Optical system and projection exposure apparatus

Abstract

An optical system (100) for a projection exposure device (1), comprising: an optical element (108); and a mount (116), the mount (116) carrying the optical element (108); wherein the mount (116) comprises an outer ring (118) in which at least a portion of the optical element (108) is housed; wherein the outer ring (118) comprises a plurality of securing portions (134), the plurality of securing portions (134) being closely connected to the optical element (108); wherein the fixed portion (134) is pivotally connected to the outer ring (118) by means of an engagement portion (142, 146); and wherein the mount (116) comprises a tool interface (172) for releasably securing a tool for replacing the optical system (100) from the illumination optical unit (4).

Description

Field of the Invention

[0001] The present invention relates to an optical system and a projection exposure apparatus incorporating such an optical system.

[0002] The content of priority application DE10 2022 214 186.5 is incorporated herein by reference in its entirety. Background Art

[0003] Microlithography is used to fabricate microstructured components, such as integrated circuits. A lithography apparatus having an illumination system and a projection system is used to perform the microlithography process. Here, an image of a mask (mask blank) illuminated by the illumination system is projected onto a substrate, such as a silicon wafer, which is coated with a photosensitive layer (photoresist) and is disposed in the image plane of the projection system, in order to transfer the mask structure onto the photosensitive coating of the substrate.

[0004] Driven by the demand for smaller structures in integrated circuit generation, DUV lithography apparatuses (deep ultraviolet, DUV) are currently being developed, which use light in the wavelength range between 30 nm and 250 nm, particularly 193 nm. In the case of such DUV lithography apparatuses, reflective optical elements (i.e., mirrors) can be used in place of the hitherto refractive optical elements (i.e., lens elements).

[0005] Such a mirror can be received in a mount. This mount is typically fixedly installed in, for example, the aforementioned projection system. Accordingly, there are no measures for replacing the mount together with the mirror. In addition, the mount itself may exert tension on the mirror, which may cause excessive stress in the mirror, thereby causing a change in the optical characteristics of the mirror. This needs to be improved. Summary of the Invention

[0006] In this context, it is an object of the present invention to provide an improved optical system.

[0007] Accordingly, an optical system for a projection exposure apparatus is proposed. The optical system includes an optical element and a mount for carrying the optical element, wherein the mount includes an outer ring, wherein the optical element is at least partially received in the outer ring, wherein the outer ring includes a fixing portion that is cohesively connected to the optical element, and wherein the fixing portion is pivotally connected to the outer ring by means of a joint portion. In this case, the mount includes a tool interface for releasably fixing a tool for replacing the optical system from an illumination optical unit.

[0008] Since the mounting is tightly connected to the optical element and bears the optical element, the mounting can be replaced together with the optical element. The pivotable fixing part ensures a significant reduction in the tension introduced by the mounting into the optical element, thereby preventing unwanted material stress in the optical element.

[0009] The optical system is in particular a mirror, such as an EUV mirror, or a mirror module, or may be so called. The optical system may be a mirror in a catadioptric system. The optical system may be part of a projection optical unit. The projection optical unit may comprise a plurality of such optical systems. However, the optical system may also be part of an illumination system. However, it is assumed hereinafter that the optical system is part of a projection optical unit. The optical system is suitable for EUV lithography. However, the optical system is also suitable for DUV lithography.

[0010] A coordinate system containing a first spatial direction or x-direction, a second spatial direction or y-direction, and a third spatial direction or z-direction can be assigned to the optical system. The optical system has a symmetry axis or central axis parallel to or coinciding with the z-direction. The optical system may be constructed substantially rotationally symmetric with respect to the central axis. However, this is not mandatory. The radial direction of the optical system is oriented perpendicular to the central axis and away from the central axis.

[0011] The optical system 100 is replaceable. That is, the optical system can be removed from the projection optical unit and inserted into the projection optical unit again. Therefore, the optical system can also be referred to as an optical exchange system or an optical exchange module. Relative tools can be provided to replace the optical system. Preferably, the optical system is replaced on-site. In the present case, "on-site" particularly means that the replacement of the optical system can be directly carried out at the operating site of the projection exposure apparatus containing this optical system. In this case, the optical system can be replaced as a whole. That is, in particular, the optical element is replaced together with the mounting. Advantageously, the exchanged optical system can be replaced by a newly developed optical system with improved optical effects, thereby also improving the performance and / or accuracy of the projection optical unit. The newly developed optical system may also include electronic components, etc.

[0012] Preferably, the optical system comprises exactly one optical element and exactly one mount. The optical element can be a mirror or a lens element. Hereinafter, it is assumed that the optical element is a mirror. The optical element comprises an optically effective surface. The optically effective surface is adapted to reflect illumination radiation, in particular DUV radiation, during operation of the optical system. In this case, a reflectivity at 193 nm is required. However, the optically effective surface can also be adapted to reflect EUV radiation. Accordingly, the optically effective surface is a reflecting surface. The optically effective surface can be realized by means of a coating. The optical element comprises a mirror substrate at which the optically effective surface is provided. The mirror substrate can be made of, for example, glass, glass-ceramics, ceramics, silicon, etc. The optically effective surface can be curved, in particular curved in a spherical cap shape or toroidally curved. The curvature of the optically effective surface can be both spherical and aspherical.

