Abstract:
An illumination system is used to illuminate a specified illumination field of an object surface with EUV radiation. The illumination system has an EUV source and a collector to concentrate the EUV radiation in the direction of an optical axis. A first optical element is provided to generate secondary light sources, and a second optical element is provided at the location of these secondary light sources, the second optical element being part of an optical device which includes further optical elements, and which images the first optical element into an image plane into the illumination field. Between the collector and the illumination field, a maximum of five reflecting optical elements are arranged. These optical elements reflect the main beam either grazingly or steeply. The optical axis, projected onto an illumination main plane, is deflected by more than 30° between a source axis portion and a field axis portion. In a first variant of the illumination system, at least an axis portion between at least two of the reflecting optical elements is inclined relative to the illumination main plane. In a second variant of the illumination system, the optical device, in addition to the second optical element includes precisely three further optical elements, i.e. a third optical element, a fourth optical element and a fifth optical element. In this second variant, the optical axis meets the third, fourth and fifth optical elements at an angle of incidence which is greater than 70°. This construction variants make possible either an increase of the EUV throughput of the illumination system for a given size, or a reduction of the size of the illumination system and thus of the associated projection exposure system for a given EUV throughput.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application is a continuation of, and claims priority under 35 U.S.C. §120 to, U.S. patent application Ser. No. 11/755,334, filed May 30, 2007, which claims priority under 35 U.S.C. §119(e)(1) to German Application Serial No. 10 2006 026 032.5, filed on Jun. 1, 2006. The contents of these applications are hereby incorporated by reference. 
     
