A method for simulating the illumination and imaging characteristics of an optical production system during object illumination and imaging using an optical measurement system.

Abstract

When simulating the illumination and imaging properties of an optical production system when illuminating and imaging an object by means of an optical measurement system of a metrology system, first an optical measurement system is provided that has an illumination optical unit for illuminating an object and a pupil diaphragm (10), in particular a displaceable pupil diaphragm, and has an imaging optical unit for imaging the object into an image plane. When simulating these properties of the optical production system by means of the optical measurement system, first a plurality of pupil diaphragms (10) are provided. Then, a measured aerial image with the plurality of pupil diaphragms (10) is recorded. From the recorded measured aerial images, a complex mask transfer function is reconstructed, and from this function and the illumination settings of the optical production system, a 3D aerial image is determined. This provides an improved simulation method.

Description

Technical Field

[0001] This patent application claims the priority of German Patent Application Publication No. 102022200372.1. The content of this document is incorporated herein by reference.

[0002] The present invention relates to a method for simulating the illumination and imaging characteristics of an optical production system during the illumination and imaging of an object by an optical measurement system. Furthermore, the present invention relates to a measurement system for performing such a method.

Background Art

[0003] Such methods and measurement systems for this purpose are known from German Patent Application Publication No. 102019208552 and German Patent Application Publication No. 102019215800. A measurement system for three-dimensionally measuring the aerial image of a lithography mask is known from International Publication No. 2016 / 012426 pamphlet. German Patent Application Publication No. 102013219524 describes an apparatus and method for determining the imaging quality of an optical system, as well as an optical system. German Patent Application Publication No. 102013219524 describes a phase search method for determining a wavefront based on the imaging of a pinhole. The expert paper by Martin et al., "A new system for a wafer lever CD metrology on photomasks", proceedings of SPIE - The International Society for Optical Engineering, 2009, 7272 describes a measurement system for determining the wafer-level critical dimension (CD).

Summary of the Invention

[0004] An object of the present invention is to improve a method for simulating the illumination and imaging characteristics of an optical production system during the illumination and imaging of an object by an optical measurement system.

[0005] According to the present invention, this object is achieved by a simulation method having the features described in claim 1.

[0006] According to the present invention, recording a measured aerial image by means of a plurality of pupil stops, in particular recording the measured aerial image at a plurality of measurement positions of a pupil stop preselected for the best possible simulation of the illumination setting of an optical production system, offers the possibility of improving the overall accuracy of the simulation method and, in particular, provides the option of reducing artifacts that depend on the illumination angle, in particular artifacts that depend on the illumination angle in the reconstructed complex mask transfer function, i.e., artifacts that depend on the illumination angle in the transfer function of the imaged object. It is then possible to correctly take into account the effect of the 3D mask. When inspecting a lithography mask, in particular when inspecting a mask used for EUV lithography, the effect of the 3D mask can be taken into account.

[0007] Within the scope of the simulation method, it is possible to accurately select one pupil stop from the plurality of pupil stops provided, and these plurality of pupil stops may differ with respect to the aperture boundary shape of the pupil stop and / or the aperture boundary orientation of the pupil stop. Alternatively, it is also possible to select and use a plurality of different pupil stops to specify different measurement positions. The pupil stops provided may in particular specify at least one of the following illumination settings, namely quadrupole, C quad, dipole, annular, conventional illumination settings. A person skilled in the art will find examples of such settings, inter alia, in pamphlet WO 2012 / 028303. First, initially, within the scope of preparing the imaging method, the best focus plane (defocus value z mThe value of z = 0) may be determined. The z increment when determining the 3D aerial image in the final step of the simulation method, i.e., the z increment when determining the aerial image from the reconstructed mask transfer function and the illumination settings of the optical production system, may be different from the defocus value which may be initially specified in the simulation method. The pixel size of the recorded measured aerial image may be sampled to fit the desired pixel resolution.

[0008] The target pupil aperture that can be specified, and the shape of its target pupil boundary, may relate to a plurality or otherwise numerous individual illumination or pupil spots, i.e., a plurality of aperture openings, for example, a plurality of aperture openings arranged in a grid. Such illumination or pupil spots may provide illumination settings used within the range of production illumination. The illumination settings can be set, for example, through an illumination optical unit having a field facet mirror and a pupil facet mirror.

[0009] The displacement drive device described in claim 2 has demonstrated its value in reproducibly specifying the pupil diaphragm measurement position. Correspondingly, this applies to an object holder that is displaceable perpendicular to the object plane.

[0010] The different aperture boundary shapes and / or aperture boundary orientations of the pupil diaphragm provided, as described in claim 3, increase the flexibility when performing this simulation method.

[0011] The simulation method described in claim 4, with the help of a certified algorithm, has particularly proven its value. With the help of an object holder displaceable by an actuator and a displacement drive for displacing the pupil diaphragm, the defocus value and / or pupil diaphragm measurement position can be specified. A piezo drive and / or a stepper motor drive can be used as the displacement drive or displacement actuator.

[0012] The recording of the measured aerial image described in claim 5 has indeed proven its value.

[0013] The central measurement position and the multiple offset measurement positions described in claim 6 have demonstrated their value within the scope of actual implementation of the simulation method. At the central measurement position, the pupil diaphragm is positioned at the center of the pupil used by the optical measurement system. Two to ten offset measurement positions, particularly two to five, for example, three or four offset measurement positions can be provided. The offset measurement positions can be uniformly distributed circumferentially around the central measurement position. The offset measurement positions may be displaced relative to the central measurement position in the Cartesian coordinate direction, or otherwise in the quadrant direction. The measurement positions may be randomly arranged circumferentially and may be arranged on one or more radii, particularly on two or three different radii. It is also possible to arrange the measurement positions completely randomly, either within the range of the measurement pupil, or otherwise partially outside the range of the measurement pupil. Where random arrangement is referred to above, the random arrangement can be determined by using an algorithmic random function.

[0014] The defocus value / measurement position combinations described in claim 7 have proven to be effective. It was found that for each defocus value, it is not necessary to target all pupil diaphragm measurement positions specified within the scope of the method. This reduces measurement time.

[0015] The pupil aperture selection method described in claim 8 ensures the best possible simulation of the target pupil aperture using the selected pupil aperture. For each pupil spot, illumination light is present within the illumination pupil. Within the scope of the selection method, distance determination of the assigned pupil spot for the target aperture boundary shape of each pupil aperture can be performed. Within the scope of the selection method, a merit function can be defined and minimized.

[0016] The illumination direction-dependent mask spectrum modeling described in claim 9 proved its value during reconstruction. This is because this modeling helps reduce the number of degrees of freedom present during optimization within the scope of this reconstruction.

