Optical module and projection exposure system

Abstract

The invention relates to an optical module (30, 40, 50) with an optical element (M3), wherein the optical element (M3) has an optical active surface (31) and is connected to a reinforcing body (32) via at least one connecting element (33, 41). The connecting element is characterized in that the connecting element (33, 41) comprises a decoupling region (34, 42.2, 42.3) by means of which a mechanical decoupling of the reinforcing body (32) and of the optical element (M3) parallel to the optical active surface (31) is produced. In the process, the material of the reinforcing body (32) can have an elastic modulus which is greater than that of the material of the optical element (M3) at least by a factor of two, preferably by a factor of three, particularly preferably by a factor of four, and / or the reinforcing body (32) can be made of a ceramic material, in particular a silicon carbide. The invention additionally relates to a projection exposure system (1, 101) for semiconductor lithography, comprising an optical module (30, 40, 50) according to one of the described embodiments.

Description

[0001] Optical module and projection exposure system

[0002] The present application claims the priorities of German patent applications DE 10 2023 116 895.9 and DE 10 2023 116 899.1 , filed on June 27, 2023, the contents of which are incorporated herein by reference in their entirety.

[0003] The invention relates to an optical module for a projection exposure system and a projection exposure system for semiconductor lithography.

[0004] 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, which is coated with photosensitive material. The minimum dimensions of the created structures depend on the resolution of the optical system used for imaging.

[0005] 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. 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. The latter emission wavelength range is also referred to as the EUV range.

[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 E UV lithography, mirrors are used almost exclusively due to the high absorption of the emission wavelengths used by most materials. To image the structures, so-called optical effective surfaces of the optical elements are exposed to useful radiation. During imaging, deviations in the position of the optical elements from an optimal target position have a massive impact on the quality of the image and thus on the quality of the manufactured components. In order to meet the high positioning requirements, the position of the majority of the mirrors is actively controlled. This type of control requires a high control bandwidth, which is dependent, among other things, on the first internal natural frequencies of the optical element orThe optical module's internal natural frequency should be above 1500 Hz. Lower natural frequencies cause the sensors required for control to begin oscillating in the low-frequency range (< 1500 Hz), which can render the rigid-body control system for positioning the mirror unstable. In addition to the optical element, an optical module includes at least the actuators and sensors required for positioning and their connection to the optical element.

[0007] The high required natural frequencies, as shown above, require a certain amount of relatively expensive materials to achieve the required rigidity, particularly with regard to the base bodies, for example, of mirror base bodies. In the past, it was proposed to arrange relatively thin optical elements on stiffening bodies made of relatively stiff materials in order to address this problem. These stiff materials did not necessarily have to be the expensive materials used in the base bodies of state-of-the-art optical elements. However, the challenge remains to compensate for the considerable deviations in the respective thermal expansion coefficients of the elements involved.

[0008] The object of the present invention is to provide an optical module in which an optical element is arranged on a separate stiffening body and in which the problem of different thermal expansion coefficients is effectively addressed. 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] An optical module according to the invention comprises an optical element and a stiffening body, wherein the optical element has an optical active surface. The optical element is connected to the stiffening body via at least one connecting element. According to the invention, the connecting element comprises a decoupling region, which creates a mechanical decoupling of the stiffening body and the optical element parallel to the optical active surface.

[0010] Decoupling in the sense of the invention means the reduction of the transmission of forces and / or moments and / or stresses between the optical element and the stiffening body. This ensures that lateral deformation of the stiffening body due to temperature changes does not lead to the introduction of adverse forces and / or moments into the optical element, or at least to a reduced extent. A possible lateral deformation of the stiffening body and / or optical element causes a displacement of the contact points of the connecting elements on the stiffening body and on the optical element, which depends on the distance from the temperature-invariant fixed point of the stiffening body or optical element. The decoupling ensures that the displacements do not lead to a deformation of the optical effective surface, which is crucial for the imaging quality, or only to a minimal extent.The decoupling can be realized actively, for example by moving an actuator, and / or passively, i.e. by a spring and / or kinematics.

[0011] In a first embodiment, the at least one connecting element can be arranged in the direction of an optical axis of the optical module between the optical element and the stiffening body. Particularly in the case of an optical element designed as a mirror, an arrangement on the rear side of the mirror is comparatively simple due to the sufficient available installation space.

[0012] In particular, the at least one connecting element can be designed as an actuator so that the connecting element can be deflected in at least one direction.

[0013] In a further embodiment, the actuator can comprise at least one region that can be deflected parallel to the optical active surface. As explained above, this makes it possible to achieve decoupling between the optical element and the stiffening body in the event of a displacement of the contact surfaces of the connecting elements on the stiffening body and on the optical element caused by a possible lateral deformation of the stiffening body and / or optical element. This applies in particular to the decoupling of the displacements of the contact surfaces of the connecting elements that occur during operation of the projection exposure system due to temperature changes in the optical element and / or stiffening body. The region can also serve to compensate for manufacturing and / or assembly tolerances that occur in the direction of the optical active surface.In particular, the actuator can comprise at least two regions that can be deflected perpendicular to each other and parallel to the optical effective surface. This allows for correction of displacements within the xy-plane formed parallel to the optical effective surface, with the value of the displacement depending on the distance of the respective contact surfaces from a temperature-invariant fixed point of the stiffening body or optical element.

[0014] Furthermore, the at least one region can be actively controllable. An actively controllable region has the advantage that, in addition to a one-time compensation for manufacturing and / or assembly tolerances during production of the optical module, the connecting element can also be adjusted during operation. The thermally induced displacements of the contact surfaces by the actuator can also be actively decoupled by the active region through a deflection parallel to the optical active surface. In a further embodiment, the actuator can comprise at least one region that can be deflected perpendicular to the optical active surface. This means that, depending on which region or regions are active, the connecting element can also be used to adjust the position and / or the predetermined surface geometry of the optical active surface relevant for imaging.

[0015] Adjusting the surface shape of the optical effective surface can be used to correct the optical effective surface of the optical element itself. In the case of an optical module of a projection exposure system, adjusting a targeted deformation of the optical effective surface can be used to correct imaging errors caused by other components of the projection exposure system. The deformation can thus be used to improve the imaging quality of the projection exposure system, analogous to the use of a manipulator.

[0016] The position primarily refers to the position of the optical element in the optical module, which itself usually has at least one active degree of freedom and can be positioned in up to six degrees of freedom.

[0017] In particular, the at least one region that can be deflected parallel to the optical active surface can be connected to an evaluation unit configured to detect mechanical stresses. This allows a displacement of the contact surfaces to be detected, which can be decoupled by actively deflecting the respective region.

