Damping assembly for damping vibrations of an element

Abstract

The invention relates to a damping assembly for damping vibrations of an element (101, 201, 301, 401), in particular in a system for microlithography, comprising an absorber mass (105, 205, 305, 405); a first component (113, 213, 313, 413) which provides a spring functionality and a damping functionality and, together with the absorber mass, forms a first vibration absorber stage; a second component (123, 223, 323, 423) which provides a spring functionality and a damping functionality and, together with the absorber mass, forms a second vibration absorber stage; and at least one support structure (150, 250, 350, 450) via which the second component is mechanically coupled to the first component.

Description

[0001]

[0002] Damping arrangement for vibration damping

[0003] of an element

[0004] The present application claims priority over German patent application DE 10 2025 111 662.8, filed on March 26, 2025. The content of this DE application is incorporated into the present application text by reference.

[0005] BACKGROUND OF THE INVENTION

[0006] Field of invention

[0007] The invention relates to a damping arrangement for vibration damping of an element, especially in a system for microlithography.

[0008] State of the art

[0009] Microlithography is used to manufacture microstructured components, such as integrated circuits or LCDs. The microlithography process is carried out in a so-called projection exposure system, which includes an illumination unit and a projection lens. The image of a mask (= reticulum) illuminated by the illumination unit is projected by the projection lens onto a substrate (e.g., a silicon wafer) coated with a photosensitive layer (photoresist) and positioned in the image plane of the projection lens, in order to transfer the mask structure onto the photosensitive coating of the substrate. In a system suitable for EUV (i.e.,In projection exposure systems designed for electromagnetic radiation with a wavelength below 30 nm, especially below 15 nm, mirrors are used as optical components for the imaging process due to the lack of translucent materials.

[0010] A common problem in the operation of projection imaging systems, particularly EUV systems, is that vibration-induced mechanical disturbances negatively impact the positional stability of system components (such as EUV mirrors) and the system's optical performance. Weakly damped mechanical resonances within the system lead to a local increase in the interference spectrum at the resonance frequencies, resulting in a deterioration of the positional stability of both passively mounted and actively controlled components. Furthermore, in controlled systems, resonances can lead to instability of the control loop. Since the materials permitted in EUV systems (e.g., metallic or ceramic) due to the required vacuum resistance exhibit only low intrinsic damping, additional damping measures are necessary to overcome or mitigate these problems.

[0011] Various damping concepts are known in the prior art. One well-known approach, for example, is to provide a damping effect via a so-called vibration damper (= "tuned mass damper") and the resulting energy dissipation.

[0012] Depending on the specific application scenario, there is a need to dampen different vibration modes (especially different resonant frequencies and different vibration directions). In the case of a vibration damper, this necessitates the use of several assemblies or components that are effective in different directions or resonant frequencies. In practice, this presents the further problem that the available installation space for the corresponding damping arrangement or vibration dampers is limited. Particularly when damping the vibrations of optical elements such as mirrors with comparatively large dimensions (e.g., one meter or more) and correspondingly large mass, providing efficient vibration damping while considering the installation space requirements poses a significant challenge.

[0013] For the state of the art, reference is made only by way of example to DE 10 2019 205 268 A1 and the publication G. Chen: “MULTI-STAGE TUNED MASS DAMPER”, Paper No. 1326, Eleventh World Conference in Earthquake Engineering, 1996, ISBN: 0080428223.

[0014] SUMMARY OF THE INVENTION

[0015] The object of the present invention is to provide a damping arrangement for vibration damping of an element, in particular in a system for microlithography, which enables particularly effective damping with a comparatively compact design and low installation space requirements.

[0016] This problem is solved by the damping arrangement according to the features of independent claim 1.

[0017] A damping arrangement for vibration damping of an element, particularly in a system for microlithography, comprises

[0018] - a retarder mass;

[0019] - a first component that provides a spring function and a damping function and, together with the damper mass, forms a first vibration damper stage; - a second component that provides a spring function and a damping function and, together with the damper mass, forms a second vibration damper stage; and

[0020] - at least one supporting structure via which the second component is mechanically coupled to the first component.

