Projection lens of a projection exposure system and projection exposure system

Abstract

The invention relates to a projection lens (110) of a projection exposure system (1,101) and a projection exposure system (1,101) with an optical module (30,40,50,70,90) with an optical element (M3) and a stiffening body (35,45,55,75.1,75.2), wherein the optical element (M3) and the stiffening body (35,45,55,75.1,75.2) are connected to each other by at least one connecting element (36,46), wherein the optical element (M3) has at least two segments (31.1,31.2,51.1,51.2, 71.1, 71.2,91).

Description

[0001] The invention relates to a projection lens of a projection exposure apparatus and a projection exposure apparatus for semiconductor lithography.

[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, particularly in the range of 13.5 nm, have been increasingly used. This emission wavelength range is also referred to as the EUV range.

[0005] The resolution requirements for producing ever smaller structures are increasing from generation to generation, so that with the same emission wavelength and constant refractive index, the aperture angle of the optical system must be larger.

[0006] In the optical system, optical elements such as lenses and mirrors are used to illuminate the structures and in particular to image them. In the field of EUV lithography, mirrors are used almost exclusively due to the high absorption of the emission wavelengths used in this field by most materials. To image the structures, so-called optical effective surfaces of the optical elements are exposed to useful radiation. The optical effective surfaces and thus the optical elements also become larger due to the larger aperture angle. The disadvantage of the larger optical elements is, on the one hand, increased manufacturing costs and, on the other hand, impacts on the technical requirements such as position stability during imaging and the manufacturability of the optical effective surfaces. These can only be manufactured with conventional manufacturing machines and / or processes at great financial expense.

[0007] The object of the present invention is to provide a projection lens and a projection exposure system in which an optical module improved under the above-mentioned aspects is implemented.

[0008] This object is achieved by a device having the features of independent claim 1. The subclaims relate to advantageous developments and variants of the invention.

[0009] A projection lens according to the invention for a projection exposure system with an optical module comprises an optical element and at least one, optionally also several, stiffening bodies, wherein the optical element and the stiffening body are connected to one another by at least one connecting element. According to the invention, the optical element has at least two segments. Segmenting the optical element achieves, among other things, that the individual optical active surfaces of the segments can be manufactured separately, thus enabling simplified production.

[0010] The segments can in particular have a constant thickness in a range between 5 mm and 60 mm, preferably between 10 mm and 40 mm.

[0011] By designing at least one connecting element as a mechanical actuator, in particular with an effective axis perpendicular to a rear side of the optical element, it can be achieved, for example, that assembly tolerances can be compensated and deviations of the optical effective surface of the optical element from its desired shape can be compensated.

[0012] It is advantageous if at least one connecting element has two serially arranged actuators that differ in terms of their travel range and resolution. In particular, one of the serially arranged actuators can be designed as a long-stroke actuator. In this case, it can have a travel range in the range of 2 to 10 micrometers and a resolution of 1 to 10 nanometers.

[0013] Furthermore, one of the serially arranged actuators can be designed as a short-stroke actuator; it can have a travel range in the range of 10 to 20 nanometers and a resolution of 1 to 10 picometers.

[0014] A combination of the long and short stroke actuators described above enables a large travel range of the combined actuator created in this way while maintaining high resolution.

[0015] The fact that at least one compensating element is arranged between at least one segment and the stiffening body results in further advantages. Particularly with highly curved optical effective surfaces of the segments, the compensating elements can be used to partially fill the gap between the rear side of the segment and the stiffening body, which widens due to the curvature, thus enabling compliance with the maximum thickness of the optical segments. Furthermore, the use of the compensating elements allows matching short- and long-stroke actuators to be arranged on opposite sides of the compensating elements, which can result in advantages during assembly, for example.

[0016] For example, at least one long-stroke actuator can be arranged between the stiffening body and the compensating element.

[0017] Similarly, at least one short-stroke actuator may be arranged between the compensating element and the at least one segment.

