Optical assembly

Abstract

An optical assembly (17) has a primary optical rod (28) for guiding illumination light (4) along an illumination light beam path from a light source to a target field. An optical follower rod (29) of the optical assembly (17) is arranged in the illumination light beam path between the primary rod (28) and the target field. An intermediate image-generating optic (30) is arranged between the primary rod (28) and the follower rod (29). This generates an intermediate image between the primary rod (28) and the follower rod (29) along exactly one imaging dimension (y) perpendicular to the illumination light beam path. The result is an optical assembly in which the illumination light, after passing through the optical assembly, has a defined polarization state. The optical assembly can be part of an illumination optic and can, in particular, be part of an optical system of a projection exposure system containing such an illumination optic.

Description

The invention relates to an optical assembly. The invention further relates to an illumination optical unit having an optical assembly of this type, an optical system having an illumination optical unit of this type, a projection exposure apparatus having an optical system of this type, a method for producing a nanostructured component by means of a projection exposure apparatus of this type, and a structured component produced by means of a method of this type.An optical assembly as a component of an illumination optical unit for projection lithography is known from WO 2005 / 015 310 A2, DE 10 2004 059 493 A1 and from WO 2016 / 188 739 A1.It is an object of the present invention to further develop an optical assembly of the type mentioned at the beginning in such a way that the illumination light is present with a defined polarization state after passing through the optical assembly, in particular that a polarization state of the illumination light which it has before entering the optical assembly is maintained.This object is achieved according to the invention by an optical assembly having the features specified in claim 1.According to the invention, it has been recognized that an undesired influence on the polarization of the illumination light when passing through an optical rod used for the light mixing can be sufficiently compensated by using the optical assembly having two optical rods and an intermediate image generating optical unit. In particular, an undesired cumulation of a geometric phase resulting from internal reflections of the illumination light on rod cladding walls and the polarization-influencing effect thereof can be avoided or reduced as a result.The intermediate image is generated along exactly one imaging dimension transversely to the illumination light beam path. This results in individual beams of the illumination light passing through the follower rod with a subtractive geometric phase accumulation in comparison with the primary rod.The rods of the optical assembly can have entry and exit surfaces with a square, rectangular, round or even hexagonal edge contour. An edge contour of the primary rod can differ in shape and / or orientation from an edge contour of the subsequent rod.Such an optical assembly with a defined polarization state of the illumination light passing through it can be used as a component of an illumination optical unit of a projection exposure apparatus for the lithographic production of micro- or nanostructured components. Alternatively, such an optical assembly can also be used as a component of a polarization DIC (differential interference contrast) microscope. Such a polarization DIC microscope is described in the technical article by Murphy, D.: Differential interference contrast (DIC) microscopy and modulation contrast microscopy, in Fundamentals of Light Microscopy and Digital Imaging, Wiley-Liss, New York, pp. 153-168 (2001). Further references to polarization DIC microscopy can be found in the Wikipedia article "Differential interference contrast microscopy", available on 12.04.2024.When the optical assembly is used in an illumination optics of a projection exposure apparatus for lithography, in particular a tangential polarization can be maintained to the desired extent in an annular illumination setting or in a dipole illumination setting.In a polarization DIC microscope, for example, a constant linear polarization can be maintained to the desired extent.An intermediate image generating optical unit according to claim 2 can be arranged in particular symmetrically to a mirror plane between the two rods, i.e. between the primary rod and the subsequent rod.An embodiment of the imaging components of the intermediate image forming optics according to claim 3 can in particular result in a compact intermediate image forming optics. The forming of the respective imaging component onto the respective rod can be produced by machining an end face of the respective rod. Alternatively, this can be done by blowing the imaging component onto the end face of the respective rod or by gluing the imaging component to the rod end face. Again alternatively, the imaging component can also be mechanically clamped together with the respective end face of the rod.An embodiment of the imaging component according to claim 4 as exactly one cylindrical optical unit is a comparatively easily producible embodiment of the imaging component, in which the exactly one cylindrical optical unit can then act on an entire bundle of the illumination light passing through the