DE102024201167A1 - OPTICAL SYSTEM, LITHOGRAPHY DEVICE AND PROCESS - Google Patents

Abstract

An optical system (100) for adapting vibration properties of a support structure (103, 110, 112) of a lithography system (1), comprising a component (101, 102), the support structure (103, 110, 112) for supporting the component (101, 102), at least one additional absorber mass (128), wherein the at least one additional absorber mass (128) is attached to or in an environment of the support structure (103, 110, 112) in order to adapt and/or manipulate the vibration properties of the support structure (103, 110, 112).

Description

The present invention relates to an optical system, a lithography system with such an optical system and a method for adapting vibration properties of a support structure of such a lithography 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 EUV lithography system, e.g. as a result of thermal influences, can be compensated.

Effects inside and outside the EUV lithography system can cause vibrations. These can have a negative impact on the microlithography process in various ways: On the one hand, the vibrations 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 vibration-critical optical elements, such as mirrors, from vibrations (so-called vibration isolation). In projection optics (POB) of EUV lithography systems, decoupling stages are used to dampen vibrations in order to filter out excitations from external disturbances and thus reduce the movements of the supporting structures and thus of the critical components. Similar problems also occur in the context of DUV systems.

A critical problem that arises in this context concerns the influence of the critical frequencies of optical elements and/or load-bearing components by various factors that occur in the design and operation of EUV and DUV systems.

One of the main problems is the interaction of the critical frequencies of the optical elements with the attachments of the EUV or DUV systems. These frequencies are essential for maintaining optical performance and accuracy. Influencing them can lead to a significant deterioration in image quality or even to a total failure of the optical components. A variety of factors lead to fluctuations in these critical frequencies, which complicates the design and operation of these highly specialized systems.

Factors that lead to a change in the critical frequencies include process fluctuations within the EUV or DUV system. These can occur due to temperature fluctuations, mechanical vibrations or other environmental variables. Material properties also play a crucial role. Fluctuations in the elastic modulus (E-modulus) or the mass of the materials used can also lead to undesirable changes in the vibration properties of the optical elements and/or the supporting components.

In addition, the assembly steps and the associated manufacturing tolerances as well as the changing contact stiffnesses are important. These factors can lead to the frequencies achieved in the final assembly deviating from those originally planned in the design phase. Finally, the limitations of the simulation models, such as the simplified geometry in the finite element method (FEM) compared to reality, also contribute to the fact that 100% protection against these frequency-critical changes is not possible.

This complexity represents a significant challenge, as any deviation from the specified frequencies can affect the performance of EUV and DUV systems. Therefore, a solution is required that allows precise control and adjustment of the critical frequencies to ensure the performance and reliability of these sophisticated optical systems.

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

Accordingly, an optical system for adapting vibration properties of a support structure of an EUV and/or DUV lithography system is proposed, comprising a component, a support structure for supporting the component, at least one additional absorber mass, wherein the at least one additional absorber mass, which can be attached subsequently or attached in a retrofit or can be selected or adjusted subsequently, is attached to or in an environment of the support structure in order to adapt and/or manipulate the vibration properties and/or a center of gravity position of the support structure, in particular subsequently or in a retrofit.

The optical system is designed to adapt vibration properties of the support structure specifically for EUV (extreme ultraviolet) and/or DUV (deep ultraviolet) lithography systems. The system is preferably intended for optical applications, especially in lithography. The support structure is designed to support one or more components. The at least one damper mass serves to influence the vibration properties of the support structure. The damper mass can preferably be attached or adapted subsequently, i.e. after the initial installation of the support structure, for example during a retrofit or during maintenance of the lithography system. This enables the vibration properties of the support structure to be flexibly adapted to changed conditions or requirements. The main function of the damper mass is to adapt and manipulate the vibration properties and/or the center of gravity of the support structure. This is particularly important in lithography, where vibrations and oscillations can affect the quality of production. The possibility of a retrofit describes a subsequent upgrade or modification of the existing optical system with the damping mass, which increases the flexibility and/or durability and/or accuracy of the lithography system. Overall, the optical system makes it possible to improve the precision and stability of EUV and DUV lithography systems through an adaptable, retrofittable component for damping vibrations.

