Optical system and projection exposure apparatus

Abstract

An optical system (100) of a projection exposure apparatus (1), comprising an optical element (108) and a mount (116) that carries the optical element (108), the mount (116) including an outer ring (118) that at least partially accommodates the optical element (108), the outer ring (118) including a fixing part (134) that is materially connected to the optical element (108), the fixing part (134) being rotatably connected to the outer ring (118) by means of articulation parts (142, 146), and the mount (116) including a tool interface (172) for releasably fixing a tool for replacement of the optical system (100) from an illumination optical unit (4).

Description

[Technical Field]

[0001] The present invention relates to an optical system and a projection exposure apparatus equipped with the optical system.

[0002] The content of the priority application German Patent Application No. 10 2022 214 186.5 is incorporated by reference in its entirety. [Background technology]

[0003] Microlithography is used in the manufacture of finely structured components, such as integrated circuits. The microlithography process is carried out using a lithography apparatus comprising an illumination system and a projection system. In this case, an image of a mask (reticle), illuminated by the illumination system, is projected by the projection system onto a substrate, e.g., a silicon wafer, that is coated with a photosensitive layer (photoresist) and positioned in the image plane of the projection system, in order to transfer the mask structure into the photosensitive coating on the substrate.

[0004] Due to the desire for ever smaller structures in the manufacture of integrated circuits, deep ultraviolet (DUV) lithography systems are currently under development that use light with wavelengths in the range of 30 nm to 250 nm, particularly 193 nm, which can use reflective optical elements, i.e., mirrors, instead of the conventional refractive optical units, i.e., lens elements.

[0005] Such mirrors may be housed in mounts. Such mounts are typically fixedly attached to a projection system, such as those described above. Therefore, it is not feasible to replace the mount along with the mirror. Furthermore, the mount itself may exert tension on the mirror, which may cause undesirable stresses in the mirror and thus changes in the optical properties of the mirror. This needs to be improved. Summary of the Invention [Problem to be solved by the invention]

[0006] In view of this, it is an object of the present invention to provide an improved optical system. [Means for solving the problem]

[0007] Therefore, an optical system of a projection exposure apparatus is proposed, the optical system comprising an optical element and a mount for carrying the optical element, the mount including an outer ring that at least partially accommodates the optical element, the outer ring including a fixing part that is materially connected to the optical element, the fixing part being pivotally connected to the outer ring by means of an articulation part, wherein the mount includes a tool interface for releasably fixing a tool for exchange of the optical system from an illumination optical unit.

[0008] The mount is physically connected to and carries the optical element, allowing the mount to be replaced together with the optical element. The pivotable fixation ensures that tension forces introduced by the mount into the optical element are significantly reduced, thereby preventing undesirable material stresses in the optical element.

[0009] The optical system may in particular be or be referred to as a mirror, for example an EUV mirror or mirror module. The optical system may be a mirror of a catadioptric system. The optical system may be part of a projection optical unit. The projection optical unit may include several such optical systems. However, the optical system may also be part of an illumination system. However, in the following it will be assumed that the optical system is part of a projection optical unit. The optical system is suitable for EUV lithography. However, the optical system may also be suitable for DUV lithography.

[0010] A coordinate system can be assigned to the optical system, including a first spatial direction or x-direction, a second spatial direction or y-direction, and a third spatial direction or z-direction. The optical system has an axis of symmetry or central axis oriented parallel to or coincident with the z-direction. The optical system can be configured to be substantially rotationally symmetric about the central axis, although this is not required. The radial direction of the optical system points away from the central axis perpendicular to the central axis.

[0011] The optical system 100 is exchangeable, i.e., it can be removed from and reinserted into the projection optical unit. Therefore, the optical system can also be referred to as an optical exchange system or optical exchange module. Corresponding tools can be provided for exchanging the optical system. Preferably, the optical system is exchanged in situ. In the present context, "in situ" means that the exchange of the optical system can be carried out directly at the operating location of the projection exposure apparatus in which the optical system is installed. In this case, the optical system is exchanged as a whole, i.e., in particular, the optical elements are exchanged together with their mounts. Advantageously, the exchanged optical system can be replaced by a newly developed optical system with improved optical effects, thereby also increasing the performance and / or accuracy of the projection optical unit. The newly developed optical system can also include, in particular, electronic components.

