Measurement apparatus, method for measuring by interferometry, processing method, optical element, and lithography system

Abstract

To provide a measurement apparatus, a method for measuring by interferometry, a processing method, an optical element, and a lithography system.SOLUTION: A measurement apparatus (1) for measuring a shape of a surface (2) of a test object (3), in particular an optical surface (2) of an optical element, by interferometry, has: an illumination device (4) with an illumination source (5) for generating an illumination wave (6); an interferometer device (7) with a splitting element (8) for splitting the illumination wave (6) into a test wave (9) directed at the surface (2) and a reference wave (10) and for combining the returning test wave (9), having interacted with the surface (2) to be measured, with the reference wave (10); a registration device (11) for registering an interference pattern and evaluating the interference pattern to determine a deviation of the measured surface (2) shape from a target shape; and a control device (12) configured to split the surface (2) to be measured into a plurality of individual areas (13) to be measured.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to a measuring device for measuring the surface of a test object, in particular the shape of an optical surface of an optical element, by interferometry, comprising an illumination device with an illumination source for generating an illumination wave, an interferometer device with a splitting element for splitting the illumination wave into a test wave and a reference wave directed to the surface, a registration device for combining the returning test wave that has interacted with the surface to be measured with the reference wave and for registering and evaluating the interference pattern in order to determine the deviation of the shape of the measured surface from a target shape, a control device configured to divide the surface to be measured into a plurality of individual areas to be measured, and a positioning device configured to position the test wave on the surface to be measured such that each individual area is fully illuminated, wherein the registration device is configured to determine the deviation of the shape of at least a part of the surface to be measured from a target shape based on data from the individual areas.

[0002] The invention also relates to a method for measuring the shape of a surface of a test object, in particular an optical surface of an optical element, by interferometry, whereby an illumination wave is split by a splitting element into a test wave and a reference wave directed to the surface, whereby the returning test wave having interacted with the surface to be measured is combined with the reference wave to generate an interference pattern, whereby the interference pattern is evaluated in order to determine the deviation of the shape of the measured surface from a target shape, whereby the surface to be measured is split into a plurality of individual areas which are measured in succession, whereby the test wave is positioned on the surface to be measured such that each individual area is fully illuminated at least approximately perpendicularly.

[0003] The invention also relates to a processing method for processing a test object, in particular an optical element, in particular for a lithography system, in particular a projection exposure apparatus for semiconductor lithography, in which the surface of the test object, in particular the shape of the optical surface of the optical element, is processed in such a way that the shape of the surface at least closely resembles a target shape.

[0004] The present invention also relates to optical elements, especially for lithography systems.

[0005] Furthermore, the invention relates to a lithography system, in particular a projection exposure apparatus for semiconductor lithography, which comprises an illumination system having a radiation source and an optical unit which comprises at least one optical element. [Background technology]

[0006] Optical elements for guiding and shaping radiation in projection exposure apparatus are known from the prior art. In known optical elements, the surfaces of the optical elements often guide and shape the light waves incident on the optical element. Therefore, precise control of the shape of the surfaces is particularly advantageous in order to form a precise wavefront with the desired properties.

[0007] The prior art discloses lithography systems that use ultraviolet light, in particular DUV (deep ultraviolet) and / or EUV (extreme ultraviolet) light, for producing microlithographic structures with the utmost precision, where the light of the radiation source is directed to the wafer to be exposed via a number of mirrors, the exact embodiment of the surface shape of the mirrors here making a decisive contribution to the quality of the exposure.

[0008] Since the requirements regarding the precision of the optical elements of a lithography system, in particular the mirror surfaces, reach, for example, fractions of a nanometer, the prior art discloses the use of interferometric methods and apparatus for the purpose of verifying the quality of the optical elements of a lithography system.

[0009] The prior art discloses the practice of verifying the optical surface of a mirror using an interferometer, whereby test light waves from the interferometer scan only a partial area of ​​the mirror in each case, and according to the prior art, deviations of the mirror in the partial area from a target shape are determined interferometrically. [Prior art documents] [Patent documents]

[0010] [Patent Document 1] U.S. Pat. No. 3,476,463 [Patent Document 2] German Patent Application Publication No. 102008009600A1 [Patent Document 3] US Patent Application Publication No. 2006 / 0132747A1 [Patent Document 4] European Patent No. 1614008B1 [Patent Document 5] U.S. Patent No. 6,573,978 [Patent Document 6] US Patent Application Publication No. 2018 / 0074303A1 Summary of the Invention [Problem to be solved by the invention]

[0011] A disadvantage of the devices and methods known from the prior art is that a part-area based scanning of the optical surface requires a lot of time in order to be able to determine the shape of the surface with the desired reliability and accuracy. [Means for solving the problem]

[0012] The invention is based on the object of developing a measuring device for measuring the shape of the surface of a test object by interferometry, which avoids the drawbacks of the prior art and in particular allows a time-efficient and accurate determination of the shape of the surface.

[0013] According to the invention, this object is achieved by a measuring device having the features of claim 1.

[0014] The invention is also based on the object of developing a method for measuring the shape of the surface of a test object by interferometry, which avoids the drawbacks of the prior art and in particular allows a time-efficient and accurate determination of the shape of the surface.

[0015] According to the invention, this object is achieved by a method having the features of claim 17 .

[0016] The invention is also based on the object of developing a processing method for processing test objects, which avoids the drawbacks of the prior art and allows in particular a time-efficient and precise processing of surfaces.

[0017] According to the invention, this object is achieved by a processing method having the features of claim 32.

[0018] The invention is also based on the object of avoiding the drawbacks of the prior art and of developing an optical element which includes in particular precisely processed surfaces.

[0019] According to the invention, this object is achieved by an optical element having the features of claim 36 .

[0020] The invention is also based on the object of developing a lithography system which avoids the drawbacks of the prior art, in particular having a very accurately shaped wavefront for exposing a wafer.

[0021] According to the invention, this object is achieved by a lithography system having the features of claim 37 .

[0022] The measuring device according to the invention for measuring the shape of the surface of a test object, in particular the optical surface of an optical element, by interferometry comprises at least the following components: an illumination device comprising an illumination source for generating an illumination wave; an interferometer device comprising a splitting element for splitting an illumination wave into a test wave and a reference wave directed to the surface; a registration device for combining a returning test wave that has interacted with the surface to be measured with a reference wave, for registering an interference pattern and for evaluating the interference pattern in order to determine a deviation of the shape of the surface to be measured from a target shape; a control device configured to divide the surface to be measured into a plurality of individual areas to be measured; a positioning device configured to position the test wave on the surface to be measured such that each individual area is fully illuminated, The registration device is configured to determine a deviation of a shape of at least a portion of the measured surface from a target shape based on the data from the individual areas.

[0023] According to the invention it is realized that the illumination device comprises at least one adjustable diaphragm device which defines a partial aperture of the interferometer device and is configured to adapt it to the respective area to be measured in each case.

[0024] The measuring device according to the invention is advantageous in that the partial openings can be adapted, preferably dynamically, to the individual areas to be measured in each case, as a result of which the surfaces can be measured particularly economically in terms of time, since the size of the partial openings can be adapted to the respective expected surface shape of the individual areas.

[0025] The control device can be configured to divide the surface to be measured into a plurality of individual areas to be measured such that the size and / or shape of the individual areas to be measured is adapted to the interferometric measurability of the expected shape of the surface to be measured in the region of the individual areas to be measured in each case, in particular the individual areas to be measured can have a larger areal extent in the region of the surface to be measured that is measurable by interferometry with higher accuracy than parts of the optical surface to be measured that are difficult to measure.

[0026] As a result of such a preferably dynamic adaptation of the individual areas to the respective extent of the surface to be measured, and as a result of the subsequent adaptation of the partial openings to the respective areas selected in such a way, it is possible to proceed with the measurement of the surface economically in terms of time or in a time-optimized manner. In other words, the measuring device according to the invention makes it possible to collect an amount of data optimized to the respective requirements for the measurement accuracy in each respective area, by collecting in each extent of the surface to be measured no more than the amount of data necessary to obtain a desired validity for the shape of the surface to be measured.

[0027] An advantageous development of the measuring device according to the invention can provide that the splitting element is designed to generate an aspheric wavefront of the test wave.

[0028] As a result of the dividing element being configured to form an aspheric wavefront of the test wave, in the case of an aspheric surface to be measured, a wavefront that is approximately matched to the surface to be formed is furthermore possible, which increases the measurement accuracy.

[0029] The illumination system and the registration system may be formed as part of the interferometer system.

[0030] It can preferably be realised that the dividing element is integrally formed.

[0031] Alternatively, the dividing element may be formed in multiple pieces.

[0032] In particular in the case of a split element formed in many parts, it may be provided that the interferometer arrangement is in the form of a Michelson interferometer and / or a Mach-Zehnder interferometer.

[0033] Subaperture may be understood to mean an area on the surface to be measured into which a test wave is supplied by the interferometer arrangement and / or into which a returning test wave is recorded by the interferometer arrangement.

[0034] The individual partial apertures are preferably significantly smaller than the diameter of the surface, for example the free-form surface of the test object, in order to obtain the highest possible spatial resolution. Measuring surfaces, in particular the free-form surface of the test object, has great advantages over full-area testing using CGH (Computer Generated Hologram), in particular leading to significantly better spatial resolution, and furthermore there are no interfering reflections that can cause high-frequency wavefront aberrations.

[0035] The adjustable diaphragm device may preferably be in the form of a variable field diaphragm in an illumination device of the measurement device or interferometric sensor.

[0036] The adjustable diaphragm device can comprise one or more diaphragms, in particular a field diaphragm. A second diaphragm or multiple diaphragms, in particular a field diaphragm or an iris diaphragm, are not required in principle but provide further freedom for optimizing the field size and field shape and thus the measurement accuracy.

[0037] Furthermore, variable incoherent illumination settings may be provided. It may be advantageous to use coherent and / or incoherent settings respectively for all measurement tasks.

[0038] The illumination wave may have a plane wavefront and thus be a planar illumination wave.

[0039] An advantageous development of the measuring device according to the invention can provide that the splitting element is designed to generate an astigmatic or toroidal wavefront as the test wave.

[0040] From the possible aspheric wavefronts of the test wave, astigmatic and / or toroidal wavefronts are particularly suitable for measuring mirrors of EUV lithography systems, which often have a nearly astigmatic and / or toroidal surface shape and / or target shape of the surface, so that the designed splitting element allows the wavefront of the test wave to approximate the surface shape of the surface to be measured.

[0041] Advantageously, it can be ensured that the dividing elements are adapted, preferably in the best possible way, to the target shape of the individual areas to be measured.

[0042] As a result, the wavefront of the test wave can be designed such that it already largely corresponds to the optical surface to be measured in the region of each individual area. In this case, potentially desired and / or undesired deviations of the shape of the measured surface from the wavefront of the test wave can be kept small and interference detection of the deviations is facilitated. This allows the shape of the measured surface to be determined particularly reliably.

[0043] In order not to correspond to a perfect adaptation, the dividing element can be adapted as optimally as possible to the target shape of the individual areas to be measured. This may be the case in particular if the target shape has a very complex embodiment but is mainly based on less complex basic shapes, in particular astigmatic and / or toroidal basic shapes. In this case, the dividing element may be adapted to the basic shape.

[0044] In an advantageous development of the measuring device according to the present invention, a set of exchangeable dividing elements is provided for measuring the surface of the test object, and the dividing elements of the set can be embodied in such a way that a dividing element adapted to the target shape of the individual area to be measured is selectable for each individual area to be measured.

[0045] By providing a set of dividing elements, it is possible in particular to measure particularly efficiently surfaces to be measured which have different dominant basic shapes in different regions, which can be particularly well approximated by the test waves formed by the various dividing elements if the dividing elements are selected according to the regions of the surface to be measured in which the respective areas to be measured are located.

[0046] A single dividing or reference element can be provided for the entire used area of ​​the surface or freeform surface to be measured. If there are surfaces or freeform surfaces to be measured with very adverse shapes, it is possible to provide two or more dividing or reference elements for testing each surface or freeform surface to be measured, whereby different areas of the surface or freeform surface to be measured are measured by two or more dividing or reference elements.

[0047] Due to the simple design of the measuring device, it is advantageous if the different regions do not consist in each case only of individual partial openings, as otherwise the measuring method would become uneconomical.

[0048] In an advantageous development of the measuring device according to the invention, the interferometer arrangement can be in the form of a Fizeau interferometer and the dividing element can be in the form of a Fizeau element having a reference surface and a rear side surface opposite the reference surface.

[0049] The embodiment of the interferometer arrangement as a Fizeau interferometer and the split element as a Fizeau element is advantageous in that the interferometer arrangement can be designed particularly compactly as a Fizeau interferometer: the reference wave and the test wave propagate along substantially the same beam path, so that no bulky interferometer arms are required.