    
     FIELD 
       [0002]    The disclosure relates to EUV illumination systems, as well as related components, systems and methods. 
       BACKGROUND 
       [0003]    Illumination systems to illuminate a specified illumination field of an object surface with EUV radiation are disclosed in U.S. Pat. No. 6,859,328 B2, US 2005/0093041 A1, U.S. Pat. No. 6,858,853 B2, US 2005/0002090 A1, US 2003/0095623 A1, U.S. Pat. No. 6,400,794 B1 and WO 01/065482 A. A collector to concentrate EUV radiation is disclosed in DE 100 45 265 A1. The illumination systems are part of a projection exposure system, and are used in micro-lithography for producing integrated circuits, to illuminate an object in the form of a mask or reticle. 
       SUMMARY 
       [0004]    The disclosure can provide illumination systems and projection exposure systems equipped with them so that either with a given size their EUV throughput is increased, i.e. the reflection losses are reduced, or with a given EUV throughput their size is reduced. 
         [0005]    According to the disclosure, this can be achieved, for example, by an illumination system with at least an axis portion of the optical axis being inclined between at least two of the optical elements relative to the illumination main plane. 
         [0006]    It has been found that in the case of illumination systems of the above-mentioned kind, the following conflicting requirements often should be taken into account: first, the number of components for EUV concentration which are designed to be reflective throughout in the illumination system should be as small as possible, because of the reflection losses. Furthermore, for spatial housing of the EUV source which can be implemented in practice, an optical axis which after the source runs essentially horizontally should be converted via the successive components of the illumination system into an optical axis which runs essentially vertically, to illuminate the object surface. Ideally, a deflection of the optical axis in the region of 90° should be carried out, so that an EUV beam which leaves the EUV source essentially horizontally is deflected into a beam which illuminates the illumination field essentially vertically, e.g. at an angle of 6° to the normal onto the illumination field. Finally, to minimise the reflection losses, the angle of incidence on the reflecting components of the illumination system, i.e. on the reflecting optical elements after the collector and preferably on the EUV collector itself, should either be very large, i.e. in the region of grazing incidence, or very small, i.e. in the region of vertical incidence. The illumination system according to the disclosure fulfils these requirements. Preferably, the optical axis meets the reflecting optical elements which are arranged successive to the collector at an angle of incidence which is either greater than 70° or less than 20°. 
         [0007]    According to the disclosure, the result is an illumination system which on the one hand supplies a high EUV throughput, because the number of reflections is minimised, and simultaneously reflections with favourable angles of reflection take place, and also makes compact construction possible, because a relatively large angle of deflection for the optical axis is implemented. Even an angle of deflection which is only slightly greater than 30° makes possible an illumination system with an overall height which does not make excessive demands on a factory for integrated circuits. In particular, even in the case of spatially extended sources, illumination systems in which the source is arranged not more than 2.5 m below the object surface in the vertical direction can be implemented. The illumination system can therefore be used in typical clean rooms. 
         [0008]    A first variant of an illumination system according to the disclosure uses an optical axis which is folded in three optical directions, at least a portion of the optical axis being inclined relative to the rest of the optical axis. This allows a particularly compact arrangement of the optical elements of the illumination system, without an obstruction being caused by these optical elements. These advantages prevail a possibly higher effort regarding optical or mechanical design, since as a rule there is no plane of mirror symmetry of the system arrangement regarding a folded system. 
         [0009]    A size of the illumination field of at least 100 mm 2  permits a high object throughput. The direct result of this is faster production of integrated circuits. 
         [0010]    An illumination system wherein the second optical element is part of an optical device which includes further optical elements, and which guides the EUV radiation reflected by the first optical element along the optical axis, and images the first optical element into the illumination field being arranged in the image plane, which coincides with the object surface, permits precise imaging of the first optical element into the image plane. 
         [0011]    Versions of the illumination system wherein (1) the optical device includes at least two further optical elements after the second optical element, i.e. a third and a fourth optical element and an axis portion of the optical axis being inclined between the third and the fourth element of the optical device relative to the illumination main plane, wherein (2) the optical device includes at least two further optical elements after the second optical element, i.e. a third and a fourth optical element and an axis portion of the optical axis being inclined between the or a first and the or a second optical element relative to the illumination main plane and wherein (3) an axis portion between the second and the third element of the optical device is inclined relative to the illumination main plane, consistently extend the partial concept according to the disclosure of folding the optical axis in the three spatial directions. Because of the differently folded portions of the optical axis, compact arrangements of the optical elements of the illumination system can be implemented. 
         [0012]    An illumination system wherein after the second optical element, a maximum of two further optical elements are provided, an axis portion of the optical axis between the collector and the first optical element being inclined relative to the illumination main plane, the source of the EUV radiation being a plasma source, permits irradiation of EUV radiation, which can hardly be obstructed by downstream optical elements of the illumination system, from the collector. An optical device having an axis portion between the first and the second optical element which is inclined relative to the illumination main plane, has particularly few optical elements, and can therefore be designed particularly efficiently in the EUV throughput. An EUV collector which concentrates the EUV radiation through exactly one reflection is known in various versions from US 2005/0002090 A1 and US 2005/0093041 A1. An EUV collector with which the EUV radiation is concentrated through two reflections is known from US 2003/0095623 A1. 
         [0013]    The versions of the illumination system wherein (1) an axis portion of the optical axis between the first and the second optical element is inclined relative to the illumination main plane and wherein (2) the optical device, in addition to the second optical element, includes precisely two further optical elements, i.e. a third optical element and a further optical element, and wherein an axis portion of the optical axis between the collector and the first optical element and an axis portion of the optical axis between the second optical element and the third optical element being inclined relative to the illumination main plane, also extend the concept of folding in the three spatial directions, so that compact arrangements result, in particular with a high angle of deflection of the optical axis. 
         [0014]    A second variant of an illumination system according to the disclosure, wherein the optical device, in addition to the second optical element, includes precisely three further optical elements, i.e. a third optical element, a fourth optical element and a fifth optical element, the optical axis meeting the third, fourth and fifth optical elements at an angle of incidence which is greater than 60°, in particular greater than 70°, allows a high angle of deflection of the optical axis even if no folding of the optical axis in the three spatial directions is used. By distributing the deflection of the optical axis to multiple optical elements, which are operated with grazing incidence, the optical axis can be efficiently deflected, without the optical elements obstructing each other. In particular, the second optical element, which can be implemented, in particular, as a pupil facet element, can be operated efficiently in grazing incidence. The second optical element can then be implemented so that a relatively large area of it is acted on in reflection, which reduces the thermal load on the second optical element. Preferably, the optical axis meets in this second variant the third, fourth and fifth optical elements at an angle of incidence which is greater than 70°. 
         [0015]    Numerical apertures of the illumination of at least 0.02, preferably at least 0.03 and illumination field sizes of at least 500 mm 2 , preferably at least 800 mm 2  ensure effective illumination of the object. 
         [0016]    As far as the projection exposure system is concerned, the initially stated object is achieved by a projection exposure system having an illumination system according to the disclosure. 
         [0017]    The advantages of this projection exposure system, of the method of microlithographic production of microstructured components, having the following steps:
       provision of a substrate, to which a layer of a light-sensitive material is applied at least in certain regions;   provision of a reticle, which has structures to be imaged;   provision of a projection exposure system according to the disclosure;   projection of at least a portion of the reticle onto an area of the light-sensitive layer of the substrate using the projection exposure system;       
 
         [0022]    and the advantages of the components being produced according to this method correspond to those which were stated above with reference to the illumination system. 
         [0023]    Embodiments of the disclosure are described in more detail below with reference to the drawings. 
     
