Drive mechanism, optical system, and lithographic apparatus

Abstract

A driving device (100) for driving and measuring an actuator (200) for actuating an optical element (310) of an optical system (300), comprising: a driving unit (110) having a frequency-dependent first transfer function (G1) configured to amplify a time-dependent AC voltage signal (W) having at least a first frequency range (F1) and a second frequency range (F2) with a gain higher by a certain factor in the first frequency range (F1) than in the second frequency range (F2) to form a driving voltage (AS) for the actuator (200); and a voltage measurement unit (120) providing a measurement voltage (U), wherein the actuator is measured in the time domain. a voltage measurement unit (120) configured to convolve a time-dependent voltage (u) of the actuator (200) with a second transfer function (G2) based on the inverse of the first transfer function (G1) and subsequently measure the time-dependent voltage to provide a measured voltage (U), and a current measurement unit (130) configured to convolve a time-dependent current (i) of the actuator (200) with a third transfer function (G3) based on the inverse of the first transfer function (G1) in the time domain and subsequently measure the time-dependent current to provide a measured current (I).

Description

[Technical field]

[0001] The present invention relates to a drive device for driving and measuring an actuator of an optical system, an optical system including such a drive device, and a lithography apparatus including such an optical system.

[0002] The content of the priority application DE 10 2022 203 255.1 is incorporated by reference in its entirety. [Background technology]

[0003] Microlithography apparatus are known which have actuable optical elements, such as an array of microlens elements or an array of micromirrors. Microlithography is used for the manufacture of finely structured components, such as integrated circuits. Microlithography processes are carried out using lithography apparatus which have an illumination system and a projection system.

[0004] Due to the desire for ever smaller structures in the manufacture of integrated circuits, EUV lithography tools are currently under development that use light with wavelengths in the range of 0.1 nm to 30 nm, specifically 13.5 nm. Because most materials absorb light at this wavelength, these EUV lithography tools must use reflective optics, i.e. mirrors, instead of the previous refractive optics, i.e. lenses.

[0005] In this case, the image of a mask (reticle) illuminated by an illumination system is projected by a projection system onto a substrate, for example a silicon wafer, which is covered with a light-sensitive layer (photoresist) and placed in the image plane of the projection system, so as to transfer the mask structures into the light-sensitive coating of the substrate. The imaging of the mask on the substrate can be improved by actuable optical elements. For example, wavefront aberrations during exposure that lead to magnified and / or blurred imaging can be compensated.

[0006] Such correction by optical elements requires wavefront detection and signal processing to determine the respective positions of the optical elements that allow the desired correction of the wavefront. In a final step, the drive signals for each optical element are amplified and output to the actuators of the optical elements.

[0007] As an example, PMN actuators (PMN; lead magnesium niobate) can be used as actuators. PMN actuators allow distance positioning in the sub-micrometer or sub-nanometer range. In this case, the actuator, whose actuator elements are stacked one on top of the other, is subjected to a force that causes a certain linear expansion as a result of the application of a DC voltage. The position set by a DC voltage (DC; direct current) can be adversely affected by external electromechanical crosstalk at the fundamental resonance point of the actuator driven by the DC voltage. This electromechanical crosstalk makes it impossible to stably set a precise positioning. In this case, the higher the applied DC voltage, the higher the mechanical resonance. The resonance point can also change over time, for example as a result of temperature drift or as a result of adhesive drift if the mechanical connection of the adhesive material changes, or as a result of hysteresis or aging. For example, impedance measurements would be useful in this situation.

[0008] However, conventional impedance measuring devices are often too costly and furthermore cannot be put in-line, i.e. used regularly in lithographic apparatus. Moreover, since the impedance value range of interest here spans several orders of magnitude and the range of interest is only a part of the total range, it turns out that integrated impedance measuring bridges, which are usually set for impedance values ​​that are too high, are not suitable for this application in lithographic apparatus.

[0009] It is also known to drive actuators of a lithographic apparatus with respective drive signals having a low frequency drive component for driving the actuator and a high frequency measurement signal component for measuring the actuator. Conventionally, such drive signals are amplified by an output stage with a uniform gain over frequency and applied as a drive voltage to the actuator. Such conventional output stages provide a uniform gain and therefore a uniform resolution over the entire frequency range. If a high gain is selected for the gain by the output stage, this high gain causes a reduction in the resolution for measuring the impedance of the actuator. However, if a low gain is selected, this is not sufficient for the application of driving the actuator. Summary of the Invention [Problem to be solved by the invention]

[0010] Against this background, it is an object of the present invention to improve the driving of actuators in optical systems. [Means for solving the problem]

[0011] According to a first aspect, a driving device is proposed for driving and measuring an actuator of an optical system. a drive unit having a frequency dependent first transfer function configured to amplify a time dependent AC voltage signal having at least a first frequency range and a second frequency range, with a gain higher by a certain factor in the first frequency range compared to the second frequency range, to form a drive voltage for the actuator; a voltage measurement unit for providing a measured voltage, the voltage measurement unit being configured to convolve, in the time domain, a time dependent voltage of the actuator with a second transfer function based on the inverse of the first transfer function, and subsequently measure the time dependent voltage to provide a measured voltage; a current measurement unit for providing a measured current, the current measurement unit being configured to convolve, in a time domain, a time-dependent current of the actuator with a third transfer function based on the inverse of the first transfer function, and subsequently measure the time-dependent current to provide a measured current; Equipped with.