[0018] In a further embodiment, the material of the stiffening body can have an E-module that is at least two times higher, preferably three times higher, and particularly preferably four times higher, than the material of the optical element. The higher the E-module, the smaller the thickness and thus the overall height of the stiffening body can be. This advantageously makes it possible to produce an optical module with a similar or even lower height than a base body known from the prior art and comprising a base body predominantly made of optical material. Furthermore, by saving on the comparatively expensive optical material, a more cost-effective optical module can be produced with the same installation space.

[0019] In addition, the stiffening body can be made of a ceramic material, particularly silicon carbide. These ceramics typically exhibit a comparatively high modulus of elasticity while being relatively lightweight. In addition to the possibility of reducing the thickness of the optical module, the weight can also be advantageously reduced. This, in turn, has positive effects on the control of the optical module, which is usually positioned via actuators.

[0020] Furthermore, the stiffening body can have at least one thickened section. This can further increase the stiffness in this area.

[0021] In particular, at least one thickened region can be designed as a stiffening rib. This makes it possible to stiffen the stiffening body even in the region in which the optical element is connected to the stiffening body via the connecting elements. The stiffening ribs can, for example, surround the optical element on at least one, preferably at least two, and particularly preferably at least three sides. The stiffening ribs can project beyond the optical active surface, i.e., have a greater height than the sum of the thicknesses of the optical element, the connecting elements, and the stiffening body below the optical element. Advantageously, the stiffening ribs can be designed such that machining of the optical active surface is still possible after assembly of the optical module.

[0022] In a further embodiment, at least one thickened region can be designed as a reference region, on which sensor elements are arranged. This makes it possible to achieve a relative movement of the sensors used, for example, for positioning the optical module up to comparatively high natural frequencies of greater than 1500 Hz, in particular over 2000 Hz. As explained above, this makes it possible to ensure stable position control of the optical module even if a lower natural frequency in the optical element and / or in the connection between the optical element and the stiffening body leads to a relative movement between the two components. The natural frequencies of the relative movements can lie in a range which has no or only negligible effects on the imaging quality of the optical module.

[0023] In a further embodiment, the optical element and / or the stiffening body can have fluid channels. A fluid can flow through the fluid channels to control the temperature of the optical element and / or the stiffening body. This can advantageously reduce the temperature deviation of the two components from their predetermined target temperature, thereby minimizing the displacement of the contact surfaces of the connecting elements on the optical element and the stiffening body, as already explained above. The smaller the deflections required for decoupling, the stiffer the decoupling regions can be designed for comparable forces and / or moments.

[0024] In particular, the optical element can be a mirror.

[0025] Furthermore, at least one connecting element can be arranged at the edge of the optical element between the optical element and the stiffening body, at least predominantly in a direction parallel to the optical active surface. In particular in the case of an optical element designed as a lens, an arrangement at the edge is necessary. In the case of a mirror, an arrangement at the edge can advantageously reduce the deformations caused by the introduction of forces and / or moments in the region of the optical active surface due to the higher rigidity in the radial direction. The arrangement at the edge can also be in addition to an arrangement of the connecting elements in the direction of the optical axis, whereby, for example, the rigidity in an xy plane parallel to the optical active surface can be increased. In a further embodiment, the at least one connecting element can comprise at least one region which can be deflected parallel to the optical axis.This allows manufacturing and / or assembly tolerances that occur during assembly of the optical assembly in the direction of the optical axis to be compensated.

[0026] In a further embodiment, the at least one connecting element can be designed as a hybrid connecting element. Hybrid refers to an active design of one region of the connecting element, for example, as an actuator in a direction parallel to the optical axis, and a passive design of a second region, for example, as a spring parallel to the optical active surface. This reduces the active degrees of freedom of the connecting element, which can advantageously minimize the increasing complexity of controlling and regulating these active degrees of freedom, which increases with the number of active degrees of freedom.

[0027] In particular, the area that can be deflected parallel to the optical axis can be designed as an actuator and the area that can be deflected parallel to the optical effective surface can be designed as a passive decoupling element. Particularly when the connecting element is arranged in the direction of the optical axis, the possibility of actively adjusting the distance between the back of the optical element and the surface of the stiffening body is advantageous. As already explained, this allows the optical effective surface to be actively adjusted and the optical element to be used as a manipulator to improve the imaging quality. In contrast, a displacement of the optical element within the optical module in the xy plane without a significant deformation of the optical effective surface can be corrected comparatively easily using the actuators usually formed on the optical module.

[0028] Alternatively, the region that can be deflected parallel to the optical axis can be designed as a passive decoupling element, and the region that can be deflected parallel to the optical active surface can be designed as an active decoupling element. This is particularly advantageous when the connecting element is arranged radially, i.e., in a direction parallel to the optical active surface. This allows the active region to be deflected for decoupling upon thermal expansion of the optical element and / or stiffening body.

[0029] In a further embodiment, the decoupling element can comprise kinematics for decoupling. The kinematics can be embodied as an active and a passive decoupling element. In its simplest form, the kinematics can be designed as a leaf spring, but can also have more complex embodiments, which are formed with levers and joints. The joints can be designed such that the forces and / or moments caused by a deflection of the connecting element at least partially compensate each other. A translation of the input movement to the output movement is also conceivable, which can be used in particular for actuators designed as active decoupling regions.

[0030] Furthermore, the kinematics, particularly in the case of a passive decoupling element, can be arranged between a base body and a receptacle for receiving an actuator. The base body can, for example, be connected to the stiffening body via an adhesive connection. The adhesive connection can be arranged on the base body both laterally and on the front side. The actuator connected to the receptacle can be connected to the optical element. The kinematics enable a deflection of the actuator receptacle relative to the base body, whereby a relative movement of the contact surfaces of the actuator can be decoupled according to the invention.

[0031] In particular, the kinematics of the decoupling element can exhibit isotropic, i.e., direction-independent, stiffness in the deflection direction. For example, the kinematics can exhibit approximately or exactly the same, for example, low, stiffness for all directions in a plane, such as the xy plane. In a direction perpendicular to this, the kinematics can exhibit comparatively high stiffness. Thus, by designing the kinematics, a high stiffness of the connecting element in the direction of the active region and a comparatively low stiffness of the connecting element in the direction of the passive region can be achieved. This makes it possible to achieve the high stiffness necessary for stable control of the optical module.This allows, for example, a lowest natural frequency of the optical module in an xy plane parallel to the optical active area of ​​at least 1500 Hz, especially greater than 2000 Hz, to be achieved, enabling stable control with a bandwidth of 150 Hz to 200 Hz. Active deflection of the active area can ensure sufficient decoupling to minimize thermally induced displacement of the contact surfaces relative to each other.

