Storage device and assembly for an optical system, optical system and mask inspection system

Abstract

Bearing device (33; 48) for an optical system for the vibration-damped mounting of at least one optical element (32) on a support frame (31). The bearing device (33; 48) has at least one vibration element that can be elastically mounted at least indirectly between the optical element (32) and the support frame (31) to absorb vibrations, and at least one eddy current damper for damping vibrations of the vibration element.

Description

[0001] The present application relates to a storage device and an assembly for an optical system, an optical system with such an assembly and a mask inspection system with such an optical system.

[0002] DE 10 2013 201 305 A1 discloses an eddy current damper and a magnet arrangement with a return plate therefor. WO 2017 / 148 650 A1 discloses a vibration isolator and a lithography system with such a vibration isolator.

[0003] It is an object of the present invention to provide an improved bearing device by means of which optical elements can be mounted in a particularly efficient vibration-damped manner.

[0004] This object is achieved by a bearing device having the features listed in claim 1.

[0005] According to the invention, it was recognized that an optical element can be mounted on a support frame with particularly efficient vibration damping if at least one vibration element is arranged between the optical element and the support frame, the vibrations of which are damped by an eddy current damper. The optical element, the support frame, and at least one bearing arrangement can form an assembly that transmits particularly few vibrations.

[0006] Advantageously, damping using eddy currents is contactless and thus low-wear and, in particular, wear-free. In particular, the damping of the vibration element can be precisely adjusted depending on the magnetic field strength used.

[0007] Furthermore, the use of elastomers for vibration damping can be eliminated. Contamination of the optics and / or pollution from elastomer components, such as fluorine, are avoided.

[0008] The optical element can be designed, in particular, as a mirror. It is particularly possible for the optical element to be designed as a highly reflective component for light in the DUV wavelength range or in the EUV wavelength range. For this purpose, the optical element can, in particular, have a coating, for example, made of ruthenium.

[0009] The DUV wavelength range includes wavelengths in the range between 150 nm and 300 nm, in particular 193 nm. The EUV wavelength range includes wavelengths in the range from 5 nm to 30 nm, in particular 13.5 nm.

[0010] It is also possible that the optical element is designed as a lens.

[0011] The optical element and the support frame are connected to one another via the bearing device, in particular elastically and with vibration damping. The bearing device can in particular have at least one spring, in particular at least two springs, which can be fastened to the support frame. The bearing device can in particular have at least one spring, in particular at least two springs, which can be fastened to the optical element. The springs serve for the (spring-)elastic mounting of further components of the bearing device, in particular the at least one vibration element, between the optical element and the support frame.By means of an elastic connection of the optical element to the bearing device and / or by means of the elastic connection of the bearing device to the support frame, it is possible to move the optical element, for example by means of an actuator, along at least one translational degree of freedom and / or to tilt it along at least one rotational degree of freedom.

[0012] However, the elastic mounting also allows vibrations, which may arise in particular in the support frame and / or propagate through the support frame, to be transmitted to the optical element. The use of a bearing device alone can mitigate the effects of these vibrations, as the bearing device can absorb vibrations and dampen them due to internal friction processes. Vibrations propagating through the bearing device can be effectively counteracted by means of the at least one vibration element. The at least one vibration element can oscillate against the vibration of the springs and / or the support frame and / or the optical element in order to dampen, in particular compensate, the vibration of the bearing device by means of vibration superposition.

[0013] The vibration element is elastically mounted at least indirectly between the optical element and the support frame. "Indirect mounting" means that additional components, in particular additional damping and / or elastic components, can be arranged between the optical element and the vibration element and / or between the support frame and the vibration element.

[0014] The eddy current damper operates according to the principle of electromagnetic induction. If an electrical conductor, particularly one designed as an extended body, moves in a magnetic field perpendicular to the direction of the magnetic field, eddy currents are induced in the conductor. According to Lenz's law, these eddy currents are directed in such a way that the magnetic field created by the eddy currents counteracts the external cause. In other words, the electrical conductor, particularly one designed as an extended body, attempts to suppress its movement in the magnetic field.

[0015] The eddy current damper comprises, in particular, at least one magnet arrangement for generating a magnetic field and an electrically conductive damping body. The at least one magnet arrangement and the at least one damping body are arranged such that vibrations of the at least one vibration element lead to a relative movement of the damping body to the magnetic field of the magnet arrangement.

[0016] By means of a bearing device according to claim 2, a particularly wide range of vibrations can be damped and, in particular, compensated. Particularly preferably, the damping element is designed to dampen and, in particular, compensate vibrations in two spatial directions, in particular vibrations in any two-dimensional superposition of these two spatial directions. For example, vibrations in a plane spanned by the two spatial directions can be damped.

[0017] Here and in the following, spatial directions are understood to mean, in particular, directions that span a space, in particular a three-dimensional space. The spatial directions can preferably be perpendicular to one another and form a suitable Cartesian coordinate system. The two spatial directions in which the at least one eddy current damper damps vibrations of the vibration element can span a two-dimensional plane in three-dimensional space. The two spatial directions are, in particular, not parallel to one another. The two spatial directions are preferably perpendicular to one another.

[0018] In particular, by using several differently aligned eddy current dampers, vibrations along all three spatial directions can be damped.

[0019] The design of the eddy current damper according to claim 3 enables damping in multiple spatial directions, particularly in one plane, by means of an eddy current damper in a simple construction. Preferably, the at least one electrically conductive damping body is mounted so as to be movable relative to the at least one magnetic field arrangement essentially in a plane that is perpendicular to the magnetic field of the at least one magnetic arrangement.

[0020] The two spatial directions in which the magnet assembly and the electrically conductive damping body are movably mounted relative to each other can span a two-dimensional plane in three-dimensional space. In particular, the two spatial directions are not parallel to each other. Preferably, the two spatial directions are perpendicular to each other.

