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WO2012034571A1 - Système d'éclairage d'un appareil d'exposition à projection microlithographique - Google Patents

Système d'éclairage d'un appareil d'exposition à projection microlithographique Download PDF

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Publication number
WO2012034571A1
WO2012034571A1 PCT/EP2010/005628 EP2010005628W WO2012034571A1 WO 2012034571 A1 WO2012034571 A1 WO 2012034571A1 EP 2010005628 W EP2010005628 W EP 2010005628W WO 2012034571 A1 WO2012034571 A1 WO 2012034571A1
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WIPO (PCT)
Prior art keywords
light
array
optical
optical elements
illumination system
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Ceased
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PCT/EP2010/005628
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English (en)
Inventor
Markus Schwab
Michael Patra
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Carl Zeiss SMT GmbH
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Carl Zeiss SMT GmbH
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Priority to PCT/EP2010/005628 priority Critical patent/WO2012034571A1/fr
Priority to TW100132835A priority patent/TW201234120A/zh
Publication of WO2012034571A1 publication Critical patent/WO2012034571A1/fr
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

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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
    • G03F7/70058—Mask illumination systems
    • G03F7/70091—Illumination settings, i.e. intensity distribution in the pupil plane or angular distribution in the field plane; On-axis or off-axis settings, e.g. annular, dipole or quadrupole settings; Partial coherence control, i.e. sigma or numerical aperture [NA]
    • G03F7/70116—Off-axis setting using a programmable means, e.g. liquid crystal display [LCD], digital micromirror device [DMD] or pupil facets
    • 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
    • G03F7/70058—Mask illumination systems
    • G03F7/70075—Homogenization of illumination intensity in the mask plane by using an integrator, e.g. fly's eye lens, facet mirror or glass rod, by using a diffusing optical element or by beam deflection

