Method for replicating the illumination and imaging properties of an optical production system when illuminating and imaging an object using an optical measuring system

Abstract

Method for replicating the illumination and imaging properties of an optical production system when illuminating and imaging an object (5), wherein the replicating is carried out using an optical measuring system of a metrology system (2), - where the optical measuring system -- a lighting optic (9) for illuminating the object (5) --- with a pupillary diaphragm (10) of the illumination optics (9) in the area of ​​an illumination pupil in a pupillary plane (11) and -- has an imaging optic (20) for imaging the object (5) onto an image plane (29), - wherein the object (5) can be moved perpendicular to an object plane (4) by the following steps: - Providing at least one pupil diaphragm (10) for specifying several measurement illumination settings generated by moving the pupil diaphragm (10) in the pupil plane (11), - Taking aerial survey photos I measin the image plane (29) for different displacement positions of the object (5) perpendicular to the object plane (4) at the different measurement illumination settings, wherein the different measurement illumination settings are specified by displacement of the pupil aperture (10), - Reconstructing a complex mask transfer function M from the recorded aerial measurement images I meas , - Determining a 3D aerial image I sim of the optical production system as a result of the simulation process from the reconstructed mask transfer function M and a given illumination setting σ target of the optical production system - the reconstruction takes into account that the progressions of the aperture edges (39) of the at least one pupil aperture (10) that effectively determine the respective measurement illumination setting change depending on the displacement position of the pupil aperture (10) beyond a mere displacement of the aperture edge (39).

Description

[0001] The invention relates to a method for replicating the illumination and imaging properties of an optical production system when illuminating and imaging an object, wherein the replicating is carried out using an optical measuring system or a metrology system. The invention further relates to a metrology system for carrying out such a method.

[0002] Such a method and a metrology system for it are known from DE 10 2019 208 552 A1, DE 10 2019 206 651 B4, and DE 10 2019 215 800 A1. A metrology system for the three-dimensional measurement of an aerial image of a lithography mask is known from WO 2016 / 012 426 A1. DE 10 2013 219 524 A1 describes a device and a method for determining the image quality of an optical system, as well as an optical system. DE 10 2013 219 524 A1 describes a phase retrieval method for determining a wavefront based on the imaging of a pinhole. From the technical article 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, a metrology system for determining a critical dimension (CD) at the wafer level is known.

[0003] DE 102 20 815 A1 and DE 102 20 816 A1 describe a reflective X-ray microscope and an inspection system for examining objects with wavelengths ≤ 100 nm. WO 2016 / 012 426 A1 discloses a method for the three-dimensional measurement of a 3D aerial image of a lithography mask. WO 2012 / 028 303 A1 discloses an optical system for EUV projection lithography. US 9,176,390 B2 discloses a method for adjusting an illumination system of a projection exposure unit for projection lithography. US 2013 / 0083321 A1 discloses a device for EUV imaging and an operating method for it. US patent 2013 / 0063716 A1 discloses an illumination optic for a metrology system for examining an object with EUV illumination light and a metrology system with such an illumination optic. The technical article by Totzeck et al.The article "How to describe polarization influence on imaging," Proceedings of SPIE, 2005, 23, deals with the description of the influence of polarization on an image. The subsequently published DE 10 2022 200 372 A1 discloses a method for replicating the illumination and imaging properties of an optical production system when illuminating and imaging an object using an optical measuring system. The subsequently published DE 10 2021 213 827 A1 discloses a method for optimizing a pupil aperture shape to replicate the illumination and imaging properties of an optical production system when illuminating and imaging an object using an optical measuring system. DE 10 2021 205 541 A1 discloses a method for determining the imaging quality of an optical system when illuminated with illumination light within an entrance pupil to be measured.DE 10 2021 205 328 B3 discloses a method for determining the imaging quality of an optical system when illuminated with illumination light within a pupil to be measured and a metrology system for this purpose.

[0004] It is an object of the present invention to improve a method for replicating the illumination and imaging properties of an optical production system when illuminating and imaging an object using an optical measuring system.

[0005] This problem is solved according to the invention by a replication method with the features specified in claim 1.

[0006] According to the invention, it has been recognized that capturing aerial images using multiple pupil apertures, in particular capturing aerial images in several measurement positions of a pupil aperture previously selected to best replicate the illumination setting of the optical production system, makes it possible to improve the overall accuracy of the reconstruction method and, in particular, to reduce artifacts, especially those dependent on the illumination angle, in the reconstructed complex mask transfer function, i.e., the transfer function of the imaged object. 3D mask effects can then be correctly taken into account. This can be considered when examining lithography masks, especially masks used for EUV lithography.

[0007] By considering the dependence of the effective aperture boundary profile on the respective displacement position of the pupillary diaphragm used during measurement, and by going beyond the mere displacement-induced shift of the aperture boundary contour, the accuracy of the 3D aerial image of the optical production system determined via replication is increased. If the pupillary diaphragm is displaced during the acquisition of the measurement aerial images in such a way that an outer aperture boundary, which in particular defines a numerical illumination aperture, remains constant in its position, this can be taken into account in the replication process and simplify the modeling of the respective aperture boundary profile in the current measurement position.

[0008] The provided pupillary diaphragm is a diaphragm of the illumination optics, wherein the pupillary diaphragm can be arranged in the area of ​​an illumination pupil, which is regularly located in a pupil plane of the illumination optics.

[0009] Additionally, the optical measuring system can have another aperture in its imaging optics for imaging the object. This additional aperture on the imaging side can be an aperture diaphragm. Any shadow effect at such an aperture diaphragm can also be taken into account in the imaging process.

[0010] In this case, part of the replication process can be, in particular, the provision of information on the respective image-side additional aperture used, especially the provision of contour information of this image-side additional aperture and also, for example, information about the thickness of an aperture body of the aperture.

[0011] Taking vignetting effects into account according to claim 2 is well suited to the practical application of pupillary diaphragm design. It has been recognized that such vignetting effects cannot be neglected when the highest possible reproduction accuracy is required.

[0012] Taking into account shadowing effects due to a finite principal beam angle of the object illumination in the optical production system according to claim 3 is well adapted to the illumination and imaging requirements of the optical production system. It has also been recognized that such shadowing effects cannot be neglected in order to meet the highest accuracy requirements for reproduction.

[0013] A field-dependent determination according to claim 4 or 5 leads to an additional improvement in the accuracy of the reproduction method, since the optical production system to be reproduced regularly has field-dependent properties of illumination and / or imaging, i.e., properties that depend on the location on the object field or on the image field.

[0014] In this field-dependent determination, a principal beam angle can be defined by two angles at the object. One of these angles is the angle of incidence, which can be measured, in particular, with respect to the normal to an object field. The other angle can be an azimuth angle, measured relative to an initial azimuth angle of 0°. This initial azimuth angle exists when the projection of the incident principal beam onto the object field is perpendicular to a field coordinate. In the case of a rectangular object field, this field coordinate can be the coordinate of the longer field extent. The azimuth angle can then indicate a deviation of the principal beam path of the object illumination from a path in a meridional plane of the optical measuring system.

[0015] Provided that both angles are taken into account, principal beam angles can be considered whose angle of incidence is greater than 4° and whose absolute azimuth angle is greater than 10°.

[0016] A correction according to claim 6, which can incorporate reconstructed spectra of a given lighting setting, accounts for the influence of the imaging optics of the optical production system on the one hand and the corresponding influence of the measuring optics of the metrology system on the other. The same reconstructed spectra can be incorporated into both correction terms. This can be used to eliminate errors that occur during spectral reconstruction. The use of corresponding correction terms in the reconstruction of the mask transfer function is known from DE 10 2019 208 552 A1 and DE 10 2019 206 651 B4.

[0017] When using a pupil diaphragm with an optimized aperture shape according to claim 7, a good reproduction of the illumination characteristics of the optical production system is achieved right from the outset. The reproduction process can then be used to achieve the highest possible reproduction accuracy.

[0018] Separate optimization for different field ranges according to claim 8 offers a further possibility for improving the accuracy of the simulation method. When simulating field heights for which no measuring pupil aperture has been provided, the simulation accuracy can be increased by using a mediation rule, particularly a weighted one.

[0019] The advantages of a metrology system according to claims 9 to 12 correspond to those already explained above with reference to the method claims.

[0020] A displacement drive for displacing the pupillary diaphragm according to claim 10 has proven effective for the reproducible specification of measurement positions for the pupillary diaphragm. This also applies accordingly to an object holder that can be displaced perpendicular to the object plane and to a displacement drive for displacing an imaging pupillary diaphragm according to claim 11.

[0021] A selection device with an aperture magazine according to claim 12 advantageously enables the pupillary aperture selection step of the simulation method. The selection can be performed, in particular, by means of a robotic actuator that removes the selected pupillary aperture from the aperture magazine and places it at its point of use in the pupillary plane. The selection device also ensures that a previously used pupillary aperture is replaced with a newly selected pupillary aperture. The previously used pupillary aperture can then be transferred from its point of use back to the aperture magazine, particularly by means of the robotic actuator.

[0022] The opening of the aperture, i.e., the illumination pupil aperture and / or the imaging pupil aperture, can be variably predefined, for example in the manner of an iris diaphragm.

[0023] The metrology system may include a light source for illumination. Such a light source may be designed as an EUV light source.

[0024] An EUV wavelength of the light source can be in the range between 5 nm and 30 nm. A light source in the DUV wavelength range, for example in the range of 193 nm, is also possible.

[0025] In the imaging procedure, exactly one pupil diaphragm can be selected from the plurality of available pupil diaphragms, which may differ in their diaphragm edge shape and / or orientation. Alternatively, several different pupil diaphragms can be selected and used to define various measurement positions. The available pupil diaphragms can, in particular, define at least one of the following illumination settings: quadrupole, C-quad, dipole, annular, conventional. Examples of such settings can be found, among other places, in WO 2012 / 028 303 A1. In preparing the imaging procedure, an initial determination of a best focal plane (defocus value z", = 0) can first be performed.Z-step values ​​in the final step of the 3D aerial image acquisition process—that is, in the aerial image acquisition from the reconstructed mask transfer function and the illumination settings of the optical production system—may differ from defocus values ​​that can be predefined in the initial reconstruction process. Pixel sizes of the acquired aerial images can be sampled to adapt to a desired pixel resolution.