[0050] With regard to the toroidal radius and / or the astigmatism radius, the Fizeau element can be particularly advantageously adapted to the test object to be measured or to the surface to be measured or to selected individual areas, for example freeform surfaces (FFS).

[0051] In an alternative configuration, dividing elements not embodied as Fizeau elements may also have a back side and / or a reference surface, and the characteristics of the back side and / or the reference surface described in relation to the Fizeau elements should then be understood to refer to the back side and / or the reference surface of the dividing element not embodied as a Fizeau element.

[0052] In an advantageous development of the measuring device according to the invention, it can be provided that the reference surface of the Fizeau element has an astigmatic and / or toroidal shape.

[0053] An aspheric or astigmatic and / or toroidal wavefront of the test wave can be particularly easily realized by means of an astigmatic and / or toroidal shaped reference surface. The astigmatic and / or toroidal shaped test and reference waves are fully guaranteed by Fizeau elements, which is advantageous for a compact construction of the interferometer arrangement.

[0054] The reference surface can be formed in a different way for each expected shape of the surface as a torus adapted in the best possible way to the expected shape of the surface.

[0055] As a result of using toroidal and / or astigmatic Fizeau elements, optimally adapted toroidal and / or astigmatic Fizeau elements can be designed, for example, for each surface to be measured, in particular for each freeform surface. As a result, the largest freeform components of the measured surface can already be compensated without additional test optics, and what remains are the higher order components of the measured surface within the subaperture and the smaller components of astigmatism that vary locally over the measured surface.

[0056] The reference surface of the Fizeau element may have a toroidal embodiment.

[0057] A purely toroidal embodiment is advantageous in that it is particularly easy to manufacture.

[0058] In the case of a toroidal embodiment of the reference surface, it may be provided that the reference surface has two toroidal radii that run perpendicular to each other, in this connection the toroidal radii of the reference surface may vary over a wide range.

[0059] The toroidal radius can be formed to correspond at least approximately to the apex radius of the surface to be measured, which allows the formation of a partial opening that is configured larger in the area of ​​the apex and smaller in the area of ​​the edge. By varying the toroidal radius, it can be achieved that the partial opening can be formed to be larger in other areas of the surface and smaller in the area of ​​the apex.

[0060] It is advantageous if the total number of sub-apertures or individual areas is determined such that, firstly, the measurement time is minimized and, secondly, the bandwidth, in particular the spatial frequency spectrum, is maximized. The compromise between the abovementioned parameters can be selected differently for each task.

[0061] The astigmatic or purely astigmatic embodiment of the reference surface is advantageous in that it allows the reference surface to be particularly easily calibrated: the astigmatic surface is almost invariant with respect to sphering around the radial center, which allows absolute calibration by means of the counter surface.

[0062] In particular, the toroidal and / or astigmatic reference surfaces can be absolutely calibrated away from the Zernike polynomials Z1 to Z6 by shift-shift calibration.

[0063] In an advantageous development of the measuring device according to the invention, the rear side of the Fizeau element can be shaped such that the illumination wave, which is preferably planar, is incident at least approximately perpendicularly on the reference surface at each point of the cross section of the illumination wave.

[0064] It is particularly advantageous if the illumination wave is incident perpendicularly to the reference surface, in order to bring about the formation of a test wave with an aspheric, in particular astigmatic and / or toroidal wavefront by the refractive Fizeau element. To achieve this, the back side is advantageously shaped accordingly. As a result of such an embodiment of the back side and the reference surface, the illumination wave can first be transformed in a space-saving manner by the Fizeau element when passing through the back side, so that the wave is incident perpendicularly to the reference surface and is transformed into an aspheric, in particular astigmatic and / or toroidal wavefront when passing through the reference surface.

[0065] Normal incidence of the illumination wave on the reference surface further enables accurate superposition of the test wave returning from the surface being measured onto the reference wave, with the test wave being aligned at least approximately parallel to the reference wave after a new pass through the reference surface.

[0066] In particular, when using interferometric methods based on multi-fringe techniques, it is possible to provide for a small, defined tilt or angle to be included or introduced between the reference wave and the test wave.

[0067] In an advantageous development of the measuring device according to the invention, it can be provided that at each point of the cross section of the illumination wave, the illumination wave is incident on the rear side of the Fizeau element at an angle of at least 0.1°, preferably at least 0.3°, relative to the surface normal.

[0068] An off-normal angle of incidence on the backside is advantageous in that troublesome retroreflection from the backside is avoided, thus introducing the wedge angle that is important for Fizeau interferometry.

[0069] The backside of a Fizeau element containing a toroidal reference surface can be shaped such that the incident plane illumination wave is normal to the reference surface at each point in the beam cross section of the plane illumination wave. In particular, the incident beam can be normal to the backside at any point in the beam cross section and a certain minimum angle to normal incidence, in particular 0.3 degrees, can be ensured not to be undershot. This can introduce a wedge angle to avoid interfering reflections.

[0070] In an advantageous development of the measuring device according to the invention, it can be provided that at each point of the cross section of the illumination wave, the illumination wave is incident on the rear side of the Fizeau element at an angle of 0.1° to 45°, preferably 1° to 10°, relative to the surface normal.

[0071] In an advantageous development of the measuring device according to the invention, the diaphragm device can comprise a circular diaphragm with an adjustable diameter and / or a rectangular diaphragm with an adjustable side length and / or a multi-blade diaphragm.

[0072] A multi-blade diaphragm may be in the form of a beam-defining device comprising a number of individual blades which can be displaced independently of one another, preferably parallel to one another, to form a sub-aperture.

[0073] The sub-apertures can be particularly easily defined by circular apertures, however, in order to fully register the surface being measured, the sub-apertures or individual areas being measured must have a large overlap, which can result in reduced time efficiency.

[0074] The use of a rectangular aperture with adjustable side length to form a partial aperture is advantageous in that the surface to be measured can be easily measured without gaps depending on the position of the rectangle and the size of the rectangle can be particularly easily adapted to the given size of the individual areas.

[0075] Furthermore, a rectangular diaphragm can be used to adapt the size of the sub-aperture in two dimensions, preferably depending on the gradient of the residual wave in these two directions.

[0076] If the diaphragm device has a variable field diaphragm in the illumination device, preferably formed as a rectangle with independently adjustable side lengths, the illumination can be limited to the region of the surface to be measured, i.e. to the individual areas, so that the above-mentioned interference reflections can be avoided. In addition to the rectangular field diaphragm, an iris diaphragm can be provided in series with a rectangular diaphragm arranged nearby, so that as a result of the combination of the two diaphragms, the measurement field shape can be optimized with an additional degree of freedom.

[0077] The embodiment of the aperture device as a multi-blade aperture is advantageous in that the control device has a particularly large geometric freedom when defining the individual measured regions, so that the individual areas can have different geometric shapes in different regions of the measured surface, however a larger overlap may be required for gap-free registration of the measured surface compared to when the individual areas are shaped as rectangles.

[0078] The aperture device of the measuring device may have a circular field diaphragm or preferably a rectangular field diaphragm adjustable in two orthogonal directions, or may have both diaphragm types connected in series.

[0079] The aperture device can be optically imaged onto the test object and / or onto the surface of the test object, whereby the size of the illuminated area or sub-aperture can be set. In particular, such imaging of the aperture device onto the surface allows for adjustment of the size of the sub-aperture or the fully illuminated area according to a gradient criterion.

[0080] An advantageous development of the measuring device according to the invention can provide that the registration device is arranged to reconstruct the shape of the surface from the individual areas.

[0081] As an example, the overall shape of the surface may be reconstructed from the registered shapes of the individual areas by a stitching method. Additionally, other interpolation methods and / or machine learning may be used.

[0082] In an advantageous development of the measuring device according to the invention, the control device can be configured to determine the number, the position, the shape and / or the overlap of the individual areas such that the measurement parameters are optimized.

[0083] Depending on the information registered in relation to the surface being measured, the measurement parameters may have different forms.

[0084] The at least one measurement parameter may preferably be measurement accuracy and / or measurement speed and / or light intensity and / or measurement throughput, especially in individual areas and / or registration devices.

[0085] In particular, the at least one measurement parameter may be the measurement accuracy of the overall surface profile of the surface being measured.

[0086] Depending on the information that is registered in relation to the surface to be measured, the term "measurement parameter optimization" can also be understood differently.

[0087] As an example, a large number of small individual areas with a large overlap with each other can be advantageous to obtain very accurate measurements of difficult to measure surfaces, i.e. surfaces with astigmatism and / or large deviations from a toroidal shape in a small space. This results in a large redundancy in the registered information, so that the surface can be determined very accurately. In this case, the measurement accuracy represents the optimized measurement parameters for the surface being measured.

[0088] In particular, the measurement accuracy can be determined by the gradient distribution in the individual areas: by means of the size of the partial openings it is possible to adjust or minimize the maximum gradient within the measurement field.

[0089] In another example, for time efficiency, the requirements on surface profile resolution can be reduced. In this case, the control device specifies large individual areas so that the surface to be measured can be fully registered using only a few records. In this case, measurement optimization is related to time efficiency and less to measurement accuracy.

[0090] In an advantageous development of the measuring device according to the present invention, the control device can be configured to determine the number, position and / or shape of the individual areas such that the maximum gradient occurring in each individual area does not exceed a limit gradient of 5 mrad, preferably 1 mrad, particularly preferably 0.5 mrad.

[0091] In particular, consideration of limit gradients can be used as a criterion for the selection and definition of the individual areas: According to these criteria, the individual areas should be selected such that the measured surface profile has a gradient in the individual areas of less than 5 mrad, preferably less than 1 mrad, particularly preferably less than 0.5 mrad, compared to the entrance profile of the test wave.

[0092] Thus, the individual areas are adapted with respect to their shape and position within the widely varying extent of the measured surface such that they still contain only partial regions with gradients below a certain threshold gradient. Further regions of the measured extent are then filled with further individual areas each of which meets the threshold gradient criterion.

[0093] Observing the above mentioned limit gradient criteria can be particularly useful to avoid interfering reflections and excessive local fringe densities on the camera of the registration device, which can, for example, result in significant retrace errors and thus reduce the measurement accuracy.

[0094] The maximum gradient of the wavefront difference between the test wave and the reference wave can be made variable. The parameter of the gradient of the wavefront difference is directly correlated with the size of the subaperture or individual area, in particular linearly to a first order in the X-direction and in the Y-direction perpendicular to the X-direction and / or linearly to a first order with respect to the diameter of the subaperture. The parameter of the maximum gradient of the wavefront difference can be further adjusted individually for each subaperture by a diaphragm device in the illumination device. As a result, the limit gradient and thus the size of the individual areas or subapertures can be balanced against the measurement accuracy, in particular against the non-correctable component of the retrace error.

[0095] Compared to prior art devices in which fixed size sub-apertures or individual areas are used, the measuring device according to the invention is advantageous in that the field size or sub-aperture can be adapted to the local maximum gradient. Due to the lack of adaptation options, most individual fields of view are unnecessarily small in devices known from the prior art. This is because the field size is given by the gradient that occurs maximally at any point on the surface of the test object being measured, especially after tilt adjustment. Limiting the measurement field size or the size of the individual areas or the size of the sub-aperture by gradient criteria is advantageous, since too large a gradient can cause a large area of ​​interference reflections that can overlap the analyzed wavefront and cause large measurement errors.

[0096] One option to avoid large measurement errors as a result of too large a gradient consists in evaluating only the central region of each individual area and ignoring the areas with too large a gradient. Such a procedure can be improved by avoiding the illumination of areas with too large a gradient, since the test waves returning from those areas as a result of the optical unit of the measuring device can also cause interference on the camera chip of the registration device in the central region of the individual surfaces or partial openings. In particular, such interference can be substantially caused by a double reflection between the reference surface and the surface to be measured, which is reflected in the opposite direction to the reference tilt due to the basic tilt between these two surfaces. Furthermore, due to the double reflection at the surface of the test object that occurs during the process, a double asphericity of the individual areas is applied to the returning test wave.

[0097] In an advantageous development of the measuring device according to the invention it can be provided that a reduction device is provided for reducing the spatial coherence of the illumination wave.

[0098] As a result, the reduction of the spatial coherence of the illumination wave can be advantageous with a view to avoiding interference reflections, since interference phenomena still occur only within the spatial coherence length of the surface to be measured. By way of example, this may be provided by the form of illumination in the pupil of the interferometer device, which defines the secondary light source.

