Optical element and projection exposure apparatus for semiconductor lithography

Abstract

The present invention relates to an optical element (Mx, 117) of a projection exposure apparatus (1, 101) for semiconductor lithography, comprising a main body (30) and at least one actuator (40) connected to the main body (30), wherein the actuator (40) is designed as a ring actuator. The present invention relates to a projection exposure apparatus for semiconductor lithography provided with the optical element, and to an optical element provided with a sensor for determining deformation of an optically effective surface, the sensor being designed to detect a signal correlated with the deformation of the optically effective surface.

Description

[Technical Field]

[0001] This application claims priority from German Patent Application No. 10 2022 116 699.6 of July 5, 2022, the contents of which are incorporated herein by reference in their entirety.

[0002] The invention relates to an optical element according to the preamble of claim 1 and to a projection exposure apparatus for semiconductor lithography comprising such an optical element. [Background technology]

[0003] In this type of projection exposure apparatus, photolithography is used to image microscopically small structures from a mask as a template onto a photoresist-coated wafer. In subsequent development and further processing steps, the desired structures, such as memory or logic elements, are created on the wafer, which is then separated into individual chips for use in electronic devices.

[0004] The creation of very small structures, down to the nanometer range, places extreme demands on the optical units of the projection exposure apparatus and therefore on the optical elements used. Furthermore, imaging aberrations, which often result from changes in ambient conditions such as temperature changes of the optical units, often occur during operation of the apparatus.

[0005] This problem is usually addressed by designing the used optical elements, such as lens elements or mirrors, to be movable or deformable in order to allow correction of the above-mentioned imaging aberrations during operation of the device. For this purpose, mechanical actuators are generally used, which can be suitable for example for targeted deformation of the surface of the optical element used for imaging, i.e. the so-called optically effective surface. This deformation can be performed from the rear side of the body of the optical element in question.

[0006] The usual challenge with locating the actuator on the back side of the body is to create a reliable mechanical connection between the actuator and the body, which should firstly ensure simple manufacturability and secondly minimize the negative impact of the connection technique on the optical performance of the optical element. Summary of the Invention [Problem to be solved by the invention]

[0007] It is an object of the invention to specify an optical element and a projection exposure apparatus for semiconductor lithography in which a simple arrangement of actuators for mechanically manipulating the optical element is implemented. [Means for solving the problem]

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

[0009] The optical element according to the present invention for a projection exposure apparatus for semiconductor lithography comprises a body and at least one actuator connected to the body, the actuator configured as a ring actuator. In this case, the ring actuator can be connected to the body via a connecting feature. The actuator can be configured as a solid-state actuator, for example, a piezo-electric or electrostrictive actuator. It serves to deform the body and thus the optically effective surface in order to generate a desired surface profile of the optically effective surface for achieving the corresponding optical effect. The optical element can be, in particular, a multilayer mirror of a projection exposure apparatus for semiconductor lithography. In this case, the ring actuator is understood to be a ring-type actuator, which can have, in particular, a substantially hollow cylindrical basic shape. This choice of actuator geometry offers significant advantages in terms of the actuator's integrability or connectability with the body.

[0010] In this regard, for example, the interlocking feature may be configured as a pin disposed on the body, and the ring actuator may simply be press-fit onto said pin.

[0011] The body and pin may be particularly monolithic, i.e., constructed as one piece, although it is also contemplated that the body and pin may be integrally connected to one another. Furthermore, interlocking and interference fit engagements are also contemplated.

[0012] In one variant of the invention, the interlocking feature can be configured as a notch arranged in the body, said notch adapting to the external geometric shape of the ring actuator.

[0013] The contact area of ​​the ring actuator with the connecting profile of the body can be conically shaped, and the contact area of ​​the connecting profile of the body with the ring actuator can also be conically shaped. This measure simplifies the attachment of the actuator to the connecting profile. The attachment itself can be achieved by shrink fitting. Other attachment techniques are also conceivable, such as pre-deflecting the actuator by applying a voltage.

[0014] The advantage of the conical shape is that in this case a certain degree of fit can be achieved by axial displacement, which also opens up the possibility of frictionally engaging and thus fixing the ring actuator in the pin or notch, for example by pressing. The measures described make it possible in principle to connect the ring actuator without adhesive, although the use of an additional integral connection is not excluded.

[0015] The actuator effect can be further improved if the connecting geometry of the ring actuator includes a properly designed mechanical transmission area, which can be specifically configured to reduce the stiffness acting on the deflection of the ring actuator, thereby keeping the force applied by the actuator moderate.

[0016] In one advantageous embodiment of the invention, the ring actuator is arranged between the body and the support structure, which can then include a coupling feature corresponding to the ring actuator, thereby allowing a simple connection of the actuator to the support structure.

[0017] In particular, the ring actuator may be connected to coupling features configured as pins or notches in the body and support structure.

[0018] The rear support of the ring actuator allows both expansions of the actuator to contribute to the deformation of the optically active surface.

[0019] Furthermore, there are various possibilities for fixing the body and the support structure. In this respect, firstly, the body can be connected to a fixed environment and the support structure can be connected to the body only via an actuator. It is also conceivable to connect the support structure to a fixed environment and hold the body via an actuator. It is also conceivable to connect the body and the support structure to each other.