rod. The cylindrical optics can also be parabolically cylindrical. The cylindrical optics can be designed as a cylindrical lens, as a cylindrical mirror or can also be designed as a Grin lens.In general, the intermediate image generating optics can be designed such that a translation invariance is present along an axis. In the axis orthogonal to this axis, optical surfaces of the intermediate image generating optics can be designed in various ways, wherein it is only required that a corresponding 1d intermediate image, i.e. an intermediate image along exactly one imaging dimension, is realized.An embodiment of the imaging component of the intermediate image generating optics according to claim 5 as a cylindrical optics array can be embodied as a 1D array, i.e. as a line of cylindrical optics, or also as a 2D array, i.e. as a grid of cylindrical optics. The respective cylindrical optics then guides either a beam layer of the entire beam of the illumination light or a beam channel of the entire beam of the illumination light.A rod design according to claim 6 has proven to be practical. Depending on the embodiment of the optical assembly, the entry surfaces and the exit surfaces for the illumination light of the primary rod and of the subsequent rod can each be configured with an edge contour with an aspect ratio different from 1. The edge contour of the rod can be, for example, hexagonal.An imaging dimension according to claim 7 can be realized by tilting the intermediate image generating optics relative to a boundary contour coordinate system of the rods such that the desired imaging dimension tilt results. The angle between the imaging dimension and the coordinates spanning the edge contour of the entry and exit surfaces of the rods may be 45°. Other angles between 10° and 80°, in particular between 30° and 60°, are also possible. If the primary rod and the follow-on rod have rectangular and in particular square entry and exit surfaces, the imaging dimension angle to the rod coordinates can be 45°. In an embodiment tilted with respect to the imaging dimension according to claim 7, a primary rod and / or a follow-up rod with an aspect ratio of exactly 1 can also be used in principle.An imaging dimension tilted in this way leads to the possibility of retardation compensation in the illumination light passing through the optical assembly. Undesired retardation effects, i.e. a phase splitting between an s- and p-intrinsic polarization of a polarization of the illumination light in the case of total reflection in each case on cladding walls of the rods, can be at least partially compensated by the tilting.A coating according to claim 8 can be used, for example, for retardation suppression. The coating can be in the form of a gradient index coating.This applies in particular to a coating according to claim 9.A retardation optical system according to claim 10 can likewise be used for retardation suppression.The at least one retardation optical unit can be arranged between the rods of the optical assembly and / or downstream of the subsequent rod in the illumination light beam path.The advantages of an illumination optical unit according to claim 11, an optical system according to claim 12, a projection exposure apparatus according to claim 13, a production method according to claim 14 and a nanostructured component according to claim 15 correspond to those already explained above with reference to the optical assembly. Part of the illumination optics can be a light source for the illumination light.The light source of the illumination system can be a mercury vapor lamp, an excimer laser or an LED light source.A structured component, in particular a microchip, for example a memory chip, can be produced.Exemplary embodiments of the invention are explained in more detail below with reference to the drawings. In these show: FIG. 1 shows, in a meridional section, main optical groups of a projection exposure apparatus for microlithography; FIG. 2 shows schematically and along an illumination light beam path with oversized spacings an optical assembly of an illumination optical unit of the projection exposure apparatus, having two optical rods and an intermediate refractive image generation optical unit which lies between them and has two cylindrical lenses, wherein in the region downstream of an exit surface of the respective rod a plan view of this exit surface is shown in each case with a course of a selected individual illumination light beam projected thereon, the 3D course of which is also shown in the associated perspective representations of the optical rods; FIG. 3 shows, in a course of the illumination light beam path through the optical assembly according to FIG. 2, a phase space mapping in a spatial space dimension for the illumination light guided by means of the optical assembly, wherein the individual beam illustrated by way of example in FIG. 2 is emphasized by a point with respect to its phase / spatial relationship and wherein, by way of example, the evolution of an ellipsoidal beam density during the propagation through the two optical rods of the optical assembly is illustrated in each case in the region of an entry surface and an exit surface of the respective rod; FIG. 4 shows a further embodiment of an optical assembly which can be used instead of the optical assembly according to FIG. 2, with a variant of the intermediate image generating optical unit, embodied as an array of cylindrical optical units; FIGS. 5 and 6 show, in two meridional sections perpendicular