OPTICAL SYSTEM, PROJECTION EXPOSURE DEVICE AND METHOD

Abstract

An optical system (100, 200A) for a projection exposure apparatus (1), comprising a first component (202), a second component (204), and a transport lock (214A) for applying a locking force (FV) to the first component (202) in order to fix the first component (202) to the second component (204) so ​​that the first component (202) is secured against relative movements with respect to the second component (204) during transport of the optical system (100, 200A), wherein the transport lock (214A) has a force transducer (226) for detecting the locking force (FV), so that the fixing of the first component (202) to the second component (204) is force-controlled.

Description

[0001] The present invention relates to an optical system for a projection exposure apparatus, a projection exposure apparatus having such an optical system and a method for transporting such an optical system.

[0002] Microlithography is used to manufacture microstructured components, such as integrated circuits. The microlithography process is carried out using a lithography system equipped with an illumination system and a projection system. The image of a mask (reticle) illuminated by the illumination system is projected by the projection system onto a substrate, such as a silicon wafer, coated with a light-sensitive layer (photoresist) and arranged in the image plane of the projection system in order to transfer the mask structure to the light-sensitive coating of the substrate.

[0003] Driven by the pursuit of ever smaller structures in the production of integrated circuits, EUV lithography systems are currently being developed that use light with a wavelength in the range of 0.1 nm to 30 nm, particularly 13.5 nm. Due to the high absorption of light at this wavelength by most materials, such EUV lithography systems require the use of reflective optics, i.e., mirrors, instead of the previously used refractive optics, i.e., lenses.

[0004] To prevent damage to the optics mentioned above or actuator units for adjusting the optics during transport of a projection system as mentioned above due to vibrations, it is necessary to use transport locks. According to internal company knowledge, such transport locks press the components of the projection system to be secured into a defined state so that these components cannot move uncontrollably relative to one another during vibrations. To prevent damage to the components to be secured, elastomers and spring elements can be used in the transport locks. To achieve controlled preload with this combination, such a transport lock must press onto the components to be secured with a defined force. According to internal company knowledge, the necessary force can be adjusted over a distance to be covered.

[0005] Against this background, it is an object of the present invention to provide an improved optical system.

[0006] Accordingly, an optical system for a projection exposure system is proposed. The optical system comprises a first component, a second component, and a transport lock for applying a locking force to the first component in order to secure the first component to the second component, such that the first component is secured against relative movement with respect to the second component during transport of the optical system. The transport lock has a force transducer for detecting the locking force, such that the securing of the first component to the second component is force-controlled.

[0007] Because the first component and the second component are secured using force control rather than displacement control, it is not necessary to consider the optical system's tolerance chain when the first component is secured to the second component using purely force control. The use of spacers is eliminated. It is possible to directly control the required locking force to lock the first component to the second component for transport. Eliminating spacers results in cost savings.

[0008] The optical system is preferably a projection optics unit of the projection exposure apparatus or part of such a projection optics unit. However, the optical system can also be an illumination system of the projection exposure apparatus or part of such an illumination system. Preferably, the first component is an optical element. However, the first component can be any desired component of the optical system. The second component can be a support structure that supports the first component. However, the second component can also be any desired component of the optical system.

[0009] The optical system can have any number of transport locks. In this case, the term “fixed” the first component to the second component by means of the transport lock means in particular that the first component cannot move relative to the second component. This is ensured by the application of the locking force. In this case, the term “force-controlled” fixing of the first component to the second component means in particular that the transport lock presses on the first component until the locking force is reached. As soon as the locking force is reached, the transport lock is preferably no longer moved. The locking force can then be observed during transport of the optical system.

[0010] Preferably, the optical system can be moved from an operating state in which the first component is not secured to the second component to a transport state in which the first component is secured to the second component. To move the optical system from the operating state to the transport state, the transport lock is preferably moved linearly relative to the second component such that the transport lock moves toward the first component to apply the closure force to the first component. The force transducer can, for example, comprise a load cell, one or more strain gauges, or the like.

[0011] According to one embodiment, the first component is arranged at least in sections within the second component.

[0012] In other words, the second component can enclose the first component. The second component can be made up of multiple parts. For example, the second component can have a first component and a second component that are detachably connected to one another. In this case, the second component can be a transport cover, for example, that is mounted on the first component of the second component for transporting the optical system. Alternatively, the second component can also be a one-piece component, in particular a component made of a single piece of material. In this case, “one-piece” or “one-part” means that the second component is not composed of different sub-components. In other words, in this case, the first component and the second component together form the second component as a continuous component.

[0013] According to a further embodiment, the first component is an optical element, wherein the second component is a support structure which supports the first component.

[0014] In particular, the first component is a mirror, particularly preferably an EUV mirror. However, the first component can also be a lens. The first component and the second component can together form a mirror module of the optical system.

[0015] According to a further embodiment, the transport lock is attached to the second component.

[0016] For example, the transport lock can be screwed into the second component. For this purpose, a receiving portion, for example in the form of a bore with an internal thread, into which the transport lock is screwed can be provided on the second component. The transport lock can, for example, have a base portion that can be grasped with the aid of a tool. An engagement portion of the transport lock is screwed into the receiving portion of the second component, wherein the force transducer can be arranged between the base portion and the engagement portion.

[0017] According to a further embodiment, the closing force can be generated by the transport lock being movable relative to the second component.

[0018] In particular, the locking force is generated by the transport lock moving linearly relative to the second component. This linear movement of the transport lock relative to the second component can be achieved by screwing the transport lock into the second component. In this case, a rotational movement of the transport lock when screwing it into the second component is converted into a linear movement of the transport lock toward the first component.

[0019] According to a further embodiment, the transport lock has a spring element for applying the locking force to the first component.

