Classifications

• • 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
  • G03F7/70341—Details of immersion lithography aspects, e.g. exposure media or control of immersion liquid supply
• • 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
  • G03F7/70966—Birefringence

Definitions

• the invention relates to an imaging system, in particular a projection objective of a microlithographic projection exposure apparatus.
• the invention relates to a projection lens which allows the use of high-index crystal materials while limiting the negative impact of intrinsic birefringence on the imaging properties.
• a “refractive index” is defined herein as “high” if its value at the given wavelength exceeds that of quartz, with a value of about 1.56 at a wavelength of 193 nm. "A number of materials are known whose refractive index is DUV and VUV wavelengths ( ⁇ 250nm) larger is about 1.6, for example, magnesium spinel having a refractive index of about 1.87 at a wavelength of 193 nm, or magnesium oxide whose refractive index at 193 nm is about 2.0.
• a problem with using these materials as lens elements is that they have intrinsic birefringence due to their cubic crystal structure, which increases with low wavelength, e.g. Measurements of the IDB-induced delay for magnesium spinel at a wavelength of 193nm have given a value of 52 nm / cm, and the IDB-induced delay for magnesia at 193nm was estimated to be about 72 nm / cm. Depending on the design conditions, such a delay can lead to lateral beam deviations in the image field which are 3 to 5 times the pattern width to be imaged.
• the object of the present invention is to provide an imaging system, in particular a projection objective of a microlithographic projection exposure apparatus, which enables the use of high-index crystal materials while limiting the negative influence of intrinsic birefringence.
• an imaging system in particular a projection objective of a microlithographic projection exposure apparatus, comprises at least one optical element which has a cubic crystal material which has a refractive index n greater than 1.6 at a predetermined working wavelength and has a numerical aperture NA on the image side , wherein the difference (n-NA) between the refractive index n and the numerical aperture NA of the imaging system is at most 0.2.
• the invention is initially based on the recognition that the effect of intrinsic birefringence does not increase linearly with shorter wavelength, but rather begins gradually and then increases dramatically with decreasing wavelength. This non-linearity is all the more pronounced as the respective working wavelength approaches the absorption edge (in the UV range) for the material in question.
• the potential of materials with the highest possible refractive indices is not exhausted, but the refractive index is chosen just as high (and not higher) as is necessary to obtain geometrically projection light even under the maximum beam angles
• Coupling projection lens and bring to imaging At the same time, according to the invention, the more moderate requirement for the height of the refractive index is exploited in order to select such a crystal material whose absorption edge lies deeper in the UV, as a result of which the intrinsic birefringence in the working wavelength has increased even smaller or less than in the case of a material with higher absorption edge is the case.
• an imaging system in particular a projection objective of a microlithographic projection exposure apparatus, comprises at least one optical element which has a cubic crystal material having a refractive index n at a predetermined working wavelength and has a picture-side numerical aperture NA of at least 1.50, the difference (n-NA) between the refractive index n and the numerical aperture NA of the imaging system is not more than 0.2.
• an imaging system in particular a projection objective of a microlithographic projection exposure apparatus, comprises at least one optical element which has a cubic crystal material which has a refractive index n at a given operating wavelength and has a planar light exit surface, and has a numerical aperture NA on the image side is smaller than the refractive index n, wherein the difference (n-NA) between the refractive index n and the numerical aperture NA of the imaging system is at most 0.2.
• the difference (n-NA) between the refractive index n of the optical element and the numerical aperture NA of the imaging system is in the range of 0.05 to 0.20, preferably in the range of 0.05 to 0.15, and more preferably in the range of 0.05 to 0.10. It is through the upper
• Limit of the refractive index achieves a limitation of the intrinsic birefringence, while the limit of the refractive index, a limitation of the total lens volume of the projection lens is achieved.
• the cubic crystal material has an oxide, for which a sufficient transmission at a comparatively high refractive index was obtained.
• the cubic crystal material comprises sapphire (Al 2 O 3 ) and a potassium or calcium oxide.
• the cubic crystal material preferably comprises at least one material selected from the group consisting of 7Al 2 O 3 -12CaO, Al 2 O 3 -K 2 O, Al 2 O 3 -3CaO, Al 2 O 3 -SiO 2 KO , Al 2 O 3 -SiO 2 -2K and Al 2 O 3 -3CaO6H 2 O.
• the proportion of sapphire (Al 2 O 3 ) causes a widening of the band gap or a shift of the absorption edge in the UV range while increasing the refractive index, so that additional components reduce the refractive index
• the cubic crystal material comprises calcium, sodium and silica.
• the cubic crystal material preferably comprises at least one material selected from the group consisting of CaNa 2 SiO 4 and CaNa 4 Si 3 O 9 .
• the cubic crystal material comprises at least one material selected from the group consisting of Sr (NO 3 ) 2 , MgONa 2 O-SiO 2 and Ca (NO 3 ) 2 .
• the optical element is preferably the image-side last refractive lens of the imaging system.
• the optical element is composed of a first partial element with refractive power and a second, substantially non-frictional partial element.
• the first subelement is preferably a substantially plano-convex lens
• the second subelement is a plane-parallel plate.
• Such a construction of the optical element has the advantage of a particularly effective correction of the spherical aberration, which is typically the largest contribution to aberrations to be handled at high apertures.
