Optical element for semiconductor lithography and projection exposure apparatus

Abstract

The invention relates to an optical element (Mx, 117) for a projection exposure system (1, 101) for semiconductor lithography, comprising a base element (30) and at least one actuator (40) connected to the base element (30), the actuator (40) being designed as a ring-shaped actuator. The invention also relates to a projection exposure system for semiconductor lithography provided with a corresponding optical element and an optical element comprising a sensor for determining a deformation of an optically effective surface wherein the sensor is designed to detect a signal permitting correlation with a deformation of an optically effective surface.

Description

[0001] This application claims the priority of German patent application DE 10 2022 116 699.6 filed on July 5, 2022, the contents of which are incorporated herein in their entirety by reference. Technical Field

[0002] The invention relates to an optical element according to the preamble of claim 1, and to a projection exposure apparatus for semiconductor lithography equipped with a corresponding optical element. Background Art

[0003] In projection exposure equipment of this type, starting from a mask as a template, microscopic structures are imaged with greatly reduced dimensions onto a wafer coated with photoresist by means of photolithographic methods. In subsequent development and further processing steps, the desired structures, such as memory or logic elements, are produced on the wafer, which is then divided into individual chips for use in electronic devices.

[0004] Due to the very small structures to be created down to the nanometer range, the optical units of projection exposure apparatuses and thus the optical elements used are subject to extreme demands. Furthermore, during operation of the corresponding apparatuses, imaging aberrations often occur which usually originate from changing ambient conditions, such as temperature changes in the optical unit.

[0005] This problem is usually solved by the optical elements used, such as lens elements or mirrors, being designed to be movable or deformable in order to be able to correct the above-mentioned imaging aberrations during operation of the device. For this purpose, mechanical actuators are usually used, which can, for example, be suitable for deforming the surface of the optical element used for imaging, the so-called optically active surface, in a targeted manner. The deformation can be carried out from the back side of the body of the respective optical element.

[0006] A general challenge of arranging the actuator on the back side of the main body is to produce a reliable mechanical connection between the actuator and the main body, wherein firstly simple producibility should be ensured and secondly, the connection technology should have minimal adverse effects on the optical properties of the corresponding optical element. Summary of the invention

[0007] The object of the invention is to specify an optical element and a projection exposure apparatus for semiconductor lithography, in which a simplified arrangement of actuators for mechanically manipulating the optical element is implemented.

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

[0009] The optical element of the projection exposure device for semiconductor lithography according to the present invention comprises a main body and at least one actuator connected to the main body, the actuator being configured as an annular actuator. In this case, the annular actuator can be connected to the main body via a connecting geometry. The actuator can be configured as a solid-state actuator, for example, as a piezoelectric actuator or an electrostrictive actuator. It is used in this case to deform the main body, and therefore also to deform the optically effective surface, so as to produce the desired surface profile of the optically effective surface, for achieving the corresponding optical effect. The optical element can be a multilayer reflector in a projection exposure device for semiconductor lithography in particular. In this case, the annular actuator should be understood as an actuator in the shape of a ring, which can in particular have a basic shape of a substantially hollow cylinder. This choice of the geometry of the actuator provides considerable advantages in terms of the integrability or possibility of connecting the actuator to the main body.

[0010] In this respect, for example, the connection geometry may be configured as a pin arranged on the body, and the annular actuator may simply be pushed onto said pin.

[0011] The body and the pin can be configured in a monolithic manner, ie in an integral manner, in particular, but it is also conceivable that the body and the pin are connected to each other in an integrally joined manner. Furthermore, an interlocking engagement and a force-locking engagement are also conceivable.

[0012] In a variant of the invention, the attachment geometry may be configured as a cutout arranged in the body, said cutout being adapted to the outer geometry of the annular actuator.

[0013] The contact area of ​​the annular actuator relative to the attachment geometry of the body can be configured in a conical manner, and likewise the contact area of ​​the attachment geometry of the body relative to the annular actuator can also be configured in a conical manner. This measure simplifies the mounting of the actuator on or in the attachment geometry. The mounting itself can be achieved by heat shrink fitting thereon or therein; other mounting techniques are also conceivable, such as pre-deflecting the actuator by applying an electrical voltage.

[0014] The choice of a conical geometry is advantageous in that, in particular, a certain fit can be achieved in this case by axial displacement. This likewise opens up the possibility of achieving a frictional engagement and thus fixing the annular actuator on a pin or in a cutout, for example by pressing. The measures described in principle make it possible to connect the annular actuator without the use of adhesives, but this does not exclude the use of an additional integral bond connection.

