Measurement arrangement for determining position of movable part

Abstract

A measurement arrangement (10, 110, 210, 310) for determining the position of a movable component (526) in a microlithographic optical system (500) comprises: an optical resonator (26) having two resonant mirrors (28, 30) surrounding a resonant cavity (32); and a movable measuring mirror (14) assigned to the movable part and arranged within the resonant cavity for guiding measuring radiation back and forth between the resonant mirrors. The measuring mirror is arranged at a working distance (34) from one of the resonant mirrors, the resonant mirror having a curvature matching the measuring mirror such that a center (31) of the curvature is arranged on the measuring mirror or at a distance lower than 10% of the working distance from the measuring mirror.

Description

[0001] This application claims priority to German Patent Application No. 10 2023 208 513.5, filed on September 4, 2023. The entire disclosure of that patent application is incorporated herein by reference. Technical Field

[0002] The present invention relates to a measurement configuration for determining the position of a movable component in a microlithography optical system, a microlithography projection exposure apparatus, an illumination device, a projection lens, an inspection device, and a coordinate measuring device, each having at least one such measurement configuration. Background Technology

[0003] Microlithography is used to fabricate microstructured components, such as integrated circuits or liquid crystal displays (LCDs). This is implemented using a so-called projection exposure apparatus, which includes an illumination device and a projection lens. In this case, a mask image located on a master mask and illuminated by the illumination device is projected through the projection lens onto a substrate (e.g., a silicon wafer) coated with a photosensitive layer (photoresist) and disposed on the image plane of the projection lens, to transfer the mask structure onto the photosensitive coating of the substrate.

[0004] During the operation of such projection lenses, the mask and wafer typically move relative to each other during scanning. The positions of some mirrors, which are movable in all six degrees of freedom, must be set and maintained with high precision relative to each other and relative to the mask and / or wafer to avoid or at least reduce aberrations and associated defects in the imaging results. This positioning may require very high precision, especially in EUV lithography.

[0005] Various methods for measuring the position of individual lens mirrors, wafers or wafer stages, and mask master planes are known in the prior art. In addition to interferometric measurement equipment, frequency-based position measurement using optical resonators is also known herein.

[0006] According to US11,274,914B2 Figure 3The structure used for this purpose includes a resonator with two resonant mirrors, a retroreflector in the form of a triple mirror, and a plane mirror serving as a measurement target on which the beam path is folded. The resonant mirrors and triple mirrors represent a measuring head housed in a projection lens within a projection exposure apparatus, and the measurement target is secured to the element whose position is to be measured within the projection exposure apparatus. The actual distance measuring facility includes a radiation source that can be tuned about its optical frequency, and it generates input-coupled radiation through a beam splitter and input-coupled to the optical resonator. In this case, the radiation source is controlled by a coupling device such that the optical frequency of the radiation source is tuned to the resonant frequency of the optical resonator and thus coupled to said resonant frequency. The input-coupled radiation output coupled via the beam splitter is analyzed by an optical frequency measuring device, which may include, for example, a frequency comb generator for determining the absolute frequency with high accuracy. If the position of the component to be measured changes in the direction of the resonator's extension, the resonant frequency of the optical resonator will also change along with the distance between it and the resonant mirror. As a result, since the frequency of the tunable radiation source is coupled to the resonant frequency of the resonator, the frequency of the input coupled radiation light will also change, and this change will be directly recorded by the frequency measuring device.

[0007] For example, US11,274,914B2 Figure 3 The planar mirror shown is superior to a triple mirror (which can also be used here) as a measurement target for optomechanical reasons, particularly to avoid the multiplicity of reflections and to reduce structural size. However, slight tilting of the planar mirror during axial displacement implemented during measurement mode can cause a lateral shift in the modes formed in the resonator on the resonant mirror used as the input coupling mirror. This reduces the coupling efficiency from the radiation field (equal to the "input coupling field") present at the input of the resonator path to the modal field (equal to the "resonator field") of the optical resonator. A reduction in coupling efficiency exceeding a certain tolerance limit can impair the measurement accuracy of the position measurement, potentially rendering the measurement unusable. Similar effects can occur when a non-planar mirror is used as the measurement target. Summary of the Invention

[0008] Basic purpose

[0009] One problem this invention aims to solve is to provide a measuring device of the type described above, thereby solving the aforementioned problems, and in particular to provide a measuring configuration with a compact structure, wherein high measurement accuracy can be obtained when determining a position.

[0010] Solution according to the invention

[0011] According to the invention, the aforementioned problem can be solved, for example, by a measurement configuration for determining the position of a movable component in a microlithography optical system. This measurement configuration includes an optical resonator with two resonant mirrors surrounding a resonant cavity; and a movable measurement mirror assigned to the component and disposed within the resonant cavity for guiding measurement radiation back and forth between the resonant mirrors. In this case, the measurement mirror is positioned at a working distance from one of the resonant mirrors, the resonant mirror having a curvature matched to the measurement mirror, such that the center of this curvature, i.e., the center of curvature of the aforementioned resonant mirror, is positioned at a distance from the measurement mirror not exceeding 20%, particularly not exceeding 10%, not exceeding 5%, or not exceeding 1% of the working distance.

[0012] The phrase "center of curvature located on the measuring mirror" should be understood to mean that the center is positioned on the reflective surface used to guide the measuring radiation back and forth. In other words, the measuring mirror is positioned at a distance not exceeding 10% of the working distance from the center of curvature of the first resonant mirror. This measuring mirror is preferably used to fold the beam path of the measuring radiation in the optical resonator. The working distance between the resonant mirror with matching curvature and the measuring mirror should be understood to mean the length of the beam path of the measuring radiation between the aforementioned resonant mirror and the measuring mirror when the measuring mirror is tilted relative to the resonant mirror. In this document, the length of the beam path is measured along the axis of the beam path.