[0026] The target pupil aperture, which can be specified, and its aperture rim shape can consist of a plurality or even a large number of individual illumination or pupil spots, i.e., a plurality of aperture openings arranged, for example, in a grid pattern. Such illumination or pupil spots can result in a lighting setting used in production lighting, which can be adjusted, for example, via a lighting optic with a field facet mirror and a pupil facet mirror.

[0027] Exemplary embodiments of the invention are explained in more detail below with reference to the drawing. This drawing shows: Fig. 1. A highly schematic side view of a metrology system for replicating the illumination and imaging properties of an optical production system for the illumination and imaging of an object, wherein the metrology system comprises an illumination optic and an imaging optic, each of which is shown in a highly schematic manner; Fig. 2A to 9D different variants of a pupil diaphragm of the metrology system, which can be arranged in the area of ​​an illumination pupil of the illumination optics; Fig. 10 An example of an illumination setting of the optical production system to be replicated, shown as an intensity distribution over an illumination pupil in a pupil plane of the optical production system; Fig. 11A to 11I represent a sequence of measurement positions of one of the pupillary diaphragms according to the Fig. 2 to 9 using the example of the pupillary diaphragm according to Fig. 2B, wherein the measurement position sequence is used within a procedure carried out with the metrology system to replicate the illumination and imaging properties of the optical production system when illuminating and imaging the object with the optical measurement system of the metrology system; Fig. 12A to 12F in a configuration that Fig. 11A to 11I show a similar representation of another version of a sequence of measurement positions of the pupillary diaphragm of the metrology system; Fig. 13A to 13I in one of the Fig. 11A to 11I show a similar representation of another version of a sequence of measurement positions of the pupillary diaphragm of the metrology system; Fig. 14A to 14C in one of the Fig. 11A to 11I show a similar representation of another version of a sequence of measurement positions of the pupillary diaphragm of the metrology system; Fig. 15 in a representation in pupil coordinates a comparison between a target illumination setting of the production system, which is to be approximated with a pupil aperture of the metrology system, and a pupil aperture candidate using the example of a pupil aperture according to Fig. 7A comparable pupillary aperture of the metrology system, wherein this comparison is part of an algorithm for selecting at least one pupillary aperture of the metrology system from the provided plurality of pupillary apertures; Fig. 16 a supervision of a binary, periodic test structure, arranged at XVI in the metrology system according to Fig. 1; Fig. 17 also under supervision accordingly Fig. 16 a field distribution of an electromagnetic field of the illumination light in the illumination light beam path at XVII in Fig. 1 after applying pressure to the test structure; Fig. 18 again under supervision after Fig. 16 a diffraction spectrum of the test structure in the illumination light beam path at XVIII in Fig. 1; Fig. 19 in a to Fig. 18 similar representations due to an aperture stop at XIX in Fig. 1. Diffraction spectrum clipped at the edges of the metrology system; Fig. 20 in one to Fig. 19. Similar representation: the diffraction spectrum, including wavefront influences indicated as contour lines, by the imaging optics of the metrology system as a measurement spectrum in the region of an exit pupil of the imaging optics at XX in Fig. 1; Fig. 21 in a to Fig. 17 similar overhead view a complex field distribution of the illumination light when applied to a spatially resolving detection device of the metrology system in the imaging light beam path at XXI in Fig. 1; Fig. 22 in a to Fig. 21 similar representation an illumination light intensity measured by the detection device at the location of the detection device at XXII in Fig. 1; Fig. 23 schematically and exaggeratedly a field variation of a lighting setting of the optical production system to be replicated, additionally depending on a main beam lighting direction; Fig. 23 A perspectivally, in this case a rectangular object field with a principal ray hitting an object field point to define two principal ray angles of incidence; Fig. 24 an interrupted section of a manufacturing sheet with a pupil aperture which can be used in the optical measuring system of the metrology system in replicating the illumination and imaging properties of the optical production system, wherein an aperture shape of the pupil aperture is optimized by means of a method for optimizing a quality of agreement between the illumination and imaging properties of the optical production system and the optical measuring system, wherein additional alignment marking apertures are shown; Fig. 25 which are used in the optimization process for the pupillary diaphragm according to Fig. 24 resulting target aperture shapes for two different main beam illumination directions; Fig. 26 an exit pupil aperture of a projection optic of the optical production system, wherein an effective inner and an effective outer aperture boundary is illustrated for two different field locations or field points; Fig. 27 in a to Fig. 26 similar representation of an exit pupil diaphragm of an imaging optic of the optical measuring system, wherein effective diaphragm boundaries for two different field locations are also shown, which correspond to the field locations of the Fig. 26 correspond; Fig. 28A to D Various variants or measurement position sequences of pupil diaphragms of the metrology system according to the type of Fig. 11 to 14 in to the Fig. 26 and Fig. 27 similar representation, showing on the one hand an ideal aperture shape and on the other hand an actually effective aperture boundary shape which depends on the respective main beam angle used for illumination; Fig. 29 a flowchart of a procedure for optimizing an aperture shape of a pupil aperture of the metrology system for replicating illumination and imaging properties of the optical production system when illuminating and imaging the object with the optical measuring system of the metrology system; Fig. Figure 30 schematically shows a momentary overlap between an illumination pupil and a pupil of the imaging optics of an optical system comprising an illumination optics and an imaging optics, to illustrate a method for optimizing the quality of agreement between the illumination and imaging properties of the optical production system and the optical measurement system. Fig. 30A an illumination pupil (left) and a projection optics exit pupil (right) of an optical production system, which is replicated via the metrology system with respect to its optical properties; Fig. 30B a sigma pupil aperture shape (left) and an NA aperture shape (right) of the optical measuring system of the metrology system for replicating pupil shapes according to Fig. 30A, which were found as part of an aperture shape optimization process; and Fig. 31 schematically a representation of the object field to illustrate an averaging of aerial photographs if no physical aperture is available at a measuring point.

[0028] To facilitate the representation of spatial relationships, a Cartesian xyz coordinate system is used below. The x-axis runs in the Fig. 1 perpendicular to the plane of the drawing, extending into it. The y-axis runs in the Fig. 1 to the left. The z-axis runs in the Fig. 1 vertically upwards.

[0029] Fig. Figure 1 shows, in a view corresponding to a meridional section, a beam path of EUV illumination light or imaging light 1 in a metrology system 2 for replicating the illumination and imaging properties of an optical production system when illuminating and imaging an object using an optical measuring system of the metrology system 2. The image shows a test structure 5 arranged in an object field 3 in an object plane 4.

[0030] An example of test structure 5 is in a supervision in the Fig. Figure 16 shows the test structure 5, which is periodic in one dimension, namely, for example, along the y-coordinate. The test structure 5 is designed as a binary test structure with absorber lines 6 and alternating multilayer lines 7 that reflect the illumination light 1. Lines 6 and 7 are vertical structures that run, for example, along the y-direction.

[0031] Metrology System 2 is used to analyze three-dimensional (3D) aerial images. One application is the reproduction of an aerial image of a lithography mask, simulating how the aerial image would appear in an optical production system, such as a projection exposure unit, for example, in a scanner. For this purpose, the image quality of Metrology System 2 itself can be measured and, if necessary, adjusted. The analysis of the aerial image can thus be used to determine the image quality of a projection optic of Metrology System 2 or, in particular, to determine the image quality of projection optics within a projection exposure unit. Metrology systems are recognized in DE 10 2019 208 552 A1, WO 2016 / 012 426 A1, and US 2013 / 0063716 A1 (see there). Fig. 3), from DE 102 20 815 A1 (see there) Fig. 9), from DE 102 20 816 A1 (see there) Fig. 2) and known from US 2013 / 0083321 A1.

[0032] The illumination light 1 is reflected and diffracted at the test structure 5. With central, initial illumination, one plane of incidence of the illumination light 1 lies parallel to the yz plane.

[0033] The EUV illumination 1 is generated by an EUV light source 8. The light source 8 can be a laser-produced plasma (LPP) or a discharge-produced plasma (DPP) source. A synchrotron-based light source, such as a free-electron laser (FEL), can also be used. The usable wavelength of the EUV light source can be in the range between 5 nm and 30 nm. In one variant of the metrology system 2, a light source with a different usable wavelength can be used instead of light source 8, for example, a light source with a usable wavelength of 193 nm.

[0034] An illumination optic 9 of the metrology system 2 is arranged between the light source 8 and the test structure 5. The illumination optic 9 serves to illuminate the test structure 5 under investigation with a defined illumination intensity distribution across the object field 3 and simultaneously with a defined illumination angle distribution, with which the field points of the object field 3 are illuminated. Such an illumination angle distribution is also referred to as an illumination setting.

[0035] The respective illumination angle distribution of the illumination light 1 is determined by a pupillary diaphragm 10, which is arranged in an illumination optics pupil plane 11. The pupillary diaphragm 10 is also referred to as a sigma diaphragm.

[0036] Fig. Figures 2A to 9D show possible embodiments of such pupil diaphragms 10, which can optionally be used in the illumination optics 9 of the metrology system 2 to specify the illumination setting. Components and functions that correspond to those already explained in a previous figure are not discussed again in detail in a subsequent figure and, where applicable, bear the same reference numerals.

[0037] Fig. Figure 2A shows a pupillary diaphragm 10 with a single central through-pole I. The radius of this through-pole I is approximately one-quarter of the diameter of a peripheral aperture diaphragm section 14 of the pupillary diaphragm 10. Via the pupillary diaphragm 10 to Fig. 2A selects central illumination angles for object field 3 with relatively little angle variation.

[0038] The Fig. Figures 2B to 2D show further variants of pupil diaphragms 10 with a central through-pole I and an increasingly larger radius. Accordingly, the angular variation of an object field illumination increases when using the pupil diaphragms 10 as shown in the figures. Fig. 2B to 2D. With the pupil aperture set to 10 after Fig. In 2D, a conventional lighting setting results in which light can pass through the lighting optics pupil plane 11 of the metrology system 2 virtually unimpeded.

[0039] Fig. Figure 3A shows a variant of a pupillary diaphragm 10 with an annular passage section I arranged around a round, central obscuration diaphragm section 12. The inner diameter of the annular passage pole I is determined according to the pupillary diaphragm. Fig. 3A approximately the size of the outer diameter of the illumination pole I of the pupillary diaphragm 10 after Fig. 2A. An outer diameter of the annular through-pole I of the pupillary diaphragm 10 according to Fig. 3A is about twice as large.

