Abstract: The present invention relates to a quartz glass blank for an optical component for transmission of ultraviolet radiation of a wavelength of 250 nm or shorter, and to a use of the quartz glass blank in microlithography in combination with ultraviolet radiation of a wavelength of 250 nm or shorter. Moreover, the invention relates to a procedure for manufacture of the quartz glass blank. A quartz glass blank of the described type should show little induced absorption and be optimized with respect to compaction and decompaction. The quartz glass blank according to the invention is characterized by the following properties: a glass structure essentially free of oxygen defect sites, an H2-content in the range of 0.1×1016 molecules/cm3 to 4.0×1016 molecules/cm3, an OH-content in the range of 125 wt-ppm to 450 wt-ppm, an SiH group-content of less than 5×1016 molecules/cm3, a refractive index inhomogeneity, ?n, of less than 2 ppm, and a stress birefringence of less than 2 nm/cm.

Abstract: It is an object of the present invention to provide a hydrogen-doped silica powder that is useful in the formation of a quartz glass crucible that is capable of pulling a silicon single crystal without causing a state having dislocations in the silicon single crystal due to peeling of quartz glass segment. It is a further object of the invention to provide a quartz glass crucible for use in pulling a silicon single crystal whose inner surface is formed by use of the hydrogen-doped silica powder and a producing method of the silica powder.

Abstract: Subjects for the invention are to obtain a quartz powder having a high purity and high quality and a process for producing the same and to obtain a glass molding formed by melting and molding the powder and extremely reduced in bubble inclusion. The invention provides a quartz powder, preferably a synthetic quartz powder obtained by the sol-gel method, which, upon heating from room temperature to 1,700° C., generates gases in which the amount of CO is 300 nl/g or smaller and the amount of CO2 is 30 nl/g or smaller.

Abstract: The present invention concerns a quartz glass blank for an optical component for the transmission of ultraviolet radiation of a wave length of 250 nm and under, as well as its utilization in microlithography in connection with ultraviolet radiation of a wavelength of 250 nm and under. Such quartz glass blank is to have low induced absorption, while being optimized in respect of compaction and de-compaction. The quartz glass blank according to the invention has the following properties: A glass structure essentially free of oxygen defect sites; a H2 content in the range of 3×1017 molecules/cm3 to 2.0×1018 molecules/cm3; an OH content in the range of 500 weight ppm to 1000 weight ppm; a SiH group content of less than 2×1017 molecules/cm3; a chlorine content in the range of 60 weight ppm to 120 weight ppm; a refractive index inhomogeneity, ?n, of less than 2 ppm; and a stress birefringence of less than 2 nm/cm.

Abstract: Highly durable silica glass containing 0.01% to 2% by weight of at least one element selected from magnesium, calcium, strontium, barium, yttrium, hafnium and zirconium. The silica glass is produced by melting a powdery material comprising a finely divided silica powder and a finely divided zirconium-containing substance by oxyhydrogen flame or plasma are to form an accumulated molten material layer, and extending the molten material layer outwardly in radial directions.

Abstract: Titania-containing silica glass bodies and extreme ultraviolet elements having low levels of striae are disclosed. Methods and apparatus for manufacturing and measuring striae in glass elements and extreme ultraviolet elements are also disclosed.

Abstract: A synthetic quartz glass for optical use, to be used by irradiation with light within a range of from the ultraviolet region to the vacuum ultraviolet region, which contains fluorine, which has a ratio of the scattering peak intensity of 2250 cm?1 (I2250) to the scattering peak intensity of 800 cm?1 (I800), i.e. I2250/I800, of at most 1×10?4 in the laser Raman spectrum, and which has an absorption coefficient of light of 245 nm of at most 2×10?3 cm?1.

Abstract: The alkali-free or alkali-poor glass body is provided with an adherent and anti-reflective coating on at least one of its sides. The coating contains P2O5 and porous SiO2, preferably in a weight ratio of SiO2 to P2O5 of 10:1 to 1:1. It has a rubbing resistance criterion according to DIN 58196, intensity of testing H50, of 2 or better. The method of providing the glass body with the coating includes dipping the glass body in a H3PO4- and SiO2-containing volatile solution, withdrawing the glass body at a speed of from 1 mm/s to 20 mm/s from the solution and tempering the glass body at a temperature of under Tg of the glass.

