DE102015220588A1 - Measuring method and measuring arrangement for an imaging optical system - Google Patents

Abstract

The invention relates to a method for measuring a wavefront error of an imaging optical system (10) of a projection exposure apparatus for microlithography. The method comprises providing the imaging optical system (10) with a plurality of optical modules (M1, M2, M3) comprising at least two optical elements (E1, E2, E3, E4, E5, E6); and a separate measurement of respective wavefront errors of the individual optical modules (M1, M2, M3).

Description

Background of the invention

The invention relates to a method for measuring a wavefront error of an imaging optical system of a projection exposure apparatus for microlithography. The imaging optical system includes a plurality of optical elements for imaging a pattern from an object plane into an image plane. Furthermore, the invention relates to a measuring arrangement for measuring an optical unit of a projection exposure apparatus for microlithography, as well as a measuring device and a method for interferometric shape measurement of optical surfaces.

A projection exposure apparatus is used in microlithography for exposing a photosensitive material on a wafer with an image of structures of a mask or a reticle. For this purpose, the projection exposure apparatus usually includes a lighting system and a projection lens. The illumination system generates a desired radiation distribution for illuminating the structures of the mask, while the projection lens images the illuminated structures with very high resolution onto the photosensitive material of the wafer.

In order to meet the imaging requirements, fabrication and positioning of the optical elements used in the projection exposure apparatus with extremely high precision is required. For this purpose, both a measurement of a complete imaging optical system as well as of individual optical elements can be carried out at a production or a readjustment of projection exposure systems currently.

In order to measure an imaging optical system of a projection exposure apparatus, phase-shifting interferometry techniques, such as shearing interferometry or point diffraction interferometry, are used in particular. In the DE 103 16 123 A1 Such an apparatus for wavefront measurement of a projection objective for microlithography by shear interferometry is described.

For a precise shape measurement of a surface of an optical element, diffractive optical arrangements are often used as so-called zero optics as the interferometric measuring device. In this case, the wavefront of a test wave is adjusted by a diffractive element, for example a computer-generated hologram (CGH) to a desired shape of the surface. Deviations from the desired shape can be determined by superposition of the reflected on the optical element test wave with a reference wave. Such a measuring device is used for example in the DE 10 2012 217 800 A1 described.

The constantly increasing demands on imaging optical systems in microlithography lead to ever greater complexity of these systems. For example, in projection objectives for ultraviolet radiation (EUV) microlithography, an increasing number of mirrors are used. However, as already mentioned above, with the measuring devices and methods described above, an imaging optical system can be measured individually only as a whole or as each optical element. When measuring a complex imaging optical system as a whole, it is difficult to associate the measured aberrations with individual optical elements. For individual measurement of the optical element, a decomposition of the complete imaging optical system may be necessary, which is associated with an ever greater amount of time due to the increasing complexity.

Underlying task

It is an object of the invention to provide an apparatus and a method, which solves the above problems and in particular the cause of a wavefront error of the imaging optical system can be determined with high accuracy and at the same time little time.

Inventive solution

According to a first aspect of the invention, the object is achieved by the method described below for measuring a wavefront error of an imaging optical system of a microlithography projection exposure apparatus. The optical system includes a plurality of optical elements for imaging a pattern from an object plane into an image plane. The method includes providing the imaging optical system with a plurality of optical modules each comprising at least two of the optical elements. Furthermore, the method comprises a separate measurement of respective wavefront errors of the individual optical modules.

In other words, several modules are provided in the imaging optical system. Each of the modules comprises at least two optical elements, preferably one after the other, arranged in the beam path of the optical system. In particular, each module as a whole can be removed from the optical system and reinserted into it. According to one embodiment Adjustment means provided for adjusting one or more modules in the optical system.

The inventive separate measurement of the individual optical modules, the cause of a wavefront error of the imaging optical system can be limited to one of the optical modules. As the next step, then, e.g. a measurement of the individual optical elements of this optical module done. A single measurement of all optical elements of the imaging optical system is not required. Thus, the time required for determining the cause of a wavefront error of the imaging optical system is kept low without loss of accuracy. Furthermore, the separate measurement of the individual optical modules also makes it possible to conclude on adjustment errors of the optical elements of the optical module bounded by the error, which are not very easily determinable by means of individual measurement and possibly by means of wavefront measurement of the imaging optical system as a whole.

According to one embodiment, the imaging optical system is a projection objective of a microlithography projection exposure apparatus. The imaging optical system may also be another imaging optical assembly from the exposure beam path of the projection exposure apparatus, such as an imaging optical assembly of an illumination system of the projection exposure apparatus. According to another embodiment, the imaging optical system may comprise at least a portion of either a projection lens or a lighting system of a projection exposure apparatus, i. either a part of the projection lens or the illumination system or the whole projection lens or the whole lighting system. According to another embodiment, at least one of the optical modules is not an imaging optic, but e.g. an optic with defocusing or jet-widening effect. According to a further embodiment, the optical modules of the imaging optical system are contained in a common housing during operation of the projection exposure apparatus.

According to one embodiment, the method according to the invention further comprises combining the measurement results for the individual optical modules into a result for the wavefront error of the entire imaging optical system. A measurement of the wavefront error of the entire imaging optical system is thus carried out by a separate measurement of the individual modules and then joining the measurement results to form an overall result. For a measurement of the entire imaging optical system after a post-processing or adaptation to specific requirements, only the respectively processed module has to be measured again. Due to the modular structure of the imaging optical system, reworking or adaptation becomes much faster and less complicated.

According to one embodiment, the imaging optical system is a projection objective of a projection exposure apparatus for microlithography, in particular an EUV projection exposure apparatus.

According to a further embodiment of the method according to the invention, the measurement of one of the optical modules comprises arranging the optical module to be measured and at least one matching module in the beam path of a measuring radiation of a wavefront measuring device such that the combination of the optical module to be measured and the at least one matching module forms imaging optical arrangement. Furthermore, the measurement comprises a determination of the wavefront error of the imaging optical arrangement by means of the wavefront measurement device. The wavefront error of the optical module to be measured can then be determined by taking a known wavefront error of the adaptation module out of the specific wavefront error of the imaging optical arrangement.

In one embodiment, the imaging optical arrangement formed by the combination of the optical module to be measured and the adaptation module can be configured such that its optical effect corresponds to the imaging optical system to be measured. Alternatively, the optical arrangement can also have other imaging properties, in particular a different focal length or a different magnification.

The adaptation module has at least one optical element. The optical element (s) of the matching module are designed and arranged such that they form, together with the module to be measured, the abovementioned imaging optical arrangement. The imaging property of the optical arrangement makes it particularly possible to use wavefront measuring devices for imaging optical systems for measuring the module.

According to one embodiment, a device for phase-shifting interferometry, in particular a device for shear interferometry or for point diffraction interferometry, is used as wavefront measuring device. For that forms the optical arrangement of the at least one matching module and the module to be measured in one embodiment, an opening positioned in the object plane of the optical arrangement of a pinhole or a coherence mask of the wavefront measuring device on a arranged in the image plane of the optical arrangement Schitter.

According to one embodiment, an adaptation module is arranged in the beam path of the wavefront measuring device in front of the module to be measured. Such an arrangement is particularly suitable for measuring a module provided last in the beam path of the imaging optical system in front of the image plane or another field plane. In a further embodiment, the adaptation module is arranged in the beam path of the wavefront measuring device after the module to be measured. This arrangement is advantageous for measuring a module provided in the beam path of the imaging optical system as the first after the object plane or another field plane.

