WO2002069054A1 - Vacuum ultraviolet transmitting silicon oxyfluoride lithography glass - Google Patents
Vacuum ultraviolet transmitting silicon oxyfluoride lithography glass Download PDFInfo
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- WO2002069054A1 WO2002069054A1 PCT/US2001/044547 US0144547W WO02069054A1 WO 2002069054 A1 WO2002069054 A1 WO 2002069054A1 US 0144547 W US0144547 W US 0144547W WO 02069054 A1 WO02069054 A1 WO 02069054A1
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- 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
- G03F7/00—Photomechanical, e.g. photolithographic, production of textured or patterned surfaces, e.g. printing surfaces; Materials therefor, e.g. comprising photoresists; Apparatus specially adapted therefor
- G03F7/70—Microphotolithographic exposure; Apparatus therefor
- G03F7/70216—Mask projection systems
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- 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
- G03F9/00—Registration or positioning of originals, masks, frames, photographic sheets or textured or patterned surfaces, e.g. automatically
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- 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
- C03B19/1407—Deposition reactors therefor
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- 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
- C03B19/1415—Reactant delivery systems
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- 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
- C03B19/1415—Reactant delivery systems
- C03B19/1423—Reactant deposition burners
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- 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
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- 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
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- 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
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- 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
- G03F1/60—Substrates
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- 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
- G03F7/00—Photomechanical, e.g. photolithographic, production of textured or patterned surfaces, e.g. printing surfaces; Materials therefor, e.g. comprising photoresists; Apparatus specially adapted therefor
- G03F7/70—Microphotolithographic exposure; Apparatus therefor
- G03F7/708—Construction of apparatus, e.g. environment aspects, hygiene aspects or materials
- G03F7/7095—Materials, e.g. materials for housing, stage or other support having particular properties, e.g. weight, strength, conductivity, thermal expansion coefficient
- G03F7/70958—Optical materials or coatings, e.g. with particular transmittance, reflectance or anti-reflection properties
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- 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
- C03B2201/07—Impurity concentration specified
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- 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
- C03B2201/07—Impurity concentration specified
- C03B2201/075—Hydroxyl ion (OH)
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- 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
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- 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
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- 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
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- 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
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- 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
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- C—CHEMISTRY; METALLURGY
- C03—GLASS; MINERAL OR SLAG WOOL
- C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
- C03B2207/00—Glass deposition burners
- C03B2207/36—Fuel or oxidant details, e.g. flow rate, flow rate ratio, fuel additives
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- C—CHEMISTRY; METALLURGY
- C03—GLASS; MINERAL OR SLAG WOOL
- C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
- C03B2207/00—Glass deposition burners
- C03B2207/36—Fuel or oxidant details, e.g. flow rate, flow rate ratio, fuel additives
- C03B2207/38—Fuel combinations or non-standard fuels, e.g. H2+CH4, ethane
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- 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
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- 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
-
- 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
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- 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
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- 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
- C03C2201/32—Doped silica-based glasses containing metals containing aluminium
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- 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
Definitions
- the present invention relates generally to lithography, and particularly to optical photolithography glass for use in optical photolithography systems utilizing vacuum ultraviolet light (NUN) wavelengths below 193 nm, preferably below 175nm, preferably below 164 nm, such as VUV projection lithography systems utilizing wavelengths in the 157 nm region.
- NUN vacuum ultraviolet light
- the invention relates to VUV transmitting glass that is transmissive at wavelengths below 193 nm, in particular, a photomask silicon oxyfluoride glass suitable for use in the Vacuum Ultraviolet (VUV) 157 nm wavelength region.
- VUV Vacuum Ultraviolet
- Refractive optics requires materials having high transmittance.
- high purity fused silica has been show to exhibit the required minimum transmittance of 99%/cm or better.
- Projection optical photolithography systems that utilize the vacuum ultraviolet wavelengths of light below 193 nm provide benefits in terms of achieving smaller feature dimensions. Such systems that utilize vacuum ultraviolet wavelengths in the 157 nm wavelength region have the potential of improving integrated circuits with smaller feature sizes.
- Current optical lithography systems used by the semiconductor industry in the manufacture of integrated circuits have progressed towards shorter wavelengths of light, such as the popular 248 nm and 193 nm wavelengths, but the commercial use and adoption of vacuum ultraviolet wavelengths below 193nm, such as 157 nm has been hindered by the transmission nature of such vacuum ultraviolet wavelengths in the 157 nm region through optical materials.
- high purity fused silica as optical elements in photolithography stems from the fact that high purity fused silica is transparent over a wide range of wavelengths, spanning from the infrared to deep ultraviolet regions. Furthermore, high purity fused silica exhibits excellent chemical durability and dimensional stability. These properties have made high purity fused silica highly suited for use as optical lenses as well as for photomask substrates in photolithography, but use has been limited to the KrF and ArF wavelength regions.
- Photomask glass qualifications are comparatively different from other optical elements used in photolithography in that they characteristically have smaller thicknesses of as low as only a few millimeters through the optical path. As such, they must meet very strict requirements for dimensional stability (warping and shrinkage) in order to ensure the extreme accuracy required to form fine circuit patterns on the photomask plate and target. And as the demand for even smaller features continues to drive the lasing wavelength further down to the 157 nm region and lower, the choice of optical materials meeting the minimum required transmittance becomes severely limited for all optical elements, but even more so for photomask substrates due to the reasons stated above.
- Crystalline materials such as calcium fluoride, barium fluoride and magnesium fluoride for example, have been shown to exhibit transmittances which are suitable for 157 nm wavelength applications. Unfortunately, these materials tend to have certain drawbacks making them unsuitable for these applications, in addition to manufacturing/economic problems. For example, calcium fluoride exhibits unacceptably high thermal expansion properties for photomask applications in the 157 nm wavelength region. Magnesium fluoride on the other hand, exhibits acceptable expansion but is unsuitable because it is naturally birefringment.
- VUV transmitting silicon oxyfluoride glasses for use at VUV wavelengths below 193nm, preferably in the F 2 Excimer Laser 157 nm region, methods of making such glass, and methods for characterizing such silicon oxyfluoride glass.
- VUV transmitting silicon oxyfluoride lithography glass suitable for use as optical elements, for use as a lens or preferably for use as a photomask substrate at VUV wavelengths below 193 nm.
- the inventive silicon oxyfluoride glass exhibits certain properties tailored for applications in the photolithography VUV wavelength region around the 157 nm Excimer laser wavelengths and below 193 nm.
- the object of the invention is achieved by use of a dry low hydroxy radical fluorine-doped SiO 2 fused synthetic silicon oxyfluoride glass which exhibits very high transmittance in the vacuum ultraviolet (VUV) wavelength region while exhibiting excellent thermal and physical properties.
- dry we mean having an OH content below 50 ppm by weight, preferably dehydrated below 10 ppm OH by weight, and most preferably below 1 ppm by weight.
- the object of the invention is further achieved by ensuring that the silicon oxyfluoride glass is essentially free of chlorine.
- the object of the invention is achieved by ensuring a low molecular hydrogen content in the glass.
- (H )content is below 1x10 molecules/cm .
- the VUV transmitting silicon oxyfluoride glass has a fluorine content in the range of 0.1 to 0.4 weight percent which inhibits laser exposure induced absorption and provides laser exposure durability with minimal transmission loss at 157.6 nm after prolonged exposure.
- the invention includes a below 193 nm VUV transmitting glass photomask substrate for photolithography at wavelengths of about 157 nm with the glass being a high purity silicon oxyfluoride glass with an OH content below 50 ppm by weight, hydrogen content below 1 x 10 17 molecules/cm 3 and a fluorine content in the 0.1 to 0.4 weight percent range.