[0015] The actuator effect can be further improved by means of a coupling geometry of an annular actuator comprising a suitably designed mechanical transmission region. In particular, in this case, the transmission region can be configured such that it reduces the stiffness against the deflection of the annular actuator, with the result that the forces applied to the parts of the actuator can be kept moderate.

[0016] In an advantageous embodiment of the invention, the annular actuator is arranged between the body and the support structure. In this case, the support structure may comprise a coupling geometry corresponding to the annular actuator, thereby providing a simple possibility of connecting the actuator to the support structure.

[0017] In particular, the annular actuator may be connected to a joining geometry configured as a pin or a cutout in the body and the support structure.

[0018] By means of the rear support of the annular actuator, both expansions of the actuator can contribute to the deformation of the optically active surface.

[0019] Furthermore, there are various possibilities for fixing the main body and the supporting structure. In this respect, firstly, the main body can be connected to the fixed world and the supporting structure can be connected to the main body only via the actuator. It is also conceivable that the supporting structure is connected to the fixed world and the main body is held by the actuator. It is also conceivable that the main body and the supporting structure are connected to each other.

[0020] In the case where the body is mounted via actuators, it is conceivable to achieve translational displacement of the body by controlling all actuators simultaneously and in the same way; however, it should be expected that the associated lateral contraction of the actuators will lead to parasitic effects. However, this effect can be minimized by one-time or regular calibration.

[0021] In another variant of the invention, the annular actuator is integrated into the support structure. In this respect, for example, the entire support structure can be made of piezoelectric material, and the actuator can be realized by integrating a suitable electrode geometry into the support structure.

[0022] The preferred actuation direction of the annular actuator may be defined by radial or axial alignment of the electrodes and the actuator material of the annular actuator in layers.

[0023] For the present invention, and in general, it is advantageous if the optical element comprises a sensor for determining the deformation of the optically active surface of the optical element, wherein the sensor is designed to detect a signal that allows correlation with the deformation of the optically active surface. In this case, it is not necessarily necessary to measure the deformation of the optically active surface directly. It is sufficient to record a signal from which the deformation of the optically active surface can be inferred.

[0024] In order to obtain such a signal, it is advantageous if the sensor comprises an interferometer, in particular a Fabry-Perot interferometer. An interferometer advantageously combines the possibility of extremely accurate and at the same time contactless measurement. In this case, it is further advantageous if both the body and the connecting geometry comprise relatively precisely manufactured optical surfaces which can serve as reflective surfaces for the interferometer.

[0025] The described measurement technique is in principle suitable for a wide variety of optical elements, in particular optical elements as described in the present application; thus, the optical element may be a deformable mirror, for example.

[0026] In this case, the deformable mirror may be a force-actuated mirror.

[0027] Furthermore, the deformable mirror may be a mirror actuated by a solid-state actuator.

[0028] The actuation direction of the actuator may be aligned perpendicularly to the contact area of ​​the actuator and the optical element; additionally or alternatively, the actuation direction of the actuator may also be aligned parallel to the contact area of ​​the actuator and the optical element.

[0029] In case of using an annular actuator, the geometry of such an actuator can be advantageously used for the effect that the sensor detects the deformation of the optically active surface through the center of the annular actuator. This offers the advantage that the measurement can be performed relatively close to the region of interest.

[0030] In principle, the invention can be implemented, for example, using piezoelectric actuators which can act bidirectionally, ie when the polarity of the control signal changes, the expansion direction of the piezoelectric actuator also changes. Piezoelectric actuators made of single-crystal lithium niobate (LiNbO3) are suitable for such applications, for example. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Exemplary embodiments and variants of the present invention are explained in more detail below with reference to the accompanying drawings, in which:

[0032] Figure 1 schematically shows a meridional section through a projection exposure apparatus for EUV projection lithography,

[0033] Figure 2 schematically shows a meridional section through a projection exposure apparatus for DUV projection lithography,

[0034] Figure 3 The annular actuator is shown in three different operating states for the purpose of illustrating the function,

[0035] Figure 4a , 4b An embodiment of the construction of a ring-shaped actuator is shown.

