Measurement setup, combination of an object and a measurement setup, and method for recording two measured quantities

Abstract

The invention relates to a measuring arrangement (100) for detecting a first measured quantity and a second measured quantity of an object (101) of a lithography system (600, 700) or an inspection system, comprising a fiber Bragg arrangement (102) which includes at least one optical fiber (103) and at least one fiber Bragg grating (104) arranged in the optical fiber, wherein light of a first wavelength is coupled or can be coupled into the fiber Bragg arrangement (102). Additionally, light of a second wavelength, which differs from the first wavelength, is coupled or can be coupled into the fiber Bragg arrangement (102).A detection and evaluation unit (105) is configured to determine the first measured quantity by means of a measurement signal based on the light of the first wavelength coupled into the fiber Bragg arrangement (102), and to determine the second measured quantity by means of a measurement signal based on the light of the second wavelength coupled into the fiber Bragg arrangement (102). The invention further relates to a combination of at least one object and at least one measurement arrangement, as well as a method for detecting two measured quantities.

Description

[0001] The invention relates to a measuring arrangement for detecting a first measured variable and a second measured variable, which differs from the first measured variable, of an object of a lithography system or an inspection system for inspecting an object for a lithography system, having a fiber Bragg arrangement comprising at least one optical fiber and at least one fiber Bragg grating arranged in the optical fiber, wherein light of a first wavelength is coupled or can be coupled into the fiber Bragg arrangement. Furthermore, the invention relates to a combination of a measuring arrangement and an object, as well as a method for detecting two measured variables.

[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 creating extremely fine structures down to the nanometer range by means of a generally reduced-size image of structures on a mask, a so-called reticle, on an element to be structured, a so-called wafer, which is provided with photosensitive material. The minimum dimensions of the created structures depend directly on the wavelength of the light used. This light is shaped in an illumination optics for optimal illumination of the reticle. Recently, light sources with an emission wavelength in the range of a few nanometers, for example between 1 nm and 120 nm, particularly in the range of 13.5 nm, have been increasingly used. This wavelength range is also referred to as the EUV range.

[0003] In addition to systems operating in the EUV range, the microstructured components are also manufactured using the commercially established DUV systems with a wavelength between 100 nm and 300 nm, particularly 193 nm. With the need to produce ever smaller structures, the requirements for optical correction in the systems have also increased. To reduce imaging errors, the optical elements of the microlithographic projection exposure system, such as the lenses or mirrors, are adjusted or positioned, or their active surface is deformed, using actuators. The actuators are preferably formed as solid-state actuators, with solid-state actuators in the sense of the present invention being electrostrictive or piezoelectric actuators.The solid-state actuators are attached to the optical element, particularly to its backside. The actuators can actuate either perpendicular to the surface or parallel to the surface. Alternatively, the actuators can also be designed as electrostatic actuators, electromagnetic actuators, Lorenz actuators, etc. By controlling each individual actuator, the position or profile of the mirror can be specifically adjusted.

[0004] Adaptive optical elements can also be used to improve imaging quality. These elements have at least one actuator for at least partial deformation of the surface of the adaptive optical element. Sensors are used to control the adaptive optical element.

[0005] A lithography system comprises a plurality of differently shaped objects whose surfaces can deform or which can be caused to vibrate due to external influences, which can affect the image quality. In addition to the optical elements themselves, support structures of the lithography system, such as the force frames or the sensor frames, can also vibrate and / or deform. In addition, temperature control elements are increasingly being used in lithography systems for temperature control, i.e. for heating or cooling. The temperature control elements typically comprise lines through which a fluid flows, which can cause the line to vibrate, which can be transmitted. In addition, it is advantageous if the temperature of the objects can be recorded and adjusted if necessary, to further improve the image quality.

[0006] In the non-patent literature “Measurement of the phase and group refractive indices, and the dispersion of the thermos-optic and strain-optic coefficients of optical fibers using weak fiber Bragg gratings”, JL Cruz et al., Appl. Optics, Vol. 60, pp. 2824-2832 (2021), a method is described in which the temperature and strain of a fiber Bragg grating can be determined using dispersion.

[0007] DE 10 2021 205 425 A1 shows an optical device with an adaptive optical element and a strain gauge formed as a fiber Bragg grating. DE 10 2020 210 024 A1 describes the use of a strain sensor to detect mirror deformation. DE 10 2022 205 227 A1 discloses a state detection system for deformable mirrors using an optical fiber. The German patent application filed under application number 102023203870.6 shows the use of fiber Bragg sensors for mirror mechatronics.

[0008] The refractive index of a strain sensor constructed as a fiber Bragg sensor is sensitive not only to strain but also to temperature changes. DE 10 2021 205 426 A1 demonstrates the separation of the influence of temperature changes and strain on a fiber Bragg sensor by using fibers with different polarizations or two differently designed fibers. One fiber is arranged in such a way that the object does not undergo mechanical expansion, so that the measurement result from this fiber exclusively describes the temperature effect.

[0009] It is an object of the invention to provide a measuring arrangement, a combination of a measuring arrangement and an object, as well as a method in which the above-mentioned disadvantages can be eliminated or at least reduced.

[0010] The problem concerning the measuring arrangement is solved by a measuring arrangement according to the features of claim 1. The problem concerning the combination is solved by a combination according to the features of claim 20. The problem concerning the method is solved by a method according to the features of claim 21. Advantageous embodiments with expedient further developments are specified in the subclaims.

[0011] The measuring arrangement is characterized in particular in that light of a second wavelength different from the first wavelength is additionally coupled or can be coupled into the fiber Bragg arrangement, and in that a detection and evaluation unit is set up to determine the first measured variable using a measurement signal which is based on the light of the first wavelength coupled into the fiber Bragg arrangement and to determine the second measured variable using a measurement signal which is based on the light of the second wavelength coupled into the fiber Bragg arrangement. This enables a differentiation between the first measured variable and the second measured variable based on a wavelength dispersion, i.e. two unknowns (the first measured variable and the second measured variable) are determined using two equations (the measurement signal of the first wavelength and the second wavelength).The first measured variable is acquired via the measurement channel based on the light of the first measured variable coupled into the fiber Bragg array, i.e., the light reflected or transmitted in the fiber Bragg array at the at least one fiber Bragg grating. Similarly, the second measured variable is acquired using the measurement signal based on the light of the second wavelength reflected or transmitted in the fiber Bragg array at the at least one fiber Bragg grating.