- the invention includes a process of making VUV transmitting glass silicon oxyfluoride glass that includes providing particles of SiO 2 , dehydrating the particles, and fluorine doping and consolidating the particles to form a dry, non-porous monolithic body of transparent fused silicon oxyfluoride glass with a fluorine content less than 0.5 weight percent.
- the invention includes a silicon oxyfluoride glass having essentially no OH groups, less than 5 x 10 molecules/cm of molecular hydrogen, and a fluorine content in the range of 0.1 to 0.4 weight %.
- the invention includes a silicon oxyfluoride lithography glass having an OH content less than 5 ppm by weight, a Cl
- the invention includes a VUV pattern printing method with the steps of providing a below 164 nm radiation source for producing VUV photons, providing a silicon oxyfluoride glass having less than 5ppm by weight OH, less than 5 ppm by weight Cl, a ⁇ 0.5 weight percent fluorine content, and 157 nm and 165 nm measured transmission of at least 75%/5 mm.
- the pattern printing method includes transmitting the VUV photons through the silicon oxyfluoride glass, forming a pattern with the VUV photons and projecting the pattern onto a VUV radiation sensitive printing pattern.
- the invention includes a VUV transmitting silicon oxyfluoride glass having a OH content less than 5 ppm by weight, a fluorine content of at least 0.1 weight %, the glass consisting essentially of Si, O, and F with an internal transmission in the wavelength range of 157 nm to 175 nm of at least 85%/cm and a 165 nm absorption less than 0.4 (absorption units/5 mm) after exposure to a 157 nm laser for 41.5 million pulses at 2mJ/cm -pulse.
- Figure 1 is a VUV spectra comparison plot of % transmission vs. wavelength (nm) with glass C containing 0.8 wt.% F in accordance with the invention.
- Figure 2 is an optical density plot of optical density vs. pathlength sample thickness for 0.8 wt. % F glass C (mm) in accordance with the invention.
- Figure 3 is a before/after F laser radiation exposure absorption spectral plot of optical density vs. wavelength (nm) for 1.1 mm thick samples with glass B having 0 % F and glass D having .2 wt. % F in accordance with the invention.
- Figure 4 is a refractive index as a function of wavelength (nm) plot for glass E
- Figure 5 is a 435.8 nm refractive index as a function of fluorine content (wt. % F) in accordance with the invention.
- Figure 6 is a 157 nm refractive index (calculated from Sellmeier fit) as a function of fluorine content (wt. % F) plot in accordance with the invention.
- Figure 7 is a coefficient of thermal expansion (CTE, 300°C-RT (ppm/°C)) as a function of fluorine content (wt. % F) in accordance with the invention.
- Figure 8 shows a method/lithography system in accordance with the invention.
- Figure 9 shows a method/lithography system in accordance with the invention.
- Figure 10 shows a method /lithography system in accordance with the invention.
- Figure 11 is a plot of 157 nm absorption of 5 mm thick samples vs. chlorine concentration (Cl wt. %) in accordance with the invention.
- Figure 12 is a plot of induced 157 nm absorption of 5 mm thick samples vs. number of pulses (MM) of a F Excimer Laser (2mJ/cm -pulse) in accordance with the invention.
- Figure 13A is an absorption spectra before and after F 2 Excimer Laser Exposure (2mJ/cm 2 -pulse) (41.5 million pulses) of a high fluorine sample ( ⁇ .5ppm OH by weight) with 1.7wt.% F.
- Figure 13B is an absorption spectra before and after F Excimer Laser Exposure
- Figure 13C is an absorption spectra before and after F Excimer Laser Exposure (4.5mJ/cm -pulse) (0.96 million pulses) of a no fluorine dry ( ⁇ .5ppm OH by weight) sample with 0wt.% F.
- Figure 14A is an absorption spectra before and after ArF Excimer Laser Exposure (9mJ/cm 2 -pulse) (153 million pulses) of a high fluorine sample ( ⁇ .5ppm OH by weight) with 1.7wt.% F.
- Figure 14B is an absorption spectra before and after ArF Excimer Laser Exposure (9mj/cm 2 -pulse) (158 million pulses) of a low fluorine sample ( ⁇ .5ppm OH by weight) with .12wt.% F.
- Figure 14C is an absorption spectra before and after ArF Excimer Laser Exposure (25mJ/cm 2 -pulse) (74 million pulses) of a no fluorine dry ( ⁇ .5ppm OH by weight) sample with 0wt.% F.
- Figure 15 is an online 157nm transmission comparison as a function of exposure time with the Y-axis % transmission at 157.6nm/6.35mm vs X-axis Number of Pulses (millions) of F 2 Excimer Laser (.2mJ/cm 2 per pulse) of a high fluorine sample ( ⁇ .5ppm OH by weight) with 1 Jwt.% F and a low fluorine sample ( ⁇ .5ppm OH by weight) with .12wt.% F.
- the transmission properties of glass in general are dependent on glass composition.
- pure silica it has been demonstrated that even trace levels (ppm or less) of metal contaminants can cause significant reductions in transmission in the ultraviolet region.
- the most important variables for controlling the VUV transmission edge of silicon oxyfluoride glass include its water or OH content, as well as its chlorine content. Specifically, we have found that the lower the OH content, the better the transmission, while the higher the chlorine content, the lower the transmission in the VUV 157 nm region.
- the amount of molecular hydrogen in the glass has to be minimized.
- the SiO 2 containing silicon oxyfluoride glass has at least .5 wt. % Fluorine.
- the silicon oxyfluoride glass has a fluorine content in the range of 0.1 to 0.4 weight percent.
- measurements of the infrared transmission of glass at 2.7 microns is used to quantify the OH content of glass.
- the inventive silicon oxyfluoride glass may be manufactured by adaptation of a variety of methods such as by hydrolysis/ pyrolysis (flame hydrolysis), thermal decomposition (soot process), and oxidation of silicon-containing compounds. Other methods include sol gel processes.
- Soot Deposition or CVD Process Typically, in this process the silicon- containing compound is heated to a constant temperature at which enough vapor pressure is generated to produce a reasonable rate of deposition.
- the vapors are entrained in a carrier gas stream and passed through a burner flame (e.g., natural gas/oxygen mixture, hydrogen/oxygen mixture) to convert the vapor into silica upon exiting the burner and to form a stream of volatile gases and finely-divided, amorphous, spherical aggregates (soot).
- a burner flame e.g., natural gas/oxygen mixture, hydrogen/oxygen mixture
- the soot is collected on a mandrel that traverses through the flame to build up a porous silica soot pre-form body.
- a porous soot pre-form body is built up by depositing soot on the end of a mandrel preferably with the deposition process vertically oriented to form a vertically oriented soot log.
- the porous silica pre-form is subjected to a subsequent high temperature treatment to consolidate the amorphous particles into a non-porous monolithic glassy fused silica body.
- the amorphous SiO 2 soot particles are exposed to a fluorine atmosphere fluorine doping agent as more fully described below. Most preferably in addition to such fluorine doping of the SiO 2 , the SiO is dehydrated in order to eliminate OH groups associated with the SiO 2 .
- Dry, fluorine-doped silica can also be formed by casting high purity silica powder to form a porous silica preform, exposing the body to a fluorinating gas, and sintering the porous preform to form a monolithic fused silica body.
- High purity silica powders can be made by either a vapor phase method or by a sol gel method. The advantage of this method is that the soot can be cast and sintered into a desired shape, such as a plate.