[0013] The curvature of one of the resonant mirrors is matched with that of the measuring mirror such that its center is positioned on the measuring mirror, or positioned at a distance not exceeding 20%, particularly not exceeding 10%, 5%, or 1% of the working distance from the measuring mirror. This matching ensures that the tilt of the measuring mirror does not cause lateral displacement or only causes a small lateral displacement on the other resonant mirror, thereby facilitating the input coupling of the measured radiation into the resonant cavity. Therefore, using the configuration according to the invention, the efficiency of coupling the input coupled field to the modal field of the resonator can be maintained at a high level, and thus high measurement accuracy can be obtained.

[0014] If the center of the first resonant mirror is positioned on the measuring mirror, the beam position on the other resonant mirror remains completely stable when the measuring mirror is tilted. This is because, even when the measuring mirror is tilted, the position of the center of curvature of the first resonant mirror remains unchanged when viewed from the other resonant mirror via the measuring mirror. If the center of curvature of the first resonant mirror deviates from its position on the measuring mirror by no more than 20% of the working distance, particularly no more than 10%, no more than 5%, or no more than 1%, i.e., only slightly, the resonator mode exhibits only a small lateral displacement on the reflection of the other resonator, which is tolerable for the effect on coupling efficiency and therefore tolerable for the effect on measurement accuracy.

[0015] According to one embodiment, one of the resonant mirrors is configured as an input coupling mirror for coupling the measurement radiation input into the resonant cavity, and the other resonant mirror is configured as a counter-reflector of the input coupling mirror, the curvature of which is matched to the measurement mirror serving as the counter-reflector.

[0016] According to another embodiment, the optical resonator is configured to form a beam path with a beam waist for measuring radiation, the beam waist being located between the measuring mirror and the first resonant mirror, its curvature matched to the measuring mirror. The beam waist should be understood to refer to a location within the optical resonator where the beam has a minimum diameter or radius. According to one embodiment, the beam path within the resonant cavity is implemented as a Gaussian beam.

[0017] According to another embodiment, the waist is positioned at a distance of at least 5% of the working distance from the measuring mirror and at a distance of at least 5% of the working distance from the first resonant mirror. According to another embodiment, the waist is positioned at a distance of at least 10%, at least 20%, or at least 40% of the working distance from the measuring mirror and at a distance of at least 10%, at least 20%, or at least 40% of the working distance from the first resonant mirror. According to another embodiment, the waist is located at the center between the measuring mirror and the first resonant mirror.

[0018] According to another embodiment, a secondary resonant mirror of the optical resonator, together with a resonant mirror whose curvature is matched to that of the measuring mirror, surrounds the resonant cavity. The center of curvature of the secondary resonant mirror is located on one side of the measuring mirror relative to the secondary resonant mirror, at a distance of at least 10% of the operating distance from the measuring mirror. Advantageously, the center is positioned at a distance of at least 10%, particularly at least 50%, of the distance between the secondary resonant mirror and the measuring mirror. According to a variation of this embodiment, the radius of curvature of the secondary resonant mirror matches the length of the resonant cavity and the radius of curvature of the first resonant mirror, thereby forming a Gaussian mode in the optical resonator.

[0019] According to another embodiment, the additional resonant mirror surrounding the resonant cavity, together with the first resonant mirror, has a curvature, wherein the radius of curvature R2 of the first resonant mirror, the radius of curvature R1 of the additional resonant mirror, and the waist distance (the relative distance a of the first resonant mirror to the working distance) are related as follows: (), or the deviation from the relationship does not exceed 10%.

[0020] According to another embodiment, the measuring mirror is configured as a plane mirror.

[0021] According to another embodiment, the optical resonator is configured such that the measurement radiation radiated at the measurement mirror and the measurement radiation reflected thereon form an angle of no more than 100 milliradians (mrad), particularly no more than 20 milliradians.

[0022] According to another embodiment, the two resonant mirrors are configured to be offset from each other relative to the incident direction of the measurement radiation at the measuring mirror. In other words, the two resonant mirrors are configured to be axially offset from each other. In this case, the two resonant mirrors are configured in a manner that is substantially aligned with each other, i.e., the corresponding incident directions of the measurement radiation on the resonant mirrors are offset from each other by less than 100 milliradians, particularly less than 20 milliradians.

[0023] According to one embodiment variation, the two resonant mirrors are configured to offset at least one thickness of one of the resonant mirrors. Therefore, the edge region of one of the resonant mirrors provided for the beam path of the measured radiation cannot be configured to overlap the other resonant mirror, and thus the tilt angle of the measuring mirror relative to the measured radiation radiated thereon cannot be reduced.

[0024] According to another embodiment, the optical resonator is configured such that the measurement radiation radiated at the measurement mirror and the measurement radiation reflected thereon form an angle of no more than 1 milliradian.

[0025] According to another embodiment, a polarizing beam splitter is disposed in the beam path of the optical resonant cavity, and the beam path of the measurement radiation between the measuring mirror and one of the resonant mirrors is deflected thereon. Advantageously, the deflection angle is approximately 90°. For this purpose, a quarter-wave plate is disposed, for example, in the beam path between the measuring mirror and the designated resonant mirror. Thus, the measuring mirror can be configured for direct retroreflection of the incident measurement radiation, i.e., the directions of the incident and reflected measurement radiation are collinear.

