Abstract:
An optical system of a microlithographic projection exposure apparatus permits comparatively flexible and fast influencing of the intensity distribution and/or the polarization state. The optical system includes at least one layer system that is at least one-side bounded by a lens or a mirror. The layer system is an interference layer system of several layers and has at least one liquid or gaseous layer portion with a maximum thickness of one micrometer (μm), and a manipulator for manipulation of the thickness profile of the layer portion.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of, and claims benefit under 35 USC 120 to, international application PCT/EP2008/059435, filed Jul. 18, 2008, which claims benefit of German Application No. 10 2007 034 641.9, filed Jul. 23, 2007 and U.S. Ser. No. 60/951,294, filed Jul. 23, 2007. International application PCT/EP2008/059435 is hereby incorporated by reference in its entirety. 
    
    
     FIELD OF THE DISCLOSURE 
     The disclosure concerns an optical system of a microlithographic projection exposure apparatus. 
     BACKGROUND 
     Microlithography is used for the production of microstructured components such as for example integrated circuits or LCDs. The microlithography process is carried out in what is referred to as a projection exposure apparatus having an illumination system and a projection objective. The image of a mask (=reticle) illuminated via the illumination system is projected via the projection objective onto a substrate (for example a silicon wafer) which is coated with a light-sensitive layer (for example photoresist) and arranged in the image plane of the projection objective in order to transfer the mask structure onto the light-sensitive coating on the substrate. 
     In some instances, in the illumination system and also in the projection objective, a desired intensity distribution and/or an initially set polarization state can be altered in an unwanted fashion. The influences which are responsible for that include in particular birefringence effects which are variable in respect of time such as what is referred to as polarization-induced birefringence (PIB), compacting in non-crystalline material (for example quartz glass) of optical components, degradation phenomena and thermal effects as well as birefringence which is present in anti-reflecting or highly reflecting layers on the optical components as a consequence of form birefringence or by virtue of different Fresnel reflection and transmission for orthogonal polarization states. 
     SUMMARY 
     In some embodiments, the disclosure provides an optical system of a microlithographic projection exposure apparatus that permits comparatively flexible and fast influencing of the intensity distribution and/or the polarization state. 
     In certain embodiments, the disclosure provides an optical system of a microlithographic projection exposure apparatus that includes at least one layer system which is at least one-side bounded by a lens or a mirror, wherein the layer system is an interference layer system of several layers and has at least one liquid or gaseous layer portion whose maximum thickness is at a maximum 1 micrometer (μm), and a manipulator for manipulation of the thickness profile of the layer portion. 
     The effect achieved by the layer system with a liquid or gaseous layer portion of a maximum thickness of a maximum of 1 micrometer (μm) is to be distinguished from the action achieved in accordance with the state of the art (for example in the case of a liquid lens) of a refractive optical element. While, in the latter case, the refractive power which influences the beam path and which is dependent on the form of the refractive lens is altered the concept of the disclosure provides that the beam path as such is not influenced in a first approximation but—in a fundamentally different form of action—it can involve influencing for example phase separation by interference effects which occur between the partial waves of the light components partially reflected a plurality of times in the layer system. 
     In other words, in accordance with the disclosure—unlike for example a liquid lens with a liquid layer of typically a few millimeters—the system does not influence the direction of individual flat waves (or beams), but essentially only the phase position of the individual flat waves is manipulated. In contrast the interference effects utilized in accordance with the disclosure, in a conventional liquid lens with a liquid layer of typically a few millimeters, because of the limited coherence length of the light, no longer play any part as the interference effects utilized in accordance with the disclosure and thus phase influencing occur only in the thickness region which is selected in the present case and which is near the wavelength. 
     Partial reflection phenomena occur at the interfaces in relation to the liquid or gaseous layer portion provided in accordance with the disclosure, wherein ultimately the effect of the layer system is determined by the superimpositioning which takes place in respect of the partial waves occurring in that situation. In that respect use is made of the fact that the action of the layer stack, as an interference phenomenon, is particularly sensitively dependent on the thicknesses of the individual layers. The concept according to the disclosure of providing a liquid or gaseous layer portion, in the case of application to a multilayer system with a multiplicity of partial layers, involves modulating the thickness of one of those partial layers in its thickness configuration, whereby the interference properties are modified. 
     The layer system is at least one-side bounded by a lens or a mirror, i.e. the layer system is arranged adjacent, at least on one side of the layer system, to a lens or a mirror. 
     Basically the layer system according to the disclosure provides that, for each of the two parameters intensity I and phase φ, both the averaged value ((I s +I p /2) and (φ s +φ p )/2)) as well as the separation of intensity (I s −I p , “diattenuation”) or the phase (φ s −φ p ) can be influenced. 
     In that respect the variation in thickness which is caused in the liquid layer portion, depending on the respective specific factors involved, that is to say the structure of the layer system as well as the arrangement thereof within the optical system, can have an effect either on the phase or also on the intensity, with a relatively high degree of sensitivity. In particular the layer design in the layer system according to the disclosure can be so selected that one of the foregoing four parameters (for example phase separation, i.e. the phase difference obtained for orthogonal polarizations states) is influenced in a deliberately specific fashion, with the other parameters remaining at least substantially unchanged. 
     In particular the layer system according to the disclosure—with the averaged intensity being influenced—can be used as a variable gray filter, for example in the projection objective, the properties of which can be manipulated on a comparatively small time scale. 
     In certain embodiments, the layer system is at least one-side bounded by a lens and the manipulator has an arrangement of actuators provided at the edge of the lens. In particular the liquid or gaseous layer portion can be arranged between two lenses, wherein at least one of those two lenses is actively deformable. In that case the manipulator can have for example an arrangement of actuators provided at the edge of a lens arranged in adjacent relationship with the layer portion. 
     In some embodiments, the layer system is at least one-side bounded by a mirror and the manipulator has an arrangement of actuators that is provided on a surface, which is not optically effective, of the mirror (for example the “rear side” of a concave mirror). 
     The concept according to the disclosure makes it possible to provide for deliberate targeted detuning of the layer system for the correction of a disturbance, which is present elsewhere in the optical system (for example the projection objective) in respect of the desired intensity distribution, insofar as reflection or the action in the transmission mode—depending on the respective arrangement of the layer system on a mirror or a refractive lens—is manipulated in positionally resolved fashion until the desired correction action is achieved, by deliberate targeted deformation of the deformable layer portion. 
     In addition a change in phase which possibly occurs in an unwanted fashion can be remedied by phase manipulators arranged elsewhere in the optical system so that intensity influencing remains as the sole net effect. Equally polarization separation which possibly occurs in an unwanted fashion can also be compensated by suitable manipulators elsewhere in the optical system. 
     Phase separation can also be set as a desired effect with the layer system according to the disclosure which includes the deformable layer portion, in order for example to compensate for a disturbance, which occurs elsewhere in the optical system, in polarization distribution (for example as a consequence of holder-induced stress refraction etc.). Influencing the above-described separation parameters (that is to say transmission or phase separation) represents a particularly advantageous use of the disclosure as basically that is relatively difficult to achieve with other approaches. 