[0099] In particular, the spatial coherence reduction described above reduces coherent interference caused by reflections and / or scattering at other optical surfaces of the interferometer device. Furthermore, the spatial coherence reduction described above also reduces reflections of the test object or large area interference that take a significantly different optical path to the registration device, in particular the camera, than the test wave and / or the reference wave. By way of example, this may also be a double reflection from the surface being measured.

[0100] In particular, the reduction device may comprise a number of reduction elements providing varying degrees of coherence reduction of the illumination wave, the reduction elements being selected and used based on the expected deviation of the measured surface from the wavefront of the test wave.

[0101] In particular, the reduction apparatus described above can be configured to create spatially extensive illumination settings to avoid coherent interference.

[0102] The widely flat illumination wave obtained afterwards can advantageously be at least approximately uniform within a given diameter, in particular within the maximum incoherent illumination pupil diameter used. The design of the illumination device can be optimized in this respect. The homogenization of the illumination wave is performed by a redistribution of the Gaussian intensity of the illumination wave at the illumination source, in particular at the fiber output, to at least approximately a top-hat or rectangular distribution. In this way, light losses at the edges of the pupil can be avoided. In this respect, reference is made in particular to US Pat. No. 5,399,433.

[0103] Lighting Wave I PV / I max The uniformity of the homogeneity I can be 1%, 5%, 10%, or 20%. PV / I max is determined as the ratio of the difference between the maximum intensity and the minimum intensity (peak-to-valley intensity) to the maximum intensity, which is expressed as a percentage. Alternatively or additionally, the uniformity can be less than 20%, preferably less than 10%, particularly preferably less than 5%, very particularly preferably less than 1%.

[0104] The reduction device may comprise a rotating diffuser and / or a rotating microlens array.

[0105] A rotating microlens array can be configured to form a secondary illumination source for forming the illumination wave.

[0106] The reduction device may comprise an inner pivoting optical unit having a group of lens elements, the inner pivoting optical unit being pivotable inwards and / or outwards to switch between spatially coherent and spatially partially coherent illumination of the surface.

[0107] By pivoting the lens element group by the inner pivoting optical unit, it is possible to switch from coherent focus to planar illumination, where a relatively small beam deviation is not important. As a result, the coherent focus position is not affected by the switching mechanism and remains stable. In particular, since the beam deviation caused by the pivoting in the inner pivoting optical unit is not very important, the illumination device can be optimized for a state with the inner pivoting optical unit pivoted outward, and therefore for a state of coherent illumination.

[0108] It may be provided that the reduction device comprises a diffuser and / or that the inner pivoting optical unit also comprises a diffuser.

[0109] The inner turning optical unit can be configured to transform the imaging properties of the illumination device, in particular an inner turning optical unit can be provided to transform a point-to-point imaging, in particular an imaging performed from an illumination source to an illumination pupil of the illumination device, into an imaging performed from a point to infinity.

[0110] It may be provided that the illumination device preferably comprises a switchable transmission mask device, preferably having one or more illumination mask elements arranged exchangeably in the illumination pupil of the measurement device.

[0111] In this case, each selected illumination mask element forms a secondary illumination source, the exact appearance of which is determined by the embodiment of the illumination mask element.

[0112] Only in some embodiments of the measurement device may a reduction device be provided.

[0113] An advantageous development of the measuring device according to the invention can provide that all optical components of the measuring device are in the form of reflective and / or refractive components.

[0114] An embodiment of the optical components of the measuring device as reflective and / or refractive components allows a particularly high light efficiency and thus a signal strength of the illumination, reference and test waves, so that when weaker illumination sources and / or shorter exposure times are used, more reliable information about the shape of the surface can be determined than when diffractive components are used.

[0115] As a result of providing only reflective and / or refractive components, it is possible to increase the amount of available light compared to systems used in the prior art. Dispersing the diffractive components, especially multi-encoded computer-generated holograms for full-area testing of freeform surfaces in test towers that generate large light losses, increases the amount of available light. As a result, the desired wide-area illumination settings can be generated very easily from an optical point of view, for example by large-area illumination of a diffuser plate that can have a transmittance of Sigma=0.5. Furthermore, simple masking in the intermediate image of the secondary light source, for example formed by a rotating microlens array, is possible.

[0116] In an advantageous development of the measuring device according to the invention, the positioning device can have six degrees of freedom.

[0117] If the positioning device has six degrees of freedom and / or is in the form of a six-axis robot, the interferometer device can be positioned in any desired orientation and at any desired position relative to the surface to be measured, allowing targeted alignment of the test wave on the optical surface to be measured.

[0118] By means of a six-axis robot, the interferometer arrangement, in particular the splitting element, can be particularly advantageously positioned such that the preferably toroidal wavefront of the test wave incident on the surface to be measured, in particular on the individual areas, is substantially perpendicular to the individual areas (except for the maximum local gradient, which is defined). The orientation of the Fizeau element can be adjusted by the six-axis robot such that the basic astigmatism of the individual areas, in particular the freeform surface, can be optimally compensated by the astigmatism of the reference surface of the Fizeau element or the Fizeau surface, i.e. the astigmatism of the Fizeau element has substantially the same orientation as the basic astigmatism of the freeform surface or the individual areas to be measured. In this case, it can be provided or is advantageous that all azimuthal orientations of the Fizeau element or the test wave are adjustable in an angular range of + / - 90 degrees around the chief ray of the test wave.

[0119] The positioning device can be configured to position the illumination device, the registration device, and the interferometer device together relative to the test object along six degrees of freedom such that the illumination device, the registration device, and the interferometer device remain positioned relative to one another in the same manner.

[0120] Alternatively or additionally, the positioning device may be configured to simply position the splitting element and / or the interferometer device relative to the test object along six degrees of freedom, and a beam steering device may be provided to appropriately direct the illumination wave to the splitting element, even when changing the location and alignment of the splitting element, particularly under the angles mentioned above.

[0121] It may be realized that the positioning device is configured to position the reference surface at a constant working distance of 0.1 cm to 10 cm, preferably 0.5 cm to 3 cm, particularly preferably 1.5 cm to 2.5 cm, from the surface of the test object. As a result of such a short cavity length between the reference surface and the surface to be measured, it is possible, for example, to set significantly larger area illumination settings compared to the prior art. As a result, very high suppression factors of coherent interference can be obtained.

[0122] In an advantageous development of the measuring device according to the invention, the dividing element and / or the positioning device can be designed in such a way that at each point of the cross section of the test wave, the test wave is incident at least approximately perpendicularly on the surface to be measured.

[0123] An incidence of the test wave on the optical surface to be measured that is as perpendicular as possible allows a reliable interferometric measurement of the surface to be measured. In order to obtain an incidence that is as perpendicular as possible, the splitting element may be configured to form the test wave that is adapted as far as possible to the surface to be measured. Furthermore, the positioning device may be configured to align the test wave that is adapted to the surface to be measured with respect to the measurement surface.

[0124] A set of splitting elements, in particular Fizeau elements, may be made available as part of the measurement device, each of said set of splitting elements being capable of generating a different astigmatic and / or toroidal test wavefront. Depending on the expected basic shape of the optical surface to be measured, in particular the surface to be measured, a positioning device and / or an exchange device provided for this purpose may for example be configured to select a suitable splitting element and use it for the measurement of the surface.

[0125] The invention also relates to a method having the features of claim 17.

[0126] In the method according to the invention for measuring the surface of a test object, in particular the shape of an optical surface of an optical element, by means of interferometry, the illumination wave is split by a splitting element into a test wave and a reference wave directed to the surface, whereby the returning test wave having interacted with the surface to be measured is combined with the reference wave to generate an interference pattern, whereby the interference pattern is evaluated to determine the deviation of the shape of the surface to be measured from a target shape, whereby the surface to be measured is split into a number of individual areas to be measured successively, whereby the test wave is positioned on the surface to be measured in such a way that each individual area is illuminated at least approximately perpendicularly and completely. According to the invention, for illuminating the individual areas, a partial aperture is provided which defines the size of the test wave to be adapted in each case to the individual area to be measured.

[0127] The method according to the invention is advantageous in that it allows taking into account the measurability of the surface to be measured in the region of each individual area by adapting the size of the test wave to the individual area to be measured, which allows a time-efficient and precise alignment of the entire surface at high light intensity.

[0128] In an advantageous development of the method according to the invention, it can be provided that the aspheric wavefront of the test wave, which is adapted to the target shape of the individual area to be measured, is formed by a dividing element.

[0129] This development is advantageous in that the formation of an aspheric wavefront of the test wave already makes it possible to adapt the test wave to the measurement surface, which allows a more time-efficient and more accurate alignment of the entire surface at high light intensity.

[0130] The measurement surface may be subdivided into a number of individual areas that are successively measured such that the size, number, position and overlap of the individual measurement areas are selected based on the deviation of the measurement surface within the individual area from the asphericity of the wavefront of the test wave.

[0131] The partial aperture may be arranged and formed by at least one variable field diaphragm in the illumination system of the interferometric sensor, whereby partial illumination of the surface to be measured is made possible by the variable field diaphragm.

[0132] The positioning device may be embodied as a six-axis robot or six-axis positioner capable of positioning the interferometer device at each point on a surface to be measured such that the toroidal and / or astigmatic wavefront of the test wave incident on the surface is substantially perpendicular to the surface to be measured.

[0133] The toroidal and / or astigmatic wavefront incident on the surface to be measured can be made to be perpendicular to the surface to be measured up to a maximum local gradient to be defined.

[0134] The orientation of the Fizeau element can be made adjustable by a positioning device so that the basic astigmatism of the surface to be measured is optimally compensated by the astigmatism of the reference surface.

[0135] In particular, it may be possible for the reference surface to be positionable by the positioning device such that the astigmatism of the reference surface has substantially the same orientation as the base astigmatism of the surface to be measured.

[0136] Advantageously, all azimuthal orientations of the interferometer arrangement around the chief ray of the illumination wave and / or the test wave are adjustable in the angular range of -90 degrees to +90 degrees.

[0137] In an advantageous development of the method according to the invention and of the measuring device according to the invention, it is possible to provide for the shape of the surface to be reconstructed from the individual areas.

[0138] Reconstructing the shape of a surface from its individual areas makes it possible to determine global information about the surface from the individual information about the individual areas.

[0139] The method according to the invention is particularly suitable for full area measurements of freeform surfaces, in particular the surfaces of mirrors in EUV projection exposure tools, by the partial aperture stitching method. In particular, the method according to the invention makes it possible to achieve a measurement accuracy of 8 pm to 12 pm for surface variations measured in the band of spatial wavelengths from 0.1 mm to 50 mm.

[0140] In this case, the individual partial openings or the individual areas can be made to be significantly smaller than the free diameter of the surface to be measured in each case, as a result of which a high spatial resolution can be achieved.

[0141] Compared to methods known from the prior art, the method according to the invention has the advantage that the spatial resolution is improved, since the individual areas or partial openings are significantly smaller than the free diameter of the surface to be inspected, in particular of a free-form surface.

[0142] Furthermore, the method according to the invention achieves high spatial resolution since distortion effects are less pronounced.

[0143] A further advantage of the method according to the invention is the avoidance of interference reflections which can generate high frequency wavefront aberrations. If the method according to the invention or the measurement device according to the invention dispenses with the use of computer generated holograms and the use of surfaces oriented perpendicular to the incident illumination wave at any point in the beam cross section is avoided, interference reflections can be effectively reduced.

[0144] Furthermore, the use of measurement structures with long cavity lengths and / or different distances can be avoided or reduced in the method according to the invention, especially when measuring optical surfaces for errors at medium and high spatial frequencies.

[0145] Test geometries or measurement structures in which the distance between the surface to be tested, in particular the aspheric surface to be tested, and the associated interference reference surface is small, i.e. test geometries or measurement structures with a short cavity length, have several advantages. The first advantage lies in the fact that there is only a small interference due to air fringes. A further advantage lies in the fact that the calibration mirror can generally have the same working distance as the test object in the case of such test geometries or measurement structures with a short cavity length. As a result, it is possible to avoid errors due to speckle propagation effects and due to different sharp imaging of the optical surfaces of the interferometer device or interferometer sensor to the registration device during calibration, in particular the interferometer camera.

[0146] As a result of the method according to the invention, it is further possible to avoid the use of computer-generated holograms and thus the occurrence of interference reflections caused by higher diffraction orders of computer-generated holograms, which advantageously allows reducing phase errors when measuring optical surfaces.

[0147] By avoiding such measurement structures, it is also possible to avoid errors due to speckle propagation effects or blurring of the writing strips of the computer-generated hologram, since the calibration of the reference surface is performed at the same distance as the measurement of the test object itself. There is a particularly effective error avoidance if the distance is selected to be small and constant.

