WO2008101676A2 - Objectif de projection catadioptrique avec ouverture numérique ultra-élevée - Google Patents

Objectif de projection catadioptrique avec ouverture numérique ultra-élevée Download PDF

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Publication number
WO2008101676A2
WO2008101676A2 PCT/EP2008/001299 EP2008001299W WO2008101676A2 WO 2008101676 A2 WO2008101676 A2 WO 2008101676A2 EP 2008001299 W EP2008001299 W EP 2008001299W WO 2008101676 A2 WO2008101676 A2 WO 2008101676A2
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WO
WIPO (PCT)
Prior art keywords
projection objective
optical element
image
catadioptric
objective according
Prior art date
Application number
PCT/EP2008/001299
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English (en)
Other versions
WO2008101676A3 (fr
Inventor
Aurelian Dodoc
Original Assignee
Carl Zeiss Smt Ag
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Application filed by Carl Zeiss Smt Ag filed Critical Carl Zeiss Smt Ag
Publication of WO2008101676A2 publication Critical patent/WO2008101676A2/fr
Publication of WO2008101676A3 publication Critical patent/WO2008101676A3/fr

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Classifications

    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B17/00—Systems with reflecting surfaces, with or without refracting elements
    • G02B17/08—Catadioptric systems
    • G02B17/0804—Catadioptric systems using two curved mirrors
    • G02B17/0812—Catadioptric systems using two curved mirrors off-axis or unobscured systems in which all of the mirrors share a common axis of rotational symmetry
    • 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
    • G03F7/70225—Optical aspects of catadioptric systems, i.e. comprising reflective and refractive elements
    • 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
    • G03F7/70275—Multiple projection paths, e.g. array of projection systems, microlens projection systems or tandem 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
    • G03F7/70216—Mask projection systems
    • G03F7/70341—Details of immersion lithography aspects, e.g. exposure media or control of immersion liquid supply
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B13/00—Optical objectives specially designed for the purposes specified below
    • G02B13/22—Telecentric objectives or lens systems

Definitions

  • the present invention relates to a catadioptric projection objective.
  • the projection objective may be used in a microlithography projection exposure machine.
  • the invention relates to a projection objective configured for immersion operation in an aperture range where the image-side numerical aperture NA is greater than 1.0.
  • the image-side numerical aperture NA is limited by the refractive index of the surrounding medium in image space adjacent to the image surface of the projection objective.
  • the theoretically possible numerical aperture NA is limited by the refractive index of the immersion medium.
  • the immersion medium can be a liquid or a solid.
  • An immersion liquid is disposed between an exit surface of the projection objective and the surface of the substrate to be exposed, which is arranged in the image surface.
  • a planar exit surface of the projection objective is arranged at a working distance smaller than the operating wavelength to the substrate to be exposed such that evanescent fields emerging from the exit surface can be used for imaging (near-field lithography).
  • Solid immersion with touching contact between the exit surface of the projection objective and the substrate is also possible. .
  • the refractive index of the material of the last optical element of the projection objective adjacent to the image surface acts as a limitation if the design of the exit surface of the projection objective is to be planar or only weakly curved.
  • the planar design is advantageous, for example, for measuring the distance between wafer and objective, for hydrodynamic behavior of the immersion medium between the wafer to be exposed and the exit surface of the projection objective, and for their cleaning.
  • the exit surface must be of planar design for solid immersion, in particular, in order to expose the wafer, which is likewise planar.
  • a last optical element designed as a plano-convex lens having a spherically or aspherically curved entry surface and a planar exit surface adjacent to the image surface of the projection objective.
  • the exit surface of the last optical element is a planar surface and an immersion liquid is used
  • a maximum aperture of rays within the last optical element corresponds to the maximum aperture of rays in the immersion liquid and to the maximum NA of the projection objective.
  • the degree of curvature of the curved entry surface influences the diameters of the lenses immediately upstream (on the object-side) of the last optical element.
  • US patent application US 2005/0179994 A1 shows catadioptric projection objectives designed for immersion lithography.
  • a last optical element shaped as a plano-convex lens serves as a field correcting optic and is appended to a Mangin mirror in an immersive configuration to raise the numerical aperture.
  • the optical connection between the Mangin mirror and the plano-convex field correcting optic is arranged to control reflection angles by limiting angles of incidence or refractive index differences.
  • It is one object of the invention to provide a catadioptric projection objective suitable for immersion lithography at NA>1 which allows obtaining very high image-side numerical aperture NA close to the physical limits provided by the transparent optical material at the image-side end of the projection objective. It is another object of the invention to provide a catadioptric projection objective having an image-side numerical aperture NA>1.4 or greater at an operating wavelength ⁇ 193 nm.
  • this invention provides a catadioptric projection objective comprising: a plurality of optical elements arranged to image a pattern provided in an object surface of the projection objective onto an image surface of the projection objective, _ .
  • the optical elements including a catadioptric optical element having a body made from a transparent material, a first surface on an object-side of the body and a second surface opposite to the first surface; wherein the second surface has a transmissive portion in a central region and a concave reflective portion in a zone around the transmissive portion; and wherein the first surface has a transmissive zone configured to transmit radiation coming from the object surface towards the second surface and oriented relative to the second surface such that at least a portion of radiation reflected by the reflective portion of the second surface is totally reflected by the transmissive portion of the first surface towards the transmissive portion of the second surface.
  • the transmissive portion of the second surface forms the exit surface of the catadioptric optical element.
  • the catadioptric optical element may contribute to generating large aperture rays directed at the exit surface of the catadioptric optical element while at the same time lens diameters in a region immediately upstream of the catadioptric optical element may be kept relatively small.
  • the concave reflective portion of the second surface which is concave if viewed from the inside of the body, provides positive optical power to generate a strongly convergent beam having a large aperture.
  • the concave reflective portion contributes to correction of image field curvature, thereby increasing the degrees of freedom available for correction purposes within the projection objective having the catadioptric last optical element.
  • a radiation beam formed by the optical elements upstream of the catadioptric optical element may enter the catadioptric optical element outside the optical axis through the transmissive portion of the first surface.
  • Entering rays may have relatively small aperture angles relative to the optical axis.
  • rays may be essentially parallel to the optical axis or may be slightly conver- _
  • a first reflection on the concave reflective portion of the second surface guides radiation at large aperture angles inwardly towards the optical axis.
  • the first reflection typically increases the aperture angles significantly.
  • a second reflection of radiation reflected by the concave reflective portion occurs on the first surface.
  • Radiation reflected by the first surface is directed at high aperture towards the transmissive portion of the second surface, which forms the exit surface of the catadioptric optical element.
  • a radiation beam having high aperture is formed by a zig-zag path of radiation within the catadioptric optical element.
  • the projection objective has an exit-side pupil surface, which is the pupil surface closest to the image surface.
