Microlithography illumination optical system and microlithography projection exposure apparatus including same
09933704 ยท 2018-04-03
Assignee
Inventors
Cpc classification
G03F7/70116
PHYSICS
G03F7/70075
PHYSICS
G03F7/70083
PHYSICS
International classification
Abstract
A microlithography illumination optical system is used to guide illumination light from a primary light source to an object field. A mirror array of the illumination optical system has a plurality of individual mirrors, which can be tilted independently of one another by actuators and are connected to associated tilting actuators. A controller is used to activate the actuators. A raster module of the illumination optical system has a plurality of raster elements to produce a spatially distributed arrangement of secondary light sources.
Claims
1. An optical system, comprising: a mirror array comprising a plurality of mirrors; a plurality of actuators, each mirror being independently tiltable via an associated actuator; a controller configured to activate the actuators; and a raster module configured to produce a spatially distributed arrangement of secondary light sources, the raster module being in a region of a plane of the optical system in which an emergent angle at which an illumination light part bundle leaves one of the raster elements is precisely allocated to a location region in an object field of the optical system on which the illumination light part bundle impinges, wherein the controller is configured so that specifying a tilting angle for each individual mirror allocates a predetermined field-dependent desired course of illumination angle intensity distributions by which object field points distributed over the object field are impinged upon, and wherein: the raster module comprises two raster arrangements arranged one behind another in a beam path of the illumination light; each of the two raster arrangements comprises a plurality of raster elements; the two raster arrangements are configured so that a diameter of the illumination light part bundle, as it impinges on an impingement face one of the raster elements of the second raster arrangement, is less than half of the impingement face of the raster element of the second raster arrangement; one of the following conditions holds: at least for certain emergent angles of the illumination light part bundles, the two raster arrangements are configured so that, depending on an impingement location on the raster elements of the second raster arrangement at least for angles of incidence which are in each case allocated to the respective impingement location of the illumination light part bundle on the raster elements of the second raster arrangement, the same emergent angle of the illumination light part bundles from the raster element results, at least for certain emergent angles of the illumination light part bundle, the two raster arrangements are configured so that small changes in an angle of incidence of the illumination light part bundles on the raster elements of the second raster arrangement lead to great changes in the emergent angle of the illumination light part bundles from the raster elements; and the optical system is a microlithography illumination optical system.
2. The optical system of claim 1, wherein the raster module is in the plane, and the plane is adjacent a pupil plane of the optical system.
3. The optical system of claim 1, wherein, at least for certain emergent angles of the illumination light part bundles, the two raster arrangements are configured so that depending on an impingement location on the raster elements of the second raster arrangement at least for angles of incidence which are in each case allocated to the respective impingement location of the illumination light part bundle on the raster elements of the second raster arrangement the same emergent angle of the illumination light part bundles from the raster element results.
4. The optical system of claim 3, wherein the same emergent angle which results depends on the impingement location.
5. The optical system of claim 1, wherein, at least for certain emergent angles of the illumination light part bundle, the two raster arrangements are configured so that small changes in an angle of incidence of the illumination light part bundles on the raster elements of the second raster arrangement lead to great changes in the emergent angle of the illumination light part bundles from the raster elements.
6. The optical system of claim 1, wherein the raster module and the controller are configured so that a predetermined distribution of actual tilting angles of the individual mirrors and a predetermined distribution of actual angles of incidence of the illumination light part bundles on the raster elements are allocated to a predetermined desired course of illumination light angle intensity distributions with which object field points distributed over the object field are impinged upon, and this allocation is present along two dimensions of the object field which are perpendicular to one another.
7. The optical system of claim 1, further comprising a Fourier lens arrangement between the mirror array and the raster module.
