Projection objective comprising an optical device

Abstract

The invention relates to a projection exposure apparatus (400, 100) comprising a projection objective (408, 107, 200) comprising an optical device (1) comprising an optical element (2) having an optically effective surface (2a) and at least one electrostrictive actuator (3) deformable by an applied control voltage, wherein the electrostrictive actuator (3) is functionally connected to the optical element (2) to influence the surface shape of the optically effective surface (2a). A control device (4) is provided to supply the control voltage to the electrostrictive actuator (3), wherein a measuring device (5) is provided which is configured to measure and / or to determine at least sometimes directly and / or indirectly the temperature and / or temperature change of the electrostrictive actuator (3) and / or its surroundings while the electrostrictive actuator (3) influences the optically effective surface (2a) of the optical element (2) to take into account temperature-dependent influences in the process of driving the electrostrictive actuator (3) by the control device (4).

Description

[0001] This application claims priority to U.S. Provisional Patent Application No. 63 / 058,745, filed July 30, 2020, and German Patent Application No. 10 2020 131389.6, filed November 26, 2020. The entire contents of the aforementioned two applications are incorporated herein by reference and form part of this application. Technical Field

[0002] A projection exposure apparatus including a projection lens, the projection lens including an optical device, optical elements, and an assembly for correcting imaging aberrations, and a method for influencing the surface shape of the optical elements by directly or indirectly measuring the temperature inside the projection lens.

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

[0004] The present invention further relates to a method for driving a projection exposure apparatus by influencing the surface shape of the optically effective surface of an optical element, the optical element being part of a projection objective, the projection objective being part of a projection exposure apparatus, and according to the method, the optical element being functionally connected to an electrostrictive actuator.

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

[0006] As semiconductor circuits continue to miniaturize, the requirements for resolution and accuracy in projection exposure devices are becoming increasingly stringent. Correspondingly strict requirements are also placed on optical components that affect the beam path within the projection exposure device.

[0007] To achieve high resolution, especially for the lithography optical unit, EUV light with a wavelength of 13.5 nm was also used, in addition to VUV and DUV wavelengths of 248 nm and 193 nm respectively.

[0008] EUV projection exposure apparatuses use mirror systems that operate with near-perpendicular or grazing incidence, with mirrors in VUV and DUV systems operating with perpendicular incidence. As achievable resolution continues to increase, the requirements for wavefront correction become correspondingly more stringent. Smaller and smaller effects become increasingly important, leading to a growing demand for passive correction methods, but active correction methods remain the primary approach.

[0009] Partially deformable mirrors are known for use in the operation of projection exposure apparatuses. In this case, local deformation is achieved by a piezoelectric element as an actuator in the form of a thin film or layer, see, for example, US20020048096. Local deformation of mirrors caused by electrostrictive materials, piezoelectric materials, piezoresistive materials, thermally resistive materials, and magnetostrictive materials is known from US7492077. Summary of the Invention

[0010] The purpose of this invention is to provide an assembly for correcting imaging aberrations of the projection lens of a projection exposure device, wherein the imaging aberrations can be corrected with high set accuracy.

[0011] Another object of the present invention is to provide a method for influencing the surface shape of the optically effective surface of an optical element, wherein the method can influence the optically effective surface with high setting accuracy. The optical element is part of a projection lens, which is part of a projection exposure apparatus.

[0012] Another object of the present invention is to provide a projection exposure apparatus for semiconductor lithography, comprising a projection objective lens, the projection objective lens including at least one optical device having optical elements for correcting imaging aberrations with high setting accuracy.

[0013] For projection exposure apparatus, this objective is achieved through the features presented below.

[0014] The present invention provides a projection exposure apparatus comprising a projection objective lens, the projection objective lens including an optical device comprising an optical element having an optically effective surface and at least one electrostrictive actuator deformable by an applied control voltage, wherein the electrostrictive actuator is functionally connected to the optical element to influence the surface shape of the optically effective surface, and wherein a control device is provided to provide the control voltage to the electrostrictive actuator, wherein a measuring device is provided configured to determine the temperature and / or temperature variation of the electrostrictive actuator and / or its surrounding environment at least sometimes when the electrostrictive actuator influences the optically effective surface of the optical element, to take into account temperature-related effects during the actuation of the electrostrictive actuator by the control device, wherein the measuring device includes a temperature sensor that measures the temperature and / or temperature variation and / or temperature distribution of the electrostrictive actuator and / or its surrounding environment, and wherein the optical element is adjacent to the intermediate focal plane of the projection exposure apparatus.

[0015] The objective of the method for influencing the surface shape of the optically effective surface of an optical element disposed in a projection exposure apparatus is achieved by the features described below.

[0016] The present invention provides a method for correcting the temperature in a projection exposure apparatus as described above, which involves influencing the surface shape of an optically effective surface of an optical element disposed in the projection exposure apparatus, wherein the optical element is functionally connected to an electrostrictive actuator, wherein the electrostrictive actuator, when supplied with a control voltage, is adapted to influence the surface shape of the optically effective surface, wherein at least sometimes when the electrostrictive actuator influences the optically effective surface of the optical element, the temperature and / or temperature changes of the electrostrictive actuator and / or its surrounding environment are directly measured and / or determined to take temperature-related effects into account during the actuation of the electrostrictive actuator.

[0017] The features described below relate to advantageous embodiments and variations of the invention.

[0018] In one embodiment of the device, the measuring device is configured to directly measure and / or indirectly determine the temperature and / or temperature changes of the electrostrictive actuator and / or its surrounding environment.

[0019] In one embodiment of the device, the measuring device measures at least one of the following variables to indirectly determine the temperature and / or temperature change: - the temperature-dependent characteristics of the electrostrictive actuator, and / or - the change in the surface shape of at least one surface of the optical element when a specific control voltage is applied to the electrostrictive actuator.

[0020] In one embodiment of the device, the measuring device continuously measures and / or determines the temperature and / or temperature changes during operation of the electrostrictive actuator.

[0021] In one embodiment of the device, the electrostrictive actuator is configured such that applying the control voltage will cause the electrostrictive actuator to undergo lateral deformation in the plane of the electrostrictive actuator.

[0022] In one embodiment of the device, the control device is configured to adjust the value of the m31- or d31- coefficient, which characterizes the transverse electrostrictive effect, based on data determined by the measuring device, for driving the electrostrictive actuator to take into account the temperature-related effects.

[0023] In one embodiment of the device, the control device is configured to take into account material parameters within the electrostrictive actuator and / or thermal changes of components in the surrounding environment of the electrostrictive actuator.

[0024] In one embodiment of the device, the electrostrictive actuator is fixed to the optical element by an adhesive or welded connection, and the control device is configured to take into account the thermal changes in stiffness and / or expansion of the adhesive or welded connection during the actuation of the electrostrictive actuator.

[0025] In one embodiment of the device, the electrostrictive actuator is disposed on the rear side of the optical element away from the optically effective surface.

[0026] In one embodiment of the device, the electrostrictive actuator is disposed on the optically effective surface of the optical element outside a light region or on one side surface of the optical element.

[0027] In one embodiment of the device, the electrostrictive actuator has a plurality of electrostrictive components.

[0028] In one embodiment of the device, the measuring device measures the capacitance and / or resistance and / or frequency-dependent impedance of the electrostrictive actuator to determine the temperature and / or temperature change.

[0029] In one embodiment of the device, the measuring device has an infrared camera for temperature detection and / or a bridge circuit for measuring the temperature-dependent characteristics of the electrostrictive actuator.

[0030] In one embodiment of the device, the temperature sensor is disposed on the rear side of the electrostrictive actuator away from the optical element.

