DE102024200534A1 - OPTICAL SYSTEM AND LITHOGRAPHY SYSTEM - Google Patents

Abstract

An optical system (200) comprising a component (202) and a vibration damper (204) for damping vibrations of the component (202), which is fastened to a surface (212) of the component (202), wherein the vibration damper (204) has a multilayer structure with several piezoelectric layers (214) and at least one damper mass (216) preferably arranged on the multilayer structure, and wherein at least one of the several piezoelectric layers (214) can be excited with an excitation frequency which includes an inherent vibration frequency of the component.

Description

The present invention relates to an optical system and a lithography system with such an optical system.

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. The image of a mask (reticle) illuminated by the illumination system is projected by the projection system onto a substrate, such as a silicon wafer, that is coated with a light-sensitive layer (photoresist) and arranged in the image plane of the projection system in order to transfer the mask structure onto the light-sensitive coating of the substrate.

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 mirrors can be attached to a support frame (force frame) and designed to be at least partially manipulable in order to enable movement of each mirror in up to six degrees of freedom and thus highly precise positioning of the mirrors relative to one another, particularly in the pm range. This means that changes in the optical properties that occur during operation of the lithography system, e.g. as a result of thermal influences, can be compensated.

Parasitic oscillations can arise from effects inside and outside the lithography system. These can have a negative impact on the microlithography process in various ways: On the one hand, the parasitic oscillations can have a direct influence on the position of a corresponding mirror and/or lens. On the other hand, they can make stable position control of the corresponding lens and/or mirror or position control with high control quality more difficult.

Accordingly, efforts are being made to isolate critical components, such as the mirrors, from the parasitic vibrations (so-called vibration isolation). DE 10 2015 210 408 A1 describes, for example, a component and a vibration damper for damping vibrations of the component. The vibration damper is attached to a surface of the component and has a piezoelectric material. The vibration damper is designed to be deformed parallel to the surface of the component in order to dampen the vibrations.

In addition, vibration dampers are known from the state of the art that are designed as spring-mass systems and are usually designed for a single fixed resonance frequency or several resonance frequencies that are close to each other. This means that these vibration dampers can no longer be adapted to changed system conditions after they have been put into use. In particular, it is not possible to subsequently change a damper frequency and/or a damper frequency width and/or a damping amplitude.

So-called p-phase materials, especially polyether-based materials, are also often used as damping materials in known vibration dampers. This group of materials is increasingly viewed critically due to negative environmental influences and its range of applications is set to be severely restricted in the coming years.

Against this background, an object of the present invention is to provide an improved optical system.

Accordingly, an optical system is proposed. The optical system has a component and a vibration damper for damping vibrations of the component. The vibration damper is attached to a surface of the component. The vibration damper has a multilayer structure with several piezoelectric layers and at least one damper mass preferably arranged on the multilayer structure. At least one of the several piezoelectric layers can be excited with an excitation frequency that includes an inherent vibration frequency of the component.

With the solution described here, vibrations of the particularly weakly damped component are preferably damped in such a way that the structural resonances and/or natural frequencies and/or natural modes of the component do not oscillate or do not oscillate so strongly. The vibration damper described here is preferably designed to be tuned to the most diverse frequencies and/or vibration shapes of the component. In this way, the vibration damper, in contrast to known vibration absorbers, can operate on a frequency range that is many times wider. frequency range. The multilayer structure with the several piezoelectric layers is attached to the weakly damped component in the stack together with the damper mass and can preferably be controlled with a high-frequency signal. If the frequency and/or the phase position of this signal is adjusted to at least one of the (natural) vibrations of the component, the vibration damper can counteract this at least one (natural) vibration of the component and thus acts as a vibration damper. The vibration damper has a simple structure, a compact design and can contribute to the comprehensive reduction of unwanted vibrations of the component.

One idea underlying the present invention is not to isolate vibrations of the component, in particular vibration modes, which are also referred to as eigenmodes, relative to a reference, for example a support, frame or support, but to dampen and/or weaken and/or smooth vibrations in the component itself. The multiple piezoelectric layers have a negligible mass in relation to the component. However, the vibration damper has an additional absorber mass. The damping is achieved in that when the component vibrates (i.e. deforms it), the vibration damper or the piezoelectric layers are also deformed due to their attachment to the component and work against it. The attachment to the component is preferably carried out in such a way that the vibration damper or the multiple piezoelectric layers introduce a force perpendicularly into the surface of the component. The plurality of piezoelectric layers are preferably each configured to be deformed perpendicular to the surface of the component for damping the vibrations of the component.

