Actuatable mirror assembly

Abstract

An actuatable mirror assembly (25) has an actuator device (31) with an actuator base unit (32) fixed to the frame and an actuator-mirror mirror carrier unit (30) which can be displaced with respect to the actuator base unit in an actuator-displacable manner. The mirror assembly (25) has at least one mirror (26) which has a reflective surface (27) and is fixed to the actuator mirror carrier unit (30). A bearing device (29) is used to fix the mirror (26) to the actuator mirror carrier unit (30). The bearing device (29) is designed such that an enclosed fixing region (33), provided hereby, of the mirror (26) on the actuator mirror carrier unit (30) has, along a fixing maximum distance, an extent (A) between maximally spaced fixing points of the bearing device (29) that is at least 15% of a typical extent (B) of the reflective surface (27) of the mirror (26). This results in an actuatable mirror assembly the usage possibilities of which are improved, in particular in the field of projection lithography.

Description

[0001] Actuable mirror assembly

[0002] This patent application claims priority from German patent application DE 10 2023 206 689.0, the contents of which are incorporated herein by reference.

[0003] The invention relates to an actuatable mirror assembly. Furthermore, the invention relates to a MEMS mirror device having at least one such mirror assembly, an optical system having at least one such MEMS mirror device, a projection exposure system having such an optical system, a method for producing a micro- or nanostructured component using such a projection exposure system, and a micro- or nanostructured component produced by such a method.

[0004] A mirror assembly is known, for example, as a field facet mirror or as a pupil facet mirror from DE 10 2021 214 237 AE. Such facet mirrors are also known in the form of micromirror devices or MEMS mirror devices, for example from WO 2016 / 146 541 A1 and from DE 10 2008 009 600 A1.

[0005] It is an object of the present invention to further develop an actuatable mirror assembly in such a way that its possible uses are improved, particularly in the field of projection lithography.

[0006] This object is achieved according to the invention by an actuatable mirror assembly having the features specified in claim 1. According to the invention, the mirror of the actuatable mirror assembly is fixed to the actuator-displaceable actuator-mirror support unit via a bearing device which, with regard to an enclosed fixing area, is spatially quite extensive compared to the typical reflection surface extension of the mirror. This ensures a particularly mechanically stable fixing of the mirror to the actuator-mirror support unit. In particular, undesirable mirror resonances or undesirable mirror tilting can then be avoided. A precise, defined mirror position can be achieved due to the extensive fixing. Furthermore, a good thermal coupling of the mirror to the actuator device can be ensured. Heat dissipated on the mirror, in particular through absorption, can then be effectively dissipated.

[0007] An enclosed fixing area is formed by at least one fixing track along which the mirror is fixed to the actuator-mirror carrier unit, wherein this at least one fixing track delimits at least 50% of the enclosed fixing area in the circumferential enclosing direction.

[0008] In particular, the result is a desired stiff and drift-stable mirror assembly.

[0009] The mirror is mechanically stably coupled to the actuator-mirror carrier unit.

[0010] The typical extension of the mirror's reflection surface can also be measured along the maximum fixation distance, along which the extension of the enclosed fixation area is specified. Alternatively, the typical extension of the mirror's reflection surface can also be determined in another way, for example, as the average of different reflection surface extensions, for example when using a mirror that deviates from a circular shape and, in particular, when using a mirror with an aspect ratio other than 1. If, for example, a rectangular mirror surface is used, the typical reflection surface extension can be the average of the two edge lengths of the rectangle. For a round mirror's reflection surface, the typical reflection surface extension corresponds to the reflection surface diameter.The extent of the enclosed fixation area along the maximum fixation distance can be at least 20%, at least 25%, at least 30%, at least 40%, or at least 50% of the typical reflection surface extent, and can even be greater. The extent of the enclosed fixation area along the maximum fixation distance is usually smaller than the typical mirror reflection surface extent.

[0011] The actuator device can have at least one actuator transducer on the actuator mirror support unit side and at least one actuator transducer on the actuator base unit side. The respective actuator transducer is an example of an actuator device of the actuator device. Multiple such actuator transducers per actuator unit are also possible.

[0012] The mirror on the one hand and the actuator-mirror support unit on the other hand can be connected or glued to the bearing device for fixing using a bonding process such as adhesive bonding, eutectic bonding, diffusion bonding, welding or soldering bonding. The bearing device can be integrally connected to the actuator-mirror support unit and in particular can be molded onto it. The bearing device can be integrally connected to a mirror body of the mirror. The bearing device can be integrally connected to the actuator-mirror support unit, in particular to a support plate of the actuator-mirror support unit. Alternatively, the bearing device can also be designed as a separate component from the mirror body and / or the actuator-mirror support unit, which is connected to the mirror body and / or the actuator-mirror support unit.

[0013] The actuator device may include at least one tilting device for tilting the actuator-mirror support unit. Several such tilting devices may also be provided.

[0014] The mirror assembly can be created in particular using MEMS manufacturing technologies, for example by lithographic structuring of layers and / or bonding processes.

