Projection objective system including optical devices

Abstract

The present invention relates to a projection exposure apparatus (400, 100) with a projection objective (408, 107, 200), which includes an optical device (1), which includes an optical element (2) with an optically effective surface (2 a) and at least one electrostrictive actuator (3) deformable by application of a control voltage, the electrostrictive actuator (3) being operatively connected to the optical element (2) for influencing the surface shape of the optically effective surface (2 a). A control device (4) is provided for supplying a control voltage to the electrostrictive actuator (3). In order to take into account temperature-dependent effects during driving of the electrostrictive actuator (3) by the control device (4), a measuring device (5) is provided which is configured to directly measure and / or indirectly determine the temperature and / or temperature changes of the electrostrictive actuator (3) and / or its surroundings at least temporarily while the electrostrictive actuator (3) is influencing the optically effective surface (2 a) of the optical element (2).

Description

Technical Field

[0001] This application claims priority to U.S. Provisional Patent Application No. 63 / 058,745, filed Jul. 30, 2020, and German Patent Application No. 10 2020 131 389.6, filed Nov. 26, 2020. The entire contents of both of the above prior applications are incorporated herein by reference and form part of this disclosure.

[0002] A projection exposure apparatus including a projection objective system including an optical device including an optical element and an assembly for correcting imaging aberration, and a method for affecting the surface shape of the optical element by direct or indirect temperature measurement within the projection objective system.

[0003] The present invention relates to a projection exposure apparatus including a projection objective system including an optical device, the optical device including an optical element having an optically effective surface, at least one electrostrictive actuator deformable by application of a control voltage, and a temperature sensor attached directly or in proximity to the optical device.

[0004] The present invention further relates to a method of driving a projection exposure apparatus by affecting the surface shape of an optically effective surface of an optical element that is part of a projection objective system that is part of the projection exposure apparatus, the method in which the optical element is functionally connected to an electrostrictive actuator.

[0005] The present invention further relates to a projection exposure apparatus for semiconductor lithography including an illumination system, the illumination system including a radiation source and an optical unit having at least one optical device.

Background Art

[0006] With the progress of miniaturization of semiconductor circuits, the requirements for the resolution and accuracy of projection exposure apparatuses are also increasing. Particularly strict requirements are also imposed on optical elements that particularly affect the beam path within the projection exposure apparatus.

[0007] In particular, to achieve high resolution in the lithography optical unit, EUV light with a wavelength of 13.5 nm is used in addition to VUV and DUV wavelengths of 248 nm and 193 nm, respectively.

[0008] EUV projection lithography systems use mirror systems that operate with nearly perpendicular or oblique incidence, whereas VUV and DUV systems use mirrors with perpendicular incidence. The achievable resolution is constantly improving, and consequently, the requirements for wavefront correction are becoming more stringent. As minimizing the effects becomes increasingly important, there is a growing demand for passive correction methods, but there is also a growing demand for active correction methods.

[0009] Locally deformable mirrors are known for their operation in projection exposure apparatuses. In this case, the local deformation is performed by a piezoelectric element acting as an actuator in the form of a thin plate, thin film, or thin layer; see, for example, Patent Document 1. Local deformation of mirrors using electrostrictive materials, piezoelectric materials, piezoelectric strain materials, thermal resistance materials, and magnetostrictive materials is known from Patent Document 2. [Prior art documents] [Patent Documents]

[0010] [Patent Document 1] U.S. Patent Application Publication No. 2002 / 0048096 [Patent Document 2] U.S. Patent No. 7,492,077 [Overview of the project] [Problems that the invention aims to solve]

[0011] The present invention aims to provide an assembly for correcting imaging aberrations in the projection objective system of a projection exposure apparatus, which can correct imaging aberrations with high setting accuracy.

[0012] The present invention also aims to provide a method for influencing the surface shape of an optically effective surface, which can influence the optically effective surface of an optical element with high setting accuracy. The optical element is part of a projection objective system, and the projection objective system is part of a projection exposure apparatus.

[0013] The present invention further aims to provide a projection exposure apparatus for semiconductor lithography equipped with a projection objective system, wherein the projection objective system includes at least one optical device including an optical element for correcting imaging aberrations with high setting accuracy. [Means for solving the problem]

[0014] This objective is achieved with respect to the projection exposure apparatus by the features described in claim 1.

[0015] The purpose of this claim is to affect the surface shape of the optically effective surface of an optical element placed in a projection exposure apparatus. 22 This is achieved through the characteristics of the product.

[0016] The dependent claims and the features described below relate to advantageous embodiments and variations of the present invention.

[0017] The optical device includes an optical element having an optically effective surface and at least one electrostrictive actuator that is deformable by the application of a control voltage. The electrostrictive actuator is functionally connected to the optical element to influence the surface shape of the optically effective surface. A control device is provided to supply a control voltage to the electrostrictive actuator.

[0018] In this context, the optical element should be understood to mean a preferably deformable optical element, and more preferably an adaptive optical element. Preferably, the optical element is a lens element, and more preferably a mirror, and more preferably a locally deformable mirror.

[0019] Optical elements, particularly lens elements or mirror elements, are optical elements of a projection objective system, and the projection objective system is part of a projection exposure apparatus.

[0020] In the optical device of the projection exposure apparatus, in order to take into account the influence of temperature dependency during the driving of the electrostrictive actuator by the control device, a measuring device is provided that is configured to obtain the temperature and / or temperature change of the electrostrictive actuator and / or its surroundings at least temporarily while the electrostrictive actuator affects the optically effective surface of the optical element.

[0021] According to the present invention, by obtaining the temperature and / or temperature change of the electrostrictive actuator and / or its surroundings, it is possible to take into account the influence of temperature dependency during the driving of the electrostrictive actuator.

[0022] Preferably, the temperature and / or temperature change of the electrostrictive actuator and / or its surroundings are directly measured and / or indirectly obtained.

[0023] Using the data of the measuring device, parasitic effects on the surface (e.g., bimetal effect) and / or changes in the refractive index of the optical element can be obtained.

[0024] The data of the measuring device enables high-precision driving of the electrostrictive actuator. Based on the desired surface shape, strict requirements regarding the applied control voltage and / or electric field strength can be derived. [[ID=​​​​​​​​​​

[0028] The optical devices in projection exposure systems enable the reduction of temperature-dependent effects, particularly those resulting from the irradiation of optical elements or from the heat generated by the electrostrictive actuators during operation.

[0029] With regard to the solution according to the present invention, it may be sufficient to affect multiple regions or sections of the optically effective surface with at least one electrostrictive actuator.

[0030] With regard to the solution according to the present invention, it may be sufficient to functionally connect the electrostrictive actuator to the optical element such that the surface shape of the optically effective surface can be affected in at least a specified area.

[0031] In relation to the solution according to the present invention, the electrostrictive actuator is deformable, and in particular expandable and contractible, by the application of a control voltage.