The component can preferably have an optical element, for example a lens or a mirror, and/or a bearing connected to an optical element and/or a sensor holder and/or a holding frame and/or actuators and/or sensors and/or heat source and/or heat sink and/or a projection lens.

The multilayer structure preferably comprises at least two, and thus several piezoelectric layers. The piezoelectric layers are preferably made of a piezoelectric material. The multilayer structure with the several piezoelectric layers can also be referred to as a piezo stack. The multilayer structure or the several piezoelectric layers are preferably used as an actuator for actuating the component. The vibration damper preferably has a natural frequency in the kHz range. The several piezoelectric layers can preferably each be operated in a wide frequency range of, for example, 0 - 100 kHz, 0 - 200 kHz, 0 - 500 kHz or 0 - 1 MHz, so that damping by the vibration damper in a wide frequency range, in particular dynamically controlled, is possible.

According to one embodiment, the at least one of the multiple piezoelectric layers can be excited with different excitation frequencies if the vibrations of the component have different vibration frequencies. Alternatively or additionally, the multiple piezoelectric layers can each be excited with different excitation frequencies if the component has multiple different vibration frequencies.

Each or at least some of the multiple piezoelectric layers can preferably be excited to oscillate separately by a corresponding excitation signal with a predetermined excitation frequency and/or an excitation amplitude. The respective excitation frequency preferably corresponds to at least one inverse oscillation frequency of the component. The respective excitation amplitude for the respective excitation frequency preferably corresponds to a respective antiphase oscillation and/or a respective inverse oscillation amplitude of the component. If the respective excitation frequency and excitation amplitude are superimposed and/or superposed with the respective oscillation frequency and oscillation amplitude, a substantially destructive oscillation interference preferably occurs, as a result of which the component is damped. This embodiment is particularly advantageous if the component is loaded with multiple oscillation frequencies. The multi-layer structure made up of multiple piezoelectric layers particularly preferably allows multiple (natural) frequencies of the component to be damped, although this is also possible with just one piezoelectric layer. Preferably, at least one of the layers of the multilayer structure can also be controlled to vibrate at multiple frequencies. The multilayer structure particularly preferably makes it possible to generate a larger stroke of the component for vibration compensation. Furthermore, the multilayer structure preferably makes it possible to use at least one of the layers as a sensor and at least one other of the layers as an actuator.

According to one embodiment, the absorber mass is arranged on or at the multilayer structure. The absorber mass is particularly preferably mass is glued and/or laminated to or on the multilayer structure, in particular to an uppermost layer of the multilayer structure.

The absorber mass can, for example, be a one-piece block of material. Alternatively, the absorber mass can also comprise several layers. The absorber mass can, for example, consist of several sheets that are layered on top of each other. This can be advantageous because the absorber mass can be subsequently adapted in terms of weight.

According to one embodiment, the vibration damper is glued to the surface of the component. Particularly preferably, the multiple piezoelectric layers are also glued to one another and/or laminated to one another.

The vibration damper is particularly preferably bonded to the surface of the component on an underside of the vibration damper formed by insulation, which preferably corresponds to an underside of a lowest of the several piezoelectric layers. The bonding is preferably carried out over the entire surface. In principle, other types of attachment are also conceivable.

According to one embodiment, the optical system comprises at least one vibration sensor which is designed to detect at least one component-specific vibration frequency on the basis of which the at least one of the plurality of piezoelectric layers can be excited.

With the help of the vibration sensor, a vibration frequency and/or phase and/or vibration amplitude of the vibration to be dampened, in particular the vibration frequency and/or phase and/or vibration amplitude of one or more vibration modes can be detected. For this purpose, the sensor can be designed, for example, as an acceleration sensor and/or as a gyro sensor. The vibration sensor is preferably set up to detect at least one vibration, in particular at least one vibration frequency and/or phase and/or vibration amplitude, of the component, preferably in real time and/or continuously. The vibration sensor preferably permanently detects and/or measures the vibrations of the component. The vibration sensor preferably detects the at least one vibration of the component as a sensor signal, from which the excitation signal for the excitation of the vibration damper can be derived and/or generated.