According to a further embodiment of the method, arranging the at least one adaptation module comprises arranging an input-side measurement module for manipulating the measurement radiation in front of the optical module to be measured, and arranging an output-side measurement module for manipulating the measurement radiation according to the optical module to be measured. Both measuring modules have at least one optical element. The one or more optical elements of the measuring modules are designed and arranged such that the two measuring modules together with the module to be measured form an imaging optical arrangement. According to one embodiment of the inventive method, measuring modules configured in this way are arranged in the measuring radiation such that the optical arrangement corresponds in its optical effect to the imaging optical system to be measured. Alternatively, the optical arrangement can also have other imaging properties, in particular a different focal length or a different magnification. The arrangement of two measuring modules is particularly suitable for measuring an optical module which is provided in the beam path of the imaging optical system between two other modules or not directly before or after a field plane of the optical system.

In one embodiment of the method according to the invention, at least one diffractive structure pattern is used in the at least one adaptation module for manipulating the wavefront of the measurement radiation. In particular, the diffractive structure pattern is operated in transmission. As a diffractive structure pattern, for example, a diffractive structure pattern of a computer-generated hologram (CGH) can be used. A computer-generated hologram is generated by computing a suitable line structure as a diffractive structure using a computer and appropriate methods such as ray tracing, and then writing the calculated line structure onto or into the surface of a substrate. The diffractive structure pattern can be arranged in the beam path of the wavefront measuring device, for example before or after the optical module to be measured. Furthermore, a diffractive structural pattern can also be arranged in each of the two measuring modules described above.

According to a further embodiment of the method, the diffractive structure pattern for manipulating the wavefront of the measuring radiation is operated in reflection. For example, a diffractive structural pattern of a CGH is used as the diffractive structural pattern. In particular, two or more successively arranged diffractive structure patterns, such as CGHs, each with a diffractive structure can be operated in reflection. The CGH or CGHs are arranged in the beam path of the wavefront measuring device, for example, before or after the optical module to be measured. Furthermore, in one embodiment, CGHs operated in reflection are used in both measurement modules. In particular, CGHs operated in reflection make it possible to measure the optical module with EUV radiation.

According to one embodiment of the method according to the invention, at least two diffractive structure patterns arranged successively in the beam path of the measuring radiation for manipulating the measuring radiation are used in the at least one adaptation module. In other words, the diffractive structure patterns are arranged such that the measurement radiation interacts successively with the two diffractive structure patterns. In particular, the first diffractive structure pattern and the second diffractive structure pattern are each arranged on a separate substrate. Such a diffractive arrangement is described for example in the patent application US 2012/0127481 A1 disclosed. For example, two CGHs arranged one behind the other in the beam path are used. Such an arrangement of diffractive structures, also called "double-CGH", allows a simultaneous change of the location and the direction of a measuring beam. In this way, it is possible to adapt the imaging properties of the optical arrangement with the module to be measured and the at least one adaptation module particularly well to the imaging properties of the optical system to be measured.

According to an embodiment according to the invention, at least two diffractive pattern patterns superimposed in the beam path for manipulating the measuring radiation are used in the at least one adaptation module. In particular, the two diffractive structural patterns are superimposed on a single substrate in the same plane. Such overlapping diffractive structure patterns for producing separate output waves with different propagation direction are described, for example, in US Pat DE 10 2012 217 800 A1 described. According to one embodiment, a complex coded CGH with two or more diffractive structural patterns superimposed on one another is used in a matching module. At a location of the diffractive structures, a different deflection of different measuring beams thus takes place. As a result of this measure, in particular more than one field point, for example a pinhole array, in the object plane of the optical arrangement can be imaged simultaneously on a shear grating in the image plane of the optical arrangement.

Furthermore, the object is achieved by the following measuring arrangement for measuring an optical unit of a projection exposure apparatus for microlithography. The measuring device includes a wavefront measuring device which is configured to measure a wavefront error of an imaging optic by means of a measuring radiation. Furthermore, the measuring arrangement contains at least one adaptation module which is configured for manipulating the wavefront of the measurement radiation such that the combination of the optical unit to be measured and the at least one adaptation module forms an imaging optical arrangement. The optical unit may in particular be one of the optical modules described above in the context of the method according to the invention and thus an optical module of an imaging optical system of a projection exposure apparatus, such as an optical module of a projection objective of the projection exposure apparatus. According to one embodiment variant, the projection exposure apparatus may be an EUV projection exposure apparatus.

Such an optical unit contains at least two optical elements, which are arranged successively, for example, in the beam path of the imaging optical system. Each optical unit is designed so that it can be removed from the optical system as a whole.

The wavefront measuring device and the adaptation module of the measuring arrangement can be designed in accordance with the embodiment variants of a wavefront measuring device or a matching module described above with reference to the method according to the invention.

By providing the said adaptation module, the measuring arrangement according to the invention enables a separate measurement of individual optical modules of an imaging optical system even in cases in which the optical modules are not imaging optics. This makes it possible to determine the cause of a wavefront error of the imaging optical system with high accuracy and with less expenditure of time compared to a single measurement of optionally contained in the optical module optical elements.

According to one embodiment of the measuring arrangement according to the invention, the adaptation module is arranged in the beam path of the wavefront measuring device in front of the optical unit to be measured. In an alternative embodiment, the adaptation module is arranged in the beam path of the wavefront measuring device after the optical unit to be measured.

According to a further embodiment of the measuring arrangement according to the invention, the at least one adaptation module comprises an input-side measuring module for manipulating the measuring radiation, which is arranged in a beam path of the measuring radiation in front of the optical unit to be measured, and an output-side measuring module for manipulating the measuring radiation, which in the beam path of Measuring radiation is arranged after the optical unit to be measured. Both measuring modules contain at least one optical element. The optical elements of the measuring modules are, for example, designed and arranged such that they form an imaging optical arrangement together with the optical unit to be measured. According to an embodiment of the measuring arrangement, the measuring modules are configured such that the optical arrangement corresponds in its optical effect to an imaging optical system to be measured, the optical unit being one of a plurality of optical modules of the optical system to be measured. In an alternative embodiment, the optical arrangement may also have other imaging properties, in particular a different focal length or a different magnification.

In accordance with a further embodiment, the at least one adaptation module has one or more diffractive structure patterns used in reflection or in transmission. For example, the at least one adaptation module contains one or more CGHs with diffractive structure patterns. According to one embodiment, at least one CGH is in the beam path of the wavefront measuring device before or after the to be measured Module or in each case provided in both measuring modules. In particular, two or more successively arranged diffractive structure patterns, such as CGHs, each with a diffractive structure can be operated in reflection.

In one embodiment of the measuring arrangement, the at least one adaptation module contains at least two diffractive structure patterns arranged one above another in a beam path of the measurement radiation or arranged one behind the other. In particular, the successive arranged diffractive structure patterns are each provided on a separate substrate, as for example in the US 2012/0127481 A1 is described. According to one embodiment, two or more CGHs arranged one behind the other in the beam path are used. According to a further embodiment, the two superimposed structural patterns are arranged on a single substrate in the same plane, as shown for example in US Pat DE 10 2012 217 800 A1 is disclosed. For example, at least one complex coded CGH with two or more diffractive structural patterns superimposed on one another can be provided in the adaptation module.

