Abstract:
An illumination optical system for projection lithography for the illumination of an illumination field has a facet mirror. An optical system, which follows the illumination optical system, has an object field which can be arranged in the illumination field of the illuminate optical system. The facet mirror has a plurality of facets to reflectively guide part bundles of a bundle of illumination light. Reflection faces of the facets are tiltable in each case. In a first illumination tilt position, the tiltable facets guide the part bundle impinging on them along a first object field illumination channel to the illumination field. In a different illumination tilt position, the tiltable facets guide the part bundle impinging on them along a different object field illumination channel to the illumination field. The reflection faces of the tiltable facets are configured so that the part bundle in the at least two illumination tilt positions is reflected with a degree of reflection R coinciding within a tolerance range of +/−10%. The result is an illumination optical system which avoids an undesired influence of the illumination tilt position of the tiltable facets on the illumination light throughput of the illumination optical system.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims priority under 35 U.S.C. §119 to German Application No. 10 2010 002 982.3, filed Mar. 17, 2010, and also under 35 U.S.C. §119(e)(1) to U.S. Provisional Application No. 61/332,295 filed May 7, 2010. The contents of both of these applications are hereby incorporated by reference in its entirety. 
    
    
     FIELD 
     The disclosure relates to an illumination optical system for projection lithography for illuminating an illumination field. An imaging optical system, which follows the illumination optical system, has an object field which can be arranged in the illumination field of the illumination optical system. Furthermore, the disclosure relates to a method for assigning at least two second facets of a second facet mirror to illumination tilt positions of one of the first facets of a first facet mirror of such an illumination optical system, as well as an illumination system with such an illumination optical system, a projection exposure system with such an illumination system, a production method for microstructured or nanostructured components using such a projection exposure system, and a microstructured or nanostructured component produced by such a production method. 
     BACKGROUND 
     Illumination optical systems with facets which can be displaced between various illumination tilt positions, namely displaceable field facets, are known from U.S. Pat. No. 6,658,084 B2 and U.S. Pat. No. 7,196,841 B2. 
     SUMMARY 
     The disclosure provides an illumination optical system that avoids an undesired influence of illumination tilt position of the tiltable facets on the illumination light throughput of the illumination optical system, in particular on a total transmission of the illumination optical system. 
     It was recognised according to the disclosure that a degree of reflection coinciding within a tolerance range for the angles of incidence of the various illumination tilt positions leads to the fact that the tiltable field facets relay the illumination light impinging on them, regardless of their illumination tilt position, with energy coinciding in accordance with the coincidence of the degree of reflection within a predetermined tolerance range to the illumination field. Assuming a reflectivity that is independent of the respective illumination tilt position of the tiltable facets, of optical components perhaps following these facets, this leads to an energetic illumination of the illumination field that is independent of the illumination tilt position within the tolerance range. The part bundle can be reflected in the at least two illumination tilt positions with a degree of reflection coinciding within a tolerance range of +/−5%, of +/−2%, of +/−1% or with a degree of reflection coinciding still better. Generally, a plurality of facets of the facet mirror are tiltable between at least two illumination tilt positions. For example, one predetermined facet group, or else all the facets of the facet mirror, may be tiltable. The tiltable facets may be tiltable between precisely two illumination tilt positions. Alternatively, the tiltable facets may also be tiltable between more than two, for example between three or even more illumination tilt positions. 
     Angles of incidence coinciding within a tolerance range can lead to the possibility of configuring the tiltable facets and in particular a reflective coating on their reflection faces in an optimised manner for this coinciding angle of incidence. No optimisation is then involved for other angles of incidence. 
     A mirror symmetry can lead to a simply structured structure of the illumination optical system. The two object field illumination channels can pass into one another by reflection about a plane which contains the incident part bundle on the reflection face and is located perpendicular to an incidence plane of the part bundle. 
     Reflective portions can allow the same degrees of reflection for angles of incidence that are very different in the various illumination tilt positions. In principle, the reflection face may also be divided into more than two reflective portions, which can then in turn be assigned in accordance with the illumination tilt positions. 
     A reflection coating can allow a particularly high degree of reflection of the facets. The reflection coating can be configured as a single-layer coating. The reflection coating may be configured as a two-layer coating. The reflection coating can be configured as a multilayer coating. The multilayer coating may, for example, have five layers, ten layers, twenty layers, thirty layers or still more layers. The multilayer coating may be configured as a coating of alternate material layers. For example, alternating molybdenum/silicon layers may be used. 
