DE102023202493A1 - CONTROL DEVICE, OPTICAL SYSTEM, LITHOGRAPHY DEVICE AND METHOD - Google Patents

Abstract

A control device (100) for controlling an actuator (200) for actuating an optical element (310) of an optical system (300), with
a control unit (110) which is designed to provide a control voltage (A) for controlling the actuator (200) in dependence on a provided control signal (S), and
a control unit (120) which is configured to provide the control signal (S) as a function of a desired position signal (P) for setting a position of the optical element (310) and a correction signal (K) which is dependent on a determined impedance (Z) of the actuator (200).

Description

The present invention relates to a control device for controlling an actuator of an optical system, an optical system with such a control device and a lithography system with such an optical system. The present invention also relates to a method for controlling an actuator for actuating an optical element of an optical system.

Microlithography systems are known that have actuatable optical elements, such as microlens arrays or micromirror arrays. Microlithography is used to produce microstructured components, such as integrated circuits. The microlithography process is carried out using a lithography system that has an illumination system and a projection system.

Driven by the pursuit of ever smaller structures in the manufacture of integrated circuits, EUV lithography systems are currently being developed that use light with a wavelength in the range of 0.1 nm to 30 nm, in particular 13.5 nm. Since most materials absorb light of this wavelength, such EUV lithography systems must use reflective optics, i.e. mirrors, instead of - as previously - refractive optics, i.e. lenses.

The image of a mask (reticle) illuminated by the illumination system is projected by the projection system onto a substrate coated with a light-sensitive layer (photoresist) and arranged in the image plane of the projection system, for example a silicon wafer, in order to transfer the mask structure onto the light-sensitive coating of the substrate. The image of the mask on the substrate can be improved using actuatable optical elements. For example, wavefront errors during exposure that lead to enlarged and/or blurred images can be compensated for.

For such a correction using the optical element, the wavefront must be detected and signal processing must be carried out to determine the respective position of an optical element, through which the wavefront can be corrected as desired. In the last step, the control signal for a respective optical element is amplified and output to the actuator of the optical element.

A PMN actuator (PMN; lead magnesium niobate), for example, can be used as an actuator. A PMN actuator enables line positioning in the sub-micrometer or sub-nanometer range. When a direct current is applied, the actuator, whose actuator elements are stacked on top of one another, experiences a force that causes a certain linear expansion. The position set by the direct current or DC voltage (DC; direct current) can be negatively influenced by external electromechanical crosstalk at the resonance points of the actuator controlled by the direct current. As a result of this electromechanical crosstalk, precise positioning can no longer be set in a stable manner. The higher the applied direct voltage, the stronger the mechanical resonances. These resonance points can also change over the long term, for example due to temperature drift or adhesive drift if the mechanical bonding of the adhesive material changes, or due to hysteresis or aging.

It is also known to control the actuators of a lithography system using a respective control signal, which has a low-frequency control component for controlling the actuator and a higher-frequency measurement signal component for measuring the actuator. Such a control signal is conventionally amplified by means of an output stage and applied to the actuator as a control voltage.

However, if, for example, a PMN actuator is only controlled by a voltage control, this can result in a deviation from the desired target position of the optical element to the actual position of the optical element due to various effects, for example due to hysteresis. Such a deviation between the target position and the actual position of the optical element is detrimental to the exposure and thus to the entire lithography system.

Against this background, one object of the present invention is to improve the control of an actuator of an optical system.

• eine Ansteuereinheit, welche dazu eingerichtet ist, eine Ansteuerspannung zur Ansteuerung des Aktuators in Abhängigkeit eines bereitgestellten Ansteuersignals bereitzustellen, und
• eine Steuereinheit, welche dazu eingerichtet ist, das Ansteuersignal in Abhängigkeit eines Soll-Positionssignals zur Einstellung einer Position des optischen Elementes und eines von einer ermittelten Impedanz des Aktuators abhängigen Korrektursignals bereitzustellen.

According to a first aspect, a control device for controlling an actuator for actuating an optical element of an optical system is proposed. The control device comprises:

• a control unit which is configured to provide a control voltage for controlling the actuator in dependence on a provided control signal, and
• a control unit which is configured to provide the control signal as a function of a desired position signal for setting a position of the optical element and a correction signal which is dependent on a determined impedance of the actuator.

Because the control signal for the actuator control unit is generated as a function of the correction signal that is dependent on the determined impedance of the actuator, a linear transmission behavior can advantageously be achieved, in particular without hysteresis effects. This takes advantage of the fact that a changed transmission behavior of control voltage for deformation of the actuator is visible in the impedance of the actuator. In this case, a change in the impedance of the actuator is included in the correction signal and consequently in the control signal for the control unit.

The actuator is in particular a capacitive actuator, for example 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 designed to actuate an optical element of the optical system. Examples of such an optical element include lenses, mirrors and adaptive mirrors.