[0032] Furthermore, the stiffening body can have at least one thickened section. This can further increase the stiffness in this area.

[0033] In particular, at least one thickened region can be designed as a stiffening rib. This makes it possible to stiffen the stiffening body even in the region in which the optical element is connected to the stiffening body via the connecting elements. The stiffening ribs can, for example, surround the optical element on at least one, preferably at least two, and particularly preferably at least three sides. The stiffening ribs can project beyond the optical active surface, i.e., have a greater height than the sum of the thicknesses of the optical element, the connecting elements, and the stiffening body below the optical element. Advantageously, the stiffening ribs can be designed such that machining of the optical active surface is still possible after assembly of the optical module.

[0034] In a further embodiment, at least one thickened region can be designed as a reference region, on which sensor elements are arranged. This makes it possible to achieve a relative movement of the sensors used, for example, for positioning the optical module up to comparatively high natural frequencies of greater than 1500 Hz, in particular above 2000 Hz. As explained above, this makes it possible to ensure stable position control of the optical module even if a lower natural frequency in the optical element and / or in the connection between the optical element and the stiffening body leads to a relative movement between the two components. The natural frequencies of the relative movements can lie in a range which has no or only a negligible effect on the imaging quality of the optical module.

[0035] In a further embodiment, the optical element and / or the stiffening body can have fluid channels. A fluid can flow through the fluid channels to control the temperature of the optical element and / or the stiffening body. This can advantageously reduce the temperature deviation of the two components from their predetermined target temperature, thereby minimizing the displacement of the contact surfaces of the connecting elements on the optical element and the stiffening body, as already explained above. The smaller the deflections required for decoupling, the stiffer the decoupling regions can be designed for comparable forces and / or moments.

[0036] In a further embodiment, the optical element can comprise a decoupling element in the region where the connecting elements are connected. The decoupling element can be formed alternatively or in addition to the decoupling regions formed in the connecting elements.

[0037] In particular, the decoupling can be achieved by cavities formed in the optical element. The cavities can be integrated into the optical element during its manufacture. This is comparatively easy, especially when the optical element is manufactured using an additive process. The cavities can generally be manufactured using the same processes as those used to manufacture the fluid channels.

[0038] A projection exposure system for semiconductor lithography according to the invention comprises an optical module according to one of the preceding embodiments. The use of the optical modules according to the invention further enables the realization of projection exposure systems even with optical elements that are becoming increasingly larger due to the numerical aperture in newer generations.

[0039] In the following, embodiments and variants of the invention are explained in more detail with reference to the drawings.

[0040] Figure 1 shows a meridional section of a projection exposure system for EUV projection lithography,

[0041] Figure 2 shows a meridional section of a projection exposure system for DUV projection lithography,

[0042] Figure 3 is a schematic representation of an optical module according to the invention,

[0043] Figure 4 is a schematic representation of a detail of another embodiment of the optical module,

[0044] Figure 5 shows another embodiment of an optical module

[0045] Figure 6 shows a further detailed view of the invention,

[0046] Figure 7a-b shows a further embodiment of a detail of the invention,

[0047] Figure 8 shows a further embodiment of a detail of the invention, and

[0048] Figure 9a-c further embodiments of an optical

[0049] module,

[0050] Figure 10 shows a further embodiment of an optical

[0051] module, and

[0052] Figure 11 shows a further embodiment of an optical

[0053] module.

[0054] In the following, the essential components of a projection exposure system 1 for microlithography are described by way of example with reference to Figure 1. The description of the basic structure of the projection exposure system 1 and its components is not intended to be limiting.

[0055] 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.

[0056] 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.

[0057] Figure 1 illustrates a Cartesian xyz coordinate system. The x-direction runs perpendicular to the drawing plane. The y-direction runs horizontally, and the z-direction runs vertically. The scanning direction in Figure 1 runs along the y-direction. The z-direction runs perpendicular to the object plane 6.

[0058] 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.

[0059] A structure on the reticle 7 is imaged onto a light-sensitive layer of a wafer 13 arranged in the region of the image field 11 in the image plane 12. 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 one another. 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.Radiation source 3 can be a plasma source, for example, an LPP (Laser Produced Plasma) or a DPP (Gas Discharged Produced Plasma) source. It can also be a synchrotron-based radiation source. Radiation source 3 can be a free-electron laser (FEL).

[0060] 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 (Gl), 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.

[0061] 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.

[0062] 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 conjugate 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. Only a few of these facets 21 are shown in Fig. 1 as examples.

[0063] 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.

[0064] 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.

[0065] Between the collector 17 and the deflecting mirror 19, the illumination radiation 16 runs horizontally, i.e. along the y-direction.

[0066] 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. 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.

[0067] 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.

[0068] The second facets 23 can have planar or alternatively convex or concave curved reflection surfaces.

[0069] The illumination optics 4 thus form a double-faceted system. This basic principle is also known as a honeycomb condenser (fly's eye integrator).

[0070] 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.

[0071] 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.

[0072] 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 (NL mirrors, normal incidence mirrors) and / or one or two mirrors for grazing incidence (GL mirrors, gracing incidence mirrors).

[0073] In the embodiment shown in Fig. 1, the illumination optics 4 has exactly three mirrors after the collector 17, namely the deflection mirror 19, the field facet mirror 20 and the pupil facet mirror 22.

[0074] 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.

[0075] 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.

[0076] 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.

[0077] 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 are doubly obscured optics. 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.

[0078] 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.

[0079] 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.

[0080] The projection optics 10 can, in particular, be anamorphic. It has, in particular, different image scales ßx, ßy in the x and y directions. The two image scales ßx, ßy of the projection optics 10 are preferably (ßx, ßy) = (+ / - 0.25, + / - 0.125). A positive image scale ß means an image without image inversion. A negative sign for the image scale ß means an image with image inversion.

[0081] 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.

[0082] The projection optics 10 results in a reduction of 8:1 in the y-direction, i.e. in the scanning direction.

[0083] 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.

[0084] 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 be different, depending on the design of the projection optics 10. Examples of projection optics with different numbers of such intermediate images in the x- and y-directions are known from US 2018 / 0074303 A1.

[0085] 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.

[0086] 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.

[0087] 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.

[0088] 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.

[0089] 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.

[0090] The projection optics 10 can, in particular, have a homocentric entrance pupil. This can be accessible. It can also be inaccessible.

[0091] 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.

[0092] 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.

[0093] 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.

[0094] The first facet mirror 20 is arranged tilted to an arrangement plane which is defined by the second facet mirror 22.

[0095] Figure 2 shows schematically in meridional section a further projection exposure system 101 for DUV projection lithography, in which the invention can also be used.

