Optical assembly with an aperture element and optical system

Abstract

The invention relates to an optical assembly comprising: an optical element, in particular a mirror having a through-hole, and an aperture element (25) arranged in the region of the through-hole (26). The aperture element (25) has a central aperture part (37) from which at least three mounting arms (38a-c) extend for attaching the aperture element (25) to the optical element, each mounting arm (38a-c) having at least one first solid-state joint (35a, b) pivotable about a first axis (X) and at least one second solid-state joint (36a, b) pivotable about a second axis (Y) perpendicular to the first axis. The invention also relates to an optical system, in particular an EUV lithography system, comprising at least one optical assembly configured as described above.

Description

Background of the invention

[0001] The invention relates to an optical assembly comprising: an optical element, in particular a mirror, which has a passage opening, and a diaphragm element arranged in the region of the passage opening. The invention also relates to an optical system, in particular an EUV lithography system, which has at least one optical assembly designed as described above.

[0002] DE102014208770A1 describes a projection optics system for imaging an object field into an image field and a projection exposure system with such a projection optics system. The projection optics system comprises a plurality of mirrors for guiding imaging light from the object field to the image field. One of the mirrors of the projection optics system has a passage opening for the imaging light to pass through. An aperture is arranged at the location of the mirror.

[0003] Components and assemblies, for example in the projection optics of an EUV lithography system, are usually connected to one another by adhesive bonding or by screws or bolts. This gives rise to the problem of aligning components or assemblies to one another, for example the problem of aligning the aperture element and the optical element described above relative to one another. In general, the correct position of two interconnected components in all three spatial directions X, Y, and Z can be achieved using spacers that compensate for incorrectly maintained distances between the interconnected components. In addition to adjusting the position, however, it is also necessary to adjust the alignment or orientation of the components with respect to three (rotational) axes Rx, Ry, and Rz in space.

[0004] The orientation of the components can be adjusted using a so-called final bonding process, ball joints, or universal joints. These three solutions have the following disadvantages: The final bonding process is very time-consuming and can only be performed once. Furthermore, the final bonding process creates a permanent connection, which requires a complicated and time-consuming alignment process. The quality of ball joints is highly dependent on the coefficient of friction, meaning they have low reproducibility. Ball joints also require a high degree of precision from the connected components, as their contact point or contact line is not well defined. There is also a risk of particle generation. Universal joints require two connections for each interface: one between the connected components and a second between the connected component and, for example, the head of a screw.The expected stiffness of this connection is therefore rather low. Since the universal joint must be subjected to axial load, the risk of buckling is high and the stability of the connection is low.

[0005] Since it is not possible to manufacture components with zero surface roughness, deformations or mechanical stresses usually occur when two or more skewed components are joined or aligned. If one of the two components is an optical element, e.g. a mirror, the deformations introduced into the mirror due to the mechanical stresses can lead to imaging errors or aberrations on the mirror surface. To avoid this, the decoupling structures described above, e.g. in the form of ball joints or universal joints, can be used when joining. A major disadvantage of these and other commonly used decoupling structures, however, is that the decoupling drastically reduces the stiffness of the connection.This can lower the natural frequency of the optical assembly and cause it to vibrate unintentionally. Object of the invention

[0006] The object of the invention is to provide an optical assembly in which the aperture element and the optical element are connected to one another via a connection that is as stress-free as possible and ideally has a high degree of rigidity. The object of the invention is also to provide an optical system comprising at least one such optical assembly. Subject of the invention

[0007] This object is achieved by an optical assembly of the type mentioned at the outset, in which the diaphragm element has a central diaphragm part from which at least three fastening arms for fastening the diaphragm element to the optical element extend, wherein a respective fastening arm has at least one first solid-state joint pivotable about a first axis and at least one second solid-state joint pivotable about a second axis perpendicular to the first axis.

[0008] The solid-state joints, which can be pivoted about two mutually perpendicular axes, create a decoupling structure that compensates for any skewed alignment of the central aperture part relative to a respective contact surface to which the respective mounting arm is connected to the optical element. This reduces the influence caused by tolerances during component manufacturing. Furthermore, only a low reaction force is transferred to the components to be connected, i.e., to the aperture element or the optical element. Tolerance compensation and correct orientation are performed individually for each of the at least three mounting arms. The aperture element can have three, four, five, etc. mounting arms.

