Temperature insensitive actuator and deformable mirror

Abstract

The invention relates to an actuator (100) for semiconductor lithography comprising an actuator element (102) having a first coefficient of thermal expansion and having a connection portion (103) at a first end for active adjustment of an optical element (300) along at least one adjustment axis (101), characterized in that the actuator (100) comprises a compensating element (104) having a second coefficient of thermal expansion with a sign corresponding to the sign of the first coefficient of thermal expansion, oriented coaxially with respect to the adjustment axis (101) and having a coupling portion (110) which is spatially fixed or fixed with respect to the optical element, and a connecting element (111) connecting the actuator element (102) and the compensating element (104) at a location remote from the coupling portion (103) and the coupling portion (110). The invention further relates to a deformable mirror.

Description

[Technical field]

[0001] This application claims priority to German Patent Application No. 10 2022 204 014.7, filed April 26, 2022, which is incorporated herein by reference in its entirety and forms part of the present disclosure.

[0002] The present invention relates to an actuator, in particular a solid-state actuator, for semiconductor lithography comprising an actuator element having a first coefficient of thermal expansion and having a connection site at a first end for active adjustment of an optical element along and / or parallel to at least one adjustment axis. [Background technology]

[0003] Projection exposure apparatuses are used in particular for producing extremely fine structures on semiconductor components or other microstructured component parts. The functional principle of these apparatuses is based on the production of extremely fine structures down to the nanometer range by generally reducing the imaging of structures on a mask, the so-called reticle, onto an element to be structured, the so-called wafer, which is provided with a light-sensitive material. The minimum dimensions of the structures to be produced directly depend on the wavelength of the light used. The light is shaped in an illumination optical unit for optimal illumination of the reticle. Recently, light sources with an emission wavelength in the range of a few nanometers, for example between 1 nm and 120 nm, in particular around 13.5 nm, are increasingly used. The wavelength range is also referred to as the EUV range.

[0004] Besides using systems operating in the EUV range, microstructured component parts are also manufactured using commercially established DUV systems with wavelengths between 100 nm and 300 nm, especially 193 nm. The demands on the optical corrections of the systems are ever increasing along with the demands to enable smaller structures to be produced. Each new generation of projection exposure tools in the EUV or DUV range increases the throughput in order to increase the profitability, but this usually leads to a higher heat load and therefore to higher thermally induced imaging aberrations.

[0005] In order to correct imaging aberrations, so-called manipulators can in particular be used in individual or all optical assemblies of the projection optical unit, which change the position and alignment of optical elements, in particular mirrors, or influence the imaging properties of optical elements by deforming the optically effective surface. In this case, the optically effective surface is understood to mean the surface of the optical element on which the used light falls during the operation of the assigned device. In this case, the used light is understood to mean the electromagnetic radiation used for imaging the structure.

[0006] In order to be able to adjust, i.e. manipulate, the optical elements, actuators, in particular solid-state actuators, are usually used, whereby the positioning is disturbed by thermal expansion resulting from an increased thermal load. In combination with a deformable optical unit, imaging aberrations result.

[0007] US Pat. No. 5,399,433 relates to the thermal expansion of solid actuators, which is compensated by CTE matching (CTE: coefficient of thermal expansion), i.e. by compensation of the coefficient of thermal expansion. In that case, the actuator comprises various materials with different coefficients of thermal expansion, so that the desired expansion behavior is obtained from the composite thus formed. Many materials that exhibit electrostrictive, piezostrictive, magnetostrictive or photostrictive behavior and are therefore particularly suitable for use as solid actuators have a positive coefficient of thermal expansion, i.e. the body expands with increasing temperature. Therefore, a combination with a material having a negative CET is necessary so that the thermal expansion behavior can be compensated. Materials with a negative CTE are only suitable to a limited extent for use in projection exposure apparatus, since they tend to degrade under general environmental conditions. Other materials, such as zirconium tungstate, pose other design and process engineering difficulties.

[0008] Furthermore, the prior art discloses an athermal lens element mount in which one end of a first mount element is connected to a lens element and the other end is connected to a compensation element disposed parallel to the first mount element. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] DE 10 2020 201 774 A1 Summary of the Invention [Problem to be solved by the invention]

[0010] It is therefore an object of the present invention to provide an actuator and a deforming mirror which eliminates or at least reduces the above-mentioned disadvantages of the prior art. [Means for solving the problem]

[0011] The object with respect to the actuator is achieved by an actuator having the features of claim 1. The object with respect to the deformable mirror is achieved by an actuator having the features of claim 1. 16 This is achieved by a deformation mirror having the features set forth in claim 1. Advantageous configurations with advantageous developments are specified in the dependent claims.

