Optical measuring arrangement for distance detection

Abstract

The invention relates to an optical measuring arrangement (100) for detecting a distance between a first component and a second component by measuring the length of at least one measuring path (101), wherein the measuring path (101) is spanned between at least two facets (102, 103) forming a measuring head, which are directly or indirectly connected or connectable to the first component, and a measuring target (104) arranged in the measuring path (101), which is directly or indirectly connected or connectable to the second component and is configured to deflect a measuring beam (105) back and forth in the measuring path (101) between the facets, wherein the second facet (103) is formed as a reflecting facet (103). The center of curvature of one of the facets (102, 103) of the measuring head is located on the measuring target (104) or at most 20% of the distance between the facet (102, 103) and the measuring target (104). The invention further relates to a projection exposure system, a lithography system, an inspection system and a coordinate measuring machine.

Description

[0001] The invention relates to an optical measuring arrangement for detecting a distance between a first component and a second component by measuring the length of at least one measuring path, wherein the measuring path is spanned between at least two facets forming a measuring head, which are directly or indirectly connected or connectable to the first component, and with a measuring target arranged in the measuring path, which is directly or indirectly connected or connectable to the second component and is configured to deflect a measuring beam back and forth in the measuring path between the facets, the second facet being a reflective facet. The invention further relates to a projection exposure system, a lithography system, an inspection system, and a coordinate measuring machine.

[0002] Projection exposure systems are used to create extremely fine structures, particularly on semiconductor devices or other microstructured components. The operating principle of these systems is based on the creation of ultra-fine structures down to the nanometer range by means of a generally reduced-size image of structures on a mask, a so-called reticle, onto a wafer, which is coated with photosensitive material. The minimum dimensions of the generated structures depend directly on the wavelength of the light used. This light is shaped in an illumination optic to optimally illuminate the reticle. Recently, light sources with emission wavelengths in the nanometer range, for example between 1 nm and 120 nm, particularly in the 13.5 nm range, have been increasingly used. This wavelength range is also known as the EUV range.

[0003] The microstructured components are manufactured not only using EUV systems but also with established DUV systems operating at wavelengths between 100 nm and 400 nm, particularly 193 nm. With the increasing demand for ever smaller structures, the requirements for optical correction in these systems have also risen. To improve efficiency, each new generation of projection exposure systems in the EUV or DUV range increases throughput.

[0004] In the operation of microlithographic projection exposure systems, where the mask and wafer are typically moved relative to each other in a scanning process, the positions of the mirrors, which are sometimes movable in all six degrees of freedom, must be set and maintained with high accuracy in order to avoid or at least reduce aberrations and associated impairments of the image result or image shifts.

[0005] Various approaches are known in the prior art for measuring the position of individual mirrors, as well as the wafer or wafer stage and the reticle or reticle stage. In the field of optical measurement arrangements, interferometric measurement arrangements, optical encoders, and frequency-based position measurement using an optical resonator are all known.

[0006] An optical measuring arrangement for frequency-based position and / or distance measurement is described, for example, in DE 10 2012 212 663 A1. This discloses a resonator in the form of a Fabry-Perot resonator with two resonator mirrors, the first of which is attached to a reference element in the form of a measuring frame rigidly connected to the housing of the projection lens of the projection exposure system, and the second resonator mirror (as a "measuring target") is attached to a mirror whose position is to be measured. The actual distance measuring device comprises a radiation source whose optical frequency can be tuned, which generates a coupling radiation that passes through a beam splitter and is coupled into the optical resonator.The radiation source is controlled by a coupling device such that its optical frequency is tuned to the resonant frequency of the optical resonator and thus coupled to this frequency. Input radiation coupled out via a beam splitter is analyzed by an optical frequency measuring device, which may include, for example, a frequency comb generator for highly accurate determination of the absolute frequency. If the position of the EUV mirror changes in the x-direction, the resonant frequency of the optical resonator also changes with the distance between the resonator mirrors, and consequently—due to the coupling of the frequency of the tunable radiation source to the resonator's resonant frequency—the optical frequency of the input radiation also changes, which is then directly registered by the frequency measuring device.

[0007] Furthermore, WO 2019 / 223968 A1 and the German patent application filed under application number 102022210369.6 disclose various resonators for position detection of a moving component.

[0008] Interferometers are a widely used optical measuring device for position and / or distance measurement. An interferometer has a reference path and a measurement path, with the light from a light source being split into the measurement path and the reference path by a beam splitter. In the measurement path, the light is directed onto the measurement target, which is a mirror, and reflected back to the beam splitter. In the reference path, the reference light beam is reflected back to the beam splitter by another reference mirror and combined with the reflected measurement beam, causing the measurement and reference beams to interfere. Heterodyne and homodyne interferometers are among the known types. A heterodyne interferometer is described, for example, in US 4,784,489 A.

[0009] In order to be able to detect relative positions or distances with high accuracy and also over large distances, the optical measuring arrangement must be as insensitive as possible to a tilting of the measuring target.

[0010] It is therefore the object of the present invention to provide an optical measuring arrangement, a projection exposure system, a lithography system, an inspection system and a coordinate measuring machine that detects the position and / or distance of a component over a large measuring range with high accuracy.

[0011] The problem relating to the optical measuring arrangement is solved by an optical measuring arrangement according to the features of claim 1. The problem relating to the projection exposure system is solved by a projection exposure system with the features of claim 17. The problem relating to the lithography system is solved by a lithography system with the features of claim 18, the problem relating to the inspection system is solved by an inspection system with the features of claim 19, and the problem relating to the coordinate measuring machine is solved by a coordinate measuring machine according to the features of claim 20. Advantageous embodiments with expedient further developments are specified in the dependent claims.

[0012] The optical measuring arrangement is characterized in particular by the fact that the center of curvature of one of the facets of the measuring head is located on the measuring target or at most 20%, preferably at most 10%, and most preferably at most 5% of the distance between the facet and the measuring target. This makes it possible to provide an optical measuring arrangement that is less sensitive to tilting of the measuring target. The term "facet" is understood to mean a polished surface. The facets, or some of the facets, can be formed as mirrors. The measuring target is preferably also formed as a facet, in particular as a reflective facet or a reflective mirror. The reflective facet preferably has a reflectivity of at least 80%, more preferably at least 90%, more preferably at least 95%, and most preferably at least 99%. The measuring target is preferably planar.