     In certain embodiments, the maximum thickness of the liquid or gaseous layer portion is at a maximum half a working wavelength (λ) of the optical system. Typical working wavelengths in a microlithographic projection exposure apparatus are less than 250 nm, for example about 193 nm or about 157 nm. In that respect, use is made of the fact that in the thickness range of between zero and λ/2, basically the entire range of action can be covered by setting a phase in the range of 0°-180°, which can also be covered with somewhat thicker layer systems (for example a layer of a thickness of 3λ/2). 
     The maximum thickness of the liquid or gaseous layer portion can be in particular in the range of between 10 and 100 nm (e.g., in the range of between 30 and 100 nm, in the range of between 50 and 100 nm). 
     In some embodiments, the layer system has an alternate succession of layers of a first layer material and a second layer material, wherein the first layer material has a refractive index of less than the refractive index of quartz glass (SiO 2 ) at a working wavelength and the second layer material has a refractive index of greater than the refractive index of quartz glass (SiO 2 ) at the working wavelength. In that respect in accordance with the disclosure it is possible in particular to use layer materials which admittedly are otherwise rather unusual but provide the deformable layer portion or the desired deformability, for example water with n=1.44 at λ=193 nm or also a suitable gel. It is also possible to use in a liquid layer portion for example the immersion liquids H 2 SO 4 , H 3 PO 4  and aqueous solutions thereof, as are referred to in US 2006/0221456 A1 (with refractive indices n in the range of 1.5-1.8 at λ=193 nm and optionally with substitution of deuterium), or cyclohexane (with a refractive index n=1.556 at λ=193 nm). 
     In that respect, in the context of layer optimization—which as such can be implemented in conventional manner—it can be predetermined that the respectively desired layer portions including the stated deformable liquid or gaseous layer portion are included in the layer system. 
     In certain embodiments, a layer portion with particularly advantageous growth or adhesion conditions can be provided in the layer system as the first (growth) layer portion. Furthermore a protective layer affording a particularly good protective action in relation to environmental influences can advantageously be selected as the outermost, uppermost layer portion of the layer stack. 
     In some embodiments, a change in a reflection capability of the layer system of at least 0.1% (e.g., at least 1%) can be set by a variation in the thickness profile of the first layer for at least one optically useable direction of incidence of light passing through the layer system. 
     In certain embodiments, a change in a transmission separation of the layer system of at least 0.1% (e.g., at least 1%) can be set by a variation in the thickness profile of the first layer for at least one optically useable direction of incidence of light passing through the layer system. 
     In some embodiments, a change in a birefringence of the layer system of at least 0.1° (e.g., at least 1°) can be set by a variation in the thickness profile of the first layer for at least one optically useable direction of incidence of light passing through the layer system. 
     In some embodiments, a change in an absorption capability of the layer system of at least k=0.001/cm (at least k=0.01/cm) can be set by a variation in the thickness profile of the first layer for at least one optically useable direction of incidence of light passing through the layer system. 
     In some embodiments, a flow movement can be produced or maintained in the liquid or gaseous layer portion in operation of the optical system, whereby it is possible to counteract an unwanted rise in temperature of the respectively adjoining optical element (lens or mirror). 
     The concept according to the disclosure can equally well be implemented both in the illumination system and also in the projection objective. 
     The disclosure further concerns an optical element, a method of modifying the imaging properties in an optical system of a microlithographic projection exposure apparatus, a microlithographic projection exposure apparatus, a process for the microlithographic production of microstructured components and a microstructured component. 
     Further configurations of the disclosure as set forth in the description and the appendant claims. 
     The disclosure is described in greater detail hereinafter by way of exemplary embodiments aspects of which are illustrated in the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In the drawings: 
         FIG. 1  shows a diagrammatic view of the structure of a layer system, 
         FIG. 2  shows a diagrammatic view of the structure of a layer system, 
         FIG. 3  shows a diagrammatic view of the structure of a microlithographic projection exposure apparatus, 
         FIGS. 4-5  show an overall meridional cross-section through specific examples of complete catadioptric projection objectives in which a layer system can be embodied, 
         FIGS. 6   a - b  show the calculated incidence angle dependency of reflection ( FIG. 6   a ) and reflection separation ( FIG. 6   b ) respectively for different reductions in thickness of a liquid layer portion, and 
         FIG. 7  shows a graph for comparing the degrees of reflection and reflection separation which can be achieved in different layer systems with a water layer and with an air layer respectively. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  shows a diagrammatic view of the structure of a layer system  100 . 
     In  FIG. 1 , the concept according to the disclosure is implemented on a concave mirror  110 , wherein arranged on the rear side of the mirror or the substrate thereof are individual actuators  105   a ,  105   b ,  105   c , . . . which are actuable independently of each other. 
     In  FIG. 1 , starting from the concave mirror  110 , individual layer portions  121  through  126  of a layer system  120  occur in succession in a direction towards the left, the layer portion  123  here forming the liquid layer portion  123  according to the disclosure. The layer portions  122  and  124  respectively adjoining that liquid layer portion  123  can if desired additionally be coated at the interface with a membrane or also with a glass plate of small thickness. 
     It will be appreciated that the disclosure is not limited to a concave mirror so that instead thereof it is also possible to use a flat mirror for the arrangement of the layer portions on that mirror. Corresponding suitable flat mirrors are available both in the illumination system and also in various designs of projection objectives, for example in the RCR design described in fuller detail hereinafter with reference to  FIG. 5 . 
     The actuators  105   a ,  105   b ,  105   c , . . . in their totality thus form a manipulator for manipulation of the thickness profile of the liquid layer portion  123  and can be for example in the form of piezoelectric elements and/or Lorentz motors. 
     As is shown in  FIG. 1  in only diagrammatic and highly exaggerated form, liquid is displaced out of the liquid layer portion  123  for example at the position of the double-headed arrow P by pressure applied by the corresponding manipulator so that the liquid layer portion  123  becomes thinner there and the layer action of the layer system  120  is influenced at that location. In that case the layer portions  124  and  125  arranged on the side of the liquid layer portion  123 , that is remote from the concave mirror  110 , ideally remain unchanged in their geometry. 
     It will be appreciated that the illustration of the layer system  120  in  FIG. 1  is not true to scale but is greatly exaggerated, in which respect in particular it is also possible to provide a larger or smaller number of layers. Typically the layer system has an alternate succession of layers of a first layer material and layers of a second layer material, wherein the first layer material has refractive index which is less than the refractive index of quartz glass (SiO 2 ) at a working wavelength of the optical system, and the second layer material has a refractive index which is greater than that of quartz glass (SiO 2 ) at the working wavelength. 
     Suitable layer materials of the “low-refractive” layer portions are for example chiolith (refractive index n=1.38 at λ=193 nm) and magnesium fluoride (MgF 2 , n(193 nm)=1.42). 
     Suitable layer materials of the “higher-refractive” layer portions are for example sapphire (Al 2 O 3 , n(193 nm)=1.81) and lanthanum fluoride (LaF 3 , n(193 nm)=1.70). 
     A specific embodiment by way of example of a layer system according to the disclosure is set out in Table 1. 
     