[0148] A further advantage of the method according to the invention and the measuring device according to the invention is the possibility of carrying out the method in standard ambient atmospheres, in particular of making a vacuum unnecessary, and even in the case of carrying out the method in standard ambient atmospheres, an accuracy of up to a few picometers can be achieved.

[0149] In particular, the reference surface can be designed to be stable and absolutely calibratable, and no further adaptive optical units that could introduce interference into the interferometric phase measurement are arranged between the reference surface and the surface to be measured, so that the test wave can propagate freely between the reference surface and the surface to be measured.

[0150] In an advantageous development of the method according to the invention, a set of exchangeable dividing elements is provided for measuring the surface of the test object, the dividing elements of the set being embodied in a manner adapted to the individual areas of the surface of the test object to be measured, such that a dividing element adapted to the target shape of the individual area to be measured is available for each individual area, and the dividing element adapted to the target shape of the individual area can be selected from the set for the purpose of measuring each individual area.

[0151] By providing a set of dividing elements and appropriately selecting the respectively optimally adapted dividing elements, it is possible in particular to measure particularly efficiently surfaces to be measured which have different dominant basic shapes in different regions, which can be particularly well approximated by the test waves formed by the various dividing elements if the dividing elements are in each case selected according to the region of the surface to be measured in which the respective area to be measured is located.

[0152] In an advantageous development of the method according to the invention, at the reference surface of the dividing element, a part of the illumination wave can be transmitted as a test wave and a part of the illumination wave can be reflected as a reference wave. By forming the test wave and the reference wave at the reference surface of the dividing element by transmission and reflection, the test wave and the reference wave can be generated with low light losses, little expenditure and high luminosity.

[0153] In an advantageous development of the method according to the invention, it can be provided that the dividing element is positioned at a distance of 0.1 cm to 10 cm, preferably 0.5 cm to 3 cm, particularly preferably 1.5 cm to 2.5 cm from the surface.

[0154] As an example, a small distance between the splitting element and the surface allows for a reduction in the spatial coherence of the illumination wave, whereby reflections of more distant non-interesting regions are advantageously masked in a coherent sense, resulting in an improved interference signal.

[0155] For full area measurements of the surface and / or figure of the test object, it is possible to provide interferometric sensors for the individual partial apertures, which are arranged at fixed working distances. In this process, it is possible to ensure that the test wave strikes the surface as perpendicularly as possible. In particular, the interferometric sensors or interferometer devices may be positioned on separate individual areas by a 6DOF (degree of freedom) positioner or a 6-axis robot.

[0156] The wavefront shape of the test wave reflected by the individual areas in each case depends here very strongly on the local surface shape and can vary significantly over the surface.

[0157] For the distances mentioned above, the air stripes have only a small effect on the propagation of the test wave.

[0158] An advantageous development of the method according to the invention can provide that the dividing elements are embodied as Fizeau elements.

[0159] The realization of the dividing elements as Fizeau elements is advantageous in that it allows the use of Fizeau interferometry, which allows particularly space-saving and reliable measurement of surfaces.

[0160] In an advantageous development of the method according to the invention, a reference surface can be provided which is embodied to match a target shape of the surface of the test object to be measured.

[0161] The reference surface of the Fizeau element may have a toroidal and / or astigmatic embodiment.

[0162] The use of exchangeable Fizeau elements with toroidal and / or astigmatic reference surfaces may be provided. Advantageously, the Fizeau elements can be adapted in terms of toroidal radius to the test object to be measured, in particular to the freeform surface.

[0163] Adapting the reference surface of the Fizeau element to the target shape of the surface to be measured is advantageous in that as a result the wavefront of the test wave receives a shape that is geometrically similar to the shape of the surface to be measured.

[0164] In an advantageous development of the method according to the invention, it is possible to provide an astigmatic and / or toroidal wavefront of the formed test wave.

[0165] The astigmatic and / or toroidal wavefront of the test wave is advantageous in that it already corresponds to a large extent to the geometric shape of mirrors, in particular mirrors of EUV projection exposure apparatus.

[0166] At each location of each individual area, in an advantageous development of the method according to the invention, the test wave can be guided as parallel as possible to the local mean surface normal and / or as perpendicular as possible to the surface.

[0167] Incidence as normal as possible to the surface should be understood to mean incidence of the test wave in which unavoidable local deviations from normal incidence on the surface are minimized. Deviations are always unavoidable when the target shape deviates from the wavefront shape of the test wave.

[0168] Incidence as parallel as possible to the local mean surface normal should be understood to mean the incidence of the test wave on the surface such that within a certain perimeter, for example an area of ​​10 mm x 10 mm or more, the deviation of the incidence direction of the test wave front from the mean surface normal is minimal in this area.

[0169] In an advantageous development of the method according to the present invention, in order to measure individual areas, the illumination device forming the illumination wave, the interferometer device forming the reference wave and the test wave and the registration device registering the interference pattern can be positioned relative to the surface such that the test wave strikes the surface as perpendicularly as possible.

[0170] The application of the method according to the invention to the determination of the surface shape is particularly advantageous, where the surface shape is derived from a basic shape and the adjustment is applied to the basic shape. The application of the method to the shape of a surface where the adjustment is to be determined by the method, but the basic shape is known, is particularly advantageous. In this case, the aspheric wavefront of the test wave can be formed in a manner that is adapted to the previously known basic shape. If the adjustment compared to the basic shape introduces only small deviations into the surface, the deviations can be determined particularly quickly, easily and reliably using the method.

[0171] The application of the method to the surface profile of a surface whose basic shape has an astigmatic shape is particularly advantageous.Furthermore, in individual areas, the adjustment can have a gradient with respect to the basic shape of less than 5 mrad, preferably less than 1 mrad, particularly preferably less than 0.5 mrad, and the adjustment is also known in advance.This is advantageous in that all that can be used to measure the entire surface is a division element that is adapted to the basic shape of the surface or a test wave that is adapted to the basic shape of the surface, while slight adjustments can be interferometrically quantified and verified with respect to their accuracy by the method.

[0172] In an advantageous development of the method according to the invention, the diaphragm device can be a circular diaphragm with an adjustable diameter and / or a rectangular diaphragm with an adjustable side length and / or a multi-blade diaphragm in such a way that the partial openings are defined by the diaphragm device.

[0173] Numerous geometric shapes of the partial openings can be defined by the aforementioned embodiment of the throttling device, which makes it possible in particular to observe in a simple manner the limit gradient criterion explained below.

[0174] The prior art discloses implementations that create ring-shaped illumination by means of diffractive elements.

[0175] The method according to the invention can be developed in that a number of rings and / or a number of regions with slight deviations from a ring shape are simultaneously generated by one or more apertures, in particular by one or more illumination mask elements.

[0176] In this case, the illumination mask elements form secondary light sources, the exact appearance of which is determined by the embodiment of the illumination mask elements.

[0177] In this case, the light losses associated with narrowing can be compensated for by a high input intensity, so that a achievable intensity of at least 500 mW at the illumination source, in particular the fiber output, and in particular at the input of the illuminator, allows the realization of the above-mentioned meaningful illumination settings to be used.

[0178] Furthermore, as mentioned above, the working distance or cavity length is preferably designed to be between 0.1 mm and 100 mm, preferably between 0.1 mm and 20 mm, and particularly preferably between 1 mm and 5 mm, so that the transmissive area within the illumination mask element can be designed to be relatively large without compromising contrast.

[0179] In an advantageous development of the method according to the invention, it can be provided that the number, the position, the shape and / or the overlap of the separate individual areas is determined in such a way that the measurement parameters are optimized.

[0180] By way of example, optimisation of the measurement parameters may be understood to mean optimising the luminous intensity of the returned recorded test wave, optimising the surface recording speed or measurement duration and / or optimising the measurement accuracy.

[0181] In an advantageous development of the method according to the invention, the number, position and / or shape of the individual areas can be determined in such a way that the maximum gradient occurring in each individual area does not exceed a limit gradient of 5 mrad, preferably 1 mrad, particularly preferably 0.5 mrad.

[0182] If exceeding the limit gradient is avoided, it is possible to obtain a data quality registered in the individual areas. If the test wave is adapted to the basic shape of the optical surface, exceeding the limit gradient makes it more difficult to interferometrically determine the deviation of the adjustment from the basic shape or the deviation of the surface shape from the shape of the test wave. The purpose of the above-mentioned method steps is therefore to limit the deviation to an amount that can be reliably determined interferometrically by limiting the range of the individual areas.

[0183] The above-mentioned method according to the invention and the above-mentioned measuring device according to the invention in particular allow full-area figure measurements of freeform surfaces of optical elements for EUV lithography with high spatial resolution, in particular the method according to the invention and the measuring device according to the invention can achieve improved spatial resolution and improved processing compared to test systems measuring over the full area.

[0184] In addition, by using an inner rotating optical unit, it is possible to switch between coherent and incoherent illumination by rotating the lens element group inward or outward, thereby eliminating the need for a second independent illumination system.

[0185] The invention also relates to a processing method having the features of claim 32.

[0186] In a processing method according to the invention, in particular for a lithography system, in particular for a projection exposure apparatus for semiconductor lithography, for processing a test object, in particular an optical element, in which the shape of a surface of the test object, in particular an optical surface of an optical element, is processed in such a way that the shape of the surface at least closely resembles a target shape. According to the invention, it is provided that the shape of the surface is determined by the above-mentioned measuring device according to the invention or any of its preferred embodiments and / or using the above-mentioned method according to the invention or any of its embodiments.

[0187] The processing method is particularly suitable for processing optical elements and for EUV projection exposure tools.

[0188] The processing method according to the invention is advantageous in that it allows a particularly reliable and rapid iterative processing of test objects or surfaces to be carried out with particularly accurate and rapid measurements using the measuring device according to the invention and / or the method according to the invention, which allows a time- and cost-efficient production of highly precisely shaped optical elements, in particular mirrors for EUV projection exposure apparatus.

[0189] In an advantageous development of the treatment method according to the invention, it is possible to provide for the treatment method to be carried out in one or more treatment steps and for the shape of the surface to be determined after each treatment step.

[0190] Iterative determination of the shape of the surface after and / or before each processing step is advantageous in that the processing steps following the determination of the shape of the surface can be adapted to the information obtained during the determination of the shape of the surface.

[0191] In an advantageous development of the treatment method according to the invention, it is possible to provide for the treatment method to be carried out in one or more treatment steps and for the shape of the surface to be determined after each treatment step.

[0192] Selecting a processing method based on the determined shape is advantageous in that, for example, a more corrective processing method can be selected if the determined shape of the surface deviates significantly from the target shape, thereby allowing a time- and cost-efficient production of the optical element.

[0193] In an advantageous development of the treatment method according to the invention, it can be provided that the treatment method is a polishing method.

[0194] The polishing method is particularly suitable for large-scale surface treatments which can be resolved and registered by the measuring device according to the invention and / or the method according to the invention.

[0195] As a result of the processing method according to the invention, it is possible in particular to avoid the smoothing processes typically used in the prior art, which allow processing surfaces without deterministic corrections in a bandwidth of spatial wavelengths between 1 mm and 10 mm.

[0196] The invention further relates to an optical element having the features of claim 36.

[0197] An optical element according to the invention, in particular a lithography system, in particular a projection exposure apparatus for semiconductor lithography, is provided with a surface of the optical element which is measured using the measurement device according to the invention or any preferred embodiment of the measurement device according to the invention and / or using the method according to the invention or any preferred embodiment of the method according to the invention and / or is treated using the above-mentioned processing method according to the invention or any preferred embodiment.

[0198] Optical elements according to the present invention are advantageous in that they have very precisely formed optical surfaces while at the same time being manufactured in a cost-effective and time-efficient manner.

[0199] In particular, the optical element may be a mirror for an EUV projection exposure apparatus.

[0200] The invention further relates to a lithography system having the features of claim 37.

[0201] A lithography system according to the invention, in particular a projection exposure apparatus for semiconductor lithography, comprises an illumination system with a radiation source and an optical unit with at least one optical element. According to the invention it is provided that at least one of the optical elements comprises an optical surface which is at least partially measured by the above-mentioned measuring device according to the invention or by any of the preferred embodiments of the measuring device according to the invention and / or by the above-mentioned method according to the invention or by any of the preferred embodiments of the method according to the invention and / or at least one of the optical elements is processed by the above-mentioned processing method according to the invention or by any of the preferred embodiments of the above-mentioned processing method and / or at least one of the optical elements is an above-mentioned optical element according to the invention.

[0202] The lithography system according to the invention is advantageous in that it allows for reliable and highly accurate exposure of wafers, since the optical elements of the lithography system have been particularly accurately measured and / or processed, At the same time, the lithography system according to the invention has certain cost advantages as a result of the efficient manufacture of the optical elements used therein.