[0036] Figure 5a-5c An embodiment of an optical element according to the present invention is shown,

[0037] Figure 6a , 6b A schematic diagram of the present invention is shown for illustrating the mode of action,

[0038] Figure 7a , 7b An embodiment of the present invention using a pin is shown,

[0039] Figure 8a , 8b An embodiment of the present invention using a cutout is shown,

[0040] Figure 9a , 9b An embodiment of the invention having a mechanical transmission region is shown,

[0041] Fig.10a , 10b Another embodiment of the invention having a mechanical transmission region is shown,

[0042] Fig.11a , 11b An embodiment of the present invention having a support structure is shown,

[0043] Fig.12 An embodiment of the present invention having an integrated actuator system is shown,

[0044] Fig.13a , 13b An embodiment of the present invention using a sensor is shown, and

[0045] Fig.14 A schematic diagram is shown regarding the control of an annular actuator for mounting purposes. DETAILED DESCRIPTION

[0046] The essential components of the microlithography projection exposure apparatus 1 are first referred to below. Figure 1 The description of the basic construction of the projection exposure apparatus 1 and its constituent parts is to be understood here as non-limiting.

[0047] An embodiment of an illumination system 2 of a projection exposure apparatus 1 has, in addition to a 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.

[0048] 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.

[0049] 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 along Figure 1 The z direction extends perpendicular to the object plane 6.

[0050] 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.

[0051] 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. Firstly, a displacement of the reticle 7 can be realized by the reticle displacement drive 9 and secondly, a displacement of the wafer 13 can be realized by the wafer displacement drive 15 so as to be synchronized with each other.

[0052] The radiation source 3 is an EUV radiation source. The radiation source 3 in particular emits EUV radiation 16, which is hereinafter also referred to as used radiation, illumination radiation or illumination light. 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).

[0053] The illumination radiation 16 emitted from the radiation source 3 is focused by a collector 17. The collector 17 may be a collector with 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 be structured and / or coated, on the one hand to optimize its reflectivity for the radiation used and on the other hand to suppress extraneous light.

[0054] 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.

[0055] 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. Alternatively or additionally, 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 with wavelengths deviating therefrom. If the first facet mirror 20 is arranged in a plane of the illumination optical unit 4 that 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 as field facets hereinafter. Figure 1 Only some of the facets 21 are shown by way of example.

[0056] The first facet 21 can be implemented as a macro facet, in particular a rectangular facet or a facet with an arcuate edge profile or an edge profile of a portion of a circle. The first facet 21 can be implemented as a plane facet or alternatively as a convexly or concavely curved facet.

[0057] 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 mirror 20 can in particular be configured as a microelectromechanical system (MEMS system). For details, reference is made to DE 10 2008 009 600 A1.

[0058] Between the collector 17 and the deflecting mirror 19 the illuminating radiation 16 travels horizontally, ie in the y-direction.

[0059] 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.

[0060] 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.

[0061] The second facets 23 can likewise be macroscopic facets which can, for example, have circular, rectangular or hexagonal boundaries, or alternatively facets consisting of micromirrors. In this respect, reference is likewise made to DE 10 2008 009 600 A1.

[0062] The second facet 23 may have a planar reflecting surface, or alternatively, a convexly or concavely curved reflecting surface.

[0063] 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).

[0064] 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.

[0065] 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 .

[0066] In a further embodiment (not shown) of the illumination optical unit 4, a transmission 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 transmission 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 transmission optical unit can in particular comprise one or two normal incidence mirrors (NI mirrors) and / or one or two grazing incidence mirrors (GI mirrors).

[0067] 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 .

[0068] 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 .

[0069] 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.

[0070] 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 .

[0071] exist Figure 1 In the example shown, the projection optical unit 10 comprises six mirrors M1 to M6. Alternative solutions 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 double-shaded optical unit. The projection optical unit 10 has an image-side numerical aperture which is greater than 0.5 and can also be greater than 0.6 and can be, for example, 0.7 or 0.75.

[0072] 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.

[0073] 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.

[0074] In particular, the projection optical unit 10 may have a deformed configuration. In particular, it has different imaging ratios βx, βy in the x-direction and the y-direction. The two imaging ratios βx, βy of the projection optical unit 10 are preferably (βx, βy) = (+ / -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.

[0075] 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.

[0076] The projection optical unit 10 results in a reduction of the dimensions in the y-direction (ie in the scanning direction) by 8:1.

[0077] 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.

[0078] 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 design 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 / 0074303A1.

[0079] 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. In particular, this can result in The far field is decomposed into a plurality of object fields 5 by means of field facets 21. The field facets 21 generate a plurality of images of the intermediate focus on the pupil facets 23 respectively assigned thereto.

[0080] The field facets 21 are imaged onto the reticle 7 with the respective assigned pupil facets 23 overlapping one another 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 overlapping different illumination channels.

[0081] 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.

[0082] 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.

[0083] 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.

[0084] The projection optical unit 10 may in particular have a concentric entrance pupil. The latter may be accessible. It may also be inaccessible.