8. An apparatus comprising: an illumination optical system which comprises: a mirror array comprising a plurality of mirrors; a plurality of actuators, each mirror being independently tiltable via an associated actuator; a controller configured to activate the actuators; and a raster module configured to produce a spatially distributed arrangement of secondary light sources, the raster module being in a region of a plane of the optical system in which an emergent angle at which an illumination light part bundle leaves one of the raster elements is precisely allocated to a location region in an object field of the optical system on which the illumination light part bundle impinges; and a projection objective, wherein: the raster module comprises two raster arrangements arranged one behind another in a beam path of the illumination light; each of the two raster arrangements comprises a plurality of raster elements; the two raster arrangements are configured so that a diameter of the illumination light part bundle, as it impinges on an impingement face one of the raster elements of the second raster arrangement, is less than half of the impingement face of the raster element of the second raster arrangement; one of the following conditions holds: at least for certain emergent angles of the illumination light part bundles, the two raster arrangements are configured so that, depending on an impingement location on the raster elements of the second raster arrangement at least for angles of incidence which are in each case allocated to the respective impingement location of the illumination light part bundle on the raster elements of the second raster arrangement, the same emergent angle of the illumination light part bundles from the raster element results, at least for certain emergent angles of the illumination light part bundle, the two raster arrangements are configured so that small changes in an angle of incidence of the illumination light part bundles on the raster elements of the second raster arrangement lead to great changes in the emergent angle of the illumination light part bundles from the raster elements; and the apparatus is a microlithography projection exposure apparatus.
9. The apparatus of claim 8, wherein the raster module is in the plane, and the plane is adjacent a pupil plane of the optical system.
10. The apparatus of claim 8, wherein, at least for certain emergent angles of the illumination light part bundles, the two raster arrangements are configured so that depending on an impingement location on the raster elements of the second raster arrangement at least for angles of incidence which are in each case allocated to the respective impingement location of the illumination light part bundle on the raster elements of the second raster arrangement the same emergent angle of the illumination light part bundles from the raster element results.
11. The apparatus of claim 10, wherein the same emergent angle which results depends on the impingement location.
12. The apparatus of claim 8 wherein, at least for certain emergent angles of the illumination light part bundle, the two raster arrangements are configured so that small changes in an angle of incidence of the illumination light part bundles on the raster elements of the second raster arrangement lead to great changes in the emergent angle of the illumination light part bundles from the raster elements.
13. The apparatus of claim 8, wherein the raster module and the controller are configured so that a predetermined distribution of actual tilting angles of the individual mirrors and a predetermined distribution of actual angles of incidence of the illumination light part bundles on the raster elements are allocated to a predetermined desired course of illumination light angle intensity distributions with which object field points distributed over the object field are impinged upon, and this allocation is present along two dimensions of the object field which are perpendicular to one another.
14. The apparatus of claim 8, further comprising a primary light source.
15. The apparatus of claim 8, wherein the raster module is in the plane, and the plane is conjugated to and is spaced apart a pupil plane of the projection objective.
16. The apparatus of claim 8, further comprising further comprising a Fourier lens arrangement between the mirror array and the raster module.
17. A method of using a microlithography projection exposure apparatus comprising an illumination optical system and a projection objective, the method comprising: using the optical system to illuminate a reticle having structures; and using the projection objective to project at least a part of the reticle onto a light-sensitive material, wherein: the illumination optical system, comprises: a mirror array comprising a plurality of mirrors; a plurality of actuators, each mirror being independently tiltable via an associated actuator; a controller configured to activate the actuators; and a raster module configured to produce a spatially distributed arrangement of secondary light sources, the raster module being in a region of a plane of the optical system in which an emergent angle at which an illumination light part bundle leaves one of the raster elements is precisely allocated to a location region in an object field of the optical system on which the illumination light part bundle impinges; the controller is configured so that specifying a tilting angle for each individual mirror allocates a predetermined field-dependent desired course of illumination angle intensity distributions by which object field points distributed over the object field are impinged upon; the raster module comprises two raster arrangements arranged one behind another in a beam path of the illumination light; each of the two raster arrangements comprises a plurality of raster elements; the two raster arrangements are configured so that a diameter of the illumination light part bundle, as it impinges on an impingement face one of the raster elements of the second raster arrangement, is less than half of the impingement face of the raster element of the second raster arrangement; and one of the following holds: at least for certain emergent angles of the illumination light part bundles, the two raster arrangements are configured so that, depending on an impingement location on the raster elements of the second raster arrangement at least for angles of incidence which are in each case allocated to the respective impingement location of the illumination light part bundle on the raster elements of the second raster arrangement, the same emergent angle of the illumination light part bundles from the raster element results, at least for certain emergent angles of the illumination light part bundle, the two raster arrangements are configured so that small changes in an angle of incidence of the illumination light part bundles on the raster elements of the second raster arrangement lead to great changes in the emergent angle of the illumination light part bundles from the raster elements.
