
• Figure 1a is a schematic representation of an arrangement for batchwise
• Figure 1 b is a schematic representation of an arrangement for continuous
• FIG. 2 shows a diagram of the course of the CTE over the temperature (0 ° C. to
• Figure 3 is a representation of the local distribution of the fluorine content over the
• Figure 4 is an illustration of the local distribution of the mean deviation of the CTE over the CA region of the blank.
• TiO 2 -SiO 2 soot particles are obtained by flame hydrolysis of
• OMCTS Octamethylcyclotetrasiloxane
• Ti titanium isopropoxide
• the loose soot particles consist of synthetic TiO 2 -SiO 2 glass, which is doped with about 8 wt .-% T1O2.
• the TiO.sub.2-SiO.sub.2 soot particles 1 are transferred via a suitable powder feed system 2 into a reaction vessel 3, in which the doping of the T1O.sub.2-SiO.sub.2 soot particles 1 with fluorine takes place.
• the reaction vessel 3 has a cylindrical shape with a vertically oriented center axis A and is heated by heating elements 4 arranged outside the vessel.
• the reaction vessel 3 is sealed at the upper end except for an opening for an exhaust gas line 5.
• the exhaust pipe 5 is connected to a dust collector 6.
• the TiO 2 -SiO 2 soot particles 1 form in the lower part of the reaction vessel 3 a powder bed 10 as a loose bed.
• a ring shower 7 which has numerous nozzle openings, from which the fluorine-containing reagent exits and on the powder bed 10 of T1O2 SiO2 soot particles 1 in the form of a substantially laminar gas flow, - - Indicated by the directional arrows 9, acts.
• the annular shower 7 is connected to a (not shown) gas circulation pump through which the fluorine-containing reagent is supplied.
• the gas inlet is indicated by the arrow with the reference numeral 8.
• reaction vessel 3 is on one
• Vibrating device 1 1 mounted to possibly put the powder bed 10 located in the container 3 by vibrations in motion.
• a charge of 80 kg of the TiO 2 -SiO 2 soot particles 1 is introduced into the reaction vessel 3.
• the TiO 2 -SiO 2 soot particles 1 have an average particle size of 120 nm (D 50 value) and a BET specific surface area of about 100 m 2 / g.
• SiF is introduced through the annular shower 7 into the
• Powder bed 10 of TiO 2 -SiO 2 -Sootpumble 1 initiated.
• the flow rate for the fluorine-containing reagent is in the range of 6-8 liters per minute, whereby the TiO 2 -SiO 2 soot particles 1 are thoroughly bathed by the fluorine reagent, while the powder bed 10 is slightly swirled.
• Reaction vessel 3 can be removed.
• the powder bed 10 of TiO 2 -SiO 2 -Sootpumblen 1 is heated by heating the reaction vessel 3 to a temperature of about 1000 ° C, so shortens the
• Treatment time to about 30 minutes.
• FIG. 1 b schematically shows the construction of a device for carrying out the method according to the invention in a rotary tube 13.
• the rotary tube 13 rotates about its longitudinal axis B.
• the to be fluorinated TiO 2 -SiO 2 - soot particles 1 are in the slightly inclined rotary tube 13 in the upper
• FIG. 1 b is a filling device for the treated with fluorine TiO 2 -SiO 2 -Sootpumble 1 with a block arrow with the
• Reference numeral 22 is schematically indicated. According to Figure 1 b, the fluorine gas (SiF or CF) is fed at the lower end of the rotary tube 13, that is, it operates on the countercurrent principle.
• the gas inlet is indicated by the arrow - - The reference numeral 18 indicated.
• the material inlet region 14 has a
• Material outlet region 17, between the process chamber 16 is arranged.
• the material outlet region 17 has a material removal device for the fluorine-doped TiO 2 -SiO 2 -Sootpumble V, which is indicated schematically in Figure 1 b with a block arrow with the reference numeral 32.
• the rotary tube 13 is brought by a heating element 4 'to the desired process temperature.
• the incoming fluorine-containing gas may be preheated.
• blade-like mixing elements 19 which receive the soot particles 1 during the rotational movement of the rotary tube 13 first and then let it trickle off again in the course. This will be the
• the TiO 2 -SiO 2 -Sootpumble 1 are continuously fed into the inlet region 14 and preheated there to about 950 ° C.
• Rotary tube 13 is about 250 cm, the diameter typically 20 cm.
• mixing elements 19 are arranged, which mix the powder bed 10 to be fluorinated soot particles 1 and thereby heat evenly.
• the material inlet region 14 passes into the process chamber 16, but is partially separated from it by a constriction in the cross section, so that the supplied soot particles 1 accumulate a little before entering the process chamber 16. As a result, too rapid passage through the material inlet region 14 is prevented. In the process chamber 16, the soot particles 1 from
• laminar fluorine reagent wherein a temperature in the range of about 1000 ° C is set. At this temperature, under the action of the fluorine-containing treatment gas and additionally by the mixing elements 19 located in the process chamber 16, a very good fluorination effect can be achieved.
• the treatment gas is preheated by the residual heat of the already fluorinated TiO 2 -SiO 2 soot particles V in the material outlet region 17 to approximately 500 ° C. before it enters the process chamber 16.
• the TiO.sub.2-SiO.sub.2 soot particles 1 Once the TiO.sub.2-SiO.sub.2 soot particles 1 have passed through the process chamber 16, they are conveyed into the material outlet region 17, in which they may optionally be subjected to an aftertreatment while supplying a further halogen-containing gas.
• the throughput of the soot particles 1 to be fluorinated is improved by about 20% in a continuous process with the rotary tube 13 compared to the batch process.