- the silica powder is a silicon oxyfluoride silica powder.
- the silica-containing starting material is preferably chlorine-free.
- Useful starting materials include silanes and siloxanes, in particular polymethylsiloanes such as polymethylcyclosiloxane, and hexamethyldisiloxane.
- Useful polymethylcyclosiloxanes include octamethylcyclotetrasiloxane, decamethylcyclopentasiloxane, hexamethylcylotrisiloxane and mixtures of these.
- Another useful chlorine-free feedstock for making chlorine-free fused silica includes methyltrimethoxysilane. If chlorine containing feedstocks and/or chlorine gas agents are utilized, subsequent production processes should be controlled to minimize chlorine in the produced glass and subsequent process steps such as fluorine doping with fluorine atomospheres should be controlled and include sufficient chlorine removing agents such as sufficient levels of fluorine doping agents and helium, and sufficient reaction times/dynamics to eliminate chlorine.
- fluorine-containing starting materials such as silicon fluoride, silicon tetrafluoride and mixtures of these, may be used in the above methods.
- fluorine source starting materials such as CF 4 and C 2 F 6 can be used along with silicon-containing starting material compounds in combustion/oxidation process reacting to produce fluorine doped silica such as silicon fluoride silica soots and powders.
- the pre-consolidated pre-form bodies formed by the above methods are exposed to a dehydrating gas agent preferably a halogen-containing atmosphere at elevated temperatures, then sintered to a monolithic fused silica body at even higher temperatures.
- a dehydrating gas agent preferably a halogen-containing atmosphere at elevated temperatures
- the dehydration process involves heating the porous silica pre-form in a He/dehydrating gas agent atmosphere (such as helium/halide, helium/Cl 2 ) at a temperature between 1000 and 1100 °C, to remove water from the silica soot, then sintering the pre-form by passing it through a high temperature zone (typically 1450-1500 °C) to form a non-porous, monolithic dry fused silica body.
- a He/dehydrating gas agent atmosphere such as helium/halide, helium/Cl 2
- the soot pre-form is exposed to an atmosphere of He and a fluorine-containing gas, such as CF 4j SiF 4 _ SF 6 , F 2 , C 2 F , C 3 Fg and mixtures of these, at temperatures in the range of 1150 to 1250 °C.
- a fluorine-containing gas such as CF 4j SiF 4 _ SF 6 , F 2 , C 2 F , C 3 Fg and mixtures of these, at temperatures in the range of 1150 to 1250 °C.
- fluorine doping is typically done at a higher temperature than the dehydration step there is a tendency for the glass to sinter and "trap" the fluorine. Further, if the fluorine doping is done before or during the dehydration step some of the fluorine will tend to outgas from the blank at the lower drying temperature. In such a process the blank will also contain more residual and detrimental chlorine. Finally, by fluorinating after the dehydration step there is an added benefit since the fluorinating gas itself tends to further dry the blank. Additionally fluorine levels can be improved by utilizing silicon oxyfluoride silica particles in the making of the pourous preform.
- Such silicon oxyfluoride silica particles are preferably achieved by combusting the silicon feedstock (such as SiCl 4 or OMCTS) along with a fluorine source (such as CF 4 or C 2 F 6 ). Additionally the fluorine doping process can be improved by retaining a large level of flourine in the porous preform prior to and during consolidation/sintering into a non-porous body. Such retention can be improved by forming a non-porous exterior layer on the porous preform body (such as high temperature radiation thermal treatment focussed on the exterior surface) and inputting the fluorine containing gas into the interior of the porous preform such that the non- porous exterior layer forms an exterior shell barrier for controlling the escape of fluorine from the porous preform body. In an embodiment the exterior surface of the porous preform body is sintered to form a non-porous shell and fluorine is inputted into the porous body.
- the silicon feedstock such as SiCl 4 or OMCTS
- a fluorine source
- the amount of fluorine incorporated in the glass ([F]) is controlled by the partial pressure of the fluorine-containing gas (P) and the temperature (T) according to the relationship:
- [F] C x e- E,RT x P
- C is a constant
- R is the gas constant
- SiF 4 + 3SiO 2 4SiO ⁇ .5 F.
- the dry fluorine doped soot pre-form is then sintered by passing it through a high temperature zone (typically 1450-1500 C) to form a non-porous, monolithic dry silicon oxyfluoride SiO glass body as described earlier.
- the atmosphere around the pre-form during the sintering step may be He or a He/fluorine-containing gas mixture, but preferably does not contain chlorine in order to minimize incorporation of chlorine into the SiO 2 glass.
- the amount of fluorine in the fused silica is preferably not below 1000 ppm, more preferably 2000 ppm or greater. In a preferred embodiment fluorine content is in the range of 0.1 to 0.4 weight percent.
- the inventive fused silica photomask blank is also preferably low in molecular hydrogen, preferably less than lxlO 17 molecules/cm , and more preferably less than 5 x 10 molecules/cm of molecular hydrogen.
- a low OH (OH content ⁇ 1 ppm) modified fused Si0 silicon oxyfluoride glass photomask substrate was doped with .8 wt % fluorine and had a lowered thermal expansion of 0.52 ppm/°C and an internal transmittance of about 84%/cm at 157 nm. Reducing the OH content to less than 50 ppm, preferably less than 10 ppm, and most preferably less than 1 ppm and doping the silica glass with fluorine provides for increased transmission at 157 nm and in lowered thermal expansion.
- the preferred 157 nm transmission photolithography fluorine doped low OH fused SiO 2 glass photomask substrate has a transmittance of at least 80%), preferably at least about 83%/cm at 157 nm, and a thermal expansion less than 0.55 ppm/°C, preferably less than 0.53 ppm/°C.
- the photomask substrate was made by forming a silica soot preform.
- the silica soot preform was formed by depositing silica soot produced by converting silicon tetrachloride (silica feedstock) into SiO 2 .
- Siloxane silica feedstocks preferably cyclic siloxanes, and most preferably octamethylcyclotetrasiloxane can be converted into SiO 2 .
- Preferably such conversion of silica feedstocks is achieved by passing the feedstock through the conversion site flame of a conversion site burner.
- the invention further includes a below 175 nm VUV lithography glass.
- the lithography glass comprises a fused silicon oxyfluoride glass.
- the silicon oxyfluoride glass has an OH content less than 5 ppm by weight, a Cl content less than 5 ppm by weight, a H 2 content less than 1 x 10 17 molecules/cm , and a fluorine content of at least 0.1% weight %, with said glass having a 157 nm internal transmission of at least 80%/cm and preferably at least 85%/cm.
- the silicon oxyfluoride glass has a below fused silica coefficient of thermal expansion that is less than 0.55 ppm/°C in the room temperature to 300°C range.
- the lithography glass has an internal transmission in the wavelength range of 157 nm to 175 nm of at least 80%/cm, and more preferably at least 85%/cm.
- the silicon oxyfluoride lithography glass has an increase of absorption at 215 nm of less than 0.1 optical density (logio transmission) per mm when exposed to at least .96 x 10 pulses of 157 nm wavelength containing F 2 excimer laser radiation at 4 m J/cm - pulse, and more preferably the increase of absorption at 215 nm is less than 0.05 optical density, and most preferably substantially no 215 nm absorption band is formed.
- the Cl content of the glass is less than 1 ppm and the OH content is less than 1 ppm, and more preferably the glass consists essentially of Si, O, and F.
- the glass is essentially free of metal to metal Si-Si bonds, and the glass is free of a 165 nm absorbing center with an internal transmission at 165 nm of at least 85%/cm.