[0021] The invention is based in particular on the concept of realizing energy dissipation for vibration damping of an element (such as an EUV mirror) by providing a plurality of (i.e. at least two) vibration damper stages which are effective for different vibration modes to be damped, wherein these vibration damper stages each utilize one and the same damper mass.

[0022] In other words, according to the invention, a damping arrangement is created in which, on the one hand, several (i.e., at least two) components are present, each with a spring function and a damping function with respect to the respective vibration modes to be damped (in particular, respective resonance frequencies and vibration directions), but on the other hand, one and the same damper mass is used for said vibration damper stages, which is used jointly in the multi-stage design according to the invention. The use of one and the same damper mass in several vibration damper stages or for damping different vibration modes of the element to be damped results in a significant reduction of the installation space required for the damping arrangement as well as a corresponding saving in material and weight.

[0023] Insofar as the damping mass of the second vibration damper stage is identical to the damping mass of the first vibration damper stage, the damping arrangement according to the invention differs in particular from two-stage vibration dampers or a series connection of two spring-mass systems, in which damping of two different ("resonance") frequencies is achieved using multiple damping masses. According to one embodiment, the first vibration damper stage is tuned to a first vibration mode to be damped, and the second vibration damper stage is tuned to a second vibration mode to be damped. The second vibration mode can be different from the first vibration mode (without the invention being limited thereto).

[0024] According to one embodiment, the first vibration mode and the second vibration mode differ from each other with respect to their respective resonant frequencies.

[0025] According to one embodiment, the first vibration mode and the second vibration mode differ from each other with respect to their respective direction of vibration.

[0026] According to one embodiment, the tiger mass has a first mass (mi) and the supporting structure has a second mass (m2), wherein the second mass (m2) is less than one fifth, in particular less than one tenth, of the first mass (mi).

[0027] According to one embodiment, the first component and / or the second component each have a spring element providing the spring functionality and a separate damping element providing the damping functionality.

[0028] According to one embodiment, the first component and / or the second component are each designed as a one-piece component in which the spring functionality and the damping functionality are integrated.

[0029] According to one embodiment, the damping arrangement further comprises: a third component which provides a spring functionality and a damping functionality and together with a damping mass forms a third vibration damper stage; wherein the third component is mechanically coupled to the second component via a support structure.

[0030] In further embodiments, the damping arrangement according to the invention can also have more than three vibration damper stages in an analogous manner.

[0031] The invention further relates to a system, in particular for microlithography, with

[0032] - an element; and

[0033] - a damping arrangement for vibration damping of this element, wherein the damping arrangement is designed according to the features described above.

[0034] According to one embodiment, the element is an optical element, in particular a mirror. In other embodiments, the element can also be, for example, an actuator component or a support or measuring frame.

[0035] According to one embodiment, the system is an optical system, in particular a microlithographic projection exposure system.

[0036] According to one embodiment, the optical system is designed for operation at a working wavelength of less than 30 nm, in particular less than 15 nm. In other applications, the optical system can also be designed for operation in the DUV range, for example, for wavelengths less than 250 nm, in particular less than 200 nm.

[0037] Further embodiments of the invention can be found in the description and the dependent claims. The invention is explained in more detail below with reference to exemplary embodiments shown in the accompanying figures.

[0038] BRIEF DESCRIPTION OF THE DRAWINGS

[0039] They show:

[0040] Figure 1 is a schematic representation to illustrate the basic structure and function of a damping arrangement according to the invention in an exemplary embodiment;

[0041] Figures 2-4 are schematic representations to illustrate further embodiments of a damping arrangement according to the invention; and

[0042] Figure 5 is a schematic representation to illustrate the possible setup of a microlithographic projection exposure system designed for operation in the EUV.

[0043] DETAILED DESCRIPTION OF PREFERRED EXECUTION FORMS

[0044] In the following, with reference to Fig. 1, a damping arrangement according to a first embodiment of the invention will first be explained. The damping arrangement according to Fig. 1 serves to dissipate vibrational energy of an element in a system, which may in particular be an optical element in a microlithographic projection exposure system.

