Measurement module for determining position of component in microlithography optical system

Abstract

The invention relates to a measurement module (10) for determining the position of a component (126) in a microlithography optical system (100), comprising: a first optical resonator (18-1) for distance measurement by irradiating a first measurement target (16-1) associated with the component with a first measurement beam (28-1); and a second optical resonator (18-2) for distance measurement by irradiating a second measurement target (16-2) associated with the component with a second measurement beam (28-2). The optical resonators (18-1, 18-2) are configured to emit two measurement beams from different directions onto respective measurement targets (16-1, 16-2).

Description

[0001] This application claims priority to German patent application 10 2023 202 412.8 of March 16, 2023. The entire disclosure of this patent application is incorporated herein by reference. TECHNICAL FIELD

[0002] The present application relates to a measurement module for determining the position of a component in a microlithography optical system, to a measurement apparatus having a plurality of measurement modules of this type and to a projection exposure apparatus having at least one measurement module of the specified type. BACKGROUND

[0003] Microlithography is used for producing microstructured components, for example integrated circuits or LCDs. This is achieved by means of so-called projection exposure apparatuses which contain an illumination device and a projection lens. In this context, an image of a mask which is located on a reticle and illuminated by means of the illumination device is projected by means of the projection lens onto a substrate, for example a silicon wafer, which is coated with a light-sensitive layer (photoresist) and is arranged in the image plane of the projection lens, in order to transfer the mask structure to the light-sensitive coating of the substrate.

[0004] During the operation of such a projection lens, the mask and the wafer are moved relative to one another in a scanning process during the operation of the projection lens, the positions of the mirrors, some of which can be moved in all six degrees of freedom, must be set and maintained with high accuracy relative to one another and also relative to the mask and / or the wafer, in order to avoid or at least reduce aberrations and the accompanying impairment of the imaging result. In EUV lithography, for example, such a position determination can require a length measurement accuracy in the order of picometers (pm) over a path length of 1 meter.

[0005] Various methods for measuring the position of individual lens mirrors as well as wafer or wafer table and reticle plane are known in the prior art. In addition to interferometric measuring arrangements, frequency-based position measurement using optical resonators is also known here. To this end, the setup used in DE 10 2012 212 663 A1 comprises a resonator in the form of a Fabry-Perot resonator with two resonator mirrors, wherein a first resonator mirror is fixed to a reference element in the form of a measuring frame, which is fixedly connected to the housing of a projection lens of a projection exposure apparatus, and a second resonator mirror, referred to as "measuring target", is fixed to an EUV mirror for the measurement of its position. The actual distance measuring apparatus comprises a radiation source, which is tunable in terms of its optical frequency, and generates input-coupled radiation, which is coupled in through a beam splitter and into the optical resonator. In that case, the radiation source is controlled by a coupling device, so that the optical frequency of the radiation source is tuned to the resonance frequency of the optical resonator and thus coupled to said resonance frequency. The input-coupled radiation output coupled through the beam splitter is analyzed by means of an optical frequency measuring device, which can comprise, for example, a frequency comb generator for the highly precise determination of the absolute frequency. If the position of the EUV mirror changes in the direction of extension of the resonator, the resonance frequency of the optical resonator also changes together with the distance between the resonator mirrors, and thus - due to the frequency of the tunable radiation source being coupled to the resonance frequency of the resonator - the optical frequency of the input-coupled radiation also changes, which is in turn recorded directly by the frequency measuring device.

[0006] If the position of a component is to be determined very meaningfully, it is often the case that a plurality of measuring modules are used, so that the position can be measured in a plurality of coordinate directions. For example, six measuring modules are used in DE 10 2018 208 147 A1 for determining the position in all six degrees of freedom of a rigid body, i.e. the displacement in the direction of the x-axis, y-axis and z-axis and the tilting about the x-axis, y-axis and z-axis. However, the installation space in the region of the component to be measured is often not sufficient to install a sufficient number of measuring modules, or the measuring modules have to be installed at disadvantageous beam angles, so that the measurement accuracy is adversely affected. Furthermore, reference is made to US2022 / 0050043A1 and US2018 / 0306696A1. SUMMARY

[0007] The problem addressed by the present application is to provide a measuring module with which the above-mentioned problems are solved and with which the position can be determined very meaningfully even in the case of tight installation space conditions.

[0008] Solution according to the application

[0009] According to the application, the aforementioned problem can be solved, for example, by a measurement module for determining a position of a component in a microlithography optical system. The measurement module comprises a first optical resonator for making a distance measurement by illuminating a first measurement target associated with the component with a first measurement beam and a second optical resonator for making a distance measurement by illuminating a second measurement target associated with the component with a second measurement beam. The optical resonators are configured to radiate the two measurement beams onto the respective measurement targets from different directions.