The optical system is preferably a projection optics of the lithography system or projection exposure system. However, the optical system can also be an illumination system. The projection exposure system can be an EUV lithography system. EUV stands for "Extreme Ultraviolet" and refers to a wavelength of the working light between 0.1 nm and 30 nm. The projection exposure system can also be a DUV lithography system. DUV stands for "Deep Ultraviolet" and refers to a wavelength of the working light between 30 nm and 250 nm.

According to one embodiment, the control device has a determination device coupled to the actuator for determining the impedance of the actuator, which changes over time. In this case, it is advantageously not necessary to measure the change in charge of the actuator directly, since the impedance of the actuator is determined, from which the charge can be deduced.

According to a further embodiment, the control unit, the drive unit, the actuator and the detection device form a control loop. The control loop preferably forms a charge amplifier for charge control.

According to a further embodiment, the determination device is configured to provide the correction signal such that it is proportional, in particular directly proportional, to the determined impedance of the actuator.

• eine zwischen dem Aktuator und der Ermittlungs-Einrichtung gekoppelte Spannungsmesseinheit, welche dazu eingerichtet ist, eine Messspannung bereitzustellen, welche indikativ für eine zeitabhängige Spannung des Aktuators ist, und
• eine zwischen dem Aktuator und der Ermittlungs-Einrichtung gekoppelte Strommesseinheit, welche dazu eingerichtet ist, einen Messstrom bereitzustellen, welcher indikativ für einen zeitabhängigen Strom des Aktuators ist.

According to a further embodiment, the control device further comprises:

• a voltage measuring unit coupled between the actuator and the detection device, which is designed to provide a measuring voltage which is indicative of a time-dependent voltage of the actuator, and
• a current measuring unit coupled between the actuator and the detection device, which is configured to provide a measuring current which is indicative of a time-dependent current of the actuator.

By providing the measuring voltage and the measuring current of the actuator, the present control device enables a fast and inline-capable impedance determination of the actuator installed in the lithography system.

According to a further embodiment, the determination device is coupled to the voltage measuring unit and the current measuring unit. The determination device is designed to determine the impedance of the actuator as a function of the provided measuring voltage and the provided measuring current.

According to a further embodiment, the control device further comprises a second control unit coupled to the determination device. The second control unit is designed to provide the correction signal based on the impedance determined by the determination device. In embodiments, the control unit and the second control unit can be implemented in a single control unit or control device, such as a microcontroller.

• einen Signalgenerator zum Bereitstellen eines zum Messen der Impedanz des Aktuators geeigneten Anregungssignals, und
• eine Summationsstelle, welche dazu eingerichtet ist, das von der Steuereinheit bereitgestellte Ansteuersignal und das von dem Signalgenerator bereitgestellte Anregungssignal zu addieren,
• wobei die Ansteuereinheit eine Verstärkerschaltung aufweist, welche dazu eingerichtet ist, das Ansteuersignal und das Anregungssignal von der Summationsstelle zu empfangen, zu verstärken und abhängig davon ausgangsseitig die Ansteuerspannung an den Aktuator bereitzustellen.

According to a further embodiment, the control device further comprises:

• a signal generator for providing an excitation signal suitable for measuring the impedance of the actuator, and
• a summation point which is designed to add the control signal provided by the control unit and the excitation signal provided by the signal generator,
• wherein the control unit comprises an amplifier circuit which is adapted to receive the control signal and the excitation signal from to receive the summation point, to amplify it and, depending on this, to provide the control voltage to the actuator on the output side.

The amplifier circuit comprises in particular a differential amplifier. After amplification of the summation signal from the control signal and the excitation signal, the signal component of the control voltage resulting from the control signal is preferably in a first frequency range and the signal component resulting from the excitation signal is in a second frequency range. The first frequency range and the second frequency range are preferably disjoint frequency ranges. The signal component of the control voltage in the first frequency range is used to control the actuator, i.e. in particular to adjust its deflection. The signal component of the control voltage in the second frequency range is used in particular to measure the actuator, in particular to measure the impedance of the actuator.

According to a further embodiment, the control unit, the summation point, the control unit, the actuator, the parallel connection of the voltage measuring unit and the current measuring unit, the detection device and the second control unit form a control loop.

According to a further embodiment, the control circuit forms a charge amplifier, in particular for charge control.

According to a further embodiment, the determination device is designed to determine the capacitance of the actuator as part of the impedance of the actuator. In this case, the control unit is designed to provide the control signal as a function of the target position signal for setting the position of the optical element and a correction signal dependent on the determined capacitance of the actuator.

Further examples for determining the impedance of an actuator can be found in the patent applications EN 10 2022 203255.1 and EN 10 2022 203 257.8 , the respective contents of which are fully incorporated by reference.

According to a second aspect, an optical system with a number of actuatable optical elements is proposed, wherein each of the actuatable optical elements of the number is assigned an actuator, wherein each actuator is assigned a control device for controlling the actuator according to the first aspect or according to one of the embodiments of the first aspect.

The optical system comprises in particular a micromirror array and/or a microlens array with a plurality of independently actuatable optical elements.

In embodiments, groups of actuators can be defined, with all actuators in a group being assigned the same control device.

According to one embodiment, the optical system is designed as an illumination optics or as a projection optics of a lithography system.

