Optical module and projection exposure system

Abstract

The invention relates to an optical module with an optical element (M3), a support structure (41, 61, 81, 101) and a shield (42, 62, 82, 102), wherein the shield (42, 62, 82, 102) is arranged between the optical element (M3) and the support structure (41, 61, 81, 101) and is connected to the support structure (41, 61, 81, 101) via at least one connecting element (40, 60, 80, 100) and wherein at least one adjusting element (43, 76, 88, 90, 92, 103) is provided for adjusting a holding force exerted by the connecting element (40, 60, 80, 100). According to the invention, the optical module is characterized in that the actuating element (43,76,88,90,92,103) is arranged on the side of the shield (42,62,82,102) facing away from the optical element (M3). Furthermore, the invention relates to a projection exposure system (1) with an optical module according to the invention.

Description

[0001] The invention relates to an optical module and a projection exposure system in which the optical module can be used.

[0002] Projection exposure systems for semiconductor lithography are used to create extremely fine structures, particularly on semiconductor devices or other microstructured components. The operating principle of these systems is based on creating extremely fine structures down to the nanometer range by means of a generally reduced-size image of structures on a mask, a so-called reticle, on an element to be structured, such as a wafer, coated with photosensitive material.

[0003] The minimum dimensions of the generated structures depend on the resolution of the optical system of the projection exposure system used for imaging. The resolution, in turn, depends directly on the wavelength of the radiation used for imaging, the so-called useful radiation, and the numerical aperture, i.e., the product of the refractive index of the surrounding medium and the aperture angle of the optical system used for imaging.

[0004] To generate the useful radiation, light sources are used that produce radiation in an emission wavelength range of 100 nm to 300 nm, known as the DUV range. Recently, light sources with an emission wavelength in the range of a few nanometers, for example between 1 nm and 120 nm, and particularly in the range of 13.5 nm, have been increasingly used. This emission wavelength range is also referred to as the EUV range. The short-wave useful radiation of an EUV projection exposure system is absorbed by all substances - including gases - within a few millimeters or centimeters, so EUV projection exposure systems must be operated under vacuum. This particularly applies to the areas in which useful radiation occurs, such as an illumination system for shaping the useful radiation and projection optics for imaging the structure, as well as the wafer area.

[0005] For process-related reasons, gases such as hydrogen with a partial pressure of 1 to 1000 Pa are introduced into the vacuum at certain intervals, particularly in the area of ​​the optical elements of the illumination system and the projection optics. This hydrogen is used to clean the optical elements and to protect them from contamination and is predominantly in molecular form (H2). In particular, the so-called active optical surfaces, i.e. those areas of the optical elements that are exposed to useful radiation to image the structure, are to be protected from contamination. However, the hydrogen can also lead to the release of substances from components that come into contact with the hydrogen, such as the support structures of the optical elements, whereby these substances can in turn settle on the active optical surfaces of the optical elements that are relevant for the imaging quality.Furthermore, if the hydrogen is applied improperly, it can also dissolve substances from the reflective layer formed on the optical elements. This effect occurs particularly when hydrogen plasma is formed from the molecular hydrogen under the influence of EUV radiation.

[0006] To prevent these effects, known as hydrogen-induced outgassing, the support structures are typically covered with shields in the prior art. The shields are arranged in such a way that, within the area enclosed by the shields, different ambient conditions can be set, particularly with higher levels of purity / freedom from particles, compared to the rest of the projection optics.

[0007] The shields absorb reflected radiation, which includes, on the one hand, the EUV radiation used for imaging and the EUV radiation scattered by other components, as well as a process-related portion of infrared radiation. The absorption of EUV radiation prevents the formation of hydrogen plasma and thus hydrogen-induced outgassing outside the shields. The absorption of infrared radiation minimizes heating of the optical elements and surrounding components, thereby reducing thermally induced deformation of the optical elements and surrounding components and the resulting deterioration in image quality.

[0008] Furthermore, the substances released by hydrogen-induced outgassing are absorbed and bound by the shielding, similar to a sacrificial anode. This protects the optical surfaces from damage caused by the unwanted substances.

[0009] The shields therefore fulfil four different functions, namely absorption of the substances released by hydrogen-induced outgassing, shielding of the components surrounding the optical elements, in particular the supporting structure, absorption of EUV radiation and / or infrared radiation, and dissipation of the heat absorbed by the absorption.