[0031] In one embodiment of the device, the temperature sensor is disposed on one side of the optical element between the electrostrictive components of the electrostrictive actuator.

[0032] In one embodiment of the device, the temperature sensor is configured to measure temperature changes of 0.1K or greater, preferably 0.03K or greater, and even more preferably 0.01K or greater.

[0033] In one embodiment of the device, the power lines for providing the control voltage to the electrostrictive actuator and the power lines for providing the operating voltage to the temperature sensor are at least partially wired together, and / or functionally and / or physically combined to form a uniform conductive track, and / or are identical.

[0034] In one embodiment of the device, the control device determines the expected wavefront effect due to changes in surface shape and / or refractive index based on data from the measuring device, and takes into account the wavefront effect during the driving of the electrostrictive actuator and / or at least one compensation member (11).

[0035] In one embodiment of the device, the compensation member is implemented as an element displaceable in the light direction or in a direction perpendicular to it, and / or an element rotatable about the light direction or about an axis perpendicular to it, and / or a deformable element, and / or a locally heatable element, and / or a locally coolable element, and / or preferably an element of a non-spherical panel displaceable relative to each other, and / or a replaceable element.

[0036] In one embodiment of the device, the optical element is a mirror, particularly a partially deformable mirror.

[0037] In one embodiment of the method, the measured data is used to determine the parasitic effects on the surface shape of the optically effective surface and / or the refractive index variation of the optical element.

[0038] In one embodiment of the method, the applied control voltage causes the electrostrictive actuator to deform laterally in the plane of the electrostrictive actuator, and the measured data is used to adjust the value of the m31- or d31- coefficient characterizing the lateral electrostrictive effect, so as to drive the electrostrictive actuator in a manner that takes into account the temperature-related effects.

[0039] In one embodiment of the method, when a specific control voltage is applied to the electrostrictive actuator, the change in the surface shape of at least one surface of the optical element, particularly the change in the surface shape of the optically effective surface, is determined, in particular by measurable aberrations, and thereby the m31- or d31- coefficient is determined.

[0040] In one embodiment of the method, at least one temperature-dependent variable of the electrostrictive actuator is determined, particularly the capacitance and / or resistance and / or frequency-dependent impedance, and thereby the m31- or d31- coefficient of the electrostrictive actuator is determined.

[0041] In one embodiment of the method, the method is used to correct imaging aberrations of a projection objective, which is part of a projection exposure apparatus. The optical apparatus includes an optical element having an optically effective surface and at least one electrostrictive actuator, wherein the electrostrictive actuator can be deformed by an applied 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 provide a control voltage to the electrostrictive actuator.

[0042] In this context, "optical element" should be understood to preferably refer to deformable optical elements, particularly adaptive optical elements. Preferably, the optical element is a lens element, and more preferably a mirror, especially a partially deformable mirror.

[0043] Optical elements, especially lens elements or mirror elements, are the optical elements of a projection lens, which is part of a projection exposure apparatus.

[0044] In the optical apparatus of the projection exposure device, a measuring device is provided, which is configured to determine, at least at times, the temperature and / or temperature changes of the electrostrictive actuator and / or its surrounding environment when the electrostrictive actuator affects the optically effective surface of the optical element, so as to take into account the temperature-related effects during the process of driving the electrostrictive actuator by the control device.

[0045] Since the temperature and / or temperature variations of the electrostrictive actuator and / or its surrounding environment are determined according to the present invention, it is possible to take temperature-related effects into account during the operation of the electrostrictive actuator.

[0046] Preferably, the temperature and / or temperature changes of the electrostrictive actuator and / or the surrounding environment are determined directly by measurement and / or indirectly by measurement.

[0047] The data from the measuring device can be used to determine parasitic effects on the surface (such as bimetallic effects) and / or the refractive index changes of optical elements.

[0048] The data from the measuring device makes it possible to drive the electrostrictive actuator with high accuracy. Precise requirements regarding the applied electrical control voltage and / or electric field strength can be derived based on the desired surface shape.

[0049] The measuring device makes it possible to measure the temperature distribution of the electrostrictive actuator itself and / or the environment surrounding the electrostrictive actuator.

[0050] The surrounding environment of an electrostrictive actuator should be understood as the area near the electrostrictive actuator, such that the temperature of the electrostrictive actuator and / or the temperature change of the electrostrictive actuator can be derived from its temperature.

[0051] In the context of this invention, the temperature and / or temperature change to be measured may be specified. In the context of this invention, measuring the absolute temperature is not absolutely necessary; measuring the temperature change may be sufficient to account for temperature-related effects during the operation of the electrostrictive actuator.

[0052] The optical design of the projection exposure apparatus makes it possible to reduce temperature-related effects, particularly those caused by irradiation of optical elements or by heat generated during operation of the electrostrictive actuator.

[0053] In the context of the solution according to the invention, it may be sufficient to affect a region or segment of the optically effective surface by means of at least one electrostrictive actuator.

[0054] In the context of the solution according to the invention, it is sufficient that the electrostrictive actuator is functionally connected to the optical element such that the surface shape of the optically effective surface is potentially influenceable, at least within a defined region.

[0055] In the context of the solution according to the invention, the electrostrictive actuator can be deformed by an applied control voltage, in particular expandable and / or contractable.

[0056] Taking into account the data from the measuring device, the control device is configured to set the desired deformation of the optically effective surface of the optical element and drive the electrostrictive actuator accordingly for this purpose.

[0057] The expansion constant of electrostrictive materials can be significantly related to temperature. Because of the measurement of the temperature and / or temperature changes and / or temperature distribution of the electrostrictive actuator, the response of the actuator material to temperature changes can be simultaneously included in the control of the actuator.

[0058] All measurement methods presented in the context of this invention can be used as alternatives or in any desired combination. Therefore, two or more measurement methods can also be combined with each other.

[0059] The temperature and / or temperature changes determined in the context of the solution according to the invention can be used to detect and / or determine the temperature distribution in the environment surrounding the electrostrictive actuator and / or in the electrostrictive actuator, in order to specifically account for temperature-related effects during the actuation of the electrostrictive actuator.

[0060] It is advantageous if the measuring device measures at least one of the following variables:

[0061] - Temperature and / or temperature change of the electrostrictive actuator, and / or

[0062] - Temperature and / or temperature changes in the environment surrounding the electrostrictive actuator, and / or

[0063] - Temperature-dependent characteristics of electrostrictive actuators, and / or

[0064] - A change in the surface shape of at least one surface of an optical element when a specific control voltage is applied to an electrostrictive actuator.

[0065] Based on data from the measuring device, particularly the determined temperature and / or temperature variations, the deformation of the optically effective surface can be inferred, for example, through simulation and / or through previously calculated tables and / or through calibration. The simulation may specifically include finite element analysis (FE calculations), which is based on the material model of the overall component and the specific design, particularly the retaining structure, adhesive or welded connections, possible components for position measurement, etc.

[0066] Changes in the effective optical surface can be converted into aberrations in the projection lens.

[0067] It is advantageous to design the electrostrictive actuator so that applying a control voltage causes lateral deformation of the electrostrictive actuator in its plane.

[0068] It can be specified that the control device is configured to adjust the value of the m31- or d31- coefficient of the characteristic transverse electrostriction effect based on the data determined by the measuring device, for driving the electrostriction actuator, to take into account temperature-related effects.

[0069] It has been shown that it is particularly suitable to determine the current value of the m31- or d31- coefficient of the piezoelectric tensor based on the determined measurement variables and to take it into account in the process of driving the electrostrictive actuator.

[0070] It is advantageous for the measuring device to continuously measure during the operation of the electrostrictive actuator.