Definitions

  • the invention generally relates to an illumination system of a microlithographic projection exposure apparatus, and in particular to an apparatus comprising an array of micromir- rors or other beam deflecting elements.
  • Microlithography is a technology for the fabrication of integrated circuits, liquid crystal displays and other micro- structured devices.
  • the process of microlithography in conjunction with the process of etching, is used to pattern features in thin film stacks that have been formed on a substrate, for example a silicon wafer.
  • a substrate for example a silicon wafer.
  • the wafer is first coated with a photoresist which is a material that is sensitive to light of a certain wavelength.
  • the wafer with the photoresist on top is exposed to projection light through a mask in a projection exposure apparatus.
  • the mask contains a circuit pattern to be imaged onto the photoresist.
  • the photoresist is developed to produce an image that corresponds to the circuit pattern contained in the mask.
  • a projection exposure apparatus typically includes an illumination system that illuminates a field on the mask that may have the shape of a rectangular or curved slit, for example.
  • the apparatus further comprises a mask stage for aligning the mask, a projection objective (sometimes also referred to as 'the lens') that images the illuminated field on the mask onto the photoresist, and a wafer alignment stage for aligning the wafer coated with the photoresist.
  • One of the essential aims in the development of projection exposure apparatus is to be able to lithographically define structures with smaller and smaller dimensions on the wafer. Small structures lead to a high integration density, which generally has a favorable effect on the performance of the microstructured components produced with the aid of such ap- paratus.
  • One approach has been to reduce the wavelength of the projection light used to image the circuit pattern onto the photoresist. This exploits that fact that the minimum size of the features that can be lithographically defined is approximately proportional to the wavelength of the projection light. Therefore the manufacturers of such apparatus strive to use projection light having shorter and shorter wavelengths.
  • the shortest wavelengths currently used are 248 nm, 193 nm and 157 nm and thus lie in the deep (DUV) or vacuum (VUV) ultraviolet spectral range.
  • the next generation of commercially available apparatus will use projection light having an even shorter wavelength of about 13.5 nm which is in the extreme ultraviolet (EUV) spectral range.
  • EUV appa- ratus contains mirrors instead of lenses because the latter absorb nearly all EUV light.
  • the illumination system of a projection exposure ap- paratus illuminates each point of the field illuminated on the mask with projection light having a well defined spatial and angular irradiance distribution.
  • the term angular irradiance distribution describes how the total light energy of a light bundle, which converges towards a particular point on the mask, is distributed among the various directions of the rays that constitute the light bundle.
  • the angular irradiance distribution of the projection light impinging on the mask is usually adapted to the kind of pattern to be imaged onto the photoresist. For example, relatively large sized features may require a different angular irradiance distribution than small sized features.
  • the most commonly used angular irradiance distributions are referred to as conventional, annular, dipole and quadrupole illumina- tion settings. These terms refer to the irradiance distribution in a pupil surface of the illumination system. With an annular illumination setting, for example, only an annular region is illuminated in the pupil surface. Thus there is only a small range of angles present in the angular irradi- ance distribution of the projection light, and all light rays impinge obliquely with similar angles onto the mask.
  • the mirror array is realized as a micro- electromechanical system (MEMS) comprising more than 1000 microscopic mirrors.
  • MEMS micro- electromechanical system
  • Each of the mirrors can be tilted about two orthogonal tilt axes.
  • radiation incident on such a mirror device can be reflected into almost any desired direction of a hemisphere.
  • a condenser lens arranged between the mirror array and a pupil surface translates the reflection angles produced by the mirrors into locations in the pupil surface.
  • This illumination system makes it possible to illuminate the pupil surface with a plurality of spots, wherein each spot is associated with one particular mirror and is freely movable across the pupil surface by tilting this mirror .
  • an illumination system comprising a dividing array of optical elements, wherein each optical element has a positive optical power and produces a converging light beam that is associated exclusively with the optical elements.
  • the illumination system further comprises a surface, for example a pupil surface or a surface on or immediately in front of an optical integrator that is arranged in the vicinity of the pupil surface.
  • the illumination system also comprises a spatial light modulator which is arranged between the dividing array and the surface and which is configured to vary an irradiance distribution on the surface.
  • the spatial light modulator comprises a beam deflection array of reflective or transparent beam deflection elements.
  • Each beam deflection element is associated with (at least) one of the optical elements of the dividing array and is configured to deflect a converging light beam produced by the associated optical element by a deflection angle that is variable in response to a control signal. Furthermore, the deflection element is configured to direct the deflected light beam towards the surface where the deflected light beam produces a light spot having a spot size.
  • at least two optical elements of the dividing array have different optical properties so that the spot sizes of the light spots associated with the at least two optical elements are different.
  • the illumination system in accordance with the present invention is thus capable of producing light spots in the surface which have different spot sizes. This is advantageous because larger light spots may be assembled so that larger quasi- continuous illuminated areas in the surface are obtained.
