Driving device, optical system, and lithography 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 driving device for driving and measuring an actuator of an optical system, an optical system provided with the driving device, and a lithography apparatus provided with the optical system.

[0002] The entire content of German Patent Application Publication No. 10 2022 203 255.1, which is a priority application, is incorporated herein by reference.

Background Art

[0003] For example, a microlithography apparatus having an operable optical element such as a microlens element array or a micromirror array is known. Microlithography is used, for example, in the manufacture of fine-structured components such as integrated circuits. The microlithography process is performed using a lithography apparatus having an illumination system and a projection system.

[0004] Due to the desire for further miniaturization of structures in the manufacture of integrated circuits, EUV lithography apparatuses using light having a wavelength in the range of 0.1 nm to 30 nm, particularly 13.5 nm, are currently under development. Since most materials absorb light of this wavelength, in such EUV lithography apparatuses, it is necessary to use a reflective optical system, i.e., a mirror, instead of a refractive optical system as before, i.e., a lens.

[0005] In this case, an image of a mask (reticle) illuminated by an illumination system is projected by a projection system onto a substrate, such as a silicon wafer, coated with a photosensitive layer (photoresist) and arranged in the image plane of the projection system, so as to transfer the mask structure to the photosensitive coating of the substrate. The imaging of the mask on the substrate can be improved by an operable optical element. As an example, it is possible to compensate for wavefront aberration during exposure that results in magnified imaging and / or defocused imaging.

[0006] Such correction using optical elements requires wavefront detection and signal processing to determine the position of each optical element, enabling the desired wavefront correction. In the final step, the drive signals for each optical element are amplified and output to the actuators of the optical elements.

[0007] For example, a PMN actuator (PMN; lead magnesium niobate) can be used as an actuator. PMN actuators enable distance positioning in the sub-micrometer or sub-nanometer range. In this case, the actuator, in which actuator elements are stacked vertically, is subjected to a force that causes a specific linear expansion as a result of the application of a DC voltage. The position set by the DC voltage (DC; direct current) may be adversely affected by external electromechanical crosstalk at the resonance point that essentially occurs in the DC-driven actuator. This electromechanical crosstalk makes it impossible to stably set precise positioning. In this case, the larger the applied DC voltage, the greater the mechanical resonance. The above resonance point may also change over time, for example, as a result of temperature drift, or as a result of adhesive drift when the mechanical bonding of the adhesive material changes, or as a result of hysteresis or aging. For example, impedance measurement would be useful in this situation.

[0008] However, conventional impedance measurement devices are often too expensive and cannot be integrated into a line, meaning they cannot be used regularly with lithography equipment. Furthermore, the impedance value range in question spans several orders of magnitude, and the range being measured represents only a fraction of the entire range. Therefore, integrated impedance measurement bridges, which are typically configured for very high impedance values, are unsuitable for this application in lithography equipment.

[0009] It is also known that the actuators of a lithography apparatus can be driven by 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 to the actuator as a drive voltage. Such conventional output stages provide uniform gain and, consequently, uniform resolution over the entire frequency range. If a high gain is selected for the output stage, this high gain causes a decrease in the resolution for measuring the actuator impedance. However, if a low gain is selected, this is insufficient for applications driving actuators. [Overview of the Initiative] [Problems that the invention aims to solve]

[0010] Given this background, the objective of the present invention is to improve the driving of the actuator in the optical system. [Means for solving the problem]

[0011] According to the first embodiment, a drive device for driving and measuring the actuator of an optical system is proposed. The drive device is 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 such that the gain in the first frequency range is higher by a specific coefficient compared to the second frequency range, thereby forming a drive voltage for an actuator. A voltage measurement unit that provides a measurement voltage, configured to convolve the time-dependent voltage of an actuator with a second transfer function based on the reciprocal of a first transfer function in the time domain, and then measure the time-dependent voltage to provide a measurement voltage, A current measuring unit that provides a measurement current, configured to convolve the time-dependent current of an actuator with a third transfer function based on the reciprocal of a first transfer function in the time domain, and then measure the time-dependent current to provide a measurement current. It is equipped with.