According to a second aspect of the invention, the object is achieved by the measuring device described below for the interferometric shape measurement of optical surfaces of a microlithography projection exposure apparatus. The measuring device contains a one-piece waveform element which has diffractive structures for generating a measuring radiation with a wavefront matched to at least two juxtaposed non-contiguous optical surfaces. In this case, the measuring device is configured to measure a relative positioning of the optical surfaces relative to one another with respect to at least one rigid body degree of freedom. Furthermore, the measuring device comprises an interferometer for interferometric measurement of the measuring radiation after interaction with the optical surfaces.

Due to the possibility of measuring the relative positioning of the optical surfaces relative to one another with respect to at least one rigid body degree of freedom, a respective shape of the optical surfaces can be determined from the interferometric measurement result taking into account the specific relative positioning. This allows the simultaneous shape measurement of both optical surfaces. This reduces the time required to measure some or all of the optical elements of an imaging optical system of the type described above with respect to the first aspect of the invention, such as a microlithography projection objective. The time for determining the cause of a wavefront error of the imaging optical system is thus reduced.

According to one embodiment, the measuring device according to the second aspect of the invention comprises an evaluation device for determining a respective shape of the optical surfaces from the interferometric measurement result, taking into account the determined relative positioning.

Further, the object according to a second aspect of the invention is achieved by the following method for interferometric shape measurement of optical surfaces of a projection exposure apparatus for microlithography. The method comprises the following steps: arranging at least two non-contiguous optical surfaces in a beam path of a measuring radiation which is generated by a diffractive structure, comprising a one-piece wave form element having a wavefront matched to the optical surfaces; Determining a relative positioning of the optical surfaces to each other with respect to at least one rigid body degree of freedom; and a simultaneous interferometric measurement of the respective shape of the optical surfaces by means of the measuring radiation taking into account the determined relative positioning.

In other words, in the measuring device according to the invention and the method, the waveform element generates, by means of its diffractive structures, a measuring radiation which is directed onto each of the optical surfaces. In addition, the wavefront of the measuring radiation reaching a surface is in each case adapted to the shape of this surface. In particular, the diffractive structures can for this purpose transform a test radiation provided, for example, by an interferometer, such that in each case one measuring wave with a correspondingly adapted wavefront is generated for each optical surface. The adaptation of the wavefront is preferably formed such that the wavefront at the location of each optical surface corresponds to the respective desired shape of the surface. In this way, a zero optics is realized for each surface, in which a surface in desired form would reflect back the measuring radiation.

As the waveform element, for example, a CGH having diffractive structures juxtaposed on a substrate is used for each of the optical surfaces. Alternatively, a complex coded CGH may also be provided with diffractive structures overlapping one another in one plane for two or more surfaces.

From the optical surfaces, the measuring radiation is reflected back, again passes through the one-piece waveform element and is then measured in the interferometer by superposition with a reference wave. In the process, a characteristic interferogram arises for each surface in the case of a deviation from the respective nominal shape. As an interferometer, for example, a Fizeau, a Michelson or a Twyman Green interferometer can be used. It is only essential to record an interferogram in the case of a superposition of the reflected measuring radiation with a reference wave. The detection of an interferogram can be done for example by a CCD camera.

In addition, a determination of the relative positioning of the optical surfaces to each other. In this case, at least one relative location or tilting coordinate is determined as a relative rigid body degree of freedom. For example, interferometric methods can be used for this purpose. An evaluation device can finally determine the shape of each optical surface and their relative positioning to each other by means of the detected interferograms and taking into account the at least one measured rigid body degree of freedom. In this case, values of further rigid body degrees of freedom can be determined with the aid of the recorded values and interferograms. Alternatively, it is also possible to provide storage of the detected interferograms and values of relative rigid body degrees of freedom for later evaluation or transmission to an external evaluation unit.

According to one embodiment, the optical surfaces are part of a projection objective of a projection exposure apparatus for microlithography, in particular an EUV projection exposure apparatus. For example, the optical surfaces are reflective surfaces of mirrors of an EUV projection objective. For example, the surfaces may be planar, spherical or aspherical with or without rotational symmetry.

An embodiment of the measuring device according to the invention is configured to measure the relative positioning of the optical surfaces relative to each other in a direction transverse to the optical surfaces. In particular, the measurement of the relative positioning takes place in the direction of a mean propagation direction of the measuring radiation. According to one embodiment, the measuring device is configured to additionally measure the relative positioning of the optical surfaces in one or both directions of extension of the optical surfaces.

According to a further embodiment of the measuring device according to the invention, the waveform element has diffractive auxiliary measuring structures for generating auxiliary waves, which are each focused on one of the optical surfaces. The auxiliary measuring structures in particular transform part of the measuring radiation to auxiliary shafts. In this case, one or more diffractive auxiliary measuring structures can be provided for each optical surface. According to one embodiment, the auxiliary measurement structures are formed as additional diffractive structures on a CGH as a waveform element.

According to a further embodiment, the measuring device has a plurality of waveform elements or a waveform element having a plurality of diffractive structures for measuring in each case a partial area of at least one of the optical surfaces. In particular, the evaluation device is designed to assemble partial measurements into an overall measurement of the optical surfaces. In particular, the measuring device can be designed to use different waveform elements designed, for example, as CGH, for successively measuring different partial regions of one or more optical surfaces. Alternatively or additionally, it is also possible to provide a closure device, eg with one or more shutters, which allows a measuring radiation to pass only for selectable partial regions. An assembly of the partial measurement to a total measurement of the surfaces can be done for example by a so-called stitching, which eg in the WO 2005/114101 A1 is described. With this measure, it is also possible to measure surfaces in which the reflected measuring radiation from two or more surfaces at least partially intersects. In such a case, which is also known to those skilled in the art as "caustic", the corresponding section of the interference pattern can no longer be unambiguously assigned to an optical surface. By successively measuring partial areas, it is possible to avoid such a convergence of the reflected measuring radiation. Furthermore, with this embodiment, even very large optical surfaces can be completely measured.

In one embodiment of the method according to the invention for the interferometric shape measurement of optical surfaces, a measurement of the relative positioning of the optical surfaces relative to one another takes place by means of auxiliary waves, which are generated with auxiliary measurement structures of the waveform element from the measurement radiation. The auxiliary measuring structures in particular transform part of the measuring radiation to auxiliary shafts. According to an embodiment variant, one or more auxiliary shafts are generated for each optical surface. The auxiliary measurement structures can be provided as additional diffractive structure patterns in a CGH as wavefront element.

According to one embodiment of the method for shape measurement, subsections of at least one of the optical surfaces are successively measured with different waveform elements or different diffractive structures of a waveform element. Subsequently, partial measurements are combined to form an overall measurement of the optical surfaces. Corresponding to the corresponding embodiment of the measuring device, different CGHs for different partial areas, a closure device for blocking the measuring radiation for specific partial areas, or both can be used successively, for example. The assembly of partial measurements is preferably carried out by the above-mentioned stitching method.