[0203] The features described in relation to one of the subject matters of the present invention, in particular the measurement device according to the invention, the method according to the invention, the processing method according to the invention, the optical element according to the invention and the lithography system according to the invention, can also be advantageously implemented for the other subject matters of the present invention. Likewise, advantages specified in relation to one of the subject matters of the present invention can also be understood in relation to the other subject matters of the present invention.

[0204] It should further be noted that terms such as "comprising", "having" or "with" do not exclude other features or steps. Furthermore, terms such as "a" or "the" referring to a step or feature in the singular do not exclude a plurality of features or steps and vice versa.

[0205] However, in the present subject matter, it may also be provided that the expressions "comprising", "having" or "with" constitute an exhaustive list of features introduced into the present invention. Thus, in the context of the present invention, one or more lists of features may for example be considered in a self-contained form for each claim respectively. By way of example, the present invention may consist solely of the features recited in claim 1.

[0206] It should be noted that terms such as "first" or "second" are used primarily for distinguishability between respective apparatus or method features, and are not intended to imply that features are interdependent or related to each other.

[0207] Hereinafter, embodiments of the present invention will be described in more detail with reference to the drawings.

[0208] Each of the figures shows preferred exemplary embodiments in which individual features of the present invention are shown in combination with one another. Features of one exemplary embodiment may also be implemented separately from other features of the same exemplary embodiment, and thus can be easily combined by a specialist to form further useful combinations and subcombinations with features of other exemplary embodiments.

[0209] Elements of identical function are designated with the same reference numbers in the figures. [Brief description of the drawings]

[0210] [Figure 1] 1 shows a meridian section of an EUV projection exposure apparatus. [Diagram 2] FIG. 1 shows a DUV projection exposure apparatus. [Diagram 3] 1 is a schematic diagram of a possible embodiment of a measuring device according to the invention; [Figure 4] 5A-5C are schematic diagrams of details from further possible embodiments of the measuring device according to the invention; [Diagram 5]3A and 3B are schematic diagrams of possible embodiments of the aperture device of the measuring device according to the invention; [Figure 6] 3 shows a schematic diagram of a possible division of the surface to be measured into a number of individual areas to be measured; [Figure 7] 2 is a schematic isometric view of a further possible embodiment of a measuring device according to the invention; [Figure 8] 3 shows a schematic diagram of a further possible embodiment of the measuring device according to the invention in a side view. [Figure 9] 4 is a schematic diagram of another side view of another possible embodiment of the measuring device according to the invention; [Figure 10] FIG. 10 is a schematic diagram of the measuring device according to FIG. 9 in a spatially folded state. [Figure 11] 2 is a schematic diagram of a possible embodiment of an illumination mask element; [Figure 12] 3A and 3B are schematic diagrams of possible embodiments of an illumination device of the measuring device according to the invention; [Figure 13] FIG. 13 shows a schematic diagram of an illumination device according to FIG. 12, with the outer-pivoted inner-pivoted optical unit removed from the beam path. [Figure 14] 2 shows another schematic view of a part of a measuring device according to the invention in side view; [Figure 15] 1 shows a detailed schematic diagram of the beam path in the area of ​​the dividing element and the surface to be measured. [Figure 16] 1 shows a block diagram of a method according to the invention; [Figure 17] FIG. 2 shows a block diagram of a processing method according to the invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0211] The essential components of a microlithography EUV projection exposure apparatus 100 as an example of a lithography system are exemplarily described below first with reference to Fig. 1. The description of the basic structure of the EUV projection exposure apparatus 100 and its components should not be construed as limiting here.

[0212] In addition to the radiation source 102, the illumination system 101 of the EUV projection exposure apparatus 100 comprises an illumination optical unit 103 for illuminating an object field 104 in an object plane 105. Exposed here is a reticle 106 that is arranged in the object field 104. The reticle 106 is held in a reticle holder 107. The reticle holder 107 is displaceable, in particular in the scanning direction, by a reticle displacement drive 108.

[0213] In Figure 1, a Cartesian xyz coordinate system has been plotted to aid in illustration. The x-direction extends vertically in the plane of the drawing. The y-direction is horizontal and the z-direction is vertical. In Figure 1, the scan direction extends in the y-direction. The z-direction extends perpendicular to the object plane 105.

[0214] The EUV projection exposure apparatus 100 comprises a projection optical unit 109. The projection optical unit 109 serves to image the object field 104 into an image field 110 in an image plane 111. The image plane 111 extends parallel to the object plane 105. Alternatively, an angle between the object plane 105 and the image plane 111 different from 0° is also possible.

[0215] The structures on the reticle 106 are imaged onto a photosensitive layer of a wafer 112, which is arranged in the region of an image field 110 in an image plane 111. The wafer 112 is held in a wafer holder 113. The wafer holder 113 is displaceable, in particular in the y-direction, by a wafer displacement drive 114. Firstly, the displacement of the reticle 106 by the reticle displacement drive 108 and secondly, the displacement of the wafer 112 by the wafer displacement drive 114 can be performed synchronously with each other.

[0216] The radiation source 102 is an EUV radiation source. The radiation source 102 emits in particular EUV radiation 115, also called used radiation, illumination radiation or projection radiation. In particular, the used radiation 115 has a wavelength in the range of 5 nm to 30 nm. The radiation source 102 can be a plasma source, for example an LPP source ("Laser Produced Plasma") or a GDPP source ("Gas Release Produced Plasma"). It may also be a synchrotron-based radiation source. The radiation source 102 can be a free electron laser (FEL).

[0217] The illumination radiation 115 emerging from the radiation source 102 is focused by a collector 116. The collector 116 may be a collector with one or more ellipsoidal and / or hyperboloidal reflective surfaces. At least one reflective surface of the collector 116 may impinge on the illumination radiation 115 with grazing incidence (GI), i.e. an angle of incidence greater than 45°, or with normal incidence (NI), i.e. an angle of incidence less than 45°. The collector 116 may be structured and / or coated, firstly to optimize its reflectivity for the radiation 115 used and secondly to suppress extraneous light.

[0218] Downstream of the collector 116, the illumination radiation 115 propagates through an intermediate focus in an intermediate focal plane 117. The intermediate focal plane 117 may represent the separation between the radiation source module comprising the radiation source 102 and the collector 116 and the illumination optical unit 103.

[0219] The illumination optical unit 103 comprises a deflection mirror 118 and a first facet mirror 119 arranged downstream in the beam path. The deflection mirror 118 may be a plane deflection mirror or a mirror with a beam-influencing effect beyond a pure deflection effect. Alternatively or additionally, the deflection mirror 118 may be in the form of a spectral filter that separates the used light wavelength of the illumination radiation 115 from external light of wavelengths deviating therefrom. The first facet mirror 119 is also referred to as a field facet mirror if it is arranged as a field plane in a plane optically conjugate with the object plane 105 of the illumination optical unit 103. The first facet mirror 119 comprises a number of individual first facets 120, also referred to as field facets in the following. Only some of these facets 120 are exemplarily shown in FIG. 1 .

[0220] The first facet 120 may be embodied in the form of a macroscopic facet, in particular in the form of a rectangular facet or a facet having an arcuate or part-circular peripheral contour. The first facet 120 may also be embodied as a planar facet or as a convexly or concavely curved facet.

[0221] As is known, for example, from US Pat. No. 5,993,949, the first facet 120 itself may also consist of a plurality of individual mirrors, in particular a plurality of micromirrors. The first facet mirror 119 may in particular be in the form of a microelectromechanical system (MEMS system). For further details, see US Pat. No. 5,993,949.

[0222] Illumination radiation 115 travels horizontally, ie, in the y-direction, between a collector 116 and a deflection mirror 118 .

[0223] In the beam path of the illumination optical unit 103, downstream of the first facet mirror 119, a second facet mirror 121 is arranged. If the second facet mirror 121 is arranged in a pupil plane of the illumination optical unit 103, it is also called a pupil facet mirror. The second facet mirror 121 can also be arranged at a distance from the pupil plane of the illumination optical unit 103. In this case, the combination of the first facet mirror 119 and the second facet mirror 121 is also called a specular reflector. Specular reflectors are known from US Pat. No. 5,399,413, US Pat. No. 5,399,423 and US Pat. No. 5,499,435.

[0224] The second facet mirror 121 comprises a plurality of second facets 122. In the case of a pupil facet mirror, the second facets 122 are also called pupil facets.

[0225] The second facet 122 may likewise be a macroscopic facet, which may for example have a circular, rectangular or hexagonal boundary, or may be a facet made up of micromirrors. In this regard, reference is also made to US Pat. No. 5,399,633.

[0226] The second facet 122 may have a planar reflective surface, or may have a reflective surface with a convex or concave curvature.

[0227] This makes the illumination optical unit 103 a dual facet system. This basic principle is also called a fly's eye integrator.

[0228] It may be advantageous for the second facet mirror 121 not to be located exactly in a plane that is optically conjugate with the pupil plane of the projection optical unit 109 .

[0229] The individual first facets 120 are imaged into the object field 104 using a second facet mirror 121. The second facet mirror 121 is the last beam-shaping mirror, or indeed the last mirror, of the illumination radiation 115 in the beam path upstream of the object field 104.

[0230] In a further embodiment (not shown) of the illumination optical unit 103, a transfer optical unit, which in particular contributes to the imaging of the first facet 120 into the object field 104, may be arranged in the beam path between the second facet mirror 121 and the object field 104. The transfer optical unit may comprise exactly one mirror or alternatively two or more mirrors arranged in succession in the beam path of the illumination optical unit 103. In particular, the transfer optical unit may comprise one or two mirrors for normal incidence (NI mirror, "normal incidence" mirror) and / or one or two mirrors for oblique incidence (GI mirror, "grazing incidence" mirror).

[0231] In the embodiment shown in FIG. 1, the illumination optical unit 103 comprises exactly three mirrors downstream of the collector 116 , in particular a deflection mirror 118 , a field facet mirror 119 and a pupil facet mirror 121 .

[0232] In a further embodiment of the illumination optical unit 103, the deflection mirror 118 can also be omitted and the illumination optical unit 103 can therefore have exactly two mirrors downstream of the collector 116, in particular a first facet mirror 119 and a second facet mirror 121.

[0233] The imaging of the first facet 120 by the second facet 122 or by means of the second facet 122 and the transfer optical unit into the object plane 105 is in principle only an approximate imaging.

[0234] The projection optical unit 109 comprises a number of mirrors Mi, which are numbered according to their location in the beam path of the EUV projection exposure apparatus 100 .

[0235] In the example shown in Fig. 1, the projection optical unit 109 comprises six mirrors M1 to M6. Alternatives with 4, 8, 10, 12 or any other number of mirrors Mi are possible as well. The penultimate mirror M5 and the last mirror M6 each have a passage opening for the illumination radiation 115. The projection optical unit 109 is a double-sided light-shielded optical unit. The projection optical unit 109 has an image-side numerical aperture that is greater than 0.5, can also be greater than 0.6, and can be, for example, 0.7 or 0.75.

[0236] The reflective surface of the mirror Mi can be in the form of a freeform surface without an axis of rotational symmetry. Alternatively, the reflective surface of the mirror Mi can be designed as an aspheric surface with exactly one axis of rotational symmetry of the reflective surface shape. As with the mirrors of the illumination optical unit 103, the mirror Mi can have a highly reflective coating for the illumination radiation 115. These coatings can be designed as multilayer coatings, in particular with alternating layers of molybdenum and silicon.

[0237] The projection optical unit 109 has a large object-image offset in the y direction between the y coordinate of the center of the object field 104 and the y coordinate of the center of the image field 110. This object-image offset in the y direction can be approximately as large as the z distance between the object plane 105 and the image plane 111.

[0238] In particular, the projection optical unit 109 can be of an anamorphic form. In particular, it has different imaging scales βx, βy in the x-direction and the y-direction. The two imaging scales βx, βy of the projection optical unit 109 are preferably (βx, βy)=(+ / -0.25, + / -0.125). A positive imaging scale β means imaging without image inversion. A negative sign of the imaging scale β means imaging with image inversion.

[0239] As a result, the projection optical unit 109 is miniaturized by a ratio of 4:1 in the x-direction, ie, the direction perpendicular to the scanning direction.

[0240] The projection optical unit 109 achieves a miniaturization ratio of 8:1 in the y direction, ie, the scanning direction.

[0241] Other imaging scales are possible as well. Imaging scales with the same sign and the same absolute value in the x and y directions are also possible, for example absolute values ​​of 0.125 or 0.25.

[0242] The number of intermediate image planes in the x- and y-directions in the beam path between the object field 104 and the image field 110 may be the same or different depending on the embodiment of the projection optical unit 109. An example of such a projection optical unit with a different number of intermediate images in the x- and y-directions is known from US Pat.