  • a single pupil surface is formed, which corresponds to the exit-side pupil surface.
  • the exit-side pupil surface is the pupil surface closest to the image surface.
  • the catadioptric optical element is arranged entirely between the exit-side pupil surface and the image surface. In this case a convergent beam directed towards the image surface may enter the catadioptric optical element, which then increases the aperture angles of radiation.
  • the catadioptric optical element forms a last optical element of the projection objective arranged directly adjacent to the image surface.
  • the transmissive portion of the second surface forms the exit surface of the projection objective.
  • At least one optical element is arranged between the catadioptric optical element and the image surface.
  • An optical element arranged between the catadioptric optical element and the image surface may form the last optical element of the projection objective arranged directly adjacent to the image surface.
  • At least one plane parallel plate is arranged between the catadioptric optical element and the image surface. At least on surface of the plane parallel plate may have an aspheric shape to improve correction.
  • At least one lens element with substantial refractive power is arranged between the catadioptric optical element and the image surface.
  • the lens element may have positive refractive power.
  • the lens element may essentially be designed as a plano-convex lens having a curved entry surface facing the catadioptric optical element and an essentially planar exit surface facing the image surface.
  • a thin layer of high-index medium such as an immersion liquid, may be arranged between the catadioptric optical element and the last optical element of the projection objective.
  • the last optical element may have an immersion liquid on both sides (object-side and image-side) during operation of the projection objective.
  • the index of refraction of that optical element adjacent to the image surface may be greater than the index of refraction of the material forming the body of the catadioptric optical element.
  • the catadioptric optical element may have various shapes depending on specific design requirements.
  • the first surface (on the object-side of the catadioptric optical element) is a planar surface. Where the first surface (provided for totally reflecting at least a portion of radiation incident from the image-side thereof) is substantially flat, the conditions for total reflection are essentially uniform in the entire zone where total reflection occurs, thereby minimizing non-uniformity of radiation intensity of reflected radiation.
  • a surface is "planar” or “substantially flat” if the radius of curvature is such that a distance (measured parallel to the optical axis) between the planar surface and a touching plane oriented orthogonal to the optical axis is less than 10 ⁇ m in the entire area of the planar surface.
  • the first surface (on the object-side of the catadioptric last element) is concave towards the second surface such that a center of curvature of the first surface is on the image-side thereof.
  • the terms “concave” and “convex” particularly refer to the optical effect of a surface. A surface which is convex when viewed from the outside becomes concave when viewed from the inside of a lens. Where the first surface is concave in this sense, a radial extension of the totally reflecting zone may be increased, thereby increasing the fraction of radiation which is totally reflected essentially without intensity losses.
  • a concave first surface provides overcorrection of image field curvature and helps to reduce overall mass of the projection objective since positive optical power provided by the concave first surface allows to reduce positive optical power in other parts of the projection objective.
  • the body of the catadioptric last optical element may be substantially formed like a biconvex lens at least in zones outside the optical axis.
  • the first surface is convex towards the second surface, thereby forming a curved surface having a center of curvature on the object-side of the catadioptric optical element.
  • a convex shape of the first surface increases the radial width of the zone exhibiting total reflection and provides an undercorrecting influence on the image field curvature.
  • the body of the last optical element may be essentially formed like a meniscus lens where both surfaces have the same sense of curvature.
  • the second surface is substantially planar in the region of the transmissive portion, thereby providing an essentially planar exit surface of the catadioptric optical element.
  • a layer thickness of an immersion fluid introduced between the exit surface of the projection objective and the substrate to be exposed may be uniform. This may be preferable from an optical point of view to obtain uniform imaging conditions throughout the image field. Further, a uniform layer thickness of a liquid immersion medium may be preferable from a fluid dynamics point of view in a scanning operation in order to avoid turbulences and/or formation of bubbles in the immersion liquid.
  • a planar exit surface of the projection objective may also allow operation of the projection objective in a solid-immersion process with touching contact between the exit surface of the projection objective and the substrate surface or in contact-free near-field-lithography where image-side working distances are typically smaller than the operating wavelength.
  • the second surface is curved in the region of the transmissive portion.
  • a radius of curvature of the transmissive portion may be the same as the radius of curvature of the reflective zone sur- rounding the transmissive portion, which allows to manufacture the entire second surface in the same machining process.
  • the transmissive portion of the second surface may have a different curvature from the curvature of the reflective portion surrounding the transmissive portion.
  • the second surface is concavely curved in the region of the transmissive portion.
  • a radius of curvature of the transmissive portion has opposite sign to the radius of curvature of the reflective zone surrounding the transmissive portion.
  • the transmissive portion may accommodate a convexly curved entry surface of a lens shaped last optical element arranged between the catadioptric optical element and the image surface.
  • the last optical element may be positioned such that a vertex of an object-side surface of the last optical element is be positioned geometrically between the first surface and the second surface of the catadioptric optical element.
  • the second surface may be spherical. In other embodiments the second surface is an aspheric surface, whereby targeted contributions to aberration correction may be obtained.
  • the maximum ray angles inside the body of the catadioptric optical element exceed a critical ray angle of total internal reflection at the first surface by a factor of at least 1.5, preferably by at least 2.0.
  • the critical angle of total internal reflection may be influenced by selecting an appropriate high-index material for the body of the catadioptric optical element.
  • the transparent body of the catadioptric optical element may be made from different materials.
  • the critical angle of total internal reflection depends upon the refractive index of the body material relative to the adjacent medium (typically air or another gas) the width of the zone or region of total reflection on the first surface may be influenced by the choice of the material of the body.
  • the material of the body of the catadioptric optical element has a refractive index n B ⁇ 1.50 at the operating wavelength ⁇ .
  • n B ⁇ 1.6 or n B ⁇ 1.7 or n B >1.8 or n B ⁇ 1.9 or n B >2.0 is fulfilled at the operating wavelength.
  • an additional optical element such as a plane parallel plate or a lens element
  • that optical element may also be made by one of those materials.
  • the index of refraction of the body of the catadioptric optical element may be smaller than the index of refraction of the material selected for the last optical element adjacent to the image surface.
  • an apodization filter element having a spatially varying transmittance is arranged at or close to a pupil surface of the projection objective.
  • a variation of local transmittance across the effective surface of the apodization filter element may be adapted to the intensity distribution of the radiation beam at the location of the apodization filter element such that the radiation intensity becomes essentially uniform across the pupil surface of the projection objective.
  • the local transmittance of the apodization filter element decreases from a center region towards the edge of the element, which . .
  • apodization filter element may account for the fact that the marginal rays may be totally reflected at the first surface, whereas other rays may be partly transmitted through the first surface.
  • an apodization filter element may be used which has a local transmittance increasing from the center to the outer edge of the element.