[0017] The displacement of the imaging pupil diaphragm described in claim 10 expands the possibilities for modeling within the scope of the simulation method.

[0018] The reconstruction described in claim 11 leads to particularly excellent simulations.

[0019] The results of the simulation method described in claim 12 also depend on the option of describing the aerial image, which is dependent on the principal ray angle of illumination by the optical production system. Therefore, when determining the 3D aerial image, different principal ray angles of illumination by the production system may be taken into consideration. This increases the power of the simulation method.

[0020] The advantages of the measurement systems described in claims 13 to 15 correspond to the advantages already described above with reference to the method claims.

[0021] The selection device having an aperture storage unit as described in claim 16 also advantageously enables the pupil aperture selection step of the simulation method. In particular, this selection can be carried out with the help of a robotic actuation system that removes each selected pupil aperture from the aperture storage unit and moves it to its use position in the pupil plane. The selection device further ensures that the last used pupil aperture is replaced with a newly selected pupil aperture. In this case, in particular, the last used pupil aperture can be returned from its use position to the aperture storage unit by the robotic actuation system.

[0022] The aperture, i.e., the aperture of the illumination pupil diaphragm and / or the imaging pupil diaphragm, may be variablely specified, for example, in the form of an iris diaphragm.

[0023] The measurement system may include a light source for illumination. This type of light source may be configured as an EUV light source.

[0024] The EUV wavelength of the light source may be in the range of 5 nm to 30 nm. Light sources in the DUV wavelength range, such as a light source of about 193 nm, are also possible.

[0025] Hereinafter, exemplary embodiments of the present invention will be described in more detail with reference to the drawings. [Brief explanation of the drawing]

[0026] [Figure 1] This is a very schematic side view of a measurement system for simulating the illumination and imaging characteristics of an optical production system when illuminating and imaging an object. The measurement system comprises an illumination optical unit and an imaging optical unit, both of which are shown in a very schematic manner in their respective cases. [Figure 2A-2D] This figure shows different deformation modes of the pupil diaphragm of a measurement system that can be placed in the area of ​​the illumination pupil of an illumination optical unit. [Figure 3A-3D] This figure shows different deformation modes of the pupil diaphragm of a measurement system that can be placed in the area of ​​the illumination pupil of an illumination optical unit. [Figure 4A-4D] This figure shows different deformation modes of the pupil diaphragm of a measurement system that can be placed in the area of ​​the illumination pupil of an illumination optical unit. [Figures 5A-5D] This figure shows different deformation modes of the pupil diaphragm of a measurement system that can be placed in the area of ​​the illumination pupil of an illumination optical unit. [Figures 6A-6D] This figure shows different deformation modes of the pupil diaphragm of a measurement system that can be placed in the area of ​​the illumination pupil of an illumination optical unit. [Figures 7A-7D] This figure shows different deformation modes of the pupil diaphragm of a measurement system that can be placed in the area of ​​the illumination pupil of an illumination optical unit. [Figures 8A-8D] This figure shows different deformation modes of the pupil diaphragm of a measurement system that can be placed in the area of ​​the illumination pupil of an illumination optical unit. [Figures 9A-9D]This figure shows different deformation modes of the pupil diaphragm of a measurement system that can be placed in the area of ​​the illumination pupil of an illumination optical unit. [Figure 10] This figure shows an example of the lighting settings for the optical production system being simulated. The lighting settings are represented by the intensity distribution across the entire surface of the illuminated pupil within the pupil plane of the optical production system. [Figure 11A-11I] This figure shows one embodiment of the measurement position sequence for one of the pupil diaphragms shown in Figures 2 to 9, using the pupil diaphragm example shown in Figure 2B. This measurement position sequence is a method performed by a measurement system and is used in a method for simulating the illumination and imaging characteristics of an optical production system when illuminating and imaging an object using the optical measurement system of the measurement system. [Figures 12A-12F] This figure shows another embodiment of the measurement position sequence for the pupil diaphragm of the measurement system, expressed in a similar manner to that in Figures 11A to 11I. [Figure 13A-13I] This figure shows another embodiment of the measurement position sequence for the pupil diaphragm of the measurement system, expressed in a similar manner to that in Figures 11A to 11I. [Figure 14A-14C] This figure shows another embodiment of the measurement position sequence for the pupil diaphragm of the measurement system, expressed in a similar manner to that in Figures 11A to 11I. [Figure 15] This figure shows a comparison, in pupil coordinate representation, between the target lighting settings of the production system intended to be approximated by the measurement system pupil diaphragm and a candidate pupil diaphragm using an example of a measurement system pupil diaphragm corresponding to the pupil diaphragm shown in Figure 7A. This comparison is part of an algorithm for selecting at least one measurement system pupil diaphragm from a given set of pupil diaphragms. [Figure 16] Figure 1 is a plan view of the periodic binary test structure placed in XVI of the measurement system. [Figure 17] This figure shows the field distribution of the electromagnetic field of the illumination light at point XVII in Figure 1, along the illumination light beam path, after irradiation of the test structure, similar to the plan view in Figure 16. [Figure 18]The diffraction spectrum of the test structure at point XVIII in Figure 1, along the illumination light beam path, is shown in a plan view, also as shown in Figure 16. [Figure 19] This figure shows the diffraction spectrum reduced at the edge by the aperture diaphragm of the measurement system, in the same representation as in Figure 18, where the aperture diaphragm is located at XIX in Figure 1. [Figure 20] This figure shows the diffraction spectrum, including wavefront effects, as indicated by contour lines from the imaging optical unit of the measurement system, as the spectrum measured in the region of the exit pupil of the imaging optical unit XX in Figure 1, in the same representation as in Figure 19. [Figure 21] The complex field distribution of the illumination light at XXI in Figure 1 on the imaging light beam path after irradiation by the spatially resolved detection device of the measurement system is shown in a plan view similar to Figure 17. [Figure 22] This figure shows the illumination light intensity measured by the detector at the location of the detector XXII in Figure 1, in the same format as in Figure 21. [Modes for carrying out the invention]

[0027] To facilitate the representation of positional relationships, we will use the Cartesian xyz coordinate system from now on. In Figure 1, the x-axis extends perpendicularly into the drawing plane. The y-axis extends to the left in Figure 1. The z-axis extends vertically upward in Figure 1.

[0028] In the diagram corresponding to the longitudinal section, Figure 1 shows the beam path of EUV illumination light or imaging light 1 within the measurement system 2 for simulating the illumination and imaging characteristics of the optical production system when illuminating and imaging an object, using the optical measurement system of the measurement system 2. In this case, a test structure 5 placed in the object field 3 of the object plane 4 is imaged.