[0010] The shields are connected to the support structures of the optical elements, which are usually made of aluminum, and are subject to very strict cleanliness requirements due to their proximity to the optical elements. The screw connections used in the prior art for mounting the shields have the disadvantage that they can generate particles in the area of ​​the optical elements. A further disadvantage is that the screw heads are also subject to hydrogen-induced outgassing when exposed to the hydrogen plasma.

[0011] The object of the present invention is to provide a device which eliminates the disadvantages of the prior art described above.

[0012] This object is achieved by a device having the features of the independent claim. The subclaims relate to advantageous developments and variants of the invention.

[0013] An optical module according to the invention comprises an optical element, a support structure, and a shield, wherein the shield is arranged between the optical element and the support structure. The shield is connected to the support structure via at least one connecting element. Furthermore, at least one adjusting element is provided for adjusting a holding force exerted by the connecting element. According to the invention, the adjusting element is arranged on the side of the shield facing away from the optical element. This ensures that particles and / or other contaminants in the form of abrasion that may occur during actuation of the adjusting element and / or during assembly of the adjusting element are generated outside the area of ​​the optical element.This keeps the abrasion away from the optical elements, which are very sensitive and can be damaged by particles in the nm range, especially in conjunction with the useful light used to image structures in a projection exposure system.

[0014] The adjusting element can be designed, for example, as a screw, spring, or magnet. Adjusting elements designed as screws and / or springs, in particular, can generate particles or dislodge manufacturing residues remaining in the thread during actuation despite intensive cleaning. These are advantageously kept away from the area of ​​the optical elements by the arrangement according to the invention.

[0015] In particular, interfaces for receiving or securing the control elements can be formed in components manufactured independently of the supporting structure. This has the advantage that, for example, threaded or poorly accessible areas of an interface in a single part can be cleaned more easily than in a supporting structure with potentially complex structures. This can have a beneficial effect on the risk of particle formation during assembly, further reducing the risk of damage to the optical elements caused by particles.

[0016] In a further embodiment, the connecting element can have a tool interface for mounting the shield on the side facing the shield. This allows the shield to be mounted from the comparatively easily accessible side of the support structure facing the optical element, which can have a positive effect on the manufacturing costs, including the cleaning costs, of the associated system. The tool interface can, for example, be formed on a clamping bolt preloaded by a spring force. According to the invention, the adjusting element designed as a spring can be arranged on the rear side of the support structure facing away from the shield. The spring can be supported on the rear side of the support structure so that it can generate the holding force for the shield in the direction of the side of the support structure facing the shield via a flange formed on the side of the clamping bolt facing the shield.

[0017] To install the shield, the clamping bolt can be slightly lifted with a suitable tool and rotated around its longitudinal axis into an assembly position. The shield can now be installed and aligned, and the clamping bolt can be aligned with the tool by lifting and rotating it again. The clamping bolt flange, with the holding force generated by the spring, presses the shielding onto a shoulder formed in the support structure, thereby fixing it in the aligned position. This lifting and lowering prevents contact between the clamping bolt and the shielding when rotating the clamping bolt, thus advantageously preventing any associated particle generation.

[0018] Furthermore, the connecting element can be captively connected to the support structure. For example, the clamping bolt can be inserted from above into a recess in the support structure, and the spring for applying the spring force can be mounted from the rear side of the support structure, facing away from the shielding, whereby the spring is thus captively arranged between the clamping bolt and the support structure.

[0019] In a further embodiment, the connecting element can comprise at least one magnet. The holding force of the shield can thus be generated without moving an actuating element and transmitted, for example, via magnetic conducting elements to the interface between the shield and the supporting structure. The shield expediently comprises a magnetizable material or a magnet in at least one area.