[0013] In particular, it is preferred that the first facet is formed as an input and output facet of the measurement path for coupling the measurement beam into and out of the measurement path, and that the second facet is curved such that its center of curvature lies on the measurement target or at most 20%, preferably at most 10%, and most preferably at most 5% of the distance between the second facet and the measurement target. The first facet is thus at least partially transmitting. This allows the beam axes of the incoming and outgoing light beams, i.e., the measurement beam, to coincide, regardless of any tilting of the measurement target. The second facet can be formed as an end facet of the measurement path.

[0014] Furthermore, it is preferred that the radius of curvature of the first facet is larger than the distance between the first facet and the measuring target and smaller than twice the distance between the first facet and the measuring target. Preferably, the radius of curvature of the first facet is larger than 1.2 times and smaller than 1.7 times the distance between the first facet and the measuring target. Particularly preferably, the radius of curvature of the first facet is larger than 1.4 times and smaller than 1.6 times the distance between the first facet and the measuring target. Most preferably, the radius of curvature of the first facet is 1.5 times the distance between the first facet and the measuring target.

[0015] Furthermore, it is advantageous if the curvature of the measuring target is selected such that the beam caustic of the measuring beam entering the measuring target through the first facet coincides with the beam caustic of the measuring beam exiting the measuring target towards the first facet. Thus, the measuring target can be curved or planar (i.e., infinitely curved). If the measuring target is curved, the first facet can be planar or curved. At least one of the components, the measuring target and the first facet, is therefore preferably curved.

[0016] Furthermore, it is advantageous if the surface of the first facet coincides with, or approximately coincides with, the phase front of the measuring beam incident upon it, i.e., the phase front of the measuring beam reflected from the measuring target and incident upon the first facet. In particular, it is advantageous if the curvature of the surface of the first facet coincides with, or approximately coincides with, the phase front, and especially its curvature, of the measuring beam reflected from the measuring target. If the optical measuring arrangement is designed as an interferometer, it is advantageous if the first facet is formed as an exit surface of a beam splitter of the interferometer. Alternatively, the at least partially transmitting first facet can also be planar.

[0017] Furthermore, it is advantageous if the measuring beam is designed to form a beam caustic with a beam waist along the measuring path, with the beam waist being formed between the measuring target and one of the facets.

[0018] Furthermore, it is advantageous if the beam caustic of the measuring beam entering through the first facet in the direction of the measuring target is chosen such that it coincides or approximately coincides with the beam caustic of the measuring beam exiting from the measuring target in the direction of the first facet (i.e., the measuring beam reflected from the measuring target in the direction of the first facet).

[0019] In one embodiment, it is preferred that the optical measuring arrangement is configured as an interferometer, particularly a heterodyne interferometer, and thus includes a reference path and a beam splitter. The beam splitter is configured to divide a light beam emitted from a light source into two parts: the measuring beam and the reference beam. The reference path preferably includes an additional reference facet, which is arranged such that the reference light beam directed by the beam splitter into the reference path is reflected back onto the beam splitter, and the beam splitter is configured to merge the measuring beam coupled out of the measuring path with the reference beam. The measuring target is preferably configured as a reflective facet, particularly as a measuring mirror. The measuring target is preferably planar.Alternatively, the measuring mirror formed as a measuring target can also be curved, and the first facet, as the input and output facet, can be flat.

[0020] In this context, it is particularly preferred if the at least partially transmitting first facet has a transmission of over 95%, preferably over 98%, and most preferably over 99.5%. Furthermore, it is advantageous if the at least partially transmitting facet has an antireflective coating, at least in some areas. The first at least partially transmitting facet is preferably formed as a surface of the beam splitter.

[0021] Furthermore, it is advantageous if the partially transmitting first facet is designed in such a way as to form a stable virtual cavity with the second facet and the measuring target, such that the beam caustic striking the second facet from the measuring mirror coincides or approximately coincides with the beam caustic emanating from the second facet.

[0022] Furthermore, it is advantageous if the measuring beam to be coupled into the measuring path is configured in such a way that its caustic matches an eigenmode of a virtual cavity formed from at least the first facet, the second facet and the measuring target.

[0023] Furthermore, it is preferred that the surface of the reference facet, and in particular its curvature, is selected such that it matches or nearly matches the phase front, and especially the curvature of the phase front, of the reference light beam incident on the reference facet. The phase front of the incident reference light beam thus deviates from the surface by a maximum of 25%, preferably by 10%, and most preferably by a maximum of 5% of the wavelength of the reference light beam used. The surface of the reference facet, onto which the reference beam incidents, is therefore preferably adapted to the curvature of the phase front of the incident reference light beam. In particular, the surface of the reference facet is identical or nearly identical to the curvature of the incident reference beam.This allows the caustic of the reference light beam reflected on the reference facet to reproduce the caustic of the incident reference light beam.

[0024] In this context, it is particularly advantageous if the reference light beam to be coupled into the reference path is configured such that its caustic coincides with an eigenmode of a virtual resonator formed from at least the first facet, the second facet, and the measuring mirror. In particular, the caustic of the reference light beam to be coupled into the reference path and the measuring beam to be coupled into the measuring path coincide and preferably correspond to an eigenmode of the resonator formed from at least the first facet, the second facet, and the measuring mirror.

[0025] Preferably, the reference facet and the first at least partially transmitting facet are formed identically. In particular, both facets have at least approximately the same curvature.

[0026] Optionally, the measuring beam and the reference light beam in the reference path can have different polarizations. The beam splitter is then configured as a polarization beam splitter. In particular, the measuring beam and the reference light beam can be orthogonally polarized to each other.

[0027] Alternatively or additionally, it is advantageous if the reference path and the measurement path each comprise a λ / 4 plate and that the beam splitter is formed as a polarization beam splitter.

[0028] Alternatively, it is advantageous if the optical measuring arrangement is formed as an optical encoder, and if the measuring target is formed as a grating.