  • the smaller spots may then be used to complete and to refine the contour of this area so that the desired irradiance distribution is accurately matched. For example, only with very small light spots it is possible to produce a rounded edge of the area to be illuminated, but with a given number of very small spots it is, on the other hand, impossible to illuminate larger areas continuously. Only the provision of smaller and larger light spots makes it possible to produce larger areas having a desired contour.
  • the optical elements of the dividing array may be refractive optical elements such as microlenses, reflective optical elements such as micromirrors, or diffractive optical elements.
  • a positive power of the optical elements means that they have a converging effect, as is the case with positive lenses, concave mirrors or diffractive optical elements having a focusing effect.
  • the beam deflection elements may be mirrors that can be tilted, and the beam deflection array may then comprise ac- tuators to tilt the mirrors.
  • the beam deflection elements may also comprise transparent elements that make use of the electro-optical or acousto-optical effect.
  • the refractive index can be varied by exposing a suitable material to electric fields or ultrasonic ways, re- spectively. These effects are then used to produce index gratings that direct impinging light into various directions.
  • the different optical property of the at least two optical elements may be the optical power. If the optical power of the at least two optical elements is different, also the con- verging effect is different, and thus the light beams emerging from the optical elements have a different angular light distribution. Since the angular light distribution of the light beams transform in the far field, or with the help of a condenser, into a spatial irradiance distribution, light spots produced by optical elements having different optical power will have a different size at the surface. If only the optical power, but not the size of the optical elements varies, the areas of the light spots in the surface will differ, but not their shape.
  • the optical elements of the dividing array usually have light entry and light exit surfaces.
  • different optical properties of the at least two optical elements may be achieved if the light entry and/or the light exit surfaces of the at least two optical elements have different areas. This ex- ploits the fact that also the areas of the light entry and/or light exit surface have an impact on the angular light distribution of the light beams emerging from the optical elements. This varying angular light distribution is then trans- formed in the far field, or by using an additional condenser, into different spot sizes at the surface.
  • one of the at least two optical elements may have a light entry or a light exit surface having a rectangular contour
  • the other of the at least two optical ele- ments may have a light entry or a light exit surface having an octagonal contour.
  • Such contours of the light entry or light exit surfaces may be preferred for symmetry reasons. But, as a matter of course, there are various other geometries that will result in different spot sizes.
  • the optical elements may be arranged in the dividing array such that the light entry or light exit surfaces of the optical elements are arranged in a periodic pattern in which light entry or light exit surfaces having a rectangular contour alternate with light entry or light exit surfaces having an octagonal contour.
  • At least five optical elements of the dividing array have different optical properties so that light spots with at least five different spot sizes are produced in the pupil surface.
  • the illumination system may comprise a light source that completely illuminates an entry surface of the dividing array.
  • the dividing array may then be configured such that all light impinging on its entry surface is directed towards the spa- tial light modulator, if diffraction and absorption is disregarded. In other words, no light is lost in the dividing array, which has a positive effect on the yield of the projection exposure apparatus.
  • the illumination system comprises a beam homogenizer that is arranged between the light source and the dividing array so as to ensure that the light source homoge- nously illuminates the entry surface of the dividing array, if diffraction is disregarded. This is advantageous because then the irradiance of the light spot produced by a particular light beam depends only on the optical properties of the associated optical element, but not additionally on its position within the dividing array.
  • light denotes any electromagnetic radiation, in particular visible light, UV, DUV, VUV and EUV light and X- rays.
  • light ray is used herein to denote light whose path of propagation can be described by a line.
  • light bundle is used herein to denote a plurality of light rays that have a common origin in a field plane.
  • light beam is used herein to denote light that passes through a particular lens or another optical element.
  • optical raster element is used herein to denote any optical element, for example a lens, a prism or a dif- fractive optical element, which is arranged, together with other optical raster elements, so that a plurality of adjacent optical channels are produced or maintained.
  • optical integrator is used herein to denote an optical system that increases the product NA-a, wherein NA is the numerical aperture and a is the illuminated field area.
  • condenser is used herein to denote an optical ele- ment or an optical system that establishes (at least approximately) a Fourier relationship between two planes, for example a field plane and a pupil plane.
  • spatial irradiance distribution is used herein to denote how the total irradiance varies over a real or imagi- nary surface on which light impinges.
  • the spatial irradiance distribution can be described by a function I s (x, y) , with x, y being spatial coordinates of a point in the surface. If applied to a field plane, the spatial irradiance distribution necessarily integrates the irradiances produced by a plurality of light bundles.
  • angular irradiance distribution is used herein to denote how the irradiance of a light bundle varies depending on the angles of the light rays that constitute the light bundle.
  • I a (a, ⁇ , x, y) .
  • surface is used herein to denote any plane or curved surface in the three-dimensional space. The surface may be part of a body or may be completely separated therefrom, as it is usually the case with a field or a pupil plane .