[0045] In the application examples described below, the element to be damped with respect to vibrations (indicated in Fig. 1 and designated "101") is a mirror which forms an oscillating mass-spring system with a predetermined resonant frequency relative to a supporting structure. However, the invention is not limited to this. In other applications, the element to be damped with respect to vibrations can also be, for example, any structural element, such as a support or measuring frame, an actuator component of an actuator used to actuate an optical element, or another element altogether.

[0046] The embodiments described below with reference to Figs. 1 to 4 have in common that, starting from the known principle of the vibration damper and the energy dissipation and associated damping effect caused by it, a damping arrangement is provided in a multi-stage design in which only a single damper mass is used for several (i.e. at least two) vibration damper stages.

[0047] As a result, a particularly compact design is implemented in each case, in which a single damping mass is used to achieve damping of different frequencies in several directions in the respective setup (where, in particular, the respective different frequencies can belong to different directions of movement).

[0048] Referring to Fig. 1, for example, the aforementioned shared damping mass is labelled “105”.

[0049] Furthermore, the embodiments described below have in common that each of these vibration damper stages comprises a component with a spring function and a damping function, wherein the components in question are mechanically coupled to one another via a supporting structure, and wherein the respective vibration damper stages are formed from said components together with one and the same damper mass. As will be explained in more detail below, the spring function and the damping function can be integrated into one and the same component or implemented in separate elements.

[0050] The damping arrangement according to Fig. 1 comprises two vibration damper stages. The first vibration damper stage has a first component 113 with spring and damping functionality, and the second vibration damper stage has a second component 123 with spring and damping functionality. While the invention is not limited to this, the spring functionality and the damping functionality are separated in each case, such that the first and second damping components each have a spring element 111 or 121 providing the spring functionality and a damping element 112 or 122 providing the damping functionality. In further embodiments, these functionalities (as illustrated below with reference to Figs. 2 and 3) can also be integrated into a single component.

[0051] The term "150" designates a support structure used to mechanically couple components of different vibration damper stages. The mass m² of this support structure 150 is significantly smaller than the mass mi of the damper mass 105, with the ratio mi / m² being at least 5, and more specifically, at least 10. Suitable materials for the support structure 150 include, for example, aluminum (Al) or any other lightweight metal. Ideally, the support structure 150 provides the stiffest possible construction with the lowest possible mass m² to couple the spring or damping elements of different vibration damper stages.

[0052] The vibration damping stages of the damping arrangement according to Fig. 1 act on different vibration modes of the element 101 to be damped. In the specific embodiment (though the invention is not limited to this), the spring element 111 of the first component 113 in the first vibration damping stage is relatively soft in the x and z directions, and thus vibration-damping (and correspondingly tuned to the vibration mode to be damped) in the y direction, while exhibiting high stiffness in the x and z directions. In contrast, the spring element 121 of the second component 123 in the second vibration damping stage is relatively stiff in the x direction and soft, or vibration-damping (and correspondingly tuned to the vibration mode to be damped) in the y and z directions. The aforementioned directions can also be reversed or selected in another suitable manner in further embodiments.

[0053] Fig. 2 shows another possible embodiment of a damping arrangement according to the invention, wherein, compared to Fig. 1, analogous or essentially functionally identical components are designated with reference numerals increased by 100. The embodiment of Fig. 2 differs from that of Fig. 1 in that the respective spring and damping functionalities of the components 213 and 223 present in the vibration damper stages are each integrated into one and the same component.

[0054] Fig. 3 shows another possible embodiment of a damping arrangement according to the invention, wherein components analogous to or essentially functionally identical to those in Fig. 2 are designated with reference numerals increased by 100. The embodiment of Fig. 3 differs from that of Fig.

[0055] 2 in particular by the fact that in the first vibration damper stage the corresponding component (in addition to the damping functionality) provides the spring functionality in such a way as a compliance or softness or damping effect here with regard to the rotational degree of freedom R z (i.e., rotation about the z-axis) is given, with high stiffness in all other degrees of freedom.