[0029] In a further alternative embodiment, it is preferred that the optical measuring arrangement is designed as a measuring arrangement for frequency-based position and / or distance measurement. The measuring path then preferably comprises an optical resonator in which a standing wave is formed. The optical resonator, comprising at least the first facet, the second facet, and the measuring target, preferably has a fineness of at least 10, more preferably at least 100, and most preferably at least 500. The measuring target is then preferably also designed as a reflective facet, in particular as a measuring mirror, and more preferably as a planar measuring mirror. Compared to the design of the measuring arrangement as an interferometer, the first facet has a lower transmissivity. The reflectivity of the first facet is, in this case, more than 95%, more preferably more than 98%, and most preferably more than 99.5%.

[0030] To improve accuracy, it is advantageous to have at least one third reflective facet in the measurement path. This facet is designed to reflect the measurement beam, reflected from a starting point of the measurement target onto the third facet, back onto or approximately back onto that starting point of the measurement target, so that the measurement beam is reflected back onto itself with a maximum angular deviation of 500 µrad. In other words, at least one third convolutional facet is present. The third facet can be arranged in a common holder with at least one of the other facets or with all facets. In particular, the second reflective facet and the third reflective facet can be arranged adjacent to each other. The facets can be arranged symmetrically or asymmetrically. The first facet can be positioned between the second and third facets. The facets can also be arranged one above the other.

[0031] Furthermore, in one embodiment, it is preferred that the second reflective facet is configured to direct the measuring beam as it traverses the measuring path from one measuring point to another on the measuring target, wherein the measuring points are spaced apart with respect to the center of curvature of the second facet, preferably being point-symmetric with respect to the center of curvature of the second facet. It is also advantageous if the distance between the center of curvature of the second facet and the measuring points is greater than 0.5 mm, preferably greater than 1 mm, and particularly preferably greater than 2 mm. In particular, it is preferred if the measuring beam is directed multiple times from one of the measuring points via the second facet to the other measuring point.

[0032] Furthermore, for the formation of a stable real or virtual resonator, it is advantageous if the third reflecting facet is curved, and if the radius of curvature is greater than the distance d between the third facet and the measurement target and less than twice the distance between the first facet and the measurement target. Preferably, the radius of curvature of the third facet is greater than 1.2 times and less than 1.7 times the distance between the third facet and the measurement target. Particularly preferably, the radius of curvature of the third facet is greater than 1.4 times and less than 1.6 times the distance between the third facet and the measurement target. Most preferably, the radius of curvature of the third facet is 1.5 times the distance between the first facet and the measurement target.

[0033] In an advantageous embodiment, the first facet can be planar. To form a stable real or virtual resonator, the third reflecting facet can also be curved.

[0034] Preferably, the second facet is curved in such a way that its center of curvature is located on the measuring target or at most 20%, preferably at most 10% and particularly preferably at most 5% of the distance between the further facet and the measuring target.

[0035] Furthermore, it is advantageous if the second and third facets are configured such that, after entering the measurement path, the measurement radiation reaches the third facet after 2n+2 reflections from the measurement target and 2n+1 reflections from the second facet, where n is a non-negative number. The optical measurement setup is configured such that a total of 4n+4 reflections occur at the measurement target per pass within the measurement path.

[0036] Furthermore, it is advantageous if the first and third facets are arranged such that the distance b between the entry point of the measurement radiation into the measurement path on the first facet and a back-reflection point on the third facet corresponds to b = N * a or a maximum deviation of 10% from b = N * a, where N is the number of reflections of the measurement path in one pass and a is the distance between the center of curvature of the first facet and a measurement point on the measurement target. The offset of the entry point relative to the back-reflection point on the third facet in the plane defined by the entry point and the measurement point is b = N * a.

[0037] Furthermore, to increase measurement accuracy, it is advantageous to have another facet that is set up to direct the measuring beam from one of the measuring points on the measuring target to the other measuring point of the measuring target.

[0038] In this context, it is advantageous if the center of curvature of at least one other reflecting facet coincides with, or approximately coincides with, the center of curvature of the second reflecting facet.

[0039] To further increase the number of additional facets and thus improve the accuracy of distance measurement, it is advantageous if at least one of the additional facets shares a common surface with the second facet. At least one of the additional facets and the second facet are preferably monolithic.

[0040] The at least one further facet can have the same curvature properties as the second reflective facet. Preferably, the at least one further facet is curved such that its center of curvature is located on the measuring target or at most 20%, preferably at most 10%, and particularly preferably at most 5% of the distance between the further facet and the measuring target.

[0041] Furthermore, it is preferred if the third facet is aligned perpendicular to the measuring beam of the measuring path incident on the third facet (at a back-reflection point) or with a deviation of less than 500 µrad. Alternatively or additionally, it is advantageous if the first facet is aligned perpendicular to or approximately perpendicular to the measuring path at the entry point.

[0042] Furthermore, it is advantageous if a plurality of optical measuring arrangements are available, which are set up for position detection of the second component, in particular for position detection of the second component or individual points of the second component in 6 degrees of freedom, and / or for detection of a deformation of the second component.

[0043] The projection exposure system is characterized in particular by the presence of at least one optical measuring arrangement. The second component of the projection exposure system to be measured can preferably be at least one or more optical elements or a support structure of the projection exposure system. The first component can be configured as a reference object, in particular as a reference frame, such that the at least one optical measuring arrangement is set up to detect the distance between the first component and the second component. It is particularly advantageous if the projection exposure system has a plurality of optical measuring arrangements configured for detecting the position of the second component or individual points of the second component, in particular in several, preferably six, degrees of freedom.Alternatively or additionally, the majority of optical measuring arrangements can also be configured to detect a deformation of the surface of the second component. By measuring the distance of the optical elements relative to a reference using the majority of optical measuring arrangements, their position or orientation, or even a deformation of the optical surface, can be detected, and the position or deformation can preferably be adjusted by means of actuators. This improves the image quality of the projection exposure system. The advantages and embodiments mentioned for the optical measuring arrangement are also applicable to the projection exposure system comprising at least one optical measuring arrangement.