  • optical power is used to denote the ability of an optical element to have a diverging or converging effect on light. A positive optical power thus has a converging effect, and a negative optical power has a diverging optical effect.
  • the term "converging effect” means that the convergence is increased, irrespective of whether the incoming light is di- verging, parallel or already converging. If the incoming light is divergent, the convergence has to be increased to such an extent that the light beams emerging from the optical elements are at least slightly converging.
  • spot size is used herein to denote the total area that is illuminated on the surface by a particular light beam associated with one of the beam deflecting elements.
  • the spot size is usually measured in units of mm 2 .
  • FIG. 1 is a schematic perspective view of a projection ex- posure apparatus in accordance with one embodiment of the present invention
  • FIG. 2 is a meridional section through an illumination
  • FIG. 3 is a perspective view of a mirror array contained in the illumination system shown in FIG. 3;
  • FIG. 4 is a top view of a dividing array contained in the illumination system shown in FIG. 3;
  • FIG. 5 is a sectional view along line V-V of the array
  • FIG. 4 is an enlarged cutout from FIG. 3 showing convergent light beams that are produced by the dividing array; is a top view on a surface on which spots produced by the light beams and having two different sizes are assembled to form a desired exemplary irradi- ance distribution; is a top view similar to FIG. 7, but with spots having all the same size; is a top view of a dividing array according to a second embodiment; is a sectional view along line X-X of the array shown in FIG. 9; is an enlarged meridional section similar to FIG. 6 for the second embodiment; is a sectional view similar to FIG.
  • FIG. 10 is a top view of a dividing array according to a third embodiment; is a sectional view along line XIV-XIV of the array shown in ' FIG. 13; is a top view of a dividing array according to a fourth embodiment; is a top view on a surface on which spots produced by the light beams and having three different sizes are assembled to form a desired circular irradiance distribution; is a top view similar to FIG. 16, but with spots having all the same size. DESCRIPTION OF PREFERRED EMBODIMENTS
  • FIG. 1 is a perspective and highly simplified view of a pro- jection exposure apparatus 10 in accordance with the present invention.
  • the apparatus 10 comprises an illumination system 12 which produces a projection light beam.
  • the latter illuminates a field 14 on a mask 16 containing a pattern 18 of fine features 19.
  • the illuminated field 14 has the shape of a ring segment which does not contain an optical axis OA of the apparatus 10.
  • other shapes of the illuminated field 14, for example rectangles, are contemplated as well.
  • a projection objective 20 containing a plurality of lenses 21 images the pattern 18 within the illuminated field 14 onto a light sensitive layer 22, for example a photoresist, which is supported by a substrate 24.
  • the substrate 24, which may be formed by a silicon wafer, is arranged on a wafer stage (not shown) such that a top surface of the light sensitive layer 22 is precisely located in an image plane of the projection objective 20.
  • the mask 16 is positioned by means of a mask stage (not shown) in an object plane of the projection objective 20. Since the latter has a magnification ⁇ with
  • the mask 16 and the substrate 24 move along a scan direction which corresponds to the Y direction indicated in FIG. 1.
  • the illuminated field 14 then scans over the mask 16 so that patterned areas larger than the illumi- nated field 14 can be continuously imaged.
  • the ratio between the velocities of the substrate 24 and the mask 16 is equal to the magnification ⁇ of the projection objective 20. If the projection objective 20 inverts the image ( ⁇ 0), the mask 16 and the substrate 24 move in opposite directions, as this is indicated in FIG. 1 by arrows Al and A2.
  • the present invention may also be used in stepper tools in which the mask 16 and the substrate 24 do not move during projection of the mask.
  • FIG. 2 is a meridional section through the illumination system 12 shown in FIG. 1:
  • the illumination system 12 includes a housing 29 and a light source 30 that is, in the embodiment shown, realized as an excimer laser.
  • the light source 30 emits projection light having a wavelength of about 193 nm.
  • the light beam emitted by the light source 30 enters a beam expansion unit indicated at 32 in which the light beam is expanded.
  • the beam expansion unit 32 may comprise several lenses or planar mirrors, for example.
  • the expanded light beam emerging from the beam expansion unit 32 and denoted with 34 has a low divergence, i. e. it is almost collimated.
  • the expanded light beam 34 now enters a dividing array 36 which divides the expanded light beam 34 into a plurality of individual converging light beams LB.
  • a dividing array 36 which divides the expanded light beam 34 into a plurality of individual converging light beams LB.
  • the dividing array 36 will be explained in more detail further below with reference to FIGS. 4 to 6.
  • the converging light beams LB then propagate through a spatial light modulator 38 that is used to produce variable spa- tial irradiance distributions in a subsequent pupil plane.
  • the spatial light modulator 38 comprises an array 40 of micromirrors 42 that can be tilted individually about two orthogonal axes with the help of actuators.
  • the actuators are controlled by a control unit 43 which is connected to an overall system control 45.
  • FIG. 3 is a perspective view of the array 40 illustrating how two of the converging light beams LB1, LB2 are reflected into different directions depending on the tilting angles of the micromirrors 42 on which the light beams LB1, LB2 impinge.
  • the array 40 comprises only 6 6 micromirrors
  • the array 40 may comprise several hundreds or even several thousands micromirrors 42.
  • the spatial light modulator 38 further comprises a prism 46 having a first plane surface 48a and a second plane surface 48b that are both inclined with respect to the optical axis OA of the illumination system 12. At these inclined surfaces 48a, 48b the light beams LB are reflected by total internal reflection.