[0015] A sensor device according to claim 2 ensures highly precise detection of the position of the mirror relative to the actuator base unit, since forces transmitted via the bearing device due to the displacement of the mirror in the actuator-mirror support unit are transmitted directly and, in particular, without distorting tilting moments to the actuator-mirror support unit and thus also to the components of the sensor device, namely to the sensor-mirror support component, whose displacement relative to the sensor base component can then be detected with high precision. A normal to the reflection surface of the mirror, which passes through the at least one fixing point directly adjacent to the sensor-mirror support component, can also pass through the sensor-mirror support component.

[0016] The respective fixing point is directly adjacent to the sensor-mirror support component, for example, if the distance between the fixing point and the sensor-mirror support component is at most 1.5 times the thickness of an intermediate support plate, which may be part of the actuator-mirror support unit.

[0017] A circumferential fixing track of the enclosed fixing area according to claim 3 leads to a further increase in stability, since a corresponding circumferential bearing track of the bearing device is present. The enclosed fixing area can then be designed as a fixing ring. The extension of the enclosed fixing area along the maximum fixing distance is determined by the ring diameter in the case of a circular fixing ring. The circumferential fixing track can also be elliptical or predefined polygonal. The enclosed fixing area can have several nested and, in particular, circumferential fixing tracks. Such fixing tracks can be arranged concentrically.

[0018] An arrangement of the fixing track according to claim 4 directly adjacent to the sensor / mirror support component as a whole leads to the possibility of particularly precise sensory detection of a displacement of the mirror relative to the actuator base unit. Exact positioning of the mirror is then possible. Several spaced-apart fixing tracks according to claim 5 can also ensure stable fixation of the mirror to the actuator / mirror support unit. The enclosed fixing area can have exactly two spaced-apart fixing tracks. These fixing tracks delimit at least 50% of the enclosed fixing area. For example, if there are two fixing tracks spaced apart by a distance A, each with a length L, which in this example run radially and parallel to each other, the following applies: L > A.

[0019] At least one straight fixing track according to claim 6 can be well adapted to a symmetry of the mirror assembly.

[0020] This applies accordingly to fixing tracks running parallel to one another according to claim 7.

[0021] A small transverse extension of the respective fixing track according to claim 8, which is accompanied by a correspondingly small transverse extension of a bearing track of the bearing device, leads to an advantageously small influence on the yoke of the reflection surface due to bearing-side forces acting on the mirror. The longitudinal extension along the path of the fixing track, to which the transverse extension is related, is given by the circumference of a circular fixing track.

[0022] An extension of the enclosed fixing area along the maximum fixing distance, adapted to the distance between two actuator devices, according to claim 9, leads to a particularly advantageous introduction of forces that has little influence on the mirror during an actuator displacement of the mirror support unit. The extension of the enclosed fixing area along the maximum fixing distance then corresponds to the distance between the two actuator devices if these two values ​​differ by no more than 30%, by no more than 20%, by no more than 10%.

[0023] Reflection surface designs according to claim 10 have proven successful when using the mirror assembly, particularly within the illumination optics of a projection exposure system. The mirror reflection surface can also be designed as a flat surface. The extension and / or path of the fixing tracks specified by the respective bearing device can be adapted to the respective curvature of the reflection surface of the mirror of the mirror assembly.

[0024] To specify a curvature of the reflective surface according to claim 11, a stress coating can be used on a mirror body of the mirror, which, for example, exerts a tensile stress on the reflective surface to create a concave shape of the mirror. The stress coating can be located above or below any additional optical coating provided on the reflective surface. Such a stress coating is known in principle from DE 10 2014 201 622 A1.

[0025] The mirror can be mounted using the bearing device in such a way that the desired curvature is achieved through the layer tension of the stress coating.

[0026] Examples of a predeterminable curvature are a spherical curvature, an aspherical curvature, or even a toric curvature. The underside of a mirror body, i.e. a side facing away from the reflection surface, can be contoured or structured to specify the curvature. Such contouring / structuring can be designed using a plurality of grooves whose profile is adapted to the symmetry of a predefined curvature of the reflection surface. If, for example, the reflection surface is to be shaped as a cylinder, the corresponding mirror body contours or structuring can be designed to be straight. If a rotationally symmetrical, e.g. concave or convex curvature of the reflection surface is desired, the corresponding contouring / structuring can be formed using concentric structures.

[0027] The mirror body can be made of silicon. A material variant of the mirror body can be a material with an anisotropic modulus of elasticity, which can be used to specifically specify a desired curvature of the mirror's reflective surface.

[0028] The advantages of the mirror assembly are particularly evident when used within a MEMS mirror device. The MEMS mirror device can comprise several tens, several hundreds, or even several thousand such mirror assemblies. The MEMS mirror device can be a field facet mirror of an illumination optics system of a projection exposure system for microlithography. Alternatively or additionally, the MEMS mirror device can form a pupil facet mirror of such an illumination optics system. It is also possible to implement such a MEMS mirror device as a facet transmission mirror of a specular reflector spaced from a pupil plane of the illumination optics system.

[0029] The advantages of an optical system according to claim 12, a projection exposure apparatus according to claim 13, a manufacturing method according to claim 14, and a component produced thereby according to claim 15 correspond to those already explained above with reference to the mirror assembly and with reference to the MEMS mirror device. The optical system can be an illumination optics and / or a projection optics of the projection exposure apparatus. The projection exposure apparatus can have an EUV or DUV light source.