[0012] Preferably, the object can be formed as an optical element, for example as a mirror or a lens. The optical element can also be formed as an adaptive optical element, i.e. have at least one actuator which is configured to deform the optical element at least in part. Alternatively or additionally, the object can also be formed as a support structure of the lithography system. In this case, the support structure can be formed as a sensor frame having at least one position sensor. Alternatively or additionally, the support structure can also be formed as a force frame having at least one optical element. Furthermore, the object can also be formed as a line.

[0013] The measuring arrangement is preferably connected or connectable to the object directly or indirectly. The measuring arrangement can be mounted on or beneath an object. It can also be arranged within an object, for example, in a conduit. The object can also be formed from multiple parts, with the measuring arrangement inserted between two parts of the object, or the object can have a receptacle in which the measuring arrangement is accommodated or can be accommodated.

[0014] Furthermore, it is also possible for the fiber Bragg arrangement to have at least two optical fibers, wherein the light of the first wavelength is coupled or can be coupled into the first optical fiber, while the light of the second wavelength is coupled or can be coupled into the second optical fiber. The first optical fiber in turn has at least one first fiber Bragg grating for reflecting light of the first wavelength and the second optical fiber has at least one fiber Bragg grating for reflecting light of the second wavelength. In order to be able to determine the influence of the first measured variable on the signal of the second measured variable and vice versa as accurately as possible, it is preferred if the first optical fiber and the second optical fiber are arranged close to one another, i.e. preferably next to one another.

[0015] However, it is particularly preferred if the fiber Bragg arrangement comprises exactly one optical fiber, wherein light of both wavelengths is coupled or can be coupled into the optical fiber. The optical fiber also has at least one first fiber Bragg grating for reflecting light of the first wavelength and at least one second fiber Bragg grating for reflecting light of the second wavelength.

[0016] Within the scope of the invention, it is of course also possible to couple any number of light beams with differing wavelengths into the fiber Bragg array, i.e., in particular, into the at least one, preferably precisely one, optical fiber. Alternatively, a number of optical fibers adapted to the number of light beams of different wavelengths can also be provided, which are preferably arranged adjacent to one another.

[0017] In order to achieve a sufficiently good separation of the first wavelength from the second wavelength, it is advantageous if the first wavelength deviates from the second wavelength by at least 80 nm, preferably by more than 200 nm and most preferably by more than 300 nm.

[0018] Within the scope of the invention, it is preferred if the at least one fiber Bragg grating has a first grating structure for reflecting light of the first wavelength and a second grating structure deviating from the first grating structure for reflecting light of the second wavelength.

[0019] In order to be able to record the first measured variable and the second measured variable at different locations or regions of the object, it is advantageous if the fiber Bragg arrangement has a plurality of fiber Bragg sensors, each comprising at least one fiber Bragg grating, wherein one of the fiber Bragg sensors is configured to reflect light of the first wavelength and another of the fiber Bragg sensors is configured to reflect light of the second wavelength. Furthermore, it is advantageous if the first fiber Bragg sensor (i.e. the at least one first fiber Bragg grating) is configured to transmit light of the second wavelength, while the second fiber Bragg sensor (i.e. the at least one second fiber Bragg grating) is configured to transmit light of the first wavelength.

[0020] In a simple embodiment, each of the fiber Bragg sensors has exactly one fiber Bragg grating, such that multiple fiber Bragg gratings and thus multiple fiber Bragg sensors are arranged spaced apart from one another in the optical fiber. Preferably, the first fiber Bragg sensors are each arranged adjacent to the other fiber Bragg sensors in the optical fiber.

[0021] In order to be able to record the influence of the first measured variable on the second measured variable and vice versa even more precisely or to verify the recorded measured variables, it is advantageous if, in addition, light of a first polarization and light of a second polarization deviating from the first polarization is coupled or can be coupled into the at least one optical fiber, and that the recording and evaluation unit is set up to additionally determine the first measured variable by means of a measurement signal which is based on the light of the first polarization coupled into the fiber Bragg arrangement and to determine the second measured variable by means of a measurement signal which is based on the light of the second polarization coupled into the fiber Bragg arrangement.In this embodiment, four measuring channels are used to determine the first and second measured variables. Two measuring channels differ in their wavelength, and two measuring channels differ in their polarization. This results in four equations for two unknown measured variables, i.e., an overdetermination. Furthermore, the light with the first polarization can be coupled or can be coupled into a first optical fiber, while the light with the second polarization can be coupled or can be coupled into another optical fiber. The light beams of different polarizations can be coupled into the same optical fiber as the light beams of different wavelengths, or into separate ones.

[0022] Furthermore, it is preferred if the fiber Bragg arrangement comprises at least one apodizing fiber Bragg grating, in particular a cosine-apodizing fiber Bragg grating or a Gaussian-apodizing fiber Bragg grating. It is particularly preferred if all fiber Bragg gratings are formed as apodizing, in particular cosine-apodizing, fiber Bragg gratings.

[0023] To improve the intensity of the measurement signal, it is preferred if the fiber Bragg arrangement has at least one fiber Bragg resonator formed from two fiber Bragg gratings. In particular, it is advantageous if the first fiber Bragg sensor for reflecting light of the first wavelength and the second fiber Bragg sensor for reflecting light of the second wavelength are both formed as fiber Bragg resonators. Alternatively, it is also possible for the light beams of different wavelengths to be coupled into a ring resonator or a hybrid fiber Bragg ring resonator instead of into a fiber Bragg resonator. The individual ring resonators can also differ in their diameter and / or length.