[0029] An example of the test structure 5 is shown in the plan view of Figure 16. The test structure 5 is periodic in one dimension, specifically, for example, along the y-coordinate. The test structure 5 is implemented as a binary test structure having an absorption line 6 and a multilayer line 7 that reflects illumination light 1, which are alternately arranged in each case. Lines 6 and 7 are vertical structures, for example, vertical structures extending along the y-direction.

[0030] Measurement system 2 is used to analyze three-dimensional (3D) aerial images (aerial image measurement system). One application is to simulate the aerial image of a lithography mask in a manner that would also appear within the optical production system of a production projection exposure apparatus, for example, within the scanning device. To this end, the imaging quality of measurement system 2 itself can be measured and optionally adjusted. As a result, the analysis of the aerial image can be used to determine the imaging quality of the projection optical unit of measurement system 2, or otherwise, in particular, the imaging quality of the projection optical unit within the projection exposure apparatus. The measurement system is known from International Publication No. 2016 / 012426, U.S. Patent Application Publication No. 2013 / 0063716 (see Figure 3 in the same document), German Patent Application Publication No. 10220815 (see Figure 9 in the same document), German Patent Application Publication No. 10220816 (see Figure 2 in the same document), and U.S. Patent Application Publication No. 2013 / 0083321.

[0031] Illumination light 1 is reflected and diffracted by the test structure 5. In the case of central initial illumination, the incident plane of illumination light 1 is parallel to the yz plane.

[0032] The EUV illumination light 1 is generated by the EUV light source 8. The light source 8 can be a laser-produced plasma (LPP) or a discharge-produced plasma (DPP). In principle, a synchrotron-based light source, such as a free electron laser (FEL), can also be used. The wavelength used for the EUV light source can be in the range of 5 nm to 30 nm. In principle, in one variant of the measurement system 2, a light source with a different wavelength, such as a light source with a wavelength of 193 nm, can also be used instead of the light source 8.

[0033] The illumination optical unit 9 of the measurement system 2 is positioned between the light source 8 and the test structure 5. The illumination optical unit 9 illuminates the test structure 5 under inspection using a predetermined illumination intensity distribution across the entire object field 3, and simultaneously using a predetermined illumination angle distribution that illuminates field points of the object field 3. Such an illumination angle distribution is also called an illumination setting.

[0034] The illumination angle distribution of each illumination light 1 is specified through a pupil diaphragm 10 positioned on the pupil plane 11 of the illumination optical unit. The pupil diaphragm 10 is also called a sigma diaphragm.

[0035] Figures 2A to 9B show possible embodiments of such pupil diaphragms 10, and these embodiments can be used as substitutes within the illumination optical unit 9 of the measurement system 2 to specify illumination settings. Components and functions corresponding to those already described in the preceding figures will not be discussed again in detail in the subsequent figures. Where applicable, such components and functions are indicated using the same reference numerals in the subsequent figures.

[0036] Figure 2A shows a pupil diaphragm 10 having a single central passing pole I. The radius of this passing pole I is approximately one-quarter of the diameter of the peripheral aperture diaphragm portion 14 of the pupil diaphragm 10. A central illumination angle for an object field 3 with relatively small angular variation is selected through the pupil diaphragm 10 as shown in Figure 2A.

[0037] Other variations of the pupil diaphragm 10 having a central passing pole I with a gradually increasing radius are shown in Figures 2B to 2D. When using the pupil diaphragm 10 according to Figures 2D, the variation in object field illumination angle increases accordingly. The pupil diaphragm 10 according to Figure 2D provides a conventional illumination setting in which light can pass through the pupil plane 11 of the illumination optical unit of the measurement system 2 without substantially obstruction.

[0038] Figure 3A shows a modified form of the pupil diaphragm 10 having a ring-shaped passing portion I arranged around a round central obscuration diaphragm portion 12. The inner diameter of the ring-shaped passing portion I of the pupil diaphragm in Figure 3A is approximately the same size as the outer diameter of the illumination pole I of the pupil diaphragm 10 in Figure 2A. The outer diameter of the ring-shaped passing portion I of the pupil diaphragm 10 in Figure 3A is approximately twice this size.

[0039] Figure 3B shows the deformation of the pupil diaphragm 10, and in comparison with Figure 2A, the outer diameter of the ring-shaped passing pole I is approximately 2.5 times its inner diameter. The central occlusion diaphragm portion 10 of the pupil diaphragm 10 in Figure 3B is the same size as the central occlusion diaphragm portion of the pupil diaphragm 10 in Figure 3A.

[0040] Figure 3C shows a modified form of the pupil diaphragm 10 having a ring-shaped passing pole I, which has an inner diameter that is approximately twice the size of the inner diameters in Figures 3A and 3B, and an outer diameter that is only slightly larger than the outer diameter of the passing pole I shown in Figure 3B. This results in a correspondingly large central occluding diaphragm portion 12.

[0041] Figure 3D shows an illumination pupil 10 having a ring-shaped illumination pole I whose ring-shaped thickness is approximately the same as that of the embodiment shown in Figure 3C. In the embodiment shown in Figure 3D, the diameter of the ring-shaped illumination pole I is maximized, and as a result, only a relatively narrow aperture diaphragm portion 14 remains on the edge side. This results in a considerably larger central occluding diaphragm portion 12, and the central occluding diaphragm portion 12 in the embodiment shown in Figure 3D is larger than the central occluding diaphragm portion 12 in the embodiment shown in Figure 3C.

[0042] By using the embodiments of the pupil diaphragm 10 shown in Figures 3A to 3D, the corresponding annular illumination settings can be achieved.

[0043] Figure 4A shows a bipolar pupil diaphragm 10 implemented as a x2 bipolar. The two poles I and II are round in each case and have diameters in each case that coincide with the diameter of pole I passing through the center of the pupil diaphragm 10 according to Figure 2A.

[0044] Figure 4B shows a bipolar pupil diaphragm 10 implemented as a y2 bipolar having poles I and II, where poles I and II are consistent with poles I and II of the embodiment according to Figure 4A in terms of their shape and size. The pupil diaphragm 10 according to Figure 4B can be produced by rotating the pupil diaphragm 10 according to Figure 4A by 90° around an axis parallel to the z-axis.

[0045] Figure 4C shows another embodiment of the x2 dipole pupil diaphragm 10 having passing poles I and II, which have a rectangular configuration with an x / y aspect ratio of approximately 1 / 4.

[0046] Figure 4D shows the y2 double polar pupil diaphragm 10 corresponding to the x2 double polar pupil diaphragm 10 in Figure 4C.

[0047] Next, Figure 5A shows a x2 double polar pupil diaphragm 10 in which each of the opened poles I and II has a circumferential spread of approximately 90°. In this case as well, the central occluding diaphragm portion 12 is located between the two passing poles I and II.