[0012] Preferably, the optical system comprises exactly one optical element and exactly one mount. The optical system may be a mirror or a lens element. In the following, the optical element is considered to be a mirror. The optical element comprises an optically effective surface. The optically effective surface is suitable for reflecting illumination radiation, in particular DUV radiation, during operation of the optical system. A reflectivity of 193 nm is required in this case. However, the optically effective surface may also be suitable for reflecting EUV radiation. Therefore, the optically effective surface is a mirror surface. The optically effective surface can be realized using a coating. The optical element comprises a mirror substrate on which the optically effective surface is provided. The mirror substrate can be made of, for example, glass, glass ceramic, ceramic, silicon, etc. The optically effective surface can be curved, in particular a curved surface or a toroidal curved surface, or a spherical crown-shaped curved surface. The curvature of the optically effective surface can be both spherical and aspherical.

[0013] Preferably, the optical element has a back side opposite to the optically effective surface. The back side may also be curved. The back side does not have defined surface properties, i.e., in particular, the back side is not a mirror surface and therefore does not have reflective properties. An outer surface of the optical element is provided between the optically effective surface and the back side. The outer surface may be cylindrical. The outer surface may be configured rotationally symmetrical about a central axis. Preferably, the outer surface extends around the entire circumference of the optical element. The optical element may be configured rotationally symmetrical about a central axis. However, this is not required.

[0014] In the present invention, the mount "carries" the optical element, particularly meaning that the optical element is fixedly connected to the mount and can be adjusted or aligned together with the mount. In particular, the mount absorbs the weight force of the optical element. The mount is preferably an integral component, particularly a component made of one material. "Integral" or "integral" here particularly means that the mount does not consist of different subcomponents, but rather that the outer ring, the fixing portion, and the articulation portion form a common component, i.e., the mount. "Integral" here particularly means that the entire mount is made of the same material. For example, the mount can be made of copper, aluminum, steel, etc. The mount can be manufactured using additive manufacturing or layered manufacturing methods, particularly 3D printing methods. Furthermore, the mount can also be manufactured using erosion methods.

[0015] The outer ring may be configured rotationally symmetrical with respect to the central axis. However, this is not required. The outer ring may also be, for example, elliptical or oval. In particular, the outer ring comprises a plurality of outer ring segments integrally connected to one another. The outer ring segments form planar or linear portions of the outer ring. Thus, the outer ring is preferably polygonal rather than circular. Therefore, in the present context, "ring" should be understood to particularly mean a closed geometric shape extending completely around the central axis. Therefore, in the present context, "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 completely around the central axis and includes or surrounds the outer surface of the optical element.

[0016] Preferably, the fixing part is part of the outer ring. The fixing part is integrally connected to the outer ring, in particular by means of an articulation part. In particular, the outer ring is materially connected to the outer surface of the optical element by means of the fixing part. In a material connection, the connection partners are held together by atomic or molecular forces. The material connection is an irreleasable connection that can only be separated by destruction of the connection means and / or the connection partners. The material connection can be implemented, for example, by adhesive bonding.

[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 parts of the outer ring are adhesively bonded to the optical element, in particular to its outer surface. For this purpose, an adhesive layer is provided on each fixing part. Thus, instead of one adhesive layer extending all around the circumference around the axis of symmetry, multiple adhesive layers separated from each other, each assigned to a fixing part, are provided on the outer surface. The adhesive layers are respectively provided between the bonding surfaces of each fixing part and the outer surface of the optical element, and materially connect each bonding surface to the outer surface.

[0018] The articulations are preferably flexures. By way of example, exactly one articulation can be assigned to each fixed part. Alternatively, several articulations, for example two articulations, can be assigned to each fixed part. In the present context, "flexure" is generally understood to mean a region of a component, in the present case the outer ring or each outer ring segment, that allows relative movement between two rigid regions of the component by bending or twisting, for example a narrowed or thinned cross section. Here, the rigid regions are, for example, the fixed part and the outer ring, between which a respective articulation in the form of a narrowed or thinned cross section is provided.

[0019] By adapting the stiffness of the articulation, its properties, in particular its deformability, can be adapted. In the present context, "stiffness" should be understood to mean in a very general sense the resistance of the body, or in the present context, the articulation, to elastic deformation due to an external load, and describes the relationship between the load on the body and its deformation. Stiffness depends on the material of the body and its geometric shape. For example, the stiffness of the articulation can be adapted as desired by different cross-sectional shapes. The articulation preferably ensures mechanical decoupling of the optical element from the mount. In the present context, "mechanical decoupling" should be understood to mean that the articulation prevents or at least reduces the transmission of forces from the mount to the optical element.

[0020] According to one embodiment, the articulation is configured to allow rotation of the fixed part in the radial direction of the optical system.

[0021] The pivot axis of each joint is therefore oriented in the z-direction or parallel to the central axis. Thus, it is possible, for example, to use the joints to compensate for thermal expansion of the optical element and / or the mount along the radial direction. Thus, each joint allows the fixation part assigned to it to move radially outward from the inner ring of the mount.