[0013] The optical element preferably has a rear side facing away from the optically effective surface. The rear side can also be curved. The rear side does not have a defined surface property. That is, in particular, the rear side is not a reflecting surface and thus does not have reflective properties. The outer surface of the optical element is provided between the optically effective surface and the rear side. The outer surface can be cylindrical. The outer surface can be configured to be rotationally symmetric with respect to the central axis. The outer surface preferably extends circumferentially completely around the optical element. The optical element can be configured to be rotationally symmetric with respect to the central axis. However, this is not mandatory.

[0014] In the present case, in fact, the mount "carrying" the optical element particularly means that the optical element is fixedly connected to the mount and that the optical element can be adjusted or aligned together with the mount. In particular, the mount carries the weight of the optical element. The mount is preferably a one-piece component, in particular a one-piece component in terms of material. Here, "one-piece" or "integral" particularly means that the mount is not composed of different subsidiary components, but that the outer ring, the fixing part and the engagement part form a common component, namely the mount. "One-piece in terms of material" particularly means that the mount is made entirely of the same material. For example, the mount can be made of copper, aluminum, steel, etc. The mount can be manufactured by means of an additive manufacturing method or a generative manufacturing method, in particular by means of a 3D printing method. Furthermore, the mount can also be manufactured by means of an etching method.

[0015] The outer ring can be constructed to be rotationally symmetric with respect to the central axis. However, this is not mandatory. For example, the outer ring can also be elliptical or oval. In particular, the outer ring includes a plurality of outer ring segments connected to each other in one piece. The outer ring segments form a planar or straight portion of the outer ring. Therefore, the outer ring is preferably not circular but polygonal. Therefore, in the present case, the "ring" should be understood to particularly refer to a closed geometric shape that extends circumferentially completely around the central axis. Therefore, in the present case, the "ring" is not necessarily circular. The outer ring is configured to extend circumferentially around the outer surface of the optical element. That is, in particular, the outer ring extends circumferentially completely around the central axis and includes or surrounds the outer surface of the optical element.

[0016] Preferably, the fixing portion is part of the outer ring. The fixing portion is in particular connected to the outer ring in one piece by means of a joint. In particular, the outer ring is tightly connected to the outer surface of the optical element by means of the fixing portion. In a tight connection, the connecting fittings are held together by atomic or molecular forces. A tight connection is a non-releasable connection that can only be separated by destroying the connecting members and / or the connecting fittings. For example, a tight connection can be implemented by an adhesive bond.

[0017] That is, the outer ring can be adhesively bonded to the optical element, in particular to the outer surface of the optical element. In particular, the fixing portion of the outer ring is adhesively bonded to the optical element, in particular to the outer surface of the optical element. For this purpose, adhesive joints are provided at each fixing portion. Therefore, instead of a single adhesive joint that extends circumferentially completely around the symmetry axis, a plurality of separate adhesive joints are provided at the outer surface, each adhesive joint being provided with a fixing portion. The adhesive joints are each arranged between the joint surface of the corresponding fixing portion and the outer surface of the optical element and tightly connect the corresponding joint surface to the outer surface.

[0018] The joint is preferably a flexure. For example, exactly one joint can be assigned to each fixing portion. Alternatively, a plurality of joints (e.g., two) can also be assigned to each fixing portion. In the present case, the "flexure" should be understood to generally mean a region of a component (e.g., a narrowed or thinned cross-section), in the present case the outer ring or the corresponding outer ring segment), which is capable of relative movement between two rigid body regions of the component by bending or twisting. Here, the rigid body regions are, for example, the fixing portion and the outer ring, and a corresponding joint is provided between the fixing portion and the outer ring in the form of a narrowed or thinned cross-section.

[0019] By adjusting the stiffness of the joint, its properties can be adjusted, especially its deformability. In the present case, "stiffness" should be understood very generally as the resistance of the body (in the present case the joint) to elastic deformation imposed on it by an external load, and conveys the relationship between the load on the body and its deformation. The stiffness is determined by the material of the body and its geometry. For example, the stiffness of the joint can be adjusted as needed by different cross-sectional geometries. The joint preferably ensures mechanical decoupling of the optical element from the base. In the present case, "mechanical decoupling" should be understood to mean that the joint prevents or at least reduces the transfer of force from the mount to the optical element.

[0020] According to one embodiment, the joint is configured such that the fixing part can pivot along the radial direction of the optical system.

[0021] The pivot axis of the corresponding joint is thus oriented parallel to the z-direction or the central axis. With the aid of the joint, it is thus possible, for example, to compensate for the thermally induced expansion of the optical element and / or the mount in the radial direction. Thus, each joint enables the fixing part assigned to the respective joint to move outwards along the radial direction away from the inner ring of the mount.

[0022] According to a further embodiment, each fixing part comprises a joint surface facing the optical element, the joint surface being tightly connected to the optical element, wherein the normals of the joint surfaces intersect each other on the central axis of the optical system.

[0023] The central axis is the optical axis of the optical system or can be so called. In each case, the joint surface is preferably flat or straight. In the present case, "normal" should be understood to mean a straight line oriented perpendicular to the respective joint surface. The normals of all joint surfaces of all fixing parts preferably intersect each other on the central axis.

[0024] According to a further embodiment, each fixing part is pivotally connected to the outer ring by means of a first joint and by means of a second joint different from the first joint.