[0012] Advantageously, the drive arrangement allows high gain in a first frequency range for driving the actuator and simultaneously high resolution in a second frequency range for measuring the actuator, in particular for measuring the impedance of the actuator.

[0013] In this case, the components of the drive voltage in the first frequency range serve to drive the actuator, i.e. in particular to control the deflection of the actuator, whereby in the first frequency range there is a higher gain compared to the second frequency range in order to drive the actuator appropriately, and before each measurement, i.e. before the voltage measurement and the current measurement, the first frequency range is attenuated and the second frequency range is amplified, so that in the second frequency range a high resolution for measuring the actuator is provided.

[0014] The driver may also be described as a frequency-dependent amplifier stage for driving actuators with integrated current and voltage measurement.

[0015] As a result of providing a measured voltage and a measured current for the actuator, the drive arrangement allows an in-line corresponding determination of the impedance behavior of the actuator, in particular an impedance determination of the actuator mounted in the lithographic apparatus. Based on the determined impedance behavior of the actuator, suitable remedial measures or countermeasures, in particular active in-line calibration or in-line damping, can also be implemented by the drive signal.

[0016] In particular, the actuator is a capacitive actuator, such as a PMN actuator (PMN; lead magnesium niobate) or a PZT actuator (PZT; lead zirconate titanate) or a LiNbO3 actuator (lithium niobate). The actuator is in particular adapted to actuate an optical element of an optical system. Examples of such optical elements include lens elements, mirrors and adaptive mirrors.

[0017] The optical system is preferably a projection optical unit of a lithography apparatus or a projection exposure apparatus. However, the optical system can also be an illumination system. The projection exposure apparatus can be an EUV lithography apparatus. EUV stands for "extreme ultraviolet" and denotes a wavelength of light used between 0.1 nm and 30 nm. The projection exposure apparatus can also be a DUV lithography apparatus. DUV stands for "deep ultraviolet" and denotes a wavelength of light used between 30 nm and 250 nm.

[0018] According to one embodiment, the driving device further comprises a determining unit coupled to the voltage measuring unit and the current measuring unit, the determining unit being configured to determine the impedance of the actuator based on the provided measured voltage and the provided measured current, in particular this embodiment of the driving device can also be referred to as a frequency dependent amplification stage for driving and measuring the impedance of the actuator.

[0019] According to yet another embodiment, the first frequency range is located between 0 Hz and 1 kHz, preferably between 0 Hz and 500 Hz, and even more preferably between 0 Hz and 300 Hz.

[0020] According to yet another embodiment, the second frequency range is located between 5 kHz and 100 kHz, preferably between 10 kHz and 100 kHz, and even more preferably between 10 kHz and 60 kHz.

[0021] According to yet another embodiment, the specific coefficient is between 100 and 2000, preferably between 500 and 1500, and even more preferably between 800 and 1200.

[0022] According to yet another embodiment, the drive unit comprises an amplifier circuit, in particular a differential amplifier.

[0023] According to yet another embodiment, the amplifier circuit of the drive unit includes an input node providing an AC voltage signal, an output node providing a drive voltage for the actuator, and an operational amplifier coupled between the input node and the output node, where a first circuit is coupled to the input node, a negative supply voltage of the drive device, and a non-inverting input of the operational amplifier, and a second circuit is coupled to the inverting input of the operational amplifier, ground, and the output node to provide a transfer function.

[0024] According to yet another embodiment, the first and second circuits each comprise a resistive circuit for adjusting the gain in a first frequency range, and for adjusting the gain in a second frequency range, each circuit further comprises a frequency-dependently connectable circuit comprising a frequency-dependent component and a resistor, for example in the form of a capacitor and a resistor connected in series.

[0025] In this case, the capacitance of the capacitor is in particular selected such that the capacitor is conductive at frequencies in the second frequency range and thus the connectable circuit is connected in a frequency-dependent manner at frequencies in the second frequency range. Each frequency range may also be referred to as a frequency band.

[0026] According to yet another embodiment, the voltage measuring unit comprises an amplifier circuit, in particular a differential amplifier.

[0027] According to yet another embodiment, the amplifier circuit of the voltage measurement unit includes an input node coupled to an output node of the amplifier circuit of the drive unit and operative to receive the time-dependent voltage of the actuator, an output node for providing the measurement voltage, and an operational amplifier coupled between the input node and the output node, where a first circuit is coupled to the output node, to a negative supply voltage of the drive device, and to an inverting input of the operational amplifier, and a second circuit is coupled to the input node, to a non-inverting input of the operational amplifier, and to ground to provide a second transfer function.

[0028] According to yet another embodiment, the first circuit and the second circuit each include a resistive circuit providing a component of the second transfer function in a first frequency range and providing a component of the second transfer function in a second frequency range, each circuit further including a frequency dependent connectable circuit including a frequency dependent component and a resistor.

[0029] By way of example, the connectable circuit is in the form of a series-connected capacitor and resistor, where the capacitance of the capacitor is selected such that the capacitor is conductive at frequencies in the second frequency range and thus the connectable circuit is connected in a frequency-dependent manner at frequencies in the second frequency range.

[0030] According to yet another embodiment, the second circuit of the amplifier circuit of the drive unit and the second circuit of the amplifier circuit of the voltage measuring unit are formed by a single circuit, which advantageously saves components of the optical system and therefore space.