[0022] According to yet another embodiment, each fixing portion includes a bonding surface facing the optical element, the bonding surfaces being materially connected to the optical element, and normals to the bonding surfaces intersect each other at the central axis of the optical system.

[0023] The central axis is, or can be referred to as, the central axis of the optical system. The cemented surfaces are preferably in any case flat or straight. In the present invention, "normal" is understood to mean a straight line oriented perpendicular to each cemented surface. Preferably, all normals to all cemented surfaces of all fixation parts intersect each other at the central axis.

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

[0025] Alternatively, it is possible to provide only one articulation, i.e. in particular the second articulation is optional. By providing two articulations, an optimal separation of the optical elements can be obtained. It is also possible to provide three or more articulations.

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

[0027] In particular, the connecting part is pivotally connected to the base of the outer ring by means of the second articulation part. Thus, the fixed part is connected to the outer ring, and thus to the base of the outer ring, only via the first articulation part, the connecting part and the second articulation part. The connecting part may be a parallelepiped. Compared to the two articulation parts, the connecting part has a significantly higher rigidity. Thus, the connecting part functions as a rigid region between the first articulation part and the second articulation part.

[0028] According to yet another embodiment, the optical element comprises an optically active surface, in particular a mirror surface, a back side opposite the optically active surface, and an outer surface extending circumferentially around the optical element, and the fixing part is only materially connected to the outer surface.

[0029] That is, in particular, the mount is only physically connected to the optical element by the adhesive layer provided on the fixing part. Preferably, therefore, the mount only contacts the optical element at the fixing part or at the adhesive layer provided on the fixing part. Preferably, therefore, no further contact points between the mount and the optical element are provided.

[0030] According to yet another embodiment, the mount includes an inner ring disposed within an outer ring, the inner ring being connected to the outer ring with stiffening ribs.

[0031] Conversely, the inner ring can also be arranged outside the outer ring. When viewed along 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 provided on the back side of the optical element. When viewed along the central axis, the inner ring can be arranged spaced apart from the back side so that the inner ring does not contact the outer ring. The stiffening ribs can also be referred to as stiffening webs. The outer ring can be stiffened using the inner ring and stiffening ribs, with the stiffening moved to the back side of the optical element. As a result, the installation space required for the optical system can be significantly reduced.

[0032] According to yet another embodiment, the two stiffening ribs are always connected to the outer ring at a common outer junction point.

[0033] When viewed along the circumferential direction of the optical system, each outer joint point is located midway between two of the above-mentioned normals to adjacent fixing parts, or conversely, each normal line is positioned between adjacent outer joint points, at which the stiffening ribs are integrally connected to the outer ring, in particular by a single piece of material.

[0034] According to yet another embodiment, the outer joining points and the fastening portions are arranged alternately.

[0035] That is, in particular, when viewed along the circumferential direction of the mount or optical system, each outer joint point is located between the fixing parts, or a fixing part is located between two outer joint points.

[0036] According to yet another embodiment, the fastening portions are each positioned centrally between two adjacent outer joining points.

[0037] Thus, as described above, the normal to each fastening portion extends in the direction of and intersects with the central axis midway between two adjacent outer joint points.

[0038] According to yet another embodiment, the two stiffening ribs are always connected to the inner ring at a common inner junction, with the outer and inner junctions being arranged alternately.

[0039] The outer and inner joints are arranged alternately when viewed in the circumferential direction. The normal to the fixing part passes through the inner joints. At the inner joints, the stiffening ribs are connected to the inner ring integrally, in particular by a single material. When viewed in the circumferential direction, there is always one inner joint between two outer joints and one outer joint between two inner joints.

[0040] According to yet another embodiment, the mount includes a vibration absorber interface for joining the vibration absorber to the mount.

[0041] Preferably, a plurality of vibration absorber interfaces are provided, arranged in an even distribution around the central axis. Preferably, three vibration absorber interfaces are provided, arranged offset by 120° relative to one another. The vibration absorber interfaces are each provided in the region of an outer joint point, whereby the vibration absorber interfaces are stiffened with stiffening ribs. The vibration absorbers can be part of the optical system. Preferably, each vibration absorber interface is assigned a vibration absorber. The vibration absorbers can be used to damp vibrations introduced into the optical system.

[0042] According to yet another embodiment, the mount includes a mount strut interface for joining the mount strut to the mount.