[0012] This drive device has the advantage of enabling high gain in a first frequency range for driving the actuator, as well as high resolution in a second frequency range for measuring the actuator, particularly for measuring the actuator's impedance.

[0013] In this case, the drive voltage component in the first frequency range drives the actuator, specifically controlling the deflection of the actuator. To properly drive the actuator, the gain is higher in the first frequency range compared to the second frequency range. Before each measurement, i.e., before voltage and current measurements, the first frequency range is attenuated and the second frequency range is amplified so that high resolution for measuring the actuator is provided in the second frequency range.

[0014] This drive device can also be described as a frequency-dependent amplification stage for driving an actuator, with integrated current and voltage measurement capabilities.

[0015] As a result of providing the measured voltage and measured current of the actuator, this drive device enables in-line determination of the actuator's impedance behavior, particularly impedance determination of actuators mounted on lithography equipment. Based on the determined impedance behavior of the actuator, appropriate corrective measures or countermeasures, especially active in-line calibration or in-line attenuation, can be implemented via the drive signal.

[0016] In particular, the actuators are capacitive actuators, such as PMN actuators (PMN; lead magnesium niobate), PZT actuators (PZT; lead zirconate titanate), or LiNbO3 actuators (lithium niobate). The actuators are configured to actuate optical elements 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 may also be an illumination system. The projection exposure apparatus may be an EUV lithography apparatus. EUV stands for "extreme ultraviolet" and indicates a wavelength of light used from 0.1 nm to 30 nm. The projection exposure apparatus may also be a DUV lithography apparatus. DUV stands for "deep ultraviolet" and indicates a wavelength of light used from 30 nm to 250 nm.

[0018] According to one embodiment, the drive device further comprises a determination unit coupled to a voltage measuring unit and a current measuring unit. The determination unit is 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 drive device can also be referred to as a frequency-dependent amplification stage for driving and measuring the impedance of the actuator.

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

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

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

[0022] In yet another embodiment, the drive unit includes an amplification circuit, particularly a differential amplifier.

[0023] According to yet another embodiment, the amplifier circuit of the drive unit includes an input node for supplying an AC voltage signal, an output node for providing a drive voltage for the actuator, and an operational amplifier coupled between the input node and the output node. Here, in order to provide a transfer function, a first circuit is coupled to the input node, the negative power supply voltage of the drive device, and the 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.

[0024] According to yet another embodiment, the first circuit and the second circuit each include a resistance circuit for adjusting the gain in a first frequency range, and in order to adjust the gain in a second frequency range, each circuit further includes a frequency-dependent connectable circuit including a frequency-dependent component and a resistor. The frequency-dependent connectable circuit including the frequency-dependent component and the resistor is, for example, in the form of a capacitor and a resistor connected in series.

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

[0026] According to yet another embodiment, the voltage measurement unit includes an amplifier circuit, particularly a differential amplifier.

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

[0028] In yet another embodiment, the first circuit and the second circuit each include a resistor circuit that provides a component of the second transfer function in a first frequency range and a component of the second transfer function in a second frequency range, and each circuit further includes a frequency-dependent connectable circuit that includes frequency-dependent components and resistors.

[0029] For example, the connectable circuit may take the form of a series-connected capacitor and resistor. In this case, the capacitance of the capacitor is selected such that the capacitor conducts at frequencies in a second frequency range, and therefore the connectable circuit is frequency-dependently connected at frequencies in the second frequency range.

[0030] In yet another embodiment, the second circuit of the amplification circuit of the drive unit and the second circuit of the amplification circuit of the voltage measurement unit are formed by a single circuit. This is advantageous in saving optical system components and therefore space.

[0031] The voltage measurement unit can also be connected to different channels or different actuators via a multiplexer. In this case, it is not possible to measure all actuators simultaneously, but the required circuitry is reduced.

[0032] According to the second aspect, an optical system is proposed that includes a plurality of operable optical elements, wherein an actuator is assigned to each of the plurality of operable optical elements, and a drive device for driving an actuator according to the first aspect or one embodiment of the first aspect is assigned to each actuator.