[0010] In this context, an optical resonator is to be understood to mean an arrangement of mirrors for reflecting light back and forth as often as possible. According to an embodiment, the optical resonators of the measurement module are each configured to ensure that the measurement radiation radiated into the associated optical resonator still has an intensity of at least 90%, advantageously still at least 99%, after at least five passes through the optical resonator, preferably after at least ten passes through the optical resonator. According to a further embodiment, the optical resonators of the measurement module are each configured to reflect the measurement radiation radiated in back and forth a plurality of times, for example at least 10 times or at least 100 times or at least 1000 times, before the measurement radiation leaves the optical resonator again, wherein leaving the optical resonator is to be understood to mean that the intensity of the measurement radiation remaining in the resonator is less than 50% of the intensity of the measurement radiation radiated in. According to a further embodiment, the optical resonators of the measurement module each have a finesse of at least 100, advantageously at least 1000.

[0011] For example, the component to be measured can be a mirror in the exposure beam path of a microlithography projection exposure apparatus, the position of which can change during operation of the projection exposure apparatus, for example as a result of a misalignment process. This component can therefore also be referred to as a movable component. A respective distance measurement is made between the respective measurement target and the respective reference element. Since the measurement targets are illuminated from different directions, the position of the component can be determined in at least two dimensions. In this case, the reference element and the measurement target of the respective optical resonator can be formed by two resonator mirrors which enclose a resonator cavity of the optical resonator. Each of the resonators comprises a resonator cavity and the measurement module can therefore also be referred to as a measurement module having a plurality of cavities. According to an embodiment, the directions of the two measurement beams deviate from one another by at least 30°.

[0012] Due to the present application, which provides the integration of two optical resonators into a single measurement module for the purpose of distance measurement with differently aligned measurement beams, the measurement module can determine the position in at least two spatial coordinate directions, i.e. meaningfully determine the position, even in the case of tight installation space conditions in the region of the component to be measured. In particular, the position is meaningfully determined compared to the case of using a measurement module with only one optical resonator. Furthermore, for example, when using a measurement module according to the present application instead of when using a conventional measurement module with only one optical resonator, fewer measurement module modules are required for a highly precise determination of the position of a component in all six degrees of freedom of a rigid body.

[0013] By integrating two optical resonators into the measurement module, the measurement axes defining the direction of the measurement beams can already be adjusted relative to one another before the measurement module is installed in a microlithography optical system. This eliminates the need to adjust the measurement axes after installation, which is very complex or can not be achieved with the desired precision if the installation space is tight in the region of the component to be measured. Furthermore, the integration of two optical resonators into the measurement module can better ensure that the adjustment of the measurement axes remains stable during operation, i.e. such that a readjustment is not necessary or at least less frequently required.

[0014] According to an embodiment, the two measurement targets are different oriented parts of a continuous measurement object. According to an embodiment variant, the two measurement targets are oriented at least 80° and preferably perpendicularly to one another.

[0015] According to a further embodiment, at least one of the measurement targets is a resonator mirror of the associated optical resonator.

[0016] According to a further embodiment, at least one of the optical resonators comprises a deflection element for changing the direction of the beam path within the associated resonator. The deflection element can in particular be a mirror element. Alternatively, it can be configured as a prism. Such a prism is advantageous because there is no loss of measurement radiation due to total internal reflection occurring therein.

[0017] According to a further embodiment, the change in direction is in an angular range of between 30° and 150°, in particular between 80° and 100°. This means that the deflection element is configured such that the direction of the measurement radiation impinging thereon is deflected by an angle of between 30° and 150°.

[0018] According to a further embodiment, the deflection element is configured to deflect the measurement radiation from the input beam path originating from the input coupling mirror of the associated resonator into the associated measurement beam.

[0019] According to another embodiment, the respective input beam paths of the two optical resonators originating from the respective input coupling mirrors of the associated resonator are arranged parallel to each other or deviate from being parallel by no more than 10°.

[0020] According to another embodiment, each of the resonators is associated with a waveguide for supplying measurement radiation. According to an embodiment variant, the waveguides each connect a measurement radiation unit to the associated resonator, wherein the measurement radiation unit provides and evaluates measurement radiation for the respective resonator.

[0021] According to another embodiment, the optical system is a microlithography projection exposure apparatus, in particular for EUV microlithography.

[0022] According to another embodiment, the measurement module is configured to perform a frequency-based length measurement on each of the two optical resonators.

[0023] To this end, the measurement module according to an embodiment variant comprises a radiation source for each of the two optical resonators, which is tunable in terms of their optical frequency in order to generate a respective measurement beam. Advantageously, the measurement module comprises a coupling module for each of the optical resonators, which is configured to couple the optical frequency of the associated radiation source to the resonance frequency of the associated optical resonator. Coupling the optical frequency to the resonance frequency is to be understood to mean that the optical frequency is aligned with the resonance frequency. In other words, the optical frequency of the associated radiation source matches the resonance frequency of the associated optical resonator, i.e. the optical frequency follows the resonance frequency.