[0043] Preferably, multiple mount strut interfaces are provided. In particular, three mount strut interfaces are provided, offset 120° from one another. Preferably, the vibration absorber interfaces and the mount strut interfaces are alternately arranged when viewed along the circumferential direction. That is, in particular, one mount strut interface is arranged between two vibration absorber interfaces, and one vibration absorber interface is arranged between two mount strut interfaces. Each mount strut interface is preferably assigned an outer joint point. This has the effect of stiffening the mount strut interface using stiffening ribs connected to the outer joint points. The mount struts are or can be referred to as so-called "A-struts." The mount seats at six spatial points. In this case, each mount strut is assigned two of these spatial points. The mount struts are used to operatively connect the mount or optical system to a fixed environment, such as a force frame. In this case, the mount struts mechanically decouple the optical system from the fixed environment to prevent undesired stresses from being introduced into the optical system.

[0044] The mount includes a tool interface for releasably securing a tool for replacement of the optics from the illumination optical unit.

[0045] Preferably, the tool interface includes a plurality of interface surfaces arranged parallel to one another. Each interface surface can be assigned a screw 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 along the z direction, the first interface surface and the second interface surface are positioned at the same height. When viewed along the z direction, the third interface surface is arranged below the second interface surface.

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

[0047] The projection exposure apparatus may comprise several optical systems. The optical systems are preferably part of the projection optical unit of the projection exposure apparatus. However, the optical systems may also be part of the illumination system. The projection exposure apparatus may be an EUV lithography apparatus. EUV stands for "extreme ultraviolet" and refers to the wavelength of light used between 0.1 nm and 30 nm. The projection exposure apparatus may also be a DUV lithography apparatus. DUV stands for "deep ultraviolet" and refers to the wavelength of light used between 30 nm and 250 nm.

[0048] In the context of the present invention, "a" or "an" or "one" should not necessarily be understood as limiting to exactly one element. Rather, there can be a plurality of elements, such as two, three, or more. Any other numbers used herein should not be understood as limiting to a precise number of elements. Instead, unless otherwise specified, the number can be increased or decreased.

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

[0050] Further possible implementations of the invention also include not explicitly mentioned combinations of the features and embodiments described above or below with respect to the exemplary embodiments, in which case a person skilled in the art will also add individual aspects as improvements or supplements to each basic form of the invention.

[0051] Further advantageous configurations and aspects of the invention are the subject of the dependent claims and also of exemplary embodiments of the invention which will be described later in this specification. The invention will be explained in more detail on the basis of preferred embodiments with reference to the attached drawings. [Brief explanation of the drawings]

[0052] [Figure 1] 1 shows a schematic diagram of an embodiment of a projection exposure apparatus for DUV projection lithography; [Figure 2] 2 shows a schematic plan view of an embodiment of the optical system of the projection exposure apparatus shown in FIG. 1. [Figure 3] 3 shows a schematic rear view of the optical system shown in FIG. 2. [Figure 4] 4 shows a detailed view of IV shown in FIG. 2. [Figure 5] A diagram of V is shown in Figure 4. [Figure 6] 3 shows a schematic diagram of an embodiment of a vibration absorber for the optical system shown in FIG. 2. [Figure 7] 3 shows a schematic diagram of one embodiment of a tool interface of the optical system shown in FIG. 2. DETAILED DESCRIPTION OF THE INVENTION

[0053] Unless otherwise specified, identical or functionally identical elements are given the same reference numerals throughout the figures. It should also be noted that illustrations in the figures are not necessarily to scale.

[0054] 1 shows a schematic diagram of a projection exposure apparatus 1, in particular a DUV lithography apparatus, equipped with a beam shaping and illumination system 2 (also referred to herein as an "illumination optical unit") and a projection optical unit 4 (also referred to herein as a "projection lens"). In this case, DUV stands for "deep ultraviolet" and refers to the wavelength of the light used, which is between 30 nm and 250 nm.

[0055] The beam shaping / illumination system 2 and the projection system 4 are preferably disposed in respective vacuum housings (not shown). Each vacuum housing is evacuated using an exhaust device (not shown). The vacuum housing is surrounded by a machine room (not shown), in which a driving device for mechanically moving or setting the optical elements can be provided. Furthermore, an electric controller and the like can also be provided in the machine room.

[0056] The projection exposure apparatus 1 comprises a light source 6. For example, an ArF excimer laser emitting radiation 8 in the deep UV range, for example at 193 nm, can be provided as light source 6. In a beam shaping and illumination system 2, the radiation 8 is focused and a desired operating wavelength (used light) is filtered out of the radiation 8. The beam shaping and illumination system 2 can comprise optical elements, not shown, for example mirrors or lens elements.

[0057] After passing through the beam shaping and illumination system 2, the radiation 8 is directed onto a photomask or reticle 10. The photomask 10 may be formed as a transmissive optical element and may be located external to the beam shaping and illumination system 2 and the projection optical unit 4. The photomask 10 has structures that are imaged in reduced form onto a wafer 12 by the projection optical unit 4.