[0026] According to another embodiment, the resonator operates in a Laguerre-Gauss mode using an azimuth index of at least 1. Therefore, the azimuth index can be, for example, 3; in this case, the radial refractive index is preferably zero. According to a variant of one embodiment, the measurement configuration includes a diffractive optics component in the form of a computer-generated hologram (CGH) for beam shaping of the measurement radiation coupled to the optical resonator, such that the resonant cavity can be coupled to a pure mode of the Laguerre-Gauss mode. Therefore, the measurement mirror can be configured for direct retroreflection of the incident measurement radiation, i.e., the directions of the incident and reflected measurement radiation are collinear.

[0027] According to another embodiment, one of the two resonant mirrors has a central notch, and the other resonant mirror is disposed within the central notch. Therefore, the measuring mirror is configured to directly reflect the incident measuring radiation, i.e., the directions of the incident and reflected measuring radiation are collinear.

[0028] According to another embodiment, the working distance is at least 2 cm, particularly at least 10 cm, at least 20 cm, or at least 50 cm.

[0029] Furthermore, according to the present invention, a microlithography projection exposure apparatus is provided. In one of the above embodiments or variations, the projection exposure apparatus includes at least one movable component and at least one measuring configuration for determining the position of the movable component. According to one embodiment variation, the projection exposure apparatus is configured to operate in the EUV wavelength range. Alternatively, the measuring configuration in one of the above embodiments or variations may also be integrated into a mask inspection apparatus or a wafer inspection apparatus.

[0030] According to one embodiment, the projection exposure apparatus includes a plurality of optical elements for guiding exposure radiation within the projection exposure apparatus, one of which acts as a movable component. This optical component may be part of a projection lens or an illumination device of the projection exposure apparatus. As those skilled in the art know, such an illumination device is used to illuminate the mask during the exposure process, and the projection lens is used to image the mask structure onto the wafer.

[0031] Furthermore, according to the present invention, an illumination device for a microlithography projection exposure apparatus is provided. In one of the above embodiments or variations, the illumination device has at least one movable component and at least one measuring configuration for determining the position of the movable component. The movable component may be a lens or a mirror of the illumination device. The illumination device may also be referred to as an illumination system or an illumination optics device.

[0032] Furthermore, according to the present invention, a projection lens for a microlithography projection exposure apparatus is provided, wherein the projection lens, in one of the above embodiments or variations thereof, has at least one movable component and at least one measuring configuration for determining the position of the movable component. The movable component may be a lens or a mirror of the projection lens.

[0033] Furthermore, according to the present invention, an inspection apparatus for inspecting the surface of a substrate is provided, wherein the inspection apparatus, in one of the above embodiments or variations thereof, has at least one movable component and at least one measuring configuration for determining the position of the movable component. The substrate may be a mask or wafer for microlithography.

[0034] The movable part may be a component of the optical system of the inspection apparatus. An example of such an inspection apparatus for mask or wafer inspection (without a measurement configuration according to the invention) is known from disclosure DE 102012205181A1, the entire contents of which are incorporated herein by reference.

[0035] Furthermore, the present invention also provides a coordinate measuring device, which, in one of the above embodiments or variations thereof, has at least one movable part and at least one measuring configuration for determining the position of the movable part.

[0036] The movable part may be a component of the optical system of a coordinate measuring device, which may also be called a coordinate measuring machine. The coordinate measuring device is used to determine the positional deviation of one or more measuring points on a test component from their corresponding nominal positions. An example of such a coordinate measuring device (without the measurement configuration according to the invention) is known from disclosure DE10 2019 213 794A1, the entire contents of which are incorporated herein by reference.

[0037] Details regarding the above-described embodiments, exemplary embodiments, and variations thereof, relating to the measuring configuration according to the invention, are explained in the accompanying drawings and the description of the claims. Individual features may be implemented individually or in combination as embodiments of the invention. Furthermore, advantageous embodiments that can be protected independently may be described, and protection may be claimed only during or after the application is pending. Attached Figure Description

[0038] The above-described features and further advantageous features of the present invention will be described in a detailed description of exemplary embodiments of the present invention or embodiments or variations thereof with reference to the accompanying schematic diagrams, wherein:

[0039] Figure 1 An embodiment of a measurement configuration according to the invention is shown, which is configured to determine the position of a movable component and includes a resonant cavity and a measurement reflector disposed therein;

[0040] Figure 2a To simplify the illustration, based on Figure 1 The beam path in the resonant cavity according to the measurement configuration of the present invention;

[0041] Figure 2b The beam path of the resonant cavity is shown in a comparative example of the measurement configuration;

[0042] Figure 3 Showing according to Figure 1 A beam generation and evaluation device for measurement configuration;

[0043] Figure 4 Showing according to Figure 1The Rayleigh length z in the resonant cavity of the measurement configuration R It is a function of the relative distance a of the waist of the resonant cavity with respect to the working distance of the measuring mirror;

[0044] Figure 5 The radius of curvature R1 of the resonant mirror defining the resonant cavity is shown as a function of the relative distance a;

[0045] Figure 6 This illustrates the correlation between different beam radii and the relative distance a in the resonant cavity;

[0046] Figure 7 Another embodiment of a measurement configuration for determining the position of a movable part according to the present invention is shown;

[0047] Figure 8 Another embodiment of a measurement configuration for determining the position of a movable part according to the present invention is shown;

[0048] Figure 9 Another embodiment of a measurement configuration for determining the position of a movable part according to the present invention is shown;

[0049] Figure 10 This diagram shows a portion of a microlithography projection exposure apparatus with movable parts, the position of which can be determined according to... Figure 1 , Figure 7 , Figure 8 and Figure 9 The measurement configuration of any one of them shall be used to determine this;

[0050] Figure 11 Showing according to Figure 10 An embodiment of a projection exposure apparatus; and

[0051] Figure 12 Showing according to Figure 11 A magnified detailed view of the projection exposure device, wherein according to Figure 1 , 7 The measurement configurations of any of 8 and 9 are integrated into it. Detailed Implementation

[0052] In the exemplary embodiments, examples, or variations thereof described below, components that are similar to each other in function or structure shall, as far as possible, have the same or similar reference numerals. Therefore, in order to understand the characteristics of individual elements in a particular exemplary embodiment, reference shall be made to the description of other exemplary embodiments or the general description of the invention.