Further, according to an embodiment of the method for interferometric shape measurement of optical surfaces, the discontinuous optical surfaces are arranged on a common substrate. In particular, the optical surfaces are positioned side by side on one side of the substrate. In this case, the optical surfaces can be formed, for example, for reflection of an illumination radiation of the projection exposure apparatus and thus represent a double mirror or multiple mirror. With the use of a substrate for multiple surfaces, a particularly compact design is realized.

According to an alternative embodiment, the non-contiguous optical surfaces are each arranged on separate substrates. Thus, for example, two or more mirrors arranged next to one another can be measured simultaneously, such as two mirrors arranged side by side with a flat angle of incidence for a projection objective of EUV microlithography. In addition to the respective shape, the relative position to each other is determined.

With regard to the above-mentioned embodiments, exemplary embodiments or variants, etc. of the inventive measuring arrangement according to the first aspect and the measuring device according to the second aspect specified features can be transferred to the respective inventive method according to the first aspect or the second aspect and vice versa. Furthermore, with regard to the above-mentioned embodiments, exemplary embodiments or variants, etc. of the method according to the invention and the inventive measuring arrangement according to the first aspect of the invention can be transferred to the measuring device according to the invention and the method according to the invention according to the second aspect of the invention and vice versa. These and other features of the embodiments according to the invention are explained in the description of the figures and the claims. The individual features can be realized either separately or in combination as embodiments of the invention. Furthermore, they can describe advantageous embodiments which are independently protectable and whose protection is possibly claimed only during or after pending the application.

Brief description of the drawings

The foregoing and other advantageous features of the invention are illustrated in the following detailed description of exemplary embodiments according to the invention with reference to the accompanying diagrammatic drawings. It shows:

1 an embodiment of a projection lens for microlithography with arranged in modules optical elements in a schematic illustration,

2 a wavefront measuring device for an imaging optical system in a schematic illustration,

3 An embodiment of a measuring arrangement with a arranged in the beam path after a module adaptation module in a schematic illustration,

4 1 shows a further exemplary embodiment of a measuring arrangement with a matching module arranged in the beam path after a module in a schematic illustration,

5 an embodiment of a measuring arrangement with a arranged in the beam path in front of a module adaptation module in a schematic illustration,

6 An embodiment of a measuring arrangement with arranged in the beam path before and after a module measuring modules in a schematic illustration,

7 an embodiment of a measuring arrangement with two successively arranged in the beam path diffractive structural patterns in a schematic illustration,

8th 1 shows an exemplary embodiment of a measuring arrangement with two diffractive structural patterns superimposed on one another in the beam path, in a schematic illustration,

9 an embodiment of a measuring device for interferometric Shape measurement of optical surfaces in a schematic illustration,

10 the embodiment according to 9 with auxiliary shafts for determining a relative position of the optical surfaces to each other in a schematic illustration,

11 a further embodiment of a measuring device for interferometric shape measurement of different portions of optical surfaces in a schematic illustration, and

12 the embodiment according to 9 with a simultaneous measurement of optical surfaces of two optical elements.

Detailed description of inventive embodiments

In the embodiments or embodiments or design variants described below, functionally or structurally similar elements are as far as possible provided with the same or similar reference numerals. Therefore, for the understanding of the features of the individual elements of a particular embodiment, reference should be made to the description of other embodiments or the general description of the invention. To facilitate the description, in some drawings a Cartesian xyz coordinate system is given, from which the respective positional relationship of the components shown in the figures results.

The 1 to 8th illustrate a first aspect of the invention. 1 shows a projection lens 10 a projection exposure system for microlithography in a schematic representation. The projection lens 10 forms a pattern of a mask or a reticle 12 on a radiation-sensitive coating of a wafer 14 from. These are the pattern of the reticle 12 in an object plane and the radiation-sensitive coating of the wafer 14 in an image plane of the projection lens 10 arranged. The projection lens 10 In this exemplary embodiment, microlithography is formed with EUV radiation (extreme ultraviolet radiation) with a wavelength of less than 100 nm, in particular a wavelength of approximately 13.5 nm or approximately 6.8 nm, and therefore contains only reflection-driven optical elements , Also on the reticle 12 the EUV radiation provided by an illumination system, not shown, is reflected. In alternative embodiments, optical elements used in transmission, such as lenses or prisms, or even a transmission reticle can be used, in particular in the case of exposure radiation in a longer-wavelength spectral range.

The projection lens 10 comprises six mirrors E1, E2, E3, E4, E5 and E6 which originate from the reticle 12 one after the other in a beam path 16 of the projection lens 10 are arranged. In 1 is an example of the beam path 16 for a field point of the reticle 12 shown. The mirror E1 has a concave mirror surface and is arranged together with the substantially planar mirror E2 in a first module M1. Furthermore, the mirror E3 with a convex mirror surface is arranged together with the concave mirror E4 in a second module M2 and the convex mirror E5 together with the concave mirror E6 in a third module M3. The modules M1, M2 and M3 thus each contain in the beam path 16 successive optical elements.

Each module M1, M2, M3 can be individually from the projection lens 10 remove and insert again. With appropriate adjusting devices in addition to an adjustment of the individual mirrors E1, E2, E3, E4, E5, E6 and an adjustment of the individual modules M1, M2, M3, each as a whole, possible. In this way, on the one hand optical properties of the projection lens can be 10 quickly adapt to changing requirements by replacing one or more modules M1, M2, M3. On the other hand, for post-processing, one of the optical elements of the projection lens 10 for the correction of aberrations only a removal and a possible disassembly of the corresponding module M1, M2 or M3 necessary.

The described modules M1, M2, M3 are only examples of possible modules. In other embodiments of the projection lens 10 For example, modules may contain more than two optical elements, such as three or four optical elements. Depending on the structure, the projection lens 10 furthermore also contain fewer or more than three modules and, in particular, optical elements not covered by any module. Furthermore, a modular construction of other components of a microlithographic projection exposure apparatus is also possible, such as a modular illumination system for illuminating the mask.

In the manufacture of optical modules or the post-processing of individual modules or optical elements contained in a module, a very precise measurement of the optical properties of the respective module is necessary. In particular, deviations from a desired wavefront change by the module must be determined with high accuracy. Such a measurement of the wavefront error of the module can be with the As a rule, it is not easy to carry out known devices for measuring projection objectives since the individual modules generally do not represent an imaging optical system.

In 2 schematically becomes a known wavefront measuring device 20 for measuring an imaging optics 22 illustrated. The wavefront measuring device 20 is designed as a shear interferometer based on phase-shifting interferometry technology and is suitable, for example, for the very precise determination of aberrations of a projection objective or another imaging optic 22 microlithography. The wavefront measuring device 20 contains a radiation source, not shown, which is an electromagnetic measuring radiation 24 provides. The wavelength of the measuring radiation 24 preferably corresponds to the wavelength of the operation of the imaging optical system 22 used radiation. In particular, EUV radiation serves as measuring radiation 24 , However, it is also possible to provide a measuring radiation with a different wavelength in the visible or invisible spectral range.