- the lithography glass is used to make a VUV transmitting photomask where VUV light is transmitted through the photomask, preferably with a surface of the lithography glass having a patterned deposited film (such as Cr) that forms a transmitting photolithography mask pattern (FIGURE 8).
- the lithography glass is used to make a VUV phase shifting photomask where the phase of VUV lithography light traveling through the glass is shifted and manipulated to form constructive and/or destructive interference patterns (FIGURE 9).
- the lithography glass with a lowered thermal expansion and a thermal expansion coefficient less than 0.55 ppm/°C is used to make a reflective photomask wherein a reflective patterned lithography mask pattern is supported by said silicon oxyfluoride glass (FIGURE 10).
- the invention further includes a pattern printing method of VUV lithography which includes providing a below 164 nm radiation source for producing VUV lithography photons, providing a silicon oxyfluoride lithography glass having less than 5 ppm by weight OH, less than 5 ppm by weight Cl, and 157 nm and 165 nm measured transmission of at least 75%/5 mm, transmitting the VUV lithography photons through the provided silicon oxyfluoride lithography glass, forming a lithography pattern with the photons, and reducing the formed lithography pattern and projecting the formed pattern onto a VUV radiation sensitive lithography printing medium to form a printed lithography pattern (FIGURE 8).
- a pattern printing method of VUV lithography which includes providing a below 164 nm radiation source for producing VUV lithography photons, providing a silicon oxyfluoride lithography glass having less than 5 ppm by weight OH, less than 5 ppm by weight Cl, and 157
- Providing the oxyfluoride lithography glass preferably includes lowering the VUV cutoff wavelength of the glass by providing an SiO 2 glass forming precursor, lowering the H 2 , the OH, and the Cl content of the glass precursor and increasing the F content of the glass precursor to provide a silicon oxyfluoride glass with a 50% transmission VUV cutoff wavelength below 160 nm.
- the provided glass consists essentially of Si, O, and F and is essentially free of Si-Si bonds.
- the invention as shown in FIGURE 8 provides a 157 nm photolithography photomask substrate photomask stage and a 157 nm photolithography device (157 nm illumination system, photomask - mask stage, 157 nm projection optics system, 157 nm wafer stage) with such a fluorine doped low OH silicon oxyfluoride photomask silica glass substrate that has an OH content less than 1 ppm, a fluorine content in the range from 0.1 to 1.5 wt.
- 157 nm internal transmittances of at least 50%, and preferably at least 65%, and most preferably at least 83%/cm at 157 nm, and preferably a thermal expansion less than 0.55 ppm, preferably less than 0.53 ppm, and most preferably less than or equal to 0.52 ppm/°C.
- Example 1 A 1209 gram, 70 cm long porous silica preform was made by the OVD method using SiCl 4 as the feedstock.
- the soot preform was dehydrated in a furnace at 1000 C for 60 minutes in an atmosphere of 0.066 slpm Cl 2 and 40.64 slpm He.
- the atmosphere was changed to 40 slpm He and the furnace temperature ramped to 1100 C over 20 minutes.
- the atmosphere was changed to 0.4 slpm CF 4 and 40 slpm He and the soot preform was held at 1100 C for 120 minutes.
- the atmosphere was then changed to 40 slpm He and the soot preform was translated at a rate of 0.5 cm min into the bottom zone of the furnace which was held at 1480 C in order to sinter it to a fully dense glassy body.
- a 5mm thick sample was cut from the glass preform and polished.
- the average F concentration of the sample was determined by microprobe analysis to be 0.17 wt.% (1700 ppm wt.).
- the average Cl concentration was determined by microprobe analysis to be 0.0011 wt.% (11 ppm wt.).
- the OH content was measured by FTIR method to be below detection limit ( ⁇ 1 ppm).
- a transmission of 67.2%/5mm at 157nm was measured using a vacuum UV spectrophotometer.
- a 1004 gram, 70 cm long porous silica preform was made by the OVD method using SiCl 4 as the feedstock.
- the soot preform was dehydrated in a furnace at 1000 C for 60 minutes in an atmosphere of 0.066 slpm Cl 2 and 40.64 slpm He.
- the atmosphere was changed to 40 slpm He and the furnace temperature ramped to 1225 C over 45 minutes.
- the atmosphere was changed to 0.8 slpm CF 4 and 39.2 slpm He and the soot preform was held at 1225 C for 120 minutes.
- the soot preform was then translated at a rate of 0.5 cm/min into the bottom zone of the furnace which was held at 1480 C under the same atmosphere in order to sinter it to a fully dense glassy body.
- a 5mm thick sample was cut from the glass preform and polished.
- the average F concentration of the sample was determined by microprobe analysis to be 0.80 wt.% (8000 ppm wt.).
- the average Cl concentration was determined by microprobe analysis to be 0.0010 wt.% (10 ppm wt.).
- the OH content was measured by FTIR method to be below detection limit ( ⁇ 1 ppm).
- a transmission of 76.8%/5mm at 157nm was measured using a vacuum UV spectrophotometer.
- Example 3 A 1016 gram, 70 cm long porous silica preform was made by the OND method using SiCl 4 as the feedstock.
- the soot preform was dehydrated in a furnace at 1000 C for 60 minutes in an atmosphere of 0.066 slpm Cl 2 and 20.64 slpm He.
- the atmosphere was changed to 16 slpm He and the furnace temperature ramped to 1225 C over 45 minutes.
- the atmosphere was changed to 4 slpm CF 4 and 12 slpm He and the soot preform was held at 1225 C for 180 minutes.
- the soot preform was then translated at a rate of 0.5 cm/min into the bottom zone of the furnace which was held at 1480 C under the same atmosphere in order to sinter it to a fully dense glassy body.
- a 5mm thick sample was cut from the glass preform and polished.
- the average F concentration of the sample was determined by microprobe analysis to be 1.48 wt.% (14800 ppm wt.).
- the average Cl concentration was determined by microprobe analysis to be 0.0020 wt.% (20 ppm wt.).
- the OH content was measured by FTIR method to be below detection limit ( ⁇ 1 ppm).
- a transmission of 73.5%/5mm at 157nm was measured using a vacuum UN spectrophotometer.
- a 1000 gram, 50 cm long porous silica preform was made by the OND method using octamethylcyclotetrasiloxane as the feedstock.
- the soot preform was placed in a furnace at 1000 C in an atmosphere of 40 slpm He. The furnace temperature was ramped to 1225 C over 45 minutes. The atmosphere was then changed to 0.8 slpm CF 4 and 39.2 slpm He and the soot preform was held at 1225 C for 120 minutes.
- the soot preform was then translated at a rate of 0.5 cm/min into the bottom zone of the furnace which was held at 1480 C under the same atmosphere in order to sinter it to a fully dense glassy body.
- a 5mm thick sample was cut from the glass preform and polished.
- the average F concentration of the sample was determined by microprobe analysis to be 0.96 wt.% (9600 ppm wt.).
- the average Cl concentration was determined by microprobe analysis to be ⁇ 0.0010 ( ⁇ 10 ppm wt.).
- the OH content was measured by FTIR method to be below detection limit ( ⁇ 1 ppm).
- a transmission of 76.8%/5mm at 157nm was measured using a vacuum UV spectrophotometer.
- a 3129 gram, 50 cm long porous silica preform was made by the OVD method using SiCl 4 as the feedstock.
- the soot preform was dehydrated in a furnace at 1100 C for 120 minutes in an atmosphere of 0.4 slpm Cl and 40 slpm He.