  • a partly reflecting layer provided on the first surface may have a local variation of reflectivity such that reflectivity decreases from a region closer to the optical axis towards locations radially outward thereof.
  • a mask element configured to block radiation in a region at and close to the optical axis is arranged at or close to a pupil surface of the projection objective.
  • the mask element may be designed to block radiation up to a predefined ray height (radial distance of a ray from the optical axis). If the mask element is positioned at or close to a pupil surface, all ray bundles originating from different field points are masked substantially in the same way such that the obscurating effect of the mask element becomes essentially independent of the field position. Where the mask element is positioned substantially outside the pupil surface, different degrees of obscuration will be obtained for different field points. Also, the resolution of the projection objective would become dependent from field-position and directions within the field.
  • a position is "at or close to a pupil surface" in an axial region around the pupil surface where the marginal ray height MRH is substantially larger than a chief ray height CRH such that the condition
  • ⁇ 0.1 is fulfilled for the ray height ratio RHR CRH/MRH.
  • Some embodiments are characterized by a particularly compact shape at the image-side end of the projection objective between the location of an exit-side pupil surface of the projection objective (the pupil surface closest to the image surface) and the image surface.
  • the projection objective has a catadioptric positive lens group including the exit-side pupil surface upstream of the image surface, wherein the catadioptric positive lens group has a maximum diameter DIA MAX and the exit-side pupil surface has a distance T PUP from the image surface such that the condition:
  • DIA MAX /T P U P >3.
  • the compact shape indicates that less lens material than in conventional systems having comparable image-side numerical aperture is needed on the image-side end of the projection objective and material consumption may be reduced when compared to conventional systems.
  • the projection objective has an exit-side pupil surface close to the image surface and three or less optical elements (including the last optical element) are arranged between the exit-side pupil surface and the image surface.
  • only one lens in addition to the catadioptric optical element is arranged between the exit-side pupil surface and the image surface.
  • the catadioptric optical element is the only optical element between the exit-side pupil surface and the image surface.
  • the projection objective may have various general designs.
  • all optical elements provided in addition to the catadioptric optical element are refractive optical elements.
  • the projection objective may have a straight optical axis common to all optical elements, thereby forming an in-line system which is easy to incorporate into conventional projection exposure machines of the step-and-repeat or step-and-scan type.
  • Embodiments may have no intermediate image (direct imaging), in other embodiments an intermediate image may be formed.
  • the projection objective has at least one intermediate image and a concave mirror arranged at or close to a pupil surface optically conjugate to an exit-side pupil surface of the projection objective.
  • the invention provides a projection objective comprising: a plurality of optical elements arranged to image a pattern provided in an object surface of the projection objective onto an image surface of the projection objective with a radiation having an operating wavelength ⁇ at an image-side numerical aperture NA > 1 ; the optical elements including a last optical element with refractive power arranged adjacent the image surface; the last optical element having a body made from a transparent material having a refractive index n L o E at the operating wavelength, where the condition NA > 0.9 • ⁇ LOE is fulfilled.
  • the invention enables constructing projection objectives having very high relative image-side NA values close to those values conventionally considered as a limit when the propagation angles between the rays limiting the beam bundle and the optical axis are considered.
  • the condition NA ⁇ 0.92 • ⁇ LOE or the condition NA ⁇ 0.93 • ⁇ LOE or the condition NA > 0.94 • ⁇ LOE is fulfilled.
  • Embodiments may further be characterized by the fact that NA does not exceed about 95 % of the refractive index of the material of the last optical element, such that the condition NA ⁇ 0.95 • n L o ⁇ may be fulfilled. Therefore, in some embodiments the aperture-index-ratio NA/n L o ⁇ takes values from the range between 0.90 and 0.95, for example about 0.91 or about 0.92 or about 0.94.
  • the projection objective is a catadioptric projection objective including at least one concave mirror.
  • the projection objective may include a catadioptric element as described above or below.
  • the catadioptric optical element may form the last optical element.
  • the catadioptric optical element may be provided in addition to the last optical element.
  • a planar or curved exit-side of the last optical element facing the image surface may form the exit surface of the projection objective immediately adjacent to the image surface.
  • another optical element such as a plane-parallel plate, may be provided between the last optical element with refractive power and the image surface.
  • NA 1.35
  • NA 1.42
  • NA 1.44
  • NA 1.6 or NA > 1.7.
  • Some embodiments may have NA > 1.80 or NA ⁇ 2.0, for example.
  • Fig. 1 shows a schematic drawing of an embodiment of a projection exposure apparatus for microlithography having an illumination system and a projection objective; . .
  • Fig. 2 shows a first embodiment of a catadioptric projection objective without intermediate image, where the catadioptric optical element forms the last optical element closest to the image surface;
  • Fig. 3 shows schematically different shapes of the catadioptric optical element
  • Fig. 4 shows perspective views on the image-side second surface of two embodiments of a catadioptric optical element
  • Fig. 5 shows a second embodiment of a catadioptric projection objective generating one intermediate image between object surface and image surface;
  • Fig. 6 shows a third embodiment of a catadioptric projection objective generating one intermediate image
  • Fig. 7 shows an embodiment of a catadioptric projection objective having exactly two intermediate images and a concave mirror at a pupil surface of a catadioptric objective part
  • Fig. 8 shows another embodiment of a catadioptric projection objective of the type shown in Fig. 7, where the catadioptric optical element forming the last optical element of the projection objective has a biconvex shape;
  • Fig. 9 shows another embodiment of a catadioptric projection objective of the type shown in Fig. 7 and 8;
  • Fig. 10 shows yet another embodiment of a catadioptric projection objective of the type shown in Fig. 7 to 9; _ . _
  • Fig. 12 shows an enlarged detail of the image-side end of the projection objective shown in Fig. 11 demonstrating the ray paths in the catadioptric optical element;
  • Fig. 15 shows a catadioptric projection objective having a plane parallel plate between the catadioptric optical element and the image surface in Fig. 15A and a detail of the image-side end portion in Fig. 15B;
  • Fig. 16 shows an embodiment catadioptric projection objective designed for contact-less near-field lithography in Fig. 16A and an enlarged detail of the image-side and portion in Fig. 16B;
  • Fig. 17 shows an embodiment of a catadioptric projection objective having a plano-convex lens between the catadioptric optical element and the image surface in Fig. 17A and an enlarged detail of the image-side end portion in Fig. 17B; . .
  • Fig. 18 shows another embodiment of catadioptric projection objective where a catadioptric optical element having a body made from diamond forms the last optical element closest to the image surface.
  • optical axis refers to a straight line or a sequence of a straight-line segments passing through the centers of curvature of optical elements.
  • the optical axis can be folded by folding mirrors (deflecting mirrors) such that angles are included between subsequent straight-line segments of the optical axis.