According to one embodiment, one of the plurality of piezoelectric layers is designed as the at least one vibration sensor.

This embodiment is advantageous because the vibration sensor is included in the vibration damper, in particular in the multilayer structure or stack of the multiple piezoelectric layers, and thus both the actuator vibration damping and the sensory vibration detection are combined in the vibration damper. The vibration sensor can preferably be designed as a piezo film. The vibration sensor can, for example, transmit the vibration frequency and/or phase and/or vibration amplitude of one or more vibration modes of the component as a sensor signal to a control device, which generates the excitation signal based on this. The control device is preferably designed to be low-noise so as not to generate even the smallest vibration amplitudes (in particular in the pm range) itself.

According to one embodiment, several, preferably at least two, vibration dampers are arranged at a distance from one another on the surface of the component and/or on another surface, for example a side surface and/or an end surface and/or a lateral surface, of the component in order to dampen several, preferably at least two, vibration modes of the component.

A larger number of vibration dampers attached to the component at different positions makes it possible to dampen several vibration modes, in particular with higher order natural frequencies. With the help of several vibration dampers and preferably a corresponding number of control signals, it is preferably possible to dampen different modes simultaneously and/or independently of one another. One vibration damper is preferably used per mode. The respective vibration damper is preferably attached to a position on the component where an amplitude maximum of the respective vibration prevails, so that the respective vibration can be dampened as effectively as possible. This embodiment enables multi-dimensional vibration damping of the component. For example, depending on the attachment position on the component, not only longitudinal vibrations but also transverse vibrations of the component can be dampened.

According to one embodiment, the vibration damper is arranged in a vacuum.

This means that the vibration damper is largely isolated from external influences. This can be advantageous, for example, in an EUV lithography system.

According to one embodiment, the plurality of piezoelectric layers are each formed as passive piezoelectric layers.

In principle, the multiple piezoelectric layers of the vibration damper can work actively or passively. In the first case (active variant), the piezoelectric material is controlled by a control device, for example. The electric field generated by the control device causes the piezoelectric material and thus the vibration damper to contract, so that the component is subjected to a force. In particular, the size and direction of the aforementioned at least two opposing forces can be adjusted using the control device. In the second case (passive variant), the piezoelectric material is connected to a resistor or other consumer in which the electrical energy that the piezoelectric material generates due to its deformation is converted in particular into heat. The passive variant has the advantage that electrical wiring for supplying energy and/or controlling the individual piezoelectric layers can be dispensed with.

The optical system is preferably a projection optics of the projection exposure system, in particular of a lithography 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 a further aspect, a lithography system is also provided which comprises at least one optical system as described above.

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 is also not to 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 die EUV-Projektionslithographie;
• 2A bis 2C zeigen in einer schematischen Seitenansicht jeweils ein Bauteil mit einem Schwingungsdämpfer gemäß einer Ausführungsform;
• 3 zeigt in einer schematischen Seitenansicht ein optisches System mit einem Bauteil und mit mehreren Schwingungsdämpfern gemäß einer Ausführungsform; und
• 4 zeigt perspektivisch ein optisches System mit einem Bauteil und mit mehreren Schwingungsdämpfern gemäß einer weiteren Ausführungsform.

Further advantageous embodiments and aspects of the invention are the subject of the subclaims 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;
• 2A until 2C each show a schematic side view of a component with a vibration damper according to an embodiment;
• 3 shows in a schematic side view an optical system with a component and with several vibration dampers according to an embodiment; and
• 4 shows in perspective an optical system with a component and with several vibration dampers according to another embodiment.

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 comprise 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 shown. The x-direction x runs perpendicular to the The y-direction y is horizontal and the z-direction z is vertical. The scanning direction is 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 on the one hand via the reticle displacement drive 9 and the wafer 13 on the other hand via the wafer displacement drive 15 can be synchronized with one another.

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 DE 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, see the DE 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 called 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 DE 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 forms 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 DE 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 be designed in particular to be anamorphic. It has in particular special different image scales βx, βy 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 B 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, superimposing 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 the 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.

2A shows an optical system 200 in a side view. The optical system 200 comprises a component 202, a vibration damper 204 and an optional vibration sensor 206.