to one another, a further variant of an intermediate image generating optical unit, which can be used either instead of the intermediate image generating optical unit according to FIG. 2 or instead of a channel of the cylindrical optical unit array according to FIG. 4, embodied as 2 foptics in a yz plane and as 4 foptics in an xz plane; FIG. 7 shows a further embodiment of an intermediate image generating optics, which can be used instead of the intermediate image generating optics shown above, embodied as reflective intermediate image generating optics; FIG. 8 shows a further embodiment of an intermediate image generating optics, which can be used instead of the intermediate image generating optics shown above, embodied as diffractive intermediate image generating optics; FIG. 9 shows a further embodiment of an intermediate image generating optics, which can be used instead of the intermediate image generating optics shown above, embodied as a Grin lens optics; FIG. 10 shows a representation similar to FIG. 2 of a further embodiment of the optical assembly, wherein an imaging dimension of an intermediate image generating optical unit tilts, namely runs at a 45° angle to x / y coordinates, which span a rectangular boundary of the entry and exit surfaces of the two optical rods of the optical assembly; FIG. 11 shows a gray scale representation of a retardation pupil of the optical primary rod of the optical assembly according to FIG. 10 guiding in the illumination light beam path; and FIG. 12 is a view similar to FIG. 11 showing a retardation pupil of the optical follower rod following in the illumination light beam path of the intermediate image forming optical system of the optical assembly according to FIG. 10.A projection exposure apparatus 1 is shown in meridional section in FIG. 1 with regard to its main optical groups.To facilitate the representation of positional relationships, an xyz-coordinate system is used below. In FIG. 1, the x-axis extends perpendicularly to the plane of the drawing out of the latter. The y-axis extends to the left in FIG. 1. The z-axis extends downward in FIG. 1.A dashed line in FIG. 1 indicates an optical axis 2 which runs through an entire optical system of the projection exposure apparatus 1, starting from a light source 3. This optical axis 2 is folded several times each by 90° in the embodiment of the projection exposure apparatus 1 illustrated in FIG. 1. Such folds can also be configured differently or, if appropriate, can also be omitted completely.The light or radiation source 3 of the projection exposure apparatus 1 generates useful light in the form of an illumination or imaging beam bundle 4, which is illustrated in FIG. 1 by edge beams. The used light 4 is also referred to as illumination light or as imaging light. The useful light 4 has a wavelength in the deep ultraviolet range (DUV), for example in the range between 100 nm and 200 nm, or in the ultraviolet range (UV) between 200 nm and 400 nm. Alternatively, the used light 4 can also have a wavelength in the extreme ultraviolet range (EUV), in particular between 5 nm and 30 nm. Exemplary wavelengths of the radiation source 3 are 365 nm, 248 nm, 193 nm. Depending on the radiation source 3 used, a used usable wavelength spectrum is narrowband, but can also be more broadband, for example when using an Hg discharge lamp.An illumination optical unit 5 of the projection exposure apparatus 1 guides the used light 4 from the radiation source 3 to an object plane 6 of the projection exposure apparatus 1. An object to be imaged by the projection exposure apparatus 1 in the form of a reticle 7 is arranged in the object plane 6. The reticle 7 is shown in dashed lines in FIG. 1. The reticle 7 is supported by a holder, not shown, for allowing controlled scanning displacement or stepwise displacement. As illustrated in FIG. 1, a transmissive reticle can be used, but also a reflective reticle, depending on the embodiment of the projection exposure apparatus 1. The reticle 7 is arranged in an object field 6a in the object plane 6.A collector 8 in the form of an ellipsoidal mirror transfers the illumination light 4 emanating from a source region of the light source 3 into an intermediate focus 9, where a shutter for controlled release of the illumination light 4 is arranged toward the components of the optical system following along the optical axis 2. In the beam path of the illumination light 4 in front of this intermediate focus shutter, a safety shutter 10 is also arranged.Arranged downstream of the intermediate focus 9 in the beam path of the illumination light 4 is a pupil shaping optical unit 11 of the illumination optical unit 5. The pupil shaping optical unit 11 additionally serves as an adjusting device for presetting different illumination settings or different illumination settings with different maximum object field illumination angles. With the pupil shaping optical unit 11, an image of the light source in the intermediate focus 9 is imaged into a pupil plane 12 of the illumination optical unit 5. the pupil shaping optical unit 11 contains an interference filter 13 and, downstream of this, an axicon module 14 with two axicon elements 15, 16. Via the axicon module 14, a maximum object field illumination angle for illuminating the object field 6 acan be preset in an adjustable manner within an illumination angle range.A pupil radius σ 90, which, for a specific pupil illumination of the pupil plane 12 or of a downstream pupil plane of the illumination optical unit 