[0020] In particular, the magnet can be designed as a permanent magnet or an electromagnet. With a permanent magnet, the magnetic force acting on the shield can be adjusted by the distance between the magnet and the shield or the conducting elements. Depending on the required holding force, the permanent magnet can be permanently installed in the support structure, and a sufficient holding force can be generated by bringing the shield closer during assembly. To facilitate positioning of the shield, the permanent magnet can also be moved into a position that creates the predetermined holding force in the shield after the shield has been aligned. In the case of an electromagnet, the holding force can be adjusted by flowing current through a coil of the electromagnet. Alternatively, a combination of a permanent magnet and an electromagnet is also conceivable.The magnetic holding force of a permanent magnet integrated into the support structure can be reduced, for example, by superimposing the magnetic force of the electromagnet for assembly. The electromagnet can therefore only be brought into the area of ​​the connecting element for assembly, so that it is designed as a tool used solely for the assembly of the shield, which can have a positive impact on the system's manufacturing costs.

[0021] In a further embodiment, a part of the connecting element can be connected to the shield in an unassembled state. This has the advantage that a potentially necessary connection process between the shield and the part of the connecting element in the region of the optical element can be avoided. In particular, the part can be integrated into the shield, as in the case of the permanent magnet explained above, for example, thereby creating an easy-to-clean, closed and flat surface on the shield.

[0022] Furthermore, the connecting element can be designed to force-fit the shield to the support structure. The force should expediently be designed such that no relative movement occurs between the shield and the support structure, even in the event of shocks caused during transport of the optical module or by earthquakes occurring during operation, thereby advantageously preventing particle formation.

[0023] Alternatively, the connecting element can be designed to form-fit the shield to the support structure. This virtually eliminates any relative movement between the shield and the support structure. The form-fit connection can also be used to align the shield, making installation comparatively easy.

[0024] In a further embodiment, the shield can have a completely closed and flat surface in the direction of the optical element when mounted. This allows the side facing the optical element to be easily cleaned, allowing particles or contaminants created during assembly to be easily removed before the optical element is mounted.

[0025] In particular, the sides of the shield and / or the connecting element facing the optical element can have a coating for absorbing radiation, especially useful light. In this context, radiation refers to both the EUV radiation of the useful light and the process-related infrared radiation, including both direct and scattered radiation. Coating closed and flat surfaces can be easier and more uniform than coating surfaces with steps or other contours.

[0026] The coating can be designed to be robust against hydrogen plasma and EUV radiation as well as infrared radiation and can additionally have an affinity for the substances of hydrogen-induced outgassing of the surrounding components, so that the outgassing substances can be at least partially absorbed or bound.

[0027] The arrangement of the adjusting elements on the side of the shielding facing away from the optical element allows for greater flexibility in the material selection for the components of the connecting element facing the optical element, allowing them to be made of a material robust against hydrogen plasma and EUV radiation. Likewise, a material with a certain affinity for the substances released during hydrogen-induced outgassing can be used.

[0028] Furthermore, the connecting elements and / or the adjusting elements, such as the shields, can be coated, for example, with a nickel-phosphorus coating. Optionally, the surface can be blackened afterward.

[0029] A projection exposure system according to the invention comprises an optical module according to one of the preceding embodiments.

[0030] In the following, embodiments and variants of the invention are explained in more detail with reference to the drawings. Fig. 1 schematically shows in meridional section a projection exposure system for EUV projection lithography, Fig. 2 a connection of a stray light shield to a support frame known from the prior art, Fig. 3 a first embodiment of a connection according to the invention, Fig. 4 shows a further embodiment of a connection according to the invention, Fig. 5 shows a further embodiment of a connection according to the invention, and Fig. 6 a further embodiment of a connection according to the invention.

[0031] In the following, with reference to the Fig. 1 describes, by way of example, the essential components of a projection exposure system 1 for microlithography. The description of the basic structure of the projection exposure system 1 and its components is not intended to be limiting.

[0032] One embodiment of an illumination system 2 of the projection exposure system 1 has, in addition to a radiation source 3, an illumination optics 4 for illuminating an object field 5 in an object plane 6. In an alternative embodiment, the light source 3 can also be provided as a separate module from the rest of the illumination system. In this case, the illumination system does not include the light source 3.

[0033] A reticle 7 arranged in the object field 5 is illuminated. The reticle 7 is held by a reticle holder 8. The reticle holder 8 can be displaced, in particular in a scanning direction, via a reticle displacement drive 9.

[0034] In the Fig. 1 shows a Cartesian xyz coordinate system for explanation. The x-direction is perpendicular to the plane of the drawing. The y-direction is horizontal and the z-direction is vertical. The scanning direction is in the Fig. 1 along the y-direction. The z-direction runs perpendicular to the object plane 6.

