Optical assembly, projection exposure system and method for semiconductor lithography

Abstract

The invention relates to an optical assembly (30) having an optical element (Mx, 117) wherein the optical element (Mx, 117) comprises a main body (31) and wherein at least one actuator (35) for deforming the main body (31) is arranged on a rear side of the main body (31) and wherein the at least one actuator (35) is connected to the rear side of the main body (33) at a first connection surface and to a back plate (36) at a second connection surface, wherein the back plate (36) is mounted only by the actuator (35).

Description

[0001] Related Applications

[0002] This application claims the priority of German patent application DE 10 2022 116 700.3 filed on July 5, 2022, the entire contents of which are incorporated herein by reference. Technical Field

[0003] The invention relates to an optical component, a projection exposure apparatus for semiconductor lithography and a method for producing an optical component. Background Art

[0004] In projection exposure equipment for semiconductor lithography, a lithography method starting with a mask as a template is used to image microscopically small structures on a wafer coated with photoresist in a greatly reduced manner. In subsequent development and further processing steps, the desired structures such as memory or logic elements are created on the wafer, which is subsequently divided into individual chips for use in electronic devices.

[0005] Due to the extremely small structures to be produced, which go down to the nanometer range, extreme requirements are placed on the optical units of the projection exposure apparatus and therefore on the optical elements used. In addition, aberrations frequently caused by fluctuating environmental conditions, such as temperature fluctuations in the optical unit, occur regularly during the operation of the corresponding apparatus. Usually, this problem is solved by the optical elements used, such as lens elements or mirrors, which have a movable or deformable embodiment in order to be able to correct the above-mentioned aberrations during the operation of the apparatus. For this purpose, mechanical actuators are usually used, which can be suitable, for example, for deforming the surface of the optical element for imaging purposes, the so-called optically effective surface, in a targeted manner. This deformation can be achieved from the back side of the body of the corresponding optical element. According to the prior art, the mechanical action of the actuator is usually made possible by means of an actuator on a back plate that is mechanically supported in the rear region of the body. When the optical element is actuated, this back plate, in particular its mounting, in turn causes parasitic deformations. The requirements on the manufacturing and assembly tolerances of the actuator and the resulting back plate can only be met with great expense. Summary of the invention

[0006] The problem addressed by the invention is to specify an optical assembly and a projection exposure apparatus in which the adverse effects caused by a back plate connected to an actuator are reduced compared to the prior art. Another problem addressed by the invention is to specify a method for producing such an assembly.

[0007] This object is achieved by a device and a method having the features of the independent claims. The dependent claims relate to advantageous developments and variants of the invention.

[0008] The optical assembly according to the invention comprises an optical element, wherein the optical element comprises a body and wherein at least one actuator for deforming the body is arranged on the back side of the body. In this case, at least two actuators are connected to the back side of the body at a first connection surface and to a back plate at a second connection surface, wherein the back plate is mounted only via the actuators.

[0009] In other words, the only connection between the backplate and the "stationary environment" consists in at least two actuators or generally a plurality of actuators. In particular, the actuators can be solid-state actuators, for example piezoelectric actuators, or magnetostrictive, electrostrictive or thermal actuators. Therefore, a uniform (e.g. thermally induced) expansion of all solid-state actuators perpendicular to the connection surface only leads to a displacement of the backplate and has no influence on the shape and attitude of the optically active surface. As is known, actuator leakage generally occurs in particular during the switch-on process, i.e. the actuator does not stabilize immediately after switching on, but moves towards the desired state. However, since the actuators generally behave similarly in this process, this effect is largely compensated by the free backplate, or no undesired deformations occur.

[0010] Furthermore, even a constant temperature gradient across the optical assembly will only result in a tilting of the backplate but no displacement or deformation of the optically active surface.

[0011] In addition to malfunctions caused by uniform variations of all actuators, the solution according to the invention also allows parasitic effects from the bonding technology to be suppressed. In particular, this includes thermally induced or moisture induced variations in the volume of the bonding substance in a perpendicular direction relative to the connection surface. In this context, a bonding substance is understood to mean any substance that establishes the bond between the actuator and the adjacent component part (in this case the body and the backplate). Examples for this purpose are adhesives, glass frits, solders, solder fillers, reactive layers made by reactive bonding, etc.

[0012] Since many actuators not only cause a desired elongation in the actuation direction, but also cause changes in the actuator geometry in the lateral direction which may lead to parasitic deformations, in a particularly preferred embodiment, at least one separation element for lateral separation purposes is arranged between the actuator and at least the body and / or the backplate.

[0013] This lateral separation also makes it possible to compensate for thermal expansion of the joining mass in the lateral directions and moisture-induced changes in geometry in these directions; similar statements apply to pressure-induced changes in volume.

[0014] In an advantageous variant of the invention, the back side of the body has at least one flat section. The resulting flat joining point allows the use of simple manufacturing methods with good roughness and very good form tolerances or flatness. Grinding, lapping, flat honing and flat polishing should be mentioned in particular here. Thus, joining methods can be used which are only able to compensate for small mechanical tolerances. In particular, these include the aforementioned joining methods.

[0015] In particular, the body may have a thickness that varies over its lateral extent. For example, installation space requirements may necessitate making the body locally thinner. In this case, the embodiments of the corresponding actuator and / or backplate may need to be adjusted accordingly.