    
     
       DESCRIPTION OF DRAWINGS 
         [0024]      FIG. 1  shows schematically a meridional section through a projection exposure system which is known from the prior art, with an illumination system to illuminate a specified illumination field of an object surface with EUV radiation, to explain the functions of the participating components; 
           [0025]      FIG. 2  shows a first embodiment of an illumination system according to the disclosure, an EUV source and a collector not being shown; 
           [0026]      FIG. 3  shows a similar representation to  FIG. 2  of a further embodiment; 
           [0027]      FIG. 4  shows a similar representation to  FIG. 2  of a further embodiment; 
           [0028]      FIG. 5  shows a similar representation to  FIG. 2  of a further embodiment; 
           [0029]      FIG. 6  shows a similar representation to  FIG. 2  of a further embodiment; 
           [0030]      FIG. 7  shows a similar representation to  FIG. 2  of a further embodiment; 
           [0031]      FIG. 8  shows a similar representation to  FIG. 2  of a further embodiment; 
           [0032]      FIG. 9  shows a similar representation to  FIG. 2  of a further embodiment; 
           [0033]      FIG. 10  shows a similar representation to  FIG. 2  of a further embodiment; and 
           [0034]      FIGS. 11 and 12  show true scale projections which reproduce the course of the optical axis in the embodiment according to  FIG. 10 . 
       
    
    