[0012] The actuator is particularly characterized in that a compensating element is present having a second thermal expansion coefficient whose sign corresponds to the sign of the first thermal expansion coefficient, and that the compensating element is oriented coaxially, in particular parallel, to the adjustment axis and has a coupling site that is spatially fixed or fixed relative to the optical element. The binding site is connected, in particular fixedly connected, to the optical element. The optical element can be, for example, a mirror or a lens element, which can also include a frame, in particular a force frame. In this case, the term fixed relative to the optical element means that the coupling site is either fixed relative to the mirror body and / or the mirror back side, or fixed relative to the lens element body and / or the lens element edge, or fixed relative to the frame, or fixed relative to a coupling site of the optical element that is coupled to the optical element or to any other reference element assigned to the optical element. Furthermore, there is a connection element that connects the actuator element and the compensation element at a location remote from the connection site or coupling site.

[0013] The compensating element, which has a second coefficient of thermal expansion, the sign of which corresponds to the sign of the first coefficient of thermal expansion, allows the expansion of the actuator element due to a change in temperature to be compensated for by the expansion of the compensating element in the same direction. In this respect, thermal expansion means that the geometry of the element changes as a whole in the case of a change in temperature, i.e. for example the length of the element increases or decreases. The thermal expansion of the element is therefore to be understood as being similar to the thermal expansion coefficient of the material.

[0014] The connection site of the actuator element is adjustable relative to the connection site, by the connection site being fixed in space or relative to a reference element assigned to the optical element, such as an optical element or a frame, i.e. fixedly connected to the optical element. In this case, the position of the connection element in space is defined by the compensation element. If the compensation element expands more than the actuator element, the connection site of the actuator element is displaced relative to the connection site in a first (negative) direction along or parallel to the adjustment axis. Conversely, if the thermal expansion of the compensation element is smaller than that of the actuator element, the connection site is displaced relative to the connection site in a second (positive) direction opposite to the first direction along or parallel to the adjustment axis. By the choice of the geometry and / or material and / or thermal expansion coefficient and / or configuration of the connection between the actuator element and the optical element, the temperature-dependent adjustment of the connection site can be influenced such that the adjustment of the connection site is temperature-independent. In this case, the term "adjustment" of the optical element encompasses a translational and / or rotational movement or displacement of the optical element (as a whole) caused by the actuator, as well as at least a regional deformation of the optical element caused by the actuator.

[0015] In this case, the actuator element may have electrostrictive, piezostrictive, magnetostrictive or photostrictive behavior. In principle, other types of actuators suitable for application in semiconductor technology, in particular in projection exposure apparatus for semiconductor technology, are also conceivable. In particular, it is preferred if the actuator element is formed as a piezo actuator element. In this case, the actuator can have a layered configuration. Similarly, the compensation element can also be formed in multiple layers. This makes it possible to combine different materials in one compensation element. The actuator can have any desired shape in this case. It can preferably be configured as a parallelepiped, cylindrical, prismatic, in particular polygonal, particularly preferably hexagonal or octagonal base. Furthermore, it is advantageous if the actuator element is embodied and controllable in such a way that it is adjustable in one or two directions with respect to the adjustment axis.

[0016] In the context of the invention, it is preferred if the actuator element and the compensation element are connected end-to-end by a connecting element, in particular at the end faces, but alternatively it is also possible for the actuator element and the compensation element to be connected to one another at any desired location. There is thus one or more local connections. It is particularly advantageous if the actuator element and the compensation element are connected to one another in a material-tight or friction-tight manner. This connection can take place by direct bonding, a material-tight bonding, i.e. gluing, welding, soldering or by pressing.

[0017] Furthermore, particularly when the actuator is used under environmental conditions within a projection exposure apparatus, it is preferred if both the first and second thermal expansion coefficients are positive, however it is also possible for both the first and second thermal expansion coefficients to be negative.

[0018] It is furthermore advantageous if the thermal expansion coefficients of the actuator element and the compensating element are matched to one another. In particular, it is advantageous if the actuator element and the compensating element are manufactured from the same substance, i.e. from the same material, particularly preferably from the same semi-finished product. In this respect, it is also advantageous if the actuator element and the compensating element are matched in size along or parallel to the adjustment axis. In the case of matched thermal expansion coefficients of the actuator element and the compensating element and matched in size along or parallel to the adjustment axis, a complete compensation of the compression or expansion of the actuator due to temperature changes is possible if the temperature distribution in the actuator is at least approximately uniform, and the actuator is temperature insensitive or athermal.