     A design of the reflection coating may take place such that the facet provided with the reflection coating has the same degrees of reflection for different angles of incidence that are assigned to the various illumination tilt positions, and in particular for very differing angles of incidence. The reflection coating may also be designed such that the coincidence of the degree of reflection is present for more than two illumination tilt positions. 
     A broadband reflection coating can allow a constant degree of reflection within a range of angles of incidence around a specified value. 
     A design of the reflection coating can allow for two specific angles of incidence around the angle of incidence with the maximum degree of reflection with the same degree of reflection within a tolerance range. The degree of reflection coinciding within the tolerance range in the at least two illumination tilt positions may be more than 2% smaller (may be more than 5% smaller, or may be more than 10% smaller) than the maximum degree of reflection of the reflection coating for the illumination light. 
     A design of the illumination optical system has proven successful in practice. The first facet mirror may be a field facet mirror and the second facet mirror may be a pupil facet mirror. Precisely one field facet and precisely one pupil facet is then assigned to each object field illumination channel. Depending on the number of illumination tilt positions, the field facet may specify a plurality of object field illumination channels, which then impinge on different pupil facets. 
     In an aspect, specific second facets, as assignment candidates, are assigned to each of the first facets of the first facet mirror to specify object field illumination channels on the second facet mirror, namely those second facets, which are located within a conic section portion of the second facet mirror, which is limited by two conic section lines. Each of the conic section lines defines sites of the same reflection angle of the part bundle reflected on the first facet to specify the respective object field illumination channel. When the respectively observed first facet is tilted in such a way that it is assigned to one of the second candidate facets within the conic section portion, it is ensured that an angle of incidence of the part bundle during the reflection on the first facet is located between the two angles of incidence defined by the conic section lines, which limit the conic section portion. The conic section portions are selected in such a way that the conic section lines limiting them belong to angles of incidence, in which a predetermined degree of reflection results during the reflection on the observed first facet. One of the two conic section lines can define the maximum permissible angle of reflection and the other of the two conic section lines can define the minimum permissible reflection angle, between which a given degree of reflection R is achieved in the reflection of the part bundle at the observed first facet. The angles of incidence predetermined by the two conic section lines of the conic section portion at the observed first facet may differ by 30°, by 20°, by 10°, by 5° or by a still smaller angle amount. The illumination optical system may have a combination of features of the two above-mentioned aspects. 
     An assignment method can allow the second facet mirror to be occupied with pupil facets assigned to the field facets via object field illumination channels in such a way that the assignment leads to degrees of reflection of the facets that are independent of the illumination tilt position of the first facets within predetermined tolerance limits. The assignment may take place with the aid of conic section portions. As a result, an advantageous reduction is produced in the combinations of first and second facets to be checked in the assignment in the course of a reflectivity optimisation. 
     The advantages of an illumination system, a projection exposure system, a production method, and a microstructured or nanostructured component correspond to those which were already discussed above with reference to the illumination optical system according to the disclosure and the method according to the disclosure. Precisely adapted illuminations can be specified on the component or unit structure to be produced, so that, in particular, semiconductor chips with extremely fine and, in particular, complex structures can be produced. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
       Embodiments of the disclosure will be described in more detail below with the aid of the drawings, in which: 
         FIG. 1  shows schematically and in relation to an illumination optical system, in meridional section, a projection exposure system for microlithography; 
         FIG. 2  shows a plan view of a facet arrangement of a field facet mirror of the illumination optical system of the projection exposure system according to  FIG. 1 ; 
         FIG. 3  shows a plan view of a facet arrangement of a pupil facet mirror of the illumination optical system of the projection exposure system according to  FIG. 1 ; 
         FIG. 4  shows, in a view similar to  FIG. 2 , a facet arrangement of a further configuration of a field facet mirror; 
