WO2002077676A1 - Element optique, procede permettant de produire cet element, et machine de projection - Google Patents
Element optique, procede permettant de produire cet element, et machine de projection Download PDFInfo
- Publication number
- WO2002077676A1 WO2002077676A1 PCT/JP2002/002368 JP0202368W WO02077676A1 WO 2002077676 A1 WO2002077676 A1 WO 2002077676A1 JP 0202368 W JP0202368 W JP 0202368W WO 02077676 A1 WO02077676 A1 WO 02077676A1
- Authority
- WO
- WIPO (PCT)
- Prior art keywords
- optical member
- optical
- fluoride
- less
- light
- Prior art date
Links
Classifications
-
- C—CHEMISTRY; METALLURGY
- C30—CRYSTAL GROWTH
- C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
- C30B29/00—Single crystals or homogeneous polycrystalline material with defined structure characterised by the material or by their shape
- C30B29/10—Inorganic compounds or compositions
- C30B29/12—Halides
-
- C—CHEMISTRY; METALLURGY
- C30—CRYSTAL GROWTH
- C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
- C30B11/00—Single-crystal growth by normal freezing or freezing under temperature gradient, e.g. Bridgman-Stockbarger method
-
- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B1/00—Optical elements characterised by the material of which they are made; Optical coatings for optical elements
- G02B1/02—Optical elements characterised by the material of which they are made; Optical coatings for optical elements made of crystals, e.g. rock-salt, semi-conductors
-
- 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
-
- 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
Definitions
- the present invention relates to an optical member made of a fluoride crystal material used in the ultraviolet and vacuum ultraviolet regions having a wavelength of 250 nm or less, a method for producing the same, and projection exposure using a stepper or scanner using the optical member in an optical system. It concerns the equipment.
- Resolution and depth of focus are determined by the wavelength of light used for exposure and the NA (numerical aperture) of the lens. If the exposure wavelength is the same, the angle of the diffracted light increases as the pattern becomes finer. If the NA of the lens is not large, the diffracted light cannot be captured. When the exposure wavelength is short, the angle of the diffracted light in the same pattern becomes small, so that the NA of the lens may be small.
- the depth of focus k 2 ⁇ ⁇ / (NA ) 2 (3)
- Equations (2) and (3) each represent a proportionality constant. From equation (2), it can be seen that the resolution can be improved by increasing the NA of the lens (that is, increasing the lens diameter) or shortening the exposure wavelength. Shortening is more focused than equation (3) It can be said to be advantageous in terms of depth.
- the exposure wavelength is now becoming shorter and shorter, and the KrF excimer laser (wavelength 248 nm) and the ArF excimer laser (wavelength
- Projection exposure apparatuses using a light source of 3 nm have appeared on the market.
- very few optical materials can be used for optical lithography at wavelengths below 250 nm, and most optical systems are designed with two types of materials: fluorite and quartz glass. .
- an F 2 laser (wavelength 1
- the optical material used for optical lithography which requires very high imaging performance, is not limited to a large aperture, but also to birefringence. It is also necessary that the internal refractive index is small and the homogeneity of the internal refractive index is excellent.
- the Bridgeman method is generally used.
- an optical member is manufactured from a fluorite crystal ingot obtained by the bridgeman method, an optical member (material) of a desired size can be cut directly from the ingot.
- a further heat treatment is performed to improve internal qualities such as birefringence and refractive index homogeneity.
- Japanese Patent Application Laid-Open No. H11-2407998 discloses that the birefringence in the optical axis direction is 2 nm / cm or less, and the birefringence in the side direction (radial direction in a plane perpendicular to the optical axis) is 5 nm.
- a method for producing a fluorite single crystal having a refractive index difference ⁇ of 2 ⁇ 10 6 or less and a nm / cm or less is disclosed.
- the optical member is required to have laser light transmission, durability, low birefringence, and uniform refractive index.
- the optical system of a projection exposure apparatus used for optical lithography has a very high resolution, so it is common to use a large number of lenses and a long optical path length to correct various wavefront aberrations.
- the transmission loss scattering loss + absorption loss
- the internal transmittance of the optical components used should be as close to 100% / cm as possible, at least 99.5% Zcm or more, and preferably 99.8% Zcm or more. Is required.
- inclusion As an index for judging the quality of a fluoride crystal material such as fluorite from the viewpoint of transmittance, there is a presence or absence of a defect inside the material called inclusion.
- the definition of inclusion is not always clear, some inclusions, when observed under condensed illumination, are observed as particles that scatter and shine light, It is called the body (Scattering body).
- the scatterer when the scatterer is present in the material, the scatterer scatters the light and the transmittance Will decrease.
- characteristics such as durability of laser transmittance, birefringence, and refractive index homogeneity are used. Even with the use of optical members with sufficient performance, the scattering of light reduces the transmittance, resulting in insufficient throughput of the entire optical system, reduced contrast, and the occurrence of flares and ghosts. could have an effect.
- a fluoride crystal material in which scatterers that can be easily observed with the naked eye are present on the entire surface is regarded as defective.
- a fluoride crystal material in which scatterers are partially distributed as shown in FIG. 2, only the small-diameter optical member 3 cut out from the scatterer-free portion 2b is used for the optical system. The rest, including diffuser 2a, is considered defective.
- the scatterer is a major factor deteriorating the optical characteristics of fluorite for optical lithography and the production yield thereof. Therefore, fluorite, or even fluorite, was used as an optical member for optical lithography. Projection exposure equipment is very expensive.
- the diameter of the optical member is small, it is possible to selectively cut out the portion without the scatterer as described above.
- an optical member having a large diameter for example, a diameter ⁇ of 200 mm
- the scatterers are mixed when cut out, it is very difficult to simultaneously improve the optical performance of the optical member and increase the diameter.
