Patent Document

CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a divisional of, and claims benefit under 35 USC 120 to, U.S. application Ser. No. 14/496,689, filed Sep. 25, 2014, now U.S. Pat. No. 9,280,060, which is a divisional of, and claims benefit under 35 USC 120 to, U.S. application Ser. No. 13/186,068, filed Jul. 19, 2011, now U.S. Pat. No. 8,873,023, which is a continuation of, and claims benefit under 35 USC 120 to, international application PCT/EP2010/000411, filed Jan. 25, 2010, which claims benefit of German Application No. 10 2009 006 685.3, filed Jan. 29, 2009. U.S. application Ser. Nos. 14/496,689, 13/186,068 and international application PCT/EP2010/000411 are hereby incorporated by reference in their entirety. 
    
    
     FIELD 
     The disclosure relates to an illumination system for microlithography for illuminating an illumination field with illumination light. The disclosure further relates to a raster arrangement for use in an illumination system of this type, a microlithographic projection exposure apparatus including an illumination system of this type, a microlithographic production method for microstructured or nanostructured components and a component which has been produced according to a method of this type. 
     BACKGROUND 
     An illumination system for microlithography is known from WO 2007/093433 A1. 
     SUMMARY 
     The disclosure provides an illumination system for microlithography with which influencing particular illumination parameters of the illumination of the illumination field or object field is possible so that undesirable influences on other illumination parameters are avoided to the greatest extent possible. 
     In one aspect, the disclosure provides an illumination system for microlithography for illuminating an object field with illumination light of a primary light source, wherein the illumination system includes a first raster arrangement with bundle-forming first raster elements which are arranged in a first plane of the illumination system or adjacent to the plane for generating a raster arrangement of secondary light sources. The illumination system also includes a transmission optics for superimposing transmission of the illumination light of the secondary light sources into the illumination field. The transmission optics include a second raster arrangement with bundle-forming second raster elements. In each case one of the raster elements of the first raster arrangement being allocated to one of the raster elements of the second raster arrangement for guiding a partial bundle of an entire bundle of the illumination light. At least one of the two raster arrangements includes at least two types of the raster elements which have different bundle-influencing effects. The raster elements of the two raster arrangements are allocated to one another in such a way that to each raster element of one of the raster element types of one of the raster arrangements is allocated at least one individual free distance between the raster element of this type and the allocated raster element of the other raster arrangement. 
     It has been found according to the disclosure that a distance-type allocation between raster elements of the raster arrangements of the illumination system allows different collecting effects exerted on the allocated partial bundles by the different types of the first raster elements of the first raster arrangements to be compensated for partially or entirely. In such a case, other effect differences between the individual raster element types which influence the partial bundles of the illumination light, in particular higher order effects, can be utilized to such an extent that the often inevitable different collecting effects of the different types of first raster elements can be neglected. If refractive raster elements are used, it is for example possible to compensate for unwanted effects exerted by different lens radii of the raster elements, thus allowing other shape contributions, for example higher order shape contributions, to be utilized for compensation of particular illumination parameters when using aspheric lens shapes. An illumination system according to the disclosure allows particular illumination parameters to be either corrected or pre-compensated for. For example, when using different types of raster elements in at least one of the raster arrangements, an ellipticity correction may be performed in such a way that undesirable influences on an intensity distribution from the different illumination directions are avoided. Reflective raster elements can be used as well. In such a case, the difference between different types of raster elements is not due to a different refractive effect of the raster elements but is caused by a different reflective effect thereof. Tilted lenses are suitable for use as raster elements as well. The raster elements may be monolithic, in other words they may be formed in one piece, in such a way that a raster arrangement is produced from a monolithic lens or substrate block. Alternatively, it is conceivable to use raster elements consisting of multiple parts; one of these parts may be a group of raster elements or even an individual raster element. A variation of the individual distance between the raster element of a particular type of one of the raster arrangements and the allocated raster element of the other raster arrangement may have the shape of the graph of a strictly monotonic function which describes the variation of distances across the bundle-guiding cross-section of the raster arrangements. Alternatively, this function may have a maximum or a minimum in the bundle-guiding cross-section. In other words, the distance variation across the cross-section may in particular have the shape of the graph of a random curve having at least one apex. Generally speaking, each of the two raster arrangements may also be provided with one type of raster elements only; a distance variation across the bundle-guiding cross-section of the raster arrangements may then be implemented in the manner of the functions or stages described above or below. The illumination system may be equipped with a primary light source; this is however not obligatory. It is conceivable as well to prepare the illumination system for later use with a primary light source which is separate from the illumination system. The free distance between the raster elements of the two raster arrangements is formed by an air gap, in other words an intermediate space which contains no solids. The two raster arrangements may be components which are separate from each other. The raster arrangement which includes at least two types of raster elements which have different bundle-influencing effects may be the first raster arrangement, the second raster arrangement or both raster arrangements. 
     At least one distance step between a first raster area including at least one raster element of the first raster element type and a second raster area including at least one raster element of the second raster element type is a discrete implementation of the distance allocation according to the disclosure. A distance step of this type can already be provided in a blank used for the production of the raster arrangement. 
     A type allocation of the raster elements to the raster areas ensures a reproducible production and a reproducible design of the illumination system. The raster areas may in each case include raster elements of the same type. 
     Raster arrangements with distance steps which are designed in such a way that the largest thickness is either in the center of the raster element and reduces gradually towards the edge or that the smallest thickness is in the center of the raster element and increases gradually towards the edge provide corresponding compensatory effects depending on the type allocation of the raster elements relative to the center and to the edge. 
     The advantages of the distance allocation are particularly apparent in a design of the raster elements as aspheric raster elements, with each of the individual raster element types having a different conical constant. 
     A desired influence on particular illumination parameters can be achieved viavia several conical constants of the various types of first raster elements. Alternatively or additionally, the bundle-influencing surfaces of the different types of raster elements may have different radii of curvature which may be compensated for to a desired extent via the distance-type allocation. In other words, a spherical design of the raster elements is conceivable as well, with the different types having different radii of curvature. The different conical constants allow a controlled intensity variation to be provided across the illumination field for correction, compensation or precompensation purposes. Alternatively or additionally, a desired influence on particular illumination parameters may be achieved via different radii or, more generally speaking, via differently designed non-rotationally symmetric freeform surfaces of the various types of first raster elements. 