[0056] In further embodiments, the compliance, softness, or damping effect in the respective vibration damper stage can also be adjusted with respect to the rotational degree of freedom R. x (i.e., rotation about the x-axis) or with respect to the rotational degree of freedom R y(i.e., rotation about the y-axis). Furthermore, in a damping arrangement according to the invention, any suitable combination with the respective configurations of the vibration damper stages of other embodiments (e.g., according to Fig. 1, Fig. 2, and Fig. 4) or a suitable combination of these embodiments with each other is also possible.

[0057] Fig. 4 shows another possible embodiment of a damping arrangement according to the invention, wherein, compared to Fig. 1, analogous or essentially functionally identical components are designated with reference numerals increased by "300". The embodiment according to Fig. 4 differs from that of Fig. 1 in that, in addition to the first and second vibration damper stages, a third vibration damper stage is provided. For this purpose, according to Fig. 4, a third component 433 (which in turn comprises a spring element 431 and a damping element 432) is provided and mechanically coupled to the second component 423 via a support structure 451. The mass m3 of the support structure 451 (as well as the mass m2 of the support structure 450) is significantly less than the mass mi of the damper mass 405, whereby the corresponding ratio mi / ms can again be, by way of example, at least 5, in particular at least 10.

[0058] According to the embodiment of Fig. 4, in the second vibration damper stage, the second component 423 or the associated spring element 421 is soft and vibration-damping (and appropriately tuned to the vibration mode to be damped) in the z-direction and comparatively stiff in all other directions or degrees of freedom, whereas in the third vibration damper stage, the component 433 or the associated spring element 431 is soft and vibration-damping (and appropriately tuned to the vibration mode to be damped) in the x-direction and comparatively stiff in all other directions or degrees of freedom.

[0059] The invention is not limited to a maximum of three vibration damper stages, so that in further embodiments, additional vibration damper stages can be provided analogously and mechanically coupled via a corresponding support component. According to Fig. 5, the projection exposure system 501 has a lighting device 502 and a projection lens 510. The lighting device 502 serves to illuminate an object field 505 in an object plane 506 with radiation from a radiation source 503 via a lighting optic 504. A reticule 507 arranged in the object field 505 is exposed. The reticule 507 is held by a reticule holder 508. The reticule holder 508 can be displaced, in particular in a scanning direction, via a reticule displacement drive 509. A Cartesian xyz coordinate system is shown in Fig. 5 for illustrative purposes. The x-direction runs perpendicular to the plane of the drawing.The y-direction runs horizontally and the z-direction runs vertically. The scan direction in Fig. 5 runs along the y-direction. The z-direction runs perpendicular to the object plane 506.

[0060] The projection lens 510 serves to image the object field 505 onto an image field 511 in an image plane 512. A structure on the reticulum 507 is imaged onto a light-sensitive layer of a wafer 513 located in the image field 511 in the image plane 512. The wafer 513 is held by a wafer holder 514. The wafer holder 514 can be moved, particularly along the y-direction, via a wafer transfer drive 515. The movement of the reticulum 507 via the reticulum transfer drive 509 and of the wafer 513 via the wafer transfer drive 515 can be synchronized.

[0061] The radiation source 503 is an EUV radiation source. Specifically, the radiation source 503 emits EUV radiation, which is also referred to as useful radiation or illumination radiation. This useful radiation has a wavelength in the range between 5 nm and 30 nm. The radiation source 503 could be, for example, a plasma source, a synchrotron-based radiation source, or a free-electron laser (FEL). The illumination radiation 516, emanating from the radiation source 503, is focused by a collector 517 and propagated through an intermediate focus in an intermediate focal plane 518 into the illumination optics 504. The illumination optics 504 has a deflecting mirror 519 and, downstream in the beam path, a first faceted mirror 520 (with schematically indicated facets 521) and a second faceted mirror 522 (with schematically indicated facets 523).