[0021] A "relative movement" is understood to mean all movements of the electrically conductive damping body in the rest frame of the magnetic field arrangement and / or all movements of the magnetic field arrangement in the rest frame of the electrically conductive damping body. Preferably, the electrically conductive damping body is movably mounted along the two spatial directions, in particular in a plane spanned by the two spatial directions, for example, on a component supporting the magnetic field arrangement.

[0022] The magnet arrangement can, in particular, comprise a permanent magnet. This enables uniform, continuous damping of the vibration element in a particularly simple manner. In particular, it is not necessary to subsequently control and / or regulate the vibration parameters. Accordingly, such an eddy current damper is particularly robust and low-maintenance.

[0023] The electrically conductive vibrating body can, in particular, be made, at least partially, of metal or comprise metallic components. Such a metal can be, for example, copper, aluminum, or steel.

[0024] With a bearing device according to claim 4, vibrations can be damped particularly precisely. In particular, even vibrations with small amplitudes can be reliably damped.

[0025] By using multiple magnetic elements, the magnetic field can be broken down into numerous partial magnetic fields, thereby increasing the flow density of the overall magnetic field through the electrically conductive damping body. This can increase the number of eddy currents induced in the electrically conductive damping body. Overall, this improves the magnetic interaction between the magnet arrangement and the electrically conductive damping body.

[0026] The two-dimensional grid structure can be designed, in particular, as a rectangular grid, in particular as a square grid structure. It is particularly possible for the magnet arrangement to comprise at least 9, in particular at least 16, in particular at least 25, and in particular at least 36 magnetic elements.

[0027] In general, the number of magnetic elements is irrelevant for the function of the eddy current damper. For example, the magnet arrangement can have more than 36 magnetic elements or fewer than nine magnetic elements.

[0028] An alternating magnetic field can be generated by means of a bearing device according to claim 5. In this case, the magnetic field can be broken down into a plurality of particularly uniform partial magnetic fields. The poles of adjacent magnets can be aligned antiparallel, in particular. The damping effect of such a magnet arrangement is particularly high. Stray magnetic fields can thus be avoided particularly efficiently.

[0029] In plan view, a magnet arrangement according to claim 5 results in particular in a chessboard-like pattern in which the individual fields of the chessboard, i.e. the end pieces of the magnetic elements provided with the magnetic north or magnetic south poles, alternate.

[0030] Stray fields can be avoided particularly efficiently using a bearing device according to claim 6. In a Halbach array, a magnetic element rotated by 90 degrees is arranged between two magnetic elements whose poles are aligned antiparallel. This allows a resulting partial magnetic field to be conducted particularly uniformly through the three magnetic elements.

[0031] Avoiding stray fields is particularly useful when multiple eddy current dampers or multiple bearing arrangements are arranged adjacent to one another, for example, when the optical element is mounted on the support frame by more than one bearing device. By avoiding stray magnetic fields, it is possible to prevent different bearing devices and / or different eddy current dampers of one or more bearing devices from influencing each other.

[0032] The above-described configuration of the eddy current damper for damping vibrations in at least two spatial directions, as well as the corresponding mounting of the at least one electrically conductive damping body with respect to the at least one magnetic field arrangement, and the described magnetic field arrangements in a two-dimensional grid are each independent aspects of the invention described here, in particular independent of the use of the eddy current damper for damping a vibration of a vibration element. In particular, the invention described here relates to an eddy current damper whose electrically conductive damping body is mounted in at least two spatial directions, in particular in one plane, relative to the at least one magnetic field arrangement.The at least one magnetic field arrangement has, in particular, a plurality of magnetic elements arranged in a two-dimensional grid structure, for example with alternating polarity or in the form of a two-dimensional Halbach array.

[0033] By means of a bearing device according to claim 7, the damping effect can be adjusted particularly flexibly. The use of at least one electromagnet makes it possible, in particular, to damp individual vibration elements particularly strongly or particularly weakly, or in particular, not at all. It is also possible, in particular, to variably adjust the degree of damping via the magnetic field strength.

[0034] In particular, it is possible for some magnetic elements to be designed as electromagnets. It is particularly possible for all magnetic elements of the magnetic arrangement to be designed as electromagnets. It is also possible, in particular, for individual magnetic elements to be designed as permanent magnets, while other magnetic elements are designed as electromagnets.

[0035] A bearing device according to claim 8 provides particularly effective vibration damping. The at least one damping mass counteracts vibrations of the intermediate mass. Oscillation of the intermediate mass and / or vibrations induced by the intermediate mass are reduced, in particular, prevented.

[0036] The intermediate mass can be designed, in particular, to absorb the vibrations of the support frame. The damper mass can be designed, in particular, to dampen and / or compensate for the vibrations absorbed by the intermediate mass.

[0037] The intermediate mass has, in particular, end faces and a lateral surface connecting the end faces. The end faces are, in particular, perpendicular to a connecting axis that corresponds to the shortest connection between the support frame and the optical element along the bearing device. The lateral surfaces can, in particular, be parallel to the connecting axis.

[0038] The intermediate mass can, for example, be designed as a cuboid-shaped body with a lateral surface comprising four side surfaces. It is particularly possible for the at least one damper mass to be arranged on one or more, in particular on each, of these side surfaces. Preferably, one damper mass is arranged on each side surface.

[0039] The intermediate mass can also be designed as a rotationally symmetrical body, in particular as a cylinder. In this case, the damper mass can be designed as a rotationally symmetrical body arranged concentrically with the intermediate mass, for example, as a cylindrical ring.

[0040] A bearing device according to one of claims 9 or 10 is particularly easy to implement. By attaching the magnet assembly to the intermediate mass or to the damper mass and the correspondingly complementary arrangement of the electrically conductive damping body, the assembly can be designed particularly compactly. A separate eddy current damper and its attachment to the masses to be damped are not required.