[0024] In this context, it is particularly advantageous if the fiber Bragg arrangement has a first fiber Bragg sensor formed as a first fiber Bragg resonator for reflecting light of the first wavelength and a second fiber Bragg sensor formed as a second fiber Bragg resonator for reflecting light of the second wavelength. Furthermore, the fiber Bragg arrangement can have a number of fiber Bragg resonators adapted to the number of wavelengths used, each for reflecting a different wavelength used. Furthermore, it is advantageous if a plurality of fiber Bragg sensors formed as resonators are provided and arranged at a distance from one another, wherein one fiber Bragg sensor reflects at least light of the first wavelength and the other fiber Bragg sensors reflect light of the second wavelength.

[0025] In order to arrange the fiber Bragg sensor for detecting the first measured variable and the second fiber Bragg sensor for detecting the second measured variable as close to each other as possible and thus to be able to better detect the influences of the measured variables on each other, it is preferred if the first fiber Bragg resonator and the second fiber Bragg resonator are arranged in such a way that a fiber Bragg grating of the other fiber Bragg resonator is (always) arranged between the fiber Bragg gratings of one resonator.

[0026] Alternatively, it is also advantageous if one fiber Bragg resonator is arranged within the other fiber Bragg resonator.

[0027] Another possibility for separating the measured values ​​is that the acquisition and evaluation unit is set up to determine the measured quantities by reading out measurement signals from the fiber Bragg arrangement of different Bragg orders.

[0028] To improve the signal-to-noise ratio and accelerate the evaluation, it is advantageous if the acquisition and evaluation unit is configured to determine the measured variables using peak-fitting methods from the at least one reflection spectrum or the transmission spectrum of the fiber Bragg array. In this context, it is particularly advantageous if the acquisition and evaluation unit is configured to determine at least one of the measured variables using a pattern curve based on a partial derivative of the acquired reflection spectrum with respect to wavelength or frequency.

[0029] Within the scope of the invention, it is particularly preferred if the acquisition and evaluation unit comprises a double-comb Fourier spectrometer for acquiring the measurement signals. With the aid of two highly stable frequency combs, which preferably have pulse rates close to one another, a plurality of spectral lines is generated which generate paired beat signals whose amplitude is each proportional to the square root of the two involved intensities. The light from the first frequency comb is or can be optically connected to the fiber Bragg arrangement. Furthermore, it is provided that the light reflected by the fiber Bragg arrangement is combined with the light from the second frequency comb and interferes. The interference is detected by means of detectors (e.g. photodiodes).The superposition of the frequency combs creates a multitude of optical beats, particularly in the radio frequency range, which reflect both the amplitude and frequency change of the fiber Bragg array. Preferably, a reference path is provided in which the light from the two frequency combs is directly superimposed, and the interference is detected by additional detectors (e.g., photodiodes). The reference path thus serves to absolutely determine the measured variable, in particular a change in strain or a change derived from the strain and / or temperature change in the measuring arrangement. The actual double-comb measurement preferably takes place in the time domain. Due to the different pulse repetition rates, the pulses from the two frequency combs always overlap. During the time in which the pulses partially overlap, a beat signal is generated, which carries the information about the frequency components involved.These frequency components are obtained by a Fourier transformation of this time signal.

[0030] Alternatively, it is advantageous if the acquisition and evaluation unit comprises a scanning interrogator comprising two lasers (dual laser scan interrogator) for acquiring the measurement signals. A cw laser with a wide wavelength range is operated with a temporal sawtooth or similar ramp, and the photosensor signal is discretely sampled and recorded synchronously with the ramp. By using a gas cell filled with a gas (e.g., acetylene) with a known spectral signature in a reference measurement branch, the correlation between a signal value at a given time and the wavelength present at that time is possible with high accuracy. The interrogator has at least two scanning laser sources. Each of the two sufficiently separated wavelength ranges is assigned its own laser source and its own conjugated photosensor, adapted to the wavelength range by means of a bandpass filter.

[0031] Within the scope of the invention, it is particularly provided that one measurement variable is a temperature and that the other measurement variable is a strain or a vibration or a deformation or a pressure or another variable derivable from the strain.

[0032] Furthermore, it is advantageous if the object is formed as an optical element, and if the optical element is or can be connected directly or indirectly to the fiber Bragg arrangement. The optical element can be, in particular, a mirror, a DUV mirror, an EUV mirror, or a lens. The measuring arrangement can thus detect two measured variables of the optical element, in particular strain and temperature.

[0033] Alternatively or additionally, it is advantageous if the object is formed as an adaptive optical element having at least one actuator, and if the adaptive optical element is or can be connected directly or indirectly to the fiber Bragg arrangement. The optical element of the adaptive optical element can in particular be a mirror, a DUV mirror, an EUV mirror, or a lens. The measuring arrangement can thus detect two measured variables of the adaptive optical element, in particular a strain or deformation of the optical element and a temperature. This can be used to detect and control the deformation of an optical element.

[0034] Alternatively or additionally, it is advantageous if the object is formed as a support structure for a lithography system, with at least one sensor and / or at least one optical element, and if the support structure is connected or connectable to at least one fiber Bragg array. The measuring arrangement thus makes it possible, for example, to detect a vibration or deformation and a temperature of the support structure. The detected vibration can additionally be damped within a control loop using a damping unit.

[0035] Alternatively or additionally, it is advantageous if the object is formed as a conduit for conducting a fluid, for example, as a conduit in a lithography system, and if at least one fiber Bragg array is arranged in or on the conduit. With the measuring arrangement, it is possible, for example, to determine a pressure in the conduit and, in addition, a temperature of the fluid flowing in the conduit via the expansion of the conduit.