[0030] The component manufactured may be a microchip, in particular a memory chip.

[0031] At least one embodiment of the invention is described below with reference to the drawing. The drawing shows:

[0032] Fig. 1 shows a schematic meridional section of a projection exposure system for EUV projection lithography;

[0033] Fig. 2 shows, greatly enlarged and in perspective, an actuatable mirror assembly of an individual mirror of a facet mirror of an illumination optics of the projection exposure system according to Fig. 1, shown in an axial section; Fig. 3 shows, in a perspective sectional view similar to Fig. 2, the mirror assembly according to Fig. 2 with a bearing for a mirror body of an individual mirror of the assembly exposed in one quadrant for illustration;

[0034] Fig. 4 in a representation according to Figure 2 an illustration of a force and position transmission between the mirror body and an actuator mirror carrier unit of the assembly via the mirror body bearing;

[0035] Fig. 5, again in a representation corresponding to Figure 2, shows exemplary heat conduction paths from a reflection surface of the mirror via the actuator mirror support unit to a frame-fixed actuator base unit of the assembly, again via the mirror body bearing;

[0036] Fig. 6 shows a greatly exaggerated effect of a stress coating on the mirror to specify a curvature of the reflection surface in a design with a “spherical curvature”;

[0037] Fig. 6 A is a plan view of the mirror according to viewing direction VI A in

[0038] Figure 6;

[0039] Fig. 7 shows a mirror with a mirror body and an actuator-mirror support unit in a further embodiment of a mirror assembly that can be used instead of the mirror assembly according to Fig. 2; and Fig. 8 shows, in a view obliquely from below, the assembly according to Fig. 7 with a toric mirror surface (cylindrical mirror surface) produced on the mirror by means of a stress coating.

[0040] In the following, the essential components of a projection exposure system 1 for microlithography are first described by way of example with reference to Figure 1. The description of the basic structure of the projection exposure system 1 and its components is not intended to be limiting.

[0041] One embodiment of an illumination system 2 of the projection exposure system 1 has, in addition to a light or radiation source 3, an illumination optics 4 for illuminating an object field 5 in an object plane 6. In an alternative embodiment, the light source 3 can also be provided as a separate module from the rest of the illumination system. In this case, the illumination system does not include the light source 3.

[0042] An object in the form of a reticle 7 arranged in the object field 5 is exposed. The reticle 7 is held by a reticle holder 8. The reticle holder 8 can be displaced, in particular in a scanning direction, via a reticle displacement drive 9.

[0043] For explanatory purposes, a Cartesian xyz coordinate system is shown in Figure 1. The x-direction runs perpendicular to the drawing plane. The y-direction runs horizontally and the z-direction runs vertically. In Figure 1, the scanning direction runs along the y-direction. The z-direction runs perpendicular to the object plane 6. The projection exposure system 1 comprises projection optics 10. The projection optics 10 serve to image the object field 5 into an image field 11 in an image plane 12. The image plane 12 runs parallel to the object plane 6. Alternatively, an angle other than 0° between the object plane 6 and the image plane 12 is also possible.

[0044] A structure on the reticle 7 is imaged onto a light-sensitive layer of a substrate in the form of a wafer 13 arranged in the image plane 12 in the region of the image field 11. The wafer 13 is held by a wafer holder 14. The wafer holder 14 can be displaced, in particular along the y-direction, via a wafer displacement drive 15. The displacement of the reticle 7, on the one hand, via the reticle displacement drive 9, and the displacement of the wafer 13, on the other hand, via the wafer displacement drive 15, can be synchronized with each other.

[0045] The radiation source 3 is an EUV radiation source. The radiation source 3 emits, in particular, EUV radiation 16, which is also referred to below as useful radiation, illumination radiation, or illumination light. The useful radiation has, in particular, a wavelength in the range between 5 nm and 30 nm. The radiation source 3 can be a plasma source, for example an LPP source (laser produced plasma) or a DPP source (gas discharged produced plasma). It can also be a synchrotron-based radiation source. The radiation source 3 can be a free-electron laser (FEL). The illumination radiation 16 emanating from the radiation source 3 is bundled by a collector 17.The collector 17 can be a collector with one or more ellipsoidal and / or hyperboloidal reflection surfaces. The at least one reflection surface of the collector 17 can be exposed to the illumination radiation 16 at grazing incidence (Gl), i.e., at angles of incidence greater than 45°, or at normal incidence (NI), i.e., at angles of incidence less than 45°. The collector 17 can be structured and / or coated, on the one hand, to optimize its reflectivity for the useful radiation and, on the other hand, to suppress stray light.

[0046] After the collector 17, the illumination radiation 16 propagates through an intermediate focus in an intermediate focal plane 18. The intermediate focal plane 18 can represent a separation between a radiation source module, comprising the radiation source 3 and the collector 17, and the illumination optics 4.