Furthermore, the wavefront measuring device contains 20 one in the object plane of the imaging optics 22 arranged opening of a pinhole 26 and one in the picture plane of the imaging system 22 arranged shear grid 28 , Instead of the pinhole 26 It is also possible to use a pinhole grid or a coherence mask. The measuring radiation 24 passes through the opening of the pinhole 26 and then spreads out with a spherical wavefront. From the imaging optics 22 becomes the measuring radiation 24 on the trellis 28 displayed. The shearing grate 28 represents a phase-shifting diffraction grating. Behind the shear grid 28 is a detector 30 the wavefront measuring device 20 arranged. By moving the shaving grate laterally 28 in the x or y direction are at the detector 30 Interference pattern detects, from which the local derivative of the wavefront in the relevant direction of movement and, ultimately, image error information of the imaging optics 22 can be determined with high accuracy. Such a wavefront measuring device is, for example, in DE 103 16 123 A1 described.

A prerequisite for measuring an optic with the wavefront measuring device 20 is that the optics to be measured the opening of the pinhole 26 on the trellis 28 maps. As mentioned above, however, this is for modules of an imaging optical system, such as the modules M1 to M3 of the projection objective 10 according to 1 , usually not the case. In the following, various embodiments of a measuring arrangement 40 for measuring an optical unit which is not suitable, the opening of the pinhole 26 on the trellis 28 each depicted together with corresponding methods. In particular, the measuring arrangement 40 configured to measure such an optical unit, which has no imaging property at all, but for example, an optics with defokussierender or Strahlaufweitender effect. The measuring arrangement according to the invention 40 is therefore suitable for the respective measurement of the individual modules M1, M2 and M3 of the projection lens 10 according to 1 ,

3 schematically illustrates a first embodiment of a measuring arrangement 40 for measuring module M1 of the projection objective 10 shown. The measuring arrangement 40 includes the wavefront measuring device 20 to 1 , Alternatively, any other optically imaging wavefront measuring device based on phase-shifting interferometry, eg, shear or point diffraction interferometry, or any other technique may also be used. Furthermore, the measuring arrangement comprises 40 an adaptation module 42 , which together with a module M1 to be measured in the beam path 44 the measuring radiation 24 is arranged. In this embodiment, the adaptation module is 42 in the beam path 44 arranged after the module M1 and contains a operated in transmission CGH 46 with a diffractive structural pattern 48 , The diffractive structural pattern 48 of the CGH 46 and thus also the adjustment module 42 are formed and arranged such that the opening of the pinhole 26 by the combination of the optical effect of the module M1 to be measured and the adaptation module 42 on the trellis 28 is shown. Alternatively or in addition to the CGH 46 can the adjustment module 42 In other embodiments, refractive or reflective optical elements, such as lenses or mirrors included.

In other words, the adjustment module complements 42 the module M1 to be measured to an imaging optical arrangement 50 , With module M1 of the projection lens 10 to 1 as an example of a module to be measured provides the adjustment module 42 in its optical effect, a replacement or an imitation of the other modules M2 and M3 of the projection lens 10 dar. With the arrangement of the adaptation module 42 in the beam path 44 behind the module M1 to be measured, this embodiment is thus particularly suitable for measuring modules which are arranged in the beam path of an imaging system immediately after the object plane or another field plane. In a survey of the optical arrangement 50 through the wavefront measuring device 20 is by means of an evaluation device, not shown, a wavefront error of the optical arrangement 50 certainly. This can be under Consideration of the known optical properties of the adaptation module 42 or the CGH 46 again very accurately determine a wavefront error of the module M1.

In 4 is another embodiment of a measuring arrangement 40 with one in the beam path 44 according to a module to be measured M1 arranged adjustment module 42 shown. The measuring arrangement 40 essentially corresponds to the measuring arrangement according to 3 , Instead of a CGH operated in transmission but are in the adaptation module 42 two CGHs operated in reflection 52 . 54 each with a diffractive structure pattern 48 contain. The two CGHs 52 . 54 are in the beam path 44 arranged one after the other. Alternatively, the adjustment module 42 contain only one or more than two CGHs used in reflection. The diffractive structural pattern 48 the CGHs 52 . 54 are configured so that they together with the module M1, the opening of the pinhole 26 on the trellis 28 depict. In addition, further diffractive, reflective or refractive optical elements, such as, for example, transmission-operated CGHs, mirrors or lenses in the adaptation module, may additionally be used 42 be provided. With the use of CGHs in reflection, the module M1 can also be used with an EUV measuring radiation 24 measured.

In 5 is another embodiment of a measuring arrangement 40 shown. The measuring arrangement 40 differs from the previous measuring arrangements by a different arrangement of the adaptation module 42 for measuring a module M3. The module M3 is a module arranged in the beam path of an imaging optical system last before an image plane or another field plane, for example the module M3 of the projection objective 10 according to 1 , The adaptation module 42 is in the beam path 44 the wavefront measuring device 20 arranged in front of the module M3. It contains a CGH operated in transmission 46 with a diffractive structure 48 , The diffractive structure 48 of the CGH 46 and thus also the adjustment module 42 are configured and arranged to form an imaging optical arrangement with the module M3 50 represents. The optical arrangement 50 forms in particular the opening of the pinhole 26 on the trellis 28 from. The adaptation module 42 thus replaces, for example, with a measurement of the module M3 of the projection objective 10 by its optical effect the modules M1 and M2. In other embodiments, the adaptation module contains 42 alternatively or additionally one or more refractive, reflective or refractive diffractive optical elements.

6 schematically shows an embodiment of a measuring arrangement 40 with one in the beam path 44 in front of a module M2 to be measured, such as the optical module M2 of the projection lens 10 according to 1 , arranged first adaptation module in the form of a first measuring module 56 and one in the beam path 44 after the module M2 arranged second adjustment module in the form of a second measuring module 58 , The measuring modules 56 . 58 each have a CGH operated in transmission 46 . 60 with a diffractive structural pattern 48 on. The diffractive structures 48 the two CGHs 46 . 60 and thus also the two measuring modules 56 . 58 are configured to form an imaging arrangement together with the module M2 50 for opening the pinhole 26 represent. When measuring the module M2 of the projection lens 10 according to 1 replaces the measuring module 56 in its optical effect, the module M1 and the measuring module 58 in its optical effect the module M3. The measuring arrangement 40 is therefore particularly suitable for modules of an imaging optical system, which are arranged neither directly before or directly after a field plane of the optical system. Alternatively or additionally, in one or both measurement modules 56 . 58 Also refractive, reflective or operated in reflection diffractive optical elements may be provided.

7 shows a further embodiment of a measuring arrangement 40 , The measuring arrangement 40 basically corresponds to the measuring arrangement according to 6 but sees in the measurement module 58 two in the beam path 44 the wavefront measuring device 20 consecutively arranged CGHs 60 . 62 each with a diffractive structure 48 in front. Such a "double-CGH" known arrangement is, for example, in the patent application US 2012/0127481 A1 described. In an alternative embodiment, one of the diffractive structures may be disposed on one side and the other of the diffractive structures on another side of a substrate.

A double CGH allows a simultaneous change of the location and the direction of a measuring beam. In this way, in some modules M2 to be measured, an imaging property of the optical arrangement can be determined 50 achieve better with the adaptation module and the module M2 to be measured. For example, in a measurement of the module M2 of the projection lens 10 through the measuring module 58 with the CGHs 60 . 62 a precise optical effect adapted to the optical module M3 to be replaced can be achieved.

In further embodiments, a double-CGH is in the beam path 44 arranged in front of the module M2 measuring module 56 or in both measuring modules 56 . 58 intended. Furthermore, two CGHs operated in reflection can also be used as double CGHs. In addition to double CGH, other refractive, reflective, or diffractive ones may be used optical elements in one or both of the measuring modules 56 . 58 be arranged.