     In a second aspect, the disclosure provides an illumination system for microlithography for illumination of an object field with illumination light of a primary light source, wherein the illumination system includes a first raster arrangement with bundle-forming first raster elements which are arranged in a first plane of the illumination system or adjacent to the plane for generating a raster arrangement of secondary light sources. The illumination system also includes a transmission optics for superimposing transmission of the illumination light of the secondary light sources into the illumination field. The transmission optics includes a second raster arrangement with bundle-forming second raster elements, and a displacement device for displacing at least one segment of the first raster arrangement relative to the second raster arrangement. 
     The displacement device according to the disclosure may be configured for displacement of the at least one segment of the first raster arrangement relative to the second raster arrangement essentially along a beam direction of the illumination light and/or essentially transverse to a beam direction of the illumination light and/or for pivoting one of the raster arrangements relative to the other raster arrangements. When the two raster arrangements are displaced relative to each other, the first raster arrangements can be displaced, the second raster arrangement can be displaced or both raster arrangements can be displaced. The segment which is displaceable via the displacement device may include exactly one of the raster elements, a group of several raster elements, in particular a raster row, a raster column or a defined raster area, may include several groups of raster elements or may include all raster elements, in other words the entire raster arrangement. The illumination system according to the first aspect including the displacement device may be combined with the illumination system according to the second aspect including the at least two types of raster elements which have different bundle-guiding effects. In other words, all features of the disclosure described above can be combined with one another. 
     A displacement device which is designed in such a way that a periodic displacement of at least one segment of the first raster arrangement relative to the second raster arrangement takes place at a period which is small compared to an exposure time of the illumination field during lithographic projection exposure may be utilized to take advantage of an averaging effect via the illumination parameter(s) to be predetermined. 
     A design of the illumination system including a measuring device for detecting an illumination intensity distribution of the illumination light and a control device which is in a signal connection with the measuring device and the displacement device allows a feedback, in other words an actuation of the displacement device to be performed depending on the measuring result of the measuring device. A feedback of this type is also referred to as online feedback loop. The measuring device is able to detect the illumination intensity distribution in the field plane of the illumination field or in a plane which is conjugated thereto and/or in a pupil plane of the illumination system or in a plane which is conjugated thereto. Detecting the illumination intensity distribution in a plane of the illumination system which is disposed between a field plane and a pupil plane is conceivable as well. In this regard, a pupil plane is a plane in which an intensity distribution of the illumination light is a measure for an illumination angle distribution of the illumination of the illumination field. 
     The disclosure also provides a production method for microstructured components. The method includes providing a substrate which is at least partially provided with a layer of a light-sensitive material; providing a reticle which is provided with structures to be imaged; providing a projection exposure apparatus including an illumination system according to the disclosure, with the structures to the imaged being arranged in the illumination field; and projecting at least a part of the reticle onto a region of the layer via the projection exposure apparatus. 
     The disclosure further provides a microstructured or nanostructured component produced by such a method. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Embodiments of the disclosure will hereinafter be explained in more detail via the drawings in which: 
         FIG. 1  is a schematic meridional section through an illumination system according to the disclosure in a microlithographic projection exposure apparatus including a raster module with a two-step raster arrangement which is shown schematically and is not according to the disclosure; 
         FIG. 2  shows an embodiment according to the disclosure of the raster module of the illumination system according to  FIG. 1  including a non-stepped first raster arrangement and a second raster arrangement which is provided with a step between individual elements; 
         FIG. 3  is a plan view of the first raster arrangement according to  FIG. 2 , with five raster areas which are in each case provided with one of a total of three different types of raster elements being shown in a schematic illustration; 
         FIG. 4  is a schematic view of a diagram illustrating intensity distributions I(x) across an illumination field illuminated by an illumination system for two of the total of three raster element types of the first raster arrangement of the raster module according to  FIG. 3 , wherein the intensity distributions I(x) are not distance compensated; 
         FIGS. 5 to 10  show further embodiments of raster modules including raster arrangements which are provided with steps between individual elements or areas; 
         FIG. 11  is a meridional section through a raster module including two reflective raster arrangements in which the distances between the raster elements of the two raster arrangements allocated to each other are individual from type to type; 
         FIG. 12  is a schematic illustration of a raster module including two raster arrangements, the illustration outlining a degree of freedom when the two raster arrangements are displaced relative to each other; 
         FIG. 13  is an illustration, similar to  FIG. 12 , of a raster module including two raster arrangements, the illustration outlining two additional degrees of freedom when the two raster arrangements are displaced relative to each other; 
         FIG. 14  is an illustration, similar to  FIG. 12 , of a raster module including two raster arrangements, with raster elements of one of the two raster arrangements being individually displaceable relative to the other raster arrangements; 
         FIG. 15  is an illustration, similar to  FIG. 12 , of a raster module including two raster arrangements, with raster elements of one of the two raster arrangements again being individually displaceable relative to the other raster arrangements; 
         FIG. 16  is an illustration, similar to  FIG. 3 , of an embodiment of a raster arrangement including three raster areas which include in each case a plurality of raster columns consisting of raster elements, with the raster areas being displaceable relative to one another; 
         FIG. 17  is an illustration, similar to  FIG. 4 , of the effect on the intensity distribution across the illumination field when the raster areas of the raster arrangement according to  FIG. 16  are displaced; 
         FIG. 18  shows the change of a telecentricity curve across the illumination field which is caused by the changing intensity distribution according to  FIG. 17 ; 
         FIG. 19  is an illustration, similar to  FIG. 16 , of another embodiment of a raster arrangement including three raster areas which are displaceable relative to one another; 
         FIG. 20  shows, in an illustration similar to  FIG. 17 , the effects on the intensity distribution across the illumination field when the raster areas of the raster arrangement according to  FIG. 19  are displaced relative to one another; and 
         FIG. 21  shows the effects on an ellipticity curve across the illumination field which are caused by the changing intensity distribution according to  FIG. 20 . 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  is a schematic illustration of a microlithographic projection exposure apparatus  1  which is a wafer scanner and is used for the production of semiconductor components and other finely structured components. In order to obtain resolutions of up to fractures of micrometers, the projection exposure apparatus  1  uses in particular deep ultraviolet light (VUV). 
     In order to facilitate the description of positional relationships, a Cartesian x-y-z coordinate system is used for the following description. The x-axis runs upward in  FIG. 1 . The y-axis is perpendicular to the drawing plane of  FIG. 1  and runs towards the observer. The z-direction runs to the right in  FIG. 1 . A scanning direction of the projection exposure apparatus  1  coincides with the y-direction. In the meridional section according to  FIG. 1 , all optical components of the projection exposure apparatus  1  are arranged in a row along an optical axis  2 . The optical axis  2  may of course also be randomly folded, in particular to obtain a compactly designed projection exposure apparatus  1 . 