[0047] The illumination optics 4 comprises a deflecting mirror 19 and, downstream of this in the beam path, a first facet mirror 20. The deflecting mirror 19 can be a flat deflecting mirror or, alternatively, a mirror with a beam-influencing effect beyond the pure deflection effect. Alternatively or additionally, the deflecting mirror 19 can be designed as a spectral filter that separates a useful light wavelength of the illumination radiation 16 from stray light of a different wavelength. If the first facet mirror 20 is arranged in a plane of the illumination optics 4 that is optically conjugate to the object plane 6 as the field plane, it is also referred to as a field facet mirror. The first facet mirror 20 comprises a plurality of individual first facets 21, which are also referred to below as field facets. Only a few of these facets 21 are shown in Fig. 1 as examples.

[0048] The first facets 21 are designed as rectangular facets or as facets with an arcuate or partially circular edge contour. The first facets 21 can be designed as flat facets or, alternatively, as convex or concave curved facets.

[0049] As is known, for example, from DE 10 2008 009 600 A1, the first facets 21 themselves are each composed of a plurality or multiplicity of individual mirrors, in particular a multiplicity of micromirrors. A mirror assembly with such an individual mirror is explained in more detail below with reference to Figures 2 et seq. The plurality or multiplicity of individual mirrors then jointly form one of the first facets 21, wherein the individual mirrors can be designed with a convex or concave curvature accordingly.

[0050] The first facet mirror 20 is designed as a microelectromechanical system (MEMS system). For details, see, for example, DE 10 2008 009 600 A1.

[0051] Between the collector 17 and the deflecting mirror 19, the illumination s radiation 16 runs horizontally, i.e. along the y-direction.

[0052] In the beam path of the illumination optics 4, a second facet mirror 22 is arranged downstream of the first facet mirror 20. If the second facet mirror 22 is arranged in a pupil plane of the illumination optics 4, it is also referred to as a pupil facet mirror. The second facet mirror 22 can also be arranged at a distance from a pupil plane of the illumination optics 4. In this case, the combination of the first facet mirror 20 and the second facet mirror 22 is also referred to as a specular reflector. Specular reflectors are known from US 2006 / 0132747 A1, EP 1 614 008 B1, and US Pat. No. 6,573,978.

[0053] The second facet mirror 22 comprises a plurality of second facets 23. In the case of a pupil facet mirror, the second facets 23 are also referred to as pupil facets.

[0054] The second facets 23 can also be macroscopic facets, which can, for example, be round, rectangular, or hexagonal, or alternatively, facets composed of individual or micromirrors. Reference is also made to DE 10 2008 009 600 A1 in this regard. If the second facets 23 are also composed of a plurality or multiplicity of individual mirrors, the second facet mirror 22 can be designed as a MEMS system corresponding to the first facet mirror 20.

[0055] The second facets 23 and, if applicable, the individual mirrors forming them may have planar or alternatively convex or concave curved reflection surfaces.

[0056] The illumination optics 4 can form a double-faceted system. This basic principle is also referred to as a fly's-eye integrator. It may be advantageous to arrange the second facet mirror 22 not exactly in a plane that is optically conjugate to a pupil plane of the projection optics 10. In particular, the pupil facet mirror 22 can be arranged tilted relative to a pupil plane of the projection optics 10, as described, for example, in DE 10 2017 220 586 A1.

[0057] With the help of the second facet mirror 22, the individual first facets 21 are imaged into the object field 5. The second facet mirror 22 is the last beam-forming mirror or actually the last mirror for the illumination radiation 16 in the beam path before the object field 5.

[0058] In a further embodiment of the illumination optics 4 (not shown), a transmission optics can be arranged in the beam path between the second facet mirror 22 and the object field 5, which transmission optics contributes in particular to the imaging of the first facets 21 into the object field 5. The transmission optics can have exactly one mirror, but alternatively also two or more mirrors, which are arranged one behind the other in the beam path of the illumination optics 4. The transmission optics can in particular comprise one or two mirrors for normal incidence (NI mirrors, normal incidence mirrors) and / or one or two mirrors for grazing incidence (GL mirrors, gracing incidence mirrors).

[0059] In the embodiment shown in Fig. 1, the illumination optics 4 has exactly three mirrors after the collector 17, namely the deflecting mirror 19, the field facet mirror 20, and the pupil facet mirror 22. In a further embodiment of the illumination optics 4, the deflecting mirror 19 can also be omitted, so that the illumination optics 4 can then have exactly two mirrors after the collector 17, namely the first facet mirror 20 and the second facet mirror 22.

[0060] The imaging of the first facets 21 by means of the second facets 23 or with the second facets 23 and a transmission optics into the object plane 6 is usually only an approximate imaging.

[0061] The projection optics 10 comprises a plurality of mirrors Mi, which are numbered according to their arrangement in the beam path of the projection exposure system 1.

[0062] In the example shown in Figure 1, the projection optics 10 comprises six mirrors M1 to M6. Alternatives with four, eight, ten, twelve, or a different number of mirrors M1 are also possible. The projection optics 10 is a doubly obscured optic. The penultimate mirror M5 and the last mirror M6 each have a passage opening for the illumination radiation 16. The projection optics 10 has an image-side numerical aperture that is greater than 0.5 and can also be greater than 0.6, for example, 0.7 or 0.75.