[0243] In each case, one of the pupil facets 122 is assigned to exactly one of the field facets 120 in order to form an illumination channel for illuminating in each case the object field 104. In particular, this can result in illumination according to the Köhler principle. The far field is decomposed into a number of object fields 104 by means of the field facets 120. The field facets 120 generate a number of images of intermediate foci on the pupil facets 122 respectively assigned to it.

[0244] By means of the assigned pupil facets 122, the field facets 120 are respectively imaged on the reticle 106 in a mutually overlapping manner for the purpose of illuminating the object field 104. The illumination of the object field 104 is in particular as uniform as possible, preferably with a uniformity error of less than 2%. The field uniformity can be achieved by overlapping different illumination channels.

[0245] The illumination of the entrance pupil of the projection optical unit 109 can be geometrically defined by the arrangement of the pupil facets. The intensity distribution at the entrance pupil of the projection optical unit 109 can be set via the selection of the illumination channels, in particular the subset of pupil facets that direct the light. This intensity distribution is also called the illumination setting.

[0246] An equally good pupil uniformity in the region of a section of the illumination pupil of the illumination optical unit 103 that is illuminated in a defined manner can be achieved by a redistribution of the illumination channels.

[0247] Further aspects and details of the illumination of the object field 104, and in particular the entrance pupil of the projection optical unit 109, are described below.

[0248] The projection optical unit 109 may in particular have a homogeneous entrance pupil, which may be accessible or may not be accessible.

[0249] The entrance pupil of the projection optical unit 109 cannot generally be illuminated exactly by the pupil facet mirror 121. When imaging a projection optical unit 109 that telecentrically images the center of the pupil facet mirror 121 onto the wafer 112, the aperture rays often do not intersect at a single point. However, it is possible to find a surface area for which the spacing of the aperture rays determined in pairs is minimal. This surface area represents the area of ​​the entrance pupil or of the real space that is conjugate thereto. In particular, this surface area has a finite curvature.

[0250] The projection optical unit 109 may have different entrance pupil positions for the tangential and sagittal beam paths. In this case, optical components of the imaging elements, in particular the transfer optical unit, must be provided between the second facet mirror 121 and the reticle 106. With the help of these optical components it is possible to take into account different attitudes of the tangential and sagittal entrance pupils.

[0251] In the arrangement of the components of the illumination optical unit 103 shown in Fig. 1, the pupil facet mirror 121 is arranged in a surface area conjugate with the entrance pupil of the projection optical unit 109. The first field facet mirror 119 is arranged at an incline with respect to the object plane 105. The first facet mirror 119 is arranged at an incline with respect to the arrangement plane defined by the deflection mirror 118.

[0252] The first facet mirror 119 is disposed so as to be inclined with respect to a plane defined by the second facet mirror 121 .

[0253] 2 shows an exemplary DUV projection exposure apparatus 200, in which the principles of the invention can in principle also be used to clean lenses and remove foreign objects. EUV-specific components, such as the collector mirror 116, are therefore not required for this purpose or may be replaced accordingly. The DUV projection exposure apparatus 200 comprises an illumination system 201, a device known as a reticle stage 202 for receiving and precisely positioning a reticle 203, by means of which the subsequent structure on the wafer 204 is determined, a wafer holder 205 for holding, moving and precisely positioning the wafer 204, and an imaging device, in particular the projection optical unit 206, with a number of optical elements, in particular lens elements 207, held by mounts 208 in a lens housing 209 of the projection optical unit 206.

[0254] Alternatively, or in addition to the illustrated lens element 207, various refractive, diffractive and / or reflective optical elements may be provided, such as mirrors, prisms, end plates, among others.

[0255] The basic functional principle of a DUV projection exposure tool 200 prepares structures introduced in a reticle 203 to be imaged onto a wafer 204 .

[0256] Illumination system 201 provides a projection beam 210 or projection radiation in the form of electromagnetic radiation required for imaging a reticle 203 on a wafer 204. The source used for this radiation may be a laser, a plasma source, etc. The radiation is shaped in illumination system 201 by optical elements such that when projection beam 210 is incident on reticle 203 it has desired properties in terms of wavefront diameter, polarization, shape, etc.

[0257] An image of the reticle 203 is produced by the projection beam 210 and transferred in an appropriately reduced form from the projection optical unit 206 onto the wafer 204. In this case, the reticle 203 and the wafer 204 can be moved synchronously, so that areas of the reticle 203 are imaged onto corresponding areas of the wafer 204 substantially continuously during a so-called scanning operation.

[0258] The gap between the last lens element 207 and the wafer 204 can be optionally replaced by a liquid medium with a refractive index greater than 1.0. The liquid medium can be, for example, high purity water. Such a setup is also called immersion lithography and provides improved photolithographic resolution.

[0259] The use of the invention is not limited to use in projection exposure apparatus 100, 200, nor to the particularly described structure. The invention is suitable for any lithography system, but in particular for projection exposure apparatuses having the described structure. The invention is also suitable for EUV projection exposure apparatuses having smaller image-side numerical apertures than those described in the context of FIG. 1. In particular, the invention is also suitable for EUV projection exposure apparatuses having image-side numerical apertures of 0.25 to 0.5, preferably 0.3 to 0.4, particularly preferably 0.33. The invention and the following exemplary embodiments should also not be understood as being limited to a particular design. The following figures show the invention in highly schematic form, purely by way of example.

[0260] It should be noted that the measuring device according to the invention, the method according to the invention for measuring the shape of a surface by interferometry, the processing method according to the invention for processing a test object and the optical elements described below can in particular be used in lithography systems, in this context in particular in projection exposure apparatus for semiconductor lithography, but can also be used in other fields of use in which precise measurements are important or in which test objects, more in particular optical elements, need to be measured or processed with high precision.

[0261] The exemplary embodiments presented below, particularly those described with reference to FIGS. 3 to 17, should be understood accordingly.

[0262] FIG. 3 shows a schematic diagram of a possible embodiment of a measuring device 1 according to the invention.

[0263] A measuring device 1 for interferometrically measuring the shape of a surface 2 of a test object 3, in particular an optical surface 2 of an optical element 3 which may be one of the optical elements 116, 118, 119, 120, 121, 122, Mi, 207, comprises an illumination device 4 having an illumination source 5 for generating an illumination wave 6, shown in solid lines in Figure 3, and an interferometer device 7 having a splitting element 8 for splitting the illumination wave 6 into a test wave 9 (shown in dotted lines in Figure 3) directed towards the surface 2 and a reference wave 10 (shown in dashed and dotted lines in Figure 3).

[0264] Furthermore, the measuring device 1 comprises a registration device 11 for registering the interference pattern and for evaluating the interference pattern in order to determine the deviation of the shape of the surface 2 to be measured from a target shape. Furthermore, the measuring device 1 comprises a control device 12 configured for dividing the surface 2 to be measured into a plurality of individual measured areas 13 (see Fig. 6) and a positioning device 14 configured for positioning the test wave 9 on the surface 2 to be measured such that each individual area 13 is fully illuminated. In this case, the registration device 11 is configured to determine the deviation of the shape of at least a part of the surface 2 to be measured from a target shape based on the data from the individual areas 13.

[0265] It is provided that the illumination device 4 comprises at least one adjustable diaphragm device 15 which defines a partial opening 16 (see FIG. 6) of the interferometer device 7 and is configured to adapt it to the individual area 13 to be measured in each case.

[0266] Preferably, the splitting element 8 is further configured to form an aspheric wavefront of the test wave 9 .

[0267] In the exemplary embodiment shown in FIG. 3, a beam splitter 24 is provided for directing the illumination wave 6 onto the splitting element 8 and for allowing the return radiation formed from the reference wave 10 and the test wave 9 to pass in the direction of the registration device 11.

[0268] In the exemplary embodiment shown in FIG. 3, the positioning device 14 is configured to position the illumination device 4, the registration device 11, and the interferometer device 7 relative to the test object 3 along six degrees of freedom such that the illumination device 4, the registration device 11, and the interferometer device 7 remain positioned relative to one another in the same manner.

[0269] Alternatively or additionally, in one embodiment (not shown), the positioning device 14 may be configured to simply position the splitting element 8 and / or the interferometer device 7 relative to the test object 3 along six degrees of freedom, and a beam steering device may be provided to appropriately direct the illumination wave 6 to the splitting element 8, even when changing the location and alignment of the splitting element 8, particularly under the angles mentioned above.

[0270] In the exemplary embodiment shown in Figure 3, a set 8a of exchangeable dividing elements 8 is preferably provided for measuring the surface 2 of the test object 3, the set 8a of dividing elements 8 being embodied in such a way that a dividing element 8 adapted to the target shape of the individual area 13 to be measured is selectable for each individual area 13 to be measured.

[0271] In order to replace the set 8a of replaceable dividing elements 8, in the exemplary embodiment shown in FIG. 3, a changing device 8b is preferably provided, which is preferably communicatively and operably connected to the control device 12 in order to select a dividing element 8 which forms a test wave 9 which is preferably best adapted as possible to the target shape of the respective area 13 to be measured.

[0272] In a preferred embodiment, not shown in Fig. 3, the exchange device 8b does not carry a plurality of divided elements 8 in the sensor. In case of an automatic exchange performed by the exchange device 8b, it can be provided that the exchange device 8b has a handling device configured to remove a first divided element 8 and then retrieve a second divided element 8 from a storage device, in particular a shelf, and attach the second divided element to the interferometer device 7.

[0273] In the exemplary embodiment shown in FIG. 3, the dividing element 8 is preferably adapted to the desired shape of the individual areas 13, in particular as adapted as possible.

[0274] In the exemplary embodiment shown in FIG. 3, the illumination device 4, the registration device 11 and the interferometer device 7 are preferably arranged rigidly on a joint frame 1a, which may also be in the form of a housing.

[0275] In the exemplary embodiment shown in FIG. 3, all optical components of the measurement device 1 are preferably in the form of reflective and / or refractive components.

[0276] FIG. 4 shows details of a further possible embodiment of the measuring device 1.

[0277] In the exemplary embodiment shown in FIG. 4, the splitting element 8 is preferably configured to shape an astigmatic and / or toroidal wavefront of the test wave 9 .

[0278] In the exemplary embodiment shown in Figures 3 and 4, the interferometer arrangement 7 is in the form of a Fizeau interferometer. Figure 4 shows an embodiment in which the dividing element 8 is in the form of a Fizeau element, preferably comprising a reference surface 17 and a back surface 18 opposite the reference surface 17.

[0279] In the exemplary embodiment shown in FIG. 4, the reference surface 17 preferably has an astigmatic and / or toroidal shape.

[0280] Additionally, the exemplary embodiment shown in FIG. 4 illustrates an embodiment in which the backside surface 18 is preferably shaped to be planar such that the illumination wave 6 is at least approximately perpendicular to the reference surface 17 at each point in the cross section of the illumination wave 6.

[0281] At each point in the cross section of the illumination wave 6 in the exemplary embodiment shown in FIG. 4, the illumination wave 6 is preferably incident on the backside surface 18 at an angle of at least 0.1 degrees, preferably at least 0.3 degrees, relative to the surface normal.

[0282] In the exemplary embodiment shown in FIG. 4, the splitting element 8 and / or the positioning device 14 are designed such that, at each point of the cross section of the test wave 9, the test wave 9 is at least approximately perpendicularly incident on the surface 2 to be measured.

[0283] FIG. 5 shows a schematic diagram of a possible embodiment of the aperture device 15 .

[0284] In the exemplary embodiment shown in Fig. 5, the aperture arrangement 15 is preferably in the form of a rectangular aperture having an adjustable side length 19. In Fig. 5, the adjustable side length 19 is represented as a double-headed arrow. In Fig. 5, the measurement field 20 enabled by the rectangular aperture is shown enclosed in a bold frame.

[0285] In this case, the measurement field 20 defines a partial opening 16 which is adapted to the respective area 13 to be measured (see FIG. 6).

[0286] In an alternative or additional embodiment of the aperture device 15, the aperture device 15 may have a circular aperture with an adjustable diameter. In a further alternative or additional embodiment, the aperture device 15 may comprise a multi-blade aperture.

[0287] The embodiment in which the aperture device 15 comprises a circular aperture and a rectangular aperture may be advantageous in order to obtain a particular geometric shape of the individual areas 13. In a series connection, a combination of some or all of the embodiments of the aperture device 15 may be advantageous.

[0288] Figure 6 shows a schematic diagram of a possible division of the surface 2 to be measured into a number of individual measured areas 13. In figure 6 the surface 2 to be measured is indicated using hatching.

[0289] The registration device 11 (see FIG. 3) is preferably configured to reconstruct the shape of the surface 2 from the individual areas 13 .