5, specifies the radius within which 90% of an illumination light energy irradiated into this pupil plane is present, serves as a measure of the maximum object field illumination angle set in each case via the pupil shaping optical unit 11. σ 90 is specified in relative pupil coordinates. The value "σ 90= 1" here indicates that an edge of a maximum exilluminable pupil of the illumination system has been reached.Arranged downstream of the pupil plane 12 is an optical assembly 17 which is designed as an illumination light mixing unit and is schematically illustrated in FIG. 1 and for which exemplary embodiments are explained below in conjunction with FIG. 2 ff. An entrance plane of the illumination light mixing unit 17 may coincide with the pupil plane 12.In the region of the illumination light mixing unit 17, an illumination light beam path is deflected by 90° by means of a folding mirror 18, so that the optical axis 2 then no longer runs along the z-direction, but rather along the y-direction of the xyz-coordinate system of FIG. 1. Instead of the folding mirror 18, a 90° deflecting prism can also be used.In the embodiment according to FIG. 1, the illumination light mixing unit 17 has a first optical rod assembly 17 ain front of the folding mirror 18 and a second optical rod assembly 17 bin the beam path after the folding mirror 18.At the exit of the illumination light 4 from the illumination light mixing unit 17, an intermediate field plane 19 of the illumination optical unit 5 is present. In this intermediate field plane 19 there is a diaphragm 20 for presetting a border-side delimitation of the object field 6 a. The aperture 20 is also referred to as an REMA aperture (reticle masking system for masking the reticle 7).The intermediate field plane 19 is imaged into the object plane 6 by an imaging optical unit 21, which is also referred to as an REMA objective. The imaging optical unit 21 contains a 90° folding mirror 21 a, so that the optical axis 2, which up to then has run along the y-direction, now runs in the z-direction. Between the field planes 19 and 6 there is a further pupil plane 22.The object field 6 ais imaged by means of a projection optical unit 23 into an image field 24 in an image plane 25. A wafer 26 is arranged in the image plane 25 in the region of the image field 24. This is carried by a holding device, not shown, with which a controlled scanning displacement of the wafer 26 or also a stepwise displacement of the wafer 26 is possible.A pupil plane 27 of the projection optical unit 23 lies between the object plane 6 and the image plane 25.FIG. 2 illustrates the optical assembly 17, which can be used, for example, instead of the rod assembly 17 aand / or instead of the rod assembly 17 bor else, if the folding via the falling mirror 18 is omitted, instead of the entire illumination light mixing unit 17.An illumination light beam path through the optical assembly 17 according to FIG. 2 runs opposite the z direction in FIG. 2 from left to right.The optical assembly 17 has an optical primary rod 28 for guiding the illumination light 4, of which an individual beam 4 iis emphasized in FIG. 2, along the illumination light beam path from the light source 3 to a target field in the form of the object field 6 a.Furthermore, the optical assembly 17 has an optical follow-up rod 29 which is arranged in the illumination light beam path between the primary rod 28 and the target field 6 a.The entry and exit surfaces of the primary rod 28 and the follower rod 29 each have a rectangular boundary. This boundary may be square, for example, or may have an x / y aspect ratio in the range between 1:5 and 5:1, for example in the range between 1:1.5 and 1.5:1.Between the primary rod 28 and the follower rod 29, the optical assembly 17 has an intermediate image generating optical unit 30 in the illumination light beam path. The intermediate image generating optical unit 30 generates an intermediate image between the primary rod 28 and the follower rod 29 along an imaging dimension y transversely to the z-extension direction of the illumination light beam path. In the xz imaging plane perpendicular thereto, no such intermediate image generation takes place.z-distances between the primary rod 28 and the intermediate image generating optics 30 on the one hand and between the intermediate image generating optics 30 and the subsequent rod on the other hand are shown with exaggerated size in FIG. 2.The intermediate image generating optics 30 has a primary imaging component 31 in the form of a cylindrical lens which is associated with the primary rod 28. Furthermore, the intermediate image generating optics 30 has a subsequent imaging component 32 in the form of a further cylindrical lens which is assigned to the subsequent rod 29. The cylindrical lenses 31, 32 represent examples of an embodiment of the primary imaging component and the subsequent imaging component as cylindrical optics, respectively.The intermediate image generating optics 30 can be embodied as 2f optics.The primary imaging component 31 can be integrally formed on the primary rod 28, in particular on its exit surface. Correspondingly, the subsequent imaging component 32 can also be formed on the subsequent rod 29, in particular on its entry surface. This can be achieved by machining the exit surface of the primary rod 28 or the entry surface of the subsequent rod 29, so that the imaging components 31, 32 can be integral components of the rods 28, 29. Alternatively, the imaging components 31, 32 can also be broken