Abstract: Radiation-induced damage to a lens material in a projection exposure system is reduced by selection of maximum design fluence values HD for lenses and at least one lens made of a material having a characteristic transition point TRC after exposure to a given amount of radiation, wherein, for instance, TRC<0.8. HD among other relationships and/or characteristics of the lenses.

Abstract: Lithographic methods are disclosed. In one such method, a pulsed ultraviolet radiation source for producing ultraviolet lithography radiation having a wavelength shorter than about 300 nm at a fluence of less than 10 mJ/cm2/pulse and a high purity fused silica lithography glass having a concentration of molecular hydrogen of between about 0.02×1018 molecules/cm3 and about 0.18×1018 molecules/cm3 are provided. A lithography pattern is formed with the ultraviolet lithography radiation; the lithography pattern is reduced to produce a reduced lithography pattern; and the reduced lithography pattern is projected onto a ultraviolet radiation sensitive lithography medium to form a printed lithography pattern. At least one of the forming, reducing, and projecting steps includes transmitting the ultraviolet lithography radiation through the high purity fused silica lithography glass. Lithography systems and high purity fused silica lithography glass are also described.

Abstract: A monolayer or multilayer film has a single layer or multiple layers of silica containing fluorine. An optical element has the forgoing film laid on a surface of a substrate. A concentration of the fluorine in the layer or layers of silica is not less than 0.1 mol % (referably, not less than 1 mol %) nor more than 10 mol %.

Abstract: Fused silica articles exhibiting improved internal transmission and decreased absorption change when irradiated with a laser when compared with fused silica articles containing lower levels of aluminum. The articles also exhibit induced transmission when irradiated with a laser. The articles also exhibit improved off-axis refractive index homogeneity.

Abstract: The present invention is a thulium doped silicate glass having an excellent fluorescent emission in the 1.4 ?m band, and the usage thereof. The silicate glass of this invention includes: 65˜95 mol % SiO2; 0.5˜30 mol % bivalent metal oxide consisting of one or more material selected from ZnO, BaO, SrO and PbO; and 1˜15 mol % of SnO2 or TiO2, wherein 3˜30 mol % oxygen of the glass composition are replaced with fluorine, and 0.01˜1 mol % of thulium ions are doped, and the fluorescence lifetime of the 3H4 level of the Tm3+ is more than 50 ?s. The silicate glass can be easily formed into a waveguide, such as optical fiber, and it has an excellent ability to splice with the optical fiber for transmission. They have excellent chemical durability and the characteristic of 1.4 ?m band fluorescent emission by suppressing the non-radiative transition through multi-phonon relaxation. Thus they have long fluorescence lifetime of the 3H4 of Tm3+.

Abstract: In one aspect, the invention provides glass beads and optical devices comprising the glass beads. In other aspects, the invention provides methods of making said glass beads and rapid glass screening methods that use glass beads. Glass beads of the invention comprise greater than 80 weight percent silica, active rare earth dopant, and modifying dopant. In another embodiment the glass beads comprise greater than 80 weight percent silica and at least 5 weight percent germania. In another embodiment, glass beads comprise and from about 20 to about 90 anion mole percent of non-oxide anion.

Abstract: Pyrogenically prepared silicon dioxide with the following physicochemical properties: 1. Average particle size (D50 value) D50?150 nm (dynamic light scattering, 30 wt %) 2. Viscosity (5 rpm, 30 wt %) ??100 m·Pas 3. Thixotropy of Ti (?(5 rpm))/(?(50 rpm))?2 4. BET surface area 30-60 m2/g 5. Compacted bulk=100-160 g/L 6. Original pH?4.5 that can be used for the preparation of dispersions and glass bodies.

Abstract: The granule consists of individual granules approximately spherical in shape, having a pore volume of 0.5 cm3, a mean diameter of pores of 50 nm or less, a specific surface area of 100 m2/g or less, and a bulk density of 0.7 g/cm3 or higher. It is produced by dispersing a fumed silica obtained by hydrolysis of a silicon compound into pure water to obtain a slurry, and drying the slurry. The granule is used for producing high purity synthetic quartz glass powder. The method further comprises: a first heat treatment under an oxygen-containing atmosphere, a second heat treatment in a temperature range of from 600 to 1100° C., and a third heat treatment in a temperature range of from 1100 to 1300° C. under an atmosphere containing hydrogen chloride; and a step of densification comprising calcining the product at a temperature not higher than 1500° C. under vacuum or in an atmosphere of gaseous hydrogen or gaseous helium.