[0025] Alternatively, exactly one joint can also be provided. That is, in particular, the second joint is optional. Providing two joints enables optimized decoupling of the optical element. More than two joints can also be provided.

[0026] According to a further embodiment, each fixing part is pivotally connected to a connecting part by means of the first joint, and the connecting part is pivotally connected to the outer ring by means of the second joint.

[0027] In particular, the connecting part is pivotally connected to the base of the outer ring by means of the second joint. Thus, the fixing part is connected to the outer ring only via the first joint, the connecting part and the second joint, in particular to the base of the outer ring. The connecting part can be a parallelepiped. Compared with the two joints, the connecting part has significantly greater rigidity. Thus, the connecting part serves as a rigid body region between the first joint and the second joint.

[0028] According to a further embodiment, the optical element comprises an optically effective surface, in particular a reflecting mirror surface, a rear side facing away from the optically effective surface, and an outer surface extending circumferentially around the optical element, wherein the fixing part is only tightly connected to the outer surface.

[0029] That is to say, in particular, the mounting base is only tightly connected to the optical element by means of an adhesive joint provided at the fixing part. Preferably, the mounting base thus contacts the optical element only through the fixing part or through the adhesive joint provided at the fixing part. Therefore, preferably, there are no additional contact points between the mounting base and the optical element.

[0030] According to a further embodiment, the mounting base comprises an inner ring arranged within the outer ring, wherein the inner ring is connected to the outer ring by means of reinforcing ribs.

[0031] Conversely, the inner ring can also be arranged outside the outer ring. Viewed in the radial direction, the inner ring is arranged within the outer ring, or the outer ring is arranged outside the inner ring. The inner ring is preferably arranged on the rear side of the optical element. When viewed along the central axis, the inner ring can be arranged at a distance from the rear side such that the inner ring does not contact the rear side. The reinforcing ribs can also be referred to as stiffening webs. The outer ring can be stiffened by means of the inner ring and the reinforcing ribs and the stiffening can be transferred to the rear side of the optical element. Thus, the mounting space required for the optical system can be significantly reduced.

[0032] According to a further embodiment, the two reinforcing ribs are always connected to the outer ring at a common external joint point.

[0033] When viewed in the circumferential direction of the optical system, the corresponding external joint point is centered between the two normals of the adjacent fixing parts (as described above). Conversely, the corresponding normals are located between two adjacent external joint points. At the external joint point, the reinforcing rib is connected to the outer ring in an integrally formed manner, in particular in a materially integrally formed manner.

[0034] According to a further embodiment, the external joint points and the fixing parts are arranged alternately.

[0035] That is to say, in particular, when viewed in the circumferential direction of the mounting base or the optical system, in each case, the external joint points are arranged between the fixing parts or the fixing parts are arranged between two external joint points.

[0036] According to a further embodiment, each of the fixing parts is centered between two adjacent outer engagement points.

[0037] As described above, the normal of each fixing part thus extends centrally between two adjacent outer engagement points in the direction of the central axis, so as to intersect the central axis.

[0038] According to another embodiment, two reinforcing ribs are always connected to the inner ring at a common inner engagement point, where the outer engagement points and the inner engagement points are alternately arranged.

[0039] When viewed along the circumferential direction, the outer engagement points and the inner engagement points are alternately arranged. The normal of the aforesaid fixing part extends through the inner engagement point. At the inner engagement point, the reinforcing rib is connected to the inner ring in an integrally formed manner, especially in a material integrally formed manner. When viewed along the circumferential direction, the inner engagement point is always arranged between two outer engagement points, and the outer engagement point is always arranged between two inner engagement points.

[0040] According to a further embodiment, the mounting base includes a vibration absorber interface for connecting a vibration absorber to the mounting base.

[0041] Preferably, a plurality of vibration absorber interfaces are provided, which are arranged in a uniformly distributed manner around the central axis. Preferably, three vibration absorber interfaces are provided, which are arranged offset by 120° relative to each other. Each of the vibration absorber interfaces is provided in the region of an outer engagement point, such that the vibration absorber interface is strengthened by means of a reinforcing rib. The vibration absorber can be part of an optical system. Preferably, a vibration absorber is assigned to each vibration absorber interface. The vibration introduced into the optical system can be attenuated by means of the vibration absorber.

[0042] According to a further embodiment, the mounting base includes a mounting post interface for engaging a mounting post to the mounting base.

[0043] Preferably, a plurality of mounting strut interfaces are provided. Specifically, three mounting strut interfaces are provided which are configured offset by 120° relative to each other. Preferably, the vibration absorber interface and the mounting strut interfaces are alternately configured when viewed in the circumferential direction. That is to say, in particular, the mounting strut interfaces are arranged between two vibration absorber interfaces and the vibration absorber interfaces are arranged between two mounting strut interfaces. Each mounting strut interface is preferably assigned an external engagement point. This has the effect that the mounting strut interface is strengthened by means of a reinforcing rib joined to the external engagement point. The said mounting strut is referred to as or may be referred to as an "A strut". The mounting base is located at six spatial points. In this case, two of these spatial points are assigned to each mounting strut. By means of the said mounting struts, the mounting base or the optical system is operatively connected to a fixed assembly, such as a force frame. In this case, the said mounting struts mechanically decouple the optical system from the fixed assembly so that no unnecessary stress is introduced into the optical system.