When designing the components of the optical system, care is always taken to ensure that critical, particularly nominal, natural frequencies of components, especially load-bearing components, are not affected by vibration excitations from outside or inside the lithography system. However, as already mentioned at the beginning, fluctuations in the lithography process, during assembly of the components of the lithography system, material properties and external influences lead to fluctuations in these natural frequencies. For example, the E-modulus of the material from which a support structure is made can affect its natural frequency. For example, E-modulus-related fluctuations of greater than 10 Hz can occur. A density fluctuation in the material of the support structure can also affect its absolute mass. Manufacturing tolerances during manufacture of the support structure or other components of the optical system can also have a negative effect on natural frequencies. For example, the flatness or surface roughness of a contact surface between the support structure and the component and/or between the support structure and a connection component can have a negative effect on the natural frequency. For example, fluctuations in contact pressure and the resulting preload force can occur. Holding chambers, their positioning and/or their preload force can also have a negative effect on the natural frequency(s) of the supporting structure. Finally, the limitations of the simulation models, such as the simplified geometry and/or idealized conditions in the finite element simulation (FEM) compared to reality, also mean that 100% protection against frequency-critical changes is not possible. Simulation inaccuracies can also lead to deviations of more than 10%. Therefore, despite thorough design, 100% protection against the absence of resonance is not possible.

However, the optical system in question makes it possible to subsequently change or manipulate the vibration properties of the support structure in order to compensate for deviations from natural frequencies, for example. By attaching the additional damper mass, it is possible to adjust the total mass of the support structure to a nominal value in order to reduce the natural frequency fluctuations. The additional damper mass also enables the center of gravity to be subsequently adjusted. The natural modes of the support structure can also be improved or reduced by attaching at least one damper mass.

It is understood that the optical system can have a vibration decoupling unit that is designed to decouple the component from a vibration of the support structure. Such a vibration decoupling unit can have one or more spring elements and one or more decoupling masses. The vibration decoupling unit can be designed in one or more stages.

According to one embodiment, the at least one additional absorber mass for manipulating a center of gravity position of the support structure is distributed on the support structure or in the environment of the support structure or divided into several parts.

Another purpose of the absorber mass in this embodiment is to manipulate the center of gravity of the support structure. This means that the absorber mass is used to change the center of mass of the support structure, which in turn affects its stability and/or behavior under different conditions. The absorber mass is attached either directly to the support structure or in its immediate vicinity. The term "in the immediate vicinity" means that the absorber mass is in direct or indirect contact with the support structure. It may be possible for an attachment or intermediate component to be arranged between the absorber mass and the support structure. This enables flexible handling of the positioning of the absorber mass in order to achieve an optimal effect on the center of gravity. The absorber mass is either distributed or divided into several parts. This distribution or segmentation enables finer tuning and more specific adjustment of the center of gravity by distributing the mass over different areas of the support structure or its surroundings. The ability to distribute or divide the absorber mass allows the optical system to be adapted to different requirements and operating conditions. Since the center of gravity position directly influences the dynamic properties of a structure, this embodiment enables precise vibration control, which is particularly important in highly sensitive applications such as lithography.

According to a further embodiment, the at least one absorber mass is arranged axially aligned with at least one center of gravity axis of the support structure.

Alternatively or additionally (i.e., and/or), the at least one absorber mass can also be arranged outside the at least one center of gravity axis of the support structure in order to actively change and/or manipulate the center of gravity position at least with regard to a spatial direction and/or orientation.

The absorber mass can be arranged in line with at least one center of gravity axis of the supporting structure. This means that the absorber mass is placed along an imaginary line that runs through the center of gravity of the supporting structure. This aims to influence the vibration and stability properties of the supporting structure along this specific axis. Additionally, or as an alternative, the absorber mass can also be arranged outside the center of gravity axis of the supporting structure. This offers additional flexibility in the design of the system in order to adapt the center of gravity position and associated properties of the supporting structure. The arrangement of the absorber mass - both in line with the axis and outside the center of gravity axis - aims to actively change or manipulate the center of gravity position of the supporting structure. This describes an influence on the dynamic properties of the supporting structure, such as its balance or alignment. The change or manipulation of the center of gravity position can refer to a specific spatial direction and/or alignment. This means that the arrangement of the absorber mass can be used specifically to optimize the supporting structure in relation to various spatial dimensions. The ability to position the damper mass both in line with the axis and outside the center of gravity axis enables flexible and precise control over the vibration characteristics and stability of the supporting structure.

According to a further embodiment, a location and/or position of the at least one absorber mass on the support structure or in the vicinity of the support structure is determined by a modal analysis.

A modal analysis is preferably a method used in structural dynamics to determine the natural frequencies, damping properties and/or mode shapes (vibration shapes) of a structure. This allows the position of the absorber mass to be determined based on a detailed study of the vibration properties of the supporting structure. The exact positioning of the absorber mass(es) is done based on the results of the modal analysis. This means that the position(s) of the mass(es) are specifically chosen to achieve optimal effects in terms of vibration reduction or stabilization of the supporting structure. The absorber mass can be attached directly to the supporting structure or close to it. This offers flexibility in the implementation of the absorber mass to influence the vibration properties of the supporting structure. By using modal analysis to position When optimizing the damper mass, the focus is on precise vibration control and improving the stability of the supporting structure.