[0009] By using flexure joints, usually in the form of spring joints, also known as "soft springs", the respective mounting arm can be easily deformed and thus compensate for any skewed alignment of the central aperture part and a contact surface on the optical element. The first and second flexure joints, which can be rotated or pivoted about mutually perpendicular axes, allow rotation of the respective contact surface relative to the central aperture part in two degrees of freedom. In this way, the alignment error between the two components can be compensated for. The flexure joints only allow rotation but not lateral offset of the mounting arms, i.e. displacement movements in the X-direction, Y-direction and Z-direction are not possible.Rotation around a third axis (Z-axis), which is perpendicular to the first and second axes, is also typically not possible.

[0010] In one embodiment, a respective fastening arm has two second solid-state joints, between which a rigid section of the respective fastening arm runs, wherein the second axis preferably runs in the transverse direction of the respective fastening arm. The two second solid-state joints are spaced from one another by the rigid section of the fastening arm. By providing two second solid-state joints, the bending of a respective second solid-state joint when compensating for tolerances can be reduced, which reduces the force transmission to the mirror. The position of the second solid-state joints on the respective fastening arm and the distance between the two second solid-state joints, i.e. the length of the rigid section, can be determined depending on the specific design of the diaphragm element or the optical assembly.

[0011] The axis about which the two second flexural joints can be rotated or pivoted is typically the transverse direction of the respective fastening arm, i.e. the second flexural joints enable tilting of the respective fastening arm or of the sections of the fastening arm connected to one another by the second flexural joints. The transverse direction of the fastening arms is typically oriented perpendicular to the Z direction, which in turn runs perpendicular to a plane in which the at least three fastening arms are connected to the central panel part. The central panel part or the plane described above can have a center or midpoint, and the longitudinal direction of the fastening arms can correspond to the radial direction relative to the midpoint of the central panel part.

[0012] In one embodiment, a section of a respective fastening arm, which in particular has the two second solid-state joints, is oriented at an angle of more than 10°, preferably more than 30°, particularly preferably more than 40° to a plane in which the at least three fastening arms are connected to the central panel part. The connection, or more precisely the connection points, of the three fastening arms define a common plane (see above). With respect to this plane, the fastening arms, or more precisely a respective section of the fastening arms, are oriented at an angle of more than 10°. The angle can also be greater than stated above and be, for example, 45° or 60°.

[0013] The inventor has recognized that the natural frequency of the aperture element or optical assembly increases if the fastening arms have at least one section that does not lie in the plane defined by the three or more connection points of the fastening arms. In particular, the two second flexure joints should not lie in this plane, but rather be spaced from each other in a direction perpendicular to this plane (Z direction). Aligning the section of the respective fastening arm at a not too small angle increases the stiffness of the aperture element or optical assembly in the direction perpendicular to this plane, along which the first, lowest natural frequency of the aperture element typically occurs. The first natural frequency of the aperture element or optical assembly should typically be on the order of more than approximately 1 kHz.

[0014] In a further embodiment, a respective fastening arm has at least one first solid-state joint arranged in a section of the fastening arm that is aligned parallel to a plane in which the at least three fastening arms are connected to the central aperture part, wherein the first axis preferably runs in the longitudinal direction of the section aligned parallel to the plane. As a rule, the at least one first solid-state joint is pivotable or rotatable in the longitudinal direction of the respective fastening arm in order to enable rotation or torsion of the respective fastening arm relative to a contact surface on the optical element. In order to increase the rigidity of the assembly in the Z direction, it is advantageous if the first axis runs parallel to a plane in which the aperture arms are connected to the central aperture part.Preferably, both the first axis and the second axis are aligned parallel to the plane in which the fastening arms are connected to the central panel part.

[0015] In the case of two first flexural joints, unlike the two second flexural joints, these are generally not spaced apart from each other in the longitudinal direction of the respective mounting arm. Rather, they are typically offset or spaced apart from each other within the cross-section of the respective mounting arm. The two first flexural joints can be offset from each other within the cross-section, particularly in the Z direction.