  • the object is a mask (reticle) bearing the pattern of a layer of an integrated circuit or some other pattern, for example, a grating pattern.
  • the image of the object is projected onto a wafer serving as a substrate that is coated with a layer of photoresist, although other types of substrates, such as components of liquid-crystal displays or substrates for optical gratings, are also feasible.
  • Fig. 1 shows schematically a microlithographic projection exposure apparatus in the form of a wafer scanner WS, which is provided for fabricating large scale integrated semiconductor components in a step-and- scan mode.
  • the projection exposure apparatus comprises as light source an ArF excimer laser L having an operating wavelength ⁇ of about 193 nm. Other operating wavelengths, such as 248 nm or 126 nm, are also possible in other embodiments.
  • a illumination system ILL arranged downstream of the light source generates, in its exit surface ES, a large, sharply delimited, homogeneously illuminated illumination field that is adapted to the telecentric requirements of the catadioptric projection objective PO arranged downstream of the illumination system.
  • the illumination system ILL has devices for selecting the illumination mode and, in the example, can be changed over between conventional on-axis illumination with a variable degree of coherence ( ⁇ ), and off-axis illumination, particularly annular illumination (having a ring shaped illuminated area in a pupil surface of the illumination system) and dipole or quadru- pole illumination.
  • ⁇ variable degree of coherence
  • off-axis illumination particularly annular illumination (having a ring shaped illuminated area in a pupil surface of the illumination system) and dipole or quadru- pole illumination.
  • a device RS reticle stage
  • a device RS for holding and manipulating a mask M in such a way that a pattern formed on the mask lies in the exit surface ES of the illumination system coinciding with the object surface OS of the projection objective PO and can be moved in this plane for a scanning operation in a scanning direction (Y-direction) perpendicular to the optical axis AX common to the illumination system and the projection objective (i.e. the Z- direction).
  • the reduction projection objective PO is designed to image an image of the pattern provided by the mask with a reduced scale of 4:1 (magnification ratio I ⁇
  • 0.25) onto a wafer W coated with a photoresist layer at an image side numerical aperture NA > 1.
  • the wafer W serving as a light-sensitive substrate is arranged in such a way that the planar substrate surface SS with the photoresist layer essentially coincides with the planar image surface IS of the projection objective.
  • the wafer is held by a device WS (wafer stage) comprising a scanner drive configured to move the wafer synchronously with the mask M in parallel with the latter.
  • the device WS also comprises manipulators configured to move the wafer both in the Z direction parallel to the optical axis and in the X and Y directions perpendicular to said axis.
  • manipulators configured to move the wafer both in the Z direction parallel to the optical axis and in the X and Y directions perpendicular to said axis.
  • a tilting device having at least one tilting axis running perpendicular to the optical axis is integrated.
  • the projection objective PO has a catadioptric optical element COE forming the last optical element LOE nearest to the image surface IS, the exit surface of said catadioptric optical element being the last optical surface (exit surface) of the projection objective PO.
  • the exposure apparatus is configured for immersion lithography at NA > 1 and includes an immersion medium guiding system (not shown) to guide a transparent, high index immersion liquid IL 1 such as pure water or water with additives, into a small gap between the exit surface of the projection objective and the substrate such that the immersion liquid completely covers the substrate surface SS of the wafer at least in the region under exposure and that the exit-side end area of the projection objective is immersed into the immersion liquid while a finite image-side working distance is set correctly.
  • the entire system is controlled by a central computer COMP.
  • the illumination system ILL includes a pupil shaping unit configured to create an effective light source formed by a predefined intensity distribution at a pupil surface P ILL of the illumination system.
  • the pupil plane P ILL is a Fourier transform surface with respect to the object surface of the projection objective PO, where the mask M is situated.
  • the exit-side pupil surface P of the projection objective PO is optically conjugated to the pupil surface P ILL of the illumination system.
  • Fig. 2 shows a meridional lens section of a projection objective 200 according to a first embodiment of the invention.
  • the projection objective 200 is designed to project an image of a pattern on a reticle arranged in the planar object surface OS (object plane) onto a planar image surface IS (image plane) at a reduction ratio 4 : 1 (magnification factor
  • 0,25) directly i.e. without forming an intermediate image.
  • An on-axis object field object field centered about the optical axis AX is imaged onto an on-axis image field with a central obscuration.
  • a single pupil surface P is formed between object surface OS and image surface IS where a chief ray CR of the projection beam intersects the optical axis AX.
  • An aperture stop AS and/or a filter element and/or a mask element may be arranged optically close to the pupil surface P.
  • the projection objective includes a plurality of 16 optical elements arranged along a straight (unfolded) optical axis AX common to all optical elements (in-line system).
  • the projection objective 200 consists of a first lens group LG 1 immediately following the object surface OS and having negative refractive power, a second lens group LG2 immediately following the first lens group and having positive refractive power, a third lens group LG3 immediately following the second lens group and having negative refractive power effective to generate a constriction of light beam passing through the projection objective, a fourth lens group LG4 immediately following the third lens group and having a positive refractive power, and a fifth lens group LG5 immediately following the fourth lens group LG4 and having positive refractive power.
  • First lens group LG 1 consists of two negative lenses
  • second lens group LG2 consists of _ _
  • negative lens group LG3 consists of three negative lenses
  • positive lens group LG4 consists of five lenses having positive optical power at least in a central region around the optical axis
  • positive lens group LG5 consists of two positive lenses and the catadiop- tric last optical element LOE.
  • the aperture stop AS is arranged between the fourth and fifth lens group. Due to this distribution of refractive power the projection objective consists of an object-side first belly B1 , an image-side second belly B2, and a waist WA arranged between the first and second belly, thereby forming a catadioptric "single-waist system".
  • pupil surface P forms the exit-side pupil surface of the projection objective immediately upstream of the image surface.
  • a local maximum DIA MAX of the diameter of the projection objective is found at or close to the pupil surface P.
  • the axial distance T P up between the axial position of the pupil surface P and the image surface IS is extraordinarily small when compared to conventional systems having comparable image-side NA.
  • the ratio DIA MAX /TPU P is slightly larger than 2 in this embodiment.
  • the catadioptric optical element COE is the last optical element in the optical train providing optical power.
  • An optically free radius (half- diameter) R LOE of the last optical element is substantially greater than corresponding free optical radii of last optical elements in conventional systems having comparable image-side NA.
  • the product between the optically free radius of the last optical element with optical power and the image-side numerical aperture NA may be larger than 130, i.e. R COE * NA>130.
  • projection objective 200 is given in Table 2.