- the atmosphere was changed to 40 slpm He and the furnace temperature ramped to 1150 C over 20 minutes.
- the atmosphere was changed to 2 slpm O2 and 20 slpm He and the temperature increased to 1200 C over an additional 20 minutes.
- the atmosphere was changed to 1.2 slpm SiF 4 , 18.8 slpm He, and 0.2 slpm O2 and the soot preform was held at 1200 C for 180 minutes.
- the soot preform was then translated at a rate of 0.5 cm/min into the bottom zone of the furnace which was held at 1480 C under the same atmosphere in order to sinter it to a fully dense glassy body.
- a 5mm thick sample was cut from the glass preform and polished.
- the average F concentration of the sample was determined by microprobe analysis to be 1.29 wt.% (12900 ppm wt.).
- the average Cl concentration was determined by microprobe analysis to be ⁇ 0.0010 wt.% ( ⁇ 10 ppm wt.).
- the OH content was measured by FTIR method to be below detection limit ( ⁇ 1 ppm).
- a transmission of 74.9%/5mm at 157nm was measured using a vacuum UV spectrophotometer.
- Comparative Example 1 A sample of commercial Corning HPFS ® brand UV excimer grade high-purity fused silica (Corning, Incorporated, Corning, NY, 14831) was obtained. The glass contained
- a 2788 gram, 70 cm long porous silica preform was made by the OVD method using SiCl 4 as the feedstock.
- the soot preform was dehydrated in a furnace at 1000 C for 50 minutes in an atmosphere of 0.066 slpm Cl 2 and 40.64 slpm He.
- the soot preform was then translated at a rate of 0.5 cm/min into the bottom zone of the furnace which was held at 1480 C under the same atmosphere in order to sinter it to a fully dense glassy body.
- a 5mm thick sample was cut from the glass preform and polished. The sample contained no fluorine.
- the average Cl concentration was determined by microprobe analysis to be 0.176 wt.% (1760 ppm wt.).
- the OH content was measured by FTIR method to be below detection limit ( ⁇ 1 ppm).
- a transmission of 21.2%/5mm at 157nm was measured using a vacuum UV spectrophotometer.
- a SiO soot preform was dehydrated (-OH removed) using a drying treatment atmosphere containing chlorine.
- the drying treatment atmosphere includes Helium in addition to the chlorine source molecules. Drying treatment atmospheres containing halides can be used to dehydrate the soot and remove -OH. Drying treatment atmospheres containing fluorine and/or bromine and/or other halides can be used, preferably with helium.
- the SiO 2 soot preform was fluorine doped using a doping treatment atmosphere of CF and helium. Silicon fluoride can also be used as a fluorine source in doping the silica with fluorine. Preferably fluorine doping is done after dehydrating the soot.
- SiO 2 soot preform was consolidated in a sintering treatment atmosphere of the CF and helium.
- Silicon fluoride (SiF ) can also be used as a fluorine source along with helium as the consolidating atmosphere.
- a photomask substrate was formed from the resulting silicon oxyfluoride glass by cutting the glass, polishing the glass and exposing to 157 nm laser radiation.
- the invention includes silicon oxyfluoride modified fused silica glasses with low OH contents and low levels of fluorine with measured transmissions of
- Low OH silica and fluorine-doped, low OH silica samples were prepared by a two-step soot consolidation process. Soot preforms were made by a flame deposition method then dried, fluorine-doped, and sintered in a high temperature furnace. High OH fused silica samples were Corning HPFS which were prepared by a one-step flame hydrolysis process. OH levels of the glasses described here were quantified by measuring the fundamental OH stretching vibration using infrared spectroscopy. Fluorine levels were measured by microprobe analysis.
- the dispersive and detector components consisted of a focused deuterium light source, a single monochromator with adjustable entrance and exit slits, and a detector interface that utilizes a photomultiplier tube. VUV transmittance measurements were made under vacuum.
- a TuiLaser ExciStar S200 F laser was used for the 157-nm exposures. The energy through the aperture was monitored using a Molectron thermal detector. Vacuum UV and UV measurements were made after exposure.
- Refractive index measurements were made on prisms. Index measurements at visible wavelengths (643.8-nm, 589.3-nm, 546.1-nm, 480.0-nm, and 435.8-nm) were made on a Bausch and Lomb low range refractometer with sodium and Hg-Cd emission lamps. A refractive index standard, certified by the National Institute of Standards and Technology (NIST), was measured along with the samples and used to correct the sample readings. Refractive index measurements at near IR wavelengths (777-nm, 1300-nm, and 1541-nm) were made on a Metricon Model 2010 Prism Coupler with laser diode sources. The accuracy of the visible and near IR measurements is estimated as ⁇ 0.0001.
- Figure 1 compares the VUV transmission spectra of Corning HPFS ® UV excimer grade fused silica, (Glass A), dry silica containing no fluorine (Glass B), and the inventive silicon oxyfluoride glass dry silica containing 0.94 wt.% fluorine (Glass C).
- Glass A contained about 860 ppm wt. OH, while the OH contents of Glasses B and C were below the detection limit of the measurement ( ⁇ lppm wt.). All of the samples were 5-mm thick and did not receive any special surface cleaning before the measurement. Glass A does not transmit at 157-nm. In Glass B the UV absorption edge is shifted to shorter wavelengths and the glass shows some transmission at 157-nm.
- the internal transmittance at 157-nm of Glass C was determined by plotting the measured optical density at 157-nm vs. thickness for three different pathlengths ( Figure 2). The data were measured on optically polished samples with 5 angstrom RA surfaces. The slope of the line yields the absorption coefficient, which is a measure of the internal transmittance of the material. The "zero -thickness" intercept of the line is a measure of surface losses due to reflections, surface scattering, and surface contamination. The internal transmittance of the glass, calculated from the slope of the line, was found to be 87.9%/cm.
- the measured 157-nm transmission of Glass C which includes internal and surface losses, was 73.8%/6.4mm. From the intercept, it is calculated that 20% of the 26.2% measured losses are due to surface losses, which are highly dependent on sample surface preparation and cleaning, and, therefore, only 6.2% are due to internal loss mechanisms within the glass. Internal loss mechanisms are scattering and absorption within the material. To separate the two mechanisms, we have made scattering measurements on the silicon oxyfluoride glass at wavelengths down to 193-nm. Measurements of scattered intensity were made on samples of silicon oxyfluoride glass and Corning HPFS ® using a 193-nm laser, vertically polarized, at a 90° scattering angle. The ratio of the measured intensities was near unity.
- the VUV measurement showed a significant increase in absorption over the entire wavelength range, 155-220nm, and formation of the 215-nm band (E' centers).
- Glass D was given a much higher exposure of 69x10 pulses at 4 mJ/cm -pulse, yet the glass exhibited a much smaller increase in absorption and the 215-nm band is not substantially detectable.
- Figure 4 shows refractive index measurements on a silicon oxyfluoride Glass E (0.8 wt.%F) at eight wavelengths in the visible and near IR.
- the relationship between refractive index and wavelength is generally described by the three-term Sellmeier equation:
- n( ⁇ ) is the refractive index at wavelength ⁇ (in ⁇ m)
- FIG. 5 shows a plot of refractive index measurements at 435.8-nm as a function of fluorine content.
- Figure 6 shows the plot of calculated 157-nm index as a function of fluorine content. From linear regressions performed on the data in Figures 5 and 6, a change in index (lOO ⁇ n/n) of -0.30% per 1 wt.% F at 435.8-nm and -0.32% per 1 wt.% F at 157-nm was calculated.
- Figure 7 shows the coefficient of thermal expansion (CTE) as a function of fluorine level.