[0016] The back plate may also have a thickness that varies over its lateral extent. For example, the back plate may have an increased thickness in its region near the edge when compared to the inner region in order to compensate for the loss of stiffness in the back plate caused by being near the edge.

[0017] In order to save installation space, it may also be advantageous for the back plate and / or the body to have a cutout, in which the actuator is at least partially arranged.

[0018] Especially in the case of strongly curved mirrors as optical elements, it may be advantageous if the back side of the body has a plurality of flat sections which do not extend parallel to one another. This allows a limited variation of the overall thickness of the body and thus also a controllable variation of its mechanical properties within its range.

[0019] Particularly in this case it is advantageous if a plurality of flat backing plates are present, each aligned parallel to the flat portion.

[0020] In an advantageous embodiment of the invention, the surface of the backplate facing the body and the surface of the backplate facing away from the body extend in each case at a constant distance from the back side of the body. This can, for example, produce a backplate of constant thickness. This variant is also conceivable for the case where the optical element is implemented as a spherical mirror with a body of constant thickness. In this case, the backplate will be a substantially similar reflection of the body.

[0021] In particular, the invention includes the case where the effective direction of at least one actuator is formed perpendicular to the connecting surface of the actuator to the body. However, it can also be applied to the case where the effective direction of at least one of the actuators is formed perpendicular to the optically effective surface.

[0022] In particular in the case where the body is not formed with a uniform thickness, it may be advantageous to form at least two actuators with different characteristics. As a result, laterally different mechanical properties of the body, such as stiffness, can be taken into account. This allows the actuators utilized to be adapted to the mechanical conditions of the body at the respective location, for example with regard to their inherent stiffness, their travel or the maximum force they can exert.

[0023] As mentioned, the optical element can be a mirror, in particular a multilayer mirror. Likewise, the mirror can be a concave mirror with a radius of curvature of the order of 180 mm-260 mm, in particular 220 mm. Such mirrors are used to fold the beam path, in particular in DUV projection exposure equipment.

[0024] In an advantageous variant of the invention, the back plate has a lower stiffness than the body and can be provided with at least one sensor, for example. The sensor can be a strain or temperature sensor.

[0025] It is also conceivable that both the back plate and the main body are equipped with additional sensor systems or with temperature control elements, such as cooling channels.

[0026] As a result of the fact that the backplate can have a lower stiffness than the body, as described above, it is possible to set a greater deformation of the backplate compared to the deformation of the active surface when controlling the actuator system in order to obtain a desired deformation of the optically active surface. This increased deformation has a positive effect in particular on the signal-to-noise ratio of the strain measurement of the backplate, for example using a fiber Bragg grating sensor. In the case where the mechanical properties of the actuator, the body and the backplate are known, the corresponding deformation of the optically active surface can then be deduced from the local deformation of the backplate based on the model.

[0027] In another embodiment, the properties (thermal expansion coefficient and thickness of the actuators used) can be chosen so that a defined temperature distribution (e.g. a thermal main mode of the system) does not lead to parasitic deformations or displacements of the optically active surface. Such parasitic deformations may be due, for example, to the fact that the heating of the actuators affects their efficiency, i.e. their respective mechanical response to changes in the control voltage. Furthermore, there is the possibility of parasitic deformations arising purely due to the usual thermal expansion or contraction of the materials involved. An appropriate choice of the materials used and / or the design of the respective geometries provides the possibility of achieving at least partial mutual compensation of the aforementioned effects.

[0028] As already mentioned, the invention is particularly suitable for use in projection exposure apparatuses for semiconductor lithography.

[0029] The method according to the invention for producing a corresponding optical component comprises the following method steps:

[0030] - connect the actuator to the back plate,

[0031] - determining the surface area tolerance of the connection surface of the actuator facing away from the back plate,

[0032] - machining the connecting surface,

[0033] - repeat the first two steps until the surface area tolerance is below a predetermined threshold,

[0034] - Connecting said actuator to the body.

[0035] In this process, the optically active surface can be machined after assembly of the actuator.The method can be carried out particularly advantageously if a plurality of actuators are arranged on a back plate, the connection surfaces of which can be machined together. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Exemplary embodiments and variants of the present invention are explained in detail below based on the accompanying drawings, in which:

[0037] Figure 1 schematically shows a meridional plane cross section of a projection exposure apparatus for EUV projection lithography,

[0038] Figure 2 schematically shows a meridional plane section of a projection exposure apparatus for DUV projection lithography,

[0039] Figure 3 A schematic diagram showing a first embodiment of the present invention,

[0040] Figure 4 Another embodiment of the present invention is shown.

[0041] Figure 5 Another embodiment of the present invention is shown.

[0042] Figure 6 Another embodiment of the present invention is shown.

[0043] Figure 7a , 7b Another embodiment of the present invention is shown.

[0044] Figure 8a-8c shows a detailed diagram of another embodiment of the present invention,

[0045] Fig. 9 shows a schematic representation of a possible separation element,

[0046] Fig.10 shows variations for designing the backplane, and

[0047] Fig.11 A flow chart showing a production method according to the present invention is shown. DETAILED DESCRIPTION

[0048] The basic components of the microlithography projection exposure apparatus 1 are first referred to Figure 1 This is described below by way of example.The description of the basic construction of the projection exposure apparatus 1 and its constituent parts is not to be interpreted as limiting here.