  • the leftmost column lists the number of the refractive, reflective, or otherwise designated surface
  • the second column indicates the aspheric surfaces (AS)
  • the third column lists the radius, r, of curvature of that surface [mm], ⁇ £0 ⁇
  • the fourth column lists the distance, d [mm], between that surface and the next surface, a parameter that is referred to as the "thickness" of the optical element
  • the fifth column lists the material employed for fabricating that optical element
  • the sixth column lists the refractive index of the material employed for its fabrication at the operating wavelength.
  • the seventh column lists the optically utilizable, clear, semi diameter (optically free radius) [mm] of the optical surface.
  • AS asphehcal surfaces
  • a first surface S1 on the object- side of the body is a planar surface.
  • a second surface S2 on the image- side of the body B may be subdivided into a circular transmissive portion TP in a central region around the optical axis AX, and a curved reflective portion RP in a rotationally symmetric zone around the transmissive portion TP.
  • the portion RP is curved convexly towards the image surface and is coated with a highly reflective coating HR to form a concave mir- _
  • the transmissive portion TP is planar and extends in a radial direction to the optical axis such that radiation exciting the body B towards the image surface to form the image field is not vignetted by the highly reflective coating HR.
  • First surface S1 is coated with a dielectric anti-reflection coating to increase transmission for radiation entering the last optical element from the object-side. Since the first surface forming the entry surface of the catadioptric last optical element and the transmissive portion of the second surface forming the exit surface of the catadioptric lens element (and the exit surface of the projection objective) are planar surfaces, the optical power of the entire last optical element corresponds to the optical power provided by the concave mirror formed by the reflective potion RP of the second surface.
  • first and second surfaces S1 , S2 are selected such that radiation totally reflected from the totally reflective zone TOT is directed towards the transmissive portion TP of the first surface at very high aperture.
  • the strongly convergent beam exits the body B at the transmissive portion and is coupled into the immersion layer IL formed between the catadioptric last optical element COE and the image surface IS, where a surface of a substrate to be exposed is arranged.
  • the angle of total internal reflection depends upon the material used for the body of the catadioptric optical element COE relative to the refractive index of the optical medium adjacent to the first surface (which is air or another gas in this embodiment).
  • Table A shows different materials suitable to form the body of the catadioptric optical element and the respective refractive index at different wavelength (248nm, 193nm and 126nm).
  • the angle of incidence of a ray at a surface is the angle included between the propagation direction of the ray and the surface normal at the point of incidence on the surface.
  • the beam impinging on first surface S1 from the image-side may include rays having angles of incidence below the critical angle of total internal reflection. Those rays may be partially reflected by first surface S1 in a partially reflecting (and partially transmitting) zone PR between the totally reflecting zone TOT and the optical axis, and may contribute to image formation.
  • total internal reflection on the object-side surface S1 of the last optical element LOE contributes to forming a large aperture convergent ray bundle forming the image. It is worth to note that it is advantageous for a substantially telecentric ray bundle to be reflected by total internal reflection on a planar surface since all rays having angles of incidence larger than the critical angle of total reflection are reflective uniformly such that the uniform obscuration or apodization is effected in for all field points.
  • An obscuration of ray bundles is effected close to pupil surface using a mask element MA configured to block radiation in a region at and close to the optical axis up to a selected height (radial distance) from the optical axis.
  • the radial coordinate of the outer edge of the circular mask elements determines the maximum size of obscuration of the ray bundle.
  • the mask element may be a separate element provided in addition to lenses.
  • the mask element may also be formed by an opaque coating on a lens surface positioned close to or at a pupil surface.
  • an apodization filter element APO having a spatially varying transmittance may be arranged at or close to a pupil surface of the pro- jection objective to compensate for non-uniformity of intensity across the beam diameter.
  • the filter function may be designed such that the ray bundle has substantially uniform intensity across the entire diameter after passing the apodization filter element.
  • the apodization filter element may be formed by a separate element provided in addition to lenses.
  • the apodization filter element may also be formed by an appropriate coating on a lens surface at or close to the pupil surface.
  • the apodization filter element may be formed by a grey filter or a grey filter coating.
  • the mask element and the apodization filter element may be formed by only one element, such as a coating having a central opaque portion and a rotationally symmetric zone around the central portion, wherein the transmittance of the element in the outer zone varies in a radial direction.
  • One optical effect of the concave mirror formed by the second surface S2 of the last optical element is to provide positive optical power to generate high aperture rays in a compact catadioptric optical element.
  • the design of the concave mirror may also be optimized to provide a desired correcting effect on image field curvature.
  • the contribution to image field curvature depends on the radius of curvature of the concave mirror such that the contribution is increased the smaller the radius of curvature becomes.
  • the catadioptric optical element COE allows further degrees of freedom for optical correction since the general shape of the first surface S1 may be varied as needed.
  • Fig. 3 shows schematically some examples. As mentioned in connection with the embodiment of Fig.
  • the fully reflective portion RP of the second surface may be concave towards the object-side.
  • the reflective portion may be spherical or aspherical.
  • the object-side first surface S1 includes a totally reflecting zone TOT where total reflection occurs, and may include adjacent zones which are partly transmissive to radiation.
  • the first surface may be pla- _
  • nar as in Fig. 3A, or concave towards the image-side (as in Fig. 3B) or convex towards the image-side (as in fig. 3C).
  • Using a concave shape generally allows to increase the angles of incidence of radiation rays on the first surface, thereby increasing the radial widths of the totally reflecting zone TOT. Further, an overcorrecting contribution to image field curvature is provided such that refractive positive power may be reduced in other parts of the projection objective, thereby contributing to lowering the material consumption.
  • providing the convex shape (Fig.
  • Fig. 4 illustrates schematically possible variants for shaping the second surface S2 of the catadioptric optical element, which mayor may not be positioned immediately adjacent to the image surface.
  • the entire second surface S2 is convex towards the image surface such that the transmissive potion TP is also convex towards the image surface and formed on the same mathematical surface.
  • the second surface is planar in a circular central region where the transmission portion TP is formed.
  • the diameter of the transmissive portion TP (formed by a non-coated aperture within the highly reflective coating of the second surface) determines the diameter of the obscuration within the system necessary to block radiation from passing the projection objective directly from the object surface to the image surface.
  • the catadioptric optical element may also be used in concatenated projection objectives having at least two imaging objective parts and at least one intermediate image formed between two adjacent imaging objective parts.
  • Fig. 5 shows a meridional lens section of a projection objective 500 having a first refractive objective part OP 1 designed to form an in- termediate image IMI from radiation coming from the object surface OS, and a second catadioptric objective part OP2 designed to image the intermediate image onto the image field in the image surface IS.
  • the remainder of the optical elements are fused silica lenses, wherein fifteen lenses form the first refractive objective part OP 1 and nine lenses are arranged between the intermediate image IMI and the last optical element LOE in the second objective part OP2.