Abstract: Aqueous dispersion comprising silicon/titanium mixed oxide powder with a BET surface area of 5 to 500 m2/g which has been prepared by flame hydrolysis and has a titanium dioxide content of 0.5 to 20 wt. %, based on the powder, water and at least one pH-regulating substance which can be removed completely from the reaction mixture on heating, the aqueous dispersion having a solids content of between 40 and 80 wt. %. A green body produced therefrom with a green density of between 40 and 85%. A shaped glass article of optical quality with a coefficient of thermal expansion of not more than 0.5×10?6/K produced from the green body.

Abstract: The present invention relates generally to UV (ultraviolet) photosensitive bulk glass, and particularly to batch meltable alkali boro-alumino-silicate glasses. The photosensitive bulk glass of the invention exhibits photosensitivity to UV wavelengths below 300 nm. The photosensitivity of the alkali boro-alumino-silicate bulk glass to UV wavelengths below 300 nm provide for the making of refractive index patterns in the glass. With a radiation source below 300 nm, such a laser, refractive index patterns are formed in the glass. The inventive photosensitive optical refractive index pattern forming bulk glass allows for the formation of patterns in glass and devices which utilize such patterned glass.

Abstract: The invention relates to a silica yarn and to woven or nonwoven fabrics produced from said yarn, which comprises 30 to 1500 ppm by weight of aluminum and 10 to 200 ppm by weight of titanium in oxidized form, the sum of the mass of the chemical elements different from Si and O being less than 5000 ppm by weight, the following elements being absent or present in a very small quantity: boron, sodium, calcium, potassium and lithium. The fabrics comprising this silica yarn have an excellent high-temperature withstand and thus retain their flexibility for a long time at above 600° C. They are useful especially in uses requiring good high-temperature flexibility, such as for furnace seals.

Abstract: A silica glass member of the present invention is one wherein when a composition thereof is expressed by SiOx, x is not less than 1.85 nor more than 1.95, wherein a concentration of hydrogen molecules included therein is not less than 1×1016 molecules/cm3 nor more than 5×1018 molecules/cm3, and wherein a difference A−B between an absorption coefficient A immediately before an end of irradiation with 1×104 pulses of ArF excimer laser light in an average one-pulse energy density of 2 mJ/cm2 and a second absorption coefficient B at 600 seconds after a stop of the irradiation with the ArF excimer laser light is not more than 0.002 cm−1. When this silica glass member is applied to an illumination optical system and/or a projection optical system in projection exposure apparatus, it becomes feasible to implement uniform exposure while reducing variation in illuminance on a reticle surface and in an exposure area on a wafer.

Abstract: The invention provides coated optical lithography elements and methods of coating optical elements, and particularly optical photolithography elements for use in below 240 nm optical photolithography systems utilizing vacuum ultraviolet light (VUV) lithography wavelengths no greater than about 193 nm, such as VUV projection lithography systems utilizing wavelengths in the 193 nm or 157 nm region. The optical devices manipulate vacuum ultraviolet lithography light less than 250 nm utilizing a deposited silicon oxyfluoride film. The deposited silicon oxyfluoride optical coating assists in the manipulation of incident light and protects the underlying optical materials, layers, and surfaces.

Abstract: The present invention relates generally to UV (ultraviolet) photosensitive bulk glass, and particularly to batch meltable alkali boro-alumino-silicate and germanosilicate glasses. The photosensitive bulk glass of the invention exhibits photosensitivity to UV wavelengths below 300 nm. The photosensitivity of the alkali boro-alumino-silicate and germanosilicate bulk glasses to UV wavelengths below 300 nm provide for the making of refractive index patterns in the glass. With a radiation source below 300 nm, such a laser, refractive index patterns are formed in the glass. The inventive photosensitive optical refractive index pattern forming bulk glass allows for the formation of patterns in glass and devices which utilize such patterned glass.

Abstract: A discharge bulb comprising an arc tube body having such a structure that a shroud glass having metal oxide (Al2O3, CeO2) added thereto is attached integrally to surround an arc tube sealing Hg, NaI, ScI and Xe gases. A total amount of addition of the metal oxide in the shroud glass is set to be 4000 ppm or more which is effective for fulfilling an electrostatic shielding function for an external electric field and less than 7000 ppm which can hold the excellent molding property of the shroud glass.