[0063] Reflection surfaces of the mirrors Mi can be designed as freeform surfaces without a rotational symmetry axis. Alternatively, the reflection surfaces of the mirrors Mi can be designed as aspherical surfaces with exactly one rotational symmetry axis of the reflection surface shape. The mirrors Mi, like the mirrors of the illumination optics 4, can have highly reflective coatings for the illumination radiation 16. These coatings can be designed as multilayer coatings, in particular with alternating layers of molybdenum and silicon.

[0064] The projection optics 10 has a large object-image offset in the y-direction between a y-coordinate of a center of the object field 5 and a y-coordinate of the center of the image field 11. This object-image offset in the y-direction can be approximately as large as a z-distance between the object plane 6 and the image plane 12.

[0065] The projection optics 10 can be designed in particular to be anamorphic. In particular, it has different image scales ß x , ß y in the x- and y-direction. The two magnifications ß x , ßy of the projection optics 10 are preferably (ß x , ß y ) = (+ / - 0.25, / +- 0.125). A positive magnification ß means an image without image inversion. A negative magnification ß means an image with image inversion.

[0066] The projection optics 10 thus leads to a reduction in the ratio 4:1 in the x-direction, i.e. in the direction perpendicular to the scanning direction.

[0067] The projection optics 10 results in a reduction of 8:1 in the y-direction, i.e. in the scanning direction.

[0068] Other magnifications are also possible. Magnifications with the same sign and absolutely identical in the x and y directions, for example, with absolute values ​​of 0, 125, or 0.25, are also possible.

[0069] The number of intermediate image planes in the x- and y-directions in the beam path between the object field 5 and the image field 11 can be the same or can be different, depending on the design of the projection optics 10. Examples of projection optics with different numbers of such intermediate images in the x- and y-directions are known from US 2018 / 0074303 A1.

[0070] Each of the pupil facets or the second facets 23 is assigned to exactly one of the field facets 21 to form an illumination channel for illuminating the object field 5. This can result in particular in illumination according to the Köhler principle.

[0071] The far field is divided into a plurality of object fields 5 using the field facets 21. The field facets 21 generate a plurality of images of the intermediate focus on the pupil facets 23 assigned to them.

[0072] The field facets 21 are each imaged onto the reticle 7 by an associated pupil facet 23, superimposed on one another, to illuminate the object field 5. The illumination of the object field 5 is, in particular, as homogeneous as possible. It preferably has a uniformity error of less than 2%. Field uniformity can be achieved by superimposing different illumination channels.

[0073] By arranging the pupil facets, the illumination of the entrance pupil of the projection optics 10 can be geometrically defined. By selecting the illumination channels, in particular the subset of the pupil facets that guide light, the intensity distribution in the entrance pupil of the projection optics 10 can be adjusted. This intensity distribution is also referred to as the illumination setting or illumination pupil fill. A similarly preferred pupil uniformity in the area of ​​defined illuminated sections of an illumination pupil of the illumination optics 4 can be achieved by redistributing the illumination channels.

[0074] Further aspects and details of the illumination of the object field 5 and in particular of the entrance pupil of the projection optics 10 are described below.

[0075] The projection optics 10 can, in particular, have a homocentric entrance pupil. This can be accessible. It can also be inaccessible.

[0076] The entrance pupil of the projection optics 10 cannot usually be precisely illuminated with the pupil facet mirror 22. When the projection optics 10 images the center of the pupil facet mirror 22 telecentrically onto the wafer 13, the aperture rays often do not intersect at a single point. However, a surface can be found in which the pairwise determined distance of the aperture rays is minimized. This surface represents the entrance pupil or a surface conjugate to it in spatial space. In particular, this surface exhibits a finite curvature.

[0077] It is possible that the projection optics 10 have different entrance pupil positions for the tangential and sagittal beam paths. In this case, an imaging element, in particular an optical component of the transmission optics, should be provided between the second facet mirror 22 and the reticle 7. With the help of this optical element, the different positions of the tangential entrance pupil and the sagittal entrance pupil can be taken into account. In the arrangement of the components of the illumination optics 4 shown in Figure 1, the pupil facet mirror 22 is arranged in a surface conjugated to the entrance pupil of the projection optics 10. The field facet mirror 20 is arranged tilted relative to the object plane 6. The first facet mirror 20 is arranged tilted relative to an arrangement plane defined by the deflection mirror 19.

[0078] The first facet mirror 20 is arranged tilted to an arrangement plane which is defined by the second facet mirror 22.

[0079] With reference to Figures 2 ff., various embodiments of an actuatable mirror assembly 25 are described below, which can be part of the first facet mirror 20 and / or the second facet mirror 22. To clarify positional relationships, a Cartesian xyz coordinate system is used in connection with these Figures 2 ff.

[0080] Figure 2 shows, in an axial section, greatly enlarged and partly in detail, a mirror assembly 25 of a micro- or individual mirror 26 of the first facet mirror 20 and / or the facet mirror 22.

[0081] The individual mirror 26 has a reflection surface 27 with an optical coating highly reflective for the illumination light 16. Above or below this optical coating, the mirror 26 has a stress coating to specify a curvature of the reflection surface 27, which is shown in Figure 2 with an exaggeratedly small radius of curvature. In fact, the curvature is significantly less pronounced than illustrated in Figure 2. The optical coating and the stress coating, neither of which is shown in detail in the drawing, are carried by a mirror body 28 of the mirror 26.