onto the corresponding inlet or outlet surfaces of the rods 28, 29 or connected, for example glued, to these surfaces. A mechanical clamping of the imaging components 31, 32 together with the respective inlet and outlet surfaces of the rods 28, 29 is also possible.FIG. 2 also illustrates the course of the individual beam 4 i through the optical assembly 17. this course is reproduced spatially in the perspective representations of the two rods 28, 29 and is additionally reproduced in the respective plan view projection in plan view of the exit surfaces which are arranged downstream of the rods 28, 29 in FIG. 2, respectively. In the projection onto the exit surface of the primary rod 28, the resulting direction of rotation of the individual beam 4 is i counterclockwise, and in the plan view projection onto the exit surface of the following rod 29, the direction of rotation of the course of the individual beam 4 is i clockwise, i.e. counterclockwise, the direction of rotation of the primary rod 28.FIG. 2 also shows a polarization vector 4 P of the linearly polarized individual beam 4 i. Due to total reflections of the individual beam 4 i at the lateral surfaces of the rods 28, 29, the linear polarization state of the individual beam 4 i is influenced as follows:On the one hand, total reflection has a retarding effect, i.e. leads to a phase difference in s- and p-polarization and thus generally to an elliptical polarization state. This retardation effect is neglected in Fig. 2 and the subject matter of Fig. 10 and claim 7.On the other hand, however, as a result of the reflections on all longitudinal sides of the rod, the output polarization is rotated by a so-called "geometric phase" or "spin reflection phase" with respect to the input polarization. This rotation of the polarization vector is illustrated in FIG. 3 with reference to an individual beam 4 i: the polarization state shown by dashed lines is parallel to the input state, but tilted by a geometric phase different from zero to the output state. (Details 33 in FIG. 2 ).The geometric phase of an individual beam can be read on the basis of its holonomic in the k-sphere, and reference may be made to the technical literature such as, for example, C. Cisowski et al., "Geometric phases of light: insights from fibre bundle theory", Rev. Mod. Phys. 94, (2022) [2202.04356 (arxiv.org)]. According to the invention, the images of the beam profiles within the two rods 28, 29 are virtually identical in the k-sphere, but with an inverse direction of rotation, i.e. have inverse geometric phases.FIG. 3 illustrates the field homogenization by the two mixing rods in the (y,k_y) section of the phase space according to Schörnmer: "Phase space approach to the use of integrator rods and optical arrays in illumination systems", Adv. Opt. Techn. Vol 1 (2012). k_y here denotes the pupil coordinate conjugated to the y coordinate; it is in particular proportional to the y component of the beam direction. The ellipses shown or their cutting as a result of the reflections on the longitudinal surfaces are illustrated here just as in the abovementioned text. Reference exemplarily shows a distribution of a beam density (also called radians) in the (y,k_y) section of the phase space at the four rod ends A, B, C, D: the beam density at the outlet (D) of the secondary rod 29 results from the shearing (B), point broadening (C) and 2nd shearing (D) of the elliptical beam density distribution at the beginning A of the primary rod 28 plus the cutting analogous to FIG. B'. Because the shear of both bars 28, 29 add up independently of the intermediate image, the superimposed fields (number of ellipse chips) also add up. The mixing rods thus continue to fulfil their actual field-homogenizing function independently of the intermediate image.The intermediate image generating optics 30 is refractive.FIG. 4 shows a further embodiment of an optical assembly 34, which can be used instead of the optical assembly 17 according to FIG. 2. Components and functions corresponding to those already explained above with reference to FIGS. 1, 2 to 3 are given the same reference numerals and will not be discussed in detail again.An intermediate image generating optics 35 is designed in the optical assembly 34 as an array of two cylindrical optics 36, 37 with respective cylindrical lenses 38. The cylindrical optics 36, 37 can be formed on the rods 28, 29 of the optical assembly 34, as already explained above in connection with the imaging components 31, 32 of the optical assembly 17. The cylindrical optics 36, 37 can be designed as a 1D array with cylindrical lenses 38 running in each case along the x-coordinate, which then act in each case for a y-layer of the entire bundle of the illumination light 4, or as a 2D array with cylindrical lenses 38 arranged distributed in a grid-like manner over the exit surface of the primary rod 28 and over the entry surface of the follower rod 29, which then act in each case for a channel of the entire bundle of the illumination light 4.By means of the intermediate image generating optics 35, an intermediate imaging takes place layer by layer or channel by channel along the imaging dimension y in accordance with what was explained above in connection with the intermediate image generating optics 30 for an entire rod aperture.The intermediate image generating optics 34 is refractive.With reference to FIGS. 5 and 6, a further embodiment of an intermediate image forming optics 40 that can be used instead of the intermediate image forming optics 