[0058] 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 an optical axis 24 of the projection optical unit 4. It should be noted that the numbers of lens elements 14, 16, 18 and mirrors 20, 22 shown here are for illustrative purposes only and are not limited to the numbers shown. More or fewer lens elements 14, 16, 18 and / or mirrors 20, 22 may be provided.

[0059] The air gap between the final lens element (not shown) and the wafer 12 can be replaced with a liquid medium 26 having a refractive index greater than 1. The liquid medium 26 can be, for example, high-purity water. Such an arrangement is also referred to as immersion lithography and has high photolithographic resolution. The medium 26 can also be referred to as an immersion liquid.

[0060] Figure 2 shows a schematic plan view of an embodiment of the optical system 100 of the projection exposure apparatus 1. Figure 3 shows a schematic rear view of the optical system 100. In the following text, reference is made simultaneously to Figures 2 and 3.

[0061] The optical system 100 can be part of a projection optical unit 4 as described above. However, the optical system 100 can also be part of a beam shaping and illumination system 2. However, in the following, it will be assumed that the optical system 100 is part of this type of projection optical unit 4. The optical system 100 is suitable for DUV lithography. However, the optical system 100 can also be suitable for EUV lithography.

[0062] The optical element 100 may be one of the mirrors 20, 22. Accordingly, the optical system 100 may be referred to as a mirror or a mirror module. The optical system 100 may be assigned a coordinate system including an x-direction x, a y-direction y, and a z-direction z. The optical system 100 has a symmetry axis or central axis 102 oriented parallel to or coincident with the z-direction z. The optical system 100 may be configured to be substantially rotationally symmetric about the central axis 102. The optical system 100 is assigned two semi-axes 104, 106 that intersect the central axis 102. The radial direction R of the optical system 100 is oriented perpendicular to the central axis 102 and points away from the central axis 102. The circumferential direction U is oriented around the central axis 102.

[0063] The optical system 100 is exchangeable, i.e. it can be removed from the described projection optical unit 4 and reinserted therein. For this purpose, corresponding tools (not shown) can be provided. Preferably, the optical system 100 is exchangeable in the field. In the present case, "in the field" means directly at the operating location of the projection exposure apparatus 1.

[0064] The optical system 100 comprises an optical element 108. The optical element 108 may be a mirror or a lens element. In the following, 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 operation of the optical system 100. The optically effective surface 110 is a mirror surface. The optically effective surface 110 can be realized by means of a coating.

[0065] The optical element 108 has a back side 112 opposite the optically effective surface 110. The back side 112 does not have defined surface properties. In particular, the back side 112 is not a mirrored surface and does not have reflective properties. An outer surface 114 of the optical element 108 is provided between the optically effective surface 110 and the back side 112. The outer surface 114 may be cylindrical. The outer surface 114 may be configured rotationally symmetrical about the central axis 102.

[0066] In addition to the optical element, the optical system 100 includes a mount 116 that supports the optical element 108. The mount 116 includes an outer ring 118 and an inner ring 120. A circumferential direction U extends along the outer ring 118 or along the inner ring 120. The outer ring 118 and the inner ring 120 may each be configured rotationally symmetrical 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. The outer ring 118 and the inner ring 120 may each have a hollow cylindrical or tubular geometric shape.

[0067] The outer ring 118 is connected to the optical element 108, in particular to the outer surface 114. For this purpose, a material connection can be provided. In a material connection, the connection partners are held together by atomic or molecular forces. The material connection is an irreleasable connection that can only be separated by destruction of the connection means and / or the connection partners. The material connection can be implemented, for example, 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.

[0068] The inner ring 120 is not connected to the optical element 108. In the orientation of Figure 3, the inner ring 120 is positioned above, but does not contact, the back side 112 of the optical element 108. That is, there may be an air gap between the back side 112 and the inner ring 120.

[0069] The inner ring 120 is connected to the outer ring 118 by means of stiffening webs or ribs 122, 124, only two of which are numbered. The stiffening ribs 122, 124 are therefore arranged between the inner ring 120 and the outer ring 118 when viewed along the radial direction R, and span the gap 126 provided between the outer ring 118 and the inner ring 120. The number of stiffening ribs 122, 124 is, in principle, arbitrary. The stiffening ribs 122, 124 extend obliquely between the outer ring 118 and the inner ring 120. The stiffening ribs 122, 124 extend completely around the central axis 102.

[0070] Two stiffening ribs 122, 124 are joined to the outer ring 118 at outer or first junction points 128. Accordingly, two stiffening ribs 122, 124 are joined to the inner ring 120 at inner or second junction points 130. That is, two stiffening ribs 122, 124 meet at each outer junction point 128, and two stiffening ribs 122, 124 meet at each inner junction point 130.