         FIG. 5  schematically shows portions of two object field illumination channels, which are assigned to the two illumination tilt positions of a shown tiltable field facet of the field facet mirror according to  FIG. 2  or  4 , an incident illumination light part bundle in the two illumination tilt positions being reflected at an angle of incidence coinciding within a tolerance range of +/−10%; 
         FIG. 6  schematically and not true to scale, shows a perpendicular projection view of a field facet of the field facet mirror according to  FIG. 2  and of the pupil facet mirror according to  FIG. 3 , three pupil facets, which are assigned to illumination tilt positions of the field facet with the same angles of incidence of the incident illumination light part bundle, being shown emphasised; 
         FIG. 7  shows a side view of the field facet according to  FIG. 6  in a first illumination tilt position; 
         FIG. 8  shows a side view of the field facet according to  FIG. 6  in a further illumination tilt position; 
         FIG. 9  shows, in a view similar to  FIG. 5 , two object field illumination channels, which are in turn assigned to various illumination tilt positions of the same field facet, the incident part bundle being reflected in the two illumination tilt positions with angles of incidence which differ by more than 10°; 
         FIG. 10  shows, in a view similar to  FIG. 7 , a further configuration of a field facet in a first illumination tilt position in a side view; 
         FIG. 11  shows the field facet according to  FIG. 10  in a further illumination tilt position; 
         FIG. 12  shows, in a graph, the dependency of a degree of reflection of a layer design on a reflection face of one of the field facets on an angle of incidence, dependencies being shown for two different layer designs by continuous and dashed lines; 
         FIG. 13  shows, detail-wise, in a view similar to  FIG. 1 , the guidance of an illumination light bundle in an alternative configuration of a field facet mirror and a pupil facet mirror of a variant of the illumination optical system, which can be used as a alternative to the illumination optical system according to  FIG. 1  in the projection exposure system; and 
         FIG. 14  shows, in a view similar to  FIG. 6 , pupil facets accessible at the same angles of incidence by way of object field illumination channels of one and the same field facet in the configuration of the illumination optical system according to  FIG. 13 . 
     
    
    
     DETAILED DESCRIPTION 
     A projection exposure system  1  for microlithography is used to produce a microstructured or nanostructured electronic semiconductor structural element. A light source  2  emits EUV radiation used for illumination in the wavelength range, for example between 5 nm and 30 nm. The light source  2  may be a GDPP source (gas discharge produced plasma) or an LPP source (laser produced plasma). A radiation source, based on a synchrotron, can also be used for the light source  2 . A person skilled in the art will, for example, find information on a light source of this type in U.S. Pat. No. 6,859,515 B2. EUV illumination light or illumination radiation  3  is used for illumination and imaging within the projection exposure system  1 . The EUV illumination light  3 , after the light source  2 , firstly runs through a collector  4 , which is, for example, a nested collector with a multishell structure known from the prior art or, alternatively, an ellipsoidally formed collector. A corresponding collector is known from EP 1 225 481 A. After the collector  4 , the EUV illumination light  3  firstly runs through an intermediate focus plane  5 , which can be used to separate the EUV illumination light  3  from undesired radiation or particle fractions. After running through the intermediate focus plane, the EUV illumination light  3  firstly impinges on a field facet mirror  6 . 
     To facilitate the description of positional relationships, a Cartesian global xyz-coordinates system is firstly drawn in the drawing in each case. The x-axis in  FIG. 1  runs perpendicular to the drawing plane and out of it. The y-axis in  FIG. 1  runs to the right. The z-axis runs upwardly in  FIG. 1 . 
     To facilitate the description of positional relationships in individual optical components of the projection exposure system  1 , a Cartesian local xyz- or xy-coordinates system is also used in each case in the following Figs. The respective local xy-coordinates, where nothing else is described, span a respective main arrangement plane of the optical component, for example a reflection plane. The x-axes of the global xyz-coordinates system and the local xyz- or xy-coordinates systems run parallel to one another. The respective y-axes of the local xyz- or xy-coordinates systems have an angle to the y-axis of the global xyz-coordinates system, which corresponds to a tilt angle of the respective optical component about the x-axis. 
       FIG. 2  shows, by way of example, a facet arrangement of field facets  7  of the field facet mirror  6 . The field facets  7  are rectangular and in each case have the same x/y-aspect ratio. The x/y-aspect ratio may, for example, be 12/5, 25/4 or 104/8. 