[0035] 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.

[0036] 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, 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.

[0037] The radiation source 3 is an EUV radiation source. The radiation source 3 emits, in particular, EUV radiation 16, which is also referred to below as useful radiation, illumination radiation, or illumination light. The useful radiation has, in particular, a wavelength in the range between 5 nm and 30 nm. The radiation source 3 can be a plasma source, for example, an LPP source (laser produced plasma) or a DPP source (gas discharged produced plasma). It can also be a synchrotron-based radiation source. The radiation source 3 can be a free-electron laser (FEL).

[0038] The illumination radiation 16 emanating from the radiation 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° relative to the normal direction of the mirror surface, 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.

[0039] 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 radiation source 3 and the collector 17, and the illumination optics 4.

[0040] 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 are also referred to below as field facets. Of these facets 21, Fig. 1 only some examples are shown.

[0041] 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.

[0042] 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.

[0043] Between the collector 17 and the deflecting mirror 19, the illumination radiation 16 runs horizontally, i.e. along the y-direction.

[0044] 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.

[0045] 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.

[0046] 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.

[0047] The second facets 23 can have planar or alternatively convex or concave curved reflection surfaces.

[0048] The illumination optics 4 thus form a double-faceted system. This basic principle is also known as a honeycomb condenser (fly's eye integrator).

[0049] It may be advantageous to arrange the second facet mirror 22 not exactly in a plane that is optically conjugated to a pupil plane of the projection optics 10. In particular, the pupil 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.

[0050] With the help of the second facet mirror 22, the individual first facets 21 are imaged into the object field 5. The second facet mirror 22 is the last beam-forming mirror or actually the last mirror for the illumination radiation 16 in the beam path before the object field 5.

[0051] 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).

[0052] 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 field facet mirror 20 and the pupil facet mirror 22.

[0053] 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.

[0054] 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.

[0055] 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.

[0056] 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 penultimate mirror M5 and the last mirror M6 each have a passage opening for the illumination radiation 16. The projection optics 10 is a doubly obscured optic. 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.

[0057] 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.

[0058] The projection optics 10 has a large object-image offset in the y-direction 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 can be approximately as large as a z-distance between the object plane 6 and the image plane 12.

[0059] The projection optics 10 can, in particular, be anamorphic. It has, in particular, different magnifications βx, βy in the x- and y-directions. The two magnifications βx, βy of the projection optics 10 are preferably (βx, βy) = (+ / - 0.25, + / - 0.125). A positive magnification β means imaging without image inversion. A negative sign for the magnification β means imaging with image inversion.

[0060] The projection optics 10 thus leads to a reduction in the ratio 4:1 in the x-direction, i.e. in the direction perpendicular to the scanning direction.

[0061] The projection optics 10 results in a reduction of 8:1 in the y-direction, i.e. in the scanning direction.

[0062] Other magnifications are also possible. Magnifications with the same sign and absolutely identical in the x and y directions, for example, with absolute values ​​of 0.125 or 0.25, are also possible.

[0063] The number of intermediate image planes in the x- and y-directions in the beam path between the object field 5 and the image field 11 can be the same or can vary 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 are known from US 2018 / 0074303 A1.

[0064] Each of the pupil facets 23 is assigned to exactly one of the field 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 field facets 21. The field facets 21 generate a plurality of images of the intermediate focus on the pupil facets 23 assigned to them.

[0065] The field facets 21 are each imaged onto the reticle 7 by an associated pupil 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.

[0066] By arranging the pupil facets, 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 pupil facets 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.

[0067] 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.

[0068] 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.

[0069] The projection optics 10 can, in particular, have a homocentric entrance pupil. This can be accessible. It can also be inaccessible.

[0070] The entrance pupil of the projection optics 10 cannot usually be precisely illuminated with the pupil facet mirror 22. When the projection optics 10 images the center of the pupil 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.

[0071] 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.

[0072] In the Fig. In the arrangement of the components of the illumination optics 4 shown in Figure 1, the pupil facet mirror 22 is arranged in a surface conjugated to the entrance pupil of the projection optics 10. The field 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.

[0073] The first facet mirror 20 is arranged tilted to an arrangement plane which is defined by the second facet mirror 22.