[0032] The control device is configured to take data from the measuring device into consideration to set a desired deformation of the optically effective surface of the optical element and, accordingly, drive an electrostrictive actuator for this purpose.

[0033] The strain constant of electrostrictive materials may be relatively temperature-dependent. As a result of measuring the temperature and / or temperature change and / or temperature distribution of the electrostrictive actuator, the response of the actuator material to temperature changes can be incidentally incorporated into the actuator control.

[0034] All measurement methods proposed in relation to the present invention can be used as alternatives or in any desired combination. Therefore, it is also possible to combine three or more measurement methods with each other.

[0035] In order to take into account the effect of temperature dependence during operation of the electrostrictive actuator as intended, the temperature and / or temperature change confirmed with respect to the solution according to the present invention can be used to detect and / or determine the temperature distribution around the electrostrictive actuator and / or the electrostrictive actuator itself.

[0036] It is advantageous for the measuring device to measure at least one of the following variables: Temperature and / or temperature change of the electrostrictive actuator, and / or Temperature and / or temperature changes around the electrostrictive actuator, and / or Temperature-dependent characteristics of electrostrictive actuators, and / or Changes in the surface shape of at least one surface of an optical element when a specific control voltage is applied to an electrostrictive actuator.

[0037] From the data of the measuring device, particularly the observed temperature and / or temperature change, the deformation of the optically effective surface can be estimated, for example, by simulation and / or pre-calculated tables and / or calibration. The simulation may include, in particular, finite element analysis (FE calculation) based on a material model and specific designs of the entire component, especially retaining structures, adhesive or solder connections, and components for position measurement.

[0038] Changes in the optically effective area can be converted into aberrations in the projected objective system.

[0039] It is advantageous if the electrostrictive actuator is designed such that lateral deformation of the electrostrictive actuator occurs within the plane of the actuator when a control voltage is applied.

[0040] The control device can be configured to adapt the values ​​of the m31 or d31 constants that characterize the electrostrictive transverse effect for driving the electrostrictive actuator, based on data confirmed by the measuring device, in order to account for the effects of temperature dependence.

[0041] Based on the confirmed measurement variables, the current values ​​of the m31 or d31 constants of the piezoelectric tensor were determined to be particularly appropriate when considered during the operation of the electrostrictive actuator.

[0042] It is advantageous for the measuring device to perform continuous measurements while the electrostrictive actuator is in operation.

[0043] In principle, a measuring device can only perform measurements temporarily while the electrostrictive actuator is operating. However, it was found to be advantageous if the measuring device could perform continuous measurements while the electrostrictive actuator was operating, enabling time-resolved and spatially-resolved measurements during operation.

[0044] Preferably, the measurement can be performed during a pause in the operation of the projection exposure apparatus, such as when the settings of the semiconductor substrate or mask or the illumination system of the projection exposure apparatus are changed according to the manufacturing process.

[0045] According to the present invention, the control device can be configured to take into account the thermal changes of material parameters within the electrostrictive actuator and / or components surrounding the electrostrictive actuator.

[0046] By having the control device consider the thermal changes of material parameters within the electrostrictive actuator and / or components surrounding the electrostrictive actuator, the effects of temperature dependence during operation of the electrostrictive actuator can be comprehensively considered. Therefore, the electrostrictive actuator can be driven with particularly high setting accuracy.

[0047] It has been recognized that it is advantageous to consider the thermal changes in stiffness and / or thermal expansion of adhesive or solder connections during the operation of an electrostrictive actuator. Therefore, the effects of the temperature dependence of adhesive or solder connections can also be considered particularly advantageous during the operation of an electrostrictive actuator. Where appropriate, it is also possible to consider the thermally-dependent changes in the stiffness and / or expansion of other components involved, such as the substrate of an optical element.

[0048] In principle, electrostrictive actuators can also be fixed to optical elements in different ways. In this case as well, the temperature-dependent changes and / or thermal expansion of the fixing material can be taken into consideration.

[0049] When the optical element is a mirror in the projection objective system, which is part of a projection exposure apparatus, it was found that placing an electrostrictive actuator on the back side of the optical element, facing away from the optically effective surface, is particularly suitable for influencing the optically effective surface.

[0050] In the above situation, where an optical element is part of a projection objective system which is part of a projection exposure apparatus, it may be sufficient for the electrostrictive actuator to be located in the region on the back side of the optical element.

[0051] According to the present invention, the electrostrictive actuator can further be positioned on the optically effective surface of the optical element outside the optical region or on the side surface of the optical element.

[0052] Placing an electrostrictive actuator on the optically effective surface of an optical element outside the optical domain may be appropriate as an alternative to or addition to placing it on the back side of the optical element. In particular, when the electrostrictive actuator is used in the case of a lens element, placing it on the optically effective surface of the optical element outside the optical domain may be advantageous. However, in principle, even in the case of a lens element, it is possible to place the electrostrictive actuator on the back side, particularly the side facing away from the optically effective surface outside the optical domain. As an addition or alternative, it is also possible to place the electrostrictive actuator on the side of the optical element.

[0053] According to the present invention, the electrostrictive actuator can have a plurality of electrostrictive components.

[0054] Embodiments of electrostrictive actuators having multiple electrostrictive components were found to be particularly suitable for influencing the optically effective surface in an appropriate manner, such as locally, and especially for deformation.

[0055] In embodiments of electrostrictive actuators having multiple electrostrictive components, it is particularly advantageous to determine the temperature distribution by measuring and / or determining the temperature of individual electrostrictive elements or groups of electrostrictive components. In this case, the temperature and / or temperature change can be measured and / or determined.

[0056] The electrostrictive actuator can preferably be embodied as an electrostrictive mat.

[0057] The electrostrictive actuator or electrostrictive mat may be embodied from or include a suitable material, such as lead magnesium niobate (PMN).

[0058] The electrostrictive actuator preferably has electrostrictive components arranged in a regular pattern.

[0059] The electrostrictive actuator, or the electrostrictive component of the electrostrictive actuator, may preferably each have a multilayer configuration.

[0060] According to the present invention, the measuring device can measure the capacitance and / or electrical resistance and / or frequency-dependent impedance of an electrostrictive actuator.

[0061] It was recognized that measuring the temperature-dependent characteristics of the electrostrictive actuator or individual electrostrictive components can be particularly advantageous. Subsequently, based on the measured variables, the temperature and / or temperature change of the electrostrictive actuator can be measured and / or estimated. Based on the relationship between the temperature change and the m31 or d31 constant, it is possible to determine the corresponding appropriate values ​​of the m31 or d31 constant for driving the electrostrictive actuator.