[0048] Next, Figure 5B shows the y2 double polar pupil diaphragm 10, which corresponds to the x2 double polar pupil diaphragm 10 shown in Figure 5A.

[0049] Figure 5C shows the x2 double polar pupil diaphragm 10 in which each pole I and II are implemented as lobular shapes, i.e., each having a biconvex shape.

[0050] Figure 5D shows the y2 double polar pupil diaphragm 10 corresponding to the x2 double polar pupil diaphragm 10 in Figure 5C.

[0051] Figure 6A shows one embodiment of a quadrupole pupil diaphragm 10 having four round passing poles I, II, III, and IV arranged within a quadrant. The diameters of these passing poles I to IV are the same as the diameter of passing pole I of the pupil diaphragm 10 in Figure 2A.

[0052] Figure 6B shows a modified form of the pupil diaphragm 10 that can be generated from the modified form shown in Figure 6A by twisting it 45° around an axis parallel to the z-axis. In this modified form, the four poles I to IV are therefore arranged as a superposition of the x² dipole pupil diaphragm and the y² dipole pupil diaphragm as shown in Figures 4A and 4B.

[0053] Figure 6C shows a variation of the corresponding quadrupole pupil diaphragm 10, which also has square passing poles I to IV arranged within a quadrant.

[0054] Next, Figure 6D shows the configuration corresponding to Figure 6B, but compared to Figure 6C, the square passing poles I to IV are rotated by 45°.

[0055] Figure 7A shows a modified form of a quadrupole pupil diaphragm 10 having sector-type poles I to IV arranged within a quadrant, each having a circumferential spread of approximately 45°. Similarly, the connecting pieces 13 between adjacent passing poles I to IV of the pupil diaphragm 10 in Figure 7A also have a circumferential spread of approximately 45° in each case. In this case as well, the central occluding diaphragm portion 12 is located at the center of the pupil diaphragm 10 in Figure 7A.

[0056] Figure 7B shows a quadrupole pupil diaphragm 10 corresponding to the embodiment in Figure 7A, which can be generated by rotating it 45° around an axis parallel to the x-axis.

[0057] Figure 7C shows a modified form of the quadrupole pupil diaphragm 10 having lobular-shaped passing poles I to IV arranged on the edge side near the opening diaphragm portion 14 along the circumferential direction around the diaphragm center.

[0058] Figure 7D shows a deformed quadrupole pupil corresponding to the deformed form shown in Figure 7C, which can be generated by rotating it 45° around an axis parallel to the z-axis.

[0059] Figure 8A shows a sextupole pupil diaphragm 10 with six round passing poles I-VI arranged to be uniformly distributed circumferentially around the aperture center. The diameters of poles I-VI are the same as the diameter of passing pole I of the pupil diaphragm 10 in Figure 2A. The distance between two adjacent poles I-VI is approximately 1 / 3 of the pole diameter.

[0060] Measuring from the x-coordinate of the pupil diaphragm 10 in Figure 8A, the six poles are located at 30°, 90°, 150°, 210°, 270°, and 330°.

[0061] Figure 8B shows a modified form of the sextupole pupil diaphragm 10 that is identical to the sextupole pupil diaphragm 10 in Figure 8A, except that the contours of the edges of the passing poles I to VI are square, in the embodiment shown in Figure 8B.

[0062] Figure 8C shows a modified form of the sextupole pupil diaphragm 10 that is identical to the sextupole pupil diaphragm 10 in Figure 8A, except that the contours of the edges of the passing poles I to VI are of the fan type. The circumferential spread of the fan-type passing poles I to VI is approximately 30°, which in each case corresponds to the circumferential spread of the connecting piece between adjacent passing poles I to VI.

[0063] Figure 8D shows a modified form of the sextupole pupil diaphragm 10 that matches the sextupole pupil diaphragm 10 in Figure 8A, except that the contours of the edges of the passing poles I to VI are approximately triangular on the edge side near the aperture diaphragm portion 14, in the embodiment shown in Figure 8D.

[0064] Figure 9A shows a modified form of the hexapole pupil diaphragm 10 that can be generated from the modified form shown in Figure 8A by rotating it 30° around an axis parallel to the z-axis.

[0065] Figure 9B shows a deformed form of the hexapole pupil diaphragm 10 that can be generated from the deformed form shown in Figure 8B by rotating it 30° around an axis parallel to the z-axis.

[0066] Figure 9C shows a modified form of the hexapole pupil diaphragm 10 that can be generated from the modified form shown in Figure 8C by rotating it 30° around an axis parallel to the z-axis.

[0067] Figure 9D shows a deformed form of the hexapole pupil diaphragm 10 that can be generated from the deformed form shown in Figure 8D by rotating it 30° around an axis parallel to the z-axis.

[0068] The pupil diaphragm 10 of the illumination optical unit 9 is implemented as a drive-displaceable diaphragm positioned in front of the object plane 4 on the illumination light beam path 15 of the illumination light 1. A drive unit used to drive the pupil diaphragm 10 is shown in Figure 16. The drive unit 16, also called a displacement drive, can displace this pupil diaphragm along the x and / or y coordinates. Through the drive unit 16, fine adjustments along the z coordinate are also possible to adjust the alignment of the position plane of the pupil diaphragm 10 with respect to the pupil plane 11 of the illumination optical unit. Furthermore, the drive unit 16 can also be designed to allow the diaphragm to be tilted around at least one tilt axis parallel to the x axis and / or parallel to the y axis. In addition, the diameters of the occluding diaphragm portion 12 and / or the opening diaphragm portion 14, and / or the sizes of poles I;I, II;I, II, III, IV;I, II, III, IV, V, VI of each embodiment of the pupil diaphragm 10 may be specified in a configurable manner, particularly in a configurable driven manner.

[0069] With the help of the displacement drive device 16, the selected pupil diaphragm 10 is moved within the pupil plane 11, at pupil coordinate k x and k y It is possible to displace it along the line.

[0070] The displacement drive device 16 may further include an aperture exchange unit that thereby exchanges a particular pupil diaphragm 10 for another particular pupil diaphragm 10. To this end, the aperture exchange unit may take each selected pupil diaphragm out of the aperture storage unit and return the exchanged diaphragm to the aperture storage unit.

[0071] The test structure 5 is held by the object holder 17 of the measurement system 2. The object holder 17 works in cooperation with the object displacement drive device 18 to displace the test structure 5, particularly along the z-coordinate.

[0072] After reflection by the test structure 5, the electromagnetic field of the illumination light 1 has a distribution 19 shown in the plan view of Figure 18, which corresponds to the plan view of Figure 17. In the field distribution 19, the amplitude and phase values ​​correspond to the absorption lines 6 and multilayer lines 7 of the test structure 5.