According to a further embodiment, the optical system has a vacuum housing in which the actuatable optical elements, the associated actuators and the control device are arranged.

According to a third aspect, a lithography system is proposed which has an optical system according to the second aspect or according to one of the embodiments of the second aspect.

The lithography system is, for example, an EUV lithography system whose working light is in a wavelength range from 0.1 nm to 30 nm, or a DUV lithography system whose working light is in a wavelength range from 30 nm to 250 nm.

• Generieren eines Ansteuersignals in Abhängigkeit eines Soll-Positionssignals zur Einstellung einer Position des optischen Elementes und eines von einer ermittelten Impedanz des Aktuators abhängigen Korrektursignals, und
• Bereitstellen der Ansteuerspannung durch die Ansteuereinheit in Abhängigkeit des generierten Ansteuersignals.

According to a fourth aspect, a method for controlling an actuator for actuating an optical element of an optical system using a control unit which controls the actuator by means of a control voltage is proposed. The method comprises the steps:

• Generating a control signal depending on a target position signal for setting a position of the optical element and a correction signal depending on a determined impedance of the actuator, and
• Provision of the control voltage by the control unit depending on the generated control signal.

The embodiments and features described for the proposed control device apply accordingly to the proposed method.

In this case, "one" is not necessarily to be understood as being limited to just one element. Rather, several elements, such as two, three or more, can also be provided. Any other counting word used here should not be understood as meaning that there is a limitation to the exact number of elements mentioned. Rather, numerical deviations upwards and downwards are possible, unless otherwise stated.

Further possible implementations of the invention also include combinations of features or embodiments described above or below with respect to the exemplary embodiments that are not explicitly mentioned. The person skilled in the art will also add individual aspects as improvements or additions to the respective basic form of the invention.

• 1 zeigt einen schematischen Meridionalschnitt einer Projektionsbelichtungsanlage für eine EUV-Projektionslithographie;
• 2 zeigt eine schematische Darstellung einer Ausführungsform eines optischen Systems;
• 3 zeigt ein schematisches Blockdiagramm einer ersten Ausführungsform einer Ansteuervorrichtung zum Ansteuern eines Aktuators zum Aktuieren eines optischen Elementes eines optischen Systems;
• 4 zeigt ein schematisches Blockdiagramm einer zweiten Ausführungsform einer Ansteuervorrichtung zum Ansteuern eines Aktuators zum Aktuieren eines optischen Elementes eines optischen Systems;
• 5 zeigt ein Diagramm zur Illustrierung einer herkömmlichen Spannungssteuerung eines Aktuators;
• 6 zeigt ein Diagramm zur Illustrierung einer Ladungsregelung eines Aktuators;
• 7 zeigt ein schematisches Blockdiagramm einer dritten Ausführungsform einer Ansteuervorrichtung zum Ansteuern eines Aktuators zum Aktuieren eines optischen Elementes eines optischen Systems;
• 8 zeigt ein schematisches Blockdiagramm einer vierten Ausführungsform einer Ansteuervorrichtung zum Ansteuern eines Aktuators zum Aktuieren eines optischen Elementes eines optischen Systems; und
• 9 zeigt ein schematisches Ablaufdiagramm einer Ausführungsform eines Verfahrens zum Ansteuern eines Aktuators zum Aktuieren eines optischen Elementes eines optischen Systems.

Further advantageous embodiments and aspects of the invention are the subject of the dependent claims and the embodiments of the invention described below. The invention is explained in more detail below using preferred embodiments with reference to the attached figures.

• 1 shows a schematic meridional section of a projection exposure system for EUV projection lithography;
• 2 shows a schematic representation of an embodiment of an optical system;
• 3 shows a schematic block diagram of a first embodiment of a control device for controlling an actuator for actuating an optical element of an optical system;
• 4 shows a schematic block diagram of a second embodiment of a control device for controlling an actuator for actuating an optical element of an optical system;
• 5 shows a diagram illustrating a conventional voltage control of an actuator;
• 6 shows a diagram illustrating a charge control of an actuator;
• 7 shows a schematic block diagram of a third embodiment of a control device for controlling an actuator for actuating an optical element of an optical system;
• 8 shows a schematic block diagram of a fourth embodiment of a control device for controlling an actuator for actuating an optical element of an optical system; and
• 9 shows a schematic flow diagram of an embodiment of a method for controlling an actuator for actuating an optical element of an optical system.

In the figures, identical or functionally equivalent elements have been given the same reference symbols unless otherwise stated. It should also be noted that the representations in the figures are not necessarily to scale.

1 shows an embodiment of a projection exposure system 1 (lithography system), in particular an EUV lithography system. An embodiment of an illumination system 2 of the projection exposure system 1 has, in addition to a light or radiation source 3, an illumination optics 4 for illuminating 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.

A reticle 7 arranged in the object field 5 is exposed. The reticle 7 is held by a reticle holder 8. The reticle holder 8 can be displaced via a reticle displacement drive 9, in particular in a scanning direction.