[0024] Advantageously, the measurement module further comprises a respective frequency measurement device for measuring the optical frequency of the respective coupled radiation source. The length of the optical resonator functionally depends on the measured optical frequency, i.e. the current length of the optical resonator can be determined from the measured optical frequency. In other words, the length of the optical resonator is encoded as the optical frequency of the tunable radiation source. Advantageously, the measurement module further comprises a respective calculation unit for determining the length of the respective optical resonator from the measured optical frequency and thus the distance between the respective input coupling mirror of the associated optical resonator and the associated measurement target.

[0025] According to another embodiment of the measurement module, the two measurement beams are aligned such that they intersect each other at the extension of the respective measurement target. Preferably, the beam axes of the extended measurement beams intersect even at points and / or spatial elements that are at most half, preferably a quarter, of the range of the spatial intersection volume comprising the extended measurement beams.

[0026] Furthermore, the invention also provides a measurement module for determining the position of a component in a microlithography optical system, having an optical resonator for carrying out a distance measurement by illuminating a measurement target associated with the component, wherein the resonator comprises a deflection element for changing the direction of the beam path within the resonator by an angle of between 30° and 150°, in particular between 80° and 100°.

[0027] Furthermore, the invention provides a measurement device for determining the position of a component in a microlithography optical system, comprising at least three measurement modules in any of the preceding embodiments or embodiment variants, wherein the measurement targets associated with the respective measurement modules are arranged on a respective measurement object, and the measurement objects are assigned to different measurement sites on the component to be measured.

[0028] According to an embodiment of the measurement device, the directions of the three measurement beams generated by the measurement modules form linearly independent vectors.

[0029] According to a further embodiment, the measurement positions assigned to the measurement object define a measurement plane, at least one of the measurement beams generated by the measurement modules is oriented transversely to this plane, and at least two of the measurement beams generated by the measurement modules have different directions, each of which is oriented substantially parallel to this plane. In this context, "substantially parallel" means a maximum deviation of + / - 10°, preferably + / - 5°, from exact parallel arrangement.

[0030] According to a further embodiment, the measurement positions assigned to the measurement object define a measurement plane, and at least three of the measurement beams generated by the measurement modules are oriented transversely to the measurement plane.

[0031] According to a further embodiment, the positions assigned to the measurement object form an isosceles triangle in the measurement plane. In this case, at least two of the measurement beams generated by the measurement modules are oriented in the direction of the symmetry axis of the isosceles triangle, at least one of the measurement beams is oriented transversely to the symmetry axis in the plane, and at least three of the measurement beams are oriented transversely to the measurement plane. For example, the positions assigned to the measurement object lie in an xy plane, and the symmetry axis of the isosceles triangle is aligned parallel to the y axis. In that case, according to the preceding embodiment, two of the measurement beams are aligned in the y direction, one measurement beam is aligned in the x direction, and three measurement beams are aligned in the z direction.

[0032] Furthermore, the invention provides a microlithography projection exposure apparatus. The latter comprises at least one component according to any of the preceding embodiments or embodiment variants and at least one measurement module or a measurement device for determining the position of a component according to any of the preceding embodiments or embodiment variants.

[0033] According to an embodiment of the projection exposure apparatus, the component to be measured is a mirror in an exposure beam path of the projection exposure apparatus, wherein the measurement module is configured to measure a vibration of the mirror. According to an embodiment variant, the mirror is part of a projection lens of the projection exposure apparatus, or, alternatively, part of an illumination system.

[0034] According to another embodiment, the projection exposure apparatus is designed for operation with EUV exposure radiation.

[0035] According to another embodiment of the projection exposure apparatus, the component to be measured is a mirror in an exposure beam path of the projection exposure apparatus, wherein the projection exposure apparatus furthermore comprises a cooling device for the mirror by means of a flowing cooling liquid, and the measurement module is configured to measure a vibration of the mirror resulting from the cooling process. According to an embodiment variant, the cooling fluid flows through the mirror; alternatively, it is also conceivable that the cooling fluid flows onto a back side of the mirror.

[0036] The features specified with respect to the aforementioned embodiments, exemplary embodiments and embodiment variants of the projection exposure apparatus according to the application are explained in the description of the figures and in the claims. The individual features can be realized individually or in combination as embodiments of the application. Furthermore, they can describe advantageous embodiments which can be protected independently and, depending on the specific case, only claimed during the pendency of the application or thereafter. BRIEF DESCRIPTION OF DRAWINGS

[0037] The aforementioned features and further advantageous features of the application will be explained with reference to the attached schematic drawings in the following detailed description of exemplary embodiments or embodiments or variant embodiments according to the application. In the drawings:

[0038] Figure 1 An embodiment of a measurement module for determining a position of a component in a microlithographic projection exposure apparatus is shown,

[0039] Figure 2 A plan view of a back side of a mirror is shown, which mirror serves as a component to be measured and is part of a projection exposure apparatus with a measurement device, which measurement device comprises Figure 1 three measurement modules of the type shown in