       
         
               
               
               
               
               
             
               
               
               
               
               
             
           
               
                 TABLE 1 
               
               
                   
               
               
                   
                   
                   
                   
                 Absorptions 
               
               
                 Layer 
                 Thickness 
                   
                 Refractive 
                 coefficient 
               
               
                 No 
                 (nm) 
                 Material 
                 index (193 nm) 
                 (k) 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                 1 
                 70.0 
                 Aluminum (Al) 
                 0.1127 
                 2.20286 
               
               
                 2 
                 19.3 
                 Chiolith (Na 5 Al 3 F 14 ) 
                 1.384 
                 0.00037 
               
               
                 3 
                 84.0 
                 Water (H 2 O) 
                 1.44 
                 0 
               
               
                 4 
                 14.9 
                 Aluminum oxide 
                 1.811 
                 0.0026 
               
               
                   
                   
                 (Al 2 O 3 ) 
               
               
                 5 
                 43.0 
                 Chiolith (Na 5 Al 3 F 14 ) 
                 1.384 
                 0.00037 
               
               
                 6 
                 25.1 
                 Aluminum oxide 
                 1.811 
                 0.0026 
               
               
                   
                   
                 (Al 2 O 3 ) 
               
               
                   
               
             
          
         
       
     
       FIG. 6 , for the above-indicated layer system and with a variation in the thickness of the liquid layer portion of water, illustrates the calculated incidence angle dependency of reflection ( FIG. 6   a ) and reflection separation ( FIG. 6   b ). In that case the thickness of the liquid layer portion is reduced stepwise with respect to the nominal starting value of 84.0 nm as shown in Table 1, wherein  FIG. 6 , for the individual curves, specifies the respective reduction in thickness in relation to that starting value (that is to say, there was a reduction in thickness by 0 nm, 14 nm, 24 nm, 34 nm, 44 nm and 54 nm). There is found to be a delicate dependency in respect of the curves on the thickness of the liquid layer, which can thus be suitably selected depending on the respectively desired effect. 
     The disclosure is not limited to a liquid medium such as for example water in regard to the layer portion which can be manipulated (“tuned”) in respect of its thickness profile, but instead it is also possible to use a gaseous medium such as for example air or another gas, wherein in the case of using the disclosure in a projection objective, that gas can in particular also be a flushing gas used in the projection objective (for example a chemically inert gas such as nitrogen (N 2 ), argon (Ar), helium (He) or mixtures thereof. 
     The use of a gaseous medium such as air in place of a liquid medium can be advantageous in particular in regard to service life of the adjoining optical components or layer portions. Embodiments for layer systems with such a gaseous layer portion are set forth hereinafter in Tables 2 and 3, in each of which an air layer is used in place of a water layer. 
     