In the 1 For explanation, a Cartesian coordinate system with an x-direction x, a y-direction y and a z-direction z is drawn. The x-direction x runs perpendicularly into the drawing plane. The y-direction y runs horizontally and the z-direction z runs vertically. The scanning direction runs in the 1 along the y-direction y. The z-direction z runs perpendicular to the object plane 6.

The projection exposure system 1 comprises a projection optics 10. The projection optics 10 serves to image the object field 5 into an image field 11 in an image plane 12. The image plane 12 runs parallel to the object plane 6. Alternatively, an angle other than 0° between the object plane 6 and the image plane 12 is also possible.

A structure on the reticle 7 is imaged onto a light-sensitive layer of a wafer 13 arranged in the area of the image field 11 in the image plane 12. The wafer 13 is held by a wafer holder 14. The wafer holder 14 can be displaced via a wafer displacement drive 15, in particular along the y-direction y. The displacement of the reticle 7 via the reticle displacement drive drive 9 and on the other hand the wafer 13 via the wafer displacement drive 15 can be synchronized with each other.

The light source 3 is an EUV radiation source. The light source 3 emits in particular EUV radiation 16, which is also referred to below as useful radiation, illumination radiation or illumination light. The useful radiation 16 has in particular a wavelength in the range between 5 nm and 30 nm. The light source 3 can be a plasma source, for example an LPP source (Laser Produced Plasma, plasma generated with the aid of a laser) or a DPP source (Gas Discharged Produced Plasma, plasma generated by means of gas discharge). It can also be a synchrotron-based radiation source. The light source 3 can be a free-electron laser (FEL).

The illumination radiation 16 that emanates from the light source 3 is bundled by a collector 17. The collector 17 can be a collector with one or more ellipsoidal and/or hyperboloidal reflection surfaces. The at least one reflection surface of the collector 17 can be exposed to the illumination radiation 16 in grazing incidence (GI), i.e. with angles of incidence greater than 45°, or in normal incidence (NI), i.e. with angles of incidence less than 45°. The collector 17 can be structured and/or coated on the one hand to optimize its reflectivity for the useful radiation and on the other hand to suppress stray light.

After the collector 17, the illumination radiation 16 propagates through an intermediate focus in an intermediate focal plane 18. The intermediate focal plane 18 can represent a separation between a radiation source module, comprising the light source 3 and the collector 17, and the illumination optics 4.

The illumination optics 4 comprise a deflection mirror 19 and a first facet mirror 20 arranged downstream of this in the beam path. The deflection mirror 19 can be a flat deflection mirror or alternatively a mirror with a beam-influencing effect beyond the pure deflection effect. Alternatively or additionally, the deflection mirror 19 can be designed as a spectral filter which separates a useful light wavelength of the illumination radiation 16 from false light of a different wavelength. If the first facet mirror 20 is arranged in a plane of the illumination optics 4 which is optically conjugated to 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 can also be referred to as field facets. Of these first facets 21, only one is shown in the 1 only a few examples are shown.

The first facets 21 can be designed as macroscopic facets, in particular as rectangular facets or as facets with an arcuate or partially circular edge contour. The first facets 21 can be designed as flat facets or alternatively as convex or concave curved facets.

As for example from the EN 10 2008 009 600 A1 As is known, the first facets 21 themselves can also be composed of a plurality of individual mirrors, in particular a plurality of micromirrors. The first facet mirror 20 can in particular be designed as a microelectromechanical system (MEMS system). For details, please refer to the EN 10 2008 009 600 A1 referred to.

Between the collector 17 and the deflection mirror 19, the illumination radiation 16 runs horizontally, i.e. along the y-direction y.

In the beam path of the illumination optics 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 optics 4, it is also referred to as a pupil facet mirror. The second facet mirror 22 can also be arranged at a distance from a pupil plane of the illumination optics 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 the US 2006/0132747 A1 , the EP 1 614 008 B1 and the US$6,573,978 .

The second facet mirror 22 comprises 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.

The second facets 23 can also be macroscopic facets, which can be round, rectangular or hexagonal, for example, or alternatively facets composed of micromirrors. In this regard, reference is also made to the EN 10 2008 009 600 A1 referred to.

The second facets 23 can have planar or alternatively convex or concave curved reflection surfaces.

The illumination optics 4 thus form a double-faceted system. This basic principle is also known as a fly's eye integrator.

It may be advantageous not to arrange the second facet mirror 22 exactly in a plane that is optically conjugated to a pupil plane of the projection optics 10. In particular, the second facet mirror 22 can be arranged tilted relative to a pupil plane of the projection optics 10, as is the case, for example, in the EN 10 2017 220 586 A1 described.

With the help of the second facet mirror 22, the individual first facets 21 are imaged in the object field 5. The second facet mirror 22 is the last bundle-forming or actually the last mirror for the illumination radiation 16 in the beam path in front of the object field 5.

In a further embodiment of the illumination optics 4 (not shown), a transmission optics can be arranged in the beam path between the second facet mirror 22 and the object field 5, which contributes in particular to the imaging of the first facets 21 in the object field 5. The transmission optics can have exactly one mirror, but alternatively also two or more mirrors, which are arranged one behind the other in the beam path of the illumination optics 4. The transmission optics can in particular comprise one or two mirrors for vertical incidence (NI mirrors, normal incidence mirrors) and/or one or two mirrors for grazing incidence (GI mirrors, grazing incidence mirrors).