[0074] Fig. Figure 2 shows a connecting element of a shield 32 with a support structure 31 of an optical module, known from the prior art and designed as a screw connection 30, as it is shown in a Fig. 1, in a sectional view. The screw connection 30 comprises an adjusting element designed as a screw 33, which connects the shield 32 to a support structure 31. An adjusting element in the sense of the invention is an element which applies the force for fixing the shield 32 to the support structure 34. In the exemplary embodiment shown, the support structure 31 is designed as a holder for a mirror M3, as used in the projection exposure system 1 ( Fig. 1) can be used, formed optical element formed

[0075] A bore 36 is formed in the support structure 31, into which an insert 35 is screwed via a thread 37. The insert 35 is made, for example, of stainless steel, which generates fewer particles when screwing in the screw 33 for fastening the shield 32 than the aluminum usually used for the production of the support structure 31.

[0076] A spacer 34 is arranged between the shield 32 and the support structure 31, creating a defined support that ensures compliance with a predetermined minimum distance between the shield 32 and the support structure 31. On the one hand, the distance enables good ventilation when evacuating the projection exposure system 1 ( Fig. 1) and, on the other hand, ensures that the shield 32 and the support structure 31 do not touch during operation, thus avoiding particle-generating friction. The screw 33 has a vent hole 38 for ventilating the bore 36.

[0077] The shield 32 is coated with a coating 39 which is robust against hydrogen plasma and EUV radiation and has an affinity for the substances of hydrogen-induced outgassing of the surrounding components and thus at least partially absorbs or binds the outgassing substances.

[0078] Fig. Figure 3 shows an embodiment according to the invention of a connecting element 40 of a shield 42 with a support structure 41 of an optical module, as shown in a Fig. 1, in a sectional view, where appropriate, corresponding elements are shown with respect to the Fig. 2 are designated by reference numerals increased by 10. The shield 42 rests on a shoulder 44 formed in the support structure 41, which shoulder ensures the defined support of the shield 42 to maintain the predetermined distance. Alternatively, the shoulder can also be formed on the shield 42. The shield 42 is pulled against the shoulder 44 by a flange 51 formed on the closed side of a sleeve 45 closed on one side, so that during assembly of the shield 42 no relative movement occurs between the flange 51 and the shield 42, thereby advantageously avoiding or at least minimizing the generation and release of particles. The sleeve 45 immerses in a recess 46 in the support structure 41.An adjusting element designed as a screw 43, which is inserted into the recess 46 from the rear side 53 of the support structure 41 facing away from the shield 42, is screwed to the sleeve 45 via a thread 47 formed in the sleeve 45, so that the sleeve 45 is pulled against the shoulder 44, as described above. The screw 43 has a vent hole 48 for venting the inside of the sleeve 45 with the thread 47. Furthermore, to reduce friction between the screw 43 and the support structure 41, a washer 50 is arranged between the two components 43, 41. The sleeve 45 can also be connected to the shield 42 prior to assembly, for example via a fit, in such a way that it can be used to align the shield 42 with respect to the support structure 41. The screw connection can be used to fix the final position and to adjust a preload.

[0079] The Fig. The embodiment shown in Figure 3 has the advantage that the particle-generating thread 47 is not arranged directly in the area of ​​the shield 42 and thus in the area of ​​the optical element designed as a mirror M3. Furthermore, the recess 46 in the support structure 41 is, in comparison to the embodiment shown in Figure 3, Fig. 2, the thread 37 is easier to manufacture and easier to clean. The single thread 47 of the connecting element 40 is formed in the sleeve 45, whereby the cleaning of the thread 47 is easier than in the Fig. 2 in the supporting structure 31 ( Fig. 2) arranged thread 37. Optionally, a seal 52 can be arranged between the shield 42 and the defined support formed as a shoulder 44. This separates the area of ​​the shield 42 from the area of ​​the rear side 53 of the support structure 41 in a gas-tight manner, whereby the penetration of undesired gaseous substances or particles into the area of ​​the mirror M3 can be advantageously prevented.

