Classifications

• • 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
  • 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
  • G02—OPTICS
  • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
  • G02B13/00—Optical objectives specially designed for the purposes specified below
  • G02B13/14—Optical objectives specially designed for the purposes specified below for use with infrared or ultraviolet radiation
  • G02B13/143—Optical objectives specially designed for the purposes specified below for use with infrared or ultraviolet radiation for use with ultraviolet radiation
• • 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
  • G03F7/70241—Optical aspects of refractive lens systems, i.e. comprising only 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
  • G03F7/7035—Proximity or contact printers
• • 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 invention relates to a microlithography projection objective with crystal elements, namely such made from materials showing birefringence and other than cubic crystal structure.
• Suitable immersion liquids are inter alia described in US 60/568,006 or DE 10 2004 051 730.4. All cited documents are incorporated into this application by reference in their entirety. Their citation in no way constitutes any declaration on their relevance for this application, and the list certainly is incomplete and many more publications relate to this art. D
• optical materials For end-closure plates or for the last-positioned lens element in immersion objectives or near-field objectives there is a need for optical materials of the highest possible index of refraction. At the same time, the materials need to be transparent, homogeneous, radiation-resistant, as well as mechanically and chemically robust. There is a material which meets all of these conditions except for optical isotropy.
• the material is sapphire or, in chemical terms, Al-0 3 . Others are MgF or LaF 3 and other uniaxial crystals.
• FIGS 1 to 8 and 10 to 13 are sketches that illustrate the principles of arrangements, or parts thereof, according to the invention.
• Figure 9 shows wavelength-dependent variation of n ⁇ and n 0 for some materials from an article.
• the sum (n o -n e )Al 2 0 3 + (n_-n e )Si0 2 equals zero for a maximum-aperture ray B maj: with an incident angle of 70° (n o refractive index of ordinary ray, n e refractive index of extraordinary ray) .
• the plate be made of two parts.
• the proposed combination consists of an Al 2 0 3 sapphire plate P. of optically negative character and an Si0 2 crystal plate P 2 of optically positive character, as illustrated in Figures 1 to 3.
• the magnitude of the birefringence changes individually with the wavelength.
• the plate thicknesses are therefore selected dependent on the wavelength, so that a birefringence of the Al 2 0 3 plate is compensated by the complementary birefringence of the Si0 2 plate. This cannot be achieved completely, because the indices of refraction are different for the two materials, so that a compromise is necessary for different incident light angles.
• an exact compensation can be achieved in particular for the highest apertures which are relevant in immersion lithography applications, e.g., for dipole illumination.
• the invention can also be used in a lens element .
• Al 2 0 3 sapphire offers one of the highest known indices of refraction for the wavelengths of 157 nm and 193 nm, it is a preferred material to use for the element in the last position of the objective.
• Elements of crystalline Si0 2 are placed (in direction of light propagation) before the Al 2 0 3 element .
• FIG 4 represents a sketch to illustrate the principle, wherein the symbol QG stands for quartz glass, QK for quartz crystal, S for sapphire (which is at the same time a lens L in the sense of Figure 1) .
• FIG. 5 An arrangement that is suitable for example for a wavelength of 193 nm is shown in Figure 5.
• a double arrow in the lenses indicates the orientation of the optical axis of the birefringence that is inherent in the materials. It is clear that the effective index of refraction in the crystals A1 2 0 3 and Si0 2 is subject to a continuous angle- dependent variation, but with tangentially polarized light there is initially no phase shift between an s-polarized and a p-polarized component. The variation of the refractive index is taken into account in the design.
• Figure 6 illustrates an example of an objective for an operating wavelength of 157 nm with CaF 2 lenses of different crystallographic orientation, for example 111 and 110, for the compensation of intrinsic birefringence with a pair of optically uniaxial crystal lenses that is compensated in accordance with the invention.
• the objective can be coupled to the object to be exposed, for example a wafer W, with the largest possible numerical aperture.
• negative optical character means that the refractive index n o of the ordinary ray is larger than the refractive index n of the extraordinary ray.
• positive optical character means that the refractive index n_ of the ordinary ray is smaller than the refractive index n e of the extraordinary ray.
• the scope of the invention includes: the compensation as described; the use of Al 2 0 3 sapphire and Si0 2 crystal in lithography optics; the placement of the elements between the aperture stop or a conjugate location of the aperture stop and the image plane of a projection objective, with special preference for placing these elements in the bottom one-third of the distance between the aperture stop and the image plane; the use of the aforementioned materials for protector plates for immersion or near-field arrangements, either by themselves without compensation, or with compensation; the use at high angles of incidence >60°, with special preference >70°; including in these applications the compensation at the highest numerical aperture values NA (above 1.3 to 1.6) on the image side; also including the use of tangentially polarized light; and further including the use in immersion objectives with a refractive index of more than 1.8 in the last optical element, with special preference for more than 2.0; and also the use at an operating wavelength of 157 nm in conjunction with the crystals CaF 2 , Si0 2 , Al 2 0 3 sapphire - in respectively different