The lighting optics 4 have in the version shown in the 1 As shown, after the collector 17 there are exactly three mirrors, namely the deflection mirror 19, the first facet mirror 20 and the second facet mirror 22.

In a further embodiment of the illumination optics 4, the deflection mirror 19 can also be omitted, so that the illumination optics 4 can then have exactly two mirrors after the collector 17, namely the first facet mirror 20 and the second facet mirror 22.

The imaging of the first facets 21 by means of the second facets 23 or with the second facets 23 and a transmission optics into the object plane 6 is usually only an approximate imaging.

The projection optics 10 comprises a plurality of mirrors Mi, which are numbered according to their arrangement in the beam path of the projection exposure system 1.

In the 1 In the example shown, the projection optics 10 comprises six mirrors M1 to M6. Alternatives with four, eight, ten, twelve or another number of mirrors Mi are also possible. The projection optics 10 is a double-obscured optics. The penultimate mirror M5 and the last mirror M6 each have a passage opening for the illumination radiation 16. The projection optics 10 has a numerical aperture on the image side that is greater than 0.5 and can also be greater than 0.6 and can be, for example, 0.7 or 0.75.

Reflection surfaces of the mirrors Mi can be designed as free-form surfaces without a rotational symmetry axis. Alternatively, the reflection surfaces of the mirrors Mi can be designed as aspherical surfaces with exactly one rotational symmetry axis of the reflection surface shape. The mirrors Mi, just like the mirrors of the illumination optics 4, can have highly reflective coatings for the illumination radiation 16. These coatings can be designed as multilayer coatings, in particular with alternating layers of molybdenum and silicon.

The projection optics 10 have a large object-image offset in the y-direction y between a y-coordinate of a center of the object field 5 and a y-coordinate of the center of the image field 11. This object-image offset in the y-direction y can be approximately as large as a z-distance between the object plane 6 and the image plane 12.

The projection optics 10 can in particular be anamorphic. In particular, it has different image scales Bx, By in the x and y directions x, y. The two image scales Bx, By of the projection optics 10 are preferably (βx, βy) = (+/- 0.25, /+- 0.125). A positive image scale β means an image without image inversion. A negative sign for the image scale B means an image with image inversion.

The projection optics 10 thus leads to a reduction in the ratio 4:1 in the x-direction x, i.e. in the direction perpendicular to the scanning direction.

The projection optics 10 leads to a reduction of 8:1 in the y-direction y, i.e. in the scanning direction.

Other image scales are also possible. Image scales with the same sign and absolutely the same in the x and y directions x, y, for example with absolute values of 0.125 or 0.25, are also possible.

The number of intermediate image planes in the x and y directions x, y in the beam path between the object field 5 and the image field 11 can be the same or can be different depending on the design of the projection optics 10. Examples of projection optics with different numbers of such intermediate images in the x and y directions x, y are known from US 2018/0074303 A1 .

Each of the second facets 23 is assigned to exactly one of the first facets 21 to form a respective illumination channel for illuminating the object field 5. This can result in particular in illumination according to the Köhler principle. The far field is broken down into a plurality of object fields 5 using the first facets 21. The first facets 21 generate a plurality of images of the intermediate focus on the second facets 23 assigned to them.

The first facets 21 are each imaged onto the reticle 7 by an associated second facet 23, superimposed on one another, to illuminate the object field 5. The illumination of the object field 5 is in particular as homogeneous as possible. It preferably has a uniformity error of less than 2%. The field uniformity can be achieved by superimposing different illumination channels.

By arranging the second facets 23, the illumination of the entrance pupil of the projection optics 10 can be defined geometrically. By selecting the illumination channels, in particular the subset of the second facets 23 that guide light, the intensity distribution in the entrance pupil of the projection optics 10 can be set. This intensity distribution is also referred to as illumination setting or illumination pupil filling.

A likewise preferred pupil uniformity in the area of defined illuminated sections of an illumination pupil of the illumination optics 4 can be achieved by a redistribution of the illumination channels.

In the following, further aspects and details of the illumination of the object field 5 and in particular of the entrance pupil of the projection optics 10 are described.

The projection optics 10 can in particular have a homocentric entrance pupil. This can be accessible. It can also be inaccessible.

The entrance pupil of the projection optics 10 cannot usually be illuminated precisely with the second facet mirror 22. When the projection optics 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, a surface can be found in which the pairwise determined distance of the aperture rays is minimal. This surface represents the entrance pupil or a surface conjugated to it in spatial space. In particular, this surface shows a finite curvature.

It is possible that the projection optics 10 have different positions of the entrance pupil for the tangential and the sagittal beam path. In this case, an imaging element, in particular an optical component of the transmission optics, should be provided between the second facet mirror 22 and the reticle 7. With the help of this optical element, the different positions of the tangential entrance pupil and the sagittal entrance pupil can be taken into account.