[0016] In a further embodiment, the respective fastening arm has a tongue section that extends within the cross-section of the fastening arm adjacent to at least one first solid-state joint, preferably between two first solid-state joints. The typically rigid tongue section of the cross-section of the fastening arm can remain stationary, while the fastening arm, or more precisely the regions within the cross-section of the fastening arm that extend outside the rigid tongue section, can be rotated about the first axis. The fastening arm can, in particular, be adjacent to a fastening section for attachment to the optical element, or the tongue section can extend entirely or partially along the fastening section.

[0017] In a further embodiment, the fastening arms each have a fastening section facing away from the central diaphragm part, which has a preferably flat contact surface that rests against a preferably flat contact surface of the optical element, in particular a fastening element of the optical element. The diaphragm element is connected to the optical element at the fastening section, typically to a fastening element provided on the optical element. As described above, the solid-state joints can compensate for a skewed alignment of the contact surface to the plane of the central diaphragm part, from which the fastening arms originate. In this way, a well-defined planar contact can be established between the contact surface of the diaphragm element and the contact surface of the optical element, without requiring high precision in the manufacture of the interconnected components.

[0018] As a rule, the contact surface is not located directly on the material of the base body of the optical element, which in the case of an EUV mirror is typically glass, in particular titanium-doped quartz glass, or a glass ceramic. Rather, the contact surface is usually formed on a fastening element of the optical element, which is typically connected to the base body of the optical element via a permanent connection, e.g. via an adhesive connection. A spacer can be provided on the fastening element in order to correct the position of the aperture element in space if necessary. The connection described above can in particular compensate for any misalignment of the fastening element relative to the base body of the optical element, which may be due, for example, to faulty bonding of the fastening element.

[0019] In a further development of this embodiment, the contact surface of a respective fastening arm is connected to the contact surface of the optical element, preferably the fastening element, via a detachable connection, preferably via a screw connection. It has proven advantageous if the aperture element or the respective fastening arm is connected to the optical element via a detachable connection.

[0020] In a further embodiment, the at least one first and / or the at least one second solid-state joint run between two separating gaps formed in the fastening arm, or the at least one first and / or the at least one second solid-state joint are designed as leaf springs. The solid-state joints are created, as is generally customary, by reducing the material thickness of the respective fastening arm. The material thickness can be reduced in different ways, for example by introducing separating gaps into the fastening arms. The separating gaps can be rounded adjacent to the respective solid-state joint and, for example, end in a semicircular end section. However, it is also possible to realize the solid-state joints using leaf springs or the like. It is not absolutely necessary for the solid-state joints to be formed integrally with the fastening arms.For example, the solid-state joints in the form of leaf springs can be connected to the mounting arm via a detachable connection, e.g. via a screw connection.

[0021] In a further embodiment, the fastening arms are formed as a single piece. The single-piece design of the fastening arms simplifies the assembly of the cover element, but such a design of the fastening arms is not absolutely necessary. The entire cover element, i.e., the fastening arms and the central cover part, can be formed as a single piece, but such a design is also not absolutely necessary. The cover element and / or the fastening element described above can be made, for example, from a metal, e.g., stainless steel, or Invar.

[0022] In a further embodiment, the central diaphragm part has at least one, in particular precisely one, diaphragm opening. The diaphragm element, which is at least partially positioned in the passage opening of the optical element, can serve as an aperture diaphragm, i.e., the edge of the diaphragm opening limits the beam path of the useful light. However, it is also possible for the diaphragm element not to serve as an aperture diaphragm, but rather to have a different optical effect, or for the diaphragm element to serve merely as a shield to protect the substrate of the optical element from the ambient atmosphere, in which, for example, a hydrogen plasma may be present.The aperture element can only be connected to the optical element via the three fastening arms, but it is also possible in principle for the aperture element to be connected to the optical element at other points, for example to adjust a gap between the aperture element and the optical element with the aid of a spacer.

[0023] A further aspect of the invention relates to an optical system, in particular an EUV lithography system, which has at least one optical assembly designed as described above. The EUV lithography system can be an EUV lithography system for exposing a wafer or another optical system that uses EUV radiation, for example an EUV inspection system, e.g. for inspecting masks, wafers or the like used in EUV lithography. The optical assembly described above can be arranged, for example, in the projection optics of the EUV lithography system. In this case, the projection optics is an optical system that is obscured - possibly multiply - and has at least one mirror that includes a passage opening for the passage of the illumination radiation or the useful radiation.It is understood that the optical assembly can also be used in other optical systems in which optical elements are provided with a passage opening, for example in lithography systems for DUV lithography.