• magnesium fluoride in crystalline form has an optically positive character.
• the compensation of birefringence in a high-aperture end- closure part of a microlithographic projection objective requires the availability of suitable degrees of freedom. If the birefringence were of exactly equal magnitude and had the same form in Al 2 0 3 as in quartz crystal, an exact solution that provides compensation for all angles would exist at least for planar-parallel plates, i.e., one would only need to use two plates of equal thickness. If lenses are used instead of plates, the possible phase differences occurring as a result of refraction and birefringence become larger and there is an increased risk that this will affect the image quality. On the other hand, with lenses one has the possibility to use a targeted variation of the radii as a further degree of freedom in addition to the thickness, as a parameter for compensation.
• MgF 2 crystal In view of its low index of refraction, it is placed preferably in a position before the more strongly refractive elements of quartz crystal and sapphire. It should be noted in this context that the uniaxial birefringent crystals Al 2 0 3 sapphire, Si0 2 , MgF 2 are compensated in an entirely different manner than the CaF 2 , SrF 2 , and BaF 2 crystals and the like which are a priori isotropic (at least in the visible range) .
• the refractive index of the successive elements is continuously increased towards the wafer (image plane) , namely up to a level of more than 2.0.
• optical path lengths for s-and p-polarization are largely equalized for the broadest possible range of angles through the simultaneous use of three crystalline materials Al 2 0 3 , Si0 2 , and MgF 2 . It should be noted that the harmful contributions for skewed rays increase the farther one moves these elements away from the wafer, i.e., from the image plane. This also provides the special possibility of a compensation based on where a lens of each of the respective materials is positioned.
• the optical path length should to the greatest extent possible meet the condition (n_-n_)Al 2 0 3 -d.
• n o represents the refractive index for the ordinary ray
• n e represents the refractive index for the extraordinary ray
• 1( d 2 , d 3 represent the respective path lengths inside the crystals. It should be the aim (and it is possible) to meet the condition particularly well in the aperture angle range from 65° to 72°.
• the scope of the invention likewise includes a lithography objective in a projection system, where the effect of birefringence of uniaxial crystal materials in end-closure plates or lenses on the image side of the objective is completely corrected for angles in the range from 65° to 72° (measured geometrically from the optical axis) .
• LaF 3 has a negative optical character and the biref ingence values likewise resemble those of Al 2 0 3 .
• LaF 3 has the advantage that the commercially available crystals, which are made in a completely different manufacturing process, currently meet higher standards of optical quality.
• LaF 3 is water-insoluble, but it does not come up to the levels of hardness and UV transmittance of Al 2 0 3 sapphire.
• Figure 8 schematically illustrates an example for an operating wavelength of 193 nm where LaF 3 is used for the last lens on the image side, in this case with a protector plate P of ⁇ -Al 2 0 3 .
• the alternative to an arrangement with an immersion fluid is an optical near field where the distance between the protector plate P and the wafer is shorter than the operating wavelength.
• the birefringence values were measured by the interference method and are more reliable than measuring the indices n o and n e by means of prisms and taking the differences.
• uniaxial crystals are compensated as follows :
• Lenses LPP of positive refractive power and positive optical character are compensated by lenses LPN of positive refractive power with negative character (Fig. 10) .
• lenses of positive refractive power can also be compensated with lenses of negative refractive power with the same character, as shown in the example of Figure 11 - with positive character in the lenses LPP, LNP (negative refractive power) , possibly supplemented by a lens LPN.
• Figure 12 shows an arrangement where lenses LPN, LNN, LPP follow each other, with LNN being a lens of negative refractive power and negative optical character.
• Figure 13 shows the four last lenses on the image side of a microlithography projection objective with the materials according to the invention as the significant mass (material) of the lenses, which may be coated with layers for antireflection, anticorrosion or the like (as in the other embodiments discussed), i.e., MgF 2 /

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• Physics & Mathematics (AREA)
• General Physics & Mathematics (AREA)
• Optics & Photonics (AREA)
• Health & Medical Sciences (AREA)
• Epidemiology (AREA)
• Public Health (AREA)
• Environmental & Geological Engineering (AREA)
• Toxicology (AREA)
• Engineering & Computer Science (AREA)
• Chemical & Material Sciences (AREA)
• Crystallography & Structural Chemistry (AREA)
• Lenses (AREA)
• Exposure Of Semiconductors, Excluding Electron Or Ion Beam Exposure (AREA)
• Crystals, And After-Treatments Of Crystals (AREA)

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• 2004
  • 2004-12-10 JP JP2006544290A patent/JP5102492B2/ja not_active Expired - Fee Related
  • 2004-12-10 WO PCT/EP2004/014100 patent/WO2005059645A2/en not_active Ceased
  • 2004-12-15 US US10/596,626 patent/US7755839B2/en not_active Expired - Fee Related
  • 2004-12-15 WO PCT/EP2004/014290 patent/WO2005059618A2/en not_active Ceased

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