- the present invention has been made in view of the above-mentioned problems of the related art, has sufficiently high optical performance (such as internal transmittance) for light having a wavelength of 250 nm or less, and is made of a fluoride crystal material. It is an object of the present invention to provide an optical member capable of improving the yield and increasing the diameter at the time of cutting, a manufacturing method thereof, and a projection exposure apparatus using the optical member.
- the present inventors firstly developed a light for optical lithography.
- a fluoride crystal material fluorite, etc.
- the internal scatterer As a result, even if scatterers are present in the optical member cut from the fluoride crystal material, if the size and number satisfy the predetermined conditions, the optical member can be used as an optical member for optical lithography. And completed the present invention.
- the optical member of the present invention is an optical member for optical lithography used with light having a wavelength of 250 nm or less, and has a maximum diameter d max [cm] of a scatterer present therein and the maximum diameter d max [cm].
- the number n s of scatterers per 1 cm 3 is represented by the following formula (1):
- the optical member of the present invention by the maximum diameter d max of the scatterer and the its 1 cm 3 per Rino number n s satisfies the condition represented by the above formula (1), wavelength 2 5 0 nm Since the optical performance (internal transmittance, etc.) for the following light is maintained at a high level, it is possible to improve the yield and increase the diameter when cutting out from a fluoride crystal material.
- the scatterer refers to a scatterer that exists inside an optical member and is observed as particles that scatter and shine light when observed under condensed illumination. Good, specifically, impurities such as vacuum or air bubbles, graphite, and calcium oxide. Many of these scatterers have an angular shape instead of a spherical shape.
- the maximum diameter d max of scattering bodies 2. 0 XI 0- 3 cm ( 2 0 ⁇ ⁇ ) or less, the number n s per 1 cm 3 of the scatterer 1 6 it is 0 or less or a maximum diameter d max of scattering bodies 4,. 0 X 1 0- 3 ⁇ ⁇ (4 0 ⁇ ⁇ ) or less, the number per 1 cm 3 of the scatterer n s Is preferably 40 or less.
- the diameter ⁇ is preferably 200 mm or more.
- the optical member of the present invention has a high level of optical performance, it is possible to realize a large-diameter ⁇ 200 mm in diameter, and use light having a wavelength of 250 mm or less. In lithography, the imaging performance can be further improved.
- the birefringence in the optical axis direction is 2 nmZcm or less
- the birefringence in the radial direction is 5 nm / cm or less
- n it may be their respective preferably not more than 2 X 1 0- 6.
- the energy density 5 0 m JZ cm 2 / pu 1 se of A r F excimer laser Kino transmittance reduction amount to have 1 0 6 pulse irradiation with light is 2. 0% / cm
- the following is preferred.
- the method comprises the steps of: melting a mixture of a fluoride powder and a Surebenja at a melting temperature equal to or higher than the melting point of the fluoride; A crystal growth step of cooling the fluoride crystal in a temperature range of 1000 ° C. to 900 ° C. at a cooling rate of 0.1 to 5 ° C., and a fluoride crystal obtained in the crystal growth step.
- the mixture of the fluoride powder and the scavenger is melted at a melting temperature higher than the melting point of the fluoride, and then the melt is crystallized.
- the number n s per 1 cm 3 is sufficiently reduced. Therefore, according to the manufacturing method of the present invention, the optical member of the present invention represented by the formula (1) can be easily and reliably obtained, and an improvement in manufacturing yield and an increase in diameter can be realized.
- the number n s per 1 cm 3 of the maximum diameter d max [cm] and the scatterer of the scattering bodies obtained in advance for the light of a specific wave length inside It is preferable to select the cutout position of the optical member based on the correlation with the transmittance decrease amount L. This makes it possible to easily and reliably obtain an optical member having a desired internal transmittance.
- the fluoride powder has an average particle diameter of 100 ⁇ m or less, and a particle diameter of 0.5 to 1.5 times the average particle diameter. It is preferable to use particles having a proportion of 50% by weight or more of the particles. By using such a fluoride powder, it is possible to suppress generate scatterer, it can be further reduced n s.
- the fluoride powder a powder in which the concentrations of Cl, Br and I are all less than 0.1 ppm.
- the concentrations of Cl, Br and I are all less than 0.1 ppm.
- the projection exposure apparatus of the present invention comprises: a reticle having a pattern; an illumination optical system for irradiating the reticle with light having a wavelength of 250 nm or less; A projection optical system for imaging a pattern on a reticle illuminated by the system on a wafer, and at least one of the illumination optical system and the projection optical system has a maximum diameter d max of a scatterer present therein and the scattering.
- the number ns per cm 3 of the body is the following formula CD:
- optical member made of a fluoride crystal that satisfies the condition represented by the following.
- the diameter ⁇ of the optical member is 200 mm or more.
- FIG. 1 is a graph showing an example of the relationship between the number n s of scatterers in 1 cm- 3 of fluorite and the internal transmittance.
- FIG. 2 is an explanatory diagram showing an example of a cutting position when a conventional optical member is cut from a fluoride crystal.
- FIG. 3 is an explanatory diagram showing an example of a cutting position when cutting the optical member of the present invention from a fluoride crystal.
- FIG. 4 is a schematic configuration diagram showing a preferred embodiment of the projection exposure apparatus of the present invention.
- FIG. 5 is a schematic configuration diagram showing a preferred example of the projection optical system according to the present invention.
- the optical member of the present invention is an optical member for optical lithography used with light having a wavelength of 250 nm or less, and has a maximum diameter d max [cm] of a scatterer present therein and the maximum diameter d max [cm].
- the number n s of scatterers per 1 cm 3 is represented by the following formula (1):
- X 1 0 - for are those consisting of 4 [satisfies fluoride crystal represented by c m- (1), wavelength 2 5 0 nm or less light It has sufficient optical characteristics (such as internal transmittance).