[0071] In principle, the measuring device may only perform measurements during the operation of the electrostrictive actuator, but it has been shown to be advantageous if the measuring device measures continuously during the operation of the electrostrictive actuator, so that the measurements can be performed in a temporally and spatially resolved manner during operation.

[0072] Preferably, the measurement can be performed when the operation of the projection exposure apparatus is paused, for example, in a controlled manner during the manufacturing process, such as when the settings of the semiconductor substrate or mask or the illumination system of the projection exposure apparatus are changed.

[0073] According to the present invention, the control device may be configured to take into account material parameters within the electrostrictive actuator and / or thermal changes of components in the environment surrounding the electrostrictive actuator.

[0074] Because the control device takes into account the material parameters inside the electrostrictive actuator and / or the thermal changes of components in the surrounding environment, it can comprehensively account for the temperature-related effects during the operation of the electrostrictive actuator. Therefore, the electrostrictive actuator can be driven with particularly high setting accuracy.

[0075] It has been recognized that it is advantageous to consider thermal changes in the stiffness and / or thermal expansion of adhesive or welded joints during the actuation of an electrostrictive actuator. Therefore, the temperature-dependent effects of adhesive or welded joints can also be considered, particularly advantageously, during the actuation of an electrostrictive actuator. Furthermore, it is possible, where appropriate, to consider thermally controlled changes in the stiffness and / or expansion of other related components (e.g., the substrate of optical elements).

[0076] In principle, electrostrictive actuators can also be fixed to optical elements in different ways; in this case, the temperature-dependent changes in the thermal expansion of the fixing material and / or its thermal expansion can then be considered.

[0077] If the optical element is a reflector of a projection lens that is part of a projection exposure apparatus, then placing an electrostrictive actuator on the rear side of the optical element away from the optically effective surface has proven particularly suitable for influencing the optically effective surface.

[0078] In the aforementioned case where the optical element is part of a projection lens and the projection lens is part of a projection exposure apparatus, it may be sufficient if the electrostrictive actuator is located in the region behind the optical element.

[0079] According to the present invention, the electrostrictive actuator may be further specified to be disposed on the optically effective surface of the optical element outside the light region or on the side surface of the optical element.

[0080] The arrangement of an electrostrictive actuator on the optically effective surface of an optical element outside the light region can be suitable as an alternative to or supplement to an arrangement on the rear side of the optical element. In particular, if an electrostrictive actuator is used in the case of a lens element, its arrangement on the optically effective surface outside the light region is advantageous. However, in principle, in the case of a lens element, the electrostrictive actuator can also be arranged on the rear side away from the optically effective surface, especially outside the light region. Furthermore, or alternatively, it is also possible to arrange the electrostrictive actuator on the side surface of the optical element.

[0081] According to the present invention, an electrostrictive actuator may be specified to have a plurality of electrostrictive components.

[0082] Embodiments of electrostrictive actuators with multiple electrostrictive components have proven particularly suitable for influencing (e.g., also locally influencing) optically effective surfaces in a suitable manner, especially for deforming optically effective surfaces.

[0083] In embodiments of electrostrictive actuators having multiple electrostrictive elements, it is particularly advantageous to determine the temperature distribution by measuring and / or determining the temperature of individual electrostrictive elements or groups of electrostrictive elements. In this case, temperature and / or temperature changes can be measured and / or determined.

[0084] The electrostrictive actuator is preferably implemented as an electrostrictive mat.

[0085] Electrostrictive actuators or electrostrictive pads may be implemented from suitable materials, such as lead magnesium niobate (PMN), or contain such materials.

[0086] The electrostrictive actuator preferably has electrostrictive components arranged in a regular pattern.

[0087] The electrostrictive actuator or the electrostrictive component of the electrostrictive actuator preferably has a multi-layer structure.

[0088] According to the present invention, a measuring device may be specified to measure the capacitance and / or resistance and / or frequency-dependent impedance of an electrostrictive actuator.

[0089] It has been recognized that measuring the temperature-dependent characteristics of electrostrictive actuators or individual electrostrictive components may be particularly advantageous. The temperature and / or temperature change of the electrostrictive actuator can then be determined and / or estimated based on the measured variables. Based on the relationship between temperature change and the m31- or d31- coefficient, it is possible to determine the appropriate value of the m31- or d31- coefficient used to drive the electrostrictive actuator.

[0090] In the context of this invention, temperature and / or temperature change need not necessarily be determined directly. The temperature and / or temperature change of an electrostrictive actuator can also be determined indirectly by measuring the temperature-dependent characteristics to be measured. For this purpose, it has proven particularly suitable to measure the local capacitance, local resistance, and / or local frequency-dependent impedance of an electrostrictive actuator, an individual electrostrictive component, or a group of electrostrictive components of an electrostrictive actuator. Other temperature-dependent characteristics can also be measured.

[0091] The measurement of temperature-related characteristics, especially capacitance, has the advantage of requiring no or very few temperature sensors. Furthermore, the measurement is performed directly within the electrostrictive actuator itself, resulting in correspondingly accurate measurements.

[0092] According to the present invention, the measuring device may be specified to have an infrared camera for temperature detection and / or a bridge circuit for measuring the temperature-dependent characteristics of an electrostrictive actuator.

[0093] Temperature measurements and / or measurements of temperature changes can be performed, for example, by an infrared camera that captures the entire or partial area of ​​the optical element on which the electrostrictive actuator acts. In this case, the measurements can preferably be performed continuously during operation.

[0094] Alternatively or additionally, at least one bridge circuit may be used. Bridge circuits are preferably operated with AC voltages of variable frequency.

[0095] According to the present invention, the measuring device may be further specified to include a temperature sensor that measures the temperature and / or temperature changes and / or temperature distribution of the electrostrictive actuator and / or its surrounding environment.

[0096] With respect to the temperature sensors (multiple) mentioned below and above, the present invention relates to preferred embodiments. In principle, in various cases, only a single temperature sensor may be used instead of multiple temperature sensors.

[0097] Measurements of temperature and / or temperature changes in electrostrictive actuators have proven particularly suitable for obtaining temporally and spatially resolved measurements during operation.

[0098] The temperature distribution of the electrostrictive actuator and / or its surrounding environment can be determined by measurement data.

[0099] The deformation of the optically effective surface can be well inferred from measurement data through simulation, through pre-calculated tables, or through calibration.

[0100] Based on the predetermined relationship between temperature and the m31- or d31- coefficient, temperature measurements can be used to determine the current temperature-related value of the m31- or d31- coefficient in a temporal and spatial analytical manner.

[0101] Temperature sensors make it possible to measure local and time-varying temperature fields to determine the current value of the m31- or d31- coefficients of the piezoelectric tensor based on these measured variables, which can be taken into account in the process of driving an electrostrictive actuator or individual electrostrictive components driving an electrostrictive actuator.

[0102] It is also possible to measure groups of electrostrictive components.

[0103] It is advantageous if the temperature sensor is positioned on the back side of the electrostrictive actuator, away from the optical elements.

[0104] Alternatively or additionally, according to the invention, the temperature sensor may be disposed on one side of the optical element between the electrostrictive components of the electrostrictive actuator, preferably on the side facing the electrostrictive actuator (particularly preferably the rear side).

[0105] It can be specified that the temperature sensor is locally disposed between the rear side of the optical element and the electrostrictive component of the electrostrictive actuator, and / or the rear side of the electrostrictive actuator or the electrostrictive component. In the context of this invention, it is not necessary to assign a temperature sensor to each electrostrictive component. It may be sufficient if the temperature sensors are preferably arranged at regular intervals or if corresponding temperature sensors are assigned to a group of electrostrictive components. In this case, the temperature sensor may preferably be disposed between two electrostrictive components and / or on the rear side of one of the electrostrictive components.