[0096] The structure of the projection exposure system 101 and the principle of imaging are comparable to the structure and procedure described in Figure 1. Identical components are designated by a reference numeral that is 100 higher than in Figure 1; thus, the reference numerals in Figure 2 begin with 101.

[0097] In contrast to an EUV projection exposure system 1 as described in Figure 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 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.

[0098] 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.

[0099] The structure of the subsequent projection optics 101 with the lens housing 119 does not differ in principle from the structure described in Figure 1, except for the additional use of refractive optical elements 117 such as lenses, prisms, end plates, and is therefore not described further.

[0100] Figure 3 shows a schematic representation of an optical module designed as a mirror module 30, which in the example shown comprises the mirror M3 from the EUV projection exposure system 1 explained in Figure 1. The mirror M3 has an optical active surface 31 indicated by a dash-dotted line, which is exposed to the useful radiation (not shown) during operation of the projection exposure system 1. Furthermore, the mirror module 30 comprises a stiffening body 32, which is arranged on the rear side 35 of the mirror M3 opposite the optical active surface 31 and is connected to the mirror M3 via connecting elements 33. The connecting elements 33 are formed in the direction of an optical axis 36 of the mirror M3, wherein the optical axis 36 corresponds to the axis of symmetry of the mirror M3 in the example shown.For curved mirrors, such as those used in EUV projection exposure systems 1, the optical axis is understood as the axis perpendicular to the mirror surface through the apex of the mirror. The connecting elements 33 can be actively designed, for example, as actuators (see Figure 4), passively designed, for example, as a flexure joint, or as a combination of both.

[0101] The stiffening body 32, in conjunction with the connecting elements 33, stiffens the mirror M3, particularly in the z-direction, the thickness of which can therefore be selected to be smaller than that of previous mirrors with the same radius.

[0102] In the embodiment shown in Figure 3, the stiffening body 32 comprises a material different from the mirror material. Suitable materials here include, for example, ceramics such as silicon carbide. Such ceramics have a comparatively high modulus of elasticity. It is advantageous if the material of the stiffening body 32 has a modulus of elasticity that is at least two times higher, preferably at least three times higher, and particularly preferably at least four times higher than that of the mirror material. This makes it possible to realize the mirror module 30 with substantially less material used while maintaining virtually unchanged overall stiffness. This has a positive effect on the installation space required as well as the overall mass and, due to the lower material requirements, also on the manufacturing costs of the mirror module 30.

[0103] By using the stiffening body 32, the necessary high control bandwidth for positioning the mirror module 30 can be achieved even with an overall thinner mirror M3. In particular, a high natural frequency of the mirror of over 1500 Hz, especially over 2000 Hz, enables stable position control of the mirror module 30. Furthermore, deformation of the optical effective surface 31, which is crucial for the imaging quality and is caused, for example, by mechanical excitation, can be kept to a minimum during operation.

[0104] The stiffness of the mirror module 30 in the lateral xy-plane, i.e. 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 33 and the stiffening body 32 is given.

[0105] The different thermal expansion coefficient between the mirror material, such as ULE®, and the ceramic of the stiffening body 32 leads to different expansions of the mirror M3 and the stiffening body 32 when the mirror M3 and the stiffening body 32 heat up during operation. The heating can be caused, for example, by absorption of the useful radiation and / or the effect of other heat sources on the components M3, 32.

[0106] This situation is shown somewhat exaggerated in Figure 3 in that, in the event of heating of the arrangement, the resulting expansion of the stiffening body 32 is shown in dashed lines, whereas, due to the very low thermal expansion coefficient of the mirror material, the expansion of the mirror M3 remains practically unchanged.

[0107] The resulting relative movement between the rear side 35 of the mirror M3 and the stiffening body 32, particularly in the xy plane, can be compensated for by decoupling areas 34 provided in the connecting elements 33. The decoupling area 34 can be created, for example, by an appropriate choice of material or a corresponding design.

[0108] A uniform extension of the mirror M3 and / or the stiffening body 32 in the z-direction across the xy-plane is, however, uncritical, since almost all mirror modules 30 are mounted on actuators (see Figure 5) in a positionable manner, so that a displacement of the optical effective surface 31 relevant for the imaging in the z-direction can be compensated by positioning the mirror module 30.

[0109] Figure 4 shows a schematic representation of a detail of another embodiment of an optical module embodied as a mirror module 40, which has a connecting element embodied as an actuator 41 and aligned in the direction of the optical axis 46. The actuator 41, embodied as a piezoelectric actuator, has three actuator regions 42.1, 42.2, 42.3 that can be controlled separately from one another by a control unit (not shown) connected to the mirror module 40. The upper region 42.1 acting in the z-direction can be used to compensate for manufacturing tolerances of the contact surface 43 on the stiffening body 32 and the contact surface 44 on the mirror M3, as well as for manufacturing tolerances of the length of the actuators 41.Depending on the component M3, 32, 41, the manufacturing tolerances can range from 2 to 20 micrometers, such as the ceramic of the stiffening body 32, or within a few nanometers for the backside 35 of the optical material of the mirror M3. The manufacturing tolerances cannot be adequately compensated by possible bonding techniques, such as adhesive bonding, laser bonding, surface-activated bonding, anodic bonding, glass frit bonding, adhesive bonding, eutectic bonding, reactive bonding, silicate bonding, or the like. The remaining deviations are typically in the range of one to three micrometers.

[0110] Furthermore, the travel path in the z-direction can be used to compensate for thermally induced deformations of the optical effective surface 31 (Figure 3). In addition, the travel path can be used for targeted deformation of the optical effective surface 31, for example, to correct other imaging errors not caused by the mirror module 40 itself.

[0111] The two lower regions 42.2, 42.3 of the actuator 41, which can be deflected perpendicular to one another in the x-direction and y-direction, as shown in Figure 4 by arrows in regions 42.2, 42.3, form the decoupling region of the connecting element designed as actuator 41, as explained in Figure 3, and act as a lateral decoupling element between the mirror M3 and the stiffening body 32. By moving the lower regions 42.2, 42.3, the actuator 41 compensates for the displacements in the xy plane that occur between the contact surfaces 43, 44 due to the different thermal expansion. The displacement of the respective contact surfaces 43, 44 can be determined, for example, using a model-based method that is based on a temperature detected by sensors (not shown) at one or more points on the mirror module 40. The displacement is determined for each of the actuators 41 arranged in the mirror module 40.

[0112] An alternative approach to determining the displacement is to alternately use the lower regions 42.2, 42.3 of actuator 41 as a sensor and as an actuator. When used as a sensor, the piezoelectric effect is utilized, i.e., the generation of an electrical voltage by generating a mechanical stress in the material. When used as an actuator, a voltage is applied so that the material expands or contracts, thus utilizing the so-called inverse piezoelectric effect.