  • a first pupil surface P1 is formed within the first objective part OP 1 where chief ray CR intersects the optical axis AX for a first time and a second pupil surface P2 forming the exit-side pupil surface of the projection objective is formed within the second objective part OP2 where the chief ray intersects the optical axis a second time before impinging on the image surface.
  • the optical correction status may be characterized by a root mean square value of the optical path difference (RMS OPD) smaller than 4.2m ⁇ across the entire field.
  • RMS OPD root mean square value of the optical path difference
  • the system of Fig. 6 has lower overall mass consumption.
  • the correction is RMS OPD ⁇ 3m ⁇ across the entire field.
  • An apodi- zation filter element APO is provided near the second pupil surface P2.
  • the specifications are given in tables 6, 6A.
  • a fourth embodiment of the catadioptric projection objective 700 is shown in Fig. 7.
  • a high index immersion fluid e.g. pure water
  • the size of the rectangular field is 26mm * 5.25mm. Specifications are summarized in Tables 7, 7A.
  • the projection objective 700 is configured to image a pattern, which is arranged on its planar object surface OS, of a mask on a reduced scale on its planar image surface IS, which is aligned parallel to the object plane, on a reduced scale.
  • the projection objective has a first, refractive objective part OP1 , which images the object field to form a first, real intermediate image IMH , a second, catadioptric objective part OP2, which images the first intermediate image to form a second real intermediate image IMI2, and a third, catadioptric objective part OP3, which images the second intermediate image on a reduced scale on the image surface IS.
  • R-C-C This type of catadioptric design will be denoted “R-C-C” type in the following, with “R” representing a refractive objective part, “C” representing a catadioptric objective part, and "-" representing an intermediate image.
  • the catadioptric second objective part OP2 has a concave mirror CM.
  • a first folding mirror FM1 is arranged in the vicinity of the first intermediate image, at an angle of 45° to the optical axis OA, such that it reflects the radiation coming from the object plane in the direction of the concave mirror CM.
  • the folding mirrors FM1 , FM2 are each located in the optical vicinity of the intermediate images, so that the light conductance value (etendue) can be kept low.
  • the folding angles in this exemplary embodiment are exactly 90°. This is advantageous for the performance of the mirror layers of the folding mirrors. Deflections by more or less than 90° are also possible, thus resulting in an obliquely positioned horizontal arm (carrying the concave mirror).
  • the first objective part OP1 comprises two lens groups LG11 , LG12 each with a positive refractive power, between which a possible diaphragm position exists at a first pupil surface P1 positioned where the chief ray CR intersects the optical axis AX.
  • the optical axis is folded through 90° at the first folding mirror FM1.
  • the first intermediate image IMH may be produced in the light path immediately downstream from the first folding mirror FM1.
  • the first intermediate image IMH acts as an object for the subsequent catadioptric objective part OP2.
  • This objective part is formed by a cata- dioptric group CG consisting of the concave mirror CM positioned essentially at a second pupil surface P2 and a negative lens NL positioned immediately ahead of the concave surface of the concave mirror optically close to the second pupil surface P2 in a region where the marginal ray height MRH is at least twice or three times as large as the chief ray height CRH.
  • the catadioptric third objective part OP3 has a first positive lens group LG31 , a second negative lens group LG32, a third positive lens group LG33 and a fourth positive lens group LG34 including the catadioptric last optical _
  • An aperture stop AS is positioned at the third pupil surface P3 between the positive lens groups LG33 and LG34, where the chief ray CR intercepts the optical axis.
  • the first surface S1 is planar.
  • All lenses and the transparent body of the catadioptric optical element COE are made of fused silica.
  • the catadioptric group CG contributes a major part of axial chromatic aberration correction and image curvature correction.
  • the Petzval correction is mainly achieved by the curvature of the concave mirror and negative lens NL close to the concave mirror, while a major part of the chromatic correction is achieved by the refractive power of the negative lens NL in front of the concave mirror (effecting predominantly chromatic length aberration CHL).
  • the last optical element LOE includes a concave mirror, formed by the reflective portion of second surface S2, and contributes to Petzval correction.
  • Fig. 8 shows another embodiment of a R-C-C type projection objective 800 having two intermediate images IMH , IMI2, a first refractive objective part OP1 , a second catadioptric objective part OP2 and a third catadioptric objective part OP3 including the catadioptric last optical element LOE.
  • the specifications are given in tables 8, 8A.
  • the body of the last optical element LOE is substantially formed as a biconvex lens such that the first surface S1 is curved to form a concave mirror for radiation reflected by the reflective portion RP of the second surface S2 towards the first surface S1 (compare Fig. 4B).
  • a field variation of light intensity may be introduced upon total reflection. If it is desired to use only radiation totally reflected on the first surface the radius of the obscured portion around the optical axis may be increased when compared to systems having a last optical element with a planar first surface.
  • a mask element MA centered about the optical axis AX with suitable diameter may be provided in the exit-side pupil surface P3 to shield radiation not totally reflected on the first surface. If it is desired that totally reflected radiation from the totally reflecting potion as well as radiation reflected from adjacent partly reflecting portions contribute to image formation, an apodization filter element APO having appropriate spatial variation of transmittance may be provided at or close to the exit-side pupil surface. The effect of an apodization filter element may also be obtained by providing an appropriate partly transmissive coating on a lens surface close to the exit-side pupil surface.
  • the biconvex catadioptric optical element COE provides a fully reflecting concave mirror in the reflective portion of the second surface, and another concave mirror, totally reflecting at least in a zone outside the optical axis, on the object-side first surface. Therefore, both reflecting surfaces provide positive optical power in a very compact arrangement. Concentrating positive optical power in the last optical element COE may be used to reduce the number of positive lenses on the image-side end of the projection objective.
  • the last optical element LOE is the only optical element arranged entirely between the image-side pupil surface P3 and the image surface IS.
  • the blunt image-side end of the projection objective is characterized by a very short distance between the exit-side pupil surface P3 and the image surface, whereby a ratio DIA MAX /T PUP ⁇ 3.0 is obtained.
  • the exit surface formed by the transmissive portion of the second surface S2 is planar and parallel to the planar first surface S1.
  • the specifications are given in tables 9, 9A.
  • the specifications are given in tables 10, 10A.
  • the exit surface of projection objective 1000 is planar, thereby allowing a uniform thickness of the immersion liquid layer.
  • Fig. 12 also shows an aperture stop AS and an obscurating mask element M both provided at the exit-side pupil surface P3.
  • a radiation beam including a plurality of rays shown schematically in Fig. 12 enters the images-side end of the projection objective at the exit-side pupil surface P3 between the inner edge of the aperture stop AS and the outer edge of the blocking mask MA 1 which defines the radius of obscuration of the projection objective.
  • Radiation enters the last optical element LOE through the refracting first surface S1 and is subsequently incident on the concave reflective portion RP of second surface S2. Radiation reflected by the concave mirror formed by the reflective portion RP is subsequently incident obliquely on planar first surface S1.