[0020] The spring element can, for example, be an elastomer block. This prevents damage to the first component when the closing force is applied. Preferably, the spring element is attached to the front of the aforementioned engagement portion of the transport lock.

[0021] According to a further embodiment, the optical system has end stop elements which limit a movement space of the first component relative to the second component.

[0022] The end stop elements can be used to prevent a travel path of an actuator unit of the first component from being exceeded, thereby reliably preventing damage to the actuator unit. Each end stop element can be rod-shaped and extend from the second component towards the first component. The first component has an opening or bore for each end stop element, in which the end stop element is received with play. In other words, the end stop elements do not touch the first component in the operating state. The end stop elements can be coated with an elastomer. Alternatively or additionally, the openings or bores provided in the first component can be lined with an elastomer. This elastomer can also be part of the end stop elements.

[0023] According to a further embodiment, the end stop elements are at least partially resiliently deformable.

[0024] The spring-elastic deformability results, on the one hand, from the previously mentioned elastomer of the end stop elements and, on the other hand, from a spring-elastic deformation of the rod-shaped end stop elements themselves. These can function as bending rods.

[0025] According to a further embodiment, the closing force is applied to the end stop elements.

[0026] In particular, the closing force in the transport state is applied to the end stop elements. In other words, the end stop elements absorb the closing force and transfer it to the second component.

[0027] According to a further embodiment, the optical system comprises a signal processing unit for receiving and processing sensor signals from the force transducer.

[0028] The signal processing unit can be a computer or comprise a computer. The signal processing unit can be coupled to an output unit. In the simplest case, the output unit can be a screen, for example, on which the reaching of the locking force can be displayed. Furthermore, the signal processing unit can be operatively connected to an electrical tool, for example in the form of a cordless screwdriver. In this case, the transport lock is screwed into the second component using the electrical tool. As soon as the locking force is reached, the signal processing unit switches the tool off, thus preventing the locking force from being exceeded.

[0029] According to a further embodiment, the signal processing unit is configured to receive and evaluate sensor signals of the force transducer during the transport of the optical system.

[0030] This makes it possible, for example, to check whether the closing force was exceeded during transport. If this is the case, it can be checked whether the first component is damaged. If the closing force was not exceeded during transport, it can be assumed that damage to the first component is ruled out.

[0031] Furthermore, a projection exposure system with such an optical system is proposed.

[0032] The optical system is preferably a projection optics system of the projection system. However, the optical system can also be an illumination system. The projection exposure system can be an EUV lithography system. EUV stands for "Extreme Ultraviolet" and refers to a wavelength of the working light between 0.1 nm and 30 nm. The projection exposure system can also be a DUV lithography system. DUV stands for "Deep Ultraviolet" and refers to a wavelength of the working light between 30 nm and 250 nm.

[0033] Furthermore, a method for transporting such an optical system for a projection exposure system is proposed. The method comprises the following steps: a) applying a locking force to a first component of the optical system so that the first component is fixed to a second component of the optical system; b) detecting the locking force so that the first component is fixed to the second component in a force-controlled manner; and c) transporting the optical system, wherein the first component is secured against relative movement with respect to the second component during transport with the aid of the locking force.

[0034] Preferably, the optical system is moved from the operating state to the transport state during step a). In particular, steps a) and b) are performed simultaneously. In other words, the application of the closure force and the detection of the closure force are performed simultaneously, so that the attachment of the first component to the second component is carried out in a force-controlled manner.

[0035] According to one embodiment, step a) is carried out manually or automatically based on sensor data concerning the closure force acquired during step b).

[0036] During manual processing, the user is notified when the required locking force is reached, for example, via an output unit as mentioned above. When the locking force is reached, the user stops moving the transport lock toward the first component. During automated processing, the signal processing unit can be coupled to an electric tool as mentioned above. As soon as the required locking force is reached, the electric tool is automatically shut off.

[0037] According to a further embodiment, step b) is carried out during step c).

[0038] In other words, the shutter force is continuously measured during transport of the optical system. This makes it possible to determine, for example, whether the shutter force was exceeded during transport. If the shutter force was exceeded, the first component can be checked for damage, for example. If the shutter force was not exceeded during transport, it can be assumed that damage to the first component can be ruled out.

[0039] In this case, "one" is not necessarily limited to exactly one element. Rather, multiple elements, such as two, three, or more, may also be included. Any other counting term used here should also not be understood as implying a limitation to the exact number of elements stated. Rather, numerical deviations, both upward and downward, are possible unless otherwise stated.

[0040] The embodiments and features described for the optical system apply to the proposed projection exposure apparatus and to the proposed method accordingly and vice versa.

[0041] Further possible implementations of the invention also include combinations of features or embodiments described above or below with respect to the exemplary embodiments that are not explicitly mentioned. In this case, the person skilled in the art will also add individual aspects as improvements or additions to the respective basic form of the invention.

[0042] Further advantageous embodiments 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 using preferred embodiments with reference to the accompanying figures. Fig. 1 shows a schematic meridional section of a projection exposure system for EUV projection lithography; Fig. 2 shows a schematic view of an embodiment of an optical system for the projection exposure apparatus according to Fig. 1; Fig. 3 shows a schematic view of a further embodiment of an optical system for the projection exposure apparatus according to Fig. 1; Fig. 4 shows a further schematic view of the optical system according to Fig. 2; Fig. 5 shows a force curve versus a distance traveled; Fig. 6 shows a schematic view of a further embodiment of an optical system for the projection exposure apparatus according to Fig. 1; Fig. Figure 7 shows a further schematic view of the optical system according to Fig. 6; Fig. 8 shows a force curve versus a travelled distance; and Fig. 9 shows a schematic block diagram of an embodiment of a method for transporting the optical system according to Fig. 2 or according to Fig. 3.