[0031] The voltage measurement units can also be connected to different channels or different actuators by a multiplexer, in which case it is not possible to measure all actuators simultaneously, but less circuitry is required.

[0032] According to a second aspect, an optical system is proposed comprising a plurality of actuatable optical elements, each of said plurality of actuatable optical elements being assigned an actuator, each actuator being assigned a drive device for driving an actuator according to the first aspect or one of the embodiments of the first aspect.

[0033] The optical system in particular comprises a micromirror array and / or a lens element array having a plurality of optical elements that are independently actuable with respect to one another.

[0034] In an embodiment, groups of actuators can be defined, with all actuators in a group being assigned the same driver.

[0035] According to an embodiment, the optical system is in the form of an illumination optical unit or a projection optical unit of a lithographic apparatus.

[0036] According to yet another embodiment, the optical system comprises a vacuum housing in which the actuatable optical element, the assigned actuator and the drive are arranged.

[0037] According to a third aspect, there is proposed a lithographic apparatus comprising an optical system according to the second aspect or one of the embodiments of the second aspect.

[0038] The lithography apparatus is, for example, an EUV lithography apparatus using light in the wavelength range of 0.1 nm to 30 nm, or a DUV lithography apparatus using light in the wavelength range of 30 nm to 250 nm.

[0039] The indefinite article "a" or "an" in this case should not necessarily be understood as limiting to exactly one element. Rather, there can be a plurality of elements, e.g., two, three, or more. Any other numbers used herein should not be understood as limiting to a precise recited number of elements. Rather, more or less numbers are possible unless otherwise indicated.

[0040] Further possible implementations of the invention also include unstated combinations of the features or embodiments described above or below with respect to the exemplary embodiments, in which case the person skilled in the art will be able to apply individual aspects as improvements or supplements to each basic form of the invention.

[0041] Further advantageous configurations and aspects of the invention are the subject of dependent claims and also of the exemplary embodiments of the invention described below. The invention is explained in more detail below on the basis of preferred embodiments and with reference to the attached drawings. [Brief description of the drawings]

[0042] [Figure 1] 1 shows a schematic meridian section of a projection exposure apparatus for EUV projection lithography. [Diagram 2] 1 shows a schematic diagram of one embodiment of an optical system. [Diagram 3] FIG. 2 shows a schematic block diagram of an embodiment of a driving device for driving and measuring actuators that actuate optical elements of an optical system. [Figure 4] The block diagram of Figure 3 is shown with a transfer function plot. [Diagram 5] 1 shows a schematic block diagram including an embodiment of a drive unit and a voltage measurement unit of a drive device for driving and measuring an actuator that actuates an optical element of an optical system. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0043] Unless otherwise indicated, identical or functionally identical elements among the figures are provided with the same reference numbers. It should also be noted that the illustrations are not necessarily drawn to scale.

[0044] 1 shows an embodiment of a projection exposure apparatus 1 (lithographic apparatus), in particular an EUV lithographic apparatus. An embodiment of an illumination system 2 of the projection exposure apparatus 1 comprises, in addition to a light source or radiation source 3, an illumination optical unit 4, which illuminates an object field 5 in an object plane 6. In an alternative embodiment, the light source 3 can also be provided as a separate module from the rest of the illumination system 2. In this case, the illumination system 2 does not include the light source 3.

[0045] A reticle 7 arranged in the object field 5 is illuminated. The reticle 7 is held by a reticle holder 8. The reticle holder 8 is displaceable in particular in the scanning direction by a reticle displacement drive 9.

[0046] For illustrative purposes, a Cartesian coordinate system with an x-direction x, a y-direction y and a z-direction z is shown in Fig. 1. The x-direction x extends perpendicular to the plane of the drawing. The y-direction y extends horizontally and the z-direction z extends vertically. In Fig. 1, the scanning direction extends along the y-direction y. The z-direction z extends perpendicular to the object plane 6.

[0047] The projection exposure apparatus 1 comprises a projection optical unit 10. The projection optical unit 10 serves to image the object field 5 into an image field 11 in an image plane 12. The image plane 12 extends parallel to the object plane 6. Alternatively, angles other than 0° between the object plane 6 and the image plane 12 are also possible.

[0048] Structures on the reticle 7 are imaged onto a photosensitive layer of a wafer 13, which is arranged in the region of the image field 11 of the image plane 12. The wafer 13 is held by a wafer holder 14. The wafer holder 14 is displaceable, in particular along the y-direction y, by a wafer displacement drive 15. The displacement of the reticle 7 firstly by the reticle displacement drive 9 and secondly by the wafer displacement drive 15 can be performed synchronously with respect to one another.

[0049] The light source 3 is an EUV radiation source. The light source 3 in particular emits EUV radiation 16, also referred to in the following as working radiation, illumination radiation or illumination light. In particular, the working radiation 16 has a wavelength in the range of 5 nm to 30 nm. The light source 3 can be a plasma source, for example an LPP (abbreviation for Laser Produced Plasma) source or a DPP (abbreviation for Gas Discharge Plasma) source. It can also be a synchrotron-based radiation source. The light source 3 can be an FEL (abbreviation for Free Electron Laser).