[0053] For ease of description, the figure shows the Cartesian xyz coordinate system, from which the corresponding positional relationships of the components shown in the figure can be clearly seen. Figure 1In the diagram, the x-direction is perpendicular to and enters the plane, the z-direction is to the right, and the y-direction is upward.

[0054] Figure 1 An embodiment 10 of a measurement configuration according to the present invention is shown. This measurement configuration 10 is configured to determine the position of a movable component of a microlithography optical system 500, which is shown in cross-sectional view in an exemplary embodiment. Figure 1 The measurement configuration 10 includes a measuring head 12 and a measuring reflector MS (reference numeral 14), which can also be referred to as a measuring target and is secured and thus assigned to a movable part. To determine the position of the movable part, the measurement configuration 10 is used to determine the distance between the measuring head 12 and the measuring reflector 14, as described in more detail below.

[0055] Figure 11 A simplified diagram of an optical system 500 in the form of a microlithography projection exposure device is shown. Figure 10 Showing according to Figure 11 The movable part is a portion of the projection exposure apparatus having a reflector 526, which in this case serves as the aforementioned movable component. In the illustrated embodiment, the movable component in the form of the reflector 526 is a component of the projection lens 516 of the projection exposure system. Alternatively, the movable component may also be a component of the illumination device 515 of the projection exposure system.

[0056] As described above, the component in this exemplary embodiment is a reflector 526, which is movably mounted. Figure 10 The support structure 502 or the housing of the optical system 500 is shown. The support structure 502 or the housing is also referred to below as the reference frame. In order to monitor the position and / or orientation of the component 526 relative to the reference frame during operation (i.e., in situ), the distance between the selected measurement point M and the support structure 502 is determined.

[0057] According to this exemplary embodiment, the positions of the six measurement points M1 to M6 (especially as shown in the example) Figure 10 In the illustrated hexapod structure, the lengths of the six legs (L1 to L6) are determined relative to relevant reference points R1 to R6 on the support structure 502. Therefore, the corresponding positions of the six measuring points M1 to M6 are determined by measuring the lengths L1 to L6, in each case by referring to the aforementioned embodiment of the measurement configuration 10 or the following examples. Figures 7 to 9 The embodiments of the described measurement configurations 110, 210 and 310.

[0058] Figure 11The microlithography projection exposure apparatus described herein and used as optical system 500 is designed to operate using EUV exposure radiation. In this document, EUV radiation should be understood as electromagnetic radiation with wavelengths less than 100 nm, particularly about 13.5 nm or about 6.8 nm. However, the invention is not limited to application in such apparatus, but can also be implemented when measuring projection exposure apparatuses with different operating wavelengths (e.g., operating wavelengths in the VUV or DUV range). In further applications, the invention can also be implemented in various microlithography optical systems, such as mask inspection apparatuses, wafer inspection apparatuses, or coordinate measuring apparatuses.

[0059] according to Figure 11 In an exemplary embodiment, the optical system 500 in the form of an EUV projection exposure apparatus includes a field plane mirror 503 and a pupil plane mirror 504. Light from a light source unit containing a plasma light source 506 and a condenser mirror 508 is guided to the field plane mirror 503. A first telescope mirror 510 and a second telescope mirror 512 are disposed downstream of the pupil plane mirror 504 in the beam path. Distributed downstream of the beam path is a deflector mirror 514, which guides the radiation incident upon it to the object field in the object plane of a projection lens 516 containing six mirrors 518, 520, 522, 524, 526, and 528. The condenser mirror 508, the field plane mirror 503, the pupil plane mirror 504, the two telescope mirrors 510 and 512, and the deflector mirror 514 together form the illumination device 515 of the projection exposure apparatus. Radiation from plasma source 506 passes through illumination device 515 and then illuminates the object field in object plane, that is, illumination device 515 illuminates object field.

[0060] A mask 530 with a reflective support structure on a mask stage 532 is positioned at the location of an object carrier. The mask is imaged onto an image plane by a projection lens 516. In the image plane, a substrate 534 coated with a photosensitive layer (photoresist) is located on a wafer stage 536.

[0061] Figure 12 Show Figure 11 A magnified detailed view of the projection exposure apparatus, which serves as the optical system 500, in the area of ​​the reflector 526, which functions as a movable component within the projection lens 516. In this case, Figure 12 The measurement configuration 10 is shown in a simplified manner, or separately in... Figure 7 , Figure 8 and Figure 9The measurement configurations 110, 210, and 310 are illustrated by way of example. For instance, in this case, the reflector 526 is movably fixed to the housing or wafer stage 536 by a support structure 502, and thus represents a movable component in this exemplary embodiment. For clarity, the support structure 502 is not shown in detail in the present case. The measurement head 12 of the measurement configuration 10, 110, 210, or 310 is fixedly configured on the housing or, for example, on a mask stage. The measurement reflector 14 is fastened to the underside of the reflector 526 relative to the side 527 of the side of the reflector 526 that reflects the exposure radiation of the projection exposure apparatus 500. According to an exemplary embodiment, the position of the reflector 526 is adjusted based on the position measurement results of the measurement configuration 10 or 110, 210, or 310, and particularly according to… Figure 10 The diagram shows alternative measurement configurations 10, 110, 210, or 310 provided by the construction.