[0019] However, depending on the configuration of the actuator and its connection to the optical element, the size and / or thermal expansion coefficient of the actuator element and the compensation element along the adjustment axis can also be different, in particular differing from each other by a multiple. In case of a temperature gradient between the coupling and connection parts of the actuator, it is advantageous if the thermal expansion coefficients and / or size along or parallel to the adjustment axis of the actuator element and the compensation element are different from each other. In this case, if the temperature in the heat transfer path in the actuator is known and the thermal resistance of the compensation element and the actuator element is known, the size along or parallel to the adjustment axis and the thermal expansion coefficient can be adapted so that the displacement due to the heat flow can be compensated. In other words, it is possible to find a pair of thermal expansion coefficients and sizes of the compensation element and the actuator element such that the displacement due to the heat flow is reduced or compensated. As an additional parameter, the thermal conductivity of the actuator element and / or the compensation element can be adapted.

[0020] It is furthermore preferred if the compensation element is formed as an additional actuator element. In this case, the actuator element and the additional actuator element can be adjustable in one or two directions along or parallel to the adjustment axis. It can furthermore be advantageous if one of the actuator element and the additional actuator element is used only for adjusting the optical element in a first direction along or parallel to the adjustment axis, whereas the other of the optical element and the additional actuator element is used only for adjusting the optical element in a direction opposite to the first direction along or parallel to the adjustment axis. This is particularly advantageous in the case of piezoelectric actuators, in particular ceramic piezoelectric actuators, but also crystalline piezoelectric actuators, in order to minimize hysteresis. It is furthermore advantageous if one of the actuator element and the additional actuator element is configured to be (exclusively) compressed, in particular by controlling it, and the other of the actuator element and the additional actuator element is configured to be (exclusively) expanded. The resulting overlap of the individual movements allows a doubling of the total movement of the actuator. It goes without saying that both, i.e. the additional actuator element and the actuator element, can also be configured to be (exclusively) compressed or (exclusively) expanded.

[0021] In order to minimize the temperature difference between the actuator element and the compensation element, it is preferable if both are in good thermal contact with each other. It is therefore advantageous if the actuator element and the compensation element are at least partially connected to each other with a gap formed between them. In other words, the actuator has an additional (second) connection. In this case, this connection can be formed by a flexure or a heat conducting element or by a ductile solid.

[0022] In a particularly preferred embodiment, the gap is at least partially filled with a liquid having a thermal conductivity higher than that of air. Thermally conductive pastes, oils, in particular transducer oils, are suitable for this purpose.

[0023] In order to ensure a good coupling to the optical element to be adjusted, it is preferred if the actuator element is formed in two parts, of which only one part is formed from an actively controllable material, i.e. a piezoelectric, electrostrictive, piezoelectric or magnetostrictive material. In order to increase the thermal resistance between the optical element and the actuator, it is preferred if a constriction is embodied in the other part. Alternatively or additionally, it is also possible for the other part, i.e. the actively controllable part of the actuator element, to have a higher thermal conduction resistance compared to said one part. Likewise, the compensation element can also be embodied in two parts, consisting of the compensation element and a second part / adapter for connection to the optical element or to a frame of the optical element. The connection to the optical element can be made, for example, material-connectively, by gluing / bonding. Alternatively, the other part can also be a constituent part of the optical element. Particularly preferably, the other part is formed from the same material as the optical element. However, it is particularly preferred that the other part can be integrally connected to the optical element or ground out of a glass block.

[0024] To simplify the design of the actuator, it is advantageous if one of the actuator element and the compensation element is formed as a hollow body and the other of the actuator element and the compensation element is accommodated in the hollow body. Preferably, one of the actuator element and the compensation element is formed as a hollow body that accommodates the other element. In this case, the hollow body can preferably be formed as a hollow cylinder or a hollow parallelepiped or a hollow prism. The element formed as a hollow body then preferably has two or more connection sites or coupling sites to the optical element.

[0025] Furthermore, there can also be several compensation elements connected to the actuator element. These can be arranged at a distance from one another, in particular at a fixed distance from one another, on the circumference of the actuator element. If the compensation elements are formed as additional actuator elements, a failure of one of the compensation elements, for example an electrical failure, can be compensated for by one of the other compensation elements.