[0020] If the body is attached via actuators, all actuators may be controlled simultaneously and similarly to achieve translational displacement of the body. However, the associated lateral contraction of the actuators should be expected to lead to parasitic effects. However, such effects can be minimized by one-time or periodic calibration.

[0021] In yet another variation of the invention, the ring actuator is integrated into the support structure. In this regard, for example, the entire support structure can be manufactured from piezoelectric material and the actuator can be realized by incorporating appropriate electrode geometries into the support structure.

[0022] The preferred actuation direction of the ring actuator can be defined by radially or axially layering the electrodes and actuator material of the ring actuator.

[0023] In the present invention, but also in general, it is advantageous if the optical element is equipped with a sensor for determining the deformation of the optically effective surface of the optical element, the sensor being designed to detect a signal that correlates with the deformation of the optically effective surface. In this case, the deformation of the optically effective surface does not necessarily have to be measured directly. It is sufficient to record a signal from which the deformation of the optically effective surface can be estimated.

[0024] To obtain such a signal, the sensor advantageously includes an interferometer, in particular a Fabry-Perot interferometer, which advantageously combines extremely accurate and contactless measurement possibilities, and in this case it is further advantageous for both the body and the coupling feature to include relatively precisely manufactured optical surfaces that can be used as reflective surfaces for the interferometer.

[0025] The described measurement technique is in principle suitable for a wide variety of optical elements, in particular the optical elements described herein, which may thus be, for example, deformable mirrors.

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

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

[0028] The actuation direction of the actuator may be aligned perpendicular to the contact area of ​​the actuator with the optical element. Additionally or alternatively, the actuation direction of the actuator may be aligned parallel to the contact area of ​​the actuator with the optical element.

[0029] When a ring actuator is used, the geometry of such an actuator can be exploited so that the sensor detects the deformation of the optically active surface through the center of the ring actuator, which has the advantage that measurements can be made relatively close to the region of interest.

[0030] In principle, the present invention can be realized, for example, using piezo actuators that can act in two directions, i.e., the direction of expansion and contraction can be changed by changing the polarity of the control signal. Piezo actuators made of single-crystal lithium niobate (LiNbO3) are, for example, suitable for such applications.

[0031] Exemplary embodiments and variants of the invention are explained in more detail below with reference to the drawings. [Brief explanation of the drawings]

[0032] [Figure 1] 1 shows a schematic meridian section of a projection exposure apparatus for EUV projection lithography; [Figure 2] 1 shows a schematic meridian section of a projection exposure apparatus for DUV projection lithography; [Figure 3] To illustrate its function, the ring actuator is shown in three different operating states. [Figure 4a] 1 shows an embodiment of a ring actuator configuration. [Figure 4b] 1 shows an embodiment of a ring actuator configuration. [Figure 5a] 1 shows an embodiment of an optical element according to the present invention. [Figure 5b] 1 shows an embodiment of an optical element according to the present invention. [Figure 5c] 1 shows an embodiment of an optical element according to the present invention. [Figure 6a] 1 shows a schematic diagram of the present invention to explain the mode of operation; [Figure 6b] 1 shows a schematic diagram of the present invention to explain the mode of operation; [Figure 7a] 1 illustrates an embodiment of the present invention using pins. [Figure 7b] 1 illustrates an embodiment of the present invention using pins. [Figure 8a] 1 illustrates an embodiment of the present invention using a notch. [Figure 8b] 1 illustrates an embodiment of the present invention using a notch. [Figure 9a] 1 illustrates an embodiment of the present invention having a mechanical transmission region. [Figure 9b] 1 illustrates an embodiment of the present invention having a mechanical transmission region. [Figure 10a] 10 illustrates yet another embodiment of the present invention having a mechanical transmission region. [Figure 10b] 10 illustrates yet another embodiment of the present invention having a mechanical transmission region. [Figure 11a] 1 illustrates an embodiment of the present invention having a support structure. [Figure 11b] 1 illustrates an embodiment of the present invention having a support structure. [Figure 12] 1 illustrates an embodiment of the present invention having an integrated actuator system. [Figure 13a] 1 illustrates an embodiment of the present invention using a sensor. [Figure 13b] 1 illustrates an embodiment of the present invention using a sensor. [Figure 14] 10 shows a schematic diagram for controlling the ring actuator for attachment. DETAILED DESCRIPTION OF THE INVENTION

[0033] The essential components of a microlithography projection exposure apparatus 1 are exemplarily described below, initially with reference to Figure 1. The description of the basic configuration of the projection exposure apparatus 1 and its components is to be understood here as non-limiting.

[0034] In addition to the radiation source 3, an embodiment of the illumination system 2 of the projection exposure apparatus 1 comprises an illumination optical unit 4 which illuminates an object field 5 in an object plane 6. In an alternative embodiment, the light source 3 can also be provided as a module separate from the rest of the illumination system. In this case, the illumination system does not include the light source 3.

[0035] 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, in particular in the scanning direction, by a reticle displacement drive 9.

[0036] For illustrative purposes, a Cartesian xyz coordinate system is shown in Figure 1. The x direction extends perpendicular to the plane of the drawing. The y direction extends horizontally and the z direction extends vertically. In Figure 1, the scanning direction extends in the y direction. The z direction extends perpendicular to the object plane 6.