According to the embodiment, the component 202 is a bending beam clamped at its opposite ends 208, 210. In principle, the component 202 can be any component of a projection exposure system 1, in particular an EUV or DUV lithography system, as for example in 1 shown. For example, the component 202 can be an optical element, in particular a lens and/or a mirror. Furthermore, the component 202 can be a bearing, an actuator, a sensor, a heat source or a heat sink. These can in turn be mechanically connected to an optical element. According to a preferred embodiment, the component 202 is part of the optical system, for example a lens, of the projection exposure system 1. For example, the component can be part of a sensor frame, which is designed to carry sensors for monitoring the mirrors M1 to M6, or of a support frame for holding the mirrors M1 to M6. There are also many other areas of application.

The vibration damper 204 is designed to dampen at least one vibration of the component 202. In principle, the vibration damper 204 can be designed to dampen any vibration of the component 202. This can in particular be vibration modes (eigenmodes), i.e. natural vibrations, of the component 202. Furthermore, the vibration damper 204 can in principle dampen bending vibrations and/or torsional vibrations and/or lateral and/or transverse vibrations of the component 202. Lateral or transverse vibrations here mean tension-compression vibrations in the component plane, i.e. vibrations without bending or torsion.

The vibration damper 204 is arranged on a surface 212 of the component 202, in particular glued to the surface 212 of the component 202. The multiple piezoelectric layers 214 are each glued to one another and/or laminated to one another. The vibration damper 204 has a multi-layer structure with multiple piezoelectric layers 214. The vibration damper 204 has at least one damper mass 216, which is preferably arranged on the multi-layer structure. In the present case, the damper mass 216 is arranged on an uppermost layer of the multiple piezoelectric layers 214 of the multi-layer structure, viewed in a z-direction. The damper mass 216 preferably corresponds to 5 to 15%, more preferably less than 10% of the vibrating mass of the component 202. The damper mass 216 can preferably be reduced depending on the amplitude. The damper mass 216 is preferably designed such that it can be adaptively adjusted to a vibration situation of the component 202. In particular, if the component 202 is arranged in a small installation space, the damper mass 216 may be reduced.

Particularly preferably, one of the piezoelectric layers 214 is designed as the vibration sensor 206, so that an arrangement of the vibration sensor 206 at a distance from the vibration damper 204 is not necessary.

Rather, the vibration sensor 206 is then integrated into the vibration damper 204 and/or encompassed by it.

At least one of the plurality of piezoelectric layers 214 can be excited with an excitation frequency that includes an oscillation frequency inherent to the component. By exciting at least one of the plurality of piezoelectric layers 214, an oscillation frequency of the component 202 can be dampened. An exemplary parasitic (i.e., not wanted per se) oscillation of the component 202 is in each case, with respect to the 2A shown rest position of the bending beam, in the 2B and 2C shown. In 2B the ends 208, 210 of the bending beam are bent against the z-direction, which results, for example, from a vibration excitation ∂A of the component 202.

The vibration sensor 206 can be configured according to 2A to 2C shown embodiment can also be arranged in an end region of the bending beam (in this case the vibration sensor 206 is not integrated into the stack). The vibration sensor 206 is designed to detect a vibration frequency and/or phase and/or the vibration amplitude ∂A in the form of a sensor signal. An expected parasitic vibration amplitude ∂A in the component 202 is preferably in the range of < 10 nm, pm, or µm. The vibration damper 204 counteracts this by applying a force +F or -F perpendicular to the surface 212 by appropriate electrical control of the layers 214.

3 shows the optical system 200 in a schematic side view according to a further embodiment. A plurality of vibration dampers 204 are arranged on the component 202. A first vibration damper 300 of the plurality of vibration dampers 204 is arranged on the surface 212 of the component 202. The vibration damper 300 is designed to dampen a first vibration, in particular a first natural frequency, of the component 202.

This is, for example, a transverse vibration with an extension direction in the y direction and an oscillation amplitude along the z direction. A second vibration damper 302 of the multiple vibration dampers 204 is arranged on a side surface 304 of the component 202. The second vibration damper 302 is designed to dampen a second vibration, in particular a second natural frequency, of the component 202. This is, for example, a longitudinal vibration with an extension direction in the y direction and an oscillation amplitude along the y direction. A respective excitation signal preferably excites a respective piezoelectric layer 214 of the respective vibration damper 204, 300, 302 to oscillate in such a way that a respective mode of the component 202 can be superimposed and thus leveled out. In particular, an inverse vibration signal is generated by the respective vibration damper 204, 300, 302 in order to dampen the respective vibration of the component 202.