[0024] Further features and advantages of the invention will become apparent from the following description of exemplary embodiments of the invention, with reference to the figures of the drawing, which illustrate details essential to the invention, and from the claims. The individual features can be implemented individually or in combination in a variant of the invention. drawing

[0025] Examples of embodiments are shown in the schematic drawing and are explained in the following description. Fig. 1 schematically shows in meridional section a projection exposure system for EUV projection lithography, Fig. 2 a schematic sectional view of an optical assembly comprising a mirror of the projection exposure system and a diaphragm element, Fig. 3a-c schematic representations of two components that are aligned parallel or skew to each other, Fig. 4a,b schematic representations of two possibilities for the correct alignment of the skewed components of Fig. 3b,c using two flexure joints each, Fig. 5 is a schematic representation of a diaphragm element having a central diaphragm part and three fastening arms, each with a first pair and a second pair of solid joints, Fig. 6 a schematic representation of a section through one of the fastening arms of the panel element of Fig. 5, Fig. 7a,b schematic representations of a fastening arm having a fastening section with a Fig. 5 and Fig. 6 has a different design, and Fig. 8a,b are schematic representations of a part of a fastening arm having a fastening section with a Fig. 5 and Fig. 6 has a different design.

[0026] In the following description of the drawings, identical reference symbols are used for identical or functionally identical components.

[0027] In the following, with reference to Fig. 1 describes, by way of example, the essential components of an optical arrangement for EUV lithography in the form of a projection exposure system 1 for microlithography. The description of the basic structure of the projection exposure system 1 and its components is not intended to be limiting.

[0028] 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.

[0029] A reticle 7 arranged in the object field 5 is illuminated. 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.

[0030] In Fig. 1 shows a Cartesian xyz coordinate system for explanation. The x-direction is perpendicular to the plane of the drawing. The y-direction is horizontal and the z-direction is vertical. The scanning direction is in the Fig. 1 along the y-direction. The z-direction runs perpendicular to the object plane 6.

[0031] The projection exposure system 1 comprises a projection system 10. The projection system 10 is used to image the object field 5 into an image field 11 in an image plane 12. A structure on the reticle 7 is imaged onto a light-sensitive layer of a wafer 13 arranged in the region of the image field 11 in the image plane 12. 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.

[0032] 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).

[0033] The illumination radiation 16 emanating from the radiation source 3 is focused by a collector mirror 17. The collector mirror 17 can be a collector mirror with one or more ellipsoidal and / or hyperboloidal reflection surfaces. The at least one reflection surface of the collector mirror 17 can be exposed to the illumination radiation 16 at grazing incidence (GI), 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 mirror 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.

[0034] After the collector mirror 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 mirror 17, and the illumination optics 4.

[0035] 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. The first facet mirror 20 comprises a plurality of individual first facets 21, which are also referred to below as field facets. Of these facets 21, Fig. 1 shows only a few examples. A second facet mirror 22 is arranged downstream of the first facet mirror 20 in the beam path of the illumination optics 4. The second facet mirror 22 comprises a plurality of second facets 23.

[0036] The illumination optics 4 thus form a double-faceted system. This basic principle is also referred to as a fly's-eye integrator. 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.

[0037] The projection system 10 comprises a plurality of mirrors Mi, which are numbered according to their arrangement in the beam path of the projection exposure system 1.

[0038] In the Fig. In the example shown in Figure 1, the projection system 10 comprises six mirrors M1 to M6. Alternatives with four, eight, ten, twelve, or a different number of mirrors M1 are also possible. The penultimate mirror M5 and the last mirror M6 each have a passage opening for the illumination radiation 16. The projection system 10 is a doubly obscured optical system. The projection optical system 10 has an image-side numerical aperture that is greater than 0.4 or 0.5 and can also be greater than 0.6, for example, 0.7 or 0.75.

[0039] The mirrors Mi, just like the mirrors of the illumination optics 4, can have a highly reflective coating for the illumination radiation 16.