  • the first surface 48a reflects the impinging light beams LB towards the micromir- rors 42 of the micromirror array 40, and the second surface 48b directs the light beams reflected from the micromirrors 42 towards an exit surface 49 of the prism 46.
  • the directions of the light beams LB, and thus the angular irradiance distribution of the light emerging from the exit surface 49 of the prism 46, can thus be varied by individually tilting the micromirrors 42 of the array 40. More details with regard to the spatial light modulator 40 can be gleaned from US
  • the angular irradiance distribution produced by the spatial light modulator 38 is transformed into a spatial irradiance distribution with the help of a first condenser 50 which directs the impinging light beams LB towards an optical inte- grator 52.
  • the optical integrator 52 comprises two optical raster plates 54a, 54b each containing two orthogonal arrays of cylindrical microlenses.
  • the optical integrator 52 produces a plurality of secondary light sources in a subsequent pupil plane 56 of the illumination system 12.
  • a second condenser 58 establishes a Fourier relationship between the pupil plane 56 and a field stop plane 60 in which an adjustable field stop 62 is arranged.
  • the second condenser 58 superimposes the light beams emerging from the secondary light sources in the field stop plane 60 so that the latter is illuminated very homogenously .
  • the field stop plane 60 is imaged by a field stop objective 64 onto a mask plane 66 in which the mask 16 is arranged with the help of a mask stage (not shown) . Also the adjustable field stop 62 is thereby imaged on the mask plane 66 and de- fines at least the short lateral sides of the illuminated field 14 extending along the scan direction Y.
  • the irradiance distribution in front of the optical integrator 52 determines the irradiance distribution in the pupil plane 56 and thus the angular irradiance distribution in the field stop plane 60 and the mask plane 66.
  • FIGS. 4 and 5 show the dividing array 36 in a bottom view and a sectional view along line V-V, respectively.
  • the dividing array 34 comprises first microlenses 70a and second microlenses 70b having different optical properties.
  • the first and second microlenses 70a, 70b are both plano-convex and thus have a positive refractive power. However, the positive refractive power is different, as will be explained with ref- erence to the sectional view of FIG. 5.
  • each microlens 70a, 70b has a planar light entrance surface 72, on which the expanded light beam 34 emerging from the beam expansion unit 32 impinges, and a convexly curved light exit surface 74.
  • the light entry surfaces 72 of the microlenses 70a, 70b are arranged in a common plane, but the first and second microlenses 70a, 70b have different light exit surfaces 74. More specifically, the light exit surface 74 of the first microlenses 70a has a radius of curvature r a which is smaller than the radius of cur- vature r b of the light exit surface 74 of the second microlenses 70b.
  • the centers of curvatures are arranged in two different planes; in other embodiments the centers of curvature may lie in the same plane, similar to what is shown in FIG. 12 for another embodiment.
  • the light exit surfaces 74 of the first and second microlenses 70a, 70b have a square contour with equal areas.
  • the pattern has been determined so that the first and second microlenses 70a, 70b alternate, i. e. each first microlens 70a has four second microlenses 70b as edge neighbors, and vice versa.
  • FIG. 6 is an enlarged cutout of FIG. 2. Only the upper portion of the illumination system 12 between the light source 30 and a plane 76 located immediately in front of the optical integrator 52 is shown.
  • the expanded light beam 34 emerging from the beam expansion unit 32 is at least substantially parallel, i. e. it has no or only a small divergence.
  • it passes through the light entry surfaces 72 of the first and second microlenses 70a, 70b of the dividing array 34 and is refracted at their convexly curved light exit surfaces 74, it will be divided into a plurality of converging light beams LB as a result of the positive refractive power of the first and second microlenses 70a, 70b.
  • the light beams associated with the first and second microlenses 70a, 70b converge to different extents. This is illustrated in FIG. 6 for two light beams LBa and LBb which emerge from a first microlens 70a and a second mi- crolens 70b, respectively.
  • the different convergence becomes clear, for example, from the fact that the stronger converging light beam LBa has its focal point directly on the asso- ciated micromirror 42, whereas the focal point of the less converging light beam LBb lies further away in the vicinity of the exit surface 49 of the prism 46.
  • the different degree of convergence, or more correctly speaking the different divergence of the light beams LBa, LBb, translates into different beam diameters w a , w b along the X direction at the position of the surface 76 which is located behind the first condenser 50.
  • This transformation from divergence into beam diameters is established by the first con- denser 50, but could also be observed in the far field if the first condenser 50 is dispensed with.
  • the different refractive power of the first and second microlenses 70a, 70b of the dividing array 36 produces at the surface 76 light spots that have different spot sizes depending on the beam diameters w a , w t> .
  • the spot size SP depends on the pitch p of the microlenses 70a, 70b, their focal length f ML and the focal length of the first condenser f c according to the following eguation (1) :
  • FIG. 7 shows an exemplary irradiance distribution at the surface 76.
  • the larger light spots that are produced by the stronger convergent light beams LBa are denoted with 78a, and the smaller light spots that are produced by the less conver- gent light beams LBb are denoted with 78b.
  • Both light spots 78a, 78b have approximately . a square shape which is a result of the square contour of the first and second microlenses 70a, 70b.
  • the ratio r a /r b has been selected such that the size of the smaller light spots 78b is about one quarter of the size of the larger light spots 78a.
  • the desired irradiance distribution at the surface 76 has a trapezoidal geometry, as it is indicated in FIG. 7 by the broken line 80, this irradiance distribution can be approximated very well with the two differently sized light sports 78a, 78b.