[0018] By arranging several long-stroke actuators in such a way that at least one compensation element is statically mounted on the stiffening body, it can be achieved, among other things, that parasitic forces and moments can be minimized.

[0019] If at least one damper is arranged between the compensating element and the stiffening body, relative movements between the compensating element and the stiffening body caused by mechanical vibrations can be reduced, thereby improving the image quality of the projection exposure system.

[0020] Cooling or tempering of the components involved can be achieved in particular by the segments and / or the compensating elements and / or the stiffening bodies having fluid channels.

[0021] By having at least one lateral decoupling element between the segments, at least one compensating element or at least one stiffening body, the effects of different thermal expansion coefficients of the elements involved can be limited.

[0022] The lateral decoupling element can be designed in particular as an actuator or as a solid-state joint.

[0023] In an advantageous variant of the invention, if a plurality of short-stroke actuators are arranged in an edge region of an optical segment with a higher packing density than in a central region, edge effects can be at least partially compensated for. Such edge effects are understood to mean, for example, the effect that, due to the lower rigidity of the material in an edge region of a segment, the material can deflect laterally during processing in the course of manufacturing the segment. After processing, the material then returns to its original position, so that the edge region can be designed with a surface that deviates from the desired shape, in particular with a raised surface. Without further measures, this region would not be available as an optical active surface.The actuators compacted in the edge area can advantageously compensate for the aforementioned effects, so that the edge area can also be used as an optical effective surface.

[0024] 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 schematically shows in meridional section a projection exposure system for DUV projection lithography, Fig. 3 a schematic representation of an optical module according to the invention, Fig. 4 shows a further embodiment of an optical module, Fig. 5a,b a further embodiment of an optical module, and Fig. 6a,b an edge of an optical element known from the prior art to explain a detail of a further embodiment of an optical module.

[0025] 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.

[0026] 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.

[0027] 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.

[0028] 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.

[0029] 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.

[0030] 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.

[0031] 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).

[0032] 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.

[0033] 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.

[0034] 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.

[0035] 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.

[0036] 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.

[0037] Between the collector 17 and the deflecting mirror 19, the illumination radiation 16 runs horizontally, i.e. along the y-direction.

[0038] 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.

[0039] 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.

[0040] 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.

[0041] The second facets 23 can have planar or alternatively convex or concave curved reflection surfaces.

[0042] The illumination optics 4 thus form a double-faceted system. This basic principle is also known as a honeycomb condenser (fly's eye integrator).

[0043] 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.

[0044] 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.

[0045] 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).

[0046] 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.

[0047] 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.

[0048] 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.

[0049] 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.

[0050] 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.

[0051] 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.

[0052] 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.

[0053] 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.

[0054] 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.

[0055] The projection optics 10 results in a reduction of 8:1 in the y-direction, i.e. in the scanning direction.

[0056] 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.

[0057] 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.

[0058] 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.

[0059] 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.

[0060] 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.

[0061] 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.

[0062] 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.

[0063] The projection optics 10 can, in particular, have a homocentric entrance pupil. This can be accessible. It can also be inaccessible.

[0064] 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.

[0065] The projection optics 10 may 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. This optical element can be used to account for the different positions of the tangential entrance pupil and the sagittal entrance pupil.

[0066] 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.

[0067] The first facet mirror 20 is arranged tilted to an arrangement plane which is defined by the second facet mirror 22.

[0068] Fig. 2 shows schematically in meridional section a further projection exposure system 101 for DUV projection lithography, in which the invention can also be used.

[0069] The structure of the projection exposure system 101 and the principle of imaging is comparable to that in Fig. 1 described structure and procedure. Identical components are provided with a 100 Fig. 1 raised reference numerals, the reference numerals in Fig. So 2 start with 101.