[0049] An embodiment of the illumination system 2 of the projection exposure apparatus 1 has, in addition to the radiation source 3, an illumination optical unit 4 for illuminating an object field 5 in an object plane 6. In an alternative embodiment, the light source 3 can also be arranged as a module separate from the rest of the illumination system. In this case, the illumination system does not comprise the light source 3.

[0050] 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 is displaceable by a reticle displacement drive 9, in particular in a scanning direction.

[0051] For the purpose of explanation, Figure 1 A Cartesian xyz coordinate system is depicted in FIG. The x direction extends perpendicular to the plane of the drawing into the drawing. The y direction extends horizontally and the z direction extends vertically. The scanning direction is Figure 1 The z direction extends perpendicular to the object plane 6.

[0052] The projection exposure apparatus 1 comprises a projection optical unit 10. The projection optical unit 10 serves to image the object field 5 into an image field 11 in an image plane 12. The image plane 12 extends parallel to the object plane 6. Alternatively, angles between the object plane 6 and the image plane 12 other than 0° are also possible.

[0053] The structures on the reticle 7 are imaged onto a photosensitive layer of a wafer 13 arranged in the region of an image field 11 in an image plane 12. The wafer 13 is held by a wafer holder 14. The wafer holder 14 can be displaced, in particular in the y direction, by a wafer displacement drive 15. The displacement of the reticle 7, firstly by the reticle displacement drive 9, and secondly by the wafer 13, can be effected synchronously with one another.

[0054] The radiation source 3 is an EUV radiation source. The radiation source 3 in particular emits EUV radiation 16, which is also referred to as used radiation, illumination radiation or illumination light in the following. In particular, the used radiation has a wavelength in the range between 5 nm and 30 nm. The radiation source 3 may be a plasma source, such as an LPP (laser produced plasma) source or a GDPP (gas discharge produced plasma) source. It may also be a synchrotron-based radiation source. The radiation source 3 may be a free electron laser (FEL).

[0055] The illumination radiation 16 emitted from the radiation source 3 is focused by a collector 17. The collector 17 may be a collector having one or more elliptical and / or hyperbolic reflective surfaces. The illumination radiation 16 may be incident on at least one reflective surface of the collector 17 at grazing incidence (GI) (i.e. at an angle of incidence greater than 45° relative to the normal direction of the reflector surface) or at normal incidence (NI) (i.e. at an angle of incidence less than 45°). The collector 17 may firstly be constructed and / or coated to optimize its reflectivity for the radiation used and secondly to suppress extraneous light.

[0056] Downstream of the collector 17, the illumination radiation 16 propagates through an intermediate focus in an intermediate focal plane 18. The intermediate focal plane 18 may constitute a separation between a radiation source module, which comprises the radiation source 3 and the collector 17, and the illumination optical unit 4.

[0057] The illumination optical unit 4 comprises a deflection mirror 19 and a first facet mirror 20 arranged downstream of the deflection mirror 19 in the beam path. The deflection mirror 19 can be a plane deflection mirror or, alternatively, a mirror with a beam influencing effect that goes beyond a pure deflection effect. In an alternative or in addition thereto, the deflection mirror 19 can be embodied as a spectral filter, which separates the used light wavelengths of the illumination radiation 16 from extraneous light at wavelengths deviating therefrom. If the first facet mirror 20 is arranged in a plane of the illumination optical unit 4 which is optically conjugate to the object plane 6 as a field plane, this facet mirror 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 hereinafter as field facets. Figure 1 Only some of the facets 21 are shown by way of example.

[0058] The first facet 21 can be implemented as a macro facet, in particular as a rectangular facet or as a facet with an arcuate edge contour or an edge contour of a part of a circle. The first facet 21 can be implemented as a plane facet or alternatively as a convexly or concavely curved facet.

[0059] As is known, for example, from DE 10 2008 009 600 A1, the first facets 21 themselves can also each consist of a plurality of individual mirrors, in particular a plurality of micromirrors. The first facet mirrors 20 can in particular be designed as a microelectromechanical system (MEMS system). For details, reference is made to DE 10 2008 009 600 A1.

[0060] Between the collector 17 and the deflection mirror 19 the illuminating radiation 16 extends horizontally, ie in the y-direction.

[0061] In the beam path of the illumination optical unit 4, the second facet reflector 22 is arranged downstream of the first facet reflector 20. If the second facet reflector 22 is arranged in the pupil plane of the illumination optical unit 4, it is also called a pupil facet reflector. The second facet reflector 22 can also be arranged at a distance from the pupil plane of the illumination optical unit 4. In this case, the combination of the first facet reflector 20 and the second facet reflector 22 is also called a specular reflector. Specular reflectors are known from US 2006 / 0132747 A1, EP 1 614 008 B1 and US 6,573,978.

[0062] 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 called pupil facets.

[0063] The second facets 23 can likewise be macroscopic facets which can, for example, have circular, rectangular or hexagonal edges, or alternatively facets consisting of micromirrors. In this respect, reference is likewise made to DE 10 2008 009 600 A1.

[0064] The second facet 23 may have a planar reflective surface, or alternatively, a convexly or concavely curved reflective surface.

[0065] The illumination optical unit 4 thus forms a two-facet system. This basic principle is also known as a fly's eye condenser (fly's eye integrator).