[0037] 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, an angle other than 0° between the object plane 6 and the image plane 12 is also possible.

[0038] The structures on the reticle 7 are imaged onto a photosensitive layer of a wafer 13, which is arranged in the region of the image field 11 of the image plane 12. The wafer 13 is held by a wafer holder 14. The wafer holder 14 is displaceable, 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 displacement drive 15, can be performed synchronously with respect to one another.

[0039] The radiation source 3 is an EUV radiation source. The radiation source 3 in particular emits EUV radiation 16, also referred to in the following as working radiation, illumination radiation or illumination light. In particular, the working radiation has a wavelength in the range of 5 nm to 30 nm. The radiation source 3 may be a plasma source, such as an LPP (Laser Produced Plasma) source or a GDPP (Gas Discharge Plasma) source. It may also be a synchrotron-based radiation source. The radiation source 3 may be a Free Electron Laser (FEL).

[0040] Illumination radiation 16 leaving radiation source 3 is focused by collector 17. Collector 17 may be a collector with one or more ellipsoidal and / or hyperbolic reflecting surfaces. Illumination radiation 16 may be incident on at least one reflecting surface of collector 17 at grazing incidence (GI), i.e. at an angle of incidence greater than 45° relative to the direction of the normal to the mirror surface, or at normal incidence (NI), i.e. at an angle of incidence smaller than 45°. Collector 17 may be structured and / or coated, firstly to optimize its reflectivity for the radiation used and secondly to suppress extraneous light.

[0041] 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 be a separation point between the radiation source module, which includes the radiation source 3 and the collector 17, and the illumination optics unit 4.

[0042] The illumination optical unit 4 comprises a deflection mirror 19 and a first facet mirror 20 arranged downstream thereof in the beam path. The deflection mirror 19 can be a plane deflection mirror or a mirror with a beam-influencing effect beyond a pure deflection effect. Alternatively or additionally, the deflection mirror 19 can be embodied as a spectral filter that separates the used optical wavelength of the illumination radiation 16 from extraneous light of wavelengths outside of it. If the first facet mirror 20 is arranged in a plane of the illumination optical unit 4 that is optically conjugate with 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, hereinafter also referred to as field facets. FIG. 1 shows only some of these facets 21 by way of example.

[0043] The first facet 21 may be embodied as a macroscopic facet, in particular as a rectangular facet, or as a facet with an arcuate or part-circular edge profile. The first facet 21 may be embodied as a planar facet or as a convexly or concavely curved facet.

[0044] The first facet 21 itself can also consist of a number of individual mirrors, in particular a number of micromirrors, as is known, for example, from DE 10 2008 009 600. The first facet mirror 20 can in particular be configured as a microelectromechanical system (MEMS system). See DE 10 2008 009 600 for further details.

[0045] Between the collector 17 and the deflection mirror 19, the illumination radiation 16 travels horizontally, i.e. in the y direction.

[0046] A second facet mirror 22 is arranged downstream of the first facet mirror 20 in the beam path of the illumination optical unit 4. If the second facet mirror 22 is arranged in the pupil plane of the illumination optical unit 4, it is also referred to as a pupil facet mirror. The second facet mirror 22 can also be arranged away from the pupil plane of the illumination optical unit 4. In this case, the combination of the first facet mirror 20 and the second facet mirror 22 is also referred to as a specular reflector. Specular reflectors are known from US Patent Application Publication No. 2006 / 0132747, EP 1 614 008 and US 6,573,978.

[0047] The second facet mirror 22 includes a plurality of second facets 23. In the case of a pupil facet mirror, the second facets 23 are also referred to as pupil facets.

[0048] The second facet 23 may likewise be a macroscopic facet which may have, for example, a circular, rectangular or hexagonal boundary, or may be a facet made up of a micromirror. In this respect, reference is also made to DE 10 2008 009 600 A1.

[0049] The second facet 23 may have a flat reflecting surface or a convexly or concavely curved reflecting surface.

[0050] The illumination optical unit 4 therefore forms a double-faceted system. This basic principle is also called a fly's eye condenser (fly's eye integrator).

[0051] It may be advantageous not to arrange the second facet mirror 22 exactly in a plane that is optically conjugate with the pupil plane of the projection optical unit 10. In particular, the pupil facet mirror 22 may be arranged at an angle with respect to the pupil plane of the projection optical unit 10, as described, for example, in DE 10 2017 220 586 A1.

[0052] The individual first facets 21 are imaged into the object field 5 by means of a second facet mirror 22. The second facet mirror 22 is the last beam-shaping mirror in the beam path upstream of the object field 5 or indeed the final mirror for the illumination radiation 16.

[0053] In yet another 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 two or more mirrors arranged one after the other in the beam path of the illumination optical unit 4. The transfer optical unit can in particular include one or two normal incidence mirrors (NI mirrors) and / or one or two grazing incidence mirrors (GI mirrors).

[0054] In the embodiment shown in FIG. 1, downstream of the collector 17 the illumination optical unit 4 comprises exactly three mirrors, in particular a deflection mirror 19 , a field facet mirror 20 and a pupil facet mirror 22 .