- the fluoride crystal according to the present invention (1 "1! ⁇ And 11 3 but is not particularly limited as long as conditions are satisfied as represented by the above formula (1), specifically, calcium fluoride crystals, fluoride Examples include lithium crystal, barium fluoride crystal, strontium fluoride crystal, magnesium fluoride crystal, etc. These fluoride crystals are preferably single crystals.
- test pieces with a diameter of 3 Omm are collected from a plurality of parts with different scatterer densities in two types of fluorite in which scatterers exist with a predetermined distribution. These test pieces are mirror polished so that the distance (thickness) between the two opposing parallel surfaces is 10 mm, the parallelism is 30 seconds or less, and the surface roughness RMS is 5 A or less. .
- the transmittance at a wavelength of 193 nm is measured using a spectrophotometer (for example, Cary5 manufactured by Varian).
- a spectrophotometer for example, Cary5 manufactured by Varian.
- a transmittance including multiple reflections can be converted to an internal transmittance using the following equations (4) and (5).
- the reflectance R on the test piece surface is represented by the following equation (4).
- the relationship between the transmittance T r and the internal transmittance T i in consideration of multiple reflection loss at the surface is expressed by the following equation (5) using R.
- the scatterer is observed with a microscope at the position where the transmittance of the test piece was measured.
- a microscope According to the standards of the Optical Glass Industry Association, when observing foreign matter or bubbles, it is desirable to measure the cross-sectional area and number using a sample of 50 m1 or more. It is very difficult to measure the spectral transmittance using such a large sample as it is because of the size of the sample chamber and other factors, and it is necessary to directly determine the relationship between the transmittance and the size and number of scatterers. I can't do that. Therefore, the present inventors measured the size and number of the scatterers at the site where the transmittance of the test piece for which the transmittance measurement was performed was measured, and determined the relationship between the scatterers and the transmittance.
- Maximum diameter d ma x and the number n s per 1 cm 3 the scatterer it can be obtained by the following procedure.
- the stage on which the test piece is placed is moved up and down so that Inside Measure the number of scatterers observed in and the maximum length of their cross section.
- This measurement was performed a total of six times with the test piece position changed little by little, and d max and n s (all averaged) were obtained from the number of counted scatterers, the area of the field of view, and the moving distance of the stage (10 mm). Value) can be obtained.
- the diameter and the number of scatterers usually show different values for each ingot.
- Fig. 1 is a graph showing an example of the relationship between the number n s of scatterers in 1 cm- 3 of fluorite and the internal transmittance, where the horizontal axis is n s and the vertical axis is the internal transmittance 1 ⁇ . It is shown.
- Maximum diameter d ma x are 2 symbols ⁇ scattering body in FIG. OX 1 0- 3 cm (2 0 m) on fluorite is obtained by plotting the internal transmittance T i to the number n s of the scattering bodies And line 1a is their approximation curve. Further, symbols in FIG. * Are those maximum diameter of the scattering body is plotted the T i for n s for fluorite 4. 0 X 1 0- 3 cm ( 4 0 ⁇ ⁇ ), line 1 b is These are approximate curves.
- Equation (6) L represents the amount of decrease in internal transmittance per 1 cm length [% Z cm], C represents the coefficient when the sample thickness is 1 cm, and d max and ns are Represents the same definition as equation (1). ]
- Equation (6) expresses the reduction amount L of Can be.
- the coefficient C is 3.1.
- equation (8) that is, from equation (1), the number per 1 cm 3 of the scatterer when the maximum diameter 2 0 mu m or less of the scatterer exists n s is 1 6 0 number below, if 1 number n s per cm 3 4 0 less if the maximum diameter is present 4 0 mu m or less of the scatterer, 9 9. internal transmittance of more than 8% / cm Is realized.
- d ma and n s are represented by the following formula (9):
- the optical member of the present invention is not limited to other light having a wavelength of 250 nm or less, for example, KrF.
- Excimer laser light wavelength 248 nm
- F 2 laser It is also effective when used with light (wavelength: 157 nm).
- fluoride powder used in the production method of the present invention examples include fluoride / resin, lithium fluoride, barium fluoride, strontium fluoride, and magnesium fluoride. It is preferable to remove impurities such as metals from these fluoride powders before using them in the pretreatment step.
- impurities such as metals
- chlorine (C 1), bromine (Br), and iodine contained in the raw materials are preferably used.
- the concentration of (I) is less than 0.1 ppm.
- C 1 when the concentration of B r and I are used satisfy fluoride powder of the, possible to further reduce the maximum diameter d ma x and the number n s per 1 cm 3 of the scatterers contained in the fluoride crystal Can be.
- cobalt (Co), cerium (Ce), lanthanum (La), yttrium (Y), iron (Fe) and lead (Pb) are less than 0.5 ppm; potassium (K ), Manganese ( ⁇ ), copper (Cu), nickel (Ni) and chromium (Cr) are less than 0.1 ppm; lithium (Li) and sodium (Na) are less than 0.2 ppm; Li (Ba) is less than 1. O ppm; strontium (S r) is preferably less than 2 ⁇ ppm.
- Scavengers have the effect of reducing the impurity concentration in the fluoride powder.
- scavengers include metal fluorides such as lead fluoride, zinc fluoride, and silver fluoride, and fluorine (F 2 ).
- Gaseous fluorides such as carbon tetrafluoride (tetrafluoromethane, CF 4 ), PTFE (polytetrafluoro And fluorine-containing organic compounds such as ethylene.
- the addition amount of the stainless steel is not particularly limited, but, for example, in the case of metal fluoride, it is preferably in the range of 0.1 to 10 mo 1% based on the fluoride powder raw material.
- the fluoride powder raw material is calcium fluoride and the stainless steel is lead fluoride, it is preferable to use 0.3 to 35 g of lead fluoride per 100 g of calcium fluoride. .