[0070] In contrast to a Fig. 1, due to the longer wavelength of the DUV radiation 116 used as useful light in the range from 100 nm to 300 nm, in particular from 193 nm, refractive, diffractive and / or reflective optical elements 117, such as lenses, mirrors, prisms, cover plates and the like, can be used in the DUV projection exposure system 101 for imaging or for illumination.The projection exposure system 101 essentially comprises an illumination system 102, a reticle holder 108 for receiving and precisely positioning a reticle 107 provided with a structure, by means of which the later structures on a wafer 113 are determined, a wafer holder 114 for holding, moving and precisely positioning this wafer 113 and a projection lens 110 with a plurality of optical elements 117, which are held via mounts 118 in a lens housing 119 of the projection lens 110.

[0071] The illumination system 102 provides DUV radiation 116 required for imaging the reticle 107 on the wafer 113. A laser, a plasma source, or the like can be used as the source for this radiation 116. The radiation 116 is shaped in the illumination system 102 via optical elements such that the DUV radiation 116, upon impinging on the reticle 107, exhibits the desired properties with regard to diameter, polarization, wavefront shape, and the like.

[0072] The structure of the subsequent projection optics 101 with the lens housing 119 does not differ in principle from that in Fig. 1 and is therefore not described further.

[0073] Fig. 3 shows a schematic representation of an optical module according to the invention designed as a mirror module 30, which in the example shown is a mirror M3 from the Fig. 1 illustrated projection exposure system 1. In the example shown, the mirror M3 comprises four segments, whereby due to the cross-sectional view of the Fig. 3 selected section between the segments, only two segments 31.1, 31.2 are shown. These each comprise an optical effective surface 32.1, 32.2, which, during operation of the projection exposure system 1, are used to image a structure of a reticle 7 ( Fig. 1) is exposed to useful light and in the Fig. 3 is shown as a dot-dash line. Due to manufacturing reasons, the optical active surfaces 32.1, 32.2 are not formed up to the edges 38 of the segments 31.1, 31.2.

[0074] The design of the mirror M3 in segments 31.1, 31.2 has the advantage that the individual optical active surfaces 32.1, 32.2 are smaller relative to the total surface of the mirror M3, allowing them to be manufactured more easily. This has a positive impact on manufacturing costs. A gap 33 is formed between the segments 31.1, 31.2 due to the design principle, although this gap has no significant influence on the imaging quality of the projection exposure system 1.

[0075] The mirror module 30 further comprises a stiffening body 35, which is arranged on the rear sides 34.1, 34.2 of the segments 31.1, 31.2 opposite the optical active surfaces 32.1, 32.2 and is connected to the segments 31.1, 31.2 via connecting elements designed as actuators 36. The stiffening body 35, in conjunction with the actuators 36, stiffens the segments 31.1, 31.2, particularly in the z-direction, which in the example is oriented perpendicular to the rear sides 34.1, 34.2. Their thickness can thus be selected to be smaller than that of previous mirrors with the same radius.

[0076] The stiffness of the mirror module 30 in the lateral xy-plane perpendicular to the z-direction is fundamentally less critical, so that even for the solution shown as an example in the figure, a sufficiently large lateral stiffness of the mirror module 30 including the connecting elements 36 and the stiffening body 35 is given.

[0077] The stiffening body 35 can be made of the same material as the segments 31.1, 31.2, which has the advantage that the components 31.1, 31.2, 35 have the same thermal expansion coefficient. This reduces or even completely eliminates lateral (xy-direction) displacements of the connection points 39.1, 39.2 of the actuators 36 on the segments 31.1, 31.2 or the stiffening body 35, with uniform heating of the components 31.1, 31.2, 35. The introduction of forces and moments caused by these displacements on the rear sides 34.1, 34.2 of the segments 31.1, 31.2 and the resulting possible deformation of the optical active surfaces 32.1, 32.2 is advantageously avoided. The stiffening body 35 can also be designed as a lightweight structure for further stiffening and to reduce its mass and thickness, which in the Fig. 3 is indicated by a dashed truss structure.