[0040] Fig. Figure 3B shows a variant of the pupillary diaphragm 10, in which, compared to the Fig. 2A The outer diameter of the annular through-pole I is approximately 2.5 times larger than the inner diameter. The central obscuration aperture section 10 is located at the pupillary diaphragm 10 according to Fig. 3B as large as the one after Fig. 3A.

[0041] Fig. 3C shows a variant of the pupillary diaphragm 10 with annular through-pole I compared to the Fig. 3A and Fig. 3B has an inner diameter approximately twice as large and an outer diameter only slightly larger than that of the through pole I according to Fig. 3B. This results in a correspondingly large central obscuration aperture section 12.

[0042] Fig. 3D shows an illumination pupil 10 with an annular illumination pole I, the ring thickness of which is approximately that of the design according to Fig. 3C corresponds, wherein a diameter of the annular lighting pole I in the design according to Fig. 3D is maximized, so that only a relatively thin aperture aperture section 14 remains at the edge. This results in a correspondingly large central obscuration aperture section 12, which, when executed according to Fig. 3D is larger than in the execution according to Fig. 3C.

[0043] With the designs of the pupillary diaphragms 10 according to the Fig. For 3A to 3D, corresponding annular lighting settings can be implemented.

[0044] Fig. Figure 4A shows a dipole pupillary diaphragm 10, designed as an x-dipole. The two poles I and II are each round and have a diameter that corresponds to the diameter of the central through-pole I of the pupillary diaphragm 10. Fig. 2A corresponds to this.

[0045] Fig. Figure 4B shows a dipole pupillary diaphragm 10, designed as a y-dipole with poles I, II, which in terms of their shape and size are those of the design according to Fig. 4A corresponds. The pupillary diaphragm 10 after Fig. 4B can be adjusted by rotating the pupillary diaphragm 10 degrees. Fig. 4A is generated around an axis parallel to the z-axis at a 90° angle.

[0046] Fig. Figure 4C shows another embodiment of an x-dipole pupillary aperture 10 with through poles I, II, which are rectangular with an x / y aspect ratio of about 1 / 4.

[0047] Fig. 4D shows one of the x-dipole pupillary apertures 10 after Fig. 4C corresponding y-dipole pupillary diaphragm 10.

[0048] Fig. Figure 5A again shows an x-dipole pupillary diaphragm 10, where each of the open poles I, II has a circumferential extent of approximately 90°. Between the two through poles I, II lies a central obscuration diaphragm section 12.

[0049] Fig. Figure 5B again shows a y-dipole pupil aperture 10 corresponding to the x-dipole pupil aperture 10 according to Fig. 5A.

[0050] Fig. Figure 5C shows an x-dipole pupillary aperture 10 in which the individual poles I, II are designed as leaflets, i.e. each has a biconvex shape.

[0051] Fig. 5D shows a y-dipole pupil aperture 10 corresponding to the x-dipole pupil aperture 10 according to Fig. 5C.

[0052] Fig. Figure 6A shows an embodiment of a quadrupole pupillary diaphragm 10 with four round through-poles I, II, III and IV arranged in the quadrants. The diameter of these through-poles I to IV corresponds to that of through-pole I of the pupillary diaphragm 10 according to [reference missing]. Fig. 2A.

[0053] Fig. Figure 6B shows a variant of the pupillary diaphragm 10, which is derived from the one shown in Figure 6B. Fig. 6A can be generated by rotating about an axis parallel to the z-axis by 45°, in which the four poles I to IV are thus a superposition of an x-dipole pupillary aperture and a y-dipole pupillary aperture according to the Fig. 4A and Fig. are arranged in 4B.

[0054] Fig. Figure 6C shows a variant of a corresponding quadrupole pupillary aperture 10 with square through poles I to IV, arranged again in the quadrants.

[0055] Fig. 6D again shows the difference compared to Fig. 6C arrangement rotated by 45° accordingly Fig. 6B, however with square through poles I to IV.

[0056] Fig. Figure 7A shows a variant of a quadrupole pupillary diaphragm 10 with sector-shaped poles I to IV arranged in the quadrants, each with a circumferential extent of approximately 45°. The webs 13 between adjacent transmission poles I to IV of the pupillary diaphragm 10 are shown. Fig. 7A also each have a circumferential extent of approximately 45°. In the center of the pupillary diaphragm 10 after Fig. 7A again contains a central obscuration aperture section 12.

[0057] Fig. 7B shows one of the versions according to Fig. 7A corresponding quadrupole pupillary aperture 10, which can be generated by rotation about an axis parallel to the x-axis by 45°.

[0058] Fig. Figure 7C shows a variant of a quadrupole pupillary diaphragm 10 with through poles I to IV in the form of leaflets, which are arranged circumferentially around a diaphragm center near the peripheral aperture diaphragm section 14.

[0059] Fig. 7D shows a variant of the quadrupole pupillary diaphragm, which is similar to the one described below. Fig. 7C corresponds to and can be generated by rotation around an axis parallel to the z-axis by 45°.

[0060] Fig. Figure 8A shows a hexapole pupillary diaphragm 10 with six round through-poles I to VI, which are arranged uniformly around the center of the diaphragm in the circumferential direction. One diameter of poles I to VI corresponds to that of the through-pole I of the pupillary diaphragm 10 according to [reference]. Fig. 2A. The distance between two adjacent poles I to VI is approximately one third of a pole diameter.

[0061] The six poles are, measured from the x-coordinate of the pupillary diaphragm 10 of the Fig. 8A arranged in positions 30°, 90°, 150°, 210°, 270° and 330°.

[0062] Fig. Figure 8B shows a variant of a hexapole pupillary diaphragm 10, which is similar to the one described below. Fig. 8A corresponds to the edge contour of the through poles I to VI, which in the execution according Fig. 8B is square.

[0063] Fig. Figure 8C shows a variant of a hexapole pupillary diaphragm 10, which is similar to the one described below. Fig. 8A corresponds to the edge contour of the through poles I to VI, which in the execution according Fig. 8C is sector-shaped. The circumferential extent of the sector-shaped through poles I to VI is approximately 30° and corresponds to the circumferential extent of the webs between each adjacent through poles I to VI.

[0064] Fig. 8D shows a variant of a hexapole pupillary diaphragm 10, which is similar to the one described below. Fig. 8A corresponds to the edge contour of the through poles I to VI, which in the execution according Fig. 8D is approximately triangular near the edge aperture section 14.

[0065] Fig. Figure 9A shows a variant of a hexapole pupillary diaphragm 10, which is derived from the one shown in Figure 9A. Fig. 8A can be generated by rotating about an axis parallel to the z-axis by 30°.

[0066] Fig. Figure 9B shows a variant of a hexapole pupillary diaphragm 10, which is derived from the one shown in Figure 9B. Fig. 8B can be generated by rotating about an axis parallel to the z-axis by 30°.

[0067] Fig. Figure 9C shows a variant of a hexapole pupillary diaphragm 10, which is derived from the one shown in Figure 9C. Fig. 8C can be generated by rotating about an axis parallel to the z-axis by 30°.

[0068] Fig. Figure 9D shows a variant of a hexapole pupillary diaphragm 10, which is derived from the one according to Fig. 8D can be generated by rotating around an axis parallel to the z-axis by 30°.

[0069] The pupil diaphragm 10 of the illumination optics 9 is designed as a driven, movable diaphragm in an illumination light beam path 15 of the illumination light 1 in front of the object plane 4. A drive unit used for the driven movement of the pupil diaphragm 10 is located in the Fig. Figure 16 is shown. The drive unit 16, also referred to as the displacement drive, allows the pupillary diaphragm to be displaced along the x-coordinate and / or along the y-coordinate. Fine adjustment along the z-coordinate to align the arrangement plane of the pupillary diaphragm 10 with the illumination optics pupil plane 11 is also possible via the drive unit 16. The drive unit 16 can also be designed to allow tilting of the diaphragm about at least one tilting axis parallel to the x-axis and / or parallel to the y-axis. Furthermore, the diameter of the obscuration diaphragm section 12 and / or the aperture diaphragm section 14 and / or the size of the poles I; I, II; I, II, III, IV; I, II, III, IV, V, VI of the respective pupillary diaphragm 10 can be adjustable and, in particular, preset by means of a drive mechanism.

[0070] Using the displacement drive 16, the selected pupillary diaphragm 10 can be moved in the pupillary plane 11 along the pupil coordinates k x and k y will be relocated.

[0071] The displacement drive 16 can also include an aperture exchange unit, which allows one specific pupil aperture 10 to be exchanged for another specific pupil aperture 10. For this purpose, the aperture exchange unit can remove the selected pupil aperture from an aperture magazine and return the exchanged aperture to the same magazine.

[0072] The test structure 5 is held by an object holder 17 of the metrology system 2. The object holder 17 interacts with an object displacement drive 18 to displace the test structure 5, particularly along the z-coordinate.

[0073] After reflection at the test structure 5, a distribution 19 of the electromagnetic field of the illumination light 1 is present, which is in the Fig. 18 in one of the Fig. The corresponding top view is shown in Figure 17. In the field distribution 19, amplitudes and phase values ​​correspond to the absorber lines 6 and the multilayer lines 7 of the test structure 5.

[0074] The illumination light 1 reflected from the test structure 5 enters an imaging optic or projection optic 20 of the metrology system 2.

[0075] In a pupil plane of the projection optics 20, a diffraction spectrum 21 results due to the periodicity of the test structure 5 (cf. Fig. 18).

[0076] The 0th diffraction order of test structure 5 is centrally located in diffraction spectrum 21. Furthermore, in the Fig. 18 also shows the + / -1st diffraction order and the + / -2nd diffraction order of the diffraction spectrum 21.

[0077] The diffraction orders of the diffraction spectrum 21, which are in the Fig. The elements shown in Figure 18 appear in this form in a pupil plane of the optical system of the metrology system 2, for example, in an entrance pupil plane 22 of the projection optics 20. An aperture diaphragm 23 of the projection optics 20 is arranged in this entrance pupil plane 22, which limits the entrance pupil 24 of the projection optics 20 at its periphery, i.e., outwards to define the numerical aperture and, if necessary, inwards to define an internal obscuration. The aperture diaphragm 23 is also referred to as the imaging pupil diaphragm of the metrology system 2. Fig. Figure 27 shows an example of such an aperture diaphragm 23 of the metrology system 2.