     An illumination system of the projection exposure apparatus  1 , the entirety of which is designated by the reference numeral  5 , serves to achieve a defined illumination of an object field or illumination field  3  in a reticle plane  4  in which a structure in the form of a reticle is arranged, which structure (not shown in more detail) is to be transmitted by projection exposure. The object field  3  and the illumination field may coincide with each other. As a rule, the object field  3  is disposed in the illumination field. An F 2 -laser with a working wavelength of 157 nm serves as primary light source  6  whose illumination light beam is coaxial with the optical axis  2 . Other DUV or UV light sources such as an ArF excimer laser with a working wavelength of 193 nm, a KrF excimer laser with a working wavelength of 248 nm and other primary light sources with higher or lower working wavelengths are conceivable as well. 
     In order to facilitate the description, components of an illumination optical system of the illumination system  5  are represented as refractive optical components. Alternatively or additionally, these components may also be replaced or supplemented by reflective components, in other words mirrors. Instead of the essentially dioptric system according to  FIG. 1 , it is therefore conceivable as well to use a catadioptric system or a catoptric system. A reflective design of the illumination system  5  may in particular be used if the primary light source  6  is an EUV light source which generates useful light with a wavelength in the range of between 5 nm and 30 nm, in particular in the range of 13.5 nm. 
     The first component on which the light beam  6 , which has a small rectangular cross-section, impinges after being emitted by the light source  6  is a beam expansion optical system  7  which generates an output beam  8  with essentially parallel light and a larger rectangular cross-section. The illumination light beam  8  has an x/y aspect ratio which may be in the range of 1 or may even be greater than 1. The beam expansion optical system  7  may include elements for coherence reduction of the illumination light  8 . Having been essentially parallelized by the beam expansion optical system  7 , the illumination light  8  then impinges on a diffractive optical element (DOE)  9  which is a computer-generated hologram (CGH) for generating an illumination light angular distribution. When passing through a Fourier lens arrangement, in other words a condenser  10  which is shown in a highly schematic illustration and which is located at a position relative to the DOE  9  that corresponds to its focal width, the angular distribution of the illumination light  8  generated by the DOE  9  is converted into a illumination light intensity distribution which is two-dimensional, in other words position-dependent in a direction perpendicular to the optical axis  2 . The intensity distribution thus generated is therefore present in a first illumination plane  11  of the illumination system  5 . Together with the condenser  10 , the DOE  9  therefore forms a light distribution device for generating a two-dimensional illumination light intensity distribution. This light distribution device is also referred to as pupil defining element (PDE). 
     In the region of the first illumination plane  11 , there is arranged a first raster arrangement  12  of a raster module  13  which is also referred to as honeycomb condenser. The raster module  13  is also referred to as field defining element (FDE). The raster module  13  serves to generate a defined intensity and illumination angle distribution of the illumination light  8 . In  FIG. 1 , the raster module  13  is only shown in a schematic illustration in order to describe the basic functioning principle thereof.  FIGS. 2 and 5  et seq. show other embodiments of the raster module  13  according to the disclosure. 
     A second raster arrangement  15  is arranged in another illumination plane  14  which is downstream of the first illumination plane  11 . The two raster arrangements  12 ,  15  form the honeycomb condenser  13  of the illumination system  5 . Arranged downstream of the other illumination plane  14  is a pupil plane  16  of the illumination system  5 . 
     Arranged downstream of the raster module  13  is another condenser  17  which is also referred to as field lens. Together with the second raster arrangement  15 , the condenser  17  images approximately the first illumination plane  11  into an intermediate field plane  18  of the illumination system  5 . In the intermediate field plane  18 , a reticle masking system (REMA)  19  may be arranged which is an adjustable shading stop for generating a sharp edge of the illumination light intensity distribution. A downstream objective  20 , which is also referred to as relay objective, images the intermediate field plane  18  onto the reticle, in other words the lithography template. A projection objective  21  is used to image the object field  3  onto a wafer (not shown in  FIG. 1 ) arranged in an image field  22  in an image plane  23 , the wafer being displaced along the y-direction intermittently or continuously. A pupil plane of the projection objective  21  is indicated at  23   a  in  FIG. 1 . If the projection exposure apparatus  1  is operated in such a way that the reticle and the wafer are displaced intermittently, then it is also referred to as stepper. If the projection exposure apparatus  1  is operated in such a way that the reticle and the wafer are displaced continuously, then it is also referred to as scanner. 
     The first raster arrangement  12  has individual first raster elements  24  which are arranged in columns and rows. The first raster elements  24  have a rectangular aperture with an x/y aspect ratio of for example 2/1. Other, in particular larger aspect ratios of the first raster elements  24  are conceivable as well. In order to facilitate the description, first raster elements  24  are hereinafter shown to have an x/y aspect ratio of 1/1 in  FIGS. 8 to 10 . 
     Alternatively, the raster arrangements  12  and  15  may in each case consist of cylindrical lenses which are arranged crosswise and disposed next to one another. Each of the raster arrangements  12 ,  15  may in this case be designed as a monolithic lens block. One of the two optical surfaces of the lens block then includes cylindrical lens surfaces which are oriented in a first direction while the opposite one of the two optical surfaces includes cylindrical lens surfaces which are oriented in a direction perpendicular thereto. 
     The meridional section according to  FIG. 1  runs along an x-raster column. The first raster elements  24  are microlenses which have a positive refractive power. In the illustration according to  FIG. 1 , these microlenses are shown to be plane convex. In the schematic illustration according to  FIG. 1 , the plane surfaces of the two raster arrangements  12 ,  15  face each other. As will hereinafter be explained via  FIGS. 2 and 5  et seq., the convex surfaces of the two raster arrangements  12 ,  15  may also be arranged in such a way as to face each other. A biconvex design is conceivable as well. The rectangular shape of the first raster elements  24  corresponds to the rectangular shape of the illumination field  3 . The first raster elements  24  are arranged in such a way as to directly abut each other in a raster which corresponds to their rectangular shape, in other words they fill essentially the entire surface. The first raster elements  24  are also referred to as field honeycombs. 
     The bundle-forming effect of the first raster elements  24  of the first raster arrangement  12  causes the illumination light  8  to be divided into a number of partial bundles  25  (cf. for example  FIG. 2 ) which number corresponds to the number of illuminated first raster elements  24 ; the partial bundles  25  are also referred to as light channels or illumination channels as they are at first guided through the raster module  13  separately from each other. The raster module  13  may be provided with several hundreds of such light channels which are in each case offset relative to each other by the respective x or y raster size when seen in the x or y direction. These light channels are superimposed in the object field  3 . 
     In order to transmit the respective partial bundle  25 , second raster elements  26  of the second raster arrangement  15  are allocated to the first raster elements  24  of the first raster arrangement  12 . The second raster elements  26  are microlenses which have a positive refractive power as well. 
       FIG. 1  shows five light channels of this type which are arranged next to one another when seen in the x-direction. In the embodiments of the raster module  13  according to the disclosure, a total of seven raster elements  24 ,  26 , which are arranged next to one another when seen in the x-direction, are shown in  FIGS. 2 and 5  et seq. for generating seven adjacent partial bundles or light channels  25 . 
     The distance of the second raster arrangement  15  from the first raster arrangement  12  approximately corresponds to the focal width of the raster elements  24 . The distance of the pupil plane  16  from the second raster arrangement  15  in turn corresponds to the focal width of the second raster elements  26 . 
     The raster elements  24 ,  26  are aspheric lenses. A sagittal height h of the each of the lens surfaces of the raster elements  24 ,  26  may be represented by the following aspheric equation: 
     