In the 1 In the arrangement of the components of the illumination optics 4 shown, the second facet mirror 22 is arranged in a surface conjugated to the entrance pupil of the projection optics 10. The first facet mirror 20 is arranged tilted to the object plane 6. The first facet mirror 20 is arranged tilted to an arrangement plane that is defined by the deflection mirror 19. The first facet mirror 20 is arranged tilted to an arrangement plane that is defined by the second facet mirror 22.

2 shows a schematic representation of an embodiment of an optical system 300 for a lithography system or projection exposure system 1, as described for example in 1 In addition, the optical system 300 of the 2 for example, it can also be used in a DUV lithography system.

The optical system 300 of the 2 has a plurality of actuatable optical elements 310. The optical system 300 is designed here as a micromirror array, wherein the optical elements 310 are micromirrors. Each micromirror 310 can be actuated by means of an associated actuator 200. For example, a respective micromirror 310 can be tilted about two axes and/or moved in one, two or three spatial axes by means of the associated actuator 200. For reasons of clarity, the reference symbols are only shown for the top row of these elements.

The control device 100 controls the respective actuator 200, for example, with a control voltage A. This sets a position of the respective micromirror 310. The Control device 100 is particularly described with reference to the 3 to 8 described.

The 3 shows a schematic block diagram of a first embodiment of a control device 100 for controlling an actuator 200 for actuating an optical element 310 of an optical system 300.

The control device 100 of the 3 has a control unit 110 which is coupled to the actuator 200, and a control unit 120 coupled to the control unit 110. The control unit 110 comprises in particular an amplifier circuit, preferably a differential amplifier. The control unit 120 generates a control signal S as a function of a target position signal P for setting the position of the optical element 310 and a correction signal K dependent on a determined impedance Z of the actuator 200 and provides the generated control signal S to the control unit 110. The target position signal P indicates the target position of the optical element 310, for example a mirror. The correction signal K depends on the determined current impedance Z of the actuator 200. The correction signal K is in particular directly proportional to the determined current impedance Z of the actuator 200.

The control unit 110 generates the control voltage A for controlling the actuator 200 depending on the control signal S provided. Consequently, the control unit 110 controls the actuator 200 by means of the control voltage A. The actuator 200 controlled by the control voltage A is connected to the optical element 310 (not shown in 3 ) and controls the optical element 310 by means of an adjustment signal E. The adjustment signal E is suitable for adjusting the position of the optical element 310.

4 shows a schematic block diagram of a second embodiment of a control device 100 for controlling an actuator 200 for actuating an optical element 310 of an optical system 300. The second embodiment according to 4 is based on the first embodiment according to 3 and includes all features of the first embodiment according to 3 . In addition, the control device 100 of the 4 a determination device 130 coupled to the actuator 200. The determination device 130 is designed to determine the impedance Z of the actuator 200, which changes over time, in particular on the basis of a measuring voltage U and a measuring current I of the actuator 200. As the 4 illustrated, the control unit 120, the drive unit 110, the actuator 200 and the detection device 130 form a control loop R. These devices forming a control advantageously form a charge amplifier.

Because the control signal S for the control unit 110 of the actuator 200 depends on the correction signal K, which depends on the determined impedance Z of the actuator 200, a linear transmission behavior of the control device 100 can advantageously be achieved, in particular without hysteresis effects.

The two different transfer behaviors, namely the conventional transfer behavior based on voltage control with hysteresis and the linear transfer behavior based on charge control proposed here, are compared by comparing the 5 and 6 clearly. Here, the 5 a diagram illustrating a conventional voltage control of the actuator and the 6 shows a diagram illustrating a charge control of the actuator 200. As the comparison of the 5 and 6 clearly shows that the voltage control is based on 5 a hysteresis, whereas in the charge control according to 6 a linear transmission behavior can advantageously be achieved.

In the present embodiments of the control device 100, it is advantageously exploited that a changed transmission behavior of control voltage A for deformation of the actuator 200 is visible in the impedance Z of the actuator 200. In the present case, a change in the impedance Z of the actuator 200 is included in the correction signal K and thus in the control signal S for the control unit 110. The determination device 130 is preferably set up to provide the correction signal K in such a way that it is proportional, preferably directly proportional, to the determined impedance Z of the actuator 200.

In embodiments, the determination device 130 is configured to determine the capacitance C of the actuator 200 as part of the impedance Z of the actuator 200. The control unit 120 can then be configured to provide the control signal S as a function of the target position signal P for adjusting the position of the optical element 310 and a correction signal K that is dependent on the determined capacitance of the actuator 200.

Furthermore, the 7 a schematic block diagram of a third embodiment of a control device 100 for controlling an actuator 200 for actuating an optical element 310 of an optical system 300. The third embodiment according to 7 is based on the second embodiment according to 4 and includes all their Features. In addition, the third embodiment of the control device 100 according to 7 a second control unit 140, a voltage measuring unit 150 and a current measuring unit 160. In embodiments, the control unit 120 and the second control unit 140 may be implemented in a single control unit or control device, such as a microcontroller.