- CTE coefficient of thermal expansion
- Table 1 summarizes the results of our optical and physical property measurements.
- the table compares properties of Corning HPFS ® (Glass A) and silicon oxyfluoride glass (Glass E) and shows the effect of changes in fluorine content on the properties of the glass. Changes in properties with F content were taken from the linear fits to measured property data similar to Figure 7.
- Glass A modified fused silica
- Glass E modified fused silica
- Photomask polishing and coating deposition experiments were performed to reveal any gross differences between the processing of silicon oxyfluoride glass and standard high purity fused silica photomask substrates.
- Polished substrates 25mm x 25mm x 1.5mm thick, were prepared from the silicon oxyfluoride glass.
- 25mm x 25mm x 6.35mm thick, substrates were also cut from a standard commercial silica photomask substrate. The substrates were cleaned in a sulfuric acid/peroxide solution and mask detergent, then spin-dried and baked at 120 °C Cr films, lOOnm thick, were deposited by sputtering.
- Substrates of Corning HPFS ® fused silica and of the silicon oxyfluoride glass were polished to 0.2nm rms surface roughness using chemical mechanical polishing.
- the theoretical transmission limit of the silicon oxyfluoride glass defined as losses due only to reflections, can be calculated from the refractive index of the material at 157-nm (n) using the formula:
- the silica glass structure can be described as a network of SiO 4 tetrahedra bonded together at all four corners and randomly oriented with respect to one another.
- Water is incorporated into the structure as ⁇ Si-OH (where ⁇ indicates bonding to the SiO network) such that the bond to the neighboring tetrahedron is broken at the OH group.
- OH produces absorption in the deep UV at ⁇ 175-nm.
- Fluorine is similarly incorporated into the structure as ⁇ Si-F with the connectivity of the network being broken at the F atom. Electronic transitions associated with the Si-F bond are expected to be at higher energies (shorter wavelengths) than those from the Si-O network bonds.
- the fluorine-doped silica structure is particularly resistant to damage by F excimer laser irradiation.
- F excimer laser irradiation we have shown that formation of E' color centers is highly suppressed in the fluorinated structure, even in silica containing a very low concentration of fluorine. It is possible that the fluorine reduces the number of precursor sites for color center formation such as weak or strained bonds and oxygen- deficient Si-Si defects.
- Chlorine content has been found to drastically effect the 157 nm transmission of the silicon oxyfluoride glass.
- a plot of 157 nm absorption of 5 mm thick silicon oxyfluoride glass samples versus the chlorine concentrations of the samples shows as in FIGURE 11 , that the 157 nm transmission is improved by low levels of chlorine, preferably with the glass chlorine free.
- Our measurements show that silicon oxyfluoride glass has similar optical, thermal and mechanical properties as standard UV excimer grade silica. The addition of fluorine to the silica structure does produce measurable changes in most of these properties. Thermal expansion, Young's modulus, and shear modulus all decrease with fluorine content, while thermal conductivity and specific heat are largely unaffected.
- the smaller thermal expansion of silicon oxyfluoride glass may prove to be a benefit in 157 nm applications and can be utilized in other lithography and photomask applications such as reflective lithography systems, particularly very short wavelength systems.
- the refractive index of the glass is also decreased by fluorine.
- the refractive index of silicon oxyfluoride glass is considerably higher at 157 nm than standard excimer grade fused silica at 193 nm.
- CaF 2 has a substantially higher thermal conductivity and lower 157 nm refractive index than silica both of which are beneficial to the photomask application, but its high thermal expansion coefficient and crystalline nature make fabrication and mask processing very difficult.
- Silicon oxyfluoride with internal transmittances as high as 87.9%/cm have been prepared. Scattering measurements indicate that scattering losses at 157-nm are very low so that the primary loss mechanism in the glass is absorption. From refractive index measurements, the theoretical limit for measured transmission (reflection losses only) is predicted to be around 88% at 157nm.
- the optical, thermal and mechanical properties of silicon oxyfluoride glass are different from those of standard UN excimer grade fused silica, due to the addition of fluorine to the glass.
- the invention includes a below 193 nm VUV transmitting glass photomask substrate for photolithography at wavelengths of about 157 nm.
- the VUV transmitting glass substrate comprises high purity oxyfluoride glass with an OH content below 50 ppm by weight, hydrogen content below 1 x 10 17 molecules cm , and a fluorine content in the range of 0.1 to 0.4 weight percent.
- the glass has a Cl content below 5 ppm, more preferably below 1 ppm, and most preferably with the glass being essentially free of chlorine.
- the glass has a molecular hydrogen content below 3 x 10 16 molecules/cm 3 , and more preferably has no detectable molecular hydrogen content.
- the glass has an OH content below 10 ppm by weight, more preferably below 1 ppm by weight, and most preferably has no detectable OH content and is essentially OH free.
- the glass is comprised of Si, O, and F and is essentially free of OH, Cl and H 2 .
- the silicon oxyfluoride glass photomask substrate has an internal transmittance at 157 nm of at least 89%/cm, most preferably with the substrate having a measured transmittance of at least 19% tluough a thickness of the photomask substrate with the substrate being about 6 mm thick, such as 6.35 mm thick.
- the invention includes a process of making a VUV transmitting glass having high resistance to optical damage to excimer laser radiation in the 157 nm wavelength region.
- the process includes providing a plurality of SiO particles and dehydrating the particles.
- the process includes fluorine doping and consolidating the particles to form a dry, non-porous monolithic body of transparent fused silicon oxyfluoride glass with a fluorine content less than 0.5 weight percent.
- the particles are reacted with a fluorine-containing gas such that the amount of fluorine incorporated into the glass resulting from consolidation is in the range of 0.1 to 0.4 weight percent.
- the fluorine-containing gas is selected from the group consisting of CF 4 , SiF 4 , F 2 , SF 6 , C F 6 , C 3 F 8 and mixtures thereof.
- the particles are doped with the fluorine-containing gas at a doping temperature in the range of 750 °C to 1050 °C, more preferably in the range of 800°C to 1000°C, and most preferably at about 800°C ( ⁇ 25°C).
- the preferred fluorine- containing gas for these preferred doping temperatures is SiF 4.
- a preferred fluorine doping furnace treatment atmosphere for these temperatures is a mixture of SiF 4 , O 2 and helium, most preferably with O 2 being present during the fluorine doping exposure.
- a preferred fluorine doping furnace treatment atmosphere is about 5% SiF ( ⁇ 2%, more . preferably ⁇ 1%) with about 80% O 2 ( ⁇ 10%, more preferably ⁇ 5%) with the remainder being helium.
- the doped particles are consolidated into silconoxyfluoride glass in a consolidation furnace sintering zone with a sintering temperature in the range of 1400°C to 1550°C.
- the particles are sintered and consolidated in a cosolidatin furnace atmosphere of pure helium, such as by down feeding the soot particle blank from a furnace doping zone in to the sintering zone after the supply of fluorine-containing SiF 4 gas and O 2 is terminated.
- the invention includes a F 2 laser-induced absorption resistant silicon oxyfluoride glass suitable for use in the 157 nm wavelength region, the glass having a stable and high transmission at 157.6 nm with a fluorine content less than 0.5 weight % such that the glass has a transmission loss at 157.6 nm ⁇ 1% after exposure to a F 2 excimer laser for 60 million pulses at 0.1 mJ/cm -pulse.
- the silicon oxyfluoride glass preferably is essentially free of OH groups, has less than 5 x 10 16 molecules/cm 3 of molecular hydrogen, and a fluorine content in the range of about 0.1 to 0.4 weight %.