[0071] The mount 116 is a unitary component, particularly a one-piece component. "Unitary" or "unitary" here particularly means that the mount 116 is not made up of different subcomponents, but rather that the outer ring 118, the inner ring 120, and the stiffening ribs 122, 124 form a common component, i.e., the mount 116. "Unitary" here particularly means that the entire mount 116 is made from the same material. For example, the mount 116 can be made from copper, aluminum, steel, etc. The mount 116 can be manufactured using additive manufacturing or additive manufacturing methods, particularly 3D printing methods. Furthermore, the mount 116 can also be manufactured using erosion methods.

[0072] Figure 4 shows a detailed view of IV shown in Figure 2. Figure 5 shows a view of V shown in Figure 4. In the following text, Figures 4 and 5 will be referred to simultaneously.

[0073] The outer ring 118 includes a plurality of outer ring segments 132, only one of which is given a reference number in FIG. 4 . The outer ring segments 132 are integrally connected to one another, particularly by a single piece of material, at outer junctions 128. The outer ring segments 132 themselves are straight, not curved. A plurality of such outer ring segments 132 form the ring-like geometric shape of the outer ring 118. That is, particularly, the outer ring 118 is polygonal, not circular. Only one outer ring segment 132 will be described in more detail below.

[0074] Each outer ring segment 132 includes a fastening portion 134, which may also be referred to as a small fastening foot. The fastening portion 134 is located centrally between two adjacent stiffening ribs 122, 124. The stiffening ribs 122, 124 begin at a central outer junction 128 between the fastening portions 134 of the outer ring segments 132 and extend diagonally inwardly against the radial direction R to the inner ring 120, where they are connected using an inner junction 130.

[0075] The outer surface 114 of the optical element 108 is materially connected to the fixing part 134. For this purpose, an adhesive layer 138 is provided between a bonding surface 136 of the fixing part 134 facing the outer surface 114 and the outer surface 144. The adhesive layer 138 materially connects the outer surface 114 to the bonding surface 136. The adhesive layer 138 may be, for example, an epoxy resin or the like. The bonding surface is an adhesive bonding surface and may therefore also be referred to as such.

[0076] A plurality of fastening portions 134 are provided. Accordingly, a plurality of adhesive layers 138 are also provided. The outer ring 118 is connected to the optical element 108 only by the fastening portions 134 and the adhesive layers 138. A normal 140 to the bonding surface 136 intersects the central axis 102. In the present invention, a "normal" or a "normal vector" should be understood to mean a line perpendicular to the bonding surface 136. The stiffening ribs 122, 124 intersect the normal 140 at the inner ring 120, in particular at each inner bonding point 130.

[0077] The fixed portion 134 is pivotally connected to the connecting portion 144 of the outer ring segment 132 by means of an articulation portion 142. The articulation portion 142 is a flexure. In the present context, a "flexure" should be understood to generally refer to a region of a component, in this case the outer ring segment 132, that allows relative movement between two rigid regions of the component by bending or twisting, such as a narrowed cross-section or thinned wall portion. The fixed portion 134 and the connecting portion 144, for example, function as rigid regions in this context.

[0078] By adapting the stiffness of the articulation section 142, its properties, in particular its deformability, can be adapted. In the present context, "stiffness" should be understood to mean in a very general sense the resistance of a body, or in the present context, a joint, to elastic deformation due to an external load, and describes the relationship between the load on the body and its deformation. Stiffness is determined by the material of the body and its geometric shape. For example, the stiffness of the articulation section 142 can be adapted as desired by using different cross-sectional shapes.

[0079] The articulation portion 142 allows the fixed portion 134 to move outward from the inner ring 120 in the radial direction R. The connecting portion 144 is joined to a base portion 148 of the outer ring segment 132 via another articulation portion 146. The articulation portion 146 is also a flexure. The articulation portion 136 is optional. The articulation portions 142, 146 may have the same or different stiffness.

[0080] Opposite the articulation portion 146, a clearance or gap 150 is provided between the base portion 148 and the fixed portion 134, separating the fixed portion 134 from the base portion 148. As shown in Figure 5, the gap 150 extends partially circumferentially around the fixed portion 134, the articulation portions 142, 146, and the connecting portion 144. The base portion 148 is planar, and the gap 150 forms a notch that allows the fixed portion 134 and the connecting portion 144 to move relative to the base 148 using the articulation portions 142, 146.

[0081] The articulations 142, 146 allow radial movement of the fixed portion 134, thereby isolating the tension forces required for the optical element 108. The fixed portion 134, which is bonded to the base 148 via the articulations 142, 146, allows only very small radial forces to be transmitted to the optical element 108. The mount 116 is bonded to the optical element 108 only via the fixed portion 134 and the corresponding adhesive layer 138.