[0033] The optical system includes, in particular, a micromirror array and / or lens element array having a plurality of optical elements that can operate independently of each other.

[0034] In this embodiment, a group of actuators can be defined, and the same drive unit can be assigned to all actuators in the group.

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

[0036] In yet another embodiment, the optical system has a vacuum housing in which an operable optical element, an assigned actuator, and a drive device are arranged.

[0037] According to the third aspect, a lithography apparatus having an optical system according to the second aspect or one embodiment of the second aspect is proposed.

[0038] Lithography equipment includes, for example, EUV lithography equipment that uses light in the wavelength range of 0.1 nm to 30 nm, or DUV lithography equipment that uses light in the wavelength range of 30 nm to 250 nm.

[0039] In this context, the indefinite article "a" or "an" should not necessarily be understood as strictly limiting to a single element. More precisely, multiple elements, such as two, three, or more, can be included. Similarly, any other numbers used here should not be understood as strictly limiting to the number of elements indicated. More precisely, unless otherwise specified, the number can be increased or decreased.

[0040] Further possible embodiments of the present invention include combinations of features or embodiments not specified above or below with respect to exemplary embodiments. In this case, those skilled in the art may add individual aspects as improvements or supplements to each basic form of the present invention.

[0041] Further advantageous configurations and aspects of the present invention are the subject of the dependent claims and the exemplary embodiments of the present invention described below. The present invention will be described in more detail below with reference to the accompanying drawings based on preferred embodiments. [Brief explanation of the drawing]

[0042] [Figure 1] This shows a schematic meridian cross-section of a projection exposure apparatus for EUV projection lithography. [Figure 2] A schematic diagram of one embodiment of the optical system is shown. [Figure 3] A schematic block diagram of one embodiment of a drive device for driving and measuring actuators that operate optical elements of an optical system is shown. [Figure 4] Figure 3 shows a block diagram with the transfer function plotted. [Figure 5] A schematic block diagram is shown, including embodiments of a drive unit and a voltage measurement unit for a drive device that drives and measures actuators that operate optical elements of an optical system. [Modes for carrying out the invention]

[0043] Unless otherwise specified, identical or functionally identical elements in the figures are given the same reference numeral. Please note that the figures are not necessarily drawn to a consistent scale.

[0044] Figure 1 shows one embodiment of a projection exposure apparatus 1 (lithography apparatus), particularly an EUV lithography apparatus. One embodiment of the illumination system 2 of the projection exposure apparatus 1 includes, in addition to a light source or radiation source 3, an illumination optical unit 4 that illuminates the object field of view 5 on the object surface 6. In an alternative embodiment, the light source 3 may be provided as a module separate 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 positioned in the object field of view 5 is illuminated. The reticle 7 is held by a reticle holder 8. The reticle holder 8 is displaceable, particularly in the scanning direction, by a reticle displacement drive 9.

[0046] Figure 1 illustrates a Cartesian coordinate system with x, y, and z directions. The x direction extends perpendicular to the plane of the figure. The y direction extends horizontally, and the z direction extends vertically. In Figure 1, the scanning direction extends along the y direction. The z direction extends perpendicular to the object plane 6.

[0047] The projection exposure apparatus 1 includes a projection optical unit 10. The projection optical unit 10 functions to form an image of the object field of view 5 onto the image field of view 11 of the image plane 12. The image plane 12 extends parallel to the object surface 6. Alternatively, angles other than 0° are possible between the object surface 6 and the image plane 12.

[0048] The structure on the reticle 7 is imaged onto the photosensitive layer of the wafer 13, which is positioned in the image field 11 region of the image plane 12. The wafer 13 is held by a wafer holder 14. The wafer holder 14 is displaceable by a wafer displacement drive 15, particularly along the y-direction y. Firstly, the displacement of the reticle 7 by the reticle displacement drive 9, and secondly, the displacement of the wafer 13 by the wafer displacement drive 15, can be performed in synchronous manner.