[0040] Fig. 2 shows an optical assembly 24, which comprises the sixth mirror M6 of the projection optics 10 of Fig. 1 and a diaphragm element 25. As described above, the sixth mirror M6 has a passage opening 26 for the passage of the illumination radiation 16, which extends through a base body or substrate 27 of the mirror M6. Outside the passage opening 26, the mirror M6 has an optical surface 24a, at which the illumination radiation 16 is reflected, which has passed through the passage opening 26, more precisely through a diaphragm opening 28 of the diaphragm element 25.

[0041] The Fig. The aperture element 25 shown in Figure 2 has three fastening sections 29a-c for fastening to the mirror M6, of which in the sectional view of Fig. 2 only a first fastening section 29a is shown. A respective fastening section 29a serves to fasten the diaphragm element 25 to one of three fastening elements provided on the mirror M6, wherein in Fig. 2, only a first fastening element 30a is shown. In the example shown, the fastening element 30a is designed in the form of a bushing that is connected to the substrate 27 of the mirror M6 by an adhesive bond.

[0042] The first fastening section 29a of the panel element 25 is connected to the associated fastening element 30a via a screw connection 31a. As shown in Fig. As can be seen in Figure 2, the screw connection 31a brings a flat contact surface 32a on the underside of the first fastening section 29a of the diaphragm element 25 into contact with a flat contact surface 33a on the top side of the first fastening element 30a. To correct the position of the diaphragm element 25 relative to the mirror M6, a flat spacer 34a is arranged between the first fastening section 29a and the associated fastening element 30a. The diaphragm element 25 is fastened to the two other fastening sections 29b, 29c in a corresponding manner.

[0043] The spacer 34a allows a correction of the position of the aperture element 25 relative to the mirror M6, but not a correction of the orientation of the aperture element 25 relative to the mirror M6.

[0044] In case the Fig. 3a-c, the cover element 25, shown simplified by a bar, and the fastening element 30a are aligned exactly parallel, as shown in Fig. As shown in Figure 3a, the positioning by means of the flat spacer 34a is sufficient and no mechanical stresses are introduced into the substrate 27 of the mirror M6.

[0045] In the event that a misorientation occurs in the form of a tilt around the Y-axis, which corresponds to the longitudinal direction of the fastening section 29a of the panel element 25, as shown in Fig. 3b, as well as in the case of a misorientation with respect to the X-axis, as shown in Fig. 3c, the connection with Fig. However, the screw connection 31a described in Figure 2 introduces mechanical stresses into the substrate 27 of the mirror M6. The mechanical stresses caused by the skewed alignment of the two contact surfaces 32a, 33a can lead to deformations on the surface 24a of the mirror M6.

[0046] In order to avoid or reduce deformations on the surface 24a of the mirror M6, the connection between the aperture element 25 and the first fastening element 30a can be Fig. 3b,c shown examples can be realized using a decoupling structure, which is described below in connection with Fig. 4a,b is described in more detail.

[0047] In Fig. 4a above is the Fig. 3b, in which the contact surface 33a of the fastening element 30a is tilted or rotated about the Y-axis relative to the contact surface 32a of the panel element 25. As shown in Fig. 4a, the aperture element 25 has two second solid-state joints 36a,b spaced apart in the X-direction, each of which is rotatable or pivotable about the Y-axis and which allow a correction of the alignment of the two contact surfaces 32a, 33a. Likewise, with the aid of two first solid-state joints 35a, 35b, which are rotatable or pivotable about the X-axis, a misorientation of the two contact surfaces 32a, 33a with respect to the X-axis can be compensated, as shown in Fig. 4b is shown.

[0048] Fig. 5 shows a diaphragm element 25 in which the Fig. 4a,b has been implemented. The aperture element 25 has a central aperture part 37, which in the illustration of Fig. 5 has the simplified shape of a plate or a circular disk. It is understood that the central aperture part 37 has an aperture 28 and is basically designed in the manner of the Fig. 2 can be formed. Three fastening arms 38a-c are attached to the central panel part 37 at equal intervals in the circumferential direction, each of which has a fastening section 29a-c at its end facing away from the central panel part 37, which can be adapted to the Fig. 2 is connected to a respective associated fastening element 30a, ... of the mirror M6.