[0106] According to the present invention, a temperature sensor can be configured to perform resistance-based measurements such that the temperature sensor comprises a material whose resistance changes with temperature and is measurable.

[0107] It is advantageous if the temperature sensor is configured to measure temperature changes of 0.1K or greater, preferably 0.03K or greater, or even better, 0.01K or greater.

[0108] It has been demonstrated that the above-described configuration of the temperature sensor is particularly suitable for determining the values ​​of the electrostrictive actuator or individual electrostrictive components that can properly drive the electrostrictive actuator.

[0109] According to the present invention, the power lines for providing control voltage to the electrostrictive actuator and the power lines for providing operating voltage to the temperature sensor may be routed jointly at least partially, and / or functionally and / or physically combined to form a uniform conductive track, and / or be identical.

[0110] In particular, when combined with a suitable control device, those connections that also essentially provide control voltage to the electrostrictive component can be used as feed lines for the temperature sensor.

[0111] The inventors have recognized that it is advantageous if the power lines of the electrostrictive component and the electrical lines for the measurement signals of the temperature sensor are routed together at least in certain sections, especially if they are functionally and / or physically combined to form a uniform conductor track.

[0112] If other sensors or other measurement points are provided additionally or alternatively in addition to the temperature sensor, they can be supplied with voltage in a similar manner where appropriate.

[0113] In the context of this invention, it can be specified that an optical device is used in the case of a projection exposure apparatus, and a measurement system is introduced when the semiconductor substrate (wafer) is changed, which measures the image. Based on the measurement, corresponding corrections can then be performed during the actuation of the electrostrictive actuator.

[0114] In the context of this invention, it can be specified that during a change in the semiconductor substrate (wafer), the actual state is first measured, and then a defined voltage is applied to the electrostrictive actuator. The change is then measured, thereby attributing the change to deformation of the optically effective surface of the optical element (particularly a mirror). The degree of deformation of the optically effective surface can then be deduced from the measurement results. Subsequently, it may also be possible to determine the present temperature, given the deviation between the expected result and the temperature change. The difference between the expected measurement result and the measured result can be attributed to temperature, and therefore temperature and / or temperature changes can also be determined in this way, and the electrostrictive actuator can then be driven accordingly to compensate for temperature changes and thus improve setting accuracy.

[0115] It is advantageous if the control device determines, based on data from the measuring device, that the expected wavefront effect is caused by changes in surface shape and / or refractive index, and takes the wavefront effect into account during the actuation of the electrostrictive actuator and / or at least one compensating member.

[0116] The inventors have recognized that it is advantageous to update the position-dependent temperature distribution of optical elements based on measurement information, which is used to determine the expected wavefront effect due to surface deformation and / or refractive index changes, and to take this wavefront variation into account when driving at least one compensation member for small aberrations. This compensation member can be not only an electrostrictive actuator, but also, or alternatively, other actuators of the optical device and / or optical system.

[0117] According to the present invention, the compensation member may be defined as an element that can move in the direction of light or in a direction perpendicular to it, and / or an element that can rotate about the direction of light or about an axis perpendicular to it, 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 move relative to each other (preferably an aspherical panel), and / or a replaceable element.

[0118] The aforementioned compensation components have proven to be particularly suitable.

[0119] The measurement methods mentioned in the context of this invention may be used alternatively or additionally. This also applies in particular to combinations of methods that directly measure temperature, temperature change, or temperature distribution, and methods that measure the temperature-dependent characteristics of an electrostrictive actuator or individual electrostrictive component and then determine the temperature, temperature change, or temperature distribution from the measured values.

[0120] The above-described method for measuring surface shape changes when a specific voltage is applied to an electrostrictive actuator can also be used in combination with other measurement methods described above.

[0121] It is advantageous if the optical element is a mirror, especially a partially deformable mirror, particularly a mirror of a projection exposure device.

[0122] The optical device according to the invention is particularly suitable for this purpose.

[0123] For the advantageous configurations and developments of this type of projection exposure device, refer accordingly to the explanations above and below.

[0124] The optical element is implemented as a lens element or a mirror of a projection objective, which is part of the projection exposure apparatus.

[0125] The present invention further relates to a method for influencing the surface shape of an optically effective surface of an optical element, according to which the optical element is functionally connected to an electrostrictive actuator, and according to which the electrostrictive actuator is adapted to influence the surface shape of the optically effective surface when a control voltage is provided to the electrostrictive actuator. According to the invention, at least sometimes when the electrostrictive actuator influences the optically effective surface of the optical element, the temperature and / or temperature changes of the electrostrictive actuator and / or its surrounding environment are directly measured and / or determined to account for temperature-related effects during the actuation of the electrostrictive actuator. The optical element is part of a projection lens, which is part of a projection exposure apparatus.

[0126] The method according to the invention can, in a particularly advantageous manner, take into account the temperature and / or temperature variations of the electrostrictive actuator or its individual electrostrictive components during actuation, and thereby determine the temperature distribution. Therefore, the surface shape of the optically effective surface can be affected with particular precision. The electrostrictive actuator is connected to an optical element, which is part of a projection lens, and the projection lens is part of a projection exposure apparatus.

[0127] For further features, configurations, and advantages, please refer similarly to the explanations of the optical device above and below.

[0128] It is advantageous if the measurement data is used to determine the parasitic effects on the surface shape of the optically effective surface and / or the variation in the refractive index of the optical element.

[0129] In one method, a voltage may be applied to cause lateral deformation of the electrostrictive actuator in the plane of the electrostrictive actuator, and the measured data is used to adjust the value of the m31- or d31- coefficient (which characterizes the lateral electrostrictive effect) to drive the electrostrictive actuator to account for temperature-related effects.

[0130] Furthermore, it can be specified that, when a specific control voltage is applied to the electrostrictive actuator, the change in the surface shape of at least one surface of the optical element (especially the optically effective surface) can be determined, particularly by measurable aberrations, and thereby the m31- or d31- coefficient can be determined.

[0131] Alternatively or additionally, it may be advantageous to determine at least one temperature-dependent variable of the electrostrictive actuator (in particular capacitance and / or resistance and / or frequency-dependent impedance), and thereby determine the m31- or d31- coefficient of the electrostrictive actuator.

[0132] From measured or determined temperature data and / or data on temperature changes, it is possible to determine the temperature distribution of the electrostrictive actuator and / or the temperature and / or temperature changes of individual electrostrictive components of the electrostrictive actuator in a simple way, and to take into account their effects accordingly.

[0133] As explained, the deformation of the optically effective surface can be well inferred from the temperature distribution through simulation, lookup tables from previous calculations, or calibration. In particular, simulations can be performed using finite element analysis (FE calculations) based on a material model. Variations in the optically effective surface can be converted into aberrations, which can be accomplished based on the sensitivity of previous calculations.

[0134] Preferably, the method according to the invention is used to correct imaging aberrations of the projection exposure device.

[0135] The method according to the invention is particularly suitable for correcting imaging aberrations in projection exposure apparatuses used for semiconductor lithography (especially EUV projection exposure apparatuses used for semiconductor lithography).

[0136] This invention relates to a projection exposure apparatus for semiconductor photolithography, comprising an illumination system including a radiation source and an optical unit having at least one optical device including optical elements for correcting imaging aberrations as described above. In this case, the optical device can be implemented according to the explanations above and below.

[0137] This invention is particularly applicable to microlithography DUV ("deep ultraviolet") and EUV ("extreme ultraviolet") projection exposure devices.

[0138] An advantageous application of the invention also relates to immersion lithography, wherein imaging aberrations are advantageously correctable.