[0044] Furthermore, at least one optical measuring arrangement according to the invention can also be used in a projection lens, in particular in a projection lens of a projection exposure system, for determining the position and / or distance of a movable or immovable component of the projection lens. It is particularly advantageous if the projection lens has a plurality of optical measuring arrangements configured for detecting the position of the second component or individual points of the component, in particular in several, preferably six, degrees of freedom. Alternatively or additionally, the plurality of optical measuring arrangements can also be configured for detecting a deformation of a surface of the component.

[0045] The invention is also applicable in a lighting system, particularly in a lighting system for a projection exposure system. The lighting system preferably comprises at least one optical measuring arrangement. The at least one optical measuring arrangement, in particular its measuring target, is directly or indirectly connected to, or connectable with, the second component to be measured. The second component can, in particular, be an optical element or a support structure. The lighting system of a lithography system comprises, in particular, a light source configured to generate light in an EUV or DUV wavelength range and a plurality of optical elements configured to redirect the light generated by the light source and couple it into the projection exposure system.In particular, it is advantageous if the lighting system comprises a plurality of optical measuring arrangements configured for position detection of the second component or individual points of the second component, especially in several, preferably six, degrees of freedom. Alternatively or additionally, the plurality of optical measuring arrangements can also be configured for detecting a deformation of a surface of the second component. The advantages and embodiments mentioned for the optical measuring arrangement also apply to the lighting system comprising at least one optical measuring arrangement.

[0046] The lithography system is characterized in particular by the presence of at least one optical measuring arrangement. The second component of the lithography system to be measured can preferably be at least one or more optical elements, support structures, stages, or masks of the lithography system. It is particularly advantageous if the lithography system has a plurality of optical measuring arrangements configured for position detection of the second component or individual points of the second component, especially in several, preferably six, degrees of freedom. Alternatively or additionally, the plurality of optical measuring arrangements can also be configured for detecting a deformation of a surface of the second component.By measuring the distance to the second components, which may be formed as optical elements, for example, using at least one, preferably several, optical measuring arrangements, their relative position or orientation, or even a deformation of the optical surface relative to a first component, i.e., a reference object, can be detected, and the position or deformation can preferably be adjusted by means of actuators. The advantages and embodiments mentioned for the optical measuring arrangement are also applicable to the lithography system comprising at least one optical measuring arrangement.

[0047] The inspection system according to the invention for checking an optical element or a wafer, wafer stage, reticle, or reticle stage comprises at least one optical measuring arrangement according to the invention. The optical measuring arrangement is configured to detect the relative position or distance of a component, for example, an optical element, a wafer, a wafer stage, a reticle, or a reticle stage. Preferably, an evaluation unit is provided that compares the detected positions or distances, in particular of structures of the component, with predetermined distances or positions of the structures or components and, in the event of a deviation by a predetermined limit value, initiates corrective action. The at least one optical measuring arrangement is directly or indirectly connected to, or connectable to, the component to be measured.The advantages and embodiments mentioned for the optical measuring arrangement also apply to the inspection system comprising at least one optical measuring arrangement. An example of such an inspection system for mask or wafer inspection (without the optical measuring arrangement according to the invention) is known from publication DE 10 2012 205 181 A1, the entire contents of which are incorporated into the present application by reference.

[0048] The invention can also be used in a measuring machine for detecting the position, geometry, or shape of a component. The measuring machine then comprises at least one optical measuring arrangement according to the invention. The at least one optical measuring arrangement is preferably connected to the component, either directly or indirectly. The measuring machine can be used, in particular, in manufacturing technology or industrial metrology in mechanical engineering, for example, in the automotive or aerospace industries. The at least one optical measuring arrangement is connected, or connectable, directly or indirectly to the component to be measured. The advantages and embodiments mentioned for the optical measuring arrangement also apply to the measuring machine comprising the at least one optical measuring arrangement.

[0049] The coordinate measuring machine according to the invention comprises at least one optical measuring arrangement according to the invention. Coordinate measuring machines are used for the inspection or measurement of components, whereby the component is typically scanned and distances or positions are determined based on the scanning. For this purpose, an optical system as well as a movable frame structure and / or a high-precision positioning system are provided, which carries the component or object to be inspected. The optical measuring arrangement is preferably connected directly or indirectly to this movable component, i.e., frame structure or positioning system. By means of the at least one optical measuring arrangement, the position or distance of the movable component can be determined, thereby controlling the scanning of the object.Furthermore, the optical measuring arrangement can also be used to detect and thus inspect the distance or position of the component itself. The advantages and embodiments mentioned for the optical measuring arrangement also apply to the coordinate measuring machine comprising at least one optical measuring arrangement. An example of such a coordinate measuring machine (without the optical measuring arrangement according to the invention) is known from German patent application DE 10 2019 213 794A1, the entire contents of which are incorporated into the present application by reference.

[0050] The optical measuring arrangement according to the invention can also be used in a measuring machine. The measuring machine comprises at least one optical measuring arrangement according to the invention. The at least one optical measuring arrangement is preferably connected to the component, either directly or indirectly. The measuring machine can be used, in particular, in manufacturing technology or industrial metrology in mechanical engineering, for example, in the automotive industry or aerospace engineering. The at least one optical measuring arrangement is connected, or connectable, directly or indirectly to the component to be measured. The advantages and embodiments mentioned for the optical measuring arrangement also apply to the measuring machine comprising the at least one optical measuring arrangement.

[0051] Further features, properties, and advantages of the present invention are described in more detail below with reference to exemplary embodiments and the accompanying figures. All features described so far and below are advantageous both individually and in any combination. The exemplary embodiments described below are merely examples and do not limit the scope of the invention. The following are shown: Fig. 1a a schematic representation of a microlithographic projection exposure system designed for operation in the EUV, Fig. 1b a schematic representation of a microlithographic projection exposure system designed for operation in DUV, Fig. 2 a schematic representation of a first embodiment of an optical measuring arrangement formed as an interferometer, Fig. 3 a schematic representation of a side view (a) and a top view (b) of a second embodiment of an optical measuring arrangement with an additional facet, Fig. 4 A schematic representation of a side view (a) and a top view (b) of a third embodiment of an optical measuring arrangement with two further facets, Fig. 5 A schematic representation of a side view (a) and a top view (b) of a fourth embodiment of an optical measuring arrangement with three further facets Fig. 6 schematic representations of facet arrangements of the exemplary embodiment according to Fig. 3, Fig. 7 schematic representations of facet arrangements of the exemplary embodiment according to Fig. 4, and Fig. 8 a schematic representation of a facet arrangement of the exemplary embodiment according to the Fig. 5.