[0049] As in Fig. As can be seen in Figure 5, the connection points of the three fastening arms 38a-c on the central panel part 37 define a plane that is oriented perpendicular to a third axis Z of an XYZ coordinate system, which runs through the center of the central panel part 37. In the example shown, the X-axis corresponds to the longitudinal direction of the first fastening arm 38a, and the Y-direction corresponds to the transverse direction of the first fastening arm 38a. The three fastening arms 38a-c are structurally identical. Therefore, for the sake of simplicity, only the structure of the first fastening arm 38a is described below.

[0050] The first fastening arm 38a has a section 39 adjacent to the central aperture part 37, which is oriented at an angle α of 45° to the XY plane of the central aperture part 37. As in Fig. As can also be seen in Figure 5, the two second flexure joints 36a, 36b, which are pivotable in the Y direction, are arranged in the section 39 adjacent to the central aperture part 37. A rigid section 40 of the first fastening arm 38a extends between the two second flexure joints 36a,b. The fact that the two second flexure joints 36a,b are attached to the section 39 oriented at an angle α to the XY plane results in the two second flexure joints 36a,b being offset from one another in the Z direction. This is advantageous for increasing the stiffness of the aperture element 25 in the Z direction, thereby increasing the lowest natural frequency of the aperture element 25.

[0051] The first mounting arm 38a has a section 41 aligned parallel to the XY plane and to which the two first flexure joints 35a,b are attached. These joints are designed to pivot about the X-axis. The section 41 aligned parallel to the XY plane adjoins the mounting section 29a, which is also aligned parallel to the XY plane.

[0052] The first fastening arm 38a has in the parallel aligned section 41 a rigid tongue section 42 which extends within the cross section Q of the first fastening arm 38a between the two first solid joints 35a, b, as shown in Fig. 6, in which the cross-section Q of the first fastening arm 38a is shown hatched. The two first solid-state joints 35a,b, which are pivotable about the X-axis, are separated from each other by the tongue section 42, which extends from the fastening section 29a in the longitudinal direction X of the first fastening arm 38a and which is separated at its end face from the remaining material of the first fastening arm 38a by a separating gap 43.

[0053] As in Fig. 6 for the upper of the two first solid-state joints 35a, this or the material region around which the rotation about the X-axis occurs runs between two separating gaps 44a, 44b introduced into the first fastening arm 38a. The two separating gaps 44a, 44b run in a straight line starting from the lateral edge of the first fastening arm 38a and have a semicircular end section in the area of ​​the first solid-state joint 35a. Fig. 5 and Fig. In the example shown in Figure 6, the fastening section 29a is connected to the remaining fastening arm 38a via the tongue section 42.

[0054] Fig. 7a,b show an alternative embodiment of the first fastening arm 38a, in which the tongue portion 42 extends in the longitudinal direction of the fastening arm 38a along the entire fastening portion 29a. The separating gaps 44a, 44b, between which a respective first solid-state joint 35a,b extends, in this example do not extend to the lateral edge of the first fastening arm 38a, but to the upper and lower edges of the first fastening arm 38a. As shown in Fig. 7a, the tongue section 42 can have an interruption 44 or an opening in order to influence the stiffness of the first solid-body joints 35a,b, but such an opening 44 is not absolutely necessary.

[0055] Fig. 8a,b show a further alternative embodiment of the first fastening arm 38a, which has only a first solid-state joint 35 in the parallel-aligned section 41. The first fastening arm 38a has a rigid tongue section 42 in the parallel-aligned section 41, which adjoins the first solid-state joint 35 within the cross-section Q of the first fastening arm 38a, as shown in Fig. 8b. The tongue section 42 is separated at its end face from the remaining material of the first fastening arm 38a by a separating gap 43. The fastening section 29a is connected to the remaining fastening arm 38a via the tongue section 42. The separating gaps 44a, 44b, between which the first solid-state joint 35 extends, extend in this example to the lateral edge of the first fastening arm 38a.

[0056] The fastening arms 38a-c with the first and second solid-state joints 35a, b; 36a, b are formed as a single piece in the examples described above. However, it is also possible to form the fastening arms 38a-c in multiple parts. For example, the first solid-state joints 35a, b and / or the second solid-state joints 36a, b can be designed as leaf springs, which are connected, for example, via a screw connection to the respective remaining fastening arm 38a-c. It is understood that fastening arms 38a-c that have first solid-state joints 35a, b and / or second solid-state joints 36a, b in the form of leaf springs can also be formed as a single piece.