4 shows the optical system 200 in a perspective view according to a further embodiment. On the component 202, which according to 4 is shown as an example as a rectangular, full-surface plate, several vibration dampers 204, 400, 402 are arranged. The vibration dampers 400, 402 are each arranged on the surface 212 of the component. The vibration dampers 400, 402 are each designed to dampen a vibration of the component in a spatial direction. The vibration damper 400 dampens a first vibration 404 that extends along the x-direction and has an amplitude in the z-direction. The vibration damper 402 dampens a second vibration 406 that extends along the y-direction and has an amplitude in the z-direction. The vibration dampers 400, 402 are arranged at a distance from one another on the surface 212 of the component 202 in order to dampen several vibration modes, for example the first vibration 404 and the second vibration 406, of the component 202.

The respective vibration damper 400, 402 receives a control signal from a control device 408, which is preferably derived from or based on at least one sensor signal generated by the vibration sensor 206 (or several vibration sensors 206).

It is also possible to design the vibration dampers 204, 400, 402 passively. This means that the energy required for the damping work is extracted from the parasitic vibration of the component 202. This energy is used to control the piezoelectric layers 214 to generate the force +F or -F.

Although the present invention has been described using exemplary embodiments, it can be modified in many ways. Particularly preferably, there is a closed control loop between the control device 408, the piezoelectric layers 214 and the vibration sensor 206. At least one of the plurality of piezoelectric layers 214 can preferably be contracted by applying a predetermined voltage that is determined by the excitation signal.

REFERENCE SYMBOL LIST

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

200

optical system

202

component

204

vibration dampers

206

vibration sensor

208

End

210

End

212

surface

214

piezoelectric layer

216

absorber mass

300

vibration dampers

302

vibration dampers

304

side surface

400

vibration dampers

402

vibration dampers

404

vibration

406

vibration

408

control device

∂A

magnitude of a vibration amplitude

+F, -F

positive or negative force

M1

Mirror

M2

Mirror

M3

Mirror

M4

Mirror

M5

Mirror

M6

Mirror

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

• DE 10 2015 210 408 A1 [0006]
• DE 10 2008 009 600 A1 [0047, 0051]
• US 2006/0132747 A1 [0049]
• EP 1 614 008 B1 [0049]
• US 6,573,978 [0049]
• DE 10 2017 220 586 A1 [0054]
• US 2018/0074303 A1 [0068]

Claims (10)

Optical system (200), comprising: a component (202); and a vibration damper (204) for damping vibrations of the component (202), which is attached to a surface (212) of the component (202), wherein the vibration damper (204) has a multilayer structure with several piezoelectric layers (214) and at least one damper mass (216) preferably arranged on the multilayer structure, wherein at least one of the several piezoelectric layers (214) can be excited with an excitation frequency that includes an inherent vibration frequency of the component. Optical system according to claim 1 , wherein in the event that the vibrations of the component (202) have different vibration frequencies, at least one of the plurality of piezoelectric layers (214) can be excited with different excitation frequencies, and/or the plurality of piezoelectric layers (214) can each be excited with different excitation frequencies. Optical system according to claim 1 or 2 , wherein the absorber mass (216) is arranged on the multi-layer structure. Optical system according to one of the Claims 1 - 3 , wherein the vibration damper (204) is glued to the surface (212) of the component (202), and wherein preferably the plurality of piezoelectric layers (214) are each glued and/or laminated to one another. Optical system according to one of the Claims 1 - 4 , wherein the optical system (200) comprises at least one vibration sensor (206) which is configured to detect at least one component-specific vibration frequency on the basis of which the at least one of the plurality of piezoelectric layers (214) can be excited. Optical system according to claim 5 , wherein one of the plurality of piezoelectric layers (214) is designed as the at least one vibration sensor (206). Optical system according to one of the Claims 1 - 6 , wherein a plurality of vibration dampers (204) are arranged at a distance from one another on the surface (212) of the component (202) and/or on a further surface (304) of the component (202) in order to dampen a plurality of vibration modes of the component (202). Optical system according to one of the Claims 1 - 7 , wherein the vibration damper (204) is arranged in a vacuum. Optical system according to one of the Claims 1 - 8 , wherein the plurality of piezoelectric layers (214) are formed as passive piezoelectric layers (214). Lithography system (1) with an optical system (200) according to one of the Claims 1 - 9 .

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