[0041] Furthermore, such an arrangement of the magnet assembly and / or the electrically conductive damping body allows the damping effect to be optimally adapted to the intermediate mass and the absorber mass. Furthermore, the magnetic field of the magnet assembly is optimally utilized.

[0042] By means of a bearing device according to claim 11, the damping of the bearing device can be adjusted particularly precisely.

[0043] By forming the intermediate mass using two partial bodies, the magnetic field in the space between the partial bodies can be adjusted and, in particular, controlled with particular precision. This allows the assembly to be precisely adapted to the damping requirements. In particular, the magnetic field directions in the space can be adjusted with particular precision, particularly parallel to a surface normal of the planes in which the magnet arrangements are arranged.

[0044] It is particularly possible that opposing magnetic elements of the opposing magnetic arrangements have mutually opposing arrangements, in particular grid structures.

[0045] In particular, it is possible for the two sub-assemblies to be connected at one end by a yoke. This not only facilitates the installation of such an assembly but also serves to specifically guide stray magnetic fields.

[0046] By means of a bearing device according to claim 12, a damping of the intermediate mass and thus a vibration-compensated mounting of the optical element in several directions, in particular in all spatial directions, can be realized particularly easily.

[0047] For this purpose, the damper mass can be attached to the intermediate mass, for example, by means of metal rods. It is also possible for the damper mass to be attached to the intermediate mass by means of elastic springs, such as coil springs and / or leaf springs.

[0048] By means of a bearing device according to claim 13, damping can be realized along all spatial degrees of freedom. In particular, it is also possible to design the damping particularly efficiently along certain degrees of freedom.

[0049] It is particularly possible that absorber masses are arranged on all side surfaces of the lateral surface of the intermediate mass, in particular on all four side surfaces of the lateral surface of a cuboid-shaped intermediate mass.

[0050] A bearing device according to claim 14 can be realized with particularly efficient installation space. By arranging the eddy current dampers directly between the intermediate mass and the support frame and / or between the intermediate mass and the optical element, vibrations of the intermediate mass can be directly damped. Additional vibration damping via one or more absorber masses is possible but not required. This can be particularly advantageous when the available installation space is limited.

[0051] A bearing device according to one of claims 15 or 16 is particularly easy to implement. Furthermore, the rigid connection of the support frame or the optical element to the magnet assembly or the electrically conductive damping body and the complementary arrangement of the electrically conductive damping body or the magnet assembly on the intermediate mass allows for optimal utilization of the available magnetic field, which can, in particular, save costs.

[0052] It is particularly possible for the bearing device to have a plurality of eddy current dampers. For example, the bearing device can have at least two, in particular at least three, and in particular at least four magnet arrangements. It is also possible for the assembly to have at least two, in particular at least three, and in particular at least four electrically conductive damping bodies. The number of magnet arrangements can, in particular, correspond to the number of electrically conductive damping bodies.

[0053] The assembly according to claim 17 has the same advantages as those already discussed above with respect to the bearing device. The assembly in particular has at least two, preferably at least three, bearing devices.

[0054] Another object of the invention is to improve an optical system.

[0055] This object is achieved by an optical system having the features listed in claim 18. The optical system can be an illumination optics and / or a projection optics for a projection exposure system or a mask inspection system.

[0056] The optical system can in particular comprise a plurality of assemblies, each having at least one of the bearing devices described above.

[0057] The optical system may comprise a light source that generates illumination light in the range of DUV wavelengths or EUV wavelengths.

[0058] Another object of the invention is to improve a mask inspection system.

[0059] This object is achieved by a mask inspection system having the features listed in claim 19.

[0060] The optical system can be part of an illumination optics of the mask inspection system and / or a projection optics of the mask inspection system.

[0061] The mask inspection system may further comprise an object plane with a mask holder arranged in the object plane for receiving lithographic masks.

[0062] Embodiments of the invention are explained in more detail below with reference to the figures. They show: Fig. 1 schematically shows an optical system with an illumination optics for a mask inspection system for use with EUV illumination light; Fig. 2 schematically shows a perspective view of an assembly with an optical element, a support frame and three bearing devices, Fig. 3 schematically shows a perspective view of a first embodiment of a bearing device, Fig. 4 the detail IV from the Fig. 3 in enlarged view, Fig. 5 a schematic representation of the kinematics of the assembly with a bearing device according to the embodiment in Fig. 3, Fig. 6 a perspective view of another embodiment of a bearing device, Fig. 7 a schematic view of the kinematics of an assembly with direct damping between the support frame and an intermediate mass, Fig. 8 a schematic representation of the kinematics of the assembly with direct damping between the optical element and the intermediate mass, Fig. 9 a schematic representation of the kinematics of the assembly with direct damping both between the support frame and the intermediate mass and between the optical element and the intermediate mass, Fig. 10A to C show an embodiment of a magnet arrangement comprising a plurality of magnet elements, in which the individual magnet elements are arranged alternately in a two-dimensional grid structure, and Fig. 11A to C show a further embodiment of a magnet arrangement comprising a plurality of magnet elements, wherein the individual magnet elements are arranged as a two-dimensional Halbach array.

[0063] Fig. Figure 1 schematically shows the structure of a possible illumination optics 1, which can be a component of an illumination system 2 of a mask inspection system. It should be noted that the illumination optics 1 shown is purely exemplary.

[0064] One, later with reference to the Fig. The bearing device described in Figures 2 to 11C can be used in conjunction with such an illumination optics 1. It is also possible for the bearing device to be used in conjunction with an illumination optics 1 that has only some of the technical features described here, and in particular none of the technical features described here.

[0065] The storage device can also be used in connection with mask inspection systems or other optical systems that are constructed completely differently and, in particular, have a completely different illumination optics 1 than the illumination optics 1 described here.