     DETAILED DESCRIPTION 
       [0035]      FIG. 1  shows a projection exposure system which is known from U.S. Pat. No. 6,859,328 B2, with an illumination system  1  to illuminate a specified illumination field  2  of a surface  3  of an object  4  with EUV radiation  5 . 
         [0036]    At top right in  FIG. 1 , a Cartesian xyz co-ordinate system is drawn, and is referred to below. The x axis points towards the observer, the y axis points to the right, and the z axis points up. The illumination field  2  extends parallel to the xy plane, and extends further in the x direction than in the y direction, so that it is rectangular. The illumination field  2  extends about 100 mm in the x direction and 8 mm in the y direction, resulting in an illumination field with a size of about 800 mm 2 . The illumination field is in any case greater than 100 mm 2 , preferably greater than 500 mm 2 . The illumination field  2  can, for instance, be curved as a ring segment of a ring field. The object  4 , which is also called a reticle, is the mask which is to be imaged onto a wafer as a substrate by a projection optical system which is connected downstream. The object  4  is arranged in an intended position plane or image plane  4   a , in which the illumination field  2  lies and which extends parallel to the xy plane. The EUV radiation  5  has a wavelength of 13.5 nm. Other EUV wavelengths, e.g. between 10 and 30 nm, are possible. Of the EUV radiation  5 , for better clarity, only beams  6  at the margin and an optical axis  7  are shown. 
         [0037]    As the source  8  of the EUV radiation  5 , a plasma source is used. Other source types for EUV radiation are also possible. 
         [0038]    A collector  9  concentrates the EUV radiation  5 , which the source  8  emits, by reflection in the direction of the optical axis  7 . Along the optical axis  7 , the EUV radiation  5  is guided by successive optical elements, which will be described. As in the case of the collector  9 , these optical elements are the optical elements which reflect the EUV radiation  5 . 
         [0039]    After the collector  9 , a first optical element  10  is used to generate secondary light sources in the illumination system  1 . The first optical element  10  is also called a field raster element. 
         [0040]    In the beam path after the first optical element  10 , at the location of the secondary light sources which the first optical element  10  generates, a second optical element  11  is arranged. This optical element is also called a pupil raster element, and is in the area of a pupil plane of the illumination system  1 . Representing the many secondary light sources which the first optical element  10  generates, in  FIG. 1  a secondary light source  1  a is indicated on the second optical element  11 . The second optical element  11  is part of an optical device  12 , which includes further optical elements. The optical device  12  guides the EUV radiation  5 , reflected by the first optical element  10 , along the optical axis  7 , and images the first optical element  10  into the image plane  4   a , which coincides with the object surface  3 . 
         [0041]    The optical device  12  includes, after the second optical element  11 , a third optical element  13 , a fourth optical element  14  and a fifth optical element  15 . 
         [0042]    The secondary light sources  1  a are imaged by the optical elements  13  to  15 , and by the reflection on the object surface  3 , into a pupil plane  16  of the schematically indicated projection optical system  16   a . From the entry into the projection optical system  16   a , the real course of the beams deviates from the course which is drawn in  FIG. 1 , for which reason the beams, from the entry into the schematically shown projection optical system  16   a , are shown dashed. An example of such a projection optical system is found in  FIG. 84  of U.S. Pat. No. 6,859,328 B2. Below the pupil plane  16 , the wafer  16   b  is arranged as a substrate, onto which the structure on the object surface  3  is to be imaged. 
         [0043]    Between the last optical element of the optical device  12 , ie. the fifth optical element  15 , and the illumination field  2 , runs a portion  17  of the optical axis  7 , called the field axis portion below. The field axis portion  17  of the optical axis lies in an illumination main plane  18 , which in the case of the illumination system  1  according to  FIG. 1  coincides with the yz plane, i.e. the drawing plane of  FIG. 1 . The field axis portion  17  of the optical axis, with the image plane  4   a , encloses an angle which is less than 90°. Below, if angles between beams or beam portions, axes or axis portions, or between beams or axes and planes are given, in each case the angle which is less than 90° is taken. 
         [0044]    Between the collector  9  and the first optical element  10 , a portion  19  of the optical axis  7 , also called the source axis portion below, is arranged. The source axis portion  19  also lies in the illumination main plane  18 . In the case of the known illumination system  1  according to  FIG. 1 , the source axis portion  19 , with the field axis portion  17  of the optical axis, encloses an angle of about 23°. 
         [0045]    Embodiments according to the disclosure of illumination systems are described below on the basis of the very schematic  FIGS. 2 to 12 . Components corresponding to those which were described above with reference to  FIG. 1  have the same reference numbers and are not discussed again in detail. 
         [0046]    In the case of the illumination system  1  according to  FIG. 2 , after the source axis portion  19 , the optical axis  7  is reflected by a field raster element, i.e. the first optical element  10 , and successively by a pupil raster element, i.e. the second optical element  11 , and by the third optical element  13 , the fourth optical element  14  and the fifth optical element  15 , before it reaches the image plane  4   a . The first optical element  10  and second optical element  11  are raster mirrors, and the fourth optical element  14  is in the form of a reflecting concave mirror. The third optical element  13  and fifth optical element  15  are in the form of reflecting convex mirrors. The raster mirrors  10 ,  11  and optical elements  14  and  15  can have aspherical imaging optical surfaces. 