[0044] The mounting base includes a tool interface for releasably securing a tool for replacing the optical system from the illumination optical unit.

[0045] Preferably, the tool interface includes a plurality of interface surfaces arranged parallel to each other. Each interface surface may be assigned a threaded hole by means of which a tool can be connected to the tool interface. Preferably, exactly three interface surfaces are provided. A first interface surface, a second interface surface and a third interface surface are provided. When viewed in the z-direction, the first interface surface and the second interface surface are located at the same height. When viewed in the z-direction, the third interface surface is arranged below the second interface surface.

[0046] Furthermore, a projection exposure apparatus incorporating such an optical system is proposed.

[0047] The projection exposure apparatus may include a plurality of such optical systems. The optical system is preferably part of the projection optical unit of the projection exposure apparatus. However, the optical system may also be part of the illumination system. The projection exposure apparatus may be an EUV lithography apparatus. EUV stands for "extreme ultraviolet" and means that the wavelength of the working light is between 0.1 nm and 30 nm. The projection exposure apparatus may also be a DUV lithography apparatus. DUV stands for "deep ultraviolet" and means that the wavelength of the working light is between 30 nm and 250 nm.

[0048] The "a" or "an" in this case is not necessarily to be understood as being restricted to exactly one element. On the contrary, a plurality of elements, such as two, three or more, may also be provided. Any other numerical values used herein should also not be understood as being restricted to the exactly stated number of elements. On the contrary, there may be numerical deviations up and down, unless otherwise stated.

[0049] The embodiments and features described for the optical system apply correspondingly to the projection exposure apparatus proposed, and vice versa.

[0050] Further possible embodiments of the invention also cover combinations of features or embodiments not explicitly mentioned in the full text regarding the exemplary embodiments. In this case, those skilled in the art will also add the respective aspects as improvements or supplements to the corresponding basic forms of the invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] Further advantageous configurations and aspects of the invention are the subject of the dependent claims and the exemplary embodiments of the invention described below. The invention will be explained in more detail below based on the preferred embodiments with reference to the accompanying drawings.

[0052] Figure 1 Schematic diagram showing an embodiment of a projection exposure apparatus for DUV projection lithography;

[0053] Figure 2 Showing according to Figure 1 Schematic plan view of an embodiment of the optical system of a projection exposure apparatus;

[0054] Figure 3 Showing according to Figure 2 Schematic rear view of an optical system;

[0055] Figure 4 Showing according to Figure 2 Detailed view IV;

[0056] Figure 5 Showing according to Figure 4 View V;

[0057] Figure 6 Showing according to Figure 2 Schematic diagram of an embodiment of a vibration absorber of an optical system; and

[0058] Figure 7 Showing according to Figure 2 Schematic diagram of an embodiment of a tool interface of an optical system.

[0059] Unless otherwise specified, the same or functionally identical elements have the same reference numerals in the drawings. Additionally, note that the illustrations in the drawings are not necessarily drawn to actual scale. DETAILED DESCRIPTION OF THE INVENTION

[0060] Figure 1Schematic illustration of a projection exposure apparatus 1, in particular a DUV lithography apparatus, which comprises a beam shaping and illumination system 2 (also referred to herein as "illumination optical unit") and a projection optical unit 4 (also referred to herein as "projection lens"). In this case, DUV stands for "deep ultraviolet" and denotes that the wavelength of the working light is between 30 nm and 250 nm.

[0061] Each of the beam shaping and illumination system 2 and the projection optical unit 4 is preferably arranged in a vacuum housing (not shown). Each vacuum housing is evacuated by means of an evacuation device (not shown). A mechanical chamber (not shown) surrounds the vacuum housing, and drive devices for mechanically moving or arranging optical elements may be provided in the mechanical chamber. Furthermore, an electrical controller or the like may also be arranged in the mechanical chamber.

[0062] The projection exposure apparatus 1 has a light source 6. For example, an ArF excimer laser emitting radiation 8 in the DUV range (e.g., 193 nm) may be provided as the light source 6. In the beam shaping and illumination system 2, the radiation 8 is focused and the desired working wavelength (working light) is filtered out from the radiation 8. The beam shaping and illumination system 2 may have optical elements (not shown), such as mirrors or lens elements.

[0063] After passing through the beam shaping and illumination system 2, the radiation 8 is guided onto a photomask or mask blank 10. The photomask 10 is formed as a transmissive optical element and may be arranged outside the beam shaping and illumination system 2 and the projection optical unit 4. The structure of the photomask 10 can be imaged in a reduced form onto a wafer 12 by the projection optical unit 4.

[0064] The projection optical unit 4 has a plurality of lens elements 14, 16, 18 and / or mirrors 20, 22 for imaging the photomask 10 onto the wafer 12. In this case, the individual lens elements 14, 16, 18 and / or mirrors 20, 22 of the projection optical unit 4 may be arranged symmetrically with respect to the optical axis 24 of the projection optical unit 4. It should be noted that the number of lens elements 14, 16, 18 and mirrors 20, 22 shown herein is purely exemplary and is not limited to the number shown. A greater or lesser number of lens elements 14, 16, 18 and / or mirrors 20, 22 may also be provided.

[0065] The air gap between the last lens element (not shown) and the wafer 12 can be replaced by a liquid medium 26 having a refractive index greater than 1. The liquid medium 26 may be, for example, high-purity water. This arrangement is also referred to as immersion lithography and has increased lithography resolution. The liquid medium 26 may also be referred to as immersion liquid.