       
         
           
             
               h 
               ⁡ 
               
                 ( 
                 x 
                 ) 
               
             
             = 
             
               
                 
                   x 
                   2 
                 
                 
                   R 
                   ⁡ 
                   
                     ( 
                     
                       1 
                       + 
                       
                         
                           1 
                           - 
                           
                             
                               ( 
                               
                                 1 
                                 + 
                                 C 
                               
                               ) 
                             
                             ⁢ 
                             
                               
                                 ( 
                                 
                                   x 
                                   R 
                                 
                                 ) 
                               
                               2 
                             
                           
                         
                       
                     
                     ) 
                   
                 
               
               + 
               
                 
                   A 
                   4 
                 
                 ⁢ 
                 
                   x 
                   4 
                 
               
               + 
               
                 
                   A 
                   6 
                 
                 ⁢ 
                 
                   x 
                   6 
                 
               
               + 
               
                 
                   A 
                   8 
                 
                 ⁢ 
                 
                   x 
                   8 
                 
               
               + 
               … 
             
           
         
       
     
     In this equation, 
     h(x) represents the sagittal height as a function of the x-coordinate (field or lens coordinate); 
     R is the radius of the microlens surface at the apex; 
     C is the conical constant; 
     A n  are aspheric expansion constants. 
     The first raster arrangement  12  has various types of first raster elements  24 , in other words various types of aspheric microlenses. The types of the first raster elements  24  have different bundle-influencing, in other words refractive effects. 
       FIG. 3  shows a division of the first raster arrangement  12  of the raster module  13  into a total of five raster areas  27  to  31 . Each of the raster areas  27  to  31  runs in the y-direction in the shape of a column. When seen in the x-direction, each of the raster areas  27  to  31  may include exactly one raster element  24  or a plurality of raster elements  24 . Usually, each of the raster areas  27  to  31  has a plurality of raster elements  24 . Each of the raster areas  27  to  31  is composed of raster elements  24  of exactly one type, in other words they have exactly one refractive effect. 
     For the following description, the schematic division according to  FIG. 2  including a total of seven raster elements  24  which are arranged next to one another when seen in the x-direction is as follows: The uppermost raster element  24  according to  FIG. 2  is part of the raster area  27 , the two raster elements  24  arranged closest thereto are part of the raster area  28 , the central raster element  24  of  FIG. 2  is part of the raster area  29 , the two raster elements  24  arranged closest thereto are part of the raster area  30  and the lowermost raster element  24  of  FIG. 2  is part of the raster area  31 . 
     The raster elements  24  in the central raster area  29  belong to type I of the raster elements which have a conical constant C in the range of 0.2 and a smallest lens radius R, in other words they have the highest refractive effect. The raster elements  24  in the raster areas  28  and  30  are of a type II with a conical constant C in the range of 0.05 and a refractive effect which is lower than that of the raster elements  24  in the raster area  29 , in other words they have a slightly larger lens radius R. The raster elements  24  in the raster areas  27  and  31  are of a type III with a conical constant C in the range of −0.1 and a lowest refractive effect, in other words a largest lens radius R. Between type I and type III, the conical constant C thus differs by 0.3. The conical constants C of the types I, II, III may also assume other values from a range of values for the conical constant C of between −0.3 and +0.3, wherein the type with the highest refractive effect has the greatest conical constant C while the type with the lowest refractive effect has the smallest conical constant C. In another embodiment, the conical constant C is in the range of 0.05 for type II, in the range of 0.1 for type I and in the range of 0.0 for type III. The conical constant C of type I may for example vary in a range of between 0.09 and 0.25. The conical constant of type II may vary in a range of between −0.09 and +0.09. The conical constant C of type III may vary in a range of between −0.25 and −0.09. 
       FIG. 4  shows an effect of the raster elements  24  of type I and III which, because of their different refractive powers, is not distance-compensated, in other words it is not according to the disclosure. The Figure shows an intensity I across a field coordinate x in the region of the object field  3 . The high refractive effect of the raster elements  24  of type I causes the allocated partial bundle  25  to be heavily constricted on the allocated entrance surfaces of the allocated second raster elements  26  which in turn causes an intensity curve  32  across the field coordinate x to be constricted as well. The conical constant C of the raster elements  24  of type I results in a “concave” intensity curve  32  across the object field  3 , in other words the intensity curve  32  is curved in such a way as to be upwardly open. 
     Due to their lower refractive powers, the bundle-guiding effects of the raster elements  24  of type III causes the partial bundles to be constricted less on the second raster elements  26  which in turn results in a broader intensity curve  33  across the field coordinate x. The conical constant C of the raster elements  24  of type III results in a “convex” intensity curve  33  across the object field  3 , in other words the intensity curve  33  is downwardly open. 
     If there is no distance compensation as will be explained below, the constricting effect of the raster elements  24  of type I, which have a higher refractive effect than the raster elements  24  of type III, results in that when integrated over the object field  3 , the intensity contribution of type I is higher than that of type III as will become apparent when comparing the intensity levels of the intensity curves  32 ,  33  across the object field  3  in  FIG. 4 . 
     According to the disclosure, this intensity difference of the curves  32 ,  33  across the object field  3  is compensated for by a variation of distances Δ between the raster elements  24 ,  26  allocated to each other via the partial bundles  25 . This will hereinafter be explained via  FIG. 2 . As discussed above, the raster elements  24  of type I have a higher refractive effect than the raster elements of type III. Therefore, the partial bundles  25   I  formed by the raster elements  24  of type I have edge rays which converge more than those of the partial bundles  25   III  generated by the raster elements  24  of type III. On the other hand, the distance Δ I  between the raster elements  24 ,  26  in the raster area  29  is smaller than the distance Δ III  between the raster elements  24 ,  26  of the raster areas  27  and  31 . So regardless of whether it is of type I or III, the partial bundle  25  impinging upon the allocated raster element  26  therefore has the same extension x 0  in the x-dimension despite the higher refractive effect of the raster elements  24  of type I compared to type III. Likewise, type III of the raster elements, which has a lower refractive effect, has a higher intensity effect across the object field  3  as the larger distance Δ III  causes the partial bundle  25   III  to be collected along the same x-dimension x 0  as the partial bundle  25   I . In the region of the object field  3 , the intensity curve  33  generated by type III is thus raised up to the intensity curve  34  which is illustrated by a dot-dashed line. When integrated over the object field  3 , the two types I and III provide the same intensity contribution despite their different refractive effects, which intensity contribution differs only in terms of its concave or convex curve which is due to the different conical constants of the types I and III. 
     The different refractive effect of the types I and III therefore allows an intensity offset correction to be performed across the used object field  3 , which is indicated in  FIG. 4  by “E-Offset” and a double-headed arrow extending along the intensity axis. 
     The refractive effect of type II of the raster elements  24  in the raster areas  28 ,  30  is between the refractive effects of types I and III, with the result that type II has a corresponding intensity-adjusting effect. The schematic illustration of the raster module  13  according to  FIG. 2  shows two different distances Δ between the allocated raster elements  24 ,  26  in the raster areas  28 ,  30 , with the result that a distance variation is obtained between individual elements of the second raster arrangement  15 . The second raster elements  26  of the second raster arrangement  15  may alternatively be arranged at a uniform distance Δ from the allocated raster elements  24  of the first raster arrangement  12  as shown in  FIG. 2  by a dashed line at  35  so that in this case, a uniform distance Δ II  is provided. 
     The distance variation with the different distances AΔ I , Δ II , Δ III  is obtained via a thickness variation of the second raster arrangement  15  which thickness variation extends across the x-direction in the manner of a ridge. The second raster arrangement  15  has a highest raster thickness S I  in the center, in other words in the raster area  29 , and a lowest thickness S III  at the edge, in other words in the raster areas  27 ,  31 . When looking at the second raster arrangement  15  which is represented by a continuous line, the thickness S measured in the z-direction decreases from element to element via distance steps  36 . 
     The distances Δ between the raster arrangements  12 ,  15  are greatly exaggerated in  FIGS. 2 and 5  et seq. when compared to the respective x-dimension of the raster elements  24 ,  26 . 
     The following tables show examples of absolute distance or air gap changes which are used when the conical constant C or the radius of curvature of the respective first raster element  24  is changed. The change of the conical constant C is referred to by ΔC in the first table. 
     When the conical constant C is changed by for example 0.05, a change of the distance Δ of 13 μm is used for compensation. 
     The change of radius is given in percent in the second table. 
     