[0066] It may be advantageous to arrange the second facet mirror 22 imprecisely in a plane optically conjugate to the pupil plane of the projection optical unit 10. In particular, the pupil facet mirror 22 may be arranged tilted relative to the pupil plane of the projection optical unit 10, as described, for example, in DE 10 2017 220 586 A1.

[0067] By means 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-shaping mirror or in fact the last mirror in the beam path upstream of the object field 5 for the illumination radiation 16 .

[0068] In a further embodiment (not shown) of the illumination optical unit 4, a transfer optical unit, which in particular contributes to the imaging of the first facet 21 into the object field 5, can be arranged in the beam path between the second facet mirror 22 and the object field 5. The transfer optical unit can have exactly one mirror, or alternatively two or more mirrors, which are arranged one after the other in the beam path of the illumination optical unit 4. The transfer optical unit can in particular comprise one or two normal incidence mirrors (NI mirrors) and / or one or two grazing incidence mirrors (GI mirrors).

[0069] exist Figure 1 In the embodiment shown in , the illumination optical unit 4 has exactly three mirrors downstream of the collector 17 , in particular a deflection mirror 19 , a field facet mirror 20 and a pupil facet mirror 22 .

[0070] In another embodiment of the illumination optical unit 4 , the deflection mirror 19 can also be omitted and the illumination optical unit 4 can therefore then have exactly two mirrors downstream of the collector 17 , specifically a first facet mirror 20 and a second facet mirror 22 .

[0071] The imaging of the first facet 21 into the object plane 6 by the second facet 23 or using the second facet 23 and the transfer optics is usually only an approximate imaging.

[0072] The projection optical unit 10 comprises a plurality of mirrors Mi which are numbered consecutively according to their arrangement in the beam path of the projection exposure apparatus 1 .

[0073] exist Figure 1 In the example shown, the projection optical unit 10 comprises six mirrors M1 to M6. Alternatives with four, eight, ten, twelve or any other number of mirrors Mi are also possible. The penultimate mirror M5 and the last mirror M6 each have a passage opening for the illumination radiation 16. The projection optical unit 10 is a doubly shielded optical unit. The projection optical unit 10 has an image-side numerical aperture greater than 0.5 and also greater than 0.6 and can be, for example, 0.7 or 0.75.

[0074] The reflective surface of the reflector Mi can be embodied as a free-form surface without an axis of rotational symmetry. Alternatively, the reflective surface of the reflector Mi can be designed as an aspherical surface with exactly one axis of rotational symmetry of the shape of the reflective surface. Just like the reflectors of the illumination optical unit 4, the reflector Mi can have a highly reflective coating for the illumination radiation 16. These coatings can be designed as multilayer coatings, in particular with alternating layers of molybdenum and silicon.

[0075] The projection optical unit 10 has a large object-image offset in the y direction between the y coordinate of the center of the object field 5 and the y coordinate of the center of the image field 11. This object-image offset in the y direction can have approximately the same magnitude as the z distance between the object plane 6 and the image plane 12.

[0076] In particular, the projection optical unit 10 can have a deformable design. In particular, it has different imaging ratios β in the x-direction and in the y-direction. x , β y The two imaging ratios β of the projection optical unit 10 x , β y Preferably, (β x , β y) = (+ / -0.25, + / -0.125). A positive imaging ratio β means imaging without image inversion. A negative sign of the imaging ratio β means imaging with image inversion.

[0077] The projection optical unit 10 thus results in a reduction in size in the x-direction, ie in a direction perpendicular to the scanning direction, by a ratio of 4:1.

[0078] The projection optical unit 10 results in a reduction of the dimensions in the y-direction, ie in the scanning direction, by 8:1.

[0079] Other imaging ratios are likewise possible. Imaging ratios with the same sign and the same absolute value in the x-direction and the y-direction, for example with an absolute value of 0.125 or 0.25, are also possible.

[0080] The number of intermediate image planes in the x-direction and in the y-direction in the beam path between the object field 5 and the image field 11 may be the same or may differ depending on the embodiment of the projection optical unit 10. Examples of projection optical units with a different number of such intermediate images in the x-direction and in the y-direction are known from US 2018 / 0074303 A1.

[0081] In each case, one of the pupil facets 23 is assigned to exactly one of the field facets 21 for the purpose of forming a corresponding illumination channel for illuminating the object field 5. This can lead in particular to an illumination according to the Köhler principle. The far field is decomposed into a plurality of object fields 5 by means of the field facets 21. The field facets 21 generate a plurality of images of the intermediate focus on the pupil facets 23 respectively assigned thereto.

[0082] The field facets 21 are imaged onto the reticle 7 in a mutually overlapping manner with the respective assigned pupil facets 23 in order to illuminate the object field 5. The illumination of the object field 5 is in particular as homogeneous as possible. It preferably has a homogeneity error of less than 2%. Field homogeneity can be achieved by overlaying different illumination channels.

[0083] The illumination of the entrance pupil of the projection optical unit 10 can be geometrically defined by the arrangement of the pupil facets. The intensity distribution in the entrance pupil of the projection optical unit 10 can be set by selecting the illumination channels, in particular the subset of pupil facets that guide the light. This intensity distribution is also called an illumination setting.

[0084] An equally preferred pupil homogeneity in the region of the portion of the illumination pupil of the illumination optical unit 4 which is illuminated in a defined manner can be achieved by redistribution of the illumination channels.