- a mixture of the fluoride powder and the scavenger is subjected to a predetermined pre-treatment in advance to remove impurities in the mixture and increase the bulk density.
- a predetermined pre-treatment for example, by filling a mixture of a fluoride powder and a stainless steel venger into a rutupo and heating and melting in a predetermined pretreatment device, it is possible to homogenize the viscosity and components of the melt.
- the crucible and the inside of the pretreatment device are kept as clean as possible in order to prevent contamination of impurities, and it is preferable that the inside of the device into which the raw material is introduced is evacuated before heating.
- the pretreatment step is performed in a Taleen room maintained at a cleanliness level better than Class 1, 000, 000.
- the treatment temperature and the holding time in the pretreatment step differ depending on the type of the fluoride powder and the scavenger.
- the temperature is preferably from 142 to 150. 0 ° C. and the holding time is preferably between 12 and 36 hours.
- the rate of temperature rise in the process of raising the temperature to the above temperature is preferably 1 to 15 ° C / hr.
- the melt having the homogenized viscosity and components is cooled at a predetermined cooling rate (preferably 10 to 30 ° C / min).
- a predetermined cooling rate preferably 10 to 30 ° C / min.
- the crystal growing step according to the present invention can be performed by, for example, the vertical Bridgeman method. That is, a mixture of a fluoride powder and a scavenger or a fluoride crystal obtained in a pretreatment step is put into a crucible and introduced into a crystal growing apparatus (crystal growing furnace), and a melting temperature (fluorine) equal to or higher than the melting point of the fluoride crystal is obtained. After melting the fluoride crystal at 140 ° C or more for calcium iodide), the melt is crystallized by lowering the crucible from the furnace at a predetermined lowering speed.
- the vertical Bridgeman method That is, a mixture of a fluoride powder and a scavenger or a fluoride crystal obtained in a pretreatment step is put into a crucible and introduced into a crystal growing apparatus (crystal growing furnace), and a melting temperature (fluorine) equal to or higher than the melting point of the fluoride crystal is obtained. After melting the fluoride crystal
- the melting temperature in the crystal growing step is, as described above, a temperature equal to or higher than the melting point of the fluoride crystal, and in the case of calcium fluoride, it is preferably from 140 to 150 ° C.
- the holding time at the melting temperature is preferably from 8 to 24 hours.
- the crucible lowering speed is preferably 0.1 to 5 mm Z hr.
- the number n s of the maximum diameter d max and per 1 cm 3 of the scatterer in the fluoride crystal is increased, while the production efficiency is less than the lower limit value It tends to decrease.
- the obtained fluoride crystal is gradually cooled to a predetermined temperature (preferably 400 to 75 ° C), but the cooling rate when cooling from 100 ° C to 900 ° C is 0 ° C. It should be 1-5 ° C / hr.
- a predetermined temperature preferably 400 to 75 ° C
- the cooling rate when cooling from 100 ° C to 900 ° C is 0 ° C. It should be 1-5 ° C / hr.
- the cooling rate is too fast, the fluoride crystals are liable to cracks, such as cracks, and the homogeneity of the refractive index is reduced.
- productivity becomes insufficient.
- Such a slow cooling step can be performed, for example, by returning the lowered crucible to the crystal growing apparatus again and controlling the temperature in the apparatus.
- the cooling rate at the time of cooling from the completion of the crystallization to 1000 ° C. is 1 to 15 ° C./hr. If the cooling rate in such a temperature range exceeds the above upper limit value, the fluoride crystal tends to crack, for example, by cracking, and the homogeneity of the refractive index tends to decrease. On the other hand, if the cooling rate is less than the lower limit, operability tends to be poor. For example, when the lowered crystal ingot is raised to near the center of the crystal growing furnace and gradually cooled, it is extremely difficult to rapidly lower the temperature immediately after crystallization due to the structure of the furnace. .
- the temperature decreasing rate in the temperature range from 0 ° C to 75 ° C is preferably 0.1 to 5 ° C / hr (more preferably 0.2 to 2 ° C / hr),
- the rate of temperature decrease from 0 ° C to the end of slow cooling is preferably from 1.0 to 15 ° CZhr.
- the crystal growth furnace is placed in a clean room with a cleanliness that is better than class 1, 000, 000 and equipped with an earthquake-resistant structure, and the temperature in the clean room is adjusted to a predetermined temperature (for example, by controlling the temperature to 25 ⁇ 1 ° C), it is possible to prevent an increase in scatterers due to disturbance from the environment outside the device.
- the pretreatment step and the crystal growth step are performed separately has been described here, it is not always necessary to separately perform the pretreatment step and the crystal growth step in the manufacturing method of the present invention.
- After melting the mixture of the fluoride powder and the scavenger in the process it is also possible to grow the crystal by lowering the crucible containing the melt while controlling the temperature or the temperature decreasing rate as described above.
- the optical member of the present invention can be obtained by cutting out a material having a desired shape from the fluoride crystal (ingot) thus obtained. Clipping position of the optical member from the fluoride crystal is chosen based on the measured value of the number n s of the maximum diameter d max and per 1 cm 3 of the resulting scattering by microscopic observation, by the production method of the present invention Since the obtained fluoride crystals have sufficiently reduced the maximum diameter d max of the scatterers and the number n s per 1 cm 3 , the production yield can be improved and the diameter can be increased. That is, as shown in FIG.
- the coefficient C in the equation (6) for the light is determined in advance. And apply the value of The formula (6), and based on measurements of the outermost diameter d ma x and 1 c m 3 per number n s of Ingo' bets microscopy by obtained scatterer, cut without measuring the internal transmittance You can estimate the internal transmittance of the position - an optical element having a desired optical performance can be easily obtained and reliably c in the present invention, the optical member cut from fluoride crystal, needs If necessary, a processing such as annealing or mirror polishing may be performed.