[0113] The effect of thermal changes on the material is slow compared to the effect of mechanical excitation, so that the alternating operation has a sufficient speed to compensate for the resulting displacements.

[0114] As a further solution, the displacement can also be determined by a position sensor 45 arranged in the immediate vicinity of the actuator 41, which detects the displacement between the mirror M3 and the actuator 41.

[0115] Figure 5 shows a further embodiment of an optical module designed as a mirror module 50, which has a stiffening body 51 optimized for different requirements. In addition to the higher E-modulus already explained above, the stiffness can be further optimized by the geometry of the stiffening body 51. The stiffening body 51 has a receiving area 52 for receiving the mirror M3. The receiving area 52 has a receiving surface 64 corresponding to the back of the mirror M3, on which the connecting elements designed as actuators 53 are arranged. For further stiffening, the receiving area 52 has stiffening ribs 54 designed as thickened regions on the sides parallel to the plane of the drawing, which are shown in Figure 5 with dashed lines and transparent.The stiffening ribs 54 are designed such that machining of the optical effective surface 31 of the mirror M3 is possible even after assembly of the mirror module 50. The receiving region 52 ensures sufficiently high rigidity, particularly in the z-direction, with a minimal thickness, whereby an overall thickness of the mirror module 50 that is less than or equal to the thickness of conventionally manufactured mirrors made of optical material can be achieved. In the embodiment shown in Figure 5, on the left side of the stiffening body 51, there is a further thickened region designed as a reference region 55, which protrudes beyond the optical effective surface 31 in the z-direction and, due to its greater thickness, is stiffer than the receiving region 52, particularly in the z-direction.Sensors or sensor targets 57 used for positioning the mirror module 50 are arranged as sensor elements on the reference surface 56 of the reference area 55, which, like the optical effective surface 31, faces upwards. Due to the very high rigidity of the reference area 55 in all degrees of freedom, the relative movement due to eigenmodes of the mirror module 50 between the three to six sensors 57 is reduced to a value that ensures a high control bandwidth for positioning the mirror module 50.

[0116] Adjacent to the reference area 55 are tabs 58 for connecting the actuators 59 used for positioning. Alternatively, the actuators 59 can also be connected in pockets 60 formed within the reference area 55, which are shown by dashed lines in Figure 5.

[0117] To optimize the stress distribution and the manufacturability of the stiffening body 51, the transitions between the various regions 52, 54, 55, 58 can, for example, have radii or other contours. The mirror M3 and the receiving region 52 of the stiffening body 51 have fluid channels designed as cooling channels 61, whereby the temperature difference between the mirror M3 and the stiffening body 51 can be reduced to a minimum. This has the advantage of minimizing the displacement of the contact surfaces 62, 63 of the actuators 53 between the mirror M3 and the stiffening body 51 due to the different thermal expansion coefficients. The smaller the displacement between the mirror M3 and the stiffening body 51, the less travel distance of the lower regions 42.2, 42.3 (Figure 4) of the actuator 41 (Figure 4), which corresponds to the structure of the actuator 53, is required.The travel path is almost proportional to the height of the lower actuator areas 42.2, 42.3, whereby the thickness of the mirror module 50 is further reduced as a result of minimizing the travel path.

[0118] The optical module 30, 40, 50 according to the invention can be adapted very variably depending on the respective requirements by selecting the materials used, the connecting elements 33, 41, 53 and the geometry of the stiffening body 32, 51, wherein the described embodiments show only individual embodiments and the invention cannot be restricted to these in any way.

[0119] Figure 6 shows a schematic representation of a detail of another embodiment of an optical module embodied as a mirror module 240 with a mirror M3, wherein the mirror module 240 has a hybrid connecting element 241 with an actuator 242 and a decoupling region embodied as a decoupling element 243. Hybrid refers here to an active design of the actuator 242 and a passive design of the decoupling element 243. The actuator 242, embodied as a piezoelectric actuator, is connected to a control (not shown) connected to the mirror module 240 and can be controlled by it. The actuator 242, acting in the z-direction, can be used to compensate for manufacturing tolerances of the elements M3, 242, 241 involved in the connection.Depending on the component M3, 232, 241, these manufacturing tolerances can range from 2 to 20 micrometers, such as the ceramic of the stiffening body 232, or within a range of a few nanometers for the backside 235 of the optical material of the mirror M3. These manufacturing tolerances cannot be adequately compensated by possible bonding techniques, such as gluing, screen printing, laser bonding, surface-activated bonding, anodic bonding, glass frit bonding, adhesive bonding, eutectic bonding, reactive bonding, silicate bonding, or the like. The remaining deviations are typically in the range of one to three micrometers.

[0120] Furthermore, the travel path in the z-direction can be used to compensate for thermally induced deformations of the optical effective surface 31 (Figure 3). In addition, the travel path can be used for the targeted deformation of the optical effective surface 31, for example, to correct imaging errors not caused by the mirror module 240 itself.

[0121] The decoupling element 243 is designed such that it has a decoupling effect in the x-direction and y-direction, which is represented in Figure 6 by double arrows in the decoupling element 243. It thus acts as a lateral decoupling between the mirror M3 and the stiffening body 232. Through its deformation, the decoupling element 243 compensates for the displacements in the xy-plane that occur between the contact surfaces 244, 245 due to the different thermal expansion. As explained above, the stiffness of the decoupling element 243 is sufficient so that the lowest natural frequency of the mirror module 240 in the xy-plane is at least greater than 1500 Hz, in particular greater than 2000 Hz. At the same time, the stiffness is low enough that the parasitic forces and moments generated by the deflection of the decoupling element 243 do not cause significant deformations of the optical effective surface 31 (Figure 3).Compared to an active solution, the displacement of the respective contact surfaces 244, 245 is passively compensated by the decoupling elements 243. Therefore, in the example shown, no determination of the displacement by a model-based method based on recorded temperature or position values ​​is required.

[0122] Figure 7a shows a detail of the mirror module 240, in which a first embodiment of a connecting element 250, as used in Figure 6 (reference numeral 241 there), is illustrated. The connecting element 250 comprises a decoupling element 251 and an actuator 252.

[0123] The decoupling element 251 has a hollow cylindrical base body 253 and a cylindrical receptacle 254, which in the example shown are connected to one another via a kinematic system 255 comprising two levers 256. The kinematic system 255 enables a relative movement of the receptacle 254 to the base body 253. The stiffness of the levers 256 is designed such that the mirror module 240 (Figure 6) has a sufficiently high natural frequency in both the z-direction and the lateral xy-direction for stable position control. In addition to the stiffness of the actuator 252, the stiffness of the connecting element 250 in the z-direction is predominantly determined by the height (z-direction) of the levers 256. The stiffness in the lateral direction (xy-plane), on the other hand, is influenced by the thickness of the levers 256, which in the example shown are designed as leaf springs, and their length.The connecting element 250 is monolithic in the example shown in Figure 7a, but it can alternatively be made up of several parts.