       
         
               
               
               
             
               
               
               
             
           
               
                   
                   
               
               
                   
                 ΔC 
                 Change of air gap [μm] 
               
               
                   
                   
               
             
             
               
                   
               
             
          
           
               
                   
                 0.05 
                 13 
               
               
                   
                 0.1 
                 27 
               
               
                   
                 0.2 
                 53 
               
               
                   
                 0.3 
                 80 
               
               
                   
                   
               
             
          
         
       
     
     
       
         
               
               
               
             
           
               
                   
                   
               
               
                   
                 Change of radius [%] 
                 Change of air gap [μm] 
               
               
                   
                   
               
             
             
               
                   
                 1 
                 16 
               
               
                   
                 2 
                 29 
               
               
                   
                 3 
                 45 
               
               
                   
                 5 
                 74 
               
               
                   
                   
               
             
          
         
       
     
       FIG. 3  shows an exemplary quadrupole illumination of the first raster arrangement  12  and therefore of the raster module  13  of the illumination system  5  of the projection exposure apparatus  1 . The first raster arrangement  12  is exposed to a total of four partial bundles which impinge upon the first raster arrangement  12  at the corners of a rhombus. In other words, the central raster area  29  is impinged by two partial bundles  25  which, when seen in the y-direction, are in each case close to the two edges of the raster area  29 . In the raster areas  27  and  31 , the first raster arrangement  12  is impinged centrally by a respective one of the partial bundles  25  when seen in the y-direction. In this quadrupole illumination, the different types I and III of the raster elements  24  allow an ellipticity variation of the illumination of the object field  3 , which is caused by other optical components of the projection exposure apparatus  1 , to be compensated for. 
     The ellipticity is a measure for assessing the quality of the illumination of the object field  3  in the object plane  4 . Determining the ellipticity allows one to better predict the distribution of energy or intensity across an entrance pupil of the projection objective  21 . To this end, the entrance pupil of the projection objective  21  is divided into eight octants which are numbered by O 1  to O 8  in the anticlockwise direction as is common practice in mathematics. The energy or intensity contribution provided by the octants O 1  to O 8  of the entrance pupil for illuminating a field point is hereinafter referred to as energy or intensity contribution I 1  to I 8 . 
     The following quantity is referred to as −45°/45° ellipticity (Elly, E −45°/45 °): 
               E       -   45     ⁢     °   /   45     ⁢   °       =         I   ⁢           ⁢   1     +     I   ⁢           ⁢   2     +     I   ⁢           ⁢   5     +     I   ⁢           ⁢   6           I   ⁢           ⁢   3     +     I   ⁢           ⁢   4     +     I   ⁢           ⁢   7     +     I   ⁢           ⁢   8               
while the following quantity is referred to as 0°/90° ellipticity (Ellx, E 0°/90 °):
 
     
       
         
           
             
               E 
               
                 0 
                 ⁢ 
                 
                   ° 
                   / 
                   90 
                 
                 ⁢ 
                 ° 
               
             
             = 
             
               
                 
                   
                     I 
                     ⁢ 
                     
                         
                     
                     ⁢ 
                     1 
                   
                   + 
                   
                     I 
                     ⁢ 
                     
                         
                     
                     ⁢ 
                     8 
                   
                   + 
                   
                     I 
                     ⁢ 
                     
                         
                     
                     ⁢ 
                     4 
                   
                   + 
                   
                     I 
                     ⁢ 
                     
                         
                     
                     ⁢ 
                     5 
                   
                 
                 
                   
                     I 
                     ⁢ 
                     
                         
                     
                     ⁢ 
                     2 
                   
                   + 
                   
                     I 
                     ⁢ 
                     
                         
                     
                     ⁢ 
                     3 
                   
                   + 
                   
                     I 
                     ⁢ 
                     
                         
                     
                     ⁢ 
                     6 
                   
                   + 
                   
                     I 
                     ⁢ 
                     
                         
                     
                     ⁢ 
                     7 
                   
                 
               
               . 
             
           
         
       
     
     The aspheric shape of the first raster elements  24  is produced in a multistage forming process. In this process, the raster arrangement  12  is at first produced in such a way as to have raster elements  24  with one and the same conical constant. Afterwards, a desired variation of the conical constants is performed which results in the different types I, II, III. This also results in the different lens radii, and therefore in the different refractive effects of the types I to III. Alternatively, the raster arrangement  12  may also be provided with the different lens radii of the types I to III in a single production step. 
       FIG. 5  shows another embodiment of a raster module  13  which is provided with distance variations between individual elements. Components and effects which correspond to those that have already been explained above with reference to  FIGS. 1 to 4  are denoted by the same reference numerals and are not discussed in detail again. 
     In the embodiment of the raster module  13  according to  FIG. 5 , the first raster arrangement  12  is provided with distance variations in the manner of a ridge between individual elements. As a result, there is a smallest distance Δ I  between the allocated raster elements  24  and  26  in the central raster area  29  while there is a largest distance Δ III  between the allocated raster elements  24  and  26 . In analogy to the above description relating to the embodiment according to  FIG. 2 , the different constricting effects of types I and III exerted on the partial bundles  25   I  to  25   III  by the raster elements  24  are distance-compensated as well, with the result that the partial bundles  25   I  to  25   III  again have the same x-extension x 0  on the raster elements  26  of the second raster arrangement  15 . Consequently, the same offset compensation of the different intensity curves is obtained as already discussed above with reference to  FIG. 4 . 
       FIG. 6  shows another embodiment of a raster module  13 . Components and effects which correspond to those that have already been explained above with reference to  FIGS. 1 and 5  are denoted by the same reference numerals and are not discussed in detail again. The raster arrangement  12  according to  FIG. 6  is designed in the manner of an inverted ridge, in other words it has a smallest thickness S 3  in the region of the center and a largest thickness S 1  at the edges. Likewise, the types I to III of the first raster elements  24  in the embodiment of the first raster arrangement according to  FIG. 6  are distributed across the x-dimension of the first raster arrangement  12  in an inverted manner as well. 
     Type III with the lowest refractive effect is disposed in the center, in other words in the raster area  29 . The raster elements  24  of type I, in other words the raster elements  24  with the highest refractive power, are disposed at the edges, in other words in the raster areas  27 ,  31 . The raster elements  24  of type II are arranged in-between, in other words in the raster areas  28  and  30 . The raster arrangement  12  according to  FIG. 6  is provided with distance steps  36  between the individual elements as well. 
     The distance Δ III , which is large compared to the distance Δ I , compensates for the refractive effect of type III which is lower than that of type I, with the result that regardless of whether the raster elements  26  are equipped with type I, II or III, the partial bundles  25   1  to  25   3  also have the same x-extension x 0  in the raster module  13  according to  FIG. 6 . 
       FIG. 7  shows another embodiment of a raster module  13 . Components and effects which correspond to those that have already been explained above with reference to  FIGS. 1 to 6  are denoted by the same reference numerals and are not discussed in detail again. 
     In  FIG. 7 , in contrast to the raster module  13  according to  FIG. 6 , it is not the first raster arrangement  12  but the second raster arrangement  15  which is an element in the shape of an inverted ridge having a smallest thickness S III  in the center and a largest thickness S I  at the edges. As a result, the distances Δ I  to Δ III  have a corresponding compensatory effect on the partial bundles  25   1  to  25   3  as already explained above with reference to the raster module  13  according to  FIG. 6 . 
       FIG. 8  shows another embodiment of a raster module  13 . Components and effects which correspond to those that have already been explained above with reference to  FIGS. 1 to 7  are denoted by the same reference numerals and are not discussed in detail again. 
     In the raster module  13  according to  FIG. 8 , both raster arrangements  12 ,  15  are provided with ridge-like steps between individual elements. The two ridges of the raster arrangements  12 ,  15  face each other, with the result that there is a lowest distance Δ I  in the raster area  29  while there is a largest distance Δ III  between the raster elements  24 ,  26  at the edges. The arrangement of the raster module  13  according to  FIG. 8  is selected if the types I and III have a larger difference in terms of their refractive effects than those of the arrangement according to  FIGS. 2 and 5 . 
       FIG. 9  shows another embodiment of a raster module  13 . Components and effects which correspond to those that have already been explained above with reference to  FIGS. 1 to 8  are denoted by the same reference numerals and are not discussed in detail again. 
     Other than in the embodiments according to  FIGS. 2 and 5 to 8  described above, the embodiment according to  FIG. 9  is only provided with three raster areas, namely the raster areas  37 ,  38  and  39 . In the schematic illustration according to  FIG. 9 , the first raster arrangement  12  of the raster module  13  according to  FIG. 9  again has a total of seven of the first raster elements  24  when seen in the x-direction. The raster elements  24  in the raster areas  37  and  39  are of type I which has the higher refractive power. The raster elements  24  of the first raster arrangement  12  in the central raster area  28  are of type III which has the lower refractive power. In the raster areas  37  and  39 , there are in each case two raster elements  24  of type I. In the raster area  38 , there are three raster elements  24  of type III which are disposed next to one another. 
     Between the raster areas  37  and  38  on the one hand and between the raster areas  38  and  39  on the other, the first raster arrangement  12  includes in each case one distance step  40 . A distance Δ I  between the raster elements  24  in the raster area  37  and the allocated raster elements  26  of the second raster arrangement  15  is smaller than a distance Δ III  between the first raster elements  24  in the raster area  38  and the allocated second raster elements  26 . As a result, the different distances Δ I  and Δ III  compensate for the different refractive effects of types I and III as already explained above with reference to the raster module  13  according to  FIG. 6 . 
       FIG. 10  shows another embodiment of a raster module  13 . Components and effects which correspond to those that have already been explained above with reference to  FIGS. 1 to 8  and in particular with reference to  FIG. 9  are denoted by the same reference numerals and are not discussed in detail again. 
     In the raster module  13  according to  FIG. 10 , the first raster arrangement  12  is inverted relative to the raster arrangement  12  according to  FIG. 9 . The raster elements  24  of type I with the higher refractive power are arranged in the central raster area  38  while the raster elements  24  of type III with the lower refractive power are arranged in the raster areas  37  and  39  at the edges. As the distance Δ III  at the edges now exceeds the distance Δ I , a compensatory effect is obtained as already explained with reference to the embodiment of the raster module  13  according to  FIG. 5 . 
     During microlithographic production of a microstructured or nanostructured component using the projection exposure apparatus  1 , a substrate is provided which is at least partially provided with a layer of a light-sensitive material. The substrate is usually a wafer. Furthermore a reticle is provided which is provided with the structure to be imaged. The projection exposure apparatus  1  is then used to project at least a portion of the reticle onto a region of the light-sensitive layer on the substrate. 
     The following is a description of another embodiment of a raster module  13  according to  FIG. 11 . Components and effects which correspond to those that have already been explained above with reference to  FIGS. 1 to 10  are denoted by the same reference numerals and are not discussed in detail again. 
     In the raster module  13  according to  FIG. 11 , the two raster arrangements  12 ,  15  are provided with reflective first raster elements  24  and with reflective second raster elements  26 . Because of their reflective powers, the raster elements  24  of the first raster arrangement  12  in the embodiment according to  FIG. 11  have different bundle-influencing effects instead of different refractive effects. Thus the raster element  24   III  of type III shown at the top of  FIG. 11  may be designed in such a way as to exert a lowest focusing effect on a partial bundle  25   III  while the raster element  24   I  of type I shown at the bottom of  FIG. 11  may be designed in such a way as to have a highest focusing effect on a partial bundle  25   I . The focusing effect exerted on the partial bundle  25   II  by the raster element  24   II  shown in-between lies between the two focusing effects of the raster elements  24   I  and  24   III . 
     The two raster arrangements  12 ,  15  are arranged in space relative to each other in such a way that an optical path length A between one of the first raster elements  24  and a second raster element  26  of the second raster arrangement  15  allocated thereto is such that the following relation applies:
 