[0049] Light source 3 is an EUV radiation source. Light source 3 emits EUV radiation 16, which is also referred to below as the radiation used, illumination radiation, or illumination light. In particular, the radiation used 16 has a wavelength in the range of 5 nm to 30 nm. Light source 3 may be a plasma source, such as an LPP (Laser-Generated Plasma) source or a DPP (Gas Discharge Plasma) source. It may also be a synchrotron-based radiation source. Light source 3 may be an FEL (Free Electron Laser).

[0050] Illumination radiation 16 emitted from light source 3 is focused by collector 17. Collector 17 may be a collector having one or more elliptical and / or hyperbolic reflecting surfaces. Illumination radiation 16 may be incident on at least one reflecting surface of collector 17 at an oblique angle (GI), i.e., at an incident angle greater than 45° with respect to the direction of the normal to the mirror surface, or at a perpendicular angle (NI), i.e., at an incident angle less than 45°. Collector 17 may be structured and / or coated to optimize reflectivity for the radiation used and to suppress external light.

[0051] Downstream of the collector 17, the illumination radiation 16 propagates through the intermediate focal point of the intermediate focal plane 18. The intermediate focal plane 18 may represent the separation between the radiation source module, which has 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 a first facet mirror 20 downstream of it in the beam path. The deflection mirror 19 may be a planar deflection mirror or a mirror having a speed of light effect beyond a pure deflection effect. Alternatively or additionally, the deflection mirror 19 may be in the form of a spectral filter that separates the wavelength of light used by the illumination radiation 16 from external light of wavelengths outside of it. When the first facet mirror 20 is positioned on the plane of the illumination optical unit 4 that is optically conjugate to the object plane 6 as a field of view, it is also referred to as a field of view facet mirror. The first facet mirror 20 includes a plurality of individual first facets 21, which may hereafter also be referred to as field of view facets. Only some of these facets 21 are shown as examples in Figure 1.

[0053] The first facet 21 can be embodied as a macroscopic facet, particularly as a rectangular facet, or as a facet having an arc-shaped or partially circular edge contour. The first facet 21 can be embodied as a planar facet, or as a convex or concave curved facet.

[0054] For example, as is known from German Patent Application Publication No. 10 2008 009 600, the first facet 21 itself can also be composed of multiple individual mirrors, particularly multiple micromirrors. In particular, the first facet mirror 20 can be embodied as a micro-electromechanical system (MEMS system). For further details, please refer to German Patent Application Publication No. 10 2008 009 600.

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

[0056] In the beam path of the illumination optical unit 4, a second facet mirror 22 is positioned downstream of the first facet mirror 20. When the second facet mirror 22 is positioned on the pupil plane of the illumination optical unit 4, it is also referred to as a pupil facet mirror. The second facet mirror 22 can also be positioned 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 U.S. Patent Application Publication No. 2006 / 0132747, European Patent No. 1614008, and U.S. Patent No. 6,573,978.

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

[0058] Similarly, the second facet 23 may be a macroscopic facet having, for example, a circular, rectangular, or hexagonal boundary, or it may be a facet composed of micromirrors. In this regard, see German Patent Application Publication No. 10 2008 009 600.

[0059] The second facet 23 may have a planar reflective surface or a curved reflective surface that is convex or concave.

[0060] Therefore, the illumination optical unit 4 forms a dual-facet system. This basic principle is also referred to as a fly-eye condenser (or integrator).

[0061] It may be advantageous not to precisely position the second facet mirror 22 on a plane optically conjugate to the pupil plane of the projection optical unit 10. In particular, the second facet mirror 22 may be positioned at an angle to the pupil plane of the projection optical unit 10, for example, as described in German Patent Application Publication No. 10 2017 220 586.

[0062] The individual first facets 21 are imaged into the object field of view 5 using the second facet mirror 22. The second facet mirror 22 is the last beam shaping mirror or, in fact, the final mirror for the illumination radiation 16 in the beam path upstream of the object field of view 5.