       
         
               
             
               
               
               
               
               
             
               
               
               
               
               
             
           
               
                 TABLE 2 
               
             
             
               
                   
               
               
                 (=Example L1 in FIG. 7): 
               
             
          
           
               
                   
                   
                   
                   
                 Absorptions 
               
               
                 Layer 
                 Thickness 
                   
                 Refractive 
                 coefficient 
               
               
                 No 
                 (nm) 
                 Material 
                 index (193 nm) 
                 (k) 
               
               
                   
               
             
          
           
               
                 1 
                 70.0 
                 Aluminum (Al) 
                 0.1127 
                 2.20286 
               
               
                 2 
                 24.4 
                 Chiolith (Na 5 Al 3 F 14 ) 
                 1.384 
                 0.00037 
               
               
                 3 
                 25.8 
                 Aluminum oxide 
                 1.811 
                 0.0026 
               
               
                   
                   
                 (Al 2 O 3 ) 
               
               
                 4 
                 40.8 
                 Chiolith (Na 5 Al 3 F 14 ) 
                 1.384 
                 0.00037 
               
               
                 5 
                 25.8 
                 Aluminum oxide 
                 1.811 
                 0.0026 
               
               
                   
                   
                 (Al 2 O 3 ) 
               
               
                 6 
                 60.3 
                 Air 
                 1 
                 0 
               
               
                 7 
                 24.8 
                 Aluminum oxide 
                 1.811 
                 0.0026 
               
               
                   
                   
                 (Al 2 O 3 ) 
               
               
                 8 
                 39.5 
                 Chiolith (Na 5 Al 3 F 14 ) 
                 1.384 
                 0.00037 
               
               
                 9 
                 23.1 
                 Aluminum oxide 
                 1.811 
                 0.0026 
               
               
                   
                   
                 (Al 2 O 3 ) 
               
               
                 10 
                 44.5 
                 Chiolith (Na 5 Al 3 F 14 ) 
                 1.384 
                 0.00037 
               
               
                   
               
             
          
         
       
     
     
       
         
               
             
               
               
               
               
               
             
               
               
               
               
               
             
           
               
                 TABLE 3 
               
             
             
               
                   
               
               
                 (=Example L2 in FIG. 7): 
               
             
          
           
               
                   
                   
                   
                   
                 Absorptions 
               
               
                 Layer 
                 Thickness 
                   
                 Refractive 
                 coefficient 
               
               
                 No 
                 (nm) 
                 Material 
                 index (193 nm) 
                 (k) 
               
               
                   
               
             
          
           
               
                 1 
                 70.0 
                 Aluminum (Al) 
                 0.1127 
                 2.20286 
               
               
                 2 
                 25.5 
                 Chiolith (Na 5 Al 3 F 14 ) 
                 1.384 
                 0.00037 
               
               
                 3 
                 25.5 
                 Aluminum oxide 
                 1.811 
                 0.0026 
               
               
                   
                   
                 (Al 2 O 3 ) 
               
               
                 4 
                 39.9 
                 Chiolith (Na 5 Al 3 F 14 ) 
                 1.384 
                 0.00037 
               
               
                 5 
                 24.8 
                 Aluminum 
                 1.811 
                 0.0026 
               
               
                   
                   
                 oxide(Al 2 O 3 ) 
               
               
                 6 
                 51.1 
                 Air 
                 1 
                 0 
               
               
                   
               
             
          
         
       
     
     The layer system in accordance with Table 2, including the layer portion of air, can be implemented in such a way that the layer portions Nos 1-5 are vapor deposited in mutually superposed relationship on a quartz substrate, the layer portions 7-10 are similarly vapor deposited on another quartz substrate, and then the two sub-layer systems formed in that way are arranged at the spacing corresponding to the air layer to be formed, relative to each other. In the layer system of Table 3, unlike the example of Table 2, the “tunable” air layer directly adjoins a quartz substrate so that only one substrate has to be coated, unlike the situation with the example of Table 2. 
     It will be appreciated that the disclosure is not limited to quartz or quartz glass as a material adjoining the layer system according to the disclosure so that instead it is also possible to use other suitable lens materials such as for example calcium fluoride (CaF 2 ), garnets, in particular lutetium aluminum garnet (Lu 3 Al 5 O 12 ) and yttrium aluminum garnet (Y 3 Al 5 O 12 ) or spinel, in particular magnesium spinel (MgAl 2 O 4 ) as materials adjoining the layer system according to the disclosure. 
     The following layer systems of Tables 4 and 5 are further embodiments by way of example of layer systems with a liquid layer of water which otherwise involve a respective structure similar to Table 2 and Table 3 respectively. As can be seen from  FIG. 7 , higher values in respect of the degree of reflection can be achieved when using air instead of water, which can be attributed to the refractive index difference in relation to the adjoining layer portion, which is greater in the case of air.  FIG. 7  also shows (being plotted on the right-hand vertical axis in  FIG. 7 ) the value (R s −R p )/(R s +R p ) for the layer systems of Tables 2-5. 
     
       
         
               
             
               
               
               
               
               
             
               
               
               
               
               
             
           
               
                 TABLE 4 
               
             
             
               
                   
               
               
                 (=Example W1 in FIG. 7): 
               
             
          
           
               
                   
                   
                   
                   
                 Absorptions 
               
               
                 Layer 
                 Thickness 
                   
                 Refractive 
                 coefficient 
               
               
                 No 
                 (nm) 
                 Material 
                 index (193 nm) 
                 (k) 
               
               
                   
               
             
          
           
               
                 1 
                 70.0 
                 Aluminum (Al) 
                 0.1127 
                 2.20286 
               
               
                 2 
                 25.6 
                 Chiolith (Na 5 Al 3 F 14 ) 
                 1.384 
                 0.00037 
               
               
                 3 
                 25.5 
                 Aluminum oxide 
                 1.811 
                 0.0026 
               
               
                   