[0036] The invention further comprises a combination of at least one object arranged in a lithography system or in an inspection system for components of a lithography system and at least one previously described measuring arrangement, wherein the at least one object is connected to the at least one measuring arrangement, wherein the measuring arrangement is configured to determine the first measured variable and the second measured variable of the object. In particular, several measuring arrangements can be directly or indirectly connected to an object. Furthermore, several objects can also be present, wherein each or at least some of the objects has at least one previously described measuring arrangement or several previously described measuring arrangements. The advantages and embodiments mentioned for the measuring arrangement are also applicable to the combination having at least one measuring arrangement.The at least one object can be an optical element, in particular a mirror or a lens, or an adaptive optical element, a support structure, or a line. The inspection system can be used in particular for inspecting masks for a lithography system, most preferably for inspecting EUV masks or DUV masks.

[0037] The method for detecting a first measurement value and a second measurement value, which differs from the first measurement value, of an object of a lithography system, with at least one previously described measuring arrangement comprises at least the following steps: • Coupling light of a first wavelength and light of a second wavelength different from the first wavelength into the at least one optical fiber of the fiber Bragg arrangement, and • Determining the first measured variable by means of a measurement signal which is based on the light of the first wavelength coupled into the fiber Bragg arrangement and determining the second measured variable by means of a measurement signal which is based on the light of the second wavelength coupled into the fiber Bragg arrangement.

[0038] The advantages and embodiments described for the measuring arrangement are also applicable to the method comprising the measuring arrangement.

[0039] Within the scope of the method, it is particularly advantageous if the measured variables are compared with target variables stored in the memory, and if the measured variable deviates from the target variable, at least one measure is initiated. The measure can, in particular, be a damping of a vibration, an actuation by means of an actuator, or a change in temperature.

[0040] The measuring arrangement can be used for measuring objects in a projection exposure system as well as in the illumination of a lithography system or even objects in an inspection system for a lithography system, e.g. during mask inspection.

[0041] Further features, properties, and advantages of the present invention are described in more detail below using embodiments with reference to the accompanying figures. All features described so far and below are advantageous both individually and in any combination. The embodiments described below are merely examples and do not limit the subject matter of the invention. They show: 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 a measuring arrangement with a mirror as an object, Fig. 3 a schematic representation of a second embodiment of a measuring arrangement with a mirror as object Fig. 4 a schematic representation of another embodiment of a fiber Bragg arrangement in an object formed as a mirror, Fig. 5 a schematic representation of another embodiment of a fiber Bragg arrangement in an object formed as a mirror, Fig. 6 a schematic representation of a further embodiment of a fiber Bragg arrangement with fiber Bragg sensors formed as resonators, Fig. 7 is a schematic representation of an interrogator comprising two scanning lasers, Fig. 8 a schematic representation of a two-frequency comb interrogator, Fig. 9 a schematic representation of an embodiment of a combination of a measuring arrangement and an object formed as an adaptive mirror, and Fig. 10 a schematic representation of a further embodiment of a combination of a measuring arrangement and an object formed as an adaptive mirror.

[0042] Fig. 1a shows a schematic representation of an exemplary projection exposure system 600 designed for operation in the EUV, in which the present invention can be implemented.

[0043] According to Fig. 1a, an illumination device in a projection exposure system 600 designed for EUV comprises 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. A first telescope mirror 605 and a second telescope mirror 606 are arranged in the light path downstream of the pupil facet mirror 604. A deflection mirror 607 is arranged downstream in the light path, which deflects the radiation incident upon it 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 by means of the projection lens into an image plane in which a substrate 661 coated with a light-sensitive layer (photoresist) is located on a wafer table 660.

[0044] The invention can be used in a DUV system as well as in Fig. 1b. A DUV system is basically like the EUV system described above from the Fig. 1a, whereby 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 from 100 nm to 300 nm.

[0045] The Fig. The DUV lithography system 700 shown in Figure 1b has a DUV light source 701. An ArF excimer laser, for example, can be provided as the DUV light source 701, which emits 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 arranged outside the systems 703. The photomask 704 has a structure that is imaged in a reduced size onto a wafer 706 or the like by means of the projection system 705. The projection system 705 has a plurality of 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 can also be provided. In particular, the beam shaping and illumination system 703 of the DUV lithography system 700 has a plurality of lenses 707 and / or mirrors 708. Furthermore, the mirrors are usually curved at their front side for beam shaping. An air gap 710 between the last lens 707 and the wafer 706 can be replaced by a liquid medium having a refractive index > 1. The liquid medium can be, for example, ultrapure water. Such a setup is also referred to as immersion lithography and has an increased photolithographic resolution.

[0046] Fig. 2 shows a schematic representation of a measuring arrangement 100 for detecting a first measured variable and a second measured variable, deviating from the first measured variable, of an object 101 of a lithography system, in particular an illumination system or a microlithographic projection exposure system 600, 700, having a fiber Bragg arrangement 102 comprising at least one optical fiber 103 and at least one fiber Bragg grating 104 arranged in the optical fiber 103, wherein light of a first wavelength is coupled into the fiber Bragg arrangement 102 by means of a first light source 109a. In addition, a light beam of a second wavelength deviating from the first wavelength is coupled into the fiber Bragg arrangement 102 by means of a second light source 109b. The optical fiber 103 is connected to the object 101 at least in some regions; for example, the optical fiber 103 is bonded to the object 101.Furthermore, a detection and evaluation unit 105 is configured to determine the first measured variable using a measurement signal based on the light of the first wavelength coupled into the fiber Bragg arrangement 102, and to determine the second measured variable using a measurement signal based on the light of the second wavelength coupled into the fiber Bragg arrangement 102. The first measured variable can be a strain, a deformation, a vibration, a pressure, or any variable derived from a strain. The second measured variable is preferably the temperature.

[0047] Based on a wavelength dispersion, two measured variables of an object 101 can thus be acquired by means of the measuring arrangement 100. The first measured variable is acquired via the measuring channel that is based on the light of the first wavelength coupled into the fiber Bragg arrangement 102, i.e., on the light of the first wavelength reflected or transmitted in the fiber Bragg arrangement 102 at the at least one fiber Bragg grating 104. Analogously, the second measured variable is acquired using the measuring signal that is based on the light of the second wavelength reflected or transmitted in the fiber Bragg arrangement 102 at the at least one fiber Bragg grating 104.