According to a further embodiment, the at least one absorber mass is attached at a location accessible from outside the lithography system.

The absorber mass is attached to one or more locations that are accessible from outside the lithography system. The absorber mass is therefore positioned so that it can be reached from outside the system and, if necessary, maintained or adjusted.

According to a further embodiment, the support structure has a support structure and/or a structural component and/or a housing component and/or a housing profile and/or a carrier profile and/or a sensor frame and/or a support part frame and/or a support frame for supporting the optical element and/or the sensor of a lithography system.

Such support structures of a lithography system preferably serve to hold various components of the lithography system and/or to position them relative to one another and/or to mount them so that they can move. In principle, the support structure can also be a bearing connected to the component and/or an actuator and/or a sensor and/or a heat source and/or heat sink and/or a projection lens. Such a support structure preferably has a predetermined rigidity and/or stability in order to enable a positioning, in particular a precise one, and/or movement and/or mounting and/or holding of a system component that is in contact with and/or connected to the support structure, such as the component. The support structure can be, for example, a base plate and/or a scaffold and/or a frame and/or a machine table and/or an arm and/or a component carrier and/or a support and/or another holder, which serves, for example, to hold and/or position the various system parts, such as a vacuum chamber, a gas supply unit, of the lithography system. The support structure can be, for example, a wafer stage or a wafer table. The sensor frame can be provided to hold and/or mount the sensor, preferably in a vibration-isolated manner from an environment. The support part frame and/or the support frame is preferably designed to bear a weight and/or absorb external forces that occur during operation of the lithography system. The support part frame and/or the support frame preferably mounts and/or holds the respective optical element and/or the respective sensor in a predetermined, in particular fixed, position relative to the support part frame and/or the support frame. Particularly preferably, a position and/or orientation of the support part frame and/or the support frame in the lithography system can be changed and/or controlled by at least one actuator.

According to a further embodiment, the component has an optical element, in particular a mirror and/or a lens and/or an aperture, and/or a sensor.

Particularly preferably, the component is a component of the lithography system that is to be decoupled from external or internal lithography system vibrations, since, for example, highly precise positioning and/or alignment and/or movement of the component is required to ensure optimal functioning of the lithography system, which could be disrupted by external or internal system vibrations. The sensor can, for example, have a position measuring sensor and/or an acceleration sensor and/or a pressure sensor and/or a force sensor and/or a light sensor and/or another sensor element.

The component has in particular six degrees of freedom, preferably three translational degrees of freedom, each along the x-direction, the y-direction and the z-direction, as well as three rotational degrees of freedom each around the x-direction, the y-direction and the z-direction. This means that a position and an orientation of the component can be determined or described using the six degrees of freedom. The “position” of the component is to be understood in particular as its coordinates or the coordinates of a measuring point provided on the component with respect to the x-direction, the y-direction and the z-direction. The “orientation” of the component is to be understood in particular as its tilting with respect to the three spatial directions. This means that the component can be tilted around the x-direction, the y-direction and/or the z-direction. This results in the six degrees of freedom for the position and orientation of the component. A “location” of the component includes both its position and its orientation.

The type of connection by which the at least one additional damper mass is attached, connected or fastened to the supporting structure or in the vicinity of the supporting structure is basically arbitrary. The type of connection is preferably a detachable connection in order to enable, for example, the exchange of the to enable at least one additional damper mass in the event of maintenance and/or repair and/or retrofitting. In principle, the at least one additional damper mass can also be attached non-detachably to the support structure or in the vicinity of the support structure. The at least one additional damper mass can be arranged on the support structure directly or indirectly, ie with the interposition of another part or another component.

Furthermore, a lithography system with at least one such optical system is proposed.

The lithography system can have several optical systems so that several components of the lithography system can be decoupled from external vibrations in the manner described here. The optical system is preferably a projection optics of the lithography system. However, the optical system can also be an illumination system. The lithography 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 lithography 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.

Furthermore, a method for adapting vibration properties of a support structure of a lithography system is proposed. The method has the following steps: providing a component, the support structure for supporting the component, and at least one additional damper mass; and attaching the at least one additional damper mass to or in an area surrounding the support structure in order to adapt and/or manipulate the vibration properties and/or a center of gravity position of the support structure, in particular subsequently or in a retrofit.