[0078] The imaging pupil aperture 23 is operatively connected to a displacement drive 25, the function of which corresponds to that of the displacement drive 16 for the sigma aperture 10.

[0079] Fig. Figure 19 shows the entrance pupil 24 and the three diffraction orders of the diffraction spectrum 21 that lie in the entrance pupil 24 for the initial illumination angle distribution, namely the 0th and the + / -1st diffraction order.

[0080] Fig. Figure 20 shows a distribution of the intensity of the illumination / imaging light 1 in an exit pupil plane of the projection optics 20. One in the Fig. The exit pupil 26 shown in 20 results as an image of the entrance pupil 24.

[0081] The pupils 24 (cf. Fig. 19) and 26 (see Fig. 20) are elliptical. With alternative specifications by means of corresponding aperture diaphragms 21, the pupils 22, 24 can also deviate from the circular shape in other ways, whereby the pupils can be at least approximately circular. A pupil radius can be calculated as the mean radius. For example, such alternative pupils can be elliptical with an aspect ratio between the semi-axes in the range between 1 and, for example, 3. In a non-figurative representation, the pupils 24 and 26 can also be circular.

[0082] The intensity distribution in the exit pupil 26 is influenced on the one hand by the images of the -1st, 0th, and +1st diffraction orders, and on the other hand by an imaging contribution from the optical system, namely the projection optics 20. This imaging contribution, which is located in the Fig. The area illustrated by the dashed contour lines in Figure 20 can be described by a transfer function of the optical system, as will be explained below. Unavoidable aberrations of the optical system result in a measurable intensity of the illumination / imaging light 1 being present in the exit pupil 26 even in regions around the diffraction orders.

[0083] The projection optics 20 image the test structure 5 onto a spatially resolving detection device 27 of the metrology system 2. The detection device 27 is designed as a camera, in particular as a CCD camera or as a CMOS camera.

[0084] The projection optic 20 is designed as a magnifying optic. The magnification factor of the projection optic 20 can be greater than 10, greater than 50, greater than 100, and even greater. Typically, this magnification factor is less than 1000.

[0085] Fig. 21 shows accordingly the Fig. 18 a complex field distribution 28 of the illumination / image light 1 in the area of ​​an image plane 29 in which the detection device 27 is arranged.

[0086] Fig. Figure 22 shows an intensity distribution 31 of the illumination / image light 1 measured by the camera 27 in an image field 30 in the image plane 29. Images of the absorber lines 6 are represented in the intensity distribution 31 as essentially dark lines 32 of low intensity and images of the multilayer lines 7 as bright lines 33 of higher intensity in the intensity distribution 31.

[0087] To replicate the illumination and imaging properties of the optical production system when illuminating and imaging the object using the example of test structure 5 with the optical measurement system 1 of the metrology system 2, the following procedure is used: First, at least one pupil aperture 10 and, for example, a plurality of pupil apertures 10, each with different aperture edge shapes, are provided to specify various measurement illumination settings. This is done by providing pupil apertures 10, for example, according to the type of pupil apertures 10 of the Fig. 2A to 9D in an aperture magazine, which the aperture changing unit, which can be part of the displacement drive 16, has access to.

[0088] Starting with a simulated lighting setup of the optical production system, a target pupil aperture with a defined aperture rim shape is specified. The target pupil aperture can be an arrangement of multiple individual pupil or aperture spots. The intensity of the individual illumination or pupil spots generally differs between them.

[0089] An example of a lighting setting to be replicated in the optical production system shows the Fig. 10. This production lighting setup in a pupil plane of an illumination optic of the optical production system is provided via a honeycomb condenser with a field facet mirror and a pupil facet mirror and has a multitude of grid-like arranged intensity spots 34 in an illumination pupil plane 35 of the production lighting optic. The intensity spots 34 can have different intensities, so that the illumination light can fall on the object field 3 from different illumination directions with correspondingly different intensities.

[0090] Fig. Figure 15 also shows in a pupil plane with pupil coordinates k x , k ya target pupil aperture 36, the shape of which depends on the illumination setting of the optical production system to be replicated, for example depending on the illumination setting according to Fig. 10, is given.

[0091] The target pupil aperture 36 can be specified by defining corresponding, in particular continuous, aperture contours. Such aperture contours can, for example, be described as polygonal lines.

[0092] These continuous openings are then approximated by a finite number of pupil spots 37 within the openings. These spots are in Fig. 15 are shown as examples.

[0093] For the specific example in Fig. 15 the aperture contour of the aperture was in Fig. 7A as measuring aperture and the aperture contour in Fig. 5A was used as the target setting. The finer the grid is created using illumination spots, the more accurately the actual aperture shape can be approximated.

[0094] The image is shown in the Fig. 15 a grid of pupil spots 37 (stars in the Fig. 15), which are arranged within the specified target pupil aperture 36. This grid arrangement of the pupil spots 37 can compensate for shadowing, in particular caused by necessary struts of the pupil aperture.

[0095] Starting from this target pupil aperture 36, at least one pupil aperture 10 is then selected from the provided plurality of pupil apertures 10 using an algorithm that qualifies deviations between the respective aperture boundary shape of the provided pupil apertures 10 and the target aperture boundary shape of the target pupil aperture 36. For this purpose, the pupil aperture 10 currently being examined during the selection process (hereinafter also: pupil aperture to be qualified) can be further subdivided within its aperture boundary into a plurality of raster-like arranged pupil spots 38, which are in the Fig. 15 are represented by circles.

[0096] During qualification, the similarity between the target illumination pupil (hereinafter also referred to as "T") and the possible measuring apertures 10 (hereinafter also referred to as "M") is determined. This can be done, for example, by calculating an overlap function Q. Q=A(M∩T)A(M∪T)=A(M\T)A(M)−A(T\M)A(T)

[0097] Here, A is a function for the (approximate) calculation of the area. The first term corresponds to the normalized area of ​​the overlap between the measuring aperture and the target illumination pupil. The second and third terms correspond to the normalized difference area between the measuring aperture and the target illumination pupil, and vice versa. The difference area refers to the area contained only in the first pupil, but not in the second.

[0098] The operators "∩", "∪", and "\" correspond to the operators intersection (∩), union (U), and difference (\) in set theory. The intersection M1 ∩ M2 of the sets / areas M1 and M2 refers to the set / area that is contained in both M1 and M2; it corresponds to the overlapping area of ​​M1 and M2. The union M1 ∪ M2 of the sets / areas M1 and M2 describes the set / area that is contained in either M1 or M2; it corresponds to the total area covered by either M1 or M2. The difference M1 \ M2 of the sets / areas M1 and M2 describes the set / area that is covered by M1 but not contained in M2.

[0099] The area function A can, for example, be implemented as counting illumination spots in the pupil. For this, the target illumination pupil and the measuring pupil are scanned with the same grating. Typically, this grating corresponds to the pupil facet grating in the scanner on which the target illumination pupil is sampled (see...). Fig. 10) Now, count the number of spots present in both pupils under illumination (first term in the formula above), as well as the number of spots present exclusively in only one of the two pupils (second and third terms in the formula above). Alternatively, it is also possible to compare the local spot density or the average local brightness.

[0100] When selecting the pupil diaphragm 10, a comparison is made between the positions of pupil spots 37 of the target aperture boundary shape and the positions of pupil spots 38 of the provided pupil diaphragms 10.

[0101] Furthermore, a majority of defocus values ​​are zm (compare Fig. 1) specified as z-distances of a position of the object holder 17 to the object plane 4 (parallel to the xy-plane).

[0102] Furthermore, the simulation method uses a plurality of measurement positions (k x , k y ) of the selected pupil aperture 10 specified.

[0103] Aerial photographs for measurement purposes are now being taken. Imeas(r→, zn, q→m) according to the type of intensity distributions 31 according to Fig. 22 in the image plane 29 at the location coordinates r→=x, y for multiple combinations of a predefined defocus value z m and a measurement position of the selected pupil diaphragm 10, parameterized via an illumination direction q→ This occurs at all positions of the object holder 17 that correspond to the previously specified defocus values ​​z. m are assigned. At least one of the specified defocus values ​​z mSeveral measurement positions (k x , k y ) the selected pupillary diaphragm 10 for the respective recording of the measurement aerial image I(x, y) is controlled via the displacement drive 16.

[0104] The sequence of Fig. Figures 11A to 11I show such a combination of a defocus value z m and a total of nine measuring positions (k x , k y ) the pupillary diaphragm 10, whereby the pupillary diaphragm 10 is adjusted according to Fig. 2B was selected to specify a conventional illumination setting. The position of the through-pole I of the pupillary diaphragm 10 relative to the position of the imaging pupillary diaphragm 23 is shown.

[0105] Fig. Figure 11A shows the pupillary diaphragm 10 centered on the imaging pupillary diaphragm 23. In this starting position after Fig. 11A an image of the pupillary diaphragm 10 is centered in the opening of the imaging pupillary diaphragm 23.

[0106] Fig. Figure 11B shows the pupillary diaphragm 10 in comparison to the imaging pupillary diaphragm 23 from the centered position after Fig. 11A by a predetermined step size in positive k x -direction shifted.

[0107] The following sequence of Fig. Figures 11C to 11I show a further displacement of the pupillary diaphragm 10 compared to the centered position after Fig. 11A in circumferential direction starting from the position after Fig. 11B shifted by 45° each. The measurement positions according to the Fig. 11C, Fig. 11E, Fig. 11G and Fig. Figure 11I shows the pupillary diaphragm 10 in the positions of the four quadrants I to IV. The measurement position according to the Fig. 11B, Fig. 11D, Fig. 11F and Fig. Figure 11H shows the pupillary diaphragm 10 in the Cartesian displacement positions +k x , +k y , -k x -k y .

[0108] An alternative sequence of measurement positions (k x, k y ) the pupillary diaphragm 10 is in the Fig. 12A to 12F are shown. This sequence of measurement positions 12A to 12F corresponds to the measurement positions according to the Fig. 11D, Fig. 11E, Fig. 11C, Fig. 11G, Fig. 11I and Fig. 11H.

[0109] Fig. Figures 13A to 13I show another variant of a sequence of measurement positions (k x , k y ) the pupillary diaphragm 10.