• a correction of the spherical aberration which is uniform over the image field, can be achieved in an advantageous manner, in particular by means of the plane-parallel subelement.
• the second substantially non-refractive element part in a structure of mutually rotated portions of the same crystal section for the respective subregions in each case substantially equal compensation paths, so that extent
• Sub-element to provide a second material with a greater refractive index than the material in the first region, said larger refractive index may also lie beyond the above-mentioned distance from the numerical aperture in particular.
• the second material is selected from the group of magnesium spinel (MgAl 2 O 4 ), yttrium aluminum garnet (Y 3 Al 5 Oi 2 ), MgO and scandium aluminum garnet (Sc 3 Al 5 Oi 2 ).
• the second subelement has an element axis and at least two subregions which have the same crystal section and are arranged rotated relative to one another around the element axis.
• the second subelement has an element axis and at least four subregions, wherein a first subarea and a second subarea each have a (111) crystal section and are mutually displaceable
• the invention further relates to a microlithographic projection exposure apparatus, a method for producing microlithographic components and a microstructured component.
• the invention also relates to the use of a material as starting material for producing an optical material
• the material being selected from the group consisting of 7Al 2 O 3 -12CaO, Al 2 O 3 -K 2 O, Al 2 O 3 -3CaO, Al 2 O 3 -SiO 2 KO, Al 2 O 3 -SiO 2 -2K, Al 2 O 3 -3CaO 6H 2 O, CaNa 2 SiO 4 , CaNa 4 Si 3 O 9 , Sr (NO 3 ) 2 , MgONa 2 O-SiO 2 and Ca (NO 3 ) 2 contains.
• FIG. 1 is a schematic representation for explaining the structure of an optical element in an imaging system according to the invention in a preferred embodiment
• FIG. 2 shows a schematic representation of the basic structure of a microlithography projection exposure apparatus which may have a projection objective according to the invention
• Fig. 1 shows only schematically the structure of an optical element 100 in an imaging system according to the invention.
• the optical element 100 is preferably in particular the image-side last lens in a microlithographic projection objective whose fundamental structure is explained below with reference to FIG. 2.
• the optical element 100 is constructed from a first partial element 10 in the form of a plano-convex lens and a second partial element 20 in the form of a plane-parallel plate, the light entry surface of the second partial element 20 being arranged directly adjacent to the light exit surface of the first partial element 10 and is preferably blown up on this.
• Fig. 1 Also shown schematically in Fig. 1 is the structure of the second sub-element 20 from a total of four sub-areas in the form of plane-parallel sub-plates 21, 22, 23 and 24.
• the second partial element 20 has a total of two partial regions, which have the same crystal section and are arranged rotated relative to one another around the element axis.
• the first sub-element 10 is made of a cubic crystalline material having such a refractive index, which is chosen as a function of the numerical aperture NA of the imaging system so that the difference (n-NA) between this refractive index n and the numerical aperture NA of the image maximum system is 0.2.
• a projection exposure apparatus 200 has an illumination device 201 and a projection objective 202.
• the projection objective 202 comprises a lens arrangement 203 with an aperture stop AP, wherein the lens arrangement 203, which is only schematically indicated, forms an optical arrangement 203
• Axis OA is defined. Between the illumination device 201 and the projection lens 202, a mask 204 is arranged, which is held by means of a mask holder 205 in the beam path. Such masks 204 used in microlithography have a structure in the micrometer-to-nanometer range, which is provided by means of the projection objective 202. For example, by a factor of 4 or 5 reduced to an image plane IP is mapped. In the image plane IP, a photosensitive substrate 206, or a wafer, positioned by a substrate holder 207 is held.
• the minimum structures which can still be resolved depend on the wavelength ⁇ of the light used for the illumination and on the image-side numerical aperture of the projection objective 202, the maximum achievable resolution of the projection exposure apparatus 200 decreasing with the wavelength ⁇ of the illumination device 201 and increasing with the image numerical aperture of the projection lens 202 increases.
• the projection lens 202 is configured as an imaging system according to the present invention.
• Fig. 2 only schematically a possible, approximate position of an optical element 100 according to the invention indicated by dashed lines, wherein the optical element is arranged according to a preferred embodiment, the image last optical element of the projection lens 202 and thus in the region of relatively high aperture angle.
• the optical element has the structure explained with reference to FIG. 1 and is thus constructed in particular of a first subelement 10 in the form of a plano-convex lens and a second subelement 20 in the form of a plane-parallel plate according to the embodiments described above.

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• Physics & Mathematics (AREA)
• General Physics & Mathematics (AREA)
• Health & Medical Sciences (AREA)
• Engineering & Computer Science (AREA)
• Environmental & Geological Engineering (AREA)
• Epidemiology (AREA)
• Public Health (AREA)
• Chemical & Material Sciences (AREA)
• Crystallography & Structural Chemistry (AREA)
• Optics & Photonics (AREA)
• Lenses (AREA)

Priority Applications (5)

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Citations (5)

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• 2006
  • 2006-08-04 JP JP2008525556A patent/JP2009505124A/ja active Pending
  • 2006-08-04 AT AT06778169T patent/ATE511124T1/de active
  • 2006-08-04 EP EP06778169A patent/EP1913445B1/de not_active Not-in-force
  • 2006-08-04 WO PCT/EP2006/065070 patent/WO2007017473A1/de not_active Ceased
  • 2006-08-04 CN CN2006800296095A patent/CN101243359B/zh not_active Expired - Fee Related
  • 2006-08-04 KR KR1020087001045A patent/KR20080028429A/ko not_active Ceased
• 2008
  • 2008-02-07 US US12/027,731 patent/US20080182210A1/en not_active Abandoned

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