  • FIG. 8 shows, for a comparison, an irradiance distribution that would be obtained if all light spots 78' had the same size, as it is known in t e prior art. It can be seen that the approximation of the desired trapezoidal irradiance dis- tribution 80 would be significantly less accurate, as compared with the irradiance distribution shown in FIG. 7.
  • the same amount of light is concentrated on the larger light spots 78a and the smaller light spots 78b.
  • the irradiance of the smaller light spots 78b is about four times as large as the irradiance of the larger light spots 78a. Often this would be an undesired effect. This could be avoided if the first and second microlenses 70a, 70b are not illuminated uniformly, thereby exploiting the fact that in the absence of a beam ho- mogenizer the laser beam has not a uniform profile.
  • first microlenses 70a may be arranged such that they are positioned at the center of the laser beam where the irradiance is higher, and the second microlenses 70b are arranged at the periphery where the irradiance is lower.
  • the reduced irradiance produced by the larger light spots 78a may be compensated for by superposing more than one, for example four, larger light spots 78a.
  • the different convergence of the light beams LBa, LBb has been achieved by providing first and second microlenses 70a, 70b having light exit surfaces 74 with different curvatures.
  • the light exit surfaces 74 of all microlenses 70a, 70b could be identical, but the second microlenses 70b having a smaller optical power may be provided with concavely curved light entry surfaces 72.
  • the curvatures of all microlenses 70a, 70b may be equal, but the first microlenses 70a have a greater refractive index, which also leads to an increased optical power.
  • the first and second microlenses 70a, 70 may be redistributed so that one half of the array consists only of first microlenses 70a having a higher refractive index, and the other half consists only of second microlenses 70b having a lower refractive index, for example.
  • first and second microlenses 70a, 70b does not have to be equal, and there may also be more different types of microlenses than two. For example, if there are five different types of microlenses which differ from each other with respect to their optical power, it would be possible to obtain five different spot sizes at the surface 76. This usually provides more flexibility to obtain a desired irradiance distribution.
  • FIGS. 16 and 17 show, in a comparison similar to FIGS. 7 and 8, exemplary irradiance distributions at the surface 76 obtained with light spots 78a, 78b, 78c of three different sizes (FIG. 16) and with light spots 78 of only one size (FIG. 17). Apparently the approximation of a conventional illumination setting, in which a circular area 80' shall be il- luminated, is much better with three spot sizes then with only one.
  • FIGS. 9 and 10 are a bottom view and a sectional view along line X-X of a dividing array 136 according to such an embodiment.
  • the microlenses 170a, 170b are planar-convex microlenses each having a planar light entry surface 172 and a convexly curved light exit surface 174.
  • the curvatures of the light exit surfaces 174 are identical for all microlenses 170a, 170b. This is illustrated in FIG. 10 by two circles 175 having an identical radius r.
  • the light exit surfaces 174 of the first and second microlenses 170a, 170b have different areas.
  • the area of the light exit surface 174 of the first microlenses 170a is more than about four times as large as the area of the light exit surface 174 of the second microlenses 170b.
  • Different areas of the light exit surfaces 174 means that the pitch p of the microlenses varies.
  • the vertices of the microlenses 170a, 170b which are located at the center of each light exit surface 174, still form a periodic grid-like pattern which corresponds to the periodic arrangement of the mi- cromirrors 42 of the mirror array 40.
  • the different areas of the light exit surfaces 174 inevitably leads also to different contours of the light exit surfaces 174.
  • FIG. 11 is a cut-out of the illumination system 12 similar to FIG. 6, but with the dividing array 36 replaced by the dividing array 136 shown in FIGS. 9 and 10. Furthermore, the illumination system shown in FIG.
  • the beam homogenizer 182 may be configured as a rod homogenizer, or it may comprise one or more arrays of optical raster elements, as it is known in the art as such.
  • the light beams LBa and LBb produced by the first and second microlenses 170a and 170b, respectively, produce also in this embodiments light spots at the surface 76 having different diameters w a and w b , respec- tively.
  • FIG. 11 also illustrates that the focal lengths of the first and second microlenses 170a, 170b are equal.
  • the focal length is selected such that the light beams LBa, LBb are focused on the micromirrors 42 of the mirror array 44.
  • the focal point will often be located elsewhere in order to avoid damages of the reflective coatings of the micromirrors 42 caused by too high irradiances . V.
  • the centers of curvature of the convexly curved light exit surfaces 174 do not lie in a common plane. Consequently, also the focal planes of the first microlenses 170a and the second microlenses 170b are slightly offset from each other. If this is, for whatever reason, not desired, the dividing array may be modified as it is shown in FIG. 12. Here the centers of curvature of the first and second microlenses
  • first and second microlenses 170a, 170b lie in a common plane, and consequently also the focal planes of the first and second microlenses 170a, 170b coincide exactly.
  • FIGS. 13 and 14 show, in a similar bottom view and cross-section, an embodiment of a dividing array 236 in which the arrays of the light exit surfaces 274 vary statistically.
  • the vertices of the microlenses 270 are still arranged in a periodic manner, as it is indicated in FIG. 14 by vertical broken lines.
  • Such wedges may be arranged either directly on the microlenses 270 or on an additional support.
  • the light exit surfaces of the microlenses may have any arbitrary shape.
  • FIG. 15 is a bottom view of a dividing array 336 according to a still further embodiment in which light exit surfaces of smaller microlenses have the shape of a rectangle, an ellipse, a star or a triangle.
  • the other larger microlenses have different polygonal shapes.
  • the vertices of the microlenses are indicated in FIG. 15 by small dots 90.