[0050] The illumination radiation 16 coming from the light source 3 is focused by a collector 17. The collector 17 may be a collector with one or more ellipsoidal and / or hyperbolic reflecting surfaces. On at least one reflecting surface of the collector 17, the illumination radiation 16 may be incident at grazing incidence (abbreviated GI), i.e. at an angle of incidence greater than 45° relative to the direction of the normal to the mirror surface, or at normal incidence (abbreviated NI), i.e. at an angle of incidence smaller than 45°. The collector 17 may be structured and / or coated, on the one hand, to optimize the reflectivity for the radiation used and, on the other hand, to suppress extraneous light.

[0051] Downstream of the collector 17, the illumination radiation 16 propagates through an intermediate focus in an intermediate focal plane 18. The intermediate focal plane 18 may represent a separation between the source module comprising the light source 3 and the collector 17 and the illumination optical unit 4.

[0052] The illumination optical unit 4 comprises a deflection mirror 19 and, downstream in the beam path, a first facet mirror 20. The deflection mirror 19 can be a plane deflection mirror or a mirror with a speed-of-light-influencing effect beyond a pure deflection effect. Alternatively or additionally, the deflection mirror 19 can be in the form of a spectral filter that separates the used optical wavelength of the illumination radiation 16 from extraneous light of wavelengths outside it. If the first facet mirror 20 is arranged in a plane of the illumination optical unit 4 that is optically conjugate with the object plane 6 as a field plane, it is also referred to as a field facet mirror. The first facet mirror 20 comprises a plurality of individual first facets 21, which may hereinafter also be referred to as field facets. Only some of these facets 21 are shown by way of example in FIG. 1.

[0053] The first facet 21 may be embodied as a macroscopic facet, in particular as a rectangular facet or as a facet with an arcuate edge profile or a part-circular edge profile. The first facet 21 may be embodied as a planar facet or as a convexly or concavely curved facet.

[0054] The first facet 21 itself can also consist of a number of individual mirrors, in particular a number of micromirrors, as is known, for example, from DE 10 2008 009 600. In particular, the first facet mirror 20 can be embodied as a micro-electromechanical system (MEMS system). See DE 10 2008 009 600 for further details.

[0055] Between the collector 17 and the deflection mirror 19, the illumination radiation 16 travels horizontally, ie along the y-direction y.

[0056] In the beam path of the illumination optical unit 4, a second facet mirror 22 is arranged downstream of the first facet mirror 20. If the second facet mirror 22 is arranged in a pupil plane of the illumination optical unit 4, it is also referred to as a pupil facet mirror. The second facet mirror 22 can also be arranged away from the pupil plane of the illumination optical unit 4. In this case, the combination of the first facet mirror 20 and the second facet mirror 22 is also referred to as a specular reflector. Specular reflectors are known from US 2006 / 0132747, EP 1 614 008 and US 6,573,978.

[0057] The second facet mirror 22 includes a plurality of second facets 23. In the case of a pupil facet mirror, the second facets 23 are also referred to as pupil facets.

[0058] The second facet 23 may likewise be a macroscopic facet, which may have, for example, a circular, rectangular or hexagonal boundary, or may be a facet made up of a micromirror. In this respect, reference is likewise made to DE 10 2008 009 600 A1.

[0059] The second facet 23 may have a planar reflective surface or a convexly or concavely curved reflective surface.

[0060] The illumination optical unit 4 therefore forms a double-faceted system. This basic principle is also called a fly's eye condenser (or integrator).

[0061] It may be advantageous not to arrange the second facet mirror 22 exactly in a plane that is optically conjugate with the pupil plane of the projection optical unit 10. In particular, the second facet mirror 22 may be arranged tilted with respect to the pupil plane of the projection optical unit 10, as described, for example, in DE 10 2017 220 586 A1.

[0062] The individual first facets 21 are imaged into the object field 5 by means of a second facet mirror 22. The second facet mirror 22 is the last beam-shaping mirror in the beam path upstream of the object field 5 or indeed the final mirror for the illumination radiation 16.

[0063] In a further embodiment, not shown, of the illumination optical unit 4, a transfer optical unit, which in particular contributes to the imaging of the first facet 21 into the object field 5, can be arranged in the beam path between the second facet mirror 22 and the object field 5. The transfer optical unit can have exactly one mirror or two or more mirrors arranged one after the other in the beam path of the illumination optical unit 4. The transfer optical unit can in particular comprise one or two normal incidence mirrors (NI mirrors) and / or one or two grazing incidence mirrors (GI mirrors).

[0064] In the embodiment shown in FIG. 1, the illumination optical unit 4 comprises exactly three mirrors downstream of the collector 17 , in particular a deflection mirror 19 , a first facet mirror 20 and a second facet mirror 22 .

[0065] In yet another embodiment of the illumination optical unit 4, there is no need for a deflection mirror 19, so that the illumination optical unit 4 can then have exactly two mirrors downstream of the collector 17, in particular a first facet mirror 20 and a second facet mirror 22.

[0066] The imaging of the first facet 21 onto the object plane 6 by the second facet 23 or by means of the second facet 23 and the transfer optical unit is often only an approximate imaging.

[0067] The projection optical unit 10 comprises a number of mirrors Mi, which are numbered according to their position in the beam path of the projection exposure apparatus 1 .