[0085] 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, it is possible to find a region 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.

[0086] 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, the different positions of the tangential entrance pupil and the sagittal entrance pupil can be taken into account.

[0087] 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.

[0088] The first facet mirror 20 is arranged to be inclined relative to an arrangement plane defined by the second facet mirror 22 .

[0089] Figure 2 Shown schematically is a meridional section through a further projection exposure apparatus 101 for DUV projection lithography, in which the invention can likewise be used.

[0090] The arrangement and imaging principle of the projection exposure apparatus 101 are similar to Figure 1 The same parts are used as in Figure 1 The reference numerals increased by 100 indicate that Figure 2 The reference numerals in the figures start from 101.

[0091] With Figure 1 Compared to the EUV projection exposure apparatus 1 described in the foregoing, refractive, diffractive and / or reflective optical elements 117 (e.g. lens elements, mirrors, prisms, terminal plates, etc.) can be used for imaging or for illumination in the DUV projection exposure apparatus 101, since the larger wavelength of the DUV radiation 116 used as the light used is in the range of 100 nm to 300 nm, in particular 193 nm. In this case, the projection exposure apparatus 101 essentially comprises an illumination system 102, a mask master holder 108 for receiving and precisely positioning a mask master 107 provided with structures, the mask master determining the subsequent structures on a wafer 113, a wafer holder 114 for holding, moving and precisely positioning the wafer 113, and a projection lens 110 having a plurality of optical elements 117 held in a lens housing 119 of the projection lens 110 by means of a mounting 118.

[0092] 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.

[0093] The arrangement of the downstream projection optical unit 110 with the lens housing 119 is in principle similar to that of the embodiment of the present invention, except for the additional use of a refractive optical element 117 (such as a lens element, a prism, a terminal plate). Figure 1 The setup described in is no different and therefore will not be described in further detail.

[0094] Figure 3 Schematic diagrams of the annular actuator 40 are shown in three different operating states. Figure 3 At the top of the embodiment, the annular actuator 40 having a hollow cylindrical recess is shown in a zero state, which is defined by half of the total possible deflection in the example shown. Starting from this zero state, the annular actuator 40 can expand, as Figure 3 15 , or contraction, as shown at the bottom of the right-hand side. As will be further explained in more detail below in conjunction with the installation and operation of the annular actuator 40, the zero state is caused by a specific zero voltage in the zero state, and the expansion and contraction of the annular actuator 40 are caused by an increase or decrease in voltage through a controller (not shown). Alternatively, if suitable materials are used, the zero state may also correspond to a voltage-free state. In this case, expansion is caused by applying a voltage with a first polarity, and contraction is caused by applying a voltage with an opposite polarity. Suitable materials for this purpose are, for example, ceramic materials, such as lead zirconate titanate (PZT), and further, for example, lithium niobate (LiNbO3) or lithium tantalate (LiTaO3).

[0095] Figure 4a and Figure 4b Two different embodiments of the annular actuator 40 are shown, which differ in the arrangement of the electrodes 42 and the actuator material 41 relative to the longitudinal axis of the annular actuator 40 .

[0096] Figure 4a An axial arrangement of a layer of actuator material 41 and electrodes 42 is shown (as is known in the case of prior art rod actuators), which are connected via lines 43 to a controller 44. Figure 4aIn the illustrated embodiment, the electrodes 42 are first arranged on the inner side of the annular actuator 40 and then on the outer side of the annular actuator 40. The two electrodes 42 may also be contacted only on the outer side or only on the inner side. The arrangement of the electrodes 42 may cause, for example, a main deflection of the annular actuator 40 in the axial direction (i.e., perpendicular to the ring plane), and the expansion and contraction of the annular actuator 40 in the radial direction is only a second-order effect.

[0097] Figure 4b FIG. 4 shows a radial arrangement of an annular actuator 40, wherein the actuator material layer 41 and the electrode layer 42 are arranged radially. In this case, the controller 44 is contacted at the upper and lower end faces of the annular actuator 40 via the line 43. Figure 4a As explained in the case of , an arrangement of the contact line 43 only at the top or only at the bottom is also conceivable here. The arrangement of the electrodes 42 causes a main deflection of the annular actuator 40 in the radial direction (i.e. parallel to the ring plane), the expansion and contraction of the annular actuator 40 in the axial direction being only a second-order effect. In principle, the ratio of the extension (ratio of the change in radius to the change in geometry along the axis of rotational symmetry) can be advantageously influenced by selecting the electrode position in combination with the selection of the electrostrictive or piezoelectric material. In an advantageous manner, the deformation effect at the optically effective surface and thus the wavefront influence in the design can be influenced.