[0026] The deformable mirror according to the invention for semiconductor lithography, comprising a mirror substrate with a reflecting surface and a mirror rear side located opposite the reflecting surface, is defined by the presence of at least one actuator as described above, comprising an actuator element connected to the mirror rear side. The deflection of the actuator at least partially deforms the mirror rear side and the mirror substrate, as a result of which, due to the stiffness of the mirror, the optically active surface of the mirror, i.e. the reflecting surface, is also at least partially deformed. As a result of the deformation of the optically active mirror surface, the imaging properties of the mirror are changed, so that the imaging aberrations of the projection optical unit can be compensated. The optically active surface is understood here to be the surface on which the used radiation, i.e. the radiation used for imaging and exposure, strikes during normal operation of the relevant device. Due to the specific configuration of the actuator, a more temperature-independent and therefore more precise adjustment of the actuator can be performed, since the adjustment / change in length of the actuator element along or parallel to the adjustment axis caused by temperature changes is compensated by a movement of the compensation element in the same direction.

[0027] In this case, the embodiments and advantages mentioned in connection with the actuator also apply to a deformable mirror having at least one actuator.

[0028] In one embodiment, the deformation mirror can have a force frame, i.e. a frame is arranged between the actuator and the rear side of the mirror. The compensation element is indirectly or directly connected to the rear side of the frame that does not face the rear side of the mirror at the coupling site. The frame further has at least one passage in which the actuator element and / or the adapter are arranged. The frame in particular has a number of passages, particularly preferably a number of passages adapted to the number of actuator elements.

[0029] Alternatively, at least one compensation element is also connected directly or indirectly (by an adapter) to the rear side of the mirror at the coupling site. This allows a so-called force frame-free, i.e. frame-free, embodiment. This embodiment is particularly characterized in that the compensation element and the actuator element are connected to the same heat source, i.e. to the rear side of the mirror. In case of an increase in the mirror temperature due to the incidence of light, the same heat input can be expected at the actuator and the compensation element. Furthermore, the manufacture of the deformable mirror is simplified.

[0030] Further features, properties and advantages of the invention are explained in more detail below on the basis of variant embodiments and with reference to the attached drawings, in which all the features mentioned above and below are advantageous individually or in any desired combination, the variant embodiments which are described below are merely examples but do not limit the subject matter of the invention. [Brief description of the drawings]

[0031] [Figure 1a] 1 shows a schematic diagram of a microlithography projection exposure apparatus designed to operate with EUV. [Figure 1b] 1 shows a schematic diagram of a microlithography projection exposure apparatus designed to operate in the DUV. [Diagram 2] 1 shows a schematic cross-sectional view of a first exemplary embodiment of an actuator according to the invention; [Diagram 3] 3 shows a schematic cross-sectional view of a second exemplary embodiment of an actuator according to the invention; [Figure 4] 13 shows a schematic cross-sectional view of a third exemplary embodiment of an actuator in which the compensation element is embodied as an additional actuator element; [Diagram 5] FIG. 13 shows a schematic diagram of a fourth exemplary embodiment with three compensation elements. [Figure 6] FIG. 5 shows a schematic cross-sectional view of the actuator shown in FIG. 4 in combination with an optical element. [Figure 7] 1 shows a schematic cross-sectional view of an actuator element. [Figure 8]FIG. 1 shows a schematic diagram of a deforming mirror with multiple actuators with a force frame. [Figure 9] FIG. 1 shows a schematic diagram of a deforming mirror with multiple actuators without a force frame. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0032] 1a shows a schematic diagram of an exemplary projection exposure apparatus 600 designed to operate with EUV, in which the invention can be implemented, i.e. in which an actuator 100 according to the invention can be used. However, the invention can also be used in other nanopositioning systems.

[0033] According to FIG. 1a, the illumination device of a projection exposure apparatus 600 designed for EUV comprises a field facet mirror 603 and a pupil facet mirror 604. Light from a light source unit comprising a plasma light source 601 and a collector mirror 602 is directed to the field facet mirror 603. A first telescope mirror 605 and a second telescope mirror 606 are arranged downstream of the pupil facet mirror 605 in the optical path. Downstream in the optical path is arranged a deflection mirror 607 which directs the incident radiation to an object field in the object plane of a projection lens comprising six mirrors 651-656. At the location of the object field a reflective structure-carrying mask 621 is arranged on a mask stage 620 and is imaged with the aid of the projection lens to an image plane, at which a substrate 661 covered with a photosensitive layer (photoresist) is located on a wafer stage 660.