30 and 34 described above will be described below. Components and functions corresponding to those already explained above with reference to FIGS. 1, 2, 3 to 4 bear the same reference numerals and are not discussed in detail again.FIG. 5 shows a yz meridional section through the intermediate image generating optical unit 40. FIG. 6 shows an xz meridional section of the intermediate image generating optical unit 40.The intermediate image generating optics 40 has a primary imaging component 41 associated with the primary rod 28. The primary imaging component 41 can be a cylindrical lens comparable to the cylindrical lens 31, but with different finite focal lengths on the one hand in the yz imaging plane and on the other hand in the xz imaging plane. Alternatively, the primary imaging component can be a cylindrical lens guiding a partial channel of the entire illumination light 4 in the manner of a cylindrical lens 38 according to FIG. 4.Furthermore, the intermediate image generating optics 40 has a subsequent imaging component 42 which is assigned to the subsequent rod 29 and whose focal lengths correspond on the one hand in the yz imaging plane and on the other hand in the xz imaging plane to those of the primary imaging component 41. The subsequent imaging component 42 is again designed, depending on the design of the intermediate image generating optics, for guiding either the entire bundle of the illumination light 4 or a sub-channel, in accordance with what was explained above in connection with the primary imaging component.Between the primary imaging component 41 and the subsequent imaging component 42, the intermediate image generating optics 40 has two further imaging components 43, 44, which are lenses, again with different focal lengths in the yz imaging plane on the one hand and in the xz imaging plane on the other hand.In the yz imaging plane, the intermediate image generation optics 40 is embodied as a 2f imaging system. A distance between the primary imaging component 41 and the subsequent imaging component 42 corresponds to twice the focal lengths of these two imaging components 41, 42 in the yz imaging plane.In the xz imaging plane, the intermediate image forming optics 40 is implemented as a 4f imaging system. A distance between the primary imaging component 41 and the imaging component 43 adjacent thereto is twice the focal lengths of these components in the xz imaging plane. A distance between the further imaging component 44 and the subsequent imaging component 42 adjacent thereto is also twice the focal lengths of these two imaging components 44, 42 in the xz imaging plane.Accordingly, the intermediate image generating optics 40 result in an imaging in the yz imaging plane with scale -1 and in the xz imaging plane with scale +1. The intermediate image generating optics 40 thus also generate an image reversal along exactly one imaging dimension y transversely to the beam path of the illumination light 4 running along the z coordinate.The intermediate image generating optics 40 is refractive.FIG. 7 shows a further embodiment of an intermediate image generating optics 45 which can be used in the optical assemblies 17 or 34 instead of the intermediate image generating optics described above. Components and functions corresponding to those already explained above with reference to FIGS. 1, 2, 3, 4, 5 to 6 are given the same reference numerals and will not be discussed in detail again.Between the primary rod 28 and the follower rod 29, the intermediate image generating optics 45 is designed as a pair of cylindrical mirrors 46, 47, the y-spacing of which corresponds to twice the focal length of these cylindrical mirrors 46, 47. This in turn results in an intermediate image in the yz plane and thus an image reversal along the imaging dimension y transversely to the illumination light beam path. In addition, the intermediate image generating optics 45 leads to a 180° convolution of the illumination light beam path, which for example is incident into the primary rod 28 in the positive z-direction and exits from the subsequent rod 29 in the negative z-direction.The intermediate image generating optics 45 is designed to be reflective.In the xz imaging plane perpendicular thereto, no such intermediate image generation takes place.With reference to FIG. 8, a further embodiment of an intermediate image generating optics 48 designed in a diffractive manner in this case is explained below. Components and functions corresponding to those already explained above with reference to FIGS. 1, 2, 3, 4, 5, 6 to 7 are given the same reference numerals and will not be discussed in detail again.The intermediate image generating optics 48 comprises a primary DOE 49 (diffractive optical element) and a subsequent DOE 50, the primary DOE being deposited on the exit surface of the primary rod 28. The following DOE is applied to the input surface of the following rod 29. The two DOEs 49, 50 have a z-spacing from one another which corresponds to twice the focal length of the DOEs 49, 50 in the yz-imaging plane. In this yz imaging plane, an intermediate image is then again generated along the y imaging dimension transversely to the illumination light beam path. In the xz imaging plane perpendicular thereto, no such intermediate image generation takes place.Referring to FIG. 9, another embodiment of an intermediate image forming optical system 51 which can be used in the optical assemblies 17 and 34 in place of the above-described intermediate image forming optical systems will