The voltage measuring unit 150 is connected between the actuator 200 and the detection device 130. The voltage measuring unit 150 is designed to provide a measuring voltage U which is indicative of a time-dependent voltage u of the actuator 200. In particular, the measuring voltage U is directly proportional to the time-dependent voltage u of the actuator 200. In embodiments, the measuring voltage U corresponds to the current voltage u of the actuator 200.

The current measuring unit 160 is connected between the actuator 200 and the detection device 130. The current measuring unit 160 is configured to provide a measuring current I which is indicative of a time-dependent current i of the actuator 200. In particular, the measuring current I is directly proportional to the time-dependent current i of the actuator 200. In embodiments, the measuring current I corresponds to the current current i of the actuator 200.

As stated above, the determination device 130 is coupled to the voltage measuring unit 150 and the current measuring unit 160. The determination device 130 is preferably designed to determine the impedance Z of the actuator 200 as a function of the provided measurement voltage U and the provided measurement current I. The second control unit 140 connected downstream of the determination device 130 is designed to provide the correction signal K based on the impedance Z determined by the determination device 130. The second control unit 140 provides the correction signal K to the control unit 120.

As the 7 shows, the control unit 120, the control unit 110, the actuator 200, the parallel connection of the voltage measuring unit 150 and the current measuring unit 160, the detection device 130 and the second control unit 140 form a control loop R. The control loop R, as explained above, preferably forms a charge amplifier for charge control.

8 shows a schematic block diagram of a fourth embodiment of a control device 100 for controlling an actuator 200 for actuating an optical element 310 of an optical system 300. The fourth embodiment according to 8 is based on the third embodiment according to 7 and includes all its features.

According to the fourth embodiment of 8 the control device 100 comprises a signal generator 170. The signal generator 170 is configured to provide an excitation signal Y suitable for measuring the impedance Z of the actuator 200.

Furthermore, the control device 100 has 8 a summation point 181, at which the control signal S provided by the control unit 120 and the excitation signal Y provided by the signal generator 170 are added. After the summation signal S + Y from the control signal S and the excitation signal Y has been amplified by the control unit 110, the signal component in the control voltage A resulting from the control signal S is preferably in a first frequency range and the signal component resulting from the excitation signal Y is in a second frequency range. The first frequency range and the second frequency range are preferably disjoint frequency ranges. The part of the control voltage A in the first frequency range is used to control the actuator 200, that is to say in particular to adjust its deflection. The part of the control voltage in the second frequency range is used in particular to measure the actuator 200, in particular to measure the impedance Z of the actuator 200.

Furthermore, the 8 that the control unit 120 can have a converter unit 190 and a further summation point 182. The converter unit 190 is set up to receive a target position TARGET for the actuator 200 and, depending on this, to supply the target position signal P, for example as a digital signal, to the summation point 182. The target position signal P and the correction signal K are then added at the summation point 182 to form the control signal S.

As the 8 illustrated, the control unit 120, the summation point 181, the control unit 110, the actuator 200, the parallel connection of the voltage measuring unit 150 and the current measuring unit 160, the detection device 130 and the second control unit 140 form a control circuit R, which preferably forms a charge amplifier for charge control.

• In Schritt S1 wird ein Ansteuersignal S in Abhängigkeit eines Soll-Positionssignals P zur Einstellung einer Position des optischen Elementes 310 und eines von einer ermittelten Impedanz Z des Aktuators 200 abhängigen Korrektursignals K generiert.
• In Schritt S2 wird die Ansteuerspannung A durch die Ansteuereinheit 110 in Abhängigkeit des generierten Ansteuersignals S bereitgestellt. Mittels der Ansteuerspannung A wird dann, wie in den 3 bis 8 gezeigt, der Aktuator 200 angesteuert.

Furthermore, the 9 a schematic flow diagram of a method for controlling an actuator 200 for actuating an optical element 310 of an optical system 300 using a control unit 110 which controls the actuator 200 by means of a control voltage voltage A. The procedure according to 9 includes steps S1 and S2:

• In step S1, a control signal S is generated as a function of a desired position signal P for setting a position of the optical element 310 and a correction signal K dependent on a determined impedance Z of the actuator 200.
• In step S2, the control voltage A is provided by the control unit 110 as a function of the generated control signal S. The control voltage A is then used, as in the 3 to 8 shown, the actuator 200 is controlled.

Although the present invention has been described using exemplary embodiments, it can be modified in many ways.