     The field facets  7  specify a reflection face of the field facet mirror  6  and are grouped in four columns each with six to eight field facet groups  8   a ,  8   b . The field facet groups  8   a  in each case have seven field facets  7 . The two additional edge-side field facet groups  8   b  of the two central field facet columns in each case have four field facets  7 . Between the two central facet columns and between the third and fourth facet rows, the facet arrangement of the field facet mirror  6  has intermediate spaces  9 , in which the field facet mirror  6  is shaded by holding spokes of the collector  4 . 
     After reflection on the field facet mirror  6 , the EUV illumination light  3  divided into beam pencils or part bundles, which are assigned to the individual field facets  7 , impinges on a pupil facet mirror  10 . 
       FIG. 3  shows an exemplary facet arrangement of round pupil facets  11  of the pupil facet mirror  10 . The pupil facets  11  are arranged around a centre in facet rings lying within one another. At least one pupil facet  11  is assigned to each part bundle of the EUV illumination light  3  reflected by one of the field facets  7  in such a way that, in each case, one facet pair that is impinged on with one of the field facets  7  and one of the pupil facets  11  specifies an object field illumination channel for the associated part bundle of the EUV illumination light  3 . The channel-wise assignment of the pupil facets  11  to the field facets  7  takes place depending on a desired illumination by the projection exposure system  1 . 
     The field facets  7  are imaged in an object plane  16  of the projection exposure system  1  via the pupil facet mirror  10  (cf  FIG. 1 ) and a following transmission optical system  15  consisting of three EUV mirrors  12 ,  13 ,  14 . The EUV mirror  14  is configured as a grazing incidence mirror. Arranged in the object plane  16  is a reticle  17 , by which an illumination region in the form of an illumination field is illuminated with the EUV illumination light  3 , the illumination field coinciding with an object field  18  of a downstream projection optical system  19  of the projection exposure system  1 . The object field illumination channels are overlaid in the object field  18 . The EUV illumination light  3  is reflected by the reticle  17 . 
     The projection optical system  19  images the object field  18  in the object plane  16  in an image field  20  in an image plane  21 . Arranged in this image plane  21  is a wafer  22 , which carries a light-sensitive layer, which is exposed during the projection exposure with the projection exposure system  1 . During the projection exposure, both the reticle  17  and the wafer  22  are scanned in a synchronised manner in the y-direction. The projection exposure system  1  is configured as a scanner. The scanning direction is also called the object displacement direction below. 
     The field facet mirror  6 , the pupil facet mirror  10  and the mirrors  12  to  14  of the transmission optical system  15  are components of an illumination optical system  23  of the projection exposure system  1 . Together with the projection optical system  19 , the illumination optical system  23  forms an illumination system of the projection exposure system  1 . 
     The field facet mirror  6  is a first facet mirror of the illumination optical system  23 . The field facets  7  are first facets of the illumination optical system  23 . 
     The pupil facet mirror  10  is a second facet mirror of the illumination optical system  23 . The pupil facets  11  are second facets of the illumination optical system  23 . 
       FIG. 4  shows a further configuration of a field facet mirror  6 . Components which correspond to those which were described above with reference to the field facet mirror  6  according to  FIG. 2 , have the same reference numerals and will only be described inasmuch as they differ from the components of the field facet mirror  6  according to  FIG. 2 . The field facet mirror  6  according to  FIG. 4  has a field facet arrangement with curved field facets  7 . These field facets  7  are arranged in a total of five columns each with a plurality of field facet groups  8 . The field facet arrangement is written into a circular limitation of a carrier plate  24  of the field facet mirror. 
     The field facets  7  of the embodiment according to  FIG. 4  all have the same area and the same ratio of width in the x-direction and height in the y-direction, which corresponds to the x/y aspect ratio of the field facets  7  of the configuration according to  FIG. 2 . 
     Precisely two of the pupil facets  11  of the pupil facet mirror  10  are assigned to each of the field facets  7  of the respective configuration of the field facet mirror  6  by way of an object field illumination channel, in each case. The pupil facet mirror  10  thus has twice as many pupil facets  11  as the field facet mirror  6  has field facets  7 . 
     Depending on the configuration of a mechanical tilting ability of the field facets  7 , more than two of the pupil facets  11  of the pupil facet mirror  10  may be assigned to one of the field facets  7  by way of respective object field illumination channels. The field facets  7  can then be displaced into a corresponding number of illumination tilting positions. 