[0062] With respect to the present invention, it is not necessary to directly determine the temperature and / or temperature change. The temperature and / or temperature change of the electrostrictive actuator can also be determined indirectly by measuring its temperature-dependent characteristics. For this purpose, it has been found particularly appropriate to measure the local capacitance and / or local electrical resistance and / or local frequency-dependent impedance of the electrostrictive actuator or individual electrostrictive components or groups of electrostrictive components of the electrostrictive actuator. Other temperature-dependent characteristics can also be measured.

[0063] Measuring temperature-dependent characteristics, particularly capacitance, has the advantage of requiring little to no temperature sensors. Furthermore, because the measurement is performed directly by the electrostrictive actuator itself, the measurement becomes correspondingly more accurate.

[0064] According to the present invention, the measuring device may have an infrared camera for temperature detection and / or an electrical bridge circuit for measuring the temperature-dependent characteristics of an electrostrictive actuator.

[0065] Temperature measurement and / or measurement of temperature changes can be performed, for example, by an infrared camera, which captures the entire or partial area of ​​the optical element on which the electrostrictive actuator acts. In this case, the measurement can preferably be performed continuously during operation.

[0066] Alternatively or in addition, at least one electrical bridge circuit can be used. The bridge circuit can preferably operate with a variable frequency AC voltage.

[0067] According to the present invention, the measuring device may further include a temperature sensor that measures the temperature and / or temperature change and / or temperature distribution of the electrostrictive actuator and / or its surroundings.

[0068] To the extent that temperature sensors(s) are referred to below and in the claims, this relates to preferred embodiments of the present invention. In principle, a single temperature sensor can be provided instead of multiple temperature sensors in any case.

[0069] Measuring the temperature and / or temperature change of an electrostrictive actuator proved particularly suitable for obtaining time- and spatially resolved measurement results during operation.

[0070] The temperature distribution of the electrostrictive actuator and / or its surroundings can be determined from the measurement data.

[0071] From the measurement data, the deformation of the optically effective surface can preferably be estimated through simulation, a pre-calculated table, or calibration.

[0072] Based on a predetermined relationship between temperature and the m31 or d31 constant, the current temperature dependence of the m31 or d31 constant can be confirmed in both time-resolved and spatially-resolved manner using temperature measurements.

[0073] The temperature sensor allows for the measurement of a local and time-varying temperature field to determine the current value of the m31 or d31 constant of the piezoelectric tensor, which can be considered during the operation of the electrostrictive actuator or individual electrostrictive components of the electrostrictive actuator, based on these measured variables.

[0074] It is also possible to measure electrostrictive components.

[0075] It is advantageous if the temperature sensor is positioned on the back side of the electrostrictive actuator, facing away from the optical element.

[0076] Alternatively or in addition, according to the present invention, the temperature sensor may be positioned between the electrostrictive components of the electrostrictive actuator on one side of the optical element, preferably the side facing the electrostrictive actuator (particularly preferably the back side).

[0077] The temperature sensor can be positioned between the back of the optical element and the electrostrictive component of the electrostrictive actuator and / or locally on the back of the electrostrictive actuator or electrostrictive component. With respect to the present invention, it is not necessary to assign a temperature sensor to each electrostrictive component. It may suffice if the temperature sensors are preferably arranged at regular intervals, or if each temperature sensor is assigned to a group of electrostrictive components. In this case, the temperature sensor can preferably be positioned between two electrostrictive components and / or on the back of one of the electrostrictive components.

[0078] According to the present invention, a temperature sensor can be configured to enable resistance-based measurement by including a material whose resistance changes with temperature to a measurable extent.

[0079] It is advantageous for the temperature sensor to be configured to measure temperature changes of 0.1K or more, preferably 0.03K or more, and more preferably 0.01K or more.

[0080] The above configuration of the temperature sensor proved to be particularly suitable for determining values ​​that enable proper driving of the electrostrictive actuator or the individual electrostrictive components of the electrostrictive actuator.

[0081] According to the present invention, the supply line that supplies a control voltage to the electrostrictive actuator and the supply line that supplies an operating voltage to the temperature sensor can be routed together at least partially and / or functionally and / or physically coupled to form a unified conduction track and / or be identical.

[0082] It may be advantageous to use a connection as a feed line for a temperature sensor that, in combination with a particularly suitable control device, effectively supplies a control voltage to the electrostrictive component as well.

[0083] In the inventors' view, it is advantageous if the power supply lines for the electrostrictive components and the measurement signal lines for the temperature sensors are routed together for at least a portion of the distance, and in particular, it is advantageous if they are functionally and / or physically coupled to form a unified conductor track.

[0084] Insofar as other sensors or other measurement points are provided in addition to or as a substitute for the temperature sensor, voltage may be supplied to them as appropriate.

[0085] In relation to the present invention, the optical device is used in a projection exposure apparatus, and a measurement system is introduced to measure the image when the semiconductor substrate (wafer) is changed. In this case, it is possible to perform corresponding corrections while the electrostrictive actuator is being driven based on the measurement.

[0086] In this invention, during the change of a semiconductor substrate (wafer), the actual state is first measured, and then a specified voltage is applied to the electrostrictive actuator. Subsequently, the change is measured, and as a result, it is possible to consider that the change is due to deformation of the optical surface of the optical element, particularly a mirror. Subsequently, the degree of deformation of the optical surface can be estimated from the measurement result. Subsequently, it is also possible to determine the temperature present, since the deviation from the expected result is due to the temperature change. Since the difference between the expected measurement result and the measurement result after measurement may be due to temperature, it is thus possible to determine the temperature and / or temperature change and drive the electrostrictive actuator accordingly, thereby compensating for the temperature change and improving the setting accuracy.

[0087] It is advantageous for the control device to confirm the wavefront effects expected as a result of changes in surface shape and / or refractive index based on data from the measuring device, and to take these wavefront effects into account when driving the electrostrictive actuator and / or at least one compensation means.

[0088] In the inventors' view, it is advantageous if the location-dependent temperature distribution of the optical element is updated based on measurement information, and this is used to confirm the wavefront effects expected as a result of surface deformation and / or changes in refractive index, and if this wavefront change is taken into consideration when driving at least one compensation means for low aberration. The compensation means may be an electrostrictive actuator, or likewise or alternatively, other actuators of the optical device and / or optical system.

[0089] According to the present invention, the compensation means can be embodied as an element that can be displaced in the optical direction or perpendicular thereto, and / or an element that can be rotated about the optical direction as an axis or about an axis perpendicular thereto, and / or a deformable element, and / or an element that can be locally heated, and / or an element that can be locally cooled, and / or an element that can be displaced relative to one another, preferably as an aspherical plate, and / or a replaceable element.

[0090] The above compensation measures were found to be particularly appropriate.

[0091] The measurement methods described in relation to the present invention can be used as alternatives or additions. This is especially true for combinations of methods that directly measure temperature, temperature change, or temperature distribution with methods that measure the temperature-dependent characteristics of an electrostrictive actuator or individual electrostrictive components and then determine the temperature, temperature change, or temperature distribution from the measured values.