- the invention includes a F 2 laser-induced absorption resistant lithography glass comprising a silicon oxyfluoride glass having an OH content less than 5 ppm, by weight, a Cl content less than 5 ppm by weight, and a fluorine content of 0.1 to 0.4 weight % with a 157 nm internal transmission of at least 80%/cm, more preferably
- the glass has a H2 content less than 1 x 10 molecules/cm .
- the silicon oxyfluoride glass is resistant to laser-induced absorption and has a 157 nm transmission loss ⁇ 1% after exposure to a 157 nm laser for 60 million pulses at 0.1 mJ/cm 2 -pulse.
- the silicon oxyfluoride glass has a resistance to 157.6 nm induced absorption, with the fluorine content inhibiting 165 nm absorption oxygen-deficient centers.
- the glass has a 165 nm absorption less than 0.4 (absorption units/5mm) after exposure to a 157 nm laser for 41.5 million pulses at 2mJ/cm -pulse of 157 nm laser, and most preferably the 165 nm absorption is less than 0.2 (absorption units/5mm).
- the Cl content is less than 1 ppm and the OH content is less than 1 ppm, preferably with the glass consisting essentially of Si, O and F.
- the glass is a VUV transmitting photomask.
- the glass is a VUV phase shifting photomask.
- the glass photomasks have a resistance to laser induced oxygen-deficient centers, preferably with the glass essentially free of metal to metal Si-Si bonds and free of a 165 nm absorbing center and has an internal transmission at 165 nm of at least 85%/cm.
- the invention includes a VUV pattern printing method.
- the pattern printing method includes providing a below 164 nm radiation source for producing VUV photons, providing a silicon oxyfluoride glass having less than 5 ppm by weight OH, less than 5 ppm by weight Cl, a less than 0.5 weight percent fluorine content, and a 157 nm and 165 nm measured transmission of at least 75%/5mm.
- the method includes transmitting the VUV photons through the silicon oxyfluoride glass, forming a pattern with the VUV photons, and projecting the pattern onto a VUV radiation sensitive printing medium to form a printed pattern.
- Embodiments of pattern printing methods of the invention are shown in FIG 8-9.
- the VUV lithography pattern printing method which includes providing a VUV lithography photon radiation source, providing a silicon oxyfluoride lithography glass with less than 1 ppm OH, transmitting the VUV lithography photons through the silicon oxyfluoride lithography glass, forming a lithography pattern with the VUV photons, and projecting the lithography pattern onto a VUV radiation sensitive lithography printing medium to form a printed lithography pattern.
- the VUV pattern printing method preferably includes lowering the VUV cut off wavelength of the silicon oxyfluoride glass by providing an SiO 2 glass forming precursor and doping with an F content to provide a silicon oxyfluoride glass with a
- the invention provides superior transmission in the VUN with the silicon oxyfluoride glasses having high purity and being dry ( ⁇ 1 ppm OH).
- the inventive glasses have provided 157 nm transmissions such as 79.8%/6.35 mm (and 90%/cm internal T).
- the silicon oxyfluoride glass is preferably utilized as components for 157nm lithography, particularly photomask substrates, pellicles, thin lenses and windows. For these lithography applications, it is not only important that the glass exhibits a high initial transmission, but the transmission must not decrease under exposure to the F 2 excimer laser.
- the glass provides a ⁇ 1% transmission loss at 157.6nm after exposure to the F 2 excimer laser for 60 million pulses at O.lmJ/cm - pulse.
- Our preferred silicon oxyfluoride glass compositions exhibit improved resistance to F 2 laser-induced abso ⁇ tion.
- fluorine to a dry silica glass improves its transmission in the vacuum ultraviolet, particularly near the UV edge (e.g., at 157nm)
- high concentrations of fluorine in the glass are detrimental to its laser damage resistance.
- the induced abso ⁇ tion in the glass is proportional to the fluorine content of the glass.
- Figure 12 is a plot of 157.6nm induced abso ⁇ tion vs.
- the low fluorine silicon oxyfluoride glass of Figure 13b (0.12 wt.% F) has good laser durability and is resistant to F 2 laser induced abso ⁇ tion and free of laser induced oxygen-deficient centers at 165 nm as compared to Figure 13a.
- ArF ArF
- the 1J wt. % F glass of Figures 12, 13a, 14a, and 15 was made from a silica soot preform.
- the silica soot preform was prepared using SiCl 4 as the source compound.
- the soot blank was held in a furnace for 60 minutes at 1100°C under a Cl 2 /He atmosphere (.066 slpm Cl 2 , 20.64 slpm He). The temperature was ramped to 1225°C over 45mins, and the soot preform was exposed to a CF /He atmosphere (4 slpm CF 4 , 12 slpm He) for 180 minutes.
- the fluorine concentration in the glass determined by microprobe analysis was 1 J wt.% F and the chlorine concentration was 14ppm wt.
- a 1.2 wt. % F glass was made from a silica soot preform.
- the silica soot preform was prepared using SiCl as the source compound.
- the soot blank was held in a furnace for 180 minutes at 1000°C under a Cl 2 /He atmosphere (0.066 slpm Cl 2 , 20.64 slpm He).
- the temperature was ramped to 1225°C over 45mins, and the soot preform was exposed to a CF /He atmosphere (1.6 slpm CF 4 , 18.4 slpm He) for 120 minutes.
- the fluorine concentration in the glass determined by microprobe analysis was 1.2 wt.% F.
- the 0.94 wt. % F glass of Figure 12 was made from a silica soot preform.
- the soot blank was held in a furnace for 60 minutes at 1100°C under a Cl /He atmosphere (0.066 slpm Cl , 40.64 slpm He). The temperature was ramped to 1225°C over 45mins, and the soot preform was exposed to a CF 4 /He atmosphere (0.8 slpm CF 4 , 39.2 slpm He) for 150 minutes.
- the fluorine concentration in the glass determined by microprobe analysis was 0.94 wt.% F.
- the .12 wt. % F glass of Figure 12, 13b, 14b, and 15 was made from a silica soot preform.
- the silica soot preform was prepared using OMCTS as the source compound.
- the soot blank was held in a furnace for 120 minutes at 1000°C under a CF 4 /He atmosphere (0.4 slpm CF 4 , 40 slpm He).
- the preform was then driven into the high temperature (max T-1480°C) part of the furnace under a pure He flow to produce a fully dense, F-SiO 2 glass.
- the fluorine concentration in the glass determined by microprobe analysis was 0.12 wt.% F.
- the dry No Fluorine glass of Figure 13c and 14c was made from a silica soot preform.
- the silica soot preform was made using OMCTS as the source compound.
- the soot preform was dried at 1 100-1150°C and sintered to a fully dense glass under a Cl /He atmosphere. Microprobe analysis showed the glass to contain no fluorine and 1290 ppmwt of chlorine.
- a .53 wt. % F glass was made from a silica soot preform.
- the silica soot preform, 892g was prepared using OMCTS as the source compound.
- the soot blank was held in a furnace for 240 minutes at 1000°C under a SiF 4 /O 2 ⁇ e atmosphere (1 slpm SiF 4 , 16slpm O2, 3 slpm He).
- the fluorine concentration in the glass determined by microprobe analysis was 0.53 wt.% F and the chlorine concentration was 19ppm wt.
- a .31 wt. % F glass was made from a silica soot preform.
- the silica soot preform was prepared using OMCTS as the source compound.
- the soot blank was held in a furnace for 240 minutes at 800°C under a SiF 4 /O 2 /He atmosphere (1 slpm SiF 4 , l ⁇ slpm O 2 , 3 slpm He).