The process steps mentioned above do not have to be carried out in the order described, but can also be carried out in a different order. Individual components of the optical system can also already be prefabricated.

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.

The embodiments and features described for the optical system apply to the proposed lithography system and the proposed method accordingly and vice versa.

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 Lithographieanlage für die EUV-Projektionslithographie;
• 2 zeigt schematisch ein optisches System gemäß einer ersten Ausführungsform;
• 3 zeigt schematisch ein optisches System gemäß einer zweiten Ausführungsform;
• 4 zeigt schematisch ein optisches System gemäß einer dritten Ausführungsform; und
• 5 zeigt ein Flussdiagramm eines Verfahrens zur Anpassung von Schwingungseigenschaften einer Tragstruktur einer Lithographieanlage.

Further advantageous embodiments and aspects of the invention are the subject of the dependent embodiments of the invention and those 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 lithography system for EUV projection lithography;
• 2 schematically shows an optical system according to a first embodiment;
• 3 schematically shows an optical system according to a second embodiment;
• 4 shows schematically an optical system according to a third embodiment; and
• 5 shows a flow chart of a method for adapting vibration properties of a support structure of a lithography 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 lithography system 1 (projection exposure system), in particular an EUV lithography system. An embodiment of an illumination system 2 of the lithography 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 purposes, 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 perpendicularly into the plane of the drawing. 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 lithography 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 using 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 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 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 lithography 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 0.2 and can also be greater than 0.3 and can be, for example, 0.33.

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 βx, βy in the x and y directions x, y. The two image scales βx, βy 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, 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 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 direction to the entrance pupil the projection optics 10 conjugated surface. 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 view of an optical system 100.

The optical system 100 has a component 101, which can be an optical element 102, for example an optical sensor, and a support structure 103 for supporting the component 101. The support structure 103 can have a support frame 110 (English: force frame) of the optical system 100. The support structure 103 can have a sensor frame 112 (English: sensor frame).

The support frame 110 is coupled to a fixed world 116 by means of a coupling element 114. Several coupling elements 114 of this type can be provided. The sensor frame 112 is coupled to the support frame 110 by means of a coupling element 118. Several coupling elements 118 of this type can be provided. The support frame 110 thus supports the sensor frame 112. The coupling elements 114, 118 can have springs. In the present case, a “fixed world” is understood to mean a region of the optical system 100 that is immobile with respect to the support frame 110.

As previously mentioned, the optical system 100 may comprise a plurality of components 101 or a plurality of optical elements 102, of which 2 however, only one is shown. The optical element 102 can be adjusted or aligned in six degrees of freedom using an actuator unit 120. The sensor frame 112 serves as a reference for a change in position of the optical element 102. The optical element 102 is connected to the support frame 110 via the actuator unit 120. The optical element 102 can be connected to the actuator unit 120 using a coupling element 122, which in turn is connected to the support frame 110 via a coupling element 124.

For example, a target position of the optical element 102 is maintained with the aid of a control unit 126. The control unit 126 can communicate with the actuator unit 120 for this purpose. The control unit 126 interacts with the sensor frame 112 in such a way that, for example, sensors attached to the sensor frame 112 measure the optical element 102, wherein the control unit 126 controls the actuator unit 120 based on sensor signals from these sensors in order to maintain the target position of the optical element 102.

The optical system 100 further comprises at least one additional absorber mass 128, which is used to adapt vibration properties of the respective support structure 103 of the lithography system 1. The at least one additional absorber mass 128 is attached to or in an environment of the support structure 103 in order to adapt and/or manipulate the vibration properties of the support structure 103. According to 2 a damper mass 128 is attached to the support frame 110. A further damper mass 128 is attached to the sensor frame 112. The at least one damper mass 128 is attached to a location accessible from outside the lithography system 1. A location and/or position of the at least one damper mass 128 on the respective support structure 103 or in the vicinity of the respective support structure 103 is determined by a modal analysis.

3 shows another embodiment of the optical system 100.

The component 101 or the optical element 102 is in this case a sensor that is carried or held by the sensor frame 112. The at least one damper mass 128, in this case two damper masses 128, is arranged in axial alignment with at least one center of gravity axis 130, 132 of a center of gravity S of the support structure 103 or the sensor frame 112. Furthermore, the at least one additional damper mass 128 is in this case divided into two damper masses 128, which are arranged distributed on the sensor frame 112.

4 shows another embodiment of the optical system 100.