       FIG. 5  illustrates the reflected guidance of a part bundle  24  of a total bundle of the illumination light  3 . A reflection face  25  of a field facet  7  shown by way of example is tiltable between a first illumination tilting position to guide the part bundle  24 , which impinges on the reflection face  25 , along a first object field illumination channel  26   1  to the object field  18  or to the illumination field, and a further illumination tilt position to guide the part bundle  24  along a further object field illumination channel  26   2  to the object field  18 . 
     Along the first illumination channel  26   1 , the part bundle  24 , after reflection on the field facet  7 , is reflected on a first pupil facet  11   1 . The pupil facet  11   1  is thus assigned to the field facet  7  by way of the object field illumination channel  26   1 . Along the object field illumination channel  26   2 , in other words in the other illumination tilt position of the field facet  7 , the part bundle  24 , after reflection on the field facet  7 , is reflected on another pupil facet  11   2  of the pupil facet mirror  10 . Only the two pupil facets  11   1  and  11   2  of the pupil facet mirror  10  are shown in the schematic view according to  FIG. 5 . An angle of incidence β 1 , with which the part bundle  24  is reflected on the reflection face  25  of the field facet mirror  7  in the first illumination tilt position assigned to the object field illumination channel  26   1 , coincides with an angle of incidence β 2 , with which the part bundle  24  in the other illumination tilt position of the field facet mirror  7  is reflected on the reflection face  25 , which is assigned to the object field illumination channel  26   2 . The angles of incidence β 1/2  are defined as the angles between the incident part bundle  24  and a normal N to the reflection face  25  of the field facet  7 . 
     The reflection face  25  carries a multilayer coating, in other words a multilayer coating with an alternating sequence of molybdenum and silicon layers. A layer design of this multilayer reflection coating  27  is optimised to high reflectivity of the field facet  7  at the angle of incidence β 1/2 . As the angle of incidence β 1/2 , when switching over the field facet mirror  7  according to  FIG. 5  between the two illumination tilt positions, which are assigned to the two object field illumination channels  26   1 ,  26   2 , does not change, the field facet mirror  7 , regardless of the illumination tilt position, has the same degree of reflection. The degrees of reflection of the field facet mirror  7  in the two illumination tilt positions, which are shown in  FIG. 5 , coincide within a tolerance range of +/−1%. 
     Instead of the multilayer reflection coating  27 , a single layer or a double layer reflection coating with a very narrow angle of incidence tolerance range may also be used. For angles of incidence in the range close to 0°, in other words perpendicular incidence, and a periodic layer stack of the multilayer reflection coating  27 , the angle of incidence tolerance range may be 7°. For angles of incidence in the range of 15°, the angle of incidence tolerance range may be in the range between 1° and 2°. When using multilayer reflection coatings with aperiodic layer stacks, in other words so-called broadband coatings, the angle of incidence tolerance range is increased. Broadband coatings of this type generally have a lower average reflectivity. 
     In a perpendicular projection along the z-axis,  FIG. 6  shows the arrangement according to  FIG. 5 . By way of example, three pupil facets  11   1 ,  11   2  and  11   3  are shown, in the direction of which the part bundle  24  incident on the field facet  7  can be reflected at the same angle of incidence β. If the tilting mechanism of the field facet  7  allows adjustment in two illumination tilt positions, two of these three pupil facets  11   1  to  11   3  can be assigned to these two illumination tilt positions, for example. If the tilting mechanism of the field facet  7  allows, for example, the specifying of three illumination tilt positions, all three pupil facets  11   1  to  11   3  can be assigned to these illumination tilt positions, for example. Basically, by corresponding orientation of a tilt axis of the respective field facet  7  and the tilt mechanism of this field facet  7  within a predetermined tolerance range for the angle of incidence β, all the pupil facets  11  of the pupil facet mirror  10  can be activated by way of object field illumination channels  26  proceeding from the field facet  7  shown in  FIG. 6 , the illumination channels being located in a conic section portion  28  of the pupil facet mirror  10  indicated schematically in  FIG. 6 . The conic section portion  28  is limited by two conic section lines  28   a ,  28   b  and additionally limited by an outer contour of the pupil facet mirror  10 . Outside this outer contour, the two conic section lines  28   a ,  28   b  are shown by dashed lines in  FIG. 6 . Depending on the geometric ratios, the conic section lines  28   a ,  28   b  may be parabolas, ellipses, circles or hyperbolas. Each of the two conic section lines  28   a ,  28   b  defines a corresponding tilt orientation in the field facet  7 , so the part bundle  24  is reflected onto the respective conic section line  28   a ,  28   b , sites of the same reflection angle of the part bundle  24  on the first facet  7  to specify the respective object field illumination channel  26 . The pupil facets  11 , which are located within the conic section portion  28 , can be achieved by reflection of the part bundle  24  on the field facet  7  at an angle of incidence, which lies between the two limit angles defined by the conic section lines  28   a ,  28   b . After specifying these limit angles, by determining the associated conic section lines  28   a ,  28   b , in other words within the entire pupil facet mirror  10 , the conic section portion  28  can be singled out, in which pupil facets  11  lie, which can be achieved by reflection of the part bundle  24  on the facet  7  at a reflection angle within these two limit angles. It is thus possible, using the conic section portion  28 , to specify a pupil facet subgroup of all pupil facets  11  or to specify a quantity of pupil facet candidates for object field illumination channel assignment to the observed field facet  7 . 