[0068] In the example shown in Fig. 1, the projection optical unit 10 comprises six mirrors M1-M6. A substitution of 4, 8, 10, 12 or any other number of mirrors Mi is likewise possible. The projection optical unit 10 is a double-shielded optical unit. The penultimate mirror M5 and the final mirror M6 each have a passage aperture for the illumination radiation 16. The projection optical unit 10 has an image-side numerical aperture which is greater than 0.5, may be greater than 0.6, and may for example be 0.7 or 0.75.

[0069] The reflective surface of the mirror Mi can be embodied as a freeform surface without an axis of rotational symmetry. Alternatively, the reflective surface of the mirror Mi can be designed as an aspheric surface with exactly one axis of rotational symmetry of the reflective surface shape. Like the mirrors of the illumination optical unit 4, the mirror Mi can have a coating that is highly reflective with respect to the illumination radiation 16. These coatings can be designed as multilayer coatings, in particular with alternating layers of molybdenum and silicon.

[0070] The projection optical unit 10 has a large object-image offset in the y-direction y between the y-coordinate of the center of the object field 5 and the y-coordinate of the center of the image field 11. In the y-direction y, this object-image offset may have approximately the same magnitude as the z-distance between the object plane 6 and the image plane 12.

[0071] The projection optical unit 10 can have, in particular, an anamorphic form. In particular, it has different imaging scales βx, βy in the x-direction x and in the y-direction y. The two imaging scales βx, βy of the projection optical unit 10 are preferably (βx, βy)=(+ / -0.25, + / -0.125). A positive imaging scale β means imaging without image inversion. A negative sign of the imaging scale β means imaging with image inversion.

[0072] The projection optical unit 10 results in a size reduction in the x-direction, ie perpendicular to the scanning direction, by a ratio of 4:1.

[0073] The projection optical unit 10 provides a size reduction of 8:1 in the y-direction, ie in the scan direction.

[0074] Other imaging scales are possible as well, including imaging scales of the same sign and the same absolute value in the x-direction x and in the y-direction y, for example 0.125 or 0.25.

[0075] The number of intermediate image planes in the x-direction x and y-direction y in the beam path between the object field 5 and the image field 11 may be the same or may differ depending on the design of the projection optical unit 10. Examples of projection optical units with different numbers of such intermediate images in the x-direction x and y-direction y are known from US 2018 / 0074303 A1.

[0076] Each of the second facets 23 is assigned to exactly one of the first facets 21 to respectively form an illumination channel for illuminating the object field 5. This makes it possible to obtain an illumination in particular according to the Köhler principle. The far field is decomposed by means of the first facets 21 into a number of object fields 5. The first facets 21 generate a number of images of intermediate foci on the respectively assigned second facets 23.

[0077] By means of the assigned second facets 23, the first facets 21 are respectively imaged onto the reticle 7 in an overlapping manner in order to illuminate the object field 5. The illumination of the object field 5 is in particular as uniform as possible. Its uniformity error is preferably less than 2%. By overlapping the different illumination channels, field uniformity can be obtained.

[0078] The illumination of the entrance pupil of the projection optical unit 10 can be geometrically defined by the arrangement of the second facets 23. By selecting the illumination channels that guide light, in particular a subset of the second facets 23, the intensity distribution in the entrance pupil of the projection optical unit 10 can be set. This intensity distribution is also called the illumination setting or illumination pupil filling.

[0079] An equally favorable pupil uniformity in the region of a defined illumination portion of the illumination pupil of the illumination optical unit 4 can be achieved by redistribution of the illumination channels.

[0080] Further aspects and details of the illumination of the object field 5, in particular the entrance pupil of the projection optical unit 10, are explained below.

[0081] The projection optical unit 10 may in particular have a concentric entrance pupil. It may be accessible. It may also be inaccessible.

[0082] The entrance pupil of the projection optical unit 10 generally cannot be illuminated exactly by means of the second facet mirror 22. In the case of imaging of the projection optical unit 10 telecentrically imaging the centre of the second facet mirror 22 onto the wafer 13, the aperture rays often do not intersect at a single point. However, it is possible to find a surface for which the determined spacing of the pair of aperture rays is minimal. This surface represents the entrance pupil or a surface conjugate thereto in real space. In particular, this surface exhibits a finite curvature.

[0083] The projection optical unit 10 may have different entrance pupil positions for the tangential and sagittal beam paths. In this case, an imaging element, in particular an optical component of the transfer optical unit, should be provided between the second facet mirror 22 and the reticle 7. This optical element can be used to take into account the different positions of the tangential and sagittal entrance pupils.

[0084] In the arrangement of the components of the illumination optical unit 4 shown in Fig. 1, the second facet mirror 22 is arranged in a plane conjugate with the entrance pupil of the projection optical unit 10. The first facet mirror 20 is arranged so as to be tilted with respect to the object plane 6. The first facet mirror 20 is arranged so as to be tilted with respect to the arrangement plane defined by the deflection mirror 19. The first facet mirror 20 is arranged so as to be tilted with respect to the arrangement plane defined by the second facet mirror 22.

[0085] Figure 2 shows a schematic diagram of an embodiment of an optical system 300, for example of a lithographic or projection exposure apparatus 1 as shown in Figure 1. Furthermore, the optical system 300 of Figure 2 can also be used, for example, in a DUV lithographic apparatus.

[0086] The optical system 300 of Fig. 2 comprises a number of actuatable optical elements 310. The optical system 300 is here designed as a micromirror array, the optical elements 310 being micromirrors. Each micromirror 310 is actuatable by an assigned actuator 200. By way of example, each micromirror 310 can be tilted about two axes and / or displaced in one, two or three spatial axes by the assigned actuator 200. For clarity, only the top row of reference numbers for these elements is shown.