[0082] The mirror 26 is fixed by means of a bearing device 29 (see also Figure 3) to an actuator-displaceable actuator-mirror carrier unit 30, which is also referred to as a rotor and in turn is part of an actuator device

[0083] 31 of the mirror assembly 25, also referred to as a MEMS unit. A bearing plane of the bearing device 29 runs parallel to the xy plane.

[0084] The mirror 26 can be tilted in particular about tilt axes 5x and / or 5y via the actuator device 31.

[0085] In addition to the actuator mirror support unit 30, the actuator device 31 also includes a frame-fixed actuator base unit 32. The actuator units 30,

[0086] 32 have transducers as actuators, which are shown schematically in Figure 2, for example. The basic actuator unit 32 is also referred to as a stator.

[0087] The mirror 26 is fixed to the actuator-displaceable actuator mirror carrier unit 30 of the actuator device 31 via the bearing device 29.

[0088] The bearing device 29 is designed such that an enclosed fixing region 33 provided thereover, which is indicated by hatching in Figure 3, above which the mirror 26 is fixed to the actuator mirror carrier unit 30, has an extension A along a maximum fixing distance between maximally spaced fixing points Fp of the bearing device 29, which extension has at least 25% of an extension B of the reflection surface 27 of the mirror 26 along the maximum fixing distance.

[0089] The maximum fixation distance, along which the extensions A and B are illustrated in Figures 2 and 3, runs along the y-axis in Figures 2 and 3.

[0090] The bearing device 29 has the shape of a circumferential bearing ring, which represents a circumferential fixing track 34 of the enclosed fixing area 33. The enclosed fixing area 33 represents an area delimited or enclosed by the fixing track 34. The closed fixing track 34 delimits 100% of the enclosed fixing area 33 in the circumferential enclosing direction. Depending on the design of the fixing track, such a delimitation of the fixing area 33 in the circumferential enclosing direction by the fixing track can also be less than 100%, but in any case delimits at least 50% of the enclosed fixing area 33.

[0091] The fixing track 34 and thus the bearing ring of the bearing device 29 runs in a circle between a support plate 35 of the actuator mirror carrier unit 30 and the mirror body 28. With these two components 35 and 28, the bearing ring of the bearing device 29 is fixed, for example, by means of a bonding process such as adhesive bonding, eutectic bonding, diffusion bonding, welding or soldering bonding or by gluing.

[0092] Part of the actuator base unit 32 is a base plate 36, which supports the transducers of the actuator base unit 32. Due to the annular fixing track 34, the extension A of the enclosed fixing area 33 along the maximum fixing distance simultaneously represents the ring diameter of the fixing track 34. In a further embodiment of the bearing device, the fixing track defined by this can also be, for example, elliptical, oval, or predefined rectangular or polygonal, e.g., polygonal. The bearing device can also have, for example, several nested circumferential fixing tracks 34i, which can, in particular, run concentrically.

[0093] The fixing track formed by the bearing device 29 has a transverse extension C, i.e., in the case of the circular fixing track 34, a radial extension that is less than one-tenth of a longitudinal extension along the path of the fixing track 34, i.e., less than one-tenth of a circumference of the fixing track 34. This transverse extension C is, in particular, less than one-tenth of a radius of the circular fixing track 34.

[0094] The fixation area extension A is slightly smaller than the distance between two actuator units 37, 38, in particular between two transducers, of the actuator-mirror support unit 30 of the actuator device 30 (see Figure 4). This leads to a direct introduction of actuator forces FA, which are illustrated by double arrows in Figure 4, between the support plate 35 and the mirror body 28 via the bearing device 29. Force introduction detours from the respective actuator unit 37, 38 to the mirror body 28 are then avoided.

[0095] The actuator units 37, 38 are tilt transducers for tilting the actuator-mirror support unit 30 relative to the actuator base unit 32. The mirror assembly 25 also includes a sensor device 38a, via which a displacement position of the actuator-mirror support unit 30 relative to the actuator base unit 32 can be detected by sensor means. The sensor device 38a has a sensor base component 38b and a sensor-mirror support component 38c.

[0096] The sensor base component 38b is fixed to the actuator base unit 32. The sensor mirror support component 38c is fixed to the actuator mirror support unit 30. The sensor device 38a operates capacitively, with comb structures of the sensor mirror support component 38c engaging complementary comb structures of the sensor base component 38b upon a corresponding displacement of the actuator mirror support unit 30 relative to the actuator base unit 32. The sensor principle of the sensor device 38a corresponds in this respect to a drive principle of the actuator device 31. For example, the sensor mirror support component 38c is constructed with a plurality of sensor transducers that are arranged radially within the comparably constructed tilt transducers 37, 38 of the actuator mirror support unit 30 and are fixed to the support plate 35 of the actuator mirror support unit 30.

[0097] The fixing area extension A (see Fig. 4) corresponds to a distance between two actuator units of the sensor-mirror support component 38c. This results in a displacement of the mirror body 28 relative to the sensor base component 38b being mediated directly via the sensor-mirror support component 38c, so that, for example, mechanical stress contributions of the mirror body 28 between fixing points Fp of the enclosed fixing area 33 of the bearing device 29 do not lead to any falsification of a sensor result of the sensor device 38a. This is illustrated in Figure 4 by the double arrows of the actuator forces FA. The respective fixing points Fp of the bearing device 29 are directly adjacent to the respective sensor-mirror support component 38c, namely, they are only spaced apart from it by the thickness of the support plate 35.