     Illumination tilt positions of the field facet  7  according to  FIG. 6  can be assigned by the following method to at least two pupil facets  11 : firstly, a first illumination tilt position of the field facet  7  is predetermined, at which one of the pupil facets  11 , for example the pupil facet  11   1  in  FIG. 6 , is impinged on by the part bundle  24  reflected by the field facet  7  by way of the assigned object field illumination channel. Within the conic section portion  28 , which is predetermined by the angle of incidence tolerance range of the multilayer reflection coating  27  on the reflection face  25  of the field facet  7 , a second illumination tilt position of the field facet  7  is then determined while retaining the angle of incidence of the part bundle  24  on the field facet  7  within the angle of incidence tolerance range. A further pupil facet, for example the pupil facet  11   2  is now selected, which, in the determined second illumination tilt position is impinged on by the part bundle  24  reflected by the field facet  7  by way of the further object field illumination channel  26 . 
     The coincidence of the angles of incidence β 1  and β 2  in the two illumination tilt positions of the field facet  7  is again made clear with the aid of  FIGS. 7 and 8 . The xyz-coordinate systems of  FIGS. 7 and 8  relate to a main reflection face of the total field facet mirror  6 . 
       FIG. 7  shows the field facet  7  in a first illumination tilt position, in which the incident part bundle  24  is reflected in the object field illumination channel  26   1  at the angle of incidence β 1 . 
       FIG. 8  shows the field facet  7  in a further illumination tilt position, in which the incident part bundle  24  is reflected by the field facet  7  in the object field illumination channel  26   2  at the angle of incidence β 2 . There applies: β 1 .=β 2 . 
     Between the two illumination tilt positions according to  FIGS. 7 and 8 , the field facet  7  is tilted by an actuator  29 , which is only shown schematically in  FIG. 7  and has a signal connection to the control device  30 , by a tilt angle  2  β 1  about a tilt axis  31  extending parallel to the y-axis. 
     The incident part bundle  24  until the reflection on the field facet  7  does not change its position in the space in  FIGS. 7 and 8 . 
     The two object field illumination channels  26   1  and  26   2  according to  FIGS. 7 and 8  pass into one another by reflection about a plane, which contains the incident part bundle  24  on the reflection face  25  and is perpendicular to the incidence plane of the part bundle  24  on the field facet  7 , in other words by reflection about a plane parallel to the yz-plane. The two object illumination channels  26   1 ,  26   2  pass into one another by reflection along the part bundle  24  which is incident on the reflection face  25 . 
       FIG. 9  shows, in a view similar to  FIG. 5 , a further configuration of a field facet  32 , which can be used instead of the field facet  7  according to  FIGS. 5 to 8 . Components or reference numerals, which have already been described above with reference to  FIGS. 1 to 8 , have the same reference numerals and will not be discussed again in detail. 
       FIG. 9  in turn shows the incident part bundle  24  and two object field illumination channels  26   1  and  26   2 . A pupil facet  11   1  is impinged upon by way of the object field illumination channel  26   1 , into which the incident part bundle  24  is directed in a first illumination tilt position shown by dashed lines in  FIG. 9 . A pupil facet  11   2  is impinged upon by way of the further object field illumination channel  26   2 , into which the incident part bundle  24  is directed in a further illumination tilt position shown by a continuous line in  FIG. 9 . The angles of incidence of the part bundle  24  in the two illumination tilt positions shown in  FIG. 9  differ absolutely by no more than 10% and differ in particular by no more than 10°. 