[0087] The driving device 100 drives each actuator 200 with, for example, a driving voltage AS, thereby setting the position of each micromirror 310. The driving device 100 will be described with particular reference to FIGS.

[0088] Figure 3 shows a schematic block diagram of an embodiment of a driving device 100 for driving and measuring an actuator 200 which actuates an optical element 310 of an optical system 300. To this end, Figure 4 shows the block diagram of Figure 3 with the transfer functions G1 to G4 plotted.

[0089] The driving device 100 shown in Figures 3 and 4 includes a driving unit 110 that drives the actuator 200, a voltage measurement unit 120 coupled to the actuator 200, a current measurement unit 130 coupled to the actuator 200, and a judgment unit 140 coupled to the voltage measurement unit 120 and the current measurement unit 130.

[0090] The drive unit 110 has a frequency-dependent first transfer function G1 (see FIG. 4) configured to amplify the time-dependent AC voltage signal W having at least a first frequency range F1 and a second frequency range F2 to a gain higher by a certain factor in the first frequency range F1 than in the second frequency range F2 to form a drive signal AS for the actuator 200. As exemplarily shown in FIG. 4, the first transfer function G1 has a first frequency range F1 of low frequencies and a second frequency range F2 of high frequencies. By way of example, the first frequency range F1 is located between 0 Hz and 1 kHz, preferably between 0 Hz and 500 Hz, more preferably between 0 Hz and 300 Hz. The second frequency range F2 is preferably located between 5 kHz and 100 kHz, more preferably between 10 kHz and 100 kHz, particularly preferably between 10 kHz and 60 kHz. The specific gain factor is in particular between 100 and 2000, preferably between 500 and 1500, more preferably between 800 and 1200.

[0091] The voltage measurement unit 120 is configured to convolve, in the time domain, the time-dependent voltage u of the actuator 200 with a second transfer function G2 based on the inverse of the first transfer function G1, and subsequently measure said time-dependent voltage to provide a measured voltage U. For this purpose, Fig. 4 shows a second transfer function G2 of the voltage measurement unit 120, which second transfer function is based on the inverse of the first transfer function G1, as a comparison between the transfer functions G2 and G1 shows. As a comparison of the transfer functions G1 and G2 in Fig. 4 shows, the first transfer function G1 provides a high gain in the frequency range F1, while the second transfer function G2 provides a low gain in the first frequency range F2. In contrast, the first transfer function G1 provides a low gain in the second frequency range F2, while the second transfer function provides a high gain in the second frequency range F2.

[0092] The components of the drive signal AS in a first frequency range F1 serve to drive the actuator 200. As a result, there is a high gain in the first frequency range F1 in order to be able to properly drive the actuator 200. Before each measurement, i.e. before the voltage measurement and before the current measurement, the first frequency range F is attenuated and the second frequency range F2 is amplified so that a high resolution for measuring the actuator 200 is provided in the second frequency range F2.

[0093] In this case, the second transfer function G2 provides high resolution in the second frequency range F2 to be measured and therefore high accuracy requirements can be defined.

[0094] The current measurement unit 130 is configured to convolve, in the time domain, a time-dependent current i of the actuator 200 with a third transfer function G3 based on the inverse of the first transfer function G1, and subsequently measure said time-dependent current to provide a measured current I. The convolution in the time domain corresponds to a multiplication in the frequency range.

[0095] To this end, figure 4 shows a third transfer function G3. Similar or equivalent to the second transfer function G2, the third transfer function G3 provides a low gain in the first frequency range F1 and a high gain in the second frequency range F2.

[0096] A determining device 140 coupled to the voltage measuring unit 120 and the current measuring unit 130 is configured to determine an impedance Z or an impedance behavior of the actuator 200 based on the provided measured voltage U and the provided measured current I.

[0097] For this purpose, the transfer function G4 of the impedance Z of the actuator 200 shown in FIG. 4 exhibits high resolution in a second frequency band F2, which may also be called the measurement frequency band.

[0098] 5 further shows a schematic block diagram including an embodiment of a driving unit 110 and a voltage measurement unit 120 of a driving device 100 for driving and measuring an actuator 200 which actuates an optical element 310 of an optical system 300. An example of a driving device 100 is shown in FIGS.

[0099] The driving unit 110 of FIG. 5 includes an amplifier circuit 111, in particular a differential amplifier.

[0100] The amplifier circuit 111 of the driving unit 110 includes an input node K1 providing an AC voltage signal W (see also Figures 3 and 4), an output node K2 providing a driving voltage AS for the actuator 200 (see also Figures 2-4), and an operational amplifier 112 coupled between the input node K1 and the output node K2. A first circuit 113 is coupled to the input node K1, a negative power supply voltage VSS of the driving device 100, and a non-inverting input of the operational amplifier 112, and a second circuit 114 is coupled to the inverting input of the operational amplifier 112, ground GND, and the output node K2 to provide a first transfer function G1 (see Figure 4).

[0101] The first circuit 113 and the second circuit 114 each include a resistive circuit 115, 116 for adjusting the gain in a first frequency range F1, and each circuit further includes a frequency-dependent connectable circuit 117, 118 including frequency-dependent components C1, C2 and resistors R5, R6 for adjusting the gain at a second frequency F2 according to a first transfer function G1.