[0098] Figure 5a A schematic diagram showing a first embodiment of the present invention is shown, wherein a reflector M is configured as X , 117 and can be applied, for example, to Figure 1 and Figure 2 An optical element of one of the illustrated projection exposure apparatuses. Figure 5a The reflector M is shown X , 117, which comprises a body 30, the body 30 having an optically effective surface 31 and a back side 32 opposite to the optically effective surface 31, viewed from below, i.e., viewed from the back side 32 of the body 30. An annular actuator 40 is arranged in the region corresponding to the optically effective surface 31, the annular actuator 40 being arranged beyond the region of the optically effective surface 31, so that deformations with positive and negative gradients can also be induced in the edge region of the optically effective surface 31. This also requires that the annular actuator 40 expands and contracts from a so-called zero position. This will be Fig.14 In principle, the annular actuators 40 can also be arranged only in the edge region or at other locations, as long as their actuation causes a deformation of the optically active surface 31 .

[0099] Figure 5b Another embodiment of the present invention is shown, in which an optical element configured as a reflector Mx, 117 is described, the reflector (similar to Figure 5bThe reflector Mx, 117 in FIG. 1 comprises a body 30 having an optically active surface 31. The reflector Mx, 117 is again shown in a perspective rear view. A connecting geometry configured as a pin 45 for the annular actuator 40 is arranged on the back side 32. As will be described below, Fig.14 As further explained in more detail in , the annular actuator 40 is mounted on the pins 45 by shrink fitting thereon, although some other connection techniques, such as adhesive bonding or joining are also possible. Contraction or expansion of the annular actuator 40 leads to contraction or expansion of the pins 45, which in turn causes a deformation of the optically active surface 31. The deformation effect can be compared with the deformation effect of an actuator acting parallel to the surface, wherein in the case of the annular actuator 40 the axial component in the deflection contributes to the deformation, albeit with only a minor contribution. The resulting deformation of the optically active surface 31 can be used to correct thermal expansion of the body 30 due to absorption of electromagnetic radiation, or to correct imaging aberrations arising elsewhere in the projection exposure apparatus 1, 101.

[0100] Figure 5c Another embodiment of the present invention is shown, in which an optical element configured as a reflector Mx, 117 is described, the reflector (similar to Figure 5b The reflector Mx, 117 in FIG. 1 comprises a body 30 having an optically effective surface 31. The reflector Mx, 117 is again shown in a rear perspective view. A connecting geometry configured as a cutout 46 for the annular actuator 40 is arranged on the back side 32. As will be described below, Fig.14 As further explained in more detail in , the annular actuator 40 is mounted in the cut-out 46 by shrink-fitting therein, but some other connection techniques, such as adhesive bonding or bonding are also possible. Contraction or expansion of the annular actuator 40 leads to contraction or expansion of the cut-out 46, which in turn causes a deformation of the optically active surface 31. The deformation effect can be compared with the deformation effect of an actuator acting parallel to the surface, wherein in the case of the annular actuator 40, the axial component in the deflection can contribute to the deformation, although with only a minor contribution. The resulting deformation of the optically active surface 31 can be used to correct thermal expansion of the body 30 due to absorption of electromagnetic radiation, or for correcting imaging aberrations generated elsewhere in the projection exposure apparatus 1, 101.

[0101] Figure 6a and 6b A detailed view of the invention is shown showing an annular actuator 40 shrink-fitted on a pin 45 in two different operating states. Depending on the operating state of the annular actuator 40, the effect on the optically active surface 31 of the body 30 is shown.

[0102] Figure 6a The annular actuator 40 is shown in a retracted operating state, as a result of which the pins are retracted, which in turn leads to a deformation 47 outside the optically active surface 31 .

[0103] Figure 6b The annular actuator 40 is shown in an extended operating state, as a result of which the constriction of the pin 45 is expanded, which in turn leads to a deformation 47 into the optically active surface 31 .

[0104] Figure 7a A first embodiment of the pin 45 is shown, which is constructed in a cylindrical manner. This has the advantage of simple production, and standard actuators can also be used for the annular actuator 40.