[0062] Figure 1 The illustrated measurement configuration 10 includes a radiation generation and evaluation device 16 for generating and evaluating measurement radiation 18, a selective optical fiber 20, a beam-shaping optical unit in the form of an input coupling lens element 22, two resonant mirrors S1 (reference numeral 28) and S2 (reference numeral 30), and the aforementioned measurement mirror 14. The two resonant mirrors 28 and 30 can be integrated into a resonator module, thus fixing them relative to each other. The resonant mirrors 28 and 30, together with the measurement mirror 14, form an optical resonator 26. Similarly, the aforementioned measurement head 12 includes at least two resonant mirrors 28 and 30 and an input coupling lens element 22. The beam generation and evaluation device 16 can also be part of the measurement head 12 or configured externally to the measurement head, such as... Figure 1 As shown.

[0063] Figure 3 An exemplary embodiment of the beam generation and evaluation apparatus 16 is described in detail. It is based on the principle that a laser 42, whose optical frequency is tunable, follows the frequency of an optical resonator 26 via a suitable control loop (according to the Pound-Drever-Hall method in the illustrated example), such that the length L of the resonator 26 to be measured is encoded as the frequency of the tunable laser 42. The laser 42 serves as a radiation source for the measurement radiation 18, which is, for example, located in the visible or infrared wavelength range.

[0064] The beam generation and evaluation apparatus 16 includes a Faraday isolator 44, an electro-optic modulator 46, a polarizing beam splitter 48, a quarter-wave plate 50, a photodetector 52, and a low-pass filter 54. A portion of the measurement radiation 18 passing through the quarter-wave plate 50 is transmitted via... Figure 1 The fiber optic cable 20 shown enters the measuring head 12. (Re-reference) Figure 3For frequency measurement purposes, a portion of the measurement radiation 18 emitted by the tunable laser 42 is output-coupled via beam splitter 56 and fed to analyzer 58 for frequency measurement. The actual frequency measurement in analyzer 58 can be achieved, for example, by comparison with a frequency reference, such as the fs frequency comb of a femtosecond laser. Figure 1 The measurement radiation 18, which exits the optical resonator 16 again via the measurement head 12, re-enters the beam generation and evaluation device 16 via the optical fiber 20 and is acquired by the photodetector 52. For further details on the function of the beam generation and evaluation device 16, please refer to DE 10 2018 208 147 A1.

[0065] As described above, the optical resonator 26 is formed by resonant mirrors 28 and 30 together with a measuring mirror 14 serving as a measurement target. In this case, resonant mirrors 28 and 30 surround the resonant cavity 32. Resonant mirror 28 serves as an input coupling mirror for coupling the measurement radiation 18 into the resonant cavity 32. Resonant mirror 30 serves as a reverse mirror of resonant mirror 28.

[0066] In the illustrated embodiment, the resonant mirror 28, which serves as the input coupling mirror, has a curved mirror surface, wherein the radius of curvature R1 is greater than the distance between the resonant mirror 28 and the measuring mirror 14. Therefore, the center of curvature ml (reference numeral 29) of the resonant mirror 28 is located on one side of the measuring mirror 14 relative to the resonant mirror 28, and thus outside the resonant cavity 32.

[0067] The resonant mirror 30, used as a retroreflector, also has a curved mirror surface, wherein the center of curvature m2 (reference numeral 31) is disposed on the measuring mirror 14, i.e., on the reflecting surface 15 of the measuring mirror. Alternatively, the center m2 may be located at a distance from the measuring mirror 14, this distance not exceeding the working distance d between the resonant mirror 30 and the measuring mirror 14. M 10% of (Figure 34).

[0068] The measuring mirror 14 is configured to guide the measuring radiation 18 back and forth between two resonant mirrors 28 and 30, which are substantially arranged in the positive z-direction and thus substantially aligned with each other. According to... Figure 1In an exemplary embodiment, resonant mirrors 28 and 30 and a measurement mirror 14 are configured such that the measurement radiation 18 radiated onto the measurement mirror 14 and the measurement radiation 18 reflected thereon produce a folding angle β (reference numeral 36) of, for example, less than 100 milliradians, and particularly less than 20 milliradians. Therefore, the orientation of the resonant mirrors 28 and 30 deviates only from the precisely aligned orientation angle β. In other words, the corresponding incident directions of the measurement radiation 18 at the resonant mirrors 28 and 30 are deviated from each other by angle β. In other words, the measurement mirror 14 functions as a folding mirror for folding the beam path of the measurement radiation 18 within the resonant cavity 32.

[0069] The advantageous effect of the measurement configuration 10 on the measurement accuracy of this resonant reflector 30 (where the center of curvature M2 of the resonant reflector is located on the measuring reflector 14 or at a distance from the measuring reflector 14 not exceeding the working distance d) M (at a distance of 10%) in the following reference Figure 2a and 2b Let me explain. Figure 2a The beam path of the measurement radiation 18 in the resonator 26 of the measurement configuration 10 is schematically depicted through the central main ray 18h. Figure 2b The beam path of a comparative example of a measurement configuration is shown, wherein the resonant mirror 60 (reverse mirror) corresponding to the resonant mirror 30 is configured to have the same curvature as the resonant mirror 28 used as the input coupling mirror. That is, the center of curvature m2 of the resonant mirror 60 is configured at a distance d from the measurement mirror 14 exceeding the working distance d. M At 10% of the position. If the measuring mirror 14 is now tilted beyond the tilt angle φ, then the principal ray 18h tilts in the region between the measuring mirror 14 and the resonant mirrors 30 and 60, which serve as counter-reflectors respectively, according to... Figure 2a and according to Figure 2b As shown by the dashed line in the configuration.