- acid fluoride Anmoniumu, PTFE, Doing Aniru in the presence of a fluorinating agent such as F 2, CF 4, since the atmosphere is fluorinated, thereby preventing the oxidation of the full Tsu fluoride crystals, d ma it is possible to further reduce the x and n s.
- the same effect can be obtained by replacing the inside of the annealing furnace with an inert gas such as argon without using a fluorinating agent.
- the treatment temperature in the annealing treatment varies depending on the type of the fluoride crystal. For example, in the case of calcium fluoride, the treatment temperature is preferably 100 to 1200 ° C.
- the manufacturing method of the present invention it is possible to sufficiently reduce the number n s per 1 cm 3 of the maximum diameter d ma x ⁇ Pi scattered of scattering bodies contained in the fluoride crystal As a result, it is possible to improve the yield and increase the diameter of the optical member of the present invention when cutting the optical member from the fluoride crystal.
- FIG. 4 is a schematic configuration diagram showing a preferred embodiment of the projection exposure apparatus of the present invention.
- 11 is a light source
- 12 is an illumination optical system
- 12a is an alignment optical system
- 12b is an illumination lens
- 13 is a reticle
- 14 is a reticle stage
- 15 is a projection.
- Optical system, 15a is an aperture
- 15b is a projection lens
- 16 is a wafer
- 17 is a wafer stage
- 18 is a reticule exchange system
- 19 is a wafer stage control system
- 20 is a main control unit. is there.
- the light source 11 for example, a K r F excimer laser, an A r F excimer Laser, etc. F 2 laser can be used.
- the light emitted from the light source 11 becomes uniform illumination light by the illumination lens of the illumination optical system 12, and illuminates the surface of the reticle 13 placed on the reticle stage 14. After passing through the pattern provided on the reticle 13, the light passes through the aperture 15 a of the projection optical system 15 and then is projected onto the surface of the wafer 16 by the projection lens 15 b to form the pattern of the reticle 13. Image the image.
- the illumination optical system 12 is provided with an alignment optical system 12 a for adjusting the relative position between the reticle 13 and the wafer 16.
- a reticle exchange system 18 and a wafer stage control system 19 are provided as accessory devices, and the entire device is controlled by a main control unit 20.
- the light emitted from the light source 11 passes through many optical members such as the alignment optical system 12a, the illumination lens 12b, and the projection lens 15b.
- the optical member of the present invention as at least one of the illumination optical system 12 or the projection optical system 15 or further as the optical member for the alignment optical system 12, the wavelength of 250 nm or less can be obtained. Sufficiently high imaging performance for light can be achieved.
- the illumination optical system 12 or the projection optical system 15 may include an optical member (lens) made of a calcium fluoride crystal that does not satisfy the condition represented by the formula (1).
- the optical path length of the optical member of the present invention is preferably at least 10% (more preferably, at least 50%) of the total optical path length of the optical member made of calcium fluoride crystal.
- FIG. 3 is a schematic configuration diagram illustrating a preferred example of a shadow optical system 15 .
- the projection optical system 15 includes, in order from a reticle R side as a first object, a first lens group G 1 having a positive power and a positive power.
- the object side (reticle R side) and the image side (wafer W side) are almost telecentric and have a reduction magnification.
- the NA of this projection optical system is 0.6, and the projection magnification is 1 Z4.
- L 4 5, L 4 to have L 6 3, L 6 5, L 6 6, 6 lenses of L 6 7 used is made of a fluoride crystal, other lenses are What consists of quartz glass is used.
- the optical path length of the optical member of the present invention is preferably 10% or more (more preferably 50% or more) of the total of the optical path lengths of the six lenses made of calcium fluoride crystal, and Is particularly preferably the optical member of the present invention.
- the temperature was raised and maintained at 300 ° C. for a predetermined time, and impurities such as water and carbon dioxide were volatilized and removed.
- the temperature was gradually increased in order to allow the calcium fluoride powder and the scavenger to sufficiently react with each other. After melting calcium fluoride with C, it was kept at the same temperature for 24 hours to homogenize the viscosity and components of the melt. Thereafter, the temperature in the apparatus was lowered to crystallize the melt.
- the calcium fluoride crystals obtained in the pretreatment step are stored as a raw material bulk in a carbon crucible that has been washed together with calcium fluoride powder and kept in a clean state, and has been cleaned and kept in a clean state. It was introduced into the grown crystal growing equipment. After evacuating the inside of the device, it was heated by a heater, and the temperature was gradually increased while controlling the temperature. After the temperature in the apparatus reached 144 ° C, the melt was held for 24 hours to homogenize the melt, and then the ruppo was pulled down at a pull-down speed of lmmZhr to crystallize the melt.
- the crucible was returned to the crystal growth apparatus, and gradually cooled to room temperature while controlling the temperature in the apparatus to obtain an ingot of calcium fluoride crystal.
- the rate of cooling during slow cooling is 3 ° C / hr up to 100 ° C, 1 ° C / hr up to 900 ° C, and 900 ° C to 5 ° C.
- the temperature was adjusted to 5 ° CZ hr until the temperature reached 500 ° C, and the temperature was lowered from 500 ° C to room temperature by leaving the furnace inside.
- a material with a diameter of 20 O mm and a thickness of 5 O mm was cut out from the lower half of the ingot, introduced into an annealing furnace together with a fluorinating agent (acid ammonium fluoride), and the furnace was evacuated and then raised.
- Temperature rate 5 The temperature was raised to 105 Q ° C at TCZhr and maintained at the same temperature for 24 hours. Thereafter, the temperature was gradually lowered to 900 ° C at a rate of 2 ° C hr, and the temperature was lowered at 5 ° C. C was gradually cooled to room temperature to obtain the desired optical member.