[0066] The illumination optics 1 can be part of the illumination system 2 of a mask inspection system, particularly for use with EUV illumination light 3. A beam path of the illumination light 3 is illustrated in the drawing via edge rays. The illumination light 3 can be used to illuminate an illumination field or object field 4 of the mask inspection system.

[0067] The illumination light 3 can be generated by an EUV light source 5 in a source region or source volume 6. The light source 5 can generate useful EUV radiation in a wavelength range between 2 nm and 30 nm, for example in the range between 2.3 nm and 4.4 nm or in the range between 5 nm and 30 nm, for example at 13.5 nm.

[0068] The light source 5 can be embodied as a plasma light source. This can be, for example, a laser plasma source (LPP; laser produced plasma) or a discharge source (DPP; discharge produced plasma). It is also possible to use a high-harmonic EUV source. Such plasma sources are known in principle as light sources for EUV projection exposure systems.

[0069] To facilitate positional relationships, a Cartesian xyz coordinate system is used below. The x-axis is perpendicular to the drawing plane of the Fig. 1. The y-axis runs in the Fig. 1 horizontally to the right and the z-axis runs in the Fig. 1 vertically upwards.

[0070] After emission by the light source 5, the illumination light 3 can first pass through an aperture diaphragm 9 that limits a bundle of the illumination light 3 at the edge.

[0071] The aperture diaphragm 9 can be designed to be interchangeable. For this purpose, for example, a diaphragm wheel can be provided, which stores various aperture diaphragm designs that can be selectively used in the beam path of the illumination light 3. Such an interchangeable aperture diaphragm design can be used to specify different input apertures for the illumination light 3.

[0072] The aperture diaphragm 9 can be designed to be interchangeable and / or adjustable and / or adjustable with respect to its diaphragm edge. This allows various diaphragm geometries of the aperture diaphragm 9 to be realized and / or adjusted. Specifiable diaphragm geometries can, for example, be round with a selectable diameter and / or elliptical with a selectable ellipse size and, if necessary, with a selectable semi-axis ratio of the ellipses. Such a semi-axis ratio of an ellipse that can be specified via the aperture diaphragm 9 can be 2:1.

[0073] Following the aperture stop 9, the illumination light beam 3 can be transferred from a coupling mirror 10 to a beam homogenization device 11 of the illumination optics 1. The coupling mirror 10 can also be part of the beam homogenization device 11. A beam homogenizing element 11a, for example a hollow waveguide, can be part of the beam homogenization device 11. In other embodiments, the beam homogenization device 11 can alternatively or additionally also have at least one facet mirror for splitting the EUV illumination light 3 into a plurality of individual beams that overlap one another to form a homogenizing mixture. In this case, the beam homogenization device can also have, for example, two facet mirrors arranged downstream of one another.

[0074] The aperture stop 9 can limit a numerical aperture of the illumination light beam 3 emitted by the source region 6 to a numerical aperture value in the range between 0.02 and 0.03, for example, in the range between 0.02 and 0.1 or between 0.05 and 0.08. A numerical aperture specified by the aperture stop 9 that is greater than 0.1, i.e., in the range between 0.1 and 0.3, can enable a greater light yield in the illumination light beam path between the source volume 6 and the illumination field 4.

[0075] An incoherent lighting setting may be used.

[0076] Alternatively or in addition to the aperture stop 9, an aperture-limiting stop can be arranged between the beam-homogenizing element 11a and a downstream optical component of the illumination optics 1. It is also possible to arrange such a further aperture stop in the beam path of the illumination light 3 after the beam-homogenizing element 11a between two downstream optical components of the illumination optics 1.

[0077] Depending on the design of the coupling optics, this can have exactly one coupling mirror, as shown in the Fig. 1 using the example of the coupling mirror 10, or may also have several coupling mirrors, e.g. two or three coupling mirrors.

[0078] The inlet opening 12 and an outlet opening 14 of the beam homogenizing element 11a can each be square or rectangular with typical dimensions in the range between 0.5 mm and 5 mm.

[0079] An aspect ratio of the entrance opening 12 and an equally sized exit opening 14 of the beam homogenizing element 11a for the illumination light 3 in an exit plane 15 can be between 0.25 and 4, for example between 0.5 and 2. A typical size of the entrance opening 12 and the exit opening 14 of the beam homogenizing element 11a can be 0.75 mm × 0.75 mm, 1.0 mm × 2.0 mm, or 1.5 mm × 2.0 mm.

[0080] One in the Fig. The imaging output mirror optics 16, schematically illustrated in FIG. 1 and arranged downstream of the beam homogenizing element 11a, can image the exit opening 14 of the beam homogenizing element 11a, located in an exit plane 15, into the illumination field 4 in an object plane 17. An image-side numerical aperture of this image can be in the range between 0.1 and 0.3.

[0081] The, for example two or more, mirrors of the output mirror optics 16 can be designed as mirrors for grazing incidence of the illumination light 3.

[0082] The aperture stop explained above, which may be used after the beam homogenizing element 11a, can be arranged between the beam homogenizing element 11a and a first mirror of the outcoupling mirror optics 16 or also between different mirrors of the outcoupling mirror optics 16.

[0083] The output mirror optics 16 can be designed in the manner of a Wolter telescope, namely a Type I Wolter optic. Such Wolter optics are described in J.D. Mangus, J.H. Underwood, "Optical Design of a Glancing Incidence X-ray Telescope," Applied Optics, Vol. 8, 1969, page 95, and the references cited therein. Instead of a paraboloid, a hyperboloid can also be used in such Wolter optics. Such a combination of an ellipsoidal mirror with a hyperboloidal mirror also represents a Type I Wolter optic.