  • a totally reflecting zone TOT is formed outside the optical axis AX on the first surface S1 where the angles of incidence of incident radiation exceed the limiting angle of total reflection at the solid-gas interface formed between the transparent material of the body B and the surrounding gas. Radiation reflected by first surface S1 is then guided through the planar transmissive portion TP of second surface S2 and enters the immersion liquid IL prior to impinging on the substrate surface.
  • Fig. 13 shows an example of a catadioptric in-line projection objective 1300 without intermediate image designed generally in accordance with the sequence of lens groups LG 1 to LG5 described in connection with Fig. 2. Specifications are given in tables 13, 13A.
  • Other optical material such as lithium fluoride (LiF) and/or magnesium fluoride (MgF) can be used for fabricating one or more of the lenses. Some of the materials, such as MgF, are birefringent at the working wavelength. Lens clocking and/or uniaxial crystal correction optical elements may be used for birefringence compensation.
  • the catadioptric optical element COE is arranged between the single pupil surface P and the image surface IS and forms the last optical element LOE of the projection objective.
  • the catadioptric optical element is effective to reduce the overall number of lenses in the fourth positive lens group LG4 and contributes to the correction of field curvature due to the overcorrecting concave mirror formed by the reflective portion of the second surface.
  • the exit surface in the transparent portion of the last optical element immediately adjacent to the image surface and in contact with a high index immersion liquid is planar.
  • Fig. 14 shows the meridional section of the catadioptric projection objective 1400 having R-C-C type generally in accordance with the sequence of lens groups and objective parts described in connection with Fig. 7, for example. Reference is made to that description.
  • the specifications are given in table 14, 14A.
  • a first refractive objective part OP1 forms a first intermediate image IMM
  • a second catadioptric objective part OP2 including concave mirror CM and a single negative lens ahead of the concave mirror near the concave mirror forms a second intermediate image IMI2
  • a third, catadioptric objective part OP3 which forms the image in the image surface.
  • the optical axis is folded in the vicinity of the intermediate images.
  • the concave mirror CM is designed as an active mirror such that the surface shape of the concave mirror can be changed during operation using appropriate actuators AC deforming the mirror surface.
  • the shape of the concave mirror can thereby be adapted to correct for aberrations, e.g.
  • a radiation heating system designed to heat one or more lenses by targeted irradiation by infrared light IR is provided as an additional means to modify dynamically the correction status of the projection objective during operation.
  • a thick meniscus lens immediately downstream of first pupil surface P1 is made from a lens material sufficiently absorbent for infrared radiation (here fused silica) and is used as an ac- tivatable correction element.
  • the arrows IR represent light beams forming a certain spatial distribution of infrared light intensity across the lens surface. All lenses are made of fused silica (SiO 2 ).
  • the exit surface of the projection objective formed by the transparent portion of the catadioptric optical element has thesame convex shape as the second surface of the catadioptric optical element.
  • the catadioptric optical element COE forms the last optical element LOE of the projection objective immediately adjacent to the image surface such that the transparent portion of the catadioptric optical element forms the exit surface of the projection objective.
  • at least one optical element is arranged between the catadioptric optical element COE and the image surface IS such that the catadioptric optical element is not the last element of the projection objective. Instead, the additional element forms the last optical element LOE.
  • Fig. 15A shows a meridional section of a catadioptric projection objective 1500 of R-C-C type having exactly two intermediate images, a single concave mirror at the pupil surface P2 of the second objective part and a catadioptric third objective part forming the image from the second in- termediate image.
  • the specifications are given in tables 15, 15A.
  • Fig. 15B shows a schematic detail of the image-side and of the projection objective during operation.
  • the catadioptric optical element COE is not the last optical element adjacent to the images surface IS. Instead, a plan parallel plate PP is positioned between the catadioptric optical element COE and the image surface IS and forms the last optical element LOE of the projection objective.
  • the transparent portion TP of catadioptric optical element COE is planar.
  • a plan parallel space between the catadioptric optical element COE and the last optical element LOE is filled with a first immersion liquid IL1
  • a plan parallel space between the last optical element LOE and the image surface is filled with a second immersion liquid IL2, which is in contact with the surface of the substrate to be exposed during operation.
  • the first and second in an immersion liquid IL1 and IL2 may be the same liquid or liquids with different refractive index.
  • the plan parallel last optical element LOE may be mounted such that this element is exchangeable without dismounting the other parts of the projection objective.
  • Providing an (exchangeable) last optical element between image surface and catadioptric optical element may act as a barrier against contamination effecting the exit surface TP of the catadioptric optical element.
  • both entry surface and exit surface of the plan parallel plate PP are planar and parallel to each other such that substantially no refractive power is provided by the last optical element LOE.
  • one or both of the surfaces of the plane parallel plate may have an aspheric shape in order to serve as correction means for correcting various for correcting various influences disturbing the imag- ing quality of the system.
  • Table 15' and 15'A show specifications of an embodiment generally identical to projection objective 1500 with the exception that the last optical element is an aspheric plan parallel plate.
  • the aspheric plan parallel plate immediately adjacent to the image surface is predominantly effective as a correction means correcting field dependent aberrations caused by remanent modifications of lens shapes (small differences from ideal shape) and/or caused by changes of index of refraction of lens materials due to ageing effects, such as compaction of fused silica irradiated with ultraviolet light.
  • Exchanging a last optical element having a first aspheric property against a second last optical element having a different aspheric shape allows to change the correcting effect in order to correct the actual aberration level, which may change during the life time of the projection objective.
  • the correction asphere formed on a surface of plan parallel last optical element LOE has a deformation smaller than 100 ⁇ m or even smaller than 50 ⁇ m or smaller than 10 ⁇ m.
  • the aspheric surface is positioned on the object-side of the last optical element LOE and has a deformation of about 5 ⁇ m.
  • the R-C-C type catadioptric projection objective 1600 of Fig. 16A, B is designed to be used in a contact-free solid immersion operation, also denoted as "near-field lithography" in this application.
  • the projection objective is designed such that the image-side working distance (axial distance between the exit surface of the projection objective and the image surface) is smaller than the operating wavelength ⁇ (see Fig. 16B).
  • the exit surface is formed by the transparent portion TP on the second surface of the catadioptric optical element COE forming the last optical element LOE. Under these conditions evanescent waves EW exiting the planar exit surface TP are able to couple into the surface of the light sensitive layer on the substrate to be exposed. No high index liquid is interposed between the exit surface of the projection objective and the substrate, such that the evanescent - -
  • Fig. 17A and 17B show another embodiment of an R-C-C type catadioptric projection objective 1700 with two intermediate images and a single concave mirror CM in the second objective part OP2.