In 8th continues to be an embodiment of a measuring arrangement 40 according to 6 each with a complex coded CGH 64 respectively. 66 in the measuring modules 56 and 58 and a second pinhole 68 shown. Each of the complex coded CGHs 64 . 66 contains two in the beam path 44 superimposed arranged diffractive pattern structure 70 , The diffractive structural pattern 70 in particular are superimposed on each other in a plane of the CGHs 64 . 66 arranged. Such complex coded CGHs are eg in the DE 10 2012 217 800 A1 described. The measuring radiation 44 from the opening of the pinhole 26 is due to one of the diffractive structures of the CGHs 64 . 66 transformed while a measuring radiation 72 from the opening of the second pinhole 68 through the other diffractive structure of the CGHs 64 and 66 is transformed. In this way, the measurement modules 56 and 58 together with the module M2 an optical arrangement 50 at the same time the opening of the first pinhole 26 and the opening of the second pinhole 68 on the trellis 28 depict. It can thus be two field points of the object plane of the optical arrangement 50 simultaneously measured.

In other embodiments, according to the measuring device according to 3 just an adjustment module 42 with a complex coded CGH in front of a module M3 to be measured, or analogously to the measuring device according to FIG 5 an adaptation module with a complex coded CGH may be provided after a module M1 to be measured. Also, in addition to the complex coded CGHs 64 . 66 further refractive, reflective or diffractive optical elements in one or both of the measuring modules 56 . 58 or in an adjustment module 42 be arranged in front of or behind the optical module to be measured.

With the exemplary embodiments described for a measuring arrangement and a method, it is possible to successively measure all optical modules of an imaging optical system, for example in the form of the projection objective 10 , carry out. According to an embodiment of the invention, one of the described methods comprises determining wavefront errors of an entire imaging optical system based on the wavefront errors determined for each module of the optical system. Analogously, an exemplary embodiment of a measuring arrangement comprises a correspondingly designed evaluation device for determining wavefront errors of the imaging optical system on the basis of the measurement results for each individual module of the optical system.

The following 9 to 12 relate to embodiments of a measuring device and a method for interferometric shape measurement of optical surfaces according to a second aspect of the invention. The exemplary embodiments of a measuring device are described in each case together with exemplary embodiments of a corresponding method.

9 illustrates a first embodiment of a measuring device 100 for the interferometric shape measurement of optical surfaces. In particular, the measuring device is suitable 100 for the simultaneous measurement of at least two on a common substrate 106 juxtaposed optical surfaces 102 and 104 , In addition to a deviation of the actual shape of the respective surface 102 respectively. 104 From a desired shape can also be the relative spatial position of the surfaces 102 and 104 determine each other. The on the same substrate 106 arranged optical surfaces 102 and 104 For example, assume the function of two mirror elements of a projection lens of a projection exposure system for EUV microlithography.

The measuring device 100 contains an interferometer 108 with a Fizeau element 110 , The structure and operation of such a Fizeau interferometer are known in the art. In particular, the interferometer includes 108 a radiation source for generating a sufficiently coherent for an interferometric measurement electromagnetic illumination radiation 112 , For this example, a laser, such as a helium-neon laser with a wavelength of about 633 nm may be provided. The illumination radiation 112 may also have a different wavelength in the visible or non-visible wavelength range of electromagnetic radiation.

The illumination radiation 112 For example, it is formed by a collimator into a collimated beam having a substantially planar wavefront. In alternative embodiments, a divergent or convergent beam with a spherical wavefront can also be generated. The collimated beam hits the Fizeau element 110 , From a Fizeau surface of the Fizeau element 110 a proportion of the illumination radiation is in the form of a reference wave 114 reflected back. A Fizeau element 110 continuous portion of the illumination radiation 112 spreads as test radiation 116 further along the optical axis 118 of the interferometer 108 and hits a waveform feature 120 on. By means of the waveform element 120 becomes of incident test radiation 116 a measuring radiation 117 is generated, which consists of two measuring waves 128 and 130 composed. After an interaction with those in the beam path of the measuring waves 128 and 130 arranged optical surfaces 102 respectively. 104 and other optical elements provided in the beam path, the measuring radiation passes 117 through the Fizeau element 110 into the interferometer 108 back and will be there with the reference wave 114 superimposed. An interferogram generated thereby at a detection plane is detected, for example, by a CCD sensor of an interferometer camera. In alternative embodiments, the interferometer may also be a Michelson, a Twyman-Green interferometer, or another suitable type of interferometer.

The waveform feature 120 contains a first diffractive structure 122 and a second diffractive structure 124 , and is in this embodiment as a CGH 126 educated. Here are the first and the second diffractive structure 122 . 124 in a plane next to each other in the CGH 126 arranged. In alternative embodiments, more than two diffractive structures can be arranged next to one another in a plane of a CGH, or a complex coded CGH with two or more diffractive structures arranged one above the other in a plane can be provided as the waveform element.

The first diffractive structure 122 is configured to be a fraction of the incident test radiation 116 one on the first optical surface 102 directed first measuring wave 128 with a to a desired shape of the first surface 102 adapted wavefront generated. Accordingly, the second diffractive structure 124 for generating one on the second optical surface 104 directed second measuring shaft 130 in the form of a measuring shaft with a to a desired shape of the second surface 104 matched wavefront from another portion of the on the waveform element 120 incident test radiation 116 educated. The adaptation of the wavefronts takes place in such a way that the wavefronts of the measuring waves 128 and 130 each at the location of the optical surfaces 102 and 104 the respective desired shape of the surfaces 102 and 104 correspond. In this way, for the first and the second optical surface 102 respectively. 104 each realized a zero optic, in which a surface in nominal form the measuring shaft 128 respectively. 130 would reflect back in itself. For simultaneous measurement of more than two surfaces, additional embodiments of the measuring device may have additional diffractive structures on the CGH 126 or a complex coded CGH be provided, which in each case to a corresponding adjustment of the measuring radiation 117 are configured for another optical surface.

The substrate 106 with the optical surfaces to be measured 102 and 104 is by means of a holding device, not shown in the beam path of the test radiation 116 arranged. From the optical surfaces 102 and 104 becomes the respective measuring wave 128 respectively. 130 reflected back, in turn, passes through the one-piece waveform element 120 and then in the interferometer 108 by superposition with the reference wave 114 measured. This results in a detection plane for each of the surfaces 102 and 104 in the case of a deviation from the respective desired form, an interferogram which is detected, for example, by a CCD sensor of an interferometer camera, not shown.

In addition to a simultaneous shape measurement of the two optical surfaces 102 and 104 done by the measuring device 100 in addition, a measurement of the relative positioning of the optical surfaces 102 and 104 to each other. This will be described below with reference to 10 described in more detail. With an evaluation device 158 Finally, a determination of the respective shape of the surfaces 102 and 104 and their relative position to each other. The evaluation device uses this 158 the detected interferograms and a measured relative positional value of the optical surfaces 102 and 104 to each other for at least one rigid body degree of freedom. Alternatively, it is also possible to store the detected interferograms and the position value for later evaluation or transmission to an external evaluation device.