be described below. Components and functions corresponding to those already explained above with reference to FIGS. 1, 2, 3, 4, 5, 6, 7 to 8 are given the same reference numerals and will not be discussed in detail again.The intermediate image generating optics 51 has a primary grin (gradient index) lens 52 and a subsequent grin lens 53. the primary grin lens 52 is associated with the primary optical rod 28 and the subsequent grin lens 53 is associated with the subsequent rod 29 in accordance with what was explained above, for example, in connection with the imaging components 31 and 32 of the embodiment according to FIGS. 2 and 36 and FIG. 37 of the embodiment according to FIG. 4. The z-distance between the two Grin lenses 52, 53 on the one hand and the focal lengths of these Grin lenses 52, 53 in the yz imaging plane are matched to one another such that an intermediate image in the yz imaging plane again arises centrally between the two Grin lenses 52, 53. In the y-imaging dimension, this in turn carries out an image reversal, whereas in the x-imaging dimension, no image reversal takes place.With reference to FIG. 10, a further embodiment of an optical assembly 54 is described below, which can be used instead of the optical assemblies 17 and 34 explained above. Components and functions corresponding to those already explained above with reference to FIGS. 1, 2, 3, 4, 5, 6, 7, 8 to 9 and in particular with reference to FIG. 2 are given the same reference numerals and will not be discussed in detail again.The optical primary rod 28 in the optical assembly 54 has a rectangular cross section with a y / x aspect ratio of approximately 1.5:1. the optical follower rod 29 of the optical assembly 54 has a rectangular cross section rotated through 90° with an x / y aspect ratio of 1.5:1 in comparison therewith.An intermediate image generating optics, for example, in the manner of the intermediate image generating optics 30 according to FIG. 2, is arranged tilted about an optical axis of the illumination light beam path such that an imaging dimension img is arranged at an angle in the range between 0° and 90° with respect to the coordinates x and y spanning the rectangular boundary of the cross sections of the rods 28, 29. An angle between the imaging dimension imgand the y-axis can be, for example, in the range between 1° and 89°, in the range between 5° and 85°, in the range between 25° and 65°, and can be, for example, 30°, 45° or even 60°.As regards the compensation of a respective cumulative geometric phase of the polarization due to the reflections at the respective rods 28, 29, the effect of the intermediate image generating optics 30 arranged tilted at the optical assembly 54 is corresponding to that explained above in connection with FIG. 2 in the case of the non-tilted intermediate image generating optics. In addition, the tilted intermediate image generating optics 30 according to FIG. 10 acts in a compensating manner for retardation, i.e. in a compensating manner for phase splitting between an s- and p-eigen polarization in the respective total reflection of the individual beams 4 i of the illumination light 4 on one of the four lateral walls of the rods 28, 29.The following proportionality relationship applies to the phase splitting ret in the first order of |k|:N x and N y are the numbers of reflections of the respective individual beam 4 i on xz and on yz jacket walls of the respective rod 28, 29. k x and k y respectively describe the pupil coordinate, that is to say the x and y components of the direction vector of the individual beam 4 i in the x and y coordinates.With reference to FIGS. 11 and 12, retardation compensation achieved in the optical assembly 54 is explained.FIG. 11 shows a view of the entry surface of the optical primary rod 28 and FIG. 12 shows a plan view of the entry surface of the optical subsequent rod 29.In gray scales, a retardation amplitude |ret| in the first order of k at exactly one reflection is according to the above formula (1). The white double arrows in FIGS. 11 and 12 correspond to the s-polarization with respect to the respective lateral surface.Illustrated in black is a closed reflection path with N x= 3, N y= 1 in the primary rod 28; the retardation effect according to formula (1) is given by the grey level of the connecting line between two pupil points emerging from one another by reflection multiplied by the number of its passes (number of reflections) and the sign 1 for k x and (-1) for k y.In the follow-on rod 29, the retardation is thus inverse to that in the primary rod 28, since the formula (1) for the follow-on rod 29 results from the fact that for the primary rod 28 x and y are exchanged in the beam data k x ↔k y, N x ↔N y.As a result, the intermediate image which is generated by means of the tilted intermediate image generation optics 30 of the optical assembly 54 also acts in a compensating manner for the retardation. This method is the preferred solution for all rods whose input fields have an x- and y-mirror symmetry, as well as rectangles, e.g. also hexagonal or circular rods.Alternatively to a rectangular rod cross section, rods with a hexagonal or also a circular cross section can also be used in the optical assemblies explained above. In the cross-sectional shape, it is only necessary that there be an x-mirror symmetry and a y-mirror symmetry.To suppress retardation, a retardation-suppressing coating can also be provided on the four lateral surfaces of the primary rod 28 and / or of the secondary rod 29.With