LIST OF REFERENCE SYMBOLS

1

Projection exposure system

2

Lighting system

3

Light source

4

Lighting optics

5

Object field

6

Object level

7

Reticle

8

Reticle holder

9

Reticle displacement drive

10

Projection optics

11

Image field

12

Image plane

13

Wafer

14

Wafer holder

15

Wafer relocation drive

16

Illumination radiation

17

collector

18

Intermediate focal plane

19

Deflecting mirror

20

first faceted mirror

21

first facet

22

second facet mirror

23

second facet

100

Control device

110

Control unit

120

Control unit

130

Investigation facility

140

second control unit

150

Voltage measuring unit

160

Current measuring unit

170

Signal generator

181

Summation point

182

Summation point

190

Converter unit

200

Actuator

300

optical system

310

optical element

A

Control voltage

ΔI

Current change

ΔV

Voltage change

E

Adjustment signal for adjusting the position of the optical element

I

Measuring current

i

time-dependent current of the actuator

K

Correction signal

M1

Mirror

M2

Mirror

M3

Mirror

M4

Mirror

M5

Mirror

M6

Mirror

P

Target position signal

Q

charge

R

Control loop

S

Control signal

S1

Process step

S2

Process step

SHOULD

Target position

U

Measuring voltage

u

time-dependent voltage of the actuator

Y

Excitation signal

Z

Impedance

QUOTES INCLUDED IN THE DESCRIPTION

This list of documents listed by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions.

Cited patent literature

• EN 102022203255 [0026]
• EN 102022203257 [0026]
• DE 102008009600 A1 [0050, 0054]
• US 2006/0132747 A1 [0052]
• EP 1614008 B1 [0052]
• US6573978 [0052]
• DE 102017220586 A1 [0057]
• US 2018/0074303 A1 [0071]

Claims (15)

Control device (100) for controlling an actuator (200) for actuating an optical element (310) of an optical system (300), with a control unit (110) which is designed to provide a control voltage (A) for controlling the actuator (200) depending on a provided control signal (S), and a control unit (120) which is designed to provide the control signal (S) depending on a target position signal (P) for setting a position of the optical element (310) and a correction signal (K) dependent on a determined impedance (Z) of the actuator (200). Control device according to Claim 1 , wherein the control device (100) has a determination device (130) coupled to the actuator (200) for determining the impedance (Z) of the actuator (200) which varies over time. Control device according to Claim 2 , wherein the control unit (120), the drive unit (110), the actuator (200) and the detection device (130) form a control loop (R). Control device according to one of the Claims 1 until 3 , wherein the determination device (130) is configured to provide the correction signal (K) such that it is proportional, in particular directly proportional, to the determined impedance (Z) of the actuator (200). Control device according to one of the Claims 1 until 4 , further comprising: a voltage measuring unit (150) coupled between the actuator (200) and the determination device (130), which is configured to provide a measuring voltage (U) which is indicative of a time-dependent voltage (u) of the actuator (200), and a current measuring unit (160) coupled between the actuator (200) and the determination device (130), which is configured to provide a measuring current (I) which is indicative of a time-dependent current (i) of the actuator (200). Control device according to Claim 5 , wherein the determination device (130) is coupled to the voltage measuring unit (150) and the current measuring unit (160) and is configured to determine the impedance (Z) of the actuator (200) as a function of the provided measuring voltage (U) and the provided measuring current (I). Control device according to Claim 6 , further comprising: a second control unit (140) coupled to the determination device (130) and configured to provide the correction signal (K) based on the impedance (Z) determined by the determination device (130). Control device according to one of the Claims 1 until 7 , further comprising: a signal generator (170) for providing an excitation signal (Y) suitable for measuring the impedance (Z) of the actuator (200), and a summation point (181) which is configured to add the control signal (S) provided by the control unit (120) and the excitation signal (Y) provided by the signal generator (170), wherein the control unit (110) has an amplifier circuit, in particular a differential amplifier, which is configured to receive the control signal (S) and the excitation signal (Y) from the summation point (181), to amplify them and, depending thereon, to provide the control voltage (A) to the actuator (200) on the output side. Control device according to Claim 8 , wherein the control unit (20), the summation point (181), the control unit (110), the actuator (200), the parallel connection of the voltage measuring unit (150) and the current measuring unit (160), the determination device (130) and the second control unit (140) form a control loop (R). Control device according to Claim 9 , wherein the control circuit (R) forms a charge amplifier. Control device according to one of the Claims 1 until 10 , wherein the determination device (130) is configured to determine the capacitance of the actuator (200) as part of the impedance (Z) of the actuator (200), wherein the control unit (120) is configured to provide the control signal (S) as a function of the desired position signal (P) for adjusting the position of the optical element (310) and a correction signal (K) dependent on the determined capacitance of the actuator (200). Optical system (300) with a number of actuatable optical elements (310), wherein each of the actuatable optical elements (310) of the number is assigned an actuator (200), wherein each actuator (200) has a control device (100) for controlling the actuator (200) according to one of the Claims 1 until 11 is assigned to. Optical system according to Claim 12 , wherein the optical system (300) is designed as an illumination optics (4) or as a projection optics (10) of a lithography system (1). Lithography system (1) with an optical system (300) according to Claim 12 or 13 . Method for controlling an actuator (200) for actuating an optical element (310) of an optical system (300) using a control unit (110) which controls the actuator (200) by means of a control voltage (A), comprising: Generating (S1) a control signal (S) as a function of a target position signal (P) for setting a position of the optical element (310) and a correction signal (K) dependent on a determined impedance (Z) of the actuator (200), and Providing (S2) the control voltage (A) by the control unit (110) as a function of the generated control signal (S).

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