[0073] The illumination light 1 reflected by the test structure 5 enters the imaging optical unit or projection optical unit 20 of the measurement system 2.

[0074] Due to the periodicity of the test structure 5, a diffraction spectrum 21 is generated within the pupil plane of the projection optical unit 20 (see Figure 18).

[0075] In diffraction spectrum 21, the zero-order diffraction of test structure 5 is central. Furthermore, Figure 18 also shows the + / -1st-order and + / -2nd-order diffractions of diffraction spectrum 21.

[0076] The diffraction of multiple orders of the diffraction spectrum 21 shown in Figure 18 appears in this form on the pupil plane of the optical system of the measurement system 2, for example, the entrance pupil plane 22 of the projection optical unit 20. The aperture diaphragm 23 of the projection optical unit 20 is located on this entrance pupil plane 22, defining the edge boundary of the entrance pupil 24 of the projection optical unit 20. The aperture diaphragm 23 is also called the imaging pupil diaphragm of the measurement system 2.

[0077] The imaging pupil diaphragm 23 is operably connected to a displacement drive device 25, the function of which corresponds to the function of the displacement drive device 16 for the sigma diaphragm 10.

[0078] Figure 19 shows the entrance pupil 24 and the three orders of diffraction, specifically the 0th and + / -1st order diffractions, of the diffraction spectrum 21 located within the entrance pupil 24 in the initial illumination angle distribution.

[0079] Figure 20 shows the intensity distribution of illumination / imaging light 1 in the exit pupil plane of the projection optical unit 20. The exit pupil 26 shown in Figure 21 is formed as the image of the entrance pupil 24.

[0080] The pupils 24 (see Figure 19) and 26 (see Figure 20) are elliptical. In alternative specifications, the pupils 22 and 24 may have different deviations from circular through a suitable aperture diaphragm 21, and these pupils may be at least substantially circular. The pupil radius can be calculated as the average radius. For example, such alternative pupils may have elliptical embodiments in which the aspect ratio between semi-axises is in the range of 1 to, for example, 3. In embodiments not shown herein, the pupils 24 and 26 may be circular.

[0081] Firstly, the images of the -1st, 0th, and +1st order diffractions, and secondly, the imaging contribution of the optical system, specifically the projection optical unit 20, contribute to the intensity distribution in the exit pupil 26. This imaging contribution, revealed by the dashed contour lines in Figure 20, can be explained by the optical system transfer function, which will be described later. Due to the unavoidable imaging aberration of the optical system, measurable intensities of the illumination / imaging light 1 exist within the exit pupil 26, even in the regions surrounding the diffractions of multiple orders.

[0082] The projection optics unit 20 forms an image of the test structure 5 toward the spatial resolution detection device 27 of the measurement system 2. The detection device 27 takes the form of a camera, particularly a CCD camera or a CMOS camera.

[0083] The projection optical unit 20 is implemented as a magnification optical unit. The magnification of the projection optical unit 20 may be greater than 10, greater than 50, greater than 100, or even greater. Generally, this magnification is less than 1000.

[0084] In a manner corresponding to Figure 18, Figure 21 shows the complex field distribution 28 of the illumination / imaging light 1 in the region where the detection device 27 of the image plane 29 is located.

[0085] Figure 22 shows the intensity distribution 31 of illumination / imaging light 1 measured by the camera 27 within the image field 30 of the image plane 29. The images of absorption lines 6 exist as substantially low-intensity dark lines 32 in the intensity distribution 31, and the images of multilayer lines 7 exist as higher-intensity bright lines 33 in the intensity distribution 31.

[0086] To simulate the illumination and imaging characteristics of an optical production system when illuminating and imaging an object, using the example of a test structure 5, by the optical measurement system 1 of the measurement system 2, the following procedure is performed. First, to specify correspondingly different measurement illumination settings, multiple pupil diaphragms 10 having different aperture boundary shapes for each case are provided. This is done by providing the pupil diaphragms 10, for example, in the form of the pupil diaphragms 10 shown in Figures 2A to 9D, in an aperture storage unit accessible to an aperture exchange unit which may be part of the displacement drive unit 16.

[0087] Next, a target pupil diaphragm is specified, having a target aperture boundary shape derived from the lighting settings of the optical production system to be simulated. The target pupil diaphragm can be an arrangement of multiple or many individual pupil spots or aperture spots. In this case, the intensity of each lighting spot or pupil spot generally differs from one spot to the other.

[0088] Figure 10 shows a first example of the illumination setting for the optical production system to be simulated. This production illumination setting in the pupil plane of the illumination optics unit of the optical production system is provided through a fly-eye integrator having a field facet mirror and a pupil facet mirror, and includes a plurality of intensity spots 34 arranged in a grid within the illumination pupil plane 35 of the production illumination optics unit. The intensity spots 34 may have different intensities, so that illumination light from different illumination directions may be incident on the object field 3 with correspondingly different intensities.

[0089] Similarly, in Figure 15, the pupil coordinate k x ,k yThis shows a target pupil diaphragm 36 in the pupil plane, and the target diaphragm boundary shape of the target pupil diaphragm is specified in a manner that depends on the lighting settings of the optical production system being simulated, for example, in a manner that depends on the lighting settings shown in Figure 10.

[0090] The target pupil diaphragm 36 can be specified by defining a suitable aperture contour, in particular, a continuous aperture contour. Such an aperture contour can be described, for example, by a chain of polygons.

[0091] Next, these continuous openings are approximated by a finite number of pupil spots 37 within the openings. Figure 15 shows examples of these spots.

[0092] In this particular example in Figure 15, the aperture contour in Figure 7A was used as the measurement aperture, and the aperture contour in Figure 5A was used as the target setting. The finer the grid of the illumination spot, the more accurately the actual aperture shape can be approximated.

[0093] Figure 15 shows the grid of pupil spots 37 (stars in Figure 15) positioned within a designated target pupil diaphragm 36. This grid arrangement of pupil spots 37 can account for shadowing, particularly shadowing resulting from the required web of the pupil diaphragm.

[0094] Next, an algorithm that determines the deviation between the aperture boundary shape of each provided pupil diaphragm 10 and the target aperture boundary shape of the target pupil diaphragm 36 selects at least one pupil diaphragm 10 from the provided pupil diaphragms 10 that originates from this target pupil diaphragm 36. To this end, the pupil diaphragm 10 currently under inspection (also referred to as the pupil diaphragm to be determined later) can be decomposed into a plurality of pupil spots 38 arranged in a grid pattern represented by the circles in Figure 15 within its aperture boundary.