[0139] It should also be noted that terms such as “comprising,” “including,” or “having” do not exclude other features or steps. Furthermore, terms such as “a” or “the” that indicate a step or feature in the singular do not exclude multiple features or steps, and vice versa.

[0140] Exemplary embodiments of the present invention are described in more detail below with reference to the accompanying drawings.

[0141] Each figure illustrates a preferred exemplary embodiment, which shows individual features of the invention combined with each other. Features of an exemplary embodiment may also be implemented separately from other features of the same exemplary embodiment, and thus can be readily linked together by those skilled in the art to form further advantageous combinations and sub-combinations of features with other exemplary embodiments. Attached Figure Description

[0142] In the diagram, components with the same function have the same component symbol.

[0143] In the diagram, schematically:

[0144] Figure 1 The EUV projection exposure apparatus is shown;

[0145] Figure 2 The DUV projection exposure apparatus is shown;

[0146] Figure 3 This demonstrates an immersion lithography projection exposure apparatus;

[0147] Figure 4 A cross-section of an optical device according to the invention, comprising optical elements and an electrostrictive actuator, is shown.

[0148] Figure 5 Showing Figure 4 A magnified view of the V-shaped detail;

[0149] Figure 6 Showing according to Figure 5 A schematic diagram, which has information about Figure 5 Alternative configuration for the temperature sensor;

[0150] Figure 7 A basic diagram showing the cross-section through the optical element and the electrostrictive actuator;

[0151] Figure 8 A basic diagram of the electrostrictive component of an electrostrictive actuator is shown to illustrate the lateral deformation of the electrostrictive component or the electrostrictive actuator.

[0152] Figure 9 An example diagram of an electrostrictive actuator with multiple electrostrictive components is shown; and

[0153] Figure 10 A basic diagram of an optical device is shown, comprising optical elements, an electrostrictive actuator, a temperature sensor, a measuring device, a control device, and a compensation component. Detailed Implementation

[0154] Figure 1The basic architecture of an EUV projection exposure apparatus 400 for semiconductor lithography, to which the present invention can be applied, is shown by way of example. The illumination system 401 of the projection exposure apparatus 400 includes, in addition to a radiation source 402, an optical unit 403 for illuminating a matter field 404 in a matter plane 405. A mask 406, disposed in the matter field 404 and held by a mask holder 407 (shown schematically), is illuminated. A projection objective 408, shown only schematically, is used to image the matter field 404 onto an image field 409 in an image plane 410. The structure on the mask 406 is imaged onto the photosensitive layer of a wafer 411, disposed in the region of the image field 409 in the image plane 410, which is held by a wafer holder 412, also shown by way of excerpt. The radiation source 402 can emit EUV radiation 413, particularly in the range between 5 nm and 30 nm. Optical elements 415, 416, 418, 419, and 420, implemented in different ways and adjustable mechanically, are used to control the radiation path of EUV radiation 413. Figure 1 In the case of the EUV projection exposure apparatus 400 shown, the optical element is implemented as an adjustable mirror in a suitable embodiment, which is mentioned below only by way of example.

[0155] EUV radiation 413 generated by radiation source 402 is aligned by a concentrator integrated in radiation source 402, such that EUV radiation 413 passes through the central focal point in the region of the intermediate focal plane 414 before striking the field plane mirror 415. Downstream of the field plane mirror 415, EUV radiation 413 is reflected by pupil plane mirror 416. With the aid of pupil plane mirror 416 and optical assembly 417 including mirrors 418, 419, and 420, the field plane of field plane mirror 415 is imaged into object field 404.

[0156] Figure 2 An exemplary DUV projection exposure apparatus 100 is shown. The projection exposure apparatus 100 includes an illumination system 103, means for receiving and accurately positioning a mask master 105 (which determines subsequent structures on a wafer 102) (referred to as a mask master stage 104), a wafer holder 106 for mounting, moving, and accurately positioning the wafer 102, and an imaging means (i.e., a projection lens 107) including a plurality of optical elements 108, wherein the optical elements 108 are secured by a mount 109 in a lens housing 140 of the projection lens 107.

[0157] The optical element 108 can be implemented as an individual refractive, diffractive, and / or reflective optical element 108, such as a lens element, a mirror, a prism, an end plate, etc.

[0158] The basic functional principle of the projection exposure device 100 provides the structure to be imaged onto the wafer 102 and introduced into the mask master 105.

[0159] The illumination system 103 provides a projected beam 111 in the form of electromagnetic radiation, which is required for imaging the mask master 105 onto the wafer 102. Lasers, plasma sources, etc., can be used as the source of this radiation. The radiation is shaped in the illumination system 103 by optical elements so that the projected beam 111 has desired characteristics regarding diameter, polarization, wavefront shape, etc., when it impacts the mask master 105.

[0160] An image of the mask master 105 is generated by projecting beam 111 and transferred to the wafer 102 in a correspondingly reduced manner by projection lens 107. In this case, the mask master 105 and the wafer 102 can move synchronously, such that during the so-called scanning process, the area of ​​the mask master 105 can be imaged onto the corresponding area of ​​the wafer 102 in a virtually continuous manner.

[0161] Figure 3 A third projection lens 200, implemented as an immersion lithography DUV projection exposure apparatus, is shown. For example, further background on such a projection lens 200 can be found in WO 2005 / 069055 A2, the contents of which are incorporated herein by reference; therefore, its specific operation will not be discussed in detail here.

[0162] With and according to Figure 2 A comparable approach to the DUV projection exposure apparatus 100 is clearly the mask stage 4, which determines the subsequent structure disposed on the wafer 102 on the wafer holder 106 or wafer stage. For this purpose, Figure 3 The projection objective 200 also includes multiple optical elements, particularly the lens element 108 and the mirror 201.

[0163] However, in the context of this invention, other elements in the beam path region of the mask master 105, 406, mask master stage 104 or mask master holder 407, wafer 102, 411, wafer holder 106, 412, or projection exposure apparatus 100, 400 or projection objective 200 may also be referred to as optical elements.

[0164] To correct imaging aberrations in projection exposure devices (e.g., projection exposure devices 100, 400, or projection objective 200), target distortion of its optical elements 108, 201, 415, 416, 418, 419, 420 may be appropriate. Imaging aberrations in EUV projection exposure device 400 can be particularly effectively corrected by one or more mirrors of projection objective 408 that are deformed in a targeted manner.

[0165] Two mirrors 201 are positioned within the optical path of the projection lens 200, with the intermediate focal plane 414 located between the mirrors.

[0166] Although the invention for correcting imaging aberrations is in principle applicable to any deformation of optical elements in any projection lens, it is particularly advantageous for deformation of optical elements 201, 415 adjacent to the intermediate focal plane 414. Therefore, in particular, Figure 3 The reflector 201 of the immersion lithography projection lens can be made deformable according to the present invention.

[0167] The use of the present invention is not limited to use in the projection exposure apparatus 100, 400 or projection objective lens 200, and is not particularly limited to the described configuration.

[0168] The present invention and the following exemplary embodiments should be further understood as not being limited to a particular design. The following figures illustrate the invention by way of example and in a highly schematic manner only.

[0169] Figures 4 to 7 and Figure 10 An optical device 1 comprising an optical element 2 and an electrostrictive actuator 3 is shown. The optical device 1 may be part of a projection exposure apparatus 100, 400 or a projection objective 200 for semiconductor lithography, particularly a part of an EUV projection exposure apparatus 400 or an immersion lithography DUV projection exposure apparatus 200.