[0066] Figure 2 Schematic plan view showing an embodiment of an optical system 100 for a projection exposure apparatus 1. Figure 3Shows a schematic rear view of the optical system 100. Hereinafter, please also refer to Figure 2 and Figure 3 .

[0067] The optical system 100 can be part of the projection optical unit 4 as described above. However, the optical system 100 can also be part of the beam shaping and illumination system 2. However, hereinafter it is assumed that the optical system 100 is part of a projection optical unit 4 of this type. The optical system 100 is suitable for DUV lithography. However, the optical system 100 can also be suitable for EUV lithography.

[0068] The optical element 100 can be one of the mirrors 20, 22. The optical system 100 can thus be a mirror or a mirror module or can be so called. A coordinate system containing the x-direction x, the y-direction y, and the z-direction z can be assigned to the optical system 100. The optical system 100 has a symmetry axis or central axis 102 that is oriented parallel to or coincides with the z-direction z. The optical system 100 can be configured to be substantially rotationally symmetric with respect to the central axis 102. Two semi-axes 104, 106 that intersect at the central axis 102 are assigned to the optical system 100. The radial direction R of the optical system 100 is perpendicular to the central axis 102 and is oriented away from the central axis 102. The circumferential direction U is oriented around the central axis line 102.

[0069] The optical system 100 is replaceable. That is, the optical system 100 can be removed from the projection optical unit 4 that has been explained and the optical system 100 can be inserted into the projection optical unit 4 again. For this purpose, a corresponding tool (not shown) can be provided. It is preferably possible to replace the optical system 100 on-site. In the present case, "on-site" means directly at the operating location of the projection exposure apparatus 1.

[0070] The optical system 100 has an optical element 108. The optical element 108 can be a mirror or a lens element. Hereinafter it is assumed that the optical element 108 is a mirror. The optical element 108 has an optically effective surface 110. The optically effective surface 110 is suitable for reflecting illumination radiation 16, in particular EUV radiation, during the operation of the optical system 100. The optically effective surface 110 is a reflecting mirror surface. The optically effective surface 110 can be realized by means of a coating.

[0071] The optical element 108 has a rear side 112 that faces away from the optically effective surface 110. The rear side 112 does not have a defined surface characteristic. That is, in particular, the rear side 112 is not a reflecting mirror surface and thus does not have reflection characteristics. The outer surface 114 of the optical element 108 is arranged between the optically effective surface 110 and the rear side 112. The outer surface 114 can be cylindrical. The outer surface 114 can be configured to be rotationally symmetric with respect to the central axis 102.

[0072] In addition to the optical element, the optical system 100 further has a mount 116 for carrying the optical element 108. The mount 116 has an outer ring 118 and an inner ring 120. The circumferential direction U extends along the outer ring 118 or along the inner ring 120. Each of the outer ring 118 and the inner ring 120 can be configured to be rotationally symmetric with respect to the central axis 102. When viewed along the radial direction R, the inner ring 120 is disposed within the outer ring 118, or the outer ring 118 is disposed outside the inner ring 120. Each of the outer ring 118 and the inner ring 120 has a hollow cylindrical or tubular geometry.

[0073] The outer ring 118 is connected to the optical element 108, in particular to the outer surface 114. For this purpose, a tight connection can be provided. In a tight connection, the connecting mating parts are held together by atomic or molecular forces. The tight connection is a non-releasable connection, which can only be separated by destroying the connecting device and / or the connecting mating parts. For example, the tight connection can be implemented by adhesive bonding. That is, the outer ring 118 can be adhesively bonded to the optical element 108, in particular to the outer surface 114.

[0074] The inner ring 120 is not connected to the optical element 108. In Figure 3 the orientation, the inner ring 120 is disposed above the rear side 112 of the optical element 108, but does not contact the said rear side. That is, an air gap can be provided between the rear side 112 and the inner ring 120.

[0075] The inner ring 120 is connected to the outer ring 118 by means of reinforcing ribs or ribs 122, 124, where only two of the reinforcing ribs or ribs are provided with reference numerals. Thus, when viewed along the radial direction R, the ribs 122, 124 are disposed between the inner ring 120 and the outer ring 118 and span the gap 126 disposed between the outer ring 118 and the inner ring 120. In principle, the number of the ribs 122, 124 is arbitrary. The ribs 122, 124 extend obliquely between the outer ring 118 and the inner ring 120. The ribs 122, 124 extend completely around the central axis 102.

[0076] In each case, the two ribs 122, 124 are joined to the outer ring 118 at the outer joining point or the first joining point 128. Thus, in each case, the two ribs 122, 124 are joined to the inner ring 120 at the inner joining point or the second joining point 130. That is, in each case, the two ribs 122, 124 intersect at the outer joining point 128, and in each case, the two ribs 122, 124 intersect at the inner joining point 130.

[0077] The mounting base 116 is a one-piece molded part, especially a part that is integrally molded in terms of material. "One-piece" or "single-piece" here specifically means that the mounting base 116 is not composed of different attached parts, but rather the outer ring 118, the inner ring 120, and the reinforcing ribs 122, 124 form a common part, namely the mounting base 116. "Integrally molded in terms of material" specifically refers in this context to the mounting base 116 being made entirely of the same material. For example, the mounting base 116 can be made of copper, aluminum, steel, etc. The mounting base 116 can be manufactured by means of additive manufacturing or generative manufacturing methods, especially by means of 3D printing methods. Furthermore, the mounting base 116 can also be manufactured by means of etching methods.