[0095] The scope of the assessment includes determining the similarity between the target illumination pupil (sometimes referred to as "T" below) and the possible measuring aperture 10 (sometimes referred to as "M" below). For example, this can be done by calculating the overlap function Q.

[0096]

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[0097] The operators "∩", "∪", and "\" correspond to the set theory operators for intersection (∩), union (∪), and relative complement (\). In this case, the intersection of sets / areas M1 and M2, M1∩M2, is intended to represent a set / area that is included in both M1 and M2, i.e., it corresponds to the overlapping area of ​​M1 and M2. The union of sets / areas M1 and M2, M1∪M2, describes a set / area that is included in either M1 or M2, i.e., it corresponds to the total area covered by either M1 or M2. The relative complement of sets / areas M1 and M2, M1\M2, describes a set / area that is covered by M1 but not included in M2.

[0098] For example, the area function A can be implemented as counting the illumination spots within the pupil. To do this, the target illumination pupil and the measurement pupil include the same grid. Usually, this grid corresponds to the pupil facet grid within the scanning device that samples the target illumination pupil thereon (see FIG. 10). Next, the number of spots present in both illumination pupils (the first term in the above formula) is counted, and similarly, the spots limited to only one of the two pupils (the second and third terms in the above formula) are counted. As an alternative to this, a comparison of the local spot density or the average local luminance can also be considered.

[0099] Therefore, the selection of the pupil aperture 10 involves a comparison between the pose of the pupil spot 37 of the target aperture boundary shape and the pose of the pupil spot 38 of the provided pupil aperture 10.

[0100] Furthermore, a plurality of defocus values z m (see FIG. 1) are specified as the z - distance of the position of the object holder 17 from the object plane 4 (parallel to the xy - plane).

[0101] Furthermore, a plurality of measurement positions (k x , k y ) of the selected pupil aperture 10 are specified within the scope of this simulation method.

[0102] Next, for each of the plurality of combinations of the specified defocus value z m and the measurement positions (k x , k y ) of the selected pupil aperture 10, the measured aerial image I(x, y) in the style of the intensity distribution 31 according to FIG. 22 is recorded in the image plane 29. This recording is performed for all positions of the object holder 17 assigned to the previously specified defocus value z m . To perform each recording of the measured aerial image I(x, y), for at least one defocus value z m among the specified defocus values z m , through the displacement drive device 16, a plurality of measurement positions (k x , k y ) of the selected pupil aperture 10 are targeted.

[0103] The sequence in Figures 11A to 11I represents a single defocus value z m and a total of 9 measurement positions (k x ,k y This shows the combination of the above, and here, to specify the conventional lighting setting, the pupil diaphragm 10 shown in Figure 2B was selected. The position of the passing pole I of the pupil diaphragm 10 relative to the position of the imaging pupil diaphragm 23 in each case is shown.

[0104] Figure 11A shows the pupil diaphragm 10 located at the center of the imaging pupil diaphragm 23. In this starting position shown in Figure 11A, the pupil diaphragm 10 is imaged at the center of the aperture of the imaging pupil diaphragm 23.

[0105] In comparison with the imaging pupil diaphragm 23, Figure 11B shows the positive k from the center position shown in Figure 11A. x This shows the pupil diaphragm 10 displaced by the specified increment in the direction.

[0106] In comparison with the center position shown in Figure 11A, the subsequent sequence of Figures 11C to 11I shows other displacements of the pupil diaphragm 10, starting from the position shown in Figure 11B and displaced 45° circumferentially in each case. Therefore, the measurement positions in Figures 11C, 11E, 11G, and 11I show the pupil diaphragm 10 at the positions of the four quadrants I to IV. The measurement positions in Figures 11B, 11D, 11F, and 11H are the Cartesian displacement position + k x , +k y , -k x , -k y This indicates pupil diaphragm 10.

[0107] Measurement position of pupil diaphragm 10 (k x ,k y Alternative sequences for ) are shown in Figures 12A to 12F. This sequence for measurement positions 12A to 12F corresponds to the measurement positions shown in Figures 11D, 11E, 11C, 11G, 11I, and 11H.

[0108] Figures 13A to 13I show the measurement position (k) of the pupil diaphragm 10. x ,k y This shows other variations of the sequence.

[0109] Figure 13A shows the pupil diaphragm 10, which is also located at the center of the imaging pupil diaphragm 23. In comparison with the imaging pupil diaphragm 23, Figure 13B shows the position of the pupil diaphragm 10 at a positive k from the center position shown in Figure 13A. x This shows the pupil diaphragm 10 displaced by the specified increment in the direction.

[0110] With respect to the imaging pupil diaphragm 23, Figure 13C shows the positive k from the center position shown in Figure 13. y This shows the pupil diaphragm 10 displaced by the same increment in each direction.

[0111] With respect to the imaging pupil diaphragm 23, Figure 13D shows a negative k starting from the central position shown in Figure 13A. x This shows the pupil diaphragm 10 displaced by the same increment in each direction.

[0112] With respect to the imaging pupil diaphragm 23, Figure 13E shows a negative k starting from the central position shown in Figure 13A. y This shows the pupil diaphragm 10 displaced by a given increment in the direction.

[0113] Measurement position (k x ,k y The completed sequence is shown in Figures 13F to 13I. The circumferential position of the pupil diaphragm 10 relative to the imaging pupil diaphragm 23 corresponds to the position shown in Figures 11C, 11E, 11G, and 11I. In contrast to these positions, the pupil diaphragm 10 in the sequence shown in Figures 13F to 13I is pushed radially outside the opening of the imaging pupil diaphragm 23, yet only the inner portion of the passing spot I of the pupil diaphragm 10 overlaps with the opening of the imaging pupil diaphragm 23. In this case, the illumination light can traverse an area slightly more than half the area of ​​the passing spot I. This gives the completed sequence shown in Figures 13A to 13I, which has two displacement radii.

[0114] Figures 14A to 14C show the measurement position (k) of the pupil diaphragm 10. x ,ky This shows other variations of the sequence. The measurement positions shown in Figures 14A to 14C correspond to the measurement positions shown in Figures 11B, 11E, and 11G.

[0115] The selection of each measurement position sequence, or optionally a subset thereof, is carried out based on the arrangement of the individual structures of the test structure 5 and / or the lighting settings of the optical production system to be simulated. For example, the measurement position sequence can be selected in a manner similar to the aperture selection algorithm (see above), taking into account all aperture positions in the sequence and selecting the sequence that maximizes the overlap between the measurement sequence and the target illumination pupil.