[0110] Fig. Figure 13A shows the pupillary diaphragm 10 centered on the imaging pupillary diaphragm 23. Fig. Figure 13B shows the pupillary diaphragm 10 in comparison to the imaging pupillary diaphragm 23 from the centered position after Fig. 13A by a predetermined step size in positive k x -direction shifted.

[0111] Fig. Figure 13C shows the pupillary diaphragm 10 relative to the imaging pupillary diaphragm 23 from the centered position after Fig. 13 in positive k y-Direction shifted by the same step size.

[0112] Fig. Figure 13D shows the pupillary aperture 10 relative to the imaging pupillary aperture 23, starting from the centered position after Fig. 13A to change the step size in negative k x -direction shifted.

[0113] Fig. Figure 13E shows the pupillary diaphragm 10 relative to the imaging pupillary diaphragm 23, starting from the centered position after Fig. 13A along the negative k y -Direction shifted by the specified step size.

[0114] The completed sequence of measurement positions (k x , k y ) show the Fig. 13F to 13I. The circumferential positions of the pupillary diaphragm 10 relative to the imaging pupillary diaphragm 23 correspond there to the positions according to the Fig. 11C, Fig. 11E, Fig. 11G and Fig. 11 I. In contrast to these positions, the sequence after the Fig. 13F to 13I: The pupillary diaphragm 10 is radially pushed out of the opening of the imaging pupillary diaphragm 23 to such an extent that only an inner part of the transmission spot I of the pupillary diaphragm 10 still overlaps with the opening of the imaging pupillary diaphragm 23. Only slightly more than half of the area of ​​the transmission spot I can then be penetrated by the illumination light. This results in a complete sequence according to the Fig. 13A to 13I with two displacement radii.

[0115] Fig. Figures 14A to 14C show another variant of a sequence of measurement positions (k x , k y ) the pupillary diaphragm 10. The measurement positions according to the Fig. 14A to 14C correspond to the measurement positions according to the Fig. 11B, Fig. 11E and Fig. 11G.

[0116] The selection of the respective measurement position sequence, or possibly subsets thereof, depends on the arrangement of individual structures of the test structure 5 and / or on the illumination setting of the optical production system to be replicated. The selection of the measurement position sequence can, for example, be analogous to the aperture selection algorithm (so), whereby all aperture positions of a sequence are considered and the sequence is selected for which the overlap of the measurement sequence with the target illumination pupil is maximal.

[0117] The positions of the pupillary diaphragm 10 that differ from the centered position relative to the imaging pupillary diaphragm 23 are also referred to as offset measurement positions. Within a measurement position sequence, two to ten such offset measurement positions can be accessed, typically two to five, for example, three or four. The offset measurement positions can be arranged uniformly around the circumference. To reduce measurement time, the measurement schemes shown ( Fig. 11 to Fig. 14) only a subset, e.g. every second measurement position, can be used.

[0118] Using the respective measurement position sequence, the specified defocus values ​​are determined. m measured. Alternatively, it is possible that only one or individual defocus values ​​are measured. m The entire respective measurement position sequence is used, whereby for other defocus values ​​z mThe aerial measurement images can be acquired at fewer measurement positions of the pupil diaphragm relative to the imaging pupil diaphragm 23. In extreme cases, for example, only a defocus value z m The entire measurement position sequence is controlled and a measurement aerial image is taken at each position, whereas with the other predefined defocus values ​​z", the measurement aerial image is only taken at one measurement position at a time, especially with centered pupil aperture 10. meas is recorded.

[0119] For example, the following defocus value / measurement position combination can be recorded: A central defocus value z m and multiple measuring positions (k x , k y ) the pupil aperture 10, i.e., in particular a centered measurement position and several offset measurement positions, as well as defocus values ​​located at maximum distances to both sides of the central defocus value z min , z max , where z are located at these positions min , z maxexactly one central measuring position (k x , k y ) the pupillary diaphragm is taken at 10.

[0120] A complex mask transfer function is then reconstructed from all the aerial measurement images acquired with the selected pupillary aperture 10. A similar reconstruction step is also described in DE 10 2019 215 800 A1.

[0121] The reconstruction is carried out within the framework of a modeled description, in which the projection optics 20 of the metrology system 2 with the illumination setting, which is specified by the pupil diaphragm 10, is described by a function σ(p→, q→), which reflects which lighting directions p→ through the pupil diaphragm 10. In contrast to the reconstruction according to, for example, DE 10 2019 215 800 A1, a change in the illumination light distribution σ due to a change in the measurement position of the pupil diaphragm 10 is not described solely by a displacement vector, but rather the description of the illumination light distribution σ incorporates a main-ray-dependent change in the effective edge contours of the pupil diaphragm 10, depending on its displacement position. The illumination light distribution is thus, on the one hand, dependent on the pupil coordinate. p→ dependent on a basic shape of the pupillary diaphragm's edge contours and on a main beam illumination direction q→, The field dependence of the illumination light distribution, which is taken into account here, is further illustrated using the figures described below:

[0122] Fig. Figure 23 schematically shows a variation of an illumination pupil BP for two different field coordinates x. 1 , x 2 The optical production system is illustrated using the example of a projection exposure system implemented as a scanner. Two illumination pupils (BP) are shown with an exaggerated degree of dependence. x1 , BP x2 of a lighting system of the optical production system according to the type of lighting setting of the Fig. 10.

[0123] With x 1 and x 2 are shown in the Fig. 23 below two different field points or field heights of the typically ring-shaped object field 3 PS of the optical production system, also known as the EUV reticle illumination field. Vertical lines at the x-coordinates x 1 , x 2This indicates that the depicted illumination pupils BP are the result of an integration over the y-component of the field. The function of the scanner projection exposure system is thus modeled. Above field 3 PS are in the Fig. Figure 23 shows the two illumination pupils BP x1 , BP x2 , thus two illuminations of the angular space corresponding with respect to these x-coordinates, each centered around a chief ray CRAl or CRA2 [Chief Ray Angle] of the respective illumination pupil BP. The chief ray illumination directions of the chief rays CRA1 and CRA2 differ from each other, with this difference being shown in the Fig. 23 is greatly exaggerated.

[0124] The following sizes are in the Fig. Figure 23 is schematically represented with a field variation: The main illumination ray CRAi of the respective illumination pupil BP typically varies continuously from field point to field point x. i of object field 3 PS . Each intensity spot 34 (image of the source volume or source plasma of the EUV light source 8) of the respective EUV illumination pupil BP xi varies in its pupil coordinate position ρyƒ,i, ρyƒ,i in its intensity I f,i ,and generally also in its shape and polarization, where f is a position in the object field 3 PS indexed and i indexed the respective intensity spot 34. ρ x , ρ y The pupil coordinates of the respective intensity spot are 34.

[0125] It should be noted in particular that the shapes of the intensity spots 34 of the respective EUV illumination pupil BP also xi depending on the direction of the main illumination beam CRAi vary. This shape dependence of the intensity spots 34 on the main beam angle CRA. i This may be due to imaging errors in the optical system.

[0126] The pupil coordinates ρ x , ρ y , which is described in the description of Fig. 23 are used, corresponding to the coordinates k x ,k y , which above, particularly in connection with the Fig. 15 were used.

[0127] Fig. Figure 23 A further clarifies the angles θ and φ used to parameterize the angle of incidence of the principal ray CRA in two angular dimensions when characterizing the incidence of a principal ray CRA on the object field 3. Here, θ is the angle of incidence of the principal ray CRA relative to a normal n on the object field 3, i.e., to a normal to the object plane 4 parallel to the xy-plane.

[0128] φ denotes an azimuth angle between a perpendicular on the object field coordinate x, again through the point of impact of the main ray CRA and a projection line of the main ray CRA in the xy-plane.

[0129] The orientation of the main ray CRA to the object field 3 can be precisely described using the two angles θ and φ.

[0130] In general, aperture vignetting effects mainly occur at angles θ ≥ 4° and φ ≥ 10°.

[0131] The angle φ indicates a deviation of the main ray from a meridional path (parallel to the yz-plane).

[0132] Metrology system 2 measures a section of the reticle, i.e., the test structure 5, in the form of an aerial image. A main beam CRA of the production system is simulated using the optical measuring system of metrology system 2, so that, as a function of a simulated main beam angle CRAi, a variation of the contour of the pupil diaphragm 10 results in the respective measurement position, which is a consequence of the inclination of the respective main beam angle CRAi of the production system, i.e., the respective main beam illumination direction.

[0133] Fig. 24 and Fig. Figure 25 illustrates this effect.

[0134] Fig. Figure 24 shows an aperture contour of an example of the pupil aperture 10. A boundary 39 of aperture openings of the pupil aperture 10, which can be used to replicate, for example, a dipole illumination setting of the optical production system, has a freeform shape that is reminiscent of an actual dipole geometry of the production illumination setting to be replicated.

[0135] Additionally, in the Fig. 24 further aperture openings 40 are shown, which are adjustment aids for positioning the pupil aperture 10 in the pupil plane 11, which are also referred to as alignment marking openings.

[0136] The pupillary diaphragm is set 10 degrees after the eye dilation. Fig. 24 is realized by generating the aperture openings in an aperture body 41 with a finite thickness.

[0137] Furthermore, in the Fig. Figure 24 shows two different principal rays (center of a beam of illumination 1 illuminating the pupil diaphragm 10 from below) CRA1 and CRA2 with different principal ray illumination directions. The two principal rays CRAl, CRA2 belong to different field points.

[0138] Among other things, the finite thickness of the aperture body 41 ensures that, when the main beam CRAi is varied, the contours of the corresponding illumination pupil are slightly offset in the angular space, as shown in the Fig. Figure 25 is shown schematically. Figure 391 shows an effective aperture boundary for illumination with the principal beam angle CRA1, and Figure 392 shows an effective aperture boundary for illumination with the principal beam angle CRA2.

[0139] In general, the illumination pupil of Metrology System 2 also varies in intensity, contour, and polarization properties when the illumination directions of the principal beams CRAi are varied. Field variation also occurs fundamentally in the respective imaging optics of Metrology System 2 and the optical production system being replicated. In the optical production system, this regularly results in a variation of the exit pupil of the optics that image the object field or illumination field into the image field as a function of the field coordinate. This exit pupil variation is independent of the respective illumination pupil of the optical production system. Similar to the situation described previously with illumination apertures, Metrology System 2 results in contour, polarization, and intensity variations for different illumination directions of the principal beams CRAi.