[0070] According to Figure 2bIn the comparative example, the principal ray 18h is also tilted in the region between the resonant mirror 28 and the measuring mirror 14, meaning that the beam path of the measuring radiation 18 has a lateral displacement on the resonant mirror 28. This displacement reduces the coupling efficiency of the input coupling field of the measuring radiation 18, which is radiated onto the resonant mirror 28 via the input coupling lens component 22, where the modal field is located in the resonator 26, thereby reducing the measurement accuracy of the measurement configuration. This effect can be mitigated by increasing the beam diameter of the measuring radiation 18 radiating onto the resonant mirror 28 to a degree that keeps the lateral displacement below the limit of 0.1 beam radius. However, this also means that the beam diameter on the measuring mirror 14 becomes substantially smaller; thus effectively focusing on the measuring mirror 14. However, this is disadvantageous for metrological reasons, as it increases the sensitivity to the local surface topography of the measuring mirror 14. Furthermore, if considering the working distance d... M Choosing a value greater than 10 mm will result in an unrealistically large beam diameter appearing on the input coupling side.

[0071] In contrast, because the curvature center m2 of the resonant reflector 30 is positioned on the measuring reflector 14, it makes the following possible... Figure 2a In the embodiment of the measurement configuration 10 according to the present invention, the lateral position of the principal ray 18h on the resonant reflector 28 is completely stable. This is because the position of the center of curvature m2 of the resonant reflector 30 remains unchanged even when the measuring reflector 14 is tilted, as seen from the resonant reflector 28 via the measuring reflector 14. If the center of curvature m2 of the resonant reflector 30 deviates from its position on the measuring reflector 14 by no more than the working distance d... M 10%, that is, only to a very small extent, seemingly according to Figure 1 In this embodiment, only a small lateral displacement of the resonator mode exists on the resonant mirror 28, the impact of which on coupling efficiency and measurement accuracy is tolerable.

[0072] According to Figure 1 In this embodiment, the beam path 18r of the measuring radiation 18 folded by the measuring mirror 14 within the optical resonator 26 corresponds to the path of the Gaussian beam. In the described embodiment, the waist T (reference numeral 38) of the Gaussian beam is located at the center between the measuring mirror 14 and the resonant mirror 30. That is, in this case, the waist distance d from the resonant mirror 30 is... T It is the working distance d M 50%, that is, the relative distance a=d T / d M It is 0.5. Figure 1 The boundary lines of the beam path 18r used to represent the measured radiation, as shown in the figure, each correspond to a position in the cross-section of the beam path, where the intensity is 1 / e of the maximum intensity at the center of the beam path.2 The corresponding beam profiles represented by these boundary lines have a beam radius r1 at reflector 28, a beam radius rm at measuring reflector 14, and a beam radius r2 at resonant reflector 30.

[0073] The radius of curvature R1 of the resonant reflector 28 is selected according to the following design rules: , Figure 5 This relationship is described for a fixed, predefined radius of curvature R2. In an alternative exemplary embodiment, the value of R1 deviates from... However, it does not exceed 10%.

[0074] The value of distance a is chosen based on the following considerations. For the Rayleigh length z in optical resonator 26... R Under the condition that the center m2 is located on the measuring mirror 14, the following relationship exists between it and the relative distance a: Please see Figure 4 As those skilled in the art know, the Rayleigh length z R This represents the distance along the optical axis required for the cross-sectional area of ​​a laser beam to double from its beam waist. For example... Figure 4 As shown, the Rayleigh length z changes when a -> 0 and a -> 1. R The length z approaches 0, and the Rayleigh length z is 0.5. R It is at its maximum value.

[0075] The beam radii r1, rm, and r2 generated as functions of a are as follows: Figure 6 As shown. When a -> 0, the beam radii r1 and rm tend to infinity, while r2 tends to 0. For a -> 1, the beam radii r1 and r2 tend to infinity, and rm tends to 0. In an exemplary embodiment, the following applies: 0.05 ≤ a ≤ 0.95, that is, the distance d from the beam waist T to the resonant reflector 30. T Or the distance d of the reflector is measured by the waist T distance. M -d T In each case, it is the working distance d. M At least 5%. For this dimension of a, the dimensions of the beam radii r1, r2, and rm are within the range that allow for the formation of stable modes in the optical resonator 26, and are within manageable limits for the mounting space required for the mirrors of the resonator 26. The sum of the beam radii r1 and r2 essentially determines the dimensions of the measurement configuration 10 in the y-direction, having values ​​similar to a = 0.05 as a = 0.95. According to another exemplary embodiment, the following conditions apply: 0.1 ≤ a ≤ 0.9 or 0.2 ≤ a ≤ 0.8. The measurement configuration 10 can be designed to be more compact and further improve mode stability for these values.

[0076] Figure 7 Another embodiment 110 of the measurement configuration according to the invention is shown, which is similar to the measurement configuration 10 for determining the position of a movable component in a microlithography optical system 500. The measurement configuration 110 differs from the measurement configuration 10 only in that the resonant mirrors 28 and 30 are offset from each other in the z-direction, that is, substantially related to the incident direction of the measurement radiation 18 at the resonant mirrors 28 and 30, i.e., along the axial direction.

[0077] In this example, the resonant mirror 30 is offset in the negative z-direction, increasing the distance from the measuring mirror 14. Therefore, the resonant mirror 30 can also be slightly offset laterally in the incident direction 18, specifically, so that the edge regions 128r and 130r of the resonant mirrors 28 and 30, which are used for the beam path of the measuring radiation 18, are not configured in an overlapping manner. Compared to the measuring configuration 10, this allows for a reduction in the folding angle β. This reduces the effect of the axial displacement of the measuring mirror 14, i.e., the displacement of the measuring mirror along the z-axis at the mode position of the resonant mirrors 28 and 30 during measurement operation. As seen from the resonant mirror 28 reflected via the measuring mirror 14, the axial displacement of the measuring mirror 14 by Δz causes a lateral displacement of the center of curvature m2 relative to the measuring mirror 14 by 2βΔz. Due to the "lever effect," the lateral displacement of the mode on the resonant mirror 28 is increased by a factor of R1 / (R1-R2). Therefore, due to the reduction in the folding angle β, the effect is reduced compared to the measurement configuration 10. Figure 1 Compared to the previous embodiment, in accordance with Figure 7 In one embodiment, the permissible lateral displacement of the measuring mirror 14 during the measurement operation can be set to be relatively large.