[0043] In the figures, identical or functionally equivalent elements are provided with the same reference numerals unless otherwise stated. Furthermore, it should be noted that the representations in the figures are not necessarily to scale.

[0044] Fig. 1 shows an embodiment of a projection exposure system 1 (lithography system), in particular an EUV lithography system. One embodiment of an illumination system 2 of the projection exposure system 1 has, in addition to a light or radiation source 3, an illumination optics 4 for illuminating an object field 5 in an object plane 6. In an alternative embodiment, the light source 3 can also be provided as a separate module from the remaining illumination system 2. In this case, the illumination system 2 does not include the light source 3.

[0045] A reticle 7 arranged in the object field 5 is exposed. The reticle 7 is held by a reticle holder 8. The reticle holder 8 can be displaced via a reticle displacement drive 9, in particular in a scanning direction.

[0046] In the Fig. For illustrative purposes, Figure 1 shows a Cartesian coordinate system with an x-direction x, a y-direction y, and a z-direction z. The x-direction x runs perpendicular to the plane of the drawing. The y-direction y runs horizontally, and the z-direction z runs vertically. The scanning direction runs in the Fig. 1 along the y-direction y. The z-direction z runs perpendicular to the object plane 6.

[0047] The projection exposure system 1 comprises a projection optics 10. The projection optics 10 serves to image the object field 5 into an image field 11 in an image plane 12. The image plane 12 runs parallel to the object plane 6. Alternatively, an angle other than 0° between the object plane 6 and the image plane 12 is also possible.

[0048] A structure on the reticle 7 is imaged onto a light-sensitive layer of a wafer 13 arranged in the image plane 12 in the region of the image field 11. The wafer 13 is held by a wafer holder 14. The wafer holder 14 can be displaced, in particular along the y-direction y, via a wafer displacement drive 15. The displacement of the reticle 7, on the one hand, via the reticle displacement drive 9, and the displacement of the wafer 13, on the other hand, via the wafer displacement drive 15, can be synchronized with each other.

[0049] The light source 3 is an EUV radiation source. The light source 3 emits, in particular, EUV radiation 16, which is also referred to below as useful radiation, illumination radiation, or illumination light. The useful radiation 16 has, in particular, a wavelength in the range between 5 nm and 30 nm. The light source 3 can be a plasma source, for example an LPP source (Laser Produced Plasma) or a DPP source (Gas Discharged Produced Plasma). It can also be a synchrotron-based radiation source. The light source 3 can be a free-electron laser (FEL).

[0050] The illumination radiation 16 emanating from the light source 3 is focused by a collector 17. The collector 17 can be a collector with one or more ellipsoidal and / or hyperboloidal reflection surfaces. The at least one reflection surface of the collector 17 can be exposed to the illumination radiation 16 at grazing incidence (GI), i.e., at angles of incidence greater than 45°, or at normal incidence (NI), i.e., at angles of incidence less than 45°. The collector 17 can be structured and / or coated, on the one hand, to optimize its reflectivity for the useful radiation and, on the other hand, to suppress stray light.

[0051] After the collector 17, the illumination radiation 16 propagates through an intermediate focus in an intermediate focal plane 18. The intermediate focal plane 18 can represent a separation between a radiation source module, comprising the light source 3 and the collector 17, and the illumination optics 4.

[0052] The illumination optics 4 comprises a deflecting mirror 19 and, downstream of this in the beam path, a first facet mirror 20. The deflecting mirror 19 can be a flat deflecting mirror or, alternatively, a mirror with a beam-influencing effect beyond the pure deflection effect. Alternatively or additionally, the deflecting mirror 19 can be designed as a spectral filter that separates a useful light wavelength of the illumination radiation 16 from stray light of a different wavelength. If the first facet mirror 20 is arranged in a plane of the illumination optics 4 that is optically conjugated to the object plane 6 as the field plane, it is also referred to as a field facet mirror. The first facet mirror 20 comprises a plurality of individual first facets 21, which can also be referred to as field facets. Of these first facets 21, Fig. 1 only some examples are shown.

[0053] The first facets 21 can be designed as macroscopic facets, in particular as rectangular facets or as facets with an arcuate or partially circular edge contour. The first facets 21 can be designed as flat facets or, alternatively, as convexly or concavely curved facets.

[0054] As is known, for example, from DE 10 2008 009 600 A1, the first facets 21 themselves can also be composed of a plurality of individual mirrors, in particular a plurality of micromirrors. The first facet mirror 20 can, in particular, be designed as a microelectromechanical system (MEMS system). For details, reference is made to DE 10 2008 009 600 A1.

[0055] Between the collector 17 and the deflecting mirror 19, the illumination radiation 16 runs horizontally, i.e. along the y-direction y.

[0056] In the beam path of the illumination optics 4, a second facet mirror 22 is arranged downstream of the first facet mirror 20. If the second facet mirror 22 is arranged in a pupil plane of the illumination optics 4, it is also referred to as a pupil facet mirror. The second facet mirror 22 can also be arranged at a distance from a pupil plane of the illumination optics 4. In this case, the combination of the first facet mirror 20 and the second facet mirror 22 is also referred to as a specular reflector. Specular reflectors are known from US 2006 / 0132747 A1, EP 1 614 008 B1, and US Pat. No. 6,573,978.

[0057] The second facet mirror 22 comprises a plurality of second facets 23. In the case of a pupil facet mirror, the second facets 23 are also referred to as pupil facets.

[0058] The second facets 23 can also be macroscopic facets, which can, for example, be round, rectangular, or hexagonal, or alternatively facets composed of micromirrors. Reference is also made to DE 10 2008 009 600 A1 in this regard.