[0084] Another embodiment of the output-coupling mirror optics 16 is described in US 10,042,248 B2. Alternatively, mirrors of the output-coupling mirror optics 16 can also have reflection surfaces in the form of freeform surfaces.

[0085] A reticle 18 to be inspected can be arranged in the object plane 17, which can be held in particular by a reticle holder 19. The reticle holder 19 can be mechanically connected to a reticle displacement drive 20, via which the reticle 18 can be displaced, in particular along an object displacement direction y, during a mask inspection. This enables a scanning displacement of the reticle 18 in the object plane 17.

[0086] The illumination field 4 can have a typical dimension in the object plane 17 that is less than 1 mm and can be less than 0.5 mm. In the illustrated embodiment, the extension of the illumination field 4 can be 0.5 mm in the x-direction and 0.5 mm in the y-direction.

[0087] The x / y aspect ratio of the illumination field 4 may correspond to the x / y aspect ratio of the exit opening 14.

[0088] The illumination field 4 can be illuminated with a Fig. 1 projection optics not shown into an image field in an image plane.

[0089] The image field can be captured by a detection device, e.g., a CCD camera or multiple CCD cameras. For details on imaging the image field, see US 10,042,248 B2 and the references cited here and in US 10,042,248 B2.

[0090] The mask inspection system makes it possible to inspect, for example, a structure on the reticle 18.

[0091] An imaging factor β1 of the input-coupling mirror optics 10 can be in the range between 0.1 and 50, thus it can reduce by a factor of 10 up to a factor of 50. An imaging factor β2 of the output-coupling mirror optics 16 can be in the range between 0.02 and 10, thus it can in turn reduce by a factor of 50 up to a factor of 50. A product β1, β2 of the two imaging factors can be in the range between 0.25 and 10 for the illumination optics 1.

[0092] The following are based on the Fig. 2 to 11C describe possible embodiments of an assembly 30 comprising a support frame 31, an optical element 32, and at least one bearing device 33, 48. The embodiments are exemplary in nature. It is possible that the bearing device 33, 48 has more or fewer technical features than those described here.

[0093] Fig. 2 shows a perspective view of the assembly 30 with the support frame 31, the optical element 32 and three bearing devices 33.

[0094] The optical element 32 can, in particular, be a mirror, in particular of the illumination optics 1, for example one or more mirrors of an input coupling optics and / or one or more mirrors of the output coupling mirror optics 16. The optical element 32 can, in particular, be a field facet mirror and / or a pupil facet mirror and / or a grazing incidence (GI) mirror. It is also possible for the optical element 32 to be one of the mirrors of the projection optics. The optical element 32 can also be a beam homogenizing element, for example the beam homogenizing element 11a.

[0095] The optical element 32 can also be designed as a lens, not shown in the figures.

[0096] The optical element 32 is elastically mounted on the support frame 31 by means of the bearing devices 33. The bearing devices 33 are designed, in particular, to dampen vibrations that arise, for example, due to the cooling of individual components of the mask inspection system or other mechanical influences in the support frame 31 or that are transmitted to the support frame 31. In particular, it is possible for the bearing devices 33 to be designed such that no vibrations of the support frame 31 are transmitted to the optical element 32.

[0097] Fig. Figures 3 to 5 show a perspective view of a first embodiment of a bearing device 33. The optical element 32 and the support frame 31 are shown schematically.

[0098] The bearing device 33 has an intermediate mass 34, which is designed, for example, as a cuboid-shaped body. The intermediate mass is elastically attached to both the support frame 31 and the optical element 32 by means of two springs 35, in the example.

[0099] An elastic fastening of the optical component 32 to the support frame 31 can, for example, make it possible, with the aid of actuators not shown in the figures, to displace the optical element 32 relative to the support frame 31 by at least one translational degree of freedom and / or to tilt it by at least one rotational degree of freedom.

[0100] The elastic fastening of the optical element 32 can reduce the transmission of vibrations and / or oscillations from the support frame 31 to the optical element 32. Furthermore, the intermediate mass 34 allows vibrations and / or oscillations of the support frame 31 to be absorbed and compensated. However, the intermediate mass 34 of the bearing device 33 can also generate vibrations, which can be transmitted to the optical element 32 by means of the elastic springs 35.

[0101] In order to compensate for the vibrations and / or oscillations of the intermediate mass 34, a damper mass 37 is elastically attached to each of the four side walls 36 of the intermediate mass 34, which are parallel to a connection direction between the support frame 31 and the optical element 32.

[0102] The damper masses 37 are each attached to the respective side surface 36 by means of elastic rods 38, for example made of metal, in such a way that the damper mass 37 can perform planar movements perpendicular to the spacing direction. This allows the damper masses 37 to oscillate against the intermediate mass 34.

[0103] The elastic rods 38 serve in particular only to fasten the intermediate mass 34 to the damper mass 37. The elastic rods 38 have hardly any, in particular essentially no, damping effect.

[0104] As particularly in the Fig. As shown in detail in Figure 4, the intermediate mass 34 has two partial bodies 39, 40 in the region of the respective side surfaces 36, which are arranged at a distance from one another and connected to one another by a yoke 41. A gap 42 is formed between the partial bodies 39, 40, which gap, in particular, has a uniform extension in a spacing direction between the partial bodies. The damper mass 37 is arranged in the gap 42.

[0105] The partial body 40 is arranged on the circumference of the partial body 39 and forms the respective outer side surfaces 36. The partial body 39 is designed as a central base body of the intermediate masses 34. The intermediate mass 34 has, in particular, a base body 39, on which the partial bodies 40 are arranged on the circumference. For reasons of better visibility of the arrangement of the damper masses 37, Fig. 3 the partial bodies 39 are not shown.

[0106] The damper mass 37 can, in particular, be made of an electrical conductor. Alternatively, the damper mass 37 can also comprise an electrically conductive damping body.