[0063] In yet another embodiment of the illumination optical unit 4 (not shown), a transfer optical unit, which contributes particularly to imaging the first facet 21 onto the object field of view 5, can be positioned in the beam path between the second facet mirror 22 and the object field of view 5. The transfer optical unit may have exactly one mirror, or two or more mirrors positioned before and after the beam path of the illumination optical unit 4. The transfer optical unit may, in particular, include one or two perpendicular incidence mirrors (NI mirrors) and / or one or two oblique incidence mirrors (GI mirrors).

[0064] In the embodiment shown in Figure 1, the illumination optical unit 4 has exactly three mirrors downstream of the collector 17, specifically 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, since there is no need for a deflection mirror 19, the illumination optical unit 4 may have exactly two mirrors downstream of the collector 17, specifically a first facet mirror 20 and a second facet mirror 22.

[0066] The imaging of the first facet 21 onto the object surface 6 by the second facet 23, or by using the second facet 23 and the transfer optics unit, is often only an approximate image.

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

[0068] In the example shown in Figure 1, the projection optical unit 10 includes six mirrors M1 to M6. Substitution with four, eight, ten, twelve, or any other number of mirrors Mi is equally possible. The projection optical unit 10 is a double-shielded optical unit. The second-to-last mirror M5 and the last mirror M6 each have a through aperture for illumination radiation 16. The projection optical unit 10 has an image-side numerical aperture greater than 0.5 and may be greater than 0.6, for example, 0.7 or 0.75.

[0069] The reflective surface of mirror Mi can be realized as a free-form surface without a rotational symmetry axis. Alternatively, the reflective surface of mirror Mi can be designed as an aspherical surface with exactly one rotational symmetry axis of the reflective surface shape. Similar to the mirrors of illumination optical unit 4, mirror Mi may have a highly reflective coating for illumination radiation 16. These coatings can be designed in particular as multilayer coatings having 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 of view 5 and the y-coordinate of the center of the image field of view 11. In the y-direction y, this object-image offset may be approximately the same magnitude as the z-distance between the object plane 6 and the image plane 12.

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

[0072] As a result, the projection optical unit 10 is reduced in size in the x-direction, i.e., perpendicular to the scanning direction, at a ratio of 4:1.

[0073] The projection optical unit 10 reduces its size in the y-direction, i.e., in the scanning direction, at a ratio of 8:1.

[0074] Other imaging scales are also possible. Imaging scales with the same sign and absolute value in the x-direction x and y-direction y, for example, absolute values ​​of 0.125 or 0.25, are also possible.

[0075] The number of intermediate image planes in the x-direction x and y-direction y in the beam path between the object field of view 5 and the image field of view 11 may be the same or may differ depending on the design of the projection optical unit 10. An example of a projection optical unit with a different number of such intermediate images in the x-direction x and y-direction y is known from U.S. Patent Application Publication No. 2018 / 0074303.

[0076] Each of the second facets 23 is assigned to exactly one of the first facets 21 to form an illumination channel that illuminates the object field of view 5. This allows illumination to be obtained, in particular, according to Köhler's principle. The distant field of view is decomposed into multiple object fields of view 5 using the first facets 21. The first facets 21 generate multiple intermediate-focus images in the second facets 23, each assigned to one of them.

[0077] The assigned second facet 23 causes the first facet 21 to overlap and image onto the reticle 7 to illuminate the object field of view 5. The illumination of the object field of view 5 is particularly uniform, preferably with a uniformity error of less than 2%. Field of view uniformity can be achieved by superimposing different illumination channels.

[0078] The illumination of the entrance pupil of the projection optical unit 10 can be geometrically defined by the arrangement of the second facet 23. By selecting the illumination channel to guide light, particularly a subset of the second facet 23, the intensity distribution in the entrance pupil of the projection optical unit 10 can be set. This intensity distribution is also referred to as illumination setting or illumination pupil filling.

[0079] Similarly desirable pupil uniformity in a defined illuminated area of ​​the illumination pupil of the illumination optical unit 4 can be achieved by redistributing the illumination channels.

[0080] Further aspects and details of the illumination of the object field of view 5, particularly the entrance pupil of the projection optical unit 10, will be described below.