[0059] The second facets 23 may have planar or alternatively convex or concave curved reflection surfaces.

[0060] The illumination optics 4 thus form a double-faceted system. This basic principle is also known as a fly's-eye integrator.

[0061] It may be advantageous not to arrange the second facet mirror 22 exactly in a plane that is optically conjugate to a pupil plane of the projection optics 10. In particular, the second facet mirror 22 can be arranged tilted relative to a pupil plane of the projection optics 10, as described, for example, in DE 10 2017 220 586 A1.

[0062] With the help of the second facet mirror 22, the individual first facets 21 are imaged into the object field 5. The second facet mirror 22 is the last bundle-forming mirror or actually the last mirror for the illumination radiation 16 in the beam path before the object field 5.

[0063] In a further embodiment of the illumination optics 4 (not shown), a transmission optics can be arranged in the beam path between the second facet mirror 22 and the object field 5, which transmission optics contributes in particular to the imaging of the first facets 21 into the object field 5. The transmission optics can have exactly one mirror, but alternatively also two or more mirrors, which are arranged one behind the other in the beam path of the illumination optics 4. The transmission optics can in particular comprise one or two mirrors for normal incidence (NI mirrors, normal incidence mirrors) and / or one or two mirrors for grazing incidence (GI mirrors, grazing incidence mirrors).

[0064] The illumination optics 4 has in the version shown in the Fig. 1, after the collector 17 there are exactly three mirrors, namely the deflection mirror 19, the first facet mirror 20 and the second facet mirror 22.

[0065] In a further embodiment of the illumination optics 4, the deflection mirror 19 can also be omitted, so that the illumination optics 4 can then have exactly two mirrors after the collector 17, namely the first facet mirror 20 and the second facet mirror 22.

[0066] The imaging of the first facets 21 by means of the second facets 23 or with the second facets 23 and a transmission optics into the object plane 6 is usually only an approximate imaging.

[0067] The projection optics 10 comprises a plurality of mirrors Mi, which are numbered according to their arrangement in the beam path of the projection exposure system 1.

[0068] In the Fig. In the example shown in Figure 1, the projection optics 10 comprises six mirrors M1 to M6. Alternatives with four, eight, ten, twelve, or a different number of mirrors M1 are also possible. The projection optics 10 is a doubly obscured optic. The penultimate mirror M5 and the last mirror M6 each have a passage opening for the illumination radiation 16. The projection optics 10 has an image-side numerical aperture that is greater than 0.5 and can also be greater than 0.6, for example, 0.7 or 0.75.

[0069] Reflection surfaces of the mirrors Mi can be designed as freeform surfaces without a rotational symmetry axis. Alternatively, the reflection surfaces of the mirrors Mi can be designed as aspherical surfaces with exactly one rotational symmetry axis of the reflection surface shape. The mirrors Mi, like the mirrors of the illumination optics 4, can have highly reflective coatings for the illumination radiation 16. These coatings can be designed as multilayer coatings, in particular with alternating layers of molybdenum and silicon.

[0070] The projection optics 10 has a large object-image offset in the y-direction y between a y-coordinate of a center of the object field 5 and a y-coordinate of the center of the image field 11. This object-image offset in the y-direction y can be approximately as large as a z-distance between the object plane 6 and the image plane 12.

[0071] The projection optics 10 can, in particular, be anamorphic. It has, in particular, different image scales ßx, ßy in the x and y directions x, y. The two image scales ßx, ßy of the projection optics 10 are preferably (ßx, ßy) = (+ / - 0.25, + / - 0.125). A positive image scale ß means an image without image inversion. A negative sign for the image scale ß means an image with image inversion.

[0072] The projection optics 10 thus leads to a reduction in the ratio 4:1 in the x-direction x, i.e. in the direction perpendicular to the scanning direction.

[0073] The projection optics 10 leads to a reduction of 8:1 in the y-direction y, i.e. in the scanning direction.

[0074] Other magnifications are also possible. Magnifications with the same sign and absolutely identical in the x and y directions (x, y), for example, with absolute values ​​of 0.125 or 0.25, are also possible.

[0075] The number of intermediate image planes in the x- and y-directions x, y in the beam path between the object field 5 and the image field 11 can be the same or can be different depending on the design of the projection optics 10. Examples of projection optics with different numbers of such intermediate images in the x- and y-directions x, y are known from US 2018 / 0074303 A1.

[0076] Each of the second facets 23 is assigned to exactly one of the first facets 21 to form a respective illumination channel for illuminating the object field 5. This can, in particular, result in illumination according to the Köhler principle. The far field is divided into a plurality of object fields 5 using the first facets 21. The first facets 21 generate a plurality of images of the intermediate focus on the second facets 23 assigned to them.

[0077] The first facets 21 are each imaged onto the reticle 7 by an associated second facet 23, superimposed on one another, to illuminate the object field 5. The illumination of the object field 5 is, in particular, as homogeneous as possible. It preferably has a uniformity error of less than 2%. Field uniformity can be achieved by superimposing different illumination channels.

[0078] By arranging the second facets 23, the illumination of the entrance pupil of the projection optics 10 can be geometrically defined. By selecting the illumination channels, in particular the subset of the second facets 23 that guide light, the intensity distribution in the entrance pupil of the projection optics 10 can be adjusted. This intensity distribution is also referred to as the illumination setting or illumination pupil fill.

[0079] A likewise preferred pupil uniformity in the area of ​​defined illuminated sections of an illumination pupil of the illumination optics 4 can be achieved by redistributing the illumination channels.

[0080] Further aspects and details of the illumination of the object field 5 and in particular of the entrance pupil of the projection optics 10 are described below.

[0081] The projection optics 10 can, in particular, have a homocentric entrance pupil. This can be accessible. It can also be inaccessible.