[0040] Figure 3 A respective sectional view of the measurement module depicted in Figure 2 is shown,

[0041] Figure 4 Another embodiment of a measurement module for determining a position of a component in a microlithographic projection exposure apparatus is shown,

[0042] Figure 5 A detailed view of a measurement radiation unit of a measurement module according to Figure 1 or Figure 4 is shown,

[0043] Figure 6 shows an embodiment of a projection exposure apparatus for EUV microlithography; and

[0044] Figure 7 Display according to Figure 6 Enlarged detail view of a projection exposure apparatus in the region of a reflector of a projection lens, wherein according to Figure 2 The measuring device is integrated in the projection lens. DETAILED DESCRIPTION

[0045] Detailed description of exemplary embodiments according to the present invention

[0046] In the exemplary embodiments or embodiments or variant embodiments described below, elements that are similar in function or structure to each other are provided with the same or similar reference numerals as much as possible. Therefore, in order to understand the features of the individual elements of a particular exemplary embodiment, reference should be made to the description of other exemplary embodiments or the general description of the present invention.

[0047] For ease of description, the accompanying drawings Figure 2 、 Figure 3 、 Figure 4 、 Figure 6 and Figure 7 Indicates a Cartesian XYZ coordinate system, from which the corresponding positional relationships of the components shown in the figures are apparent. Figure 2 , the Z direction extends perpendicularly into the plane of the figure, the X direction extends to the left, and the Y direction extends upward.

[0048] Figure 1 An embodiment of a measurement module 10 for determining the position of a component in a microlithography optical system is depicted. Figure 6 This optical system is shown in a simplified representation in the form of a microlithography projection exposure apparatus 100, which will be described in more detail below. The mirror 126 of the projection lens 116 of the projection exposure apparatus 100 serves as the aforementioned component to be measured. The position of this component can be changed during operation of the projection exposure apparatus 100, and it can therefore also be referred to as a movable component.

[0049] according to Figure 1 The measuring module 10 includes a measuring head 12 and a measuring object 14, which includes two measuring targets 16-1 and 16-2 in the form of reflective surfaces of the measuring object 14. In the embodiment shown, the measuring object 14 is a cuboid, wherein the reflective surfaces serving as measuring targets 16-1 and 16-2 are oriented perpendicular to each other; more specifically, the first measuring target 16-1 is oriented in the negative x-direction of the xy coordinate system of the measuring module 10 and the second measuring target 16-2 is oriented in the positive y-direction of the xy coordinate system of the measuring module 10. At this point, it should be noted that Figure 1The xy-coordinate system of the measurement module 10 specified in the middle differs from the fact that the XYZ-coordinate system contained in Figure 2 , 3 , 4, 6 and 7. In other words, the two measurement targets 16-1 and 16-2 are different oriented parts of the continuous measurement object 14.

[0050] The measurement object 14 is attached to the back of the mirror 126 used as the component to be measured, i.e. both measurement targets 16-1 and 16-2 are also attached to the component to be measured and are thus associated with said component. In order to determine the position of the mirror 126, the measurement module 10 is used to determine the distance between the measurement head 12 and the measurement object 14 in the x and y directions; more specifically, the distance ax between the measurement head 12 and the first measurement target 16-1 in the x direction and the distance ay between the measurement head 12 and the second measurement target 16-2 in the y direction, as described in detail below.

[0051] The measurement module 10 comprises two optical resonators 18-1 and 18-2. The first optical resonator 18-1 comprises a resonator cavity 20-1 enclosed by two resonator mirrors of the resonator 18-1. In this case, the first resonator mirror is formed by an input coupling mirror 22-1 through which the first measurement radiation 24-1 is radiated into the resonator cavity 20-1. The second resonator mirror is formed by the first measurement target 16-1.

[0052] The input coupling mirror 22-1 has a curved mirror surface, while the first measurement target 16-1 is formed by a planar mirror surface. The measurement radiation 24 in the resonator cavity 20-1 thus forms a Gaussian beam whose waist is located on the mirror surface of the measurement target 16-1. The beam path of the measurement radiation 24-1 emanating from the input coupling mirror 22-1, i.e. the first part of the Gaussian beam, is also referred to as the input beam path 26-1 of the first optical resonator 18-1. The part of the Gaussian beam incident on the measurement target 16-1 is also referred to as the measurement beam 28-1.

[0053] The second optical resonator 18-2 of the measurement module 10 comprises a resonator cavity 20-2 enclosed by two resonator mirrors of the resonator 18-2, and a deflection element in the form of a deflection mirror 30a. The first resonator mirror is formed by an input coupling mirror 22-2 through which the second measurement radiation 24-2 is radiated into the resonator cavity 20-2. The deflection element 30a serves to change the direction of the measurement radiation 24-2 by 90°. In alternative embodiments, the direction can also be changed by other angles, but these angles should lie in an angular range between 30° and 150°, in particular between 80° and 100°. In other words, the deflection mirror 30a deflects the measurement radiation 24-2 coming from the input coupling mirror 22-1 by 90°. The deflected measurement radiation then impinges perpendicularly on the second measurement target 16-2 as a measurement beam 28-2.