Δ I &lt;Δ II &lt;Δ III .
 
     This individual allocation of distances Δ I  to Δ III  to type I to III of the first raster element  24  results in a compensating effect as already explained above for example with reference to the raster module  13  according to  FIG. 2 . 
     The two raster arrangements  12 ,  15  of the embodiments explained above may also be arranged in the beam path of the illumination light  8  in the opposite order. 
       FIG. 12  is a schematic illustration of another embodiment of the raster module  13  including raster arrangements  12 ,  15  with raster elements  24 ,  26 . Components and effects which correspond to those that have already been explained above with reference to  FIGS. 1 to 11  are denoted by the same reference numerals and are not discussed in detail again. 
     In the raster module  13  according to  FIG. 12 , the two raster arrangements  12 ,  15  are displaceable in the z-direction, in other words perpendicular to the xy-planes spanned by the two raster arrangements  12 ,  15 , along a displacement path Δ Z . In the embodiment shown in  FIG. 12 , it is the second raster arrangement  15  that is displaced in the z-direction. To this end, the second raster arrangement  15  is mechanically connected to a displacement device  41 . The displacement device  41  may be a linear displacement unit suitable for the displacement of optical components or a micromechanical actuator. 
     An output coupling mirror  42  is arranged in the beam path downstream of the second raster arrangement  15  which output coupling mirror  42  is partially permeable to the illumination light  8 . Via the output coupling mirror  42 , a partial beam  43  of the illumination light  8  is transmitted to a position-sensitive detector  44  such as a CCD array. The detector  44  is in a signal connection with the displacement device  41  via a central control device not shown in the drawing. The detector  44  detects an illumination intensity distribution of the partial beam  43  which allows conclusions to be drawn about an illumination intensity distribution and/or an illumination angle distribution of the illumination light  8  in the object plane  4 . 
     The Δ Z  displacement of the raster arrangement  15  relative to the raster arrangement  12  allows an offset correction of the intensity across the used object field  3  to be performed as already explained above with reference to  FIG. 4 . The larger a distance Z between the two raster arrangements  12 ,  15 , the smaller an x-extension of the illumination field, with the result that the intensity is focused more in the object field  3 . 
     Furthermore, the Δ Z  displacement may be used to achieve an offset of ellipticity, in other words of the quantities E −45°/45 ° or E 0°/90 °, for example, which have already been discussed above. The Δ Z  displacement also allows a uniformity of an illumination of the object field  3  to be adjusted. The uniformity is defined as the normalized scan-integrated total energy SE (x) for an x-value in the object field  3 , in other words a field height. The uniformity U is such that
 
 U (in percent)=100( SE ( x   max )− SE ( x   min ))/( SE ( x   max )+ SE ( x   min )),
 
with SE(x max ) being the total energy for the x-value x max  with the highest scan-integrated total energy. SE(x min ) on the other hand is the total energy for the x-value x min  with the lowest scan-integrated total energy.
 
     Furthermore, the Δ Z  displacement may be used to perform an offset correction of a telecentricity. 
     The telecentricity is a measure for a chief illumination angle direction of the energy or intensity of the illumination light incident on the object field  3 . 
     A chief ray of a light bundle allocated to a field point is defined for each field point of the illuminated object field. The chief ray has the energy-weighted direction of the light bundle emitted by this field point. Ideally, the chief ray of each field point is parallel to the principal ray determined by the illumination optical system or the projection objective  21 . 
     The direction of the principal ray {right arrow over (s)} 0  (x,y) is known from the design data of the illumination optical system or the projection objective  21 . The principal ray of a field point is defined by the connection line between the field point and the central point of the entrance pupil of the projection objective  21 . The direction of the chief ray at a field point x, y in the object field in the object plane  3  is obtained as follows: 
     
       
         
           
             
               
                 s 
                 → 
               
               ⁡ 
               
                 ( 
                 
                   x 
                   , 
                   y 
                 
                 ) 
               
             
             = 
             
               
                 1 
                 
                   
                     E 
                     ~ 
                   
                   ⁡ 
                   
                     ( 
                     
                       x 
                       , 
                       y 
                     
                     ) 
                   
                 
               
               ⁢ 
               
                 ∫ 
                 
                   
                     ⅆ 
                     u 
                   
                   ⁢ 
                   
                     ⅆ 
                     
                       v 
                       ⁡ 
                       
                         ( 
                         
                           
                             
                               u 
                             
                           
                           
                             
                               
                                   
                               
                             
                           
                           
                             
                               v 
                             
                           
                         
                         ) 
                       
                     
                   
                   ⁢ 
                   
                     
                       E 
                       ⁡ 
                       
                         ( 
                         
                           u 
                           , 
                           v 
                           , 
                           x 
                           , 
                           y 
                         
                         ) 
                       
                     
                     . 
                   