[0107] The partial bodies 39, 40 each have a magnet arrangement 43, 44. The base body 39 has, in particular, a magnet arrangement 43 on its circumferential side surfaces. The magnet arrangement 43 comprises a plurality of magnet elements 45. The magnet arrangement 44 comprises a plurality of magnet elements 46. The magnet elements 45, 46 of the magnet arrangements 43, 44 are arranged in a two-dimensional grid structure. Exemplary grid arrangements are described below with reference to the Fig. 10A to 10C and 11A to 11C are explained in more detail.

[0108] The magnet arrangements 43, 44 and the respective magnet elements 45, 46 are arranged on the partial bodies 39, 40 in such a way that a magnetic field B is established in the intermediate space 42, which field extends from the first magnet arrangement 43 on the partial body 39 through the intermediate space 42 to the second magnet arrangement 44 of the second partial body 40, and thereby flows through the absorber mass 37.

[0109] Movements, such as vibrations and / or oscillations, of the intermediate mass 34 are transmitted to the absorber mass 37 via the elastic rods 38. Due to the elasticity of the rods 38, the absorber mass 37 moves relative to the intermediate mass 34, in particular the absorber mass 37 oscillates against the intermediate mass 34. The absorber mass 37 represents or comprises an electrical conductor moving in the magnetic field B. According to Lenz's law, eddy currents are induced in the absorber mass 37 or its electrical conductors, which are directed such that the counter magnetic field generated by the eddy currents and not shown in the figures counteracts the external cause, i.e. the magnetic field B. This results in an eddy current damper acting between the intermediate mass 34 and the absorber mass 37. This dampens the movement of the absorber mass 37, in particular its oscillations.Since the absorber mass 37 is elastically coupled to the intermediate mass 34 via the rods 38, damping of the absorber mass 37 also damps movements, in particular vibrations and / or oscillations of the intermediate mass 34, and in particular suppresses them.

[0110] In order for eddy currents to be induced in the absorber mass 37, the movement of the absorber mass 37 must, according to the third Maxwell equation, necessarily have a movement component perpendicular to the direction of the magnetic field B. In the illustrated embodiment, the absorber mass 37 is attached to the intermediate mass 34 via the rods 38 in such a way that movement of the absorber mass in all directions perpendicular to the direction of the magnetic field B is possible.

[0111] As a result, the interaction of the intermediate mass 34 and a single absorber mass 37 can dampen oscillations and / or vibrations of the intermediate mass 34 in two spatial directions perpendicular to each other, and all possible superpositions of these two spatial directions, namely perpendicular to the magnetic field direction.

[0112] By arranging two damper masses 37 on two, in particular perpendicular, side surfaces 36 of the intermediate mass 34, damping of oscillations and / or vibrations in all three spatial directions can be achieved. By using three or four damper masses 37 arranged along the four side surfaces 36 of the intermediate mass 34, particularly effective and uniform damping of vibrations and / or oscillations can be achieved.

[0113] Fig. Figure 5 schematically illustrates the kinematics of the bearing arrangement 33, whereby for the sake of clarity only one damper mass 37 is shown. The support frame 37, the optical element 32, the intermediate mass 34 and the damper mass 37 are coupled masses with masses m0, m1, m2 and m T The springs 35 between the support frame 31 (m0) and the intermediate mass 34 (m2) have a spring constant or a modulus of elasticity c 02 The springs between the optical element 32 (m1) and the intermediate mass 34 (m2) have a spring constant or a modulus of elasticity c 12 . The rods 38 have a modulus of elasticity c T . The space between intermediate mass 34 (m2) and absorber mass 37 (m T ) formed eddy current damper has a damping constant d T The bearing arrangement allows a functional separation between elastic fastening and damping. In particular, the elastic constant c Tand damping constant d T can be selected independently of each other. This allows for particularly flexible and precise adjustment of the bearing device for vibration decoupling.

[0114] In further embodiments not shown in the figures, the second partial body 40 and the yoke 41 can be omitted to realize the electromagnetic damping of the damper mass 37. In such a case, the intermediate mass 34 comprises only one magnet arrangement 44 with the respective magnetic elements 45. In this case, the magnetic field B will extend from one magnetic element 45 to an adjacent magnetic element 45, through the damper mass 37.

[0115] In the Fig. Figure 6 shows a further embodiment of an assembly 47 with a support frame 31 and an optical element 32. Identical components bear the same reference numerals and will not be explained in detail again.

[0116] The assembly 47 has a bearing device 48. The bearing device 48 comprises an intermediate mass 49, which is connected by means of elastic springs 35 to both the support frame 31 and the optical element 32. The intermediate mass 49 has four magnet arrangements 50, which are attached directly to the circumferential side surfaces of the intermediate mass 49. The magnet arrangements 50 each comprise a plurality of magnet elements 51, which are arranged in a two-dimensional grid structure. Exemplary suitable magnet arrangements 50 are described below with reference to the Fig. 10A to C and 11A to C are explained in more detail.

[0117] Basically, in the exemplary embodiment according to Fig. 6 a magnetic field B whose magnetic field lines are closed over adjacent magnetic elements 51.

[0118] The bearing device 48 further comprises four fastening plates 52, which are assigned to the respective circumferential side surfaces and of which in the Fig. 6 For the sake of clarity, only two are shown.

[0119] The fastening plates 52 are, in particular, rigidly connected to the support frame 31. The fastening plates 52 are not connected to the intermediate mass 49.

[0120] The mounting plates 52 each have an electrically conductive damping body 53, which is arranged on the mounting plate 52 such that the electrically conductive damping body 53 is spaced apart from the respective magnet arrangement 50. It is also possible for the mounting plates 52 themselves to be conductive. A separate damping body 53 can then be dispensed with.