[0078] Figure 8 Another embodiment 210 of the measurement configuration according to the invention is shown, which is similar to the measurement configuration 10 used to determine the position of movable components in a microlithography optical system 500. Measurement configuration 210 differs from measurement configuration 10 in that polarized measurement radiation 218 is radiated to optical resonator 26, for example by using an upstream polarizer 260, and a polarization beamsplitter 262 and a quarter-wave plate 264 are arranged in the beam path of the measurement radiation 18 between the resonant mirror 28 and the measurement mirror 14. The measurement radiation 18 reflected back by the measurement mirror 14 is deflected by the polarization beamsplitter 262 by 90°. The resonant mirror 30 is arranged at a corresponding position below the polarization beamsplitter 262, oriented laterally to the resonant mirror 28.

[0079] The folding angle β can be reduced to less than 1 milliradian, and particularly 0 milliradian, guiding the beam path from the resonant mirror 28 and the measuring mirror 14 to the measuring radiation 18 of the resonant mirror 30 via output coupling. Therefore, the direction of the measuring radiation 18 traveling to the measuring mirror 14 and the direction of the reflected measuring radiation 18 are collinear. This further reduces the influence of axial displacement of the measuring mirror 14, i.e., the displacement of the measuring mirror 14 along the z-axis at its mode position at the resonant mirrors 28 and 30 during measurement operation, and thus further increases the allowable axial displacement of the measuring mirror 14.

[0080] Figure 9 Another embodiment 310 of the measurement configuration according to the invention is shown, which is similar to the measurement configuration 10 for determining the position of a movable component in a microlithography optical system 500. Similar to that according to... Figure 8 In the measurement configuration 210, the direction of the measurement radiation 18 traveling to the measurement reflector 14 and the direction of the reflected measurement radiation 18 are collinear in the measurement configuration 310.

[0081] Measurement configuration 310 and according to Figure 1 The difference in measurement configuration 10 is that resonator 26 operates in a Laguerre-Gaussian mode with an azimuth index of at least 1; in the present case, a Laguerre-Gaussian mode 366 with an azimuth index of 3 and a radial index of 0 is generated. Coupling to said Laguerre-Gaussian mode 366 can be implemented by appropriate beam shaping, for example by a CGH not shown in the figure. By generating a Laguerre-Gaussian mode 366 in optical resonator 26 that substantially defines a ring-shaped intensity distribution, it can be used as a retroreflector (similar to that according to...). Figure 1 The resonant mirror 330 is configured as an input coupling mirror (similar to the one according to the resonant mirror 30). Figure 1 The resonant reflector 28) is located in the central notch 368 of the resonant reflector 328.

[0082] Based on Figure 8 In the manner of embodiment 210, due to this collinear configuration, at the mode positions of the resonant reflectors 328 and 330 in embodiment 310, this reduces the influence of the axial displacement of the measuring reflector 14, that is, the displacement of the measuring reflector 14 along the z-axis during the measurement operation, and thus increases the allowable axial displacement of the measuring reflector 14.

[0083] The foregoing description of exemplary embodiments, examples, or variations thereof will be understood through examples. This disclosure enables those skilled in the art to understand the invention and its related advantages, and secondly covers alternatives and modifications to the described structures and methods that are also understood by those skilled in the art. Therefore, all such alternatives and modifications, as long as they fall within the scope of the invention as defined in the appended claims, and their equivalents, are intended to be protected by the claims.

[0084] List of reference numerals

[0085] 10 Measurement Configuration

[0086] 12 Measuring Head

[0087] 14 Measuring the reflecting mirror

[0088] 15 Reflective Surface

[0089] 16-beam generation and evaluation device

[0090] 18. Measuring radiation

[0091] Beam path for measuring radiation in an 18r resonator

[0092] The central main ray of the measured radiation in the 18h resonator

[0093] 20 optical fibers

[0094] 22 Input coupling lens element

[0095] 26 Optical Resonators

[0096] 28 Resonant Reflectors

[0097] 29 Center of curvature m1

[0098] 30 resonant reflectors

[0099] 31 Center of curvature m2

[0100] 32 resonant cavity

[0101] 34 Working distance d M

[0102] 36 Folding angle β

[0103] 38 Waist-cinching T-shirt

[0104] 42 Lasers

[0105] 44 Faraday Isolator

[0106] 46 Electro-optic modulator

[0107] 48 Polarizing optical beam splitter

[0108] 50 quarter-wave plate

[0109] 52 Photodetectors

[0110] 54 Low-pass filter

[0111] 56 beam splitters

[0112] 58 Analyzer

[0113] 110 Measurement Configuration

[0114] 128r edge area

[0115] 130r Measurement Configuration

[0116] 210 Measurement Configuration

[0117] 218 Polarization Measurement of Radiation

[0118] 260 polarizer

[0119] 262 Polarization beam splitter

[0120] 264 quarter-wave plate

[0121] 310 Measurement Configuration

[0122] 328 resonant mirror

[0123] 330 resonant mirror

[0124] 366 Laguerre-Gaussian Model

[0125] 368 Central Incision

[0126] 500 Optical System

[0127] 502 Support Structure

[0128] 503 field-division mirror

[0129] 504 Pupil-shaped Plane-reflecting Mirror

[0130] 506 Plasma Source

[0131] 508 Concentrating Mirror

[0132] 510 First Telescope Reflector

[0133] 512 Second Telescope Reflector

[0134] 514 Deflecting Mirror

[0135] 515 lighting fixtures

[0136] 516 Projection Lens

[0137] 518, 520, 522, 524, 528 Reflectors of the projection lenses

[0138] 526 The reflector of the projection lens as a movable part

[0139] 527 Reflection side

[0140] 530 mask

[0141] 532 Mask Stage

[0142] 534 base plate

[0143] 536 chip station

[0144] R1 is the radius of curvature of the resonant mirror.