                   
                 (Al 2 O 3 ) 
               
               
                 4 
                 39.7 
                 Chiolith (Na 5 Al 3 F 14 ) 
                 1.384 
                 0.00037 
               
               
                 5 
                 24.8 
                 Aluminum oxide 
                 1.811 
                 0.0026 
               
               
                   
                   
                 (Al 2 O 3 ) 
               
               
                 6 
                 41.5 
                 Water (H 2 O) 
                 1.44 
                 0 
               
               
                 7 
                 22.6 
                 Aluminum oxide 
                 1.811 
                 0.0026 
               
               
                   
                   
                 (Al 2 O 3 ) 
               
               
                 8 
                 42.7 
                 Chiolith (Na 5 Al 3 F 14 ) 
                 1.384 
                 0.00037 
               
               
                 9 
                 23.0 
                 Aluminum oxide 
                 1.811 
                 0.0026 
               
               
                   
                   
                 (Al 2 O 3 ) 
               
               
                 10 
                 32.1 
                 Chiolith (Na 5 Al 3 F 14 ) 
                 1.384 
                 0.00037 
               
               
                   
               
             
          
         
       
     
     
       
         
               
             
               
               
               
               
               
             
               
               
               
               
               
             
           
               
                 TABLE 5 
               
             
             
               
                   
               
               
                 (=Example W2 in FIG. 7): 
               
             
          
           
               
                   
                   
                   
                   
                 Absorptions 
               
               
                 Layer 
                 Thickness 
                   
                 Refractive 
                 coefficient 
               
               
                 No 
                 (nm) 
                 Material 
                 index (193 nm) 
                 (k) 
               
               
                   
               
             
          
           
               
                 1 
                 70.0 
                 Aluminum (Al) 
                 0.1127 
                 2.20286 
               
               
                 2 
                 25.6 
                 Chiolith (Na 5 Al 3 F 14 ) 
                 1.384 
                 0.00037 
               
               
                 3 
                 25.4 
                 Aluminum oxide 
                 1.811 
                 0.0026 
               
               
                   
                   
                 (Al 2 O 3 ) 
               
               
                 4 
                 39.9 
                 Chiolith (Na 5 Al 3 F 14 ) 
                 1.384 
                 0.00037 
               
               
                 5 
                 24.6 
                 Aluminum oxide 
                 1.811 
                 0.0026 
               
               
                   
                   
                 (Al 2 O 3 ) 
               
               
                 6 
                 34.5 
                 Water (H 2 O) 
                 1.44 
                 0 
               
               
                   
               
             
          
         
       
     
       FIG. 2  is a diagrammatic view showing the structure of a layer system  200 , this view also not being true to scale but being greatly exaggerated. 
     Referring to  FIG. 2 , what is referred to as a bidirectional active lens element (=“BALE”)  210 , a layer portion  220  according to the disclosure or an interference layer system with a liquid or gaseous layer portion according to the disclosure and a further lens  230  held independently of the lens element  210  are arranged in a condition of bearing flush against each other. The bidirectional active lens element  210  is manipulated in positionally resolved fashion by way of actuators arranged at the edge in basically known manner in respect of its thickness, thereby once again achieving specific desired manipulation of the thickness distribution of the layer portion  220 . In an alternative configuration the layer portion  220  can also be arranged between two lens elements which are respectively manipulatable in their thicknesses. 
     It will be appreciated that the disclosure is not limited to curved lens surfaces so that instead it is also possible to use plane plates for the arrangement of the layer portion according to the disclosure. 
       FIG. 3  is an only diagrammatic view showing the structure in principle of a microlithographic projection exposure apparatus. In this case the concept according to the disclosure can be implemented equally both in the illumination system and also in the projection objective. 
     The microlithographic projection exposure apparatus has an illumination system  301  and a projection objective  302 . The illumination system  301  serves for illuminating a structure-bearing mask (reticle)  303  with light from a light source unit  304  which for example includes an ArF laser for a working wavelength of 193 nm as well as a beam shaping optical mechanism for producing a parallel light beam. The parallel light beam of the light source unit  304  is firstly incident on a diffractive optical element  305  (also referred to as a “pupil defining element”) which, by way of an angle radiation characteristic defined by the respective diffracting surface structure, produces in the pupil plane P 1  a desired intensity distribution (for example dipole or quadrupole distribution). Disposed downstream of the diffractive optical element  305  in the light propagation direction is an optical unit  306  including a zoom objective for producing a parallel light beam of variable diameter, and an axicon lens. Different illumination configurations are produced via the zoom objective in conjunction with the upstream-disposed diffractive optical element  305  in the pupil plane P 1  depending on the respective zoom position and the position of the axicon elements. In the illustrated example the optical unit  306  further includes a deflection mirror  307 . Disposed downstream of the pupil plane P 1  in the light propagation direction is a light mixing device  308  disposed in the beam path and which for example in per se known manner can have an arrangement of microoptical elements that is suitable for achieving a light mixing effect. The light mixing device  308  is followed in the light propagation direction by a lens group  309 , downstream of which is disposed a field plane F 1  with a reticle masking system (REMA) which is projected by an REMA objective  310  following in the light propagation direction onto the structure-bearing mask (reticle)  303  arranged in the field plane F 2 , and thereby limits the illuminated region to the reticle. The image of the structure-bearing mask  303  is formed with the projection objective  302  which in the illustrated embodiment has two pupil planes PP 1  and PP 2  on a substrate  311  or a wafer provided with a light-sensitive layer. 
     One or more layer systems according to the disclosure can be used in the illumination system  301  and/or the projection objective  302 , for example in the proximity of a pupil plane and/or a field plane of the illumination system  301  and/or the projection objective  302  respectively. Depending on the respectively desired effect the layer system according to the disclosure can be used both in field-near relationship, pupil-near relationship and also at an intermediary position. Thus for example in the case of correction to be implemented for a disturbance in intensity and/or polarization distribution, the correction action of the layer system is generally correspondingly better, the better the positioning in question of the layer system used as the correction element, in terms of its arrangement in field-near, pupil-near or intermediary relationship (that is to say for example in respect of the subaperture ratio), corresponds to the corresponding location of the disturbance to be corrected. Ideally, the arrangement of the layer system in dependence on the location to be expected for the defect to be corrected can already be taken into consideration in the design of the optical system. 
     Referring to  FIG. 4  shown therein is a meridional section of a specific projection objective  400 . The design data of that projection objective  400  are set out in Table 6. In that respect the number of the respective refractive or otherwise significant optical surface is identified in column 1, the radius of that surface (in mm) is identified in column 2, optionally a reference to an asphere at that surface is identified in column 3, the spacing, referred to as thickness, of that surface in relation to the following surface (in mm) is identified in column 4, the material following the respective surface is identified in column 5 and the optically usable free half-diameter (in mm) of the optical component is identified in column 6. 
     The aspheric constants are set forth in Table 7. The surfaces which are identified in  FIG. 4  with bold dots and specified in Tables 6 and 7 are aspherically curved, wherein the curvature of those surfaces is given by the following aspheric formula: 
     