[0170] Optical element 2 may be a lens element or a mirror. Preferably, optical element 2 is an adaptive optics element (especially a deformable lens element or a deformable mirror), particularly an adaptive optics element of projection exposure apparatus 100, 400 or projection objective 200 (preferably EUV projection exposure apparatus 400 or immersion lithography DUV projection objective 200). Particularly preferably, optical element 2 is implemented as mirror 201 of immersion lithography DUV projection objective 200 or mirror 415, 416, 418, 419, 420 of EUV projection exposure apparatus 400. Very particularly preferably, optical element 2 is disposed between mask master 105, 406 and wafer 102, 411. Very particularly preferred, the optical element 2 is implemented as one of the mirrors of the projection lens 408 of the EUV projection exposure apparatus 400, as the lens element 108 of the DUV projection exposure apparatus 100, or as the mirror 201 of the immersion lithography DUV projection lens 200.

[0171] The optical element 2 according to the present invention can also be implemented as a lens element 108 of a DUV projection exposure device 100 or an immersion lithography DUV projection objective lens 200.

[0172] Optical device 1 is preferably part of an assembly for correcting imaging aberrations of projection exposure device 100, 400 or projection objective 200, and for this purpose, optical element 2 is implemented as a lens element or mirror of projection exposure device 100, 400 or projection objective 200.

[0173] In the exemplary embodiment, an optical device 1 including optical elements 2 is shown in more detail, particularly for a projection exposure apparatus, based on lens elements, especially mirrors, but not limited thereto. The optical device can be any optical device 1 including any optical element 2. The exemplary embodiment should be understood accordingly.

[0174] The electrostrictive actuator 3 is designed to deform by an applied control voltage. The electrostrictive actuator 3 is functionally connected to the optical element 2 to affect the surface shape of the optically effective surface 2a of the optical element 2.

[0175] A control device 4 is provided to supply control voltage to the electrostrictive actuator 3. The control device 4 is schematically shown in… Figure 10 middle.

[0176] A measuring device 5 is further provided, configured to directly measure and / or indirectly determine the temperature and / or temperature changes of the electrostrictive actuator and / or its surrounding environment, at least sometimes when the electrostrictive actuator 3 affects the optically effective surface 2a of the optical element 2. Based on the data and / or measured variables, it is then possible to take into account temperature-related effects during the actuation of the electrostrictive actuator 3.

[0177] Taking into account the data from the measuring device 5, the control device 4 is configured to set the desired deformation of the optically effective surface 2a and drive the electrostrictive actuator accordingly.

[0178] Measuring device 5 is schematically shown in Figure 10 middle.

[0179] In an exemplary embodiment, the measuring device 5 is specified to measure at least one of the following variables:

[0180] - Temperature and / or temperature change of electrostrictive actuator 3, and / or

[0181] - Temperature and / or temperature changes in the environment surrounding the electrostrictive actuator 3, and / or

[0182] - Temperature-dependent characteristics of electrostrictive actuators, and / or

[0183] - When a specific voltage is applied to the electrostrictive actuator 3, the change in the surface shape of at least one surface 2a of the optical element 2 is used to detect the sensor deviation of the temperature sensor by measuring the surface shape and comparing it with a known setpoint value (e.g., from a lookup table, etc.), and to correct it as appropriate.

[0184] Measurements of temperature and / or temperature changes in the environment surrounding an electrostrictive actuator should be understood to mean that measurements are taken near the electrostrictive actuator such that the measured temperature or temperature change still allows for conclusions about the temperature and / or temperature changes of the electrostrictive actuator, for example, through simulation or previously calculated tables.

[0185] Preferably, the measuring device 5 is configured to perform continuous measurements during operation of the electrostrictive actuator 3. In this case, measurements can also be performed during pauses in the operation of the projection exposure apparatus 100, 400 or the projection objective 200, for example, when the semiconductor substrate, particularly the wafers 411, 102 or the mask of the projection exposure apparatus 100, 400, is changed.

[0186] It can also be specified that the measuring device 5 performs measurements only when the electrostrictive actuator 3 affects the optically effective surface 2a of the optical element 2.

[0187] In an exemplary embodiment, the measuring device 5 is specified to measure and / or determine the temperature distribution of the electrostrictive actuator 3, and the measuring device 5 is configured accordingly and a corresponding number of measuring points are provided.

[0188] In an exemplary embodiment, the electrostrictive actuator 3 is configured such that applying a voltage causes the electrostrictive actuator 3 to deform laterally in the plane of the electrostrictive actuator 3.

[0189] Based on the data determined by the measuring device 5, the control device 4 is configured to adjust the value of the m31- or d31- coefficient (which characterizes the transverse electrostrictive effect) to drive the electrostrictive actuator 3, taking into account temperature-related effects.

[0190] The m31- or d31- coefficient or its effect on the electrostrictive actuator (lateral deformation) is, in principle, as follows: Figure 7 and Figure 8 As shown. In this case, Figure 7 The m33- or d33- coefficients are also specified, but this is only for completeness. In the exemplary embodiment, it is specified that the m31- or d31- coefficients are taken into account, rather than the m33- or d33- coefficients.

[0191] The control device 4 is configured to take into account the material parameters within the electrostrictive actuator 3 and / or the thermal changes of components in the surrounding environment of the electrostrictive actuator 3.

[0192] like Figures 4 to 7 and Figure 10 As shown, the electrostrictive actuator 3 can preferably be fixed to the optical element 2 by adhesive 6. Other variations of the fixing method are also possible here, particularly welding, but fixing by adhesive 6 or an adhesive layer has proven particularly suitable. The optical element is part of a projection objective, which is part of a projection exposure apparatus.

[0193] In an exemplary embodiment, the electrostrictive actuator 3 is disposed on the rear side 2b of the optical element 2 away from the optically effective surface 2a.

[0194] Alternatively and / or additionally, the electrostrictive actuator 3 may also be disposed on the optically effective surface 2a outside the light region of the optical element or on the side surface of the optical element 2 (both not shown).

[0195] The electrostrictive actuator 3 may extend over a section or a portion of the rear side 2b of the optical element 2, or over the entire rear side 2b of the optical element 2. It may also be specified that multiple electrostrictive actuators 3 are used, distributed in various cases over portions of the area, preferably over portions of the rear side 2b of the optical element 2.

[0196] In the context of the solution according to the invention, it may also be specified that the electrostrictive actuator 3 affects only a segment of the optically effective surface 2a of the optical element 2 in each case.

[0197] In an exemplary embodiment, the control device 4 is configured to take into account the thermal changes in stiffness and thermal expansion of the adhesive 6 during the actuation of the electrostrictive actuator 3. Therefore, the actuation of the electrostrictive actuator 3 can be performed while taking into account the effects of temperature changes in the adhesive 6, such that the effect of temperature changes in the adhesive 6 on the optically effective surface 2a of the optical element 2 is considered during the actuation of the electrostrictive actuator 3. Therefore, thermal control changes in the expansion or stiffness of the welded connections and / or the substrate of the optical element can also be considered.

[0198] In an exemplary embodiment, the electrostrictive actuator 3 is specified to have a plurality of electrostrictive components 7. This is shown by way of example. Figures 4 to 7 , Figure 10 And especially Figure 9 The electrostrictive actuator 3 is preferably implemented as an electrostrictive pad. One or more actuators 3 may be mounted below the reflector substrate. In this case, the actuators 3 may also be combined into one or more units. The distribution of the electrostrictive components 7 of the electrostrictive actuator 3 (especially in the embodiment as a pad) is preferably regular, wherein... Figure 9 The example shown is for this situation, not a limitation.

[0199] According to the present invention, the measuring device 5 may be specified to measure the temperature-dependent characteristics of the electrostrictive actuator 3, particularly the capacitance and / or resistance and / or frequency-dependent impedance of the electrostrictive actuator.