     A multilayer reflection coating  33  on the reflection face  25  of the field facet  32  has a layer design with a large angle of incidence tolerance range, thus reflects the incident part bundle  24  over a range of angles of incidence, which also include the angles of incidence of the object field illumination channels  26   1 ,  26   2 , with a degree of reflection, which coincides within a tolerance range of +/−10%. A reflection coating of this type is also called a broadband reflection coating. The dependency of the degree of reflection R on the angle of incidence is shown by dashed lines as the degree of reflection curve  34  in  FIG. 12 . The degree of reflection R is defined here as the energy ratio E out /E in  between the energy E out  of the part bundle  24  reflected by the field facet  7  and the energy E in  of the part bundle  24  which is incident on the field facet  7 . The reflectivity R within small tolerance range is constant about R=0.6 between a minimum angle of incidence β min  in the range of about 9.5° and a maximum angle of incidence β max  in the range from about 17.3°, and fluctuates within the range [β min , β max ] only between limit values R=0.58 and R=0.62. 
     A plurality of pupil facets  11   1 , which can be achieved within the angle of incidence tolerance range [β min , β max ] by corresponding illumination tilt positions of the filed facet  32 , are shown by way of example in  FIG. 9 . By way of example, depending on the mechanical design of the tilt adjustment of the field facet  32  according to  FIG. 9 , two or more pupil facets  11   1 ,  11   2  . . . ,  11   n  can be selected from the pupil facets  11   i  and are then impinged upon by way of object field illumination channels  26   1 ,  26   2  . . .  26   n . Because of the course of the degree of reflection curve  34 , the energy of the part bundle  24  guided by way of the various object field illumination channels  26   i  is constant within a tolerance range of +/−10% regardless of the respective illumination tilt position of the field facet  32 . 
     With the aid of  FIGS. 10 and 11 , a further configuration of a reflection coating on a field facet  35  will be described below, which can be used instead of the field facets  7  or  32 . Components or reference variables, which have already been described above with reference to  FIGS. 1 to 8 , have the same reference numerals and will not be described again in detail. 
     A reflection face  36  of the field facet  35  is divided into two reflective portions  37 ,  38 , the degrees of reflection R of which are optimised for one of two illumination tilt positions of the field facet  35 , in each case. The first reflective portion  37  carries a first reflection coating, which is configured as a single layer, double layer or multi-layer coating and is optimised for a first angle of incidence β 1  for the incident part bundle  24 . The second reflective portion  38  carries a further reflection coating, which in turn can be configured as a single layer, double layer or multi-layer coating and is maximised for a second angle of incidence β 2  of the incident part bundle  24  with regard to its degree of reflection. The degree of reflection R of the reflective portion  37  for the angle of incidence β 1  coincides here within a tolerance range of +/−10% with the degree of reflection R of the reflective portion  38  for the angle of incidence β 2 . A coincidence of the degrees of reflection within a tolerance range of 5%, of 2%, of 1% or less than 1% is also possible by corresponding design of the reflection coatings of the reflective portions  37 ,  38 . 
       FIG. 10  shows the field facet  35  in a first illumination tilt position, in which the incident part bundle  24  is deflected with the angle of incidence β 1  into a first object field illumination channel  26   1 . Exclusively the reflection coating of the reflective portion  37  acts in this first illumination tilt position. 
       FIG. 11  shows the field facet  35  in a second illumination tilt position, in which the incident part bundle  24  is deflected at the angle of incidence β 2  into a further object field illumination channel  26   2 . Exclusively the reflection coating of the reflective portion  38  acts in this further illumination tilt position. 
     Because of the coinciding degrees of reflection R, the part bundle  24  reflected into the illumination channels  26   1 ,  26   2 , after reflection on the field facet  35 , has the same energy, regardless of the respective illumination tilt position. 
     A further design of a reflection coating, which is used instead of the reflection coating  33  of the field facet  32  according to  FIG. 9 , is described below with the aid of a degree of reflection curve  39  shown by a continuous line in  FIG. 12 . 