Abstract: Lithographic methods are disclosed. In one such method, a pulsed ultraviolet radiation source for producing ultraviolet lithography radiation having a wavelength shorter than about 300 nm at a fluence of less than 10 mJ/cm2/pulse and a high purity fused silica lithography glass having a concentration of molecular hydrogen of between about 0.02×1018 molecules/cm3 and about 0.18×1018 molecules/cm3 are provided. A lithography pattern is formed with the ultraviolet lithography radiation; the lithography pattern is reduced to produce a reduced lithography pattern; and the reduced lithography pattern is projected onto a ultraviolet radiation sensitive lithography medium to form a printed lithography pattern. At least one of the forming, reducing, and projecting steps includes transmitting the ultraviolet lithography radiation through the high purity fused silica lithography glass. Lithography systems and high purity fused silica lithography glass are also described.

Abstract: High purity synthetic quartz glass particles are derived from alkali metal silicate and have a total amount of metal impurities content of at least 1 &mgr;g/g and, in particular, have oxygen-deficient defects. The high-purity synthetic quartz glass particles having high viscosity similar to natural quartz and high-purity similar to known synthetic quartz can be provided at a low cost.

Abstract: A process for producing fluorine-containing glass. An SiO2 soot is synthesized by hydrolyzing SiCl4. The soot is heated in a chlorine-compound-free atmosphere containing a fluorine compound gas to form a fluorine-containing silica glass. The glass contains not more than 10 ppm OH group, not more than 10 ppm Cl, and not less than 1,000 ppm F. The concentration ratio of F/Cl is 10,000 or more.

Abstract: A method of fabricating a halogen-doped glass includes providing a gel monolith having a first halogen content. The method further includes reducing an impurity concentration of the gel monolith. The method further includes consolidating the gel monolith into a glass having a second halogen content. The second halogen content is less than or equal to the first halogen content. A halogen-doped glass has a fluorine content in a range between approximately 0.5 wt. % and approximately 4 wt. %, a chlorine content less than 100 parts per million, and an OH content less than one part per million.

Abstract: In one aspect, the invention provides glass beads and optical devices comprising the glass beads. In other aspects, the invention provides methods of making said glass beads and rapid glass screening methods that use glass beads. Glass beads of the invention comprise greater than 80 weight percent silica, active rare earth dopant, and modifying dopant. In another embodiment the glass beads comprise greater than 80 weight percent silica and at least 5 weight percent germania. In another embodiment, glass beads comprise and from about 20 to about 90 anion mole percent of non-oxide anion.

Abstract: Subjects for the invention are to obtain a quartz powder having a high purity and high quality and a process for producing the same and to obtain a glass molding formed by melting and molding the powder and extremely reduced in bubble inclusion.

Abstract: Fused silica members having high internal transmission and low birefringence are disclosed. Methods of making such fused silica members are also disclosed. According to the present invention, fused silica members having an internal transmission equal to or greater than 99.65%/cm at 193 nm and having an absolute maximum birefringence along the use axis of less than or equal to 0.75 nm/cm are provided.

Abstract: Lithographic methods are disclosed. In one such method, a pulsed ultraviolet radiation source for producing ultraviolet lithography radiation having a wavelength shorter than about 300 nm at a fluence of less than 10 mJ/cm2/pulse and a high purity fused silica lithography glass having a concentration of molecular hydrogen of between about 0.02×1018 molecules/cm3 and about 0.18×1018 molecules/cm3 are provided. A lithography pattern is formed with the ultraviolet lithography radiation; the lithography pattern is reduced to produce a reduced lithography pattern; and the reduced lithography pattern is projected onto a ultraviolet radiation sensitive lithography medium to form a printed lithography pattern. At least one of the forming, reducing, and projecting steps includes transmitting the ultraviolet lithography radiation through the high purity fused silica lithography glass. Lithography systems and high purity fused silica lithography glass are also described.

Abstract: Pyrogenically prepared silicon dioxide with the following physicochemical properties:

Abstract: Highly durable silica glass containing 0.01% to 2% by weight of at least one element selected from magnesium, calcium, strontium, barium, yttrium, hafnium and zirconium. The silica glass is produced by melting a powdery material comprising a finely divided silica powder and a finely divided zirconium-containing substance by oxyhydrogen flame or plasma are to form an accumulated molten material layer, and extending the molten material layer outwardly in radial directions.