• the fluorinated TiO 2 -SiO 2 soot particles are stirred into an aqueous dispersion in a stirred vessel by intensive stirring and homogenized.
• the aqueous dispersion may contain additives that improve the wettability of the fluorinated TiO 2 -SiO 2 soot particles.
• a nitrogen stream heated to about 100 ° C. acts on the dispersion.
• Granulating the aqueous dispersion can also be sprayed in a hot air stream to form a spray granules.
• the granules are well suited for further processing in a dry pressing process. However, it is also possible first to glaze the granules into a grain and only then to join a shaping process to form the blank.
• the granules are filled into a mold and isostatically processed at a pressure of 100 MPa to form a compact.
• the dimensions of the form take into account the shrinkage in the subsequent vitrification of the compact ("near-net-shape-method"), so that the shaping can do without further forming steps.
• the thus produced compact is in - - thermally dried a drying oven, then converted into the sintering furnace, where first a conditioning treatment at 600 ° C under an atmosphere of nitrous oxide (N 2 O) follows.
• the compact is first pre-sintered at 1600 ° C under He atmosphere and then vitrified at about 1800 ° C.
• the result is a slightly brownish, plate-shaped blank of titanium-doped, high-siliceous glass with a given fluorine content.
• Distribution of the titanium and the fluorine in the blank is particularly homogeneous by application of the method according to the invention. Any usual subsequent homogenization measures can be omitted here.
• the blank made of fluorine-doped TiO 2 -SiO 2 glass with a diameter of 30 cm and a thickness of 5.7 cm is subjected to an annealing treatment to reduce mechanical stresses and to set a given fictitious temperature.
• the blank is heated for a holding time of 8 hours under air and atmospheric pressure to 950 ° C and then with a cooling rate of 4 ° C / h to a
• the TiO 2 -SiO 2 blank is cooled at a higher cooling rate of 50 ° C / h to a temperature of 300 ° C, whereupon the furnace is turned off and the blank is left to the free cooling of the furnace.
• a small surface layer is removed from the blank, which has been damaged by the preceding process steps.
• a plan side is polished so that the blank has a diameter of 29.5 cm and a thickness d of 5 cm.
• the blank thus obtained consists of particularly homogenized, fluorine-doped TiO 2 -SiO 2 glass which contains 7.7% by weight of titanium dioxide and 4600 ppm by weight of fluorine.
• the mean fictive temperature measured over the entire thickness is 820 ° C. - -
• the fictitious temperature of a comparative material designated V1 of TiO 2 -SiO 2 glass, but without fluorine doping, is 960 ° C higher than the blank according to the invention.
• the mean thermal expansion coefficient is determined interferometrically by the method as described in: "R. Schödel, Ultra-high accuracy thermal expansion measurements using PTB's precision interferometer "Meas. Sei. Technol. 19 (2008) 084003 (1 pp)".
• Coefficient of expansion CTE varies with about 6 ppb / K.
• the comparative material V1 with these properties is no longer suitable for the high demands with regard to the image quality in EUV lithography, but can still be said to be adequate for other selected applications, such as material for the production of measurement standards or as substrate material for large astronomical mirrors become.
• the diagram of Figure 2 shows the coefficient of thermal expansion CTE as a function of temperature.
• Curve 1 shows a particularly flat course of the CTE for the fluorine-doped TiO 2 -SiO 2 blank produced by the process according to the invention.
• the slope of the CTE is 0.75 ppb / K 2 in the temperature range from 20 ° C to 40 ° C.
• curve 2 for the comparative material V1 of a TiO 2 -SiO 2 glass having a titanium dioxide content of 7.4 wt .-%, but without fluorine doping a very steep curve of the CTE over the temperature can be seen.
• the slope of the CTE is for the
• the local fluorine distribution is represented by a blank produced by the process according to the invention (curve 3) and, in comparison, by a comparison material V2 (curve 4).
• the measured values on which the curves are based are in the optically used range,
• CA range determined in positions of 50 to 100 mm distance from each other.
• comparison material V2 is based on a TiO 2 -SiO 2 soot body (not soot particles), which was doped with fluorine by acting at 800 ° C, a gas stream of 20% SiF in helium for 3 hours on the soot body. This was followed by a vitrification step at about 1400 ° C to form a preform.
• the fictitious temperature is also around 820 ° C.
• the average titanium oxide content and fluorine content of the reference material V2 are - as well as in the blank produced according to the invention - at 7.7 wt .-% and at 4600 ppm by weight. Accordingly, a value of the same order of magnitude as the blank produced according to the invention is also achieved with respect to the slope of the CTE above the temperature. In contrast, however, the homogeneity with respect to the fluorine distribution and the local variation of the CTE (see FIG. 4) in the comparison material V2 is relatively poor.
• FIG. 4 shows the local distribution of the mean deviation of the CTE (delta CTE) in the CA range of the fluorine-doped TiO 2 -SiO 2 blank produced by the method according to the invention (curve 5) and, in comparison, for the blank from the comparison material 2S 2 (curve 6) can be seen.
• the very homogeneous fluorine distribution shown in FIG. 3 correlates in FIG. 4 with an equally homogeneous local distribution for the mean deviation of the CTE of the blank produced according to the invention.
• the local distribution of the delta CTE from the comparison material V2 shows large deviations for the CTE of up to 12 ppb / K, in particular in the edge regions of the optically used region.
• the material V2 is therefore unsuitable for use in EUV lithography, since such a material would lead to aberrations and is therefore unacceptable.
• inventive blank compared to the comparative material V1 and V2 summarized in tabular form.
• Titanium oxide content 7.7 7.4 7.7

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• 2013
  • 2013-11-12 DE DE102013112396.1A patent/DE102013112396B3/de active Active
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