[0105] Figure 7b A second embodiment of the pin 48 is shown, in which case the contact area relative to the annular actuator is configured in a conical manner. This has the advantage that the fixing of the annular actuator 40 can be achieved at least partially by pushing the annular actuator 40 forward purely geometrically onto the pin 48. As in the case of mounting on the cylindrical pin 45, the annular actuator 40 can also be configured in a hollow cylindrical manner, in which case the hollow cylindrical inner shape of the annular actuator 40 is adapted to the conical outer geometry of the pin 48 during the shrink fit on the pin 48 by the regional expansion of the inner diameter of the annular actuator 40. The resulting prestress of the pin 48, which changes during the axial expansion of the annular actuator 40, can be taken into account in the control. Alternatively, the inner geometry of the annular actuator 40 can also be configured in a manner corresponding to the pin 48, so that the contact area of ​​the annular actuator 40 relative to the pin 48 is configured in a conical manner. The advantages of the conical design in this case are the compensation of diameter tolerances and the possibility of an axial press fit.

[0106] Figure 8a and 8b The connecting geometry in the form of cutouts 46, 49 is shown in a variant of the invention. Figure 7a and Figure 7b The content described also applies in principle to Figure 8a and Figure 8b In the illustrated embodiment, the description in this case of course refers to the corresponding inner surface of the cutout and the corresponding outer surface of the annular actuator 40, and the annular actuator 40 is axially press-fitted or radially press-fitted or shrink-fitted into place using thermal linear expansion.

[0107] Figure 9a and 9b as well as Fig.10a and 10b A modification of the invention is shown for use with pins 45, 48 configured and Figure 7a and 7b The connection geometry described in the embodiment and the cutouts 46, 49 are formed and Figure 8a and 8bThe connection geometry is described in the following. The connection geometry includes a mechanical transmission area, which includes a recess 50, which will be described below based on being constructed as follows Figure 9a The embodiment of the cylindrical pin 45 shown is explained in detail. A recess 50 is formed centrally in the pin 45 and extends beyond the pin into the body 30. Firstly, the recess 50 leads to a reduction in the stiffness of the pin 45 and the body 30, whereby the deformation of the optically active surface 31 can advantageously be appropriately modified with the same deflection of the annular actuator 40. Secondly, the shape of the deformation on the optically active surface 31 of the body can also be adjusted, whereby this can be adjusted in almost any desired way by means of additive methods and the associated possibilities of free geometric design, in particular during the production of the body 30 and the pins 45, 48 or the corresponding cutouts 46, 49. Figure 9a The effect of the recess 50 explained can be applied to Figure 9b , 10a and the embodiment shown in 10b.

[0108] Fig.11a Another embodiment of the invention is shown, in which an optical element configured as a reflector Mx, 117 is shown. The reflector comprises, in addition to a body 30 having an optically active surface 31, a support structure configured as a back plate 51, wherein the back plate 51 comprises tapered pins 48 corresponding to the tapered pins 48 configured in the body 30. The annular actuators 40 are configured in the form of sleeves, so that they can be connected to the pins 48 of the back plate 51 and to the pins 48 of the body 30. The back plate 51 serves as a support structure and is connected to the body 30 or to some other structure configured for absorbing forces, or is supported on the body 30 by the annular actuators 40. The support by means of the annular actuators 40 is possible because the annular actuators 40 are not deflected in one direction in most cases for deformations of the optically active surface 31, and the non-deflecting annular actuators 40 perform the support of the back plate 51. Fig.11b Another embodiment of the present invention is shown. Fig.11a 5, including a support structure configured as a back plate 51. This differs only in the connection geometry configured as a conical cutout 49. All further explanations match the description given, so reference is made to them.

[0109] Fig.12 Another embodiment of the invention is shown, which comprises a support structure with an integrated annular actuator 40. In this case, the backing plate 54 of the support structure is made of the actuator material 41, and only the area of ​​the annular actuator 40 is formed with electrodes 42. Its function is similar to Fig.11a The functions of the embodiments described in are the same.

[0110] Fig.13aAnother embodiment of the invention is shown, in which a detailed view of the optical elements of a reflector Mx, 117 configured with a sensor 60 is shown. The reflector Mx, 117 comprises a body 30 having an optically active surface 31 and an annular actuator 40 shrink-fitted on a tapered pin 48. Fig.13a In the embodiment shown, the sensor 60 is configured in the manner of a Fabry-Perot interferometer. The interferometer comprises a light source 61 which emits a light beam 62 in the direction of the back side of the body 30, the light beam undergoing normal incidence on the back side. The sensor 60 uses the end face of the pin 48 which partially transmits the wavelength of use of the light beam 62 as a first mirror surface 64, and uses the optically effective surface 31 as a second mirror surface 65, wherein the detector 63 detects the superposition of reflections from the first mirror surface 64 and the second mirror surface 65. From the phase difference between the detected light beams caused by the deformation of the body, the change in the distance between the two mirror surfaces 64, 65 can be determined, and from this change the deformation of the optically effective surface 31 can then be determined. One advantage of the configuration of the sensor 60 in the center of the annular actuator 40 is that the deformation caused by the annular actuator 40 can be detected directly from the back side of the body 30 at the starting position. Compared with the detection of the deformation from the optically effective surface 31, the accessibility from the back side of the body 30 is significantly better.