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Exposure And Positioning Against Photoresist Photosensitive Materials (AREA)
  • Microscoopes, Condenser (AREA)
  • Lenses (AREA)

Abstract

L'invention porte sur un système d'éclairage d'un appareil d'exposition à projection microlithographique, lequel système comprend un réseau de division (36; 136; 236) d'éléments optiques (70a, 70b; 170a, 170b; 270). Chaque élément optique a une puissance optique positive, et produit un faisceau de lumière convergent (LBa, LBb). Un modulateur spatial de lumière (38) est disposé entre le réseau de division (36; 136; 236) et une surface (76), et est configuré de façon à faire varier une distribution de la densité de flux énergétique dans la surface (78). Le modulateur comprend un réseau (40) de miroirs configurés chacun de façon à dévier un faisceau de lumière convergent (LBa, LBb) produit par l'élément optique associé d'un angle de déviation qui est variable en réponse à un signal de commande. Chaque miroir dirige le faisceau de lumière dévié vers la surface (76) où le faisceau de lumière dévié produit un point lumineux (78a, 78b, 78c). Au moins deux éléments optiques (70a, 70b; 170a, 170b; 270) du réseau de division (36; 136; 236) ont des propriétés optiques différentes, de sorte que les tailles des points lumineux soient différentes.
PCT/EP2010/005628 2010-09-14 2010-09-14 Système d'éclairage d'un appareil d'exposition à projection microlithographique Ceased WO2012034571A1 (fr)

Priority Applications (2)

Application Number Priority Date Filing Date Title
PCT/EP2010/005628 WO2012034571A1 (fr) 2010-09-14 2010-09-14 Système d'éclairage d'un appareil d'exposition à projection microlithographique
TW100132835A TW201234120A (en) 2010-09-14 2011-09-13 Illumination system of a microlithographic projection exposure apparatus

Applications Claiming Priority (1)

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PCT/EP2010/005628 WO2012034571A1 (fr) 2010-09-14 2010-09-14 Système d'éclairage d'un appareil d'exposition à projection microlithographique

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WO2012034571A1 true WO2012034571A1 (fr) 2012-03-22