[0092] The above method, which includes measuring a change in surface shape when a specific voltage is applied to an electrostrictive actuator, can also be used in combination with the other above measurement methods.

[0093] The optical element is particularly advantageous if it is a mirror in a projection exposure apparatus, especially a locally deformable mirror.

[0094] The optical device according to the present invention is particularly suitable for this purpose.

[0095] For advantageous configurations and developmental forms of this type of projection exposure apparatus, please refer to the corresponding descriptions above and below.

[0096] The optical element is embodied as a lens element or mirror in the projection objective system, which is part of a projection exposure apparatus.

[0097] The present invention further relates to a method for influencing the surface shape of the optically effective surface of an optical element, wherein the optical element is functionally connected to an electrostrictive actuator, and the electrostrictive actuator is suitable for influencing the surface shape of the optically effective surface when a control voltage is supplied. According to the present invention, in order to account for the effects of temperature dependence during operation of the electrostrictive actuator, the temperature and / or temperature change of the electrostrictive actuator and / or its surroundings are directly measured and / or indirectly determined at least temporarily while the electrostrictive actuator is influencing the optically effective surface of the optical element. The optical element is part of a projection objective system, and the projection objective system is part of a projection exposure apparatus.

[0098] The method according to the present invention particularly advantageously allows for considering the temperature and / or temperature changes of the electrostrictive actuator or individual electrostrictive components of the electrostrictive actuator during the operation of the electrostrictive actuator, and for determining the temperature distribution therefrom. Therefore, it is possible to influence the surface shape of the optically effective surface with particular precision. The electrostrictive actuator is connected to an optical element, the optical element is part of a projection objective system, and the projection objective system is part of a projection exposure apparatus.

[0099] For further features, configuration, and advantages, please refer to the above and below descriptions of optical devices.

[0100] It would be advantageous if the parasitic effect on the surface shape of the optically effective surface and / or the change in the refractive index of the optical element could be determined using the measurement data.

[0101] In this method, the application of voltage causes lateral deformation of the electrostrictive actuator in the plane of the electrostrictive actuator, and the values ​​of the m31 or d31 constants that characterize the electrostrictive lateral effect for driving the electrostrictive actuator can be adapted using measurement data so as to take into account the effects of temperature dependence.

[0102] Furthermore, when a specific control voltage is applied to the electrostrictive actuator, a change in the surface shape of at least one of the surfaces of the optical element, particularly the optically effective surface, can be confirmed by a measurable aberration, from which the m31 or d31 coefficient can be determined.

[0103] Alternatively or additionally, it may be advantageous if at least one temperature-dependent variable of the electrostrictive actuator, in particular capacitance and / or electrical resistance and / or frequency-dependent impedance, can be determined and the m31 or d31 constant of the electrostrictive actuator can be derived from there.

[0104] From measured or determined temperature data and / or data on temperature changes, it is possible in a simple manner to determine the temperature distribution of the electrostrictive actuator and / or the temperature and / or temperature changes of the individual electrostrictive components of the electrostrictive actuator, and to consider their effects accordingly.

[0105] From the temperature distribution, as described above, the deformation of the optically effective surface can preferably be estimated by simulation, a pre-calculated lookup table, or calibration. The simulation can be performed using a finite element analysis (FE calculation) method based on a material model. The change in the optically effective surface can be converted into aberrations, which can be done based on a pre-calculated sensitivity.

[0106] It is preferable to use the method according to the present invention to correct the imaging aberration of a projection exposure apparatus.

[0107] The method according to the present invention is particularly suitable for correcting imaging aberrations in projection exposure apparatuses for semiconductor lithography, and especially in EUV projection exposure apparatuses for semiconductor lithography.

[0108] The present invention relates to a projection exposure apparatus for semiconductor lithography equipped with an illumination system, wherein the illumination system includes a radiation source and an optical unit having at least one optical device, and the optical device includes an optical element for correcting imaging aberration as described in any one of claims 1 to 20. In this case, the optical device can be embodied as described above and below.

[0109] The present invention is particularly suitable for use with microlithography DUV ("deep ultraviolet") or EUV ("extreme ultraviolet") projection exposure systems.

[0110] One advantageous application of the present invention relates to immersion lithography, where imaging aberrations can be advantageously corrected.

[0111] It should be further noted that terms such as "equip," "include," or "possess" do not exclude other features or steps. Furthermore, terms such as "a(n)" or "the" indicating a step or feature in the singular form do not exclude multiple features or steps, and vice versa.

[0112] Exemplary embodiments of the present invention will be described in more detail below with reference to the drawings.

[0113] Each figure shows a preferred exemplary embodiment illustrating individual features of the present invention in combination with each other. Features of one exemplary embodiment can also be implemented separately from other features of the same exemplary embodiment and can therefore be readily combined by those skilled in the art to form more favorable combinations and subcombinations with features of other exemplary embodiments.

[0114] In the diagram, functionally identical elements are given the same reference numeral. [Brief explanation of the drawing]

[0115] [Figure 1] This shows an EUV projection exposure system. [Figure 2] This shows a DUV projection exposure system. [Figure 3] This shows an immersion lithography projection exposure system. [Figure 4] This shows a cross-section of an optical device according to the present invention, which includes an optical element and an electrostrictive actuator. [Figure 5] A magnified view of detail V from Figure 4 is shown. [Figure 6] Figure 5 shows a diagram with an alternative arrangement of the temperature sensor compared to Figure 5. [Figure 7] The basic cross-sectional diagrams of optical elements and electrostrictive actuators are shown. [Figure 8] This diagram shows the basic structure of an electrostrictive component of an electrostrictive actuator, illustrating the lateral deformation of the electrostrictive component or electrostrictive actuator. [Figure 9] An illustrative diagram of an electrostrictive actuator having multiple electrostrictive components is shown. [Figure 10] This diagram shows a basic optical device including optical elements, electrostrictive actuators, temperature sensors, measuring devices, control devices, and compensation means. [Modes for carrying out the invention]

[0116] Figure 1 shows an example of the basic configuration of an EUV projection exposure apparatus 400 for semiconductor lithography to which the present invention can be applied. The illumination system 401 of the projection exposure apparatus 400 includes, in addition to the radiation source 402, an optical unit 403 for illuminating the object field of view 404 in the object plane 405. A reticle 406, positioned in the object field of view 404 and held by a schematicly illustrated reticle holder 407, is illuminated. The projection objective system 408, only schematicly illustrated, plays the role of imaging the object field of view 404 into the image field of view 409 in the image plane 410. The structure of the reticle 406 is imaged onto the photosensitive layer of a wafer 411 positioned in the region of the image field of view 409 in the image plane 410, and the wafer is held by a wafer holder 412, also partially illustrated. The radiation source 402 can emit EUV radiation 413 in particular in the range of 5 nanometers to 30 nanometers. Optical elements 415, 416, 418, 419, and 420, which are optically distinct and mechanically adjustable, are used to control the radiation path of the EUV radiation 413. In the EUV projection exposure apparatus 400 shown in Figure 1, the optical elements are embodied as adjustable mirrors in appropriate embodiments, which are merely mentioned as examples below.