- the internal transmittance for light having a wavelength of 19.3 nm showed a high value of 99.9% / cra.
- Example 2 To 50 kg of the same calcium fluoride powder as in Example 1, 1.6 g (about 1 mol%) of lead fluoride was added as a scavenger, followed by sufficient stirring. The mixture was co-washed with a calcium fluoride raw material, placed in a clean carbon crucible, and introduced into a cleaned, clean pretreatment device. Here, in order to avoid mixing of impurity elements and dust at the time of mixing / stirring and at the time of loading the raw materials, these operations were performed in a class 10/000 clean / frame. After evacuating the inside of the apparatus, the apparatus was kept at 300 ° C. for a predetermined time, and impurities such as water and carbon dioxide were volatilized and removed.
- impurities such as water and carbon dioxide were volatilized and removed.
- the calcium fluoride crystals obtained in the pretreatment process are used as raw material, and are stored in a clean carbon crucible that has been washed together with calcium fluoride raw material, and then cleaned and cleaned. It was introduced into the sample room of the kept crystal growth equipment.
- the removal of calcium fluoride crystals from the crucible after the pretreatment step and the filling of the calcium fluoride crystal into the crucible during the growth step are of class 10 and 0. Performed in a clean room at 00.
- the crystal growth equipment is class 10
- the temperature was gradually increased while controlling the temperature by heating with a heater, and was maintained for 24 hours after the temperature reached 144 ° C. Was performed.
- the melt was crystallized by lowering the ruppo at a lowering speed of 0.3 mmZhr.
- the crucible was returned to the crystal growth apparatus, and gradually cooled to room temperature while controlling the temperature in the apparatus to obtain an ingot of calcium fluoride crystal.
- the rate of cooling during slow cooling is 3 ° C / hr, up to 100 ° C, 10 ° C.
- the diameter and thickness of the upper and lower halves of this ingot are 200 mm and 200 mm, respectively.
- a 50 mm material was cut out, introduced into an annealing furnace together with a fluorinating agent, and the inside of the furnace was evacuated.Then, the temperature was raised to 150 ° C at a rate of 50 ° C / hr and the same temperature was reached. For 24 hours. After that, the temperature was gradually cooled to 900 ° C. at a temperature lowering rate of 2 ° C./hr, and further gradually cooled to room temperature at a temperature lowering rate of 5 ° C./hr to obtain a target optical member.
- the internal transmittance for light with a wavelength of 193 nm was as high as 99.9% / cm.
- Table 1 shows the amount of birefringence, the difference in refractive index, and the amount of decrease in transmittance in the axial or radial direction.
- an optical member was produced in the same manner as in Example 1 except that the temperature reduction rate up to 500 ° C. after crystallization was set to 30 ° C./hr.
- the resulting maximum diameter of the scatterer included in the optical member d ma x and 1 cm 3 of Pieces number n s, and the wavelength 1 9 3 nm light internal transmittance against the (A r F excimer laser light), light Table 1 shows the amount of birefringence, the difference in refractive index, and the amount of decrease in transmittance in the axial or radial direction.
- Example 1 Comparative Example 1 Comparative Example 2 ⁇ diameter d raax [ju
- Example 1 fi 7 L 6 5 L 6 6 L internal transmittance six lenses and to any other lens use the optical member of Example 1 fi 7, including a quartz glass lens (scattering loss: about 9 9.8% / cm), the projection exposure apparatus shown in FIG. 4 was manufactured.
- a projection exposure apparatus was manufactured in the same manner as in Example 3 except that the optical member obtained in Comparative Example 1 was used instead of the optical member of Example 1.
- the present invention has sufficiently high optical performance (such as internal transmittance) for light having a wavelength of 25011 m or less, and has a high yield when cutting out from a fluoride crystal material.
- optical performance such as internal transmittance
- an optical member capable of improving and increasing the diameter, a method of manufacturing the same, and a projection exposure apparatus using the optical member. Therefore, according to the present invention, high forming performance in microfabrication technology on a wafer is realized.
Description
Claims
Priority Applications (6)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
DE60239921T DE60239921D1 (de) | 2001-03-15 | 2002-03-13 | Ür eine projektionsvorrichtung |
JP2002575675A JP4172273B2 (ja) | 2001-03-15 | 2002-03-13 | 光学部材およびその製造方法、投影露光装置 |
US10/276,434 US6850371B2 (en) | 2001-03-15 | 2002-03-13 | Optical member and method of producing the same, and projection aligner |
AT02705138T ATE508378T1 (de) | 2001-03-15 | 2002-03-13 | Verfahren zur herstellung eines optischen glieds für eine projektionsvorrichtung |