[0055] In yet another embodiment of the illumination optical unit 4, the deflection mirror 19 can also be omitted, so that the illumination optical unit 4 then has exactly two mirrors after the collector 17, specifically a first facet mirror 20 and a second facet mirror 22.

[0056] The imaging of the first facet 21 onto the object plane 6 by the second facet 23 or by means of the second facet 23 and the transfer optical unit is generally only an approximate imaging.

[0057] The projection optical unit 10 comprises a number of mirrors Mi, which are numbered consecutively according to their location in the beam path of the projection exposure apparatus 1 .

[0058] 1, the projection optical unit 10 includes six mirrors M1 to M6. 4, 8, 10, 12 or any other number of mirrors Mi are equally possible. The penultimate mirror M5 and the final mirror M6 each have a passage aperture for the illumination radiation 16. The projection optical unit 10 is a double-shielded optical unit. The projection optical unit 10 has an image-side numerical aperture that is greater than 0.5, may be greater than 0.6, and may be, for example, 0.7 or 0.75.

[0059] The reflective surface of the mirror Mi can be embodied as a freeform surface without an axis of rotational symmetry. Alternatively, the reflective surface of the mirror Mi can be designed as an aspheric surface, with exactly one axis of rotational symmetry of the reflective surface shape. Like the mirrors of the illumination optical unit 4, the mirror Mi can have a coating that is highly reflective with respect to the illumination radiation 16. These coatings can be designed as multilayer coatings, in particular with alternating layers of molybdenum and silicon.

[0060] Projection optical unit 10 has a large object-image offset in the y direction between the y coordinate of the center of object field 5 and the y coordinate of the center of image field 11. This object-image offset in the y direction can be approximately as large as the z distance between object plane 6 and image plane 12.

[0061] In particular, the projection optical unit 10 can have an anamorphic configuration. In particular, it has different imaging scales βx, βy in the x and y directions. The two imaging scales βx, βy of the projection optical unit 10 are preferably (βx, βy)=(+ / -0.25, + / -0.125). A positive imaging scale β means imaging without image inversion. A negative sign of the imaging scale β means imaging with image inversion.

[0062] The projection optical unit 10 results in a size reduction in the x-direction, ie perpendicular to the scanning direction, by a ratio of 4:1.

[0063] The projection optical unit 10 provides a size reduction of 8:1 in the y-direction, ie the scan direction.

[0064] Other imaging scales are possible as well, including imaging scales of the same sign and magnitude in the x and y directions, for example 0.125 or 0.25.

[0065] The number of intermediate image planes in the x and y directions in the beam path between the object field 5 and the image field 11 may be the same or may differ depending on the design of the projection optical unit 10. An example of a projection optical unit with a different number of such intermediate images in the x and y directions is known from US Patent Application Publication No. 2018 / 0074303.

[0066] Each pupil facet 23 is assigned to exactly one of the field facets 21 in order to form a respective illumination channel that illuminates the object field 5. In particular, this makes it possible to obtain 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 intermediate foci on the respectively assigned pupil facets 23.

[0067] The field facets 21 are each imaged onto the reticle 7 in an overlapping manner by means of the assigned pupil facets 23 in order to illuminate the object field 5. The illumination of the object field 5 is in particular as uniform as possible. Its uniformity error is preferably less than 2%. By overlapping the different illumination channels, field uniformity can be achieved.

[0068] The illumination of the entrance pupil of the projection optical unit 10 can be geometrically defined by the arrangement of the pupil facets. By selecting the illumination channels, and in particular the subset of pupil facets, that direct light, the intensity distribution at the entrance pupil of the projection optical unit 10 can be set. This intensity distribution is also referred to as the illumination setting.

[0069] A similarly favorable pupil uniformity in the region of a defined illuminated portion of the illumination pupil of the illumination optical unit 4 can be achieved by redistribution of the illumination channels.

[0070] Further aspects and details of the illumination of the object field 5, in particular the entrance pupil of the projection optical unit 10, are explained below.

[0071] The projection optical unit 10 may in particular have a concentric entrance pupil, which may be accessible, or which may be inaccessible.

[0072] The entrance pupil of the projection optical unit 10 generally cannot be illuminated exactly using the pupil facet mirror 22. In the case of imaging of the projection optical unit 10 telecentrically imaging the center of the pupil facet mirror 22 onto the wafer 13, the aperture rays often do not intersect at a single point. However, it is possible to find a surface at which the determined separation between pairs of aperture rays is minimal. This surface represents the entrance pupil or a surface conjugate to it in real space. In particular, this surface exhibits a finite curvature.

[0073] The projection optical unit 10 may have different entrance pupil positions for the tangential and sagittal beam paths. In this case, an imaging element, in particular an optical component of the transfer optical unit, should be provided between the second facet mirror 22 and the reticle 7. This optical element can be used to take into account the different positions of the tangential and sagittal entrance pupils.

[0074] 1 of the components of the illumination optical unit 4, the pupil facet mirror 22 is arranged in a plane conjugate with the entrance pupil of the projection optical unit 10. The field facet mirror 20 is arranged so as to be inclined with respect to the object plane 6. The first facet mirror 20 is arranged so as to be inclined with respect to the arrangement plane defined by the deflection mirror 19.