Abstract: An optical element of a lithographic projection apparatus includes a Si/Mo multilayer structure, an outer capping layer and an interlayer positioned between the multilayer structure and the outer capping layer. The interlayer has a thickness of between 0.3 and 0.7 times the wavelength of the incident radiation. The interlayer may be C or Mo and has a thickness of between 6.0 and 9.0 nm. The interlayer may include an inner interlayer including Mo next to the multilayer structure and an outer interlayer including C next to the capping layer. The outer interlayer is at least 3.4 nm thick and the capping layer is Ru and at least 2.0 nm thick.

Abstract: A lithographic apparatus having a supply to a space in the apparatus of a composition including at least one of one or more perhalogenated C1-C6 alkanes and one or more compounds including one or more nitrogen atoms and one or more atoms selected from hydrogen, oxygen and halogen. The activation of the alkane(s) and compound(s) provides reactive species which are capable of highly selective etching of hydrocarbon species while minimizing damage to sensitive optical surfaces.

Abstract: High purity silicon oxyfluoride glass suitable for use as a photomask substrates for photolithography applications in the VUV wavelength region below 190 nm is disclosed with the silicon oxyfluoride glass having a preferred fluorine content<0.5 weight percent. The inventive silicon oxyfluoride glass is transmissive at wavelengths around 157 nm, making it particularly useful as a photomask substrate at the 157 nm wavelength region. The inventive photomask substrate is a “dry,” silicon oxyfluoride glass which exhibits very high transmittance in the vacuum ultraviolet (VUV) wavelength region while maintaining the excellent thermal and physical properties generally associated with high purity fused silica. In addition to containing fluorine and having little or no OH content, the inventive silicon oxyfluoride glass suitable for use as a photomask substrate at 157 nm is also characterized by having less than 1×1017 molecules/cm3 of molecular hydrogen and low chlorine levels.

Abstract: Rolls include a core and a glass outer coating on the core. The glass can be electrically charged and discharged. The outer coatings have smooth finishes and controlled electrical properties. The outer coatings can also provide selected mechanical, chemical and thermal properties. The rolls can be used in various applications in which controlled electrical properties are desired. For example, the rolls can be used as charge donor rolls in electrostatographic imaging apparatus.

Abstract: A process of manufacturing a silica glass article comprising the steps of: (1) irradiating a silica glass article with electromagnetic waves to generate defects therein; and (2) immersing the thus irradiated silica glass article in an atmosphere comprising a hydrogen gas, thereby providing the resulting silica glass article with a characteristic that is effective for preventing it substantially from increasing its absorption within an ultraviolet region due to ultraviolet ray irradiation. Also disclosed are a silica glass article or a glass fiber produced according to the manufacturing process.

Abstract: The invention relates to a method for producing porous SiO2 green bodies having an extremely high green density, or porous SiO2 green bodies having an internal density gradient which is adjusted in a targeted manner. The inventive method is characterised in that a porous SiO2 green body known per se and consisting of amorphous SiO2 is redensified by electrophoretically depositing SiO2 particles in the pores of the green body.

Abstract: Extremely high solids content silica dispersions are useful for forming green bodies of near net shape as compared to the shape of the bodies after sintering. The green bodies are particularly useful for sintering to form low impurity-containing crucibles for single crystal silicon production.

Abstract: Fused silica articles exhibiting improved internal transmission and decreased absorption change when irradiated with a laser when compared with fused silica articles containing lower levels of aluminum. The articles also exhibit induced transmission when irradiated with a laser.

Abstract: An object of the present invention is to provide a synthetic quartz glass optical material having a high optical transmittance for a radiation 157 nm in wavelength emitted from F2 excimer laser and a high resistance against irradiation of a F2 excimer laser radiation, yet having a uniformity suitable for such a fine patterning using a F2 excimer laser, and to provide an optical member using the same. The problems above are solved by a synthetic quartz glass optical material for F2 excimer lasers having an OH group concentration of 0.5 ppm or lower, a fluorine concentration of 0.1 to 2 mol %, a hydrogen molecule concentration of 5×1016 molecules/cm3 or lower, a difference between the maximum and minimum fluorine concentrations within 20 mol ppm, and a difference between the maximum and minimum refraction indices of 2×10−5 or lower.