[0290] The individual areas 13 are defined by respective partial openings 16 .

[0291] The control device 12 (see FIG. 1) is preferably further configured to determine the number, position, shape and / or overlapping individual areas 13 such that a measurement parameter is optimized. In the present exemplary embodiment shown in FIG. 6, the measurement parameter is the measurement accuracy of the overall surface profile of the surface being measured.

[0292] In the exemplary embodiment shown in Figures 3 to 6, the control device 12 is preferably configured to determine the number, position and / or shape of the individual areas 13 such that the maximum gradient of each individual area 13 does not exceed a limit gradient of 5 mrad, preferably 1 mrad, particularly preferably 0.5 mrad.

[0293] 6 thus shows variable sized partial openings 16 arranged on the surface 2 to be tested, in particular on a freeform surface. In the exemplary embodiment shown in FIG. 6, the size of the individual partial openings 16 is limited by the maximum allowed gradient within the individual areas 13.

[0294] FIG. 7 shows an isometric view of a schematic diagram of a further possible embodiment of the measuring device 1.

[0295] In this case, the aperture arrangement 15 is arranged in a telescope formed by lens elements 21. An illumination mask element 22 is arranged in the Fourier plane. The aperture arrangement 15 is imaged by an illumination lens 23 onto a surface 2 (not shown) to be measured.

[0296] After passing through the illumination lens 23, the illumination wave 6 is transmitted through a beam splitter 24 and subsequently impinges on a splitting element 8 (simply shown as a plate in FIG. 7 ) which forms a test wave 9 that impinges on the surface 2 of the test object 3. The returning test wave 9 and reference wave 10 are reflected by the beam splitter 24 onto a parabolic focusing mirror 25.

[0297] A parabolic focusing mirror 25 focuses the radiation formed by the test wave 9 superimposed with the reference wave 10 onto a secondary aperture arrangement 26, which makes it possible to further define the shape of the individual areas 13.

[0298] The radiation formed by the superposition of the test wave 9 and the reference wave 10, after passing through the secondary aperture device 26, strikes a parabolic eye mirror 27 which reflects the radiation onto a sensor chip 28. The parabolic focusing mirror 25, the secondary aperture device 26, the parabolic eye mirror 27 and the camera chip 28 are in this case part of the registration device 11.

[0299] FIG. 8 shows a schematic diagram of a further possible embodiment of the measuring device 1 in a side view.

[0300] For reference numbers, please refer to the list of reference numbers and assignments in FIG.

[0301] The dividing element 8 may have an at least approximately rectangular embodiment, with side lengths of 50 mm to 200 mm, preferably 120 mm to 140 mm.

[0302] FIG. 9 shows a schematic side view of a further possible embodiment of the measuring device 1.

[0303] 9, the illumination source 5 is formed by an optical waveguide 29. The illumination wave 6 is focused by a lens element 21 onto the reduction device 30.

[0304] In this case, a reduction device 30 is provided, which is arranged to reduce the spatial coherence of the illumination wave 6 .

[0305] In the exemplary embodiment shown in FIG. 9, the reduction device 30 is embodied as a rotating diffuser plate 30a.

[0306] Alternatively or additionally, the reduction device 30 may be in the form of a rotating microlens array that may act as a secondary light source.

[0307] 8 and 9, the illumination lens 23 is in the form of a lens element in each case. Alternatively or additionally, the illumination lens 23 may be in the form of a lens element system.

[0308] In the exemplary embodiment shown in Figure 9, the secondary aperture device 26 is preferably in the form of a mask plate, which can be positioned by a suitable displacement device in the beam path so that the radiation passes through a suitable opening in the mask plate.

[0309] The illumination wave 6 is deflected by a deflection mirror 31 before entering the beam splitter 24 and the test object 3. The beam path shown in Fig. 9 is simplified since the structure of the measuring device 1 is in a certain sense three-dimensional and is shown in a folded or expanded form.

[0310] Figure 10 shows a schematic diagram of the measuring device 1 according to figure 9 in a spatially folded state. A deflection mirror 31 and parabolic mirrors 25 and 27 enable the spatial folding of the measuring device 1. Regarding the assignment of reference numbers, reference is made to the declarations and explanations relating to figure 9.

[0311] FIG. 11 shows a schematic diagram of a possible embodiment of the illumination mask element 22 .

[0312] In the embodiment shown in Fig. 11, the regions of the illumination mask element 22 colored black are each opaque. Thus, the illumination mask element 22 shown on the left has only three thin opaque rings, whereas the illumination mask element 22 shown on the right corresponds to a substantially closed aperture. The intermediate forms depicted in the middle block the illumination waves 6 to different extents.

[0313] In particular, the contrast of the interference pattern can be increased and improved by an illumination mask element 22 shown in FIG.

[0314] FIG. 12 shows a schematic diagram of a possible embodiment of the lighting device 4.

[0315] In the exemplary embodiment shown in FIG. 12, the reduction device 30 comprises an inner pivoting optical unit 32 and a diffuser 32a.

[0316] The inner turning optical unit 32 in turn comprises a group of lens elements 21 arranged and configured such that the diffuser 32a is uniformly illuminated after passage of the illumination wave 6 through the telescope.

[0317] The swivel optical unit 32 allows switching between coherent and incoherent illumination by the illumination wave 6 by swiveling the inner swivel optical unit 32 into or out of the beam path of the measurement device 1. In the exemplary embodiment shown in Fig. 12, the inner swivel optical unit 32 comprises three lens elements 21, so that there is no need to use two separate optical systems.

[0318] The inner swivel optical unit 32 can be configured to transform the imaging properties of the illumination device 4. In particular, the inner swivel optical unit 32 can be provided to transform point-to-point imaging, in particular imaging performed from the illumination source 5 to the illumination pupil 5a, into imaging performed from a point to infinity.

[0319] Figure 13 shows a schematic diagram of the illumination device 4 according to Figure 12, with the inner pivoting optical unit 32 removed from the beam path. This results in a point-like illumination of the diffuser 32a. The switch between spatially coherent illumination and partially coherent illumination is therefore performed by pivoting the inner pivoting optical unit 32. The exact appearance of the secondary light source is determined by the arrangement of a suitable illumination mask element 22 (see Figure 11) in the illumination pupil 5a.

[0320] FIG. 14 shows a further schematic diagram of part of the measuring device 1 in side view.

[0321] In particular, the imaging beam path is shown in Fig. 14. Fig. 14 makes it clear that the intensity distribution of the illumination wave 6 at the location of the diaphragm arrangement 15 is imaged onto the plane of the surface 2 of the test object 3 to be measured. Furthermore, Fig. 14 also shows the diaphragm arrangement 15 and the illumination mask element 22. The fact that a number of illumination mask elements 22 are shown should indicate that an exchange device for the illumination mask elements 22 is provided in order to make it possible to exchange these in a simple manner.

[0322] Reference is now made to FIG. 9 in relation to further reference numerals.

[0323] FIG. 15 shows a detailed schematic diagram of the dividing element 8 and the beam path in the region of the surface 2 to be measured.

[0324] It is clear that the dividing element 8 is inclined at a working angle 33 with respect to the surface 2 to be measured. This results in a reference angle 34 between the returning test wave 9 and the returning reference wave 10.

[0325] It is further evident from FIG. 15 that the interfering reflected wave 35 is deflected away from the beam paths of the reference wave 10 and the test wave 9 .

[0326] The embodiment of the measuring device 1 described in relation to Figures 3 to 15 is particularly suitable for carrying out a method for measuring the shape of a surface 2 of a test object 3 by interferometry.

[0327] FIG. 16 shows a block diagram of a method for measuring the shape of a surface 2 of a test object 3, in particular an optical surface 2 of an optical element 3, which may be one of the optical elements 116, 118, 119, 120, 121, 122, Mi, 207, by interferometry.

[0328] In the illumination block 36 the illumination wave 6 is split by a splitting element 8 into a test wave 9 and a reference wave 10 which are directed towards the surface 2 .

[0329] In the interference block 37, the returning test wave 9 which has interacted with the surface 2 being measured is combined with the reference wave 10 to produce an interference pattern.

[0330] In evaluation block 40 the interference pattern is evaluated to determine the deviation of the shape of the measured surface 2 from a target shape.

[0331] In a division block 38, the surface 2 to be measured is divided into a number of individual areas 13 which are measured successively.

[0332] In a positioning block 39, the test wave 9 is positioned on the surface 2 to be measured such that each individual area 13 is fully illuminated at least approximately perpendicularly.

[0333] To illuminate the individual areas 13, the partial aperture 16, which defines the size of the test wave 9, is adapted to the respective individual area 13 to be measured in a field stop block 41. Preferably, the field stop block 41 is arranged in time after the dividing block 38 and before the positioning block 39.

[0334] Blocks 36 to 41 are preferably executed in a specified chronological order. A different sequence or parallel execution of multiple blocks may also be advantageous, in particular the chronological sequence of blocks 36 to 41 shown in FIG.

[0335] In the exemplary embodiment shown in FIG. 16, it is also provided that an aspheric wavefront of the test wave 9, adapted to the target shape of the individual area 13 to be measured, is formed by the splitting element 8 as part of the illumination block 36.

[0336] Within the illumination block 36, preferably furthermore, a set 8a of exchangeable dividing elements 8 is provided for measuring the surface 2 of the test object 3, the dividing elements 8 of the set 8a being embodied in such a way adapted to the individual areas 13 of the surface 2 of the test object 3 to be measured, such that a dividing element 8 adapted to the target shape of the individual area 13 to be measured is available for each individual area 13, such that a dividing element 8 adapted to the target shape of the individual area 13 can be selected from the set 8a for the purpose of measuring each individual area 13. The set 8a of exchangeable dividing elements 8 is preferably stored in a storage device, in particular on a shelf.

[0337] As part of the evaluation block 40, preferably the shape of the surface 2 which is reconstructed from the individual areas 13 is provided.

[0338] As part of the illumination block 36 , preferably, at the reference surface 17 of the dividing element 8 , a part of the illumination wave 6 is further provided which is transmitted as a test wave 9 and a part of the illumination wave 6 which is reflected as a reference wave 10 .

[0339] It is preferable that within the positioning block 39 the dividing element 8 is positioned at a distance of 0.1 cm to 10 cm, preferably 0.5 cm to 3 cm, particularly preferably 1.5 cm to 2.5 cm, from the surface 2 .

[0340] As part of the illumination block 36, it is preferably possible for the dividing element 8 to be embodied as a Fizeau element.

[0341] Similarly, within the illumination block 36, the reference surface 17 of the Fizeau element can be embodied so as to match the preferably average and / or mean target shape of the surface 2 of the test object 3 to be measured.

[0342] Furthermore, astigmatism and / or shaping of a toroidal wavefront of the test wave 9 may be provided as part of the illumination block 36 .

[0343] The positioning block 39 and / or the illumination block 36 may be arranged so that the test wave 9 is directed as perpendicular as possible to the surface 2 and / or as parallel as possible to the average surface normal at each location of each individual area 13.

[0344] The positioning block 39 is preferably equipped with an aperture device 15 for measuring individual areas 13 and may include a method step of positioning an interferometer device 7 forming an illumination wave 6, a reference wave 10 and a test wave 9 relative to the surface 2 so that the test wave 9 hits the surface 2 as perpendicularly as possible.

[0345] Within the illumination block 36, it is preferred that the partial opening 16 is defined by the aperture device 15 by a circular aperture with an adjustable diameter and / or a rectangular aperture with an adjustable side length and / or by a multi-blade aperture.

[0346] At least one of the blocks 36 to 41 may provide a method step in which individual areas 13 of the surface 2 are measured by alignment through partial openings 16 assigned to each individual area 13 .

[0347] The division block 38 may include a method step in which the number, position, shape and / or overlap of the separate individual areas 13 is determined such that the measurement parameters are optimized.

[0348] In particular, the division block 38 can preferably include a method step in which the number, position and / or shape of the individual areas 13 are determined such that the maximum gradient occurring within each individual area 13 does not exceed a limit gradient of 5 mrad, preferably 1 mrad, particularly preferably 0.5 mrad.

[0349] 17 shows a block diagram for processing a test object 3, in particular an optical element 116, 118, 119, 120, 121, 122, Mi, 207 for a lithography system 100, 200, in particular a projection exposure apparatus 200, 300 for semiconductor lithography. In a processing block 42, the shape of the surface 2 of the test object 3, in particular the optical surface 2 of the optical element 116, 118, 119, 120, 121, 122, Mi, 207, is processed such that the shape of the surface 2 at least closely resembles a target shape.

[0350] In decision block 43, the shape of the surface 2 is determined by one or more of the measurement devices 1 described in the context of Figures 3 to 15 and / or using the methods described above in one or more of the preferred embodiments described.