[0124] The base body 253 has a contact surface 258.1 on its outer surface with the stiffening body 232 (Figure 6), via which the connecting element 250 can be connected to the stiffening body 232 (Figure 6) via an adhesive bond. Alternatively, the connecting element 250 can also be connected to the stiffening body 341 via a contact surface 258.2 formed in the positive z-direction in Figure 6a (Figure 11).

[0125] The actuator 252 has on its upper side directed in the positive z-direction a contact surface 257 for connection to the mirror M3 (Figure 7).

[0126] Figure 7b shows the connecting element 250 (Figure 7a) in a deflected state in a plan view. The actuator 252 (Figure 7a) is not shown, so that the contact surface 259 of the receptacle 254 between the actuator 252 and the decoupling element 251 can be seen. The deformation of the levers 256 is clearly visible, which enables at least a local displacement of the mirror M3 (Figure 6) connected via the actuator (not shown) in the region of the contact surface 245 of the actuator 242 (Figure 6) on the mirror M3 and the stiffening body 232 (Figure 6) connected to the base body 253 via the connecting element 250.

[0127] Figure 8 shows a further embodiment of a connecting element 260 in a plan view, wherein, as in Figure 7b, no actuator is shown. The structure of the connecting element 260 is similar to the connecting element 250 explained in Figure 7a, wherein, where appropriate, corresponding elements are designated by reference numerals increased by 10 compared to the designation in Figure 7b. In contrast to the kinematics 255 explained in Figure 7a, the kinematics 265 has three levers 266.1, 266.2, 266.3, which are aligned concentrically to the outer surface of the receptacle 264 and are each connected radially to the inner outer surface of the base body 263. The levers 266.1, 266.2, 266.3 have a greater thickness compared to the lever 266 (Figure 7b). In the example shown, the levers 266.1, 266.2, 266.3 each have recesses 267 at three locations, so that the thickness is locally reduced to a minimum. This has the advantage of increasing the rigidity of the levers 266.1, 266.2, 266.3 can be adjusted radially almost independently of the stiffness in the z-direction, specifically in accordance with the requirements for the lateral (xy-plane) stiffness of the connecting element 260. In particular, the lateral stiffnesses can be designed such that the stiffness in the xy-plane is isotropic, i.e. independent of direction. The recesses 267 are also designed alternately from the receptacle 264 to the base body 263 and from the base body 263 to the receptacle 264. This has the advantage that the deflection of the receptacle 264 relative to the base body 263 causes lower forces and / or moments, since these are at least partially canceled out by the alternating arrangement of the local minima in the thickness of the levers 266.1, 266.2, 266.3.

[0128] The connecting element 260 is also manufactured monolithically in the example shown.

[0129] Figure 9a shows a schematic representation of another embodiment of a mirror module 270 with an optical element designed as a mirror M3, which is connected to a stiffening body 272 via connecting elements 273. The mirror M3 has bulges 277 on its rear side 276 opposite the optical active surface 271, which bulges comprise a contact surface 281 for connecting the connecting elements 273. The connecting elements 273 are connected to the mirror M3 by actuators 274 at the contact surfaces 281. In the example in Figure 9a, decoupling elements 278 in the form of two springs 278.1, 278.2 are shown. The first spring 278.1 represents the stiffer connection of the connecting element 273 in the z-direction and is connected via a first contact surface 280.1 to the surface 286 of the stiffening body 272 opposite the rear side 276 of the mirror M3. The second spring 278.2 represents the decoupling connection in the xy direction, whereby in the example shown, only one spring 278.2 is shown in the y direction. The second spring 278.2 is connected via a second contact surface 280.2 to an arm 279 formed on the stiffening body 272 in the z direction.

[0130] The mirror module 270 further comprises additional actuators 283, which are arranged radially between a flange 282 of the stiffening body 272 and the mirror M3. The actuators 283 are connected to the stiffening body 272 via contact surfaces 284 of the flange 282 and to the mirror M3 via the lateral surface 285, which is at least partially designed as a contact surface.

[0131] The additional actuators 283 increase the rigidity in the lateral (xy-plane) direction and have at least one degree of freedom in the radial direction and one degree of freedom in the z-direction. This degree of freedom, together with the actuators 274 of the connecting elements 273, is controlled by a control (not shown) to compensate for deformations of the optical effective surface 271. The radial degrees of freedom can be used to compensate for the thermal deformations occurring due to different thermal expansion coefficients of the materials of the mirror M3 and the stiffening body 272 and the resulting change in the distance between the contact surfaces 284, 285 by tracking, i.e., controlling the actuators 283. The radial degree of freedom of the actuators 283 thus acts as an active decoupling region of the connecting element embodied as actuator 283.Depending on requirements, the actuators 283 can also be used for additional deformation of the mirror M3 and the optical active surface 271 arranged thereon.

[0132] Figure 9b shows a schematic representation of another embodiment of a mirror module 290. This differs from the mirror module 270 explained in Figure 9a only in the radially arranged connecting element 293, which includes a decoupling element 292 for connecting an actuator 291 to the flange 282. The actuator 291 has at least one degree of freedom in the radial direction and no degree of freedom in the z-direction and is designed, for example, as an electrostrictive actuator. To compensate for the movement in the z-direction between the mirror M3 and the stiffening body 272, a decoupling element 292, which is represented as a spring in the example shown in the figure, is arranged between the actuator 291 and the contact surface 284. The decoupling element 292 is therefore soft in the z-direction and stiff in the radial direction.The radial degree of freedom of the actuators 283 thus acts as an active decoupling area of ​​the connecting element 293.

[0133] Furthermore, Figure 9b shows an alternative connecting element 294 which, in comparison to the hybrid connecting elements 273, which have a decoupling region designed as a passive decoupling element 278, has an active decoupling region designed as an actuator 295. The actuator 295, comparable to the actuator 291 of the radially arranged connecting element 293, is deflected when the mirror M3 and the stiffening body 272 expand differently to decouple the two components M3, 272 in such a way that no forces, moments and / or stresses are caused or transmitted, thus decoupled. The connecting element 294 can also be used in the embodiment shown in Figure 9a as an alternative to the hybrid connecting elements 273.