[0054] The second measurement target 16-2 forms the second resonator mirror of the optical resonator 18-2. The input coupling mirror 22-2 has a curved mirror surface, while the second measurement target 16-2 represents a planar mirror surface. In a similar manner to the measurement radiation 24-1 in the first resonator 18-1, the measurement radiation 24-2 thus forms a Gaussian beam, the waist of which lies on the mirror surface of the second measurement target 16-2. The beam path of the measurement radiation 24-2 which emanates from the input coupling mirror 22-2 and extends up to the deflection mirror 30a is also referred to as the input beam path 26-2 of the second optical resonator 18-2. The portion of the Gaussian beam which impinges on the measurement target 16-2 represents the aforementioned measurement beam 28-2.

[0055] The optical resonators 18-1 and 18-2 are arranged such that their input beam paths 26-1 and 26-2 are arranged parallel to one another or deviate from a parallel arrangement by a maximum of 10°. Due to the configuration of the second optical resonator 18-2 with the deflection mirror 30a, the optical resonators 18-1 and 18-2 are configured to radiate the two measurement beams 28-1 and 28-2 onto the respective measurement targets 16-1 and 16-2 from different directions, namely in the specific embodiment according to Figure 1 from the positive x-direction and the negative y-direction, respectively. In the embodiment shown, the directions of the two measurement beams 28-1 and 28-2 deviate from one another by 90°; in general, they deviate by at least 30°, in particular by at least 80°.

[0056] In Figure 1In the embodiment shown, the two measurement beams 28-1 and 28-2 are aligned such that their extensions through the respective measurement targets 16-1 and 16-2 intersect one another, i.e. the virtual beam paths of the measurement beams 28-1 and 28-2 have at least one overlap. In the embodiment depicted, the measurement beams 28-1 and 28-2 are even so precisely aligned with one another that the respective beam axes 29-1 and 29-2 of the measurement beams 28-1 and 28-2, which are also referred to as measurement axes of the measurement module 10, intersect at a virtual intersection point 32.

[0057] The measurement module 10 further comprises two measurement radiation units 34-1 and 34-2, which are each connected to a waveguide 36 in the form of an optical fiber for supplying the two optical resonators 18-1 and 18-2 with the respective measurement radiation 24-1 and 24-2. The measurement radiation 24-1 and 24-2 generated by the respective measurement radiation units 34-1 and 34-2 is input-coupled into the respective optical resonator 18-1 and 18-2 by means of a respective input-coupling lens 38 via the input-coupling mirrors 22-1 and 22-2. Furthermore, the measurement radiation 24-1 and 24-2 exiting the respective optical resonator 18-1 and 18-2 via the respective input-coupling lens 38 and the respective waveguide 36 is fed back into the associated measurement radiation unit 34-1 and 34-2 and evaluated there. The measurement radiation units 34-1 and 34-2 are arranged outside the measurement head 12 in embodiments according to Figure 1 Alternatively, these can also be integrated into the measurement head 12, in which case the waveguides 36 can optionally be omitted.

[0058] The structure of the measurement radiation units 34 is described below with reference to Figure 5 The measurement radiation units 34 shown describe the structure of the measurement radiation units 34-1 and 34-2 in exemplary fashion. It is based on the principle that a laser 40, which is tunable in terms of optical frequency, follows the frequency of the optical resonator 18-1 or 18-2 by means of a suitable control loop (according to the Pound-Drever-Hall method in the example shown) such that the length of the resonator 18-1 or 18-2 to be measured ultimately is encoded as the frequency of the tunable laser 40. The laser 40 serves as a radiation source for the measurement radiation 24-1 or 24-2, which is for example in the visible or infrared wavelength range.

[0059] The measurement radiation units 34 comprise a Faraday isolator 42, an electro-optical modulator 44, a polarization beam splitter 46, a quarter-wave plate 48, a photodetector 50 and a low-pass filter 52. The portion of the measurement radiation 24-1 or 24-2 that passes through the quarter-wave plate 48 enters the optical resonator 18-1 or 18-2 via the waveguide 36 depicted in Figure 1 Reference is made back to Figure 5For the purpose of frequency measurement, a portion of the measurement radiation 24 emitted by the tunable laser 40 is output coupled via the beamsplitter 54 and fed to a frequency measurement device in the form of an analyser 56 for frequency measurement. The actual frequency measurement in the analyser 56 can be implemented, for example, by comparison with a frequency reference, for example a fs frequency comb of a femtosecond laser. According to Figure 1 The measurement radiation 24 which leaves the optical resonator 18-1 or 18-2 again via the input coupling mirror 22-1 or 22-2 re-enters the measurement radiation unit 34 via the associated optical waveguide 36 and is captured by the photodetector 50. For further details regarding the function of the measurement radiation unit 34, reference is made to DE 10 2018 208 147 A1. The measured frequency of the respective measurement radiation 24-1 or 24-2 has a functional relationship to the length of the associated optical resonator 18-1 or 18-2 and thus to the distance between the associated input coupling mirror 22-1 and 22-2 and the associated measurement target 16-1 or 16-2. From the measured optical frequencies of the measurement radiation 24-1 and 24-2, the measurement module 10 thus calculates the respective distances of the measurement targets 16-1 and 16-2 from the associated input coupling mirrors 22-1 and 22-2 and thus the position of the measurement object in both coordinate directions.