[0200] In an exemplary embodiment, the measuring device 5 may also be provided with an infrared camera for temperature detection and / or a bridge circuit for measuring the temperature-dependent characteristics of the electrostrictive actuator 3. These variations are not shown in the exemplary embodiment, but are feasible to those skilled in the art. The above measurement method may be used alternatively or additionally.

[0201] In an exemplary embodiment, such as Figures 4 to 7 and Figure 10 As shown, the specified measuring device 5 includes a temperature sensor 8, which measures the temperature and / or temperature changes and / or temperature distribution of the electrostrictive actuator and / or its surrounding environment.

[0202] According to the present invention, the temperature sensor 8 may be assigned to each electrostrictive component 7 or a group of electrostrictive components. Figure 4 , Figure 5 and Figure 6 A temperature sensor 8 is shown as an example in each case, but multiple temperature sensors 8 may also be provided; in particular, each electrostrictive component 7 may be assigned a temperature sensor 8.

[0203] According to Figure 4 and Figure 5 In an exemplary embodiment, the temperature sensor 8 is disposed on the rear side 3a of the electrostrictive actuator 3 away from the optical element 2. In an exemplary embodiment, the temperature sensor 8 is specifically located on the rear side 3a of one of the electrostrictive components 7 of the electrostrictive actuator 3.

[0204] Figure 6 The alternative positioning is shown in the image. According to... Figure 6 In an exemplary embodiment, the temperature sensor 8 is located on one side of the optical element 2, specifically at the rear 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, which may also be used with, for example... Figure 4 and 5 The positioning shown is used in combination.

[0205] If the electrostrictive actuator 3 corresponds to or is similar to Figure 9 The variant shown is implemented in the way that... Figure 6 In the exemplary embodiment shown, the temperature sensor 8, which may be configured between the electrostrictive components 7, is disposed in the gap or free space 3b of the electrostrictive actuator 3.

[0206] The temperature sensor 8 can be configured to enable resistance-based measurements, specifically by including a material whose resistance changes with temperature in a measurable manner. Preferably, the temperature sensor 8 is configured to reliably detect temperature changes of 0.1 K, more preferably 0.03 K, and even more preferably about 0.01 K.

[0207] In an exemplary embodiment, a power line 9 for providing a control voltage to the electrostrictive actuator 3 or its electrostrictive component 7 and a power line 10 for providing an operating voltage to the temperature sensor 8 are provided for measurement in which they are at least partially co-wired and / or combined to form a uniform conductive track.

[0208] In an exemplary embodiment, the control device 4 may be specified to determine the expected wavefront effect caused by changes in surface shape and / or refractive index based on data from the measuring device 5, and to take into account the wavefront effect during the driving of the electrostrictive actuator 3 and / or at least one compensation member 11.

[0209] Figure 10 A compensation component 11 is schematically shown.

[0210] Without further specific detail, one or more compensation members 11 may be implemented as elements that can be displaced in the direction of light or in a direction perpendicular to it, and / or elements that can rotate about the direction of light or about an axis perpendicular to it, and / or deformable elements, and / or locally heated elements, and / or locally cooled elements, and / or elements that can move relative to each other (preferably aspherical panels), and / or replaceable elements.

[0211] Figure 10 The diagram schematically illustrates how data from temperature sensor 8 (or from other measurement methods or other measurement points) is acquired by measuring device 5 and provided to control device 4. Control device 4 can then drive electrostrictive actuator 3, specifically providing values ​​for the m31- or d31- coefficients characterizing the transverse electrostrictive effect, for driving electrostrictive actuator 3 and taking into account temperature-related effects during the process. Alternatively or supplementarily, similarly... Figure 10 As shown, the data from the control device 4 can also be specified to drive the compensation member 11 accordingly for small aberrations, so that temperature-related effects can be taken into account accordingly.

[0212] Figure 8 An example is given of the lateral deformation of the electrostrictive actuator 3 based on the coefficients m31- or d31-. Figure 8 The dashed lines in the diagram show the state of the electrostrictive actuator 3 or electrostrictive component 7 in a plan view, for example, the state of the rear side 3a after voltage is applied. The solid lines indicate the state of the electrostrictive actuator 3 or electrostrictive component 7 before voltage is applied.

[0213] Figure 4 An advantageous configuration of the optical device 1 is shown, but the solution according to the invention is not limited to this configuration.

[0214] As already explained, the electrostrictive actuator 3 is preferably attached to the rear side 2b of the optical element 2 via adhesive 6 or an adhesive layer; this also... Figure 5 and Figure 6 The corresponding explanation was provided in a magnified manner.

[0215] In an exemplary embodiment, the electrostrictive actuator 3 is composed of a plurality of electrostrictive components 7. The electrostrictive actuator 3 may be implemented as an electrostrictive pad.

[0216] Voltage is supplied to the electrostrictive actuator 3 or its electrostrictive component 7 via power line 9 or electrical contact. In this case, power line 9 may be specified to lead directly to electrostrictive component 7. Alternatively, for direct contact of electrostrictive component 7, an electrical contact or conductive layer may be provided at the rear side 3a of the electrostrictive component, which then contacts the power line, such as... Figure 5 and 6 As shown.

[0217] According to Figures 4 to 6 In an exemplary embodiment, an insulating layer 12 is also provided at the rear side 3a of the electrostrictive actuator 3 or its electrostrictive component 7, which at least partially shields the electrical contact or conductive layer 9 outward.

[0218] Figure 5 The configuration of the temperature sensor 8 at the rear side 3a of the electrostrictive actuator 3 is shown. In this case, the voltage supply is provided by the power line 10, which is at least partially wired together with the power line 9.

[0219] Figure 6 An alternative diagram is shown, in which the temperature sensor 8 is disposed in the gap or free space 3b between the electrostrictive members 7 at the rear side 2b of the optical element 2.

[0220] Figure 5 and Figure 6 Mixing is also possible; in particular, it is possible to specify the use of more temperature sensors 8, especially to assign a corresponding temperature sensor 8 to each electrostrictive component 7 or a group of electrostrictive components 7.

[0221] like Figure 5 and Figure 6As shown, the temperature sensor 8 can preferably be fixed to the rear side 2b of the optical element 2 by the adhesive layer 6a or to the rear side 3a of the electrostrictive actuator 3 or its electrostrictive component 7. During the actuation of the electrostrictive actuator, thermal changes in stiffness and / or thermal expansion of the adhesive layer 6a and / or other related components during actuation can also be taken into account, if appropriate. This may be advantageous for reducing drift and / or correcting drift.

[0222] This exemplary embodiment is also used to describe the optical element 2 used in the optical device 1, as shown above.

[0223] This exemplary embodiment further illustrates a method for influencing the surface shape of the optically effective surface 2a of an optical element 2. According to this method, at least sometimes when the electrostrictive actuator 3 influences the optically effective surface 2a of the optical element 2, the temperature and / or temperature variations and / or temperature distribution of the electrostrictive actuator 3 and / or its surrounding environment are directly measured and / or determined to account for temperature-related effects during the actuation of the electrostrictive actuator 3. Preferably, the above measurements are performed at least sometimes when the actuator 3 actively influences the surface 2a of the optical element 2 (i.e., when a voltage is present at the actuator 3). The measured data can then 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 projection lenses (408, 107, 200), the projection lenses (408, 107, 200)... 200) includes an optical device (1) comprising an optical element (2) having an optically effective surface (2a) and at least one electrostrictive actuator (3) deformable by an applied control voltage, wherein the electrostrictive actuator (3) is functionally connected to the optical element (2) to influence the surface shape of the optically effective surface (2a), and wherein a control device (4) is provided to provide the control voltage to the electrostrictive actuator (3), wherein a measuring device (5) is provided, configured to determine the temperature and / or temperature variations of the electrostrictive actuator (3) and / or its surrounding environment at least sometimes when the electrostrictive actuator (3) influences the optically effective surface (2a) of the optical element (2), to take into account temperature-related effects during the actuation of the electrostrictive actuator (3) by the control device (4). The measuring device (5) includes a temperature sensor (8) that measures the temperature and / or temperature changes and / or temperature distribution of the electrostrictive actuator (3) and / or its surrounding environment. The optical element is located near the central focal plane of the projection exposure device.