[0082] The entrance pupil of the projection optics 10 cannot usually be precisely illuminated with the second facet mirror 22. When the projection optics 10 images the center of the second facet mirror 22 telecentrically onto the wafer 13, the aperture rays often do not intersect at a single point. However, a surface can be found in which the pairwise determined distance of the aperture rays is minimized. This surface represents the entrance pupil or a surface conjugate to it in spatial space. In particular, this surface exhibits a finite curvature.

[0083] It is possible that the projection optics 10 have different entrance pupil positions for the tangential and sagittal beam paths. In this case, an imaging element, in particular an optical component of the transmission optics, should be provided between the second facet mirror 22 and the reticle 7. With the help of this optical element, the different positions of the tangential entrance pupil and the sagittal entrance pupil can be taken into account.

[0084] At the Fig. In the arrangement of the components of the illumination optics 4 shown in Figure 1, the second facet mirror 22 is arranged in a surface conjugate to the entrance pupil of the projection optics 10. The first facet mirror 20 is arranged tilted relative to the object plane 6. The first facet mirror 20 is arranged tilted relative to an arrangement plane defined by the deflection mirror 19. The first facet mirror 20 is arranged tilted relative to an arrangement plane defined by the second facet mirror 22.

[0085] Fig. 2 shows a schematic view of an embodiment of an optical system 100 for the projection exposure apparatus 1.

[0086] The optical system 100 can be a projection optics unit 10 as previously mentioned or part of such a projection optics unit 10. Therefore, the optical system 100 can also be referred to as a projection optics unit. However, the optical system 100 can also be an illumination system 2 as previously explained or part of such an illumination system 2. Therefore, the optical system 100 can alternatively also be referred to as an illumination system.

[0087] However, it is assumed below that the optical system 100 is a projection optics 10 or part of such a projection optics 10. The optical system 100 is suitable for EUV lithography. However, the optical system 100 can also be suitable for DUV lithography.

[0088] The optical system 100 may comprise a plurality of optical elements 102, of which Fig. 2, however, only one is shown. Therefore, only one optical element 102 will be discussed below. The optical element 102 can be one of the mirrors M1 to M6. Accordingly, the optical element 102 is a mirror, in particular an EUV mirror. However, the optical element 102 can also be a lens.

[0089] In addition to the optical element 102, the optical system has a support frame 104 (force frame) and a sensor frame 106 (sensor frame). The support frame 104 is coupled to a fixed world 110 by means of a coupling element 108. The coupling element 108 can comprise springs. Several such coupling elements 108 can be provided. A "fixed world" is understood here to be a region of the optical system 100 that is immovable with respect to the support frame 104. For example, the fixed world 110 can be a base frame of the optical system 100.

[0090] The sensor frame 106 is coupled to the support frame 104 by means of a coupling element 112. The coupling element 112 may comprise springs. Several such coupling elements 112 may be provided. The support frame 104 thus supports the sensor frame 106. In other words, the sensor frame 106 is not directly coupled to the fixed world 110, but indirectly or indirectly via the support frame 104.

[0091] The optical element 102 can be adjusted or aligned in six degrees of freedom using an actuator unit 114. This allows a change in the position of the optical element 102. For example, the optical element 102 can be moved from an actual position, in which the optical element 102 does not meet certain optical specifications, to a desired target position in which the optical element 102 meets the optical specifications. The sensor frame 106 serves as a reference for a change in the position of the optical element 102 as mentioned above.

[0092] The optical element 102 is connected to the support frame 104 via the actuator unit 114. The optical element 102 can be connected to the actuator unit 114 by means of a coupling element 116, which in turn is connected to the support frame 104 via a coupling element 118. The coupling elements 116, 118 can comprise springs. Any number of coupling elements 116, 118 can be provided.

[0093] With the help of a control and regulation unit 120, for example, a target position of the optical element 102 as mentioned above is maintained. For this purpose, the control and regulation unit 120 can communicate with the actuator unit 114, which aligns or adjusts the optical element 102 based on control signals from the control and regulation unit 120. The control and regulation unit 120 interacts with the sensor frame 106 in such a way that, for example, sensors attached to the sensor frame 106 measure the optical element 102, wherein the control and regulation unit 120 controls the actuator unit 114 based on sensor signals from these sensors in order to maintain the target position of the optical element 102.

[0094] To prevent components of the optical system 100, such as the optical element 102 and / or the actuator unit 114, from being damaged by vibrations during transport of the optical system 100, transport locks (TLs) can be used (not shown). Such transport locks press the components to be secured into a defined state so that they cannot move uncorrelatedly due to vibrations. To prevent damage to the components, elastomers and spring elements can be used in the transport locks. To achieve controlled preload, such a transport lock must press on the components to be secured with a defined force.

[0095] Fig. 3 shows a schematic view of another embodiment of an optical system 200A. Fig. 4 shows a further schematic view of the optical system 200A. The following refers to the Fig. 3 and Fig. 4 received at the same time.

[0096] The 200A optical system can Fig. 2, wherein the optical system 200A is shown more schematically than the optical system 100. The optical system 200A comprises a first component 202. The first component 202 can be the previously mentioned optical element 102. Alternatively, the first component 202 can also be, for example, a sensor frame 106 as previously mentioned. In principle, the first component 202 can be any desired component of the optical system 200A.

[0097] In addition to the first component 202, the optical system 200A comprises a second component 204. The second component 204 can be a support structure that supports the first component 202. For example, the first component 202 and the second component 204 together can form a mirror module of the optical system 200A. In principle, the second component 204 can be any desired component of the optical system 200A. The second component 204 can enclose the first component 202. In other words, the first component 202 can be arranged within the second component 204. However, this is not mandatory.