[0062] The projection lens 510 has a plurality of mirrors Mi (i = 1, 2, ...), which are numbered according to their arrangement in the beam path of the projection exposure unit 501. In the example shown in Fig. 5, the projection lens 510 has six mirrors M1 to M6. Alternatives with four, eight, ten, twelve, or any other number of mirrors Mi are also possible. The penultimate mirror M5 and the last mirror M6 each have an aperture for the illumination radiation 516. The projection lens 510 is a double-obscured optical system. The projection lens 510 has an image-side numerical aperture, which, by way of example, can be larger than 0.3, and in particular larger than 0.5, and furthermore, in particular larger than 0.6.

[0063] Even though the invention has been described with reference to specific embodiments, numerous variations and alternative embodiments are apparent to the person skilled in the art, for example, through the combination and / or exchange of features of individual embodiments. Accordingly, it is understood to the person skilled in the art that such variations and alternative embodiments are included in the present invention, and that the scope of the invention is limited only to the extent of the appended claims and their equivalents.

Claims

Patent claims 1. Damping arrangement for vibration damping of an element (101 , 201 , 301 , 401 ), in particular in a system for microlithography, comprising: • a retarder mass (105, 205, 305, 405); • a first component (113, 213, 313, 413) which provides a spring functionality and a damping functionality and together with the damper mass (105, 205, 305, 405) forms a first vibration damper stage; • a second component (123, 223, 323, 423) which provides a spring function and a damping function and, together with the damper mass (105, 205, 305, 405), forms a second vibration damper stage; and • at least one supporting structure (150, 250, 350, 450) via which the second component (123, 223, 323, 423) is mechanically coupled to the first component (113, 213, 313, 413).

2. Damping arrangement according to claim 1, characterized in that the first vibration damper stage is tuned to a first vibration mode to be damped and the second vibration damper stage is tuned to a second vibration mode to be damped.

3. Damping arrangement according to claim 2, characterized in that the second vibration mode is different from the first vibration mode.

4. Damping arrangement according to claim 3, characterized in that the first vibration mode and the second vibration mode differ from each other with respect to their respective resonance frequencies.

5. Damping arrangement according to claim 3 or 4, characterized in that the first vibration mode and the second vibration mode differ from each other with respect to the respective direction of vibration.

6. Damping arrangement according to one of the preceding claims, characterized in that the tiger mass (105, 205, 305, 405) has a first mass (mi) and the supporting structure (150, 250, 350, 450) has a second mass (m2), wherein the second mass (m2) is less than one fifth, in particular less than one tenth, of the first mass (mi).

7. Damping arrangement according to one of the preceding claims, characterized in that the first component (113, 413) and / or the second component (413, 423) each comprise a spring element (111, 121, 411, 421) providing the spring functionality and a separate damping element (112, 412, 122, 422) providing the damping functionality.

8. Damping arrangement according to one of the preceding claims, characterized in that the first component (213, 313, 323) and / or the second component (213, 223, 313, 323) are each designed as a one-piece component in which the spring functionality and the damping functionality are integrated.

9. Damping arrangement according to one of the preceding claims, characterized in that it further comprises: • a third component (433) which provides a spring functionality and a damping functionality and together with the damper mass (405) forms a third vibration damper stage; • wherein the third component (433) is mechanically coupled to the second component (423) via a supporting structure (451).

10. System, especially for microlithography, with an element (101 , 201 , 301 , 401 ); and a damping arrangement for vibration damping of this16 Elements (101 , 201 , 301 , 401 ) wherein the damping arrangement is configured according to one of the preceding claims.

11. System according to claim 10, characterized in that the element (101 , 201 , 301, 401) is an optical element, in particular a mirror.

12. System according to claim 10, characterized in that the element is an actuator component.

13. System according to claim 10, characterized in that the element is a support frame or a measuring frame.

14. System according to one of claims 10 to 13, characterized in that the system is an optical system, in particular a microlithographic projection exposure system.

15. System according to claim 14, characterized in that this optical system is designed for operation at a working wavelength of less than 250 nm, in particular less than 200 nm.

16. System according to claim 15, characterized in that this optical system is designed for operation at a working wavelength of less than 30 nm, in particular less than 15 nm.

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