[0060] Figure 6 A simplified illustration of the aforementioned microlithography projection exposure apparatus 100 with a mirror 126 is shown, which is used as a component for the measurement performed by the measurement module 10. As shown, the mirror 126 is mounted on a support structure 138, for example in the form of a reference frame or housing of the projection lens 116 of the projection exposure apparatus 100. Figure 7

[0061] According to Figure 6 The projection exposure apparatus 100 according to

[0062] According to Figure 6 ​The illumination optical unit 105 comprises, in the exemplary embodiment, a field facet mirror 102, a pupil facet mirror 104 and two telescope mirrors 110 and 112. Exposure radiation 101 generated by an EUV radiation source comprising a plasma radiation source 106 and a collector mirror 108 is initially turned onto the field facet mirror 102 and from there onto the pupil facet mirror 104. The first telescope mirror 110 and the second telescope mirror 112 are arranged in the beam path downstream of the pupil facet mirror 104. A deflection mirror 114 is arranged downstream of the beam path, which deflects the radiation incident thereon onto an object field in an object plane of a projection lens 116, which comprises six mirrors 118, 120, 122, 124, 126 and 128.

[0063] A mask 130 carrying a reflective structure on a mask stage 132 is arranged at the position of the object carrier, which is imaged by the projection lens 116 into an image plane, wherein a substrate 134 in the form of a wafer coated with a radiation-sensitive layer (photoresist) is located on a wafer stage 136.

[0064] As Figure 7 indicated and in accordance with an embodiment for monitoring the position and / or the alignment of the mirror 126 relative to a support structure 138 during operation, i.e. in situ, the position of three measurement objects 14A, 14B and 14C arranged on a back surface 146 of the mirror 126 opposite the mirror surface 144 is determined in each case in two measurement coordinates by means of three measurement modules 10 (here referred to as measurement modules 10A, 10B and 10C) according to Figure 1 The measurement coordinates are obtained by determining the distances axand ayin the coordinate system of the measurement module 10.

[0065] Figure 2 A plan view of the back surface 146 of the mirror 126 is shown, on which the measurement objects 14A, 14B and 14C are arranged. In Figure 3 the respective arrangement of the measurement modules 10A, 10B and 10C in combination with the respective associated measurement objects 14A, 14B and 14C is shown in sectional views along the section lines I-I', II-II' and III-III'. The measurement modules 10A, 10B and 10C form a measurement device.

[0066] The distances axl and ayl measured by the measurement module 10A thus represent the positional deviation of the measurement object 14A from the target position in the coordinate directions Y and Z of the mirror coordinate system. Furthermore, the distances ax2 and ay2 measured by the measurement module 10B represent the positional deviation of the measurement object 14B from the target position in the coordinate directions Y and Z of the mirror coordinate system. Finally, the distances ax3 and ay3 measured by the measurement module 10C represent the positional deviation of the measurement object 14C from the target position in the coordinate directions X and Z of the mirror coordinate system.

[0067] The respective intersection points 10A, 10B and 10C of the beam axes 29-1 and 29-2 of the measurement modules 32A, 32B and 32A are referred to in the following as the respective measurement positions on the mirror 126, which are assigned to the respective measurement targets 16-1 and 16-2. These positions are each located inside the measurement objects 14A, 14B and 14C and, due to the arrangement of the measurement objects 14A, 14B and 14C on the back face 146 of the mirror 126, are referred to as measurement positions on the mirror 126 assigned to the measurement objects 14A, 14B and 14C. The measurement positions in the form of the intersection points 32A, 32B and 32C define a measurement plane extending parallel to the XY coordinate plane. The measurement beams 28-2 of the measurement modules 10A, 10B and 10C are each oriented in the y direction and are thus transverse to the measurement plane. The measurement beams 28-1 of the measurement modules 10A, 10B and 10C are oriented parallel to the measurement plane, respectively. The measurement beams 28-1 of the measurement modules 10A and 10B have the same direction (parallel to the Y coordinate axis), while the measurement beam 28-1 of the measurement module 10C has a differently oriented direction (parallel to the X coordinate axis).