[0075] The first facet mirror 20 is disposed so as to be inclined with respect to the disposition plane defined by the second facet mirror 22 .

[0076] FIG. 2 shows diagrammatically in meridian section a further projection exposure apparatus 101 for DUV projection lithography in which the invention can also be used.

[0077] The configuration and imaging principle of the projection exposure apparatus 101 are identical to those described in Figure 1. Identical components are designated by reference numerals that are 100 higher than those in Figure 1, i.e. the reference numerals in Figure 2 start with 101.

[0078] 1, since the wavelength of the DUV radiation 116 used as the light is large, in the range of 100 nm to 300 nm, in particular about 193 nm, refractive, diffractive and / or reflective optical elements 117, such as lens elements, mirrors, prisms, end plates, etc., can be used for imaging or illumination in the DUV projection exposure apparatus 101. The projection exposure apparatus 101 essentially comprises in this case an illumination system 102, a reticle holder 108 for receiving and precisely positioning a reticle 107 provided with structures and determining the subsequent structures on a wafer 113, a wafer holder 114 for holding, moving and precisely positioning said wafer 113, and a projection lens 110 with a number of optical elements 117, which are held by mounts 118 in a lens housing 119 of the projection lens 110.

[0079] Illumination system 102 provides the DUV radiation 116 required for imaging reticle 107 onto wafer 113. A laser, plasma source, etc. can be used as the source of this radiation 116. The radiation 116 is shaped by optics in illumination system 102 so that upon incidence on reticle 107, the DUV radiation 116 has desired properties with respect to diameter, polarization, wavefront shape, etc.

[0080] Besides the additional use of refractive optical elements 117 such as lens elements, prisms, end plates, etc., the configuration of the downstream projection optical unit 101 with the lens housing 119 is essentially the same as that described in FIG. 1 and therefore will not be described in further detail.

[0081] FIG. 3 shows a schematic diagram of a ring actuator 40 in three different operating states. At the top of FIG. 3, the ring actuator 40, which has a hollow cylindrical recess, is shown in a zero state, defined in the illustrated example at half of its total possible deflection. From this zero state, the ring actuator 40 can expand, as shown in the lower left of FIG. 3, or contract, as shown in the lower right. As will be described in more detail below in FIG. 15 in connection with the installation and operation of the ring actuator 40, the zero state occurs for a specific zero voltage at the zero state, and expansion and contraction of the ring actuator 40 are caused by increasing or decreasing the voltage by a controller (not shown). Alternatively, if appropriate materials are used, the zero state can also correspond to a no-voltage state. In this case, expansion is caused by application of a voltage having a first polarity, and contraction is caused by application of a voltage having the opposite polarity. Suitable materials for this are, for example, ceramic materials, such as lead zirconate titanate (PZT), as well as, for example, lithium niobate (LiNbO) or lithium tantalate (LiTaO).

[0082] 4a and 4b show two different embodiments of a ring actuator 40 that differ in the placement of the electrodes 42 and actuator material 41 relative to the longitudinal axis of the ring actuator 40. FIG.

[0083] Figure 4a shows an axial arrangement of layers of actuator material 41 and electrodes 42 connected to a controller 44 via electrical wires 43, as known for rod actuators from the prior art. In the embodiment shown in Figure 4a, the electrodes 42 are arranged first inside the ring actuator 40 and then outside it, although it is also possible to have both electrodes 42 contact only the outside or only the inside. The arrangement of the electrodes 42 can, for example, cause a primary deflection of the ring actuator 40 in the axial direction, i.e. perpendicular to the ring plane, with radial expansion and contraction of the ring actuator 40 being only a secondary effect.

[0084] FIG. 4b shows a radial configuration of the ring actuator 40, in which layers of actuator material 41 and electrodes 42 are arranged radially. In this case, contact with the controller 44 is made via electrical wires 43 at the top and bottom surfaces of the ring actuator 40. As already explained for FIG. 4a, an arrangement in which electrical wires 43 contact only at the top or bottom is also conceivable. This arrangement of electrodes 42 results in a primary deflection of the ring actuator 40 in the radial direction, i.e., parallel to the ring plane, while axial expansion and contraction of the ring actuator 40 are only secondary effects. In principle, the ratio of expansion and contraction (the ratio between the change in radius and the change in geometry along the axis of rotational symmetry) can be advantageously influenced by the choice of electrode position as well as the choice of electrostrictive or piezoelectric material. This allows for advantageous influence of the deformation effect on the optically active surface and, therefore, the wavefront impact of the design.

[0085] FIG. 5a shows a schematic diagram of a first embodiment of the invention, illustrating an optical element configured as a mirror Mx, 117 and applicable to one of the projection exposure apparatuses described in FIGS. 1 and 2. FIG. 5a shows the mirror Mx, 117 with a body 30 having an optically effective surface 31 and an opposite back side 32, in a view from below, i.e., looking at the back side 32 of the body 30. The ring actuator 40 is arranged in the area corresponding to the optically effective surface 31, and is arranged beyond the area of ​​the optically effective surface 31 so that deformations with positive and negative gradients can also be caused in the edge areas of the optically effective surface 31. This requires the ring actuator 40 to also expand and contract from a so-called zero position. In principle, the ring actuator 40 can also be arranged only in the edge areas or elsewhere, as long as it deforms the optically effective surface 31 when actuated.