[0140] Fig. 26 and Fig. 27 show this connection.

[0141] The Fig. Figure 26 shows aperture contours of an aperture diaphragm 42, which is used in the exit pupil of the imaging optics of the optical production system.

[0142] Fig. Figure 27 shows aperture contours of the aperture diaphragm 23 of the metrology system 2, again for two field locations corresponding to the field locations of the Fig. 26 correspond.

[0143] At 391 (floatable) in the Fig. Figure 26 shows an effective boundary of an aperture diaphragm 42 for a first principal beam angle CRA1. Figure 392 (dashed line) shows the diaphragm boundary of the aperture diaphragm 42 for a different second principal beam angle CRA2.

[0144] Accordingly, also in the Fig. 27 the effective aperture boundaries 391, 392 of the aperture diaphragm 23 for the two principal beam angles CRA1 and CRA2 are shown.

[0145] A variation of the field point leads to a change in the aperture boundary, the intensity distribution (apodization) and the phase and polarization effect, which can be described via a Jones pupil J_Production system_1 / 2 or J_Metrology system_1 / 2 for two field & main beam variants CRA1 and CRA2 in the optical systems.

[0146] Details on this topic, and in particular on the Jones formalism, can be found in M. Totzeck, P. Gräupner, T. Heil, A. Göhnermeier, O. Dittmann, D. Krähmer, V. Kamenov, J. Ruoff, and D. Flagello, “How to describe polarization influence on im-aging,” Proc. SPIE 5754, 23-37 (2005), as well as in the textbook “Field Guide to Polarization” by E. Collett, SPIE Press Book, 2005.

[0147] To replicate the aerial image properties of the optical production system with the metrology system 2, especially in the sub-nanometer range, i.e., on the picometer scale, the following dependencies must generally be taken into account: - a field dependency of an illumination pupil of the optical production system; - a principal beam angle dependency of the metrology system illumination pupil; - a field dependency of an exit pupil of the imaging optics of the optical production system; - a principal beam angle dependence of an exit pupil of the imaging optics 20 of the metrology system 2

[0148] These effects can be taken into account in the simulation method described here, both in the reconstruction described below and in the forward propagation described below.

[0149] In the Fig. 28A to 28D are in accordance with the above explanations regarding the Fig. 24 and Fig. 25 deviations of effective aperture edges of the pupillary diaphragm 10 due to different illumination directions of principal rays CRA1, CRA2 illustrated.

[0150] Due to the finite thickness of the aperture base body 41, the effective aperture contours of the respective pupil 10 differ in the measurement positions according to the Fig. 11A ( Fig. 28A), Fig. 11E ( Fig. 28B), Fig. 11G ( Fig. 28°C) and 11°C ( Fig. 28D).

[0151] The border 39 of the respective pupillary diaphragm 10 is in the Fig. 28A to 28D are shown as solid lines in an ideal shape 39 and as dashed lines representing the effective aperture boundary 391 for a specific illumination direction of a principal beam CRA. This respective effective aperture boundary 391 results, for example, from shadowing effects, as explained above. It should be noted that in the various measurement positions shown in the Fig. Figures 28A to 28D show that only the inner aperture boundary varies depending on the measurement position, whereas the variation of the outer aperture boundary is independent of the measurement position, since the same outer boundary is rotationally invariant in each case.

[0152] For typical measurement sequences with metrology system 1, several focus stacks (variation of z) are used. m , cf. Fig. 1) The measurements were taken with the aperture diaphragm 23 in the same position, but with the pupil diaphragm 10 in different measurement positions. While the effective aperture contour of the aperture diaphragm 23 remains the same, the effective aperture boundary of the pupil diaphragm 10 of the metrology system 2 differs at the respective measurement position, as shown by the comparison of the effective aperture boundaries 391 in the Fig. Illustrated in sections 28A to 28D.

[0153] The (known) effective aperture contours 39 ican be taken into account in the reconstruction of the complex mask spectrum. The effective aperture contours 39 i These values ​​can be determined, for example, through optical simulations (e.g., via ray tracing) of the illumination and projection optics. Furthermore, it is also possible to measure them directly via pupil imaging. For this purpose, a Bertrand optic can be used, for example.

[0154] Each direction of illumination generates a complex-valued field distribution in the object plane 4 through interaction with the test structure 5. m(r→, p→) (compare field distribution 19 in the Fig. 17). It is explicitly taken into account that this distribution is not only dependent on the field point. r→, but also from the direction of the lighting p→ depends. In the entrance pupil 24 of the imaging optics 20, the field distribution interferes to form a diffraction spectrum that is also complex-valued. M(k→, p→) (compare diffraction spectrum 21 in the Fig. 19), which corresponds to the Fourier transform of the field distribution m of the test structure 5. The propagation through the projection optics 20 of the metrology system 2 can be modeled by multiplication with the known complex-valued transfer function P of the projection optics 20: P(k→, z)=NA(k→)ei2πλz1−|k|2

[0155] This is NA(k→)=1 ƒu¨r |k|≤NA 0 ƒu¨r |k|>NA the clipping by the numerical aperture of the imaging optics 20, i.e. by the imaging pupil aperture 23, and ei2πλz1−|k|2 The wavefront error caused by a defocus z (displacement by the object holder 17). For this clipping by the aperture diaphragm 23, the effective aperture boundary 39 is now used. i in accordance with the explanations, in particular regarding Fig. Set to 27.

[0156] The propagated spectrum (compare Fig. 21) now interferes with the field distribution 28 in the image plane 29. The camera measures the intensity 31 of the field distribution 28 integrated over all illumination directions of the illumination system. That is, the one with the defocus z and the illumination direction q→ The measured aerial image can be described as follows and simulated by inserting a candidate for the mask spectrum M: Isim(r→, z, q→)=∫dp→σ(p→, q→)|∫dk→M(k→, p→)P(k→, z)eik→r→|2

[0157] This is r→ the xy position of the intensity measurement, i.e. the respective pixel of camera 27. q→ is the direction of lighting and p→ is the pupil coordinate. A direction of illumination. q→ corresponds to the center of an aperture of the respective pupil aperture 10 in the respective measuring position.

[0158] For σ(p→, q→) The effective aperture boundaries of the pupillary diaphragms 10 at the different measurement positions are determined according to the explanations above, particularly in connection with the Fig. Used in 28A to 28D.

[0159] The goal now is to analyze the mask spectra M(k→, p→) to certain. These are k→ the pupil coordinates in the entrance pupil 24 of the projection optics 20 and p→ the direction of the lighting.

[0160] The Fourier transform of the respective mask spectrum is the corresponding mask transfer function.

[0161] The reconstructed spectra can then be used to adapt the aerial image for any other lighting setting. σtarget(p→) and any defocus z target This can be calculated. This is also known as forward propagation.

[0162] The determination of M(k→, p→) This can be formulated as an optimization problem: The spectra are sought. M(k→, p→) for the deviation F between the defocus positions z1, z2...z N and the directions of lighting q→1, q→2…q→M measured aerial photographs I meas and are minimal in the simulated aerial images. The following optimization problem needs to be solved: minM(k→, p→)F=minM(k→, p→)∑n∑m∫dr→|Isim(r→, zn, q→m)−Imeas(r→, zn, q→m)|2

[0163] For every direction of lighting p→ A separate spectrum is reconstructed.

[0164] The reconstructed direction-dependent spectrum can be used to create a simulated aerial image I sim for the target illumination setting σ target and the goal defocus z target to be calculated: Isim(r→, z, xm)=∫dp→σtarget(p→, xm)|∫dk→M(k→, p→)P(k→, ztarget, xm)eik→r→|2

[0165] Setting the target illumination setting σ target It also depends on the field position x m an intensity measurement position on object field 3. This dependence corresponds to the variation that is in the Fig. 23 is shown as an example.

[0166] For each intensity measurement position, an actual intensity distribution BP is thus determined. xm The intensity distribution used in the illumination pupil BP of the optical production system can be determined from an optical simulation of the optical production system or from a measurement of an illumination unit of the optical production system. This actual intensity distribution in the illumination pupil of the optical production system is assumed to be known.

[0167] A dependence of the contour of the exit pupil of the imaging optics of the optical production system on the field position on the one hand and / or on the principal beam angle on the other can be taken into account by a field-dependent transfer function of the imaging optics of the optical production system: P(k→, z, xm)=NAScanner(k→, xm)ei2πλz1−|k|2 NAScanner(k→, xm) The description of the aperture boundary is 39. m the aperture diaphragm 42 of the optical production system depends on the field position x m (see also the above description regarding Fig. 26).

[0168] The reconstruction therefore takes into account that the contours of the pupil apertures 10 at the respective measurement position, i.e., measurement illumination settings that are defined by aperture contours 39 of the pupil aperture 10, change depending on the respective displacement position of the pupil aperture 10 beyond a mere displacement of the edge contours.

[0169] Using equation (4), the simulated aerial image I can then be calculated. sim with the respective measured aerial image I meas This can be compared, which can be used to reconstruct the mask spectrum M and, accordingly, the complex mask transfer function.

[0170] From equation (4) the 3D aerial image can be calculated using the reconstructed mask transfer function M and the lighting setting σ. targetof the optical production system. In this way, it is possible to determine what the aerial image of test structure 5 would look like if it were imaged by the optical production system.

[0171] As an alternative to the method described in the previous section, a correction approach using propagation of the reconstructed mask spectrum is also possible instead of a completely synthetic calculation of the images, analogous to DE 10 2019 206 651 A1. For this purpose, a correction term Δ is calculated: Δ=Isim(r→, z, xm)−Isim(r→, z, q→)

[0172] The two terms Isim(r→, z, xm) and Isim(r→, z, q→) These correspond to those in formulas (4) and (2) above. A prerequisite for this is that measurements are taken for the same focus positions and aperture positions as the target settings.

[0173] The correction term Δ corresponds to the difference in the aerial images caused by the CRA / field dependency. The CRA / field dependency can therefore be corrected as follows: I(r→, z, xm)−Imeas(r→, zn, q→m)+Δ

[0174] With this correction approach, systematic / constant errors in the reconstruction of the mask spectrum are compensated for, i.e., equal deviations in Isim(r→, z, xm) and Isim(r→, z, q→), and do not contribute undesirably to the final image. This makes it possible to preserve effects / properties present in the measurement data, even if these are not considered in the imaging model of the object reconstruction. An example is 3D masking effects in a reconstruction with a simple imaging model without explicitly considering 3D masking effects. In the limiting case of a reconstruction with a negligible residual, i.e., F → 0 in equation (3), both methods (propagation and correction approach) are equivalent.