[0082] Because the back side 112 of the optical element 108 does not need to have defined optical properties, the installation space above the back side 112 can be used to stiffen the mount 116. For this purpose, the inner ring 120 is positioned above the back side 112 and stiffened using stiffening ribs 122, 124. As a result, the optical system 100 requires only slightly more installation space than the optical element 108 alone. The inner ring 120 and stiffening ribs 122, 124 function as a support structure for the outer ring 118. The weight of the stiffening ribs 122, 124 is optimized, allowing the mount 116 to be both highly rigid and light in weight.

[0083] 3, the mount 116, and in particular the outer ring 118, includes a plurality of vibration absorber interfaces 152, 154, 156. Preferably, exactly three vibration absorber interfaces 152, 154, 156 are provided, evenly distributed about the central axis 102. In particular, the vibration absorber interfaces 152, 154, 156 are positioned on the outer ring 118 at a 120° offset relative to one another.

[0084] A vibration absorber (known as a Tuned Mass Damper, TMD) is provided at each absorber interface 152, 154, 156. Each absorber interface 152, 154, 156 may be provided at one of the outer junction points 128 where the two stiffening ribs 122, 124 meet. As a result, high stiffness can be achieved in the region of the absorber interface 152, 154, 156.

[0085] FIG. 6 shows a schematic diagram of one embodiment of the vibration absorber 158.

[0086] Such a vibration absorber 158 may be provided at each of the vibration absorber interfaces 152, 154, 156. However, only the vibration absorber interface 152 will be described below. The vibration absorber 158 includes a vibration absorber mass 160. The vibration absorber mass 160 may be curved in an arc and have a geometry that matches the geometry of the outer ring 118 of the mount 116. The vibration absorber mass 160 is attached to the outside of the outer ring 118 when viewed along the radial direction R.

[0087] In addition to the absorber mass 160, the absorber 158 comprises a spring 162 and a damper 164. The absorber mass 160 is joined to the 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 adhesive or elastomers. In this case, the elastically deformable components perform both the spring function of the spring 162 and the damping function of the damper 164.

[0088] The vibration absorber mass 160 can vibrate along the x-direction x and the y-direction y. In the z-direction z, the vibration absorber mass 160 is positioned at the height of the center of gravity of the optical system 100. Vibrations of the optical system 100 can be damped using the vibration absorber 158. The natural frequency of the vibration absorber 158 can be influenced or set, for example, by modifying the vibration absorber mass 160 and / or by modifying the stiffness of the spring 162.

[0089] As shown in FIG. 3 , the mount 116 includes multiple mount strut interfaces 166, 168, 170 in addition to the vibration absorber interfaces 152, 154, 156. Preferably, exactly three mount strut interfaces 166, 168, 170 are provided, evenly distributed around the central axis 102. In particular, the mount strut interfaces 166, 168, 170 are positioned on the outer ring 118 so that they are offset 120° from one another. In this case, the mount strut interfaces 166, 168, 170 are centered between the vibration absorber interfaces 152, 154, 156. Each mount strut interface 166, 168, 170 is assigned an outer junction point 128 where the two stiffening ribs 122, 124 meet. As a result, high stiffness is achieved in the region of the mount strut interfaces 166, 168, 170. The mount strut interfaces 166, 168, 170 are disposed outwardly of the outer ring 118 when viewed along the radial direction R.

[0090] Each mount strut interface 166, 168, 170 is assigned a mount strut (not shown). Thus, three mount struts are provided. The mount struts are, or may be referred to as, so-called A-struts. The mount 116 seats at six spatial points. In this case, each mount strut is assigned two of these spatial points. Using the mount struts, the mount 116 or optical system 100 is operatively connected to a fixed environment, such as a force frame. In this case, the mount struts mechanically isolate the optical system 100 from the fixed environment to prevent undesired stresses from being introduced into the optical system 100.

[0091] FIG. 7 shows a schematic diagram of one embodiment of the tool interface 172.

[0092] Figure 7 corresponds to view VII shown in Figure 6. View VII is a view looking perpendicularly toward the tool interface 172. In addition to the vibration absorber interfaces 152, 154, 156 and the mount strut interfaces 166, 168, 170, the mount 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. The interface surfaces 174, 176, 178 are provided on the outside of the outer ring 118 when viewed along the radial direction R.

[0093] All of the interface surfaces 174, 176, and 178 are oriented parallel to one another. In this case, the first interface surface 174 is set back a distance a (FIG. 3) from the interface surfaces 176 and 178 in the orientation shown in FIG. 7 . When viewed along the z direction z, the first interface surface 174 and the second interface surface 176 are positioned at the same height. When viewed along the z direction z, the third interface surface 178 is positioned below the interface surfaces 174 and 176. A screw hole 180, 182, and 184 is assigned to each interface surface 174, 176, and 178. Each screw hole 180, 182, and 184 is positioned in the center of its assigned interface surface 174, 176, and 178. The screw holes 180, 182, and 184 can be used to connect a tool to the tool interface 172 for replacement of the optical system 100.