         [0047]    In the case of the version according to  FIG. 2 , between the collector (not shown) and the illumination field  4   a  five reflecting optical elements, i.e. optical elements  10 ,  11 ,  13 ,  14 ,  15 , are therefore arranged. The optical axis  7  meets the optical elements  10 ,  11 ,  13  and  14  at an angle of incidence which is less than 20° (steep incidence; normal incidence). The optical axis  7  meets the fifth optical element  15  at an angle of incidence which is greater than 70° (grazing incidence). As is usual in optics, the angles of incidence are defined as the angles between the axis portion which is incident in each case on the optical element and the normal onto the struck surface of this optical element. 
         [0048]    An axis portion  20  of the optical axis between the third optical element  13  and the fourth optical element  14  is inclined to the illumination main plane  18 , which is indicated in  FIG. 2  by a dashed version of the axis portion  20 . The illumination main plane  18  is defined in  FIG. 2 , as in  FIG. 1 , by the field axis portion  17  and the intersection with the image plane  4   a , and coincides with the drawing plane of  FIG. 2 . Because of the inclination of the axis portion  20 , the fourth optical element  14  is displaced relative to the third optical element  13  by a positive amount in the x direction. All other axis portions except axis portion  20  run parallel to the illumination main plane  18 . The result of this is that the fifth optical element  15  is also displaced relative to the third optical element  13  in the positive x direction, so that in the x projection which is reproduced by  FIG. 2 , the fifth optical element  15  comes to lie over the third optical element  13 . The result is a compact arrangement of the optical elements of the illumination system  1 . 
         [0049]    In the case of the version according to  FIG. 2 , the projection of the source axis portion  19  onto the illumination main plane  18 , with a projection of the field axis portion  17  onto the illumination main plane  18 , encloses an angle of about 40°. 
         [0050]      FIG. 3  shows another version according to the disclosure of the illumination system. Components corresponding to those which were described above with reference to  FIGS. 1 and 2  have the same reference numbers and are not discussed again in detail. 
         [0051]    In the case of the illumination system  1  according to  FIG. 3 , an axis portion  21  of the optical axis between the first optical element  10  and the second optical element  11  runs obliquely to the illumination main plane  18 , which lies in the image plane of  FIG. 3 . Apart from the axis portion  21 , all other portions of the optical axis  7  run parallel to the illumination main plane  18 . Because of the inclination of the axis portion  21 , the second optical element  11  is arranged relative to the first optical element  10  displaced in the positive x direction. The result of this is that the further optical elements  13  to  15  are also arranged relative to the first optical element  10  displaced in the positive x direction. The third optical element  13  can therefore be very close to the first optical element  10  in the y and z directions. 
         [0052]    The optical axis  7  meets the optical elements  10 ,  11 ,  13  and  14  at an angle of incidence which is less than 20°. The optical axis  7  meets the fifth optical element  15  at an angle of incidence which is greater than 70°. The projection of the source axis portion  19  onto the illumination main plane  18 , with the projection of the field axis portion  17  onto the illumination main plane  18 , encloses an angle of about 55°. 
         [0053]      FIG. 4  shows another version according to the disclosure of the illumination system. Components corresponding to those which were described above with reference to  FIGS. 1 to 3  have the same reference numbers and are not discussed again in detail. 
         [0054]    In the case of the version of the illumination system  1  according to  FIG. 4 , the axis portions  21  are inclined between the first optical element  10  and the second optical element  11 , the axis portion  20  between the third optical element  13  and the fourth optical element  14 , and additionally an intermediate axis portion  22  is inclined between the second optical element  11  and the third optical element  13 , relative to the illumination main plane  18 , which in  FIG. 4  too coincides with the drawing plane. This inclination is such that the second optical element  11  is arranged relative to the first optical element  10  displaced in the positive x direction. The third optical element  13  is in turn displaced relative to the second optical element  11  in the positive x direction. The fourth optical element  14  is displaced relative to the third optical element  13  in the positive x direction. All other portions of the optical axis  7  except the axis portions  20  to  22  run parallel to the illumination main plane  18 . 
         [0055]    In particular, the result is that the fifth optical element  15  is also arranged relative to the third optical element  13  displaced in the positive x direction. The optical elements  10 ,  13 ,  15  can therefore, as shown in  FIG. 4 , be arranged overlapping in the y and z directions. Alternatively, it is possible to displace the second optical element  11  relative to the first optical element  10  in the positive x direction, the third optical element  13  relative to the second optical element  11  in the positive x direction and the fourth optical element  14  relative to the third optical element  13  in the negative x direction. In this case, it is necessary to ensure that the fifth optical element  15  and the first optical element  10  do not obstruct each other. 
         [0056]    The angle of incidence below which the optical axis  7  falls on the optical elements  10 ,  11 ,  13  and  14  is less than 20°. The angle of incidence below which the optical axis  7  falls on the fifth optical element  15  is greater than 70°. The angle which a projection of the source axis portion  19  onto the illumination main plane  18  encloses with a projection of the field axis portion  17  onto the illumination main plane  18  is about 70°. 
         [0057]      FIG. 5  shows another version according to the disclosure of an illumination system. Components corresponding to those which were described above with reference to  FIGS. 1 to 4  have the same reference numbers and are not discussed again in detail. 