[0175] As pupillary diaphragm 10 of the metrology system 2, either basic diaphragm shapes corresponding to those described above, particularly in connection with the Fig. 2 to 9 have been explained, or at least one pupillary diaphragm 10 can be used, the diaphragm boundary of which has been optimized according to a procedure described below, which is further illustrated by the Fig. 29 is described: In a preliminary step 45, a starting aperture shape of the sigma aperture 10, 10 is first defined. dc , selected as the initial design candidate for the replication.

[0176] As part of the optimization, this start aperture shape is 10 dc in a modification step 46, so that a slightly modified aperture shape with regard to its boundary shape 10 dcnew in production step 47.

[0177] In verification step 48, it is now checked whether this modified aperture shape 10 dcnew at least one manufacturing constraint relating to the manufacture of this modified aperture shape 10 dcnew fulfilled. If verification step 48 shows that at least one edge test section of the modified aperture shape 10 is satisfied. dcnewIf the manufacturing constraints are not met (decision "N" of verification step 48), modification step 46 and production step 47 are repeated based on the final design candidate. This continues until verification step 48 is completed with a given modification aperture shape 10. dcnew compliance with the specified manufacturing boundary conditions results in (decision “J” of verification step 48).

[0178] In a determination step 49, the quality of agreement between the illumination and imaging properties of the optical production system and the illumination and imaging properties of the optical measuring system is then transmitted.

[0179] As part of this agreement quality determination, a value of at least one merit function is calculated. This merit function incorporates a comparison of optical illumination and imaging parameters between a pupil overlap area of ​​an illumination pupil and an imaging pupil of the optical production system on the one hand, and a corresponding pupil overlap area of ​​an illumination pupil with an aperture of sigma 8 and an imaging pupil with an aperture of NA 11 of the optical measuring system on the other.

[0180] Fig. Figure 30 shows such a pupil overlap area A r,ϕ between an illumination pupil BP and an imaging pupil AP.

[0181] A Center Z Ar,ϕ The exit pupil (AP) is located at Cartesian coordinates. σxi, σyi. Instead of Cartesian coordinates σ x , σ yPolar coordinates can also be selected, which are in the Fig. 30 are also shown. σ ϕ This denotes the distance between a center Z B the illumination pupil BP and the center Z A the exit pupil AP. Φ denotes the angle between the distance σ ϕ and for example the σ y -axis, as in the Fig. 30 is marked. In the case shown, ϕ is 90°.

[0182] As part of determining the quality of agreement using such a pupil overlap area A r , ϕ The overlap will be at different support points σxi, σyi, The areas that are scanned are evaluated. The following evaluation terms are used: Dr,ϕ=∫Ar,ϕdσxdσyI(σx, σy) Tr,ϕ=∫Ar,ϕdσxdσyσϕ(σx, σy)I(σx, σy)

[0183] D is a term that represents a simple summation of the intensities I(σ). x,σ y ) over the respective pupil overlap area A r,ϕ describes. This D-term (according to equation (8)) correlates with an image size CD (critical dimension), i.e. a width of a structure along a given direction.

[0184] In connection with the definition of the parameter CD, reference is made to US 9,176,390 B.

[0185] The T-term (according to equation (9)) represents a further value with the distance σ. ϕ This represents a weighted integral over the overlap region A. In this formulation of the T-term, it is simplified to assume that the exit pupil does not exhibit apodization. This T-term correlates with the imaging telecentricity parameter. This can include the sensitivity of an object structure offset as a function of the defocus position of the substrate onto which the object is imaged.

[0186] For a given pupil-diaphragm shape of the pupillary diaphragm 10, the matching quality for all possible overlap areas A is determined. r,ϕ The following optimization rules were applied: Dr,ϕdc−Dr,ϕt=0 for all value pairs r,ϕ Tr,ϕdc−Tr,ϕt=0 for all value pairs r,ϕ dc here stands for the respective design candidate, i.e., the aperture shape of the pupil aperture 10 currently under consideration. t stands for the target illumination pupil of the optical production system, i.e., in particular a projection exposure system in the form of a scanner.

[0187] The optimization requirements according to equations (10) and (11) are generally not met. To determine the quality of the match, the aperture shape of the design candidate dc is varied until the optimization requirements (10) and (11) yield minimum values.

[0188] In addition to the optimization parameters D and T, other parameters that correlate with further illumination or imaging parameters can also be used to determine the accuracy of the image. An example of such a parameter is: HVr,ϕ=Dr,ϕ−Dr,ϕ−90°=∫Ar,ϕdσxdσyI(σx, σy)−∫Br,ϕdσxdσyI(σx, σy)

[0189] This HV term correlates with an imaging parameter "HV asymmetry," which quantifies the difference in critical dimensions (CDs) along a vertical and a horizontal dimension. Depending on the structures to be imaged on object 5, the HV term can be relevant, for example, when imaging horizontal or vertical lines, especially those with the same periodicity and target CD, or when imaging so-called contact holes, i.e., structures with an xy aspect ratio in the range of 1. An HV asymmetry can then be understood as the difference between the two CDs, i.e., for horizontal (h) and vertical (v) lines, CD h - CD v or in the case of contact holes with extensions in the x and y directions CD x - CD y .

[0190] When determining the HV term according to the above equation (12), the difference between two D terms according to equation (8) is calculated at the location of two defined overlap regions A r,ϕ and B r,ϕ calculated by rotating 90° around the coordinate origin Z B (cf.) Fig. 30) are rotated relative to each other. To calculate the integral in the overlap region, the overlap between, for example, the entrance pupil BP and an exit pupil AP' rotated by 90° is considered.

[0191] There is also a corresponding optimization rule for the HV term: HVr,ϕdc−HVr,ϕt=0 for all value pairs r,ϕ

[0192] The overlap areas used A r,ϕ After comparative calculation, they cover the entire illumination pupil of the optical production system on the one hand and of the illumination optics 9 of the metrology system 2 on the other.

[0193] Fig. 30A and Fig. Figure 30B shows two pairs of pupils on one side of the optical production system ( Fig. 30A) and on the other hand the optical measuring system of metrology system 2 ( Fig. 30B), which are compared with each other as part of the conformity quality assessment, which are discussed above in connection with, in particular, the Fig. 30 was explained.

[0194] Fig. Figure 30A on the left shows an illumination of a lighting pupil for an x-dipole lighting setting. Fig. Figure 30A on the right shows an exit pupil of the projection optics of the optical projection system with a central approximately elliptical pupil obscuration.

[0195] The lighting setting to be replicated (compare Fig. The optical production system (30A left) can be composed of a multitude of individual spots in the illumination pupil, corresponding to a faceted design of the illumination optics of the optical production system, for example, a design with a field faceted mirror and a pupil faceted mirror, or a design in which a MEMS mirror configuration is used within the illumination optics. The size of the respective individual spot in Fig. 30A on the left is a measure of the brightness of this single spot, i.e., the illuminance intensity from the direction of illumination assigned to this single spot.

[0196] Fig. Figure 30B shows on the left a target aperture shape of the pupil aperture 10 obtained with the optimization procedure for replicating the illumination and imaging properties of the optical production system with the illumination setting and the exit pupil according to Fig. 30A. Fig. Figure 30B shows on the right the exit pupil of the imaging optics of the optical measuring system with the central obscuration, which is generated via the aperture diaphragm or NA diaphragm 23.

[0197] A merit function E can be used to determine the quality of conformance, since, in general, the conformance requirements according to equations (10), (11), and (13) do not all equal 0 simultaneously. This merit function can be written, as usual, as a weighted error minimization function: E(I(σx, σy))=wD∑i,ϕ(Di,ϕ(I(σx, σy))−Di,ϕ(It(σx, σy)))2 +wT∑i,ϕ(Ti,ϕ(I(σx, σy))−Ti,ϕ(It(σx, σy)))2+…

[0198] I here denotes the aperture shape of the pupillary diaphragm 10 dcnew , which are to be evaluated using the merit function. I tdenotes the target illumination pupil of the optical production system for which optimization is to be performed. D and T denote the evaluation terms discussed above in connection with equations (10) and (11). Additionally, the merit function E can also be extended, for example, by the evaluation term HV (see equations (12) and (13)).

[0199] The merit function I can also be extended by the requirement for a minimum transmission of the pupillary diaphragm 10 dcnew to be expanded.

[0200] In step 49 of the investigation, in addition to the target illumination pupil of the optical production system, a pupil transfer function of the optical production system and a pupil transfer function of the optical measuring system of the metrology system 2 can also be included.

[0201] For this purpose, the D-term defined above in connection with equation (8) can be written as follows: Dr,ϕ=∫−∞+∞∫−∞+∞dσxdσyI(σx, σy)Pr,ϕ(σx, σy)

[0202] P is an apodization function, i.e., an energetic component of the pupillary transfer function.

[0203] This allows for the apodization of the exit pupil to be taken into account.

[0204] During step 49 of the analysis, compliance with an optimization criterion is checked in an optimization query step 50. An example of such an optimization criterion is the Boltzmann criterion of simulated annealing: fulfills r <P(dc, dcnew)mit P(dc, dcnew)=e−β(E(dcnew)−E(dc)) Here, r is a uniformly distributed random number from the interval [0, 1 [ (the exact value "1" is therefore excluded from this interval) and β is a control parameter that continuously increases during the simulated annealing optimization. E(dc new) and E(dc) are the merit functions that resulted for the aperture shapes of the pupil aperture 10 in the last and the previous optimization step.

[0205] Provided the Boltzmann criterion is met, i.e., the optimization is not yet complete (decision J in query step 50), the current aperture shape will be 10. dcew as initial aperture shape 10 dc The next modification is set, which occurs in predefined step 51. In predefined step 51, the control parameter β is also increased. Thus, the optimization criterion is tightened in predefined step 51. The process then continues with modification step 46, and steps 47 to 50 are repeated until, in optimization query step 50, it is determined that either the Boltzmann criterion is no longer met or the control parameter β is greater than a predefined value (query result N in query step 50).