[0034] The invention can also be used in a DUV device as shown in figure 1. The DUV device is in principle constructed like the above mentioned EUV device from figure 1a, mirrors and lens elements can be used as optical elements of the DUV device, the light source of the DUV device emitting the used radiation in the wavelength range of 100 nm to 300 nm.

[0035] The DUV lithography apparatus 700 shown in FIG. 1b comprises a DUV light source 701. As an example, an ArF excimer laser emitting radiation 702 in the DUV range, for example at 193 nm, can be provided as the DUV light source 701. A beam shaping and illumination system 703 directs the DUV radiation 702 to a photomask 704. The photomask 704 can be embodied as a transmissive optical element and arranged outside the system 703. The photomask 704 has a structure that is imaged in a reduced form, e.g. onto a wafer 706, by a projection system 705. The projection system 705 comprises a number of lens elements 707 and / or mirrors 708 for imaging the photomask 704 onto the wafer 706. In this case, the individual lens elements 707 and mirrors 708 of the projection system 705 can be arranged symmetrically with respect to an optical axis 709 of the projection system 705. It should be noted that the number of lens elements 707 and mirrors 708 of the DUV lithography apparatus 700 is not limited to the number shown. A greater or lesser number of lens elements 707 and / or mirrors 708 can also be provided. In particular, the beam shaping and illumination system 703 of the DUV lithography apparatus 700 includes a number of lens elements 707 and mirrors 708. Furthermore, the mirrors are generally curved at the front side for beam shaping purposes. The air gap 710 between the last lens element 707 and the wafer 706 can be replaced by a liquid medium having a refractive index greater than 1. The liquid medium can be, for example, high purity water. Such an arrangement is also called immersion lithography and has a high photolithography resolution. The actuator according to the invention can be used for adjusting and / or deforming the lens elements 707 and / or mirrors 708 of the DUV lithography apparatus 700, in particular of its projection system 705.

[0036] 2 shows a first exemplary embodiment of an actuator 100 for semiconductor lithography according to the invention. This actuator comprises an actuator element 102, which has a first thermal expansion coefficient and a connection site 103 at a first end for active adjustment of an optical element 300 (not shown in more detail), for example a lens element or a mirror, along or parallel to at least one adjustment axis 101 (in this case the z-axis). Furthermore, there is a compensation element 104, which has a second thermal expansion coefficient of a sign corresponding to the sign of the first thermal expansion coefficient. Thus, both the compensation element 104 and the actuator element 102 can have a positive or negative thermal expansion coefficient. The compensation element 104 is oriented coaxially, in particular parallel, to the adjustment axis 101. Furthermore, the compensation element 104 has at least one coupling site 110, which is spatially fixed or fixed relative to the optical element 300 or a reference element assigned to the optical element 300, for example the frame 200. That is to say, the coupling site 103 is movable relative to the coupling site 110. The actuator element 102 and the compensation element 104 are connected by a connection element 111 at a position remote from the connection site 103 and the coupling site 110. In this case, the actuator element 102 can be formed from a material exhibiting an actively controllable behavior, in particular electrostrictive, piezostrictive, magnetostrictive or photostrictive behavior. Particularly preferably, the actuator element 102 is formed as a piezoelectric actuator element. In this case, the piezoelectric actuator element preferably has a plurality of piezostrictive layers stacked one on top of the other. The use of a relaxor ferroelectric, such as lead magnesium niobate (PMN), is also a particularly preferred embodiment. If the actuator 100 is formed as a piezoelectric actuator 100, it is preferably formed as a crystalline piezoelectric actuator, for example based on a niobate, such as lithium niobate.

[0037] In this case, the actuator 100 shown in Fig. 2 has an adjustment axis 101 in the z-direction, so that an optical element 300 (not shown in more detail), such as a mirror or lens element, can be adjusted along or parallel to the z-axis. In this case, the actuator 100 is characterized in that the distance between the connection site 103 and the coupling site 110 along or parallel to the adjustment axis 101 is temperature independent. If the thermal expansion of the compensation element 104 is greater than that of the actuator element 102, the connection site 103 is displaced in the negative z-direction relative to the coupling site 110. In contrast, if the thermal expansion of the compensation element 104 is smaller than that of the actuator element 102, the connection site 103 is displaced in the positive z-direction relative to the coupling site 110 in Fig. 2. By appropriate selection of the geometry, in particular the length, and the thermal expansion coefficients, materials, of the optical element 300 and the actuator 100, as well as the connections between them, it is possible to realize an athermal design of the actuator 100, i.e. a temperature independent adjustment along or in particular parallel to the adjustment axis 101.