[0048] The object 101, which is directly or indirectly connected to the measuring arrangement 100, can be formed as an optical element 110, for example as a mirror or a lens. The optical element 110 can also be formed as an adaptive optical element, i.e. have at least one actuator 111 that is configured to deform the optical element 110 at least in part. Alternatively or additionally, the object 101 can also be formed as a support structure of the lithography system. The support structure can be formed as a sensor frame having at least one position sensor. Alternatively or additionally, the support structure can also be formed as a force frame having at least one optical element 110. Likewise, the object 101 can also be formed as a line through which a fluid flows. The measuring arrangement 100 can be mounted on or below an object.It can also be located in an object, for example in a pipe.

[0049] In the present embodiment of the Fig. 2, the fiber Bragg arrangement 102 has precisely one optical fiber 103, wherein light beams of both wavelengths are coupled into the same optical fiber 103. The optical fiber 103 also has at least one first fiber Bragg grating 104 for reflecting light of the first wavelength and at least one second fiber Bragg grating 104 for reflecting light of the second wavelength. Alternatively, the fiber Bragg arrangement 102 can also have at least one fiber Bragg grating 104, wherein this at least one fiber Bragg grating 104 has a first grating structure for reflecting light of the first wavelength and a second grating structure different from the first grating structure for reflecting light of the second wavelength.

[0050] Of course, it is also possible to couple any number of light beams with differing wavelengths into the fiber Bragg array 102, i.e., in particular, into the at least one, preferably precisely one, optical fiber 103. Alternatively, a number of optical fibers 103 adapted to the number of light beams of different wavelengths can also be present, preferably arranged adjacent to one another. In this context, a fiber Bragg grating 104 can, of course, also have more than two grating structures for reflecting light of different wavelengths.

[0051] In order to achieve a sufficiently good separation of the first wavelength from the second wavelength, the first wavelength deviates from the second wavelength by at least 80 nm, preferably by more than 200 nm and most preferably by more than 300 nm.

[0052] Furthermore, the fiber Bragg gratings 104 are formed here as an apodizing fiber Bragg grating 104, in particular a cosine-apodizing fiber Bragg grating 104 or a Gaussian-apodizing fiber Bragg grating 104, in order to suppress overshoot in the acquired spectra.

[0053] Another possibility for separating the measured values, not shown in detail, is that the acquisition and evaluation unit 105 is set up to determine the measured variables by reading out measurement signals of the fiber Bragg arrangement 102 of different Bragg orders.

[0054] Furthermore, it is also possible for the fiber Bragg arrangement 102 to have at least two optical fibers 103, wherein the light of the first wavelength is coupled into the first optical fiber, while the light of the second wavelength is coupled into the second optical fiber. The first optical fiber 103 in turn has at least one first fiber Bragg grating 104 for reflecting light of the first wavelength, and the second optical fiber 103 has at least one fiber Bragg grating 104 for reflecting light of the second wavelength. In order to be able to determine the influence of the first measured variable on the signal of the second measured variable and vice versa as accurately as possible, the first optical fiber 103 and the second optical fiber 103 should be arranged close to one another, i.e. preferably next to one another.

[0055] To improve the signal-to-noise ratio and accelerate the evaluation, the acquisition and evaluation unit 105 is preferably configured to determine the measured variables using peak-fitting free methods from the at least one reflection spectrum or the transmission spectrum of the fiber Bragg array 102. In particular, the acquisition and evaluation unit 105 is configured to determine at least one of the measured variables using a pattern curve based on a partial derivative of the acquired reflection spectrum with respect to wavelength or frequency.

[0056] Fig. 3 shows a further exemplary embodiment of the measuring arrangement 100, which differs in that light of a first polarization is additionally coupled into the at least one optical fiber 103 by means of an additional light source 109c, and light of a second polarization deviating from the first polarization is additionally coupled into the at least one optical fiber 103 by means of a further light source 109d. The detection and evaluation unit 105 is in turn configured to additionally determine the first measured variable by means of a measurement signal based on the light of the first polarization coupled into the fiber Bragg arrangement 102, and to determine the second measured variable by means of a measurement signal based on the light of the second polarization coupled into the fiber Bragg arrangement 102.Thus, four measurement channels are used to determine the first and second measured variables. Two measurement channels differ in their wavelength, and two measurement channels differ in their polarization. Thus, there are four equations for two unknown measured variables, i.e., an overdetermination. Furthermore, the light with the first polarization can be coupled into a first optical fiber, while the light with the second polarization is coupled into another optical fiber 103. The light beams of different polarizations can be coupled into the same optical fiber 103 as the light beams of different wavelengths, or into separate ones.

[0057] The examples of implementation according to the Fig. 4 and Fig. 5 show a measuring arrangement 100 for the spatially resolved detection of two measured variables. For this purpose, the fiber Bragg arrangement 102 has a plurality of fiber Bragg sensors 106. Each fiber Bragg sensor 106 comprises at least one fiber Bragg grating 104, wherein one of the fiber Bragg sensors 106a is configured to reflect the light of the first wavelength and another of the fiber Bragg sensors 106b is configured to reflect light of the second wavelength. Furthermore, the first fiber Bragg sensor 106a (i.e., the at least one first fiber Bragg grating) is configured to transmit the second wavelength, while the second fiber Bragg sensor 106b (i.e., the at least one second fiber Bragg grating) is configured to transmit the first wavelength.Alternatively, each of the fiber Bragg sensors 106 can be configured to reflect at least light of the first wavelength and light of the second wavelength, for example by forming the grating from grating structures that differ from one another and reflect different wavelengths. In an embodiment that is easy to implement, each of the fiber Bragg sensors 106 has exactly one fiber Bragg grating 104, such that a plurality of fiber Bragg gratings 104 and thus a plurality of fiber Bragg sensors 106 are arranged at a distance from one another in the optical fiber 103. Preferably, the first fiber Bragg sensors 106a are each arranged adjacent to the other fiber Bragg sensors 106b in the optical fiber 103. The first fiber Bragg sensors 106a can also be arranged in a different optical fiber 103 than the second fiber Bragg sensors 106b.The distribution of the first fiber Bragg sensors 106a and the second fiber Bragg sensors 106b within the optical fiber 103 can be arbitrary.