[0080] Fig. Fig. 4 shows a further embodiment of a connecting element 60 of a shield 62 with a support structure 61 of an optical module, as shown in a Fig. 1, in a sectional view, where appropriate, corresponding elements are shown with respect to the Fig. 3 are designated by reference numerals increased by 20. The shield 62 rests on a shoulder 64 formed in the support structure 61 and is fixed thereto by a clamping bolt 65. Alternatively, as in the Fig. 3, the shoulder may also be formed on the shield 62. The clamping bolt 65 has a cylindrical cross-section and includes a flange 72 at its end directed toward the shield 62 for clamping the shield 62 onto the shoulder 64. The clamping bolt 65 is guided in a recess 66 in the support structure 61.

[0081] The clamping force for clamping the shield 62 is generated by an actuating element designed as a spring 76 arranged in the recess 66, which is supported on a shoulder 71 of the recess 66. The spring 76 is connected to the clamping bolt 65 via a spring receptacle 77, wherein the spring receptacle 77 is screwed to the clamping bolt 65 by a screw 63 via a thread 67 in a blind hole (not separately designated) in the clamping bolt 65 against a stop 79 on the clamping bolt 65.

[0082] The screw 63 has a vent hole 68 for venting the blind hole. The underside of the spring receptacle 77 facing away from the spring 76 has a recess 73.1 which, under the spring force, at least partially encloses a corresponding elevation 73.2 formed on a locking ring 70 when the clamping bolt 65 is aligned accordingly about its longitudinal axis and engages in this position. The locking ring 70 is held in the recess 66 by a clamping ring 75, wherein the rotation of the locking ring 70 about its longitudinal axis is blocked by the insertion of a radially formed lug (not shown) on the locking ring 70 into a corresponding recess (likewise not shown) in the support structure 61, thus preventing the locking ring 70 from rotating when the clamping bolt 65 is aligned.

[0083] To install the shield 62, the clamping bolt 65 is lifted with a tool (not shown), such as pliers, at a corresponding tool interface 78 in the area of ​​the flange 72 and rotated by 90°. This position is defined by a second detent formed at 90° to the detent 73.1, 73.2 described above. The shield 62 can be placed on the shoulder 64 via the clamping bolt 65 and fixed by lifting and rotating the clamping bolt 65 again by 90° in the opposite direction, which is defined by the detent 73.1, 73.2. This has the advantage of avoiding particle-causing friction between the shield 62 and the flange 72.

[0084] Alternatively, the area with the recess 66 can be manufactured as a separate component and inserted into the support structure 61 via a screw or adhesive connection. This has the advantage that a material robust against hydrogen plasma and EUV radiation can be used for the application, so that direct contact between the aluminum preferably used for the support structure 61 and the hydrogen plasma and EUV radiation present during operation can be avoided.

[0085] As in the Fig. 3, can also be used in the Fig. 4, a seal (not shown) may be arranged between shield 62 and shoulder 64.

[0086] Fig. Fig. 5 shows a further embodiment of a connecting element 80 of a shield 82 with a support structure 81 of an optical module, as shown in a Fig. 1, in a sectional view, where appropriate, corresponding elements are shown with respect to the Fig. 4 are designated by reference numerals increased by 20. The shield 82 is fixed to a shoulder 84 of the support structure 81 by a magnetic force. Alternatively, the shoulder can also be formed on the shield 82. The magnetic force is generated by an actuating element arranged in the support structure 81 and designed as a permanent magnet 88, wherein in the Fig. 5, the magnetic force is transmitted via two magnetic conducting elements 83, which are also formed in the support structure 81, to the front side 86 of the support structure 81, which is directed towards the shield 82. The area 85 of the shield 82 opposite the shoulder 84 comprises a magnetizable material, which is attracted to the shoulder 84 by the magnetic force, wherein the Fig. 5 shows a view before mounting the shield 82.

[0087] Alternatively, instead of the permanent magnet 88 and the magnetic guide elements 83, permanent magnets 90 can be arranged in the shoulder 84 and a corresponding permanent magnet 91 can be arranged in the shield. A combination of a permanent magnet 90 arranged in the region of the shoulder 84 and a region 85 with magnetizable material in the shield 82 is also conceivable.