[0121] The electrically conductive damping body 53 is particularly cuboid-shaped. The electrically conductive damping body 53 is arranged such that a side surface of the electrically conductive damping body 53 is parallel to a side surface of the intermediate mass 49, and thus parallel to the magnet arrangement 50.

[0122] The magnetic field B generated by the individual magnetic elements 51 of the magnetic arrangement 50 penetrates the electrically conductive damping body 53.

[0123] Since the electrically conductive damping body 53 is rigidly attached to the support frame 31 by means of the fastening plate 52, movements such as oscillations and / or vibrations of the support frame 31 are transmitted to the electrically conductive damping body 53 by means of the fastening plate 52. Relative movements of the intermediate mass 49 and the support frame 31 lead to a relative movement of the electrically conductive damping body 53 to the magnetic field B. This movement is damped according to Lenz's rule for the same reasons as already explained for the Fig. 3 to 5. This results in an eddy current damper acting between the support frame 31 and the intermediate mass 49. Thus, vibrations of the intermediate mass 49 can be damped directly via the support frame 31 and vice versa.

[0124] Fig. 7 shows analogous to Fig. 5 schematically shows the resulting kinematics. The eddy current brake acting between the support frame 31 (m0) and the intermediate mass 49 (m2) has a damping constant d 02 which is independent of the spring constant or the elastic modulus c 02 can be chosen.

[0125] The Fig. 8 and Fig. 9 schematically show further variants of storage devices 48, whereby the representation and nomenclature of the Fig. 5 corresponds.

[0126] The bearing device 48 from Fig. 8 allows the optical element 32 and the intermediate mass 49 to be coupled in a vibration-damping manner. The damping constant d 12 can be independent of the spring constant or the modulus of elasticity c 12 be elected.

[0127] It is also possible, in particular, that both the intermediate mass 49 and the support frame 31, as well as the intermediate mass 49 and the optical element 37 are coupled to a bearing device 48 in a vibration-damping manner, as is shown schematically, for example, in the Fig. 9. The damping constants d 02 and d 12 can be determined independently of each other; in particular, they can be the same or different.

[0128] In further embodiments not shown in the figures, eddy current dampers can act both between the intermediate mass and the support frame and / or the optical element, as well as between the intermediate mass and the absorber mass. For example, magnet arrangements can be arranged on the outer circumferential surfaces of the partial bodies 40, which interact with electrically conductive damping bodies attached to the optical element or the support frame.

[0129] In the Fig. 10A to C is an example of a magnet assembly 55 with a plurality of magnetic elements 56 ij and a magnet arrangement 57 with a plurality of magnetic elements 58 ij shown schematically. Fig. Figure 10A shows a front view of the magnet assembly 55. Fig. 10C shows a top view of the magnet arrangement 57. The magnet arrangements 55, 57 can be arranged opposite each other. Fig. 10B shows a cross section along the section line AA in Fig. 10A or BB in Fig. 10C by the two opposing magnet arrangements 55, 57.

[0130] Both the magnet arrangement 55 and the magnet arrangement 57 form, at least in plan view, a two-dimensional grid structure, wherein the magnet elements 56 ij , or 58 ij occupy the individual grid spaces.

[0131] The magnetic elements 56 ij , 57 ijare designed as, for example, cuboid-shaped bar magnets. The magnetic elements 56 ij , 57 ij can be designed in particular as electromagnets.

[0132] The magnet arrangements 55, 57 are designed as square grids of the same size.

[0133] Mathematically, such a lattice structure can be described using matrices. The individual magnetic elements 56 ij or 58 ij represent the entries of the respective matrix, where according to mathematical consensus the index i describes the row number and the index j the column number of the respective entry.

[0134] According to the embodiment in the Fig. 10A and Fig. 10B are the individual magnetic elements 56 ij or 58 ij arranged alternately. This means in particular that adjacent magnetic elements 56 ijor 58 ij have different polarities. Two magnetic elements are considered adjacent if and only if the sum of row index i and column index j of the two elements differs by exactly one.

[0135] In the case of the magnet arrangement 55, it is particularly important that all magnetic elements 56 ij , where the sum of row index i and column index j is an even number, at least in plan view, form a magnetic north pole, whereas all magnetic elements 56 ij , where the sum of row index i and column index j results in an odd number, at least in plan view, form a magnetic south pole.

[0136] The reverse applies to the magnet arrangement 57. All magnetic elements 58 ij , where the sum of row index i and column index j is an even number, form, at least in plan view, a magnetic south pole, whereas all magnetic elements 58 ij, where the sum of row index i and column index j results in an odd number, at least in plan view, form a magnetic north pole.

[0137] Due to the complementary design of the magnet arrangements 55 and 57, an attractive force arises between the magnet arrangements 55 and 57. In particular, a magnetic field B is created that can extend from the magnet arrangement 55 to the magnet arrangement 57. Accordingly, such magnet arrangements 55 and 57 can be used, for example, in connection with a Fig. The assembly described in 3 to 5 can be used.

[0138] It is also possible that the magnet arrangement 55 or the magnet arrangement 57 in connection with an embodiment according to the Fig. 6 to 9 are used.

[0139] In the Fig. 11A to C are further embodiments of a magnet arrangement 59 with magnetic elements 60 ijand a magnet arrangement 61 with magnetic elements 62 ij The representation is analogous to that in the Fig. 10A to 10C.

[0140] The magnetic elements 60 ij the magnet arrangement 59 and the magnet elements 62 ij The magnet arrangement 61 is arranged in a so-called Halbach array. In a Halbach array, the magnetic elements 60 ij , 62 ij , which form a magnetic north pole or a magnetic south pole in plan view, of magnetic elements 60 i-1j , 60 i+1j , 60 ij-1 , 60 ij+1 or 62 i-1j , 62 i+1j , 62 ij-1 , 62 ij+1 surrounded by magnetic elements, which, compared to the 60 ij or 62 ij have been rotated by 90 degrees. This allows the resulting magnetic field B to be conducted particularly uniformly. In particular, the arrangement of the magnetic elements 60 ij , 62ij control and, in particular, avoid stray magnetic fields particularly efficiently.