[0081] The projection optics unit 10 may have a concentric entrance pupil, which can be made accessible or inaccessible.

[0082] The entrance pupil of the projection optical unit 10 cannot generally be accurately illuminated using the second facet mirror 22. When the projection optical unit 10 images the center of the second facet mirror 22 telecentrically onto the wafer 13, the aperture rays often do not intersect at a single point. However, it is possible to find a plane where the distance between pairs of aperture rays is minimized. This plane represents the entrance pupil or its conjugate plane in real space. In particular, this plane exhibits a finite curvature.

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

[0084] In the arrangement of the components of the illumination optical unit 4 shown in Figure 1, the second facet mirror 22 is positioned on a plane conjugate to the entrance pupil of the projection optical unit 10. The first facet mirror 20 is positioned at an angle with respect to the object surface 6. The first facet mirror 20 is positioned at an angle with respect to the arrangement plane defined by the deflection mirror 19. The first facet mirror 20 is positioned at an angle with respect to the arrangement plane defined by the second facet mirror 22.

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

[0086] The optical system 300 in Figure 2 has multiple operable optical elements 310. The optical system 300 is designed here as a micromirror array, where the optical elements 310 are micromirrors. Each micromirror 310 is operable by an assigned actuator 200. For example, each micromirror 310 can be tilted around two axes and / or displaced around one, two, or three spatial axes by the assigned actuator 200. For clarity, only the reference numerals of the top row of these elements are shown.

[0087] The drive unit 100 drives each actuator 200, for example, with a drive voltage AS. This sets the position of each micromirror 310. The drive unit 100 will be described in more detail with reference to Figures 3 to 5.

[0088] Figure 3 shows a schematic block diagram of one embodiment of a drive device 100 that drives and measures an actuator 200 that operates the optical elements 310 of the optical system 300. For this purpose, Figure 4 shows the block diagram of Figure 3 with the transfer functions G1 to G4 plotted.

[0089] The drive device 100 shown in Figures 3 and 4 comprises a drive unit 110 for driving 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 determination 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 Figure 4) configured to amplify a time-dependent AC voltage signal W having at least a first frequency range F1 and a second frequency range F2 such that the gain in the first frequency range F1 is higher by a specific coefficient compared to the second frequency range F2, thereby forming a drive signal AS for the actuator 200. As illustrated in Figure 4, the first transfer function G1 has a low-frequency first frequency range F1 and a high-frequency second frequency range F2. For example, the first frequency range F1 is located at 0Hz to 1kHz, preferably 0Hz to 500Hz, and more preferably 0Hz to 300Hz. The second frequency range F2 is located at 5kHz to 100kHz, more preferably 10kHz to 100kHz, and particularly preferably 10kHz to 60kHz. The specific gain coefficient is particularly 100 to 2000, preferably 500 to 1500, and more preferably 800 to 1200.

[0091] The voltage measurement unit 120 is configured to measure the time-dependent voltage u of the actuator 200 in the time domain by convolving it with a second transfer function G2 based on the reciprocal of a first transfer function G1, and then measuring the time-dependent voltage to provide a measurement voltage U. For this purpose, Figure 4 shows the second transfer function G2 of the voltage measurement unit 120, which is based on the reciprocal of the first transfer function G1, as shown by the comparison between transfer functions G2 and G1. As shown by the comparison of transfer functions G1 and G2 in Figure 4, the first transfer function G1 yields a high gain in the frequency range F1, while the second transfer function G2 yields a low gain in the first frequency range F2. Conversely, the first transfer function G1 yields a low gain in the second frequency range F2, while the second transfer function yields a high gain in the second frequency range F2.

[0092] The component of the drive signal AS in the first frequency range F1 drives the actuator 200. As a result, a high gain is obtained in the first frequency range F1 in order to properly drive the actuator 200. Before each measurement, i.e., before voltage measurement and 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 that is being measured, and therefore high accuracy requirements can be specified.