[0117] The EUV radiation 413 generated by the radiation source 402 is aligned by a collector incorporated in the radiation source 402 so that the EUV radiation 413 passes through the intermediate focal point in the region of the intermediate focal plane 414 before it enters the field facet mirror 415. Downstream of the field facet mirror 415, the EUV radiation 413 is reflected by the pupil facet mirror 416. Using the pupil facet mirror 416 and the optical assembly 417, which includes mirrors 418, 419, and 420, the field facets of the field facet mirror 415 are imaged into the object field of view 404.

[0118] Figure 2 shows an exemplary DUV projection exposure apparatus 100. The projection exposure apparatus 100 comprises an illumination system 103, a device called a reticle stage 104 for housing and precisely positioning a reticle 105 used to determine the structure to be formed on a wafer 102, a wafer holder 106 for mounting, moving, and precisely positioning the wafer 102, and an imaging device, i.e., a projection objective system 107, which includes a number of optical elements 108 held by a mount 109 of the lens housing 140 of the projection objective system 107.

[0119] The optical element 108 can be embodied as individual refraction, diffraction, and / or reflection optical elements 108, such as lens elements, mirrors, prisms, end plates, etc.

[0120] The basic functional principle of the projection exposure apparatus 100 is that the structure introduced into the reticle 105 is imaged onto the wafer 102.

[0121] The illumination system 103 provides a projection beam 111 in the form of electromagnetic radiation necessary for imaging the reticle 105 onto the wafer 102. A laser, plasma source, etc., can be used as the source of the radiation. When the projection beam 111 is incident on the reticle 105, the radiation is shaped by optical elements in the illumination system 103 so that it has desired characteristics in terms of diameter, polarization, wavefront shape, etc.

[0122] The projection beam 111 generates an image of the reticle 105, which is then reduced in size by the projection objective system 107 and transferred to the wafer 102. In this case, since the reticle 105 and the wafer 102 can move synchronously, multiple regions of the reticle 105 can be imaged onto corresponding regions of the wafer 102 virtually continuously during the so-called scanning process.

[0123] Figure 3 shows the third projection objective system 200 as an immersion lithography DUV projection exposure apparatus. For further background information on the projection objective system 200, please refer to, for example, International Publication No. 2005 / 069055, the corresponding content of which is incorporated herein by reference. Therefore, the exact function will not be described in detail at this time.

[0124] Clearly, similar to the DUV projection exposure apparatus 100 shown in Figure 2, there is a reticle stage 4 used to determine the structure on the wafer 102 placed in the wafer holder 106 or wafer stage. For this purpose, the projection objective system 200 in Figure 3 similarly includes multiple optical elements, particularly lens elements 108 and mirrors 201.

[0125] However, with respect to the present invention, other elements of the beam path region of the reticles 105, 406, the reticle stage 104 or the reticle holder 407, the wafers 102, 411, the wafer holders 106, 412, or the projection exposure apparatus 100, 400 or the projection objective system 200 may also be referred to as optical elements.

[0126] For correcting imaging aberrations in projection exposure apparatuses, such as projection exposure apparatuses 100, 400, or projection objective system 200, the desired deformation of their optical elements 108, 201, 415, 416, 418, 419, and 420 may be suitable. Imaging aberrations in EUV projection exposure apparatus 400 can be corrected particularly efficiently by deforming one or more mirrors of projection objective system 308 as desired.

[0127] Two mirrors 201 are provided within the beam path of the projection objective system 200, and an intermediate focal plane 414 is located between the mirrors.

[0128] The present invention for correcting imaging aberration is, in principle, suitable for the deformation of any optical element in any projection objective system, but it can be used particularly advantageously for the deformation of optical elements 201 and 415 adjacent to the intermediate focal plane 414. Therefore, the mirror 201 of the immersion lithography projection objective system in Figure 3, in particular, can be embodied in a deformable manner according to the present invention.

[0129] The use of the present invention is not limited to use in a projection exposure apparatus 100, 400 or projection objective system 200, particularly in the configuration described above.

[0130] The present invention and the following exemplary embodiments should be understood as not being limited to any particular design. The following figures illustrate the invention in a very schematic manner, merely as an example.

[0131] Figures 4 to 7 and Figure 10 show an optical device 1 including an optical element 2 and an electrostrictive actuator 3. The optical device 1 may be part of a projection exposure apparatus 100, 400 or projection objective system 200 for semiconductor lithography, and in particular part of an EUV projection exposure apparatus 400 or an immersion lithography DUV projection exposure apparatus 200.

[0132] The optical element 2 may be a lens element or a mirror. Preferably, the optical element 2 is an adaptive optical element of a projection exposure apparatus 100, 400 or projection objective system 200, preferably an EUV projection exposure apparatus 400 or immersion lithography DUV projection objective system 200, particularly a deformable lens element or a deformable mirror. Particularly preferably, the optical element 2 is embodied as a mirror 201 of the immersion lithography DUV projection objective system 200 or as mirrors 415, 416, 418, 419, 420 of the EUV projection exposure apparatus 400. Particularly very preferably, the optical element 2 is positioned between the reticles 105, 406 and the wafers 102, 411. Particularly preferably, the optical element 2 is embodied as one of the mirrors of the projection objective system 408 of the EUV projection exposure apparatus 400, as a lens element 108 of the DUV projection exposure apparatus 100, or as a lens element 201 of the immersion lithography DUV projection objective system 200.

[0133] The optical element 2 according to the present invention can also be embodied as a lens element 108 of a DUV projection exposure apparatus 100 or an immersion lithography DUV projection objective system 200.

[0134] The optical device 1 is preferably part of an assembly that corrects imaging aberrations of the projection exposure apparatus 100, 400, or projection objective system 200. For this purpose, the optical element 2 is embodied as a lens element or mirror of the projection exposure apparatus 100, 400, or projection objective system 200.

[0135] The optical device 1, including the optical element 2, is described in more detail in the exemplary embodiments, particularly based on the lens elements of a projection exposure apparatus, especially mirrors, but is not limited thereto. The optical device can be any optical device 1 including any optical element 2. The exemplary embodiments should be understood as appropriate.

[0136] The electrostrictive actuator 3 is designed to be deformable by the application of a control voltage. The electrostrictive actuator 3 is functionally connected to the optical element 2 in order to influence the surface shape of the optically effective surface 2a of the optical element 2.

[0137] A control device 4 is provided to supply a control voltage to the electrostrictive actuator 3. The control device 4 is schematically shown in Figure 10.