[0088] Furthermore, the arrangement of a permanent magnet 90 in the region of the shoulder 84 can be combined with an electromagnet 92 instead of the permanent magnet 88. The electromagnet 92 can be designed such that its magnetic field, which is in the Fig. 5 by elliptical lines, the effect of the magnetic field of the permanent magnet 90 is completely compensated or at least minimized such that the shield 82 can be easily removed and / or positioned. The electromagnet 92 can be activated for assembly and deactivated after the shield 82 has been aligned on the shoulder 84, whereby the shield 82 is securely held on the shoulder 84 by the magnetic force generated by the permanent magnet 90. Any other combination of type and arrangement of magnets in the support structure 81 and / or the shield 82 is also conceivable. The use of magnetic force has the advantage that the shield 82 can be assembled and disassembled without relative movement and thus particle-free or almost particle-free.

[0089] Fig. 6 shows a further embodiment according to the invention of a connecting element 100 of a shield 102 with a support structure 101 of an optical module, as shown in a Fig. 1, in a sectional view, where appropriate, corresponding elements are shown with respect to the Fig. 5 are designated by reference numerals increased by 20. The shield 102 is connected to the shoulder 104 of the support structure 101 by an integrated screw 103 as an adjusting element. Alternatively, the shoulder can also be formed on the shield 102. Integrated in this context means that the screw 103 is arranged in an insert 105, which is screwed into a recess 106 in the support structure 101 via a thread 107, so that the screw 103 is no longer visible after the support structure 101 and the shield 102 are connected.

[0090] Screwing the screw 103 into a thread 123 formed in an insert 112 arranged in the shield 102 is made possible by a screw adapter 108, which is arranged in a housing 113 of the insert 105. The screw adapter 108 comprises a spring 115, which is supported on one side against a spring receptacle 114 and on the other side presses against a magnet 116, which in turn is in contact with the screw 103. The spring 115 ensures that the screw adapter 108 always rests against a stop 119 in the housing 113 and that the screw 103 protrudes from the housing 113. When screwed in, the screw 103 attracts the shield 102 via the thread 123 in the insert 112 to the shoulder 104 formed on the support structure 101. Furthermore, the spring 115 causes a contact force of the screw 103 on the thread 123, which ensures that the screw 103 rests on the thread 123 and thus that the screw 103 grips the thread 123.

[0091] The magnet 116 in the screw adapter 108 has a driver 117, which drives an attachment 118 connected to the screw 103 via corresponding lugs 124.1, 124.2. The magnet 116 is rotated by a tool 120 placed on the outer side 125 of the support structure and can thus screw the screw 103 into or unscrew it from the thread 123 depending on the direction of rotation. The tool 120 has an axis 121 with at least two alternately polarized magnets 122.1, 122.2, which rotate the magnet 116 in the screw adapter 108.

[0092] The thread 123 is in the Fig. 6, the thread 123 is formed in an insert 112, which is screwed into a recess 111 in a flange 110 of the shield 102. Alternatively, the thread 123 can also be cut directly into the flange 110. The flange 110 can be manufactured integrally with the shield 102 or can be connected to the shield 102 via an adhesive bond, a welded bond, or any other suitable joining technique.

[0093] The integrated screw connection has the advantage that the shield 102 has a closed surface in the direction of the area in which the optical element, designed as a mirror M3, is arranged. This can optionally be provided, as explained above, with a coating 109, which optimally absorbs the undesirable substances caused by hydrogen-related outgassing. A closed surface facilitates the production of the coating and increases the absorption area for undesirable substances. It can be used on surfaces without a coating, such as screw heads ( Fig. 2), missions ( Fig. 3) or clamping bolts ( Fig. 4) can be omitted, thereby advantageously avoiding potential sources of hydrogen-induced outgassing. Furthermore, thanks to the integrated screw connection, the support structure 101 can have a closed surface, particularly on the rear side of the support structure 101 facing away from the shielding, which is comparatively easy to clean.