[0078] Figure 4 Shows in accordance with Figure 2 detail view IV. Figure 5 Shows in accordance with Figure 4 view V. Please refer simultaneously to Figure 4 and Figure 5 .

[0079] The outer ring 118 comprises a plurality of outer ring segments 132, and only one outer ring segment is labeled with a reference numeral in Figure 4 . The outer ring segments 132 are integrally molded with each other at the outer joint 128, especially integrally molded in terms of material. The outer ring segments 132 themselves are not curved but straight. A plurality of such outer ring segments 132 form the annular geometry of the outer ring 118. That is, in particular, the outer ring 118 is not circular but polygonal. Only one outer ring segment 132 will be discussed in more detail below.

[0080] Each outer ring segment 132 comprises a fixing portion 134. The fixing portion 134 can also be referred to as a small fixing leg. The fixing portion 134 is centrally arranged between two adjacent reinforcing ribs 122, 124. The reinforcing ribs 122, 124 start from the outer joint 128 that is centrally located between the fixing portions 134 of the outer ring segment 132 and extend obliquely in a direction opposite to the radial direction R towards the inner ring 120 and are connected thereto by means of an inner joint 130.

[0081] The outer surface 114 of the optical element 108 is tightly connected to the fixing portion 134. For this purpose, an adhesive joint 138 is provided between the joint surface 136 of the fixing portion 134 and the outer surface 114, said joint surface facing the outer surface 114. The adhesive joint 138 tightly connects the outer surface 114 to the joint surface 136. The adhesive joint 138 can be, for example, epoxy resin, etc. The joint surface is an adhesive joint surface and can therefore also be so called.

[0082] A plurality of fixing parts 134 are provided. Accordingly, a plurality of adhesive joints 138 are also provided. The outer ring 118 is connected to the optical element 108 only by means of the fixing parts 134 and the adhesive joints 138. The normal 140 of the joint surface 136 intersects the central axis 102. In the present case, the "normal" or "normal vector" should be understood to mean the vertical line of the joint surface 136. The reinforcing ribs 122, 124 intersect the normal 140 at the inner ring 120, particularly at the respective inner joint points 130.

[0083] The fixing part 134 is pivotally connected to the connecting part 144 of the outer ring segment 132 by means of a joint part 142. The joint part 142 is a flexible part. In the present case, the "flexible part" should be understood to generally denote a region of a component (such as a narrowed or thinned cross-section), in this example the outer ring segment 132, which enables relative movement between two rigid body regions of the component by bending or twisting. The rigid body regions acting here are the fixing part 134 and the connecting part 144.

[0084] By adjusting the stiffness of the joint part 142, its characteristics, particularly its deformability, can be adjusted. In the present case, the "stiffness" should be understood to very generally denote the resistance of a body (in the present case the joint part 142) to elastic deformation imposed on it by an external load, and conveys the relationship between the load applied to the body and its deformation. The stiffness is determined by the material of the body and its geometry. For example, the stiffness of the joint part 142 can be adjusted as required by different cross-sectional geometries.

[0085] The joint part 142 enables the fixing part 134 to move radially away from the inner ring 120 and outwards. The connecting part 144 is joined to the base 148 of the outer ring segment 132 via another joint part 146. The joint part 146 is also a flexible part. The joint part 146 is optional. The joint parts 142, 146 can have the same or different stiffnesses.

[0086] Backward from the joint part 146, a void or gap 150 is provided between the base 148 and the fixing part 134, which separates the fixing part 134 from the base 148. As Figure 5 shown, the gap 150 extends circumferentially around the fixing part 134, the joint parts 142, 146 and the connecting part 144. The base 148 is planar, and the gap 150 forms a notch, which enables the fixing part 134 and the connecting part 144 to move relative to the base 148 by means of the joint parts 142, 146.

[0087] By means of the joints 142, 146, the fixing part 134 can be moved in the radial direction. This can decouple the tension required for the optical element 108. The fixing part 134 joined to the base 148 via the joints 142, 146 allows only a very small radial force to be transmitted to the optical element 108. The mounting seat 116 is joined to the optical element 108 only via the fixing part 134 and the corresponding adhesive joints 138.

[0088] Since the rear side 112 of the optical element 108 does not need to have defined optical properties, the mounting space above the rear side 112 can be used to strengthen the mounting seat 116. For this purpose, the inner ring 120 is positioned above the rear side 112 and strengthened by means of the reinforcing ribs 122, 124. Thus, the optical system 100 only has a mounting space that is slightly larger than the optical element 108 itself. The inner ring 120 and the reinforcing ribs 122, 124 serve as a load-bearing structure for the outer ring 118. The reinforcing ribs 122, 124 are optimized in terms of weight so that the mounting seat 116 has high rigidity and at the same time is lightweight.

[0089] Please refer back immediately to Figure 3 , the mounting seat 116 (in particular the outer ring 118) comprises a plurality of vibration absorber interfaces 152, 154, 156. Preferably, exactly three vibration absorber interfaces 152, 154, 156 are provided, which are arranged in a uniformly distributed manner around the central axis 102. Specifically, the vibration absorber interfaces 152, 154, 156 are positioned at the outer ring 118 with an offset of 120° relative to each other.