[0098] The second component 204 can be multi-part and have a first component 206 and a second component 208. The components 206, 208 can be firmly connected to one another. In particular, the components 206, 208 can be connected to one another in one piece, in particular using a single material. "Single-piece" or "one-part" in this case means that the components 206, 208 are not separable from one another, but rather that the components 206, 208 together form the second component 204 as a single component. "Integral" in this case means that the second component 204 is made entirely of the same material. Alternatively, the first component 206 and the second component 208 can also be designed to be separable from one another. For example, the components 206, 208 are screwed together. In this case, the second component 208 can be, for example, a so-called transport cover.

[0099] Between the first component 202 and the second component 204, a plurality of end stop elements 210, 212 are arranged. The number of end stop elements 210, 212 is arbitrary. In the present case, the end stop elements 210, 212 are arranged between the first component 206 of the second component 204 and the first component 202. The end stop elements 210, 212 are firmly connected to the second component 204, in particular to the first component 206. The end stop elements 210, 212 limit the freedom of movement of the first component 202 relative to the second component 204 such that the aforementioned actuator unit 114 cannot reach a position in which the actuator unit 114 is damaged. In a Fig. In the operating state Z1 of the optical system 200A shown in Figure 3, the end stop elements 210, 212 do not contact the first component 202.

[0100] The end stop elements 210, 212 can be rod-shaped, in particular flexible rod-shaped, and extend out of the second component 204, in particular out of the first component 206, and into openings or bores provided in or on the first component 202. In the operating state Z1, however, the end stop elements 210, 212 do not contact the walls of these openings or bores provided in the first component 202.

[0101] The end stop elements 210, 212 can be resiliently deformable, at least in sections. For example, the end stop elements 210, 212 are bending rods. Furthermore, the end stop elements 210, 212 can be coated, for example, with an elastomer, which also allows resilient deformation.

[0102] Alternatively, the openings or bores provided in the first component 202 can be lined with an elastomer, which also allows for resilient deformation. This elastomer provided in the openings or bores is also part of the end stop elements 210, 212. The resilient deformability of the end stop elements 210, 212 is described in the Fig. 3 and Fig. 4 is illustrated by the fact that the end stop elements 210, 212 are shown as springs.

[0103] The optical system 200A further comprises a transport lock 214A. With the aid of the transport lock 214A, the first component 202 can be fixed to the second component 204 in such a way that the first component 202 cannot move relative to the second component 204 during transport of the optical system 200A. With the aid of the transport lock 214A, the optical system 200A can be Fig. 3 shown operating state Z1 into one shown in the Fig. 4 and vice versa. The optical system 200A can have any number of transport locks 214A.

[0104] The transport lock 214A is attached to the second component 204, in particular to the second part 208. The second component 204, in particular the second part 208, can have a receiving section 216, in particular in the form of a threaded bore, into which the transport lock 214A is screwed. The transport lock 214A comprises a base section 218. The base section 218 can, for example, have an external hexagon. The base section 218 can, for example, be gripped with a tool to screw the transport lock 214A into the receiving section 216.

[0105] Furthermore, the transport lock 214A comprises an engagement portion 220, which may have an external thread that engages an internal thread of the receiving portion 216. A mechanical end stop 222 is attached to the engagement portion 220 and can come into contact with the second component 208 when the transport lock 214A is screwed into the receiving portion 216. The mechanical end stop 222 thus limits the maximum distance by which the transport lock 214A can be moved relative to the second component 204, in particular to the second component 208.

[0106] A spring element 224 is attached to the front of the engagement portion, which spring element points toward the first component 202. In the operating state Z1, however, the spring element 224 does not contact the first component 202. In the transport state Z2, the spring element 224 rests against the first component 202. The spring element 224 can be an elastomer block.

[0107] A force transducer 226 of the transport lock 214A is arranged between the spring element 224 and the engagement section 220. The force transducer 226 can be or comprise a load cell, a strain gauge, or the like. Depending on the design, the sensor design for the force transducer 226 can be freely selected. The operating principle of the force transducer 226 can be freely selected. For example, the operating principle can be analog, digital, or mechanical. The force transducer 226 can be freely positioned within the transport lock 214A.

[0108] The force transducer 226 is assigned a signal processing unit 228, which is suitable for receiving and processing sensor signals from the force transducer 226. The force transducer 226 is operatively connected to the signal processing unit 228 via a data connection 230. The data connection 230 can be wired or wireless. A cable feedthrough is provided for the data connection 230. A suitable connection for signal evaluation is provided on the force transducer 226.

[0109] The signal processing unit 228 can be a computer or have a computer. An output unit 232 is connected to the signal processing unit 228. In the simplest case, the output unit 232 can be a screen that displays, for example, a force measured by the force transducer 226. The output unit 232 is coupled to the signal processing unit 228 via a data connection 234. The data connection 234 can be wired or wireless. Furthermore, an electric tool 236, for example in the form of a cordless screwdriver, can be coupled to the signal processing unit 228 via a data connection 238. The data connection 238 is wired or wireless.

[0110] The functionality of the transport lock 214A is explained below using the Fig. 3 and Fig. 4 and the Fig. 5, which describes a force curve of a force F measured by the force transducer 226 over a path w along the z-direction z.

[0111] The Fig. 4 shows the optical system 200A in the transport state Z2. In the transport state Z2, the first component 202 is fixed to the second component 204 such that the first component 202 is secured against relative movement with respect to the second component 204 during transport of the optical system 200A. To move the optical system 200A from the operating state Z1 to the transport state Z2, the transport lock 214A is displaced along the z-direction z with respect to the second component 204. This can be done by screwing the transport lock 214A into the receiving section 216. This screwing in of the transport lock 214A can be done either manually or with the aid of an electric tool 236 as previously mentioned.