[0085] Further aspects and details of the illumination of the object field 5 and in particular the entrance pupil of the projection optical unit 10 are described below.

[0086] The projection optical unit 10 may in particular have a concentric entrance pupil. The latter may be accessible. It may also be inaccessible.

[0087] The entrance pupil of the projection optical unit 10 cannot usually be accurately illuminated using the pupil facet mirror 22. In the case of an imaging of the projection optical unit 10 with the center of the pupil facet mirror 22 telecentrically imaged onto the wafer 13, the aperture rays usually do not intersect at a single point. However, a region can be found in which the spacing of the aperture rays determined in pairs becomes minimal. This region represents the entrance pupil or a region in real space conjugate therewith. In particular, this region exhibits a finite curvature.

[0088] It may be the case that the projection optical unit 10 has different positions of the entrance pupil for the tangential beam path and for the sagittal beam path. In this case, an imaging element, in particular an optical component of the transmission optical unit, should be provided between the second facet mirror 22 and the reticle 7. With the aid of this optical element, different positions of the tangential entrance pupil and the sagittal entrance pupil can be taken into account.

[0089] exist Figure 1 In the arrangement of the components of the illumination optical unit 4 shown, the pupil facet mirror 22 is arranged in a region conjugate to the entrance pupil of the projection optical unit 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 the arrangement plane defined by the deflection mirror 19.

[0090] The first facet mirror 20 is arranged to be inclined relative to an arrangement plane defined by the second facet mirror 22 .

[0091] Figure 2 A meridional plane section is schematically shown of a further projection exposure apparatus 101 for DUV projection lithography, in which the present invention can likewise be used.

[0092] The construction and imaging principle of the projection exposure device 101 are similar to Figure 1 The same components are provided by Figure 1 Reference numerals indicate values ​​increased by 100; therefore, Figure 2 The reference numerals in the figures start from 101.

[0093] With Figure 1Compared to the EUV projection exposure apparatus 1 described in the foregoing, a refractive, diffractive and / or reflective optical element 117 (e.g. a lens element, a reflector, a prism, a terminal plate, etc.) can be used for imaging or for illumination in the DUV projection exposure apparatus 101, since the longer wavelength of the DUV radiation 116 used as the used light is in the range of 100 nm to 300 nm, in particular in the order of 193 nm. In this case, the projection exposure apparatus 101 essentially comprises an illumination system 102, a mask master holder 108, a wafer holder 114 and a projection lens 110, the mask master holder 108 being used for receiving and precisely positioning a mask master 107 provided with a structure, the mask master determining the subsequent structure on a wafer 113, the wafer holder 114 being used for holding, moving and precisely positioning the same wafer 113, and the projection lens 110 having a plurality of optical elements 117, which are held in a lens housing 119 of the projection lens 110 by means of a mounting 118.

[0094] The illumination system 102 provides the DUV radiation 116 required for imaging the reticle 107 on the wafer 113. Lasers, plasma sources, etc. can be used as sources of this radiation 116. The radiation 116 is shaped in the illumination system 102 with the aid of optical elements so that when the DUV radiation 116 is incident on the reticle 107, the DUV radiation 116 has the desired characteristics regarding the diameter, polarization, shape, etc. of the wavefront.

[0095] The structure of the downstream projection optical unit 110 with the lens housing 119 is essentially the same as that of the downstream projection optical unit 110 except for the additional use of a refractive optical element 117 (such as a lens element, a prism, a terminal plate). Figure 1 The structure described in is no different and therefore will not be described in more detail.

[0096] In the schematic diagram, Figure 3 A first embodiment of the invention is shown, in which an optical assembly 30 is depicted. The latter comprises a mirror MX 117 designed and capable of being used Figure 1 and Figure 2 , an actuator 35 and a support structure designed as a back plate 36 of one of the projection exposure apparatuses 1, 101 explained in . The reflector Mx, 117 comprises a body 31 with an optically active surface 32, wherein the body 31 is mounted on a bearing 34, for example a frame of the projection exposure apparatus 1, 101. The actuator 35 is arranged between the body 31 and the back plate 36 and is connected to the body 31 on the back side 33 of the body 31 opposite to the optically active surface 32. The actuator 35 can be connected to the body 31 and the back plate 36 by an adhesive connection not shown separately in the figure, wherein other types of connection, such as adhesive bonding or welding, can also be applied.

[0097] The actuators 35 are controlled by a controller (also not shown in the figure) in such a way that the deflection of the actuators 35 causes a deformation of the optically active surface 32. The back plate 36 is deformed due to the different degrees of deflection of the actuators 35 and thus sets a deformation of the body 31, which depends on the ratio of the stiffness of the body 31 to the stiffness of the back plate 36 and thus sets a deformation of the optically active surface 32. Therefore, some actuators 35 hold the back plate firmly in its position, whereby another part of the actuator 35 can be supported on the back plate 36, thus causing a deformation. In this case, the back plate 36 is only mounted by the actuators 35 and is therefore not connected to the frame or the body 31 of the mirror Mx, 117 or any other part. This is advantageous because uniform effects (e.g. temperature rise or drift in the control of the actuators 35) acting in the same way on all actuators 35 have no effect on the optically active surface 32 and only result in a displacement of the free back plate 36. In the figure, three strain sensors 49 for measuring the deformation of the back plate 37 . 3 are depicted by way of example on the back plate 37 . 3 .