[0078] Alternatively, the stiffening body 35 can comprise a material different from the mirror material, such as a ceramic, in particular silicon carbide, which has a modulus of elasticity that is at least 2 times higher, preferably at least 3 times higher, in particular at least 4 times higher than the mirror material. This makes it possible to realize the mirror module 30 with substantially less material usage while maintaining virtually unchanged overall stiffness. This has a positive effect, among other things, on the installation space required as well as the overall mass and, due to the lower material requirement, also on the manufacturing costs of the mirror module 30.

[0079] The effective axes 37 of the actuators 36 are aligned perpendicular to the rear surfaces 34.1, 34.2 of the mirror M3 in the z-direction. The actuators 36 are used, among other things, to compensate for manufacturing and / or assembly tolerances of the stiffening body 35 and the segments 31.1, 31.2. Furthermore, the actuators 36 can deform the optical segments 31.1, 31.2, thereby correcting deviations of the optical effective surfaces 32.1, 32.2 relevant for imaging from their desired shape. To minimize the forces required to deform the segments 31.1, 31.2, the thickness of the segments 31.1, 31.2 is limited to a range between 10 mm and 40 mm.

[0080] Fig. Figure 4 shows a further embodiment of an optical module, shown in a sectional view and designed as a mirror module 40, with an optical element designed as a mirror M3. The structure of the mirror module 40 is similar to that shown in Figure 4. Fig. 3 explained mirror module 30, where appropriate identical elements with opposite designation in Fig. 3 are designated by reference numerals increased by 10.

[0081] The connecting elements 46 each have two actuators 48, 49 arranged in series. These differ in their travel range and resolution, with the so-called long-stroke actuator 48 shown below in the figure having a comparatively large travel range and low resolution, while the upper so-called short-stroke actuator 49 has a short travel range and high resolution. The ratio of travel range to resolution in actuators, particularly piezoelectric actuators, depends predominantly on the resolution of the electronics used for control, which can typically achieve a resolution in the range of one ten-thousandth to one hundred-thousandth.The total travel can in particular be between 2 nm and 20 µm, wherein the long-stroke actuator 48 can realize at least twice the travel of the short-stroke actuator 49, preferably five times, more preferably 10 times, in particular even more than 100 times.

[0082] The long-stroke actuator 48 can have a maximum travel in the range of 2 to 10 micrometers and, in combination with the control electronics, can be configured to achieve an accuracy in the range of 1 to 10 nanometers.

[0083] The resolution of the long-stroke actuator can be 0.01 to 1 nanometer, preferably 0.01 to 0.1 nanometer. The short-stroke actuator 49 can have a travel range in the range of 10 to 20 nanometers and a resolution of 1 to 10 picometers. The travel range of the short-stroke actuator 49 is advantageously greater than or equal to the resolution of the long-stroke actuator 48. The combination of a long-stroke actuator 48 and a short-stroke actuator 49 thus enables a large travel range with high resolution.

[0084] The long-stroke actuator 48 is primarily used to correct assembly and manufacturing tolerances, which depend on the material used, in particular for the stiffening body 45, and the manufacturing technologies applied, and can range from 2 to 10 micrometers. Furthermore, the long-stroke actuator 48 is used to correct possible changes in the distance between the stiffening body 45 and the segments 41.1, 41.2 during operation. This distance can be caused, for example, by settling effects and / or drift effects due to the connection technologies used between the components 41.1, 41.2, 45, 48, 49, such as gluing or bonding, as well as thermal effects due to the slow heating of the mirror module 40 during operation of the projection exposure system 1.

[0085] The short-stroke actuator 49 is primarily used to correct parasitic deformations of the optical active surfaces 42.1, 42.2, which can be caused by forces and moments acting on the segments 32.1, 32.2. Furthermore, the imaging quality of the projection exposure system 1 can be advantageously improved by a predetermined deformation of the optical active surfaces 42.1, 42.2. In this case, imaging errors caused by other optical elements or components of the projection exposure system can also be corrected.