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Publication number Priority date Publication date Assignee Title
US8699121B2 (en) 2011-05-06 2014-04-15 Carl Zeiss Smt Gmbh Illumination system of a microlithographic projection exposure apparatus
WO2014056513A1 (fr) * 2012-10-08 2014-04-17 Carl Zeiss Smt Gmbh Système d'éclairage d'appareil d'exposition par projection microlithographique
US9671699B2 (en) 2012-10-27 2017-06-06 Carl Zeiss Smt Gmbh Illumination system of a microlithographic projection exposure apparatus
US10281823B2 (en) 2015-05-13 2019-05-07 Carl Zeiss Smt Gmbh Illumination system of a microlithographic projection exposure apparatus

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EP1262836A1 (fr) 2001-06-01 2002-12-04 Asml Appareil lithographique
WO2005026843A2 (fr) 2003-09-12 2005-03-24 Carl Zeiss Smt Ag Systeme d'eclairage pour une installation d'exposition de projection de microlithographie
US20060087634A1 (en) 2004-10-25 2006-04-27 Brown Jay M Dynamic illumination uniformity and shape control for lithography
US7061582B2 (en) 2002-09-19 2006-06-13 Samsung Electronics Co., Ltd. Exposure apparatus including micro mirror array and exposure method using the same
US20090115990A1 (en) 2007-11-06 2009-05-07 Nikon Corporation Illumination optical apparatus, exposure apparatus, and device manufacturing method
WO2009080231A1 (fr) * 2007-12-21 2009-07-02 Carl Zeiss Smt Ag Système d'éclairage pour éclairer un masque dans un appareil d'exposition par projection microlithographique
EP2146248A1 (fr) * 2008-07-16 2010-01-20 Carl Zeiss SMT AG Système d'illumination d'un appareil d'exposition à projection microlithographique
US20100060873A1 (en) * 2007-04-25 2010-03-11 Carl Zeiss Smt Ag Illumination system for illuminating a mask in a microlithographic exposure apparatus
WO2010034472A1 (fr) * 2008-09-29 2010-04-01 Carl Zeiss Smt Ag Systeme d'eclairage d'un appareil d'exposition par projection microlithographique

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EP1262836A1 (fr) 2001-06-01 2002-12-04 Asml Appareil lithographique
US7061582B2 (en) 2002-09-19 2006-06-13 Samsung Electronics Co., Ltd. Exposure apparatus including micro mirror array and exposure method using the same
WO2005026843A2 (fr) 2003-09-12 2005-03-24 Carl Zeiss Smt Ag Systeme d'eclairage pour une installation d'exposition de projection de microlithographie
US20060087634A1 (en) 2004-10-25 2006-04-27 Brown Jay M Dynamic illumination uniformity and shape control for lithography
US20100060873A1 (en) * 2007-04-25 2010-03-11 Carl Zeiss Smt Ag Illumination system for illuminating a mask in a microlithographic exposure apparatus
US20090115990A1 (en) 2007-11-06 2009-05-07 Nikon Corporation Illumination optical apparatus, exposure apparatus, and device manufacturing method
WO2009080231A1 (fr) * 2007-12-21 2009-07-02 Carl Zeiss Smt Ag Système d'éclairage pour éclairer un masque dans un appareil d'exposition par projection microlithographique
EP2146248A1 (fr) * 2008-07-16 2010-01-20 Carl Zeiss SMT AG Système d'illumination d'un appareil d'exposition à projection microlithographique
WO2010034472A1 (fr) * 2008-09-29 2010-04-01 Carl Zeiss Smt Ag Systeme d'eclairage d'un appareil d'exposition par projection microlithographique

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US8699121B2 (en) 2011-05-06 2014-04-15 Carl Zeiss Smt Gmbh Illumination system of a microlithographic projection exposure apparatus
WO2014056513A1 (fr) * 2012-10-08 2014-04-17 Carl Zeiss Smt Gmbh Système d'éclairage d'appareil d'exposition par projection microlithographique
JP2015501552A (ja) * 2012-10-08 2015-01-15 カール・ツァイス・エスエムティー・ゲーエムベーハー マイクロリソグラフィ投影露光装置の照明系
US9261695B2 (en) 2012-10-08 2016-02-16 Carl Zeiss Smt Gmbh Illumination system of a microlithographic projection exposure apparatus
US9671699B2 (en) 2012-10-27 2017-06-06 Carl Zeiss Smt Gmbh Illumination system of a microlithographic projection exposure apparatus
US10281823B2 (en) 2015-05-13 2019-05-07 Carl Zeiss Smt Gmbh Illumination system of a microlithographic projection exposure apparatus

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