EP02705138A EP1369708B1 (en) | 2001-03-15 | 2002-03-13 | Method of producing an optical member for a projection aligner |
US10/973,260 US7166163B2 (en) | 2001-03-15 | 2004-10-27 | Optical member, method of manufacturing the same, and projection exposure system |
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP2001-74127 | 2001-03-15 | ||
JP2001074127 | 2001-03-15 |
Related Child Applications (2)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
US10/276,434 A-371-Of-International US6850371B2 (en) | 2001-03-15 | 2002-03-13 | Optical member and method of producing the same, and projection aligner |
US10/973,260 Division US7166163B2 (en) | 2001-03-15 | 2004-10-27 | Optical member, method of manufacturing the same, and projection exposure system |
Publications (1)
Publication Number | Publication Date |
---|---|
WO2002077676A1 true WO2002077676A1 (fr) | 2002-10-03 |
Family
ID=18931447
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
PCT/JP2002/002368 WO2002077676A1 (fr) | 2001-03-15 | 2002-03-13 | Element optique, procede permettant de produire cet element, et machine de projection |
Country Status (6)
Country | Link |
---|---|
US (2) | US6850371B2 (ja) |
EP (1) | EP1369708B1 (ja) |
JP (1) | JP4172273B2 (ja) |
AT (1) | ATE508378T1 (ja) |
DE (1) | DE60239921D1 (ja) |
WO (1) | WO2002077676A1 (ja) |
Cited By (5)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JP2006315916A (ja) * | 2005-05-13 | 2006-11-24 | Hitachi Chem Co Ltd | フッ化物単結晶及びその育成方法、並びにレンズ |
JP2006315918A (ja) * | 2005-05-13 | 2006-11-24 | Hitachi Chem Co Ltd | フッ化物単結晶及びその育成方法、並びにレンズ |
JP2006315917A (ja) * | 2005-05-13 | 2006-11-24 | Hitachi Chem Co Ltd | フッ化物単結晶及びその育成方法、並びにレンズ |
JP2007008744A (ja) * | 2005-06-29 | 2007-01-18 | Hitachi Chem Co Ltd | フッ化物単結晶の製造方法 |
US8016942B2 (en) | 2004-12-22 | 2011-09-13 | Tokuyama Corporation | Process for producing metal fluoride single crystal |
Families Citing this family (12)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US6683710B2 (en) | 2001-06-01 | 2004-01-27 | Optical Research Associates | Correction of birefringence in cubic crystalline optical systems |
AU2002305890A1 (en) * | 2001-06-08 | 2002-12-23 | Hair Patrol Llc | Animal bathing system |
US7453641B2 (en) * | 2001-10-30 | 2008-11-18 | Asml Netherlands B.V. | Structures and methods for reducing aberration in optical systems |
US6970232B2 (en) * | 2001-10-30 | 2005-11-29 | Asml Netherlands B.V. | Structures and methods for reducing aberration in integrated circuit fabrication systems |
US6995908B2 (en) * | 2001-10-30 | 2006-02-07 | Asml Netherlands B.V. | Methods for reducing aberration in optical systems |
JP2003238152A (ja) * | 2002-02-19 | 2003-08-27 | Canon Inc | 結晶製造方法 |
JP2005534611A (ja) * | 2002-08-07 | 2005-11-17 | コーニング インコーポレイテッド | <200nmレーザリソグラフィーのための散乱のないUV光学フッ化物結晶素子および方法 |
US6958864B2 (en) * | 2002-08-22 | 2005-10-25 | Asml Netherlands B.V. | Structures and methods for reducing polarization aberration in integrated circuit fabrication systems |
US7033433B2 (en) * | 2003-01-24 | 2006-04-25 | Corning Incorporated | Crystal growth methods |
US7399360B2 (en) * | 2003-07-03 | 2008-07-15 | Hitachi Chemical Company, Ltd. | Crucible and method of growing single crystal by using crucible |
US20070222962A1 (en) * | 2004-08-10 | 2007-09-27 | Nikon Corporation | Illumination Optical Equipment, Exposure System and Method |
DE102005044697B4 (de) * | 2005-09-19 | 2011-07-21 | Hellma Materials GmbH & Co. KG, 07745 | Verfahren zur Herstellung von CAF2-Einkristalle mit erhöhter Laserstabilität, CAF2-Einkristalle mit erhöhter Laserstabilität und ihre Verwendung |
Citations (8)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JPH09315894A (ja) * | 1996-03-22 | 1997-12-09 | Canon Inc | フッ化物結晶及びフッ化物結晶レンズの製造方法 |
EP0869203A2 (en) * | 1997-03-31 | 1998-10-07 | Canon Kabushiki Kaisha | Fluoride crystal, optical article, and production method |
EP0939147A2 (en) * | 1998-02-26 | 1999-09-01 | Nikon Corporation | A manufacturing method for calcium fluoride and calcium fluoride for photolithography |
EP0972863A1 (en) | 1998-07-16 | 2000-01-19 | Nikon Corporation | Method for annealing single crystal fluoride and method for manufacturing the same |
EP0995820A1 (en) * | 1998-10-21 | 2000-04-26 | Canon Kabushiki Kaisha | Fluoride refining method and fluoride crystal manufacturing method, and optical part and aligner using same |
EP1026548A2 (en) * | 1999-02-03 | 2000-08-09 | Nikon Corporation | Optical member for photolithography and photolithography apparatus |
JP2000256095A (ja) * | 1999-03-11 | 2000-09-19 | Canon Inc | フッ化物結晶の熱処理方法 |
JP2000281492A (ja) * | 1999-03-30 | 2000-10-10 | Canon Inc | フッ化物結晶の熱処理方法、光学部品の作製方法及び光学装置 |
Family Cites Families (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JPH1160382A (ja) | 1997-08-05 | 1999-03-02 | Nikon Corp | 蛍石単結晶、およびこれを用いた光リソグラフィー装置 |
JPH11240798A (ja) | 1998-02-26 | 1999-09-07 | Nikon Corp | 蛍石の製造方法及び光リソグラフィー用の蛍石 |
TW581747B (en) * | 1999-02-16 | 2004-04-01 | Nikon Corp | Synthetic quartz glass optical member for ultraviolet light |