[0038] In this case, the position of the connection element 111 is determined by the size of the compensating element 104 along or parallel to the adjustment axis 101. In the simple case, if the temperature distribution in the actuator 100 is uniform and the thermal expansion coefficients of the compensating element 104 and the actuator element 102 match each other and the size / length along or parallel to the adjustment axis 101 match each other, the thermal expansion of the compensating element 104 due to temperature leads to a displacement of the connection element 111 along the negative z-axis. With the above assumptions, the absolute value of the thermal expansion of the actuator element 102 matches the absolute value of the thermal expansion of the compensating element 104, i.e., a displacement due to temperature of the connection site 103 of the actuator element 102 in the positive z-direction is compensated by a displacement of the same absolute value in the negative z-direction of the connection element 111 caused by the compensating element 104.

[0039] 2 further shows that in this case the compensating element 104 is terminally connected to the actuator element 102 by a connecting element 111. This connection can be made by a material-fitting joint such as direct bonding, gluing, welding, soldering, or by a friction-fitting engagement such as pressing.

[0040] The dimensions of the actuator element 102 and the compensation element 104 along or parallel to the adjustment axis 101 are in this case further matched. Furthermore, the compensation element 104 is formed as a hollow cylinder which accommodates the hollow element 102.

[0041] However, the thermal expansion coefficients and the magnitude along or parallel to the adjustment axis 101 of the compensation element 104 and the actuator element 102 can also differ from each other, in particular by a multiple.

[0042] In an alternative embodiment (not shown in more detail), for example when there is a temperature gradient between the coupling portion 110 and the connection portion 103 of the actuator 100, it is advantageous if the thermal expansion coefficients and / or the magnitude along or parallel to the adjustment axis 101 of the actuator element 102 and the compensation element 104 are different from each other. In this case, if the temperature in the heat transfer path in the actuator 100 is known and the thermal resistance of the compensation element 104 and the actuator element 102 is known, the magnitude along or parallel to the adjustment axis 101 and the thermal expansion coefficient can be adapted so that the displacement / length change due to the heat flow can be compensated. In other words, it is possible to find a pair of thermal expansion coefficients and magnitudes of the compensation element 104 and the actuator element 102 such that the displacement / length change due to the heat flow is reduced or compensated. The thermal conductivity of the actuator element 102 and / or the compensation element 104 and / or the connection element 111 can be adapted as an additional parameter.

[0043] Fig. 3 shows yet another exemplary embodiment of an actuator 100 according to the invention, in which a gap 106 embodied between the actuator element 102 and the compensation element 104 at least partially thermally connects the elements, i.e. the elements are in thermal contact with each other. This allows to improve the thermal conductivity and minimize the temperature difference between the elements 102, 104. The partial connection can be achieved by incorporating a thermal bridge, in particular a (flexible) flexure, a thermally conductive element, or by filling the gap 106 with a liquid having a thermal conductivity higher than that of air. By way of example, thermally conductive pastes and oils, in particular transducer oils, are also suitable in this case. Likewise, the gap 106 can be completely or partially filled with an elastic material, such as a metal, a solder or a plastic. The paste can be embodied as an elastic composition and can be mixed with metallic and / or ceramic elements, such as particles and / or fibers, to increase the thermal conductivity.

[0044] Figure 4 shows yet another exemplary embodiment of an actuator 100 according to the invention, in which the compensation element 104 is formed as an additional actuator element 105. In this case, the additional actuator element 105 is preferably embodied identically to the actuator element 102, i.e. if the actuator 102 is formed as a piezoelectric actuator element, the additional actuator element 105 is also formed as a piezoelectric actuator element. The arrows 112, 113 in Figure 4 here indicate the application of an electric field. If the additional actuator element 105 is in particular configured to be compressed under its control, whereas the actuator element is configured to expand, as diagrammatically shown by the arrows in Figure 6, the total movement of the actuator 100 can be increased.

[0045] 5 shows yet another exemplary embodiment of an actuator 100 according to the invention with a number of compensating elements 104 arranged around the circumference of the actuator element 102, where the compensating elements 104 in this case are formed as additional actuator elements 105. In case of malfunction of one of the compensating elements 104, the remaining compensating elements 104 / additional actuator elements 105 are able to compensate for the length change due to temperature of the actuator element 102.