[0068] In an evaluation device, which is not shown in the figures, the measured distances axl, ayl, ax2, ay2, ax3 and ay3, as well as the distance L between the beam axis 29-1 of the measurement modules 10A and 10B, the distance Ha between the connection line 142 between the optical center 140 of the mirror surface 144 and the beam axis 29-2 of the measurement modules 10A and 10B, and the distance Hb between the optical center 140 and the beam axis 29-2 of the third measurement module 10C are used to determine the coordinates of all the degrees of freedom of the rigid body of the misalignment of the mirror 126, i.e. the X coordinate, the Y coordinate and the Z coordinate, as well as the tilt values Tx, Ty and Tz (tilt with respect to the X coordinate axis, the Y coordinate axis or the Z coordinate axis), as follows:

[0069]

[0070] The effect of the misalignment or mispositioning of the mirror 526 thus determined on the imaging quality of the projection exposure apparatus 100 is corrected by means of a compensation measure, for example a position change of another mirror in the projection lens 116, a combination of other mirrors in the projection lens 116, the mask table 132 and / or the wafer table 136. As an alternative or in addition thereto, the positioning of the mirror relative to the support structure can also be corrected by means of an adjustment device which is optionally provided.

[0071] Figure 2 A mirror 126 in an embodiment variant is shown, wherein a coolant inlet 58 and a coolant return 60 are provided for cooling the mirror 126. On the inside or back 146 of the mirror 126, the mirror comprises a cooling line through which a cooling fluid flows when the mirror 126 is cooled. Alternatively, the cooling fluid can also flow directly onto the back 146. The aforementioned misalignment or mispositioning of the mirror determined by means of the measurement modules 10A, 10B and 10C can be traced back to the following mechanisms. First, according to the embodiment variant, the mounting of the mirror 126 on the support structure 138 configured as a reference frame is not implemented completely rigidly in order to minimize deformations of the mirror surface 144 caused by the mounting process. However, this can lead to a misalignment of the mirror 126 due to fluctuations in the fluid pressure in the cooling line or due to sound waves propagating through the cooling fluid. In turn, the misalignment of the mirror 126 can lead to lateral imaging errors (also referred to as "line-of-sight errors") of the projection exposure apparatus 100. These errors can be eliminated by measuring the position using the measurement modules 10A, 10B and 10C and by corresponding aforementioned compensation or correction measures.

[0072] Figure 4 Another embodiment of a measurement module 10 for determining the position of a component in a microlithography optical system is depicted. This embodiment differs from the embodiment according to Figure 1 only in that the deflection element is embodied as a deflection prism 30b instead of a deflection mirror. In this case, the measurement radiation 24 is deflected at the transition between the prism glass and the surrounding environment by total internal reflection. As a result, no intensity loss occurs in this embodiment.

[0073] The above description of exemplary embodiments, embodiments or variant embodiments is to be understood as exemplary. The disclosure thus achieved firstly enables a person skilled in the art to understand the present application and the advantages associated therewith and secondly includes changes and modifications to the structures and methods described which are also obvious to a person skilled in the art within the understanding thereof. Therefore, all such changes and modifications, as far as they fall within the scope of the present application defined according to the claims below, and equivalents thereof are intended to be covered by the protection afforded by the claims.