[0098] Figure 4 Another embodiment of the present invention is shown, in which a mirror MX, 117 is designed and can be used for Figure 1 and Figure 2 1, 101. The optical assembly 30 of the optical element of one of the projection exposure apparatuses 1, 101 explained in . The reflector Mx, 117 comprises a body 31 having an optically active surface 32 formed concavely. The optical assembly 30 further comprises a back plate 36 and an actuator 35, which is arranged between the back plate 36 and the back side 33 of the body 31. The back side 33 and the back plate 36 have a flat embodiment. This is advantageous because the actuator 35 is also arranged in a plane and can be post-processed after the initial connection to the back plate 36 in order to achieve an optimal adaptation to the back side 33. As a result, the adhesive gap of the adhesive connection between the actuator 35 and the body 31 can be configured in such a way that the influence of the adhesive on the connection stiffness is negligible. Laterally varying material thicknesses of the body 31 can be compensated by differently designed actuators and control of the actuator 35.

[0099] Figure 5 Another embodiment of the present invention is shown, in which a mirror MX, 117 is designed and can be used for Figure 1 and Figure 2 1, 101. The optical assembly 30 is an optical element of one of the projection exposure apparatuses 1, 101 explained in the foregoing. The reflector Mx, 117 comprises a body 31 having an optically active surface 32 formed concavely. The optical assembly 30 further comprises three back plates 37.1, 37.2, 37.3 and an actuator 35 arranged between the back plates 37.1, 37.2, 37.3 and the back side 33 of the body 31. The body 31 is designed so that it is in contact with the back plate 37.1, 37.2, 37.3. Figure 4Compared to the embodiment explained in FIG. 1 , the distance difference between the back side 33 of the body 31 in the form of three flat surfaces and the optically effective surface 32 is minimized. Figure 4 As explained in , the back plates 37 . 1 , 37 . 2 , 37 . 3 are flat and can therefore be easily produced, and the actuator 35 can be in the form of a standard actuator.

[0100] Figure 6 Another embodiment of the present invention is shown, in which a mirror MX, 117 is designed and can be used for Figure 1 and Figure 2 The optical assembly 30 of the optical element of one of the projection exposure apparatuses 1, 101 explained in the above. The reflector Mx, 117 comprises a body 31 having an optically active surface 32 formed concavely. Figure 5 Unlike the body depicted in , the body 31 in the illustrated embodiment has a constant thickness, which results in a convex or spherical back side 33. The optical component 30 also includes a concave back plate 39, which corresponds to the geometry of the optically active surface 32 and the body 31. The actuator 35 includes a spherical engagement surface 38 on both sides in order to ensure a constant thickness adhesive gap in the adhesive connection. Having a back plate 39 and a body 31 with a constant thickness is advantageous because the components have a constant stiffness, whereby all actuators need to apply a comparable force in order to cause the same deformation of the optically active surface 32. This increases the number of similar components, thereby reducing production costs.

[0101] Figure 7a and 7b Another embodiment of the invention is shown in two operating states, wherein a device having a reflector Mx, 117 designed as a reflector and capable of being used for Figure 1 and Figure 2 The optical assembly 30 of the optical element in one of the projection exposure apparatuses 1, 101 explained in the above. The mirror Mx, 117 comprises a body 31 having a flat optically effective surface 32. Furthermore, the optical assembly 30 comprises four back plates 40.1, 40.2, 40.3, 40.4. Two respective shear actuators 41 which perform a shearing movement parallel to the optically effective surface 32 when a voltage is applied are arranged between each back plate 40.1, 40.2, 40.3, 40.4 and the back side 33 of the body 31.

[0102] in this case, Figure 7a The so-called zero state is shown, in which the optically active surface 32 of the body 31 is not deformed, i.e. corresponds to its target surface shape. The shear actuator 41 deflects from the no-voltage zero position, with the result that the body 31 is deformed in one direction out of its zero position according to the applied voltage. This is advantageous because the optically active surface 32 can be completely processed before the assembly of the actuator 41.

[0103] Figure 7b The same optical component 30 is shown in a deflected operating state. The actuator 41 arranged between the two central backplates 40.2, 40.3 and the body 31 is deflected and causes a deformation of the body 31 and thus of the optically active surface 32. Although the two actuators of the backplates 40.2, 40.3 are in Figure 7b 1 , 40.2, 40.3, 40.4 are deflected relative to each other, but it may also be the case that only one actuator 41 of a back plate 40.1 , 40.2, 40.3, 40.4 is deflected or that corresponding actuators 41 from two adjacently arranged back plates 40.1 , 40.2, 40.3, 40.4 are deflected.

[0104] Figure 8a , 8b 8 c show different embodiments of actuators 42 , 44 , 46 which are deflected parallel to the optically active surface 32 .

[0105] Figure 8a An optical element embodied as a reflector Mx, 117 is shown, which has an actuator 42 on the left, whose end face 43 is connected to the back side 33 of the body 31. The electric field of the actuator 42 is formed perpendicularly to the optically active surface 32, while the deflection extends parallel to the optically active surface 32, as already explained above. In contrast, the actuator 44 on the right side of the reflector Mx is connected to the body 31 via its longitudinal side 45. The actuator 44 is designed as a stack actuator with a piezoelectric material, wherein Figure 8a The electric field and the deflection in the embodiment depicted in FIG. 5 are formed parallel to the optically active surface 32 .