[0086] In principle, a wide variety of actuators can be used as long- and short-stroke actuators. Both primarily force-generating actuators, such as Lorenz actuators, and primarily displacement-generating actuators, such as solid-state actuators, can be used.

[0087] Solid-state actuators are advantageous for stiffening segments 41.1 and 41.2 due to their inherent rigidity. Force actuators typically require closed-loop control. However, the low lateral stiffness of force actuators is advantageous in this case, particularly with regard to compensating for varying thermal expansions.

[0088] Solid-state actuators can be implemented, for example, using piezoelectric and / or electrostrictive actuators. Multi-axis functionality can be achieved by combining several single-axis actuators. These can be implemented as a single actuator unit with multiple control lines or created from individual actuators through joining processes.

[0089] Multiaxiality can also be achieved by different directions of the applied field.

[0090] Furthermore, the solid-state actuator can be realized using the photostrictive, magnetostrictive or thermostrictive effect or a combination of the aforementioned effects.

[0091] In a particularly preferred embodiment, a combination of several separately controllable piezo areas is used, wherein transverse piezo actuators can advantageously be combined with shear piezo actuators.

[0092] Both the long-stroke actuator 48 and the short-stroke actuator 49 can also be designed as multi-axis actuators.

[0093] Fig. Figure 5a shows a further embodiment of an optical module, shown in a sectional view as a mirror module 50, with an optical element designed as a mirror M3. The basic structure of the mirror module 50 is identical to that shown in Fig. 4 explained mirror module 40, where appropriate identical elements with the designation in Fig. 4 are designated by reference numerals increased by 10. The strongly concave shape of the mirror M3 shown in the embodiment and the limitation of the maximum thickness of the optical segments 51.1, 51.2 explained above result in the mirror module 50 being Fig. 4 has additional compensating elements 60.1, 60.2 between the segments 51.1, 51.2 and the stiffening body 55. These compensate for the remaining distance between the rear sides 54.1, 54.2 of the segments 51.1, 51.2 and the stiffening body 55 arranged parallel to the xy plane, thus enabling compliance with the maximum thickness of the optical segments 51.1, 51.2. The additional compensating elements 60.1, 60.2 have the advantage that the long-stroke actuator 58 and the short-stroke actuator 59 do not have to be directly connected to one another, thus simplifying assembly.

[0094] In the example shown in the figure, the long-stroke actuators 58 with their effective axes 56 are arranged between the stiffening body 55 and the compensating elements 60.1, 60.2 and, as explained above, compensate for assembly and manufacturing tolerances. In this case, the compensating elements 60.1, 60.2 are not deliberately deformed by the long-stroke actuators 58, but rather moved almost as rigid bodies. This has the advantage that the thickness of the compensating elements 60.1, 60.2 is not subject to any restrictions.

[0095] The short-stroke actuators 59 with their effective axes 57 are arranged between the compensating elements 60.1, 60.2 and the segments 51.1, 51.2 and deform the optical effective surfaces 52.1, 52.2 such that they correspond to the predetermined desired shapes.

[0096] The Fig. The embodiment of the mirror module 50 shown in Figure 5a further comprises actuators 61 for positioning the mirror module 50 in up to six degrees of freedom. The actuators 61 are supported on a module support frame 62. The arrangement of the mirror module 50 on a module support frame 62 has the advantage that the mirror module 50 can be more easily handled, tested, and calibrated as a standalone module. This is advantageous both during assembly and production and during a possible replacement of a mirror module in the field, particularly in a modular design of the projection exposure systems 1. In this case, the optical active surfaces 52.1, 52.2 can be aligned with a reference (not shown) on the module support frame 62.The reference is in turn aligned to a central support frame of the projection exposure systems 1, whereby the mirror M3 is positioned almost at the same position as the replaced mirror after the replacement.