18. The method of claim 17, wherein the raster module is in the plane, and the plane is conjugated to and is spaced apart from a pupil plane of the projection objective.
19. The method of claim 17, further comprising a Fourier lens arrangement between the mirror array and the raster module.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
(1) Embodiments of the disclosure will be described in more detail below with the aid of the drawings, in which:
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DETAILED DESCRIPTION
(15)
(16) To facilitate the showing of positional relationships, a Cartesian xyz coordinate system is reproduced in the drawing. The x-direction runs upwardly in
(17) A scanning direction of the projection exposure system 1 runs in the y-direction, in other words perpendicular to the plane of the drawing in
(18) An illumination system designated as a whole by 5 of the projection exposure system 1 is used for the defined illumination of an object or illumination field 3 in an object or reticle plane 4, in which a structure to be transferred in the form of a reticle, not shown in more detail, is arranged. The illumination system 5 includes a primary light source 6 and an illumination optical system 7 with the optical components for guiding illumination or imaging light 8 to the object field 3. The primary light source 6 is an ArF laser with a working wavelength of 193 nm, the illumination light beam of which is oriented coaxially with respect to the optical axis 2. Other UV light sources, for example an F.sub.2 excimer laser with a 157 nm working wavelength, a KrF excimer laser with a 248 nm working wavelength and primary light sources with larger or smaller working wavelengths are also possible.
(19) A beam of illumination light 8 coming from the light source 6 with a small rectangular cross section initially impinges on a beam widening optical system 9, which produces an exiting beam of the illumination light 8 with substantially parallel light and a larger rectangular cross section. The beam widening optical system 9 may contain elements which reduce undesired effects of the coherence of the illumination light 8. The illumination light 8 substantially parallelised by the beam widening optical system 7 then impinges on a micro mirror array (Multi Mirror Array, MMA) 10 to produce an illumination light angle distribution. The micro mirror array 10 has a large number of rectangular individual mirrors 11 arranged in an xy-raster. Each of the individual mirrors 11 is connected to an associated tilting actuator 12. Each of the tilting actuators 12 is connected by a control line 13 to a controller 14 to activate the actuators 12. The actuators 12 can be actuated independently of one another by the controller 14. Each of the actuators 12 can adjust a predetermined x-tilting angle (tilting in the xz-plane) and, independently thereof, a y-tilting angle (tilting in the yz-plane) of the individual mirror 11, so that an angle of reflection AS.sub.x of an illumination light part bundle 15 reflected by the associated individual mirror 11 can be predetermined in the xz-plane and, accordingly, an angle of reflection AS.sub.y, not shown in the drawing, can be predetermined in the yz-plane.
(20) The angle distribution produced by the MMA 10 of angles of reflection AS of the illumination light part bundles 15 is transformed when passing through a Fourier lens arrangement or a capacitor 16, which is positioned at the spacing of its focal length from the MMA 10, into a two-dimensional, location-dependent illumination light intensity thus distribution perpendicular to the optical axis 2. The intensity distribution thus produced is therefore present in a first illumination plane 17 of the illumination system 5. Together with the Fourier lens arrangement 16, the MMA 10 is thus a light distribution device to produce a two-dimensional illumination light intensity distribution.
(21) Arranged in the region of the first illumination plane 17 is a first raster arrangement 18 of a raster module 19, which is also called a honeycomb capacitor. Angles of incidence ER.sub.x in the xz-plane (cf
(22) The raster module 19 is used to produce a spatially distributed arrangement of secondary light sources, in other words of images of the primary light source 6 and therefore to the production of a defined illumination angle distribution of the illumination light leaving the raster module 19.