[0138] A measuring device 5 is further provided, configured to directly and / or indirectly measure the temperature and / or temperature change of the electrostrictive actuator and / or its surroundings, at least temporarily, while the electrostrictive actuator 3 is affecting the optically effective surface 2a of the optical element 2. Subsequently, it is possible to consider the effects of temperature dependence during the operation of the electrostrictive actuator 3 based on the data and / or measured variables.

[0139] The control device 4 is configured to take into account the data from the measuring device 5 to set a desired deformation of the optically effective surface 2a and, accordingly, drive an electrostrictive actuator for this purpose.

[0140] The measuring device 5 is schematically shown in Figure 10.

[0141] In an exemplary embodiment, the measuring device 5 is configured to measure at least one of the following variables: Temperature and / or temperature change of electrostrictive actuator 3, and / or The ambient temperature and / or temperature change of the electrostrictive actuator 3, and / or Temperature-dependent characteristics of electrostrictive actuator 3, and / or A change in the surface shape of at least one surface 2a of the optical element 2 when a specific control voltage is applied to the electrostrictive actuator 3, for detecting the sensor deviation of the temperature sensor by comparing it with a known set value (e.g., from a lookup table) by measuring the surface shape, and correcting it if appropriate.

[0142] The measurement of the temperature and / or temperature change around the electrostrictive actuator should be understood to mean that the measurement is performed adjacent to the electrostrictive actuator so that the measured temperature or temperature change can still be used to draw conclusions about the temperature and / or temperature change of the electrostrictive actuator, for example, through simulation or a pre-calculated table.

[0143] Preferably, the measuring device 5 is configured to perform continuous measurements while the electrostrictive actuator 3 is operating. In this case, the measurements can also be performed during pauses in the operation of the projection exposure apparatus 100, 400 or the projection objective system 200, for example, when changing the semiconductor substrate of the projection exposure apparatus 100, 400, particularly the wafers 411, 102 or the mask.

[0144] The measuring device 5 can also be configured to perform measurements only temporarily while the electrostrictive actuator 3 is affecting the optically effective surface 2a of the optical element 2.

[0145] In an exemplary embodiment, the measuring device 5 is configured to measure and / or determine the temperature distribution of the electrostrictive actuator 3, and for that purpose, the measuring device 5 is configured accordingly and provided with a corresponding number of measurement points.

[0146] In an exemplary embodiment, the electrostrictive actuator 3 is implemented such that a voltage is applied to cause lateral deformation of the electrostrictive actuator 3 in its plane.

[0147] The control device 4 is configured to adapt the values ​​of the m31 or d31 constants that characterize the electrostrictive transverse effect for driving the electrostrictive actuator 3, based on data confirmed by the measuring device 5, in order to account for the effects of temperature dependence.

[0148] The effect (lateral deformation) of the m31 or d31 constant or the electrostrictive actuator is shown in principle in Figures 7 and 8. In this case, Figure 7 also shows the m33 or d33 constant, but this is only for completeness. In exemplary embodiments, the m31 or d31 constant is considered instead of the m33 or d33 constant.

[0149] The control device 4 is configured to take into account the material parameters within the electrostrictive actuator 3 and / or the thermal changes of the components surrounding the electrostrictive actuator 3.

[0150] As shown in Figures 4-7 and Figure 10, the electrostrictive actuator 3 can preferably be fixed to the optical element 2 by adhesive 6. Other fixing methods, particularly soldering, are also possible here, but fixing by adhesive 6 or an adhesive layer was found to be particularly suitable. The optical element is part of the projection objective system, and the projection objective system is part of the projection exposure apparatus.

[0151] In an exemplary embodiment, the electrostrictive actuator 3 is positioned on the back side 2b of the optical element 2, facing away from the optically effective surface 2a.

[0152] Alternatively and / or additionally, the electrostrictive actuator 3 may be positioned on the optically effective surface 2a of the optical element outside the optical region or on the side surface of the optical element 2 (neither of which is shown).

[0153] The electrostrictive actuator 3 can extend to a section or partial region of the back side 2b of the optical element 2, or to the entire back side 2b of the optical element 2. Alternatively, multiple electrostrictive actuators 3 can be used, each distributed to a partial region, preferably a partial region of the back side 2b of the optical element 2.

[0154] With regard to the solution according to the present invention, the electrostrictive actuator 3 can also be configured to affect only one section of the optically effective surface 2a of the optical element 2 in any case.

[0155] In an exemplary embodiment, the control device 4 is configured to take into account the thermal changes of the stiffness and / or thermal expansion of the adhesive 6 while the electrostrictive actuator 3 is being driven. Therefore, by considering the effect of temperature changes in the adhesive 6 when driving the electrostrictive actuator 3, the effect of temperature changes in the adhesive 6 on the optically effective surface 2a of the optical element 2 is taken into account while the electrostrictive actuator 3 is being driven. Consequently, thermal changes in the solder connections of the optical element and / or the expansion or stiffness of the substrate can also be taken into account.

[0156] In exemplary embodiments, the electrostrictive actuator 3 is configured to have multiple electrostrictive components 7. This is shown, for example, in Figures 4-7, Figure 10, and especially in Figure 9. The electrostrictive actuator 3 can preferably be embodied as an electrostrictive mat. One or more actuators 3 can be fitted under a mirror substrate. In this case, the actuators 3 can also be combined to form one or more units. In particular in one embodiment, the distribution of the electrostrictive components 7 of the electrostrictive actuator 3 as a mat is preferably regular, and Figure 9 is an example of this but not limited to it.

[0157] According to the present invention, the measuring device 5 can measure the temperature-dependent characteristics of the electrostrictive actuator 3, particularly the capacitance and / or electrical resistance and / or frequency-dependent impedance of the electrostrictive actuator.

[0158] In an exemplary embodiment, the measuring device 5 may have an infrared camera for temperature detection and / or an electrical bridge circuit for measuring the temperature-dependent characteristics of the electrostrictive actuator 3. While not shown in the exemplary embodiment, such modifications are feasible to those skilled in the art. The above measurement methods may be used as alternatives or additions.

[0159] In an exemplary embodiment, as shown in Figures 4 to 7 and Figure 10, the measuring device 5 includes a temperature sensor 8 that measures the temperature and / or temperature change and / or temperature distribution of the electrostrictive actuator and / or its surroundings.

[0160] According to the present invention, the temperature sensor 8 can be assigned to each electrostrictive component 7 or group of electrostrictive components. Figures 4, 5, and 6 show one temperature sensor 8 as an example in each case, but multiple temperature sensors 8 can be provided, and in particular, each of the electrostrictive components 7 can be assigned a temperature sensor 8.

[0161] In the exemplary embodiments shown in Figures 4 and 5, the temperature sensor 8 is positioned on the back side 3a of the electrostrictive actuator 3, facing away from the optical element 2. In the exemplary embodiments, the temperature sensor 8 is located particularly on the back side 3a of the electrostrictive component 7 of the electrostrictive actuator 3.