     The degree of reflection curve  39  does not run substantially constantly along the angle of incidence range [β min , β max ] by a specific value of the degree of reflection, but has a course there of the degree of reflection curve  39  with a maximum R max  of the degree of reflection lying between the two angles of incidence β min , β max , wherein there applies: R max ≈0.71. In the two limit angles of incidence β min  and β max , the reflection coating with the degree of reflection curve  39  in each case also has the same degree of reflection R of 0.6. As long as the field facet, for example the field facet  32  according to  FIG. 9 , is operated with illumination tilt positions, which correspond to angles of incidence for the incident part bundle  24 , which, within a tolerance range, in each case correspond to the angles of incidence β min  or β max , the part bundle  24  reflected by the field facet  32  by these illumination tilt positions, regardless of the selected illumination tilt position, in turn has the same energy. 
     With the aid of  FIGS. 13 and 14 , a further configuration of an illumination optical system  40  will be described below, which can be used instead of the components  10  to  14  of the illumination optical system  23  according to  FIG. 1  in the projection exposure system  1 . Components or reference variables which have already been described above with reference to  FIGS. 1 to 12 , have the same reference numerals and will not be described again in detail. 
     A pupil facet mirror  41 , in the illumination optical system  40 , has a through-opening  42  for the illumination light  3 . After passing through the through-opening  42 , the illumination light  3  is firstly reflected on the field facets  7  of the field facet mirror  6  and then on the pupil facets, not shown in detail, of the pupil facet mirror  41  and directed from there to the object field  18  where the various object field illumination channels  26  overlap. Two object field illumination channels  26  defining the edge of the bundle of illumination light  3  and two object field illumination channels  26   1  and  26   2  assigned to the two illumination tilt positions of a schematically shown facet  7  are shown in  FIG. 13 . This field facet  7  is in turn impinged upon in  FIG. 13  by a part bundle  24  of the illumination light  3 . The two angles of incidence β 1  and β 2  of the part bundle  24  assigned to the object field illumination channels  26   1 ,  26   2  are the same within a tolerance range of +/−10%. Because of the virtually symmetrical structure of the illumination optical system  40  for the beam path of the illumination light  3  in the region of the field facet mirror  6  and of the pupil facet mirror  41 , a higher degree of coincidence of the angles of incidence β 1 , β 2  can also be achieved for the illumination tilt positions of the field facets  7  of the field facet mirror  6 , for example a coincidence within a tolerance range of +−5%, of +−2%, of +−1% or an even better coincidence. 
     Between the two illumination tilt positions, the field facet  7  according to  FIG. 13  is tilted about an x-axis parallel tilt axis  31  about by an angle of 12°. 
     The total bundle of the illumination light  3  has a numerical aperture of 0.125 in the region of an intermediate focus  43  close to the throughput through the through-opening  42  of the field facet mirror  41 . The illumination light illuminates the object field  18  by way of all the object field illumination channels  26  with a numerical aperture of 0.125. 
       FIG. 14  shows, in a view similar to  FIG. 6 , the pupil facets  11  of the pupil facet mirror  41 , which can be impinged upon by one and the same field facet  7  with the same angle of incidence β within a predetermined tolerance range for the incident part bundle  24 . These pupil facets  11  lie within a ring  44 , which represents a special case of a conic section. Three selected pupil facets  11   1 ,  11   2 ,  11   3 , which lie within the ring  44 , are shown in  FIG. 14 . That which was already stated above in conjunction with the corresponding assignment for the field facet  7  according to  FIG. 6  applies to the assignment of these pupil facets  11   1  to  11   3  to illumination tilt positions of the field facets  7  according to  FIG. 14 . 
     The conic section portion  28  may, even region-wise, have the shape of an ellipse, a parabola, a hyperbola or a ring. 
     During the projection exposure, the reticle  17  and the wafer  22 , which carries a light-sensitive coating for the EUV illumination light  3 , are provided. At least one portion of the reticle  17  is then projected on the wafer  22  with the aid of the projection exposure system  1 . Finally, the light-sensitive layer exposed with the EUV illumination light  3  is developed on the wafer  22 . The microstructured or nanostructured component, for example a semiconductor chip, is produced in this manner. 
     The embodiments described above were described with the aid of an EUV illumination. As an alternative to an EUV illumination, a UV or a VUV illumination can also be used, for example with illumination light with a wavelength of 193 nm.