[0141] The Fig. 11A and Fig. The magnet arrangements 59, 61 shown in Figure 11B are designed to be complementary. This allows the Fig. 11A to 11C shown magnetic elements both in assemblies according to the Fig. 3 to 5 as well as in connection with assemblies according to the Fig. Use the embodiment described in 6 to 9. QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] DE 10 2013 201305 A1 WO 2017 / 148 650 A1

[0002] US 10,042,248 B2 [0084,0 Zitierte Nicht-Patent Literature

[0000] JD Mangus, JH Underwood „Optical Design of a Glancing Incidence X-ray Telescope“, Applied Optics, Vol. 8, 1969, Page

Claims

[1] Bearing device (33; 48) for an optical system for the vibration-damped mounting of at least one optical element (32) on a support frame (31), the bearing device (33; 48) comprising: - at least one vibration element which can be elastically mounted at least indirectly between the optical element (32) and the support frame (31) to absorb vibrations, and - at least one eddy current damper to dampen vibrations of the vibration element. [2] Bearing device (33; 48) according to claim 1, characterized by that the at least one eddy current damper is designed to dampen vibrations of the vibration element in at least two spatial directions. [3] Bearing device (33; 48) according to one of the preceding claims, characterized bythat the eddy current damper comprises at least one magnet arrangement (43, 45; 50; 55, 57; 59, 61) and at least one electrically conductive damping body (53), wherein the electrically conductive damping body (53) and the magnet arrangement (43, 45; 50; 55, 57; 59, 61) are mounted so as to be movable relative to one another in at least two spatial directions. [4] Bearing device (33; 48) according to one of the preceding claims, characterized by that the magnet arrangement (43, 45; 50; 55, 57; 59, 61) comprises a plurality of magnet elements (44, 46; 51; 56 ij , 58 ij , 60 ij , 61 ij ) arranged in a two-dimensional lattice structure. [5] Bearing device (33; 48) according to claim 4, characterized by that the poles of two adjacent magnetic elements (44, 46; 51; 56 ij , 58 ij , 60 ij , 61 ij ) are aligned in opposite directions. [6] Bearing device (33; 48) according to claim 4, characterized bythat the magnetic elements (44, 46; 51; 56 ij , 58 ij , 60 ij , 61 ij ) are arranged in a two-dimensional Halbach array. [7] Bearing device (33; 48) according to one of the preceding claims, characterized by that the at least one eddy current damper has at least one electromagnet. [8] Bearing device (33; 48) according to one of the preceding claims, characterized by that the vibration element has an intermediate mass (34; 49) and at least one elastic damper mass (37) fastened to the intermediate mass, wherein the at least one eddy current damper is formed between the damper mass (37) and the intermediate mass (34; 49). [9] Bearing device (33; 48) according to claim 8, characterized bythat the at least one magnet arrangement (43, 45; 50; 55, 57; 59, 61) is fastened to the intermediate mass (34; 49) and the at least one absorber mass (37) is designed as an electrically conductive damping body (53) or comprises the electrically conductive damping body (53). [10] Bearing device (33; 48) according to claim 8, characterized by that the at least one magnet arrangement (43, 45; 50; 55, 57; 59, 61) is fastened to the absorber mass (37) and the intermediate mass (34; 49) is designed as an electrically conductive damping body (53) or comprises the electrically conductive damping body (53). [11] Bearing device (33; 48) according to claim 8 or 9, characterized byin that the intermediate mass (34; 49) has at least two interconnected partial bodies (39; 40) between which an intermediate space (42) is formed, wherein the damper mass (37) is movably arranged in the intermediate space (42), wherein a magnet arrangement (43, 45; 50; 55, 57; 59, 61) is arranged on the surfaces of the partial bodies (39, 40) facing the intermediate space (42). [12] Bearing device (33; 48) according to one of claims 8 to 11, characterized by that the at least one absorber mass (37) is arranged on the intermediate mass (34; 49) in such a way that a distance between the absorber mass (37) and the intermediate mass (34; 49) is fixed and the absorber mass (37) is movably mounted perpendicular to the distance direction relative to the intermediate mass (34; 49). [13] Bearing device (33; 48) according to one of claims 8 to 12, characterized by that at least two absorber masses (37) are arranged on different side walls (36) of the intermediate mass (34; 49). [14] Bearing device (33; 48) according to one of the preceding claims, characterized by that the vibration element has an intermediate mass (34; 49), wherein the at least one eddy current damper is formed between the intermediate mass (34; 49) and the support frame (31) and / or between the intermediate mass (34; 49) and the optical element (32). [15] Bearing device (33; 48) according to claim 14, characterized by that at least one magnet arrangement (43, 45; 50; 55, 57; 59, 61) is fastened to the intermediate mass (34; 49) and that the at least one electrically conductive damping body (53) is fastened to the optical element (32) or the support frame (31). [16] Bearing device (33; 48) according to claim 14, characterized bythat the at least one magnet arrangement (43, 45; 50; 55, 57; 59, 61) is fastened to the optical element (32) or the support frame (31) and that the at least one electrically conductive damping body (43) is fastened to the intermediate mass (34; 49). [17] Assembly (30; 47) for an optical system, comprising - an optical element (32), - a supporting frame (31) and - at least one bearing device (33; 48) according to one of the preceding claims, by means of which the optical element (32) is mounted on the support frame (31). [18] Optical system comprising an assembly (30; 47) according to claim 17. [19] Mask inspection system (1) with an optical system according to claim 18.

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