(23) A second raster arrangement 21 is arranged in a further illumination plane 20. The illumination plane 17 is in or close to a front focal plane of individual elements of the second raster arrangement 21. The two raster arrangements 18, 21 are a honeycomb capacitor of the illumination optical system 7. The further illumination plane 20 is a pupil plane of the illumination system 5 or is adjacent to a pupil plane of the illumination system 5. The raster module 19 is therefore also designated the field-defining element (FDE).
(24) The emergent angles AR.sub.x in the xz-plane (cf.
(25) Arranged downstream of the raster module 19 is a further capacitor 22, which is also called a field lens. Together with the second raster arrangement 21, the capacitor 22 images the first illumination plane 17 in a field intermediate plane 23 of the illumination system 5. A reticle marking system (REMA) 24, which is used as an adjustable shading mask to produce a sharp edge of the illumination light intensity distribution, may be arranged in the field intermediate plane 23. A following lens system 25 images the field intermediate plane 23 on the reticle, in other words, the lithography master, which is located in the reticle plane 4. Using a projection lens system 26, the reticle plane 4 is imaged on a wafer or image plane 27 on the wafer, not shown in
(26) The first raster arrangement 18 has individual first raster elements 28, which are arranged column-wise and line-wise in the xy-plane. The first raster elements 28 have a rectangular aperture with an x/y aspect ratio of, for example, 1/1. Other, in particular greater x/y-aspect ratios of the first raster elements 28, for example 2/1, are possible.
(27) The meridional section according to
(28) The raster construction and the function of the raster module 19 basically correspond to that which is described in WO2007/093433 A1.
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(30) No refractive effect of the Fourier lens arrangement 16 is shown in a simplified manner in
(31) Components which correspond to those which were discussed above with reference to the figures already described, have the same reference numerals and will not be described again in detail.
(32) The illumination light part bundle 15.sub.1 shown at the top in
(33) The two raster elements 28, 30 allocated to one another via the light path of the illumination light part bundle 15.sub.1, on the one hand, of the first raster arrangement 18, and, on the other hand, of the second raster arrangement 21 predetermine an illumination light channel.
(34) A substantially higher number of channels are present in the case of the real raster module 19 than shown in the drawing, for example a few hundred, a few thousand or even a few tens of thousands of channels of this type. The second raster elements 30 of the second raster arrangement 21, in each case allocated to the channels, are arranged in the light path behind the first raster elements 28 of the first raster arrangement 18. The second raster elements 30 are also configured as microlenses with, in particular, a positive refractive power. The second raster elements 30 are also called pupil honeycombs, which are arranged in the second illumination plane 20, in other words in a pupil plane of the illumination optical system 7. The second illumination plane 20 is conjugated to a pupil plane 31 of the projection lens system 26. The second raster elements 30, together with the field lens 22, image the first raster elements 28 arranged in the second illumination plane 17, in other words the field honeycombs, in the field intermediate plane 23. The images of the first raster elements 28 are thus superimposed in the field intermediate plane 23.
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(36) The second illumination light part bundle 15.sub.2 shown in
(37) Taking into account the refractive effect of the Fourier lens arrangement 16, the angle of reflection AS.sub.x2 of the illumination light part bundle 15.sub.2 from the individual mirror 11.sub.2 may be approximately identical to the angle of reflection AS.sub.x1 of the illumination light part bundle 15.sub.1 if these impinge upon the same raster element 28 of the first raster arrangement 18. Because of the fact that the illumination light part bundles 15.sub.1, 15.sub.2 are emitted from different locations from the MMA 10, in other words from different individual mirrors 11, and therefore impinge at different locations on the Fourier lens arrangement 16, a difference is then nevertheless produced between the two angles of incidence of the illumination light part bundles 15.sub.1, 15.sub.2 on the first raster arrangement 18. This situation, in which the same angles of incidence of various illumination light part bundles 15.sub.1, 15.sub.2 are transferred to the Fourier lens arrangement 16 at different emergent angles, is not shown in
(38) After passing through the first raster element 28, the second illumination light part bundle 15.sub.2 impinges on a second location region 29 of the same second raster element 30 as the first illumination light part bundle 15.sub.1. The second location region 29 specifies an impingement location of the second illumination light part bundle 15.sub.2 on this second raster element 30. The two location regions 29 and 29, in which the two illumination light part bundles 15.sub.1, 15.sub.2 impinge on the second raster element 30, are spatially separated from one another in the embodiment shown. Alternative embodiments are possible, in which the location regions 29 and 29, in which the two illumination light part bundles 15.sub.1, 15.sub.2 impinge on the second raster element 30, partially overlap one another.