[0097] Fig. Figure 5b shows a further embodiment of an optical module, shown in a sectional view and designed as a mirror module 70, with an optical element designed as a mirror M3, wherein the section in this embodiment runs through the two visible segments 71.1, 71.2 of the mirror M3. The structure of the mirror module 70 is similar to that shown in Fig. 5a, where appropriate identical elements with the designation in Fig. 5a 20 are designated by increased reference numerals. In contrast to the Fig. In the mirror module 50 explained in Figure 5a, the optical segments 71.1, 71.2 of the mirror module 70 are formed with a constant thickness. This has the advantage that the forces applied by the short-stroke actuators 79 to deform the segments 71.1, 71.2 are approximately equal across the segments 71.1, 71.2, thereby minimizing the parasitic forces and moments acting on the segments 71.1, 71.2.

[0098] The mirror module 70 also has two stiffening bodies 75.1, 75.2. The stiffening bodies 75.1, 75.2 are positioned and aligned with each other on the module support frame 83 using spacers 84 manufactured to a predetermined thickness. Alternatively, the spacers 84 can be replaced by actuators (not shown) for positioning the stiffening bodies 75.1, 75.2 on the module support frame 83.

[0099] The long-stroke actuators 78 are in the Fig. 5b, the compensating elements 80.1, 80.2 are arranged in such a way that the compensating elements 80.1, 80.2 are statically determinately mounted on the stiffening bodies 75.1, 75.2. This statically determinate mounting has the advantage that the parasitic forces and moments acting on the compensating elements 80.1, 80.2 can be minimized. Furthermore, the processing of only three individual connection points for the long-stroke actuators 78 is simpler than the processing of a large number of connection points, as in the embodiment shown in Fig. 5a, with a plurality of long-stroke actuators 58, which has a positive effect on the manufacturing costs of the stiffening bodies 75.1, 75.2 and, due to the reduced number of long-stroke actuators 78, also on the manufacturing costs of the mirror module 70. Furthermore, this allows a reduction in the travel distance of the long-stroke actuators 78, whereby they advantageously have a higher resolution, as explained above.

[0100] In addition to the long-stroke actuators 78, the Fig. In the embodiment shown in Figure 5b, dampers 81 are arranged between the compensating elements 80.1, 80.2 and the stiffening bodies 75.1, 75.2. These dampen possible relative movements caused by mechanical vibrations between the compensating elements 80.1, 80.2 and the stiffening bodies 75.1, 75.2, which has a positive effect on the image quality of the projection exposure system 1.

[0101] Furthermore, in the example shown, the segments 71.1, 71.2, the compensating elements 80.1, 80.2, and the stiffening bodies 75.1, 75.2 have fluid channels 85 through which a fluid 86, e.g., water, flows to cool the components 71.1, 71.2, 75.1, 75.2, 80.1, 80.2. This is particularly advantageous when the stiffening bodies 75.1, 75.2 are made of a different material than the optical material of the segments 71.1, 71.2. The cooling minimizes the displacement of the connection points of the actuators 78, 79 due to the different expansions of the components 71.1, 71.2, 75.1, 75.2, 80.1, 80.2 caused by the different thermal expansion coefficients of the materials. Ideally, lateral decoupling between the components 71.1, 71.2, 75.1, 75.2, 80.1, 80.2 can be dispensed with.In the event that lateral decoupling is necessary, this can be implemented actively, for example, in the form of actuators acting in the x-direction and y-direction, or passively, for example, in the form of flexure joints or a combination of active and passive decoupling. The actuators and / or flexure joints can be configured as part of the long-stroke actuators 78 and / or the short-stroke actuators 79.

[0102] Fig. Figure 6a shows a schematic diagram to explain a machining method known from the prior art for one of the mirrors shown of an optical module 90. To produce the surface 93 comprising the optical effective surface 92 of an optical segment 91 of the mirror M3 explained in the previous figures, the surface 93 is machined with a tool 96. Due to the lateral (xy direction) missing material at the edge 95, which has a supporting effect and thus influences the rigidity in the z direction running perpendicular to the optical effective surface 92, the rigidity in the edge region 94 is lower and the material can yield during machining. After machining and thus after the removal of the vertical pressure, the edge region 94 returns to its original shape, so that the Fig. 6 shown unevennesses in the edge area 94. Due to these unevennesses 97, the Fig. 6a, the optical effective surface 92 indicated by a dot-dash line is not formed up to the edge 95, so that an area 98 at the edge 95 remains unused for imaging.