[0090] At each vibration absorber interface 152, 154, 156, a vibration absorber (referred to as: tuned mass damper (TMD)) is provided. Each vibration absorber interface 152, 154, 156 can be arranged at one of the outer joints 128 where two reinforcing ribs 122, 124 intersect. Thus, high rigidity can be obtained in the region of the vibration absorber interfaces 152, 154, 156.

[0091] Figure 6 A schematic view showing an embodiment of the vibration absorber 158.

[0092] This vibration absorber 158 can be arranged at each vibration absorber interface 152, 154, 156. However, only the vibration absorber interface 152 will be discussed below. The vibration absorber 158 comprises an absorber mass 160. The absorber mass 160 can be bow-shaped and its geometry is adapted to the geometry of the outer ring 118 of the mounting seat 116. When looking along the radial direction R, the absorber mass 160 is attached to the outer side of the outer ring 118.

[0093] In addition to the absorber mass 160, the vibration absorber 158 further includes a spring 162 and a damper 164. The absorber mass 160 is coupled to the vibration absorber interface 152 by means of the spring 162 and the damper 164. The spring 162 and the damper 164 can be realized in particular by elastically deformable components, for example in the form of a viscous joint or an elastomer. In this case, the elastically deformable component performs the spring function of the spring 162 and the damping function of the damper 164.

[0094] The absorber mass 160 can vibrate along the x-direction x and along the y-direction y. Along the z-direction z, the absorber mass 160 is positioned at the center of gravity height of the optical system 100. The vibration of the optical system 100 can be attenuated by means of the vibration absorber 158. The natural frequency of the vibration absorber 158 can be influenced or set by, for example, a change in the absorber mass 160 and / or a change in the stiffness of the spring 162.

[0095] As Figure 3 shown, in addition to the vibration absorber interfaces 152, 154, 156, the mounting base 116 further includes a plurality of mounting pillar interfaces 166, 168, 170. Preferably, exactly three mounting pillar interfaces 166, 168, 170 are provided, which are arranged in a uniformly distributed manner around the central axis 102. Specifically, the mounting pillar interfaces 166, 168, 170 are positioned at the outer ring 118 with an offset of 120° relative to each other. In this case, the mounting pillar interfaces 166, 168, 170 are centered between the vibration absorber interfaces 152, 154, 156. Each mounting pillar interface 166, 168, 170 is assigned an external engagement point 128, where two reinforcing ribs 122, 124 intersect. Therefore, high stiffness can also be obtained in the region of the mounting pillar interfaces 166, 168, 170. When viewed in the radial direction R, the mounting pillar interfaces 166, 168, 170 are arranged at the outer ring 118 on the outside.

[0096] Each mounting pillar interface 166, 168, 170 is assigned a mounting pillar (not shown). Therefore, three mounting pillars are provided. The mounting pillars are so-called A-columns or can be so named. The mounting base 116 is arranged at six spatial points. In this case, each mounting pillar is assigned two of these spatial points. By means of the mounting pillars, the mounting base 116 or the optical system 100 is operatively connected to a fixed group, such as a force frame. In this case, the mounting pillars mechanically decouple the optical system 100 from the fixed group so that no unwanted stress is introduced into the optical system 100.

[0097] Figure 7 Schematic diagram showing an embodiment of the tool interface 172.

[0098] Figure 7 Corresponding to according toFigure 6 View VII. View VII is vertically oriented towards the tool interface 172. In addition to the vibration absorber interfaces 152, 154, 156 and the mounting strut interfaces 166, 168, 170, the mounting base 116 further includes a tool interface 172 to which a tool (not shown) for replacing the optical system 100 from the illumination optical unit 4 can be coupled. The tool interface 172 includes a first interface surface 174, a second interface surface 176, and a third interface surface 178. The tool abuts against the interface surfaces 174, 176, 178. When viewed in the radial direction R, the interface surfaces 174, 176, 178 are provided at the outer ring 118 of the outer side surface.

[0099] All the interface surfaces 174, 176, 178 are oriented parallel to each other. In this case, the first interface surface 174 oriented in Figure 7 is set back by a distance a ( Figure 3 ) relative to the interface surfaces 176, 178. When viewed along the z-direction z, the first interface surface 174 and the second interface surface 176 are located at the same height. When viewed along the z-direction z, the third interface surface 178 is located below the interface surfaces 174, 176. Each of the interface surfaces 174, 176, 178 is assigned a threaded hole 180, 182, 184. Each of the threaded holes 180, 182, 184 is located at the center of the interface surface 174, 176, 178 assigned to it. By means of the threaded holes 180, 182, 184, the tool can be connected to the tool interface 172 to replace the optical system 100.

[0100] Thus, the optical system 100 can be easily replaced. Due to the compact design of the mounting base, the mounting space required for the optical system 100 is very small. A positioning accuracy of several micrometers can be achieved. By means of the fixing part 134 joined to the outer ring 118 via the joints 142, 146, the tension can be decoupled so that only minute deformations are transferred. By means of the reinforcing ribs 122, 124, the total stiffness of the optical system 100 can be increased in the case where the demand for the stroke of the optical system 100 increases and the mounting space becomes smaller.