[0057] Contrary to what was shown above, the second solid-state joints 36a,b can be arranged closer to the fastening section 29a than the first solid-state joints 35a,b, i.e., the arrangement of the first and second solid-state joints 35a,b; 36a,b along the longitudinal direction X of the first fastening arm 38a and correspondingly along the two other fastening arms 38b, 38c can be reversed. It is understood that the mirror M5, which also has a through-opening, can also be designed in the manner described above.

[0058] The type of connection between the aperture element 25 and the mirror M6 described above enables compensation for any misalignment of the aperture element 25 relative to the mirror M6 while avoiding the problems associated with other types of connections, e.g., a time-consuming and complex final bonding process. Furthermore, unlike a connection in the form of a ball joint, no particles are formed, and the connection described here is more reproducible than a connection with a ball joint. Furthermore, the stiffness of the connection described here is lower than that of a ball joint, so that fewer deformations are introduced into the mirror M6, more precisely into the optical surface 24a. Nevertheless, a comparatively high first natural frequency can be achieved with the optical assembly 24 described here. 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] DE102014208770A1

[0002]

Claims

[1] Optical assembly (24) comprising: an optical element, in particular a mirror (M6), which has a passage opening (26), and a diaphragm element (25) arranged in the region of the passage opening (26), characterized by , that the diaphragm element (25) has a central diaphragm part (37) from which at least three fastening arms (38a-c) for fastening the diaphragm element (25) to the optical element (M6) extend, wherein a respective fastening arm (38a-c) has at least one first solid-state joint (35a, b; 35) pivotable about a first axis (X) and at least one second solid-state joint (36a, b) pivotable about a second axis (Y) perpendicular to the first. [2] Optical assembly according to claim 1, wherein a respective fastening arm (38a-c) has two second solid-state joints (36a,b) between which a rigid section (40) of the respective fastening arm (38a-c) extends, wherein the second axis (Y) preferably extends along a transverse direction of the respective fastening arm (38a-c). [3] Optical assembly according to claim 1 or 2, wherein a section (39) of a respective fastening arm (38a-c), which in particular has the two second solid-state joints (36a, b), is aligned at an angle (α) of more than 10°, preferably of more than 30°, particularly preferably of more than 40° to a plane (X,Y) in which the at least three fastening arms (38a-c) are connected to the central diaphragm part (37). [4] Optical assembly according to one of the preceding claims, in which a respective fastening arm (38a-c) has at least one first solid-state joint (35a, b; 35) which is arranged in a section (41) of the fastening arm (38a-c) which is aligned parallel to a plane (X,Y) in which the at least three fastening arms (38a-c) are connected to the central diaphragm part (37), wherein the first axis (X) preferably runs along a longitudinal direction of the section (41) aligned parallel to the plane (X,Y). [5] Optical assembly according to one of the preceding claims, wherein the respective fastening arm (38a-c) has a tongue portion (42) extending within the cross-section (Q) of the fastening arm (38a-c) adjacent to at least one first solid-state joint (35), preferably between two first solid-state joints (35a, b). [6] Optical assembly according to one of the preceding claims, in which the fastening arms (38a-c) each have a fastening section (29a-c) facing away from the central diaphragm part (37), which has a preferably planar contact surface (33a-c) which bears against a preferably planar contact surface (32a, ...) of the optical element (M6), preferably a fastening element (30a, ...) of the optical element (M6). [7] Optical assembly according to claim 6, wherein the contact surface (33a-c) of a respective fastening arm (38a-c) is connected to the contact surface (32a-c) of the optical element (M6), in particular of the fastening element (30a, ...), via a detachable connection, preferably via a screw connection (31a, ...). [8] Optical assembly according to one of the preceding claims, in which the at least one first and / or the at least one second solid-state joint (35a,b; 36a,b) runs between two separating gaps (44a,b) formed in the fastening arm (38a-c) or in which the at least one first and / or the at least one second solid-state joint (35a,b; 36a,b) are designed as leaf springs. [9] Optical assembly according to one of the preceding claims, in which the fastening arms (38a-c) are formed in one piece. [10] Optical assembly according to one of the preceding claims, wherein the central diaphragm part (37) has at least one diaphragm opening (28). [11] Optical system, in particular EUV lithography system (1), comprising: at least one optical assembly (24) according to one of the preceding claims.

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