[0052] Fig. Figure 1a shows a schematic representation of an exemplary projection exposure system 600 designed for operation in EUV, in which the present invention can be implemented. However, the invention can also be used in other nanopositioning systems.

[0053] According to Fig. 1a A lighting device in a projection exposure system 600 designed for EUV has a field facet mirror 603 and a pupil facet mirror 604. The light from a light source unit, which comprises a plasma light source 601 and a collector mirror 602, is directed onto the field facet mirror 603. In the light path after the pupil facet mirror 604, a first telescope mirror 605 and a second telescope mirror 606 are arranged. Further down the light path is a deflecting mirror 607, which directs the incident radiation onto an object field in the object plane of a projection lens comprising six mirrors 651-656. At the location of the object field, a reflective structure-bearing mask 621 is arranged on a mask table 620, which is imaged into an image plane by means of the projection lens, in which a substrate 661 coated with a light-sensitive layer (photoresist) is located on a wafer table 660.

[0054] The invention can be used in a DUV system as well as in Fig. 1b is shown. A DUV system is basically the same as the EUV system described above. Fig. 1a constructed, wherein mirrors and lenses can be used as optical elements in a DUV system and the light source of a DUV system emits useful radiation in a wavelength range of 100 nm to 400 nm.

[0055] The in Fig. The DUV lithography system 700 shown in Figure 1b has a DUV light source 701. For example, an ArF excimer laser can be used as the DUV light source 701, emitting radiation 702 in the DUV range at, for example, 193 nm. A beam shaping and illumination system 703 directs the DUV radiation 702 onto a photomask 704. The photomask 704 is designed as a transmissive optical element and can be located outside the system 703. The photomask 704 has a structure which is reduced in size and projected onto a wafer 706 or the like by means of the projection system 705. The projection system 705 has several lenses 707 and / or mirrors 708 for imaging the photomask 704 onto the wafer 706. Individual lenses 707 and / or mirrors 708 of the projection system 705 can be arranged symmetrically to the optical axis 709 of the projection system 705.It should be noted that the number of lenses 707 and mirrors 708 of the DUV lithography system 700 is not limited to the number shown. More or fewer lenses 707 and / or mirrors 708 may be used. In particular, the beam shaping and illumination system 703 of the DUV lithography system 700 has several lenses 707 and / or mirrors 708. Furthermore, the mirrors are typically curved on their front surface for beam shaping. An air gap 710 between the last lens 707 and the wafer 706 can be replaced by a liquid medium with a refractive index > 1. The liquid medium can be, for example, highly purified water. Such a setup is also called immersion lithography and offers increased photolithographic resolution.

[0056] Fig. Figure 2 shows a first embodiment of an optical measuring arrangement 100 for detecting the relative position and / or distance between a first component (not shown) and a movable or immovable second component by measuring the length of at least one measuring path 101. The measuring path 101 is spanned between at least two facets 102, 103, which are directly or indirectly connected or connectable to the first component, and a measuring target 104 arranged in the measuring path 101, which is directly or indirectly connected or connectable to the second component and is configured to deflect a measuring beam 105 back and forth in the measuring path 101 between the facets 102, 103. The first facet 102 is preferably at least partially transmitting, and the second facet 103 is a reflective facet.The center of curvature 115 of one of the facets 102, 103, in particular the second facet, is located on the measuring target 104 or at most 20%, preferably at most 10%, and particularly preferably at most 5% of the distance between the facet 102, 103 and the measuring target 104. This makes it possible to provide an optical measuring arrangement 100 that is less sensitive to a tilting of the measuring target 101. The first component can, for example, be a reference frame or a support structure, while the second component can, for example, be an optical element.

[0057] The one in Fig. The optical measuring arrangement 100 shown in Figure 2 is configured as an interferometer, in particular as a heterodyne interferometer. The optical measuring arrangement 100 therefore additionally comprises a reference path 110 and a beam splitter 108. The beam splitter 108 is configured to split a light beam emitted from a light source (not shown) into the measuring path 101 as a measuring beam 105 and into the reference path 110 as a reference beam 109, and to combine the measuring beam 105 coupled out of the measuring path 101 with the reference beam 109. The measuring target 104 is preferably configured as a reflective facet, in particular as a measuring mirror, and more preferably as a planar measuring mirror. The first at least partially transmitting facet 102 and the second facet 103 form an open cavity with the measuring target 104, in which the measuring beam 105 propagates as a light wave.Furthermore, the at least partially transmitting first facet 102 is formed as a surface of the beam splitter 108 or arranged on it. The facets 102 and 103 are formed as polished surfaces, but can also be formed as mirrors. The measuring target 104 and the reflective second facet 103 preferably have a reflectivity of at least 95%, more preferably at least 98%, more preferably at least 99%, and most preferably at least 99.5%. In this case, the center point 115 of the curvature of the second facet 103 is located on the measuring target or at most 20%, more preferably at most 10%, and more preferably at most 5% of the distance between the second facet 103 and the measuring target 104. This allows the beam axes of the incoming and outgoing measuring beams 105 to coincide, regardless of any tilting of the measuring target 104.