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

[0095] For this purpose, Figure 4 shows the third transfer function G3. Similar to or equivalent to the second transfer function G2, the third transfer function G3 yields low gain in the first frequency range F1 and high gain in the second frequency range F2.

[0096] The determination device 140, coupled to the voltage measurement unit 120 and the current measurement unit 130, is configured to determine the impedance Z or impedance behavior of the actuator 200 based on the provided measurement voltage U and the provided measurement current I.

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

[0098] Furthermore, Figure 5 shows a schematic block diagram including embodiments of the drive unit 110 and voltage measurement unit 120 of the drive device 100, which drives and measures the actuator 200 that operates the optical elements 310 of the optical system 300. Examples of the drive device 100 are shown in Figures 3 and 4.

[0099] The drive unit 110 in Figure 5 includes an amplification circuit 111, in particular a differential amplifier.

[0100] The amplification circuit 111 of the drive unit 110 includes an input node K1 that supplies an AC voltage signal W (see also Figures 3 and 4), an output node K2 that receives the drive voltage AS of the actuator 200 (see also Figures 2 to 4), and an operational amplifier 112 coupled between the input node K1 and the output node K2. To provide a first transfer function G1 (see Figure 4), a first circuit 113 is coupled to the input node K1, the negative power supply voltage VSS of the drive device 100, and the 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.

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

[0102] The resistor circuit 115 of the first circuit 113 includes 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 the 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 includes a series-connected capacitor C1 and resistor R5. In this case, the capacitance of capacitor C1 is selected so that capacitor C1 conducts only at frequencies in the second frequency range F2, and therefore the circuit 117 is connected in a frequency-dependent manner at frequencies in the second frequency range F2.

[0103] The resistor 116 of the second circuit 114 includes a resistor R1 connected between the earth 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 has a capacitor C2 and a resistor R6 connected in series.

[0104] The connectable circuit 118 has the same function as connectable circuit 117. In this case, the capacitance of capacitor C2 is selected so that capacitor C2 conducts only at frequencies in the second frequency range, and therefore circuit 118 is connected in a frequency-dependent manner at frequencies in the second frequency range.

[0105] The above is a detailed description of the drive unit 110 shown in Figure 5. Next, please focus on the detailed description of the voltage measurement unit 120 shown in Figure 5. The voltage measurement unit 120 in Figure 5 includes an amplification circuit 121, in particular a differential amplifier.

[0106] The amplification circuit 121 of the voltage measurement unit 120 includes an input node K3 that is coupled to the output node K2 of the amplification circuit 111 of the drive unit 110 to receive the time-dependent voltage u of the actuator 200, an output node K4 that provides the 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, the first circuit 123 is coupled to the output node K4, the negative power supply voltage VSS of the drive unit 100, and the inverting input of the operational amplifier 122, and the second circuit 124 is coupled to the input node K3, the non-inverting input of the operational amplifier 122, and earth GND. In the embodiment shown in Figure 5, the second circuit 114 of the amplification circuit 111 of the drive unit 110 and the second circuit 124 of the amplification circuit 121 of the voltage measurement unit 120 are formed by a single circuit, i.e., they are identical. This is advantageous in that it saves components of the optical system 300, particularly space.

[0107] As shown in Figure 5, the first circuit 123 and the second circuit 124 of the amplification circuit 121 of the voltage measurement unit 120 each have resistor circuits 125 and 126 that provide 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, and these circuits each further have frequency-dependent connectable circuits 127 and 118.

[0108] Since the second circuit 124 of the voltage measurement unit 120 corresponds to the second circuit 114 of the drive unit 110, only the first circuit 123 of the amplification circuit 121 of the voltage measurement unit 120 will be described in detail below to avoid repetition. The first circuit 123 has a resistor circuit 125 that includes 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 resistors R1 and R2 in resistor circuit 116 and resistors R1 and R2 in 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 power supply voltage VSS. In this case, the capacitance of capacitor C3 is selected such that capacitor C3 conducts only at frequencies in the second frequency range F2.