         [0058]    In the case of the illumination system  1  according to  FIG. 5 , the third optical element  13  and the fourth optical element  14  are omitted. The fifth optical element  15 , i.e. the element under which the optical axis  7  strikes with an angle of incidence greater than 70°, is present in the case of the illumination system  1  according to  FIG. 5 . To preserve the correspondence of this optical element  15  to the illumination system according to  FIGS. 1 to 4 , in relation to the illumination system  1  according to  FIG. 5  the term “fifth optical element  15 ” is retained, although strictly speaking in this case it is the third optical element. 
         [0059]    In the case of the illumination system  1  according to  FIG. 5 , the source axis portion  19  is inclined to the illumination main plane  18 , which in the case of the version according to  FIG. 5  coincides with the drawing plane. The other axis portions run parallel to the illumination main plane  18 . The result is that the optical elements  10 ,  11  and  15  are displaced relative to the source (not shown in  FIG. 5 ) and the collector (not shown in  FIG. 5 ) in the positive x direction. From the point of view of  FIG. 5 , therefore, the source and the collector are behind the optical elements  10 ,  11  and  15 . In contrast to the versions according to  FIGS. 1 to 4 , in the case of the version according to  FIG. 5  the EUV radiation from the collector (not shown) comes from the right. The projections on the one hand of the source axis portion  19  and on the other hand of an axis portion  23  between the second optical element  11  and the fifth optical element  15  onto the illumination main plane  18  intersect. 
         [0060]    The optical axis  7  meets the first optical element  10  at an angle of incidence which is less than 20°. The optical axis  7  meets the optical elements  11  and  15  at an angle of incidence which is greater than 70°. 
         [0061]    In the case of the illumination system  1  according to  FIG. 5  and the version according to the disclosure and  FIG. 6 , which is described below, a plasma source is preferably used as the source. In the case of the versions according to  FIGS. 5 and 6 , the collector is in such a form that the EUV radiation is preferably concentrated by a single reflection on the collector, and at most by two reflections on the collector. 
         [0062]    In the case of the version according to  FIG. 5 , the angle between a projection of the source axis portion  19  onto the illumination main plane  19  and a projection of the field axis portion  17  onto the illumination main plane  18  is about 60°. 
         [0063]      FIG. 6  shows another version according to the disclosure of an illumination system  1 . Components corresponding to those which were described above with reference to the versions according to  FIGS. 1 to 5  have the same reference numbers and are not discussed again in detail. 
         [0064]    Like the version according to  FIG. 5 , the version according to  FIG. 6  has, after the second optical element  11  and before the image plane  4   a , only the optical element  15 , which here too, to preserve the correspondence to the versions according to  FIGS. 1 to 4 , is called the “fifth optical element  15 ”. In the case of the versions according to  FIGS. 5 and 6 , therefore, the optical device  12  includes only the two optical elements  11 ,  15 . In the case of the versions according to  FIGS. 5 and 6 , therefore, the third optical element  13  and fourth optical element  14  are missing. 
         [0065]    In the case of the version according to  FIG. 6 , the EUV radiation comes from the collector (not shown) on the left. 
         [0066]    The source axis portion  19  is inclined relative to the illumination main plane  18 , which in the case of the version according to  FIG. 6  too coincides with the drawing plane. The adjacent axis portion  21  between the first optical element  10  and the second optical element  11  is also inclined relative to the illumination main plane. The other axis portions, i.e. the axis portion  23  between the second optical element  11  and the fifth optical element  15  and the field axis portion  17 , run parallel to the illumination main plane  18 . The result is that the first optical element  10  is arranged relative to the collector (not shown) displaced in the positive x direction. Alternatively, it is possible to arrange the first optical element  10  relative to the collector displaced in the negative x direction. Relative to the first optical element  10 , the subsequent optical elements  10 ,  15  are displaced in the positive x direction. The fifth optical element  15  can therefore overlap with the first optical element  10  in the y and z directions, as shown in  FIG. 6 . 
         [0067]    The optical axis  7  meets the optical elements  10  and  11  at an angle of incidence which is less than 20°. In the case of the version according to  FIG. 6 , the optical axis  7  meets the fifth optical element  15  at an angle which is greater than 70°. 
         [0068]    In the case of the illumination system  1  according to  FIG. 7 , the angle between a projection of the source axis portion  19  onto the illumination main plane  18  and a projection of the field axis portion  17  onto the illumination main plane  18  is about 65°. 
         [0069]      FIG. 7  shows another version according to the disclosure of an illumination system. Components corresponding to those which were described above with reference to  FIGS. 1 to 6  have the same reference numbers and are not discussed again in detail. 
         [0070]    As in the case of the version according to  FIG. 5 , in  FIG. 7  the EUV radiation which the collector emits is incident from the right. 
         [0071]    In the case of the version according to  FIG. 7 , the optical device  12  includes three optical elements, i.e. in addition to the second optical element  11 the third optical element  13  and the optical element  15 , which because it corresponds to the fifth optical element of the versions according to  FIGS. 1 to 6  is still called the “fifth optical element  15 ”. In the case of the version according to  FIG. 7 , therefore, the fourth optical element  14  is missing. 