[0074] List of reference signs

[0075] 10, 10A, 10B, 10C measurement module

[0076] 12 measurement head

[0077] 14, 14A, 14B, 14C measurement object

[0078] 16-1 first measurement target

[0079] 16-2 second measurement target

[0080] 18-1 first optical resonator

[0081] 18-2 second optical resonator

[0082] 20-1 first resonator cavity

[0083] 20-2 second resonator cavity

[0084] 22-1 input coupling mirror

[0085] 22-2 input coupling mirror

[0086] 24-1 first measurement radiation

[0087] 24-2 second measurement radiation

[0088] 26-1 input beam path

[0089] 26-2 input beam path

[0090] 28-1 first measurement beam

[0091] 28-2 second measurement beam

[0092] 29-1 beam axis of the first measurement beam

[0093] 29-2 beam axis of the second measurement beam

[0094] 30a deflection mirror

[0095] 30b deflection prism

[0096] 32 virtual intersection point

[0097] 34-1 first measurement radiation unit

[0098] 34-2 second measurement radiation unit

[0099] 36 waveguide

[0100] 38 input coupling lens

[0101] 40 laser

[0102] 42 Faraday isolator

[0103] 44 electro-optical modulator

[0104] 46 polarizing beam splitter

[0105] 48 quarter-wave plate

[0106] 50 photodetector

[0107] 52 low-pass filter

[0108] 54 beam splitter

[0109] 56 analyzer

[0110] 58 coolant inlet

[0111] 60 coolant return

[0112] 100 microlithographic projection exposure apparatus

[0113] 101 exposure radiation

[0114] 102 field facet mirror

[0115] 104 pupil facet mirror

[0116] 105 illumination optical unit

[0117] 106 plasma light source

[0118] 108 condenser mirror

[0119] 110 first telescope mirror

[0120] 112 second telescope mirror

[0121] 114 deflection mirror

[0122] 116 projection lens

[0123] 117 exposure beam path

[0124] 118, 120, 122, 124, 128 mirrors of the projection lens

[0125] 126 mirror of the projection lens, used as component to be measured

[0126] 130 mask

[0127] 132 mask table

[0128] 134 substrate

[0129] 136 wafer table

[0130] 138 support structure

[0131] 140 optical center

[0132] 142 connecting line

[0133] 144 mirror surface

[0134] 146 back surface

Claims

1. A measurement module (10) for determining a position of a component (126) in a microlithography optical system (100), having: - a first optical resonator (18-1) for making a distance measurement by illuminating a first measurement target (16-1) associated with the component with a first measurement beam (28-1), and - a second optical resonator (18-2) for making a distance measurement by illuminating a second measurement target (16-2) associated with the component with a second measurement beam (28-2), the optical resonators (18-1, 18-2) being configured to radiate the two measurement beams onto the corresponding measurement targets (16-1, 16-2) from different directions.

2. The measurement module according to claim 1, the two measurement targets (16-1, 16-2) being differently oriented portions of a continuous measurement object (14).

3. The measurement module according to any one of the preceding claims, at least one of the measurement targets (16-1, 16-2) being a resonator mirror of the associated optical resonator. wherein 4. The measurement module according to any one of the preceding claims, at least one of the optical resonators (18-2) comprising a deflection element (30a, 30b) for changing a direction of a beam path within the associated resonator (18-2).

5. The measurement module according to claim 4, the direction change being in an angular range between 30° and 150°. wherein 6. The measurement module according to claim 4 or 5, the deflection element (30a, 30b) being configured to deflect measurement radiation from an input beam path (26-2) originating from an input coupling mirror (22-2) of the associated resonator into the associated measurement beam (28-2).

7. The measurement module according to claim 6, respective input beam paths (26-1, 26-2) of the two optical resonators originating from respective input coupling mirrors (22-1, 22-2) of the associated resonators being arranged parallel to each other or deviating from parallel by no more than 10°. wherein 8. The measurement module according to any one of the preceding claims, each of the resonators (18-1, 18-2) being associated with a waveguide (36) for supplying measurement radiation (24-1, 24-2).

9. The measurement module according to any one of the preceding claims, the optical system being a microlithography projection exposure apparatus (100). wherein 10. The measurement module according to any one of the preceding claims, being configured to perform a separate frequency-based length measurement on each of the two optical resonators (18-1, 18-2).

11. The measurement module according to any one of the preceding claims, the two measurement beams being aligned such that they intersect each other (32) through an extension of the respective measurement target. wherein, ​ ​ wherein ​ ​ wherein, ​ ​ wherein ​ ​ wherein ​ ​ ​ ​ wherein ​ 12. A measurement module (10) for determining a position of a component (126) in a microlithography optical system (100), the microlithography optical system (100) having an optical resonator (18-2) for distance measurement by illuminating a measurement target (16-2) associated with the component, wherein, the resonator comprising a deflection element (30a, 30b) for changing a direction of a beam path within the resonator (18-2) by an angle between 30° and 150°.

13. A measurement apparatus (10A, 10B, 10C) for determining a position of a component (126) in a microlithography optical system, at least three measurement modules (10A, 10B, 10C) comprising any of the preceding claims, wherein, measurement targets (16-1, 16-2) associated with respective measurement modules are arranged on respective measurement objects (14A, 14B, 14C), and the measurement objects are assigned to different measurement locations (32A, 32B, 32C) on the component.

14. The measurement apparatus according to claim 13, wherein the measurement locations (32A, 32B, 32C) assigned to the measurement objects (14A, 14B, 14C) define a measurement plane, at least one of the measurement beams (28-2) generated by the measurement modules is oriented transversely to the measurement plane, and at least two of the measurement beams (28-1) generated by the measurement modules have different directions, each of which is oriented substantially parallel to the measurement plane.

15. The measurement apparatus according to claim 13 or 14, wherein, the measurement locations (32A, 32B, 32C) assigned to the measurement objects (14A, 14B, 14C) define a measurement plane, and at least three of the measurement beams (28-1) generated by the measurement modules are oriented transversely to the measurement plane.

16. A microlithography projection exposure apparatus (100) having at least one component (126) and at least one measurement module (10, 10A, 10B, 10C) according to any one of claims 1 to 12 or a measurement apparatus according to any one of claims 12 to 15 for determining a position of the component.

17. The projection exposure apparatus according to claim 16, wherein the component is a mirror (126) in an exposure beam path (117) of the projection exposure apparatus, wherein the projection exposure apparatus further comprises a cooling device (58, 69) for the mirror by means of a flowing cooling liquid, and the measurement module (10) is configured to measure vibrations of the mirror resulting from the cooling process.

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