                 
               
             
           
         
       
     
     E(u,v,x,y) is the energy distribution for the field point x, y as a function of the pupil coordinates u, v, in other words it depends on the illumination angle seen by the respective field point x, y. {tilde over (E)}(x,y)=∫dudvE(u, v, x, y) is the total energy incident on the point x, y. 
     A for example central object field point x 0 , y 0  sees the radiation of partial radiation bundles from directions u, v which are defined by the position of the respective raster elements  26  on the second raster arrangement  15 . In this illumination example, the chief ray s travels along the principal ray only if the different energies or intensities of the partial radiation bundles or illumination channels allocated to the raster elements  26  combine to form a chief ray direction which is integrated over all raster elements  26  and which is parallel to a principal ray direction of the illumination light  8 . This is only the case under ideal circumstances. In practical application, there is a deviation between the chief ray direction {right arrow over (s)}(x,y) and the principal ray direction {right arrow over (s)} 0 (x,y) which is referred to as telecentricity error {right arrow over (t)}(x,y):
 
{right arrow over ( t )}( x,y )={right arrow over ( s )}( x,y )− {right arrow over (s)}   0 ( x,y )
 
     In the practical application of the projection exposure apparatus  1 , it is not the local telecentricity error at a particular object field point (x,y) to be corrected but the telecentricity error which is scan-integrated at x=x 0 . This telecentricity error is obtained as follows: 
     
       
         
           
             
               
                 T 
                 → 
               
               ⁡ 
               
                 ( 
                 
                   x 
                   0 
                 
                 ) 
               
             
             = 
             
               
                 
                   ∫ 
                   
                     
                       ⅆ 
                       y 
                     
                     ⁢ 
                     
                       
                         E 
                         ~ 
                       
                       ⁡ 
                       
                         ( 
                         
                           
                             x 
                             0 
                           
                           , 
                           y 
                         
                         ) 
                       
                     
                     ⁢ 
                     
                       
                         t 
                         → 
                       
                       ⁡ 
                       
                         ( 
                         
                           
                             x 
                             0 
                           
                           , 
                           y 
                         
                         ) 
                       
                     
                   
                 
                 
                   ∫ 
                   
                     
                       ⅆ 
                       y 
                     
                     ⁢ 
                     
                       
                         E 
                         ~ 
                       
                       ⁡ 
                       
                         ( 
                         
                           
                             x 
                             0 
                           
                           , 
                           y 
                         
                         ) 
                       
                     
                   
                 
               
               . 
             
           
         
       
     