[0116] A pose of the pupil diaphragm 10 that differs from the central position relative to the imaging pupil diaphragm 23 is also called an offset measurement position. Within the range of the measurement position sequence, 2 to 10 such offset measurement positions can be targeted, which is typically 2 to 5 offset measurement positions, for example, 3 or 4 offset measurement positions. The offset measurement positions can be distributed uniformly in the circumferential direction. To reduce measurement time, it is also possible to use only a subset of the shown measurement plan (Figures 11 to 14), for example, by using every other measurement position.

[0117] The specified defocus value z m All of these are measured with the help of their respective measurement position sequences. In alternative embodiments, only one defocus value, or individual defocus values ​​z m For this only, it is possible to use the entire sequence of each measurement position, and for other defocus values ​​z m In this case, the measured aerial image is recorded for a smaller number of measurement positions of the pupil diaphragm relative to the imaging pupil diaphragm 23. In extreme cases, for example, the entire measurement position sequence is taken up, and one defocus value z m It is possible to record each measured aerial image only for that, while other specified defocus values ​​z mIn this case, the measured aerial image I is obtained at each individual measurement position, particularly in the case of the centrally located pupil diaphragm 10. meas Only (x,y) is recorded.

[0118] For example, the following combinations of defocus value / measurement position, namely the central defocus value z m And, multiple measurement positions of the pupil diaphragm 10 (k x ,k y ), that is, in particular, the combination of the central measurement position and multiple offset measurement positions, and the defocus value z that is offset to the maximum extent on both sides from the central defocus value. min , z max And these positions z min , z max The precisely single central measurement position (k) of the pupil diaphragm 10 adopted in this method x ,k y ) can be recorded as a combination.

[0119] Next, the complex mask transfer function is reconstructed from the entire measured aerial image recorded using the selected pupil diaphragm 10. A similar reconstruction step is also described in German Patent Application Publication No. 102019215800.

[0120] This reconstruction is carried out within the scope of the modeled description, within which the projection optical unit 20 of the measurement system 2, having the illumination settings specified by the pupil diaphragm 10, is in the illumination direction passing through the pupil diaphragm 10.

[0121]

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[0122] Each illumination direction, as a result of its interaction with the test structure 5, exhibits a complex-valued field distribution in the object plane (4).

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[0124]

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[0125] The objective here is to mask spectrum

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[0126] Using the reconfigured spectrum, you can adjust any other lighting settings.

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[0127] As an optimization problem

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[0128] Lighting direction

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[0129] The simplest solution is the Hopkins approximation, which assumes that the spectrum displaces by the same amount in the case of a displacement in the direction of illumination. That is,

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[0130] Spectrum and illumination direction

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[0131] in this case,

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[0132] As an example, the following function

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[0133] Within the range of reconstruction of the complex mask transfer function M, the mask spectrum depends on the illumination direction.

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[0134] Next, we create a mask spectrum that minimizes the difference between the measured aerial image and the simulated aerial image.

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[0135] Thus, with respect to the Hopkins approximation, the number of free parameters increases by only N, and N is usually small.

[0136] Using this direction-dependent reconstructed spectrum, the target illumination setting σ target and target defocus z target Simulated aerial image I sim It is possible to calculate this.

[0137]

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[0138] Next, equation (6) is given by the simulated aerial image I sim and the measured aerial images I meas This allows for comparison between the two, and this can be used to reconstruct the mask spectrum M, and therefore the complex mask transfer function.

[0139] From equation (6), the reconstructed mask transfer function M and the illumination setting σ of the optical production system are obtained. target With the help of this, a 3D aerial image can be calculated. In this way, it is possible to determine what the aerial image of the test structure 5 resembles when it is imaged by the optical production system.

[0140] In this modified version of the simulation method, multiple different pupil diaphragms 10 are used to measure various measurement positions (k x ,k y It is also possible to specify ).

[0141] To prepare for this simulation method, it is possible to record an aerial image stack to determine which z-pose of object plane 4 best provides a sharp image within the image plane 29 (the zero z-pose).

[0142] Aerial image I sim The z increment used in equation (6) when determining the defocus value z is the defocus value specified within the range of this simulation method. m It may be different from that.

[0143] To match the desired pixel resolution, recorded measurement aerial image I meas The pixel size may be resampled.

[0144] In the simulation method, multiple k values ​​of the imaging pupil diaphragm 23 x ,k y The position can also be set via the displacement drive device 25.

[0145] Therefore, when reconstructing the mask transfer function, it is possible to take into account the imaging aberrations of the optical measurement system, particularly the imaging aberrations of the imaging optical unit 20 of the measurement system 2.

[0146] 3D aerial image I meas Determination and / or simulated aerial image I sim The calculation may be performed using a different principal ray angle of illumination than the principal ray angle of illumination for the reconstruction of the mask transfer function.

[0147] To select each pupil aperture 10 from a plurality of pupil apertures 10 provided, each having a different aperture boundary shape and / or aperture boundary orientation in each case, the measurement system 2 has a selection device, which is not shown in detail in the drawings. This selection device has an aperture storage unit, which stores a plurality of pupil apertures 10, each having a different aperture boundary shape and / or aperture boundary orientation in each case to specify correspondingly different measurement illumination settings.

[0148] In the selection step of this simulation method, the last inserted pupil diaphragm is first removed from its use position in the pupil plane 11 and supplied to the diaphragm storage unit in the selection device with the help of the actuator system of the selection device, in particular with the help of the robotic actuator system. Subsequently, the pupil diaphragm 10 selected according to this simulation method is selected from the diaphragm storage unit and inserted into its use position in the pupil plane 11 with the help of the robotic actuator system.

Claims

1. A method for simulating the illumination and imaging characteristics of an optical production system during illumination and imaging of an object (5) using an optical measurement system of a measurement system (2), - The optical measurement system is an illumination optical unit (9) for illuminating the object (5), k x ,k y The illumination optical unit (9) has a pupil diaphragm (10) in the region of the illuminated pupil within the pupil plane (11), and the imaging optical unit (20) is used to form an image of the object (5) on the image plane (29). The aforementioned method involves the following steps, namely, - A step of providing multiple pupil diaphragms (10) to specify different measurement illumination settings, - Measured aerial image I in the image plane (29) by the plurality of pupil diaphragms (10) meas The steps include recording (x, y) and - The recorded aerial image of the measurement (I meas The steps include: ) to reconstruct the complex mask transfer function (M) from, - As a result of the simulation method, the reconstructed mask transfer function (M) and the illumination settings (σ) of the optical production system are obtained. target ) from the optical production system, 3D aerial image (I sim ) and Includes, - The 3D aerial image (I) of the optical production system sim ) is determined for different positions (z) of the object (5) perpendicular to the object plane, The optical measuring system is characterized by comprising a displacement drive device (16) for displacing the pupil diaphragm (10) in the kx and / or ky directions, and comprising an object holder (17) that can be displaced perpendicular to the xy object plane (4) by an actuator.