[0145] The radius of curvature S2 of the resonant mirror R2

Claims

1. A measurement arrangement (10; 110, 210; 310) for determining a position of a movable component (526) in a microlithography optical system (500), comprising: an optical resonator (26) having two resonator mirrors (28, 30) enclosing a resonator cavity (32); and a movable measurement mirror (14) assigned to the movable component and arranged within the resonator cavity for guiding measurement radiation back and forth between the resonator mirrors; the measurement mirror being arranged at an operating distance (34) from one of the resonator mirrors having a curvature matching the measurement mirror, such that a center (31) of the curvature is arranged on the measurement mirror or at a distance of less than 20% of the operating distance from the measurement mirror; one of the resonator mirrors (28) being configured as an input coupling mirror for input coupling measurement radiation (18) into the resonator cavity and the other resonator mirror (30) being configured as a counter mirror to the input coupling mirror, the other resonator mirror (30) having a curvature matching the measurement mirror as the counter mirror; the optical resonator (26) being configured to form a beam path for the measurement radiation (18) and having a beam waist (38) between the measurement mirror (14) and the first resonator mirror (30) having a curvature matching the measurement mirror; the beam waist (38) being arranged at a distance of at least 5% of the operating distance (34) from the measurement mirror (14) and at a distance of at least 5% of the operating distance (34) from the first resonator mirror (30); the further resonator mirror (28) being part of the optical resonator and enclosing the resonator cavity (32) together with the resonator mirror (30) having a curvature matching the measurement mirror (14), and a center (29) of curvature of the further resonator mirror being located on a side of the measurement mirror opposite to the further resonator mirror and at a distance of at least 10% of the operating distance (34) from the measurement mirror; the measurement mirror being configured as a planar mirror; the optical resonator (26) being configured such that an angle between measurement radiation (18) radiating at the measurement mirror (14) and measurement radiation reflected on the measurement mirror (14) does not exceed 100 milliradians; the two resonator mirrors being offset with respect to each other with respect to an incidence direction of the measurement radiation at the measurement mirror (14); the optical resonator being configured such that an angle between measurement radiation radiating at the measurement mirror and measurement radiation reflected on the measurement mirror does not exceed 1 milliradian; a polarization beam splitter being optically arranged in the beam path of the optical resonator cavity and a beam path of the measurement radiation between the measurement mirror and one of the resonator mirrors being deflected at the polarization beam splitter; the resonator being operated in a Laguerre-Gaussian mode having an azimuthal index of at least 1. ​ ​ ​ ​ 2. The measurement configuration of claim 1, wherein, ​ 3. The measurement arrangement of claim 1 or 2, wherein, ​ 4. The measurement configuration of claim 3, wherein, ​ 5. The measurement arrangement of any of the preceding claims, wherein, ​ 6. The measurement arrangement of claim 3 or 4, wherein, The further resonator mirror (28) surrounding the resonator cavity (32) together with the first resonator mirror (30) has a curvature, and the following relation exists between the radius of curvature R2 of the first resonator mirror, the radius of curvature Rl of the further resonator mirror (28), and the relative distance a of the beam waist from the first resonator mirror with respect to the working distance (34): ), or a deviation of not more than 10% from this relation.

7. The measurement arrangement of any of the preceding claims, wherein, ​ 8. The measurement arrangement of any of the preceding claims, wherein, ​ 9. The measurement configuration (110) of claim 8, wherein ​ 10. The measurement arrangement of any of the preceding claims, wherein, ​ 11. The measurement arrangement of any of the preceding claims, wherein, ​ 12. The measurement arrangement of any one of claims 1 to 10, wherein, ​ 13. The measurement arrangement of any one of claims 1 to 10 or of claim 12, wherein, One of the two resonant mirrors has a central cut-out, the other being arranged at the central cut-out.

14. The measurement arrangement of any of the preceding claims, wherein, The working distance is at least 2 cm.

15. Microlithographic projection exposure apparatus comprising at least one movable component and at least one measurement arrangement for determining the position of the movable component according to any one of the preceding claims.

16. Projection exposure apparatus according to claim 15, comprising a plurality of optical components, wherein the plurality of optical components are used for guiding exposure radiation in the projection exposure apparatus, one of the plurality of optical components acting as the movable component.

17. Illumination device (515) for a microlithographic projection exposure apparatus comprising at least one movable component and at least one measurement arrangement for determining the position of the movable component according to any one of claims 1 to 14.

18. Projection lens (516) for a microlithographic projection exposure apparatus comprising at least one movable component and at least one measurement arrangement for determining the position of the movable component according to any one of claims 1 to 14.

19. Inspection apparatus for inspecting a surface of a substrate, in particular for inspecting a surface of a mask or a wafer in microlithography, the inspection apparatus comprising at least one movable component and at least one measurement arrangement for determining the position of the movable component according to any one of claims 1 to 14.

20. Coordinate measuring apparatus comprising at least one movable component and at least one measurement arrangement for determining the position of the movable component according to any one of claims 1 to 14.

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