[0106] Figure 8b The schematic structure of a bimorph actuator 46 is schematically shown, comprising a first actuator layer 47 and a second actuator layer 48. The two actuator layers 47, 48 can deflect in opposite directions (by Figure 8b ), and thus one actuator layer 47 expands while the other actuator layer 48 contracts, thereby causing deformation in the actuator 46.

[0107] Figure 8c An optical element designed as a reflector Mx, 117 is shown, which has Figure 8b . It is connected to the back side 33 of the body 31 by an adhesive connection, and the body 31 deforms in the event of a deflection of the bimorph actuator. The function is similar to that of an actuator arranged in a surface normal manner, which uses deformations caused by secondary effects of geometric changes perpendicular to the main deflection. However, it differs in that the main contribution to the deformation is caused by the deformation of the bimorph actuator 46 itself, as shown in FIG. Figure 8brather than by contraction of the material in the body 31 due to changes in the geometry of the actuator.

[0108] Fig. 9 An advantageous variant of the invention is shown, in which a separation element 120 is used. In this case, the body 31 is connected to the free back plate 36 via the actuator 35 in the manner already described. In the example shown, the mechanical separation in the region of the connection of the actuator 35 to the body 31 is achieved by a separation element embodied as a free cutout 120 in the body 31. If, for example, the actuator 35 is embodied as a cylindrical solid-state actuator, the separation element 120 can be realized as an all-round annular groove. In the example shown, the separation element 120 is formed only in the body 31. It goes without saying that corresponding measures can also be envisaged for the back plate 36.

[0109] Fig.10 An embodiment of the invention is shown in which the back plate 36' is designed such that its thickness varies laterally. Furthermore, the back plate 36' has a cutout 121 in which the actuator 35 is partially arranged. By means of the laterally varying thickness of the back plate 36' it is achieved that the stiffness of the back plate 31' is comparable to that in the inner region, even in its edge region. Furthermore, a certain amount of installation space can be saved by arranging the actuator 35 in the cutout 121. In this case, Fig.10 The measures shown in do not necessarily need to be used in combination; of course, it is also conceivable in each case to use only a backing plate with a laterally varying thickness or a backing plate with cutouts.

[0110] Fig.11 A possible method for producing an optical component according to the invention is described.

[0111] In a first method step 51 , the actuator is connected to the back plate.

[0112] In a second method step 52 , the surface area tolerance of the connection surface of the actuator facing away from the back plate is determined.

[0113] In a third method step 53 , the connecting surface is processed.

[0114] In a fourth method step 54 the two preceding steps are repeated until the surface area tolerance is below a predetermined threshold value.

[0115] In a fifth method step 55 , the actuator is connected to the body.

[0116] Reference numerals list

[0117] 1Projection exposure equipment

[0118] 2 Lighting System

[0119] 3 Radiation Sources

[0120] 4 Illumination optical unit

[0121] 5. Physical Field

[0122] 6 Object Plane

[0123] 7. Mask Master

[0124] 8 Mask Master Holder

[0125] 9Mask displacement driver

[0126] 10 Projection optics unit

[0127] 11 Image Field

[0128] 12 Image plane

[0129] 13 Chip

[0130] 14 Wafer Holder

[0131] 15 Chip displacement driver

[0132] 16 EUV Radiation

[0133] 17 Collector

[0134] 18 Intermediate focal plane

[0135] 19 Deflecting mirror

[0136] 20 Faceted Mirrors

[0137] 21 Facets

[0138] 22 Faceted Mirrors

[0139] 23 Facets

[0140] 30 Optical components

[0141] 31 Subject

[0142] 32 Optically effective surface

[0143] 33 Back side of the body

[0144] 34 Main bearing

[0145] 35 Actuator

[0146] 36, 36' backboard

[0147] 37.1-37.3 Split back panel

[0148] 38 Spherical joint surface

[0149] 39 Back Panel

[0150] 40.1-40.4 Split back panel

[0151] 41 Shear actuator

[0152] 42 Shear actuator

[0153] 43 End face

[0154] 44 Conventional Actuator

[0155] 45 longitudinal side

[0156] 46 Dual-Chip Actuator

[0157] 47 Actuator layer 1

[0158] 48 Actuator layer 2

[0159] 49 Strain Sensor

[0160] 51 Method Step 1

[0161] 52 Method Step 2

[0162] 53 Method Step 3

[0163] 54 Method Step 4

[0164] 55 Method Step 5

[0165] 101 Projection Exposure Equipment

[0166] 102 Lighting System

[0167] 107 Mask

[0168] 108 Mask Holder

[0169] 110 Projection Optics Unit

[0170] 113 chip

[0171] 114 Wafer Holder

[0172] 116 DUV radiation

[0173] 117 Optical Components

[0174] 118 support

[0175] 119 lens housing

[0176] M1-M6 Reflector

[0177] 120 annular groove

[0178] 121 incision

Claims

1. An optical assembly (30) having an optical element (117), wherein the optical element (Mx, 117) comprises a body (31), and wherein at least two actuators (35) for deforming the body (31) are arranged on the back side of the body (31), and wherein the at least two actuators (35) are connected to the back side of the body (33) at a first connection surface and to a back plate (36) at a second connection surface, wherein the back plate (36) is mounted only by means of the actuators (35), in The back plate (36') has a thickness that varies over its lateral extent.