[0098] A normal N to the reflection surface 27 of the mirror 26 of the mirror assembly 25, which passes through the respective fixing point of the enclosed fixing area 33, also passes through the sensor mirror carrier components 38c, as is also illustrated in Figure 4.

[0099] The fixing points Fp of the bearing device 29 located in the sectional plane of Figure 4, which lie on the fixing track 34, are therefore arranged directly adjacent to the sensor mirror carrier component 38c.

[0100] In the embodiment shown in Figure 4, the fixation area extension A is equal to the distance D between the central areas of the sensor transducers 38c. The following applies in principle: 0.7 D < A < 1.3 D.

[0101] Figure 5 illustrates the course of two exemplary heat conduction paths 39, 40 between the reflection surface 27 and the base plate 36 of the assembly 25. These heat conduction paths 39, 40 run via the bearing device 29, the actuator-mirror support unit 30 with the sensor-mirror support component 38c and the actuator base unit 32 up to the base plate 36. Due to the large proportion of the enclosed fixing area 33 compared to the reflection surface 33, a corresponding path is comparatively short when integrated over the entire reflection surface 27, resulting in good heat transfer between the reflection surface 27 and the base plate 36. Radiation absorbed by the respective mirror 26 during operation of the projection exposure system 1 then does not lead to undesired thermal deformations of the mirror body 28 or the reflection surface 27. The temperature increase of the mirror can be minimized.

[0102] A corresponding actuator or sensor-transducer arrangement is described in WO 2016 / 146 541 Al.

[0103] Due to the rotational symmetry of the fixation of the mirror body 28 to the support plate 35 about a central axis MA of the mirror 26, a symmetry of this bearing fixation corresponds to a symmetry of the spherical curvature of the reflection surface 27, which is impressed on the mirror 26 via the stress coating.

[0104] Figure 6 illustrates, again in a greatly exaggerated manner, these symmetry relationships with a correspondingly concavely curved reflection surface 27.

[0105] The fixation track 34 runs along a constant sagittal angle of the reflection surface 27. Within the fixation track 34, this sagittal angle is smaller due to the concave design of the reflection surface 27, and outside the fixation track 34, the sagittal angle of the reflection surface 27 is larger. Due to the small transverse extension C of the fixation track 34, there is only a very slight influence on the desired curvature of the reflection surface 27, which is imposed by the stress coating of this reflection surface 27.

[0106] Figures 6 and 6A show exemplary iso-displacements IL of the mirror deformation generated by the stress coating in the mirror body 28. These isolines IL extend according to the rotationally symmetrical concavely curved reflection surface 27 in the form of circles concentric with a center of the reflection surface 27.

[0107] The isolines IL of the top view of the reflection surface 27 according to Figure 6A show the rotationally symmetric spherical deformation of the mirror body.

[0108] With reference to Figures 7 and 8, a further embodiment of an actuatable mirror assembly 42 is described below, which can be used instead of the mirror assembly 25. Components and functions that correspond to those already explained above with reference to Figures 1 to 6, and in particular with reference to Figures 2 to 6, have the same reference numerals and will not be discussed in detail again. In particular, a structure of a sensor device of the mirror assembly 42 corresponds to that described above in connection with the mirror assembly 25 (cf. the sensor device 38a there). This sensor device is not shown in the mirror assembly 42.

[0109] The mirror assembly 42 is designed such that a corresponding stress coating on the reflection surface 27 results in a concave or convex cylindrical mirror design of the mirror 26.

[0110] A bearing device 43 of the mirror assembly 42, whose bearing function corresponds to that of the bearing device 29 of the mirror assembly 25, comprises two bearing strips 44, 45, which have two spaced-apart fixing tracks, which in turn form an enclosed fixing area 46 between them, which is indicated by dashed lines in Figure 7. In the embodiment of the mirror assembly 42, the enclosed fixing area 46 has, along a maximum fixing distance running parallel to the angle bisector of the coordinate axes x and y of the coordinate system, an extension A between maximally spaced fixing points of the bearing device 43, which is at least 15% of a typical extension B of the reflection surface 27 of the mirror 26. This extension A, i.e. the distance between the two bearing strips 44, 45, is smaller than a length L of the respective bearing strip 44, 45.Here too, the fixing tracks, i.e. the bearing strips 44, 45, limit at least 50% of the fixing area 46 enclosed by them.

[0111] Figure 7 illustrates an edge length along the y-coordinate as the typical extension B of the reflection surface 27. Alternatively, the typical extension B can be, for example, the mean of the two edge lengths of the, in this case, rectangular reflection surface 27. The typical reflection surface extension can also be measured along the maximum fixation distance and, in the case of the rectangular or square reflection surface 27 according to Figure 7, is then the length of a diagonal of this reflection surface 27.

[0112] The two bearing strips 44, 45 and thus the two fixing tracks of the mirror assembly 42 are designed as straight fixing tracks which are spaced apart from each other by the extent A along the fixing maximum distance.