[0134] Figure 9c shows a schematic representation of another embodiment of a mirror module 120. In contrast to the mirror modules 270, 290 shown in Figures 9a, 9b, additional connecting elements designed as actuators 321 are arranged between the rear side 276 of the mirror M3 and the stiffening body 272 to stiffen the mirror module 320. The actuators 321 each have one degree of freedom in the z-direction, x-direction, and y-direction. These increase the stiffness between the mirror M3 and the stiffening body 272 in the xy-direction. The number of actuators 321 or the ratio between actuators 321 and hybrid connecting elements 273 depends, on the one hand, on the stiffness requirements of the mirror module M3 in the xy-direction and, on the other hand, on the control system, which becomes comparatively more complex with increasing active degrees of freedom.For decoupling, the actuators 321 are actively deflected accordingly in the x-y direction in the event of a thermally induced different displacement of the contact surfaces of the actuators 321 on the stiffening body 272 and the back 276 of the mirror M3.

[0135] Figure 10 shows a schematic representation of a further embodiment of a mirror module 330 according to the invention. The mirror module 330 is constructed identically to the mirror module 290 in Figure 9b. In contrast to the examples explained above, the mirror M3 has a series of cooling channels 331 in the region below the optical active surface 271, through which a fluid, in particular ultrapure water, flows to control the temperature of the mirror M3. The connection for the connecting element 273, designed as a bulge 332, is decoupled from a base body 333 of the mirror M3 compared to the bulge 277 (Figure 9b), wherein the bulge 332 and the base body 333 are monolithic. The decoupling 334 is achieved by creating cavities 335 and webs 336, which act as springs, in the material of the mirror M3.The decoupling 334 minimizes the parasitic forces and moments introduced at the contact surface 281 of the bulge 332 by the connection of the actuator 283. These can be caused, for example, by an adhesive used for the connection or by assembly and manufacturing tolerances.

[0136] Figure 11 shows a further embodiment of an optical module designed as a mirror module 340, which has a stiffening body 341 optimized for different requirements. In addition to the higher E-modulus already explained above, the stiffness can be further optimized by the geometry of the stiffening body 341. The stiffening body 341 has a receiving area 342 for receiving the mirror M3. The receiving area 342 has through-holes 354, in which shoulders 355 are formed as contact surfaces for the connection of the connecting elements 343. The base bodies 356 of the decoupling elements 357 of the connecting elements 343 are connected at the end face to the shoulder 355, for example via an adhesive connection (not shown), as explained in Figure 7a.Other possible bonding techniques include laser bonding, surface activated bonding, anodic bonding, glass frit bonding, adhesive bonding, eutectic bonding, reactive bonding, silicate bonding or the like.

[0137] The actuators 358 of the connecting elements 343 are connected to the rear side 359 of the mirror M3 through the through-bore 354, which tapers in the direction of the mirror M3 above the shoulder 355. For further stiffening, the receiving area 342 has stiffening ribs 344, which are shown in Figure 11 with dashed lines and transparent. The stiffening ribs 344 are designed such that machining of the optical effective surface 31 of the mirror M3 is possible even after the assembly of the mirror module 340. The receiving area 342 ensures sufficiently high stiffness, particularly in the z-direction, with a minimal thickness, whereby an overall thickness of the mirror module 340 that is less than or equal to the thickness of conventionally manufactured mirrors made of optical material can be achieved.

[0138] In the embodiment shown in Figure 11, a reference region 345 is formed on the left side of the stiffening body 341, which protrudes beyond the optical active surface 31 in the z-direction and, due to its greater thickness, is stiffer than the receiving region 342, particularly in the z-direction. The sensors 347 used for positioning the mirror module 340 are arranged on the reference surface 346 of the reference region 345, which, like the optical active surface 31, is directed upwards. Due to the very high stiffness of the reference region 345 in all degrees of freedom, the relative movement due to eigenmodes of the mirror module 340 between the three to six sensors 347 is reduced to a value that ensures a high control bandwidth for positioning the mirror module 340.

[0139] Adjacent to the reference area 345 are tabs 348 for connecting the actuators 349 used for positioning. Alternatively, the actuators 349 can also be connected in pockets 350 formed within the reference area 345, which are shown by dashed lines in Figure 11.

[0140] To optimize the stress distribution and the manufacturability of the stiffening body 341, the transitions between the various regions 342, 344, 345, 348 can, for example, have radii or other contours. The mirror M3 and the receiving region 342 of the stiffening body 341 have cooling channels 351, which can reduce the temperature difference between the mirror M3 and the stiffening body 341. This has the advantage of reducing the displacement of the contact surfaces 352, 353 of the connecting elements 343 between the mirror M3 and the stiffening body 341 due to the different thermal expansion coefficients. The smaller the displacement between the mirror M3 and the stiffening body 341, the less travel has to be compensated by the decoupling element 357, whereby a stiffer structure is possible with the same mechanical load on the levers 266 arranged in the decoupling elements 357 (Figure 8).

[0141] List of reference symbols

[0142] 1 projection exposure system

[0143] 2 Lighting system

[0144] 3 Radiation source

[0145] 4 Lighting optics

[0146] 5 Object field

[0147] 6 Object level

[0148] 7 reticles

[0149] 8 reticle holders

[0150] 9 Reticle displacement drive

[0151] 10 Projection optics

[0152] 11 Image field

[0153] 12 Image plane

[0154] 13 wafers

[0155] 14 wafer holders

[0156] 15 Wafer relocation drive

[0157] 16 EUV radiation

[0158] 17 Collector

[0159] 18 Intermediate focal plane

[0160] 19 Deflecting mirrors

[0161] 20 facet mirrors

[0162] 21 facets

[0163] 22 facet mirrors

[0164] 23 facets

[0165] 30 Optical module

[0166] 31 optical effective area

[0167] 32 stiffening bodies

[0168] 33 Connecting element

[0169] 34 Decoupling area

[0170] 35 Rear Mirror 36 Optical Axis 0 Optical Module

[0171] 41 Connecting element

[0172] 42.1-42.3 Actuator areas

[0173] 43 Contact surface stiffening element

[0174] 44 Contact surface optical element

[0175] 45 displacement sensor

[0176] 46 Optical axis

[0177] 50 Optical Module

[0178] 51 stiffening bodies

[0179] 52 Recording area

[0180] 53 Connecting element

[0181] 54 stiffening ribs

[0182] 55 Reference range

[0183] 56 Area Reference Range

[0184] 57 Sensor positioning mirror module

[0185] 58 tab

[0186] 59 actuators for positioning mirror module

[0187] 60 bag

[0188] 61 cooling channels

[0189] 62 Contact surface stiffening element

[0190] 63 Contact surface optical element

[0191] 64 recording area

[0192] X x-direction y y-direction z z-direction

[0193] 101 Projection exposure system

[0194] 102 Lighting system

[0195] 107 reticles

[0196] 108 reticle holders

[0197] 110 Projection optics 113 Wafer

[0198] 114 wafer holders

[0199] 116 DUV radiation

[0200] 117 optical element

[0201] 118 versions

[0202] 119 lens housings

[0203] M1-M6 mirrors

[0204] 242 Actuator

[0205] 243 Decoupling element

[0206] 244 Contact surface stiffening element

[0207] 245 Contact surface optical element

[0208] 250 connecting element

[0209] 251 Decoupling element

[0210] 252 Actuator

[0211] 253 basic bodies

[0212] 254 Actuator mount

[0213] 255 Kinematics

[0214] 256 levers

[0215] 257 Contact surface to mirror

[0216] 258.1 , Contact surface to stiffening body OKQ O 259 Contact surface actuator to decoupling element