[0351] In an iteration block 44, the processing method is preferably carried out in one or more processing steps within the processing block 42, following each processing step providing a shape of the surface 2 which is determined within a decision block 43.

[0352] As part of the decision block 43, a processing method for subsequent processing steps can be provided that is determined based on the determined shape of the surface 2.

[0353] In particular, in process block 42, the process method may be a polishing method.

[0354] In the exemplary embodiment shown in Figures 3 to 15, the surface 2 and the test object 3 result in an optical element 116, 118, 119, 120, 121, 122, Mi, 207, in particular for a lithography system. In this case, the surface 2 of the optical element 116, 118, 119, 120, 121, 122, Mi, 207 has been measured using a measurement device 1 or a method according to the above-mentioned embodiments. Alternatively or additionally, it is possible to provide the surface 2 of the optical element 116, 118, 119, 120, 121, 122, Mi, 207, which is processed using one of the above-mentioned processing method embodiments. [Explanation of symbols]

[0355] 1. Measuring equipment 1a Frame 2 surface 3 Test Object 4. Lighting equipment 5 illumination source 5a illumination pupil 6. Lighting Wave 7 Interferometer device 8 Division Elements 8a Set of division elements 8b Exchange device 9 Test Wave 10 Reference wave 11 Registration device 12 Control device 13 Individual Areas 14 Positioning device 15 Squeezing device 16 partial opening 17 Reference plane 18 Back side 19 Side Length 20 Measurement field of view 21 Lens Elements 22 Lighting Mask Element 23 Lighting Lens 24 Beam splitter 25 Parabolic focusing mirror 26 Secondary squeezing device 27 Parabolic Eye Mirror 28 Camera Chip 29 Optical waveguide 30 Reduction Device 30a Rotating diffuser 31 Deflection Mirror 32 Inner rotating optical unit 32a Diffuser 33 Working angle 34 Reference Angle 35 Interference reflected waves 36 Lighting Block 37 Interference Block 38 Split Block 39 Positioning Block 40 Rating Block 41 Field aperture block 42 Processing Blocks 43 Decision Block 44 Repeat Blocks 100 EUV projection exposure equipment 101 Lighting System 102 Radiation source 103 Illumination optical unit 104 Object field of view 105 Object plane 106 Reticle 107 Reticle Holder 108 Reticle Displacement Drive Unit 109 Projection Optical Unit 110 Image Field of View 111 Image Plane 112 Wafer 113 Wafer holder 114 Wafer Displacement Drive Device 115 EUV / used / illumination radiation 116 Collector 117 Intermediate focal plane 118 Deflection Mirror 119 First facet mirror / field facet mirror 120 1st Facet / Field Facet 121 Second Facet Mirror / Pupil Facet Mirror 122 Second Facet / Pupil Facet 200 DUV projection exposure equipment 201 Lighting System 202 Reticle Stage 203 Reticle 204 Wafer 205 Wafer Holder 206 Projection Optical Unit 207 Lens Elements 208 Mount 209 Lens Housing 210 Projection Beam Mi Mirror

Claims

1. A measuring device (1) for measuring the shape of the surface (2) of a test object (3), particularly the optical surface (2) of optical elements (116, 118, 119, 120, 121, 122, Mi, 207) by interferometry, A lighting device (4) equipped with a lighting source (5) for generating an illumination wave (6), An interferometer device (7) comprising a splitting element (8) for splitting the illumination wave (6) into a test wave (9) directed toward the surface (2) and a reference wave (10), and for coupling the return test wave (9) that has interacted with the surface (2) to be measured with the reference wave (10), A registration device (11) for registering interference patterns and evaluating interference patterns is provided in order to determine the deviation of the shape of the surface (2) to be measured from the target shape. A control device (12) configured to divide the surface (2) to be measured into a plurality of individual areas (13) to be measured, The system includes a positioning device (14) configured to position the test wave (9) on the surface (2) to be measured so that each of the individual areas (13) is fully illuminated, The registration device (11) is configured to determine the deviation of at least a portion of the shape of the surface (2) being measured from the target shape based on the data from the individual areas (13), The measuring device (1) is characterized in that the illumination device (4) comprises at least one adjustable aperture device (15) configured to define a partial opening (16) of the interferometer device (7) and to adapt it to the individual areas (13) to be measured in each case.

2. The measuring device (1) according to claim 1, characterized in that the dividing element (8) is configured to form an aspherical wavefront of the test wave (6).

3. The measuring apparatus (1) according to claim 1, characterized in that the dividing element (8) is configured to form an astigmatic aberration and / or a toroidal wavefront as a test wave (6).

4. A set (8a) of interchangeable segmenting elements (8) is provided for measuring the surface (2) of the test object (3), and the segmenting elements (8) of the set (8a) are embodied such that a segmenting element (8) that conforms to the target shape of the individual area (13) to be measured can be selected for each individual area (13) to be measured, as described in claim 1.

5. The measuring device (1) according to claim 1, characterized in that the interferometer device (7) is in the form of a Fizeau interferometer, and the dividing element (8) is in the form of a Fizeau element having a reference surface (17) and a back surface (18) opposite to the reference surface (17).

6. The measuring device (1) according to claim 5, characterized in that the reference surface (17) of the Fizeau element (8) has astigmatic and / or toroidal shape.

7. The measuring device (1) according to claim 5, characterized in that the back surface (18) of the Fizeau element (8) is shaped such that the illumination wave (6), which is preferably planar, is incident on the reference plane (17) at least substantially perpendicularly at each point in the cross-section of the illumination wave (6).

8. The measuring device (1) according to claim 5, characterized in that at each point in the cross-section of the illumination wave (6), the illumination wave (6) is incident on the back surface (18) of the Fizeau element (8) at an angle of at least 0.1°, preferably at least 0.3°, with respect to the surface normal.

9. The measuring device (1) according to claim 1, characterized in that the aperture device (15) comprises a circular aperture having an adjustable diameter, and / or a rectangular aperture (19) having an adjustable side length, and / or a multi-blade aperture.

10. The measuring device (1) according to claim 1, characterized in that the registration device (11) is configured to reconstruct the shape of the surface (2) from the individual areas (13).

11. The measuring device (1) according to claim 1, characterized in that the control device (12) is configured to determine the number, position, shape and / or overlap of the individual areas (13) so as to optimize the measurement parameters.

12. The measuring device (1) according to claim 1, characterized in that the control device (12) is configured to determine the number, position and / or shape of each of the individual areas (13) such that the maximum gradient occurring within each of the individual areas (13) does not exceed a limit gradient of 1 mrad, preferably 0.1 mrad.

13. The measuring device according to claim 1, characterized in that the reduction device (30) is provided for reducing the spatial coherence of the illumination wave (6).

14. The measuring device (1) according to claim 1, characterized in that all optical components of the measuring device (1) are in the form of reflective and / or refractive components.

15. The measuring device (1) according to claim 1, characterized in that the positioning device (14) has six degrees of freedom.

16. The measuring device (1) according to claim 1, characterized in that the dividing element (8) and / or the positioning device (14) are designed to be incident at least substantially perpendicularly to the surface (2) on which the test wave (9) is measured at each point in the cross-section of the test wave (9).

17. A method for measuring the shape of the surface (2) of a test object (3), particularly the optical surface (2) of optical elements (116, 118, 119, 120, 121, 122, Mi, 207), by interferometry, thereby, The splitting element (8) splits the illumination wave (6) into a test wave (9) directed towards the surface (2) and a reference wave (10), thereby, The return test wave (9) that interacts with the surface (2) being measured is coupled with the reference wave (10) to generate an interference pattern, thereby, The interference pattern is evaluated to determine the deviation of the shape of the surface (2) being measured from the target shape, thereby, The surface (2) to be measured is divided into a plurality of individual areas (13) to be measured consecutively, thereby, The test wave (9) is positioned on the surface (2) to be measured such that each of the individual areas (13) is completely illuminated at least substantially vertically. A method characterized in that, in order to illuminate the individual areas (13), a partial opening (16) defining the size of the test wave (9) is adapted to the individual areas (13) to be measured in each case.

18. The method according to claim 17, characterized in that the aspherical wavefront of the test wave (9) that conforms to the target shape of the individual areas (13) to be measured is formed by the dividing element (8).

19. The method according to claim 17, characterized in that the shape of the surface (2) is reconstructed from the individual areas (12).

20. The method according to claim 17, wherein a set (8a) of interchangeable segment elements (8) is provided for measuring the surface (2) of the test object (3), the segment elements (8) of the set (8a) are embodied in a manner that conforms to the individual areas (13) of the surface (2) of the test object (3) to be measured, such that a segment element (8) conforming to the target shape of the individual areas (13) of the individual areas (13) is available for each of the individual areas (13), and the segment element (8) conforming to the target shape of the individual areas (13) is selected from the set (8a) for the purpose of measuring each of the individual areas (13).

21. The method according to claim 17, characterized in that, at the reference surface (17) of the dividing element (8), a portion of the illumination wave (6) is transmitted as the test wave (9), and a portion of the illumination wave (6) is reflected as the reference wave (10).

22. The method according to claim 17, characterized in that the dividing element (8) is positioned at a distance of 0.1 cm to 10 cm, preferably 0.5 cm to 3 cm, and particularly preferably 1.5 cm to 2.5 cm from the surface (2).

23. The method according to claim 17, characterized in that the dividing element (8) is embodied as a Fizeau element.

24. The method according to claim 21, characterized in that the reference surface (17) is embodied in such a way as to conform to the target shape of the surface (2) of the test object (3) to be measured.

25. The method according to claim 17, characterized in that astigmatism and / or a toroidal wavefront are formed in the test wave (9).

26. The method according to claim 17, characterized in that at each location in each of the individual areas (13), the test wave (9) is guided as parallel as possible to the local mean surface normal and / or as perpendicular as possible to the surface (2).

27. The method according to claim 17, characterized in that, in order to measure the individual areas (13), the illumination device (4) that forms the illumination wave (6), the interferometer device (7) that forms the reference wave (10) and the test wave (9), and the registration device (11) that registers the interference pattern are positioned with respect to the surface (2) such that the test wave (9) strikes the surface (2) as perpendicularly as possible.

28. The method according to claim 17, characterized in that the partial opening (16) is defined by an aperture device (15) by a circular aperture having an adjustable diameter and / or a rectangular aperture (19) having an adjustable side length and / or a multi-blade aperture.

29. The method according to claim 17, characterized in that the individual areas (13) of the surface (2) are measured by registration of a partial opening (16) assigned to each of the individual areas (13).

30. The method according to claim 17, characterized in that the number, position, shape and / or overlap of the individual areas (13) are determined so as to optimize the measurement parameters.

31. The method according to claim 17, characterized in that the number, position and / or shape of the individual areas (13) are determined such that the maximum gradient occurring within each of the individual areas (13) does not exceed a limit gradient of 5 mrad, preferably 1 mrad, and particularly preferably 0.5 mrad.

32. A processing method for processing a test object (3), particularly an optical element (116, 118, 119, 120, 121, 122, Mi, 207), particularly for a projection exposure apparatus (100, 200) for a lithography system, particularly for semiconductor lithography, wherein the shape of the surface (2) of the test object (3), particularly the optical surface (2) of the optical element (116, 118, 119, 120, 121, 122, Mi, 207), is processed such that the shape of the surface (2) approximates at least a target shape. A processing method characterized in that the shape of the surface (2) is determined by the measuring device (1) described in claim 1 and / or by the method described in claim 17.

33. The processing method according to claim 32, characterized in that the processing method is performed in one or more processing steps, and the shape of the surface (2) is determined after each processing step.

34. The processing method according to claim 32, characterized in that the processing method of the subsequent processing step is determined based on the determined shape of the surface (2).

35. The processing method according to claim 32, characterized in that the processing method is a polishing method.

36. Optical elements (116, 118, 119, 120, 121, 122, Mi, 207) for projection exposure apparatus (100, 200) in particular for lithography systems, especially for semiconductor lithography, An optical element characterized in that the surface (2) of the optical element (116, 118, 119, 120, 121, 122, Mi, 207) is measured using the measuring device (1) described in claim 1 and / or the method described in claim 17.

37. A lithography system having an illumination system (101, 201) having a radiation source (102) and an optical unit (103, 109, 206) equipped with at least one optical element (116, 118, 119, 120, 121, 122, Mi, 207), particularly a projection exposure apparatus (100, 200) for semiconductor lithography, At least one of the optical elements (116, 118, 119, 120, 121, 122, Mi, 207) is The device comprises an optical surface (2) that is at least partially measured by the measuring device (1) described in claim 1, and / or A lithography system comprising an optical surface (2) that is at least partially measured using the method described in claim 17.

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