[0103] Fig. Figure 6b shows an arrangement according to the invention of short-stroke actuators 133 on the back 132 of an optical segment 131 for compensating the unevenness 97 caused by the machining (in the Fig. 6b not visible) in the edge area 134 of the mirror M3. The Fig. The short-stroke actuators 133 explained in Figure 5a are arranged in the edge region 134 with a higher packing density than in the central region 135. The high packing density results in a higher resolution when correcting deformations on the Fig. 6b invisible surface 93 ( Fig. 6a). The high resolution allows the correction of the predominantly short-wavelength irregularities 97 ( Fig. 6a), whereby the optical effective surface advantageously extends to the edge 95 ( Fig. 6a) can be introduced.

[0104] In the central region 135, in which predominantly long-wave deformations caused, for example, by natural frequencies or thermal effects have to be corrected, a lower packing density is sufficient.

[0105] The arrangement of the short-stroke actuators 133 according to the invention can ensure the formation of the optical effective surface 93 up to the edge 95 ( Fig. 6a). This leads to an advantageous minimization of the unused area 98 ( Fig. 6a) of the individual optical segments 72.1, 72.2 ( Fig. 5b), so that the area of ​​the mirror M3 not used for imaging is directed to the necessary slit 73 explained above ( Fig. 5b) between the individual segments 71.1, 71.2 ( Fig. 5b), thereby improving the image quality. A further advantage of the design of the optical effective surface 92 ( Fig. 6a) to the edge 95 ( Fig. 6a) is a positive effect on the manufacturing costs due to the reduced material usage for the optical module 90.

[0106] The Fig. The arrangement of the short-stroke actuators 133 shown in Figure 6b can be used in all embodiments explained above and can also be used for the use of the edge area of ​​one-piece mirrors. 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 Optical module 31.1,31.2 Mirror segment 32.1, 32.2 optical effective area 33 gap 34.1, 34.2 back segments 35 stiffening bodies 36 Actuator 37 Effective axis 38 rand 39.1, 39.2 Connection points 40 Optical Module 41.1,41.2 Mirror segment 42.1,42.2 optical effective area 43 gap 44.1,44.2 back segments 45 stiffening bodies 46 connecting element 47 Effective axis 48 long-stroke actuator 49 Short-stroke actuator 50 Optical Module 51.1,51.2 Segment optical element 52.1,52.2 optical effective area 53 gap 54.1,54.2 back segments 55 stiffening bodies 56 Effective axis 57 Effective axis 58 long-stroke actuator 59 Short-stroke actuator 60.1,60.2 Compensating element 61 Actuator 62 module support frames 70 Optical Module 71.1,71.2 Mirror segment 72.1,72.2 optical effective area 73 gap 74.1,74.2 back segments 75.1,75.2 Stiffening body 76 Effective axis 77 Effective axis 78 long-stroke actuator 79 Short-stroke actuator 80.1,80.2 Actuator 81 dampers 82 Gap stiffening segment body 83 Supporting structure 84 spacers 85 Fluid channel 86 Fluid 90 optical module 91 segments 92 optical effective area 93 Surface 94 Marginal area 95 Rand 96 tools 97 Unevenness 98 unused area of ​​the optical segment 101 Projection exposure system 102 Lighting system 107 reticles 108 reticle holders 110 Projection optics 113 wafers 114 wafer holders 116 DUV radiation 117 optical element 118 versions 119 lens housings 130 Optical Module 131 Optical Segment 132 Back Segment 133 actuators 134 Marginal area 135 midrange 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 [0036, 0040] US 2006 / 0132747 A1