[0217] 260 connecting element

[0218] 263 basic bodies

[0219] 264 Actuator mount

[0220] 265 Kinematics

[0221] 266 levers

[0222] 267 recess

[0223] 270 mirror module

[0224] 271 optical effective area

[0225] 272 stiffening bodies

[0226] 273 Connecting element 274 Actuator

[0227] 276 Rear view mirror

[0228] 277 bulge

[0229] 278 Decoupling element

[0230] 278.1 , Springs O7Q O 279 Arm

[0231] 280.1 ,280 Contact surface stiffening body

[0232] 281 Contact surface optical element

[0233] 282 flange

[0234] 283 Actuator (radially arranged)

[0235] 284 Contact surface connection

[0236] 285 Contact surface lateral surface mirror

[0237] 286 Surface stiffening body

[0238] 290 mirror module

[0239] 291 Actuator

[0240] 292 spring

[0241] 293 connecting element

[0242] 294 connecting element

[0243] 295 Actuator

[0244] 320 mirror module

[0245] 321 Actuator

[0246] 330 mirror module

[0247] 331 Cooling channel

[0248] 332 bulge

[0249] 333 basic bodies

[0250] 334 Decoupling

[0251] 335 cavity

[0252] 336 jetty

[0253] 340 mirror module

[0254] 341 stiffening body

[0255] 342 Mounting area connecting element

[0256] Stiffening ribs

[0257] Reference range

[0258] Area reference range

[0259] Sensor positioning mirror module

[0260] tab

[0261] Actuators for positioning mirror module

[0262] Bag

[0263] Cooling channels

[0264] Contact surface stiffening element

[0265] Contact surface optical element

[0266] Through hole

[0267] Paragraph

[0268] Basic body

[0269] Decoupling element

[0270] Actuator

[0271] Back mirror

Claims

Patent claims 1 . Optical module (30, 40, 50) with an optical element (M3), wherein the optical element (M3) has an optical active surface (31) and is connected to a stiffening body (32) via at least one connecting element (33, 41), wherein the connecting element (33, 41) comprises a decoupling region (34, 42.2, 42.3) by means of which a mechanical decoupling of the stiffening body (32) and the optical element (M3) parallel to the optical active surface (31) is created, characterized in that the material of the stiffening body (32) has an E-modulus that is at least two times higher, preferably three times higher, particularly preferably four times higher than the material of the optical element (M3).

2. Optical module according to claim 1, characterized in that the stiffening body (32) is made of a ceramic material, in particular silicon carbide.

3. Optical module (30, 40, 50) with an optical element (M3), wherein the optical element (M3) has an optical active surface (31) and is connected to a stiffening body (32) via at least one connecting element (33, 41), wherein the connecting element (33, 41) comprises a decoupling region (34, 42.2, 42.3) by means of which a mechanical decoupling of the stiffening body (32) and the optical element (M3) parallel to the optical active surface (31) is created, characterized in that the stiffening body (32) is made of a ceramic material, in particular of silicon carbide.

4. Optical module (30, 40, 50) according to one of claims 1 to 3, characterized in that the at least one connecting element (33, 41) is directed in the direction of an optical Axis (36,46) of the optical module (30) is arranged between the optical element (M3) and the stiffening body (32).

5. Optical module (30,40,50) according to one of claims 1 to 4, characterized in that the at least one connecting element is designed as an actuator (41).

6. Optical module (30,40,50) according to claim 5, characterized in that the actuator (41) comprises at least one region (42.2,42.3) which can be deflected parallel to the optical active surface (31).

7. Optical module (30,40,50) according to claim 6, characterized in that the actuator (41) comprises at least two regions (42.2,42.3) which can be deflected perpendicular to one another and parallel to the optical active surface (31).

8. Optical module (30,40,50) according to one of claims 6 or 7, characterized in that the at least one region (42.2,42.3) is actively controllable.

9. Optical module (30,40,50) according to one of claims 5 to 8, characterized in that the actuator (41) comprises at least one region (42.1) which can be deflected perpendicular to the optical active surface (31).

10. Optical module (30, 40, 50) according to one of claims 6 to 9, characterized in that the at least one region (42.2, 42.3) which can be deflected parallel to the optical active surface (31) is connected to an evaluation unit which is designed to detect mechanical stresses.

11. Optical module (50) according to one of the preceding claims, characterized in that the stiffening body (51) has at least one thickened region (54,55).

12. Optical module (50) according to claim 11, characterized in that at least one thickened region (54) is designed as a stiffening rib.

13. Optical module (50) according to claim 11 or 12, characterized in that at least one thickened region (55) is designed as a reference region on which sensor elements (57) are arranged.

14. Optical module (50) according to one of the preceding claims, characterized in that the optical element (M3) and / or the stiffening body (51) have fluid channels (61).

15. Optical module (50) according to one of the preceding claims, characterized in that the optical element (M3) is a mirror.

16. Optical module (330,340) according to one of the preceding claims, characterized in that the at least one connecting element (41 ,250,260,273,283,293,294,321 ,343) at least one area (242,252,274,291 ) which can be deflected parallel to the optical axis (36,46) - and wherein the at least one connecting element (41 ,250,260,273,283,293,294,321 ,343) at least one area (43,251 ,278,295,257) which is parallel to the optical effective surface (31 ,41 ,271 ) is deflectable, - and wherein the at least one connecting element (41,250,260,273,283,293,294,321,343) as a hybrid connecting element (241 ,273) is trained - and wherein the region (242,252,274,291,258) which can be deflected parallel to the optical axis (36,46) is designed as a passive decoupling element (292) and the region (43,251,278,295,257) which can be deflected parallel to the optical active surface (31,41,271) is designed as an actuator (283,291).

17. Projection exposure system (1, 101) for semiconductor lithography, comprising an optical module (330,340) according to one of the preceding claims.

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