         [0072]    The source axis portion  19  is inclined relative to the illumination main plane  18 , which in the case of the version according to  FIG. 7  too coincides with the drawing plane. In the case of the version according to  FIG. 7 , the axis portion  21  between the first optical element  10  and the second optical element  11  is inclined to the illumination main plane  18 . The axis portion  22  between the second optical element  11  and the third optical element  13  is also inclined relative to the illumination main plane  18 . The subsequent axis portions run parallel to the illumination main plane  18 . The result is that the first optical element  10  is arranged relative to the collector displaced in the positive x direction. The second optical element  11  is arranged relative to the first optical element  10  displaced in the positive x direction. The third optical element  13  and the fifth optical element  15  are arranged relative to the second optical element  11  displaced in the positive x direction. In the case of the version according to  FIG. 7 , the fifth optical element  15  can therefore overlap with the second optical element  11  in the y and z directions, as shown in  FIG. 7 . In the case of the version according to  FIG. 7 , it is also possible to combine a displacement in the positive x direction with a displacement in the negative x direction. 
         [0073]    The optical axis  7  meets the optical elements  10 ,  11  and  13  at an angle of incidence which is less than 20°. The optical axis  7  meets the fifth optical element  15  at an angle of incidence which is greater than 70°. 
         [0074]    In the case of the illumination system  1  according to  FIG. 6 , the angle between a projection of the source axis portion  19  onto the illumination main plane  18  and a projection of the field axis portion  17  onto the illumination main plane  18  is about 55°. 
         [0075]      FIG. 8  shows another version according to the disclosure of an illumination system  1 . Components corresponding to those which were described above with reference to  FIGS. 1 to 7  have the same reference numbers and are not discussed again in detail. 
         [0076]    Like the versions according to  FIGS. 1 to 4 , the version according to  FIG. 8  has an optical device  12  with a total of four optical elements. These include the second optical element  11 , i.e. the pupil raster element, and downstream from it the third optical element  13 , which in contrast to the other described embodiments is in the form of a concave mirror in the case of the version according to  FIG. 8 . The optical device  12  according to  FIG. 8  also includes the fourth optical element  14  and the fifth optical element  15 . Also in contrast to the versions according to  FIG. 1 to 4 , in the case of the version according to  FIG. 8  the third optical element  13  and the fourth optical element  14  are operated in grazing incidence, so that the optical axis  7  meets the optical elements  13 ,  14  at an angle which is greater than 70°. This also applies to the optical element  15 . In contrast, in the case of the version according to  FIG. 8 , the optical axis  7  is applied to the optical elements  10  and  11  at an angle of incidence which is less than 20°. The version according to  FIG. 8  has no axis portion which is inclined to illumination main plane  18 , which here too coincides with the drawing plane of  FIG. 8 . 
         [0077]    In the case of the version according to  FIG. 8 , the angle between the source axis portion  19  and the field axis portion  17  is about 80°. 
         [0078]      FIG. 9  shows another version according to the disclosure of an illumination system  1 . Components corresponding to those which were described above with reference to the versions according to  FIGS. 1 to 8  have the same reference numbers and are not discussed again in detail. 
         [0079]    The version according to  FIG. 9  is comparable to the version according to  FIG. 6 , the last optical element  15 , i.e. the mirror, to which grazing incidence is applied in the version according to  FIG. 6  being absent in the case of the version according to  FIG. 9 . The field axis portion  17  therefore runs between the second optical element  11  and the image plane  4   a.    
         [0080]    The optical axis  7  meets the optical elements  10  and  11  at an angle of incidence which is less than 20°. 
         [0081]    In the case of the illumination system  1  according to  FIG. 9 , the angle between a projection of the source axis portion  19  onto the illumination main plane  18  and a projection of the field axis portion  17  onto the illumination main plane  18  is about 38°. 
         [0082]    Modifications of the other versions according to  FIGS. 2 to 8  without the last optical element  15  which is operated in grazing incidence are also possible. 
         [0083]    Combinations of the x displacement in the positive or negative direction other than those described above in relation to the versions according to the disclosure are also possible. 
         [0084]      FIGS. 10 to 12  show another version according to the disclosure of an illumination system  1 . Components corresponding to those which were described above with reference to the versions according to  FIGS. 1 to 9  have the same reference numbers and are not discussed again in detail. 
         [0085]    Similarly to the illumination system  1  according to  FIG. 3 , the one in  FIGS. 10 to 12  has five optical elements, i.e. the optical elements  10 ,  11 ,  13 ,  14  and  15 . In contrast to the illumination system  1  according to  FIG. 3 , in the case of the version according to  FIGS. 10 to 12 , apart from the last axis portions  23  and  17  all axis portions  19 ,  21 ,  22  and  20  are inclined to the illumination main plane  18 , which coincides with the yz plane. 
         [0086]      FIG. 10  shows this version of the illumination system  1  schematically in overview. 
         [0087]      FIG. 11  shows a true to scale projection of the axis portions  19 ,  21 ,  22 ,  20 ,  23 ,  17  onto the xz plane. The optical elements  10 ,  11 ,  13 ,  14 ,  15  and the object  4  are indicated in  FIG. 11  by crosses. The scaling of the x and y axes is true to scale in mm. The zero point of the x axis and z axis is arbitrarily chosen to be at the location of the object  4 . 
         [0088]      FIG. 12  shows the corresponding projection of the illumination system according to  FIGS. 10 and 11  onto the yz plane. 
         [0089]    The following table clarifies the positions of the optical elements  10 ,  11 ,  13 ,  14 ,  15  in the xyz co-ordinates according to  FIGS. 11 and 12 : 
         [0000]    
       