10 shows the embodiment according to 9 with auxiliary shafts 132 and 136 for determining a relative position of the optical surfaces 102 and 104 to each other. For generating a first auxiliary shaft 132 is in the CGH 126 of the waveform element 120 next to the diffractive structures 122 and 124 a first auxiliary measuring structure 134 arranged. The first auxiliary measuring structure 134 contains a diffractive structure pattern which is configured such that it consists of a portion of the incident test radiation 116 the to a set point 140 the first surface 102 focused first auxiliary wave 132 generated.

Furthermore, in the CGH 126 next to the diffractive structures 122 and 124 and the first auxiliary measuring structure 134 a second auxiliary measuring structure 138 arranged. The second auxiliary measuring structure 138 contains a diffractive structure pattern, which is designed such that it consists of a proportion of the incident test radiation 116 one to a set point 142 the second surface 104 focused second auxiliary wave 136 generated.

After a return reflection of the auxiliary shafts 132 and 136 at the respective points 140 and 142 the optical surfaces 102 and 104 these are in the interferometer 108 by overlaying with the reference wave 114 measured interferometrically. With the aid of the evaluation unit, a deviation of the optical surface becomes very accurate 102 respectively. 104 at each point 140 respectively. 142 measured from the desired focus point. Together with the through the auxiliary measuring structures 134 and 138 each set angles between the optical axis 118 of the interferometer 108 and the directions of propagation of the auxiliary shafts 132 and 136 becomes, for example, the relative z-coordinate of the optical surfaces 102 and 104 to each other with respect to the points 140 . 142 certainly. The z-axis of the relative position of the surfaces 102 . 104 to each other describing coordinate system is parallel to the optical axis here 118 or substantially parallel to the mean propagation direction of the measuring radiation 117 and thus across the optical surfaces 102 and 104 arranged. A determination of the relative x-coordinate, y-coordinate and the tilting coordinates of the two optical surfaces 102 and 104 to each other is then carried out by evaluating the measured reflected waves measuring the surface or the determined shapes of the surfaces 102 and 104 taking into account the known relative z-coordinate.

In other embodiments of the measuring device 100 For example, auxiliary auxiliary auxiliary structures may be provided on the waveform element so as to determine a deviation from further points of the optical surfaces from a desired focus. Furthermore, planar or spherical adjustment structures can additionally be arranged next to the optical surfaces on the substrate, which are measured in their spatial position with the aid of auxiliary shafts with a planar or spherical wavefront.

11 shows a further embodiment of a measuring device 100 for the simultaneous shape measurement of juxtaposed optical surfaces 102 and 104 , The measuring device 100 essentially corresponds to the measuring device according to 9 and 10 , In contrast to this is the first diffractive structure 122 of the CGH 126 of the waveform element 120 configured such that it consists of a proportion of the measuring radiation 116 one only on a first subarea 144 the first optical surface 102 directed measuring shaft 128 with a to a desired shape of the first portion 144 adapted wavefront generated.

For measuring a second subarea 146 the first optical surface 102 is another waveform feature 148 with a correspondingly configured diffractive structure 150 in a CGH 152 intended. For measuring the second subarea 146 takes place after a measurement of the first subarea 144 and the second optical surface 104 by means of the first waveform element 120 an exchange of waveform elements 120 and 148 in the measuring device 100 , For this purpose, the measuring device 100 a non-illustrated exchange device included. Subsequently, a measurement of the second portion 146 by means of the second waveform element 148 carried out. Combining the partial measurement to a total measurement of the optical surface 102 done by the evaluation 158 with a so-called stitching method or another suitable method.

In this way, surfaces can be measured, in which due to the shape of the surfaces, the reflected measuring radiation 116 at least partially crosses. In such a case, the corresponding section of the interferogram can no longer be assigned to the respective optical surface. By successively measuring partial areas, such a running together of the reflected measuring radiation is prevented.

Correspondingly, it is also possible to measure two partial areas of the second surface 104 or measuring more than two subregions of the surfaces 102 and 104 be provided in succession by further waveform elements. As an alternative or in addition to an exchange of waveform elements, the measuring device may also contain a closure device, eg with one or more shutters, which allows a measuring radiation to pass only for selectable subregions of the surfaces. In such an embodiment, the waveform element may contain a diffractive structure for each subregion. For example, several diffractive structures can be provided next to each other on a CGH as a waveform element for a subregion of a surface.

In 12 becomes the embodiment of the measuring device 100 to 9 with a simultaneous measurement of an optical surface 102 a first optical element 154 and an optical surface 104 a second optical element 156 shown. Both optical elements 154 and 156 have their own substrate 106 and are fixed with an adjustment device, not shown, in their spatial position adjustable to each other. Here are the optical surfaces 102 and 104 next to each other in the beam path of the measuring waves 128 and 130 comprehensive measuring radiation 117 arranged. Together with the adjustment device put the two optical elements 154 and 156 , similar to the combination of substrate with the two optical surfaces 102 and 104 according to 9 , a total module to be measured. For example, the optical elements 154 and 156 two juxtaposed grazing incidence mirrors (G-mirrors) for a Projection objective or a lighting system of a projection exposure system of EUV microlithography. G mirrors are mirrors that are illuminated under grazing incidence, ie at a shallow angle of incidence. A flat angle of incidence in this context means an angle of incidence which deviates at least 45 °, in particular at least 60 ° or at least 70 °, from a surface normal of the irradiated mirror. With the measuring device 100 to 9 or another measuring device described above is simultaneously a measurement of both surfaces 102 and 104 and the relative positioning of the surfaces 102 and 104 to each other feasible.

The above description of exemplary embodiments is to be understood by way of example. The disclosure thus made makes it possible for the skilled person, on the one hand, to understand the present invention and the associated advantages, and on the other hand, in the understanding of the person skilled in the art, also encompasses obvious modifications and modifications of the structures and methods described. It is therefore intended that all such alterations and modifications as fall within the scope of the invention as defined by the appended claims, as well as equivalents, be covered by the scope of the claims.

LIST OF REFERENCE NUMBERS

10

projection lens

12

 reticle

14

 wafer

16

 beam path

E1-6

 mirror

M1-M3

 modules

20

 Wavefront measurement device

22

 imaging optics

24

 measuring radiation

26

 pinhole

28

 shear grid

30

 detector

32

 Input level

40

 measuring arrangement

42

 matching module

44

 beam path

46

 CGH

48

 diffractive structural pattern

50

 imaging optical arrangement

52, 54

 CGHs in Refexion

56

 input-side measuring module

58

 output-side measuring module

60, 62

 CGHs in transmission

64, 66

 complex coded CGHs

68

 second pinhole

70

 superimposed diffr. structures

72

 measuring radiation

100

 measurement device

102

 first optical surface

104

 second optical surface

106

 substratum

108

 interferometer

110

 Fizeau element

112

 illumination radiation

114

 reference wave

116

 probing

117

 measuring radiation

118

 optical axis

120

 Waveform element

122

 first diffractive structure

124

 second diffractive structure

126

 CGH

128

first measuring shaft

130

 second measuring shaft

132

 first auxiliary shaft

134

 first auxiliary measuring structure

136

 second auxiliary shaft

138

second auxiliary measuring structure

140

 Point of 1st surface

142

 Point of 2nd surface

144

 first subarea

146

 second subarea

148

second waveform element

150

 diffractive structure

152

 CGH

154

 first optical element

156

 second optical element

 158

evaluation

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 10316123 A1 [0004, 0069]
• DE 102012217800 A1 [0005, 0023, 0031, 0079]
• US 2012/0127481 A1 [0022, 0031, 0076]
• WO 2005/114101 A1 [0043]