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(40) The impingement location or location region 29 (or 29, cf
(41) The surface design of an entry face 33 and/or an exit face 34 of the second raster elements 30 of the second raster arrangement 21 of the raster module 19 can be designed in such a way that for specific emergent angles AR.sub.x, this emergent angle is identical for specific combinations of the impingement location of the illumination light part bundle 15 on the second raster element 30 and the angle of incidence ER.sub.x of the illumination light part bundle 15 on this second raster element 30, while for other exit angles, AR.sub.x is in turn dependent on the impingement location and/or on the angle of incidence ER.sub.x. This can be used, on the one hand, to sharply define the field edges of the object field 3 and, on the other hand, to predetermine an intensity distribution of specific illumination directions on the object field 3, as will be described below.
(42) The entry faces 33 and/or the exit faces 34 of the raster elements 30 may be spherical, aspherical and, in particular conical in design.
(43) The controller 14 is configured in such a way that a predetermined distribution of actual tilting angles of the individual mirrors 11 of the MMA 10 and, as a result, a predetermined distribution of actual angles of incidence ER.sub.x, ER.sub.y of the illumination light part bundles 15 on the first raster elements 28 is allocated to a predetermined desired course of illumination angle intensity distributions, with which object field points over the object field 3 are impinged upon.
(44) This will be described in more detail below with the aid of
(45) The Fourier lens arrangement or the capacitor 16 between the MMA 10 and the raster module 19 is left out in the schematic
(46) Alternative illuminations for the raster module 19, which are shown in
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(48) The actual tilting angle distribution according to
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(50) The corresponding field dependency of the illumination intensity from the direction of the pole I.sub.2 is shown on the left in
(51) The I(x)-dependency for the I.sub.3-pole is shown at the bottom in
(52) The I.sub.x-dependency for the illumination intensity from the direction of the I.sub.4-pole is shown on the right in
(53) Depending on the design of the refractive effects of the first raster elements 28 and the second raster elements 30, a large bandwidth of other desired courses of illumination angle intensity distributions, with which object field points are impinged upon over the object field, can be predetermined. A desired distribution of angles of incidence ER.sub.x, ER.sub.y of the illumination light part bundles 15 on the raster elements 28 of the raster module 19 is then firstly determined for the predetermined desired course, during the adjustment of the illumination optical system 7 to prepare the operation of the projection exposure system 1. A distribution of desired tilting angles of the individual mirrors 11 is then allocated to this determined desired angle of incidence distribution. A desired tilting angle is therefore predetermined for each individual mirror 11. Finally, the tilting actuators 12 of the individual mirrors 11 are activated in such a way that the actual tilting angles of the individual mirrors 11 coincide with the associated desired tilting angles.
(54) A degree of dependency of the desired course I(x) of the illumination angle intensity distributions, with which the object field points are impinged upon over the object field 3, on the distribution of actual angles of incidence ER.sub.x, ER.sub.y of the illumination light part bundles 15 on the first raster elements 28 or ER.sub.x, ER.sub.y on the second raster elements 30 can be influenced by the positional relationship of the two raster arrangements 18, 21 of the raster module 19 with respect to the at least one pupil plane of the illumination optical system 7. Depending on whether, for example, the second illumination plane 20 coincides with a pupil plane of the illumination optical system 7 or whether a defined spacing is present between the second illumination plane 20 and the pupil plane of the illumination optical system 7, a weaker or stronger dependency of the desired course of illumination angle intensity distributions on the actual angle of incidence ER.sub.x may result.