[0058] In the embodiment according to the Fig. The second facet 103 is formed as an end facet of the measurement path 101. The first facet 102 is formed as an at least partially transmitting input and output facet of the measurement path 101 for coupling the measurement beam 105 into the measurement path 101 and for coupling the measurement beam 105 out of the measurement path 101. The curvature of the phase front 106 of the measurement beam 105 entering the measurement target 104 through the at least partially transmitting first facet 102 is chosen such that it coincides or approximately coincides with the curvature of the phase front 106 of the measurement beam 105 exiting the measurement target 104 towards the first facet 102 at the same point (i.e., at the same location).The first facet 102 is preferably formed, in particular curved, in such a way that it coincides or approximately coincides with the phase front 106 of the measuring beam 105 incident on it, i.e. deviates by a maximum of 10%, preferably 5%, particularly preferably 3% from the wavelength of the measuring beam 105 used. The curvature of the surface of the first facet 102 is therefore identical to the curvature of the phase front 106 of the measuring beam 105 incident upon it. Furthermore, the radius of curvature of the at least partially transmitting first facet 102 is preferably larger than the distance d between the first facet 102 and the measuring target 104 and smaller than twice the distance between the first facet 102 and the measuring target 104. To reduce cyclic errors, the first facet 102 can also have a convex lens surface or be formed as a convex lens.In another alternative embodiment, the first facet 102 can also be planar, while the measuring target 104 is curved. Furthermore, both the measuring target 104 and the first facet 102 can be curved, or the measuring target can be planar and the first facet curved. Additionally, the at least partially transmitting first facet 102 can form a virtual cavity with the second facet 103 and the measuring target 104, such that the ray caustic extending from the measuring target 104 onto the second facet 103 at least approximately coincides with the ray caustic extending from the second facet 103. The caustic of the measuring beam 105 to be coupled into the measuring path 101 also preferentially matches a eigenmode of a virtual cavity formed from at least the first facet 102, the second facet 103 and the measuring target 104.The at least partially transmitting first facet 102 has a transmission of over 95%, preferably over 98%, and particularly preferably over 99.5%. It can also have an antireflective coating, at least in some areas.

[0059] If the measuring target 104 is planar, the measuring beam 105 forms a beam path with a beam waist 118 along the measuring path 101, wherein the beam waist 118 is formed between the measuring target 104 and one of the facets 102, 103.

[0060] The reference path 110 also includes a reference facet 111, which is arranged such that the reference light beam 109 directed from the beam splitter 108 into the reference path 110 is reflected back onto the beam splitter 108 and interferes there with the measuring beam 105 coupled out of the measuring path 101. The curvature of the surface of the reference facet 111 is preferably selected such that it corresponds to, or approximately corresponds to, the curvature of the phase front 106 of the reference light beam 109 incident on the reference facet 111. The curvature of the phase front 106 of the incident reference light beam 109 thus deviates from the surface by a maximum of 10%, preferably by 5%, and most particularly by a maximum of 3% of the wavelength used of the reference light beam 109. This allows the caustic of the reference light beam 109 reflected on the reference facet 111 to reproduce the caustic of the incident reference light beam 109.

[0061] The reference light beam 109 to be coupled into the reference path 110 is preferably configured such that its caustic coincides with an eigenmode of a stable virtual cavity formed from at least the first facet 102, the second facet 103, and the measurement target 104. Consequently, the caustic of the reference light beam 109 to be coupled into the reference path 110 and the caustic of the measurement beam 105 to be coupled into the measurement path 101 coincide at least approximately and preferably each coincide with an eigenmode of the stable virtual cavity formed from at least the first facet 102, the second facet 103, and the measurement target 104.

[0062] The reference facet 111 and the first at least partially transmitting facet 102 are identical in this case, but can of course also differ from each other. In particular, both facets 111 and 102 exhibit at least approximately the same curvature.

[0063] To divide the light beam emitted by the light source into a reference path 110 and a measurement path, the measurement beam 105 in measurement path 101 and the reference light beam 109 in reference path 110 have different polarizations. Reference path 110 and measurement path 101 each comprise a λ / 4 plate.

[0064] Alternatively, the in Fig. The optical measuring arrangement 100 shown in Figure 2 can also be configured as an optical measuring arrangement for frequency-based position measurement. In this case, unlike the interferometer, the first facet 102 is configured as a highly reflective facet and is part of an optical resonator comprising at least the measuring target 104 and the second facet 103, in which a standing wave is generated in the measuring path 101. The reference path 110 can be omitted. The frequency measurement is referenced by means of another external cavity or a frequency comb. An example of such an optical measuring arrangement is described in DE 10 2021 203 126 A1, which is incorporated in its entirety here.

[0065] The in the Fig. 3, Fig. 4 to Fig. The five illustrated embodiments show optical measuring arrangements 100 that have a third facet 112 and optionally further reflective facets 107, i.e., further convolution facets. The third reflective facet 112 redirects the measuring beam 105 originating from the measuring target 104 back onto the measuring target 104. In doing so, the third reflective facet 112 redirects the measuring beam 105 reflected from a starting point 113 of the measuring target 104 onto the third reflective facet 112 back onto, or approximately back to, this starting point 113 of the measuring target 104. Fig. Figure 3 shows an optical measuring arrangement 100 with exactly one third reflective facet 112. Fig. Figure 4 shows an optical measuring arrangement 100 in which, in addition to the third reflective facet 112, the measuring path also has a further facet 107, which is configured to direct the measuring beam 105 from one measuring point 114a on the measuring target 104 to the other measuring point 114b on the measuring target 104. Fig. Figure 5 shows an optical measuring arrangement 100, whose measuring path 101 has two further reflective facets 107 in addition to the third reflective facet 112. The concept of the optical measuring arrangement 100 described here can also be extended to include any number of further reflective facets 107. The measuring beam 105 is directed multiple times from one of the measuring points 114a,b via the second facet 103 to the other measuring point 114b,a.

[0066] The third facet 112 and each additional reflective facet 107 increase the accuracy of the distance and / or position detection of the component, as the measuring path is traversed more frequently during detection. The third facet 112 and / or the at least one additional facet 107 can be arranged with at least one of the other facets 102, 103, or with all facets 102, 103, 112 except the measuring target 104 in a common holder 119 or socket. In particular, the second reflective facet 103, the third reflective facet 112, and / or the additional reflective facets 107 can be arranged adjacent to each other ( Fig. 6a, Fig. 6c, Fig. 7a,b). The second facet 103 can be arranged between the first facet 102 and the third reflective facet 112 ( Fig. 6b). Facets 102, 103, 107, 112 can also be arranged arbitrarily on top of each other. This is shown in the Fig. 6, Fig. 7 to Fig. 8 shown. In the Fig. 6b) shows a symmetrical arrangement of facets 102, 103, 112, while in the Fig. 6c) An asymmetrical arrangement of the facets 102, 103, 112 is shown. The surface of the third facet 112 and / or the further facet 107 preferably lies at least approximately in the same plane as the surface of the first facet 102. The third facet 112 is aligned perpendicular to the measuring beam 105 incident on the third facet 112 at a back-reflection point 117 of the measuring path 101 or with a deviation of less than 500 µrad. It is also advantageous if the first facet 102 is aligned perpendicular to the measuring path 101 at its entry point 116.