[0162] An alternative positioning is shown in Figure 6. In the exemplary embodiment shown in Figure 6, the temperature sensor 8 is positioned on one side of the optical element 2, and in the exemplary embodiment, on the back side 2b of the optical element 2 facing the electrostrictive actuator 3, between the electrostrictive components 7 of the electrostrictive actuator 3. This is an alternative and / or additional positioning of the temperature sensor 8 and can be used in combination with the positioning shown in Figures 4 and 5.

[0163] In the exemplary embodiment shown in Figure 6, a temperature sensor 8, which may be positioned between the electrostrictive components 7, is positioned in the gap or free space 3b of the electrostrictive actuator 3, corresponding to or embodied in the modified form shown in Figure 9.

[0164] The temperature sensor 8 can be configured to enable resistance-based measurement, in particular by including a material whose resistance changes with temperature to a measurable degree. Preferably, the temperature sensor 8 is configured to readily detect temperature changes of 0.1K, preferably 0.03K, and more preferably about 0.01K.

[0165] In an exemplary embodiment, a supply line 9 that supplies a control voltage to the electrostrictive actuator 3 or its electrostrictive component 7 and a supply line 10 that supplies a measurement operating voltage to the temperature sensor 8 are routed together at least partially and / or coupled to form a unified conduction track.

[0166] In an exemplary embodiment, the control device 4 may, based on data from the measuring device 5, confirm the wavefront effect expected as a result of the change in surface shape and / or the change in refractive index, and take the wavefront effect into account when driving the electrostrictive actuator 3 and / or at least one compensation means 11.

[0167] The compensation mechanism 11 is schematically shown in Figure 10.

[0168] In a manner not described in more detail, one or more compensation means 11 can be embodied as an element displaceable in the optical direction or perpendicular thereto, and / or an element rotatable about the optical direction as an axis or an axis perpendicular thereto, and / or a deformable element, and / or an element that can be locally heated, and / or an element that can be locally cooled, and / or an element that is displaceable relative to one another, preferably as an aspherical plate, and / or a replaceable element.

[0169] Figure 10 schematically illustrates how data from the temperature sensor 8 (or data from some other measurement method or other measurement point) is acquired by the measurement device 5 and made available to the control device 4. The control device 4 then drives the electrostrictive actuator 3, making available the values ​​of the m31 or d31 constants that characterize the electrostrictive transverse effect for driving the electrostrictive actuator 3, and in the process the influence of temperature dependence can be taken into account. Alternatively or additionally, as also shown in Figure 10, the influence of temperature dependence can also be taken into account by correspondingly driving the compensation means 11 for low aberration using the data from the control data 4.

[0170] Figure 8 shows an example of lateral deformation of the electrostrictive actuator 3 according to the m31 or d31 constant. The dashed line in Figure 8 shows the state of the electrostrictive actuator 3 or electrostrictive component 7, for example, the rear side 3a, in a plan view after voltage is applied. In this case, the solid line shows the state of the electrostrictive actuator 3 or electrostrictive component 7 before voltage is applied.

[0171] Figure 4 shows one advantageous configuration of the optical device 1, but the solutions according to the present invention are not limited to this configuration.

[0172] As already explained, the electrostrictive actuator 3 is preferably connected to the back side 2b of the optical element 2 by an adhesive 6 or adhesive layer, which is shown in enlarged view in corresponding Figures 5 and 6.

[0173] In an exemplary embodiment, the electrostrictive actuator 3 comprises a plurality of electrostrictive components 7. The electrostrictive actuator 3 can be embodied as an electrostrictive mat.

[0174] Voltage is supplied to the electrostrictive actuator 3 or its electrostrictive component 7 via a supply line 9 or electrical contacts. In this case, the supply line 9 can be directly connected to the electrostrictive component 7. Alternatively, for direct contact with the electrostrictive component 7, electrical contacts or a conductive layer may be provided on the back side 3a of the electrostrictive component, and this electrical contact or conductive layer may further contact the power supply line as shown in Figures 5 and 6.

[0175] In the exemplary embodiments shown in Figures 4 to 6, an insulating layer 12 is also provided on the back side 3a of the electrostrictive actuator 3 or its electrostrictive component 7, which shields the electrical contacts or conductive layer 9 from the outside, at least partially.

[0176] Figure 5 shows the arrangement of the temperature sensor 8 on the back side 3a of the electrostrictive actuator 3. In this case, the voltage is supplied by a supply line 10 which is routed together with the supply line 9, at least partially.

[0177] Figure 6 shows an alternative diagram in which the temperature sensor 8 is positioned on the back side 2b of the optical element 2 in the gap or free space 3b between the electrostrictive components 7.

[0178] A combination of Figures 5 and 6 is also possible. In particular, more temperature sensors 8 can be used, and each temperature sensor 8 can be assigned to each electrostrictive component 7 or group of electrostrictive components 7.

[0179] As shown in Figures 5 and 6, the temperature sensor 8 can preferably be fixed to the back side 2b of the optical element 2 or to the back side 3a of the electrostrictive actuator 3 or its electrostrictive component 7 by an adhesive layer 6a. The thermal changes in stiffness and / or expansion of the adhesive 6a and / or other components involved during the operation of the electrostrictive actuator can also be taken into account, where appropriate, during the operation of the electrostrictive actuator. This may be advantageous for drift reduction and / or drift correction.

[0180] This exemplary embodiment is claimed 22 As shown, this is also useful in explaining the optical element 2 used in optical device 1.

[0181] This exemplary embodiment also helps to illustrate a method for influencing the surface shape of the optically effective surface 2a of the optical element 2, wherein the temperature and / or temperature change and / or temperature distribution of the electrostrictive actuator 3 and / or its surroundings are directly measured and / or indirectly determined, at least temporarily, while the electrostrictive actuator 3 is influencing the optically effective surface 2a of the optical element 2, in order to account for the effect of temperature dependence during the operation of the electrostrictive actuator 3. Preferably, the measurement is performed at least temporarily while the actuator 3 is actively influencing the surface 2a of the optical element 2, i.e., while a voltage is present in the actuator 3. Subsequently, the measurement data can be used to determine parasitic effects on the surface shape of the optically effective surface 2a and / or changes in the refractive index of the optical element 2.