[0058] Furthermore, the fiber Bragg arrangement 102 can be arranged as in Fig. 4 shown on the surface or near the surface of or in the object 116. Alternatively and as shown in Fig. 5 or additionally, the fiber Bragg arrangement 102 can also be arranged in the body of the object 101. In this case, the object can also be formed from multiple parts, and the fiber Bragg arrangement 102 of the measuring arrangement 100 is inserted between two parts of the object 101, or the object 101 can have a receptacle in which the fiber Bragg arrangement 102 of the measuring arrangement 100 is accommodated.

[0059] The fiber Bragg arrangement 102 according to the Fig. 6 differs in that, to improve the intensity of the measurement signal, the fiber Bragg sensors 106 are formed as fiber Bragg resonators 107, each comprising two fiber Bragg gratings 104 configured to reflect the first wavelength and / or the second wavelength. Alternatively, it is also possible for the light beams of different wavelengths to be coupled into a ring resonator or a hybrid fiber Bragg ring resonator instead of into a fiber Bragg resonator 107. The individual ring resonators can also differ in their diameter.

[0060] Preferably, the fiber Bragg arrangement 102 comprises at least one first fiber Bragg sensor 106a formed as a first fiber Bragg resonator 107a for reflecting light of the first wavelength and at least one second fiber Bragg sensor 106b formed as a second fiber Bragg resonator 107b for reflecting light of the second wavelength. The first fiber Bragg resonator 107a is configured to transmit light of the second wavelength and the second fiber Bragg resonator 107b is configured to transmit light of the first wavelength. For the sake of simplicity, the embodiments according to Fig. 5 shows the case of a measuring arrangement 100 with two different wavelengths. However, the concept can also be applied and extended to any number of wavelengths and even to differently polarized light. Thus, the fiber Bragg arrangement 102 can have a number of fiber Bragg resonators 107 adapted to the number of wavelengths used, each for reflecting a different wavelength used. For spatially resolved detection of the measured variables, a plurality of fiber Bragg sensors 106 designed as first fiber Bragg resonators 107a and a plurality of fiber Bragg sensors 106 designed as second fiber Bragg resonators 107b can be arranged spaced apart from one another in the optical fiber 103 or in a plurality of optical fibers 103.

[0061] In order to arrange the fiber Bragg sensor 106 for detecting the first measured variable and the second fiber Bragg sensor 106 for detecting the second measured variable as close to each other as possible and thus to be able to better detect the influences of the measured variables on each other, one fiber Bragg resonator 107 is arranged within the other fiber Bragg resonator 107. This is shown in the Fig. 6A), where λ L is the first wavelength and λ S the second wavelength and L L the length of the first fiber Bragg resonator 107a and L L the length of the second fiber Bragg resonator 107b.

[0062] Alternatively and as in the Fig. 6B), the at least first fiber Bragg resonator 107a and the at least second fiber Bragg resonator 107b are arranged such that between the fiber Bragg gratings 104 of one fiber Bragg resonator 107a, 107b there is always a fiber Bragg grating 104 of the other fiber Bragg resonator 107b, 107a arranged.

[0063] The Fig. 7 and Fig. 8 show the acquisition and evaluation unit 105 in more detail. In the embodiment according to the Fig. 7, the acquisition and evaluation unit 105 for acquiring the measurement signals comprises a scanning interrogator comprising two lasers 109a, 109b (dual laser scan interrogator). A cw laser with a wide wavelength tunable is operated with a temporal sawtooth or comparable ramp, and the signal from the photosensor (not shown in detail) is discretely sampled and recorded synchronously with the ramp. By using a gas cell 121 filled with a gas (e.g., acetylene) with a known spectral signature in a reference path 118, the correlation between a signal value at a point in time and the wavelength present at that point in time is possible with high accuracy. The interrogator has at least two scanning laser sources 109a, 109b.Each of the two sufficiently separated wavelength ranges is assigned its own laser source and its own conjugated detector (e.g. a photosensor) adapted to the wavelength range by means of a bandpass filter.

[0064] Alternatively and preferably, the acquisition and evaluation unit 105 comprises a double-comb Fourier spectrometer, which is shown in more detail in the Fig. 8. With the help of two highly stable frequency combs 113, 114, which preferably have pulse rates that are close to one another, a large number of spectral lines are generated which generate paired beat signals whose amplitude is proportional to the square root of the two intensities involved. The light of the first frequency comb 113 is optically connected to the fiber Bragg arrangement 102. The light reflected by the fiber Bragg arrangement 102 is combined with the light of the second frequency comb 114 and interferes. The interference is detected by the detectors 120 (e.g. photodiodes). The superposition of the frequency combs 113, 114 creates a large number of optical beats, in particular in the radio frequency range, which reflect both the amplitude and frequency change of the fiber Bragg arrangement 102.In the reference path 118, the two frequency combs 113, 114 are directly superimposed on one another, and the interference is detected by additional detectors 120 (e.g., photodiodes). The reference path 118 serves to determine the absolute measurement variable, in particular a change in strain, or a change derived from the strain and / or temperature change of the measuring arrangement 102. The actual double-comb measurement preferably takes place in the time domain. Due to the different pulse repetition rates, the pulses of the two frequency combs 113, 114 always overlap. During the time in which the pulses partially overlap, a beat signal is generated, which carries the information about the frequency components involved. These frequency components are obtained by a Fourier transformation of this time signal.