Claims (19)

Method for measuring a wavefront error of an imaging optical system ( 10 ) of a projection exposure apparatus for microlithography with a plurality of optical elements (E1, E2, E3, E4, E5, E6) for imaging a pattern ( 12 ) from an object plane to an image plane, comprising the steps of: - providing the imaging optical system ( 10 ) with a plurality of optical modules (M1, M2, M3) comprising at least two optical elements (E1, E2, E3, E4, E5, E6), and - separate measurement of respective wavefront errors of the individual optical modules (M1, M2, M3). Method according to Claim 1, in which the measurement of one of the optical modules (M1, M2, M3) arranges the optical module (M1, M2, M3) to be measured and at least one matching module ( 42 . 56 . 58 ) in the beam path ( 44 ) of a measuring radiation ( 24 ) a wavefront measuring device ( 20 ), that the combination of the optical module to be measured (M1, M2, M3) and the at least one adaptation module ( 42 . 56 . 58 ) an imaging optical arrangement ( 50 ), and the measurement further comprises determining the wavefront error of the imaging optical assembly ( 50 ) by means of the wavefront measuring device ( 20 ). Method according to Claim 2, in which the arrangement of the at least one adaptation module ( 56 . 58 ) arranging an input-side measuring module ( 56 ) for manipulating the measuring radiation ( 24 ) in front of the optical module (M1, M2, M3) to be measured, and arranging an output-side measuring module ( 58 ) for manipulating the measuring radiation ( 24 ) according to the optical module (M1, M2, M3) to be measured. Method according to Claim 2 or 3, in which in the at least one adaptation module ( 42 . 56 . 58 ) at least one diffractive structural pattern ( 48 ) for manipulating the wavefront of the measuring radiation ( 24 ) is used. Method according to Claim 4, in which the diffractive structural pattern ( 48 ) for manipulating the wavefront of the measuring radiation ( 24 ) is operated in reflection. Method according to one of claims 4 to 5, wherein in the at least one adaptation module ( 42 . 56 . 58 ) at least two in the beam path ( 44 ) of the measuring radiation ( 24 ) successively arranged diffractive structural patterns ( 48 ) for manipulating the measuring radiation ( 24 ) be used. Method according to one of Claims 4 to 6, in which in the at least one adaptation module ( 42 . 56 . 58 ) at least two in the beam path ( 44 ) superposed diffractive structural patterns ( 70 ) for manipulating the measuring radiation ( 24 ) be used. Measuring arrangement ( 40 ) for measuring an optical unit (M1, M2, M3) of a projection exposure apparatus for microlithography, comprising: - a wavefront measuring device ( 20 ) which is configured to have a wavefront error of an imaging optic ( 22 ) by means of a measuring radiation ( 24 ), and - at least one adaptation module ( 42 . 56 . 58 ), which is used for such manipulation of the wavefront of the measuring radiation ( 24 ) is configured such that the combination of the optical unit to be measured (M1, M2, M3) and the at least one adaptation module ( 42 . 56 . 58 ) an imaging optical arrangement ( 50 ). Measuring arrangement according to Claim 8, in which the at least one adaptation module ( 56 . 58 ) comprises: an input-side measuring module ( 56 ) for manipulating the measuring radiation ( 24 ), which in a beam path ( 44 ) of the measuring radiation ( 24 ) in front of the optical unit (M1, M2, M3) to be measured, and an output-side measuring module ( 58 ) for manipulating the measuring radiation ( 24 ), which in the beam path ( 44 ) of the measuring radiation ( 24 ) is arranged after the optical unit to be measured (M1, M2, M3). Measuring arrangement according to claim 8 or 9, wherein the at least one adaptation module ( 42 . 56 . 58 ) one or more diffractive structural patterns operated in reflection or in transmission ( 48 ) having. Measuring arrangement according to one of claims 8 to 10, wherein the at least one adaptation module ( 42 . 56 . 58 ) at least two in one beam path ( 44 ) of the measuring radiation ( 24 ) superposed or successively arranged diffractive structural patterns ( 48 . 70 ) contains. Measuring device ( 100 ) for the interferometric shape measurement of optical surfaces ( 102 . 104 ) of a microlithography projection exposure apparatus comprising: a one-piece wave form element ( 120 ), which diffractive structures ( 122 . 124 ) for generating a measuring radiation ( 128 . 130 ) with at least two juxtaposed non-contiguous optical surfaces ( 102 . 104 ) has adapted wavefronts, wherein the measuring device ( 100 ) is configured to allow relative positioning of the optical surfaces ( 102 . 104 ) with respect to each other at least of a rigid body degree of freedom, and further comprises: an interferometer ( 108 ) for the interferometric measurement of the measuring radiation ( 128 . 130 ) after interaction with the optical surfaces ( 102 . 104 ), as well as an evaluation device ( 158 ) for determining a respective shape of the optical surfaces ( 102 . 104 ) from the interferometric measurement result taking into account the determined relative positioning. Measuring device according to claim 12, which is configured to control the relative positioning of the optical surfaces ( 102 . 104 ) to each other in a direction transverse to the optical surfaces ( 102 . 104 )). Measuring device according to Claim 12 or 13, in which the waveform element ( 120 ) diffractive auxiliary measuring structures ( 134 . 138 ) for generating auxiliary shafts ( 132 . 136 ), which in each case on one of the optical surfaces ( 102 . 104 ) are focused. Measuring device according to one of claims 12 to 14, which comprises a plurality of waveform elements ( 120 . 148 ) or a waveform element having a plurality of diffractive structures for measuring in each case a partial area ( 144 . 146 ) at least one of the optical surfaces ( 102 . 104 ) having. Method for the interferometric shape measurement of optical surfaces ( 102 . 104 ) of a microlithography projection exposure apparatus comprising the steps of: arranging at least two non-contiguous optical surfaces ( 102 . 104 ) in a beam path of a measuring radiation ( 128 . 130 ), which differs from a diffractive structure ( 122 . 124 ), one-piece waveform element ( 120 ) to the optical surfaces ( 102 . 104 ) generated wavefronts, - determining a relative positioning of the optical surfaces ( 102 . 104 ) with respect to at least one rigid body degree of freedom, and - simultaneous interferometric measurement of the respective shape of the optical surfaces ( 102 . 104 ) by means of the measuring radiation ( 128 . 130 ) taking into account the specific relative positioning. Method according to claim 16, wherein a measurement of the relative positioning of the optical surfaces ( 102 . 104 ) to each other by means of auxiliary shafts ( 132 . 136 ), which with auxiliary measuring structures ( 134 . 138 ) of the waveform element ( 120 ) from the measuring radiation ( 116 ) be generated. The method of claim 16 or 17, wherein successively with different waveform elements ( 120 . 148 ) or different diffractive structures of a waveform element respectively subregions ( 144 . 146 ) at least one of the optical surfaces ( 102 . 104 ) and then assembling partial measurements into a total measurement of the optical surfaces ( 102 . 104 ) he follows. A method according to any one of claims 16 to 17, wherein the non-contiguous optical surfaces ( 102 . 104 ) on a common substrate ( 106 ) are arranged.

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