Claims

1. A projection exposure apparatus (400, 100) comprising at least a projection objective system (408, 107, 200), wherein the projection objective system (408, 107, 200) and / or illumination system (401, 103) includes a plurality of optical elements (2), wherein at least one of the plurality of optical elements (2), the optical element (415) adjacent to the intermediate focal plane (414) of the illumination system (401, 103), or the optical element (201) adjacent to the intermediate focal plane (414) of the projection objective system (200), is configured as an optical device (1), and the optical device (1) comprises the optical element (2) having an optically effective surface (2a) and at least one electrostrictive actuator (3) that can be deformed by the application of a control voltage. In a projection exposure apparatus (400, 100), the electrostrictive actuator (3) is functionally connected to the optical element (2) to influence the surface shape of the optical effective surface (2a), a control device (4) is provided to supply a control voltage to the electrostrictive actuator (3), and a measuring device (5) is provided to determine the temperature and / or temperature change of the electrostrictive actuator (3) and / or its surroundings at least temporarily while the electrostrictive actuator (3) is influencing the optical effective surface (2a) of the optical element (2), in order to take into account the effect of temperature dependence during the operation of the electrostrictive actuator (3) by the control device (4), The measurement device (5) is a projection exposure apparatus that includes a temperature sensor (8) for measuring the temperature and / or temperature change and / or temperature distribution of the electrostrictive actuator (3) and / or its surroundings.

2. The apparatus (400, 100) according to claim 1, wherein the measuring device (5) is configured to directly measure the temperature and / or temperature change of the electrostrictive actuator (3) and / or its surroundings.

3. The apparatus (400, 100) according to claim 1 or 2, wherein the measuring device (5) is an apparatus for continuously measuring and / or determining temperature and / or temperature change during the operation of the electrostrictive actuator (3).

4. An apparatus (400, 100) according to any one of claims 1 to 3, wherein the electrostrictive actuator (3) is implemented such that a lateral deformation of the electrostrictive actuator (3) occurs in the plane of the electrostrictive actuator (3) when a control voltage is applied.

5. An apparatus (400, 100) according to any one of claims 1 to 4, wherein the control device (4) is configured to adapt the value of the m31 or d31 constant that characterizes the electrostrictive transverse effect for driving the electrostrictive actuator (3) based on data confirmed by the measuring device (5) in order to take into account the effect of temperature dependence.

6. An apparatus (400, 100) according to any one of claims 1 to 5, wherein the control device (4) is configured to take into account material parameters within the electrostrictive actuator (3) and / or thermal changes of components surrounding the electrostrictive actuator (3).

7. The apparatus (400, 100) according to any one of claims 1 to 6, wherein the electrostrictive actuator (3) is fixed to the optical element (2) by adhesive (6) or solder connection, and the control device (4) is configured to take into account the thermal changes of rigidity and / or expansion of the adhesive (6) or solder connection while the electrostrictive actuator (3) is being driven.

8. In the apparatus (400, 100) according to any one of claims 1 to 7, the electrostrictive actuator (3) is positioned on the back side (2b) of the optical element (2) facing away from the optically effective surface (2a).

9. An apparatus (400, 100) according to any one of claims 1 to 8, wherein the electrostrictive actuator (3) is positioned on the optically effective surface (2a) of the optical element (2) outside the optical region or on the side surface of the optical element.

10. In the apparatus (400, 100) according to any one of claims 1 to 9, the electrostrictive actuator (3) is an apparatus having a plurality of electrostrictive components (7).

11. An apparatus (400, 100) according to any one of claims 1 to 10, wherein the measuring device (5) is an apparatus for measuring the capacitance and / or electrical resistance and / or frequency-dependent impedance of the electrostrictive actuator (3) in order to determine the temperature and / or temperature change.

12. The apparatus (400, 100) according to any one of claims 1 to 11, wherein the measuring device (5) is an apparatus having an infrared camera for temperature detection and / or an electrical bridge circuit for measuring the temperature-dependent characteristics of the electrostrictive actuator (3).

13. The apparatus (400, 100) according to any one of claims 1 to 12, wherein the temperature sensor (8) is positioned on the back side (3a) of the electrostrictive actuator (3) facing away from the optical element (2).

14. The apparatus (400, 100) according to any one of claims 1 to 13, wherein the temperature sensor (8) is positioned between the electrostrictive components (7) of the electrostrictive actuator (3) on one side (2b) of the optical element (2).

15. The apparatus (400, 100) according to any one of claims 1 to 14, wherein the temperature sensor (8) is configured to measure a temperature change of 0.1 K or more.

16. An apparatus (400, 100) according to any one of claims 1 to 15, wherein the supply line (9) that supplies a control voltage to the electrostrictive actuator (3) and the supply line (10) that supplies an operating voltage to the temperature sensor (8) are at least partially routed together and / or functionally and / or physically coupled to form a unified conduction track and / or are identical.

17. An apparatus (400, 100) according to any one of claims 1 to 16, wherein the control device (4) confirms the wavefront effect expected as a result of a change in surface shape and / or a change in refractive index based on the data from the measuring device (5), and takes the wavefront effect into consideration while driving the electrostrictive actuator (3) and / or at least one compensation means (11).

18. The apparatus (400, 100) according to claim 17, wherein the compensation means (11) is embodied as an element that can be displaced in the optical direction or perpendicular thereto, and / or as an element that can be rotated about the optical direction as an axis or about an axis perpendicular thereto, and / or as a deformable element, and / or as an element that can be locally heated, and / or as an element that can be locally cooled, and / or as an element that can be displaced relative to each other, and / or as an aspherical plate, and / or as a replaceable element.

19. An apparatus (400, 100) according to any one of claims 1 to 18, wherein the optical element (2) is a mirror.

20. A method for influencing the surface shape of an optically effective surface (2a) of an optical element (2) arranged in a projection exposure apparatus according to any one of claims 1 to 19, wherein the optical element (2) is functionally connected to an electrostrictive actuator (3), and the electrostrictive actuator (3) is suitable for influencing the surface shape of the optically effective surface (2a) when a control voltage is supplied, wherein, in order to take into account the effect of temperature dependence during operation of the electrostrictive actuator (3), data of the temperature and / or temperature change of the electrostrictive actuator (3) and / or its surroundings are directly measured at least temporarily while the electrostrictive actuator (3) is influencing the optically effective surface (2a) of the optical element (2).

21. A method according to claim 20, wherein the parasitic effect on the surface shape of the optically effective surface (2a) and / or the change in refractive index of the optical element (2) are determined using the data.

22. A method according to claim 20 or 21, wherein the application of a control voltage causes lateral deformation of the electrostrictive actuator (3) in the plane of the electrostrictive actuator (3), and the value of an m31 or d31 constant that characterizes the electrostrictive lateral effect for driving the electrostrictive actuator (3) is adapted using measurement data to take into account the effect of temperature dependence.

23. A method according to claim 22, wherein when a specific control voltage is applied to the electrostrictive actuator (3), a change in the surface shape of at least one of the surfaces (2a, 2b) of the optical element (2) is observed, and the m31 or d31 constant is determined therefrom.

24. A method according to claim 22 or 23, wherein at least one temperature-dependent variable of the electrostrictive actuator (3) is determined, and the m31 or d31 constant of the electrostrictive actuator (3) is determined therefrom.

25. A method used to correct imaging aberrations of a projection objective system (107, 403, 200) which is part of a projection exposure apparatus (100, 400), according to any one of claims 20 to 24.

Images