The component 101 or the optical element 102 is in this case a sensor that is carried or held by the sensor frame 112. The at least one absorber mass 128, in this case two absorber masses 128, is arranged outside the at least one center of gravity axis 130, 132 of the support structure 103 or the sensor frame 112. Furthermore, the at least one additional absorber mass 128 is arranged distributed on the support structure 103 or the sensor frame 112 for manipulating a center of gravity position of the center of gravity S of the support structure 103 or the sensor frame 112. As can be seen from 4 As can be seen schematically, the arrangement of the absorber masses 128 shifts the position of the center of gravity S towards S'.

5 shows a flow chart of a method for adapting vibration properties the supporting structure 103, 110, 112 of the lithography system 1.

In a step S1, a component 101, 102, the support structure 103, 110, 112 for supporting the component 101, 102, and at least one additional damping mass 128 are provided.

In a step S2, the at least one additional damper mass 128 is attached to or in an environment of the support structure 103, 110, 112 in order to adapt and/or manipulate the vibration properties of the support structure 103, 110, 112.

Optionally, in a step S3, which may be included in step S2, an adjustment of the at least one additional absorber mass 128 and/or a manipulation of the center of gravity S (see 3 and 4 ) of the support structure 103, 110, 112 by positioning the at least one absorber mass 128 to optimize at least one eigenmode of the support structure 103, 110, 112.

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

REFERENCE SYMBOL LIST

1

lithography 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

optical system

101

component

102

optical element

103

supporting structure

110

supporting frame

112

sensor frame

114

coupling element

116

solid world

118

coupling element

120

actuator unit

122

coupling element

124

coupling element

126

control unit

128

absorber mass

130

center of gravity axis

132

center of gravity axis

M1

Mirror

M2

Mirror

M3

Mirror

M4

Mirror

M5

Mirror

M6

Mirror

S

focus

S'

focus

S1

process step

S2

process step

S3

process step

x

x-direction

y

y-direction

z

z-direction

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 2008 009 600 A1 [0052, 0056]
• US 2006/0132747 A1 [0054]
• EP 1 614 008 B1 [0054]
• US 6,573,978 [0054]
• DE 10 2017 220 586 A1 [0059]
• US 2018/0074303 A1 [0073]

Claims (10)

Optical system (100) for adjusting vibration properties of a support structure (103, 110, 112) of a lithography system (1), comprising a component (101, 102), the support structure (103, 110, 112) for supporting the component (101, 102), at least one additional damper mass (128), wherein the at least one additional damper mass (128) is attached to or in an environment of the support structure (103, 110, 112) in order to adjust and/or manipulate the vibration properties of the support structure (103, 110, 112). Optical system according to claim 1 , wherein the at least one additional absorber mass (128) for manipulating a center of gravity position of the support structure (103, 110, 112) is arranged distributed or divided on the support structure (103, 110, 112) or in the vicinity of the support structure (103, 110, 112). Optical system according to claim 2 , wherein the at least one absorber mass (128) is arranged axially aligned with at least one center of gravity axis (130, 132) of the support structure (103, 110, 112), and/or is arranged outside the at least one center of gravity axis (130, 132) of the support structure (103, 110, 112). Optical system according to one of the Claims 1 - 3 , wherein a location and/or position of the at least one absorber mass (128) on the support structure (103, 110, 112) or in the vicinity of the support structure (103, 110, 112) is determined by a modal analysis. Optical system according to one of the Claims 1 - 4 , wherein the at least one absorber mass (128) is attached to a location accessible from outside the lithography system (1). Optical system according to one of the Claims 1 - 5 , wherein the support structure (103, 110, 112) comprises a support structure and/or a structural component and/or a sensor frame (112) and/or a support part frame and/or a support frame for supporting an optical element (102) and/or a sensor. Optical system according to one of the Claims 1 - 6 , wherein the component (101) has an optical element (102), in particular a mirror (M1 - M6) and/or a lens and/or an aperture, and/or a sensor. Lithography system (1) with an optical system (100) according to one of the Claims 1 - 7 . Method for adapting vibration properties of a support structure (103, 110, 112) of a lithography system (1), comprising the steps: a) providing (S1) a component (101, 102), the support structure (103, 110, 112) for supporting the component (101, 102), and at least one additional damper mass (128), and b) attaching (S2) the at least one additional damper mass (128) to or in an environment of the support structure (103, 110, 112) in order to adapt and/or manipulate the vibration properties of the support structure (103, 110, 112). procedure according to claim 9 , wherein the attachment (S2) comprises adjusting (S3) the at least one additional absorber mass (128) and/or manipulating a center of gravity (S, S') of the support structure (103, 110, 112) by positioning the at least one absorber mass (128) to optimize at least one eigenmode of the support structure (103, 110, 112).

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