       
         
           
             
               
                 
                   
                     P 
                     ⁡ 
                     
                       ( 
                       h 
                       ) 
                     
                   
                   = 
                   
                     
                       
                         
                           
                             ( 
                             
                               1 
                               / 
                               r 
                             
                             ) 
                           
                           · 
                           
                             h 
                             2 
                           
                         
                         
                           1 
                           + 
                           
                             
                               1 
                               - 
                               
                                 
                                   ( 
                                   
                                     1 
                                     + 
                                     cc 
                                   
                                   ) 
                                 
                                 ⁢ 
                                 
                                   
                                     ( 
                                     
                                       1 
                                       / 
                                       r 
                                     
                                     ) 
                                   
                                   2 
                                 
                                 ⁢ 
                                 
                                   h 
                                   2 
                                 
                               
                             
                           
                         
                       
                       + 
                       
                         
                           C 
                           1 
                         
                         ⁢ 
                         
                           h 
                           4 
                         
                       
                       + 
                       
                         
                           C 
                           2 
                         
                         ⁢ 
                         
                           h 
                           6 
                         
                       
                     
                     = 
                     … 
                   
                 
               
               
                 
                   ( 
                   1 
                   ) 
                 
               
             
           
         
       
     
     In that formula P is the camber height of the surface in question parallel to the optical axis, h is the radial spacing from the optical axis, r is the radius of curvature of the surface in question, cc is the conic constant (identified in Table 7 by K) and C1, C2, . . . are the aspheric constants set out in Table 7. 
     As shown in  FIG. 4  the projection objective  400  in a catadioptric structure has a first optical subsystem  410 , a second optical subsystem  420  and a third optical subsystem  430 . In that respect, the term “subsystem” is always used to denote such an arrangement of optical elements, by which a real object is imaged into a real image or an intermediate image. In other words any subsystem, starting from a given object or intermediate image plane, always includes all optical elements as far as the next real image or intermediate image. 
     The first optical subsystem  410  includes an arrangement of refractive lenses  411 - 417  and forms the image of the object plane “OP” as a first intermediate image IMI 1 , the approximate position of which is indicated by an arrow in  FIG. 4 . That first intermediate image IMI 1  is imaged by the second optical subsystem  420  as a second intermediate image IMI 2 , the approximate position of which is also indicated by an arrow in  FIG. 4 . The second optical subsystem  420  includes a first concave mirror  421  and a second concave mirror  422  which are each “cut off” in a direction perpendicular to the optical axis in such a way that light propagation can respectively occur from the reflecting surfaces of the concave mirrors  421 ,  422  towards the image plane “IP”. The second intermediate image IMI 2  is imaged by the third optical subsystem  430  into the image plane IP. The third optical subsystem  430  includes an arrangement of refractive lenses  431 - 443 . 
     A layer system according to the disclosure can be arranged in the case of the projection objective  400  of  FIG. 4  for example on one of the concave mirrors  421  or  422  or also on both concave mirrors  421  and  422  for example involving the structure shown in  FIG. 1 . 
       FIG. 5  shows a meridional section of a further specific complete projection objective  500  which is disclosed in WO 2004/019128 A2 (see therein  FIG. 19  and Tables 9 and 10). The projection objective  500  includes a first refractive subsystem  510 , a second catadioptric subsystem  530  and a third refractive subsystem  540  and is therefore also referred to as a “RCR-system”. The first refractive subsystem  510  includes refractive lenses  511  through  520 , downstream of which in the beam path a first intermediate image IMI 1  is produced. The second subsystem  530  includes a double-folding mirror with two mirror surfaces  531  and  532  which are arranged at an angle relative to each other, wherein light entering from the first subsystem  510  is firstly reflected at the mirror surface  531  in the direction towards the lenses  533  and  534  and a subsequent concave mirror  535 . The concave mirror  535  in per se known manner permits effective compensation of the image field curvature produced by the subsystems  510  and  540 . The light reflected at the concave mirror  535  is reflected after again passing through the lenses  534  and  533  at the second mirror surface  532  of the double-folding mirror so that the optical axis OA is accordingly folded twice through 90°. The second subsystem  530  produces a second intermediate image IMI 2  and the light issuing therefrom impinges on the third refractive subsystem  540  which includes refractive lenses  541  through  555 . The second intermediate image IMI 2  is reproduced on the image plane IP by the third refractive subsystem  540 . 
     A layer system according to the disclosure can be arranged in the case of the projection objective  500  of  FIG. 5  for example on the concave mirror  535  and/or on the flat mirror surface or surfaces  531  and/or  532 , once again for example involving the structure shown in  FIG. 1 . 
     Even if the disclosure has been described by reference to specific embodiments numerous variations and alternative embodiments will be apparent to the man skilled in the art, for example by combination and/or exchange of features of individual embodiments. Accordingly it will be appreciated by the man skilled in the art that such variations and alternative embodiments are also embraced by the present disclosure and the scope of the disclosure is limited only in the sense of the accompanying claims and equivalents thereof. 
     