- the fluorine concentration in the glass determined by microprobe analysis was 0.31 wt.% F.
- a .26 wt. % F glass was made from a silica soot preform.
- the silica soot preform was prepared using OMCTS as the source compound.
- the soot blank was held in a furnace for 240 minutes at 800°C under a SiF 4 /O 2 /He atmosphere (0.6 slpm SiF 4 , l ⁇ slpm O 2 , 3.4 slpm He).
- the fluorine concentration in the glass determined by microprobe analysis was 0.26 wt.%) F and the chlorine concentration was 15ppm wt.
- a .17 wt. % F glass was made from a silica soot preform.
- the silica soot preform was prepared using SiCl 4 as the source compound.
- the soot blank was held in a furnace for 60 minutes at 1000°C under a Cl 2 /He atmosphere (0.066 slpm Cl 2 , 40.64 slpm He). The temperature was ramped to 1100°C over 20mins, and the soot preform was exposed to a CF 4 /He atmosphere (0.4 slpm CF 4 , 40 slpm He) for 120 minutes.
- the fluorine concentration in the glass determined by microprobe analysis was 0.17 wt.%.
- a .05 wt. % F glass was made from a silica soot preform.
- the silica soot preform was prepared using OMCTS as the source compound.
- the soot blank was held in a furnace for 120 minutes at 800°C under a SiF 4 /O 2 /He atmosphere (1 slpm SiF 4 , 4 slpm O 2 , 15 slpm He).
- the SiF 4 and O 2 were turned off and the preform was held at 800°C under a pure He atmosphere for 120 minutes.
- the fluorine concentration in the glass determined by microprobe analysis was 0.05 wt.% F.
- our silicon oxyfluoride glass has a fluoride content less than 0.5 wt. % F.
- Our ⁇ 0.5 wt. % F dry silicon oxyfluoride glass exhibits good laser durability and suitability for applications involving exposure to F 2 excimer laser radiation.
- Our preferred composition range for attaining both high initial transmission and low induced absorption is 0.1-0.4 wt.% F.
- the invention includes a VUV transmitting silicon oxyfluoride glass having an OH content less than 5 ppm by weight, a fluorine content of at least 0.1 weight %.
- the glass consists essentially of Si, O and F with the glass having an internal transmission in the wavelength range of 157 nm to 175 nm of at least 85%/cm.
- the glass has a 165 nm abso ⁇ tion less than 0.4 (abso ⁇ tion units/5 mm) after exposure to a 157 nm laser for 41.5 million pulses at 2mJ/cm -pulse.
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Abstract
Description
Claims
Priority Applications (3)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
EP01995254A EP1368711A4 (en) | 2001-02-24 | 2001-11-28 | Vacuum ultraviolet transmitting silicon oxyfluoride lithography glass |
KR10-2003-7011150A KR20040030512A (en) | 2001-02-24 | 2001-11-28 | Vacuum ultraviolet transmitting silicon oxyfluoride lithography glass |
JP2002568111A JP2004525409A (en) | 2001-02-24 | 2001-11-28 | Vacuum ultraviolet transparent silicon oxyfluoride lithography glass |
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US27113601P | 2001-02-24 | 2001-02-24 | |
US60/271,136 | 2001-02-24 |
Publications (1)
Publication Number | Publication Date |
---|---|
WO2002069054A1 true WO2002069054A1 (en) | 2002-09-06 |
Family
ID=23034342
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
PCT/US2001/044547 WO2002069054A1 (en) | 2001-02-24 | 2001-11-28 | Vacuum ultraviolet transmitting silicon oxyfluoride lithography glass |
Country Status (5)
Country | Link |
---|---|
EP (1) | EP1368711A4 (en) |
JP (1) | JP2004525409A (en) |
KR (1) | KR20040030512A (en) |
TW (1) | TW554260B (en) |
WO (1) | WO2002069054A1 (en) |
Cited By (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
WO2005085952A1 (en) * | 2004-03-09 | 2005-09-15 | Asahi Glass Company, Limited | Photomask substrate made of synthetic quartz glass and photomask |
Families Citing this family (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JP4792146B2 (en) * | 2004-02-25 | 2011-10-12 | Hoya株式会社 | Mask blank glass substrate manufacturing method, mask blank manufacturing method, exposure mask manufacturing method, reflective mask blank manufacturing method, and reflective mask manufacturing method |
KR101005978B1 (en) * | 2010-05-24 | 2011-01-05 | 최문열 | Decoration bar wrapped with aluminum metal bar and method of manufacturig the same |
Citations (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US5707908A (en) * | 1995-01-06 | 1998-01-13 | Nikon Corporation | Silica glass |
US5837024A (en) * | 1996-12-02 | 1998-11-17 | Heraeus Quarzglas Gmbh | Process for the production of quartz glass bodies |
US5935733A (en) * | 1996-04-05 | 1999-08-10 | Intel Corporation | Photolithography mask and method of fabrication |
Family Cites Families (5)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
EP1043282A4 (en) * | 1998-10-28 | 2004-03-31 | Asahi Glass Co Ltd | Synthetic quartz glass and method for production thereof |
JP3654500B2 (en) * | 1998-12-26 | 2005-06-02 | 信越石英株式会社 | Quartz glass material and optical member for F2 excimer laser optical member |
US6265115B1 (en) * | 1999-03-15 | 2001-07-24 | Corning Incorporated | Projection lithography photomask blanks, preforms and methods of making |
US6242136B1 (en) * | 1999-02-12 | 2001-06-05 | Corning Incorporated | Vacuum ultraviolet transmitting silicon oxyfluoride lithography glass |
WO2002021217A1 (en) * | 2000-09-08 | 2002-03-14 | Corning Incorporated | Vacuum ultraviolet transmitting direct deposit vitrified silicon oxyfluoride lithography glass photomask blanks |
-
2001
- 2001-10-02 TW TW090124463A patent/TW554260B/en not_active IP Right Cessation
- 2001-11-28 WO PCT/US2001/044547 patent/WO2002069054A1/en not_active Application Discontinuation
- 2001-11-28 KR KR10-2003-7011150A patent/KR20040030512A/en not_active Application Discontinuation
- 2001-11-28 JP JP2002568111A patent/JP2004525409A/en active Pending
- 2001-11-28 EP EP01995254A patent/EP1368711A4/en not_active Withdrawn
Patent Citations (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US5707908A (en) * | 1995-01-06 | 1998-01-13 | Nikon Corporation | Silica glass |
US5935733A (en) * | 1996-04-05 | 1999-08-10 | Intel Corporation | Photolithography mask and method of fabrication |
US5837024A (en) * | 1996-12-02 | 1998-11-17 | Heraeus Quarzglas Gmbh | Process for the production of quartz glass bodies |
Non-Patent Citations (1)
Title |
---|
See also references of EP1368711A4 * |
Cited By (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
WO2005085952A1 (en) * | 2004-03-09 | 2005-09-15 | Asahi Glass Company, Limited | Photomask substrate made of synthetic quartz glass and photomask |
US7491475B2 (en) | 2004-03-09 | 2009-02-17 | Asahi Glass Company, Limited | Photomask substrate made of synthetic quartz glass and photomask |
Also Published As
Publication number | Publication date |
---|---|
KR20040030512A (en) | 2004-04-09 |
EP1368711A4 (en) | 2006-07-19 |
TW554260B (en) | 2003-09-21 |
JP2004525409A (en) | 2004-08-19 |
EP1368711A1 (en) | 2003-12-10 |
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