[0094] Therefore, the optical system 100 can be easily replaced. Due to the compact design of the mount, the optical system 100 requires little installation space. Positioning accuracy of a few microns can be achieved. The fixing part 134, which is joined to the outer ring 118 via the articulation parts 142, 146, can be used to decouple tension forces so that only small deformations are transmitted. In situations where the movement requirements of the optical system 100 increase and the installation space becomes smaller, the stiffening ribs 122, 124 can be used to increase the overall stiffness of the optical system 100.

[0095] While the present invention has been described with reference to exemplary embodiments, various modifications are possible. [Explanation of symbols]

[0096] 1. Projection exposure equipment 2 Beam shaping and illumination system 4. Illumination optical unit 6 light source 8. Radiation 10 Photomask 12 wafers 14 Lens Elements 16 lens elements 18 Lens Elements 20. Mirror 22 Mirror 24 Optical axis 26 Medium 100 Optical system 102 Center axis 104 half axis 106 half axis 108 Optical Elements 110 Optically effective surface 112 rear side 114 Exterior 116 Mount 118 Outer Ring 120 Inner ring 122 Stiffening rib 124 Stiffening rib 126 Gap 128 Junction 130 Junction 132 outer ring segments 134 Fixed part 136 Joint surface 138 Adhesive layer 140 Normal 142 Joints 144 Connection 146 Joints 148 Base 150 Gap 152 Vibration absorber interface 154 Vibration absorber interface 156 Vibration absorber interface 158 Vibration absorber 160 Vibration absorber mass 162 Spring 164 Damper 166 Mounting strut interface 168 Mounting strut interface 170 Mounting strut interface 172 Tool Interface 174 Interface Surface 176 Interface Surface 178 Interface Surface 180 screw holes 182 screw hole 184 screw hole a distance R Radial direction R circumferential direction xx direction x yy direction y zz direction z

Claims

1. An optical system (100) of a projection exposure apparatus (1), an optical element (108); a mount (116) that supports the optical element (108); the mount (116) including an outer ring (118) that at least partially houses the optical element (108); the outer ring (118) includes a fixing portion (134) materially connected to the optical element (108); the fixed portion (134) is pivotally connected to the outer ring (118) by means of articulation portions (142, 146); and The mount (116) includes a tool interface (172) for releasably securing a tool for replacement of the optical system (100) from the illumination optical unit (4).

2. 2. The optical system of claim 1, wherein the articulation portions (142, 146) are configured to allow rotation of the fixed portion (134) in a radial direction (R) of the optical system (100).

3. 3. The optical system according to claim 1, wherein each fixing portion (134) includes a bonding surface (136) facing the optical element (108), the bonding surfaces being materially connected to the optical element (108), and normals (140) to the bonding surfaces (136) intersect each other at the central axis (102) of the optical system (100).

4. 4. The optical system according to claim 1, wherein each fixed portion (134) is rotatably 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. 5. The optical system of claim 4, wherein each fixed portion (134) is rotatably connected to a connecting portion (144) using the first joint portion (142), and the connecting portion (144) is rotatably connected to the outer ring (118) using the second joint portion (146).

6. 6. The optical system according to claim 1, wherein the optical element (108) comprises an optically effective surface (110), in particular a mirror surface, a back side (112) opposite the optically effective surface (110), and an outer surface (114) extending circumferentially around the optical element (108), and the fixing part (134) is only materially connected to the outer surface (114).

7. 7. The optical system of claim 1, wherein the mount (116) includes an inner ring (120) disposed within the outer ring (118), the inner ring (120) being connected to the outer ring (118) using stiffening ribs (122, 124).

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

9. 9. The optical system of claim 8, wherein the outer joint points (128) and the fixed portions (134) are alternately arranged.

10. 10. The optical system according to claim 8 or 9, wherein the fixed portion (134) is positioned centrally between two adjacent outer joint points (128), respectively.

11. 11. The optical system according to claim 8, wherein two stiffening ribs (122, 124) are always connected to the inner ring (120) at a common inner junction point (130), and the outer junction point (128) and the inner junction point (130) are alternately arranged.

12. The optical system of any one of claims 1 to 11, wherein the mount (116) includes a vibration absorber interface (152, 154, 156) for joining a vibration absorber (158) to the mount (116).

13. The optical system of any one of claims 1 to 12, wherein the mount (116) includes a mount strut interface (166, 168, 170) for joining a mount strut to the mount (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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