[0086] FIG. 5b shows yet another embodiment of the invention, illustrating an optical element configured as a mirror Mx, 117, which, like the mirror Mx, 117 of FIG. 5b, comprises a body 30 with an optically active surface 31. The mirror Mx, 117 is again shown in a perspective view from the back side. A coupling feature configured as a pin 45 for a ring actuator 40 is arranged on the back side 32. The ring actuator 40 is attached to the pin 45 by shrink fitting, as will be described in more detail below in FIG. 14, although some other technique is also possible, such as adhesive bonding or bonding. Contraction or expansion of the ring actuator 40 leads to a constriction or expansion of the pin 45, which in turn causes a deformation of the optically active surface 31. This deformation effect can be compared to that of an actuator acting parallel to the surface; in the case of the ring actuator 40, the axial component of the deflection contributes to the deformation, albeit only secondary. The resulting deformation of the optically active surface 31 can be used to compensate for thermal expansion of the body 30 due to absorption of electromagnetic radiation or to compensate for imaging aberrations occurring elsewhere in the projection exposure apparatus 1, 101.

[0087] FIG. 5c shows yet another embodiment of the invention, illustrating an optical element configured as a mirror Mx, 117, which, like the mirror Mx, 117 of FIG. 5b, comprises a body 30 with an optically active surface 31. The mirror Mx, 117 is again shown in a perspective view from the rear side. A coupling feature configured as a notch 46 for a ring actuator 40 is arranged on the rear side 32. The ring actuator 40 is attached to the notch 46 by shrink fitting, as will be described in more detail below in FIG. 14, although some other techniques are also possible, such as adhesive bonding or bonding. Contraction or expansion of the ring actuator 40 leads to contraction or expansion of the notch 46, which in turn causes a deformation of the optically active surface 31. This deformation effect can be compared to that of an actuator acting parallel to the surface; in the case of the ring actuator 40, the axial component of the deflection can contribute to the deformation, although only as a secondary contribution. The resulting deformation of the optically active surface 31 can be used to compensate for thermal expansion of the body 30 due to absorption of electromagnetic radiation or to compensate for imaging aberrations occurring elsewhere in the projection exposure apparatus 1, 101.

[0088] 6a and 6b show detailed views of the present invention showing ring actuator 40 shrink-fitted onto pin 45 in two different operating states. Depending on the operating state of ring actuator 40, the effect on optically active surface 31 of body 30 is shown.

[0089] FIG. 6 a shows the ring actuator 40 in a contracted operating state, where the pins are necked down, causing an outward deformation 47 of the optically active surface 31 .

[0090] FIG. 6 b shows the ring actuator 40 in an extended operating state, where the neck of the pin 34 widens, causing an inward deformation 47 of the optically active surface 31 .

[0091] 7a shows a first embodiment of a cylindrically configured pin 45. This has the advantage that it is simple to manufacture and that standard actuators can also be used for the ring actuator 40.

[0092] FIG. 7b shows a second embodiment of the pin 48, in which the contact surface with the ring actuator is configured conically. This has the advantage that the ring actuator 40 can be fixed at least partially by simply sliding the ring actuator 40 over the pin 48 and forcing it geometrically forward. As in the case of mounting on the cylindrical pin 45, the ring actuator 40 can likewise be configured hollow cylindrical, with the hollow cylindrical interior shape of the ring actuator 40 then adapting to the conical exterior geometry of the pin 48 during shrink-fitting by means of a local expansion of the inner diameter of the ring actuator 40. The resulting prestress of the pin 48, which varies with the axial expansion of the ring actuator 40, can be taken into account in the control. Alternatively, the internal geometry of the ring actuator 40 can be configured to correspond to the pin 48, so that the contact area of ​​the ring actuator 40 with the pin 48 is configured conically. The advantages of a conical design in this case are the compensation of diameter tolerances and the possibility of an axial press-fit.

[0093] Figures 8a and 8b show interlocking features configured as notches 46, 48 in one variant of the invention. What has been said with respect to Figures 7a and 7b also applies in principle to the embodiment shown in Figures 8a and 8b, with the description naturally relating to the corresponding inner surfaces of the notches and the outer surface of the ring actuator 40, which is either axially pressed or radially pressed or shrink-fit into place using linear thermal expansion.

[0094] 9a and 9b and 10a and 10b show variants of the present invention relating to the coupling features configured as pins 45, 48 and described in FIGS. 7a and 7b, and the coupling features configured as notches 46, 49 and described in FIGS. 8a and 8b. The coupling features include a mechanical transmission region including a recess 50, which will be described in detail below based on an embodiment configured as a cylindrical pin 45 as shown in FIG. 9a. The recess 50 is formed in the center of the pin 45 and extends beyond the pin to the body 30. First, the recess 50 reduces the stiffness of the pin 45 and the body 30, so that the deformation of the optically effective surface 31 is advantageously and appropriately changed for the same deflection of the ring actuator 40. Second, the shape of the deformation of the optically effective surface 31 of the body can also be adjusted, and therefore can be adjusted in virtually any desired way, especially during the manufacturing of the body 30 and the pins 45, 48 or the notches 46, 49 using additive manufacturing methods and the associated free geometric design possibilities. The effect of the recess 50 described with respect to Figure 9a is also applicable to the embodiments shown in Figures 9b, 10a and 10b.