[0102] The resistor circuit 115 of the first circuit 113 comprises a resistor R3 connected between the input node K1 and the non-inverting input of the operational amplifier 112, and a resistor R4 coupled between a negative power supply voltage VSS and the non-inverting input of the operational amplifier 112. Furthermore, the connectable circuit 117 of the first circuit 113 comprises a series-connected capacitor C1 and resistor R5. In this case, the capacitance of the capacitor C1 is selected such that the capacitor C1 is only conductive at frequencies in the second frequency range F2, and thus the circuit 117 is connected in a frequency-dependent manner at frequencies in the second frequency range F2.

[0103] The resistors 116 of the second circuit 114 include a resistor R1 connected between ground GND and the inverting input of the operational amplifier 112, and a resistor R2 connected between the inverting input of the operational amplifier 112 and the output node K2. The connectable circuit 118 of the second circuit 114 includes a capacitor C2 and a resistor R6 connected in series.

[0104] The connectable circuit 118 has a function equivalent to the connectable circuit 117. In this case, the capacitance of the capacitor C2 is selected such that the capacitor C2 is only conductive at frequencies in the second frequency range and thus the circuit 118 is connected in a frequency-dependent manner at frequencies in the second frequency range.

[0105] Above is the detailed description of the driving unit 110 shown in Fig. 5. Please pay attention to the detailed description of the voltage measurement unit 120 shown in Fig. 5. The voltage measurement unit 120 in Fig. 5 includes an amplifier circuit 121, in particular a differential amplifier.

[0106] The amplifier circuit 121 of the voltage measurement unit 120 comprises an input node K3 coupled to the output node K2 of the amplifier circuit 111 of the driving unit 110 and serving to receive the time-dependent voltage u of the actuator 200, an output node K4 providing a measurement voltage U, and an operational amplifier 122 coupled between the input node K3 and the output node K4. To provide a second transfer function G2, a first circuit 123 is coupled to the output node K4, to the negative supply voltage VSS of the driving device 100 and to the inverting input of the operational amplifier 122, and a second circuit 124 is coupled to the input node K3, to the non-inverting input of the operational amplifier 122 and to ground GND. In the embodiment shown in Fig. 5, the second circuit 114 of the amplifier circuit 111 of the driving unit 110 and the second circuit 124 of the amplifier circuit 121 of the voltage measurement unit 120 are formed by a single circuit, i.e. they are identical. This advantageously saves components of the optical system 300, in particular space.

[0107] As shown in FIG. 5, the first circuit 123 and the second circuit 124 of the amplifier circuit 121 of the voltage measurement unit 120 each have a resistive circuit 125, 126 providing a portion of the second transfer function G2 in the first frequency range F1 and a portion of the second transfer function G2 in the second frequency range F2, said circuits further comprising frequency-dependent connectable circuits 127, 118, respectively.

[0108] Since the second circuit 124 of the voltage measurement unit 120 corresponds to the second circuit 114 of the driving unit 110, to avoid repetition, only the first circuit 123 of the amplifier circuit 121 of the voltage measurement unit 120 will be described in detail below. The first circuit 123 has a resistor circuit 125 including a resistor R1 coupled between the output node K4 and the inverting input of the operational amplifier 122, and a resistor R2 coupled between the inverting input of the operational amplifier 112 and the negative power supply voltage VSS. The resistance values ​​of the resistors R1, R2 of the resistor circuit 116 and the resistance values ​​of the resistors R1, R2 of the resistor circuit 125 may be the same or different depending on the application.

[0109] The connectable circuit 127 of the first circuit 123 includes a capacitor C3 and a resistor R7 connected in series between the inverting input of the operational amplifier 112 and the negative supply voltage VSS. In this case, the capacitance of the capacitor C3 is selected such that the capacitor C3 is only conductive at frequencies in the second frequency range F2.

[0110] Although the invention has been described with respect to exemplary embodiments, it can be varied in many ways. [Explanation of symbols]

[0111] 1. Projection exposure equipment 2. Lighting system 3 light source 4. Illumination optical unit 5 Object field of view 6 Object plane 7 Reticle 8 Reticle Holder 9 Reticle Displacement Drive 10 Projection optical unit 11 Image field 12 Image plane 13 Wafer 14 Wafer holder 15 Wafer Displacement Drive 16 Lighting radiation 17 Collector 18 Intermediate focal plane 19 Deflection Mirror 20 1st Facet Mirror 21 First Facet 22 Second Facet Mirror 23 Second Facet 100 Drive unit 110 Drive unit 111 Differential Amplifier 112 Operational Amplifier 113 1st circuit 114 2nd circuit 115 Resistance circuit 116 Resistance circuit 117 Connectable circuits 118 connectable circuits 120 Voltage Measuring Unit 121 Differential Amplifier 122 Operational Amplifier 123 1st circuit 124 2nd circuit 125 Resistance circuit 127 connectable circuits 130 Current Measuring Unit 200 Actuator 300 Optical system 310 Optical Elements A Amplitude AS drive voltage C1 Capacitor C2 Capacitor C3 Capacitor f frequency F1 First frequency range F2 Second frequency range G1 Transfer coefficient G2 Transfer coefficient G3 Transfer coefficient G4 Transfer coefficient GND Earth I Measured current i Actuator current K1 input node K2 output node K3 input node K4 output node M1 Mirror M2 Mirror M3 Mirror M4 Mirror M5 Mirror M6 Mirror R1 Resistor R2 resistance R3 resistance R4 resistance R5 resistance R6 resistance R7 resistance U Measurement voltage u Actuator voltage VSS negative supply voltage W AC voltage signal Z impedance