Abstract: A pyrogenic process is used to prepare alkali-doped silica particles. Particles produced by this process exhibit homogeneous doping, reduced agglomeration, greater stability and higher removal rates. Aqueous dispersions containing alkali-doped pyrogenic silica with average particle size less than 100 nm are used for polishing surfaces (CMP).

Abstract: A modified silica glass composition for providing a reduction in the multiphonon quenching for a rare-earth dopant comprising: SiO2 in a host material; a rare-earth dopant; a first SiO2 modifier; and a second SiO2 modifier; such that said first modifier and said second modifier reduce multiphonon quenching of the rare-earth dopant contained therein.

Abstract: A photolithography apparatus has an exposure light source for emitting exposure light with a wavelength of 400 nm or less, a reticle with a pattern original image formed therein, an illumination optical system for illuminating the reticle with exposure light, a projection optical system for projecting the pattern image from the reticle onto a photosensitive plate and an alignment system for aligning the reticle and the photosensitive plate. At least some of the synthetic silica glass members composing the illumination optical system, the projection optical system and the reticle consist of synthetic silica glass members which, upon 1×104 pulse irradiation with an ArF excimer laser at an energy density from 0.1 &mgr;J/cm2·p to 200 mJ/cm2·p, have a loss factor no greater than 0.0050 cm−1 at 193.4 nm measured after irradiation, a hydrogen molecule concentration from 1×1016 molecules/cm3 to 2×1018 molecules/cm3 and a loss factor no greater than 0.

Abstract: The present invention is a thulium doped silicate glass having an excellent fluorescent emission in the 1.4 &mgr;m band, and the usage thereof. The silicate glass of this invention includes: 65˜95 mol % SiO2; 0.5˜30 mol % bivalent metal oxide consisting of one or more material selected from ZnO, BaO, SrO and PbO; and 1˜15 mol % of SnO2 or TiO2, wherein 3˜30 mol % oxygen of the glass composition are replaced with fluorine, and 0.01˜1 mol % of thulium ions are doped, and the fluorescence lifetime of the 3H4 level of the Tm3+ is more than 50 &mgr;s. The silicate glass can be easily formed into a waveguide, such as optical fiber, and it has an excellent ability to splice with the optical fiber for transmission. They have excellent chemical durability and the characteristic of 1.4 &mgr;m band fluorescent emission by suppressing the non-radiative transition through multi-phonon relaxation. Thus they have long fluorescence lifetime of the 3H4 of Tm3+.

Abstract: Fused silica articles containing at least 50 ppb aluminum are disclosed. The fused silica articles containing these levels of aluminum exhibit improved internal transmission and decreased absorption change when irradiated with a laser when compared with fused silica articles containing lower levels of aluminum.

Abstract: Highly durable silica glass comprising silica having incorporated therein aluminum and at least one element (M) selected from group 2A elements, group 3A elements and group 4A elements of the periodic table. Preferably, the sum of aluminum and element (M) is at least 30 atomic % based on the amount of total metal elements in the silica glass, and the atomic ratio of aluminum to element (M) is in the range of 0.05 to 20.

Abstract: A silica glass member of the present invention is one wherein when a composition thereof is expressed by SiOx, x is not less than 1.85 nor more than 1.95, wherein a concentration of hydrogen molecules included therein is not less than 1×1016 molecules/cm3 nor more than 5×1018 molecules/cm3, and wherein a difference A−B between an absorption coefficient A immediately before an end of irradiation with 1×104 pulses of ArF excimer laser light in an average one-pulse energy density of 2 mJ/cm2 and a second absorption coefficient B at 600 seconds after a stop of the irradiation with the ArF excimer laser light is not more than 0.002 cm−1. When this silica glass member is applied to an illumination optical system and/or a projection optical system in projection exposure apparatus, it becomes feasible to implement uniform exposure while reducing variation in illuminance on a reticle surface and in an exposure area on a wafer.

Abstract: The invention pertains to an amorphous silica particle comprising 0.1 to 105 ppm boron atoms, and optionally 0.05 to 15 wt. % aluminum atoms wherein the boron and aluminum atoms are covalently bonded to the oxygen atoms of the silica network. The amorphous silica particles arc used as a reinforcing filler for rubber articles, particularly for tires, more particularly for tire treads.