[0095] FIG. 11a illustrates yet another embodiment of the present invention showing an optical element configured as a mirror Mx, 117. This mirror, in addition to comprising a body 30 having an optically active surface 31, also comprises a support structure configured as a backplate 51, which includes conical pins 48 corresponding to the conical pins 48 configured on the body 30. The ring actuator 40 is configured in the form of a sleeve, so that it can be connected to both the pins 48 on the backplate 51 and the pins 48 on the body 30. The backplate 51 serves as a support structure and is either connected to the body 30 or some other structure configured to absorb forces, or is supported on the body 30 via the ring actuator 40. Support via the ring actuator 40 is possible because the ring actuator 40, which does not deflect all the way in one direction due to deformation of the optically active surface 31 in most cases, provides support for the backplate 51. FIG. 11b illustrates yet another embodiment of the present invention, with a support structure configured as a backplate 51 as in the embodiment illustrated in FIG. 11a. It differs only in the coupling geometry which is configured as a conical notch 49. All other descriptions are consistent with the description, so please refer to them.

[0096] Figure 12 shows yet another embodiment of the invention, which comprises a support structure with an integrated ring actuator 40. In this case, the backplate 54 of the support structure is made from actuator material 41, and electrodes 42 are formed only in the area of ​​the ring actuator 40. The functionality is identical to that of the embodiment described in Figure 11a.

[0097] FIG. 13a illustrates yet another embodiment of the invention, showing a detailed view of an optical element configured as a mirror Mx, 117 with a sensor 60. The mirror Mx, 117 comprises a body 30 with an optically active surface 31 and a ring actuator 40 shrink-fitted onto a conical pin 48. In the embodiment shown in FIG. 13a, the sensor 60 is configured as a Fabry-Perot interferometer. This interferometer comprises a light source 61 emitting a light beam 62 toward the rear side of the body 30, with the light beam being normally incident on the rear side. The sensor 60 uses the end face of the pin 48, which is partially transparent to the wavelength of the light beam 62, as a first mirror surface 64, and the optically active surface 31 as a second mirror surface 65. A 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 deformation of the body, the change in the distance between the two mirror surfaces 64, 65 can be determined, and from that the deformation of the optically active surface 31 can be determined. One advantage of the configuration of the sensor 60 at the center of the ring actuator 40 is that the deformation caused by the ring actuator 40 can be detected directly at the location of the deformation from the rear surface of the main body 30. Accessibility from the rear surface of the main body 30 is significantly higher than detection of deformation from the optically effective surface 31.

[0098] Figure 13b illustrates yet another embodiment of the invention, showing a detailed view of an optical element configured as a mirror Mx, 117 with a sensor 60. The mirror Mx, 117 comprises a support structure 51 as described in Figure 11a and a sensor 60, again configured like a Fabry-Perot interferometer. Unlike the arrangement described in Figure 13a, the sensor 60 uses the two end faces of a conical pin 48 formed in the backplate 51 and the body 30 as the first mirror surface 64 and the second mirror surface 65. The deformation of the optical surfaces can be estimated using calibration data or model-based predictions, e.g., FEM.

[0099] FIG. 14 shows a diagram illustrating the process of attaching a ring actuator to a coupling feature configured as a notch. The outer diameter of the ring actuator is shown on the ordinate of the diagram, and the control voltage is shown on the abscissa. In the illustrated embodiment, the ring actuator is controlled only with a positive voltage, and as the voltage increases, the diameter of the ring actuator decreases. For attachment, the ring actuator must be designed so that its diameter falls within the allowable diameter range T of the notch. A The first voltage range S is clearly smaller than M The voltage range S for control during operation B The voltage range for installation is S M and the ring actuator has a maximum notch diameter tolerance T A Voltage S that results in the following diameter G The voltage range for operation is S B is the so-called zero voltage S corresponding to the voltage at which the optically effective surface has a given surface shape. N This can be achieved by reworking the optically active surface after the ring actuators are installed, so that all rings are at zero voltage S N Alternatively, the zero voltage S N The deformation caused by the above can be maintained during the manufacturing of the optically active surface. [Explanation of symbols]

[0100] 1. Projection exposure equipment 2. Lighting system 3 Radiation source 4. Illumination optical unit 5 Object field of view 6 Object plane 7 Reticle 8 Reticle Holder 9 Reticle Displacement Drive 10 Projection optical unit 11 Image field 12 Image plane 13 wafers 14 wafer holder 15 Wafer Displacement Drive 16 EUV radiation 17 Collector 18 Intermediate focal plane 19 Deflecting mirror 20 Faceted Mirror 21 Facets 22 Faceted Mirror 23 Facets 30 Main Unit 31 Optically effective surface 32 Back side of the main body 40 Ring Actuator 41 Actuator Materials 42 electrodes 43 Electric wire 44 Controller 45-pin 46 Notch 47 Transformation 48 pin, conical 49 Notched, conical 50 recess 51 Backplate 54 Integrated backplate 60 sensors 61 Light source 62 Laser Beam 63 detector 64 First mirror surface 65 Second mirror surface 101 Projection exposure equipment 102 Lighting System 107 Reticle 108 Reticle Holder 110 Projection optical unit 113 wafers 114 Wafer holder 116 DUV radiation 117 Optical Elements 118 Mount 119 Lens Housing M1~M6 mirrors S N Zero point voltage S M Voltage range for installation S B Voltage Range for Operation S G Notch tolerance range lower limit voltage T A Notch Tolerance