Claims

1. A driving device (100) for driving and measuring an actuator (200) that operates an optical element (310) of an optical system (300), comprising: a drive unit (110) having a frequency-dependent first transfer function (G1) configured to amplify a time-dependent AC voltage signal (W) having at least a first frequency range (F1) and a second frequency range (F2) with a gain that is higher by a certain factor in the first frequency range (F1) than in the second frequency range (F2) to form a drive voltage (AS) for the actuator (200); a voltage measurement unit (120) for providing a measured voltage (U), the voltage measurement unit (120) being configured to convolve, in the time domain, a time-dependent voltage (u) of the actuator (200) with a second transfer function (G2) based on the inverse of the first transfer function (G1), and subsequently measure the time-dependent voltage to provide the measured voltage (U); a voltage measurement unit (130) for providing a measured current (I), the current measurement unit (130) being configured to convolve, in the time domain, a time-dependent current (i) of the actuator (200) with a third transfer function (G3) based on the inverse of the first transfer function (G1), and subsequently measure the time-dependent current to provide the measured current (I); A drive unit comprising:

2. 2. The drive device according to claim 1, a determining unit (120) coupled to the voltage measuring unit (120) and the current measuring unit (130) for determining an impedance (Z) of the actuator (200) based on the provided measured voltage (U) and the provided measured current (I); A drive unit further comprising:

3. 3. The drive device according to claim 1, said first frequency range (F1) is located between 0 Hz and 1 kHz, preferably between 0 Hz and 500 Hz, and more preferably between 0 Hz and 300 Hz; and / or The second frequency range (F2) is located between 5 kHz and 100 kHz, preferably between 10 kHz and 100 kHz, more preferably between 10 kHz and 60 kHz.

4. In the drive device according to any one of claims 1 to 3, A driving device, wherein the specific coefficient is 100 to 2000, preferably 500 to 1500, and more preferably 800 to 1200.

5. In the drive device according to any one of claims 1 to 4, The driving unit (110) is a driving device having an amplifier circuit (111), in particular a differential amplifier.

6. 6. The drive device according to claim 5, The amplifier circuit (111) of the drive unit (110) has an input node (K1) that supplies the AC voltage signal (W), an output node (K2) that provides the drive voltage (AS) for the actuator (200), and an operational amplifier (112) coupled between the input node (K1) and the output node (K2), and a first circuit (113) is coupled to the input node (K1), a negative power supply voltage (VSS) of the drive device (100), and a non-inverting input of the operational amplifier (112), and a second circuit (114) is coupled to the inverting input of the operational amplifier (112), ground (GND), and the output node (K2) to provide the first transfer function (G1).

7. 7. The drive device according to claim 6, The first circuit (113) and the second circuit (114) each have a resistive circuit (115, 116) for adjusting the gain in the first frequency range (F1), and for adjusting the gain in the second frequency range (F2), each circuit further has a frequency-dependent connectable circuit (117, 118) including frequency-dependent components (C1, C2) and resistors (R5, R6).

8. In the drive device according to any one of claims 1 to 7, The voltage measuring unit (120) is a driver having an amplifier circuit (121), in particular a differential amplifier.

9. 9. The drive device according to claim 8, the amplifier circuit (121) of the voltage measurement unit (120) comprises an input node (K3) coupled to the output node (K2) of the amplifier circuit (111) of the drive unit (110) and serving to receive the time-dependent voltage (u) of the actuator (200), an output node (K4) providing the measurement voltage (U), and an operational amplifier (112) coupled between the input node (K3) and the output node (K4); A driver in which a first circuit (123) is coupled to the output node (K4), the negative power supply voltage (VSS) of the driver (100), and the inverting input of the operational amplifier (122), and a second circuit (124) is coupled to the input node (K3), the non-inverting input of the operational amplifier (122), and ground (GND) to provide the second transfer function (G2).

10. 10. The drive device according to claim 9, The first circuit (123) and the second circuit (124) each have a resistive circuit (125, 116) providing a component of the second transfer function (G2) in the first frequency range (F1) and providing a component of the second transfer function (G2) in the second frequency range (F2), each circuit further comprising a frequency dependent connectable circuit (127, 118) including a frequency dependent component (C3, C2) and a resistor (R7, R6).

11. 11. The drive device according to claim 9 or 10, A driving device, wherein the second circuit (114) of the amplifier circuit (111) of the driving unit (110) and the second circuit (124) of the amplifier circuit (121) of the voltage measurement unit (120) are formed by a single circuit.

12. An optical system (300) comprising a plurality of actuatable optical elements (310), each of the plurality of actuatable optical elements (310) being assigned an actuator (200), each actuator (200) being assigned a drive device (100) for driving the actuator (200) according to any one of claims 1 to 11.

13. 13. The optical system according to claim 12, The optical system (300) is in the form of an illumination optical unit (4) or a projection optical unit (10) of a lithographic apparatus (1).

14. A lithographic apparatus (1) comprising an optical system (300) according to claim 12 or 13.

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