[0067] Fig. It can be seen from Figure 3 that the third facet 112 is curved. For the formation of a stable real optical resonator for frequency-based position and / or distance detection, or a stable virtual resonator for an interferometer, it is advantageous if the radius of curvature R of the third facet 112 is greater than the distance d between the next facet 112 and the measurement target 104, and less than twice the distance 2d between the next facet 112 and the measurement target 104. In particular, it is advantageous if the radius of curvature R of the third facet is given by... R=32d±x%, where x is less than 20%, preferably less than 15%, and most preferably less than 10%.

[0068] The measuring path 101 is configured such that the measuring beam 105, as it traverses the measuring path 101, strikes the measuring target 104 at at least two different measuring points 114a,b, each spaced apart from the center point 115 of the curvature of the second facet 103. In particular, the measuring points 114a,b are point-symmetric with respect to the center point 115 of the curvature of the second reflecting facet 103. The distance between the center point 115 of the curvature of the second facet 103 and the measuring points 114a,b is at least 0.5 mm, preferably at least 1 mm, and particularly preferably at least 2 mm.

[0069] The second reflecting facet 103 and the third facet 112 are arranged such that the measuring beam 105, after entering the measuring path 101, reaches the third reflecting facet 112 after 2n+2 reflections from the measuring target 104 and 2n+1 reflections from the second reflecting facet 103, where n is a non-negative number. This is, for example, in the Fig. 3 shown. This relationship also applies to embodiments which additionally include further reflective facets 107, if the second reflective facet 103 and the further reflective facets 107 form a common surface.

[0070] The first facet 102 and the third facet 112 are preferably arranged such that the distance b between the entry point 116 of the measuring beam 105 into the measuring path 101 on the first facet 102 and a back-reflection point 117 on the third facet 112 corresponds to b = N*a or a maximum deviation of 10% from b = N*a, where N is the number of reflections of the measuring path 101 in one pass and a is the distance between the midpoint 115 of the curvature of the second facet 103 and a measuring point 114a,b on the measuring target 104. The offset of the entry point 116 relative to the back-reflection point 117 on the third facet 112 in the plane defined by the entry point 116 and the measuring point 114a,b is b = N*a.

[0071] The exemplary embodiment according to Fig. 4 differs in that the optical measuring arrangement 100 additionally has a further reflective facet 107 which is designed to direct the measuring beam 105 from one of the measuring points 114a on the measuring target 104 to the other of the measuring points 114b of the measuring target 104.

[0072] In the Fig. Figure 7 shows possible arrangements of the first facet 102, the second facet 103, the third facet 112, and the further reflective facet 107. The second facet 103 and at least one further facet 107 can form a common polished surface, as shown in the Fig. 7b). The facets 103, 107 can also be arranged separately from each other. Preferably, the center of curvature of the at least one further reflective facet 107 lies on the measuring target 104 or at most 20%, preferably at most 10%, and particularly preferably at most 5% of the distance between the further reflective facet 107 and the measuring target 104. The center of curvature of the further reflective facet 107 coincides at least approximately with the center of curvature 115 of the second reflective facet 103.

[0073] The exemplary embodiment according to the Fig. Figure 5 differs in that the optical measuring arrangement 100 has two additional reflective facets 107. The facets 102, 103, 112 can be used, for example, in the Fig. Figure 8 shows how they can be arranged. In particular, one or more of the further reflective facets 107 can form a common polished surface with the second facet 103.

[0074] The in the Fig. 2, Fig. 3, Fig. 4, Fig. 5, Fig. 6, Fig. 7 to Fig.The optical measuring arrangements 100 shown in Figure 8 can be configured as interferometers or as optical measuring arrangements 100 for frequency-based position and / or distance measurement. If the optical measuring arrangement 100 is configured as an optical encoder, the measurement target 104 of the measurement path 101 is configured as a diffraction grating. If the optical measuring arrangement 100 is configured for frequency-based position and / or distance measurement, the measurement path 101 includes an optical resonator designed to generate a standing wave. The optical resonator is formed at least from the first facet 102, the second facet 103, and the measurement target 104, but can also include the third reflecting facet 112 and further reflecting facets 107. The first facet 102 has a lower transmissivity compared to the configuration of the optical measuring arrangement 100 as an interferometer.The reflectivity of the first facet 102 is, in this case, more than 95%, preferably more than 98%, and most preferably more than 99.5%. If the optical measuring arrangement 100 is configured as an interferometer, the first facet 102 is semi-transmitting. The first facet 103 can also have an antireflective coating. The measuring target 104 is configured as a reflective facet or as a measuring mirror (preferably planar). The measuring path 101 can form a virtual resonator in which the measuring beam propagates as a wave. REFERENCE MARK LIST 100 Optical measuring arrangement 101 Measurement path 102 first facet 103 second facet 104 measuring target 105 Measuring beam 106 Phase Front 107 more reflective facets 108 beam splitters 109 Reference light beam 110 Reference path 111 Reference facet 112 third reflective facet 113 Starting point (of the measurement target) 114 Measuring point (of the measuring target) 115 Center of curvature (of the second facet) 116 Entry point (measurement path) 117 Reflection point (further facet) 118 Beam waist 119 bracket 120 λ / 4 plates 121 additional facets 600 Projection exposure system 601 Plasma light source 602 Collector mirrors 603 Field faceted mirror 604 pupil facet mirrors 605 first telescope mirror 606 second telescope mirror 607 Deflection mirror 620 mask table 621 Mask 651 Mirror (projection lens) 652 Mirror (projection lens) 653 Mirror (projection lens) 654 Mirror (projection lens) 655 Mirror (projection lens) 656 Mirror (projection lens) 660 wafer table 661 coated substrate 700 DUV lithography system 701 DUV light source 702 DUV radiation / beam path 703 Beam shaping and illumination system (DUV) 704 Photomask 705 Projection System 706 wafers 707 lens 708 mirrors 709 optical axis QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. 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