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 said body (30), said actuators being designed to deform an optically effective surface (31) of said optical element (Mx, 117), the at least two actuators (40) are configured as ring actuators; At least one of the ring actuators (40) is connected to the body (30) via a coupling feature (45, 46, 48, 49); The optical element is characterized in that the connecting features (45, 48) are configured as pins (45, 48) arranged on the body (30).

2. 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), the at least two actuators (40) are configured as ring actuators; At least one of the ring actuators (40) is connected to the body (30) via a coupling feature (45, 46, 48, 49); The optical element, characterized in that the connecting features (46, 49) are configured as notches (46, 49) arranged in the body (30).

3. 2. The optical element (Mx, 117) according to claim 1, An optical element, characterized in that the body (30) and the pins (45, 48) are monolithically constructed.

4. 2. The optical element according to claim 1, An optical element, characterized in that the body (30) and the pins (45, 48) are integrally connected to each other.

5. The optical element (Mx, 117) according to any one of claims 1 to 4, An optical element, characterized in that the contact area of ​​at least one ring actuator (40) with the connecting features (48, 49) of the body (30) is configured conically.

6. The optical element (Mx, 117) according to any one of claims 1 to 4, An optical element, characterized in that the contact area of ​​the coupling geometry (48, 49) of the body (30) with at least one ring actuator (40) is configured conically.

7. The optical element (Mx, 117) according to any one of claims 1 to 4, An optical element, characterized in that at least one ring actuator (40) is connected to said coupling features (48, 49) by shrink fitting.

8. The optical element (Mx, 117) according to any one of claims 1 to 4, An optical element, characterized in that the coupling features (48, 49) of at least one ring actuator (40) comprise a mechanical transmission area (50).

9. 9. The optical element (Mx, 117) according to claim 8, The optical element is characterized in that the mechanical transmission region (50) is configured to reduce stiffness acting against the deflection of the ring actuator (40).

10. The optical element (Mx, 117) according to any one of claims 1 to 4, An optical element, characterized in that at least one ring actuator (40) is arranged between said body (30) and a support structure (51, 54).

11. 11. The optical element (Mx, 117) according to claim 10, The optical element is characterized in that the support structure (51) includes coupling features (48, 49) corresponding to at least one ring actuator (40).

12. 11. The optical element (Mx, 117) according to claim 10, An optical element, characterized in that at least one ring actuator (40) is connected to coupling features configured as pins (48) or notches (49) of said body (30) and said support structure (51, 54).

13. 11. The optical element (Mx, 117) according to claim 10, An optical element, characterized in that at least one ring actuator (40) is integrated into said support structure (54).

14. The optical element (Mx, 117) according to any one of claims 1 to 4, An optical element characterized in that the electrodes (42) and actuator material (41) of at least one ring actuator (40) are layered in the radial or axial direction.

15. 1. An optical element (Mx, 117) of a projection exposure apparatus (1, 101) for semiconductor lithography, the optical element (Mx, 117) comprising a sensor (60) for determining deformation of an optically effective surface (31) of the optical element (Mx, 117), the sensor (60) being designed to detect a signal that correlates with the deformation of said optically effective surface (31).

16. 16. The optical element (Mx, 117) according to claim 15, The optical element, wherein the sensor (60) includes an interferometer.

17. 17. The optical element (Mx, 117) according to claim 16, The optical element, wherein the sensor (60) includes a Fabry-Perot interferometer.

18. An optical element (Mx, 117) according to any one of claims 15 to 17, An optical element characterized by being a deformable mirror.

19. 19. The optical element (Mx, 117) according to claim 18, The optical element is characterized in that the deformable mirror is a force-activated mirror.

20. 19. The optical element (Mx, 117) according to claim 18, The optical element is characterized in that the deformable mirror is a mirror actuated by a solid actuator.

21. An optical element (Mx, 117) according to any one of claims 15 to 17, An optical element (Mx, 117) according to claims 1 to 4.

22. 22. The optical element (Mx, 117) according to claim 21, An optical element, characterized in that the actuation direction of at least one ring actuator (40) is aligned perpendicular to the contact area of ​​said ring actuator (40) with the optical element (Mx, 117).

23. 22. The optical element (Mx, 117) according to claim 21, An optical element, characterized in that the actuation direction of at least one ring actuator (40) is aligned parallel to the contact area of ​​said ring actuator (40) with the optical element (Mx, 117).

24. 22. The optical element (Mx, 117) according to claim 21, The optical element is characterized in that the sensor (60) detects deformation of the optically effective surface (31) through the center of at least one ring actuator (40).

25. A projection exposure apparatus (1, 101) comprising an optical element (Mx, 117) according to any one of claims 1 to 4, 15 to 17.

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