the aid of the projection exposure apparatus 1, at least a part of the reticle 7 is imaged onto a region of a light-sensitive layer on the wafer 26 for the lithographic production of a micro- or nanostructured component. Depending on the embodiment of the projection exposure apparatus 1 as a scanner or as a stepper, the reticle 7 and the wafer 26 are continuously moved in the scanner mode or step by step in the stepper mode in a time-synchronized manner in the y direction.References included in the specificationThis list of documents cited by the applicant has been produced in an automated manner and is only included for the better information of the reader. The list is not part of the German patent application or utility model application. The DPMA does not take any adhesion for any faults or omissions.Patent Literature citedWO 2005 / 015 310 A2

[0002] DE 10 2004 059 493 A1

[0002] WO 2016 / 188 739 A1

[0002] Cited Non-Patent LiteratureMurphy, D.: Differential interference contrast (DIC) microscopy and modulation contrast microscopy, in Fundamentals of Light Microscopy and Digital Imaging, Wiley-Liss, New York, pp. 153-168 (2001)

[0008] Differential interference contrast microscopy", retrievable on 12.04.2024

[0008] C. Cisowski et al., "Geometric phases of light: insights from fibre bundle theory", Rev. Mod. Phys. 94, (2022) [2202.04356 (arxiv.org)

[0055] Schörnmer: "Phase space approach to the use of integrator rods and optical arrays in illumination systems", Adv. Opt. Techn. Vol. 1 (2012)

[0056]

Claims

Optical assembly (17; 34; 54) - having an optical primary rod (28) for guiding illumination light (4) along an illumination light beam path from a light source (3) to a target field (6a), - having an optical subsequent rod (29) which is arranged in the illumination light beam path between the primary rod (28) and the target field (6a), - wherein between the primary rod (28) and the subsequent rod (29) there is arranged an intermediate image generating optical unit (30; 35; 40; 45; 48; 51) which generates between the primary rod (28) and the subsequent rod (29) an intermediate image along exactly one imaging dimension (y; img) transversely to the illumination light beam path.Optical assembly according to claim 1, characterised in that the intermediate image generating optics (30; 35; 40; 45; 48; 51) - comprise at least one primary imaging component (31; 36; 41; 46; 49; 52) associated with the primary rod (28) and - comprise at least one subsequent imaging component (32; 37; 42; 47; 50; 53) associated with the subsequent rod (29).Optical assembly according to Claim 2, characterized in that - the primary imaging component (31; 36; 41; 49; 52) is integrally formed on the primary rod (28), and / or - the subsequent imaging component (32; 37; 42; 47; 50; 53) is integrally formed on the subsequent rod (29).Optical assembly according to Claim 2 or 3, characterized in that the primary imaging component (31; 36; 41; 46; 49; 52) and / or the subsequent imaging component (32; 37; 42; 47; 50; 53) is designed as exactly one cylindrical optical unit.Optical assembly according to Claim 2 or 3, characterized in that the primary imaging component (36) and / or the subsequent imaging component (37) is designed as an array of cylindrical optics (38).Optical assembly according to one of Claims 1 to 5, characterized in that the primary rod (28) and the subsequent rod (29) have inlet and outlet surfaces for the illumination light (4) each having a rectangular edge contour.Optical assembly according to Claim 6, characterized in that the imaging dimension (y; img) of the intermediate image generating optical unit (30; 35; 40; 45; 48; 51) runs at an angle different from 0° and from 90° with respect to the coordinates (x, y) which span the edge contour of the entry and exit surfaces of the primary rod (28) and of the subsequent rod (29).Optical assembly according to one of Claims 1 to 7, characterized in that lateral surfaces of the primary rod (28) and / or of the follow-on rod (29) have a coating which is designed in such a way that it suppresses a retardation effect of total reflection on the lateral surfaces.Optical assembly according to Claim 8, characterized in that the coating has an effective refractive index gradient for different states of polarization of the illumination light (4).Illumination optical unit (5) having an optical assembly (17; 34; 54) according to one of Claims 1 to 9 for guiding the illumination light (4) from the light source (3) to the target field (6a) in the form of an object field in which an object (7) to be imaged can be arranged.Optical system having an illumination optical unit according to Claim 10 and having an imaging optical unit (21) for imaging the object field (6a) into an image field (24) in which a section of a substrate (26) can be arranged.Projection exposure apparatus having an optical system according to Claim 11 and having a light source (3) for the illumination light (4).Method for producing structured components, having the following steps: - providing a wafer (26) on which a layer of a light-sensitive material is at least partially applied, - providing a reticle (7) which has structures to be imaged, - providing a projection exposure apparatus (1) according to Claim 12, - projecting at least part of the reticle (7) onto a region of the layer of the wafer (26) with the aid of the projection exposure apparatus (1).A patterned device produced by a method according to claim 13.

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