[0046] Fig. 6 shows the coupling of the actuator 100 to an optical element 300, for example to a mirror or lens element. In this case the compensation element 104 is formed as an additional actuator element 105. In this case the arrows in Fig. 6 indicate that the actuator element 102 is arranged to expand, whereas the additional actuator element 105 is arranged to compress along or parallel to the adjustment axis 101. This doubles the total movement of the actuator. Adjustment of the actuator 100 introduces a bending moment into the mirror, resulting in an at least partial deformation of the mirror substrate 301 and thus of the optical surface, i.e. the reflecting surface 302. In this case the reference 304 denotes the reflecting surface in the undeformed state and the reference 305 denotes the deformation profile after adjustment of the actuator 100.

[0047] 7 shows the actuator element 102 in an enlarged view with respect to the connection of the optical element 300. In this case, the actuator element 102 is preferably formed in two pieces, of which only one part 109 is formed from an actively controlled material, in particular an electrostrictive, piezostrictive, magnetostrictive or photostrictive material. The other part 108, the adapter, further preferably has a constriction 107 to increase the thermal resistance between the optical element 300 and the actuator element 102. Furthermore, the constriction 107 serves to mechanically decouple potentially unwanted moments. The compensation element 104 can be formed in two pieces, just like the actuator element 102.

[0048] FIG. 8 shows a first exemplary embodiment of a deformable mirror 300 with a mirror substrate 301 having a reflecting surface 302 and a mirror rear side 303 located opposite the reflecting surface. In this case, a number of actuators 100 are connected to the mirror rear side 303 by means of connection sites 103. If, as in this case, the actuator elements 102 are formed in two parts, the actuator elements 102 are connected to the mirror rear side 303 by means of the other part 108, i.e. by means of an adapter 108. Alternatively, the other part 108 can also be a constituent part of the deformable mirror 300. Particularly preferably, the other part 108 is formed from the same material as the mirror 300. The other part 108 can be bonded to the mirror substrate 301 or to the mirror rear side 303, but it is particularly preferred that it can be integrally connected to the mirror substrate 301 or be ground out of a glass block. Adjustment of the actuator element 102 relative to the compensation element 104 along or parallel to the adjustment axis 101 introduces a bending moment into the mirror substrate 301 resulting in at least a partial deformation of the mirror 300 , as shown diagrammatically by the deformation profile 305 .

[0049] The deformation mirror 300 shown in FIG. 8 comprises a force frame, i.e. a frame 200 is arranged between the actuator 100 and the mirror rear side 303. The compensation element 104 is connected at a coupling site 110 to the frame rear side 202 not facing the mirror rear side 303, such that the coupling site 110 is fixed relative to the frame 200. The frame 200 or the mirror body 301 comprises a bearing site (not shown in more detail) for mounting the deformation mirror 300. However, the compensation element 104 can also be made in two parts, like the actuator elements 102, with the other part / adapter 108 being connected to the frame rear side 202. The frame 200 has a number of passages 201 adapted to the number of actuator elements 102, in which the actuator elements 102, in this case the other part 108 / adapter of the actuator elements 102, are movably arranged. FIG. 8 further shows that the size of the actuator elements 102, i.e. said one part 109 of the actuator element, is different from the size of the compensation element 104 along or parallel to the adjustment axis 101.

[0050] 9 is embodied without a force frame, i.e. the compensation element 104 is also connected to the mirror rear side 303 at the coupling site 110, so that the coupling site 110 is fixed relative to the mirror, in particular relative to the mirror rear side 303, or to a connecting site embodied in the mirror rear side 303 and connecting the coupling site 110 to the mirror rear side 303. The mirror body 301 has a bearing site (not shown in more detail) for mounting the deformation mirror 300. In this case, both the actuator element 102 and the compensation element 104 are formed in two parts, with the other part / adapter 108 being connected to the mirror rear side 303. This simplifies the manufacture of the deformation mirror 300 and further makes it possible to connect the actuator element 102 and the compensation element 104 to the same heat source, i.e. to the mirror rear side 303, so that an increase in the mirror temperature has the same effect on the compensation element 104 and on the actuator element 102. [Explanation of symbols]