US6683714B1 (en) * | 1999-06-25 | 2004-01-27 | Corning Incorporated | Birefringence minimizing fluoride crystal optical VUV microlithography lens elements and optical blanks |
-
2002
- 2002-03-13 JP JP2002575675A patent/JP4172273B2/ja not_active Expired - Fee Related
- 2002-03-13 US US10/276,434 patent/US6850371B2/en not_active Expired - Lifetime
- 2002-03-13 DE DE60239921T patent/DE60239921D1/de not_active Expired - Lifetime
- 2002-03-13 EP EP02705138A patent/EP1369708B1/en not_active Expired - Lifetime
- 2002-03-13 WO PCT/JP2002/002368 patent/WO2002077676A1/ja active Application Filing
- 2002-03-13 AT AT02705138T patent/ATE508378T1/de not_active IP Right Cessation
-
2004
- 2004-10-27 US US10/973,260 patent/US7166163B2/en not_active Expired - Lifetime
Patent Citations (8)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JPH09315894A (ja) * | 1996-03-22 | 1997-12-09 | Canon Inc | フッ化物結晶及びフッ化物結晶レンズの製造方法 |
EP0869203A2 (en) * | 1997-03-31 | 1998-10-07 | Canon Kabushiki Kaisha | Fluoride crystal, optical article, and production method |
EP0939147A2 (en) * | 1998-02-26 | 1999-09-01 | Nikon Corporation | A manufacturing method for calcium fluoride and calcium fluoride for photolithography |
EP0972863A1 (en) | 1998-07-16 | 2000-01-19 | Nikon Corporation | Method for annealing single crystal fluoride and method for manufacturing the same |
EP0995820A1 (en) * | 1998-10-21 | 2000-04-26 | Canon Kabushiki Kaisha | Fluoride refining method and fluoride crystal manufacturing method, and optical part and aligner using same |
EP1026548A2 (en) * | 1999-02-03 | 2000-08-09 | Nikon Corporation | Optical member for photolithography and photolithography apparatus |
JP2000256095A (ja) * | 1999-03-11 | 2000-09-19 | Canon Inc | フッ化物結晶の熱処理方法 |
JP2000281492A (ja) * | 1999-03-30 | 2000-10-10 | Canon Inc | フッ化物結晶の熱処理方法、光学部品の作製方法及び光学装置 |
Cited By (6)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US8016942B2 (en) | 2004-12-22 | 2011-09-13 | Tokuyama Corporation | Process for producing metal fluoride single crystal |
JP2006315916A (ja) * | 2005-05-13 | 2006-11-24 | Hitachi Chem Co Ltd | フッ化物単結晶及びその育成方法、並びにレンズ |
JP2006315918A (ja) * | 2005-05-13 | 2006-11-24 | Hitachi Chem Co Ltd | フッ化物単結晶及びその育成方法、並びにレンズ |
JP2006315917A (ja) * | 2005-05-13 | 2006-11-24 | Hitachi Chem Co Ltd | フッ化物単結晶及びその育成方法、並びにレンズ |
JP2007008744A (ja) * | 2005-06-29 | 2007-01-18 | Hitachi Chem Co Ltd | フッ化物単結晶の製造方法 |
JP4591236B2 (ja) * | 2005-06-29 | 2010-12-01 | 日立化成工業株式会社 | フッ化物単結晶の製造方法 |
Also Published As
Publication number | Publication date |
---|---|
US6850371B2 (en) | 2005-02-01 |
US20050081777A1 (en) | 2005-04-21 |
DE60239921D1 (de) | 2011-06-16 |
JP4172273B2 (ja) | 2008-10-29 |
JPWO2002077676A1 (ja) | 2004-07-15 |
EP1369708A1 (en) | 2003-12-10 |
US7166163B2 (en) | 2007-01-23 |
US20030089299A1 (en) | 2003-05-15 |
ATE508378T1 (de) | 2011-05-15 |
EP1369708A4 (en) | 2008-12-31 |
EP1369708B1 (en) | 2011-05-04 |
Similar Documents
Publication | Publication Date | Title |
---|---|---|
WO2002077676A1 (fr) | Element optique, procede permettant de produire cet element, et machine de projection | |
EP1394590A1 (en) | Method for growing a calcium fluoride crystal | |
EP1154046B1 (en) | Fluoride crystalline optical lithography lens element blank | |
US7754011B2 (en) | Method of manufacturing a calcium fluoride single crystal | |
KR20000010474A (ko) | 불화물 단일결정의 열처리방법 및 제조방법 | |
EP0987538A1 (en) | Light-transmitting optical element for optical lithography apparatus | |
JP2005503313A (ja) | フォトリソグラフィ用uv光透過フッ化物結晶 | |
JP2007332000A (ja) | 人工水晶部材およびその製造方法、ならびにそれを用いた光学素子 | |
JP4092515B2 (ja) | 蛍石の製造方法 | |
WO2002085808A1 (fr) | Element en verre de silice et aligneur de projection | |
JP2005001933A (ja) | 金属フッ化物体とその製造方法 | |
US7014703B2 (en) | Method for annealing group IIA metal fluoride crystals | |
JP4419291B2 (ja) | フッ化物単結晶の検査方法 | |
JP2008201644A (ja) | BaLiF3単結晶体の製造方法 | |
JP4360161B2 (ja) | フッ化物結晶から形成された光学部材の製造方法 | |
JP2005534611A (ja) | <200nmレーザリソグラフィーのための散乱のないUV光学フッ化物結晶素子および方法 | |
JP5682894B2 (ja) | 蛍石 | |
JP2012096955A (ja) | フッ化金属単結晶の熱処理方法 | |
JP2004307289A (ja) | 結晶製造方法 | |
JP2652847C (ja) |
Legal Events
Date | Code | Title | Description |
---|---|---|---|
ENP | Entry into the national phase |
Ref country code: JP Ref document number: 2002 575675 Kind code of ref document: A Format of ref document f/p: F |
|
AK | Designated states |
Kind code of ref document: A1 Designated state(s): JP US |
|
AL | Designated countries for regional patents |
Kind code of ref document: A1 Designated state(s): AT BE CH CY DE DK ES FI FR GB GR IE IT LU MC NL PT SE TR |
|
WWE | Wipo information: entry into national phase |
Ref document number: 10276434 Country of ref document: US |
|
121 | Ep: the epo has been informed by wipo that ep was designated in this application | ||
WWE | Wipo information: entry into national phase |
Ref document number: 2002705138 Country of ref document: EP |
|
WWP | Wipo information: published in national office |
Ref document number: 2002705138 Country of ref document: EP |