[0094] The use of the integrated screw connection is not limited to the attachment of shields 102 as shown in the present example. It is certainly conceivable to connect any components of projection exposure systems 1 with each other as shown in the example in Fig. 6 executed. List of reference symbols 1 projection exposure system 2 Lighting system 3 Radiation 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 EUV radiation 17 Collector 18 Intermediate focal plane 19 Deflecting mirrors 20 facet mirrors 21 facets 22 facet mirrors 23 facets 30 connecting elements 31 Supporting structure 32 Shielding 33 Screw 34 spacer element 35 deployment 36 bore 37 threads 38 vent hole 39 Coating 40 connecting elements 41 Supporting structure 42 Shielding 43 Screw 44 spacer element 45 sleeve 46 recess 47 threads 48 vent hole 49 Coating 50 Washer 51 flange 52 Seal 53 Rear side of supporting structure 60 connecting elements 61 Supporting structure 62 Shielding 63 Screw 64 paragraph 65 clamping bolts 66 recess 67 threads 68 vent hole 69 Coating 70 locking ring 71 paragraph 72 flange 73.1,73.2 elevation, deepening of the detent 74 Back of supporting structure 75 clamping ring 76 spring 77 Spring retainer 78 Tool interface 79 paragraph 80 connecting elements 81 Supporting structure 82 Shielding 83 magnetic guide element 84 paragraph 85 magnetic area of ​​the shield 86 Front of supporting structure 87 Rear side supporting structure 88 permanent magnet 89 Coating 90 magnet support structure 91 Magnetic Shielding 92 Electromagnet 100 connecting elements 101 Supporting structure 102 Shielding 103 Screw 104 paragraph 105 Use of supporting structure 106 recess 107 threads 108 Adapter screw 109 Coating 110 flange 111 recess 112 Insert flange shielding 113 housings 114 Spring retainer 115 spring 116 Magnet 117 drivers 118 screw attachment 119 attack 120 tools 121 Axis 122.1,122.2 Magnet 123 thread insert shielding 124.1, 124.2 Nose M1-M6 mirrors 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 [0042, 0046] US 2006 / 0132747 A1

[0044] EP 1 614 008 B1

[0044] US 6,573,978

[0044] DE 10 2017 220 586 A1

[0049] US 2018 / 0074303 A1

[0063]

Claims

[1] Optical module with an optical element (M3), a support structure (41,61,81,101) and a shield (42,62,82,102), wherein the shield (42,62,82,102) is arranged between the optical element (M3) and the support structure (41,61,81,101) and is connected to the support structure (41,61,81,101) via at least one connecting element (40,60,80,100), wherein at least one adjusting element (43,76,88,90,92,103) is provided for adjusting a holding force exerted by the connecting element (40,60,80,100), characterized by that the adjusting element (43,76,88,90,92,103) is arranged on the side of the shield (42,62,82,102) facing away from the optical element (M3). [2] Optical module according to claim 1, characterized by that the adjusting element (43,76,88,90,92,103) is designed as a screw (43,103), spring (76) or as a magnet (88,90,92). [3] Optical module according to claim 1 or 2, characterized bythat an interface (47,67,77) for receiving or fixing the actuating element (43,76,88,90,92,103) is formed in a component manufactured independently of the supporting structure (41,61,81,101). [4] Optical module according to one of the preceding claims, characterized by that the connecting element (40,60,80,100) has a tool interface (78) for mounting the shield (42,62,82,102) on the side facing the shield (42,62,82,102). [5] Optical module according to one of the preceding claims, characterized by that the connecting element (40,60,80,100) is securely connected to the supporting structure (41,61,81,101). [6] Optical module according to one of the preceding claims, characterized by that the connecting element (40,60,80,100) has at least one magnet (88,90,92). [7] Optical module according to claim 6, characterized by that the magnet is designed as a permanent magnet (88,90) or electromagnet (92). [8] Optical module according to one of the preceding claims, characterized by that a part (85,91,120) of the connecting element (40,60,80,100) is connected to the shield (42,62,82,102) in an unassembled state. [9] Optical module according to one of the preceding claims, characterized by that the connecting element (40,60,80,100) is designed to connect the shield (42,62,82,102) to the supporting structure (41,61,81,101) in a force-fitting manner. [10] Optical module according to one of claims 1 to 8, characterized by that the connecting element (40,60,80,100) is designed to positively connect the shield (42,62,82,102) to the supporting structure (41,61,81,101). [11] Optical module according to one of the preceding claims, characterized by that the shield (42,62,82,102) has a completely closed and flat surface in the direction of the optical element (M3) in the mounted state. [12] Optical module according to one of the preceding claims, characterized by that the sides of the shield (42,62,82,102) and / or of the connecting element (40,60,80,100) directed towards the optical element (M3) have a coating (49,69,89,109) for absorbing electromagnetic radiation, in particular useful light (16). [13] Projection exposure system (1) with an optical module according to one of the preceding claims.

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