[0112] As previously mentioned, neither the end stop elements 210, 212 nor the spring element 224 contact the first component 202 in the operating state Z1. If the transport lock 214A is now displaced along the z-direction z towards the first component 202, a gap between the spring element 224 and the first component 202 is initially bridged. This gap is shown in the Fig. 5 with a path w1. During the path w1, the movement of the transport lock 214A occurs without force, so that the force transducer 226 does not measure any force F during the path w1.

[0113] As soon as the spring element 224 contacts the first component 202, the spring element 224 is compressed over a distance w2. The first component 202 is moved along the z-direction z in the direction of the end stop elements 210, 212. As soon as the first component 202 contacts the end stop elements 210, 212, these are also compressed, as shown in the Fig. 5 is illustrated by a path w3. During the path w3, the spring element 224 and the end stop elements 210, 212 are elastically deformed and compressed until a desired closing force FV is reached.

[0114] As soon as the locking force FV is reached, a user stops the displacement of the transport lock 214A relative to the second component 204, for example, based on a signal output at the output unit 232. This signal can be acoustic or optical, for example. If an electrical tool 236 as mentioned above is used, it is automatically switched off when the locking force FV is reached. The fastening of the first component 202 to the second component 204 is thus force-controlled. The optical system 200A can now be transported in the transport state Z2.

[0115] If, for example, the force transducer 226 fails, the mechanical end stop 222, by contacting the second component 204, can prevent further displacement of the transport lock 214A relative to the second component 204, thus reliably preventing damage to the first component 202. The signal processing unit 228 can also receive and evaluate sensor signals from the force transducer 226 during transport of the optical system 200A. For example, after transport, it can be checked whether the closure force FV was exceeded during transport.

[0116] The application of the closure force FV for positioning the components 202, 204 for transporting the optical system 200A is thus not path-controlled, but directly force-controlled. The force transducer 226 reproduces the force F during the movement of the optical system 200A from the operating state Z1 to the transport state Z2, so that the defined closure force FV can be adjusted.

[0117] Fig. 6 shows a schematic view of another embodiment of an optical system 200B. Fig. 7 shows a further schematic view of the optical system 200B. The following refers to the Fig. 6 and Fig. 7 were received at the same time.

[0118] The optical system 200B differs in its structure and function from the optical system 200A only in that the optical system 200B has an alternative design of a transport lock 214B.

[0119] In contrast to the transport lock 214A, the transport lock 214B is not force-controlled, but rather displacement-controlled. The transport lock 214B operates purely mechanically. Therefore, the transport lock 214B does not have the previously mentioned force transducer 226. The transport lock 214B has a base section 218 as mentioned above, from which an engagement section 220 with a front-mounted spring element 224 extends at the front.

[0120] The transport lock 214B includes a disk-shaped spacer 240. The spacer 240 is threaded onto the engagement portion 220 and rests against the base portion 218. A thickness d of the spacer 240 is calculated in advance such that the closure force FV can be achieved in a path-controlled manner.

[0121] The functionality of the transport lock 214B is explained below using the Fig. 6 and Fig. 7 and the Fig. 8, which describes a force curve of a force F over a path w along the z-direction z, is explained.

[0122] Initially, the optical system 200B is in an operating state Z1 as previously mentioned, in which neither the end stop elements 210, 212 nor the spring element 224 contact the first component 202. In order to separate the optical system 200B from the operating state Z1 described in the Fig. 6 shown operating state Z1 into one shown in the Fig. 7, the transport lock 214B is displaced relative to the second component 204. This can be done by screwing the transport lock 214B into the receiving section 216.

[0123] As in the Fig. As shown in Figure 8, the transport lock 214B initially travels a forceless distance w1. As soon as the spring element 224 contacts the first component 202, the spring element 224 is compressed over a distance w2. Subsequently, the end stop elements 210, 212 are also elastically deformed and compressed, as shown in Figure 8. Fig. 8 is shown with the aid of a path w3. The thickness d of the spacer 240 is dimensioned such that the closure force FV is reached after the path w3.

[0124] When the closing force FV is reached, the spacer 240 rests against the second component 204, in particular against the second part 208 of the second component 204. If an attempt is now made to displace the transport lock 214B further relative to the second component 204, for example, by screwing the transport lock 214B further into the receiving section 216, the force F remains constant because a mechanical short circuit occurs due to the contact of the spacer 240 with the second component 204.

[0125] The main difference between the transport locks 214A, 214B is that with the transport lock 214A, the closing force FV is not adjusted indirectly via the travel w, or in other words via the thickness d of the spacer 240, but directly by absorbing the force F with the force transducer 226. With the travel-controlled transport lock 214B, it is necessary to consider an entire tolerance chain of the end stop elements 210, 212, the second component 204, the first component 202 up to the transport lock 214B when designing the thickness of the spacer 240. However, the tolerance of the thickness d of the spacer 240 must also be considered.

[0126] With the principle of force-controlled closure using the transport lock 214A, this tolerance chain is of lesser importance. A traveled distance w with the transport lock 214A only needs to be designed to reliably provide sufficient force F. By directly monitoring a force-displacement signal from the force transducer 226, the required closure force FV can be directly controlled.

[0127] Advantageously, the tolerance chain no longer needs to be considered with the transport lock 214A. This also reduces the need for supplier data. The spacer 240 can be omitted with the transport lock 214A. Spacer routines with checks are eliminated. Component pairing through the tolerance chain is no longer required with the transport lock 214A. The required locking force FV for locking the components 202, 204 for transporting the optical system 200A can be directly monitored with the transport lock 214A.