2. The optical component (30) according to claim 1, in At least one separation element for lateral separation purposes is arranged between the actuator (35) and at least the body (31) and / or the back plate (36).

3. The optical component (30) according to claim 1 or 2, in The back side of the main body (33) has at least one flat portion.

4. The optical component (30) according to any one of claims 1 to 3, in The body (31) has a thickness that varies over its lateral extent.

5. The optical component (30) according to any one of claims 1 to 4, in The back plate (36') and / or the body (31) has a cutout (121), and the actuator (35) is at least partially arranged in the cutout (121).

6. The optical component (30) according to any one of the preceding claims, in The back side of the main body (33) has a plurality of flat portions extending non-parallel to each other.

7. The optical component (30) according to claim 6, in There are a plurality of planar backing plates (36), each backing plate being aligned parallel to the planar portion.

8. The optical component (30) according to any one of the preceding claims, in The effective direction of at least one of the actuators (35) is formed perpendicular to a connection surface between the actuator (35) and the body (31).

9. The optical component (30) according to any one of the preceding claims, in The effective direction of at least one of the actuators (35) is formed perpendicular to the optically effective surface (32).

10. The optical component (30) according to any one of the preceding claims, in At least two actuators (35) are formed to have different characteristics.

11. The optical component (30) according to any one of the preceding claims, in The optical element (Mx, 117) is a mirror, in particular a multilayer mirror.

12. The optical component (30) according to claim 11, in The reflector (Mx, 117) is a concave mirror, and its radius of curvature is 180 mm-260 mm, in particular, in the order of 220 mm.

13. The optical component (30) according to any one of the preceding claims, in The back plate (36) has lower rigidity than the main body (31).

14. The optical component (30) according to any one of the preceding claims, in The back plate (36) is provided with at least one sensor (49).

15. The optical component (30) according to claim 14, in The at least one sensor (49) is a strain or temperature sensor (49).

16. An optical assembly (30) having an optical element (117), wherein the optical element (Mx, 117) comprises a body (31), and wherein at least two actuators (35) for deforming the body (31) are arranged on the back side of the body (31), and wherein the at least two actuators (35) are connected to the back side of the body (33) at a first connection surface and to a back plate (36) at a second connection surface, wherein the back plate (36) is mounted only by means of the actuators (35), in The back side of the body (33) has a plurality of flat portions extending non-parallel to each other, and there are a plurality of flat back plates (36), each back plate being aligned parallel to the flat portions.

17. The optical component (30) according to claim 16, in At least one separation element for lateral separation purposes is arranged between the actuator (35) and at least the body (31) and / or the back plate (36).

18. The optical component (30) according to claim 16 or 17, in The body (31) has a thickness that varies over its lateral extent.

19. The optical component (30) according to any one of claims 16 to 18, in The back plate (36') and / or the body (31) has a cutout (121), and the actuator (35) is at least partially arranged in the cutout (121).

20. The optical component (30) according to any one of claims 16 to 19, in A surface of at least one back plate (36) facing the main body (31) and a surface of at least one back plate (36) facing away from the main body (31) extend at a constant distance from the back side of the main body (33).

21. The optical component (30) according to any one of claims 16 to 20, in The effective direction of at least one of the actuators (35) is formed perpendicular to a connection surface between the actuator (35) and the body (31).

22. The optical component (30) according to any one of claims 16 to 21, in The effective direction of at least one of the actuators (35) is formed perpendicular to the optically effective surface (32).

23. The optical component (30) according to any one of claims 16 to 22, in At least two actuators (35) are formed to have different characteristics.

24. The optical component (30) according to any one of claims 16 to 23, in The optical element (Mx, 117) is a mirror, in particular a multilayer mirror.

25. The optical component (30) according to claim 24, in The reflector (Mx, 117) is a concave mirror, and its radius of curvature is 180 mm-260 mm, in particular, in the order of 220 mm.

26. The optical component (30) according to any one of claims 16 to 25, in The back plate (36) has lower rigidity than the main body (31).

27. The optical component (30) according to any one of claims 16 to 26, in The back plate (36) is provided with at least one sensor (49).

28. The optical component (30) according to claim 27, in The at least one sensor (49) is a strain or temperature sensor (49).

29. A projection exposure apparatus (1, 101) for semiconductor lithography having an optical assembly (30) as claimed in any one of the preceding claims.

30. A method for manufacturing an optical component (30) having an optical element (Mx, 117), wherein: The optical element (Mx, 117) comprises a body (31) having an optically active surface (32), at least one actuator (35) for deforming the optically active surface (32), and a back plate (39), wherein the actuator (35) is arranged between the body (31) and the back plate (36), and the method comprises the following method steps: - connecting the actuator to the back plate, - determining the surface area tolerance of the connection surface of the actuator facing away from the back plate, - machining the connecting surface, - repeat the first two steps until the surface area tolerance is below a predetermined threshold, - Connecting the actuator to the body.

31. The method according to claim 30, in The optically active surface (32) is processed after assembly of the actuator (35).

32. The method according to claim 30 or 31, in A plurality of actuators (35) are arranged on the back plate (36).

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