[0000] DE 10 2012 212 663 A1

[0006] WO 2019 / 223968 A1

[0007] US 4,784,489 A

[0008] DE 10 2012 205 181 A1

[0047] DE 10 2019 213 794A1

[0049] DE 10 2021 203 126 A1

[0064]

Claims

Optical measuring arrangement (100) for detecting a distance between a first component and a second component by measuring the length of at least one measuring path (101), wherein the measuring path (101) is spanned between at least two facets (102, 103) forming a measuring head, which are directly or indirectly connected or connectable to the first component, and a measuring target (104) arranged in the measuring path (101), which is directly or indirectly connected or connectable to the second component and is configured to deflect a measuring beam (105) back and forth in the measuring path (101) between the facets, wherein the second facet (103) is formed as a reflecting facet (103), characterized in that a center of curvature of one of the facets (102, 103) of the measuring head is located on the measuring target (104) or at most 20% of the distance between the facet (102, 103) and the The measuring target (104) is located away. Optical measuring arrangement (100) according to claim 1, characterized in that the first facet (102) is formed as an input and output facet of the measuring path (101) for coupling the measuring beam (105) into the measuring path (101) and for coupling the measuring beam (105) out of the measuring path (101), and that the second facet (103) is formed in such a curved manner that its center of curvature is located on the measuring target (104) or at most 20% of the distance between the second facet (103) and the measuring target (104). Optical measuring arrangement (100) according to one of claims 1 or 2, characterized in that the radius of curvature of the first facet (102) is selected to be larger than the distance between the first facet (102) and the measuring target (104) and smaller than twice the distance between the first facet (102) and the measuring target (104). Optical measuring arrangement (100) according to one of claims 1 to 3, characterized in that a curvature of the measuring target is selected such that a beam caustic of the measuring beam entering through the first facet (102) in the direction of the measuring target (104) coincides with the beam caustic of the measuring beam exiting from the measuring target (104) in the direction of the first facet (102). Optical measuring arrangement (100) according to one of claims 1 to 4, characterized in that a beam caustic of the measuring beam (105) entering through the at least partially transmitting first facet (102) in the direction of the measuring target is selected such that it coincides or approximately coincides with the beam caustic of the measuring beam (105) exiting from the measuring target (104) in the direction of the first facet (102). Optical measuring arrangement (100) according to one of claims 1 to 5, characterized in that the surface of the first facet (102) coincides or approximately coincides with the phase front of the measuring beam (105) reflected from the measuring target and incident on the first facet (102). Optical measuring arrangement (100) according to one of claims 1 to 6, characterized in that a reference path (110) is additionally provided, and that a beam splitter (108) is provided which is configured to split a light beam emitted by a light source as the measuring beam (105) into the measuring path (101) and as a reference light beam (109) into the reference path (110), that the reference path (110) additionally comprises a reference facet (111) which is arranged such that the reference light beam (109) directed by the beam splitter (108) into the reference path (110) is reflected back onto the beam splitter (108), and that the beam splitter (108) is configured to combine the measuring beam (105) coupled out of the measuring path (101) with the reference light beam (109). Optical measuring arrangement (100) according to claim 7, characterized in that the surface of the reference facet (111) coincides or approximately coincides with the phase front (106) of the reference light beam (109) incident on the reference facet (111). Optical measuring arrangement (100) according to one of claims 1 to 8, characterized in that the measuring path (101) is formed as an optical resonator in which a standing wave is formed. Optical measuring arrangement (100) according to one of claims 1 to 9, characterized in that at least one third reflective facet (112) is provided in the measuring path (101) which is configured to reflect the measuring beam (105) reflected from a starting point (113) of the measuring target (104) onto the third reflective facet (112) back onto or approximately onto this starting point (113) of the measuring target (104). Optical measuring arrangement (100) according to claim 9 or 10, characterized in that the second reflective facet (103) is configured to direct the measuring beam (105) as it passes through the measuring path (101) from one measuring point (114a) on the measuring target (104) to another measuring point (114b) on the measuring target (104), wherein the measuring points (114a,b) are spaced apart with respect to the center point (115) of the curvature of the second facet (103). Optical measuring arrangement (100) according to claim 11, characterized in that the measuring beam (105) is directed multiple times from one of the measuring points (114a,b) via the second facet (103) to the respective other measuring point (114b,a). Optical measuring arrangement (100) according to one of claims 10 to 12, characterized in that the third reflecting facet (112) is curved, and that the radius of curvature is greater than the distance between the third facet (112) and the measuring target (104) and less than twice the distance between the third facet (112) and the measuring target (104). Optical measuring arrangement (100) according to one of claims 10 to 13, characterized in that the second reflecting facet (103) and the third facet (112) are arranged such that the measuring beam (105) after entering the measuring path (101) hits the third reflecting facet (112) after 2n+2 reflections from the measuring target (104) and 2n+1 reflections from the second reflecting facet (103), where n is a non-negative number. Optical measuring arrangement (100) according to one of claims 10 to 14, characterized in that the first facet (102) and the third reflecting facet (112) are arranged such that the distance b between an entry point (116) of the measuring beam (105) into the measuring path (101) on the first facet (102) and a back-reflection point (116) on the third reflecting facet (112) corresponds to b=N*a or a maximum deviation of 10% of b=N*a, where N is the number of reflections of the measuring path (101) in one complete pass and a is the distance between the center of curvature of the second facet (102) and a measuring point (114) on the measuring target (104). Optical measuring arrangement (100) according to one of claims 10 to 15, characterized in that a further facet (107) is provided which is configured to direct the measuring beam (105) from one of the measuring points (114a,b) on the measuring target (104) to the other measuring point (114b,a) of the measuring target (104). Projection exposure system (600, 700) with at least one optical measuring arrangement (100) according to one of claims 1 to 16 . Lithography system with at least one optical measuring arrangement (100) according to one of claims 1 to 16 . Inspection system for inspecting the shape, position or geometry of an object with at least one optical measuring arrangement (100) according to one of claims 1 to 16. Coordinate measuring machine with at least one optical measuring arrangement (100) according to one of claims 1 to 16 .

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