[0110] Although the present invention has been described in terms of exemplary embodiments, it can be modified in various ways. [Explanation of Symbols]

[0111] 1. Projection exposure apparatus 2. Lighting System 3 light source 4. Illumination Optical Unit 5 Object field of view 6 Object plane 7 Reticle 8 Reticle holders 9. Reticle displacement drive 10 Projection Optical Unit 11 Image field 12 Image plane 13 wafers 14 Wafer holder 15 Wafer Displacement Drive 16 Illumination Radiation 17 Collector 18 Intermediate focal plane 19. Polarizing mirror 20 First 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 Measurement Unit 121 Differential Amplifier 122 Operational Amplifier 123 1st circuit 124 2nd circuit 125 Resistance circuit 127 Connectable Circuits 130 Current Measurement Unit 200 Actuators 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 transmission coefficient G2 Transfer coefficient G3 Transfer coefficient G4 Transfer coefficient GND (Ground) I Measured current i Actuator current K1 input resolution 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 drive device (100) for driving and measuring an actuator (200) that operates an optical element (310) of an optical system (300), 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) such that the gain in the first frequency range (F1) is higher by a specific coefficient compared to the second frequency range (F2), thereby forming the drive voltage (AS) of the actuator (200), A voltage measuring unit (120) that provides a measurement voltage (U), configured to convolve the time-dependent voltage (u) of the actuator (200) with a second transfer function (G2) based on the reciprocal of the first transfer function (G1) in the time domain, and then measure the time-dependent voltage to provide the measurement voltage (U), A voltage measuring unit (130) that provides a measurement current (I), and a current measuring unit (130) configured to convolve the time-dependent current (i) of the actuator (200) with a third transfer function (G3) based on the reciprocal of the first transfer function (G1) in the time domain, and then measure the time-dependent current to provide the measurement current (I), and A drive system equipped with this.

2. In the drive device according to claim 1, A determination unit (120) is coupled to the voltage measurement unit (120) and the current measurement unit (130) and determines the impedance (Z) of the actuator (200) based on the provided measured voltage (U) and the provided measured current (I). A drive system further equipped with [the following].

3. In the drive device according to claim 1 or 2, The first frequency range (F1) is located between 0 Hz and 1 kHz, and / or The second frequency range (F2) is a drive device located between 5 kHz and 100 kHz.

4. In the drive device according to claim 1 or 2, The aforementioned specific coefficient is between 100 and 2000 in the drive device.

5. In the drive device according to claim 1 or 2, The drive unit (110) is a drive device having an amplification circuit (111), particularly a differential amplifier.

6. In the drive device according to claim 5, The amplification 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) of the actuator (200), and an operational amplifier (112) coupled between the input node (K1) and the output node (K2), wherein the first circuit (113) is coupled to the input node (K1), the negative power supply voltage (VSS) of the drive device (100), and the non-inverting input of the operational amplifier (112), and the second circuit (114) is coupled to the inverting input of the operational amplifier (112), ground (GND), and the output node (K2) in order to provide the first transfer function (G1).

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

8. In the drive device according to claim 6, The voltage measurement unit (120) is a drive device having an amplification circuit (121), particularly a differential amplifier.

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

10. In the drive device according to claim 9, The first circuit (123) and the second circuit (124) each have resistor circuits (125, 116) that provide a component of the second transfer function (G2) in the first frequency range (F1) and a component of the second transfer function (G2) in the second frequency range (F2), and each circuit further has frequency-dependent connectable circuits (127, 118) that include frequency-dependent components (C3, C2) and resistors (R7, R6), and the drive device.

11. In the drive device according to claim 9, The second circuit (114) of the amplification circuit (111) of the drive unit (110) and the second circuit (124) of the amplification circuit (121) of the voltage measuring unit (120) are a drive device formed by a single circuit.

12. An optical system (300) comprising a plurality of operable optical elements (310), wherein an actuator (200) is assigned to each of the plurality of operable optical elements (310), and a drive device (100) for driving the actuator (200) according to claim 1 or 2 is assigned to each actuator (200).

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

14. A lithography apparatus (1), comprising the optical system (300) described in claim 12.

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