[0111] Fig.13b Another embodiment of the present invention is shown in which a detailed view of the optical elements of a reflector Mx, 117 configured with a sensor 60 is shown. The reflector Mx, 117 includes such as has been described in Fig.11a The support structure 51 illustrated in FIG. 1 and the sensor 60 also configured in the manner of a Fabry-Perot interferometer. Fig.13a In contrast to the arrangement illustrated in , the sensor 60 uses the two end faces of the tapered pin 48 formed at the back plate 51 and the body 30 as the first and second mirror surfaces 64 and 65. The deformation of the optical surface can be derived with the aid of calibration data or prediction based on a model, such as FEM.

[0112] Fig.14 A diagram is shown for illustrating the process of installing an annular actuator into a joint geometry configured as a cutout. The outer diameter of the annular actuator is indicated on the ordinate of the diagram and the control voltage is indicated on the abscissa. In the embodiment shown, the annular actuator is controlled with positive voltage only and the diameter of the annular actuator decreases as the voltage increases. For installation purposes, the annular actuator is controlled in a first voltage range S M is controlled so that the diameter is definitely smaller than the diameter range T of the cutout affected by the tolerance A . Used in operation S B The voltage range for control during the period is lower than the voltage range for installation S Mand below the annular actuator has a maximum diameter tolerance T less than or equal to the cutout A The voltage of the diameter S G . The voltage range for operation S B Including the so-called zero voltage S N , corresponding to the voltage at which the optically active surface has its predetermined surface shape. This can be achieved by re-machining the optically active surface again after installing the annular actuators, all of which are connected with their zero voltage S N Alternatively, by zero voltage S N The induced deformation can also be maintained during the production of the optically active surface.

[0113] Reference numerals list

[0114] 1 Projection exposure equipment

[0115] 2 Lighting system

[0116] 3 Radiation sources

[0117] 4 Illumination optical unit

[0118] 5. Material Field

[0119] 6 Object Plane

[0120] 7. Mask Master

[0121] 8 Reticle Holder

[0122] 9 Mask Master Displacement Driver

[0123] 10 Projection Optics Unit

[0124] 11 Image Field

[0125] 12 Image planes

[0126] 13 chips

[0127] 14 Wafer Holder

[0128] 15 chip displacement driver

[0129] 16EUV radiation

[0130] 17 Collector

[0131] 18 Intermediate focal plane

[0132] 19 Deflecting mirror

[0133] 20 facet reflector

[0134] 21 facets

[0135] 22 facet mirror

[0136] 23 facets

[0137] 30 Main Body

[0138] 31 Optically effective surface

[0139] 32 Back side of the main body

[0140] 40 Ring Actuator

[0141] 41Actuator Material

[0142] 42 electrodes

[0143] Line 43

[0144] 44 Controller

[0145] 45 pins

[0146] 46 incision

[0147] 47 Deformation

[0148] 48 pins, tapered

[0149] 49 cut, tapered

[0150] 50 recesses

[0151] 51 Back Panel

[0152] 54 integrated backplane

[0153] 60 sensors

[0154] 61 Light Source

[0155] 62 laser beams

[0156] 63 detector

[0157] 64 first reflector surface

[0158] 65 second reflector surface

[0159] 101 Projection exposure equipment

[0160] 102 Lighting System

[0161] 107 Mask Master

[0162] 108 Reticle Master Holder

[0163] 110 Projection optics unit

[0164] 113 Chip

[0165] 114 Wafer Holder

[0166] 116 DUV radiation

[0167] 117 Optical Components

[0168] 118 Mounting parts

[0169] 119 Lens housing

[0170] M1-M6 Reflectors

[0171] S N Zero voltage

[0172] S M Voltage range for installation

[0173] S B Voltage range for operation

[0174] S G The voltage at the lower tolerance range of the cutout

[0175] T A Tolerance of cutout

Claims

1. An optical element (Mx, 117) of a projection exposure apparatus (1, 101) for semiconductor lithography, comprising a body (30) and at least two actuators (40) connected to the body (30), the actuators being designed to deform an optically effective surface (31) of the optical element (Mx, 117), It is characterized in that The at least two actuators (40) are configured as ring-shaped actuators.