[0038] EP 1 614 008 B1

[0038] US 6,573,978

[0038] DE 10 2017 220 586 A1

[0043] US 2018 / 0074303 A1

[0057]

Claims

[1] Projection lens (110) of a projection exposure system (1,101) with an optical module (30,40,50,70,90) with an optical element (M3) and a stiffening body (35,45,55,75.1,75.2), wherein the optical element (M3) and the stiffening body (35,45,55,75.1,75.2) are connected to one another by at least one connecting element (36,46), characterized by that the optical element (M3) has at least two segments (31.1,31.2,51.1,51.2, 71.1, 71.2,91). [2] Projection lens (110) according to claim 1, characterized by that the at least one connecting element is designed as a mechanical actuator (36). [3] Projection lens (110) according to claim 2, characterized by that an effective axis of at least one mechanical actuator (36) is aligned perpendicular to a rear side (34.1,34.2) of the optical element (M3). [4] Projection lens (110) according to claim 2 or 3, characterized bythat at least one connecting element (46) has two serially arranged actuators (48, 49) which differ in terms of their travel path and their resolution. [5] Projection lens (110) according to claim 4, characterized by that one of the serially arranged actuators (48) is designed as a long-stroke actuator and has a travel path in the range of 2 to 10 micrometers and a resolution of 1 to 10 nanometers. [6] Projection lens (110) according to claim 4 or 5, characterized by that one of the serially arranged actuators (49) is designed as a short-stroke actuator and has a travel path in the range of 10 to 20 nanometers and a resolution of 1 to 10 picometers. [7] Projection lens (110) according to one of the preceding claims, characterized by that at least one compensating element (60.1,60.2) is arranged between at least one segment (51.1, 51.2) and the stiffening body (55). [8] Projection lens (110) according to claim 5 and 7, characterized by that at least one long-stroke actuator (58,78) is arranged between the stiffening body (55,75.1,75.2) and the compensating element (60.1,60.2,80.1,80.2). [9] Projection lens (110) according to claim 8, characterized by that a plurality of long-stroke actuators (78) are arranged such that the at least one compensating element (80.1, 80.2) is mounted in a statically determined manner on the stiffening body (75.1, 75.2). [10] Projection lens (110) according to claim 6 and 7 characterized by that at least one short-stroke actuator (59) is arranged between the compensating element (60.1,60.2) and the at least one segment (51.1,51.2). [11] Projection lens (110) according to one of claims 7 to 10, characterized by that at least one damper (81) is arranged between the compensating element (80.1, 80.2) and the stiffening body (75.1, 75.2). [12] Projection lens (110) according to one of the preceding claims, characterized by that the segments (71.1, 71.2) and / or the compensating elements (80.1, 80.2) and / or the stiffening bodies (75.1, 75.2) have fluid channels (85). [13] Projection lens (110) according to one of the preceding claims, characterized by that at least one lateral decoupling element is present between the segments (71.1, 71.2), at least one compensating element (80.1, 80.2) or at least one stiffening body (75.1, 75.2). [14] Projection lens (110) according to claim 13, characterized by that the lateral decoupling element is designed as an actuator. [15] Projection lens (110) according to claim 13, characterized by that the lateral decoupling element is designed as a solid-body joint. [16] Projection lens (110) according to one of claims 6 to 15, characterized bythat a plurality of short-stroke actuators (133) are arranged in an edge region (134) of an optical segment (131) with a higher packing density than in a central region (135). [17] Projection lens (110) according to one of the preceding claims, characterized by that several stiffening bodies (75.1,75.2) are present. [18] Projection lens (110) according to one of the preceding claims, characterized by that the segments (31.1, 31.2) have a constant thickness in a range between 5 mm and 60 mm, preferably between 10 mm and 40 mm. [19] Projection lens (110) according to one of the preceding claims, characterized by that the optical element is a mirror (M3). [20] Projection exposure apparatus (1,101) for semiconductor lithography with a projection objective (110) according to one of the preceding claims.

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