     In other words, the telecentricity error is corrected which is integrated by a point (x, e.g. x 0 ) on the reticle moving through the object field  3  in the object plane  4  during the scanning process, wherein a difference is made between an x-telecentricity error and a y-telecentricity error. The x-telecentricity error T x  is defined as the deviation of the chief ray from the principal ray in the direction perpendicular to the scanning direction, in other words across the field height. The y-telecentricity error T y  is defined as a deviation of the chief ray from the principal ray in the scanning direction. 
     The illumination parameters are controllable via the detector  44 , the central control device and the displacement device  41 , thus allowing the raster module  13  to be operated as a corrective element which can be used during the operation to adjust actual values of the illumination parameters to predetermined desired values. To this end, the central control device evaluates the illumination parameters of the partial beam  43  detected by the detector  44  which allow conclusions to be drawn about the illumination parameters of the illumination light  8 . Depending on the actual values of the illumination parameters determined in this manner, the second raster arrangement  15  is then displaced by correspondingly actuating the displacement device  41  via the central control device. 
       FIG. 13  is an illustration similar to  FIG. 12  of another embodiment of a raster module  13  with different degrees of freedom for displacement between the two raster arrangements  12  and  15 . Components which correspond to those which have already been explained above with reference to the embodiments described above and in particular with reference to the embodiment according to  FIG. 12  are denoted by the same reference numerals and are not discussed in detail again. 
     In the raster module  13  according to  FIG. 13 , the second raster arrangement  15  is displaceable relative to the first raster arrangement  12  in the x-direction and in the y-direction along displacement paths Δ x , Δ y . To this end, the raster module  13  is again equipped with a displacement device  41  which is mechanically coupled with the second raster module  15 . 
     A Δ x  or Δ y  displacement of the second raster arrangement  15  relative to the first raster arrangement  12  allows a relative x or y position of the illumination field to be defined relative to the object field  3 . A tilt dependence of the telecentricity across the field height x, a so-called telecentricity tilt, as well as a tilt dependence of the ellipticity across the field height x are also adjustable via a Δ x  or Δ y  displacement. 
     Combined with a Δ x  or Δ y  displacement, an additional Δ Z  displacement, which—corresponding to the description of the raster module  13  according to  FIG. 12 —is conceivable for the raster module  13  according to  FIG. 13  as well, allows an intensity offset of the illumination light  8  to be adjusted across the object field  3 . 
     If the raster module includes a raster arrangement such as the raster arrangement  12  which is divided into raster areas having different bundle-influencing effects such as the raster areas  27  to  31  according to  FIG. 3 , then a Δ x  or Δ y  displacement results in a tilt change of the ellipticity across the object field  3 . This may be used to adjust an ellipticity tilt across the field height x. 
     A parameter control via a detector and the central control device as described above for the raster module  13  according to  FIG. 12  is conceivable for the raster module  13  according to  FIG. 13  as well. 
       FIG. 14  is an illustration similar to  FIG. 12  of another embodiment of a raster module  13  with different degrees of freedom for displacement between the two raster arrangements  12  and  15 . Components which correspond to those which have already been explained above with reference to the embodiments described above and in particular with reference to the embodiment according to  FIG. 12  are denoted by the same reference numerals and are not discussed in detail again. 
     In the raster module  13  according to  FIG. 14 , it is again the second raster arrangement  15  which is displaceable along the z-direction relative to the first raster arrangement  12 . The individual raster elements  26  of the second raster arrangement  15  are displaceable individually and independently of one another along displacement paths Δ Z1 , Δ Z2 , . . . , Δ ZN . Each of the raster elements  26  is mechanically coupled with an allocated displacement device  41  as schematically indicated in  FIG. 14 . The displacement devices  41  provide for the individual displacement of the raster elements  26  in the z-direction. An individual displacement device  41  may be allocated to each of the raster elements  26 . The displacement of the raster elements  26  via the displacement devices  41  is again controlled by the central control device which is not shown. An illumination parameter control via a detector and the central control device as described above for the raster module  13  according to  FIG. 12  is conceivable for the raster module  13  according to  FIG. 14  as well. 
     Depending on the position of the z-displaced raster element  26 , locally varying the distances Δ Zi  allows a size of the illumination field segment belonging to the illumination channel to be defined in an adjustable manner, the size of the illumination field segment being determined by the associated illumination channel. Consequently, the ellipse offset can be adjusted as well. A course of the ellipse across the object field  3  may for instance be influenced by varying the distances Δ Zi  in such a way that a predetermined distribution is achieved. This allows the ellipse to be corrected. Likewise, the uniformity may also be adjusted by varying the distances Δ Zi . 
     In the raster modules  13  according to  FIGS. 12 to 14 , the displacement devices  41  explained above may be designed in such a way that a periodic displacement of at least one segment of the first raster arrangement  12 , in other words at least one of the raster elements  24 , a group of raster elements  24  or the entire first raster arrangement  12 , relative to at least one segment of the second raster arrangement  15 , in other words relative to at least one raster element  26 , at least a group of raster elements  26  or relative to the entire raster arrangement  15  takes place at a period which is small compared to a time of exposure of the object or illumination field  3 . A displacement device  41  which is able to perform a periodic displacement of this type is also referred to as wobbler. 
     A wobbler of this type displaces the raster arrangement  15  or segments thereof at a time constant which is such that the illumination channels are displaced each time a light pulse is generated by the primary light source  6 . During the time of exposure of a particular segment on a wafer to be illuminated via the projection exposure apparatus  1 , this segment is impinged by for example 30 light pulses of the light source  6 . During these 30 light pulses, a periodic displacement of the wobbler may occur. 
       FIG. 15  is an illustration similar to  FIG. 12  of another embodiment of a raster module  13  with different degrees of freedom for displacement between the two raster arrangements  12  and  15 . Components which correspond to those which have already been explained above with reference to the embodiments described above and in particular with reference to the embodiment according to  FIG. 12  are denoted by the same reference numerals and are not discussed in detail again. 
     A displacement device  41  for the raster elements  26  of the second raster arrangement  15  ensures an individual x, y displacement of the raster elements  26  along displacement paths Δ X1 , Δ X2 , . . . , Δ XN  or Δ Y1 , Δ Y2 , . . . Δ YN , respectively. This x, y displacement results in a pupil-dependent displacement of the illumination channels which are displaced in the object field  3 . This may be used for optimizing a superimposition of the illumination channels in the object field  3  and therefore for optimizing the intensity distribution across the object field  3 . The x or y displacement Δ Xi , Δ Yi  results in a tilt dependence of the intensity distribution of the respective illumination channel of the displaced raster element  26 , which has corresponding effects on the uniformity. This allows a tilt dependence of the telecentricity to be corrected. 
     The effects of an x displacement of raster areas of a first raster arrangement  12  will hereinafter be explained in more detail via  FIGS. 16 to 18 . Components or functions which correspond to those that have already been discussed above with reference to  FIGS. 1 to 15  are denoted by the same reference numerals and are not explained in detail again. 
     The first raster arrangement  12  according to  FIG. 16  has three raster areas  45 ,  46 ,  47  which have different bundle-influencing effects, in other words they include raster elements  24  with different conical constants, for example, corresponding to the above description relating to the raster areas  27  to  31  of the first raster arrangement  12  according to  FIG. 3 . 
     Starting from a reference position of the three raster areas  45  to  47  relative to one another, the raster area  45  on the left-hand side of  FIG. 16  is displaced to the left relative to the central raster area  46  by a path −Δ X  while the raster area  47  on the right-hand side of  FIG. 16  is displaced to the right relative to the stationary central raster area  46  by a path Δ X . 
     The two displacements −Δ X , Δ X  cause the intensity curve across the object field to change as shown in  FIG. 17 . Corresponding to  FIG. 4 ,  FIG. 17  shows an I(x) diagram of the scan-integrated intensity across the field height x. When the raster area  45  is displaced by the path −Δ X , this results in a tilted intensity curve  48  with a highest intensity at the left-hand edge of the object field  3  according to  FIG. 17  and a lowest intensity at the right-hand edge of the object field  3  according to  FIG. 17 . Displacing the raster area  47  by the path Δ X  results in an intensity curve  49  with an opposite tilt, in other words with a lowest intensity at the left-hand field edge of  FIG. 17  and a highest intensity at the right-hand field edge of  FIG. 17 . 
     The tilted intensity curves  48 ,  49  result in a telecentricity curve  50  across the object field  3  as shown in  FIG. 18 . This is due to the fact that on the left-hand edge of the object field  3  according to  FIG. 18 , it is the intensity contribution from the raster area  47  that is most dominant while on the right-hand edge of the object field  3  according to  FIG. 18 , it is the intensity contribution from the raster area  45  that is most dominant. 
     The effect of a relative displacement of raster areas  45 ,  47  relative to the stationary central raster area  46  of the second raster arrangement  15  on particular illumination parameters of the illumination of the object field  3  is explained via  FIGS. 19 to 21 . Components which correspond to those that have already discussed above with reference to  FIGS. 1  to  18  and in particular with reference to  FIGS. 16 to 18  are denoted by the same reference numerals and are not described in detail again. 
     In contrast to  FIG. 16  which shows the first raster arrangement  12 , it is the second raster arrangement  15  which is shown in  FIG. 19 . 
     Starting from a reference position of the raster areas  45  to  47  relative to one another, a displacement according to  FIG. 19  is performed in such a way that the raster area  45  is displaced to the right relative to the raster area  46  in  FIG. 19  by a path Δ X  while the raster area  47  is displaced relative to the stationary central raster area  46  by a path Δ X  as well. The two outer raster areas  45 ,  47  are therefore both displaced relative to the central raster area  46  in the same direction, namely in the positive x-direction. 
     The central raster area  46  on the one hand and the two outer raster areas  45 ,  47  on the other are composed of raster elements having different bundle-guiding effects. The central raster area  46  includes raster elements of a first bundle-influencing type I, for example with a first conical constant. The two outer raster areas  45 ,  47  include raster elements  26  of a second type II having another bundle-influencing effect, in particular a conical constant which differs from that of type I. 
     The Δ X  displacements of the two outermost raster areas  45 ,  47  relative to the central raster area  46  result in a tilt of the field-dependent intensity distribution of type II which is such that the left field edge is impinged by a higher intensity than the right field edge (compare intensity curve  51  in  FIG. 20 ). As the central raster area  46  is not displaced, the intensity curve  52  thereof remains unchanged across the object field  3 . 
     The tilt of the intensity curve  51  results in a corresponding tilt of an ellipticity curve  53  which is shown in  FIG. 21 . The ellipticity curve  53  shown in  FIG. 21  may be the curve of the ellipticity E −45°/45 ° or the curve of the ellipticity E 0°/90 °. The tilt of the ellipticity curve  53  results in an ellipticity offset  54  on the right-hand side of the object field  3  according to  FIG. 21 . 
     Starting from a reference position, the displacement paths Δ X , Δ Y  for the raster arrangements  12 ,  15  or for the groups or areas of raster elements  24 ,  26  or for the individual raster elements  24 ,  26  may be in a range of between −10 μm and +10 μm. Consequently, the absolute total displacement paths may amount to 20 μm. An absolute Δ Z  displacement path for the raster arrangements  12 ,  15  or for the groups or areas of raster elements  24 ,  26  or for the individual raster elements  24 ,  26  may amount to 30 μm. 
     The displacement in the z-direction is a displacement which is performed essentially along a beam direction of the illumination light. The x or y displacement is a displacement which is performed essentially transverse to the beam direction of the illumination light  8 . 
     Alternatively, the displacement device  41  may be designed in such a way that one of the two raster arrangements  12 ,  15  is pivotable relative to the other one of the two raster arrangements  15 ,  12  about a pivot axis which is for example parallel to the x-axis or to the y-axis. In this case, the displacement device  41  is designed as a pivot drive for at least one of the two raster arrangements  12 ,  15 . 
     Depending on the design of the raster module, the types of raster elements described above may be parts of the first raster arrangement  12  and/or parts of the second raster arrangement  15 .

Technology Category: 3