(55) Depending on the specification of an actual tilting angle distribution of the individual mirrors 11 of the MMA 10, predetermined intensity distributions of the illumination light part bundles 15 on the raster module 19 and correspondingly predetermined intensity distributions in the pupil plane 31 may result. A further example to supplement the quadrupole intensity distribution described above in conjunction with
(56) The ratios in the guidance of an illumination light part bundle 15 with the two raster elements 28, 30, allocated to a light channel, of the raster arrangements 18, 21 of the raster module 19 will be described in detail below with the aid of
(57) Components which correspond to those which were discussed above with reference to the already described figures, have the same reference numerals and will not be described again in detail.
(58) During the guidance of the illumination light part bundle 15 according to
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(61) In comparison to the bundle guidances according to
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(63) If the parameter pair condition according to the isolines 36, 37 according to
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(68) The effect of a raster module 19 with a second raster arrangement 21 with second raster elements 30, the entry faces 33 of which are formed according to the design according to
(69) Components which correspond to those which were discussed above with reference to the figures already described, have the same reference numerals and will not be described again in detail.
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(73) To produce the raster module 29 with the second raster arrangement 21 with second raster elements 30 to specify emergent angle dependencies corresponding to those which were described above with reference to
(74) In an alternative production method for the raster module 19, classes of desired dependencies AR(ER, AO) of a course of resulting constant emergent angles AR.sub.x of the illumination light part bundles 15 from the second raster elements 30 are determined depending on the impingement location AO of the illumination light part bundles 15 on these raster elements 30 of the second raster arrangement 21 and depending on the angle of incidence ER.sub.x of the illumination light part bundles 15 on these raster elements 30, which can be achieved with typical face designs of the entry faces 33 and/or the exit faces 34 of the second raster elements 30. These classes of desired dependencies AR(ER, AO) may have isoline courses of parameter pairs of angles of incidence ER.sub.x and of impingement locations AO, which lead to the same emergent angles AR.sub.x, as described above in conjunction with
(75) The effect of the raster module 19 on the illumination light part bundles 15 was described above primarily in the xz-plane. Corresponding effects and dependencies are also produced in the yz-plane. This can be used in order to define the y-field edges of the object field 3 and to also predetermine an intensity distribution from the illumination angles predetermined by an illumination setting over the object field 3 in the y-direction. This may, in particular, be used in the case of the configuration of the projection exposure system 1 as a stepper, in which the entire object field 3 is simultaneously, in other words, not by a scanning method, illuminated and imaged.
(76) In the described embodiments, the raster elements 28, 30 are dioptric, in other words refractive raster elements. In principle, the raster elements 28, 30 may also be designed as catoptric, in other words reflective raster elements.
(77) It was already stated above that no refractive effect of the Fourier lens arrangement 16 is shown in a simplified manner in
(78) The course of two illumination light part bundles 15.sub.1 and 15.sub.2 from the respective individual mirrors 11.sub.1 and 11.sub.2 of the micro mirror array 10 is in turn shown. The two part bundles 15.sub.1, 15.sub.2 have angles of reflection AS.sub.x1 and AS.sub.x2 from the individual mirrors 11.sub.1 and 11.sub.2. The refractive effect of the Fourier lens arrangement 16 leads to the conversion of these angles of reflection AS.sub.x1 and AS.sub.x2 to angles of reflection AS.sub.x1 and AS.sub.x2 after the Fourier lens arrangement 16. The angles of incidence ER.sub.x1 and ER.sub.x2 of the two illumination light part bundles 15.sub.1, 15.sub.2 on the entry face 33 of the same raster element 30 of the second raster arrangement 21 are also shown. In the view according to
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(81) A substrate or a wafer in the wafer plane 27 is firstly provided for the microlithographic production of microstructured or nanostructured components with the projection exposure system 1. At least one layer of a light-sensitive material is applied to the wafer. A reticle having structures to be imaged is furthermore provided in the reticle plane 4. The part of the reticle arranged in the object field 3 is then projected, using the projection exposure system 1, onto a region of the layer arranged in the image field.
(82) From the foregoing, it is apparent that the two raster arrangements 18, 21, at least for specific emergent angles AR.sub.xm of the illumination light part bundle 15, are configured in such a way that small changes in the angle of incidence ER.sub.x of the illumination light part bundles 15 on the raster elements 30 of the second raster arrangement 21 lead to great changes in the emergent angle AR.sub.x of the illumination light part bundles 15 from the raster elements 30.