2. The apparatus (400, 100) as claimed in claim 1, wherein the measuring device (5) is configured to directly measure and / or indirectly determine the temperature and / or temperature changes of the electrostrictive actuator (3) and / or its surrounding environment.

3. The apparatus (400, 100) as claimed in claim 1 or 2, wherein the measuring device (5) measures at least one of the following variables to indirectly determine the temperature and / or temperature change: - The temperature-dependent characteristics of the electrostrictive actuator (3), and / or - The change in surface shape of at least one surface (2a, 2b) of the optical element (2) when a specific control voltage is applied to the electrostrictive actuator (3).

4. The apparatus (400, 100) as claimed in claim 1, wherein the measuring device (5) continuously measures and / or determines the temperature and / or temperature change during operation of the electrostrictive actuator (3).

5. The apparatus (400, 100) as claimed in claim 1 or 2, wherein the electrostrictive actuator (3) is configured such that applying the control voltage will cause the electrostrictive actuator (3) to undergo lateral deformation in the plane of the electrostrictive actuator (3).

6. The apparatus (400, 100) as claimed in claim 1 or 2, wherein the control device (4) is configured to adjust the value of the m31- or d31- coefficient characterizing the transverse electrostriction effect based on data determined by the measuring device (5) for driving the electrostriction actuator (3) to take into account the temperature-related effects.

7. The apparatus (400, 100) as claimed in claim 1 or 2, wherein the control device (4) is configured to take into account material parameters within the electrostrictive actuator (3) and / or thermal changes of components in the surrounding environment of the electrostrictive actuator (3).

8. The apparatus (400, 100) as claimed in claim 1 or 2, wherein the electrostrictive actuator (3) is fixed to the optical element (2) by an adhesive (6) or a welded connection, and the control device (4) is configured to take into account the thermal changes in stiffness and / or expansion of the adhesive (6) or the welded connection during the actuation of the electrostrictive actuator (3).

9. The apparatus (400, 100) as claimed in claim 1 or 2, wherein the electrostrictive actuator (3) is disposed on the rear side (2b) of the optical element (2) away from the optically effective surface (2a).

10. The apparatus (400, 100) as claimed in claim 1 or 2, wherein the electrostrictive actuator (3) is disposed on the optically effective surface (2a) of the optical element (2) outside a light region or on one side surface of the optical element (2).

11. The apparatus (400, 100) as claimed in claim 1 or 2, wherein the electrostrictive actuator (3) has a plurality of electrostrictive components (7).

12. The apparatus (400, 100) as claimed in claim 1 or 2, wherein the measuring device (5) measures the capacitance and / or resistance and / or frequency-dependent impedance of the electrostrictive actuator (3) to determine the temperature and / or temperature change.

13. The apparatus (400, 100) as claimed in claim 1 or 2, wherein the measuring device (5) has an infrared camera for temperature detection and / or a bridge circuit for measuring the temperature-dependent characteristics of the electrostrictive actuator (3).

14. The device (400, 100) as claimed in claim 1 or 2, wherein the temperature sensor (8) is disposed on the rear side (3a) of the electrostrictive actuator (3) away from the optical element (2).

15. The device (400, 100) as claimed in claim 1 or 2, wherein the temperature sensor (8) is disposed on one side (2b) of the optical element (2) between the electrostrictive components (7) of the electrostrictive actuator (3).

16. The apparatus (400, 100) as claimed in claim 1 or 2, wherein the temperature sensor (8) is configured to measure temperature changes of 0.1 K or greater.

17. The apparatus (400, 100) of claim 16, wherein the temperature change is 0.03 K or greater.

18. The apparatus (400, 100) of claim 16, wherein the temperature change is 0.01 K or greater.

19. The apparatus (400, 100) as claimed in claim 1 or 2, wherein the power line (9) for providing the control voltage to the electrostrictive actuator (3) and the power line (10) for providing the operating voltage to the temperature sensor (8) are at least partially wired together, and / or functionally and / or physically combined to form a uniform conductive track, and / or are identical.

20. The apparatus (400, 100) as claimed in claim 1 or 2, wherein the control device (4) determines the expected wavefront effect due to changes in surface shape and / or refractive index based on data from the measuring device (5), and takes into account the wavefront effect during the driving of the electrostrictive actuator (3) and / or at least one compensation member (11).

21. The apparatus (400, 100) of claim 20, wherein the compensation member (11) is implemented as an element displaceable in the light direction or in a direction perpendicular thereto, and / or an element rotatable about the light direction or about an axis perpendicular thereto, and / or a deformable element, and / or a locally heatable element, and / or a locally coolable element, and / or an element displaceable relative to each other, and / or a replaceable element.

22. The device (400, 100) as claimed in claim 21, wherein the elements that are displaceable relative to each other are aspherical panels.

23. The device (400, 100) as claimed in claim 1 or 2, wherein the optical element (2) is a mirror.

24. The apparatus (400, 100) as claimed in claim 23, wherein the optical element (2) is a partially deformable mirror.

25. A method for correcting the temperature in a projection exposure apparatus as claimed in any one of claims 1 to 24, comprising influencing the surface shape of an optically effective surface (2a) of an optical element (2) disposed in the projection exposure apparatus, wherein the optical element (2) is functionally connected to an electrostrictive actuator (3), wherein the electrostrictive actuator (3) is adapted to influence the surface shape of the optically effective surface (2a) when supplied with a control voltage, wherein at least sometimes when the electrostrictive actuator (3) influences the optically effective surface (2a) of the optical element (2), the temperature and / or temperature variation of the electrostrictive actuator (3) and / or its surrounding environment are directly measured and / or determined to take into account temperature-related effects during the actuation of the electrostrictive actuator (3).

26. The method of claim 25, wherein the measured data is used to determine the parasitic effects on the surface shape of the optically effective surface (2a) and / or the refractive index variation of the optical element (2).

27. The method of claim 25 or 26, wherein applying the control voltage causes the electrostrictive actuator (3) to undergo lateral deformation in the plane of the electrostrictive actuator (3), and the measured data is used to adjust the value of the m31- or d31- coefficient characterizing the lateral electrostrictive effect for driving the electrostrictive actuator (3) in a manner that takes into account the temperature-related effects.

28. The method of claim 27, wherein, when a specific control voltage is applied to the electrostrictive actuator (3), the change in the surface shape of at least one surface (2a, 2b) of the optical element (2) is determined, and thereby the m31- or d31- coefficient is determined.

29. The method of claim 28, wherein the at least one surface is the optically effective surface (2a).

30. The method of claim 28, wherein the change is determined by measurable aberrations.

31. The method of claim 27, wherein at least one temperature-dependent variable of the electrostrictive actuator (3) is determined, and thereby the m31- or d31- coefficient of the electrostrictive actuator (3) is determined.

32. The method of claim 31, wherein the at least one temperature-dependent variable is capacitance and / or resistance and / or frequency-dependent impedance.

33. The method of claim 25 or 26, wherein the method is used to correct imaging aberrations of a projection objective (107, 403, 200), which is part of a projection exposure apparatus (400, 100).

Images