[0065] The Fig. 9 and Fig. 10 each show a combination of a measuring arrangement 100 and an object 101. The object 101 is formed as an optical element 110, in particular as an adaptive optical element 110. This comprises a body 108 and at least one actuator 111 for the region-wise deformation of the surface 116 of the optical element 110, in particular a mirror. The fiber Bragg arrangement 102 is in the Fig. 9, arranged on the rear side of the optical element 110 facing away from the active surface of the optical element 110. Alternatively, and as shown in the Fig.10, the fiber Bragg array 102 can also be incorporated into the body 108 of the optical element 110. The fiber Bragg array 102 can thus be incorporated into, on, or beneath the surface of the object 101 or the optical element 110. Alternatively, the at least one optical fiber 103 can also be fused or directly bonded. A further alternative is monolithic manufacturing with the surface. Monolithic manufacturing techniques offer several advantages over adhesive-based integration methods. In particular, creep, flow, volume changes, and outgassing of the adhesive may pose problems for the long-term stability and functionality of components (e.g., optical coatings) within the microlithographic projection exposure system when used.A wide range of manufacturing processes are available for monolithic production, similar to those already used for the production of photonic integrated circuits (PICs) or the writing of optical fibers into substrates. These manufacturing processes include, in particular, direct writing by locally changing the refractive index using laser radiation, for example, in the ultraviolet (UV) range or with ultrashort pulse lasers (fs range), ion beams, or electron beams. Other manufacturing methods include lithographic techniques, which allow optical fibers (103) and active sensor structures to be applied close to the surface through processes such as exposure, development, etching, and material deposition.While lithographic techniques are particularly suitable for near-surface regions, direct writing methods offer the possibility of structuring sensor structures and optical fibers in three dimensions (3D), even deep below the surface of the optical element.

[0066] The fiber Bragg arrangement 102 is optically connected 119 to the acquisition and evaluation unit 105, for example via the optical fiber 103 of the fiber Bragg arrangement 102 or via an additional optical fiber. Furthermore, a control unit 115 is provided, which is configured to compare the acquired measured variables with stored or storable target variables and to initiate measures within a control loop to compensate for or at least reduce deviations of the acquired measured variables from the target variables. In the present case, the optical element 110 is formed as an adaptive mirror, in particular an adaptive EUV or DUV mirror, or as a lens. Thus, the measuring arrangement 100 can detect two measured variables of the adaptive optical element 110, in particular a strain and a temperature. This can be used to detect and control the deformation of an optical element 110.

[0067] If the object 101 is formed as a support structure for a lithography system, with at least one sensor and / or at least one optical element 110, which is connected or connectable to at least one fiber Bragg array 102, the measuring array 100 can, for example, detect a vibration or deformation and a temperature of the support structure. The detected vibration can additionally be damped within the framework of a control loop using a damping unit.

[0068] Alternatively, if the object 101 is formed as a conduit for conducting a fluid in a lithography system and is connected to at least one fiber Bragg arrangement 102, a pressure in the conduit and additionally a temperature of the fluid flowing in the conduit can be determined by means of the measuring arrangement 100 via the expansion of the conduit.

[0069] Within the scope of the invention, any number of objects 101 can be connected to any number of measuring arrangements 100 or fiber Bragg arrangements 102.

[0070] The method for detecting several measured variables of an object 101 of a lithography system, with at least one previously described measuring arrangement 100, comprises at least the following steps: • Coupling light of a first wavelength and light of a second wavelength deviating from the first wavelength into the at least one optical fiber 103 of the fiber Bragg arrangement 102, and • Determining the first measured variable by means of a measurement signal which is based on the light of the first wavelength coupled into the fiber Bragg arrangement 102 and determining the second measured variable by means of a measurement signal which is based on the light of the second wavelength coupled into the fiber Bragg arrangement 102.

[0071] The control unit 115 compares the measured variables with the target values ​​stored in memory. If the measured variable deviates from the target value, at least one action is initiated. This action can, in particular, be a vibration dampening, an actuator activation, or a temperature change. LIST OF REFERENCE SYMBOLS 100 measuring arrangement 101 objects 102 fiber Bragg array 103 optical fibers 104 Fiber Bragg Grating 105 Recording and evaluation unit 106 Fiber Bragg Sensor 106a first fiber Bragg sensor 106b second fiber Bragg sensor 107 Fiber Bragg Resonator 107a first fiber Bragg resonator 107b second fiber Bragg resonator 108 Body of the optical element (mirror body) 109 Laser source 109a first laser source 109b second laser source 110 optical element 111 Actuator 112 Frequency comb 113 first frequency comb 114 second frequency comb 115 Control unit 116 Surface of the optical element 117 Voltage source 118 Reference 119 Connection to the acquisition and evaluation unit 120 detector 121 Gas cell 600 projection exposure system 601 plasma light source 602 collector mirror 603 field facet mirror 604 Pupillary facet mirror 605 first telescope mirror 606 second telescope mirror 607 Deflecting 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 mirrors (projection lens) 660 wafer table 661 coated substrate 700 DUV lithography system 701 DUV light source 702 DUV radiation / beam path 703 Beam Forming and Illumination System (DUV) 704 Photomask 705 projection system 706 wafers 707 lens 708 mirrors 709 optical axis QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] DE 10 2021 205 425 A1

[0007] DE 10 2020 210 024 A1

[0007] DE 10 2022 205 227 A1

[0007] DE 102023203870.6

[0007] DE 10 2021 205 426 A1

[0008] Zitierte Nicht-Patentliteratur

[0000] Measurement of the phase and group refractive indices, and the dispersion of the thermos-optic and strain-optic coefficients of optical fibers using weak fiber Bragg gratings“, J.L. Cruz et al., Appl. Optics, Vol 60, pp. 2824-2832 (2021

[0006]