[0051] 100 Actuator 101 Adjustment axis 102 Actuator element 103 Connection Site 104 Compensation element 105 Additional Actuator Element 106 Gap 107 Stenosis 108 Adapter / other part 109 First part of actuator element 110 Binding Site 111 Connection means 112 Electric field direction of additional actuator element 113 Electric field direction of actuator element 200 frames Aisle 201 202 Rear side of frame 300 Mirror 301 Mirror substrate 302 Reflective surface 303 Rear mirror 304 Undeformed Optical Surface Profile 305 Deformation Profile 600 Projection exposure equipment 601 Plasma Light Source 602 Collector mirror 603 Field of view facet mirror 604 Eye Facet Mirror 605 First Telescope Mirror 606 No. 2 Telescope Mirror 607 Deflection Mirror 620 Mask Stage 621 Mask 651 Mirror (projection lens) 652 Mirror (projection lens) 653 Mirror (projection lens) 654 Mirror (projection lens) 655 Mirror (Projection Lens) 656 Mirror (projection lens) 660 Wafer Stage 661 Coated Substrate 700 DUV Lithography Equipment 701 DU light source 702 DUV Radiation / Beam Path 703 Beam shaping and projection system (DUV) 704 Photomask 705 Projection system 706 Wafer 707 Lens Element 708 Mirror 709 Optical axis

Claims

1. An actuator (100) for semiconductor lithography, comprising: An actuator (100) comprising an actuator element (102) having a first coefficient of thermal expansion and having a connection site (103) at a first end for active adjustment of an optical element (300) along at least one adjustment axis (101), a second coefficient of thermal expansion having a sign corresponding to the sign of the first coefficient of thermal expansion; is oriented coaxially with respect to said adjustment axis (101); and a compensating element (104) having a binding site (110) that is fixed in space or relative to the optical element; a connection element (111) that connects the actuator element (102) and the compensation element (104) at a position away from the connection portion (103) and the coupling portion (110); An actuator characterized by:

2. 2. The actuator (100) of claim 1, wherein the actuator element (102) and the compensation element (104) are connected end to end by the connecting element (111).

3. The actuator (100) of claim 1 or 2, wherein both the first and second thermal expansion coefficients are positive.

4. The actuator (100) according to any one of claims 1 to 3, characterized in that the first thermal expansion coefficient and the second thermal expansion coefficient of the actuator element (102) and the compensation element (104) are mutually consistent.

5. The actuator (100) according to any one of claims 1 to 4, characterized in that the actuator element (102) and the compensation element (104) have the same size along the adjustment axis (101).

6. The actuator (100) according to any one of the preceding claims, characterized in that the compensation element (104) is formed as an additional actuator element (105).

7. 7. The actuator (100) according to claim 6, characterized in that the actuator element (102) and the further actuator element (105) are bi-directionally or uni-directionally adjustable along the adjustment axis.

8. 7. The actuator (100) of claim 6, wherein one of the actuator element (102) and the additional actuator element is configured to be compressed along the adjustment axis (101), and the other of the actuator element (102) and the additional actuator element is configured to be expanded along the adjustment axis (101).

9. An actuator (100) according to any one of claims 1 to 8, characterized in that the actuator element (102) and the compensation element (104) are at least partially interconnected with a gap (106) formed therebetween.

10. 10. The actuator (100) of claim 9, wherein the gap (106) is at least partially filled with a liquid having a thermal conductivity greater than that of air.

11. The actuator (100) according to any one of claims 1 to 10, characterized in that the actuator element (102) is formed in two parts, only one part (109) of which includes an electrostrictive and / or piezoelectric and / or magnetostrictive element.

12. The actuator (100) according to claim 11, characterized in that a constriction (107) is embodied in the other part (108) of the actuator element (102).

13. 12. The actuator (100) according to claim 11, characterized in that the other part (108) of the actuator element has a greater thermal resistance than the one part (109).

14. An actuator (100) as described in any one of claims 1 to 13, characterized in that one of the actuator element and the compensation element is formed as a hollow body, and the other of the actuator element and the compensation element is contained in the hollow body.

15. The actuator (100) according to any one of the preceding claims, characterized in that there are a plurality of compensation elements (104) connectable to the actuator element (102).

16. A deformable mirror (300) for lithography, comprising a mirror substrate (301) having a reflective surface (302) and a mirror back side (303) located opposite the reflective surface, and at least one actuator (100) according to any one of claims 1 to 15, the at least one actuator (100) comprising an actuator element (102) connectable to the mirror back side (303).

17. 17. A deformable mirror (300) according to claim 16, characterized in that a frame (200) is arranged between the actuator (100) and the mirror rear side (303), the compensation element (104) is connected to a frame rear side (202) that does not face the mirror rear side (303) at the coupling portion (110), the frame (200) has at least one passage (201) in which the actuator element (102) is movably arranged.

18. 17. A deforming mirror (300) according to claim 16, characterized in that at least one compensation element (104) is also connected directly or indirectly to the rear mirror side (303) at the coupling site (110).

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