[0101] Although the present invention has been described based on exemplary embodiments, the present invention can be modified in various ways.

[0102] List of reference numerals

[0103] 1 Projection exposure apparatus

[0104] 2 Beam shaping and illumination system

[0105] 4 Projection optical unit

[0106] 6 Light source

[0107] 8 Radiation

[0108] 10 Photomask

[0109] 12 Wafer

[0110] 14 Lens element

[0111] 16 Lens element

[0112] 18 Lens element

[0113] 20 Mirror

[0114] 22 Mirror

[0115] 24 Optical axis

[0116] 26 Medium

[0117] 100 Optical system

[0118] 102 Central axis

[0119] 104 Semi-axis

[0120] 106 Semi-axis

[0121] 108 Optical element

[0122] 110 Optically effective surface

[0123] 112 Rear side

[0124] 114 Outer surface

[0125] 116 Mount

[0126] 118 Outer ring

[0127] 120 Inner ring

[0128] 122 Reinforcing rib

[0129] 124 Reinforcing rib

[0130] 126 Gap

[0131] 128 Joint point

[0132] 130 Joint point

[0133] 132 Outer ring segment

[0134] 134 Fixing part

[0135] 136 Joint surface

[0136] 138 Adhesive joint part

[0137] 140 Normal

[0138] 142 Joint

[0139] 144 Connection part

[0140] 146 Joint

[0141] 148 Base

[0142] 150 Gap

[0143] 152 Vibration absorber interface

[0144] 154 Vibration absorber interface

[0145] 156 Vibration absorber interface

[0146] 158 Vibration absorber

[0147] 160 Absorber mass

[0148] 162 Spring

[0149] 164 Damper

[0150] 166 Mounting strut interface

[0151] 168 Mounting strut interface

[0152] 170 Mounting strut interface

[0153] 172 Tool interface

[0154] 174 Interface surface

[0155] 176 Interface surface

[0156] 178 Interface surface

[0157] 180 Screw hole

[0158] 182 Screw hole

[0159] 184 Screw hole

[0160] a Distance

[0161] R Radial direction

[0162] U Circumferential direction

[0163] x x - direction

[0164] y y - direction

[0165] z z - direction

Claims

1. An optical system (100) for a projection exposure apparatus (1), comprising: an optical element (108); and a mount (116) that carries the optical element (108); wherein the mount (116) includes an outer ring (118), and at least a part of the optical element (108) is received in the outer ring (118); wherein the outer ring (118) includes a fixing portion (134) that is tightly connected to the optical element (108); wherein the fixing portion (134) is pivotally connected to the outer ring (118) by means of a joint portion (142, 146); and wherein the mount (116) includes a tool interface (172) for releasably fixing a tool for replacing the optical system (100) from an illumination optical unit (4).

2. The optical system according to claim 1, wherein the joint portion (142, 146) is configured such that the fixing portion (134) can perform a pivoting movement along a radial direction (R) of the optical system (100).

3. The optical system according to claim 1 or 2, wherein each fixing portion (134) includes a joint surface (136) facing the optical element (108), and the joint surface is tightly connected to the optical element (108); and wherein normals (140) of the joint surface (136) intersect each other on another central axis (102) of the optical system (100).

4. The optical system according to any one of claims 1 - 3, wherein each fixing portion (134) is pivotally connected to the outer ring (118) by means of a first joint portion (142) and a second joint portion (146) different from the first joint portion (142).

5. The optical system according to claim 4, wherein each fixing portion (134) is pivotally connected to a connecting portion (144) by means of the first joint portion (142), and wherein the connecting portion (144) is pivotally connected to the outer ring (118) by means of the second joint portion (146).

6. The optical system according to any one of claims 1 - 5, wherein the optical element (108) includes: an optically effective surface (110), in particular a reflective mirror surface; a rear side surface (112) facing away from the optically effective surface (110); and an outer surface (114) that extends circumferentially around the optical element (108); and wherein the plurality of fixing portions (134) are only tightly connected to the outer surface (114).

7. The optical system according to any one of claims 1 - 6, wherein the mount (116) includes an inner ring (120) disposed inside the outer ring (118), and wherein the inner ring (120) is connected to the outer ring (118) by means of reinforcing ribs (122, 124).

8. The optical system according to claim 7, wherein the two reinforcing ribs (122, 124) are always connected to the outer ring (118) at a common outer joint point (128).

9. The optical system according to claim 8, wherein the external engagement points (128) and the fixing parts (134) are arranged alternately.

10. The optical system according to claim 8 or 9, wherein each of the fixing parts (134) is centered between two adjacent external engagement points (128).

11. The optical system according to any one of claims 8-10, wherein the two reinforcing ribs (122, 124) are always connected to the inner ring (120) at a common internal engagement point (130), and wherein the external engagement points (128) and the internal engagement points (130) are arranged alternately.

12. The optical system according to any one of claims 1-11, wherein the mounting base (116) includes vibration absorber interfaces (152, 154, 156) for engaging a vibration absorber (158) to the mounting base (116).

13. The optical system according to any one of claims 1-12, wherein the mounting base (116) includes mounting pillar interfaces (166, 168, 170) for engaging mounting pillars to the mounting base (116).

14. A projection exposure apparatus (1) comprising an optical system (100) according to any one of claims 1 to 13.

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