  • the specifications are given in tables 17, 17A.
  • Fig. 17B shows a schematic detail of the image-side and portion of the projection objective.
  • a single lens LOE forming the last optical element is arranged between the catadioptric optical element COE and the image surface.
  • the last optical element LOE is formed as a planoconvex lens having a convex entry surface facing the catadioptric optical element COE, and a planar exit surface facing the image surface IS.
  • the transparent portion TP of the catadioptric optical element is concave towards the image surface IS such that the center of curvature is on the image-side thereof.
  • a thin layer of a first immersion liquid IL1 having essentially uniform thickness is provides between the transparent portion of the catadioptric optical element and the last optical element LOE.
  • a uniform thickness layer of a second immersion liquid IL2 is provided between the planar exit surface of last optical element and the image surface.
  • the immersion Liquid IL1 , II2 may have the same or different refractive index.
  • One advantage of this arrangement is that only a small volume of very high index material is required to form the last optical element LOE.
  • the refraction in the last optical element LOE makes the ray angles smaller.
  • the concave shape of the exit surface of the catadioptric optical element enables a reduced obscuration of this arrangement.
  • the immersion liquid IL1 between the catadioptric optical element COE and the last optical element LOE is effective to lower the refractive action of the convex entry surface of the last optical element. This allows for a small size of this last optical element, which may be advantageous since high index material are in limited supply. Also, absorption effects within the high index material are reduced where the size is kept small. All lenses upstream of the catadioptric optical element are made of fused silica.
  • Fig. 18 shows a catadioptric projection objective 1800 of type R-C-C with a general arrangement of imaging objectives part OP1 , OP2 and OP3 and two intermediate images IMM , IMI2 as explained above e.g. in connection with Fig. 7.
  • Diamond is used as high-index material for the body B of the catadioptric optical element COE forming the last optical element LOE of the projection objective immediately adjacent to the image surface.
  • the exit surface of the catadioptric optical element formed by the transparent portion of the second surface is convex towards the image surface and has the same shape as the second surface in the reflective portion.
  • Fused silica is used for all other lens elements.
  • calcium fluoride (CaF 2 ) is used for one or more lenses close to field surfaces (object surface, intermediate images).
  • a deformable concave mirror CM at the pupil of the second objective part OP2 and/or a lens element irradiation technique as explained in connection with Fig. 14 may be used to dynamically influence the optical properties of the projection objective during operation.
  • Some lens elements may be dynamically moved along the optical axis and/or perpendicular thereto to compensate for induced errors due to lens heating and/or atmospheric .
  • Controlling the movements of selected lenses by appropriate manipulators and/or controlling the reflecting shape of the concave pupil mirror CM allows for a dynamic operation control during the exposure process.
  • the image-side numerical aperture NA obtained for an operating wavelength ⁇ is very close to a theoretical limit usually considered in view of the fact that propagation angles of rays travelling towards the image surface should not exceed certain limits.
  • NA should not substantially exceed approximately 95 % of the refractive index of a last medium on the image side.
  • Table B summarizes for all examples discussed above the values for the image-side numerical aperture NA (maximum NA when used with a fully open aperture stop), the material of a last optical element LOE with refractive power arranged adjacent to the image surface, the refractive index ⁇ LOE of a transparent material forming the last optical element, the operating wavelength and the aperture-index-ratio NA/ ⁇ L O E -
  • the value NA/ ⁇ LOE indicates how close the actual values for the image- side NA comes to the value theoretically possible in view of the refractive index of the last optical element with refractive power.
  • the systems described above may be complete systems for forming a real image (e.g. on a wafer) from a real object.
  • the systems may be used as partial systems of larger systems.
  • the "object" for a system mentioned above may be an image formed by an imaging system (relay system) upstream of the object plane.
  • the image formed by a system mentioned above may be used as the object for a system (relay system) downstream of the image plane.

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Abstract

Un objectif de projection catadioptrique comporte une pluralité d'éléments optiques disposés le long d'un axe optique pour représenter un motif, prévu dans une surface objet de l'objectif de projection, sur une surface image de l'objectif de projection. Lesdits éléments optiques comprennent un élément optique catadioptrique dont le corps est fait d'un matériau transparent; une première surface sur un côté objet du corps et une seconde surface opposée à la première surface. La seconde surface est munie d'une partie transmissive dans une zone centrale autour de l'axe optique et une partie réfléchissante concave dans une zone entourant la partie transmissive. La première surface comporte une zone transmissive configurée pour transmettre un rayonnement provenant de la surface objet vers la seconde surface et orientée par rapport à la seconde surface de telle sorte qu'au moins une partie du rayonnement réfléchi par la partie réfléchissante de la seconde surface est entièrement réfléchie par la partie transmissive de la première surface vers la partie transmissive de la seconde surface.
PCT/EP2008/001299 2007-02-23 2008-02-20 Objectif de projection catadioptrique avec ouverture numérique ultra-élevée WO2008101676A2 (fr)

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Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2014002377A (ja) * 2012-06-08 2014-01-09 Canon Inc 反射屈折光学素子及び反射屈折光学素子を含む光学系
US8947775B2 (en) 2012-06-08 2015-02-03 The Arizona Board Of Regents On Behalf Of The University Of Arizona Catadioptric optical system with total internal reflection for high numerical aperture imaging
US9329373B2 (en) 2013-02-13 2016-05-03 Canon Kabushiki Kaisha Catadioptric optical system with multi-reflection element for high numerical aperture imaging

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2683394A (en) * 1951-09-08 1954-07-13 American Optical Corp Wide aperture optical projection lens system
US5930055A (en) * 1994-09-29 1999-07-27 Eisenberg; Yeshayahu S. Lens apparatus
US6493156B1 (en) * 1999-05-27 2002-12-10 Lg Electronics Inc. High resolution lens

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2683394A (en) * 1951-09-08 1954-07-13 American Optical Corp Wide aperture optical projection lens system
US5930055A (en) * 1994-09-29 1999-07-27 Eisenberg; Yeshayahu S. Lens apparatus
US6493156B1 (en) * 1999-05-27 2002-12-10 Lg Electronics Inc. High resolution lens

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2014002377A (ja) * 2012-06-08 2014-01-09 Canon Inc 反射屈折光学素子及び反射屈折光学素子を含む光学系
US8947775B2 (en) 2012-06-08 2015-02-03 The Arizona Board Of Regents On Behalf Of The University Of Arizona Catadioptric optical system with total internal reflection for high numerical aperture imaging
US8947773B2 (en) 2012-06-08 2015-02-03 Canon Kabushiki Kaisha Catadioptric optical element and optical system including same
US9329373B2 (en) 2013-02-13 2016-05-03 Canon Kabushiki Kaisha Catadioptric optical system with multi-reflection element for high numerical aperture imaging

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