       
         
               
             
               
               
               
               
               
               
             
               
               
               
               
               
               
             
           
               
                 TABLE 6 
               
             
             
               
                   
               
               
                 (DESIGN DATA FOR FIG. 4): 
               
             
          
           
               
                 Sur- 
                   
                   
                   
                   
                 Half- 
               
               
                 face 
                 Radius 
                 Asphere 
                 Thickness 
                 Material 
                 diameter 
               
               
                   
               
             
          
           
               
                 1 
                 0.000000 
                   
                 −0.011620 
                 LV193975 
                 75.462 
               
               
                 2 
                 585.070331 
                 AS 
                 17.118596 
                 SIO2V 
                 76.447 
               
               
                 3 
                 −766.901651 
                   
                 0.890161 
                 HEV19397 
                 78.252 
               
               
                 4 
                 145.560665 
                   
                 45.675278 
                 SIO2V 
                 85.645 
               
               
                 5 
                 2818.543789 
                 AS 
                 40.269525 
                 HEV19397 
                 83.237 
               
               
                 6 
                 469.396236 
                   
                 29.972759 
                 SIO2V 
                 75.894 
               
               
                 7 
                 −193.297708 
                 AS 
                 21.997025 
                 HEV19397 
                 73.717 
               
               
                 8 
                 222.509238 
                   
                 27.666963 
                 SIO2V 
                 57.818 
               
               
                 9 
                 −274.231957 
                   
                 31.483375 
                 HEV19397 
                 52.595 
               
               
                 10 
                 0.000000 
                   
                 10.117766 
                 SIO2V 
                 44.115 
               
               
                 11 
                 0.000000 
                   
                 15.361487 
                 HEV19397 
                 47.050 
               
               
                 12 
                 26971.109897 
                 AS 
                 14.803554 
                 SIO2V 
                 54.127 
               
               
                 13 
                 −562.070426 
                   
                 45.416373 
                 HEV19397 
                 58.058 
               
               
                 14 
                 −510.104298 
                 AS 
                 35.926312 
                 SIO2V 
                 76.585 
               
               
                 15 
                 −118.683707 
                   
                 36.432152 
                 HEV19397 
                 80.636 
               
               
                 16 
                 0.000000 
                   
                 199.241665 
                 HEV19397 
                 86.561 
               
               
                 17 
                 −181.080772 
                 AS 
                 −199.241665 
                 REFL 
                 147.684 
               
               
                 18 
                 153.434246 
                 AS 
                 199.241665 
                 REFL 
                 102.596 
               
               
                 19 
                 0.000000 
                   
                 36.432584 
                 HEV19397 
                 105.850 
               
               
                 20 
                 408.244008 
                   
                 54.279598 
                 SIO2V 
                 118.053 
               
               
                 21 
                 −296.362521 
                   
                 34.669451 
                 HEV19397 
                 118.398 
               
               
                 22 
                 −1378.452784 
                   
                 22.782283 
                 SIO2V 
                 106.566 
               
               
                 23 
                 −533.252331 
                 AS 
                 0.892985 
                 HEV19397 
                 105.292 
               
               
                 24 
                 247.380841 
                   
                 9.992727 
                 SIO2V 
                 92.481 
               
               
                 25 
                 103.088603 
                   
                 45.957039 
                 HEV19397 
                 80.536 
               
               
                 26 
                 −1832.351074 
                   
                 9.992069 
                 SIO2V 
                 80.563 
               
               
                 27 
                 151.452362 
                   
                 28.883857 
                 HEV19397 
                 81.238 
               
               
                 28 
                 693.739003 
                   
                 11.559320 
                 SIO2V 
                 86.714 
               
               
                 29 
                 303.301679 
                   
                 15.104783 
                 HEV19397 
                 91.779 
               
               
                 30 
                 1016.426625 
                   
                 30.905849 
                 SIO2V 
                 95.900 
               
               
                 31 
                 −258.080954 
                 AS 
                 10.647394 
                 HEV19397 
                 99.790 
               
               
                 32 
                 −1386.614747 
                 AS 
                 24.903261 
                 SIO2V 
                 108.140 
               
               
                 33 
                 −305.810572 
                   
                 14.249112 
                 HEV19397 
                 112.465 
               
               
                 34 
                 −11755.656826 
                 AS 
                 32.472684 
                 SIO2V 
                 124.075 
               
               
                 35 
                 −359.229865 
                   
                 16.650084 
                 HEV19397 
                 126.831 
               
               
                 36 
                 1581.896158 
                   
                 51.095339 
                 SIO2V 
                 135.151 
               
               
                 37 
                 −290.829022 
                   
                 −5.686977 
                 HEV19397 
                 136.116 
               
               
                 38 
                 0.000000 
                   
                 0.000000 
                 HEV19397 
                 131.224 
               
               
                 39 
                 0.000000 
                   
                 28.354383 
                 HEV19397 
                 131.224 
               
               
                 40 
                 524.037274 
                 AS 
                 45.835992 
                 SIO2V 
                 130.144 
               