         
               
               
               
               
               
             
               
               
               
               
               
             
           
               
                   
                   
               
               
                   
                 Optical element 
                 x position 
                 y position 
                 z position 
               
               
                   
                   
               
             
             
               
                   
               
             
          
           
               
                   
                 10 
                 −132 
                 −265 
                 −260 
               
               
                   
                 11 
                 220 
                 −885 
                 −960 
               
               
                   
                 13 
                 −150 
                 −156 
                 −450 
               
               
                   
                 14 
                 0 
                 −350 
                 −820 
               
               
                   
                 15 
                 0 
                 −40 
                 −380 
               
               
                   
                   
               
             
          
         
       
     
         [0090]    The following table gives the angle of incidence of the optical axis  7  onto the optical elements  10 ,  11 ,  13 ,  14 ,  15 : 
         [0000]    
       
         
               
               
               
             
           
               
                   
                   
               
               
                   
                   
                 Angle of incidence 
               
               
                   
                 Optical element 
                 to surface normal 
               
               
                   
                   
               
             
             
               
                   
                 10 
                 7.5° 
               
               
                   
                 11 
                 6.5° 
               
               
                   
                 13 
                  12° 
               
               
                   
                 14 
                 10.5°  
               
               
                   
                 15 
                  75° 
               
               
                   
                   
               
             
          
         
       
     
         [0091]    The following table shows the angles of the projections of the axis portions  19 ,  21 ,  22 ,  20 ,  23  and  17  to the xz and yz planes. The second column gives the angle of the projection of the axis portions onto the yz plane to the xz plane, and the third column gives the angle of the projection of the axis portions onto the xz plane to the yz plane. 
         [0000]    
       
         
               
               
               
             
           
               
                   
               
               
                 Axis portion of 
                 yz projection 
                 xz projection 
               
               
                 optical axis 7 
                 angle to xz plane 
                 angle to yz plane 
               
               
                   
               
             
             
               
                 19 
                 57° 
                 23° 
               
               
                 21 
                 41° 
                 21° 
               
               
                 22 
                 55° 
                 23° 
               
               
                 20 
                 29° 
                 20° 
               
               
                 23 
                 36° 
                  0° 
               
               
                 17 
                  6° 
                  0° 
               
               
                   
               
             
          
         
       
     
         [0092]    The angles of the second column of the above table can be read directly from  FIG. 12 , and are the angles of the axis portion projections (shown there) to the z axis. Correspondingly, the angles of the third column of the above table are the angles of the axis portion projections (shown in  FIG. 11 ) to the z axis. 
         [0093]    In column 2 of the above table, it can be seen directly that the angle between a projection of the source axis portion  19  onto the illumination main plane  18  and a projection of the field axis portion  17  onto the illumination main plane is 51°. 
         [0094]    Below is another table, giving the orientation of the optical elements  10 ,  11 ,  13 ,  14  and  15 . For this purpose, for each of the optical elements  10 ,  11 ,  13 ,  14  and  15 , a local element co-ordinate system, the origin of which is defined by the intersection of the optical axis  7  with the mirror surface, is defined. The normal vector points to the mirror surface in the z′ direction of the local element co-ordinate system. The element co-ordinate systems x′, y′, z′ are obtained from the xyz co-ordinate system by rotation first by an angle a around the x axis and then by an angle b around the new y′ axis. Since it is assumed for simplicity that the optical elements  10 ,  11 ,  13 ,  14 ,  15  are spherical mirrors, a rotation of the element co-ordinate system x′, y′, z′ around the z axis is irrelevant. The following angles of rotation convert the stationary x, y, z co-ordinate system into the appropriate element co-ordinate system: 
         [0000]    
       
         
               
               
               
             
           
               
                   
               
               
                 Optical element 
                 Angle of rotation a 
                 Angle of rotation b 
               
               
                   
               
             
             
               
                 10 
                 −49.3° 
                 157.9° 
               
               
                 11 
                 −48.3° 
                 −21.9° 
               
               
                 13 
                 −25.6° 
                 −24.0° 
               
               
                 14 
                 146.3° 
                    7.2° 
               
               
                 15 
                   69.1° 
                    180° 
               
               
                   
               
             
          
         
       
     
         [0095]    In the case of all versions according to the disclosure, i.e. according to  FIGS. 2 to 9 , the numerical aperture of the illumination of the object surface  3  is greater than 0.02. Preferably, the numerical aperture is greater than 0.03, preferably in the region of 0.05. 
         [0096]    The illumination device  1  according to the versions presented above is used to produce microstructured components on the wafer as follows: first the wafer, onto which a layer of a light-sensitive material is applied at least in certain regions, is provided. The object  4 , with a mask which shows the structures to be imaged, is also provided. Then, using the projection illumination system, at least a portion of the object  4  is projected onto a portion of the light-sensitive layer on the wafer.