[0128] Eliminating the spacer 240 results in cost savings. In particular, calculation, assembly, inspection, components, measurements, and logistics are eliminated. The design of the transport lock 214A is simpler for both design and process. Pairing of transport locks 214A or transport covers with specific first components 202 is no longer necessary. Specific transport locks 214A can be freely used in any optical system 200A.

[0129] Fig. 9 shows a schematic block diagram of a method for transporting the optical system 200A.

[0130] In the method, in a step S1, the locking force FV is applied to the first component 202, so that the first component 202 is secured to the second component 204. Meanwhile, in a step S2, the locking force FV is detected, so that the securing of the first component 202 to the second component 204 can be carried out in a force-controlled manner. Subsequently, in a step S3, the optical system 200A can be transported, wherein the first component 202 is secured against relative movement with respect to the second component 204 during transport with the aid of the locking force FV.

[0131] Step S1 is preferably performed manually or automatically based on sensor data concerning the closure force FV acquired during step S2. As previously mentioned, the sensor data is acquired using the force transducer 226 and evaluated using the signal processing unit 228. Step S1 can then be performed automatically using an electric tool 236 as previously mentioned.

[0132] Preferably, step S2 is performed during step S3. This means, in particular, that the shutter force FV can be continuously detected during transport of the optical system 200A. For this purpose, it is possible, for example, to check whether the shutter force FV was exceeded during transport, so that in this case, damage to the first component 202 may be expected.

[0133] Although the present invention has been described using exemplary embodiments, it can be modified in many ways. LIST OF REFERENCE SYMBOLS 1 projection exposure system 2 Lighting system 3 Light source 4 Lighting optics 5 Object field 6 Object level 7 reticles 8 reticle holders 9 Reticle displacement drive 10 Projection optics 11 Image field 12 Image plane 13 wafers 14 wafer holders 15 Wafer relocation drive 16 Illumination radiation 17 Collector 18 Intermediate focal plane 19 Deflecting mirrors 20 first facet mirror 21 first facet 22 second facet mirror 23 second facet 100 optical system 102 optical element 104 supporting frames 106 sensor frames 108 coupling element 110 solid world 112 coupling element 114 Actuator unit 116 coupling element 118 coupling element 120 control and regulation unit 200A optical system 200B optical system 202 Component 204 Component 206 component 208 component 210 End stop element 212 End stop element 214A transport lock 214B Transport lock 216 Recording section 218 Base Section 220 intervention section 222 End stop 224 spring element 226 force transducers 228 Signal processing unit 230 data connection 232 output unit 234 Data connection 236 tools 238 Data connection 240 spacers d thickness F Force FV locking force M1 mirror M2 mirror M3 mirror M4 mirror M5 mirror M6 mirror S1 step S2 step S3 step w way w1 way w2 way w3 way x x-direction y y-direction z z-direction Z1 operating state Z2 transport condition QUOTES CONTAINED IN THE DESCRIPTION

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

[0000] DE 10 2008 009 600 A1 [0054, 0058] US 2006 / 0132747 A1

[0056] EP 1 614 008 B1

[0056] US 6,573,978

[0056] DE 10 2017 220 586 A1

[0061] US 2018 / 0074303 A1

[0075]

Claims

[1] Optical system (100, 200A) for a projection exposure apparatus (1), comprising a first component (202), a second component (204), and a transport lock (214A) for applying a locking force (FV) to the first component (202) in order to fix the first component (202) to the second component (204) so that the first component (202) is secured against relative movements with respect to the second component (204) during transport of the optical system (100, 200A), wherein the transport lock (214A) has a force transducer (226) for detecting the closing force (FV), so that the fixing of the first component (202) to the second component (204) is force-controlled. [2] Optical system according to claim 1, wherein the first component (202) is arranged at least partially within the second component (204). [3] The optical system of claim 1 or 2, wherein the first component (202) is an optical element (102), and wherein the second component (204) is a support structure supporting the first component (202). [4] Optical system according to one of claims 1-3, wherein the transport lock (214A) is attached to the second component (204). [5] Optical system according to claim 4, wherein the closure force (FV) can be generated by the transport lock (214A) being movable relative to the second component (204). [6] Optical system according to one of claims 1-5, wherein the transport lock (214A) comprises a spring element (224) for applying the closure force (FV) to the first component (202). [7] Optical system according to one of claims 1-6, comprising end stop elements (210, 212) which limit a movement space of the first component (202) relative to the second component (204). [8] Optical system according to claim 7, wherein the end stop elements (210, 212) are at least partially resiliently deformable. [9] Optical system according to claim 7 or 8, wherein the closure force (FV) is applied to the end stop elements (210, 212). [10] Optical system according to one of claims 1-9, comprising a signal processing unit (228) for receiving and processing sensor signals of the force transducer (226). [11] Optical system according to claim 10, wherein the signal processing unit (228) is configured to receive and evaluate sensor signals of the force transducer (226) during the transport of the optical system (100, 200A). [12] Projection exposure apparatus (1) with an optical system (100, 200A) according to one of claims 1-11. [13] Method for transporting an optical system (100, 200A) for a projection exposure apparatus (1), comprising the following steps: a) applying (S1) a closure force (FV) to a first component (202) of the optical system (100, 200A) so that the first component (202) is fixed to a second component (204) of the optical system (100, 200A), b) detecting (S2) the closure force (FV) so that the fixing of the first component (202) to the second component (204) is carried out in a force-controlled manner, and c) transporting (S3) the optical system (100, 200A), wherein the first component (202) is secured against relative movements with respect to the second component (204) during transport by means of the locking force (FV). [14] Method according to claim 13, wherein step a) is carried out manually or automatically based on sensor data relating to the closure force (FV) acquired during step b). [15] A method according to claim 13 or 14, wherein step b) is performed during step c).

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