2. The method according to claim 1, characterized in that, in order to specify correspondingly different measurement illumination settings, the plurality of pupil diaphragms (10) each have different aperture boundary shapes and / or aperture boundary orientations in each case.

3. The above method further involves the following steps, namely, - Lighting settings of the optical production system (σ target The steps include specifying a target pupil aperture (36) having a target aperture boundary shape derived from ), - A step of selecting at least one pupil diaphragm (10) from among the plurality of pupil diaphragms by an algorithm that determines the deviation between the aperture boundary shape of each pupil diaphragm (10) and the target aperture boundary shape, - As the z distance of the object holder position from the xy object plane (4), a plurality of defocus values z m specifying step, and - Multiple measurement positions (k) of the selected at least one pupil diaphragm (10) x ,k y ) and the step of specifying The method according to claim 1, characterized by including the following:

4. The measured aerial image I meas (x, y) is the specified defocus value (z m ) and the specified measurement position (k) of the pupil diaphragm (10) x ,k y For each of the multiple combinations of ) the specified defocus value z m Recorded at all object holder positions assigned to the measurement, and the aerial image (I meas For each of the aforementioned records, the specified defocus value z m at least one of the defocus values ​​z m For a plurality of the specified measurement positions (k x ,k y The method according to claim 3, characterized in that the target is )

5. The specified measurement position (k) of the pupil diaphragm (10) x ,k y The method according to claim 3, characterized in that the measurement includes a central measurement position and a plurality of offset measurement positions surrounding the central measurement position.

6. The measured aerial image (I meas ) applies to at least the following defocus value / measurement position combinations, i.e., - Center defocus value (z m ) and the multiple measurement positions of the pupil diaphragm (k x ,k y ) in combination with, - The aforementioned center defocus value (z m The center defocus value (z) is offset to the maximum extent from ). m The defocus values ​​(z) on both sides of the xy object plane (4) that are perpendicular to the xy object plane (4) min , z max ) and the exact one measurement position (k) of the pupil diaphragm (10) at each of those positions x ,k y ) combination The method according to claim 3, characterized in that it is recorded for.

7. The method according to claim 3, characterized in that when selecting the pupil aperture (10), a comparison is made between the position of the pupil spot (37) of the target aperture boundary shape and the position of the pupil spot (38) of the provided pupil aperture (10).

8. A method for simulating the illumination and imaging characteristics of an optical production system during illumination and imaging of an object (5) using an optical measurement system of a measurement system (2), - The optical measurement system comprises an illumination optical unit (9) for illuminating the object (5), the illumination optical unit (9) having a pupil diaphragm (10) in the region of the illuminated pupil within the pupil plane (11), and an imaging optical unit (20) for forming an image of the object (5) on the image plane (29), The aforementioned method involves the following steps, namely, - A step of providing multiple pupil diaphragms (10) to specify different measurement illumination settings, - A step of recording the measured aerial image I meas (x, y) in the image plane (29) by the plurality of pupil diaphragms (10), - A step of reconstructing the complex mask transfer function (M) from the recorded measured aerial image (I meas), - As a result of the simulation method, the 3D aerial image (I sim) of the optical production system is determined from the reconstructed mask transfer function (M) and the lighting settings (σ target) of the optical production system. Includes, - The 3D aerial image (I sim) of the optical production system is determined for different positions (z) of the object (5) perpendicular to the object plane, During the reconstruction of the complex mask transfer function (M), the illumination direction [Math 1] A method characterized in that the mask spectrum, which depends on the illumination direction, is modeled as the product of the illumination direction-independent mask spectrum and the illumination direction-dependent correction function.

9. A method for simulating the illumination and imaging characteristics of an optical production system during illumination and imaging of an object (5) using an optical measurement system of a measurement system (2), - The optical measurement system comprises an illumination optical unit (9) for illuminating the object (5), the illumination optical unit (9) having a pupil diaphragm (10) in the region of the illuminated pupil within the pupil plane (11), and an imaging optical unit (20) for forming an image of the object (5) on the image plane (29), The aforementioned method involves the following steps, namely, - A step of providing multiple pupil diaphragms (10) to specify different measurement illumination settings, - A step of recording the measured aerial image I meas (x, y) in the image plane (29) by the plurality of pupil diaphragms (10), - A step of reconstructing the complex mask transfer function (M) from the recorded measured aerial image (I meas), - As a result of the simulation method, the 3D aerial image (I sim) of the optical production system is determined from the reconstructed mask transfer function (M) and the lighting settings (σ target) of the optical production system. Includes, - The 3D aerial image (I sim) of the optical production system is determined for different positions (z) of the object (5) perpendicular to the object plane, The optical measurement system includes an imaging pupil diaphragm (23) in the pupil region of the imaging optical unit (20), and a plurality of measurement positions of the imaging pupil diaphragm (23) are specified, and the measured aerial image (I meas A method characterized in that a plurality of specified measurement positions of the imaging pupil diaphragm (23) are set when recording the image.

10. The method according to claim 1 or 2, characterized in that the imaging aberration of the optical measurement system is taken into consideration when reconstructing the mask transfer function (M).

11. Said 3D aerial image (I sim The method according to claim 1 or 2, characterized in that the is determined using a principal illumination ray angle different from the principal illumination ray angle used in the reconstruction of the mask transfer function (M).

12. A measuring system (2) for carrying out the method according to claim 1 or 2, - The optical measurement system is an illumination optical unit (9) for illuminating the object (5), k x ,k y The illumination optical unit (9) has a pupil diaphragm (10) in the region of the illuminated pupil within the pupil plane (11), and the imaging optical unit (20) is used to form an image of the object (5) on the image plane (29). Measurement system (2).

13. - The optical measuring system controls the pupil diaphragm (10) x and / or k y It is equipped with a displacement drive device (16) for displacing in the direction, - The optical measurement system includes an object holder (17) that can be displaced perpendicular to the xy object plane (4) by an actuator. The measurement system according to claim 12.

14. The optical measurement system uses an imaging pupil diaphragm (23) positioned in the pupil region of the imaging optical unit (20) x and / or k y The measurement system according to claim 12, characterized by comprising a displacement drive device (25) for displacing in a direction.

15. A selection device for selecting at least one pupil diaphragm from a plurality of pupil diaphragms, the selection device comprising a diaphragm storage unit including a plurality of pupil diaphragms (10), wherein the plurality of pupil diaphragms (10) each have a different diaphragm boundary shape and / or diaphragm boundary orientation in order to specify correspondingly different measurement illumination settings, the measurement system according to claim 12.

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