[0206] If the optimization criterion is then reached in the optimization query step 50 (query result N), the pupil aperture 10 is manufactured in a production step 52 with the target aperture shape that occurred in the optimization with the smallest merit function value E.

[0207] Such a target aperture shape 39 shows the Fig. 24.

[0208] For each lighting setting of the optical production system, exactly one as above can be used in connection with the Fig. 29 to 30B explains the use of an optimized pupillary diaphragm 10.

[0209] For a given selection of field points x i For example, for three field points (left x-field edge, field center, right x-field edge), individually optimized apertures can be designed so that the apertures for this field point x ior, for this illumination direction of the respective main beam CRAi, the contributions of the optical production system on the one hand and the metrology system 2 on the other hand are taken into account more completely, and a correspondingly improved reproduction of the aerial image of the optical production system is achieved. This specification of individually optimized aperture boundaries can be applied to the pupil aperture 10, to the aperture aperture 23, and can also be applied to both apertures 10 and 23 simultaneously.

[0210] The three pupillary diaphragms 10 and, if applicable, three aperture diaphragms 23, thus optimized, are then available for metrology system 2. Matching the field point x to be measured. m In object field 3, the corresponding aperture or aperture pair consisting of pupillary diaphragm and aperture diaphragm can then be used.

[0211] If there is no coincidence between a field point x to be measured mA mediation rule can be used for a given field point, for which the respective aperture has been optimized with regard to its boundary. An example of such a mediation rule is: 〈A(x, y)〉m=A(x, y)rΔxm−iΔx+A(x, y)iΔxr−mΔx

[0212] A(x, y) denotes the aerial image measured with the metrology system 2.

[0213] Fig. Figure 31 shows the definitions of the distances Δx according to the formula (15) above. The index m denotes the field point on the mask at which a section is to be measured. For this field point of object field 3, there is no dedicated aperture. Two aerial photographs are now taken at point x. m Recorded: Once with the field point x adjacent to the left 1 , and once with the value for a field point x adjacent to the right rThe aperture is designed and available. Weighting is simply linear with the corresponding relative distances, as shown in the formula above. In the limiting case that x m e.g. x r As the weighting increases, the aerial image A(x, y) is obtained. r .

[0214] In one variant of the simulation method, several different pupillary diaphragms 10 can also be used to specify the different measurement positions (k x , k y ) can be used.

[0215] To prepare for the replication procedure, an aerial image stack can be taken to ensure which z-position of the object plane 4 provides an optimally sharp image onto the image plane 29 (zero point of the z-position).

[0216] z-step sizes used in equation (2) for determining the aerial image I sim The defocus values ​​used may differ from those specified in the simulation procedure. m differentiate.

[0217] Pixel sizes of the recorded aerial measurement images I meas can be resampled to adapt to a desired pixel resolution.

[0218] In a simulation process, several k can also be used. x , k y The positions of the imaging pupil diaphragm 23 can be adjusted via the displacement drive 25.

[0219] When reconstructing the mask transfer function, imaging errors of the optical measuring system, in particular imaging errors of the imaging optics 20 of the metrology system 2, can be taken into account.

[0220] Determining the 3D aerial image I meas and / or the calculation of the simulated aerial image I sim can be performed with a different main illumination beam angle than the reconstruction of the mask transfer function.

[0221] Metrology system 2 has a selection device, not shown in detail in the drawing, for selecting the respective pupil aperture 10 from the provided plurality of pupil apertures 10, each with different aperture edge shapes and / or aperture edge orientations. This selection device has an aperture magazine in which the plurality of pupil apertures 10, each with different aperture edge shapes and / or aperture edge orientations, are held for specification according to different measurement illumination settings.

[0222] In the selection step of the simulation procedure, the last inserted pupillary diaphragm is first removed from its position in the pupil plane 11 using an actuator of the selection device, in particular a robotic actuator, and fed into the diaphragm magazine of the selection device. Subsequently, the pupillary diaphragm 10 selected according to the simulation procedure is selected from the diaphragm magazine and inserted into its position in the pupil plane 11 using the robotic actuator.

[0223] The problem and solution presented above can, in principle, be applied analogously to account for machine-specific characteristics in aerial image emulation. For example, EUV illumination pupils differ from machine to machine depending on the light source, and especially the specific EUV light source, used. The combination of an aperture emulating the ideal system with a simulation method that incorporates the machine-specific component is particularly attractive.

[0224] This requires that the machine-specific characteristics are known, e.g., via a qualification or, in the case of EUV source types, via the corresponding numerical models. Similarly, machine-specific components of metrology system 2 can also be taken into account.

[0225] In general, the approaches described above can be used to simulate specific properties of the optical production system, such as crosstalk effects between different illumination channels of a honeycomb condenser system in the lighting optics of the optical production component, and / or crosstalk effects between different x-coordinate-dependent intensity correction apertures in the lighting optics of the optical production system. For example, the insertion depths of corresponding x-coordinate-dependent aperture fingers that correct the illumination intensity, as well as their influence on the aerial image, can be simulated.

Claims

[1] Method for replicating the illumination and imaging properties of an optical production system for the illumination and imaging of an object (5), wherein the replicating is carried out using an optical measuring system of a metrology system (2), - where the optical measuring system -- a lighting optic (9) for illuminating the object (5) --- with a pupillary diaphragm (10) of the illumination optics (9) in the area of ​​an illumination pupil in a pupillary plane (11) and -- has an imaging optic (20) for imaging the object (5) onto an image plane (29), - wherein the object (5) can be moved perpendicular to an object plane (4) by the following steps: - Providing at least one pupil diaphragm (10) for specifying several measurement illumination settings generated by moving the pupil diaphragm (10) in the pupil plane (11), - Taking aerial survey photos I measin the image plane (29) for different displacement positions of the object (5) perpendicular to the object plane (4) at the different measurement illumination settings, wherein the different measurement illumination settings are specified by displacement of the pupil aperture (10), - Reconstructing a complex mask transfer function M from the recorded aerial measurement images I meas , - Determining a 3D aerial image I sim of the optical production system as a result of the simulation process from the reconstructed mask transfer function M and a given illumination setting σ target of the optical production system - the reconstruction takes into account that the progressions of the aperture edges (39) of the at least one pupil aperture (10) that effectively determine the respective measurement illumination setting change depending on the displacement position of the pupil aperture (10) beyond a mere displacement of the aperture edge (39). [2] Method according to claim 1, characterized by , that in determining a change in the course of the aperture edges (39) of the at least one pupil aperture (10) when specifying the measurement illumination settings, shadowing effects due to a finite thickness of a base body (41) of the pupil aperture (10) are taken into account. [3] Method according to claim 1 or 2, characterized by, that in determining a change in the course of the aperture edges (39) of the at least one pupil aperture (10) when specifying the measurement illumination settings, shadowing effects due to a principal beam angle (CRAi) of illumination of the object (5) in the optical production system, which is greater than 4°, are taken into account. [4] Method according to any one of claims 1 to 3, characterized by , that a field-dependent determination of a change in the course of the aperture edges of the at least one pupil aperture (10) is carried out when the measurement illumination settings are specified. [5] Method according to any one of claims 1 to 4, characterized by , that in determining a change in the course of the aperture edges of the at least one pupil aperture (10) when specifying the measurement illumination settings, a field dependence of imaging properties of an imaging optic of the optical production system is taken into account. [6] Method according to any one of claims 1 to 5, characterized by , that at least one of the following correction terms is included in the reconstruction of the mask transfer function M: - a calculated aerial image (Isim(r→, z, xm)) at the associated defocus value and field height, which is generated by simulating an image with the imaging optics of the optical production system including reconstructed spectra of the object (5), and / or - a calculated aerial image (Isim(r→, z, q→)) at the associated defocus value, which is generated by simulating an image with the measuring imaging optics (20) including the reconstructed spectra. [7] Method according to any one of claims 1 to 6, characterized by , that a pupillary aperture (10) is used when taking the measurement aerial images, the shape of which is optimized using the following process steps: - Specification (45) of a start aperture shape (10 dc ) the pupillary diaphragm (10) as a starting design candidate for replication, - Modifying (46) the start aperture shape (10 dc ), so that a modification aperture shape (10 dcnew ) is created, which differs from the last specified aperture shape (10 dc ) differs, - Check (48) at least one manufacturing boundary condition relating to the manufacture of the modified aperture shape (10 dcnew ) and repeat the “Modify” and “Verify” steps until verification (48) shows compliance with the manufacturing constraint, - Determining (49) a quality of agreement between the illumination and imaging characteristics of the optical production system and the illumination and imaging characteristics of the optical measurement system, once the manufacturing boundary conditions are met, - Repeat the steps “Modif i“decorate”, “verify” and “determine” until the conformance quality reaches a predefined optimization criterion, which is verified via a query step (50), - Production (52) of a target aperture shape resulting from the achievement of the optimization criterion as an optimized pupil aperture shape (39) after achieving the optimization criterion. [8] Method according to claim 7, characterized by , that the aperture boundary (39) for several field areas and in particular for several field heights (x m ) is optimized separately, resulting in multiple pupil apertures (10) which can each be used to replicate the properties of the optical production system in the corresponding field area. [9] Metrology system (2) for carrying out a method according to any one of claims 1 to 8, - wherein the optical measuring system comprises an illumination optic (9) for illuminating the object (5) with a pupil aperture (10) in the area of ​​an illumination pupil in a pupil plane (11) and an imaging optic (20) for imaging the object (5) in the image plane (29), - with a selection device for selecting at least one pupillary diaphragm from a plurality of pupillary diaphragms. [10] Metrology system according to claim 9, - wherein the optical measuring system has a displacement drive (16) for displacing the pupillary diaphragm (10) in at least one displacement direction in the pupillary plane (11), - wherein the optical measuring system has an object holder (17) that can be moved by actuator perpendicular to an object plane (4). [11] Metrology system according to claim 9 or 10, characterized by, that the optical measuring system has a displacement drive (25) for displacing an imaging pupil diaphragm (23) which is arranged in the region of a pupil of the imaging optics (20), in at least one displacement direction in a pupil plane (22) of the imaging optics (20). [12] Metrology system according to any one of claims 9 to 11, characterized by , that the selection device has an aperture magazine with a plurality of pupil apertures (10) each with different aperture edge shapes and / or aperture edge orientations for specifying according to different measurement illumination settings.

Images