Claims

[1] Measuring arrangement (100) for detecting a first measured variable and a second measured variable, which differs from the first measured variable, of an object (101) of a lithography system (600, 700) or an inspection system, with a fiber Bragg arrangement (102) which comprises at least one optical fiber (103) and at least one fiber Bragg grating (104) arranged in the optical fiber, wherein light of a first wavelength is coupled or can be coupled into the fiber Bragg arrangement (102), characterized bythat light of a second wavelength deviating from the first wavelength is additionally coupled or can be coupled into the fiber Bragg arrangement (102), and that a detection and evaluation unit (105) is set up to determine the first measured variable by means of a measurement signal which is based on the light of the first wavelength coupled into the fiber Bragg arrangement (102) and to determine the second measured variable by means of a measurement signal which is based on the light of the second wavelength coupled into the fiber Bragg arrangement (102). [2] Measuring arrangement (100) according to claim 1, characterized by that the first wavelength deviates from the second wavelength by at least 80nm, preferably by more than 200nm and most preferably by more than 300nm. [3] Measuring arrangement (100) according to claim 1 or 2, characterized bythat the at least one fiber Bragg grating (104) has a first grating structure for reflecting light of the first wavelength and a second grating structure deviating from the first grating structure for reflecting light of the second wavelength. [4] Measuring arrangement (100) according to claim 1 or 2, characterized by in that the fiber Bragg arrangement (102) has a plurality of fiber Bragg sensors (106) comprising at least one fiber Bragg grating (104), wherein one of the fiber Bragg sensors (106) is configured to reflect light of the first wavelength and another of the fiber Bragg sensors (106) is configured to reflect light of the second wavelength. [5] Measuring arrangement (100) according to claim 4, characterized by that one fiber Bragg sensor (106) is arranged adjacent to the other fiber Bragg sensor (106) in the optical fiber (103). [6] Measuring arrangement (100) according to one of claims 1 to 5, characterized bythat additionally light of a first polarization and light of a second polarization deviating from the first polarization is or can be coupled into the at least one optical fiber (103) and that the detection and evaluation unit (105) is set up to additionally determine the first measured variable by means of a measurement signal which is based on the light of the first polarization coupled into the fiber Bragg arrangement (102) and to determine the second measured variable by means of a measurement signal which is based on the light of the second polarization coupled into the fiber Bragg arrangement (102). [7] Measuring arrangement (100) according to one of claims 1 to 6, characterized by that the fiber Bragg arrangement (102) comprises at least one apodizing fiber Bragg grating (104). [8] Measuring arrangement (100) according to one of claims 1 to 7, characterized bythat the fiber Bragg arrangement (102) has at least one fiber Bragg resonator (107) which comprises at least two fiber Bragg gratings (104). [9] Measuring arrangement (100) according to claim 8, characterized by that the fiber Bragg arrangement (102) has a first fiber Bragg sensor (106a) formed as a first fiber Bragg resonator (107a) for reflecting the light of the first wavelength and a second fiber Bragg sensor (106b) formed as a second fiber Bragg resonator (107b) for reflecting the light of the second wavelength. [10] Measuring arrangement (100) according to claim 9, characterized by that the first fiber Bragg resonator (107a) and the second fiber Bragg resonator (107b) are arranged such that a fiber Bragg grating (104) of the other fiber Bragg resonator (107a, 107b) is arranged between the fiber Bragg gratings (104) of one fiber Bragg resonator (107a, 107b). [11] Measuring arrangement (100) according to claim 9, characterized bythat one fiber Bragg resonator (107a, 107b) is arranged within the other fiber Bragg resonator (107b, 107a). [12] Measuring arrangement (100) according to one of claims 1 to 11, characterized by that the detection and evaluation unit (105) is arranged to determine the measured variables by reading out measurement signals of the fiber Bragg arrangement (102) of different Bragg orders. [13] Measuring arrangement (100) according to one of claims 1 to 12, characterized by that the acquisition and evaluation unit (105) comprises a double-comb Fourier spectrometer for detecting the measurement signals. [14] Measuring arrangement (100) according to one of claims 1 to 12, characterized in that for detecting the measuring signals the detection and evaluation unit (105) comprises a scanning interrogator comprising two laser sources (109). [15] Measuring arrangement (100) according to one of claims 1 to 14, characterized bythat the first measured quantity is a temperature and that the second measured quantity is a strain or a vibration or a deformation or a pressure or a quantity derived from the strain. [16] Measuring arrangement (100) according to one of claims 1 to 15, characterized by that the object (101) is formed as an optical element (110), and that the optical element is connected or connectable to the fiber Bragg arrangement (102). [17] Measuring arrangement (100) according to one of claims 1 to 15, characterized by that the object (101) is formed as an adaptive optical element (110) having at least one actuator (111) and that the adaptive optical element (110) is connected or connectable to the fiber Bragg arrangement (102). [18] Measuring arrangement (100) according to one of claims 1 to 15, characterized bythat the object (101) is formed as a support structure for a lithography system, with at least one sensor and / or at least one optical element (110), and that the support structure is connected or connectable to at least one fiber Bragg arrangement (102). [19] Measuring arrangement (100) according to one of claims 1 to 17, characterized by that the object (101) is formed as a conduit for conducting a fluid, and that at least one fiber Bragg arrangement (102) is arranged in or on the conduit. [20] Combination of at least one object (101) arranged in a lithography system (600, 700) or in an inspection system and at least one measuring arrangement (100) according to one of claims 1 to 19, characterized by that the at least one object (101) is connected or connectable to the at least one measuring arrangement (100) and the measuring arrangement is configured to determine the first measured variable and the second measured variable of the object. [21] Method for detecting a first measurement variable and a second measurement variable, which deviates from the first measurement variable, of an object (101) of a lithography system (600, 700) or an inspection system, with at least one measuring arrangement (101) according to one of the preceding claims, comprising the steps: a. coupling light of a first wavelength and light of a second wavelength different from the first wavelength into the at least one optical fiber (103) of the fiber Bragg arrangement (102), and b. Determining the first measured variable by means of a measurement signal which is based on the light of the first wavelength coupled into the fiber Bragg arrangement (102) and determining the second measured variable by means of a measurement signal which is based on the light of the second wavelength coupled into the fiber Bragg arrangement (102). [22] Method according to claim 21, characterized bythat the measured values ​​determined are compared with target values ​​stored or that can be stored in a memory and that if the measured values ​​determined deviate from the target values, at least one measure is taken. [23] Method according to claim 22, characterized by that the at least one measure is a damping of a vibration or an actuation by means of an actuator or an adjustment of the temperature.

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