               
                 41 
                 −348.286331 
                   
                 0.878010 
                 HEV19397 
                 129.553 
               
               
                 42 
                 184.730622 
                   
                 45.614622 
                 SIO2V 
                 108.838 
               
               
                 43 
                 2501.302312 
                 AS 
                 0.854125 
                 HEV19397 
                 103.388 
               
               
                 44 
                 89.832394 
                   
                 38.416586 
                 SIO2V 
                 73.676 
               
               
                 45 
                 209.429378 
                   
                 0.697559 
                 HEV19397 
                 63.921 
               
               
                 46 
                 83.525032 
                   
                 37.916651 
                 CAF2V193 
                 50.040 
               
               
                 47 
                 0.000000 
                   
                 0.300000 
                 SIO2V 
                 21.480 
               
               
                 48 
                 0.000000 
                   
                 0.000000 
                 SIO2V 
                 21.116 
               
               
                 49 
                 0.000000 
                   
                 3.000000 
                 H2OV193B 
                 21.116 
               
               
                 50 
                 0.000000 
                   
                 0.000000 
                 AIR 
                 16.500 
               
               
                   
               
             
          
         
       
     
     
       
         
               
             
               
               
               
               
               
               
             
               
               
               
               
               
             
           
               
                 TABLE 7 
               
               
                   
               
               
                 (ASPHERIC CONSTANTS for FIG. 4): 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                   
                 2 
                 5 
                 7 
                 12 
                 14 
               
               
                   
               
               
                 K 
                 0 
                 0 
                 0 
                 0 
                 0 
               
               
                 C1 
                   −5.72E−02 
                   −4.71E−02 
                   1.75E−01 
                   −8.29E−02 
                   −4.35E−02 
               
               
                 C2 
                   −2.97E−07 
                   7.04E−06 
                   −1.17E−05 
                   −1.87E−07 
                   1.59E−06 
               
               
                 C3 
                   1.03E−12 
                   1.09E−10 
                   1.34E−09 
                   −7.04E−10 
                   −6.81E−11 
               
               
                 C4 
                   2.76E−14 
                   −2.90E−14 
                   −5.44E−14 
                   6.65E−14 
                   5.03E−15 
               
               
                 C5 
                   −1.51E−18 
                   −1.55E−21 
                   −1.82E−18 
                   −1.33E−17 
                   −1.68E−23 
               
               
                 C6 
                   −1.04E−24 
                   5.61E−23 
                   2.56E−22 
                   2.46E−21 
                   −2.36E−23 
               
               
                 C7 
                 0.000000e+00 
                 0.000000e+00 
                 0.000000e+00 
                 0.000000e+00 
                 0.000000e+00 
               
               
                 C8 
                 0.000000e+00 
                 0.000000e+00 
                 0.000000e+00 
                 0.000000e+00 
                 0.000000e+00 
               
               
                 C9 
                 0.000000e+00 
                 0.000000e+00 
                 0.000000e+00 
                 0.000000e+00 
                 0.000000e+00 
               
               
                   
               
               
                   
                 17 
                 18 
                 23 
                 31 
                 32 
               
               
                   
               
               
                 K 
                  −197.849 
                  −204.054 
                 0 
                 0 
                 0 
               
               
                 C1 
                   −2.94E−02 
                   5.77E−02 
                   −7.06E−02 
                   3.41E−02 
                   −4.85E−02 
               
               
                 C2 
                   2.63E−07 
                   −5.00E−07 
                   4.11E−06 
                   4.07E−08 
                   9.88E−07 
               
               
                 C3 
                   −6.11E−12 
                   2.67E−11 
                   −1.18E−10 
                   8.10E−11 
                   7.37E−11 
               
               
                 C4 
                   1.11E−16 
                   −5.69E−16 
                   2.92E−15 
                   −4.34E−15 
                   −6.56E−15 
               
               
                 C5 
                   −2.01E−21 
                   1.89E−20 
                   −3.23E−20 
                   7.59E−19 
                   6.53E−19 
               
               
                 C6 
                   2.08E−26 
                   −1.49E−25 
                   2.18E−25 
                   −3.41E−23 
                   −2.88E−23 
               
               
                 C7 
                 0.000000e+00 
                 0.000000e+00 
                 0.000000e+00 
                 0.000000e+00 
                 0.000000e+00 
               
               
                 C8 
                 0.000000e+00 
                 0.000000e+00 
                 0.000000e+00 
                 0.000000e+00 
                 0.000000e+00 
               
               
                 C9 
                 0.000000e+00 
                 0.000000e+00 
                 0.000000e+00 
                 0.000000e+00 
                 0.000000e+00 
               
               
                   
               
             
          
           
               
                   
                   
                 34 
                 40 
                 43 
               
               
                   
               
               
                   
                 K 
                 0 
                 0 
                 0 
               
               
                   
                 C1 
                   1.59E−02 
                   −4.10E−02 
                   −3.89E−02 
               
               
                   
                 C2 
                   −1.51E−06 
                   3.04E−07 
                   4.76E−06 
               
               
                   
                 C3 
                   6.62E−13 
                   5.71E−11 
                   −2.23E−10 
               
               
                   
                 C4 
                   1.72E−15 
                   −1.72E−15 
                   8.89E−15 
               
               
                   
                 C5 
                   −9.36E−20 
                   −9.60E−22 
                   −2.41E−19 
               
               
                   
                 C6 
                   2.36E−24 
                   3.81E−25 
                   3.43E−24 
               
               
                   
                 C7 
                 0.000000e+00 
                 0.000000e+00 
                 0.000000e+00 
               
               
                   
                 C8 
                 0.000000e+00 
                 0.000000e+00 
                 0.000000e+00 
               
               
                   
                 C9 
                 0.000000e+00 
                 0.000000e+00 
                 0.000000e+00