2. The optical element (Mx, 117) according to claim 1, It is characterized in that At least one of the annular actuators (40) is connected to the body (30) via a connecting geometry (45, 46, 48, 49).

3. The optical element (Mx, 117) according to claim 2, It is characterized in that The connection geometry (45, 48) is configured as a pin (45, 48) arranged on the body (30).

4. The optical element (Mx, 117) according to claim 3, It is characterized in that The body (30) and the pins (45, 48) are configured in a monolithic manner.

5. The optical element according to claim 3, It is characterized in that The body (30) and the pins (45, 48) are connected to each other in an integrally combined manner.

6. The optical element (Mx, 117) according to claim 2, It is characterized in that The attachment geometry (46, 49) is configured as a cutout (46, 49) disposed in the body (30).

7. An optical element (Mx, 117) according to any one of claims 2 to 6, It is characterized in that The contact area of ​​at least one annular actuator (40) relative to the connecting geometry (48, 49) of the body (30) is configured in a conical manner.

8. An optical element (Mx, 117) according to any one of claims 2 to 7, It is characterized in that The connection geometry (48, 49) of the body (30) is configured in a conical manner relative to a contact area of ​​at least one annular actuator (40).

9. An optical element (Mx, 117) according to any one of claims 2 to 8, It is characterized in that At least one annular actuator (40) is connected to the joint geometry (48, 49) by shrink fitting thereon or therein.

10. An optical element (Mx, 117) according to any one of claims 2 to 9, It is characterized in that The coupling geometry (48, 49) of at least one annular actuator (40) includes a mechanical transmission region (50).

11. The optical element (Mx, 117) according to claim 10, It is characterized in that The transmission region (50) is configured such that it reduces stiffness against deflection of the annular actuator (50).

12. An optical element (Mx, 117) according to any one of the preceding claims, It is characterized in that At least one annular actuator (40) is arranged between the body (30) and the support structure (51, 54).

13. The optical element (Mx, 117) according to claim 12, It is characterized in that The support structure (51) includes a connection geometry (48, 49) corresponding to at least one annular actuator (40).

14. The optical element (Mx, 117) according to claim 12 or 13, It is characterized in that At least one annular actuator (40) is connected to the body (30) and the support structure (51, 54) by a connecting geometry configured as a pin (48) or a notch (49).

15. The optical element (Mx, 117) according to claim 12, It is characterized in that At least one annular actuator (40) is integrated into the support structure (54).

16. An optical element (Mx, 117) according to any one of the preceding claims, It is characterized in that The electrodes (42) and actuator material (41) of at least one annular actuator (40) are aligned radially or axially in a layer.

17. An optical element (Mx, 117) of a projection exposure device (1, 101) for semiconductor lithography, wherein the optical element (Mx, 117) comprises a sensor (60) for determining a deformation of an optically effective surface (31) of the optical element (Mx, 117), wherein the sensor (60) is designed to detect a signal that allows correlation with the deformation of the optically effective surface (31).

18. The optical element (Mx, 117) according to claim 17, It is characterized in that The sensor (60) comprises an interferometer.

19. The optical element (Mx, 117) according to claim 18, It is characterized in that The sensor (60) comprises a Fabry-Perot interferometer.

20. An optical element (Mx, 117) according to any one of claims 17 to 19, It is characterized in that The optical element (Mx, 117) is a deformable mirror.

21. The optical element (Mx, 117) according to claim 20, It is characterized in that The deformable mirror is a force actuated mirror.

22. An optical element (Mx, 117) according to claim 20 or 21, It is characterized in that The deformable mirror is a mirror actuated by a solid-state actuator.

23. An optical element (Mx, 117) according to any one of claims 17 to 22, It is characterized in that The optical element (Mx, 117) is an optical element (Mx, 117) according to claims 1 to 16.

24. The optical element (Mx, 117) according to claim 23, It is characterized in that The actuation direction of at least one actuator (40) is aligned perpendicularly to the contact area of ​​the actuator (40) and the optical element (Mx, 117).

25. An optical element (Mx, 117) according to claim 23 or 24, It is characterized in that The actuation direction of at least one actuator (40) is aligned parallel to the contact area of ​​the actuator (40) and the optical element (Mx, 117).

26. An optical element (Mx, 117) according to any one of claims 23 to 25, It is characterized in that The sensor (60) detects the deformation of the optically active surface (31) through the center of at least one annular actuator (40).

27. A projection exposure apparatus (1, 101) having an optical element (Mx, 117) as claimed in any one of claims 1 to 26.

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