[0113] Figure 8 shows, in a view obliquely from below, again with exaggerated curvature, a cylindrical surface effect of the stress coating on the reflection surface 27 of the mirror body 28 of the mirror assembly 42 according to Figure 7. Between the corners of the reflection surface 27 which are horizontally furthest away in Figure 8, the reflection surface 27 is bent in a cylindrical concave manner.

[0114] The two bearing strips 44, 45 of the bearing device 43 run to a good approximation along constant sagittal values ​​of the reflection surface 27.

[0115] In the mirror assembly 42, the mirror body 28 has a contour 47 on its underside facing away from the reflection surface 27 to define a cylindrical curvature of the reflection surface 27. The contour 47 is formed by a plurality of equidistant, parallel grooves 48 formed in the underside of the mirror body 28, the course of which can be seen in the partially broken section of the mirror body 28 in Figure 7. The grooves 48 run parallel to the bearing strips 44, 45.

[0116] In the area of ​​the bearing strips 44, 45, a groove 48B is formed in the underside of the mirror body 28 which is wider than the other grooves.

[0117] This forms a solid-state tilting joint of the mirror body 28, which enables a deformation of the mirror body 28 and thus of the reflection surface 27 due to a corresponding effect of the stress coating.

[0118] A corresponding contouring can also be present on the mirror body 28 of the mirror assembly 25, for example in the form of concentrically running circular or elliptical grooves. To produce a microstructured component, in particular a highly integrated semiconductor device, for example a memory chip, using the projection exposure system 1, the reticle 7 and the wafer 13 are first prepared. Subsequently, a structure on the reticle 7 is projected onto a light-sensitive layer on the wafer 13 using the projection optics 10 of the projection exposure system 1. By developing the light-sensitive layer, a micro- or nanostructure is then created on the wafer 13, and from this, the micro- or nanostructured component is produced.

Claims

Patent claims 1. Actuatable mirror assembly (25; 42) - with an actuator device (31), comprising — a frame-fixed actuator base unit (32) and — an actuator mirror carrier unit (30) which can be displaced relative to the actuator base unit (32), - with at least one mirror (26) with a reflection surface (27) which is fixed to the actuator-mirror carrier unit (30), - with a bearing device (29; 43) for fixing the mirror (26) to the actuator mirror carrier unit (30), - wherein the bearing device (29; 43) is designed such that an enclosed fixing area (33; 46) of the mirror (26) on the actuator-mirror support unit (30) along a fixing maximum distance has an extension (A) between maximally spaced fixing points Fp of the bearing device (29; 43) which is at least 15% of a typical extension (B) of the reflection surface (27) of the mirror (26).

2. Mirror assembly according to claim 1, characterized by a sensor device (38a) - with a sensor base component (38b) which is fixed to the actuator base unit (32), - with a sensor mirror carrier component (38c) which is fixed to the actuator mirror carrier unit (30), - wherein at least one of the fixing points (Fp) of the sensor mirror carrier component (38c) is arranged directly adjacent.

3. Mirror assembly according to claim 1 or 2, characterized in that the enclosed fixing area (33) has a circumferential fixing track (34).

4. Mirror assembly according to claim 3, characterized in that the fixing track (34) is arranged directly adjacent to the sensor mirror carrier component (38c).

5. Mirror assembly according to claim 1 or 2, characterized in that the enclosed fixing region (46) has at least two fixing tracks (44, 45) spaced apart from one another.

6. Mirror assembly according to claim 5, characterized in that at least one or all of the spaced-apart fixing tracks (44, 45) are designed as straight fixing tracks.

7. Mirror assembly according to claim 5 or 6, characterized in that the spaced-apart fixing tracks (44, 45) run parallel to one another.

8. Mirror assembly according to one of claims 1 to 7, characterized in that the fixing track (33; 46) has a transverse extension (C) transverse to the track which is less than 10% of a longitudinal extension along the track of the fixing track (33; 46).

9. Mirror assembly according to one of claims 1 to 8, characterized in that the extension (A) of the enclosed fixing area (33; 46) along the maximum fixing distance corresponds to a distance (D) between two actuator devices (37, 38) of the actuator device (31).

10. Mirror assembly according to one of claims 1 to 9, characterized in that the reflection surface (27) of the mirror (26) is concave or convex with respect to the direction of curvature and spherical or toric with respect to the shape of the curvature or as a cylindrical mirror.

11. Mirror assembly according to one of claims 1 to 10, characterized in that a mirror body (28) of the mirror (26) has a stress coating for producing a curvature or a curvature profile of the reflection surface (27).

12. Mirror assembly according to one of claims 1 to 11, characterized in that an underside of a mirror body (28) of the mirror (26) is contoured and / or structured to specify a curvature of the reflection surface (27).

13. Optical system with at least one mirror assembly according to one of claims 1 to 12.

14. Projection exposure apparatus with an optical system according to claim 13.

15. Method for producing a structured component with the following process steps: - providing a reticle (7) and a wafer (13), - Projecting a structure on the reticle (7) onto a light-sensitive layer of the wafer (13) with the aid of the projection exposure apparatus according to claim 14, - Creating a micro- and / or nanostructure on the wafer (13).

16. A structured component produced by a method according to claim 15.

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